2024-03-29T01:18:23Zhttps://tore.tuhh.de/dspace-cris-server/oai/requestoai:tore.tuhh.de:11420/30722019-08-09T03:14:36Zcom_11420_1col_11420_2
Adhesion between a power-law indenter and a thin layer coated on a rigid substrate
Antonio
Papangelo
Adhesion
Layer
JKR model
Adhesion Enhancement
600
In the present paper we investigate indentation of a power-law axisymmetric rigid probe in adhesive contact with a "thin layer" laying on a rigid foundation for both frictionless unbounded and bounded compressible cases. The investigation relies on the "thin layer" assumption proposed by Johnson, i.e. the layer thickness being much smaller than the radius of the contact area, and it makes use of the previous solutions proposed by Jaffar and Barber for the adhesiveless case. We give analytical predictions of the loading curves and provide indentation, load and contact radius at the pull-off. It is shown that the adhesive behavior is strongly affected by the indenter shape; nevertheless below a critical thickness of the layer (typically below 1 µm) the theoretical strength of the material is reached. This is in contrast with the Hertzian case, which has been shown to be insensitive to the layer thickness. Two cases are investigated, namely, the case of a free layer and the case of a compressible confined layer, the latter being more "efficient", as, due to Poisson effects, the same detachment force is reached with a smaller contact area. It is suggested that high sensitive micro-/nanoindentation tests may be performed using probes with different power law profiles for characterization of adhesive and elastic properties of micro-/nanolayers.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.045134
Facta Universitatis, Series: Mechanical Engineering 1 (16): 19-28 (2018)
eng
1
6356c7171f12583aed4beb6d9d160e9e
https://tore.tuhh.de/bitstreams/738a6a26-8554-4f3b-b00f-cdbf4d3c9bd0/download
http://hdl.handle.net/11420/3072
10.15480/882.2366
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/122232022-04-05T12:18:57Zcom_11420_1col_11420_2
iNeP - integrierte Netzentwicklungsplanung für die Energieträger Strom, Gas und Wärme
Daniela
Vorwerk
Detlef
Schulz
Stefan
Micheely
Oliver Henry
Koch
Cristoph
Cosler
Johannes
Heise
Marwan
Mostafa
Alexander
Povel
Christian
Töbermann
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021
BookPart
Text
publishedVersion
urn:nbn:de:gbv:830-882.0180036
Stand der Technik und Digitalisierung bei integrierten Energiesystemen, Sektorenkopplungs- und Mobilitätstechnologien. - Hamburg : HSU, 2021. - (Hamburger Beiträge zum technischen Klimaschutz ; Bd. 3). - Seite 47-56 (2021)
ger
1
2c6acd56450843e983428b108231a5fe
https://tore.tuhh.de/bitstreams/5e74de36-c2da-4ab5-8998-dde6bbd7a1d8/download
http://hdl.handle.net/11420/12223
10.15480/882.4282
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/154132023-06-16T06:13:08Zcom_11420_1col_11420_2
Capillary cohesion of different granular materials determined from uniaxial compression and water retention tests
Dennis
Heinrich
Marius
Milatz
In this conference contribution, we present and discuss the results for capillary cohesion of different granular materials determined through different approaches. First, we consider macroscopic uniaxial compression tests with varying degrees of saturation. Second, we derive theoretical capillary cohesion from the water retention curve (WRC) measured in macroscopic water retention experiments. Finally, capillary cohesion is calculated from air-water interfacial areas and solid-water interfacial areas extracted from CT images acquired during a cyclic water retention experiment. An attempt is made to link the macroscopic results of capillary cohesion based on microscopic insights from CT imaging experiments.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0221861
E3S Web of Conferences 382: 02003 (2023)
eng
1
dc3f42588f36feb02c985e21139ac50d
https://tore.tuhh.de/bitstreams/9d9fb0ca-c2a0-4caf-b633-0dac2bfb4753/download
http://hdl.handle.net/11420/15413
10.15480/882.5188
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/37172019-11-06T06:36:10Zcom_11420_1col_11420_2
Digital twin for real-time data processing in logistics
Hendrik
Haße
Bin
Li
Norbert
Weißenberg
Jan
Cirullies
Boris
Otto
Digital Twin
Real-time
KPI
IoT
330
Purpose: Key performance indicators (KPIs) are an essential management tool. Realtime KPIs for production and logistics form the basis for flexible and adaptive production systems. These indicators unfold their full potential if they are seamlessly integrated into the “Digital Twin” of a company for data analytics.
Methodology: We apply the Design Science Research Methodology for Information Systems Research for deriving a digital twin architecture.
Findings: Research in the field of digital twins is at an early state, where the main objective is to find new applications for this technology. The majority of digital twin applications relate to the fields of manufacturing. Finally, it became apparent that existing architectures are too generic for usage in logistics.
Originality: The approach presented is an affordable solution for stakeholders to start with a digital transformation, based on standards and therefore highly technology-independent. The combined use of a lambda architecture with a semantic layer for flexible KPI definition is a special case.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-09-26
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.054049
Hamburg International Conference of Logistics (HICL) 27: 3-28 (2019)
eng
1
88707b6fcf64df357897a69329a5a9bb
https://tore.tuhh.de/bitstreams/4da1b0e8-30e9-4726-adfc-4b2eda554551/download
http://hdl.handle.net/11420/3717
10.15480/882.2462
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/113992022-01-13T16:35:36Zcom_11420_1col_11420_2
Praxisbericht: Fachwissenschaft und Berufspraxis verbunden durch kollaboratives Peer Teaching im Studium des Lehramts an Beruflichen Schulen
Katharina
Bartsch
Ake
Ewald
Dirk
Herzog
peer teaching
collaborative learning
teacher education
vocational schools
Die Fachsystematik der beruflichen Fachrichtungen im Studium des Lehramts an Beruflichen Schulen steht in einem anhaltenden Widerspruch zu der Handlungsorientierung an den Schulen. Jedoch ist es aufgrund der Anforderungen an einzelne Fachrichtungen nicht immer einfach, diesen aufzulösen. In dieser Studie wird ein didaktisches Konzept vorgestellt, welches mittels eines Peer-Teaching-Ansatzes die Fachsystematik der fachwissenschaftlichen Lehrinhalte durch auf den späteren Lehrerberuf bezogene Lehrmethoden ergänzt. Das Konzept wurde in zwei Lehrveranstaltungen der beruflichen Fachrichtung Metalltechnik in Hamburg zur Anwendung gebracht und evaluiert. Es hat zu einer erhöhten Motivation und Selbstständigkeit der Studierenden bei gleichbleibender akademischer Leistung geführt.
The systematic nature of the vocational fields in the training programme for teachers at vocational schools is in continuing contradiction to the action orientation at schools. Because of the requirements for individual specializations, it is not always easy to resolve this issue. This study presents a didactic concept that uses a peer-teaching approach to supplement the subject systematics of the subject-specific teaching content with teaching methods that are related to the later teaching profession. The concept was applied and evaluated in two teaching events of the professional field of metal technology in Hamburg. It has led to an increased motivation and in- dependence of the students while maintaining the same academic performance.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-12-14
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0168767
Journal of Technical Education (JOTED), 8(2), 81–97
ger
1
0f9aa64ead25abc250967fd2206aaf3c
https://tore.tuhh.de/bitstreams/690fa458-5426-461a-adac-edfc0cf4b07a/download
http://hdl.handle.net/11420/11399
10.15480/882.4073
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/7652010-02-17T07:05:42Zcom_11420_1col_11420_2
Orthopädische Trennverfahren unter besonderer Berücksichtigung des Strahlschneidens
Water-jet-cutting in orthopedic surgery
Matthias
Honl
Orthopädie
Endoprothese
Wasserstrahl
Bandscheibe
orthopedic surgery
joint replacement, water jet
model, spinal disc
610
Bei verschiedenen orthopädischen Operationen,finden sich Probleme, die den Trennprozess betreffen: bei der mikroinvasiven Nukleotomie wird der Nukleus pulposus durch einen kleinen Arbeitskanal abgetragen. Mechanische Werkzeuge oder ein LASER erlauben keinen gewebeselektiven Materialabtrag, und bergen die Gefahr andere Gewebe, wie z.B. den Anulus fibrosus zu schädigen.
Bei der Endoprothesenrevision muss gesunder Knochen geopfert werden, weil bisher bekannte Trennverfahren für den Materialabtrag im Spalt zwischen Knochen und Prothese ungeeignet sind. Bei der Endoprothesenimplantation oder der Osteotomie fehlt bisher ein athermisches Trennverfahren mit hoher geometrischer Genauigkeit. Das Trennen mit Hochdruckflüssigkeitsstrahlen hat sich u.a. beim Bearbeiten von thermosensiblen Verbundwerkstoffen bewährt. Der entscheidende Vorteil einer medizinischen DWS-Anwendung liegt in der Möglichkeit des selektiven Materialabtrags und im athermischen Trennprozess.
Ziel der vorliegenden Arbeit war es, die Eignung der DWS-Technik für operative Trennprozesse in der Orthopädie zu hinterfragen und den Materialabtragsprozess im Gewebe zu untersuchen.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2005-10-28
2005
Other
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-8497
ger
1
cd7e47c6ed031b1a822161ea1ac8d2e3
https://tore.tuhh.de/bitstreams/e008c433-0fc5-4036-adee-2231b541303c/download
http://tubdok.tub.tuhh.de/handle/11420/765
10.15480/882.763
http://doku.b.tu-harburg.de/doku/lic_mit_pod.php
oai:tore.tuhh.de:11420/111642021-12-09T07:37:12Zcom_11420_1col_11420_2
How blockchain interrelates with trust in the supply chain context : insights from tracing sustainability in the metal industry
Abbas
Batwa
Andreas
Norrman
Ala
Arvidsson
Artificial Intelligence
Blockchain
Purpose: Blockchain technology (BCT) is argued to deliver a trustless system where trust is driven by technology rather than individuals or organizations. This paper studies this claim using insights related to tracing sustainability features in the metal industry.
Methodology: The results of this study are based on multiple case studies of two supply chains (steel and copper) piloting a traceability solution for tracing metal sustainability throughout the supply chain. The data are collected and analyzed from multiple actors using sources such as interviews and secondary documents.
Findings: The study empirically supported that even if the BCT is applied, there will be a need for: benevolence, integrity, ability, and credibility dimensions of trust. Hence, a trustless system is still not yet applicable. Moreover, to remove the need for the trusted third party certificates, there are boundary conditions such as governance structures and standardizations that must be addressed first.
Originality: The concept of trust in the novel phenomena of the BCT was investigated from different point of views, such as the supplier and the buyer views. Moreover, different contexts were examined such as the commercial and the sustainability contexts. Therefore, this paper is among the first to handle the issue of trust from these regards.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021-12-01
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0161679
Hamburg International Conference of Logistics (HICL) 31: 329-351 (2021)
eng
1
ea0b83190f0b2a1c0a90f68445d9795e
https://tore.tuhh.de/bitstreams/90493beb-318e-49de-bcd7-601f23615aa6/download
http://hdl.handle.net/11420/11164
10.15480/882.3955
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/13052016-06-15T11:06:33Zcom_11420_1col_11420_2
Life cycle assessment of electricity production from airborne wind energy
Stefan
Wilhelm
LCA
Life Cycle Assessment
AWE
Airborne Wind Energy
620
Die globale Energieversorgung ist eng mit einigen der größten Herausforderungen unserer Gesellschaft verbunden. Ein steigender Anstieg muss gedeckt werden, während konventionelle Energiequellen erschöpfen und beträchtliche Mengen an Treibhausgasen freisetzen. Um sich dieser Thematik zu stellen werden zunehmend Technologien zur Nutzung erneuerbarer Energien befürwortet, insbesondere in der stromerzeugenden Industrie. Die Forschung hat gezeigt, dass erneuerbare Energien den konventionellen in vielen Umweltaspekten überlegen sind, jedoch aber nicht frei von Lasten sind. Die Hauptverursachung von Lasten ist dabei aber auf andere Phasen des Lebenszyklus als dem Betrieb verschoben. Die aufkommende Flugwindenergietechnologie als neuer Stakeholder innerhalb der erneuerbaren Energien stellt eine aus ökologischer Sicht vielversprechende Alternative dar, da sie Windressourcen von herausragender Qualität mit geringem Materialaufwand zugänglich macht. Bisher existiert jedoch noch keine ökologische Bewertung dieser Technologie.
Die Ziele dieser Studie sind (1) die Bestimmung der Umweltlasten der Stromerzeugung mit Flugwindenergie (FWE) in den Kategorien Klimaerwärmung und Verbrauch von Energieressourcen, (2) die Identifizierung der Hauptkontributoren zu diesen Kategorien, (3) die Bestimmung der energetischen Amortisationszeit und (4), einer Bewertung, ob der Einsatz dieser Technologie die Umweltlasten durch Stromerzeugung für diese Kategorien verringert würden. Es wurde ein FWE-Design gewählt, welches als zukünftig potentiell dominierendes Design eingeschätzt werden könnte. Auch wenn Unsicherheiten durch die Analyse eines bestimmten Systems hervorgerufen werden, können die Ergebnisse dieser Studie als eine erste Referenz für Systementwickler und Entscheidungsträger dienen, um ihre Unterstützung oder Engagement für diese Technologie zu beurteilen.
Zu diesem Zweck wurde eine Ökobilanz durchgeführt, welche die Verfolgung von Umweltindikatoren von der Wiege bis zur Bahre ermöglicht. Spezifische 1,8 MW-FWE-Anlagen wurden definiert und in einem 300-MW-Park unter Schwachwindbedingungen untersucht. Das Modell verfolgt für realistisch erachtete oder konservative Designentscheidungen. Es ist zu erwarten, dass sich die Ergebnisse daher im oberen Wertebereich befinden. Die Ergebnisse des Modells werden in dieser Studie präsentiert, diskutiert und in einer Sensitivitätsstudie auf ihre Robustheit hin untersucht. Ein Vergleich zu ähnlichen konventionellen Windenergieparks und dem Strommix im Netz erlauben eine bessere Einordnung der Ergebnisse.
Die Ergebnisse der Umweltindikatoren für das Treibhausgaspotential (GWP) ist 5,611gCO2-äq./kWh. 65% davon treten in der Phase Rohstoffgewinnung und Herstellung auf, 3% während der Installation, 28% während des Betriebs und 4 % bei der Entsorgung. Der kumulierte Energieaufwand (CED oder KEA) ist 75,2kJ-äq./kWh. Die während des gesamten Lebenszyklus aufgewendete Energie entspricht 2,1% des gesamten produzierten Stroms und ist nach fünf Monaten bzw. 153 Tagen Betrieb amortisiert. Dies entspricht einem Energieausbeuteverhältnis von 48. Inklusive der Austauschmaterialien verursacht das Zugseil 5,5 und 8,1% des GWP und CED. Geringere Lebensdauern haben einen signifikanten Einfluss, höhere jedoch einen marginalen. Die Umweltauswirkungen durch die Flügelherstellung entstehen zu 75% durch das kohlefaserverstärkte Epoxidharz, entsprechen jedoch nur 2,6 und 5,6% des GWP und CED. Der größte Beitrag entsteht durch den Generator und das Getriebe, welche bei Austausch aller Getriebe für 35 und 30% des GWP und CED verantwortlich sind. Insgesamt stammen 30% der Umweltauswirkungen von Windparkinfrastruktur und 70% von den FWE-Einheiten selbst. Die letztgenannte Zahl ist diejenige, die von den FEW-Anlagenherstellern direkt beeinflusst werden kann.
Verglichen mit einer konventionellen Windenergieanlage die auf ähnliche Weise modelliert wurde, verbrauchte der FWE-Park 23% der Masse, verursacht 49% des GWP und verbraucht 55% des CED. Die energetische Amortisationszeit ist dabei 2 Mal geringer. Verglichen mit dem deutschen Strommix verursacht der Park 0,87% des GWP und verbraucht 0,74% des CED. Selbst mit einem konservativen Ansatz bestätigt die Studie die Erwartungen von geringen Umweltauswirkungen in den betrachteten Kategorien und präsentiert erste numerische Ergebnisse.
Global energy supply is closely linked with some of the greatest challenges of our society. A rising demand has to be met whereas conventional energy sources are depleting and emit considerable amounts of greenhouse gases. Renewable energy technologies are increasingly promoted to face these issues, especially in the electricity industry. Research has shown, that renewables are superior to conventional energy technologies in many environmental aspects but are not free of burdens. However, the main causes of impacts are shifted to other life cycle phases than operation. The emerging of airborne wind energy
(AWE), as a new stakeholder within the renewables, presents an ecologically promising option since it accesses wind resources of outstanding quality with little material consumption. As of now, there is no environmental assessment of this new technology available. The goals of this study are (1) the determination of environmental burden of electricity generation with AWE on the categories global warming and consumption of energy resources, (2) the identification of main contributors to these categories, (3) the determination of the energy payback time and (4) an assessment whether use of this technology would lower impact of electricity supply in the mentioned categories. An AWE design is chosen for the investigations, which appears possible to become a dominating design. Even though uncertainties arise from the analysis of a specific design, the outcomes of the study could serve as a first reference for system developers and for decision-makers to evaluate support or engagement in this technology.
To this end, a life cycle assessment (LCA) was executed, which allows tracking of category indicators from cradle to grave. Specific AWE facilities of 1.8 MW were defined and analyzed in a 300 MW plant under low wind conditions. The modeling follows an estimated dominating design or conservative choices. The results are expected to be on the upper range. The results of the model are presented and discussed and checked for robustness in a sensitivity study. A comparison to a similar conventional wind power plant and the electricity grid mix allows a better classification of the results. The category indicator result in global warming potential (GWP) is 5.611 gCO2-eq./kWh. 65 % of that occur in the phase raw material and manufacturing, 3 % during installation, 28 % during operation and 4 % in disposal. The cumulated energy demand (CED) is 75.2 kJ-eq./kWh. The invested energy during the entire life cycle is 2.1 % of the total generated electricity and is recovered after 5 months or 153 days of operation. This corresponds with an energy yield ratio of 48%. The tether accounts for 5.5 and 8.1 % in GWP and CED, including its replacements. Lower lifetimes have significant influence, higher are with marginal effect. The environmental effects from the wing manufacture arise by 75% from the carbon fiber reinforced polymer but are only 2.6 and 5.6 % in GWP and CED. The biggest contribution is from generator and gearbox, which account for 35 and 30 % in GWP and CED respectively, including replacement of all gearboxes. In total, 30 % of the impacts come from balance of station components and 70 % from the AWE facility. The latter is the percentage that the system developer can influence directly. Compared to a conventional wind plant that was modeled in a similar way, the AWE plant consumed 23 % of the mass, causes 49 % of the GWP and consumes 55 % of the CED. Energy payback time was 2 times lower. Compared to German electricity mix the plant causes 0.87 % of the GWP and has 0.74 % of the CED. Even with a conservative approach the study confirms the expectation of low impact in the considered categories and presents first numerical results.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-08
2015-08
Other
Text
publishedVersion
urn:nbn:de:gbv:830-88214415
eng
1
d7f3e090e8156631d5ed143d6bd6e5ad
https://tore.tuhh.de/bitstreams/9a7034cd-46ad-479a-9d6c-2370915b8216/download
http://tubdok.tub.tuhh.de/handle/11420/1305
10.15480/882.1302
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/452462024-01-23T14:21:37Zcom_11420_1col_11420_2
Entwicklung eines chemischen Schnelltestverfahrens mit Gesteinsmehl zur Detektion alkalireaktiver Gesteinskörnung
Gyde
Hartmut
Frank
Schmidt-Döhl
A.
Püstow
Die Alkalikieselsäure Reaktion (AKR) führt zu schweren bis irreparablen Schäden in Bauwerken und kann nur durch präventives Testen der Gesteinskörnung vermieden werden, allerdings haben die angewandten Testverfahren noch Potential zur Optimierung, welches auf schnellere und präzisere Verfahren hoffen lässt. Am Institut für Baustoffe, Bauphysik und Bauchemie der Technischen Universität Hamburg wird ein neues Testverfahren entwickelt, welches den chemischen Testverfahren ähnelt. Anders als bei den üblichen chemischen Verfahren wird die Reaktivität der Gesteinskörnung nicht von dem Masseverlust oder Konzentration einzelner Komponenten bestimmt. In diesem Ansatz wird die Reaktivität der Gesteinskörnung aus der Veränderung chemischer Parameter, die infolge der Lösung von Gesteinsmehl in hochkonzentrierter heißer Lauge hervorgerufen werden, abgeleitet. Während des Versuchs werden der pH-Wert, das Redoxpotential und die elektrische Leitfähigkeit aufgezeichnet. Die Zeitverläufe dieser Parameter haben mathematisch quantifizierbare Eigenschaften, wie Geschwindigkeitskonstanten, stationäre Zustände oder Extrempunkte anhand derer die Reaktivität der Gesteinskörnung gefolgert werden soll. Dies basiert auf der Annahme, dass sich das Lösungsverhalten verschieden reaktiver Materialien unterscheidet. Die bisherigen Ergebnisse zeigen sich wiederholende Ergebnisse und eine Differenzierbarkeit der quantifizierbaren Punkte bezüglich der jeweiligen Proben.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023
ConferencePaper
Text
publishedVersion
10.15480/882.9116
21. ibausil - Internationale Baustofftagung (2023)
ger
1
62afafd40771626f3b4c90c839b491fd
https://tore.tuhh.de/bitstreams/3b11399d-7f94-4e5f-9923-abe3aed411b4/download
https://hdl.handle.net/11420/45246
10.15480/882.9116
https://creativecommons.org/licenses/by-nc/4.0/
oai:tore.tuhh.de:11420/17152018-07-19T09:20:08Zcom_11420_1col_11420_2
Einbindung von Brennstoffzellenanlagen in schiffstechnische Systeme
Christoph
Gentner
Brennstoffzelle
HT-PEM
Energieversorgung auf Schiffen
Methanol
Schiffsentwurf
620
Die Hochtemperatur-Polymerelektrolytmembran-Brennstoffzellentechnik (HT-PEM) wird hinsichtlich ihrer Eignung zur elektrischen Energieversorgung schiffstechnischer Systeme untersucht. Dazu wird das dynamische und stationäre Verhalten einer Pilot-Brennstoffzellenanlage analysiert. Zur Modellkalibrierung werden Experimente an einem Methanolreformer, der Synthesegas für den Zellstapel liefert, durchgeführt. Ein thermodynamisches Modell des Brennstoffzellensystems (Verdampfer, Methanolreformer, Zellstapel) mit Automation wird erstellt und wesentliche Betriebsparameter werden darüber ermittelt. Ergebnisse für eine Dieselgenerator- und eine HT-PEM-Energieversorgung werden verglichen.
The high temperature polymer electrolyte (HT-PEM) fuel cell technology is investigated with regard to its suitability for the electrical energy supply of marine systems. For this purpose, the dynamic and stationary behavior of a pilot fuel cell system is analyzed. For model calibration, experiments are carried out on a methanol reformer, which supplies synthesis gas for the HT-PEM fuel cell stack. A thermodynamic model of the fuel cell system (evaporator, methanol reformer, cell stack) with automation is created and operational parameters are simulated. Results between a diesel generator and an HT-PEM power supply are compared.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-07-03
2018
Other
Text
publishedVersion
urn:nbn:de:gbv:830-88221802
ger
1
b10127834465bcde14f572da0611c872
https://tore.tuhh.de/bitstreams/2113cbc8-6907-47f8-b529-7d4a4abd49c2/download
http://tubdok.tub.tuhh.de/handle/11420/1715
10.15480/882.1712
https://creativecommons.org/licenses/by-nc-nd/3.0/de/
oai:tore.tuhh.de:11420/16932018-06-20T06:08:39Zcom_11420_1col_11420_2
Interface elasticity effects in polymer-filled nanoporous metals
Jana
Wilmers
Andrew
McBride
Swantje
Bargmann
composite
nanoporous
multiphysics
interface
micromechanics
620
A continuum formulation for electroactive composites made from nanoporous gold and ionconducting polymer is proposed. A novel extension of surface elasticity theory is developed to account for the high surface-to-volume ratio of nanoporous gold, and to capture the
chemoelectromechanical coupling that occurs on the interface between the metal and the polymer. This continuum formulation accounts for the fully non-linear behaviour exhibited by the composite.
The balance of linear momentum, Gauß's flux theorem and a relation for the transport of charge carriers are introduced in the bulk material as well as on the interface to describe the nonlinear multiphysics and highly coupled response of the actuator. The resulting system of nonlinear equations is solved using the finite element method. A series of numerical examples is presented to elucidate the theory.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2016-11-22
Article
Text
publishedVersion
urn:nbn:de:gbv:830-88221477
Journal of the Mechanics and Physics of Solids (99): 163-177 (2017)
eng
1
5b62a015c8ba761461f186a8a8574396
https://tore.tuhh.de/bitstreams/bc015495-9314-4a73-8473-56e941611d2f/download
http://tubdok.tub.tuhh.de/handle/11420/1693
10.15480/882.1690
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/12822016-02-11T07:13:17Zcom_11420_1col_11420_2
USB devices phoning home
Roland
Schilling
Frieder
Steinmetz
USB
rogue chanel
device behavior vs. user intent
600
USB is a versatile standard defining various features to allow maximum flexibility for evices. This flexibility, by design, leads to complex device configurations, combining multiple functions into one, making it impossible for users to identify the function of a device by its looks. This can be exploited by crafting programmable USB devices, looking and behaving like an ordinary flash drive that also expose virtual network devices and other functionality to their host OS. This paper outlines such a device, exploiting several USB features to establish a rogue HTTP channel used to leak data stored on the device’s disk to an internet back end. We describe the device itself and its architecture and our conclusions and methods for dealing with the issues presented in a user–friendly way.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2016-02-09
WorkingPaper
Text
publishedVersion
urn:nbn:de:gbv:830-88213917
23. DFN-Konferenz "Sicherheit in vernetzten Systemen"
eng
1
0cebc645a8197fbe5df9c0f4c6715bfd
https://tore.tuhh.de/bitstreams/c8e23b88-214b-4006-9597-1795e1c8cc55/download
http://tubdok.tub.tuhh.de/handle/11420/1282
10.15480/882.1279
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/80652020-11-30T10:14:14Zcom_11420_1col_11420_2
Correlating surface cation composition and thin film microstructure with the electrochemical performance of lanthanum strontium cobaltite (LSC) electrodes
Ghislain M.
Rupp
Andreas
Limbeck
Markus
Kubicek
Alexander
Penn
Michael
Stöger-Pollach
Gernot
Friedbacher
Jürgen
Fleig
La0.6Sr0.4CoO3-δ thin films of varying thicknesses (20-170 nm) were prepared by pulsed laser deposition on yttria-stabilized zirconia (100) substrates, and their electrochemical electrode performance was correlated with the chemical surface composition and microstructure (e.g. porosity, surface area). The surface cation composition was analyzed by an atomic etching procedure with on-line inductively coupled plasma optical emission spectrometry detection. The surface sensitivity of the method was increased by dynamically switching the etching reagent during the on-line analysis and quantitative results for even the top atomic layer were obtained. A water-soluble Sr-rich surface species could be quantified on top of the LSC films and in combination with electrochemical analysis of the films by impedance spectroscopy an improved understanding of the surface exchange resistance could be obtained. Microstructural features such as the effective porosity of the films became accessible by a combination of these methods.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2014-02-26
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0114953
Journal of Materials Chemistry A 2 (19): 7099-7108 (2014-05-21)
eng
1
3cab973f3ff49a0019f0ac7bac8df33c
https://tore.tuhh.de/bitstreams/6b064cb9-a500-4c30-ab20-ef2cad7d99b0/download
http://hdl.handle.net/11420/8065
10.15480/882.3517
https://creativecommons.org/licenses/by/3.0/
oai:tore.tuhh.de:11420/9592011-02-07T13:24:38Zcom_11420_1col_11420_2
Über eine Belüftungstheorie in der Nähe der freien Wasseroberfläche
In-Haeng
Song
620
Über eine Belüftungstheorie in der Nähe der freien Wasseroberfläche
In dieser Arbeit handelt es sich um eine Analyse des Belüftungsverlaufs auf dem Tragflügel, wie z.B. des Belüftungsbeginns und der Belüftungserscheinungen hinsichtlich der Dicke und Länge. Es ist ein Unterdruckfeld im Spitzenwirbel nötig zur Luftansaugung. In dieser Arbeit wird eine Bedingung für den Belüftungsbeginn unter Berücksichtigung der Wasseroberflä.chenbedingung eingeführt, dabei wird ein Ansatz des Kernradius des Spitzenwirbels bei turbulenter Strömung angewendet. Die Belüftungsschicht wird in 2-dimensionaler Betrachtungsweise mit der auf dem Singularitätenverfahren basierenden linearisierten Profiltheorie analysiert unter Berücksichtigung der linearisierten Wasseroberflächenbedingung. Die Singularitäten lassen sich durch Iterationsverfahren bestimmen. Für die Belüftung ist eine offene Modellschicht ohne Zusammenfallstrecke geeignet. Die Dicke der Belüftung unterliegt keiner Schließungsbedingung. Bei der nicht an der Profilvorderkante beginnenden Belüftung wird eine Lösungsmethode angegeben, bei der die zusätzliche Quellenbelegung in zwei Bereiche aufgeteilt wird und unter Berücksichtigung der gegenseitigen Wechselwirkung die Quellenbelegungen bestimmt werden. Die Belüftungsausdehnung wird durch die freie Wasseroberfläche trotz hoher Froudezahlen in hohem Maße beeinflußt.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1992
Report
Text
publishedVersion
urn:nbn:de:101:1-201505272884
ger
1
de43f91fd0abc774e35d9159231f01ed
https://tore.tuhh.de/bitstreams/055c4f54-bcf0-4c4f-bcde-64eabb737b61/download
http://tubdok.tub.tuhh.de/handle/11420/959
10.15480/882.957
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/19312018-12-14T05:58:39Zcom_11420_1col_11420_2
Crystal plasticity modeling of fully lamellar titanium aluminide alloys
Jan Eike
Schnabel
titanium aluminides
crystal plasticity
micromechanics
600
In der vorliegenden Arbeit wird ein thermomechanisch gekoppeltes, defektdichtebasiertes
Kristallplastizitätsmodell vorgestellt. Dieses Modell berücksichtigt die Entwicklung von Versetzungsdichten und Zwillingsvolumenfraktionen auf verschiedenen Gleit- und Zwillingssystemen in Folge von plastischer Verformung und Erholungsvorgängen. Die Berücksichtigung von Versetzungsdichten und Zwillingsvolumenfraktionen erlaubt eine physikalisch motivierte Modellierung des Verfestigungsverhaltens und ermöglicht eine physikalisch sinnvolle Darstellung der Dissipation und der in Form von Defekten im Kristallgitter gespeicherten Energie im Rahmen der hier angewandten thermomechanischen Modellierung. Im Rahmen dieser Arbeit wurde das vorgestellte Kristallplastizitätsmodell angewendet um verschiedene Aspekte des plastischen Verformungsverhaltens lamellarer Titanaluminidlegierungen zu untersuchen.
Nach der Kalibrierung des Verfestigungsmodells gegen experimentelle Ergebnisse
wurde dieses erfolgreich angewendet um charakteristische Merkmale der makroskopischen Spannungs-Dehnungsantwort lamellarer Titanaluminide mit den Verfestigungsinteraktionen auf der Mikroskala in Beziehung zu setzen. Durch die Kombination numerischer Studien und experimenteller Ergebnisse aus der Literatur war es außerdem möglich den relativen Beitrag der verschiedenen koexistierenden mikrostrukturellen Grenzflächen zur makroskopischen Fließspannung zu identifizieren und folglich zu modellieren. Mit dieser mikrostruktursensitiven Modellformulierung wurde der Einfluss der mikrostrukturellen Parameter auf die inhomogene Mikroplastizität von lamellaren Titanaluminiden untersucht. Aufgrund der defektdichtebasierten Formulierung ermöglichte das Modell die Untersuchung von Trends im statischen Erholungsverhalten. Schließlich wurde das Modell um die Temperaturanomalie des Fließpunkts lamellar Titanaluminidlegierungen erweitert.
In the present thesis, a thermomechanically coupled, defect density based crystal plasticity
model is presented. This model accounts for the evolution of dislocation densities and twinned volume fractions on different slip and twinning systems during plastic deformation and thermal recovery. Considering the evolution of dislocation densities and twinned volume fractions allows a physics based formulation of the work hardening model and enables a physically meaningful representation of dissipation and stored energy of cold work in the applied thermomechanical framework. In the course of this thesis, the presented crystal plasticity model was applied to investigate several aspects of the plastic deformation behavior of fully lamellar titanium aluminide alloys. After calibrating the work hardening model to fit experimental results, it was successfully used to relate specifics of the macroscopic stress-strain response of fully lamellar titanium aluminides to the work hardening interactions on the microscale. By combining numerical studies and experimental findings from literature, it was further possible to identify and consequently model the relative contribution of the different coexisting microstructural
interfaces to the macroscopic yield strength. With this microstructure sensitive
model formulation, the influence of the microstructural parameters on the inhomogeneous
microplasticity of fully lamellar titanium aluminides was studied. Due to its defect density
based formulation, the model enabled trends in the static recovery behavior to be investigated. Finally, the model was extended in order to account for the anomalous dependence of the yield strength of fully lamellar titanium aluminides on temperature.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-06-25
2018
Other
Text
publishedVersion
urn:nbn:de:gbv:830-882.024671
eng
1
59861e64b8092e6b14d8a8fb366fe1df
https://tore.tuhh.de/bitstreams/ed58e4ce-fc75-4ae0-8e70-9d0a401fe3c5/download
http://tubdok.tub.tuhh.de/handle/11420/1931
10.15480/882.1928
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/16032018-03-23T12:46:44Zcom_11420_1col_11420_2
Computation of springing transfer functions
Heinrich
Söding
springing
hull vibration
seaway
transfer function
Rankine source method
620
Ship vibrations excited continually by regular waves are predicted by a potential method. It takes into account the interaction of the oscillatory flow with the steady flow due to the ship's forward speed, including steady ship waves and squat, but it excludes non-linear oscillatory wave forces. A three-dimensional Rankine source patch method is used both for the steady and the oscillatory flow. Vibration damping by an immersed transom, wave radiation, bilge keels, propeller, and hatch cover friction are approximated. Application to a large containership demonstrates that, in this example, damping is mostly attributable to the transom.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2009-09-01
Article
Text
publishedVersion
urn:nbn:de:gbv:830-88220060
Proceedings of the Institution of Mechanical Engineers, Part M: Journal of Engineering for the Maritime Environment 3 (223): 291-304 (2009)
eng
1
795fd3ee779b4bf5ba4926f7da4418a2
https://tore.tuhh.de/bitstreams/275d4c30-0ac7-4fc7-9b74-3fc97647db99/download
http://tubdok.tub.tuhh.de/handle/11420/1603
10.15480/882.1600
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/8262010-07-26T13:00:52Zcom_11420_1col_11420_2
Augen-Blicke : technische Entwicklungen in der Photographie
At a glance : technical developments in photography
Thomas
Hapke
photographie
camera
history
770
Katalog einer Ausstellung mit dem Titel "Augen-Blicke : technische Entwicklungen in der Photographie" vom 31.10.1994 bis 16.12.1994 in der Universitätsbibliothek der Technischen Universität Hamburg-Harburg.
Catalog of an exhibition entitled "Augen-Blicke : technische Entwicklungen in der Photographie" from 31.10.1994 to 16.12.1994 at the University Library of Hamburg University of Technology.
In addition to a brief overview of the history of photography, the exhibition offers exemplary highlights from the history of photographic technology on the basis of book collections of the University Library. Cameras from the end of the last century up to our time are exhibited. Small focal points are the so-called box cameras, two-lens reflex cameras and the development of the 35 mm reflex camera. The exhibition is rounded off by the topics of underwater photography, an area that places additional technical demands on the technology, as well as a look at the development of hobby photography and the digital photography of our days.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2010
Other
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-9111
Augen-Blicke : technische Entwicklungen in der Photographie ; Ausstellung vom 31.10.1994 bis 16.12.1994 in der Universitätsbibliothek der Technischen Universität Hamburg-Harburg / Thomas Hapke. - Hamburg : Technische Universität Hamburg-Harburg, 1994
ger
1
df78150b8f880303484f4ce4a9db9dd5
https://tore.tuhh.de/bitstreams/2647b6da-b8d6-4132-8738-1e226f1923b8/download
https://hdl.handle.net/11420/826
10.15480/882.824
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/153862023-06-09T04:10:07Zcom_11420_1col_11420_2
Experimental study on the effect of extreme waves on a LNG carrier
Marco
Klein
Shan
Wang
Günther F.
Clauss
C. Guedes
Soares
Breather solutions
Draupner wave
Extreme wave events
Wave-structure interaction
This paper presents a comprehensive experimental study on the effect of extreme waves on a LNG carrier. The LNG carrier model was equipped with a variety of sensors to measure motions, green water height on deck as well as local and global loads. Experiments in transient wave packets provided the general performance in waves in terms of response amplitude operators and were accompanied by tests in regular waves with two different wave steepness. These tests allowed detailed insights into the nonlinear behavior of the vertical wave bending moment in steep waves showing that green water on deck can contribute to a decrease of vertical wave bending moment. Afterwards, systematic model tests in irregular waves were performed to provide the basis for statistical analysis. It is shown that the generalized extreme value distribution model is suitable for the estimation of the extreme peak values of motions and loads. Finally, model tests in tailored extreme wave sequences were conducted comparing the results with the statistical analysis. For this purpose, analytical breather solutions of the nonlinear Schrödinger equation were applied to generate tailored extreme waves of certain critical wave lengths in terms of ship response. Besides these design extreme waves, the LGN carrier was also investigated in the model scale reproduction of the real-world Draupner wave. By comparing the motions, vertical wave bending moment, green water column and slamming pressures it is concluded that the breather solutions are a powerful and efficient tool for the generation of design extreme waves of certain critical wave lengths for wave/structure investigations on different subjects.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-04-15
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0221490
Journal of Marine Science and Application 22 (1): 52-74 (2023-04-15)
eng
1
7a3d70d7975a1b24e7a84014d3b45ca5
https://tore.tuhh.de/bitstreams/834f883e-adb3-486b-9c45-0e2891e44149/download
http://hdl.handle.net/11420/15386
10.15480/882.5171
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/812006-01-18T08:40:22Zcom_11420_1col_11420_2
Neue Wege in Technik und Naturwissenschaften– Zum Berufswahlverhalten von Mädchen und jungen Frauen
Martina
Schuster
Almut
Sülzle
Gabriele
Winker
Andrea
Wolffram
geschlechtstypisches Berufswahlverhalten
Berufsorientierung
300
Womit kann geschlechtstypisches Berufs- und Studienwahlverhalten erklärt werden und wie kann das Berufswahlspektrum von jungen Frauen erweitert werden? Um auf diese Fragen eine Antwort zu geben, hat das Wirtschaftsministerium Baden-Württemberg auf Empfehlung des Landesausschusses für Berufsbildung das Gutachten „Neue Wege in Technik und Naturwissenschaften – Zum Berufswahlverhalten von Mädchen und jungen Frauen“ in Auftrag gegeben. Die Ergebnisse zeigen eindrucksvoll, wie stark das Berufswahlverhalten junger Frauen bis zum heutigen Tag durch ihre Geschlechterrolle geprägt ist und welche Faktoren die typisch weibliche Berufsentscheidung beeinflussen. Schließlich werden auf Grundlage der Ergebnisse konkrete Empfehlungen für künftige Modellversuche gegeben.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2004
WorkingPaper
Text
publishedVersion
urn:nbn:de:gbv:830-opus-1375
ger
1
726f29624d0dee5141c82e4b35b9f6fd
https://tore.tuhh.de/bitstreams/272f8fd7-8d05-49f4-ad74-01e3f35307f5/download
http://tubdok.tub.tuhh.de/handle/11420/81
10.15480/882.79
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/146112023-01-23T12:58:19Zcom_11420_1col_11420_2
Densification of nanoporous metals during nanoindentation: The role of structural and mechanical properties
Norbert
Huber
Ilona
Ryl
Theodore Yao-tsu
Wu
Murilo P.
Hablitzel
Birthe
Zandersons
Claudia
Richert
Erica
Lilleodden
Densification
Finite element simulation
Image processing
Nanoindentation
Nanoporous metal
The analysis of the densification behavior of nanoporous metals in nanoindentation is challenging in simulations and experiments. A deeper understanding of the densification behavior provides valuable information about the different deformation mechanisms in nanoindentation and compression experiments. The developed two-scale model allows for predicting the densification field for variable microstructure and elastic–plastic behavior. It could be shown that the penetration depth of the densification field is mainly controlled by the ratio of the macroscopic work hardening rate to yield stress. The shape as well as the value at characteristic isolines of densification depend mainly on the macroscopic plastic response of the nanoporous material. This could be confirmed by nanoindentation experiments, where the densification under the indenter was measured for ligament sizes from 35 to 150 nm. Although the depth of the densification field was underpredicted by the simulations, the experiments confirmed the predicted trends. Graphical abstract: [Figure not available: see fulltext.]
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0209124
Journal of Materials Research 38: 853-866 (2023)
eng
1
2e024e514af8a1d61f416e9f54769dd2
https://tore.tuhh.de/bitstreams/8e35b2ae-1d77-47ea-b7a3-8eb2830ee753/download
http://hdl.handle.net/11420/14611
10.15480/882.4969
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/11302013-08-23T07:46:55Zcom_11420_1col_11420_2
Die Bewertung und numerische Optimierung von Wärmeübertragern anhand einer Energieentwertungszahl
Assessment and numerical optimization of heat exchangers based on an energy devaluation number
Tammo
Wenterodt
Entropieproduktion
Numerische Strömungssimulation
Wärmeübertragung
Energieeffizienz
entropy generation
530
Es werden das Konzept des entropischen Potenzials und die Energieentwertungszahl entwickelt. Ihre Vorteile gegenüber anderen Bewertungskriterien für Wärmeübertrager werden demonstriert. Dazu wird ein neues Verfahren für die automatisierte Geometrieoptimierung von Wärmeübertragern durch CFD-Rechnungen vorgestellt. Dieses basiert auf der Beschreibung von Oberflächen durch Fourierkoeffizienten und deren Optimierung durch einen evolutionären Algorithmus.
The entropic potential concept as well as the energy devaluation number is developed. Their advantage over common evaluation criteria for heat exchangers is demonstrated. For that purpose, a new method for the automated geometry optimization of heat exchangers based on CFD calculations is presented. It is based on the description of surfaces by Fourier coefficients and their optimization by an evolutionary algorithm.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2013-08-14
2013
Other
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-12251
ger
1
0ad845ba808b87a906cf099449608499
https://tore.tuhh.de/bitstreams/cfce4fc7-8274-4758-9d28-d0cb9b8de66d/download
http://tubdok.tub.tuhh.de/handle/11420/1130
10.15480/882.1128
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/436742023-10-11T06:08:31Zcom_11420_1col_11420_2
Aviation fuel production pathways from lignocellulosic biomass via alcohol intermediates : a technical analysis
Steffen
Voß
Stefan
Bube
Martin
Kaltschmitt
Biofuel
Sustainable aviation fuel
Process modelling
Technical comparison
Energy efficiency
In order to achieve the goal of limiting global warming to 1.5 °C, also the growing aviation industry needs to take measures to reduce their greenhouse gas emissions. Various renewably sourced aviation fuels can significantly reduce greenhouse gas emissions and most of them, except for example liquid hydrogen or LNG, can be used in the existing infrastructure without airport or aircraft modifications. As most of these renewably sourced fuel types are not (yet) produced at commercial scale, many technological assessment parameter (e.g. carbon or energy efficiency) are uncertain. Thus, the goal of this study is to compare two different process routes, both being based on biochemical and thermochemical conversion steps. The processes evaluated against conversion efficiency of the available raw feedstock and process energy requirements. The evaluation uses theoretical and biochemical carbon efficiency as well as energy efficiency as indicators. A steady-state flowsheet simulation for two biogenic process paths via biogas and bioethanol as intermediate products is carried out on the basis of literature data. In addition, the optional use of solid residue from the biotechnological process step by combustion for direct heat supply cases are studied. In the ethanol-based route, about 23% of the carbon in the feed can be recovered as kerosene, whereas this is only about 19% in the biogas route. Simultaneously, the ethanolbased route without the combustion of the residue has an energy efficiency of 28%, while the biogas route has an efficiency of 24%.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-09-03
Article
Text
publishedVersion
10.15480/882.8711
Fuel communications 17: 100093 (2023)
eng
1
d76b535f87cb2dbab036de22a1545181
https://tore.tuhh.de/bitstreams/39468898-b3f5-484c-b282-8349a4571467/download
https://hdl.handle.net/11420/43674
10.15480/882.8711
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/119702022-03-10T13:09:58Zcom_11420_1col_11420_2
Simulation of granular materials with the discrete element method to investigate their suitability as crash-absorber in ship collisions
Sonja
Kraus
Christian
Woitzik
Maksym
Dosta
Alexander
Düster
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021-12
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0175920
Proceedings in Applied Mathematics and Mechanics 21 (1): e202100036 (2021-12)
eng
1
c0f6518a6ca003d3171f6b3750e7fde0
https://tore.tuhh.de/bitstreams/05513e2a-13e4-4e38-acd0-0ded0afb9eeb/download
http://hdl.handle.net/11420/11970
10.15480/882.4744
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/451622024-01-19T08:35:21Zcom_11420_1col_11420_2
Impact of soil texture and heterogeneity on complex interactions between surface soil salinity and saltwater intrusion in coastal regions
Vahid
Sobhi Gollo
Eva
González
Jörg
Elbracht
Peter
Fröhle
Nima
Shokri
Soil salinization, referring to the excessive accumulation of soluble salts in soil to a degree that adversely influences vegetation and environmental health, is an unfolding challenge threatening soil health, vegetation and consequently food security with serious socio-economics implications (Hassani et al., 2020, 2021). High salinities in the root zone reduce water and nutrient uptake and result in soil infertility, freshwater contamination at the surface and the loss of biodiversity.Here, we concentrate on soil salinization in coastal areas due to saltwater intrusion and the groundwater salinization, partly influenced by climate change. In low-lying coastal regions where, saline groundwater levels are shallow, saltwater intrusion poses risks to vegetation and soil health since the soluble salt could be transported toward the surface. This causes soil salinization depending on the competition between upward capillary forces and the limiting downward gravity and viscous forces. Several parameters influence such a competition including soil texture and heterogeneity. We developed a quantitative framework, using software package FEFLOW, to delineate the regional impact of soil textures and arrangements on salt transport toward the surface in low-lying coastal regions. The model includes a wide range of hydrologic, soil and climate related factors such as hydraulic heads, soil properties, and groundwater recharge. We evaluated the performance of the developed model using field data measured in the "Alte Land" located in north Germany near the Elbe estuary - an agriculturally significant low-lying region threatened by increasing soil surface salinity.The evaluation of the model against field-data was followed by conducting the simulation under several hypothetical scenarios differing in soil textures, layering and arrangements to investigate how these parameters would influence soil surface salinity driven by the saltwater intrusion in coastal areas. Our results highlight the prominent effects of different soil textures and arrangements on the regional surface soil salinity and the amount of salt deposited close to the surface. This agrees with the conclusions of laboratory experiments which were conducted in other studies at scales much smaller than the one investigated in our analysis (Shokri-Kuehni et al., 2020). Our results suggest that an effective soil remediation strategy for salinity treatment would require high resolution 3D mapping of soil properties which influences soil salinization. Our findings shed new light on the dominant parameters influencing surface soil salinity in coastal areas threatened by the saltwater intrusion as a result of the projected climate changes.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-05-15
ConferencePaper
Text
publishedVersion
10.15480/882.9072
EGU General Assembly (2023)
eng
1
a0fe9c5250141b4c6bb30e174fa5fc49
https://tore.tuhh.de/bitstreams/4d96dc0d-34dd-4656-b738-1281d4381437/download
https://hdl.handle.net/11420/45162
10.15480/882.9072
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/144492023-01-02T10:29:36Zcom_11420_1col_11420_2
Functionalization of carbon electrodes with nanotitania by atomic layer deposition
Graciano B. de
Souza
Dachamir
Hotza
Rolf
Janßen
Kaline
Pagnan Furlan
Carlos R.
Rambo
Carbon fibers are materials with a very high surface area and are interesting for applications such as filters, fire-resistant heat insulation, photocatalysis, and capacitor electrodes. Moreover, thermal burnout can easily remove these fibers, making them ideal templates for high-precision coatings or keeping them within the coated structure, generating nanostructured composites. In this work, two different substrates, carbon felt and bacterial nanocellulose were coated by TiO2 with atomic layer deposition (ALD). After deposition, the templates were pyrolyzed or further removed by burnout in the air. The microstructure evolution of the 3D interlocked-fibers structures was characterized by scanning electron microscopy and nitrogen adsorption surface area after each step. Stable anatase was present as a single TiO2 phase even after heat treatment at 800°C. Moreover, electrochemical impedance spectroscopy and constant current charge-discharge were employed to investigate the electrochemical properties of the samples. Our results show that all samples display a uniform layer after ALD and that the surface area decreases with an increasing number of ALD cycles. After burnout, the 3D structures presented a straw-like appearance to the shells. Nonetheless, both samples presented a power density comparable to a porous NiO/C, with the pyrolyzed bacterial nanocellulose sample displaying a higher pseudocapacitance performance than the carbon-felt samples.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-10-12
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0206919
Advances in Materials Science and Engineering: 9575845 (2022-01)
eng
1
3dae0fc62758738e010024d7c97fec97
https://tore.tuhh.de/bitstreams/517c08fb-bf93-4cf5-a9ee-d450066b369c/download
http://hdl.handle.net/11420/14449
10.15480/882.4809
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/59942020-04-30T05:46:22Zcom_11420_1col_11420_2
A Collaborative approach for an integrated modeling of urban air transportation systems
Malte
Niklaß
Niclas
Dzikus
Majed
Swaid
Jan
Berling
Benjamin
Lührs
Alexander
Lau
Ivan
Terekhov
Volker
Gollnick
urban air mobility
collaborative design
system of systems
demand modeling
vertiport modeling
route optimization
flight scheduling
trajectory simulation
conflict detection
cost and revenue modeling
The current push in automation, communication, and electrical energy storage technologies has the potential to lift urban mobility into the sky. As several urban air mobility (UAM) concepts are conceivable, all relevant physical effects as well as mutual interrelations of the UAM system have to be addressed and evaluated at a sufficient level of fidelity before implementation. Therefore, a collaborative system of systems modeling approach for UAM is presented. To quickly identify physical effects and cross-disciplinary influences of UAM, a pool of low-fidelity physical analysis components is developed and integrated into the Remote Component Environment (RCE) workflow engine. This includes, i. a., the disciplines of demand forecast, trajectory, vertiport, and cost modeling as well as air traffic flow and capacity management. The definition and clarification of technical interfaces require intensive cooperation between specialists with different areas of expertise. To reduce this communication effort, the Common Parametric Aircraft Configuration Schema (CPACS) is adapted and used as central data exchange format. The UAM system module is initially applied for a 24-hour simulation of three generic networks in Hamburg City. After understanding the basic system-level behavior, higher level analysis components and feedback loops must be integrated in the UAM system module for evaluation and optimization of explicit operating concepts.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-04-28
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.089251
Aerospace 7 (5): 50 (2020)
eng
1
65552644fca4f8d54fcc3486354e97d8
https://tore.tuhh.de/bitstreams/9ef22b46-60b1-4957-8148-fca73cfaf8bc/download
http://hdl.handle.net/11420/5994
10.15480/882.2752
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/8392010-08-25T07:37:34Zcom_11420_1col_11420_2
Messung und Berechnung von Schweißeigenspannungen an einer schiffbaulichen Konstruktion
Ernst-Detlev
Egge
620
Messung und Berechnung von Schweißeigenspannungen an einer schiffbaulichen Konstruktion
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1981
Report
Text
publishedVersion
urn:nbn:de:101:1-201505261824
ger
1
ca6c8e53b48f604a1ace5da91d6f3dc2
https://tore.tuhh.de/bitstreams/b7b6d9db-c307-4e95-8843-5db6d90c19f6/download
http://tubdok.tub.tuhh.de/handle/11420/839
10.15480/882.837
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/1252006-02-10T14:12:23Zcom_11420_1col_11420_2
Komplexitätsmanagement durch systemische Selbstskalierung
Kai
Paetow
Marco
Schmitt
300
004
Skalierbarkeit und Skalierung von Mulitagentensystemen sind in der Informatik
Probleme von entscheidender Bedeutung. Die bisherige Debatte ist vor allem durch
die Unbestimmtheit dieser beiden zentralen Begriffe erschwert. Daher wird in dieser Arbeit der Versuch unternommen, Skalierung aus soziologischer Sicht begrifflichkategorial klar zu definieren und theoretisch stärker zu reflektieren. Die hier geleistete begriffliche und konzeptionelle Arbeit orientiert sich an Niklas Luhmanns Theorie sozialer Systeme, der allgemeinen Komplexitätswissenschaft sowie an Ansätzen aus der Organisations- und Managementforschung. Skalierung wird als Operationalisierung von Komplexität verstanden. Durch die differenztheoretische Entfaltung des Skalierungsbegriffs wird ein heuristisches Instrumentarium gewonnen, das die Bezugspunkte des systemischen Komplexitätsmanagements deutlich benennt. Die hierbei eingenommene Perspektive auf MAS wird letztlich auf ein evolutionstheoretisches Fundament gestellt. Abschließend werden die Ergebnisse der Theoriearbeit in Form einiger Vorschläge zur Reorientierung der Skalierungsdebatte präsentiert.
In computer science, scalability and actual scaling processes of multiagent systems are problems of much concern. So far, the debate has been inhibited by the indeterminacy of both of these central terms. From a sociological point of view, it is tried to define the notions of scalability and scaling process more clearly and to reflect them in a profound theoretical context. The terminological and conceptual framework, developed here, is guided by Niklas Luhmann’s theory of social systems, general complexity science, and some approaches from organization and management research. Scaling processes are understood as operationalizations of complexity. By decomposing the term “scaling” difference-theoretically, a heuristic tool is achieved that clearly
denotes the points of reference of complexity management. The perspective on MAS
is built on an evolution-theoretical fundament. Finally, the results of this theoretically oriented paper are presented as proposals for a re-framing of the debate on scalability.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2003-02
WorkingPaper
Text
publishedVersion
urn:nbn:de:gbv:830-opus-1822
ger
1
745fb9172404bee22149b8976622aec9
https://tore.tuhh.de/bitstreams/cda728fa-9c22-4a27-ba15-64f6e1e39f8e/download
http://tubdok.tub.tuhh.de/handle/11420/125
10.15480/882.123
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/4562008-11-07T08:00:58Zcom_11420_1col_11420_2
Effects of redox processes on acid-producing potential and metal mobility in sediments
Jihua
Hong
Ulrich
Förstner
Wolfgang
Calmano
550
Redox processes can significantly affect the acid-producing potential and metal bioavailability in sediments. Many oxidation reactions producing acid can occur in natural aquatic sediment systems and human-affected environments. S, Fe, and N are the most important elements involved in redox processes of sediment/water systems. The actual extent of acidification in a sediment/water system depends not only on APP, but also on the acid neutralizing capacity (ANC) of the system.
Periodic redox processes leading to "ferrolysis", "split" of sulfate, and the volatilization of H2S can cause changes in APP, and then affect metal transformation and bioavailability. The effects of redox and pH variations on the mobility of metals has been successfully assessed by pore water chemistry, which reflects the interactions of metals in aqueous and solid systems under changing redox environments with depth of sediments. Redox reactions, especially reoxidation of anoxic sediments, can lead to metal release from contaminated sediments. The bioavailability of metals in sediments depends on metal species, especially metal sulfide species.
A lack of understanding of the kinetic processes controlling acid production and about the accurate determination of ANC quantitatively limits our ability to predict apparent APP. Heavy sulfide (AVS) may control the toxicity of heavy metals in anoxic sediments, under changing redox conditions AVS is oxidized and dissolved metal sulfates are released. Furthermore, the acidity which follows sulfide oxidation may accelerate metal release. Thus, assessment of the relationship between metal sulfides and their bioavailability in periodic redox environments needs much more research.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1994
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-5295
Jerry L. Hamelink ... (eds.) Bioavailability : physical, chemical, and biological interactions ; proceedings of the 13. Pellston Workshop, Pellston, Mich., August 1992, Boca Raton, Fla., 1994, pp. 119-41
eng
1
339e95fda1a870ef980debee263ef88b
https://tore.tuhh.de/bitstreams/63773baa-d1a5-4bc3-a833-7e04d14ebaad/download
http://tubdok.tub.tuhh.de/handle/11420/456
10.15480/882.454
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/121832022-04-06T04:10:37Zcom_11420_1col_11420_2
Damage tolerance of high-performance composites
Johann
Körbelin
Damage Tolerance
Thin-Ply
Graphene
Low-Velocity Impact
Hochleistungsfaservebundwerkstoffe sind Strukturwerkstoffe, die eine geringe Dichte mit hoher Steifigkeit und Festigkeit kombinieren. Hohe Sicherheits- und Zuverlässigkeitsanforderungen an Strukturbauteile erfordern die Berücksichtigung und eine detaillierte Kenntnis der Schadenstoleranz von Materialien und Strukturen. Der multiskalige Aufbau von Verbundwerkstoffen führt zum Auftreten verschiedener Versagensarten und einem komplexen Versagensverhalten, bei dem das Matrixversagen auf der Mikroebene den Versagensprozess auf allen höheren Betrachtungsebenen beeinflusst. Folglich hat die auftretende Matrixschädigung einen entscheidenden Einfluss auf die Schadenstoleranz. Die Forschungshypothese dieser Arbeit lautet:
Das Verständnis und die Anpassung des Schädigungsverhaltens der Matrix ist grundlegend für die Verbesserung der Schadenstoleranz von Hochleistungsfaservebundwerkstoffen.
Um das Schädigungsverhalten der Matrix anzupassen, wurden kohlenstofffaserverstärkte Kunststoffe (CFK) mit einer mit Few-Layer Graphene (FLG) modifizierten Matrix mit Schichtdicken von Ultra-Thin-Ply (28 μm / 30 g/m2) bis Thick-Ply (220 μm / 240 g/m2) untersucht. Die FLG-Modifikation führt zu zusätzlichen Schädigungsmodi in der Matrix und erhöht so die interlaminare Energiefreisetzungsrate (ERR) der Verbundwerkstoffe unter Mode I und Mode II Belastungen. Die Modifizierung führt zu einer Erhöhung der Schadensiniitierungspannung von gekerbten Zugproben für alle Schichtdicken, wodurch der nutzbare Lastbereich vergrößert und somit die Schadenstoleranz verbessert wird. Bei Ultra-Thin-Ply Laminaten wird die Kerbfestigkeit durch eine durch Reduktion der Spannungskonzentrationen durch die Bildung von Schäden am FLG auf der Mikroskala in hochbelasteten Bereichen erhöht. Bei Low-Velocity-Schlagschäden (LVI) verringert die Modifikation bei allen Schichtdicken den auftretenden Schaden, jedoch führt dies nur bei dickschichtigen Laminaten zu einer deutlichen Verbesserung der Druckfestigkeit über alle betrachteten Schichtdicken.
Als weiterer Ansatz zur Beeinflussung der Matrixschädigung wurden bioinspirierte helikoide Lagenaufbauten mit einem Winkel von 2.07° zwischen den einzelnen Lagen untersucht. Aufgrund des kleinen Winkels zwischen den Lagen unterdrücken die Laminate die Bildung von Delaminationen und es treten nur unterkritische Matrixrisse vor dem endgültigen Versagen auf. Dies führt zu einer deutlich erhöhten Druckrestfestigkeit nach LVI im Vergleich zum 45°-quasi-isotropen (QI) Lagenaufbauten, trotz eines geringeren Anteils an Fasern in Lastrichtung. Dieser geringe Anteil an Fasern in Lastrichtung führt zu einer geringen Zugfestigkeit. Bei gekerbten Proben führt das Auftreten von Matrixrissen jedoch zu einer Reduzierung der Spannungkonzentration, wodurch die Laminate nahezu keinerlei Kerbempfindlichkeit aufweisen und trotz des geringen Anteils lastorientierter Fasern ähnliche Kerbfestigkeiten wie bei 45°-QI Lagenaufbauten erreichen.
Zusätzlich wurde in dieser Arbeit der Einfluss der Temperatur auf den aus LVI resultierenden Schaden und die Restfestigkeit untersucht, um die Einflussfaktoren der Schadenstoleranz besser zu verstehen. Da die mechanische Leistungsfähigkeit der Matrix mit steigender Umgebungstemperatur abnimmt, ist das Verhalten von CFK ebenfalls abhängig von der Temperatur. Es wurden LVIs mit Energien zwischen 8 J und 25 J und Temperaturen von -20 °C bis 80 °C untersucht. Die Ergebnisse zeigen eine hohe Sensitivität des Schädigungsverhaltens zur Temperatur. Mit steigender Temperatur verkleinert sich die Delaminationsfläche und es kommt zum Faserbruch auf der Seite des Schlagschadens, was eine Reduzierung der Restzugfestigkeit zur Folge hat. Die Restdruckfestigkeit wurde bei 20 °C und 80 °C bestimmt. Die Ergebnisse zeigen, dass eine erhöhte Temperatur während der Druckbeanspruchung einen entscheidenderen Einfluss auf die Restfestigkeit hat als die Schlagenergie. Um das Verständnis über den Einfluss der Temperatur auf die LVI und die Restfestigkeit zu vertiefen, wurden temperaturabhängige Materialeigenschaften bestimmt und in ein Kontinuumsschädigungsmodell (CDM) implementiert, um das progressive Versagen von CFK unter Temperatureinfluss numerisch zu beschreiben. LVI-Simulationen bestätigen, dass das Materialmodell die Schädigung bei unterschiedlichen Temperaturen und Schlagenergien sowie die anschließende Restdruckfestigkeit vorhersagen kann. Die Ergebnisse zeigen, dass nicht eine Erhöhung der interlaminaren ERR zu einer Verringerung der Delaminationsgröße führt, sondern die temperaturbedingte Veränderung der intralaminaren Schädigung und des gesamten Strukturverhaltens.
High-performance composite laminates are structural materials that combine low density with high stiffness and strength. High safety and reliability requirements for structural parts require the consideration and detailed knowledge about damage tolerance of materials and structures.
The multi-scale nature of composites results in the occurrence of different failure modes and a complex failure behaviour where matrix failure at the micro-level influences the failure process at all higher observation levels. Consequently, the occurring matrix damage has a decisive influence on the damage tolerance. The research hypothesis of this thesis is:
Understanding and adapting the matrix's damage behaviour is fundamental to improving the damage tolerance of high-performance composites.
To adapt the matrix's damage behaviour, carbon-fibre reinforced plastics (CFRP) with a few-layer graphene (FLG) modified matrix with layer thicknesses varying from ultra-thin-ply (28 μm / 30 g/m2) to thick-ply (220 μm / 240 g/m2) were investigated. The FLG modification introduces additional damage modes into the matrix and significantly increases the composites mode I and mode II inter-laminar energy release rates (ERR). The modification increases the damage initiation stress of the notched tensile specimen and the usable design space and damage tolerance. For ultra-thin-ply laminates, the notched strength is increased due to crack blunting because the FLGs initiate distributed damage on the microscale in highly stressed areas. The damage resulting from low-velocity impact (LVI) decreases with the FLG modification for all layer thickness, but only the residual compressive strength of thick-layer laminates improves. Additionally, the FLG modification leads to a considerable improvement of the compressive strength.
As another approach to influence the matrix damage, bio-inspired laminates with a helicoidal layup with a pitch angle of 2.07° were realised. Due to the small angle between the ply, the laminates suppress the formation of delamination damage and only exhibit subcritical matrix cracking before final failure. As a result, the compressive residual strength after LVI is significantly increased compared over 45°-quasi-isotropic (QI) layup, despite a lower proportion of 0}{\degree} fibres in the load direction. Due to the low portion of load oriented fibres, the unnotched tensile strength is lower than 45°-QI layups. However, the formation of helicoidal matrix damage leads to crack blunting, and as a result, almost no notch sensitivity occurs, and similar notched strengths as 45°-QI layups are achieved, despite the low portion of load oriented fibres.
Additionally, this thesis investigated the influence of temperature on LVI and the residual strength to further understand the influencing factors of damage tolerance. Because the matrix's mechanical performance decreases with increasing environmental temperature, the composite's damage behaviour is temperature-sensitive. LVIs with impaction energies between 8 J and 25 J and temperature ranging from -20 °C to 80 °C were investigated. A change in temperature leads to a substantial change in damage behaviour. With increasing temperature, the delamination area reduces and fibre-failure occurs on the impacted side, which reduces the residual tensile strength considerably. The compressive residual strength was determined at 20 °C and 80 °C. The results point out that an elevated temperature during compressive loading has a more decisive influence than the impaction energy. To further understand the influence of temperature on the impact damage and the residual strength, temperature- dependent material properties were determined and implemented into a continuum damage model (CDM) to describe CFRP's progressive failure under temperature influence. LVI simulations validated that the material model could predict the damage resulting from different temperatures and impact energies and following residual compressive strength. The results reveal that not an increase of the inter-laminar ERR cause a reduction in delamination size but the change in intralaminar damage and overall structural response.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-01-28
2022
Other
Text
publishedVersion
urn:nbn:de:gbv:830-882.0179554
Technische Universität Hamburg (2022)
eng
1
da7319216511fb8cb4e67cd3ee416fe2
https://tore.tuhh.de/bitstreams/c0a88941-ccb8-4f31-b4fe-88b382eee371/download
http://hdl.handle.net/11420/12183
10.15480/882.4276
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/23112019-04-17T05:19:58Zcom_11420_1col_11420_2
Dynamic simulation and investigation of the startup process of a postcombustion-capture plant
Thomas
Marx-Schubach
Gerhard
Schmitz
600
Carbon capture is an important possibility to reduce carbon dioxide emissions. To be able to study the startup process of such an amine-scrubbing process, a startup model of a postcombustion-capture plant (pcc-plant) was developed in the Modelica language and validated with measured data from a pilot plant in Heilbronn, Germany. Afterward, the process was scaled up in the model to handle the entire flue-gas flow of a 875 MW coal-fired power plant, resulting in three parallel capture plants. A case study was carried out to investigate the startup process of the pcc-plant in detail, indicating that the startup time increased drastically when the plant is operating at partial load. The startup time for a cold start from the beginning of steam flow to a 90% carbon-capture rate is t = 1900 s at full load and t = 11 075 s at 15% load. The total heat demand in the reboiler of one pcc-plant is 326 GJ at full load and 370 GJ at 15% load. Other results show that the startup time increases linearly with increasing total amount of solvent and that the steam flow rate and solvent flow rate have a high impact on the startup time. © 2018 American Chemical Society.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-12-12
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.030592
Industrial and Engineering Chemistry Research 49 (57): 16751-16762 (2018-12-12)
eng
1
88f7f847b1ca8308767e5be691d2343e
https://tore.tuhh.de/bitstreams/2ab83dbc-8d4c-4fa2-a6e7-33e23e4b2f13/download
http://hdl.handle.net/11420/2311
10.15480/882.2182
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/16562018-05-24T09:05:06Zcom_11420_1col_11420_2
Ein technisches System für die kollaborative OER-Entwicklung im Experimentierfeld der TUHH
Axel
Dürkop
Andreas
Böttger
Tina
Ladwig
Sönke
Knutzen
OER
Docker
HOOU
Partizipation
Kollaboration
GitLab
000
370
620
Der Artikel führt ein in ein umgesetztes Konzept zur kollaborativen Entwicklung von Open Educational Ressources (OER) im Experimentierfeld der HOOU an der TUHH. Dabei werden Erfahrungen sowohl aus dem sozialen und organisatorischen Prozess berichtet als auch informationstechnische Systeme und ihr Zusammenspiel vorgestellt.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018
WorkingPaper
Text
publishedVersion
urn:nbn:de:gbv:830-88220867
ger
1
dfd90c06de8f02c03443e5254e501641
https://tore.tuhh.de/bitstreams/179f1990-03d0-4ec0-899d-0487b0e71c48/download
http://tubdok.tub.tuhh.de/handle/11420/1656
10.15480/882.1653
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/18732018-11-22T12:41:17Zcom_11420_1col_11420_2
Design of an added plan with social responsibility
Kathya Alexandra
Suesca Rozo
Andrés Felipe
Santos Hernández
Steel transformation
Added planning
Optimization
Social responsibility
330
380
For decades and worldwide, steel has been one of the most important commodity in the development of the industry due to its multiple uses. At present, the offer of steel in Colombia is too low compared to the sector’s demand. This has caused market speculation and a low added value regarding all products made with steel.
In such a competitive market, the organizations involved have been developing
strategies to improve their incomes, some of these are developed in the operations area, where the planning is the most important part regarding the cost reduction,
minimize the rate of rotation of the personal in the operations area and increment in the effectivity of the supplies chain. Having this need and tendency created, the investigation group designed an added planning model, based on the case of an enterprise that transforms steel in cloves. Using this model in the enterprise will guarantee decrease the shortage in posterior periods and as consequence lower the costs and wastes caused by shortfalls, the costs of keeping an inventory and costs due to high lead time to market. Furthermore, the model will minimize the rate of rotation of the personal in the operations area, this will result encouraging social responsibility which contribute to the organization’s productivity.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-09-13
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.023812
Hamburg International Conference of Logistics (HICL) 2018
eng
1
d5b1dd1ab4e5d8291c62cab8573c6e56
https://tore.tuhh.de/bitstreams/8e251381-dddc-48de-9946-66fec671a509/download
http://tubdok.tub.tuhh.de/handle/11420/1873
10.15480/882.1870
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/436972023-10-13T08:32:06Zcom_11420_1col_11420_2
Development of Modular Architectures for Product–Service Systems
Christoph
Rennpferdt
Marc
Züfle
Marco
Bagusat
Dennis
Bender
Dieter
Krause
modularization
product architecture
Product–Service Systems
PSS
variety-induced complexity
Driven by servitization, an increasing number of manufacturing companies are transforming from being a pure product provider to a provider of Product–Service Systems (PSS). PSS offer unique benefits to both providers and customers by combining physical products and intangible services. However, this results in an increase in variety for the provider, which causes an increase in variety-induced complexity and, finally, also in costs. This correlation is proven based on the literature; possible approaches to manage the complexity are presented and the current research gap is addressed. To address the gap, a method for the development of modular architectures for PSS is presented in this paper. The method comprises five phases and supports companies from identifying PSS-based business models up to modularizing product components and service components. To validate this method, it is first applied to the example of a product family of pressure-reducing valves and then its results are discussed afterwards. It is proven that this method is suitable for the development of modular PSS architectures, but there is also a need for further research, which is described in the Conclusions section.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-09-01
Article
Text
publishedVersion
10.15480/882.8722
Sustainability 15 (18): 14001 (2023)
eng
1
af3235549e1697480bfe4a1b0e0ea280
https://tore.tuhh.de/bitstreams/8acb0dcb-ac52-43e7-aeb6-89900278ee8a/download
https://hdl.handle.net/11420/43697
10.15480/882.8722
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/152872023-05-25T07:55:22Zcom_11420_1col_11420_2
Wirkungen des fahrerlosen Fahrens im Logistiksystem
Sandra
Tjaden
Fahrerloses Fahren
Logistik
System dynamics
Wirkungen
Straßengüterverkehr
Mit Einführung des fahrerlosen Fahrens wird sich das Logistiksystem verändern. Die Wirkungen sind in der bestehenden Literatur bislang jedoch wenig diskutiert. Die Arbeit analysiert die Wirkungen des fahrerlosen Fahrens im Logistiksystem und ermittelt mögliche Rückkopplungsschleifen. Die Ergebnisse basieren auf einer Literaturanalyse und einem dreistufigen Modellansatz, der die Wirkungen sowohl qualifiziert als auch quantifiziert und die Ableitung von Gestaltungsoptionen zulässt, mit denen die relevanten Akteure unerwünschte Wirkungen reduzieren können.
The driverless driving will change the logistics system in the future. These changes are little discussed in the existing literature so far. This work helps to understand the effects of driverless driving in the logistics system. The findings are based on a literature review and a three-stage model approach, which qualifies the effects as well as quantifies them and allows the derivation of design options, which can be used by the relevant actors to reduce undesirable effects.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-02-10
2023
Other
Text
publishedVersion
urn:nbn:de:gbv:830-882.0219433
Technische Universität Hamburg (2023)
ger
1
b1a438e18e97f3d0d3d95e4e12a794c6
https://tore.tuhh.de/bitstreams/d7fcc8b2-0677-4553-b786-c91021c9c406/download
http://hdl.handle.net/11420/15287
10.15480/882.5104
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/16742018-06-06T04:28:27Zcom_11420_1col_11420_2
Low powered, tunable and ultra-light aerographite sensor for climate relevant gas monitoring
Oleg
Lupan
Vasile
Postica
Matthias
Mecklenburg
Karl
Schulte
Yogendra Kumar
Mishra
Bodo
Fiedler
Rainer
Adelung
620
Increasing atmospheric CO2 gas pollution and emergence of new types of green energy sources require continuous environmental monitoring. In this context, fast, efficient, light, robust, and reliable gas
sensors that can work at room temperature are in high demand. We report on a low-powered type of ultra-light sensor, based on a 3-D-microtube network from a 2-D graphene/nanographite, called
aerographite, and a method to tune the nanosensor’s selectivity by a simple variation of the applied bias voltage. Adequate selectivity to CO2 and ultra-fast sensing of H2 by applying 1 V and 5 V, respectively, is obtained. At ultra-low applied bias voltages (1–100 mV) only very low power consumption (z3.6 nW for 1 mV) is needed. This is most important, as it can be run by energy harvesting methods. The presented results are of the highest interest in terms of low-cost production of ultra-light and ultra-low-power consumption gas sensors for environmental monitoring of greenhouse gases and their simplicity from the technological/engineering points of view.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2016-09-27
Article
Text
publishedVersion
urn:nbn:de:gbv:830-88221226
Journal of Materials Chemistry A 42 (4): 16723-16730 (2016)
eng
1
b906a8cec23b5fc814da67e7bb2ae09d
https://tore.tuhh.de/bitstreams/f0203574-41e7-4b3c-8956-5aca1aa649eb/download
http://tubdok.tub.tuhh.de/handle/11420/1674
10.15480/882.1671
https://creativecommons.org/licenses/by/3.0/
oai:tore.tuhh.de:11420/127452022-05-31T09:06:22Zcom_11420_1col_11420_2
Area moment of inertia and other physical quantities for special cross-sectional areas of bend specimens
Hans
Jelitto
area moment of inertia
second moment of area
Stress analysis
Strain analysis
Young's modulus
Analytical solution
In Bezug auf Materialien der Natur mit außergewöhnlichen Eigenschaften besteht ein Fokus unserer Forschung in Perlmutt-inspirierten Materialien. Auf der Basis von 3D-Druck war es möglich, winzige Biegeproben für Drei-Punkt-Biegetests (3PB) zu präparieren. Allerdings ist ihr Querschnitt nicht rechteckig, sondern hat eine spezielle geometrische Form. Deshalb wurden analytische Berechnungen zum Flächenträgheitsmoment und zu anderen physikalischen Größen für eine korrekte Analyse der Messdaten durchgeführt.
With regard to materials in nature having extraordinary properties, one focus of our research is nacre-inspired materials. On the basis of 3D-printing, it was possible to prepare tiny bending bars in order to be tested in three-point bending (3PB). However, their cross sections are not rectangular but have a special geometric shape. Therefore, analytical calculations concerning the area moment of inertia and other physical quantities were performed for the correct analysis of the measured data.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-05-31
Report
Text
publishedVersion
urn:nbn:de:gbv:830-882.0186306
Technische Universität Hamburg (2022)
eng
1
a5ec2e08fd51c56ed86a4a202407d333
https://tore.tuhh.de/bitstreams/059fc96a-dc1f-4eb6-8f44-66667e865984/download
http://hdl.handle.net/11420/12745
10.15480/882.4355
https://creativecommons.org/licenses/by-nc-sa/4.0/
oai:tore.tuhh.de:11420/135482022-09-06T05:21:44Zcom_11420_1col_11420_2
“Boiling water is not too hot for us!” : preferred living spaces of heat-loving microbes
Skander
Elleuche
Carola
Schröder
Nadine
Stahlberg
Garabed
Antranikian
microorganisms
hot springs
geysers
enzymes
Do you like to stay at the beach on a hot summer day? Sun bathing, chilling, and playing beach games? If it gets too hot, you can quickly cool off in the lukewarm ocean. Can you believe that there are living organisms on our planet that would still freeze on the hottest day of the year? These tiny creatures are called heat-loving microbes, and they do not grow at temperatures lower than 50°C, but they feel most comfortable in boiling water near volcanoes at the bottom of the ocean or in hot springs. Can you imagine that most of these hot places are not located in deserts, but on volcanic islands in the Atlantic Ocean and near the North Pole? And do you have an idea about the importance of such microbes for use in industry and in scientific laboratories?
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2017-02-02
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0195940
Frontiers for Young Minds 5 (): 01 (2017-02-02)
eng
10
25dbdad729dd29a96466ea214261bfec
https://tore.tuhh.de/bitstreams/77a169b3-e8f2-42a5-bd60-458668327e7c/download
http://hdl.handle.net/11420/13548
10.15480/882.4578
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/18782018-11-26T06:59:05Zcom_11420_1col_11420_2
Supply chain sustainability performance indicators : a content analysis based on published standards and guidelines
Muhammad Amad
Saeed
Wolfgang
Kersten
sustainable supply chain management
performance measurement
content analysis
sustainability performance indicators
330
The goal of this paper is to provide researchers and practitioners with the required guidance to achieve a better assessment of the sustainability-related performance of an organization and its supply chain (SC). In order to achieve this, standards and guidelines covering three sustainability dimensions (economic, social, and environmental) were analyzed for the identification of sustainability performance indicators (SPIs). A content analysis approach was applied for the data collection and analysis. Twelve international standards and guidelines were identified and selected for the purpose of conducting an analysis to integrate the latest findings on SPIs in sustainable supply chain management (SSCM). The findings of the content analysis revealed 232 original set of instances of sustainability-related information, of which 46% were related to the environmental dimension, 43% were related to the social dimension and 11% were related to the economic dimension of sustainability. In order to provide a better understanding and evaluation, each sustainability dimension was characterized using attribute categories. A descriptive evaluation of the academic literature, standards, and guidelines resulted in 18 attribute categories. Collected indicators were classified according to these attribute categories. In-depth analysis, restructuring, standardizing of attribute categories and indicators have led to 70 unique and coherent SPIs. Out of which 49% indicators were identified as environmental SPIs, 37% as social SPIs and 14% as economic SPIs. The results revealed a complete lack of agreement among the current standards on how to measure the sustainability-related performance of an organization and its SC.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2017-12-28
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.023916
Logistics Research 1 (10) : (2017), art. no. 12
eng
1
312015fdd90bc098af2ac0e7a2b78210
https://tore.tuhh.de/bitstreams/fea8d936-1cec-4e96-8eed-36cdf859bd0d/download
http://tubdok.tub.tuhh.de/handle/11420/1878
10.15480/882.1875
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/12242015-03-10T13:52:41Zcom_11420_1col_11420_2
Bulk nested-network nanoporous gold via dealloying
Zhen
Qi
dealloying
nanoporous metals
hierarchical sturcture
bulk nanomaterial
structure control
620
Eine Zwei-Schritt Entlegierungs-Strategie wurde durch kontrollierte Entlegierung geschaffen, um hierarchisches nanoporöses Gold, das zwei deutlich differenzierbare Ebenen aus Ligamenten hat, aus einem massiven Festkörper herzustellen. Ausgehend von einer verdünnten Lösung von Au in Ag, ergibt kontrollierte elektrochemische Korrosion nanoporöses Ag-Au als Zwischenprodukt. Vergröberung der porösen Legierung schafft die großen Ligamente der oberen Hierarchieebene. Diese werden dann wieder Entlegiert, was die die feinen Ligamente der unteren Hierarchieebene schafft. Das Material zeigt eine verbesserte Ladungstransport-Kinetik bei einer gleichzeitig großen spezifischen Oberfläche. Ähnliche Zwei-Schritt-Strategie wie für die verdünnte Ag-Au Legierung, eine Ag-Au-Pt Legierung wurde ausgewählt, um hierarchisches nanoporöses Gold mit einer ultrafeinen unteren Hierarchieebenen-Ligamentgröße herzustellen. Die untere Hierarchieebenen-Ligamentgröße ist so klein wie 6 nm.
A two-step dealloying strategy has been established via controlled dealloying to fabricate hierarchical nanoporous gold which has two well distinguished levels of ligaments from a bulk solid. Starting out from a dilute solid solution of Au in Ag, controlled electrochemical corrosion yields nanoporous Ag-Au alloy as an intermediate product. Coarsening of the porous alloy creates the large ligaments of the upper hierarchy level. Those are then again dealloyed, which creates the fine ligaments of the lower hierarchy level. The material exhibits enhanced charge transport kinetics while maintaining a large specific surface area. Similar two-step dealloying strategy as the dilute Ag-Au alloy, a Ag-Au-Pt alloy was chosen to fabricate hierarchical nanoporous gold with an ultrafine lower hierarchy level ligament size. The lower hierarchy level ligament size is as small as 6 nm.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-01-07
2015
Other
Text
publishedVersion
urn:nbn:de:gbv:830-88212356
eng
1
0d86d19f1d83040e031cd3d5f36f7670
https://tore.tuhh.de/bitstreams/ea4378e8-cccc-43f8-875b-fb738ab301ba/download
http://tubdok.tub.tuhh.de/handle/11420/1224
10.15480/882.1222
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/61872020-05-27T10:38:01Zcom_11420_1col_11420_2
Mechanical properties of nanoporous metals : model experiments and technology-relevant materials
Lukas
Lührs
nanoporous metals
mechanical properties
electrochemical dealloying
tension-compression asymmetry
nanoporous CuNi
nanoporous copper-nickel
nanoporous gold
actuation
functional nanomaterials
In dieser Arbeit werden die mechanischen Eigenschaften von nanoporösen Metallen untersucht. Modellversuche an makroskopischen Proben finden eine ausgeprägte Zug-Druck Asymmetrie im Nanobereich, die auf den Einfluss der Oberflächenspannung zurückzuführen ist. Darüber hinaus wird ein Syntheseschema entwickelt, um nanoporöse Metalle mittels Entlegieren aus kostengünstigen Ausgangsmaterialien herzustellen. Dieses Material weist erhebliche mechanische Stabilität und Funktionalisierungsmöglichkeiten auf.
In this thesis mechanical properties of nanoporous metals are investigated. Model experiments on macroscopic samples find a distinct tension-compression asymmetry at the nanoscale that can be attributed to the interaction of the surface tension. Moreover, a synthesis scheme is developed to fabricate nanoporous metals by dealloying from cost- efficient precursor materials. This material proves considerable mechanical stability and functionalization opportunities.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-05-20
2020
Other
Text
publishedVersion
urn:nbn:de:gbv:830-882.092045
Technische Universität Hamburg (2020)
eng
1
b48ec0cfa3f937516eca5bd7046ca8c2
https://tore.tuhh.de/bitstreams/2227288a-eb03-477a-b92b-0110a0429de1/download
http://hdl.handle.net/11420/6187
10.15480/882.2778
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/6392009-08-14T14:31:06Zcom_11420_1col_11420_2
Analyse von natürlichem Modellseegang
Sigismund
Kastner
620
Analyse von natürlichem Modellseegang
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1968
Report
Text
publishedVersion
urn:nbn:de:101:1-201505223878
Schiffstechnik Bd. 15 1968 Heft 75
ger
1
e647635fda6c4f509b1114ccb3ccb5b9
https://tore.tuhh.de/bitstreams/9d7dd7e9-ab16-4b15-81c0-557c255f9332/download
http://tubdok.tub.tuhh.de/handle/11420/639
10.15480/882.637
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/12662015-11-27T11:53:51Zcom_11420_1col_11420_2
Sustainability in Logistics and Supply Chain Management
Logistics
Supply Chain Management
Supply Chain
Sustainability
Sustainability Supply Chain Management
600
The HICL-Conference celebrates its 10th anniversary, indicating major interest in the research fields of supply chain management and logistics. They are dedicated to make recommendations for new approaches and solutions that enable companies to cope with current and future challenges in supply chains and logistics.
The second volume of the 2015 conference provides valuable insights into
the highly relevant topic of sustainability in logistics and supply chains.
Contributions concern achievement of sustainability and application of
sustainability concepts in various supply chains.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-08
ConferenceProceedings
Text
publishedVersion
urn:nbn:de:gbv:830-88213433
eng
1
637d3c621b148600bc63062daa060b27
https://tore.tuhh.de/bitstreams/f1ced99e-0e44-4cbf-a20c-3c2019349742/download
http://tubdok.tub.tuhh.de/handle/11420/1266
10.15480/882.1263
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/139402022-11-07T10:45:49Zcom_11420_1col_11420_2
Analysis of potential benefit and maturity level of digital procurement
Sascha
Stradner
Uwe
Brunner
Innovation Management
Technology Management
Purpose: Procurement departments are facing major challenges of digitalization. To meet future business requirements, managers are forced to arrange investments for the digitalization of procurement processes. Current studies show that the maturity level of procurement digitalization is still lacking due to missing benefit assessments of investments.
Methodology: For this purpose, the benefit potentials of digitalized procurement are analyzed based on a systematic literature analysis, followed by qualitative expert interviews to evaluate hypotheses derived from the literature. Moreover, the expert interviews provide information about the current maturity level of digitalization in procurement.
Findings: The systematic literature analysis and qualitative expert interviews provide 24 potential benefits, which are summarized in six categories. The expert interviews indicate that increasing of efficiency, process transparency and data quality are seen as the main benefit potentials of digital procurement. In terms of maturity, the experts confirm potentials that need to be exploited to enable future procurement at competitive prices.
Originality: Current research on digital procurement is forcing superficial concepts of digitalization measures. A well-founded assessment of potential benefits of the implementation in companies is still missing, which leads to critical barriers in digitalization and missing adaption to rapidly changing market conditions.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-09
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0200917
Hamburg International Conference of Logistics (HICL) 33: 375-402 (2022)
eng
1
74fc398406e210531b0e3ff4e6a405db
https://tore.tuhh.de/bitstreams/c0f602c4-561c-4e85-bbed-7b79c5d4dabd/download
http://hdl.handle.net/11420/13940
10.15480/882.4712
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/431172023-09-01T05:26:01Zcom_11420_1col_11420_2
Approximation algorithms for coupled task scheduling minimizing the sum of completion times
David Simon
Fischer
Péter
Györgyi
Approximation algorithms
Coupled task problem
Single machine scheduling
Total completion times
In this paper we consider the coupled task scheduling problem with exact delay times on a single machine with the objective of minimizing the total completion time of the jobs. We
provide constant-factor approximation algorithms for several variants of this problem that are known to be N P-hard, while also proving N P-hardness for two variants whose complexity
was unknown before. Using these results, together with constant-factor approximations for the makespan objective from the literature, we also introduce the first results on bi-objective
approximation in the coupled task setting.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-04-25
Article
Text
publishedVersion
10.15480/882.8478
Annals of Operations Research (2023)
eng
1
178d964c187642b4072714f63a9eb7ad
https://tore.tuhh.de/bitstreams/04b1ff11-c095-4667-b4cf-f02cbe3d50c9/download
https://hdl.handle.net/11420/43117
10.15480/882.8478
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/682005-12-16T10:20:30Zcom_11420_1col_11420_2
Numerical methods for sparse nonlinear eigenvalue problems
Heinrich
Voß
nonlinear eigenvalue problem
iterative projection method
Jacobi–Davidson method
Arnoldi method
rational Krylov method
510
This paper surveys numerical methods for general sparse nonlinear eigenvalue problems with special emphasis on iterative projection methods like Jacobi–Davidson, Arnoldi or rational Krylov methods. We briefly sketch a new approach to structure preserving projection methods, but we do not review the rich literature on polynomial eigenproblems which take advantage of a linearization of the problem.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2004-01
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-opus-1213
Proc. XVth Summer School on Software and Alg. of Num Math., Hejnice, Czech Republik
eng
1
93ad1401bc8bd2048ff82dcdf0eedb10
https://tore.tuhh.de/bitstreams/1c2ecf4f-1cb7-40cc-97b3-7904094242f3/download
http://tubdok.tub.tuhh.de/handle/11420/68
10.15480/882.66
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/16962018-06-21T11:37:43Zcom_11420_1col_11420_2
Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials
Benjamin
Klusemann
Swantje
Bargmann
Yuri
Estrin
nanocrystalline material
gradient plasticity
higher order gradient terms
constitutive modeling
530
500
620
The proposed modeling approach for nanocrystalline materials is an extension of the local phase mixture model introduced by Kim et al (2000 Acta Mater. 48 493–504). Local models cannot account for any non-uniformities or strain patterns, i.e. such models describe the behavior correctly only as long as it is homogeneous. In order to capture heterogeneities, the phase mixture model is augmented with gradient terms of higher order, namely second and fourth order. Different deformation mechanisms are assumed to operate in grain interior and grain boundaries concurrently. The deformation mechanism in grain boundaries is associated with diffusional mass transport along the boundaries, while in the grain interior dislocation glide as well as diffusion controlled mechanisms are considered. In particular, the mechanical response of nanostructured polycrystals is investigated. The model is capable of correctly predicting the transition of flow stress from Hall–Petch behavior in conventional grain size range to an inverse Hall–Petch relation in the nanocrystalline grain size range. The consideration of second- and fourth-order strain gradients allows non-uniformities within the strain field to represent strain patterns in combination with a regularization effect. Details of the numerical implementation are provided.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2016-11-02
Article
Text
publishedVersion
urn:nbn:de:gbv:830-88221515
Modelling and Simulation in Materials Science and Engineering 8 (24): 085016 (2016)
eng
1
f335e6944fa23ec37dfac03cedb8f812
https://tore.tuhh.de/bitstreams/585bd828-2ce9-4ea4-95f2-0d5851667065/download
http://tubdok.tub.tuhh.de/handle/11420/1696
10.15480/882.1693
https://creativecommons.org/licenses/by/3.0/
oai:tore.tuhh.de:11420/84522021-01-15T11:23:30Zcom_11420_1col_11420_2
Predictability of vibration loads from experimental data by means of reduced vehicle models and machine learning
Leo
Dostal
Helge Johannes
Grossert
Daniel-André
Dücker
Malte
Grube
Daniel
Kreuter
Kai
Sandmann
Benjamin
Zillmann
Robert
Seifried
Nowadays electric cars are in the spotlight of automotive research. In this context we consider data based approaches as tools to improve and facilitate the car design process. Hereby, we address the challenge of vibration load prediction for electric cars using neural network based machine learning (ML), a data-based frequency response function approach, and a hybrid combined model. We extensively study the challenging case of vibration load prediction of car components, such as the traction battery of an electric car. We show using experimental data from Fiat 500e and VWeGolf cars that the proposed ML approach is able to outperform the classical model estimation by means of ARX and ARMAX models. Moreover, we evaluate the performance of a hybrid-ML concept for combination of ML and ARMAX. Our promising results motivate further research in the field of vibration load prediction using machine learning based approaches in order to facilitate design processes.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-09-28
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0120938
IEEE Access 8: 177180-177194 (2020)
eng
1
46d467a73d06556d5622fc0d7cda92e2
https://tore.tuhh.de/bitstreams/0030ee29-74da-4ba1-813c-055bc6f8a7d3/download
http://hdl.handle.net/11420/8452
10.15480/882.3567
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/11812014-07-11T04:54:22Zcom_11420_1col_11420_2
Simulation und Modellierung des anaeroben Prozesses der Biogaserzeugung mit verschiedenen Substraten
Modelling of biogas production with differents substrates
Christian Jose
Rojas Reina
Anaerober Prozess
ADM1
Cofermente
Kinetik
Simulation
anaerobic process
ADM1
coferments
kinetics
simulation
570
Es wird eine Simulation des anaeroben Prozesses in Biogasanlagen beschrieben, die es erlaubt den Prozess für den Einsatz verschiedener realer Substrate zu optimieren. Als Basis zur Modellierung wird das ADM1-Modell (Anaerobic Digestion Model No. 1) verwendet. Es wurden Batch-Versuche mit verschiedenen Substraten sowie Experimente in einem kontinuierlichen Laborreaktor durchgeführt. Anhand der experimentellen Ergebnisse erfolgten eine Parametrisierung und Modifikationen im Modell. Nach der Validierung des Modell im Labor wurde die Simulation einer großtechnischen Biogasanlage realisiert.
A simulation of the anaerobic process of a biogas production for different substrates was realized (manure, lipid rich substrate, organic waste and maissilage). The simulation was based on the Anaerobic Digestion Model No. 1 (ADM1). The experimental work comprehends batch-experiments and experiments in a continuous stirred-tank reactor at lab scale with different substrates used in a biogas production. The comparison between the experiments and the simulations of the process leads to a modification in ADM1. Furthermore a classification of substrates was developed according to their biodegradability to meet the fractions of the ADM1 simulation. The model was used for the simulation of a biogas plant fed with manure and food waste as substrates.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2014-07-07
2014
Other
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-12796
ger
1
e10f16802eb3290d66f6a79d5860efa7
https://tore.tuhh.de/bitstreams/07ab53c6-409b-4f67-81a5-590a0f89518a/download
http://tubdok.tub.tuhh.de/handle/11420/1181
10.15480/882.1179
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/108642021-11-10T09:28:28Zcom_11420_1col_11420_2
Shear-induced anisotropy in rough elastomer contact
R.
Sahli
G.
Pallares
A.
Papangelo
M.
Ciavarella
C.
Ducottet
N.
Ponthus
J.
Scheibert
True contact between randomly rough solids consists of myriad individual microjunctions. While their total area controls the adhesive friction force of the interface, other macroscopic features, including viscoelastic friction, wear, stiffness, and electric resistance, also strongly depend on the size and shape of individual microjunctions. We show that, in rough elastomer contacts, the shape of microjunctions significantly varies as a function of the shear force applied to the interface. This process leads to a growth of anisotropy of the overall contact interface, which saturates in the macroscopic sliding regime. We show that smooth sphere-plane contacts have the same shear-induced anisotropic behavior as individual microjunctions, with a common scaling law over 4 orders of magnitude in the initial area. We discuss the physical origin of the observations in light of a fracture-based adhesive contact mechanics model, described in the companion article, which captures the smooth sphere-plane measurements. Our results shed light on a generic, overlooked source of anisotropy in rough elastic contacts, not taken into account in current rough contact mechanics models.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-05-30
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0157668
Physical Review Letters 122 (21): 214301 (2019)
eng
1
089cf0b9b3877823e1e5fbfa747e2dad
https://tore.tuhh.de/bitstreams/31fce051-2d1c-410f-b832-cdbe997ae04b/download
http://hdl.handle.net/11420/10864
10.15480/882.4203
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/49852020-02-21T07:57:26Zcom_11420_1col_11420_2
Improving the quality and quantity of source-separated household food waste in areas of different socio-economic characteristics: a case study from Lübeck, Germany
Steffen
Walk
David
Wardle
Stefan
Deegener
Ina
Körner
food waste
waste composition analysis
waste valorization
circular Economy
socio-economic assessment
A method aiming at improving source-separation performance of household food waste (FW) was investigated in two areas with different socio-economic characteristics in Lübeck, Germany.This included the test of a new FW collection system including the distribution of small collection buckets to each household. In addition, an information event was organized and households were provided with information material includingawaste sorting guide. The study also aimed at assessing the FW avoidance potential. A method for waste composition analysis for FW from households was applied for the assessment. Both areasshowed an increase ofthe source-separation of FW from 17.4% to 60.3% (A, socio-economic lowarea) and from 16.6% to 65.7% (B, socio-economic mediumarea) respectively. Compared to the waste compositionin the bio-waste (BW) bin prior the investigation, macro-impurities (including paperwaste) reduced from around 6.1% to 0.6%(A) and from 13.6% to 1.2% (B). In this respect, the investigated collection system showed a significant improvement to the regular waste collection system.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-09
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.074513
International Conference on Environmental Science and Technology Rhodos : 00484 (2019)
eng
1
4df2516a9fafefb9ae012f7b31bb1f80
https://tore.tuhh.de/bitstreams/4494a848-cda7-4c79-a6ba-1ab068ab1bf5/download
http://hdl.handle.net/11420/4985
10.15480/882.2676
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/37802019-11-14T07:04:33Zcom_11420_1col_11420_2
Cyber-attack impact estimation for a port
Sandra
König
Stefan
Rass
Stefan
Schauer
Cyber-attack
Cascading effects
Port security
Supply chain
Purpose: We investigate consequences of a cyber-attack on a port through a simulation model. Motivated by the impact of NotPetya on the container company A.P. Møller-Maersk and the entire supply chain we propose a method to estimate the consequences. Such estimation is a first step towards the identification of protection measures. Methodology: We represent a port as a network of interdependent cyber and physical assets. The operational state of each component is measured on a 3-tier scale and may change due to external problems. The components reaction on security incidents is modeled using Mealy automata. Findings: An implementation of the model as a network of coupled Mealy automata allows simulation of the dynamics after a security incident. This gives an overview on the expected condition of each component over time. The results can be visualized to identify parts that are particularly at danger. Originality: The approach takes into account different kind of information on the cyber and physical system but also learns from past incidents. The automata simulation model provides estimate on the future behavior. Existing data may be used for validation.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-09-26
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.054849
Hamburg International Conference of Logistics (HICL) 28: 163-183 (2019)
eng
1
de650f59d8cb53219523c2d2f1510f87
https://tore.tuhh.de/bitstreams/09d7e975-d20e-42dd-87b0-b7788e27ef4a/download
http://hdl.handle.net/11420/3780
10.15480/882.2496
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/117032022-02-15T09:58:17Zcom_11420_1col_11420_2
Estimating Weibull parameters using Mabchour’s method (MMab) for wind power at RAWA City, Iraq
Amani I.
Altmimi
Safaa J.
Al-Swaiedi
Oday Ibraheem
Abdullah
wind energy
wind power density
Weibull distribution
Mabchour’s Method (MMab)
Wind power is one of the most important sources of renewable energy. In this research paper, we developed an approach to select the optimum site among four different locations in Iraq (Talafar, Nasiriyah, Baghdad and RAWA) according to wind power density. Based on the optimization process, it was found that the RAWA city is the optimal site. We adopted Mabchour’s Method (MMab) to estimate the Weibull distribution parameters (c, k) for RAWA city at two heights (10 m and 50 m) for the period (2017–2019). It was found that the Mabchour technique (MMab) produced accurate results with minimum consumed time and effort. This was because the values of <i>k</i> and <i>c</i> were close to each other. Additionally, the coefficient values of the results of the Weibull measurements were very close to the average wind speeds that we measured. The values of the correlation coefficients between the Weibull scale parameters and the form were calculated and were equal to R2 = 0.9971. The minimum value of the coefficient of variation (COV) for turbulence intensity was found to be 26% in July 2018, when the wind speeds reached their maximum. The highest error of wind power density between measured data (PM) and Weibull distribution (PW) was found to be 4.48%, at a height of 50 m.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-01-22
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0172331
Applied System Innovation 5 (1): 14 (2022)
eng
1
96860600a06e091471ba9dfab4a85a4e
https://tore.tuhh.de/bitstreams/dd0cffff-5aeb-49e7-a3cc-70e2bdd656fc/download
http://hdl.handle.net/11420/11703
10.15480/882.4157
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/5222009-08-10T11:13:03Zcom_11420_1col_11420_2
Über Widerstandsverhältnisse von Zweikörperschiffen
Klaus
Eggers
620
Über Widerstandsverhältnisse von Zweikörperschiffen
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1955
Report
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-5993
ger
1
ba529fd2f7a7c76d72f6d95f20b5eae0
https://tore.tuhh.de/bitstreams/c54ce31a-bbd6-455e-b64e-184e03f04902/download
http://tubdok.tub.tuhh.de/handle/11420/522
10.15480/882.520
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/116572022-02-11T05:33:29Zcom_11420_1col_11420_2
CONSERVE: A framework for the selection of techniques for monitoring containers security
Rodi
Jolak
Thomas
Rosenstatter
Mazen
Mohamad
Kim
Strandberg
Behrooz
Sangchoolie
Nasser
Nowdehi
Riccardo
Scandariato
Attack analysis
Container monitoring
Intrusion detection
Security
Software and systems engineering
Virtualization
Context: Container-based virtualization is gaining popularity in different domains, as it supports continuous development and improves the efficiency and reliability of run-time environments. Problem: Different techniques are proposed for monitoring the security of containers. However, there are no guidelines supporting the selection of suitable techniques for the tasks at hand. Objective: We aim to support the selection and design of techniques for monitoring container-based virtualization environments. Approach:: First, we review the literature and identify techniques for monitoring containerized environments. Second, we classify these techniques according to a set of categories, such as technical characteristic, applicability, effectiveness, and evaluation. We further detail the pros and cons that are associated with each of the identified techniques. Result: As a result, we present CONSERVE, a multi-dimensional decision support framework for an informed and optimal selection of a suitable set of container monitoring techniques to be implemented in different application domains. Evaluation: A mix of eighteen researchers and practitioners evaluated the ease of use, understandability, usefulness, efficiency, applicability, and completeness of the framework. The evaluation shows a high level of interest, and points out to potential benefits.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-04
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0172019
Journal of Systems and Software 186: 111158 (2022-04)
eng
1
efbfcf569e90a7648d7dccc64de08025
https://tore.tuhh.de/bitstreams/cf770952-22c8-45e2-af2d-0cf2caa747e9/download
http://hdl.handle.net/11420/11657
10.15480/882.4139
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/9482011-02-07T13:01:40Zcom_11420_1col_11420_2
Gestaltung und Festigkeit unter Wasser geschweißter Dopplungen
Hubertus
von Selle
620
Gestaltung und Festigkeit unter Wasser geschweißter Dopplungen
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1991
Report
Text
publishedVersion
urn:nbn:de:101:1-201505272771
ger
1
7bc7d914e92a33f847e98333dda30805
https://tore.tuhh.de/bitstreams/9ec03882-259e-4db2-acd0-4feb20a78720/download
http://tubdok.tub.tuhh.de/handle/11420/948
10.15480/882.946
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/112242021-12-10T09:53:14Zcom_11420_1col_11420_2
Robotic process automation in logistics: Implementation model and factors of success
Jan
Krakau
Carsten
Feldmann
Victor
Kaupe
HICL and Practice
Excellence in Logistics and Supply Chain Management
Purpose: Robotic process automation (RPA) refers to software robots (bots) that automate repetitive, rule-based tasks in a business process. In this study, the research questions regarding logistics applications are as follows: (1) What are suitable use cases for RPA in logistics? (2) Which criteria support the selection of appropriate processes? (3) How should a procedure model for implementation be designed to systematically support the introduction while considering critical success factors?
Methodology: This study follows the design science research process by Peffers et al. (2006). The research gap was identified through an extensive literature analysis, reflecting the state of research. Insights gained were compared with empirical data from the use of RPA at a case company.
Findings: A procedure model was designed to systematically consider success factors for an implementation, comprising (1) initiation; (2) piloting; (3) deployment; and (4) ongoing governance, maintenance, and continuous improvement.
Originality: RPA can contribute to solving challenges such as increased service demands from customers, combined with cost pressures and a shortage of skilled labor. The procedure model closes a research gap, both from a scientific perspective and from the practitioners’ viewpoint, supporting an efficient and effective implementation. The consideration of knowledge from both theory and practice ensures practical relevance and significantly expands the state of research.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021-12-01
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0162325
Hamburg International Conference of Logistics (HICL) 32: 219-256 (2021)
eng
1
ac3a31335ec09a3b63ba3945f13406e7
https://tore.tuhh.de/bitstreams/59a5c799-e1cc-4e2e-a757-fecf2aa6198a/download
http://hdl.handle.net/11420/11224
10.15480/882.4005
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/459652024-02-29T08:46:36Zcom_11420_1col_11420_2
Berichte der Fachtagung Baustatik – Baupraxis 15 : 04. und 05. März 2024, Hamburg
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2024
ConferenceProceedings
Text
publishedVersion
10.15480/882.9247
Oesterle, Bastian, Bögle, Annette, Weber, Wolfgang, Striefler, Lukas (Eds.): Berichte der 15. Fachtagung Baustatik - Baupraxis (2024)
ger
1
d72a7b5ad3bc537ff3b774126973869f
https://tore.tuhh.de/bitstreams/1f0981fe-6c67-42c7-b10f-41f4856ac569/download
https://hdl.handle.net/11420/45965
10.15480/882.9247
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/13232016-09-21T04:53:29Zcom_11420_1col_11420_2
15. Seminar der LIBER Architecture Group
Inken
Feldsien-Sudhaus
Bibliotheksbau
020
Die Nationalbibliothek in Madrid war die diesjährige gastgebende Institution für das 15. Seminar der LIBER Architecture Group vom 12. bis zum 17. April 2010. Das kombinierte Angebot von Besichtigungen und Vorträgen verbunden mit der Möglichkeit des Austausches fand wieder Teilnehmerinnen aus vielen Ländern Europas. Neben den klassischen Themen zu Fragen des Bibliotheksbaus beschäftigten sich auch einige Vorträge mit den Entwicklungen des Web und seiner Technologien sowie den Auswirkungen auf Servicean- gebote der Bibliotheken. Aber auch Themen wie die Sanierung und Erweiterung von vorhandenen Gebäuden fanden ihren Raum. Die Tagung war perfekt von den spanischen Kol leginnen vor Ort organisiert.
This year the National Library of Spain in Madrid hosted the 15th Seminar of the LIBER Architecture Group from 12th to 17th of April 2010. The innovative offer of tours and speeches as well as the possibility of program exchanges attracted interested participants from every corner of Europe. Of course, subjects such as renovation and extension of existing facilities abounded. This year to enhance more subjects of the day, several talks were directed towards the development of internet services within the library. These new internet technologies present interesting challenges for libraries wishing to implement these new programs. As expected, the Spanish team had organized the meeting in an excellent manner and every aspect of the conference was well thought through.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2010-05
Article
Text
publishedVersion
urn:nbn:de:gbv:830-88214791
ABI-Technik. Band 30.2010, Heft 2, Seiten 100–113
ger
1
d8487a5dfa9a1d3b0430e6914b067136
https://tore.tuhh.de/bitstreams/02d7d16d-7094-4e12-984e-5dd77b772724/download
http://tubdok.tub.tuhh.de/handle/11420/1323
10.15480/882.1320
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/8992010-12-30T10:29:03Zcom_11420_1col_11420_2
Bestimmung und Beurteilung der Manövrierfähigkeit von Schiffen unter dem Aspekt der Kollisionsvermeidung
Bernd
Hampel
620
Bestimmung und Beurteilung der Manövrierfähigkeit von Schiffen unter dem Aspekt der Kollisionsvermeidung
Die Beurteilung der Manövrierfähigkeit eines Schiffes unter dem Aspekt der Kollisionsvermeidunq ist. für alle Beteiligten wie z.B. Schiffsführung und Reeder, wichtig. Die Manövriereigenschaften eines Schiffes und die Art und Weise der Nutzung seines Manövriervermögens haben entscheidenden Anteil an dem Erfolg des erforderlichen Ausweichmanövers. Gemessen werden kann die Manövrierfähigkeit mit einer nautischen Kenngrösse: erforderlicher Manöverabstand bzw. erforderliche Manöverzeit. Als Beurteilungsmass der Manövrierfähigkeit dient dann die Anzahl der Kollisionen pro Zeiteinheit, die das betrachtete Schiff in einem bestimmten Modellverkehr erfährt.
Zur Simulation der Ausweichbewegungen der Schiffe wurden zwei verschiedene Manövermodelle zusammengestellt. Die Berechnungsverfahren dazu und die Methode zur Abschätzung der Kollisionsrate werden beschrieben. Für ein Beispiel wurden die Berechnungen durchgeführt, um die nautischen Kenngrössen zu bestimmen und den Erfolg des gewählten Ausweichmanövers abzuschätzen. Ferner wird eine mögliche Verwendung der Ergebnisse demonstriert.
The assessment of the maneuverlng capability of a ship with regard to collision avoidance is of importance to all concerned, e.g. ship masters, ship owners, shipbuilders and vessel traffic designers. For in ca se of an impending collision, the physical maneuverability of the ship as well as the kind and manner of its utilization by the navigator-in-charge will have a decisive share in the success of the necessary evasive maneuver. The maneuvering capabilty can be assessed by means of a nautical measure: the required maneuvering range (or the required maneuvering time) to avoid a collision. The maneuvering capability can then be quantified in terms of the mean collision rate, i .e. the average number of collisions expected for the given ship per unit time in a given model traffic.
Two different maneuvering models have been set up to simulate the evasive motions of ships. The simulation algorithms and the method for estimating the collision rate are described. Sample calculations have been performed and the nautical measures determined for one case, in oder to estimate the success of the chosen evasive maneuver. Moreover, a possible practical application of the results is demonstrated.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1987
Report
Text
publishedVersion
urn:nbn:de:101:1-201505262340
ger
1
963a6fec492a9d07a34ab3f39390fc0f
https://tore.tuhh.de/bitstreams/6f12bc6f-3d64-4a48-9233-f3367f00ef04/download
http://tubdok.tub.tuhh.de/handle/11420/899
10.15480/882.897
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/32802019-09-04T04:44:10Zcom_11420_1col_11420_2
First-order average consensus for cooperative control problems using novel weighting strategies
Furugh
Mirali
Antonio
Mendez Gonzalez
Herbert
Werner
average consensus
cooperative control
distributed
Multi-agent systems
networks
600
In this paper we show how average consensus can be guaranteed in cooperative control schemes for multi-agent systems, even when normalised or weighted Laplacians are used. First we present weighting strategies for improving the performance that can be applied in a distributed manner (only local information is used), based on a recently proposed importance matrix. Then we modify the first-order consensus protocol, such that average consensus is guaranteed. It is then shown how this scheme can be used to improve the performance of cooperative control schemes. For this purpose, the effect of a formation reference on the consensus states is explicitly stated. A simulation result with second order LTI agent models illustrates the proposed approach.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2017-10-18
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.047832
IFAC-PapersOnLine 1 (50): 14302-14307 (2017)
eng
1
d6a796e70c34e6d11486ddf191b6ffcc
https://tore.tuhh.de/bitstreams/dc4b48c9-32c4-4202-ac5a-cbff00ff0051/download
http://hdl.handle.net/11420/3280
10.15480/882.3477
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/81942020-12-11T05:32:08Zcom_11420_1col_11420_2
Regional spatial analysis of the offshore wind potential in Japan
Yannek
Bardenhagen
Toshihiko
Nakata
offshore wind
Japan
offshore wind potential
regional analysis
This study presents an approach for estimating the offshore wind potential of Japan. Bathymetry data (1 km mesh) and near shore wind speed data of the year 2018 were used to assess the potential. A turbine with a peak power of 10.6 MW was employed for the analysis. The potential was calculated for multiple regions. These regions are based on the service areas of the major electricity supply companies in Japan. Overall, the results show that Japan has the potential to produce up to 32,028 PJ electricity per year. The electricity demand of 2018 amounts to 3231 PJ. The potential is therefore large enough to cover Japan’s electricity needs ten-times over. The capacity that could theoretically be installed amounts to 2720 GW, which is a multiple of the current worldwide installed capacity of 29.1 GW (2019). In addition to the huge potential, the regional assessment shows that the regions vary greatly in their potential; of all the considered regions, Hokkaido and Kyushu have the highest overall potential.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-11-29
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0117760
Energies 13 (23): 6303 (2020)
eng
1
bb1110eff5896a00aa2c1b4730f497e6
https://tore.tuhh.de/bitstreams/71ed9d69-3ac4-456b-95d3-58568e2ebb28/download
http://hdl.handle.net/11420/8194
10.15480/882.3187
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/23062019-04-15T05:10:49Zcom_11420_1col_11420_2
Laser metal deposition of bionic aluminum supports: reduction of the energy input for additive manufacturing of a fuselage
Markus
Heilemann
Jaco
Beckmann
Detlev
Konigorski
Claus
Emmelmann
laser metal deposition
additive manufacturing
aluminum
bionic
aerospace
620
Additively manufactured components made of metallic material are subject to special consideration for many R&D departments, since the process control is not yet sufficiently reliable and therefore an extensive quality assurance is necessary. For this reason, few structural components for aviation have been established so far. In this paper, a feasibility study for the use of laser metal deposition (LMD) for the additive manufacturing of a fuselage made of aluminum is carried out. The result is a parameter set with a minimized energy input. However, due to a welding length of 58 m the overall energy input is high and large distortion arises.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.030513
Procedia CIRP (74): 136-139 (2018)
eng
1
952b2a43aad883605de9015657494ad3
https://tore.tuhh.de/bitstreams/63cc9e22-21c9-4d68-b59d-25d3edee23f4/download
http://hdl.handle.net/11420/2306
10.15480/882.2181
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/111862021-12-13T07:49:33Zcom_11420_1col_11420_2
Design of a DLT-based document management system in road transport
Roger
Heines
Sandro
Rüttimann
Reinhard
Jung
Artificial Intelligence
Blockchain
Purpose: While the transportation sector enters a new phase of digital transformation, Distributed Ledger Technologies brought a new paradigm in the design of IS with numerous pilot-cases in logistics. Despite the various benefits (e.g., security, availability) little is empirically known about the development of such solutions. Where practitioners face numerous design decisions, we complement research by deriving six design principles for the construction of an applicable artifact in road transport.
Methodology: We follow design-science-research to generate design knowledge based on a literature review, a morphological analysis, and case studies on DLT-driven applications for document management. We refine the results and demonstrate practicability via an instantiation based on expert interviews to provide generalizability in terms of actionable guidelines.
Findings: We extend theory showing that DLT is an effective solution for cross-border information exchange. The design principles address the data architecture, access and storage across multiple stakeholders, and the way how data is exchanged. The results may further accelerate the adoption of DLT-based applications in logistics.
Originality: We bridge the gap between technology and practical utilization by evaluating existing cross-industry use cases combining elements from the business, legal, and information technology perspective. Additionally, the instantiation of an applicable solution is further the result of an inter-organizational development process involving feedback of various practitioners (e.g., carrier, authorities).
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021-12-01
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0161835
Hamburg International Conference of Logistics (HICL) 31: 275-299 (2021)
eng
1
0f0c6d707d69cbf09351fd96d522b601
https://tore.tuhh.de/bitstreams/90122cec-d718-4819-b314-a7d8abe2e919/download
http://hdl.handle.net/11420/11186
10.15480/882.3971
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/19522019-01-02T08:17:06Zcom_11420_1col_11420_2
Comparison of analytical approaches predicting the compressive strength of fibre reinforced polymers
Christian
Leopold
Sergej
Harder
Timo
Philipkowski
Wilfried
Liebig
Bodo
Fiedler
fibre reinforced polymer
compression
analytical models
prediction
shear properties
microbuckling
kinking
glass fibres
carbon fibres
540
620
Common analytical models to predict the unidirectional compressive strength of fibre reinforced polymers are analysed in terms of their accuracy. Several tests were performed to determine parameters for the models and the compressive strength of carbon fibre reinforced polymer (CFRP) and glass fibre reinforced polymer (GFRP). The analytical models are validated for composites with glass and carbon fibres by using the same epoxy matrix system in order to examine whether different fibre types are taken into account. The variation in fibre diameter is smaller for CFRP. The experimental results show that CFRP has about 50% higher compressive strength than GFRP. The models exhibit significantly different results. In general, the analytical models are more precise for CFRP. Only one fibre kinking model’s prediction is in good agreement with the experimental results. This is in contrast to previous findings, where a combined modes model achieves the best prediction accuracy. However, in the original form, the combined modes model is not able to predict the compressive strength for GFRP and was adapted to address this issue. The fibre volume fraction is found to determine the dominating failure mechanisms under compression and thus has a high influence on the prediction accuracy of the various models.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-12-11
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.025129
Materials 11 (12): 2517 (2018)
eng
1
97a800dc3ead69f1765faa86eb28ca4c
https://tore.tuhh.de/bitstreams/926ee8f5-7070-4107-a570-f938a24c33f5/download
http://tubdok.tub.tuhh.de/handle/11420/1952
10.15480/882.1949
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/153752023-06-08T09:22:34Zcom_11420_1col_11420_2
Nanoindentation creep of supercrystalline nanocomposites
Cong
Yan
Büsra
Bor
Alexander
Plunkett
Berta
Domènech
Verena
Maier-Kiener
Diletta
Giuntini
Creep
Nanocomposites
Nanoindentation
Supercrystals
Supercrystalline nanocomposites (SCNCs) are inorganic-organic hybrid materials with a unique periodic nanostructure, and thus they have been gaining growing attention for their intriguing functional properties and parallelisms with hierarchical biomaterials. Their mechanical behavior remains, however, poorly understood, even though its understanding and control are important to allow SCNCs’ implementation into devices. An important aspect that has not been tackled yet is their time-dependent deformation behavior, which is nevertheless expected to play an important role in materials containing such a distribution of organic phase. Hereby, we report on the creep of ceramic-organic SCNCs with varying degrees of organic crosslinking, as assessed via nanoindentation. Creep strains and their partial recoverability are observed, hinting at the co-presence of viscoelasticity and viscoplasticity, and a clear effect of crosslinking in decreasing the overall material deformability emerges. We rationalize our experimental observations with the analysis of stress exponent and activation volume, resulting in a power-law breakdown behavior and governing deformation mechanisms occurring at the organic sub-nm interfaces scale, as rearrangement of organic ligands. The set of results is reinforced by the evaluation of the strain rate sensitivity via strain rate jump tests, and the assessment of the effect of oscillations during continuous stiffness measurement mode.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-07
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0221356
Materials and Design 231: 112000 (2023-07)
eng
1
3381d9c0f3c25255acfec00ee1f4220c
https://tore.tuhh.de/bitstreams/5104b7c0-69d0-4509-9db7-54f45fa2fdf1/download
http://hdl.handle.net/11420/15375
10.15480/882.5165
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/16842018-06-13T10:57:08Zcom_11420_1col_11420_2
Three-dimensional Aerographite-GaN hybrid networks: single step fabrication of porous and mechanically flexible materials for multifunctional applications
Arnim
Schuchardt
Tudor
Braniste
Yogendra Kumar
Mishra
Mao
Deng
Matthias
Mecklenburg
Marion A.
Stevens-Kalceff
Simion
Raevschi
Karl
Schulte
Lorenz
Kienle
Rainer
Adelung
Ion
Tiginyanu
organic-inorganic
nanostructures
mechanical and structural
properties and devices
self-assembly
620
Three dimensional (3D) elastic hybrid networks built from interconnected nano- and microstructure building units, in the form of semiconducting-carbonaceous materials, are potential candidates for
advanced technological applications. However, fabrication of these 3D hybrid networks by simple and versatile methods is a challenging task due to the involvement of complex and multiple synthesis processes.
In this paper, we demonstrate the growth of Aerographite-GaN 3D hybrid networks using ultralight and extremely porous carbon based Aerographite material as templates by a single step hydride vapor phase epitaxy process. The GaN nano- and microstructures grow on the surface of Aerographite tubes and follow the network architecture of the Aerographite template without agglomeration. The synthesized 3D networks are integrated with the properties from both, i.e., nanoscale GaN structures and Aerographite in the form of flexible and semiconducting composites which could be exploited as next generation materials for electronic, photonic, and sensors applications.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-03-06
Article
Text
publishedVersion
urn:nbn:de:gbv:830-88221341
Scientific Reports (5): Art.-Nr. 8839 (2015)
eng
1
04d503b5a3f3c88697a152f1b0661736
https://tore.tuhh.de/bitstreams/c73b7dfb-969e-421b-8f08-03d73a152944/download
http://tubdok.tub.tuhh.de/handle/11420/1684
10.15480/882.1681
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/441702023-11-22T13:43:20Zcom_11420_1col_11420_2
Beyond compression ratio : a throughput analysis of memory compression techniques for GPUs
Manuel
Renz
Sohan
Lal
GPUs
memory compression
throughput
bandwidth
off-chip memory
Memory compression is increasingly used as a technique to synthetically increase the off-chip memory bandwidth of GPUs by transferring data in a compressed format between on-chip and off-chip memory. The increased memory bandwidth results in a speedup for the bandwidth-limited applications. State-of-the-art memory compression techniques often target a high compression ratio, however, a high compression ratio alone is not sufficient for full integration into throughput-oriented GPUs. To deploy a memory compression technique, the throughput of the compression technique has to keep up with the bandwidth of the off-chip memory of GPUs. Unfortunately, the throughput of the state-of-the-art memory compression techniques is often not discussed in detail and mostly the emphasis is only placed on the achieved compression ratio. In this work, we present a throughput analysis of several state-of-the-art memory compression techniques and study their capability to match modern GPUs memory bandwidth. We implement several memory compression techniques in hardware and synthesize designs using Synopsys Design Compiler with 14 nm ASIC libraries to analyze the throughput, area, and power consumption. Our analysis shows that simple compression techniques that have moderate compression ratios but higher throughput are more suitable for practical implementation in GPUs considering the area (up to 11.8× lower), power consumption (up to 7× lower), and the complexity of implementation.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023
ConferencePaper
Text
publishedVersion
10.15480/882.8824
41st IEEE International Conference on Computer Design (ICCD 2023)
eng
1
f3bdf6c19c3eb5f669468b776f661242
https://tore.tuhh.de/bitstreams/c29e942f-3970-47d5-8c61-c80bb28226c8/download
https://hdl.handle.net/11420/44170
10.15480/882.8824
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/455862024-02-13T09:50:52Zcom_11420_1col_11420_2
Rye bran as a component in the diets of lactating sows : effects on sow and piglet performance
Christian
Homann
Volker
Wilke
Isabell
Eckey
Bussarakam
Chuppava
Martin
Kaltschmitt
Andreas
Zimmermann
Christian
Visscher
by-products
nutrition
performance
piglets
pigs
rye
rye bran
sows
From a cost and sustainability perspective, the use of by-products such as rye bran in sow diets is of particular interest. Rye bran has valuable ingredients that have potential benefits for the gut health of sows. The aim of this study was to investigate the effects of including 15% rye bran in the sows’ feed on the performance of sows and piglets. The feeding started one week before the farrowing date and ended at weaning. Performance was evaluated by measuring sow (n = 175) and piglet body weight (n = 1372) and sows’ backfat thickness (n = 80). These data were additionally used to calculate the colostrum intake of the suckling piglets and the sows’ milk production. It was found that there were no differences in the performance parameters between the experimental and control groups. However, this study showed that the piglets with light birth weight (LBW (<1000 g)) and medium birth weight (MBW (1000-1500 g) consumed more colostrum when the sows were fed rye bran (LBW: C/R 203.0 +/- 39.2 g/214.3 +/- 35.9 g; MBW: 291.3 +/- 39.0 g/298.5 +/- 36.4 g). It can be concluded that including 15% rye bran in the feed of lactating sows has no obvious negative effects on the performance of sows and piglets. Further studies are needed to evaluate the possible positive effects of rye bran.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2024-01-24
Article
Text
publishedVersion
10.15480/882.9167
Animals 14 (3): 380 (2024)
eng
1
c9c2f6984f86fe17cb2ed99859ef8f67
https://tore.tuhh.de/bitstreams/4cce4f00-82fe-4bb4-b1f6-719685a6cf02/download
https://hdl.handle.net/11420/45586
10.15480/882.9167
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/451452024-01-18T08:42:14Zcom_11420_1col_11420_2
Benchmarking for the indoor localization of autonomous mobile robots in intralogistics
Markus
Knitt
Yousef
Elgouhary
Jakob
Schyga
Hendrik
Rose
Jochen
Kreutzfeldt
Benchmarking
Intralogistics
Intralogistik
Localization
Lokalisierung
Robotics
Robotik
This paper introduces a novel approach to benchmarking Indoor Localization Systems (ILS) for mobile robots in warehouse and manufacturing contexts. The study focuses on diverse localization technologies commonly used in mobile robotics and implements transparent and comparable performance metrics, an automated experimental procedure, as well as an intuitive performance visualization approach. Experiments were conducted using a custom-built robot equipped with various sensors, including LiDAR, Ultra-Wideband (UWB), and vision systems. A process for systematically analyzing the impact of environmental factors such as lighting, reflectivity, and obstacles on localization performance is proposed. The results provide insights into system robustness and accuracy under different conditions. The study enables more efficient experimental analysis of sensor fusion and optimization strategies for achieving optimal performance and offers a workflow to efficiently investigate sensor fusion concepts using real data.
In diesem Beitrag wird ein neuartiger Ansatz zum Benchmarking von Indoor-Lokalisierungssystemen (ILS) für mobile Roboter in Lager- und Produktion-sumgebungen vorgestellt. Die Studie konzentriert sich auf verschiedene Lokalisierungstechnologien, die üblicherweise in der mobilen Robotik verwendet werden, und implementiert transparente und vergleichbare Leistungsmetriken, ein automatisiertes Experimentierverfahren und einen intuitiven Ansatz zur Leistungsvisualisierung. Die Experimente wurden mit einem speziell angefertigten Roboter durchgeführt, der mit verschiedenen Sensoren ausgestattet war, darunter LiDAR-, UWB- und Vision-Systeme. Es wird eine Methode vorgeschlagen, um die Auswirkungen von Umgebungsfaktoren wie Beleuchtung, Reflektivität und Hindernisse auf die Lokalisierungsleistung systematisch zu analysieren. Die Ergebnisse geben Aufschluss über die Robustheit und Genauigkeit des Systems unter verschiedenen Bedingungen. Die Studie ermöglicht eine effizientere experimentelle Analyse von Sensorfusions- und Optimierungsstrategien, um eine optimale Leistung zu erzielen, und bietet einen Arbeitsablauf für die effiziente Untersuchung von Sensorfusionskonzepten anhand realer Daten.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-09-26
ConferencePaper
Text
publishedVersion
10.15480/882.9062
Logistics Journal : Proceedings 2023: 5809 (2023)
eng
1
6efd57daeb5206b48eecc418f7c9d538
https://tore.tuhh.de/bitstreams/88bc2240-615b-4ade-a32d-7760891cab75/download
https://hdl.handle.net/11420/45145
10.15480/882.9062
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/10272011-10-17T08:03:32Zcom_11420_1col_11420_2
Die Wirkung von Ultraschall auf die mikrobiologische Diversität und Abbauleistung eines biologischen Reaktors zur Abwasserreinigung
The effect of ultrasound on the microbial diversity and the purification rate of a biological reactor for wastewater treatment
Izabela
Banduch
Biomasse
Belebtschlamm
Aktivität
Abwasserreinigung
Ultraschall
biomass
activated sludge
activity
wastewater treatment
ultrasound
620
Seit der Etablierung des Belebtschlammverfahens im Alltag ist man auf der Suche nach neuen Lösungen um den biologischen Prozess der Abwasserreinigung nachhaltig und wirtschaftlich zu optimieren. Der in dieser Arbeit untersuchte Einsatz des Ultraschalls zeigte sich als geeignete Technik. Nach der Ultraschalleinwirkung werden optimale morphologische Veränderungen in der Flockenstruktur erreicht, infolge dessen wird die mikrobielle Aktivität im Belebtschlamm gesteigert. Darüber hinaus durch Auflösung eines Teils des Belebtschlammes wird eine Verringerung der überschüssigen Biomasse beobachtet.
Since the establishment of the activited sludge process in everyday life, we are constantly in search of new solutions to optimize the biologic process of sewage purification in a sustinable and economic way. The application of ultrasonic sound, which is investigated in this thesis, manifests itself as a qualified technique. After the influence of ultrasound an optimal morphological modification in the flake structure is achieved and the microbial activity in the activated sludge is enhaced. Furthermore, we can observe a reduction of the excess biomass by pro-rata dissolution of the activated sludge.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011-08-18
2011
Other
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-11202
ger
1
ac19574ce0f25a0b9310db20e288d889
https://tore.tuhh.de/bitstreams/85dbe958-ccf6-4fc8-9a1c-ddafdfeecedd/download
http://tubdok.tub.tuhh.de/handle/11420/1027
10.15480/882.1025
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/19342019-01-07T11:31:30Zcom_11420_1col_11420_2
Dealloying-based interpenetrating-phase nanocomposites matching the elastic behavior of human bone
Ilya
Okulov
Jörg
Weissmüller
Jürgen
Markmann
610
530
The long-term performance of orthopedic implants depends crucially on a close match between the mechanical behavior of bone and of the implant material. Yet, the present man-made materials with the required biocompatibility and strength are substantially stiffer than bone. This mismatch results in stress shielding, which can lead to the loss of bone mass and may even lead to a revision surgery. Here we report a new materials design strategy towards metal-polymer composites that are based on constituents with established biocompatibility and that can be matched to bone. Ti-based nanoporous alloys, prepared by liquid-metal dealloying, are infiltrated with epoxy to form interpenetrating-phase nanocomposites. At up to 260 MPa, their yield strength is technologically interesting for a deformable light-weight material. More importantly, Young's modulus can be adjusted between 4.4 and 24 GPa, which affords matching to bone. As another parallel to bone, the strength of the composite materials is strain-rate dependent. These findings suggest that the novel composite materials may provide the basis for promising future implant materials.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2017-02-02
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.024827
Scientific reports 1 (7): 20 (2017)
eng
1
76ec246aae79163d5b0edc5b2507a825
https://tore.tuhh.de/bitstreams/6018a20f-6a21-4d4a-acb3-1e54628be4d7/download
http://tubdok.tub.tuhh.de/handle/11420/1934
10.15480/882.1931
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/153562023-06-07T09:24:42Zcom_11420_1col_11420_2
Status Quo und Potenzial handlungsorientierter Hochschuldidaktik mit Hilfe des Lernmanagementsystems : „ILIAS“ am Beispiel der beruflichen Lehrerbildung an der Leibniz Universität Hannover
Johannes
Schäfers
Lernmanagementsystem
Lehrkräftebildung
Hochschuldidaktik
Innerhalb des Bildungssektors geht der Trend seit Jahrzehnten, wie in vielen anderen gesellschaftlichen Bereichen, hin zur Digitalisierung von ganzen Systemen, Prozessen und Abhandlungen. Einen besonders großen Ansprung dieses Digitalisierungstrends kann seit der Erfindung und Einführung des Internets in den 1970er Jahren sowie des „World Wide Web“ und deren Weiterentwicklung zur Jahrtausendwende beobachtet werden. Durch die digitale Vernetzung der Gesellschaft und die damit gestiegenen Möglichkeiten des WWW stehen die Menschen heutzutage vor deutlich veränderten Herausforderungen als noch im 20. Jahrhundert. Ein deutliches Umdenken und die damit verbundenen Veränderungen in allen gesellschaftlichen Bereichen, nicht nur in Deutschland, sind besonders seit Anfang 2020 zu beobachten. Weltweit kommt es, aufgrund der „Covid19-Pandemie“ (vgl. Robert Koch-Institut 2020), zu bedrohlichen und teilweise kritischen Lebensumständen. Ein neuartiges Virus ist in der Folge international für deutlich über 300.000 Todesfälle (vgl. John-Hopkins-Universität 2020) verantwortlich. Um den öffentlichen Ansprüchen und Forderungen trotz der Krise gerecht zu werden sowie in Bezug auf die Weiterführung des Studiums an Hochschulen und Universitäten besonders den Empfehlungen wie u. a. des Niedersächsischen Ministeriums für Wissenschaft und Kultur (vgl. MWK 2020) zu befolgen, findet in allen Lebensbereichen eine beispiellose Zunahme an Digitalisierung statt. Von diesen Auswirkungen ist auch besonders der Bildungssektor betroffen. Durch die Schließung der öffentlichen Bildungseinrichtungen, wie u. a. auch die Leibniz Universität Hannover, werden ab dem Sommersemester 2020 Präsenzveranstaltungen durch Fernlehrveranstaltungen bzw. die Online-Lehre ersetzt. Alltägliche und sonst gängige Lehr-Lernsituationen müssen digital ersetzt oder zumindest digital angereichert werden, was es für eine bestimmte Dauer – wie der Covid19-Pandemie – einfacher machen kann den Lernenden auch in diesen Zeiten eine zeit- und ortsunabhängig Lernstoffvermittlung zu gewährleisten. In dieser Arbeit werden die Grundlagen des Status Quo des Bildungssektors beschrieben, die sich durch die Digitalisierung und besonders der Einführung von „Lernmanagementsystemen“ in den letzten Jahren erschlossen haben. Im Fokus steht dabei besonders das Potenzial, dass sich aus der Herangehensweise der „handlungsorientierten Hochschuldidaktik“ mit Hilfe der Lernmanagementsysteme verzeichnen lässt. So stellt sich die Frage des Mehrwerts von Lernmanagementsystemen zu konventionellen Lehr-Lernformen, insbesondere in Zeiten wie der COVID19-Pandemie. Außerdem wird das Potenzial der digitalen Unterstützung und hierbei besonders des Lernmanagementsystems „ILIAS“ in der beruflichen Lehrerbildung an der Leibniz Universität Hannover ergründet. Unter anderem durch die dabei eingesetzte Forschungsmethodik der Expertenund Fachinterviews wird im Kern dieser Arbeit schließlich eine abschätzende Annahme über die Entwicklungen des momentanen digitalen Wandels bzw. der zukünftigen Weiterentwicklung der Lehrerbildung an der LUH gebildet.
Within the education sector, the trend for decades, as in many other areas of society, has been towards the digitisation of entire systems, processes and treatises. A particularly large push of this digitisation trend can be observed since the invention and introduction of the internet in the 1970s as well as the "World Wide Web" and its further development at the turn of the millennium. Due to the digital networking of society and the resulting increase in the possibilities of the WWW, people today face significantly different challenges than they did in the 20th century. A clear rethinking and the associated changes in all areas of society, not only in Germany, can be observed especially since the beginning of 2020. Worldwide, due to the "Covid19 pandemic" (cf. Robert Koch Institute 2020), threatening and in part critical living conditions are occurring. As a result, a novel virus is responsible for well over 300,000 deaths internationally (cf. John Hopkins University 2020). In order to meet public demands and requirements in spite of the crisis, as well as to follow the recommendations of, among others, the Lower Saxony Ministry of Science and Culture (cf. MWK 2020) with regard to the continuation of studies at colleges and universities in particular, an unprecedented increase in digitalisation is taking place in all areas of life. The education sector is also particularly affected by these effects. Due to the closure of public educational institutions, including Leibniz Universität Hannover, face-to-face courses will be replaced by distance learning or online teaching from the summer semester of 2020. Everyday and otherwise common teaching-learning situations will have to be digitally replaced or at least digitally enriched, which can make it easier for a certain duration - such as the Covid19 pandemic - to guarantee learners a time- and location-independent delivery of learning material. This paper describes the basics of the status quo of the education sector, which have been opened up by digitalisation and especially the introduction of "learning management systems" in recent years. The focus is particularly on the potential that can be registered from the approach of "action-oriented higher education didactics" with the help of learning management systems. This raises the question of the added value of learning management systems to conventional forms of teaching-learning, especially in times such as the COVID19 pandemic. In addition, the potential of digital support, and in particular of the learning management system "ILIAS", in vocational teacher training at Leibniz Universität Hannover is being explored. Among other things, the research methodology of expert and subject interviews used for this purpose will finally form the core of this work and provide an estimative assumption about the developments of the currently used learning management system.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-06-11
2021-03-26
Other
Text
publishedVersion
urn:nbn:de:gbv:830-882.0220759
Leibniz Universität Hannover (2021)
ger
1
96df400c6aa83845d7d798bd9f7ee07e
https://tore.tuhh.de/bitstreams/3c94dcea-98ed-4ff3-8f97-c5918c7a828b/download
http://hdl.handle.net/11420/15356
10.15480/882.5153
https://creativecommons.org/licenses/by-sa/3.0/
oai:tore.tuhh.de:11420/146912023-01-30T09:04:15Zcom_11420_1col_11420_2
Wet-environment Evapotranspiration and Precipitation Standardized Index (WEPSI) for drought assessment and monitoring
Ali
Khoshnazar
Gerald A.
Corzo Perez
Vitali
Diaz
Milad
Aminzadeh
Roberto Adolfo
Cerón Pineda
drought index
Lempa River basin
mutual information
WEAP
WEPSI
wet-environment evapotranspiration
Drought assessment and monitoring are essential for its proper management. Drought indices play a fundamental role in this. This research introduces the Wet-environment Evapotranspiration and Precipitation Standardized Index (WEPSI) for drought assessment and monitoring. WEPSI incorporates water supply and demand into the drought index calculation. WEPSI considers precipitation (P) for water supply and wet-environment evapotranspiration (ETw) for water demand. We use an asymmetric complementary relationship to calculate ETw with actual (ETa) and potential evapotranspiration (ETp). WEPSI is tested in the transboundary Lempa River basin in the Central American dry corridor. ETw is estimated based on evapotranspiration data calculated using the Water Evaluation And Planning (WEAP) system hydrological model. To investigate the performance of WEPSI, we compare it with two well-known meteorological indices (Standardized Precipitation Index and Standardized Precipitation Evapotranspiration Index), together with a hydrological index (Standardized Runoff Index), in terms of statistical metrics and mutual information (MI). We compare WEPSI-derived droughts and historical information, including crop production, cereal yield, and the Oceanic Nino Index (ONI). Results show WEPSI has the highest correlation and MI, and the lowest deviation. It is consistent with the records of the crop production index, cereal yield, and the ONI. Findings show that WEPSI can be used for agricultural drought assessments.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-10-27
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0210085
Hydrology Research 53 (11): 1393-1413 (2022-11-01)
eng
1
62f88a916662ad4c8ced40db4b262764
https://tore.tuhh.de/bitstreams/1d8e813b-85a6-465c-99c1-8e7c14c1470f/download
http://hdl.handle.net/11420/14691
10.15480/882.4901
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/17522018-09-25T11:02:08Zcom_11420_1col_11420_2
Energy efficient operation of variable speed submersible pumps : simulation of a ground water well field
Alexander
Sperlich
Dino
Pfeiffer
Jens
Burgschweiger
Enrique
Campbell
Marcus
Beck
Regina
Gnirß
Mathias
Ernst
EPANET
ground water
well field
genetic algorithm
submersible pumps
variable speed
permanent magnet synchronous motors
620
Due to their lower energy consumption, permanent magnet synchronous motor (PMSM) submersible pumps have been introduced in ground water well field operation. Besides direct savings of energy, the introduction of PMSM pumps together with the required variable frequency converters offers new operational scenarios to meet the seasonally varying water demand. In this work, potential energy savings of variable speed submersible pumps were investigated. A ground water well field consisting of 13 wells and their transport pipes was modeled in the hydraulic modeling software EPANET 2.0. Using MS visual basic for applications, EPANET was coupled with MS Excel and a genetic algorithm to identify the most energy efficient combination of pump speeds. For the simulated well field, the total specific energy demand required for pumping was significantly lower in partial load operation as compared to nominal pump speed operation. For low and moderate flow scenarios, energy savings in the range of 20% compared to nominal speed operation can be achieved. These findings were confirmed by a monitoring campaign in the well field. Combining hydraulic simulation and optimization using genetic algorithms, the best efficiency scenario for operation of ground water well fields can be found.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-09-15
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.05844
Water 10 (9): 1255 (2018)
eng
1
5b5901a7272031c3683118c20ac59add
https://tore.tuhh.de/bitstreams/dbec3750-7791-49e3-8eba-8b783e5a1103/download
http://tubdok.tub.tuhh.de/handle/11420/1752
10.15480/882.1749
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/24782019-04-25T10:49:10Zcom_11420_1col_11420_2
LPV control of a gyroscope with inverted pendulum attachment
Patrick J. W.
Koelewijn
Pablo S. G.
Cisneros
Herbert
Werner
Roland
Toth
A linear parameter varying (LPV) optimal L2 gain controller is designed with mixed-sensitivity shaping to stabilize an inverted pendulum attached to a control moment gyroscope (CMG). Swing-up of the pendulum is achieved by a start-up LPV controller for which the reference is designed by an energy regulator. The LPV performance controller is enabled as soon as the pendulum enters into its operating range of ±0.15 rad. Based on both simulation and experimental results, it is demonstrated that stabilization of the pendulum is achieved for varying gimbal angles and rotational speed of the flywheel.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-11-23
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.032636
IFAC-PapersOnLine 26 (51): 49-54 (2018)
eng
1
1dbbee8d37a4a316d78a291637ffa4f0
https://tore.tuhh.de/bitstreams/27ada8b1-27ca-4f29-b8d7-1eacbb67d5cc/download
http://hdl.handle.net/11420/2478
10.15480/882.3471
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/7852010-04-19T11:25:32Zcom_11420_1col_11420_2
Spielen(d) lernen mit DISCUS : Förderung von Informationskompetenz mit einem E-Learning-Projekt der Universitätsbibliothek der TU Hamburg-Harburg
Playfully learning to play with DISCUS : promotion of information literacy with an e-learning project of the TUHH university library
Thomas
Hapke
Oliver
Marahrens
information literacy
e-learning
020
Vorstellung des Online-Tutorials DISCUS (Developing Information Skills & Competence for University Students) zur Förderung von Informationskompetenz. DISCUS ist ein eLearning-Projekt der Universitätsbibliothek der TU Hamburg-Harburg und soll die Nutzung elektronischer Fachinformation optimieren und dadurch erfolgreichere Forschungsergebnisse und Studienabschlüsse ermöglichen.
Description of the online tutorial DISCUS (Developing Information Skills & Competence for University Students) for promoting information literacy. DISCUS is an e-learning projekt of the TUHH university library and tries to optimise the use of electronical information systems and to facilitate more successful research results and final degrees in studying.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2004
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-8699
Information Professional 2011 : Strategien -Allianzen - Netzwerke. 26. Online-Tagung der DGI. Frankfurt am Main vom 15. bis 17. Juni 2004. Proceedings / hrsg. von Marlies Ockenfeld. Frankfurt am Main: DGI, 2004. Hier: S. 203-217.
ger
1
47dbe893103bb30f9aa7cf1377acf010
https://tore.tuhh.de/bitstreams/ddba1ceb-4b16-4e62-8ca7-536f6ff603d9/download
http://tubdok.tub.tuhh.de/handle/11420/785
10.15480/882.783
http://doku.b.tu-harburg.de/doku/lic_mit_pod.php
oai:tore.tuhh.de:11420/107732021-11-04T11:53:03Zcom_11420_1col_11420_2
Feeless micropayments as drivers for new business models : two exemplary application cases
Marvin
Klein
Christian
Stummer
cryptocurrency
micropayments
business models
subscription model
self-generated data
Upcoming cryptocurrency approaches claim to enable feeless micropayments. Assuming that this promise will be kept, this is likely to give rise to new business models that entail transactions worth fractions of a cent. In this mini review, we describe two exemplary application cases and outline the associated research activities for each. The first case considers subscription models in consumer markets for which feeless micropayments might be used to expand and, thus, enrich the range of plans by offering shorter subscription times. The second case is concerned with prosumers who might be willing to sell self-generated data (e.g., data generated through their smart meters).
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021-03-18
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0156637
Frontiers in blockchain 4 : 641508 (2021)
eng
1
dc912111b14917fa092fd71fb2f88d08
https://tore.tuhh.de/bitstreams/6ad08515-17d5-49a5-906d-62f3a009c9a1/download
http://hdl.handle.net/11420/10773
10.15480/882.3868
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/92022021-04-07T06:31:27Zcom_11420_1col_11420_2
BIM-based description of intelligent transportation systems for roads
Mahsa
Mirboland
Kay
Smarsly
intelligent transportation systems
semantic modeling
Building Information Modeling (BIM)
Industry Foundation Classes (IFC)
vehicular cloud
EXPRESS
STEP
Intelligent transportation systems (ITS) provide safer, greener, and more convenient mobility, while reducing the impact on the environment. In recent years, simulation platforms have been employed to study ITS applications, mostly focusing on traffic-related simulations. Despite several research studies on ITS applications and simulation platforms, formal semantic descriptions of intelligent transportation systems have not been addressed yet. In this paper, a semantic model describing intelligent transportation systems for roads is proposed. The semantic model is devised to provide a basis for designing ITS simulation platforms. Building upon the semantic model, an extension to an open building information modeling (BIM) standard, i.e., the Industry Foundation Classes (IFC) schema, is presented. The IFC schema extension is verified and validated using a BIM-based simulation scenario of ITS for roads. It is shown that the proposed IFC-compliant description of ITS for roads provides a formal basis for generating BIM-based simulations and hence facilitates ITS infrastructure modeling in BIM projects. It is concluded that the present work represents a cornerstone for designing BIM-based ITS simulation platforms. In future endeavors, potential standardization and formalization efforts may be discussed.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021-03-23
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0130614
Infrastructures 6 (4): 51 (2021-03-23)
eng
1
74ef44cf6002b10f38813d2a257360e3
https://tore.tuhh.de/bitstreams/93e4b30d-fc8e-406a-930f-490c49680700/download
http://hdl.handle.net/11420/9202
10.15480/882.3414
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/426022023-08-10T05:46:39Zcom_11420_1col_11420_2
Primäre Emissionsminderungsmaßnahmen von Hackschnitzelfeuerungen insbesondere zur Reduzierung von Feinstaubemissionen (AdHock)
Joachim
Gerth
Martin
Kaltschmitt
Isabel
Höfer
Daniel
Harms
Christian
Gollmer
Seit der Jahrtausendwende stagniert der Rückgang der Feinstaubemissionen in Deutschland zusehends. Als eine Konsequenz dieser Entwicklung müssen seit dem Inkrafttreten der 2. Stufe der 1. BImSchV im Januar 2015 die Feinstaubemissionen neuer Biomassefeuerungsanlagen deutlich reduziert werden. Damit besteht hier Forschungsbedarf im Hinblick auf die Entwicklung effizienter und kostengünstiger Primär- und Sekundärmaßnahmen; Das Ziel dieses Forschungsvorhabens "AdHock" ist es, primäre bzw. brennstoffseitige Maßnahmen zur Minderung der Feinstaub- und ggf. der Stickstoffoxidemissionen bei der Verbrennung von Hackschnitzeln in handelsüblichen Feuerungsanlagen zu identifizieren, zu untersuchen und zu bewerten. Dazu sollen zunächst ausgehend von Brennstoffanalysen und den bisher bekannten Schadstoffbildungsmechanismen Zuschlagstoffe identifiziert werden, mit denen primär der Fest-Dampf- Partikel-Austragspfad unterdrückt werden kann und ggf. die NOx-Emissionen vermindert werden können; d. h., diese Zuschlagstoffe sollen aerosolbildende Elemente wie Kalium, Chlor oder Schwefel vermehrt in die (Rost-)Asche einbinden ohne gleichzeitig die NOX-Emissionen zu erhöhen bzw. im Maximalfall diese zusätzlich zu reduzieren. Die Bearbeitung des Projektes soll innerhalb von zwei Jahren erfolgen. Dabei sollen die chemischen Vorgänge der Asche- und Feinstaubbildung identifiziert und verstanden werden und zudem Zuschlagstoffe zu deren Beeinflussung festgelegt werden. Zur Identifizierung der Zuschlagstoffe wird eine Bewertungsmatrix entwickelt. Insgesamt wird das Projekt in 5 Arbeitspakete eingeteilt. Während der Projektlaufzeit soll auf zwei Meilensteine drauf hin gearbeitet werden, sodass die Einhaltung des zeitlichen Rahmens erleichtert werden soll.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-09
Report
Text
publishedVersion
10.15480/882.8161
Fachagentur Nachwachsende Rohstoffe e.V. : 1-80 (2019-09)
ger
1
7c3152e0ebfc47b612fb261ab1a8eac9
https://tore.tuhh.de/bitstreams/93934c9b-8329-42a2-88b3-3bd7ccc26fae/download
https://hdl.handle.net/11420/42602
10.15480/882.8161
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/83702021-01-19T09:24:53Zcom_11420_1col_11420_2
Entwicklung eines Gesamtmodells der Arbeitsproduktivität und der logistischen Zielgrößen
Robert
Glöckner
Arbeitsproduktivität
Logistische Zielgrößen
Modellierung
Die Arbeitsproduktivität ist für produzierende Unternehmen von großer Bedeutung. Diese Arbeit beschreibt ein vollständiges Modell der Arbeitsproduktivität. Es soll Unternehmen dabei helfen, die Einflussgrößen der Arbeitsproduktivität und deren Zusammenwirken besser zu verstehen, um so gezielt Verbesserungsmaßnahmen ableiten zu können. Das Modell beschreibt die Einflüsse auf die Arbeitsproduktivität mit Hilfe von Stell- und Regelgrößen und formuliert zugehörige Aufgaben zur Beeinflussung der Stellgrößen. Ein detailliertes Kopplungsmodell beschreibt zudem detailliert Wechselwirkungen zwischen der Arbeitsproduktivität und den logistischen Zielgrößen.
Labor productivity is of great importance for manufacturing companies. This work presents a comprehensive labor productivity model. Its goal is to help manufacturing companies to under-stand the relevant influencing factors of labor productivity and their interdependencies. The described model uses control and actuating variables to describe labor productivities influenc-ing factors. It defines tasks to address the control variables. By this the model supports the purposeful improvement of labor productivity. In addition this work presents a coupling model to describe the interdependencies of labor productivity and logistic objectives.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-11-03
2020
Other
Text
publishedVersion
urn:nbn:de:gbv:830-882.0120199
Wissen schafft Innovation (2020)
ger
1
a221f060423c90d32f8f3321d1b502bd
https://tore.tuhh.de/bitstreams/46b65acc-bde4-4ab7-858b-ae7f908a5e85/download
http://hdl.handle.net/11420/8370
10.15480/882.3231
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/12582015-10-29T12:54:05Zcom_11420_1col_11420_2
TUHH Spektrum Oktober 2015
000
620
Campushelden: Studieren und sich für andere engagieren - Roboter unter Wasser im Einsatz gegen Gefahrenstoffe - Reifeprüfung: Wie Erstsemester den Start am besten meistern - Ausgepackt! Eine Aktion der Photo-AG
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-10
Other
Text
publishedVersion
urn:nbn:de:gbv:830-88213233
ger
1
dcc6044703fd633e7a0c5b3a8ec15a55
https://tore.tuhh.de/bitstreams/119c706d-2e39-4342-9f68-85fc4ecf9fd4/download
http://tubdok.tub.tuhh.de/handle/11420/1258
10.15480/882.1255
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/37542019-11-13T07:27:38Zcom_11420_1col_11420_2
New concepts for cybersecurity in port communication networks
Nils
Meyer-Larsen
Rainer
Müller
Katja
Zedel
Port communication network
Maritime cybersecurity
Port community system
Maritime blockchain
Purpose: Seaports are to a growing extent controlled by IT systems. Smooth information exchange is crucial for business. Downtimes give rise to substantial financial losses and supply bottlenecks, due to the interconnections in a complex alliance of port stakeholders‘ systems. Hence, Cyber security in an important aspect in Port Communication Systems. Methodology: The project SecProPort will develop a holistic IT security architecture for port communication networks, which will support the security requirements of the stakeholders‘ operating procedures, protect them against sabotage, and prevent third parties from illicitly gathering sensitive data or getting unauthorized access to the communications network. Findings: The desired architecture is to be implemented by first analyzing typical attack scenarios targeted at the data processed in the port communication alliance. The next step entails designing the actual security architecture for the alliance and installing a prototype in collaboration with the application partners. Originality: SecProPort aims at a holistic approach with respect to secure port communications networks, rather than addressing individual stakeholders. The architecture will also provide resilience measures for minimizing the impact on other actors in the alliance in case of an incident, and returning to normal operation in a controlled manner.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-09-26
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.054507
Hamburg International Conference of Logistics (HICL) 27: 543-558 (2019)
eng
1
2378a25f676cef17cdff4ab011e86a46
https://tore.tuhh.de/bitstreams/1df52926-4394-468c-8aa0-92af1c76787d/download
http://hdl.handle.net/11420/3754
10.15480/882.2483
https://creativecommons.org/licenses/by-sa/4.0/
oai:tore.tuhh.de:11420/141522022-11-28T08:53:12Zcom_11420_1col_11420_2
Optimising bioreactor processes with in-situ product removal using mathematical programming: a case study for propionate production
Lucas,
Hauwaert
van der
Alberte
Regueira
Ludwig
Selder
An-Ping
Zeng
Miguel
Mauricio-Iglesias
Biotechnology
Design under uncertainty
Downstream processing
Kinetic modelling
Operational design
Product inhibition
Designing and operating bioreactors with in-situ product removal (ISPR) can be challenging, particularly in discontinuous systems, where the ISPR and substrate feeding need to be effectively scheduled. Mathematical models can help assess different scheduling regimes in the fermentation medium and provide a means to optimise the process. Focusing on a propionate production case study, a model of a co-culture batch fermentation with electrodialysis (the ISPR system), was developed. Using this model, the product yield and/or the productivity were maximised by 1) single objective optimisation maximising the product yield (0.49 gpropionate /gglucose) or productivity (0.75 gpropionate/L/h), 2) multi objective optimisation to pursue trade-off solutions between the yield and productivity and 3) a stochastic optimisation maximising the productivity robustly (0.64 gpropionate/L/h) to account for uncertainties associated to the model parameters. With this contribution it is demonstrated that, through mathematical models, ISPR can be implemented and adapted to the user's objectives.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-11-06
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0203466
Computers and Chemical Engineering 168: 108059 (2022-12-01)
eng
1
f00fc53c93df2a46844819ed6f8a417f
https://tore.tuhh.de/bitstreams/b4e167d2-0bac-442a-8762-c8460ee6b896/download
http://hdl.handle.net/11420/14152
10.15480/882.4753
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/542005-12-13T15:27:28Zcom_11420_1col_11420_2
TUHH Spektrum September 2004
TUHH Spektrum September 2004
600
620
000
Windenergieanlage, Stahl für Fährschiffe, Hochwasserschutz, Logistik
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2004-09
Other
Text
publishedVersion
urn:nbn:de:gbv:830-opus-1077
ger
1
b6b8e82da8bd3c8d2e73a43cab53cf00
https://tore.tuhh.de/bitstreams/e45f181f-da7c-4f43-ba50-26e3a1e0ac10/download
http://tubdok.tub.tuhh.de/handle/11420/54
10.15480/882.52
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/4712009-02-16T09:46:00Zcom_11420_1col_11420_2
Über den Reibungswiderstand der Platte
Karl
Wieghardt
620
Über den Reibungswiderstand der Platte
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1973
Report
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-5449
ger
1
f77ded94ca0ce353b0ae13f9f4bbea46
https://tore.tuhh.de/bitstreams/1142488d-c4a6-417c-b65e-11f1d27c7e0f/download
http://tubdok.tub.tuhh.de/handle/11420/471
10.15480/882.469
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/95452021-05-18T03:27:40Zcom_11420_1col_11420_2
Partial pole placement using static output feedback
Manuel
Pusch
Julian
Theis
Daniel
Ossmann
Blending of inputs and outputs
Modal control
Multivariable systems
Pole assignment
Static feedback control
For many dynamical systems it is required to specifically shift individual poles, especially when these poles are lightly damped or even unstable. To achieve that, a preferably large number of effectors and measurements are installed leading to multivariable control problems. In this paper, a novel control approach is presented for placing either a single pole or a conjugate complex pole pair at a predefined location using rank-one static output feedback. Rank-one feedback can be interpreted as blending inputs and outputs to define a single input and single output loop with a desirable root locus along which the pole is moved. The corresponding controller synthesis is reduced to an unconstrained optimization problem in a single variable that aims at minimizing the feedback gain. Although the approach is derived for a single pole or conjugate complex pole pair, it is easily extended to multiple poles. To this end, a repeated design and superposition of rank-one feedback gains is proposed. It is further shown how residual system dynamics as well as subsequently designed gains can be efficiently decoupled from each other in order to avoid undesired interactions and spillover effects. The effectiveness of the proposed control approach is demonstrated by means of a numerical example.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0135214
IFAC-PapersOnLine 53 (2): 4527-4533 (2020)
eng
1
83d8110ff9dc4fe8c27466f62af54696
https://tore.tuhh.de/bitstreams/b8d93346-621b-4b05-971e-50e86964485d/download
http://hdl.handle.net/11420/9545
10.15480/882.3535
https://creativecommons.org/licenses/by-nc-nd/4.0/
oai:tore.tuhh.de:11420/3212008-04-09T12:20:25Zcom_11420_1col_11420_2
Approximate inverses of almost singular matrices still contain useful information
Siegfried M.
Rump
510
It is well-known that, roughly spoken, a matrix inversion on a computer working in base B with t digits precision in the mantissa applied to a matrix of condition Bk produces approximately t-k correct digits of the inverse. For condition >> Bt one might conclude that an approximate inverse contains virtually useless information.
In this note we will show that the latter is not true. An approximate inverse may still be useful, e.g. as a preconditioner. An extended set of examples show that preconditioning a matrix using an approximate inverse (computed in t digits precision) lowers the condition number by a factor Bt. As an example we develop an algorithm for solving systems of linear equations up to condition B2t strictly using t digits precision for all calculations and only allowing for double precision accumulation of inner products.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1990
Report
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-3925
Berichte des Forschungsschwerpunktes Informations- und Kommunikationstechnik 90.1: (1990)
eng
1
de7af3ca517a7d9502bb634563ff9534
https://tore.tuhh.de/bitstreams/1632bda6-546a-4abf-82d6-5f3bdb99af59/download
http://tubdok.tub.tuhh.de/handle/11420/321
10.15480/882.319
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/12492015-07-13T04:43:37Zcom_11420_1col_11420_2
Sicherheit und Datenschutz in nicht-interaktiven Crowdsourcing Szenarien
Tobias
Jeske
Sicherheit
Datenschutz
Crowdsourcing
Zero-Knowledge
Smart Grid
Floating Car Data
GPU
004
Beim nicht-interaktiven Crowdsourcing senden Endgeräte einem Provider Daten in Echtzeit und ohne Benutzerinteraktion, wodurch sich Anforderungen an die Sicherheit und den Datenschutz ergeben. In dieser Arbeit werden diese Anforderungen erstmals vollständig definiert und anhand von zwei Szenarien veranschaulicht. Es kann unter anderem gezeigt werden, dass bei modernen Navigationssystemen ein Benutzer-Tracking möglich ist und Echtzeitverkehrsdaten unerkannt manipuliert werden können. Zur Vermeidung solcher Angriffe werden zwei Protokolle auf Basis von Zero-Knowledge Protokollen vorgestellt und deren Praktikabilität auf verschiedenen Endgeräten nachgewiesen. Die Implementierung von Zero-Knowledge Protokollen ist zeitaufwendig. Aus diesem Grund wird eine domänenspezifische Eingabesprache eingeführt, um die Beschreibung von Zero-Knowledge Protokollen zu vereinfachen. Ein Compiler übersetzt die Eingabesprache in eine beliebige Zielsprache. Dabei erfolgt die Beschreibung des Compilerzwischencodes durch spezielle Makros, wodurch bestehender C++ Code leichter als bei anderen Compilerkonzepten integriert werden kann. Auf Grund der speziellen Darstellung des Zwischencodes ist eine automatische Optimierung von rechenintensiven Langzahloperationen möglich. Durch Grafikkarten und die Einführung neuer Algorithmen lässt sich der Durchsatz an modularen Exponentiationen gegenüber einer CPU-Implementierung verzehnfachen.
In non-interactive crowdsourcing scenarios devices send data to a provider in real-time without user interaction, which leads to security and privacy demands. This thesis completely defines and illustrates these requirements for the first time using two scenarios. Among other things, it can be shown that user tracking is possible in modern navigation systems and that real-time traffic data can be manipulated unnoticed. In order to avoid such attacks two protocols are presented on the basis of zero-knowledge protocols and their practicality is proven on different devices. The implementation of zero-knowledge protocols is time-consuming. For this reason, a domain-specific input language is introduced in order to simplify the description of zero-knowledge protocols. A compiler translates the input language into an arbitrary target language. The intermediate code of the compiler is described by special macros, which make the integration of existing C++ code easier than in other compiler concepts. Due to the special presentation of the intermediate code, an automatic optimization of compute-intensive long-number operations is possible. Compared to a CPU implementation, graphics cards and the introduction of new algorithms increase the throughput of modular exponentiations by a factor of ten.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-06-03
2015-07
Other
Text
publishedVersion
urn:nbn:de:gbv:830-88212917
ger
1
5b4834f7977c1f88481fefd62bba2291
https://tore.tuhh.de/bitstreams/437c0960-674a-4f5c-b611-415238dc5709/download
http://tubdok.tub.tuhh.de/handle/11420/1249
10.15480/882.1246
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/113472021-12-20T12:01:08Zcom_11420_1col_11420_2
Analysis of semi-open queueing networks using lost customers approximation with an application to robotic mobile fulfilment systems
Sonja
Otten
Ruslan
Krenzler
Lin
Xie
Hans
Daduna
Karsten
Kruse
Semi-open queueing network
Backordering
Lost customers
Product form approximation
Robotic mobile fulfilment system
Warehousing
We consider a semi-open queueing network (SOQN), where one resource from a resource pool is needed to serve a customer. If on arrival of a customer some resource is available, the resource is forwarded to an inner network to complete the customer’s order. If no resource is available, the new customer waits in an external queue until one becomes available (“backordering”). When a resource exits the inner network, it is returned to the resource pool. We develop a new solution approach. In a first step we modify the system such that new arrivals are lost if the resource pool is empty (“lost customers”). We adjust the arrival rate of the modified system such that the throughputs in all nodes of the inner network are pairwise identical to those in the original network. Using queueing theoretical methods, in a second step we reduce this inner network to a two-station system including the resource pool. For this two-station systems, we invert the first step and obtain a standard SOQN which can be solved analytically. We apply our results to storage and delivering systems with robotic mobile fulfilment systems (RMFSs). Instead of sending pickers to the storage area to search for the ordered items and pick them, robots carry shelves with ordered items from the storage area to picking stations. We model the RMFS as an SOQN to determine the minimal number of robots.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-06
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0167925
OR Spectrum 44 (2): 603-648 (2022-06)
eng
1
8c59793121ac89929cd1ff71be30fddc
https://tore.tuhh.de/bitstreams/4a3c4b8b-6251-4690-b554-7fac55bc3e3e/download
http://hdl.handle.net/11420/11347
10.15480/882.4053
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/432972023-09-26T08:17:20Zcom_11420_1col_11420_2
Production, scaling and application of nanostructured metal multilayers as post-weld treatment
Jakob
Brunow
nanostructured materials
fatigue
welding
post-weld treatment
electrodeposition
Cu/Ni Nanostructured Metal Multilayer coatings are introduced as a new post-weld
treatment method.
Steel specimen with a double V-groove butt-weld are coated with a Cu/Ni NMM
coating with an overall thickness of 9 μm, consisting of a 1 μm Ni base layer, a
nanolaminate structure with a bilayer thickness of 50 nm and Cu and Ni single layer
thicknesses of 15 nm and 35 nm respectively. The coating is electroplated onto the
steel substrate with a single bath method.
The coated steel specimens are tested in tension-tension fatigue and the corresponding
S-N curves are calculated from the fatigue results.
SEM, TEM and EDX investigations provide insights into the material characterization
of the nanolaminate structure and the understanding of NMM failure mechanisms.
Cu/Ni Nanostrukturierte Metall Multilayer werden als neue Schweißnahtnachbehandlungsmethode
vorgestellt.
Stahlproben mit einer geschweißten Doppel-V-Stumpfnaht werden mit Cu/Ni 9 μm
dicken NMM beschichtet, die aus einer 1 μm Ni Grundbeschichtung, einer Doppelschichtdicke
von 50 nm und Cu/Ni Einzelschichtdicken von 15 nm und 35 nm
bestehen. Die Beschichtung wird galvanisch mit einem Einzelbadverfahren auf die
Stahlgrundlage aufgebracht.
Die beschichteten Stahlproben werden im Zugschwellbereich auf Ermüdung getestet
und die dazugehörigen Wöhlerkurven werden aus den Ermüdungsergebnissen berechnet.
REM, TEM und EDX Untersuchungen geben Einblicke in die Materialcharakterisierung
der Nanolaminatstrukturen und dem Verständnis von NMM Versagensmechanismen.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-09-01
2023
Other
Text
publishedVersion
10.15480/882.8567
Technische Universität Hamburg (2023)
eng
1
30d6c9e53ffaaca6ed970d17f49ebc52
https://tore.tuhh.de/bitstreams/28982078-f57a-47f8-9852-b949fc88230a/download
https://hdl.handle.net/11420/43297
10.15480/882.8567
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/5132009-08-10T11:59:11Zcom_11420_1col_11420_2
Über Hilfsmittel zur Untersuchung der Stabilitätseigenschaften von Seeschiffen
Hans
Thieme
620
Über Hilfsmittel zur Untersuchung der Stabilitätseigenschaften von Seeschiffen
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1955
Report
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-5900
ger
1
32c61b17d97f61df1593860095373144
https://tore.tuhh.de/bitstreams/2a23b8f1-6a9f-4219-a634-cc27313dc67e/download
http://tubdok.tub.tuhh.de/handle/11420/513
10.15480/882.511
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/3082008-03-25T12:09:00Zcom_11420_1col_11420_2
Solution of linear and nonlinear algebraic problems with sharp, guaranteed bounds
Siegfried M.
Rump
510
In this paper new methods for solving algebraic problems with high accuracy are described. They deliver bounds for the solution of the given problem with an automatic verification of the correctness. Examples of such problems are systems of linear equations, algebraic eigenvalue problems, nonlinear systems, polynomial zeros, evaluation of arithmetic expressions, linear, quadratic and convex programming and others. The new methods apply for these problems over the space of real numbers, complex numbers as well as real intervals and complex intervals.
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1984
Article
Text
publishedVersion
urn:nbn:de:gbv:830-tubdok-3790
Computing (1984) Suppl. 5, 147-68
eng
1
19d7897c15f1c864dba9b963547c80d5
https://tore.tuhh.de/bitstreams/7cd27a93-bcc6-447c-8401-62ff4ec8f3ec/download
http://tubdok.tub.tuhh.de/handle/11420/308
10.15480/882.306
http://doku.b.tu-harburg.de/doku/lic_ohne_pod.php
oai:tore.tuhh.de:11420/82002020-12-11T08:01:19Zcom_11420_1col_11420_2
Maturity improvements in flood protection asset management across the North Sea Region
Berry
Gersonius
Bart
Vonk
Richard M.
Ashley
Frank
den Heijer
Wouter Jan
Klerk
Natasa
Manojlovic
Jeroen
Rijke
Paul
Sayers
Assela
Pathirana
North Sea Region countries depend heavily on flood protection infrastructure, such as dikes, dams, sluices and flood gates. Knowledge on where, when and how much to invest to ensure functioning is of crucial importance for asset owners and operators. This requires asset management approaches that are adaptable, respond to feedback and function within various contexts. The FAIR (Flood defense infrastructure Asset management & Investment in Renovation, adaptation, optimisation and maintenance) project has developed a unique framework to ensure that asset management processes are adaptive, comprehensive and make effective connections across strategic, tactical and operational contexts. The framework has for the first time informed an assessment of maturity of five flood protection asset management organisations in the North Sea Region, using a seven-factor maturity assessment model. This paper describes the self-assessment process and the self-reported maturity changes during the project. Maturity assessments were undertaken on two occasions, at the start of the project, and again toward the end. This has revealed how the baseline level of maturity for each organisation developed over the course of the three-year project. The observed maturity changes indicate that adopting the FAIR framework has added value in improving current approaches to asset management.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-12-10
Article
Text
publishedVersion
urn:nbn:de:gbv:830-882.0117804
Infrastructures 5 (12): 112 (2020)
eng
1
b15bad0a76b43ebf530459fc9a19bb4b
https://tore.tuhh.de/bitstreams/9f7814ef-a1e3-49f1-bfeb-8cea6ab3c120/download
http://hdl.handle.net/11420/8200
10.15480/882.3192
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/51492020-03-05T06:45:25Zcom_11420_1col_11420_2
Konzept und Versuchsergebnisse zur Elimination von Mikroschadstoffen aus kommunalem Abwasser durch Nanofiltration und Festbettreaktor (MicroStop)
Bastian
Büning
Dorothea
Rechtenbach
Joachim
Behrendt
Ralf
Otterpohl
Mikroschadstoffelimination
Nanofiltration
Festbettreaktor
Innovation Kläranlage
Bologischer Abbau
Da die derzeitige Abwasserreinigung nicht für die Elimination von Mikroschadstoffen ausgelegt ist, gelangen diese unter anderem aus dem kommunalen Abwasser über die Kläranlagen in die aquatische Umwelt. Das Projekt MicroStop untersucht eine Kombination von einem Festbettreaktor und einer Nanofiltrationsanlage zur Elimination von Mikroschadstoffen. Die Versuche zeigen, dass durch die Nanofiltration im Durschnitt über 95 % der ausgewählten, detektierten Mikroschadstoffe eliminiert werden können und dieses Verfahren somit eine geeignete Barriere für diese Schadstoffe darstellt. Parallel zu den Nanofiltrationsversuchen wird der biologische Abbau von Mikroschadstoffen in zwei Festbettreaktoren untersucht. Die Versuchsergebnisse zeigen, dass ein signifikanter biologischer Abbau verschiedener Mikroschadstoffe in den Reaktoren stattfindet.
Since the current wastewater-treatment plants are not designed for the elimination of micropollutants, these are released into the aquatic environment. The MicroStop project investigates a combination of a fixed-bed reactor and a nanofiltration plant for the elimination of micropollutants. The experiments show that nanofiltration can eliminate on average over 95% of the selected, detected micropollutants and that this process therefore represents a suitable barrier for these pollutants. Parallel to the nanofiltration experiments, the biological degradation of micropollutants is being investigated in two fixed-bed reactors. The test results show that a significant biological degradation of various micropollutants takes place in the reactors.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-10-29
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.076685
Verfahren der Wasseraufbereitung und Abwasserbehandlung 13. Aachener Tagung Wassertechnologie : Begleitbuch 153-160 (2019)
ger
1
9529dc0206cc8cf5f3c004c208000f9a
https://tore.tuhh.de/bitstreams/d9582b31-f8bc-4fe3-99be-8ecb6a9a2f49/download
http://hdl.handle.net/11420/5149
10.15480/882.2691
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/15262018-02-12T08:56:01Zcom_11420_1col_11420_2
On the optimization of laser shock peening induced residual stresses
Sergey
Chupakhin
620
Die Flugzeugindustrie sucht nach neuen kosteneffizienten Ansätzen zur Erhöhung der Lebensdauer von Komponenten sowie zur Durchführung von Reparatur- und Wartungsarbeiten an zunehmend älter werdenden Flugzeugen. Ein vielversprechender Lösungsansatz besteht in der Anwendung von Verfahren zur Erzeugung von oberflächennahen Eigenspannungen, um Rissinitiierung zu vermeiden sowie die Ausbreitung bereits vorhandener Risse zu verzögern.
Jedoch unterliegen konventionelle Oberflächenmodifikationsverfahren gewissen Einschränkungen hinsichtlich der maximalen Eigenspannungswerten, der erzielbaren Eindringtiefen von Druckeigenspannungen und, aufgrund von geometrischen Randbedingungen, der Komplexität der zu behandelnden Strukturen. Daher gibt es eine starke ökonomische Motivation der Industrieunternehmen, neuartige eigenspannungsbasierte Ansätze der Ermüdungslebensdauer zu erforschen, obwohl der Effekt der Eigenspannungen nicht in den etablierten Regelwerken des Schadenztoleranzdesigns berücksichtigt wird.
Das Laser Shock Peening (LSP) ist eine vielversprechende Methode, höhere Lebensdauern zu erzielen. Es hat sich gezeigt, dass lasergenerierte Druckeigenspannungen in Strukturen eine Verlangsamung der Ermüdungsrissausbreitung bewirken. Jedoch existiert aufgrund der Komplexität des LSP-Prozesses kein umfassendes Modell, das die Vorhersage von Eigenspannungsfeldern in Abhängigkeit der Prozessparameter erlaubt, weshalb eine Erhöhung der Lebensdauer durch Anwendung des LSP-Prozesses schwierig vorhersagbar ist.
Darüber hinaus ist die Bohrlochmethode eine bewährte Technik zur ortsabhängigen Bestimmung von Eigenspannungen in metallischen Strukturen durch Messung von Dehnungsrelaxationen in der Umgebung eines an der Materialoberfläche eingebrachten Bohrlochs. Die Berechnung von Eigenspannungswerten aus den gemessenen Dehnungsrelaxationen basiert hierbei auf der Annahme, dass linear-elastisches Materialverhalten vorliegt und demzufolge die Eigenspannungswerte geringer als die Streckgrenze sind. Messbohrungen, welche infolge Überschreitung der Steckgrenze zu plastischen Verformungen in der Bohrlochumgebung führen, liefern jedoch ein verfälschtes Ergebnis. Daher ist zunächst die Entwicklung einer Methode erforderlich, mit der die durch plastische Verformung verfälschte Ergebnisse entsprechend korrigiert werden können und die zudem auf ein breites Spektrum von LSP-behandelten Werkstoffen anwendbar ist.
Ziel der vorliegenden Arbeit ist es, eine praktisch anwendbare Methode zur Korrektur der mit der Borhlochmethode gemessenen Eigenspannungen zu entwickeln, auf diesem Wege um die Auswirkung der LSP-Behandlung auf das Ermüdungsrisswachstum präzise zu ermitteln und für die Einbringung maßgeschneiderter Eigenspannungsmessungen zu nutzen.
Im ersten Schritt wird die Methode zur Korrektur der mittels Borlochmethode bestimmten Eigenspannungen entwickelt, die bis zur Streckgrenze des Werkstoffes reichen können. Diese Korrekturmethode basiert auf der Kombination von Finite-Element-Modellierung und der Anwendung eines neuronalen Netzes. Die experimentelle Validierung der Korrekturmethode erfolgte durch Dreipunktbiegeversuche an der Aluminiumlegierung AA2024-T3 durch Messung von Spannungsprofilen mit linearem Gradient. Die Anwendbarkeit der entwickelten Korrekturmethode für die Messung der durch die LSP-Behandlung generierten hohen Eigenspannungen wird demonstriert. Im Unterschied zur Literatur besteht die Neuheit der entwickelten Korrekturmethode darin, dass in praktischer und eleganter Weise ein breites Spektrum an Eigenspannungsprofielen für unterschiedliches Werkstoffverhalten bestimmt und korrigiert werden kann ohne dass das Messverfahren an sich geändert werden müsste. Diese Korrekturmethode kann auch deshalb in der Industrie eingesetzt werden.
Im zweiten Schritt wird der LSP-Prozess hinsichtlich der erzeugten Eigenspannungsprofile mit Hilfe der statistischen Versuchsplanung (Design of Experiment) optimiert. Diese Vorgehensweise umfasst LSP-Behandlungen mit unterschiedlichen Parametern und anschließender Messung von LSP-induzierten Eigenspannungsprofilen mit der Bohrlochmethode. Danach wird das Regressionsmodell in die experimentellen Daten eingepasst, um Beziehungen zwischen LSP-Parametern und Eigenspannungsprofilen zu identifizieren. Mittels Experimenten wird gezeigt, dass das Regressionsmodell geeignet ist, eine genaue Vorhersage eines Eigenspannungsprofils durch Vorgabe von LSP-Parametern zu treffen und umgekehrt.
Im dritten Schritt wird das Regressionsmodell zur gezielten Erzeugung von Eigenspannungen in C(T)50-Proben, an denen Ermüdungsrissausbreitungsversuche durchgeführt werden, angewendet. Die Ermüdungsrissausbreitungsversuche zeigen, dass die Ermüdungsrissausbreitung in AA2024-T3 durch LSP-generierte Druckeigenspannungen erschwert wird. Die nachgewiesene signifikante Lebensdauererhöhung liefert die notwendige Voraussetzung für die Akzeptanz des LSP-Verfahrens zur Behandlung von metallischen Strukturen seitens der Industrie.
Abschließend wird gezeigt, (i) dass die aus der Kombination von FEM und neuronalem Netz entwickelte Korrekturmetode eine robuste Bestimmung auch bei stark ungleichmäßigen Spannungsprofilen in unterschiedlichen Materialien ermöglicht; (ii) das Regressionsmodell eine Vorhersage der Eigenspannungsprofile durch Vorgabe von LSP-Prozessparametern liefert, was zur Kosteneffizienz beiträgt; (iii) wird für den Labormaßstab gezeigt, dass LSP die Lebensdauer von Aluminiumstrukturen der Luftfahrt signifikant erhöht.
There is a strong economic motivation of the aircraft industry to explore novel residual stress-based approaches for the fatigue life extension, repair, and maintenance of the growing fleet of ageing aircrafts, although the effect of residual stresses is not taken into account by the established damage tolerance evaluation methods. Laser shock peening — the most promising life enhancement technique — has already demonstrated great success in regard to the mitigation of fatigue crack growth via deep compressive residual stresses. However, no comprehensive model exists which allows the prediction of generated residual stress fields depending on the laser peening parameters.
Furthermore, the hole drilling method — a well-established technique for determining non-uniform residual stresses in metallic structures — is based on measuring strain relaxations at the material surface caused by the stress redistribution while drilling the hole. However, the hole drilling method assumes linear elastic material behavior and therefore, when measuring high residual stresses approaching the material yield strength, plastic deformation occurs, which in turn leads to errors in stress determination.
In the light of these two points, the present work aims to optimize the laser shock peening process in regard to high residual stress profiles, their correct measurement by the hole drilling method and demonstration of the fatigue crack growth retardation through the laser peening treatment on the laboratory scale.
First, the methodology for the correction of the residual stresses approaching the material yield strength when measuring by the hole drilling is established and experimentally validated. The correction methodology utilizes FE modelling and artificial neural networks. In contrast to the recent studies, the novelty of this methodology lies in the practical and elegant way to correct any non-uniform stress profile for a wide range of stress levels and material behaviors typically used in industrial applications. Therefore, this correction methodology can be applied in industry without changing the procedure of hole drilling measurement.
Second, the laser shock peening process is optimized in regard to the generated residual stress profiles using design of experiments techniques. The strategy involves laser peening treatment with different parameters and subsequent measurement of induced residual stress profiles through hole drilling. The measured stress profiles are subjected to correction using the neural network methodology. After that the regression model is fitted into the experimental data in order to find the relationship between the laser peening parameters and the stress profiles’ shapes. In the final stage, it is experimentally demonstrated that the established regression model provides an accurate prediction of the residual stress profile when using defined laser peening parameters and vice versa.
Third, the regression model obtained in the design of experiments study is used for generating the desired residual stresses in the C(T)50 AA2024-T3 specimens for the fatigue crack propagation test. Significant retardation of the fatigue crack propagation of specimens due to the presence of deep compressive residual stresses is experimentally demonstrated on the laboratory scale.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2017-12-06
2018
Other
Text
publishedVersion
urn:nbn:de:gbv:830-88218498
eng
1
f0464fb5b3f1a270f825d092a6b56945
https://tore.tuhh.de/bitstreams/38dc4919-e47a-4a32-b08b-3fab1870c431/download
http://tubdok.tub.tuhh.de/handle/11420/1526
10.15480/882.1523
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/137142022-10-07T06:08:56Zcom_11420_1col_11420_2
Generation and evaluation of input values for computational analysis of transport processes within tissue cultures
Ehsan
Fattahi
Shahed
Taheri
Arndt F.
Schilling
Thomas
Becker
Ralf
Pörtner
computational models
experimental techniques
fluidics
organotypic tissue cultures
transport processes
Techniques for tissue culture have seen significant advances during the last decades and novel 3D cell culture systems have become available. To control their high complexity, experimental techniques and their Digital Twins (modelling and computational tools) are combined to link different variables to process conditions and critical process parameters. This allows a rapid evaluation of the expected product quality. However, the use of mathematical simulation and Digital Twins is critically dependent on the precise description of the problem and correct input parameters. Errors here can lead to dramatically wrong conclusions. The intention of this review is to provide an overview of the state-of-the-art and remaining challenges with respect to generating input values for computational analysis of mass and momentum transport processes within tissue cultures. It gives an overview on relevant aspects of transport processes in tissue cultures as well as modelling and computational tools to tackle these problems. Further focus is on techniques used for the determination of cell-specific parameters and characterization of culture systems, including sensors for on-line determination of relevant parameters. In conclusion, tissue culture techniques are well-established, and modelling tools are technically mature. New sensor technologies are on the way, especially for organ chips. The greatest remaining challenge seems to be the proper addressing and handling of input parameters required for mathematical models. Following Good Modelling Practice approaches when setting up and validating computational models is, therefore, essential to get to better estimations of the interesting complex processes inside organotypic tissue cultures in the future.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-11-04
ReviewArticle
Text
publishedVersion
urn:nbn:de:gbv:830-882.0198247
Engineering in Life Sciences 22 (11): 681-698 (2022-11-04)
eng
1
e6fe5039b88cfcd4187f13a6f8a7ca84
https://tore.tuhh.de/bitstreams/484ecde2-8bd9-4593-bd6a-e113ba71e863/download
http://hdl.handle.net/11420/13714
10.15480/882.4731
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/90382021-03-10T08:32:09Zcom_11420_1col_11420_2
RANS model for bow wave breaking of a KRISO Container Ship under different speeds
Anzheng
Yu
Decheng
Wan
Bow wave breaking
KRISO Container Ship
RANS model
RANS model combined with VOF method is used to simulate the bow wave breaking of KCS model in the present work. Numerical simulations under seven Froude numbers are conducted in our inhouse CFD solver naoe-FOAM-SJTU. The results of total resistance coefficient and wave pattern at Fr=0.26 are used for CFD validation. The results of resistance coefficients and wave surface on ship hull under different Froude numbers are analysed, the overall results show that present numerical methods can deal with the complex flow around ship model. Comparisons of bow wave between model test and CFD at Fr=0.26, 0.35, 0.425 are given, the vorticities induced by bow wave breaking is also analysed. In order to figure out the mechanism of bow wave breaking, detail analysis of wave cuts is provided at Fr=0.35, both plunging and spilling wave-breaking are found as well as air-entertainment and splash. Present RANS model can accurately capture the overturning of bow wave but cannot deal with the unsteady capillary wave which is found in model test.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-09
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0128544
11th International Workshop on Ship and Marine Hydrodynamics (IWSH2019), Paper 72
eng
1
ab250cc6d3a08e6bef6c926b918321d0
https://tore.tuhh.de/bitstreams/37c5c863-8c9c-4c94-a228-8cda716130c9/download
http://hdl.handle.net/11420/9038
10.15480/882.3363
http://rightsstatements.org/vocab/InC/1.0/
oai:tore.tuhh.de:11420/123302022-04-21T08:19:10Zcom_11420_1col_11420_2
Modeling ℝ³ needle steering in Uppaal
Sascha
Lehmann
Antje
Rogalla
Maximilian
Neidhardt
Anton
Reinecke
Alexander
Schlaefer
Sibylle
Schupp
Medical cyber-physical systems are safety-critical, and as such, require ongoing verification of their correct behavior, as system failure during run time may cause severe (or even fatal) personal damage. However, creating a verifiable model often conflicts with other application requirements, most notably regarding data precision and model accuracy, as efficient model checking promotes discrete data (over continuous) and abstract models to reduce the state space. In this paper, we approach the task of medical needle steering in soft tissue around potential obstacles. We design a verifiable model of needle motion (implemented in Uppaal Stratego) and a framework embedding the model for online needle steering. We mitigate the conflict by imposing boundedness on both the data types, reducing from R3 to Z3 when needed, and the motion and environment models, reducing the set of allowed local actions and global paths. In experiments, we successfully apply the static model alone, as well as the dynamic framework in scenarios with varying environment complexity and both a virtual and real needle setting, where up to 100% of targets were reached depending on the scenario and needle.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-03-21
ConferencePaper
Text
publishedVersion
urn:nbn:de:gbv:830-882.0181391
Electronic proceedings in theoretical computer science 355: 40-59 (2022)
eng
1
a177c65e02811bc2783bc63626044193
https://tore.tuhh.de/bitstreams/0113169d-9019-4a56-9792-7b3d35a931cd/download
http://hdl.handle.net/11420/12330
10.15480/882.4623
https://creativecommons.org/licenses/by/4.0/
oai:tore.tuhh.de:11420/252004-02-10T15:47:40Zcom_11420_1col_11420_2
TUHH Spektrum Wintersemester 2001/2002
620
000
Nach den Terroranschlägen, In-situ Abdeckung mit aktiven Barriere-Systemen, Abfallwirtschaft und Deponietechnik in der Russischen Föderation, Technologiecluster Luftfahrt stärken, 5 neue Studiengänge, The management of EC projects by TuTech, Umwelt-Monitoring in Osteuropa
Technische Universität Hamburg-Harburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2001-11
Other
Text
publishedVersion
urn:nbn:de:101:1-201505222864
ger
1
1b761b8bf58681645e01e02980f8ab1a
https://tore.tuhh.de/bitstreams/c49c41bb-eaa0-4d09-b74b-81e33a22d011/download
http://tubdok.tub.tuhh.de/handle/11420/25
10.15480/882.23
http://rightsstatements.org/vocab/InC/1.0/
xMetaDissPlus///col_11420_2/100