2024-03-29T10:34:01Zhttps://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:11420/33752019-09-17T05:59:24Zcom_11420_1col_11420_2093
Complex machine dynamics: systematic recurrence quantification analysis of disk brake vibration data
Merten
Stender
Sebastian
Oberst
Merten
Tiedemann
Norbert
Hoffmann
Brake squeal
Instantaneous embedding
Nonlinear time series analysis
Recurrence plot analysis
Time series classification
Complex machine dynamics, as caused by friction-induced vibrations and related to brake squeal, have gained significant attention in research and industry for decades. Today, remedies heavily rely on experimental testing due to the low prediction quality of numerical models. However, there is considerable lack of in-depth studies in characterizing self-excited oscillations encoded in scalar measurements. We complement previous works on phase-space reconstruction and recurrence plots analysis to a larger data base by applying a novel systematic approach using a large data base. This framework considers appropriate delay embedding, time series partitioning into squealing and non-squealing parts and comparison to operational parameters of the brake system. By means of recurrence plot analysis, we illustrate that friction-excited vibrations are multi-scale in nature. Results confirm the existence of low-dimensional attractors in squealing regimes with increasing values of determinism and periodicity with rising vibration levels. It is shown that the squeal propensity can be directly linked to recurrence quantification measures. Using determinism and the clustering coefficient as metrics, we show for the first time that is possible to predict instabilities in regions of non-squealing conditions.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-09
Article
Text
publishedVersion
/11420/3375
Nonlinear Dynamics 4 (97): 2483-2497 (2019-09)
eng
http://hdl.handle.net/11420/3375
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:11420/50082020-02-24T16:30:29Zcom_11420_1col_11420_2093
i-PI 2.0 : a universal force engine for advanced molecular simulations
Venkat
Kapil
Mariana
Rossi
Ondrej
Marsalek
Riccardo
Petraglia
Yair
Litman
Thomas
Spura
Bingqing
Cheng
Alice
Cuzzocrea
Robert
Meißner
David M.
Wilkins
Benjamin A.
Helfrecht
Przemyslaw
Juda
Sébastien P.
Bienvenue
Wei
Fang
Jan
Kessler
Igor
Poltavsky
Steven
Vandenbrande
Jelle
Wieme
Clémence
Corminboeuf
Thomas D.
Kühne
David E.
Manolopoulos
Thomas E.
Markland
Jeremy O.
Richardson
Alexandre
Tkatchenko
Gareth A.
Tribello
Veronique
Van Speybroeck
Michele
Ceriotti
Physics - Chemical Physics
Physics - Chemical Physics
Progress in the atomic-scale modelling of matter over the past decade has been tremendous. This progress has been brought about by improvements in methods for evaluating interatomic forces that work by either solving the electronic structure problem explicitly, or by computing accurate approximations of the solution and by the development of techniques that use the Born-Oppenheimer (BO) forces to move the atoms on the BO potential energy surface. As a consequence of these developments it is now possible to identify stable or metastable states, to sample configurations consistent with the appropriate thermodynamic ensemble, and to estimate the kinetics of reactions and phase transitions. All too often, however, progress is slowed down by the bottleneck associated with implementing new optimization algorithms and/or sampling techniques into the many existing electronic-structure and empirical-potential codes. To address this problem, we are thus releasing a new version of the i-PI software. This piece of software is an easily extensible framework for implementing advanced atomistic simulation techniques using interatomic potentials and forces calculated by an external driver code. While the original version of the code was developed with a focus on path integral molecular dynamics techniques, this second release of i-PI not only includes several new advanced path integral methods, but also offers other classes of algorithms. In other words, i-PI is moving towards becoming a universal force engine that is both modular and tightly coupled to the driver codes that evaluate the potential energy surface and its derivatives.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-04
Article
Text
publishedVersion
/11420/5008
Computer Physics Communications (236): 214-223 (2019-04)
eng
http://hdl.handle.net/11420/5008
oai:tore.tuhh.de:11420/121742022-03-31T10:01:58Zcom_11420_1col_11420_2093
Self-organization concepts for the information-and communication layer of autonomous logistic processes
Markus
Becker
Andreas
Timm-Giel
Carmelita
Görg
As described in Chapter 2.2 on Historical Autonomy in ICT, self-organisation is a well-known concept in information-and communication technology. In this chapter it is shown how self-organisation can be employed in the Information-and Communication Layer of Autonomous Logistic Processes.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2007-12-01
BookPart
Text
publishedVersion
/11420/12174
Understanding Autonomous Cooperation and Control in Logistics: The Impact of Autonomy on Management, Information, Communication and Material Flow: 207-213 (2007-12-01)
eng
http://hdl.handle.net/11420/12174
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:11420/70512020-08-14T08:25:50Zcom_11420_1col_11420_2093
Temperaturinduzierte, bleibende Verformungen von Brückensegmenten bei der Herstellung im Kontaktverfahren
Ra'ed
Abendeh
Christian
Brockmann
Oliver
Fischer
Günter Axel
Rombach
Experimental and numerical investigations regarding the irreversible temperature induced bowing deformations in match-cast segments will be presented. Recommendations to reduce this unavoidable effect are given.
Es wird über experimentelle und numerische Untersuchungen bezüglich temperaturinduzierter Verformungen (“Bowing”) von Hohlkastensegmenten bei der Herstellung im Kontaktverfahren am Beispiel der weltweit größten Segmentbrücke berichtet. Empfehlungen zur Reduzierung der unvermeidbaren Imperfektion, welche unter anderem zu Paßproblemen zwischen den Fertigteilen sowie einer ungleichförmigen Spannungsverteilung im Querschnitt führen können, werden gegeben.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2005-03
Article
Text
publishedVersion
/11420/7051
Beton- und Stahlbetonbau 3 (100): 207-215 (2005-03)
ger
http://hdl.handle.net/11420/7051
oai:tore.tuhh.de:11420/59872020-04-30T03:18:16Zcom_11420_1col_11420_2093
Massenspektrometrische Online-Analyse-Verfahren zur Bilanzierung des Kraftstoffeintrags in Motoröl
Andreas
Behn
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018
2018
Other
Text
publishedVersion
/11420/5987
Shaker Verlag (2018)
ger
http://hdl.handle.net/11420/5987
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:11420/65522020-07-02T02:44:16Zcom_11420_1col_11420_2093
A novel approach to alginate aerogels: carbon dioxide induced gelation
Pavel
Gurikov
Raman
Subrahmanyam
Dirk
Weinrich
Marc
Fricke
Irina
Smirnova
A novel technique for the preparation of alginate aerogels, that utilizes high pressure CO2, is presented. In pressurized carbon dioxide at 5 MPa and 298 K, a suspension of calcium carbonate dispersed in a sodium alginate solution undergoes irreversible gelation without additional pH modifiers or crosslinkers. Solvent exchange to ethanol at ambient conditions followed by supercritical drying with carbon dioxide resulted in alginate aerogels with remarkable properties compared to the state of the art. They are very light with densities down to 0.06 ± 0.02 g cm-3, translucent and possess a fibrillar structure with both meso- and macroporosity. For selected samples, the surface area and mesopore volume are found to be 545 ± 77 m2 g-1 and 6.98 cm3 g-1, respectively. Thermal conductivity measurements using the hot-wire method revealed excellent thermal insulation properties: thermal conductivity was determined to be in the range of (18-22) ± 2 mW m-1 K-1. Although the initial aerogels are flexible to a certain extent, they can be classified as viscoplastic materials and their compression indicates improved flexibility and retained mesoporosity. A possible approach for the production of alginate aerogels in an integrated one-pot process - that combines gelation, solvent exchange and supercritical drying - is outlined.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2014-12-22
Article
Text
publishedVersion
/11420/6552
RSC Advances 11 (5): 7812-7818 (2015)
eng
http://hdl.handle.net/11420/6552
oai:tore.tuhh.de:11420/44012020-01-17T10:57:28Zcom_11420_1col_11420_2093
Detecting respiratory artifacts from video data
Sven-Thomas
Antoni
Robert
Plagge
Robert
Dürichen
Alexander
Schlaefer
Detecting artifacts in signals is an important problem in a wide number of research areas. In robotic radiotherapy motion prediction is used to overcome latencies in the setup, with robustness effected by the occurrence of artifacts. For motion prediction the detection and especially the definition of artifacts can be challenging. We study the detection of artifacts like, e.g., coughing, sneezing or yawning. Manual detection can be time consuming. To assist manual annotation, we introduce a method based on kernel density estimation to detect intervals of artifacts on video data. We evaluate our method on a small set of test subjects. With 86 intervals of artifacts found by our method we are able to identify all 70 intervals derived from manual detection. Our results indicate a more exact choice of intervals and the identification of subtle artifacts like swallowing, that where missed in the manual detection.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-02-25
ConferencePaper
Text
publishedVersion
/11420/4401
Informatik aktuell: 227-232 (2015)
eng
http://hdl.handle.net/11420/4401
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:11420/36502019-10-24T09:26:07Zcom_11420_1col_11420_2093
A O(m) self-stabilizing algorithm for maximal triangle partition of general fraphs
Brahim
Neggazi
Volker
Turau
Mohammed
Haddad
Hamamache
Kheddouci
fault-tolerance
Self-stabilizing algorithms
triangle packing
triangle partition
tripartite matching
380
The triangle partition problem is a generalization of the well-known graph matching problem consisting of finding the maximum number of independent edges in a given graph, i.e., edges with no common node. Triangle partition instead aims to find the maximum number of disjoint triangles. The triangle partition problem is known to be NP-complete. Thus, in this paper, the focus is on the local maximization variant, called maximal triangle partition (MTP). Thus, paper presents a new self-stabilizing algorithm for MTP that converges in O(m) moves under the unfair distributed daemon.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2017-06-21
Article
Text
publishedVersion
/11420/3650
Parallel Processing Letters 2 (27): 1750004 (2017)
eng
http://hdl.handle.net/11420/3650
oai:tore.tuhh.de:11420/25522019-04-30T04:44:09Zcom_11420_1col_11420_2093
Manufacturing of a hierarchical carbon foam with tailored catalytically Me/Me x O y particles
Janik
Marx
Felix
Wilhelmy
Hubert
Beisch
Bodo
Fiedler
Carbon foams are characterised by their high specific surface areas (SSAs) in combination with ultra-low densities. Due to these unique properties, carbon foams are particularly suitable for applications such as catalysts, where high surface area is essential. Metals or metal oxides are added to the carbon structure to increase the catalytically effectiveness. In this study, we present a new and efficient manufacturing method, with the potential for a large-scale production resulting in a 3D hierarchical carbon foam with incorporated catalytically metal or metal oxides. The manufacturing starts with the preparation of a ceramic zinc oxide (ZnO) precursor powder containing catalytically active materials (Me/MexOy), uniaxial pressing and sintering yielding to templates. The replication of the template morphology into a hollow carbon structure in the chemical vapour deposition (CVD) process, in which the catalytic materials remain in the carbon foam. Furthermore, the morphology of these structures and the grain size distribution are investigated using scanning electron (SEM) and transmission electron microscopy (TEM). The final amount of catalytically particles is analysed by thermal gravimetric analysis (TGA). Finally, the SSA of the synthesised carbon-based catalysts is measured by Brunauer-Emmett-Teller (BET) method.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-09
Article
Text
publishedVersion
/11420/2552
Vacuum (155): 490-495 (2018-09)
eng
http://hdl.handle.net/11420/2552
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:11420/128112022-06-03T07:43:51Zcom_11420_1col_11420_2093
Solid (formula presented) and co in nanoporous glasses
Patrick
Huber
Dirk
Wallacher
Klaus
Knorr
(Formula presented) and CO condensed into nanoporous glasses have been investigated by vapor pressure measurements and x-ray diffraction as a function of temperature and fractional filling. The pore material is stable with respect to bulk condensation for any fractional filling. The adsorbate on the pore walls has to be distinguished from the capillary condensate in the center of the pores. This distinction can be made not only in the liquid, but also in the solid state. The solid capillary condensate is quasi-hcp at higher temperatures. (Formula presented) remains in this state down to the lowest temperatures, even in pores as large as 130 Å diameter, whereas CO transforms into the orientationally ordered (Formula presented) phase. On heating an orientationally disordered intermediate phase with a fcc center-of-mass lattice is observed.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1999-11-01
Article
Text
publishedVersion
/11420/12811
Physical Review B - Condensed Matter and Materials Physics 60 (18): 12666-12674 (1999)
eng
http://hdl.handle.net/11420/12811
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:11420/429542023-08-24T08:42:43Zcom_11420_1col_11420_2093
Industry 4.0 and its impact on supply chain risk management
Meike
Schröder
Marius
Indorf
Wolfgang
Kersten
Industry 4.0
Chain management
Supply chain
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2014
ConferencePaper
Text
publishedVersion
/11420/42954
In: Proceedings of the 14th International Conference on Reliability and Statistics in Transport and Communication 204 : 114-125 (2014)
eng
https://hdl.handle.net/11420/42954
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:11420/79982020-11-26T13:43:16Zcom_11420_1col_11420_2093
Wake volume of injected bubbles in fluidized beds: A magnetic resonance imaging velocimetry study
Christopher M.
Boyce
Alexander
Penn
M.
Lehnert
Klaas Paul
Pruessmann
Christoph Rüdiger
Müller
Bubbles
Fluidization
Magnetic resonance imaging
Velocimetry
Wakes
Rapid magnetic resonance imaging (MRI) was used to determine the volume of wakes of bubbles injected into incipiently fluidized beds. MRI was used to generate 2D maps of particle velocity surrounding bubbles with a temporal resolution of 18 ms. The bubble rise velocity, ub, was determined from the change in bubble position in successive maps, and pixels of particles which had an upward velocity greater than or equal to 0.8 ub were considered to be in the “wake” if they were below the bubble and in the “crown” if they were above the bubble. Results show that (i) the wake volume is much larger than the crown volume and (ii) the ratio of the wake volume to bubble volume increases as the bubble rises in the bed but decreases with increasing bubble volume. The influence of two bubbles interacting on bubble wake volume is also investigated. Comparison with geometric theory for wake volume exposes flaws in this theory for fully developed bubbles, bubbles near the distributor and interacting bubbles.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-12-01
Article
Text
publishedVersion
/11420/7998
Powder Technology (357): 428-435 (2019-12-01)
eng
http://hdl.handle.net/11420/7998
oai:tore.tuhh.de:11420/120342022-03-21T07:27:13Zcom_11420_1col_11420_2093
Effect of TNL flow control schemes for the HSDPA network performance
Thushara
Weerawardane
Andreas
Timm-Giel
Carmelita
Görg
Gennaro Ciro
Malafronte
Stephan
Hauth
Flow Control
HSDPA
Node-B
RNC
HSDPA (High Speed Downlink Packet Access) is an extension of the current UMTS (Universal Mobile Telecommunications System) technology with the objective to increase the data rate and to reduce the latency in the downlink. The main focus of this investigation is to optimise the Iub interface to provide the best end user performance at minimum cost for UMTS HSDPA network. An adaptive credit-based flow control mechanism for UTRAN transport has been developed, tested and validated in the HSDPA simulation model. In this paper, the HSDPA performance with the new adaptive credit-based flow control mechanism is compared with the generic ON/OFF flow control mechanism. The results confirm that the adaptive credit-based flow control mechanism can significantly improve the performance and therefore reduce the required bandwidth at the Iub interface meeting a specified performance: The better bandwidth utilisation and improved statistical multiplexing is achieved by reducing the burstiness of the traffic over the Iub interface. Finally, a recommendation for the required bandwidth at the Iub interface is given for bursty HSDPA traffic.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2009-01-01
Article
Text
publishedVersion
/11420/12034
Journal of Communications 4 (2): 78-88 (2009-01-01)
eng
http://hdl.handle.net/11420/12034
oai:tore.tuhh.de:11420/143682022-12-15T08:58:26Zcom_11420_1col_11420_2093
Population protocols for exact plurality consensus : how a small chance of failure helps to eliminate insignificant opinions
Gregor
Bankhamer
Petra
Berenbrink
Felix
Biermeier
Robert
Elsässer
Hamed
Hosseinpour
Dominik
Kaaser
Peter
Kling
population protocols
plurality consensus
randomized algorithms
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-07
ConferencePaper
Text
publishedVersion
/11420/14368
Proceedings of the Annual ACM Symposium on Principles of Distributed Computing (): 224-234 (2022-07-20)
eng
http://hdl.handle.net/11420/14368
oai:tore.tuhh.de:11420/83072021-01-06T12:41:20Zcom_11420_1col_11420_2093
Filter helix implementation in traveling wave tube tapers
Elke
Gehrmann
Frauke K. H.
Gellersen
Arne F.
Jacob
A filter helix consisting of periodic pitch discontinuities can be implemented in the transmission line of a traveling wave tube (TWT) to act as a stopband filter for the second harmonic. This contribution investigates the possibility of integrating such filters in tube regions with tapered helix pitch. Simulation of an L-band TWT predicts increased output power for optimized filter design.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2014-03
ConferencePaper
Text
publishedVersion
/11420/8307
8th German Microwave Conference (GeMiC 2014)
eng
http://hdl.handle.net/11420/8307
oai:tore.tuhh.de:11420/100622021-08-10T04:39:49Zcom_11420_1col_11420_2093
Application of incremental Gaussian mixture models for characterization of wind field data
Jinkyoo
Park
Kay
Smarsly
Kincho H.
Law
Dietrich
Hartmann
Structural responses and power output of a wind turbine are strongly affected by the wind field acting on the wind turbine. Knowledge about the wind field and its variations is essential not only for designing, but also for cost-efficiently managing wind turbines. Wind field monitoring collects and stores wind field time series data. Over time the amount of data can be overwhelming. Furthermore, the correlation among the wind field statistical features is difficult to capture. Here, we explore the use of online machine learning to study the characteristics of wind fields, while effectively condensing the amount of monitoring data. In particular, incremental Gaussian mixture models (IGMM) are constructed to represent the joint probability density functions for wind field features, whose parameters are continuously updated as new data set is collected. The monitoring data recorded from an operating wind turbine in Germany is employed to test and compare the IGMM with conventional machine learning approach that uses an entire historical data set.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2013-09
ConferencePaper
Text
publishedVersion
/11420/10062
Structural Health Monitoring 2013 1: 553-560 (2013-01-01)
eng
http://hdl.handle.net/11420/10062
oai:tore.tuhh.de:11420/121892022-04-04T05:24:53Zcom_11420_1col_11420_2093
Deterministic witnesses for claim-first transactions
Michael
Borkowski
Christoph
Ritzer
Stefan
Schulte
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018
Report
Text
publishedVersion
/11420/12189
Whitepaper, Technische Universität Wien, 2018
eng
http://hdl.handle.net/11420/12189
oai:tore.tuhh.de:11420/121442022-03-30T10:49:12Zcom_11420_1col_11420_2093
3D FE analysis of the installation process of spudcan foundations
Gang
Qiu
Sascha
Henke
Jürgen
Grabe
The risk of rapid uncontrolled penetration ("punch-through") exposes jack-ups to significant risk during installation in strong over weak layered soils. An example for this is a thin sand layer overlying a weaker stratum of clay. Contact problems and large mesh distortions, which lead to convergence problems in FEsimulations may occur if this problem is simulated using conventional FE-method. In recent years, the Coupled Eulerian-Lagrangian method (CEL) has been used to solve geomechanical boundary value problems involving large deformations. In this paper, three dimensional finite element analyses using the CEL formulation are carried out to simulate the installation process of spudcan foundations. A Lagrangian mesh is used to discretize the spudcan foundation, whereas an Eulerian mesh is used for the subsoil. The clay is modeled as elasto-plastic DRUCKER-PRAGER material and a hypoplastic constitutive law is used to describe the sand. The numerical results are compared with existing analytical solutions and centrifuge model test data. © 2011 Taylor & Francis Group, London.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011
ConferencePaper
Text
publishedVersion
/11420/12144
Frontiers in Offshore Geotechnics II - Proceedings of the 2nd International Symposium on Frontiers in Offshore Geotechnics, ISFOG 2010 : Perth, Australia, 8 - 10 November 2010 (): 685-690 (2011)
eng
http://hdl.handle.net/11420/12144
oai:tore.tuhh.de:11420/82352020-12-14T07:44:00Zcom_11420_1col_11420_2093
Process synthesis of flexible and sustainable processes consisting of membrane separations and reactive distillation for the production of biodiesel
Kathrin
Werth
Paul
Behling
Annchristin
Hnida
Mirko
Skiborowski
Due to global competition and an increasing demand for reduced emissions the development of sustainable and efficient processes based on renewable resources becomes more and more important. Furthermore, the fluctuating qualities of renewable feedstock necessitate highly flexible processes. Fatty esters are promising new building blocks for the chemical industry and can be produced by the transesterification of virgin vegetable oils. However, nowadays fatty esters are mainly used as biodiesel, an alternative fuel in future based on renewable resources [1,2]. Due to the high raw material costs for the virgin vegetal oils [3], no economic production is possible. A promising approach to lower the production costs is the application of cheap low-quality oils, such as waste cooking oil or crude non-edible oil [4,5]. These low quality oils contain a high amount of free fatty acids, which lead to undesired side reactions in the alkaline catalyzed transesterification reaction [6,7]. Consequently, new process concepts are necessary to enable the application of low-quality oils as a feedstock.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-11
ConferencePaper
Text
publishedVersion
/11420/8235
AIChE Annual Meeting (2015)
eng
http://hdl.handle.net/11420/8235
oai:tore.tuhh.de:11420/25432019-04-26T07:04:23Zcom_11420_1col_11420_2093
On the sensitivity of adhesion between rough surfaces to asperity height distribution
Michele
Ciavarella
Antonio
Papangelo
There has been a long debate about the validity of asperity models in the contact between rough surfaces, much of it concentrated on relatively minor aspects of the solution for the special case of Gaussian random processes for roughness, like the exact value of the area–load slope or the extent of the linear regime. It is shown here that in the case of adhesion, the behavior is extremely sensitive to the shape of the height distribution. We show for example results for Weibull distributions, which has been suggested in a number of practical cases from macroscopic to nanoscopic roughness. Pull-off force is found to vary by several orders of magnitude both lower and higher than in the Gaussian case, whereas the “stickiness” criterion on the adhesion parameter changes by an order of magnitude. Additionally, in some operations like chemical-mechanical polishing, tails are almost completely removed and a sharp peak develops instead of a tail: modeling this with contact on the bounded side of the Weibull distribution, stickiness seems to occur for any level of roughness. Some qualitative comparison with recent numerical experiments is attempted.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-01
Article
Text
publishedVersion
/11420/2543
Physical Mesomechanics 1 (21): 59-66 (2018-01)
http://hdl.handle.net/11420/2543
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:11420/107782021-11-04T11:06:51Zcom_11420_1col_11420_2093
Performance evaluation in composting of sewage sludge with different bulking agents
Wenjing
Lu
Rong
Ye
Zhongyuan
Ming
Chao
Pan
Yawar
Abbas
Rainer
Stegmann
Hongtao
Wang
Bulking agent
Composting
Sewage sludge
Wood chips
Increasing sewage sludge production has become a new environmental problem in China because of its huge amounts of sludge, heavy metal concentrations, and potential pathogen risk. Composting with appropriate bulking agents is an effective method to treat sewage sludge. In this research project, wood chips, ceramsite, and plant ash were used as bulking agents during sewage sludge composting over a period of 44 days (in winter) at a pilot scale. The results indicated that wood chips were an efficient bulking agent to enhance composting performance while ceramsite failed to initialize sewage sludge composting. In addition, a lower weight ratio between sewage sludge and wood chips significantly improved the composting process. A ratio of 3-1 (wet basis) resulted in an increase of composting temperature in two days from 13°C up to 67°C and maintained high temperatures of more than 55°C over some time. In addition, moisture content decreased from 78% to 50%, and a decline of volatile solids from 61% to 47% was observed. The addition of plant ash facilitated a further decrease in moisture content and the germination index of the compost rose from 85.3% to 106.3%. Furthermore, in the compost derived from the 3∶1 ratio of sludge to wood chips, all monitored heavy metal concentrations were far below the limit levels.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-06-01
Article
Text
publishedVersion
/11420/10778
Journal of Environmental Engineering 146 (6): 05020002 (2020-06-01)
eng
http://hdl.handle.net/11420/10778
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:11420/107532021-11-02T14:48:31Zcom_11420_1col_11420_2093
Course: Energy efficiency in embedded systems - A system-level perspective for computer scientists
Ulf
Kulau
Computer science
Course
Embedded systems
Energy efficiency
The improvement of the energy efficiency of embedded devices has always been an important research topic. Nowadays with more and more autonomous devices, e.g. IoT, this topic is yet popular as questions arise "how to power all these devices?" or "how to enable lifetimes of years or decades?". As theses challenges are not solely an issue of computer architects, this course specifically addresses computer scientists. While computer scientists would not be able to influence the basic architecture of an e.g. MCU, the knowledge on the basics, the architectures, mechanisms and software paradigms should sensitize students how to implement energy efficiency on system level.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-09
ConferencePaper
Text
publishedVersion
/11420/10753
European Workshop on Microelectronics Education (EWME 2018)
eng
http://hdl.handle.net/11420/10753
oai:tore.tuhh.de:11420/124662022-05-05T04:27:06Zcom_11420_1col_11420_2093
Pulse shaping during laser percussion drilling by using fiber laser radiation
Hermann
Uchtmann
Jens
Dietrich
Ingomar
Kelbassa
Laser percussion drilling is commonly used for drilling holes such as cooling holes in the aerospace industry. Flash lamp pumped Nd:YAG laser sources are state of the art for drilling. For a short time pulsed diode pumped laser sources such as fiber lasers with high average power are available coming along with benefits due to the productivity and reproducibility of drilled holes [1]. Pulse shaping can be done easily with these laser sources. The temporal intensity distribution of each pulse - intrapulse shaping - and the intensity in a sequence of pulses - interpulse shaping - can be modulated by the laser control software. The temporal intensity distribution using intrapulse shaping has no visible influence on the drilling results. The same energy is required to get a through hole. Thus using rectangular pulses which can be emitted by fiber lasers the pulse peak power can be lower. Using interpulse shaping by increasing the pulse peak power within a sequence of pulses the hole geometry can be modified due to a smaller diameter and a rectangular hole entrance. Furthermore the spatter on the workpiece surface is less and can be removed by wiping by hand. Thus economic benefits are established by using pulse shaping during laser percussion drilling with fiber lasers due to lower required pulse peak power and the disappearance of finishing steps like grinding.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2012-09
ConferencePaper
Text
publishedVersion
/11420/12466
ICALEO 2012 - 31st International Congress on Applications of Lasers and Electro-Optics: 49-53 (2012-01-01)
eng
http://hdl.handle.net/11420/12466
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:11420/145982023-01-19T14:34:06Zcom_11420_1col_11420_2093
Strategizing in the virtual age : an ethnographic study of strategizing practices in digital strategy workshops
Lydia
Schuster
Stephanie
Schrage
Pauline
Reinecke
Thomas
Wrona
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021
ConferenceObject
Text
publishedVersion
/11420/14598
Strategic Management Society Conference 2021
eng
http://hdl.handle.net/11420/14598
oai:tore.tuhh.de:11420/60442020-05-05T07:43:12Zcom_11420_1col_11420_2093
Performance evaluation of the flow in micro junctions : head change versus head loss coefficients
Bastian
Schmandt
Heinz
Herwig
Losses due to the flow through conduit components in a pipe system can be characterised by head loss coefficients. They basically account for the dissipation in the flow field or, in a more general sense, for the entropy generation due to the conduit component under consideration. When only one single mass flow rate is involved, an entropy based approach is straight forward and m can be used as a general reference quantity. If, however, the mass flow rate is split or united like in junctions, some new aspects appear. In our study the general approach for these kind of conduit components is discussed. Like for single mass flow rates losses are accounted for by determining the entropy generation rates. New aspects for the branchedflows are an additional parameter, the splitting ratio, and the fact that there is an energy transfer between the single branches that has to be accounted for appropriately. It turns out that this energy transfer changes the total head in each flow brach in addition to a sole loss of total head. Therefore, the coefficients should be named head change coefficients when this effect occurs. As an example the flow through a T-shaped junction is considered, for which head loss coefficients are determined for both branches and discussed with respect to their physical meaning. Copyright © 2013 by ASME.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2013
ConferencePaper
Text
publishedVersion
/11420/6044
Proceedings of the ASME 11th International Conference on Nanochannels, Microchannels, and Minichannels - 2013 : single phase gas flow ... / presented at ASME 2013 11th International Conference on Nanochannels, Microchannels and Minichannels ; June 16 - 19, 2013 Sapporo, Japan / sponsored by ASME. - New York, NY : ASME, 2013. - Paper no. ICNMM2013-73031, V001T02A001; 8 pages
eng
http://hdl.handle.net/11420/6044
oai:tore.tuhh.de:11420/28232019-06-26T05:57:56Zcom_11420_1col_11420_2093oai: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:11420/106862021-10-28T07:46:57Zcom_11420_1col_11420_2093
Advances in soil evaporation physics-A review
Dani
Or
Peter
Lehmann
Ebrahim
Shahraeeni
Nima
Shokri
Globally, evaporation consumes about 25% of solar energy input and is a key hydrologic driver with 60% of terrestrial precipitation returning to the atmosphere via evapotranspiration. Quantifying evaporation is important for assessing changes in hydrologic reservoirs and surface energy balance and for many industrial and engineering applications. Evaporation dynamics from porous media reflect interactions between internal liquid and vapor transport, energy input for phase change, and mass transfer across air boundary layer. We reviewed recent advances on resolving interactions between soil intrinsic properties and evaporation dynamics with emphasis on the roles of capillarity and wettability affecting liquid phase continuity and capillary driving forces that sustain Stage I evaporation. We show that soil water characteristics contain information for predicting the drying front depth and mass loss at the end of Stage I and thus derive predictions for regional-scale evaporative water losses from soil textural maps. We discuss the formation of secondary drying front at the onset of Stage II evaporation and subsequent diffusion-controlled dynamics. An important aspect for remote sensing and modeling involves nonlinear interactions between wet evaporating surfaces and air boundary layer above (evaporation rate is not proportional to surface water content). Using pore scale models of evaporating surfaces and vapor transport across air boundary layer, we examined the necessary conditions for maintenance of nearly constant evaporation while the surface gradually dries and the drying front recedes into the soil. These new insights could be used to improve boundary conditions for models that are based on surface water content to quantify evaporation rates. © Soil Science Society of America, All rights reserved.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2013-11
Article
Text
publishedVersion
/11420/10686
Vadose Zone Journal 12 (4): (2013-11
eng
http://hdl.handle.net/11420/10686
oai:tore.tuhh.de:11420/26302019-05-06T11:03:56Zcom_11420_1col_11420_2093
Mining latency guarantees for RTL designs
Jan
Malburg
Heinz
Riener
Görschwin
Fey
Guaranteed response times are crucial for control applications. Analyzing the communication latency, i.e., the time needed to transfer data from one end-point to another, in complex on-chip communication architectures is hard. In this paper, we formally define the problem of mining latency guarantees and present a pragmatic approach to mine symbolic conditions that guarantee a latency requirement. The verification problems handled in this approach are inherently multi-valued modeling bit-vectors of the underlying designs. We use the approach to infer the optimal transfer conditions for a bus bridge and an SPI-connection in less than a minute using only up to 5,000 clock cycles of simulation data.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-07-19
ConferencePaper
Text
publishedVersion
/11420/2630
The International Symposium on Multiple-Valued Logic: 68-73 (2018)
eng
http://hdl.handle.net/11420/2630
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:11420/143012022-12-06T14:16:21Zcom_11420_1col_11420_2093
Description of the temperature, humidity, and concentration distribution in gas-liquid-solid fluidized beds
Stefan
Heinrich
Lothar
Mörl
Communication: The computation of the drying kinetics in fluidized bed spraying granulation plants is possible with the models introduced. Starting from mass and energy balances, the models describe the influences of local liquid input, nonideal solid and liquid mixing, heat transport by the solids, and the height-dependent degree of wetness. Conclusions about the existence of an active zone and constant gas temperatures in the central region of the fluidized bed are made.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1999-02
Article
Text
publishedVersion
/11420/14301
Chemical Engineering and Technology 22 (2): 118-122 (1999-02)
eng
http://hdl.handle.net/11420/14301
oai:tore.tuhh.de:11420/28972019-07-08T08:44:25Zcom_11420_1col_11420_2093
Robust autopilot design for landing a large civil aircraft in crosswind
Julian
Theis
Daniel
Ossmann
Frank
Thielecke
Harald
Pfifer
A comprehensive autolanding design for a representative model of a twin-engined commercial aircraft is presented in this paper. To facilitate the design task and minimize control law switching, a cascaded control structure is selected which resembles integrator chains. Classical loopshaping and robust control techniques are used to design the individual control loops. The emphasis is on providing a complete and comprehensive qualitative design strategy. The control system's ability to safely land the aircraft despite strong crosswind in a variety of possible scenarios is demonstrated in an industry-grade verification campaign. Nonlinear Monte Carlo simulations of the airliner model are used to assess the risk of unsafe landing conditions and provide insight into the performance characteristics and limitations of the proposed control system.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-07
Article
Text
publishedVersion
/11420/2897
Control Engineering Practice (76): 54-64 (2018-07)
http://hdl.handle.net/11420/2897
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:11420/103312021-09-13T12:01:35Zcom_11420_1col_11420_2093
Inland waterway efficiency through skipper collaboration and joint speed optimization
Christof
Defryn
Julian
Golak
Alexander
Grigoriev
Veerle
Timmermans
Congestions
Lock scheduling
Mechanism design
Online scheduling
Social welfare
We address the problem of minimizing the aggregated fuel consumption by the vessels in an inland waterway (a river) with a single lock. The fuel consumption of a vessel depends on its velocity and the slower it moves, the less fuel it consumes. Given entry times of the vessels into the waterway and the deadlines before which they need to leave the waterway, we decide on optimal velocities of the vessels that minimize their private fuel consumption. Presence of the lock and possible congestions on the waterway make the problem computationally challenging. First, we prove that in general Nash equilibria might not exist, i.e., if there is no supervision on the vessels velocities, there might not exist a strategy profile from which no vessel can unilaterally deviate to decrease its private fuel consumption. Next, we introduce simple supervision methods to guarantee existence of Nash equilibria. Unfortunately, though a Nash equilibrium can be computed, the aggregated fuel consumption of such a stable solution is high compared to the consumption in a social optimum, where the total fuel consumption is minimized. Therefore, we propose a mechanism involving payments between vessels, guaranteeing Nash equilibria while minimizing the fuel consumption. This mechanism is studied for both the offline setting, where all information is known beforehand, and online setting, where we only know the entry time and deadline of a vessel when it enters the waterway.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-07
ConferencePaper
Text
publishedVersion
/11420/10331
International Conference on Mathematical Optimization Theory and Operations Research (MOTOR 2019)
eng
http://hdl.handle.net/11420/10331
oai:tore.tuhh.de:11420/80722020-11-30T12:33:58Zcom_11420_1col_11420_2093
Akzeptanz von automatisierten Kleinbussen im ÖPNV in Lauenburg (Elbe) bei Einwohnern und Fahrpersonal
Rebekka
Mantel
Tyll
Diebold
Automatisierter ÖPNV
Akzeptanz
Die Automatisierung und Vernetzung im Öffentlichen Personennahverkehr (ÖPNV) verspricht nachfrageorientierte, bedarfsgerechte und zugängliche Angebote und somit eine attraktivere öffentliche Mobilität für große Bevölkerungsgruppen. Mit fortschreitender Entwicklung der Automatisierungsstufen beginnen immer mehr Pilotprojekte mit dem Testbetrieb automatisierter Kleinbusse im privaten sowie öffentlichen Raum.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-11
Article
Text
publishedVersion
/11420/8072
In: V+T Verkehr und Technik 11(73): 379-384 (2020-11)
ger
http://hdl.handle.net/11420/8072
oai:tore.tuhh.de:11420/76732020-10-27T06:43:08Zcom_11420_1col_11420_2093
Nonlinear vibration localisation in a symmetric system of two coupled beams
Filipe
Fontanela
Alessandra
Vizzaccaro
Jeanne
Auvray
Björn
Niedergesäß
Aurélien
Grolet
Loic
Salles
Norbert
Hoffmann
Clearance nonlinearity
Symmetry breaking bifurcation
Vibration localisation
Nonlinear Sciences - Pattern Formation and Solitons
Nonlinear Sciences - Pattern Formation and Solitons
We report nonlinear vibration localisation in a system of two symmetric weakly coupled nonlinear oscillators. A two degree-of-freedom model with piecewise linear stiffness shows bifurcations to localised solutions. An experimental investigation employing two weakly coupled beams touching against stoppers for large vibration amplitudes confirms the nonlinear localisation.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2021-03
Article
Text
publishedVersion
/11420/7673
Nonlinear Dynamics 103 (4): (2021-03)
eng
http://hdl.handle.net/11420/7673
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:11420/466062024-03-18T12:28:58Zcom_11420_1col_11420_2093
Frame dislocation of body middle rings in endovascular stent tube grafts
Peter
Heilberger
Thomas W.
Umscheid
Nabil
Chakfé
Dieter
Raithel
Wolf Joachim
Stelter
Michael
Morlock
Jean Georges
Kretz
A.
Schröder
Herbert
Imig
Dislocation
Endovascular stent grafts
Secondary leakage
Objectives: to understand the cause, and purpose a mechanism for frame dislocation in endovascular grafts. Materials and methods: five tube grafts were explanted due to secondary distal leakage 15-21 months after operation. One bifurcated graft was removed during emergency operation after aortic rupture caused by secondary leakage. A second bifurcated graft was harvested from a patient with thrombotic occlusion of one limb, who died after transurethral prostatic resection. The inside of the grafts were examined endoscopically. The stent was inspected after removal of the fabric, broken ligatures were counted and examined by scanning electron microscopy. The fabric strength was tested by probe puncture. Results: we found 17-44% of the stent ligatures of the body middle rings to be loose. The knots were intact. Degradation of the polyester textile was not observed. Conclusions: continuous movements in the grafted aorta and blood pressure impose permanent stress to the stent frame and the polyester fabric resulting in morphological changes in the body middle ring of grafts. The clinical implications of the suture breakages are unknown although they may be related to distal secondary leakage in tube grafts.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
1999
Article
Text
publishedVersion
/11420/46606
European Journal of Vascular and Endovascular Surgery 17 (1): 28-34 (1999)
eng
https://hdl.handle.net/11420/46606
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:11420/117772022-02-28T09:05:35Zcom_11420_1col_11420_2093
Raman-induced nonreciprocity in silicon photonic-crystal waveguides : benefits of slow light for optical isolators
Michael
Krause
Sascha
Meyne
Hagen
Renner
Ernst
Brinkmeyer
The Raman-induced nonreciprocity of light propagation in photonic-crystal silicon waveguides is analysed. Although the Raman gain increases in the slow-light regime, the nonreciprocity is smaller. Thus, it is interesting that Raman-pumped optical isolators benefit from slow-light operation. Significant reductions in pump power and/or device length are found to be possible. © 2011 The Institution of Engineering and Technology.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011-12-08
Article
Text
publishedVersion
/11420/11777
Electronics Letters 47 (25): 1392-1393 (2011)
eng
http://hdl.handle.net/11420/11777
oai:tore.tuhh.de:11420/62802020-06-09T07:16:26Zcom_11420_1col_11420_2093
Structural design with joints for maximum dissipation
Merten
Stender
Antonio
Papangelo
Allen M.
Orville
Matthew
Brake
Christoph
Schwingshackl
Merten
Tiedemann
Design
Dissipation
Joints
Nonlinear dynamics
Optimization
Many engineered structures are assembled using different kinds of joints such as bolted, riveted and clamped joints. Even if joints are often a small part of the overall structure, they can have a massive impact on its dynamics due to the introduction of nonlinearities. Thus, joints are considered a design liability. Significant effort has been spent in joint characterization and modelling, but a predictive joint model is still non-existent. To overcome these uncertainties and ensure certain safety standards, joints are usually overdesigned according to static considerations and their stiffness. Especially damping and nonlinearity are not considered during the design process. This can lead to lower performance, lower payload, and as result of the joints structural dynamic models often do a poor job of predicting the dynamic response. However, it is well-known that, particularly for metal structures, joints represent the main source of energy dissipation. In this work a minimal model is used to show how structural performance can be improved using joints as a design variable. Common optimization tools are applied to a nonlinear joint model in order to damp undesired structural vibrations. Results illustrate how the intentional choice of joint parameters and locations can effectively reduce vibration level for a given operating point of a jointed structure.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2016-01
ConferencePaper
Text
publishedVersion
/11420/6280
A. Brandt, R. Singhal (eds.), Shock & Vibration, Aircraft/Aerospace, Energy Harvesting, Acoustics & Optics, Volume 9, Conference Proceedings of the Society for Experimental Mechanics Series: 179-188 (2016-01)
eng
http://hdl.handle.net/11420/6280
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:11420/77272020-10-30T13:43:31Zcom_11420_1col_11420_2093
Biodegradation of phenolic compounds present in palm oil mill effluent as single and mixed substrates by Trametes hirsuta AK04
Anukool
Kietkwanboot
Sumate
Chaiprapat
Rudolf
Müller
Oramas
Suttinun
Agro-industrial wastewater
biodegradation kinetics
biological treatment
Haldane model
white-rot fungi
The ability of white-rot fungus, Trametes hirsuta AK04, to utilize phenolics as single and mixed substrates was determined in mineral medium and palm oil mill effluent (POME). The strain AK04 was able to rapidly metabolize all ten phenolics as single and mixed substrates at all test concentrations. With single substrates, between 78 and 98% removal was achieved within seven days. The biomass yield increased with increasing concentration from 100 to 500 mg L−1 but slightly decreased when the concentration was increased up to 1,000 mg L−1. When fitted to a Haldane model, the groups of benzoic and cinnamic acid derivatives gave significantly higher maximum specific growth rates than other phenolics. Phenol exhibited the lowest affinity and highest inhibitory effects on fungal metabolism. In mixed substrates, the total concentration ranges of phenolics mixtures between 1,000 and 6,000 mg L−1 did not affect the fungal growth rate and the strain AK04 showed a high degree of resistance to their toxic effects. The addition of glucose and yeast extract enhanced the degradation rates of individual phenolics in the substrate mixtures, demonstrating the advantage of this strain for treating complex media, such as industrial wastewater.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-07-02
Article
Text
publishedVersion
/11420/7727
Journal of environmental science and health 8 (55): 989-1002 (2020-07-02)
eng
http://hdl.handle.net/11420/7727
oai:tore.tuhh.de:11420/107422021-11-02T11:02:02Zcom_11420_1col_11420_2093
First feasibility analysis of ballistocardiography on a passenger flight
Marie Cathrine
Wolf
Nico
Jähne-Raden
Henrike
Gutschleg
Ulf
Kulau
Mario
Kallenbach
Klaus Hendrik
Wolf
Accelerometry
Ballistocardiography
Micro-Electrical-Mechanical Systems
The project SCARAB2 (Scalable, Robust and Adaptive on Board Ballistocardiography) aims to use Ballistocardiography (BCG) to monitor flight passengers. In order to show that recorded BCG data from flights give evaluable information even in the noisy environment of an airplane, we monitored a heart-healthy passenger using BCG. Furthermore, we show that there can be a conclusion to heart activities from the recorded ballistocardiogram by comparing the data to a concurrently recorded electrocardiogram (ECG).
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-08
ConferencePaper
Text
publishedVersion
/11420/10742
17th World Congress on Medical and Health Informatics (MEDINFO 2019)
eng
http://hdl.handle.net/11420/10742
oai:tore.tuhh.de:11420/455552024-02-07T12:52:35Zcom_11420_1col_11420_2093
A Benchmark for Different Implementations of Zero-Knowledge Proof Systems
Max
Kobelt
Michael Peter
Sober
Stefan
Schulte
Zero-Knowledge Proofs (ZKPs) ensure privacy in sensitive applications, including blockchains, anonymous verifiable voting, and secure auctions. In recent years, a number of ZKP implementations have been presented. The diversity of available solutions raises the need to compare the implementations to discover their strengths and weaknesses. Unfortunately, the collection of ZKP implementations is highly heterogeneous, aggravating a just comparison between different implementations. Hence, there is a strong need for a benchmarking solution to measure and collect metrics to compare different ZKP implementations. Therefore, we design and implement a benchmarking solution for ZKPs. The proposed solution allows users to gather performance metrics of different ZKP implementations and aids the decision-making process of selecting the right implementation for a specific use case. The system is highly configurable and allows the integration of novel ZKP systems. Further, we demonstrate the solution’ s applicability by benchmarking two popular ZKP implementations.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-12
ConferencePaper
Text
publishedVersion
/11420/45555
IEEE International Conference on Blockchain (Blockchain 2023)
eng
https://hdl.handle.net/11420/45555
oai:tore.tuhh.de:11420/459532024-02-23T10:02:42Zcom_11420_1col_11420_2093
NPD-SCM alignment in mass customization
Nizar
Abdelkafi
Margherita
Pero
Thorsten
Blecker
Andrea
Sianesi
Mass Customization
Product Architecture
Supply Chain
Supply Chain Management
Supply Chain Performance
This chapter aims to develop a new product development supply chain management alignment framework for mass customization. A case study conducted in industry motivates this framework. Variety, modularity, and innovativeness are the product features that should be taken into account when studying alignment in a mass customization setting. From the supply chain viewpoint, configuration, collaboration, and coordination complexities are the variables that matter. We formulate ten propositions explaining the relationships between the variables of the framework. It must be noted that innovativeness, a variable that has so far been neglected with respect to the alignment question, plays a critical role in supply chain management decisions.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011
BookPart
Text
publishedVersion
/11420/45953
Mass Customization (Springer Series in Advanced Manufacturing) Seite 69-85 (2011)
eng
https://hdl.handle.net/11420/45953
oai:tore.tuhh.de:11420/32652019-09-02T11:48:34Zcom_11420_1col_11420_2093
Mode Conversion Due to Residual Via Stubs in Differential Signaling
Jonathan
Cedeño-Chaves
Katharina
Scharff
Allan
Carmona-Cruz
Heinz-Dietrich
Brüns
Renato
Rimolo-Donadio
Christian
Schuster
Back-drilling
differential signaling
mode conversion
printed circuit board
signal integrity
via stub
Mode conversion is an important source of degradation in differential links, which can be induced by a trace length mismatch or asymmetric ground via configurations. This paper explores another source of mode conversion caused by asymmetric residual via stubs. These remnant via stubs can be present because of multiple reasons, such as residual stubs due to process tolerances or errors during back-drilling. Different via configurations have been analyzed through full-wave simulations. Results show a large impact on mode conversion with an increment of around -35 and -15 dB when the residual stub difference changes from 2 to 14 mil at the fundamental frequency of 17.5 GHz. Furthermore, an estimation approach of mode conversion as a function of via stub asymmetry is proposed.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-06
ConferencePaper
Text
publishedVersion
/11420/3265
IEEE 23rd Workshop on Signal and Power Integrity (SPI 2019)
eng
http://hdl.handle.net/11420/3265
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:11420/61632020-05-15T12:50:12Zcom_11420_1col_11420_2093
Towards the understanding of hip squeak in total hip arthroplasty using analytical contact models with uncertainty
Sebastian
Oberst
Zhi
Zhang
Graeme Michael
Campbell
Michael
Morlock
Joseph C. S.
Lai
Norbert
Hoffmann
Biomechanics
Contact conditions
Friction
Osteoarthritis in hip joints affects patients' quality of life such that often only costly orthopaedic surgeries i.e. total hip arthroplasty (THA) provide relief. Common implant materials are metal alloys, steel or titanium-based, plastics such as ultra-high molecular weight polyethylene, or biocompatible alumina and composite ceramics. Hard-on-hard (HoH) bearing articulations, i.e. ceramic-on-ceramic, or hard-on-soft combinations are used. HoH implants have been known to suffer from squeaking, a phenomenon commonly encountered in friction-induced self-excited vibrations. However, the frictional contact mechanics, its dynamics related to impingement, the effect of socket position, stem configuration, bearing size and patient characteristics are poorly understood. This study gives an overview of the state of the art biomechanical research related to squeaking in THA, with a focus on the effects of friction, stability, related wear and lubrication. An analytical model is proposed to study the onset of friction-induced vibrations in a simplified hemispherical hip stem rubbing in its bearing by varying the contact area. Preliminary results of the complex eigenvalue analysis and stick-slip motion analysis indicate that an increased contact fosters the development of instabilities, even at very small values of the friction coefficient owing to large local contact pressures.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2016-08-21
ConferencePaper
Text
publishedVersion
/11420/6163
International Congress and Exposition on Noise Control Engineering: Towards a Quieter Future, INTER-NOISE: 5539-5549 (2016-08-21)
eng
http://hdl.handle.net/11420/6163
oai:tore.tuhh.de:11420/50312020-02-26T15:01:55Zcom_11420_1col_11420_2093
Adapted Design for Variety: Consideration of the Software-Domain
Christoph
Rennpferdt
Dieter
Krause
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019
ConferencePaper
Text
publishedVersion
/11420/5031
IEEE International Conference on Industrial Engineering and Engineering Management, IEEM: 950-954 (2019)
eng
http://hdl.handle.net/11420/5031
oai:tore.tuhh.de:11420/31902019-08-26T09:05:36Zcom_11420_1col_11420_2093
Generation of data sets for semi-empirical models of circulated fluidized bed boilers using hybrid Euler-Lagrange technique
Wojciech P.
Adamczyk
Kari
Myöhänen
Ernst-Ulrich
Hartge
Jouni
Ritvanen
Adam
Klimanek
Timo
Hyppänen
Ryszard A.
Białecki
The primary goal when designing a CFB boiler is to ensure its high energy efficiency. Additional constraints come from environmental regulations, which are constantly becoming more difficult to assess, and require improvements in the boiler design process. Local on-site measurements are often restricted to short distances inward from the furnace wall, leaving most of the core unmeasured. Computer simulations are practically the only feasible tools to investigate the combustion processes and to support the design of CFB units. Three-dimensional steady-state semi-empirical CFB furnace models predict adequate results within reasonable times but these models require tuning to existing objects, which obviously excludes their application for new object design. The present study represents a step toward using the hybrid Euler–Lagrange (HEL) technique to model flow variables in order to replace the measured data. The information collected using the HEL model for an arbitrary furnace can be used to tune a semi-empirical model. To validate the HEL model, measurements of a 235 MWe CFB were used. The simulations show good agreement between the numerical and experimental results, indicating that the presented idea is worth investigating in the future.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-01-15
Article
Text
publishedVersion
/11420/3190
Energy (143): 219-240 (2018-01-15)
eng
http://hdl.handle.net/11420/3190
oai:tore.tuhh.de:11420/43562020-01-13T14:50:40Zcom_11420_1col_11420_2093
Zwischenergebnisse zum BMBF-Projekt „DigiBAU“ im Komzet-Netzwerk BAU UND ENERGIE
Franz Ferdinand
Mersch
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019-10-30
ConferenceObject
Text
publishedVersion
/11420/4356
BMBF-Abschlussveranstaltung „MELINDA“ im KOMZET-Netzwerk BAU UND ENERGIE, Rutesheim: (2019-10-30)
ger
http://hdl.handle.net/11420/4356
oai:tore.tuhh.de:11420/39092019-11-28T07:17:35Zcom_11420_1col_11420_2093
Modeling adsorption on energetically heterogeneous surfaces with an extended SAFT-VR approach
Johannes
Kern
Monika
Johannsen
Adsorption
Carbon dioxide
Equation of state
Heterogeneous surface
SAFT-VR
Adsorption equilibria of methanol/carbon dioxide mixtures on plain silica particles at 308 K and pressures of 10.1 MPa, 12.7 MPa, 15.1 MPa and 20.1 MPa were measured with the frontal analysis by characteristic points (FACP) method using supercritical fluid chromatography. The data show a bimodal adsorption energy distribution and cannot be sufficiently modeled with a two-dimensional SAFT-VR approach. Therefore, an extension of SAFT-VR is proposed to model adsorption on heterogeneous surfaces and applied to the presented data. It can be described by the extended model with very low ARDs between 1.0% and 2.4%.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018
Article
Text
publishedVersion
/11420/3909
Journal of Supercritical Fluids (133): 70-76 (2018)
eng
http://hdl.handle.net/11420/3909
oai:tore.tuhh.de:11420/122662022-04-08T06:13:41Zcom_11420_1col_11420_2093
Stability of temporary submarine slopes
Julian
Bubel
Christina
Rudolph
Jürgen
Grabe
Shallow foundation structures for offshore wind turbines offer ecological benefits compared to pile foundations as less noise is emitted at sea floor level during construction process. On the other hand, shallow offshore foundations can rarely be placed on top of the sea floor. Weak soils usually need to be excavated to place the foundation structure on more stable ground and thus, anthropogenic submarine slopes result. Steep but stable slopes meet both economic and ecologic aims as they minimise material movement and sediment disturbance. After Terzaghi [1] the angle b between slope and the horizontal of the ground surface of coarse-grained soil is at most equal to the critical state friction angle jc. However, it can be observed that natural submarine slopes of sandy soils are always much more shallow. Particularly fine-grained, cohesionless or almost cohesionless soils failed in the past, although the slope angle was much smaller than the critical state friction angle jc. Artificial (temporary) slopes do not appear and behave as natural submarine slopes, since the latter are already shaped by perpetual loads of waves, tide and mass movements. Physical simulations of different scales are used to analyse the stability of artificial submarine slopes with sandy soil of the North Sea. The study focuses on gravitational forces and impacts from the excavation processes. The simulations and theoretical considerations result in suggested slope angles for future shallow offshore foundations of wind farms in the North Sea. Copyright © 2011 by ASME.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011
ConferencePaper
Text
publishedVersion
/11420/12266
Proceedings of the International Conference on Offshore Mechanics and Arctic Engineering - OMAE Vol. 7 (): 991-999 (2011)
eng
http://hdl.handle.net/11420/12266
oai:tore.tuhh.de:11420/55392020-03-28T16:07:35Zcom_11420_1col_11420_2093
How to Use and Derive Stylized Facts for Validating Simulation Models
Matthias
Meyer
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019
BookPart
Text
publishedVersion
/11420/5539
Computer Simulation Validation (2019)
eng
http://hdl.handle.net/11420/5539
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:11420/35422019-10-11T05:49:11Zcom_11420_1col_11420_2093
Parametric structural analysis for a platform supply vessel at conceptual design phase–a sensitivity study via design of experiments
Sthefano L.
Andrade
Henrique M.
Gaspar
Sören
Ehlers
parametric model
structural sensitivity analysis
response surface methodology
620
Parametric structural design is a promising alternative for hull design, capable of combining weight reduction, material efficiency and safety. The challenge of investigating a large space of alternatives created by the parametric model is caused by the high amount of engineering time required to model, analyse and evaluate each of the possible configurations. The objective of this paper is thus to demonstrate the application of a design of experiments sensitivity study for a parametrically modelled global structure of a platform supply vessel with a focus on mass reduction during the conceptual design phase (CDP). The focus on CDP allows for simplifications in the model, thus gaining computational time by reducing discretisation. As a result, knowledge on the impact of design variables on various combined responses is obtained and used to determine a viable alternative within the solution space that has better material usage in comparison to a base case design.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2017-03-21
Article
Text
publishedVersion
/11420/3542
Ships and Offshore Structures (12): S209-S220 (2017)
eng
http://hdl.handle.net/11420/3542
oai:tore.tuhh.de:11420/84982021-01-20T09:57:23Zcom_11420_1col_11420_2093
Die nichtlineare Berechnung ebener Rahmen aus Stahl- oder Spannbeton mit Berücksichtigung der durch das Aufreißen bedingten Achsendrehung
Uwe
Pfeiffer
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2004
2004
Other
Text
publishedVersion
/11420/8498
Cuvillier 3-86537-298-8: (2004)
ger
http://hdl.handle.net/11420/8498
oai:tore.tuhh.de:11420/462142024-03-05T11:03:43Zcom_11420_1col_11420_2093
Editorial Model Predictive Control for Energy Systems: Economic and Distributed Approaches
Antonio
Ferramosca
Timm
Faulwasser
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020
Editorial
Text
publishedVersion
/11420/46214
Optimal Control Applications and Methods 41 (1): 1-2 (2020)
eng
https://hdl.handle.net/11420/46214
oai:tore.tuhh.de:11420/467022024-03-21T13:29:03Zcom_11420_1col_11420_2093
A mesoscopic friction model based on surface roughness and its statistical description
Bernhard Andreas
Stingl
Norbert
Hoffmann
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011
ConferencePaper
Text
publishedVersion
/11420/46702
Proceedings of the ASME International Mechanical Engineering Congress and Exposition - 2011 : November 11 - 17, 2011, Denver, Colorado, USA. - New York, NY, 2012. - Pt. A + B. - Seite 517-518
eng
https://hdl.handle.net/11420/46702
oai:tore.tuhh.de:11420/127732022-06-01T05:19:38Zcom_11420_1col_11420_2093
A model generator for simulation and testing of RDCs
Kai
Schories
Heinrich
Rotgang
Frank
Thielecke
Simulation of avionics equipment is essential due to the complex nature of its development and integration process. Throughout the development process, executable component models are used to demonstrate the feasibility and the compliance of the system design with respect to its functional requirements. In later development phases, there is the need for system integration tests where a mix of real and simulated equipment is used to verify the overall system behavior. Since Boeing 777 and Airbus A380 programs, IMA1 technology has entered several civil aircraft systems. In recent programs like Boeing 787 and Airbus A350 the number of IMA components has significantly increased. In this paper we present a simulation model for a new IMA component - the common Remote Data Concentrator (CRDC)2, which is developed by Thales-Diehl for the Airbus A350 XWB. Building simulation models of IMA components is in general a challenging task due to their complexity on both software and hardware level. The particular challenges faced here, have their roots in two areas. The first is due to the configurable functional behavior of the CRDC, whilst the second comes from its versatile and configurable interface. Together, this leads to a potentially infinite number of unique model instances where each instance constitutes a different CRDC configuration. Moreover, since simulating IMA components always requires stimulation from external models and/or real equipment connected through a set of standardized interfaces, another important aspect is the need for a standardized model integration process which ensures compliance among all system component models and which facilitates an automated integration on a system simulation platform. Our solution is a software tool called SiToRDC which comprises (1) a model generator and (2) a functional core model of the CRDC. The model generator is used to process a user-supplied set of configuration files which parameterize the interface and functions of the core model. The result of the generation process is a CRDC model instance provided as a set of ANSI C-language modules. Those modules are then distributed to simulation workshops where platform integration will take place. We will describe the principal architecture of the SiToRDC toolchain and show how to build CRDC models for different simulation workshops. Copyright © 2011 SAE International.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011-10-18
Article
Text
publishedVersion
/11420/12773
SAE International journal of aerospace 4 (2): 1031-1037 (2011)
eng
http://hdl.handle.net/11420/12773
oai:tore.tuhh.de:11420/27152019-05-27T11:15:43Zcom_11420_1col_11420_2093
On the use of a metasurface prism in gap-waveguide technology to reduce the dispersion of leaky-wave antennas
Lei
Wang
Jose Luis
Gomez-Tornero
Eva
Rajo-Iglesias
Oscar
Quevedo-Teruel
Leaky-wave antennas (LWAs) feature the advantages of high directivity, wide impedance bandwidth, and their ability to scan with frequency. However, the dispersive beam-scanning makes the LWAs very difficult to be utilized in systems that require high-speed data transfer, wide band and high directive antennas. This paper proposes a simple but effective method to reduce the dispersion of LWAs by loading with a metasurface prism realized in gap-waveguide technology. Naturally combining the two technologies, a leaky-wave gap waveguide antenna and a dispersive prism, a low-dispersive gap-waveguide leaky-wave antenna is achieved, with a specific radiation direction that in this example is =4l°. The main radiation direction varies only ±0.5° from 11.5 to 13.0 GHz, with side-lobe levels lower than -13 dB. A 20% half-power gain-drop frequency bandwidth has been obtained. The realized gain varies from 16.4 to 16.8 dBi with a narrow half-power beamwidth of 5°. The full-wave simulations in HFSS agree well with the theoretical calculations.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018
ConferencePaper
Text
publishedVersion
/11420/2715
European Conference on Antennas and Propagation (EuCAP 2018)
eng
http://hdl.handle.net/11420/2715
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:11420/147022023-01-31T17:18:47Zcom_11420_1col_11420_2093
Zum Verhältnis von Rissinitiierung und -ausbreitung an gekerbten Proben mit Schweißnahtcharakteristik
Moritz
Braun
Claas
Fischer
Jörg
Baumgartner
Igor
Varfolomeev
Matthias
Hecht
Ziel dieser Studie ist es, das Verhältnis von Ermüdungslebensdauern bis zu Rissinitiierung und bis zu Bruch in Schweißverbindungen anhand von künstlich gekerbten Proben mit Schweißnahtcharakteristiken unterschiedlicher Kerbschärfe (unterschiedliche Radien und Öffnungswinkel) zu quantifizieren. Die Experimente zeigen, dass der untersuchte Zusammenhang im Wesentlichen von der Kerbschärfe. dem Belastungsniveau und dem Spannungsverhältnis abhängt. Während die experimentell ermittelte Gesamtlebensdauer gut mit einem bruchmechanisch basierten Ansatz beschrieben wird, führt die Rückrechnung der Anrisslebensdauer zu einer sehr großen Streuung
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2022-02
ConferencePaper
Text
publishedVersion
/11420/14702
54. Tagung des Arbeitskreis Bruchmechanik und Bauteilsicherheit (2022)
eng
http://hdl.handle.net/11420/14702
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:11420/72122020-09-02T05:16:55Zcom_11420_1col_11420_2093
The Resistive-Reactive Class-J Power Amplifier Mode
Christian
Friesicke
Rüdiger
Quay
Arne
Jacob
Class-J
losses
power amplifiers (PAs)
This letter introduces a theory which considers the effect of lossy second-harmonic terminations on the voltage waveform, output power, and efficiency of power amplifiers (PAs) operated in the class-J mode. To this end, the conventional (reactive) class-J mode is extended to a resistive-reactive class-J mode with complex fundamental and second-harmonic load impedances. The theory is experimentally validated by performing on-wafer active load-pull measurements on an AlGaN/GaN HEMT power device with 0.25μ gate length and a total gate periphery of 6x200μ. The measured waveforms are de-embedded to the internal current-generator of the device, where they exhibit the theoretically predicted behavior.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015-10
Article
Text
publishedVersion
/11420/7212
IEEE Microwave and Wireless Components Letters 10 (25): 7185478 (2015-10)
eng
http://hdl.handle.net/11420/7212
oai:tore.tuhh.de:11420/83832021-01-12T07:13:31Zcom_11420_1col_11420_2093
An efficient AlGaN/GaN HEMT power amplifier MMIC at K-Band
Christian
Friesicke
Jutta
Kühn
Peter
Brückner
Rüdiger
Quay
Arne F.
Jacob
This paper presents an efficient power amplifier MMIC at K-Band (20 GHz) designed for a 0.25 μm AlGaN/GaN HEMT process on three-inch s.i.-SiC substrates. A low-loss network topology is used for second-harmonic output matching to achieve high PAE. The measured amplifier has a maximum PAE of 41% and an associated output power of 31.4dBm when operated at a drain voltage of 20V. At 35V drain voltage, the amplifier exhibits a PAE of 34% and an associated output power of 34 dBm.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2012-10
ConferencePaper
Text
publishedVersion
/11420/8383
European Microwave Integrated Circuits Conference (EuMIC 2012)
eng
http://hdl.handle.net/11420/8383
oai:tore.tuhh.de:11420/30612019-08-07T07:13:03Zcom_11420_1col_11420_2093
The influence of stem design on critical squeaking friction with ceramic bearings
Na
Fan
Michael
Morlock
Nicholas
Bishop
Gerd
Huber
Norbert
Hoffmann
Michele
Ciavarella
Guang X.
Chen
Arne
Hothan
Florian
Witt
ceramic bearing
squeaking
stem design
critical friction
000
620
610
Ceramic-on-ceramic hip joints have been reported to squeak, a phenomenon that may occur in compromised lubrication conditions. One factor related to the incidence of in vivo squeaking is the stem design. However, it has not yet been possible to relate stem design to squeaking in deteriorating lubrication conditions. The purpose of this study was to determine critical friction factors for different stem designs. A hip simulator was used to measure the friction factor of a ceramic bearing with different stem designs and gradually deteriorating lubrication represented by evaporation of a volatile fluid lubricant. The critical squeaking friction factor was measured at the onset of squeaking for each stem. Critical friction was higher for the long cobalt chrome (0.32 ± 0.02) and short titanium stems (0.39 ± 0.02) in comparison with a long titanium stem (0.29 ± 0.02). The onset of squeaking occurred at a friction factor lower than that measured for dry conditions, in which squeaking is usually investigated experimentally. The results suggest that shorter or heavier stems might limit the possibility of squeaking as lubrication deteriorates. The method developed can be used to investigate the influence of design parameters on squeaking probability. Copyright © 2013 Orthopaedic Research Society.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2013-06-27
Article
Text
publishedVersion
/11420/3061
Journal of Orthopaedic Research 10 (31): 1627-1632 (2013)
eng
http://hdl.handle.net/11420/3061
oai:tore.tuhh.de:11420/77512020-11-03T11:44:06Zcom_11420_1col_11420_2093
Effect of microwave-assisted deep eutectic solvent pretreatment on lignocellulosic structure and bioconversion of wheat straw
Asli
Isci
Gizem Melissa
Erdem
Simel
Bagder Elmaci
Ozge
Sakiyan
Anne
Lamp
Martin
Kaltschmitt
bioethanol
deep eutectic solvent
microwave
pretreatment
wheat straw
In this study, it was aimed to investigate the efficacy of microwave assisted deep eutectic solvent (MW-DES) pretreatment on the structure of wheat straw as well as the sugar and ethanol yields. The samples were treated with choline chloride: formic acid at different mole ratios (1:2, 1:3, and 1:4), microwave power (270, 360, and 450 W) and pretreatment time (2, 5, and 8 min). MW-DES pretreatment has a significant impact on lignocellulosic structure, which was also verified by XRD and SEM analysis. It was found that xylan is the most affected constituent of biomass during MW-DES pretreatment. Severe conditions can solubilize up to 90% of the xylan into liquid phase. The removal of xylan and lignin during MW-DES pretreatment led to highly digestible and fermentable wheat straw fibers. Enzymatic hydrolysis of pretreated wheat straw fibers revealed that MW-DES pretreatment was vastly effective at achieving very high sugar yields (99% glucose, 85% xylose yield). A linear correlation between xylan removal and glucose release during enzymatic hydrolysis was observed. The maximum total sugar release (619 mg/g pretreated wheat straw fibers) being twice as much of conventional deep eutectic solvent (DES) pretreatment, was observed at 1:3 mol ratio, 360 W microwave power and 8 min retention time. The theoretical ethanol yield using Escherichia coli KO11 was 81.5%.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-08-04
Article
Text
publishedVersion
/11420/7751
Cellulose 27: 8949-8962 (2020)
eng
http://hdl.handle.net/11420/7751
oai:tore.tuhh.de:11420/146762023-01-26T07:31:48Zcom_11420_1col_11420_2093
Periplasmic electron transfer via the c-type cytochromes Mtra and FccA of Shewanella oneidensis Mr-1
Björn
Schütz
Marcus
Schicklberger
Johannes
Kürmann
Alfred M.
Spormann
Johannes
Gescher
Dissimilatory microbial reduction of insoluble Fe(III) oxides is a geochemically and ecologically important process which involves the transfer of cellular, respiratory electrons from the cytoplasmic membrane to insoluble, extracellular, mineral-phase electron acceptors. In this paper evidence is provided for the function of the periplasmic fumarate reductase FccA and the decaheme c-type cytochrome MtrA in periplasmic electron transfer reactions in the gammaproteobacterium Shewanella oneidensis. Both proteins are abundant in the periplasm of ferric citrate-reducing S. oneidensis cells. In vitro fumarate reductase FccA and c-type cytochrome MtrA were reduced by the cytoplasmic membrane-bound protein CymA. Electron transfer between CymA and MtrA was 1.4-fold faster than the CymA-catalyzed reduction of FccA. Further experiments showing a bidirectional electron transfer between FccA and MtrA provided evidence for an electron transfer network in the periplasmic space of S. oneidensis. Hence, FccA could function in both the electron transport to fumarate and via MtrA to mineral-phase Fe(III). Growth experiments with a ΔfccA deletion mutant suggest a role of FccA as a transient electron storage protein.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2009-12-15
Article
Text
publishedVersion
/11420/14676
Applied and Environmental Microbiology 75 (24): 7789-7796 (2009-12)
eng
http://hdl.handle.net/11420/14676
oai:tore.tuhh.de:11420/113832022-01-03T12:33:26Zcom_11420_1col_11420_2093
Cyber-physical systems security : experimental analysis of a vinyl acetate monomer plant
Dieter
Gollmann
Pavel
Gurikov
Alexander
Isakov
Marina
Krotofil
Jason
Larsen
Alexander
Winnicki
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2015
ConferencePaper
Text
publishedVersion
/11420/11383
Proceedings of the 1st ACM Workshop on Cyber-Physical System Security. - New York, NY : ACM, 2015.
eng
http://hdl.handle.net/11420/11383
oai:tore.tuhh.de:11420/126042022-05-16T04:20:16Zcom_11420_1col_11420_2093
Computational Modeling for the Stochastic Yarn Variability of Braided Composites Due to Manufacturing Processes
Georgios
Balokas
Benedikt
Kriegesmann
Steffen
Czichon
Raimund
Rolfes
The several manufacturing stages a braided textile must go through until its completion, append random material defects in terms of geometry. These uncertainties are not only difficult to predict, but also hard to be minimized, and since they mostly occur in lower scales, they significantly affect the response of materials with such a heterogeneous nature. Realistic numerical, multiscale models should account for the variability of their representative volume elements, thus have the ability to include spatial randomness.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2018-06
ConferenceObject
Text
publishedVersion
/11420/12604
9th GRACM International Congress on Computational Mechanics (2018)
eng
http://hdl.handle.net/11420/12604
oai:tore.tuhh.de:11420/445342023-12-08T11:44:16Zcom_11420_1col_11420_2093
Adaptive meshfree methods for wave propagation problems in saturated soil
Anne
Schönewald
Otto von
Estorff
ES-RPIM
H-adaptive refinement
Porous media
Stress energy error estimate
Weakened weak form
An h-adaptive procedure for the dynamic analysis of saturated soils, based on meshfree methods, is presented. For modelling the soil Biot's u, p-formulation is used. It is discretized by the meshfree edge based radial point interpolation method (ES-RPIM), which employs the weakened weak (W2) form of the partial differential equation (PDE). For spatial integration so called smoothing domains are adopted, which are reused for the error estimate within the adaptive method. Here, the stress energy error norm is adopted, which incorporates both field variables, u and p, at the same time. In areas, where the estimated error is large, a local refinement strategy inserts additional field points. This is straightforward in meshfree methods, due to their flexibility in terms of the field point distribution. The reliability of the error estimate is tested on the numerical example of squeezing a wet sponge. The estimated error is compared with the exact error, which is obtained from the analytical solution. The modelling of the wave propagation in a half plane loaded by a strip foundation demonstrates the functionality of the proposed method. It is shown, that the adaptively refined model performs highly efficient.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2011
ConferencePaper
Text
publishedVersion
/11420/44534
8th International Conference on Structural Dynamics (EURODYN 2011)
eng
https://hdl.handle.net/11420/44534
oai:tore.tuhh.de:11420/50672020-02-28T15:26:45Zcom_11420_1col_11420_2093
Experimental investigation of temporary electronics cooling with regularly structured composite latent heat storage
Ekkehard
Lohse
Gerhard
Schmitz
This study shows results of the experimental investigation of regularly structured composite latent heat storage. Common solid-liquid phase change materials used as latent heat storages have a low thermal conductivity, which leads to high temperature differences inside large phase change material volumes. This drawback is compensated by the combination with specially designed frame structures made of aluminum to enhance the transport of thermal energy inside the regularly structured composite latent heat storage. A prototype is investigated experimentally on a test rig, where the heat load and temperatures are measured while the phase change process is observed optically. The experimental data are compared to a solid block phase change material heat storage and to the results of a transient Finite Element Method (FEM) simulation.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2013-10-03
Article
Text
publishedVersion
/11420/5067
HVAC & R Research 7 (19): 814-822 (2013-10-03)
eng
http://hdl.handle.net/11420/5067
oai:tore.tuhh.de:11420/57052020-04-14T08:24:38Zcom_11420_1col_11420_2093
Autoclave pre-treatment of green wastes – Effects of temperature, residence time and rotation speed on fuel properties
Marvin
Scherzinger
Tim-André
Kulbeik
Martin
Kaltschmitt
Autoclave pre-treatment
Green biomass wastes
Solid fuel
Green biomass wastes are typically characterized by various disadvantages such as low storability and limited calorific value complicating their energetic use. In order to counteract this, different heat-induced pre-treatment options came into discussion. One of these possibilities being particularly suitable for green biomass is the autoclave pre-treatment. Thus, the aim of this study was to investigate the influence of treatment temperature, residence time and rotation speed during autoclave pre-treatment of green biomass waste streams on various fuel specific characteristic values. Therefore, a 3-level and 3-factor Box-Behnken design was used. Autoclave pre-treatment was carried out in a technical-scale rotary reactor at temperatures of 130, 150 and 170 °C, residence times of 1, 2 and 3 h and rotation speeds of 5, 10 and 15 min−1. Besides the solid products provided based on such a pre-treatment the steam phase was condensed to a large extent. Therefore, the possibility of using this liquid as a substrate for anaerobic digestion was investigated additionally. The investigations showed that the treatment temperature was found to be the main influencing parameter during autoclave pre-treatment for all statistically considered target values. Generally, an increase in temperature led to an increase of higher heating value and grindability as well as a decrease in equilibrium moisture content. An increase in residence time was found to cause an increase of higher heating value and a decrease of equilibrium moisture content, but compared to the effect of treatment temperature residence time had a much smaller effect.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2020-08-01
Article
Text
publishedVersion
/11420/5705
Fuel (273): 117796 (2020-08-01)
eng
http://hdl.handle.net/11420/5705
oai:tore.tuhh.de:11420/34092019-09-24T08:34:12Zcom_11420_1col_11420_2093
Optimal virtual network embedding: Node-link formulation
Márcio
Melo
Susana
Sargento
Ulrich
Killat
Andreas
Timm-Giel
Jorge
Carapinha
embedding
heuristics
ILP model
mapping
NP-hard
optimization
Virtual networks
Network Virtualization is claimed to be a key component of the Future Internet, providing the dynamic support of different networks with different paradigms and mechanisms in the same physical infrastructure. A major challenge in the dynamic provision of virtual networks is the efficient embedding of virtual resources into physical ones. Since this problem is known to be NP-hard, previous research focused on designing heuristic-based algorithms; most of them either do not consider a simultaneous embedding of virtual nodes and virtual links, or apply link-path formulation, leading to non-optimal solutions. This paper proposes an integer linear programming (ILP) formulation to solve the online virtual network embedding problem as a result of an objective function striving for the minimization of resource consumption and load balancing. To this end 3 different objective functions are proposed and evaluated. This approach applies multi-commodity flow constraint to accomplish a node-link formulation that optimizes the allocation of physical network resources. This proposal is evaluated against state of the art heuristics. The performance of the heuristics related to Virtual Network (VN) request acceptance ratio is, at least, 30% below the one of the Virtual Network Embedding Node-Link Formulation (VNE-NLF) method. From the three cost functions evaluated, the Weighted Shortest Distance Path (WSDP) is the one which embeds more VNs and also requires, on average, less physical resources per embedding. © 2013 IEEE.
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2013-12
Article
Text
publishedVersion
/11420/3409
IEEE Transactions on Network and Service Management 4 (10): 6616685 (2013-12)
eng
http://hdl.handle.net/11420/3409
oai:tore.tuhh.de:11420/52912020-03-11T13:21:02Zcom_11420_1col_11420_2093
Entscheidungskonferenz - Ausbildungs- und Unterrichtsverfahren. Ein Kompendium für Lehrkräfte in Schule und Betrieb
Hannes
Ranke
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2019
BookPart
Text
publishedVersion
/11420/5291
wbv Bielefeld, 6. Auflage: 132-137 (2019)
ger
http://hdl.handle.net/11420/5291
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:11420/441762023-11-16T09:08:40Zcom_11420_1col_11420_2093
Engineering-informed design space reduction for PCB-Based power delivery networks
Christian Morten
Schierholz
Youcef
Hassab
Christian
Schuster
Artificial neural network (ANN)
design space exploration
machine learning
physics-based (PB)
power delivery network
printed circuit board (PCB)
An engineering-informed approach to reduce a feasible design space for printed circuit board (PCB)-based power delivery networks (PDNs) of high-speed digital systems, is proposed. A reduction in the sampling of a factor of three decades from more than × 106 sampling points to × 103 sampling points is achieved. This enables to generate data samples for training machine learning (ML) tools being applicable in the design process of the PDNs for a subset of the formerly defined design space. Reducing the complexity is performed by focusing on a specific problem namely a PCB with two via arrays and a fixed PCB size. First a data-driven sensitivity analysis of the different PCB design parameters is performed reducing the design space of parameter variations which show a very small impact on the PDN impedance. Second, a physics-informed and data-supported reduction of the PCB stackup is performed showing the possibility to cover a wide range of stackups with minimal stackup definition. All investigations are performed in the frequency range from mathrm {1∼ MHz} to mathrm {1∼ GHz} , relevant for investigations of the decoupling of PCB-based PDNs. Based on a developed PDN design flow, artificial neural networks (ANNs) are trained to predict key features of the electromagnetic (EM) behavior of the PDN. All generated data samples are provided in the SI/PI-database as Touchstone files (https://www.tet.tuhh.de/en/si-pi-database).
Technische Universität Hamburg. Universitätsbibliothek
Hamburg
Denickestr. 22, 21071 Hamburg
2023-10-01
Article
Text
publishedVersion
/11420/44176
IEEE transactions on components, packaging and manufacturing technology 13 (10): 1613-1623 (2023-10-01)
eng
https://hdl.handle.net/11420/44176
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/
xMetaDissPlus///com_11420_1/100