TY - JOUR A1 - Zhuang, Xiaoying A1 - Huang, Runqiu A1 - Rabczuk, Timon A1 - Liang, C. T1 - A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage JF - Mathematical Problems in Engineering N2 - A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 ER - TY - JOUR A1 - Zhuang, Xiaoying A1 - Huang, Runqiu A1 - Liang, Chao A1 - Rabczuk, Timon T1 - A coupled thermo-hydro-mechanical model of jointed hard rock for compressed air energy storage JF - Mathematical Problems in Engineering N2 - Renewable energy resources such as wind and solar are intermittent, which causes instability when being connected to utility grid of electricity. Compressed air energy storage (CAES) provides an economic and technical viable solution to this problem by utilizing subsurface rock cavern to store the electricity generated by renewable energy in the form of compressed air. Though CAES has been used for over three decades, it is only restricted to salt rock or aquifers for air tightness reason. In this paper, the technical feasibility of utilizing hard rock for CAES is investigated by using a coupled thermo-hydro-mechanical (THM) modelling of nonisothermal gas flow. Governing equations are derived from the rules of energy balance, mass balance, and static equilibrium. Cyclic volumetric mass source and heat source models are applied to simulate the gas injection and production. Evaluation is carried out for intact rock and rock with discrete crack, respectively. In both cases, the heat and pressure losses using air mass control and supplementary air injection are compared. KW - Energiespeicherung KW - Druckluft KW - Kaverne KW - Modellierung Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170428-31726 ER - TY - JOUR A1 - Zhao, Jun-Hua A1 - Lu, Lixin A1 - Rabczuk, Timon T1 - Binding energy and mechanical stability of single- and multi-walled carbon nanotube serpentines JF - The Journal of Chemical Physics N2 - Binding energy and mechanical stability of single- and multi-walled carbon nanotube serpentines KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 U6 - http://dx.doi.org/10.1063/1.4878115 ER - TY - JOUR A1 - Zhao, Jun-Hua A1 - Kou, Liangzhi A1 - Jiang, Jin-Wu A1 - Rabczuk, Timon T1 - Tension-induced phase transition of single-layer molybdenum disulphide (MoS2) at low temperatures JF - Nanotechnology N2 - Tension-induced phase transition of single-layer molybdenum disulphide (MoS2) at low temperatures KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 U6 - http://dx.doi.org/10.1088/0957-4484/25/29/295701 ER - TY - JOUR A1 - Zhao, Jun-Hua A1 - Jiang, Jin-Wu A1 - Jia, Yue A1 - Guo, Wanlin A1 - Rabczuk, Timon T1 - A theoretical analysis of cohesive energy between carbon nanotubes, graphene and substrates JF - Carbon N2 - Explicit solutions for the cohesive energy between carbon nanotubes, graphene and substrates are obtained through continuum modeling of the van der Waals interaction between them. The dependence of the cohesive energy on their size, spacing and crossing angles is analyzed. Checking against full atom molecular dynamics calculations and available experimental results shows that the continuum solution has high accuracy. The equilibrium distances between the nanotubes, graphene and substrates with minimum cohesive energy are also provided explicitly. The obtained analytical solution should be of great help for understanding the interaction between the nanostructures and substrates, and designing composites and nanoelectromechanical systems. KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 U6 - http://dx.doi.org/10.1016/j.carbon.2013.01.041 SP - 108 EP - 119 ER - TY - THES A1 - Zhao, Jun-Hua T1 - Multiscale modeling of nanodevices based on carbon nanotubes and polymers T1 - Multiskalige Modellierung von auf Kohlenstoffnanoröhren und Polymeren basierenden Nanobauteilen N2 - This thesis concerns the physical and mechanical interactions on carbon nanotubes and polymers by multiscale modeling. CNTs have attracted considerable interests in view of their unique mechanical, electronic, thermal, optical and structural properties, which enable them to have many potential applications. Carbon nanotube exists in several structure forms, from individual single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) to carbon nanotube bundles and networks. The mechanical properties of SWCNTs and MWCNTs have been extensively studied by continuum modeling and molecular dynamics (MD) simulations in the past decade since the properties could be important in the CNT-based devices. CNT bundles and networks feature outstanding mechanical performance and hierarchical structures and network topologies, which have been taken as a potential saving-energy material. In the synthesis of nanocomposites, the formation of the CNT bundles and networks is a challenge to remain in understanding how to measure and predict the properties of such large systems. Therefore, a mesoscale method such as a coarse-grained (CG) method should be developed to study the nanomechanical characterization of CNT bundles and networks formation. In this thesis, the main contributions can be written as follows: (1) Explicit solutions for the cohesive energy between carbon nanotubes, graphene and substrates are obtained through continuum modeling of the van der Waals interaction between them. (2) The CG potentials of SWCNTs are established by a molecular mechanics model. (3) The binding energy between two parallel and crossing SWCNTs and MWCNTs is obtained by continuum modeling of the van der Waals interaction between them. Crystalline and amorphous polymers are increasingly used in modern industry as tructural materials due to its important mechanical and physical properties. For crystalline polyethylene (PE), despite its importance and the studies of available MD simulations and continuum models, the link between molecular and continuum descriptions of its mechanical properties is still not well established. For amorphous polymers, the chain length and temperature effect on their elastic and elastic-plastic properties has been reported based on the united-atom (UA) and CG MD imulations in our previous work. However, the effect of the CL and temperature on the failure behavior is not understood well yet. Especially, the failure behavior under shear has been scarcely reported in previous work. Therefore, understanding the molecular origins of macroscopic fracture behavior such as fracture energy is a fundamental scientific challenge. In this thesis, the main contributions can be written as follows: (1) An analytical molecular mechanics model is developed to obtain the size-dependent elastic properties of crystalline PE. (2) We show that the two molecular mechanics models, the stick-spiral and the beam models, predict considerably different mechanical properties of materials based on energy equivalence. The difference between the two models is independent of the materials. (3) The tensile and shear failure behavior dependence on chain length and temperature in amorphous polymers are scrutinized using molecular dynamics simulations. Finally, the influence of polymer wrapped two neighbouring SWNTs’ dispersion on their load transfer is investigated by molecular dynamics (MD) simulations, in which the SWNTs' position, the polymer chain length and the temperature on the interaction force is systematically studied. T3 - ISM-Bericht // Institut für Strukturmechanik, Bauhaus-Universität Weimar - 2014,1 KW - Mehrskalenmodell KW - Kohlenstoff Nanoröhre KW - Polymere KW - Multiscale modeling KW - Carbon nanotubes KW - Polymers Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20140130-21078 ER - TY - JOUR A1 - Zhao, Jiyun A1 - Jiang, Jin-Wu A1 - Wang, L. A1 - Guo, Wanlin A1 - Rabczuk, Timon T1 - Coarse-grained potentials of single-walled carbon nanotubes JF - Journal of the Mechanics and Physics of Solids N2 - Coarse-grained potentials of single-walled carbon nanotubes KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 ER - TY - JOUR A1 - Zhang, Yancheng A1 - Zhuang, Xiaoying A1 - Muthu, Jacob A1 - Mabrouki, Tarek A1 - Fontaine, Michaël A1 - Gong, Yadong A1 - Rabczuk, Timon T1 - Load transfer of graphene/carbon nanotube/polyethylene hybrid nanocomposite by molecular dynamics simulation JF - Composites Part B Engineering N2 - Load transfer of graphene/carbon nanotube/polyethylene hybrid nanocomposite by molecular dynamics simulation KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 SP - 27 EP - 33 ER - TY - JOUR A1 - Xu, G. A1 - Mourrain, B. A1 - Galligo, A. A1 - Rabczuk, Timon T1 - High-quality construction of analysis-suitable trivariate NURBS solids by reparameterization methods JF - Computational Mechanics N2 - High-quality construction of analysis-suitable trivariate NURBS solids by reparameterization methods KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 ER - TY - THES A1 - Wiedemeyer, Nina T1 - Buchfalten: Material Technik Gefüge der Künstlerbücher N2 - Bücher werden nicht erst seit ihrer industriellen Produktion aus gefalzten Papierbogen zusammengesetzt – schon mittelalterliche Codices wurden aus gefalteten Pergamenthäuten konstruiert. Fokus dieser Studie über das Medium Buch ist daher die Kulturtechnik der Faltung. Anders als in der philosophischen Auseinandersetzung mit dem Begriff der Falte, ist die Buchfalte keine anti-lineare Figur, sondern ein operationales Falzscharnier, welches Anordnungen im Buchraum bestimmt und Ornamente hervorbringt. Mediengeschichtliche Fragestellungen sind auf Analysen von Buchmaterial und Künstlerbüchern vom 19. Jahrhundert bis zur Gegenwart basiert. Mit den Büchern u.a. von Christian Boltanski, Hanne Darboven und Hans-Peter Feldmann werden Erkenntnisse über buchgeschichtliche Zusammenhänge gewonnen und das Künstlerbuch in eine Geschichte des Mediums Buch eingestellt. KW - Buch; Buchkunst; Falte; Ornament; Papier KW - Boltanski, Christian; Faltung; Feldmann, Hans-Peter; Künstlerbuch; Van de Velde, Henry Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20141210-23337 UR - http://e-pub.uni-weimar.de/opus4/frontdoor/index/index/docId/2252 N1 - Die Original-Arbeit (weiterführender Link) wurde auf Grund kollorierter Abbildungen zurückgezogen und mit s/w-Abbildungen neu eingestellt (Anforderung VG Wort) ER - TY - THES A1 - Wiedemeyer, Nina T1 - Buchfalten: Material Technik Gefüge der Künstlerbücher N2 - Bücher werden nicht erst seit ihrer industriellen Produktion aus gefalzten Papierbogen zusammengesetzt – schon mittelalterliche Codices wurden aus gefalteten Pergamenthäuten konstruiert. Fokus dieser Studie über das Medium Buch ist daher die Kulturtechnik der Faltung. Anders als in der philosophischen Auseinandersetzung mit dem Begriff der Falte, ist die Buchfalte keine anti-lineare Figur, sondern ein operationales Falzscharnier, welches Anordnungen im Buchraum bestimmt und Ornamente hervorbringt. Mediengeschichtliche Fragestellungen sind auf Analysen von Buchmaterial und Künstlerbüchern vom 19. Jahrhundert bis zur Gegenwart basiert. Mit den Büchern u.a. von Christian Boltanski, Hanne Darboven und Hans-Peter Feldmann werden Erkenntnisse über buchgeschichtliche Zusammenhänge gewonnen und das Künstlerbuch in eine Geschichte des Mediums Buch eingestellt. KW - Papier KW - Falte KW - Buch KW - Buchkunst KW - Ornament KW - Faltung KW - Künstlerbuch KW - Boltanski, Christian KW - Van de Velde, Henry KW - Feldmann, Hans-Peter Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20140806-22527 UR - http://e-pub.uni-weimar.de/opus4/frontdoor/index/index/docId/2333 N1 - Arbeit auf Grund kollorierter Abbildungen zurückgezogen und mit s/w-Abbildungen neu eingestellt (Anforderung VG Wort) ; Siehe Link zum aktuellen Dokument ER - TY - THES A1 - Wellnitz, Felix T1 - BAUKLIMATISCHE ERTÜCHTIGUNG UND NACHHALTIGE INSTANDSETZUNG DENKMALGESCHÜTZTER VERWALTUNGSBAUTEN DER 1950er JAHRE AM BEISPIEL DER EHEMALIGEN BAYERISCHEN LANDESVERTRETUNG VON SEP RUF IN BONN N2 - Viele Baudenkmale sind dem Konflikt aus baulichem Instandsetzungsbedarf für eine zeitgemäße Nutzung und einer sich möglicherweise daraus ergebenden Gefährdung der Denkmalsubstanz ausgesetzt. Gründe sind steigende Energiekosten für den Gebäudebetrieb, zeitgemäße Anforderungen an Behaglichkeit und Arbeitsschutz, sowie die Vermeidung von Schäden an der Substanz aufgrund baulicher Mängel des konstruktiven Wärme- und Feuchteschutzes. Gleichzeitig gilt für viele Bauten aber auch die Notwendigkeit regelmäßiger Nutzung und Bewirtschaftung, um den Erhalt überhaupt zu sichern. Die energetische Ertüchtigung von Baudenkmalen scheitert in diesem Spannungsfeld oft am unlösbaren Konflikt zwischen dem Erhalt der bauzeitlichen Substanz auf der einen und der notwendigen energetischen Optimierung der Gebäudehülle auf der anderen Seite. Zielsetzung dieser Fallstudie ist die beispielhafte Entwicklung einer bauklimatischen und denkmalgerechten Ertüchtigungsstrategie am Beispiel eines Verwaltungsgebäudes der Nachkriegsmoderne als Beitrag zur Lösung dieses Konfliktes. KW - Denkmalpflege KW - Bauklimatik KW - Bauphysik KW - Sanierung KW - Nachkriegsmoderne KW - Ertüchtigung Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20140919-23031 ER - TY - THES A1 - Walsdorf, Joern T1 - M-Learning: Lernen im mobilen Kontext an Hochschulen N2 - A fundamental characteristic of human beings is the desire to start learning at the moment of birth. The rather formal learning process that learners have to deal with in school, on vocational training or in university, is currently subject to fundamental changes. The increasing technologization, overall existing mobile devices, the ubiquitous access to digital information, and students being early adaptors of all these technological innovations require reactions on the part of the educational system. This study examines such a reaction: The use of mobile learning in higher education. Examining the subject m-learning first requires an investigation of the educational model e-learning. Many universities already established e-learning as one of their educational segments, providing a wide range of methods to support this kind of teaching. This study includes an empirical acceptance analysis regarding the general learning behavior of students and their approval of e-learning methods. A survey on the approval of m-learning supplements the results. Mobile learning is characterized by both the mobility of the communication devices and the users. Both factors lead to new correlations, demonstrate the potential of today's mobile devices and the probability to increase the learning performance. The dissertation addresses these correlations and the use of mobile devices in the context of m-learning. M-learning and the usage of mobile devices not only require a reflection from a technological point of view. In addition to the technical features of such mobile devices, the usability of their applications plays an important role, especially with regard to the limited display size. For the purpose of evaluating mobile apps and browser-based applications, various analytical methods are suitable. The concluding heuristic evaluation points out the vulnerability of an established m-learning application, reveals the need for improvement, and shows an approach to rectify the shortcoming. KW - Mobile Learning KW - M-Learning KW - E-Learning KW - Electronic Learning KW - Learning on demand KW - Mobiles Lernen Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20140304-21361 ER - TY - JOUR A1 - Völske, Michael A1 - Gollub, Tim A1 - Hagen, Matthias A1 - Stein, Benno T1 - A keyquery-based classification system for CORE JF - D-Lib Magazine N2 - We apply keyquery-based taxonomy composition to compute a classification system for the CORE dataset, a shared crawl of about 850,000 scientific papers. Keyquery-based taxonomy composition can be understood as a two-phase hierarchical document clustering technique that utilizes search queries as cluster labels: In a first phase, the document collection is indexed by a reference search engine, and the documents are tagged with the search queries they are relevant—for their so-called keyqueries. In a second phase, a hierarchical clustering is formed from the keyqueries within an iterative process. We use the explicit topic model ESA as document retrieval model in order to index the CORE dataset in the reference search engine. Under the ESA retrieval model, documents are represented as vectors of similarities to Wikipedia articles; a methodology proven to be advantageous for text categorization tasks. Our paper presents the generated taxonomy and reports on quantitative properties such as document coverage and processing requirements. KW - Massendaten KW - Taxonomie KW - Dynamic Taxonomy Composition, Keyquery, Classification Systems, Reverted Index, Big Data Problem Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20170426-31662 ER - TY - JOUR A1 - Völker, Conrad A1 - Mämpel, Silvio A1 - Kornadt, Oliver T1 - Measuring the human body’s micro‐climate using a thermal manikin JF - Indoor Air N2 - The human body is surrounded by a micro‐climate which results from its convective release of heat. In this study, the air temperature and flow velocity of this micro‐climate were measured in a climate chamber at various room temperatures, using a thermal manikin simulating the heat release of the human being. Different techniques (Particle Streak Tracking, thermography, anemometry, and thermistors) were used for measurement and visualization. The manikin surface temperature was adjusted to the particular indoor climate based on simulations with a thermoregulation model (UCBerkeley Thermal Comfort Model). We found that generally, the micro‐climate is thinner at the lower part of the torso, but expands going up. At the head, there is a relatively thick thermal layer, which results in an ascending plume above the head. However, the micro‐climate shape strongly depends not only on the body segment, but also on boundary conditions: the higher the temperature difference between the surface temperature of the manikin and the air temperature, the faster the air flow in the micro‐climate. Finally, convective heat transfer coefficients strongly increase with falling room temperature, while radiative heat transfer coefficients decrease. The type of body segment strongly influences the convective heat transfer coefficient, while only minimally influencing the radiative heat transfer coefficient. KW - Raumklima KW - Mikroklima KW - Wärmeübertragung KW - Strömungsmechanik KW - thermal manikin KW - climate chamber KW - micro climate KW - heat transfer coefficient KW - CFD KW - thermography Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20181025-38153 UR - https://onlinelibrary.wiley.com/doi/abs/10.1111/ina.12112 N1 - This is the peer reviewed version of the following article: "Measuring the human body’s micro‐climate using a thermal manikin", which has been published in final form at https://doi.org/10.1111/ina.12112. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions. IS - 24, 6 SP - 567 EP - 579 ER - TY - JOUR A1 - Vu-Bac, N. A1 - Lahmer, Tom A1 - Zhang, Yancheng A1 - Zhuang, Xiaoying A1 - Rabczuk, Timon T1 - Stochastic predictions of interfacial characteristic of polymeric nanocomposites (PNCs) JF - Composites Part B Engineering N2 - Stochastic predictions of interfacial characteristic of polymeric nanocomposites (PNCs) KW - Angewandte Mathematik KW - Stochastik KW - Strukturmechanik Y1 - 2014 SP - 80 EP - 95 ER - TY - JOUR A1 - Vu-Bac, N. A1 - Lahmer, Tom A1 - Keitel, Holger A1 - Zhao, Jun-Hua A1 - Zhuang, Xiaoying A1 - Rabczuk, Timon T1 - Stochastic predictions of bulk properties of amorphous polyethylene based on molecular dynamics simulations JF - Mechanics of Materials N2 - Stochastic predictions of bulk properties of amorphous polyethylene based on molecular dynamics simulations KW - Angewandte Mathematik KW - Stochastik KW - Strukturmechanik Y1 - 2014 SP - 70 EP - 84 ER - TY - THES A1 - Udrea, Mihai-Andrei T1 - Assessment of Data from Dynamic Bridge Monitoring N2 - The focus of the thesis is to process measurements acquired from a continuous monitoring system at a railway bridge. Temperature, strain and ambient vibration records are analysed and two main directions of investigation are pursued. The first and the most demanding task is to develop processing routines able to extract modal parameters from ambient vibration measurements. For this purpose, reliable experimental models are achieved on the basis of a stochastic system identification(SSI) procedure. A fully automated algorithm based on a three-stage clustering is implemented to perform a modal parameter estimation for every single measurement. After selecting a baseline of modal parameters, the evolution of eigenfrequencies is studied and correlated to environmental and operational factors. The second aspect deals with the structural response to passing trains. Corresponding triggered records of strain and temperature are processed and their assessment is accomplished using the average strains induced by each train as the reference parameter. Three influences due to speed, temperature and loads are distinguished and treated individually. An attempt to estimate the maximum response variation due to each factor is also carried out. KW - automatic modal analysis KW - stochastic subspace identification KW - modal tracking KW - modal parameter estimation KW - clustering KW - Messtechnik Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20140429-21742 ER - TY - THES A1 - Torrado, Valentina T1 - Die Präsenz des Abjekten in der zeitgenössischen Kunstproduktion N2 - Die Arbeit fokussiert die Rolle des Abjekten in der zeitgenössischen Kunst und hier insbesondere die Rolle der Künstler aus den wohlhabenden – sogenannten postindustriellen – Ländern. Die Arbeit mit abjekten Themen in der Kunstproduktion ist sehr präsent, jedoch aus einer anderen, eher individualistischen Perspektive. Die wichtigsten Orte der Kunst (Galerien, Museen, Kulturzentren) sind Räume der Legitimation dieser Art von Produktion, dabei wird das Potential der Provokation hinterfragt. Die klassische Avantgarde, besonders der Dadaismus, hat das Abjekte zu Beginn des 20. Jahrhunderts als künstlerisches Material genutzt. Das Spiel mit Grenzüberschreitungen durch die Darstellung des Verbotenen und Ekelerregenden machte das Abjekte zur produktiven Kraft auch auf sozialer Ebene, weil es als Mittel dem gesellschaftlichen Protest und der sozialen Kritik diente. KW - Abjekt KW - Ekel KW - Obdachlos Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:gbv:wim2-20140225-21297 ER - TY - JOUR A1 - Thai, Chien H. A1 - Ferreira, A.J.M. A1 - Bordas, Stéphane Pierre Alain A1 - Rabczuk, Timon A1 - Nguyen-Xuan, Hung T1 - Isogeometric analysis of laminated composite and sandwich plates using a new inverse trigonometric shear deformation theory JF - European Journal of Mechanics N2 - Isogeometric analysis of laminated composite and sandwich plates using a new inverse trigonometric shear deformation theory KW - Angewandte Mathematik KW - Strukturmechanik Y1 - 2014 SP - 89 EP - 108 ER -