TUHH Open Research
TORE is the repository for Open Access publications and for research data of the Hamburg University of Technology (TUHH). As a research information system, TORE makes the TUHH's research landscape visible to the outside world. Institutes and working groups, researchers, their publications, research data and projects are presented here.
Members of the TUHH can publish their scientific work such as dissertations, preprints or accepted manuscripts as well as research data here and make them available in the long term.
TUHH Institutions
104
Researchers
991
Projects
1443
Publications
15373
Research Data
101
Conferences
3159
Recent Additions
- PublicationNew support size bounds for integer programming, applied to makespan minimization on uniformly related machines(Schloss Dagstuhl – Leibniz-Zentrum für Informatik, Dagstuhl Publishing, 2023)
; ; Mixed-integer linear programming (MILP) is at the core of many advanced algorithms for solving fundamental problems in combinatorial optimization. The complexity of solving MILPs directly correlates with their support size, which is the minimum number of non-zero integer variables in an optimal solution. A hallmark result by Eisenbrand and Shmonin (Oper. Res. Lett., 2006) shows that any feasible integer linear program (ILP) has a solution with support size s ≤ 2m · log(4m∆), where m is the number of constraints, and ∆ is the largest absolute coefficient in any constraint. Our main combinatorial result are improved support size bounds for ILPs. We show that any ILP has a solution with support size s ≤ m · (log(3A_{max}) + √(log(A_{max}))), where A_{max} := ∥A∥_1 denotes the 1-norm of the constraint matrix A. Furthermore, we show support bounds in the linearized form s ≤ 2m · log(1.46A_{max}). Our upper bounds also hold with A_{max} replaced by √m∆, which improves on the previously best constants in the linearized form. Our main algorithmic result are the fastest known approximation schemes for fundamental scheduling problems, which use the improved support bounds as one ingredient. We design an efficient approximation scheme (EPTAS) for makespan minimization on uniformly related machines (Q||Cmax). Our EPTAS yields a (1 + ε)-approximation for Q||Cmax on N jobs in time 2^O(1/ε log3(1/ε) log(log(1/ε))) + O(N), which improves over the previously fastest algorithm by Jansen, Klein and Verschae (Math. Oper. Res., 2020) with run time 2^O(1/ε log4(1/ε)) + N^O(1). Arguably, our approximation scheme is also simpler than all previous EPTASes for Q||Cmax, as we reduce the problem to a novel MILP formulation which greatly benefits from the small support.Publication Type: Conference PaperPublisher DOI:10.4230/LIPIcs.ISAAC.2023.13 - PublicationMorsels: Explicit virtual memory objects(Association for Computing Machinery, Inc, 2023-10-23)
; ; The tremendous growth of RAM capacity - now exceeding multiple terabytes - necessitates a reevaluation of traditional memory-management methods, which were developed when resources were scarce. Current virtual-memory subsystems handle address-space regions as sets of individual 4-KiB pages with demand paging and copy-on-write, resulting in significant management overhead. Although huge pages reduce the number of managed entities, they induce internal fragmentation and have a coarse copy granularity.To address these problems, we introduce Morsels, a novel virtual-memory-management paradigm that is purely based on hardware data structures and enables the efficient sharing of virtual-memory objects between processes and devices while being well suited for non-volatile memory. Our benchmarks show that Morsels reduce the mapping time for a 6.82-GiB machine-learning model by up to 99.8 percent compared to conventional memory mapping in Linux.Publication Type: Conference PaperPublisher DOI:10.1145/3609308.3625267 - PublicationNutzung von Motion-Capture-Technologien zur individuellen Ergonomieanalyse in der Produktion(2023)Musculoskeletal disorders are the main cause of sick leave in the manufacturing sector. One reason for this is that companies do not sufficiently consider the individual characteristics and capabilities of employees when designing their work. This dissertation presents a method for an individual ergonomics analysis in manufacturing. The method records worker capabilities and the individual strain at the workplace with the help of a motion capture system. The individual assessment helps companies find targeted workplace improvement measures.Publication Type: ThesisThesis Type: Doctoral Thesis
- PublicationAnalyse und Optimierung von Suchvorgängen in der industriellen Produktion(2023)In industrial production, search processes appear whenever material or information is needed. Although searching is a fundamental activity within production processes, existing models within production management are not capable of analyzing search processes. This work presents an approach for modeling industrial search processes and describes an analysis procedure for evaluating search efforts in production. In addition, an improvement procedure for systematically deriving measures to reduce search efforts is described. The entire method was successfully applied and evaluated in a low-volume, high-variance production environment.Publication Type: ThesisThesis Type: Doctoral Thesis
- PublicationKrümmungs-Kapazitäts-Beziehungen gewellter Elektroden in elektrochemischen Doppelschichtkondensatoren(2023)
; Like capacitors, the storage mechanism of electrochemical double-layer capacitors is based on the formation of electrostatic fields between the electrodes and a double layer formed by the ions in the electrode-electrolyte interface. Beside cycle stability and the charging and discharging speed the performance is also characterized by the capacity of the electrodes. However the capaitance is strongly influenced by the size of the electrode surface on which it is possible for the electrolyte ions to accumulate in the form of a double layer. Due to their high surface area, amorphous carbons are considered typical electrode materials for common supercapacitors. Among others, these electrodes are characterized by convex and concave curvatures, among other things. However, the interaction of convex and concave regions and their superposition have rarely been investigated. In addition this work demonstrates a large impact of nanoscale surface curvatures, either convex or concave, on the capacitive performance of supercapacitors. Molecular dynamics simulations of trilayer graphene electrodes with convex and concave curved regions of different curvature radii are performed to describe this interaction in more detail. A 1.5 M solution of the ionic liquid 1-butyl-3-methylimidazoliumhexafluorophosphate [BMI][PF6] and acetonitil as solvent serves as the electrolyte. The definition of constant potentials at the electrodes allows the determination of the charge of each electrode atom depending on the time-dependent electrolyte configuration. The results show a variable behavior of the differential capacitance with respect to different curvature radii both for the overall electrode and when the concave and convex regions were plotted separately. Furthermore, this work describes the influence of the electrode curvature on the orientation of the cations adsorbed on the electrode surface and the composition of the ionic layer accumulated in the electrode-electrolyte-interface and correlates this influence with the differential capacitance peaks. The evaluation of more exhaustive simulations of selected systems by using the Unbinned Weighted Histogram Analysis Method (UWHAM) provides a higher statistical accuracy and allows the results to be presented as a continuous function of the applied potential. These calculations also reveals potential-dependent fluctuations of the differential capacitance, the compostion of the ionic layer and the cation orientation. If the curvature radii are of the same order of magnitude as the ions, the restricted space in the electrode-electrolyte interface causes a reduced number of possibilities for the orientation of the ions within this interface. This leads to changes in free energy compared to flat electrodes or electrodes with significantly larger curvature radii. Furthermore, the capacitance peaks of the negative electrode can be related not only to variations in the composition of the Helmholtz layer of the negative electrode, but also to variations at the positive electrode. It is found that both the applied potential and the electrode curvature determine the occurrence of capacitive peaks in the convex and concave regions and thus determine the capacitive performance of the electrode. Furthermore, by calculating a charge-charge covariance matrix from the charge fluctuations of the electrode atoms, the influence of individual atomic electrode charges or defined regions of the electrode on the distinct nontrivial features of the differential capacitance can be quantified in a sophisticated manner. This method can also be applied to more complex electrode models with different pore geometries, thus showing the influence of different morphological characteristics on the capacitance. For this reason, the method presented here can serve as a tool in defining design criteria of future electrodes.Publication Type: ThesisThesis Type: Doctoral Thesis
Recent Additions
- Research DataAnhang zum Sammelbandartikel - Sozial, ökologisch oder technisch-verkehrlich – Straßenkonzepte als Ansatzpunkt für multifunktionale Straßenräume(2023-11-09)Anhang zum Beitrag in Kreutz, S. und Stokman, A. (Hrsg.) (2024): Transformation urbaner linearer Infrastrukturlandschaften - Wie Straßen und Gewässer zu attraktiven und klimaangepassten Stadträumen werden können. oekom Verlag. Die vorliegenden Tabellen stammen aus dem Sammelbandartikel: Sozial, ökologisch oder technisch-verkehrlich? – Straßenkonzepte als Ansatzpunkt für multifunktionale Straßenräume, der im Sammelband: Transformation urbaner linearer Infrastrukturlandschaften - Wie Straßen und Gewässer zu attraktiven und klimaangepassten Stadträumen werden können, erschienen ist. Die Tabelle in Anhang 1 gibt eine Übersicht der im Rahmen des Artikels durchgeführten Literatur-Review zu Straßenkonzepten und gibt Auskunft über die Autoren, das Publikationsjahr und den geographischen Bezug. Neben der Überblicksfunktion der verwendeten Literatur können zudem die zeitlichen Entwicklungs- und Anwendungshorizonte, als auch die geographische Verbreitung von Straßenkonzepten verdeutlicht werden. Anhang 2 gibt einen Überblick der im Rahmen des Literatur-Reviews herausgearbeiteten Maßnahmen und deren Ziele bzw. Eigenschaften. Dabei werden die jeweiligen Maßnahmen übergeordneten Zielkategorien zugeordnet, die induktiv aus den herausgearbeiteten Maßnahmen abgeleitet werden und auf eine Vielzahl an fachdisziplinären Perspektiven zurückzuführen ist.Data Type: Text
- Research DataEnhancing 3D reconstruction accuracy of multi-voltage FIB tomography images using multimodal machine learning(2023-11-09)
; ; ; ; ; ; This dataset contains simulated multi-voltage FIB tomography data of hierarchical nanoporous gold, trained machine learning model weights and segmentation results of synthetic and real hierarchical nanoporous gold data. For more information, please refer to the published research article: Enhancing 3D reconstruction accuracy of multi-voltage FIB tomography images using multimodal machine learning.Data Type: Dataset - Research DataRole of slice thickness quantification in the 3D reconstruction of FIB tomography data of nanoporous materials(2023-11-02)
; ; ; ; ; ; This dataset contains synthetic structures of hierarchical nanoporous gold, which mimics real hierarchical nanoporous gold structures, segmentation results and repositioned interpolated structures of the real hierarchical nanoporous gold dataset and trained weights of machine learning model used for interpolation. For more information, please refer to the published research article: Role of slice thickness quantification in the 3D reconstruction of FIB tomography data of nanoporous materials.Data Type: Dataset - Research DataDissertation Melanie Tabea Knoll - Appendix 6.4: Detachment of biomaterial - OCT and video time lapse(2023-10-13)In bioelectrochemical systems (BES), the conversion of chemical energy into electrical energy and vice versa can be catalyzed by electroactive microorganisms. The microorganism-electrode interaction is a key factor that can limit sufficient space-time yield required for industrial applications. Providing the organisms with an artificial scaffold that enhances this interaction compared to the naturally formed biofilm matrix can significantly improve the productivity of these systems. In the context of the dissertation, such a hybrid biomaterial was established by embedding the electroactive model organism Shewanella oneidensis in an agarose hydrogel. The possibility of detaching the hybrid biofilm material should be investigated, as the recovery of the biomaterial could be essential in future application processes and reveal the maximum number of electrons that can be supplied before the material degrades. The latter is an important parameter for the potential application of the biomaterial in bioelectrosynthesis, a process in which organisms grow on the cathode as a source of electrons and energy and where the biomaterial could have similar beneficial effects on productivity to those shown in this thesis for anodic systems. Synthetic biofilm detachment was induced by applying a negative current to a sprayed hydrogel in a BES flow cell reactor. Detachment from two electrode materials, a graphite plate and a graphite felt, was visualized using video recording and optical coherence tomography (OCT). The graphite felt resulted in partial detachment of parts of the biofilm, whereas the graphite plate resulted in complete detachment of the biomaterial as a whole.Data Type: Video
- Research DataSupplementary material to article with title: Development and Assessment of a Methodology for Abstraction of Topology Optimization Results to Enable the Substitution of Optimized Beams(2023-10-10)
; ; ; The data is supplementary material to the article with title "Development and Assessment of a Methodology for Abstraction of Topology Optimization Results to Enable the Substitution of Optimized Beams" of the International Congress on Applications of Lasers & Electro-Optics (ICALEO) 2023, 16-19 October 2023, Chicago, Illinois, United States. A more detailed background on the files is given in the article. Mph-files can be opened with the software COMSOL Multiphysics 6.0. Implemented submethodologies can be viewed using the Application Builder of the Software.Data Type: Simulation Data