TY - JOUR A1 - Laumer, Tobias A1 - Stichel, Thomas A1 - Amend, Philipp A1 - Schmidt, Michael T1 - Simultaneous laser beam melting of multimaterial polymer parts JF - Journal of Laser Applications N2 - By simultaneous laser beam melting (SLBM), parts consisting of different polymer powders can be additively manufactured within one building process. Besides the advantages of conventional LBM, e.g., not needing additional tools and being able to realize parts with almost any geometry, different product requirements can be achieved within a single part. Product requirements may be different chemical resistances or haptic material properties. Therefore, SLBM enlarges the application field for additive manufacturing in general. In the process, two different materials are deposited on the building platform and preheated a few degrees below the melting temperature of the lower melting polymer by infrared emitters. Afterward, a CO2 laser (λ = 10.6 μm) provides the energy for the temperature difference between the preheating temperatures of both materials. Finally, a digital light processing chip is used to achieve simultaneous and flexible energy deposition for melting both preheated polymers. By illuminating the chip with a laser, parts of the beam can be flexibly guided onto the powder bed or into a beam trap. As laser, a single mode thulium laser (λ = 1.94 μm) is used. After melting the layer, a new layer is deposited and the process starts anew. In this paper, polypropylene and polyamide 12 are used as materials. After analyzing the material and melting behavior during the process by a high-resolution thermal imaging system, the parts are qualified regarding their material compatibility at the boundary zone and porosity by cross sections. KW - additive manufacturing KW - material qualification KW - Multi-Material Parts KW - new processes Y1 - 2015 U6 - https://doi.org/10.2351/1.4906303 SN - 1938-1387 SN - 1042-346X VL - 27 IS - S2 PB - Laser Institute of America ER - TY - GEN A1 - Herrmann, David A1 - Schaeffer, Leon A1 - Böhm, Valter ED - Flores, Paulo ED - Marques, Filipe ED - Da Rodrigues Silva, Mariana T1 - Theoretical considerations on 2D multistable tensegrity structures based on equilateral triangles T2 - MMT Symposium (Mechanism and Machine Theory Symposium): Book of Abstracts ; June 26-28, 2024. - Guimarães, Portugal Y1 - 2024 SN - 978-989-33-6448-2 IS - 1. edition SP - 403 EP - 404 PB - Departamento de Engenharia Mecânica, Universidade do Minho CY - Guimarães, Portugal ER - TY - CHAP A1 - Chow, Rosan T1 - Design Research: Making of a Connected Discipline Part 1 T2 - 15th International Conference of the European Academy of Design (EAD Conference), Online and in Person in Brazil, Finland, India, Spain and the UK, 16-20 October 2023 N2 - Despite the existence of societies, journals, conferences, and doctoral programs that generate increasing numbers of doctorates and research publications design research is not a coherent intellectual field with a clear boundary of its subject matter, nor an academic discipline founded on a consensual understanding of its purpose, methodology and pedagogical curriculum; subsequently, there is hardly any commonality across doctoral programs and the assessment of a doctoral degree is difficult if not impossible, so criticised the late design historian Victor Margolin. He called to unify and bound design research to solve these problems. While agreeing with his critiques and appreciating his good intentions, I will argue that his call is impractical as well as undesirable due to the social circumstances and the nature of design inquiry and the changing academic research practice which tend towards inter/transdisciplinarity. Efforts should rather be directed to join fragmented design research in an evolving and inclusive manner to establish a dynamically connected discipline. KW - Design Studies KW - Connected Discipline KW - Fragmented Adhocracy KW - Design Research KW - Transdisciplinary Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-67665 SN - 2318-6968 SP - 200 EP - 207 PB - Editora Blucher CY - São Paulo ER - TY - CHAP A1 - Chow, Rosan T1 - Design Research: Making of a Connected Discipline Part 2 T2 - 15th International Conference of the European Academy of Design (EAD Conference), Online and in Person in Brazil, Finland, India, Spain and the UK, 16-20 October 2023 N2 - In “Design Research: Making of a Connected Discipline Part 1”, I argue that the social circumstances and the nature of design inquiry and the changing academic research practice which tend towards inter/ trans-disciplinarity render building a unified and bounded discipline unrealistic and undesirable. In place of unified and bounded, I suggest connected to be a more viable concept to think about disciplinary research in design. Here in Part 2, I make some suggestions to start making of a connected discipline. KW - Design Research KW - Design Studies KW - Research Through Design KW - Connected Discipline Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:898-opus4-67675 SN - 2318-6968 VL - 11 SP - 208 EP - 214 PB - Editora Blucher CY - São Paulo ER - TY - JOUR A1 - Sýkora, Miroslav A1 - Holicky, Milan A1 - Jung, Karel A1 - Diamantidis, Dimitris T1 - Human safety criteria for risk-based structural design JF - International Journal of Safety and Security Engineering N2 - Risk and reliability criteria are well established in many industrial sectors such as the offshore, chemi- cal or nuclear industries. Comparative risk thresholds have been specified to allow a responsible organization or regulator to identify activities, which impose an acceptable level of risk concerning the participating individuals, or society as a whole. The scope of this contribution is to present target reliability criteria based on acceptable human safety levels. Application of theoretical principles is illustrated by examples of railway engineering structures. Initially it is shown how civil engineering structures for which human safety criteria play a role are classified according to Eurocodes. Examples include bridges, tunnels or station buildings. The general concepts for risk acceptance are then briefly reviewed, particularly in their relation to the target reliability criteria. The distinction between the two types of criteria is made: group risk and the acceptance criterion based on the Life Quality Index LQI approach introduced by ISO 2394:2015. The differences between the criteria for new and existing structures are discussed. The application is illustrated by an example of a bridge crossing an important railway line. It appears that while benefits and costs of a private stakeholder or public authority are reflected by economic optimisation, the society should define the limits for human safety to achieve uniform risks for various daily-life activities and across different industrial sectors. Keywords: group risk, human safety, individual risk, Life Quality Index, railway, risk acceptance, structure, target reliability KW - individual risk KW - group risk KW - human safety KW - Life Quality Index KW - railway KW - risk acceptance KW - structure KW - target reliability Y1 - 2018 U6 - https://doi.org/10.2495/SAFE-V8-N2-287-298 VL - 8 IS - 2 SP - 287 EP - 298 PB - WIT Press ER - TY - JOUR A1 - Hoenicka, Markus A1 - Kaspar, Marcel A1 - Schmid, Christof A1 - Liebold, Andreas A1 - Schrammel, Siegfried T1 - Contact-free monitoring of vessel graft stiffness - proof of concept as a tool for vascular tissue engineering JF - Journal of tissue engineering and regenerative medicine N2 - Tissue-engineered vessel grafts have to mimic the biomechanical properties of native blood vessels. Manufacturing processes often condition grafts to adapt them to the target flow conditions. Graft stiffness is influenced by material properties and dimensions and determines graft compliance. This proof-of-concept study evaluated a contact-free method to monitor biomechanical properties without compromising sterility. Forced vibration response analysis was performed on human umbilical vein (HUV) segments mounted in a buffer-filled tubing system. A linear motor and a dynamic signal analyser were used to excite the fluid by white noise (0-200 Hz). Vein responses were read out by laser triangulation and analysed by fast Fourier transformation. Modal analysis was performed by monitoring multiple positions of the vessel surface. As an inverse model of graft stiffening during conditioning, HUV were digested proteolytically, and the course of natural frequencies (NFs) was monitored over 120 min. Human umbilical vein showed up to five modes with NFs in the range of 5-100 Hz. The first natural frequencies of HUV did not alter over time while incubated in buffer (p = 0.555), whereas both collagenase (-35%, p = 0.0061) and elastase (-45%, p < 0.001) treatments caused significant decreases of NF within 120 min. Decellularized HUV showed similar results, indicating that changes of the extracellular matrix were responsible for the observed shift in NF. Performing vibration response analysis on vessel grafts is feasible without compromising sterility or integrity of the samples. This technique allows direct measurement of stiffness as an important biomechanical property, obviating the need to monitor surrogate parameters. Copyright (C) 2016 John Wiley & Sons, Ltd. KW - ANEURYSMS KW - ARTERIES KW - Biomechanics KW - BIOREACTOR KW - BLOOD-VESSELS KW - BYPASS GRAFTS KW - CONSTRUCTS KW - design KW - extracellular matrix KW - human umbilical vein KW - IN-VITRO KW - MECHANICAL-PROPERTIES KW - proteolysis KW - small calibre graft KW - vascular tissue engineering Y1 - 2017 U6 - https://doi.org/10.1002/term.2186 VL - 11 IS - 10 SP - 2828 EP - 2835 PB - Wiley ER - TY - CHAP A1 - Zheng, Jihong A1 - Fuhrmann, Thomas A1 - Xu, Boqing A1 - Schreiner, Rupert A1 - Jia, Hongzhi A1 - Zhang, Wei A1 - Wang, Ning A1 - Seebauer, Gudrun A1 - Zhu, Jiyan T1 - Curriculum design and German student exchange for Sino-German Bachelor program majored in optoelectronics engineering T2 - 14th Conference on Education and Training in Optics and Photonics (ETOP 2017), 29-31.05.2017, Hangzhou, China, 29-31.05.2017 N2 - Different higher education backgrounds in China and Germany led to challenges in the curriculum design at the beginning of our cooperative bachelor program in Optoelectronics Engineering. We see challenges in different subject requirements from both sides and in the German language requirements for Chinese students. The curriculum was optimized according to the AS IIN criteria, which makes it acceptable and und erstandable by both countries. German students are integrated into the Chinese class and get the sa me lectures like their Chinese colleagues. Intercultural and curriculum challenges are successfully solved. The results are summarized to provide an example for other similar international programs. KW - cooperative bachelor program KW - optoelectronics KW - microsystems KW - student exchange Y1 - 2017 U6 - https://doi.org/10.1117/12.2269574 PB - SPIE ER - TY - CHAP A1 - Tahedl, Michael A1 - Borchsenius, Fredrik A1 - Taras, Andreas T1 - Efficient earthquake simulation of stiff and high DOF bridge expansion joint models with Python T2 - Proceedings of the 10th ECCOMAS Thematic Conference on MULTIBODY DYNAMICS: December 12-15, 2021, Budapest, Hungary N2 - Various types of seismic protection devices has been developed to protect structures like bridges from collapse during an earthquake event, such as hydraulic or metallic hysteresis dampers and spherical pendulum bearings. The expansion joints however, which are already included in most large-span bridges, are not considered as an earthquake protection device regardless of the significant friction forces they produce. These friction forces can be seen as damping forces between the shaking environment and the oscillating bridge. To investigate the effect of those damping forces during different earthquake loads, a multibody dynamics simulation model of the expansion joints will be created. This model should be accurate enough to represent the generation of the damping forces and effects of the geometric setup of the expansion joints. Because large expansion joints for large-span bridges are of special interest, the number of degrees of freedom (DOF) becomes very high. Because this models include stiff bushings, implicit solvers need to be used to gain a stable simulation. Expansion joints are almost unique constructions for every specific bridge, which requires a automated model generation. Because of its excellent modules for numerical mathematics, the scripting language Python is used. To create an efficient simulation model, several optimization techniques such as Just-In-Time (JIT) compilation and parallelization are implemented and tested. KW - Parallelization KW - Optimization KW - Python KW - Earthquake Engineering Y1 - 2021 SN - 978-963-421-870-8 U6 - https://doi.org/10.3311/ECCOMASMBD2021-196 SP - 172 EP - 183 PB - Budapest University of Technology and Economics CY - Budapest, HU ER - TY - CHAP A1 - Holicky, Milan A1 - Diamantidis, Dimitris A1 - Sýkora, Miroslav ED - de Wilde, W. P. ED - Hernández, S. ED - Kravanja, S. T1 - Economically optimum structural design BT - methodology and case study T2 - High Performance and Optimum Design of Structures and Materials III (HPSM/OPTI 2018) ; Ljubljana, Slovenia 11.07.2018 - 13.07.2018 N2 - Codes of practice aim to assure structures have acceptable risks to the public and the minimum total costs over the working life of a design. However, current codified criteria for structural design correspond to a broad range of reliability levels, specified for dissimilar reference periods even though their recalculation for different periods is uncertain due to unknown dependence of failure events in time. In this contribution, target reliability levels are specified on the basis of probabilistic risk optimization considering the objective function as a sum of various costs including effects of time to failure and discounting. A case study presents probabilistic optimization of the roof of a stadium for 4,000 spectators and illustrates the effect of the considered input parameters. Failure consequences and relative cost of safety measure are shown to be major factors affecting the optimum reliability level. Less important factors are the discount rate and working life. Large uncertainty in failure cost estimates seems to have only a marginal effect on derived optimum reliability levels. KW - failure consequences KW - risk acceptance KW - probabilistic optimization KW - target reliability, KW - stadium KW - total cost KW - working life Y1 - 2018 U6 - https://doi.org/10.2495/hpsm180151 SP - 143 EP - 153 PB - WIT ER - TY - JOUR A1 - Agranovsky, Mark A1 - Boman, Jan A1 - Hasanov, Alemdar A1 - Felea, Raluca A1 - Frikel, Jürgen A1 - Krishnan, Venky A1 - Novikov, Roman A1 - Ramlau, Ronny A1 - Sebu, Cristiana T1 - Research biography of a distinguished expert in the field of inverse problems: Professor Eric Todd Quinto JF - Journal of Inverse and Ill-posed Problems N2 - This article gives a brief overview of the research in microlocal analysis, tomography, and integral geometry of Professor Eric Todd Quinto, Robinson Professor of Mathematics at Tufts University, along with the collaborators and colleagues who influenced his work. Y1 - 2022 U6 - https://doi.org/10.1515/jiip-2022-0031 SN - 1569-3945 VL - 30 IS - 4 SP - 613 EP - 617 PB - De Gruyter ER - TY - CHAP A1 - Schmid, Michael A1 - Mottok, Jürgen T1 - Investigation of Scheduling Algorithms for DAG. Tasks through Simulations T2 - ERTS 2022, 11th European Congress Embedded Real Time Systems: 1-2 June, Toulouse, France N2 - In the real-time systems sector, various task models and corresponding tests exist to model and verify the schedulability of task sets on the system at hand. While those models and schedulability tests have intensively been studied from a theoretical point of view, it is hard to ma e use of them to compare the actual execution behavior of scheduling algorithms on a real system. In contrast to schedulability tests, simulators can help to investigate the performance of specific scheduling algorithms. One of the most generalized task models to describe parallel tasks is the Directed Acyclic Graph model that allows to represent tasks as a series of subtasks that depict the potentially parallel computations and precedence constraints that denote the order in which the subtasks are allowed to execute. In this paper, we investigate various scheduling algorithms for the Directed Acyclic Graph model. For that, we first recapitulate the examined scheduling algorithms in detail and point out relevant differences. Subsequently, we present the evaluation of different global and federated scheduling algorithms using fine-grained parallel tasks. To this end, we generate random Directed Acyclic Graph tasks and simulate their execution on multiprocessor systems using scheduling algorithms such as global rate-monotonic and semi-federated scheduling as well as global scheduling policies using the thread pool model. KW - real-time KW - scheduling KW - task models KW - simulation Y1 - 2022 UR - https://hal.archives-ouvertes.fr/hal-03700472/document ER - TY - JOUR A1 - Reindl, Thomas A1 - Meisner, Dennis A1 - Hierl, Stefan T1 - Benchmarking of plastic-based Additive Manufacturing Processes JF - RTejournal - Forum für Rapid Technologie N2 - Additive Manufacturing (AM) is a future-oriented manufacturing technology that is experiencing an enormous boom in the times of Industry 4.0. As a result, various AM technologies and printer models from different manufacturers are entering the market over a short time span. With the advancing establishment of this manufacturing technology for series applications, the expectations and requirements of the fabricated components are also increasing. However, a major challenge is the application-specific selection of the most suitable AM process due to a lack of comparable data. Furthermore, there needs to be more know-how regarding the geometrical and mechanical characteristics of AM parts. This paper addresses this problem by comparing the three most common plasticbased AM processes in the areas of surface quality, dimensional accuracy, and mechanical properties. Roughness measurements, evaluation of a benchmark artifact, tensile tests, and load increase tests are carried out. Based on the results, the individual possibilities and limitations of the compared AM processes can be detected. KW - Additive Manufacturing KW - benchmark artifact KW - dimensional accuracy KW - Fused Layer Modeling KW - mechanical properties KW - Multi Jet Fusion KW - process benchmark KW - Selective Laser Sintering KW - surface quality Y1 - 2023 U6 - https://doi.org/https://doi.org/10.58134/fh-aachen-rte_2023_002 PB - Fachhochschule Aachen ER - TY - JOUR A1 - De, Sangita A1 - Premek, Brada A1 - Mottok, Jürgen T1 - Derivation of Optimized Threshold of Semantic Alignment Metrics for Intepretation of Interoperability and Reusability of Cross-enterprise Vehicle Service Interface Models JF - Informatica N2 - Over the past decade, cars have turned gradually into real cyber physical systems. The collaboration of services between the service-oriented, cross-enterprise vehicle application frameworks has increased to generate novel, smart and complicated vehicle services. Consequently, from an interoperability perspective, semantically mapping of vehicle service component’s interface ontological models emerged as a big research interest in automotive application domain that manipulates several cross-enterprise synergy knowledge applications frameworks. The ontological metamodeling lays the foundation for building semantic bridge and exploring semantic associations between service components’ interface models based on the domain knowledge for semantic interoperability. Also, several semantic quality metrics has been defined over time for the vehicle service interface ontological metamodels. The empirically evaluated values of these metrics can be used to assess progress in cross-enterprise interoperability between the service and the clients’ APIs ontological models in vehicle domain. Despite potential benefits of semantic alignment quality metrics, the effective use of these metrics for vehicle service interface ontologies have proven elusive. Yes, such metrics can be used successfully for quantification, but then they mostly fail to provide adequate annotations in subsequent decision-making in the direction of semantic interoperability and reusability. The effective use of ontology semantic alignment quality metrics is basically hindered in the absence of the meaningful thresholds. In fact, the absence of an effective and meaningful threshold for the semantic similarity measure between various vehicle service interface ontological metamodels, motivates this research work which not only proposes a design approach to an optimized threshold for the semantic similarity metrics but also applies this threshold on few defined semantic alignment quality metrics. This paper also uses a real-world vehicle domain industrial case study to illustrate the design approach. KW - interface KW - automotive services KW - semantic KW - metrics KW - optimized threshold KW - framework KW - metamodels KW - ontologies Y1 - 2023 U6 - https://doi.org/10.31449/inf.v47i7.4739 SN - 0350-5596 VL - 47 IS - 7 PB - Slovenian Society Informatika ER -