--- _id: '48896' abstract: - lang: eng text: Hardness of Multi-Objective (MO) continuous optimization problems results from an interplay of various problem characteristics, e. g. the degree of multi-modality. We present a benchmark study of classical and diversity focused optimizers on multi-modal MO problems based on automated algorithm configuration. We show the large effect of the latter and investigate the trade-off between convergence in objective space and diversity in decision space. author: - first_name: Jeroen full_name: Rook, Jeroen last_name: Rook - first_name: Heike full_name: Trautmann, Heike last_name: Trautmann - first_name: Jakob full_name: Bossek, Jakob id: '102979' last_name: Bossek orcid: 0000-0002-4121-4668 - first_name: Christian full_name: Grimme, Christian last_name: Grimme citation: ama: 'Rook J, Trautmann H, Bossek J, Grimme C. On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems. In: Proceedings of the Genetic and Evolutionary Computation Conference Companion. GECCO’22. Association for Computing Machinery; 2022:356–359. doi:10.1145/3520304.3528998' apa: Rook, J., Trautmann, H., Bossek, J., & Grimme, C. (2022). On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems. Proceedings of the Genetic and Evolutionary Computation Conference Companion, 356–359. https://doi.org/10.1145/3520304.3528998 bibtex: '@inproceedings{Rook_Trautmann_Bossek_Grimme_2022, place={New York, NY, USA}, series={GECCO’22}, title={On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems}, DOI={10.1145/3520304.3528998}, booktitle={Proceedings of the Genetic and Evolutionary Computation Conference Companion}, publisher={Association for Computing Machinery}, author={Rook, Jeroen and Trautmann, Heike and Bossek, Jakob and Grimme, Christian}, year={2022}, pages={356–359}, collection={GECCO’22} }' chicago: 'Rook, Jeroen, Heike Trautmann, Jakob Bossek, and Christian Grimme. “On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems.” In Proceedings of the Genetic and Evolutionary Computation Conference Companion, 356–359. GECCO’22. New York, NY, USA: Association for Computing Machinery, 2022. https://doi.org/10.1145/3520304.3528998.' ieee: 'J. Rook, H. Trautmann, J. Bossek, and C. Grimme, “On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems,” in Proceedings of the Genetic and Evolutionary Computation Conference Companion, 2022, pp. 356–359, doi: 10.1145/3520304.3528998.' mla: Rook, Jeroen, et al. “On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems.” Proceedings of the Genetic and Evolutionary Computation Conference Companion, Association for Computing Machinery, 2022, pp. 356–359, doi:10.1145/3520304.3528998. short: 'J. Rook, H. Trautmann, J. Bossek, C. Grimme, in: Proceedings of the Genetic and Evolutionary Computation Conference Companion, Association for Computing Machinery, New York, NY, USA, 2022, pp. 356–359.' date_created: 2023-11-14T15:59:00Z date_updated: 2023-12-13T10:50:24Z department: - _id: '819' doi: 10.1145/3520304.3528998 extern: '1' keyword: - configuration - multi-modality - multi-objective optimization language: - iso: eng page: 356–359 place: New York, NY, USA publication: Proceedings of the Genetic and Evolutionary Computation Conference Companion publication_identifier: isbn: - 978-1-4503-9268-6 publisher: Association for Computing Machinery series_title: GECCO’22 status: public title: On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems type: conference user_id: '102979' year: '2022' ... --- _id: '21004' abstract: - lang: eng text: 'Automated machine learning (AutoML) supports the algorithmic construction and data-specific customization of machine learning pipelines, including the selection, combination, and parametrization of machine learning algorithms as main constituents. Generally speaking, AutoML approaches comprise two major components: a search space model and an optimizer for traversing the space. Recent approaches have shown impressive results in the realm of supervised learning, most notably (single-label) classification (SLC). Moreover, first attempts at extending these approaches towards multi-label classification (MLC) have been made. While the space of candidate pipelines is already huge in SLC, the complexity of the search space is raised to an even higher power in MLC. One may wonder, therefore, whether and to what extent optimizers established for SLC can scale to this increased complexity, and how they compare to each other. This paper makes the following contributions: First, we survey existing approaches to AutoML for MLC. Second, we augment these approaches with optimizers not previously tried for MLC. Third, we propose a benchmarking framework that supports a fair and systematic comparison. Fourth, we conduct an extensive experimental study, evaluating the methods on a suite of MLC problems. We find a grammar-based best-first search to compare favorably to other optimizers.' author: - first_name: Marcel Dominik full_name: Wever, Marcel Dominik id: '33176' last_name: Wever orcid: ' https://orcid.org/0000-0001-9782-6818' - first_name: Alexander full_name: Tornede, Alexander id: '38209' last_name: Tornede - first_name: Felix full_name: Mohr, Felix last_name: Mohr - first_name: Eyke full_name: Hüllermeier, Eyke id: '48129' last_name: Hüllermeier citation: ama: 'Wever MD, Tornede A, Mohr F, Hüllermeier E. AutoML for Multi-Label Classification: Overview and Empirical Evaluation. IEEE Transactions on Pattern Analysis and Machine Intelligence. Published online 2021:1-1. doi:10.1109/tpami.2021.3051276' apa: 'Wever, M. D., Tornede, A., Mohr, F., & Hüllermeier, E. (2021). AutoML for Multi-Label Classification: Overview and Empirical Evaluation. IEEE Transactions on Pattern Analysis and Machine Intelligence, 1–1. https://doi.org/10.1109/tpami.2021.3051276' bibtex: '@article{Wever_Tornede_Mohr_Hüllermeier_2021, title={AutoML for Multi-Label Classification: Overview and Empirical Evaluation}, DOI={10.1109/tpami.2021.3051276}, journal={IEEE Transactions on Pattern Analysis and Machine Intelligence}, author={Wever, Marcel Dominik and Tornede, Alexander and Mohr, Felix and Hüllermeier, Eyke}, year={2021}, pages={1–1} }' chicago: 'Wever, Marcel Dominik, Alexander Tornede, Felix Mohr, and Eyke Hüllermeier. “AutoML for Multi-Label Classification: Overview and Empirical Evaluation.” IEEE Transactions on Pattern Analysis and Machine Intelligence, 2021, 1–1. https://doi.org/10.1109/tpami.2021.3051276.' ieee: 'M. D. Wever, A. Tornede, F. Mohr, and E. Hüllermeier, “AutoML for Multi-Label Classification: Overview and Empirical Evaluation,” IEEE Transactions on Pattern Analysis and Machine Intelligence, pp. 1–1, 2021, doi: 10.1109/tpami.2021.3051276.' mla: 'Wever, Marcel Dominik, et al. “AutoML for Multi-Label Classification: Overview and Empirical Evaluation.” IEEE Transactions on Pattern Analysis and Machine Intelligence, 2021, pp. 1–1, doi:10.1109/tpami.2021.3051276.' short: M.D. Wever, A. Tornede, F. Mohr, E. Hüllermeier, IEEE Transactions on Pattern Analysis and Machine Intelligence (2021) 1–1. date_created: 2021-01-16T14:48:13Z date_updated: 2022-01-06T06:54:42Z department: - _id: '34' - _id: '355' - _id: '26' doi: 10.1109/tpami.2021.3051276 keyword: - Automated Machine Learning - Multi Label Classification - Hierarchical Planning - Bayesian Optimization language: - iso: eng page: 1-1 project: - _id: '1' name: SFB 901 - _id: '3' name: SFB 901 - Project Area B - _id: '10' name: SFB 901 - Subproject B2 - _id: '52' name: Computing Resources Provided by the Paderborn Center for Parallel Computing publication: IEEE Transactions on Pattern Analysis and Machine Intelligence publication_identifier: issn: - 0162-8828 - 2160-9292 - 1939-3539 publication_status: published status: public title: 'AutoML for Multi-Label Classification: Overview and Empirical Evaluation' type: journal_article user_id: '5786' year: '2021' ... --- _id: '21808' abstract: - lang: eng text: "Modern services consist of interconnected components,e.g., microservices in a service mesh or machine learning functions in a pipeline. These services can scale and run across multiple network nodes on demand. To process incoming traffic, service components have to be instantiated and traffic assigned to these instances, taking capacities, changing demands, and Quality of Service (QoS) requirements into account. This challenge is usually solved with custom approaches designed by experts. While this typically works well for the considered scenario, the models often rely on unrealistic assumptions or on knowledge that is not available in practice (e.g., a priori knowledge).\r\n\r\nWe propose DeepCoord, a novel deep reinforcement learning approach that learns how to best coordinate services and is geared towards realistic assumptions. It interacts with the network and relies on available, possibly delayed monitoring information. Rather than defining a complex model or an algorithm on how to achieve an objective, our model-free approach adapts to various objectives and traffic patterns. An agent is trained offline without expert knowledge and then applied online with minimal overhead. Compared to a state-of-the-art heuristic, DeepCoord significantly improves flow throughput (up to 76%) and overall network utility (more than 2x) on realworld network topologies and traffic traces. It also supports optimizing multiple, possibly competing objectives, learns to respect QoS requirements, generalizes to scenarios with unseen, stochastic traffic, and scales to large real-world networks. For reproducibility and reuse, our code is publicly available." article_type: original author: - first_name: Stefan Balthasar full_name: Schneider, Stefan Balthasar id: '35343' last_name: Schneider orcid: 0000-0001-8210-4011 - first_name: Ramin full_name: Khalili, Ramin last_name: Khalili - first_name: Adnan full_name: Manzoor, Adnan last_name: Manzoor - first_name: Haydar full_name: Qarawlus, Haydar last_name: Qarawlus - first_name: Rafael full_name: Schellenberg, Rafael last_name: Schellenberg - first_name: Holger full_name: Karl, Holger id: '126' last_name: Karl - first_name: Artur full_name: Hecker, Artur last_name: Hecker citation: ama: Schneider SB, Khalili R, Manzoor A, et al. Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning. Transactions on Network and Service Management. 2021. doi:10.1109/TNSM.2021.3076503 apa: Schneider, S. B., Khalili, R., Manzoor, A., Qarawlus, H., Schellenberg, R., Karl, H., & Hecker, A. (2021). Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning. Transactions on Network and Service Management. https://doi.org/10.1109/TNSM.2021.3076503 bibtex: '@article{Schneider_Khalili_Manzoor_Qarawlus_Schellenberg_Karl_Hecker_2021, title={Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning}, DOI={10.1109/TNSM.2021.3076503}, journal={Transactions on Network and Service Management}, publisher={IEEE}, author={Schneider, Stefan Balthasar and Khalili, Ramin and Manzoor, Adnan and Qarawlus, Haydar and Schellenberg, Rafael and Karl, Holger and Hecker, Artur}, year={2021} }' chicago: Schneider, Stefan Balthasar, Ramin Khalili, Adnan Manzoor, Haydar Qarawlus, Rafael Schellenberg, Holger Karl, and Artur Hecker. “Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning.” Transactions on Network and Service Management, 2021. https://doi.org/10.1109/TNSM.2021.3076503. ieee: S. B. Schneider et al., “Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning,” Transactions on Network and Service Management, 2021. mla: Schneider, Stefan Balthasar, et al. “Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning.” Transactions on Network and Service Management, IEEE, 2021, doi:10.1109/TNSM.2021.3076503. short: S.B. Schneider, R. Khalili, A. Manzoor, H. Qarawlus, R. Schellenberg, H. Karl, A. Hecker, Transactions on Network and Service Management (2021). date_created: 2021-04-27T08:04:16Z date_updated: 2022-01-06T06:55:15Z ddc: - '000' department: - _id: '75' doi: 10.1109/TNSM.2021.3076503 file: - access_level: open_access content_type: application/pdf creator: stschn date_created: 2021-04-27T08:01:26Z date_updated: 2021-04-27T08:01:26Z description: Author version of the accepted paper file_id: '21809' file_name: ris-accepted-version.pdf file_size: 4172270 relation: main_file file_date_updated: 2021-04-27T08:01:26Z has_accepted_license: '1' keyword: - network management - service management - coordination - reinforcement learning - self-learning - self-adaptation - multi-objective language: - iso: eng oa: '1' project: - _id: '1' name: SFB 901 - _id: '4' name: SFB 901 - Project Area C - _id: '16' name: SFB 901 - Subproject C4 publication: Transactions on Network and Service Management publisher: IEEE status: public title: Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning type: journal_article user_id: '35343' year: '2021' ... --- _id: '33854' abstract: - lang: eng text: "Macrodiversity is a key technique to increase the capacity of mobile networks. It can be realized using coordinated multipoint (CoMP), simultaneously connecting users to multiple overlapping cells. Selecting which users to serve by how many and which cells is NP-hard but needs to happen continuously in real time as users move and channel state changes. Existing approaches often require strict assumptions about or perfect knowledge of the underlying radio system, its resource allocation scheme, or user movements, none of which is readily available in practice.\r\n\r\nInstead, we propose three novel self-learning and self-adapting approaches using model-free deep reinforcement learning (DRL): DeepCoMP, DD-CoMP, and D3-CoMP. DeepCoMP leverages central observations and control of all users to select cells almost optimally. DD-CoMP and D3-CoMP use multi-agent DRL, which allows distributed, robust, and highly scalable coordination. All three approaches learn from experience and self-adapt to varying scenarios, reaching 2x higher Quality of Experience than other approaches. They have very few built-in assumptions and do not need prior system knowledge, making them more robust to change and better applicable in practice than existing approaches." author: - first_name: Stefan Balthasar full_name: Schneider, Stefan Balthasar id: '35343' last_name: Schneider orcid: 0000-0001-8210-4011 - first_name: Holger full_name: Karl, Holger id: '126' last_name: Karl - first_name: Ramin full_name: Khalili, Ramin last_name: Khalili - first_name: Artur full_name: Hecker, Artur last_name: Hecker citation: ama: 'Schneider SB, Karl H, Khalili R, Hecker A. DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning.; 2021.' apa: 'Schneider, S. B., Karl, H., Khalili, R., & Hecker, A. (2021). DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning.' bibtex: '@book{Schneider_Karl_Khalili_Hecker_2021, title={DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning}, author={Schneider, Stefan Balthasar and Karl, Holger and Khalili, Ramin and Hecker, Artur}, year={2021} }' chicago: 'Schneider, Stefan Balthasar, Holger Karl, Ramin Khalili, and Artur Hecker. DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning, 2021.' ieee: 'S. B. Schneider, H. Karl, R. Khalili, and A. Hecker, DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning. 2021.' mla: 'Schneider, Stefan Balthasar, et al. DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning. 2021.' short: 'S.B. Schneider, H. Karl, R. Khalili, A. Hecker, DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning, 2021.' date_created: 2022-10-20T16:44:19Z date_updated: 2022-11-18T09:59:27Z ddc: - '004' department: - _id: '75' file: - access_level: open_access content_type: application/pdf creator: stschn date_created: 2022-10-20T16:41:10Z date_updated: 2022-10-20T16:41:10Z file_id: '33855' file_name: preprint.pdf file_size: 2521656 relation: main_file file_date_updated: 2022-10-20T16:41:10Z has_accepted_license: '1' keyword: - mobility management - coordinated multipoint - CoMP - cell selection - resource management - reinforcement learning - multi agent - MARL - self-learning - self-adaptation - QoE language: - iso: eng oa: '1' project: - _id: '4' name: 'SFB 901 - C: SFB 901 - Project Area C' - _id: '16' name: 'SFB 901 - C4: SFB 901 - Subproject C4' - _id: '1' name: 'SFB 901: SFB 901' status: public title: 'DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning' type: working_paper user_id: '477' year: '2021' ... --- _id: '32558' abstract: - lang: eng text: With the rapid progress of technological development, self-efficacy in reference to digital devices (i.e., information and computer technology [ICT] self-efficacy) is an important driver that helps students to deal with technological problems and support their lifelong learning processes. Schools, peers, and home learning environments are important sources for the development of positive self-efficacy. Expanding on previous research, we investigated the associations between different aspects of the digital home learning environment and students’ ICT self-efficacy. The moderation effects of gender were also tested. A total of 651 children answered a questionnaire about different digital home learning environment dimensions and estimated their ICT self-efficacy using an adapted scale—Schwarzer and Jerusalem’s (1999) general self-efficacy scale. Using the structural equation modeling technique, a digital home learning environment containing six different qualities of parental support was investigated. Families’ cultural capital, parents’ attitudes toward the Internet, and shared Internet activities at home contributed positively to ICT self-efficacy. We observed small gender differences, with the moderation effect being nonsignificant. The results help researchers and practitioners to understand how different dimensions of the digital home learning environment support ICT self-efficacy. We will discuss how parents can enhance the home learning environment and how teachers can integrate this knowledge into formal education. author: - first_name: Sabrina full_name: Bonanati, Sabrina last_name: Bonanati - first_name: Heike M. full_name: Buhl, Heike M. id: '27152' last_name: Buhl citation: ama: Bonanati S, Buhl HM. The digital home learning environment and its relation to children’s ICT self-efficacy. Learning Environments Research. 2021;25(2):485-505. doi:10.1007/s10984-021-09377-8 apa: Bonanati, S., & Buhl, H. M. (2021). The digital home learning environment and its relation to children’s ICT self-efficacy. Learning Environments Research, 25(2), 485–505. https://doi.org/10.1007/s10984-021-09377-8 bibtex: '@article{Bonanati_Buhl_2021, title={The digital home learning environment and its relation to children’s ICT self-efficacy}, volume={25}, DOI={10.1007/s10984-021-09377-8}, number={2}, journal={Learning Environments Research}, publisher={Springer Science and Business Media LLC}, author={Bonanati, Sabrina and Buhl, Heike M.}, year={2021}, pages={485–505} }' chicago: 'Bonanati, Sabrina, and Heike M. Buhl. “The Digital Home Learning Environment and Its Relation to Children’s ICT Self-Efficacy.” Learning Environments Research 25, no. 2 (2021): 485–505. https://doi.org/10.1007/s10984-021-09377-8.' ieee: 'S. Bonanati and H. M. Buhl, “The digital home learning environment and its relation to children’s ICT self-efficacy,” Learning Environments Research, vol. 25, no. 2, pp. 485–505, 2021, doi: 10.1007/s10984-021-09377-8.' mla: Bonanati, Sabrina, and Heike M. Buhl. “The Digital Home Learning Environment and Its Relation to Children’s ICT Self-Efficacy.” Learning Environments Research, vol. 25, no. 2, Springer Science and Business Media LLC, 2021, pp. 485–505, doi:10.1007/s10984-021-09377-8. short: S. Bonanati, H.M. Buhl, Learning Environments Research 25 (2021) 485–505. date_created: 2022-08-03T05:53:48Z date_updated: 2022-08-29T06:36:37Z department: - _id: '427' doi: 10.1007/s10984-021-09377-8 intvolume: ' 25' issue: '2' keyword: - Digital media use - Gender - Home learning environment - ICT self-efcacy - Motivation - Parental involvement language: - iso: eng main_file_link: - open_access: '1' url: https://link.springer.com/content/pdf/10.1007/s10984-021-09377-8.pdf oa: '1' page: 485-505 publication: Learning Environments Research publication_identifier: issn: - 1387-1579 - 1573-1855 publication_status: published publisher: Springer Science and Business Media LLC status: public title: The digital home learning environment and its relation to children’s ICT self-efficacy type: journal_article user_id: '42165' volume: 25 year: '2021' ... --- _id: '37136' abstract: - lang: eng text: This study examines the relation between voluntary audit and the cost of debt in private firms. We use a sample of 4,058 small private firms operating in the period 2006‐2017 that are not subject to mandatory audits. Firms decide for a voluntary audit of financial statements either because the economic setting in which they operate effectively forces them to do so (e.g., ownership complexity, export‐oriented supply chain, subsidiary status) or because firm fundamentals and/or financial reporting practices limit their access to financial debt, both reflected in earnings quality. We use these factors to model the decision for voluntary audit. In the outcome analyses, we find robust evidence that voluntary audits are associated with higher, rather than lower, interest rate by up to 3.0 percentage points. This effect is present regardless of the perceived audit quality (Big‐4 vs. non‐Big‐4), but is stronger for non‐Big‐4 audits where auditees have a stronger position relative to auditors. Audited firms’ earnings are less informative about future operating performance relative to unaudited counterparts. We conclude that voluntary audits facilitate access to financial debt for firms with higher risk that may otherwise have no access to this form of financing. The price paid is reflected in higher interest rates charged to firms with voluntary audits – firms with higher information and/or fundamental risk. author: - first_name: Riste full_name: Ichev, Riste last_name: Ichev - first_name: Jernej full_name: Koren, Jernej last_name: Koren - first_name: Urska full_name: Kosi, Urska id: '54068' last_name: Kosi - first_name: Katarina full_name: Sitar Sustar, Katarina last_name: Sitar Sustar - first_name: Aljosa full_name: Valentincic, Aljosa last_name: Valentincic citation: ama: 'Ichev R, Koren J, Kosi U, Sitar Sustar K, Valentincic A. Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk.; 2021.' apa: 'Ichev, R., Koren, J., Kosi, U., Sitar Sustar, K., & Valentincic, A. (2021). Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk.' bibtex: '@book{Ichev_Koren_Kosi_Sitar Sustar_Valentincic_2021, title={Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk}, author={Ichev, Riste and Koren, Jernej and Kosi, Urska and Sitar Sustar, Katarina and Valentincic, Aljosa}, year={2021} }' chicago: 'Ichev, Riste, Jernej Koren, Urska Kosi, Katarina Sitar Sustar, and Aljosa Valentincic. Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk, 2021.' ieee: 'R. Ichev, J. Koren, U. Kosi, K. Sitar Sustar, and A. Valentincic, Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk. 2021.' mla: 'Ichev, Riste, et al. Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk. 2021.' short: 'R. Ichev, J. Koren, U. Kosi, K. Sitar Sustar, A. Valentincic, Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk, 2021.' date_created: 2023-01-17T15:03:08Z date_updated: 2023-01-18T13:40:40Z department: - _id: '635' - _id: '186' - _id: '551' keyword: - private firms - voluntary audit - cost of debt - self‐selection bias - risk language: - iso: eng main_file_link: - url: https://papers.ssrn.com/sol3/papers.cfm?abstract_id=3853927 status: public title: 'Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk' type: working_paper user_id: '88603' year: '2021' ... --- _id: '22930' abstract: - lang: eng text: Self-piercing riveting is an established technique for joining multi-material structures in car body manufacturing. Rivets for self-piercing riveting differ in their geometry, the material used, the condition of the material and their surface condition. To shorten the manufacturing process by omitting the heat treatment and the coating process, the authors have elaborated a concept for the use of stainless steel with high strain hardening as a rivet material. The focus of the present investigation is on the evaluation of the influences of the rivet’s geometry and material on its deformation behaviour. Conventional rivets of types P and HD2, a rivet with an improved geometry made of treatable steel 38B2, and rivets made of the stainless steels 1.3815 and 1.4541 are examined. The analysis is conducted by means of multi-step joining tests for two material combinations comprising high-strength steel HCT70X and aluminium EN AW-5083. The joints are cut to provide a cross-section and the deformation behaviour of the different rivets is analysed on the basis of the measured changes in geometry and hardness. In parallel, an examination of the force-stroke curves provides further insights. It can be demonstrated that, besides the geometry, the material strength, in particular, has a significant influence on the deformation behaviour of the rivet. The strength of steel 1.4541 is seen to be too low for the joining task, while the strength of steel 1.3815 is sufficient, and hence the investigation confirms the capability of rivets made of 1.3815 for joining even challenging material combinations. author: - first_name: Benedikt full_name: Uhe, Benedikt id: '38131' last_name: Uhe - first_name: Clara-Maria full_name: Kuball, Clara-Maria last_name: Kuball - first_name: Marion full_name: Merklein, Marion last_name: Merklein - first_name: Gerson full_name: Meschut, Gerson id: '32056' last_name: Meschut orcid: 0000-0002-2763-1246 citation: ama: 'Uhe B, Kuball C-M, Merklein M, Meschut G. Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening. In: Daehn G, Cao J, Kinsey B, Tekkaya E, Vivek A, Yoshida Y, eds. Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series. Springer; 2021:1495-1506. doi:10.1007/978-3-030-75381-8_124' apa: Uhe, B., Kuball, C.-M., Merklein, M., & Meschut, G. (2021). Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening. In G. Daehn, J. Cao, B. Kinsey, E. Tekkaya, A. Vivek, & Y. Yoshida (Eds.), Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series. (pp. 1495–1506). Springer. https://doi.org/10.1007/978-3-030-75381-8_124 bibtex: '@inbook{Uhe_Kuball_Merklein_Meschut_2021, place={Cham}, title={Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening}, DOI={10.1007/978-3-030-75381-8_124}, booktitle={Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series.}, publisher={Springer}, author={Uhe, Benedikt and Kuball, Clara-Maria and Merklein, Marion and Meschut, Gerson}, editor={Daehn, Glenn and Cao, Jian and Kinsey, Brad and Tekkaya, Erman and Vivek, Anupam and Yoshida, Yoshinori}, year={2021}, pages={1495–1506} }' chicago: 'Uhe, Benedikt, Clara-Maria Kuball, Marion Merklein, and Gerson Meschut. “Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening.” In Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series., edited by Glenn Daehn, Jian Cao, Brad Kinsey, Erman Tekkaya, Anupam Vivek, and Yoshinori Yoshida, 1495–1506. Cham: Springer, 2021. https://doi.org/10.1007/978-3-030-75381-8_124.' ieee: 'B. Uhe, C.-M. Kuball, M. Merklein, and G. Meschut, “Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening,” in Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series., G. Daehn, J. Cao, B. Kinsey, E. Tekkaya, A. Vivek, and Y. Yoshida, Eds. Cham: Springer, 2021, pp. 1495–1506.' mla: Uhe, Benedikt, et al. “Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening.” Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series., edited by Glenn Daehn et al., Springer, 2021, pp. 1495–506, doi:10.1007/978-3-030-75381-8_124. short: 'B. Uhe, C.-M. Kuball, M. Merklein, G. Meschut, in: G. Daehn, J. Cao, B. Kinsey, E. Tekkaya, A. Vivek, Y. Yoshida (Eds.), Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series., Springer, Cham, 2021, pp. 1495–1506.' date_created: 2021-08-04T14:02:32Z date_updated: 2023-04-28T09:20:35Z department: - _id: '157' doi: 10.1007/978-3-030-75381-8_124 editor: - first_name: Glenn full_name: Daehn, Glenn last_name: Daehn - first_name: Jian full_name: Cao, Jian last_name: Cao - first_name: Brad full_name: Kinsey, Brad last_name: Kinsey - first_name: Erman full_name: Tekkaya, Erman last_name: Tekkaya - first_name: Anupam full_name: Vivek, Anupam last_name: Vivek - first_name: Yoshinori full_name: Yoshida, Yoshinori last_name: Yoshida keyword: - Self-piercing riveting - Lightweight design - Deformation behaviour - Stainless steel - High nitrogen steel language: - iso: eng page: 1495-1506 place: Cham publication: Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series. publication_status: published publisher: Springer quality_controlled: '1' status: public title: Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening type: book_chapter user_id: '38131' year: '2021' ... --- _id: '22274' abstract: - lang: eng text: 'The use of high-strength steel and aluminium is rising due to the intensified efforts being made in lightweight design, and self-piercing riveting is becoming increasingly important. Conventional rivets for self-piercing riveting differ in their geometry, the material used, the condition of the material and the coating. To shorten the manufacturing process, the use of stainless steel with high strain hardening as the rivet material represents a promising approach. This allows the coating of the rivets to be omitted due to the corrosion resistance of the material and, since the strength of the stainless steel is achieved by cold forming, heat treatment is no longer required. In addition, it is possible to adjust the local strength within the rivet. Because of that, the authors have elaborated a concept for using high nitrogen steel 1.3815 as the rivet material. The present investigation focusses on the joint strength in order to evaluate the capability of rivets in high nitrogen steel by comparison to conventional rivets made of treatable steel. Due to certain challenges in the forming process of the high nitrogen steel rivets, deviations result from the targeted rivet geometry. Mainly these deviations cause a lower joint strength with these rivets, which is, however, adequate. All in all, the capability of the new rivet is proven by the results of this investigation. ' author: - first_name: Benedikt full_name: Uhe, Benedikt id: '38131' last_name: Uhe - first_name: Clara-Maria full_name: Kuball, Clara-Maria last_name: Kuball - first_name: Marion full_name: Merklein, Marion last_name: Merklein - first_name: Gerson full_name: Meschut, Gerson id: '32056' last_name: Meschut orcid: 0000-0002-2763-1246 citation: ama: 'Uhe B, Kuball C-M, Merklein M, Meschut G. Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel. In: ; 2021. doi:10.25518/esaform21.1911' apa: Uhe, B., Kuball, C.-M., Merklein, M., & Meschut, G. (2021). Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel. 24th International Conference on Material Forming (ESAFORM), Liège, Belgien. https://doi.org/10.25518/esaform21.1911 bibtex: '@inproceedings{Uhe_Kuball_Merklein_Meschut_2021, title={Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel}, DOI={10.25518/esaform21.1911}, author={Uhe, Benedikt and Kuball, Clara-Maria and Merklein, Marion and Meschut, Gerson}, year={2021} }' chicago: Uhe, Benedikt, Clara-Maria Kuball, Marion Merklein, and Gerson Meschut. “Strength of Self-Piercing Riveted Joints with Conventional Rivets and Rivets Made of High Nitrogen Steel,” 2021. https://doi.org/10.25518/esaform21.1911. ieee: 'B. Uhe, C.-M. Kuball, M. Merklein, and G. Meschut, “Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel,” presented at the 24th International Conference on Material Forming (ESAFORM), Liège, Belgien, 2021, doi: 10.25518/esaform21.1911.' mla: Uhe, Benedikt, et al. Strength of Self-Piercing Riveted Joints with Conventional Rivets and Rivets Made of High Nitrogen Steel. 2021, doi:10.25518/esaform21.1911. short: 'B. Uhe, C.-M. Kuball, M. Merklein, G. Meschut, in: 2021.' conference: end_date: 2021-04-16 location: Liège, Belgien name: 24th International Conference on Material Forming (ESAFORM) start_date: 2021-04-14 date_created: 2021-05-31T10:17:37Z date_updated: 2023-04-28T09:20:05Z department: - _id: '157' doi: 10.25518/esaform21.1911 keyword: - Self-piercing Riveting - Joining Technology - Rivet Geometry - Rivet Material - High Nitrogen Steel - Joint Strength language: - iso: eng quality_controlled: '1' status: public title: Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel type: conference user_id: '38131' year: '2021' ... --- _id: '21436' abstract: - lang: eng text: Ultrasonic wire bonding is a solid-state joining process, used in the electronics industry to form electrical connections, e.g. to connect electrical terminals within semiconductor modules. Many process parameters affect the bond strength, such like the bond normal force, ultrasonic power, wire material and bonding frequency. Today, process design, development, and optimization is most likely based on the knowledge of process engineers and is mainly performed by experimental testing. In this contribution, a newly developed simulation tool is presented, to reduce time and costs and efficiently determine optimized process parameter. Based on a co-simulation of MATLAB and ANSYS, the different physical phenomena of the wire bonding process are considered using finite element simulation for the complex plastic deformation of the wire and reduced order models for the transient dynamics of the transducer, wire, substrate and bond formation. The model parameters such as the coefficients of friction between bond tool and wire and between wire and substrate were determined for aluminium and copper wire in experiments with a test rig specially developed for the requirements of heavy wire bonding. To reduce simulation time, for the finite element simulation a restart analysis and high performance computing is utilized. Detailed analysis of the bond formation showed, that the normal pressure distribution in the contact between wire and substrate has high impact on bond formation and distribution of welded areas in the contact area. author: - first_name: Reinhard full_name: Schemmel, Reinhard id: '28647' last_name: Schemmel - first_name: Viktor full_name: Krieger, Viktor last_name: Krieger - first_name: Tobias full_name: Hemsel, Tobias id: '210' last_name: Hemsel - first_name: Walter full_name: Sextro, Walter id: '21220' last_name: Sextro citation: ama: Schemmel R, Krieger V, Hemsel T, Sextro W. Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization. Microelectronics Reliability. 2021;119:114077. doi:https://doi.org/10.1016/j.microrel.2021.114077 apa: Schemmel, R., Krieger, V., Hemsel, T., & Sextro, W. (2021). Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization. Microelectronics Reliability, 119, 114077. https://doi.org/10.1016/j.microrel.2021.114077 bibtex: '@article{Schemmel_Krieger_Hemsel_Sextro_2021, title={Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization}, volume={119}, DOI={https://doi.org/10.1016/j.microrel.2021.114077}, journal={Microelectronics Reliability}, author={Schemmel, Reinhard and Krieger, Viktor and Hemsel, Tobias and Sextro, Walter}, year={2021}, pages={114077} }' chicago: 'Schemmel, Reinhard, Viktor Krieger, Tobias Hemsel, and Walter Sextro. “Co-Simulation of MATLAB and ANSYS for Ultrasonic Wire Bonding Process Optimization.” Microelectronics Reliability 119 (2021): 114077. https://doi.org/10.1016/j.microrel.2021.114077.' ieee: 'R. Schemmel, V. Krieger, T. Hemsel, and W. Sextro, “Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization,” Microelectronics Reliability, vol. 119, p. 114077, 2021, doi: https://doi.org/10.1016/j.microrel.2021.114077.' mla: Schemmel, Reinhard, et al. “Co-Simulation of MATLAB and ANSYS for Ultrasonic Wire Bonding Process Optimization.” Microelectronics Reliability, vol. 119, 2021, p. 114077, doi:https://doi.org/10.1016/j.microrel.2021.114077. short: R. Schemmel, V. Krieger, T. Hemsel, W. Sextro, Microelectronics Reliability 119 (2021) 114077. date_created: 2021-03-10T09:37:02Z date_updated: 2023-09-21T14:15:33Z department: - _id: '151' doi: https://doi.org/10.1016/j.microrel.2021.114077 intvolume: ' 119' keyword: - Ultrasonic heavy wire bonding - Co-simulation - ANSYS - MATLAB - Process optimization - Friction coefficient - Copper-copper - Aluminium-copper language: - iso: eng page: '114077' publication: Microelectronics Reliability publication_identifier: issn: - 0026-2714 publication_status: published quality_controlled: '1' status: public title: Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization type: journal_article user_id: '210' volume: 119 year: '2021' ... --- _id: '46318' abstract: - lang: eng text: 'Multi-objective (MO) optimization, i.e., the simultaneous optimization of multiple conflicting objectives, is gaining more and more attention in various research areas, such as evolutionary computation, machine learning (e.g., (hyper-)parameter optimization), or logistics (e.g., vehicle routing). Many works in this domain mention the structural problem property of multimodality as a challenge from two classical perspectives: (1) finding all globally optimal solution sets, and (2) avoiding to get trapped in local optima. Interestingly, these streams seem to transfer many traditional concepts of single-objective (SO) optimization into claims, assumptions, or even terminology regarding the MO domain, but mostly neglect the understanding of the structural properties as well as the algorithmic search behavior on a problem’s landscape. However, some recent works counteract this trend, by investigating the fundamentals and characteristics of MO problems using new visualization techniques and gaining surprising insights. Using these visual insights, this work proposes a step towards a unified terminology to capture multimodality and locality in a broader way than it is usually done. This enables us to investigate current research activities in multimodal continuous MO optimization and to highlight new implications and promising research directions for the design of benchmark suites, the discovery of MO landscape features, the development of new MO (or even SO) optimization algorithms, and performance indicators. For all these topics, we provide a review of ideas and methods but also an outlook on future challenges, research potential and perspectives that result from recent developments.' author: - first_name: Christian full_name: Grimme, Christian last_name: Grimme - first_name: Pascal full_name: Kerschke, Pascal last_name: Kerschke - first_name: Pelin full_name: Aspar, Pelin last_name: Aspar - first_name: Heike full_name: Trautmann, Heike id: '100740' last_name: Trautmann orcid: 0000-0002-9788-8282 - first_name: Mike full_name: Preuss, Mike last_name: Preuss - first_name: André H. full_name: Deutz, André H. last_name: Deutz - first_name: Hao full_name: Wang, Hao last_name: Wang - first_name: Michael full_name: Emmerich, Michael last_name: Emmerich citation: ama: 'Grimme C, Kerschke P, Aspar P, et al. Peeking beyond peaks: Challenges and research potentials of continuous multimodal multi-objective optimization. Computers & Operations Research. 2021;136:105489. doi:https://doi.org/10.1016/j.cor.2021.105489' apa: 'Grimme, C., Kerschke, P., Aspar, P., Trautmann, H., Preuss, M., Deutz, A. H., Wang, H., & Emmerich, M. (2021). Peeking beyond peaks: Challenges and research potentials of continuous multimodal multi-objective optimization. Computers & Operations Research, 136, 105489. https://doi.org/10.1016/j.cor.2021.105489' bibtex: '@article{Grimme_Kerschke_Aspar_Trautmann_Preuss_Deutz_Wang_Emmerich_2021, title={Peeking beyond peaks: Challenges and research potentials of continuous multimodal multi-objective optimization}, volume={136}, DOI={https://doi.org/10.1016/j.cor.2021.105489}, journal={Computers & Operations Research}, author={Grimme, Christian and Kerschke, Pascal and Aspar, Pelin and Trautmann, Heike and Preuss, Mike and Deutz, André H. and Wang, Hao and Emmerich, Michael}, year={2021}, pages={105489} }' chicago: 'Grimme, Christian, Pascal Kerschke, Pelin Aspar, Heike Trautmann, Mike Preuss, André H. Deutz, Hao Wang, and Michael Emmerich. “Peeking beyond Peaks: Challenges and Research Potentials of Continuous Multimodal Multi-Objective Optimization.” Computers & Operations Research 136 (2021): 105489. https://doi.org/10.1016/j.cor.2021.105489.' ieee: 'C. Grimme et al., “Peeking beyond peaks: Challenges and research potentials of continuous multimodal multi-objective optimization,” Computers & Operations Research, vol. 136, p. 105489, 2021, doi: https://doi.org/10.1016/j.cor.2021.105489.' mla: 'Grimme, Christian, et al. “Peeking beyond Peaks: Challenges and Research Potentials of Continuous Multimodal Multi-Objective Optimization.” Computers & Operations Research, vol. 136, 2021, p. 105489, doi:https://doi.org/10.1016/j.cor.2021.105489.' short: C. Grimme, P. Kerschke, P. Aspar, H. Trautmann, M. Preuss, A.H. Deutz, H. Wang, M. Emmerich, Computers & Operations Research 136 (2021) 105489. date_created: 2023-08-04T07:28:34Z date_updated: 2023-10-16T12:58:42Z department: - _id: '34' - _id: '819' doi: https://doi.org/10.1016/j.cor.2021.105489 intvolume: ' 136' keyword: - Multimodal optimization - Multi-objective continuous optimization - Landscape analysis - Visualization - Benchmarking - Theory - Algorithms language: - iso: eng page: '105489' publication: Computers & Operations Research publication_identifier: issn: - 0305-0548 status: public title: 'Peeking beyond peaks: Challenges and research potentials of continuous multimodal multi-objective optimization' type: journal_article user_id: '15504' volume: 136 year: '2021' ... --- _id: '48853' abstract: - lang: eng text: In practise, it is often desirable to provide the decision-maker with a rich set of diverse solutions of decent quality instead of just a single solution. In this paper we study evolutionary diversity optimization for the knapsack problem (KP). Our goal is to evolve a population of solutions that all have a profit of at least (1 - {$ϵ$}) {$\cdot$} OPT, where OPT is the value of an optimal solution. Furthermore, they should differ in structure with respect to an entropy-based diversity measure. To this end we propose a simple ({$\mu$} + 1)-EA with initial approximate solutions calculated by a well-known FPTAS for the KP. We investigate the effect of different standard mutation operators and introduce biased mutation and crossover which puts strong probability on flipping bits of low and/or high frequency within the population. An experimental study on different instances and settings shows that the proposed mutation operators in most cases perform slightly inferior in the long term, but show strong benefits if the number of function evaluations is severely limited. author: - first_name: Jakob full_name: Bossek, Jakob id: '102979' last_name: Bossek orcid: 0000-0002-4121-4668 - first_name: Aneta full_name: Neumann, Aneta last_name: Neumann - first_name: Frank full_name: Neumann, Frank last_name: Neumann citation: ama: 'Bossek J, Neumann A, Neumann F. Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms. In: Proceedings of the Genetic and Evolutionary Computation Conference. GECCO ’21. Association for Computing Machinery; 2021:556–564. doi:10.1145/3449639.3459364' apa: Bossek, J., Neumann, A., & Neumann, F. (2021). Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms. Proceedings of the Genetic and Evolutionary Computation Conference, 556–564. https://doi.org/10.1145/3449639.3459364 bibtex: '@inproceedings{Bossek_Neumann_Neumann_2021, place={New York, NY, USA}, series={GECCO ’21}, title={Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms}, DOI={10.1145/3449639.3459364}, booktitle={Proceedings of the Genetic and Evolutionary Computation Conference}, publisher={Association for Computing Machinery}, author={Bossek, Jakob and Neumann, Aneta and Neumann, Frank}, year={2021}, pages={556–564}, collection={GECCO ’21} }' chicago: 'Bossek, Jakob, Aneta Neumann, and Frank Neumann. “Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms.” In Proceedings of the Genetic and Evolutionary Computation Conference, 556–564. GECCO ’21. New York, NY, USA: Association for Computing Machinery, 2021. https://doi.org/10.1145/3449639.3459364.' ieee: 'J. Bossek, A. Neumann, and F. Neumann, “Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms,” in Proceedings of the Genetic and Evolutionary Computation Conference, 2021, pp. 556–564, doi: 10.1145/3449639.3459364.' mla: Bossek, Jakob, et al. “Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms.” Proceedings of the Genetic and Evolutionary Computation Conference, Association for Computing Machinery, 2021, pp. 556–564, doi:10.1145/3449639.3459364. short: 'J. Bossek, A. Neumann, F. Neumann, in: Proceedings of the Genetic and Evolutionary Computation Conference, Association for Computing Machinery, New York, NY, USA, 2021, pp. 556–564.' date_created: 2023-11-14T15:58:54Z date_updated: 2023-12-13T10:45:22Z department: - _id: '819' doi: 10.1145/3449639.3459364 extern: '1' keyword: - evolutionary algorithms - evolutionary diversity optimization - knapsack problem - tailored operators language: - iso: eng page: 556–564 place: New York, NY, USA publication: Proceedings of the Genetic and Evolutionary Computation Conference publication_identifier: isbn: - 978-1-4503-8350-9 publication_status: published publisher: Association for Computing Machinery series_title: GECCO ’21 status: public title: Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms type: conference user_id: '102979' year: '2021' ... --- _id: '48860' abstract: - lang: eng text: In the area of evolutionary computation the calculation of diverse sets of high-quality solutions to a given optimization problem has gained momentum in recent years under the term evolutionary diversity optimization. Theoretical insights into the working principles of baseline evolutionary algorithms for diversity optimization are still rare. In this paper we study the well-known Minimum Spanning Tree problem (MST) in the context of diversity optimization where population diversity is measured by the sum of pairwise edge overlaps. Theoretical results provide insights into the fitness landscape of the MST diversity optimization problem pointing out that even for a population of {$\mu$} = 2 fitness plateaus (of constant length) can be reached, but nevertheless diverse sets can be calculated in polynomial time. We supplement our theoretical results with a series of experiments for the unconstrained and constraint case where all solutions need to fulfill a minimal quality threshold. Our results show that a simple ({$\mu$} + 1)-EA can effectively compute a diversified population of spanning trees of high quality. author: - first_name: Jakob full_name: Bossek, Jakob id: '102979' last_name: Bossek orcid: 0000-0002-4121-4668 - first_name: Frank full_name: Neumann, Frank last_name: Neumann citation: ama: 'Bossek J, Neumann F. Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem. In: Proceedings of the Genetic and Evolutionary Computation Conference. GECCO ’21. Association for Computing Machinery; 2021:198–206. doi:10.1145/3449639.3459363' apa: Bossek, J., & Neumann, F. (2021). Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem. Proceedings of the Genetic and Evolutionary Computation Conference, 198–206. https://doi.org/10.1145/3449639.3459363 bibtex: '@inproceedings{Bossek_Neumann_2021, place={New York, NY, USA}, series={GECCO ’21}, title={Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem}, DOI={10.1145/3449639.3459363}, booktitle={Proceedings of the Genetic and Evolutionary Computation Conference}, publisher={Association for Computing Machinery}, author={Bossek, Jakob and Neumann, Frank}, year={2021}, pages={198–206}, collection={GECCO ’21} }' chicago: 'Bossek, Jakob, and Frank Neumann. “Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem.” In Proceedings of the Genetic and Evolutionary Computation Conference, 198–206. GECCO ’21. New York, NY, USA: Association for Computing Machinery, 2021. https://doi.org/10.1145/3449639.3459363.' ieee: 'J. Bossek and F. Neumann, “Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem,” in Proceedings of the Genetic and Evolutionary Computation Conference, 2021, pp. 198–206, doi: 10.1145/3449639.3459363.' mla: Bossek, Jakob, and Frank Neumann. “Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem.” Proceedings of the Genetic and Evolutionary Computation Conference, Association for Computing Machinery, 2021, pp. 198–206, doi:10.1145/3449639.3459363. short: 'J. Bossek, F. Neumann, in: Proceedings of the Genetic and Evolutionary Computation Conference, Association for Computing Machinery, New York, NY, USA, 2021, pp. 198–206.' date_created: 2023-11-14T15:58:55Z date_updated: 2023-12-13T10:45:37Z department: - _id: '819' doi: 10.1145/3449639.3459363 extern: '1' keyword: - evolutionary algorithms - evolutionary diversity optimization - minimum spanning tree - runtime analysis language: - iso: eng page: 198–206 place: New York, NY, USA publication: Proceedings of the Genetic and Evolutionary Computation Conference publication_identifier: isbn: - 978-1-4503-8350-9 publication_status: published publisher: Association for Computing Machinery series_title: GECCO ’21 status: public title: Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem type: conference user_id: '102979' year: '2021' ... --- _id: '48854' abstract: - lang: eng text: We contribute to the theoretical understanding of randomized search heuristics for dynamic problems. We consider the classical vertex coloring problem on graphs and investigate the dynamic setting where edges are added to the current graph. We then analyze the expected time for randomized search heuristics to recompute high quality solutions. The (1+1) Evolutionary Algorithm and RLS operate in a setting where the number of colors is bounded and we are minimizing the number of conflicts. Iterated local search algorithms use an unbounded color palette and aim to use the smallest colors and, consequently, the smallest number of colors. We identify classes of bipartite graphs where reoptimization is as hard as or even harder than optimization from scratch, i.e., starting with a random initialization. Even adding a single edge can lead to hard symmetry problems. However, graph classes that are hard for one algorithm turn out to be easy for others. In most cases our bounds show that reoptimization is faster than optimizing from scratch. We further show that tailoring mutation operators to parts of the graph where changes have occurred can significantly reduce the expected reoptimization time. In most settings the expected reoptimization time for such tailored algorithms is linear in the number of added edges. However, tailored algorithms cannot prevent exponential times in settings where the original algorithm is inefficient. author: - first_name: Jakob full_name: Bossek, Jakob id: '102979' last_name: Bossek orcid: 0000-0002-4121-4668 - first_name: Frank full_name: Neumann, Frank last_name: Neumann - first_name: Pan full_name: Peng, Pan last_name: Peng - first_name: Dirk full_name: Sudholt, Dirk last_name: Sudholt citation: ama: Bossek J, Neumann F, Peng P, Sudholt D. Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem. Algorithmica. 2021;83(10):3148–3179. doi:10.1007/s00453-021-00838-3 apa: Bossek, J., Neumann, F., Peng, P., & Sudholt, D. (2021). Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem. Algorithmica, 83(10), 3148–3179. https://doi.org/10.1007/s00453-021-00838-3 bibtex: '@article{Bossek_Neumann_Peng_Sudholt_2021, title={Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem}, volume={83}, DOI={10.1007/s00453-021-00838-3}, number={10}, journal={Algorithmica}, author={Bossek, Jakob and Neumann, Frank and Peng, Pan and Sudholt, Dirk}, year={2021}, pages={3148–3179} }' chicago: 'Bossek, Jakob, Frank Neumann, Pan Peng, and Dirk Sudholt. “Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem.” Algorithmica 83, no. 10 (2021): 3148–3179. https://doi.org/10.1007/s00453-021-00838-3.' ieee: 'J. Bossek, F. Neumann, P. Peng, and D. Sudholt, “Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem,” Algorithmica, vol. 83, no. 10, pp. 3148–3179, 2021, doi: 10.1007/s00453-021-00838-3.' mla: Bossek, Jakob, et al. “Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem.” Algorithmica, vol. 83, no. 10, 2021, pp. 3148–3179, doi:10.1007/s00453-021-00838-3. short: J. Bossek, F. Neumann, P. Peng, D. Sudholt, Algorithmica 83 (2021) 3148–3179. date_created: 2023-11-14T15:58:54Z date_updated: 2023-12-13T10:51:34Z department: - _id: '819' doi: 10.1007/s00453-021-00838-3 intvolume: ' 83' issue: '10' keyword: - Dynamic optimization - Evolutionary algorithms - Running time analysis language: - iso: eng page: 3148–3179 publication: Algorithmica publication_identifier: issn: - 0178-4617 status: public title: Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem type: journal_article user_id: '102979' volume: 83 year: '2021' ... --- _id: '19609' abstract: - lang: eng text: "Modern services comprise interconnected components,\r\ne.g., microservices in a service mesh, that can scale and\r\nrun on multiple nodes across the network on demand. To process\r\nincoming traffic, service components have to be instantiated and\r\ntraffic assigned to these instances, taking capacities and changing\r\ndemands into account. This challenge is usually solved with\r\ncustom approaches designed by experts. While this typically\r\nworks well for the considered scenario, the models often rely\r\non unrealistic assumptions or on knowledge that is not available\r\nin practice (e.g., a priori knowledge).\r\n\r\nWe propose a novel deep reinforcement learning approach that\r\nlearns how to best coordinate services and is geared towards\r\nrealistic assumptions. It interacts with the network and relies on\r\navailable, possibly delayed monitoring information. Rather than\r\ndefining a complex model or an algorithm how to achieve an\r\nobjective, our model-free approach adapts to various objectives\r\nand traffic patterns. An agent is trained offline without expert\r\nknowledge and then applied online with minimal overhead. Compared\r\nto a state-of-the-art heuristic, it significantly improves flow\r\nthroughput and overall network utility on real-world network\r\ntopologies and traffic traces. It also learns to optimize different\r\nobjectives, generalizes to scenarios with unseen, stochastic traffic\r\npatterns, and scales to large real-world networks." author: - first_name: Stefan Balthasar full_name: Schneider, Stefan Balthasar id: '35343' last_name: Schneider orcid: 0000-0001-8210-4011 - first_name: Adnan full_name: Manzoor, Adnan last_name: Manzoor - first_name: Haydar full_name: Qarawlus, Haydar last_name: Qarawlus - first_name: Rafael full_name: Schellenberg, Rafael last_name: Schellenberg - first_name: Holger full_name: Karl, Holger id: '126' last_name: Karl - first_name: Ramin full_name: Khalili, Ramin last_name: Khalili - first_name: Artur full_name: Hecker, Artur last_name: Hecker citation: ama: 'Schneider SB, Manzoor A, Qarawlus H, et al. Self-Driving Network and Service Coordination Using Deep Reinforcement Learning. In: IEEE International Conference on Network and Service Management (CNSM). IEEE; 2020.' apa: Schneider, S. B., Manzoor, A., Qarawlus, H., Schellenberg, R., Karl, H., Khalili, R., & Hecker, A. (2020). Self-Driving Network and Service Coordination Using Deep Reinforcement Learning. In IEEE International Conference on Network and Service Management (CNSM). IEEE. bibtex: '@inproceedings{Schneider_Manzoor_Qarawlus_Schellenberg_Karl_Khalili_Hecker_2020, title={Self-Driving Network and Service Coordination Using Deep Reinforcement Learning}, booktitle={IEEE International Conference on Network and Service Management (CNSM)}, publisher={IEEE}, author={Schneider, Stefan Balthasar and Manzoor, Adnan and Qarawlus, Haydar and Schellenberg, Rafael and Karl, Holger and Khalili, Ramin and Hecker, Artur}, year={2020} }' chicago: Schneider, Stefan Balthasar, Adnan Manzoor, Haydar Qarawlus, Rafael Schellenberg, Holger Karl, Ramin Khalili, and Artur Hecker. “Self-Driving Network and Service Coordination Using Deep Reinforcement Learning.” In IEEE International Conference on Network and Service Management (CNSM). IEEE, 2020. ieee: S. B. Schneider et al., “Self-Driving Network and Service Coordination Using Deep Reinforcement Learning,” in IEEE International Conference on Network and Service Management (CNSM), 2020. mla: Schneider, Stefan Balthasar, et al. “Self-Driving Network and Service Coordination Using Deep Reinforcement Learning.” IEEE International Conference on Network and Service Management (CNSM), IEEE, 2020. short: 'S.B. Schneider, A. Manzoor, H. Qarawlus, R. Schellenberg, H. Karl, R. Khalili, A. Hecker, in: IEEE International Conference on Network and Service Management (CNSM), IEEE, 2020.' date_created: 2020-09-22T06:28:22Z date_updated: 2022-01-06T06:54:08Z ddc: - '006' department: - _id: '75' file: - access_level: open_access content_type: application/pdf creator: stschn date_created: 2020-09-22T06:29:16Z date_updated: 2020-09-22T06:36:00Z file_id: '19610' file_name: ris_with_copyright.pdf file_size: 642999 relation: main_file file_date_updated: 2020-09-22T06:36:00Z has_accepted_license: '1' keyword: - self-driving networks - self-learning - network coordination - service coordination - reinforcement learning - deep learning - nfv language: - iso: eng oa: '1' project: - _id: '1' name: SFB 901 - _id: '4' name: SFB 901 - Project Area C - _id: '16' name: SFB 901 - Subproject C4 publication: IEEE International Conference on Network and Service Management (CNSM) publisher: IEEE status: public title: Self-Driving Network and Service Coordination Using Deep Reinforcement Learning type: conference user_id: '35343' year: '2020' ... --- _id: '19976' abstract: - lang: eng text: The aim to reduce pollutant emission has led to a trend towards lightweight construction in car body development during the last years. As a consequence of the resulting need for multi-material design, mechanical joining technologies become increasingly important. Mechanical joining allows for the combination of dissimilar materials, while thermic joining techniques reach their limits. Self-piercing riveting enables the joining of dissimilar materials by using semi-tubular rivets as mechanical fasteners. The rivet production, however, is costly and time-consuming, as the rivets generally have to be hardened, tempered and coated after forming, in order to achieve an adequate strength and corrosion resistance. A promising approach to improve the efficiency of the rivet manufacturing is the use of high-strength high nitrogen steel as rivet material because these additional process steps would not be necessary anymore. As a result of the comparatively high nitrogen content, such steels have various beneficial properties like higher strength, good ductility and improved corrosion resistance. By cold bulk forming of high nitrogen steels high-strength parts can be manufactured due to the strengthening which is caused by the high strain hardening. However, high tool loads thereby have to be expected and are a major challenge during the production process. Consequently, there is a need for appropriate forming strategies. This paper presents key aspects concerning the process design for the manufacturing of semi-tubular self-piercing rivets made of high-strength steel. The aim is to produce the rivets in several forming stages without intermediate heat treatment between the single stages. Due to the high strain hardening of the material, a two stage forming concept will be investigated. Cup-backward extrusion is chosen as the first process step in order to form the rivet shank without forming the rivet foot. Thus, the strain hardening effects in the area of the rivet foot are minimized and the tool loads during the following process step can be reduced. During the second and final forming stage the detailed geometry of the rivet foot and the rivet head is formed. In this context, the effect of different variations, for example concerning the final geometry of the rivet foot, on the tool load is investigated using multistage numerical analysis. Furthermore, the influence of the process temperature on occurring stresses is analysed. Based on the results of the investigations, an adequate forming strategy and a tool concept for the manufacturing of semi-tubular self-piercing rivets made of high-strength steel are presented. citation: ama: Kuball C-M, Uhe B, Meschut G, Merklein M, eds. Process Design for the Forming of Semi-Tubular Self-Piercing Rivets Made of High Nitrogen Steel. Vol 50.; 2020:280-285. doi:10.1016/j.promfg.2020.08.052 apa: Kuball, C.-M., Uhe, B., Meschut, G., & Merklein, M. (Eds.). (2020). Process design for the forming of semi-tubular self-piercing rivets made of high nitrogen steel (Vol. 50, pp. 280–285). https://doi.org/10.1016/j.promfg.2020.08.052 bibtex: '@book{Kuball_Uhe_Meschut_Merklein_2020, series={Procedia Manufacturing}, title={Process design for the forming of semi-tubular self-piercing rivets made of high nitrogen steel}, volume={50}, DOI={10.1016/j.promfg.2020.08.052}, year={2020}, pages={280–285}, collection={Procedia Manufacturing} }' chicago: Kuball, Clara-Maria, Benedikt Uhe, Gerson Meschut, and Marion Merklein, eds. Process Design for the Forming of Semi-Tubular Self-Piercing Rivets Made of High Nitrogen Steel. Vol. 50. Procedia Manufacturing, 2020. https://doi.org/10.1016/j.promfg.2020.08.052. ieee: C.-M. Kuball, B. Uhe, G. Meschut, and M. Merklein, Eds., Process design for the forming of semi-tubular self-piercing rivets made of high nitrogen steel, vol. 50. 2020, pp. 280–285. mla: Kuball, Clara-Maria, et al., editors. Process Design for the Forming of Semi-Tubular Self-Piercing Rivets Made of High Nitrogen Steel. Vol. 50, 2020, pp. 280–85, doi:10.1016/j.promfg.2020.08.052. short: C.-M. Kuball, B. Uhe, G. Meschut, M. Merklein, eds., Process Design for the Forming of Semi-Tubular Self-Piercing Rivets Made of High Nitrogen Steel, 2020. date_created: 2020-10-12T08:30:08Z date_updated: 2022-01-06T06:54:17Z department: - _id: '157' doi: 10.1016/j.promfg.2020.08.052 editor: - first_name: Clara-Maria full_name: Kuball, Clara-Maria last_name: Kuball - first_name: Benedikt full_name: Uhe, Benedikt id: '38131' last_name: Uhe - first_name: Gerson full_name: Meschut, Gerson id: '32056' last_name: Meschut orcid: 0000-0002-2763-1246 - first_name: Marion full_name: Merklein, Marion last_name: Merklein intvolume: ' 50' keyword: - high nitrogen steel - self-piercing riveting - joining by forming - bulk forming - tool design language: - iso: eng page: 280-285 publication_status: published quality_controlled: '1' series_title: Procedia Manufacturing status: public title: Process design for the forming of semi-tubular self-piercing rivets made of high nitrogen steel type: conference_editor user_id: '38131' volume: 50 year: '2020' ... --- _id: '17370' abstract: - lang: eng text: " We consider a natural extension to the metric uncapacitated Facility Location Problem (FLP) in which requests ask for different commodities out of a finite set \\( S \\) of commodities.\r\n Ravi and Sinha (SODA 2004) introduced the model as the \\emph{Multi-Commodity Facility Location Problem} (MFLP) and considered it an offline optimization problem.\r\n The model itself is similar to the FLP: i.e., requests are located at points of a finite metric space and the task of an algorithm is to construct facilities and assign requests to facilities while minimizing the construction cost and the sum over all assignment distances.\r\n \ In addition, requests and facilities are heterogeneous; they request or offer multiple commodities out of $S$.\r\n A request has to be connected to a set of facilities jointly offering the commodities demanded by it.\r\n In comparison to the FLP, an algorithm has to decide not only if and where to place facilities, but also which commodities to offer at each.\r\n\r\n To the best of our knowledge we are the first to study the problem in its online variant in which requests, their positions and their commodities are not known beforehand but revealed over time.\r\n We present results regarding the competitive ratio.\r\n On the one hand, we show that heterogeneity influences the competitive ratio by developing a lower bound on the competitive ratio for any randomized online algorithm of \\( \\Omega ( \\sqrt{|S|} + \\frac{\\log n}{\\log \\log n} ) \\) that already holds for simple line metrics.\r\n Here, \\( n \\) is the number of requests.\r\n \ On the other side, we establish a deterministic \\( \\mathcal{O}(\\sqrt{|S|} \\cdot \\log n) \\)-competitive algorithm and a randomized \\( \\mathcal{O}(\\sqrt{|S|} \\cdot \\frac{\\log n}{\\log \\log n} ) \\)-competitive algorithm.\r\n Further, we show that when considering a more special class of cost functions for the construction cost of a facility, the competitive ratio decreases given by our deterministic algorithm depending on the function." author: - first_name: Jannik full_name: Castenow, Jannik id: '38705' last_name: Castenow - first_name: Björn full_name: Feldkord, Björn id: '22704' last_name: Feldkord - first_name: Till full_name: Knollmann, Till id: '39241' last_name: Knollmann orcid: 0000-0003-2014-4696 - first_name: Manuel full_name: Malatyali, Manuel last_name: Malatyali - first_name: Friedhelm full_name: Meyer auf der Heide, Friedhelm id: '15523' last_name: Meyer auf der Heide citation: ama: 'Castenow J, Feldkord B, Knollmann T, Malatyali M, Meyer auf der Heide F. The Online Multi-Commodity Facility Location Problem. In: Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures. ; 2020. doi:10.1145/3350755.3400281' apa: Castenow, J., Feldkord, B., Knollmann, T., Malatyali, M., & Meyer auf der Heide, F. (2020). The Online Multi-Commodity Facility Location Problem. In Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures. https://doi.org/10.1145/3350755.3400281 bibtex: '@inproceedings{Castenow_Feldkord_Knollmann_Malatyali_Meyer auf der Heide_2020, title={The Online Multi-Commodity Facility Location Problem}, DOI={10.1145/3350755.3400281}, booktitle={Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures}, author={Castenow, Jannik and Feldkord, Björn and Knollmann, Till and Malatyali, Manuel and Meyer auf der Heide, Friedhelm}, year={2020} }' chicago: Castenow, Jannik, Björn Feldkord, Till Knollmann, Manuel Malatyali, and Friedhelm Meyer auf der Heide. “The Online Multi-Commodity Facility Location Problem.” In Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures, 2020. https://doi.org/10.1145/3350755.3400281. ieee: J. Castenow, B. Feldkord, T. Knollmann, M. Malatyali, and F. Meyer auf der Heide, “The Online Multi-Commodity Facility Location Problem,” in Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures, 2020. mla: Castenow, Jannik, et al. “The Online Multi-Commodity Facility Location Problem.” Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures, 2020, doi:10.1145/3350755.3400281. short: 'J. Castenow, B. Feldkord, T. Knollmann, M. Malatyali, F. Meyer auf der Heide, in: Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures, 2020.' date_created: 2020-07-14T07:53:20Z date_updated: 2022-01-06T06:53:10Z ddc: - '000' department: - _id: '63' doi: 10.1145/3350755.3400281 external_id: arxiv: - '2005.08391' file: - access_level: closed content_type: application/pdf creator: tillk date_created: 2020-07-14T07:56:52Z date_updated: 2020-07-14T07:56:52Z file_id: '17373' file_name: 3350755.3400281.pdf file_size: 1271416 relation: main_file success: 1 file_date_updated: 2020-07-14T07:56:52Z has_accepted_license: '1' keyword: - Online Multi-Commodity Facility Location - Competitive Ratio - Online Optimization - Facility Location Problem language: - iso: eng project: - _id: '1' name: SFB 901 - _id: '2' name: SFB 901 - Project Area A - _id: '5' name: SFB 901 - Subproject A1 publication: Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures publication_identifier: isbn: - '9781450369350' publication_status: published status: public title: The Online Multi-Commodity Facility Location Problem type: conference user_id: '39241' year: '2020' ... --- _id: '20143' author: - first_name: Mortaza full_name: Otroshi, Mortaza id: '71269' last_name: Otroshi orcid: 0000-0002-8652-9209 - first_name: Moritz full_name: Rossel, Moritz last_name: Rossel - first_name: Gerson full_name: Meschut, Gerson id: '32056' last_name: Meschut orcid: 0000-0002-2763-1246 citation: ama: Otroshi M, Rossel M, Meschut G. Stress state dependent damage modeling of self-pierce riveting process simulation using GISSMO damage model. Journal of Advanced Joining Processes. 2020;1. doi:10.1016/j.jajp.2020.100015 apa: Otroshi, M., Rossel, M., & Meschut, G. (2020). Stress state dependent damage modeling of self-pierce riveting process simulation using GISSMO damage model. Journal of Advanced Joining Processes, 1. https://doi.org/10.1016/j.jajp.2020.100015 bibtex: '@article{Otroshi_Rossel_Meschut_2020, title={Stress state dependent damage modeling of self-pierce riveting process simulation using GISSMO damage model}, volume={1}, DOI={10.1016/j.jajp.2020.100015}, journal={Journal of Advanced Joining Processes}, publisher={Elsevier}, author={Otroshi, Mortaza and Rossel, Moritz and Meschut, Gerson}, year={2020} }' chicago: Otroshi, Mortaza, Moritz Rossel, and Gerson Meschut. “Stress State Dependent Damage Modeling of Self-Pierce Riveting Process Simulation Using GISSMO Damage Model.” Journal of Advanced Joining Processes 1 (2020). https://doi.org/10.1016/j.jajp.2020.100015. ieee: 'M. Otroshi, M. Rossel, and G. Meschut, “Stress state dependent damage modeling of self-pierce riveting process simulation using GISSMO damage model,” Journal of Advanced Joining Processes, vol. 1, 2020, doi: 10.1016/j.jajp.2020.100015.' mla: Otroshi, Mortaza, et al. “Stress State Dependent Damage Modeling of Self-Pierce Riveting Process Simulation Using GISSMO Damage Model.” Journal of Advanced Joining Processes, vol. 1, Elsevier, 2020, doi:10.1016/j.jajp.2020.100015. short: M. Otroshi, M. Rossel, G. Meschut, Journal of Advanced Joining Processes 1 (2020). date_created: 2020-10-20T14:49:15Z date_updated: 2022-04-25T07:49:50Z department: - _id: '157' doi: 10.1016/j.jajp.2020.100015 intvolume: ' 1' keyword: - Self-pierce riveting - Ductile fracture - Damage modeling - GISSMO damage model language: - iso: eng main_file_link: - open_access: '1' oa: '1' publication: Journal of Advanced Joining Processes publisher: Elsevier quality_controlled: '1' status: public title: Stress state dependent damage modeling of self-pierce riveting process simulation using GISSMO damage model type: journal_article user_id: '71269' volume: 1 year: '2020' ... --- _id: '35298' abstract: - lang: ger text: Im Artikel werden drei verschiedene Lernzugänge (kom-petenzorientiertes, ästhetisches und biographisches Lernen) vorgestellt und aus theoretischer Perspektive deren motivierender Gehalt für selbstreguliertes Lernen in Praxisphasen des Lehramtsstudiumsherausgearbeitet. Als theoretische Grund-lage dient die Selbstbestimmungstheorie als zentrale motivationale Theorie zur Erklärung selbstbestimmten Handelns. - lang: eng text: The article addresses how motivational learning approaches (competency-oriented, aesthetic and biographical) can contribute to the professionalization of preservice teachers during a long-term internship. As a theoretical basis, the self-determination theory serves as a central motivational theory for explaining self-determined action. alternative_title: - Ein Blick auf kompetenzorientiertes, ästhetisches und biographisches Lernen im Lehramtsstudium author: - first_name: Carina full_name: Caruso, Carina id: '23123' last_name: Caruso - first_name: Christine full_name: Adammek, Christine last_name: Adammek - first_name: Sabrina full_name: Bonanati, Sabrina last_name: Bonanati - first_name: Sybille full_name: Wiescholek, Sybille last_name: Wiescholek citation: ama: Caruso C, Adammek C, Bonanati S, Wiescholek S. Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen. Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion. 2020;3(1):18-33. doi:10.4119/hlz-2540 apa: Caruso, C., Adammek, C., Bonanati, S., & Wiescholek, S. (2020). Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen. Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion, 3(1), 18–33. https://doi.org/10.4119/hlz-2540 bibtex: '@article{Caruso_Adammek_Bonanati_Wiescholek_2020, title={Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen}, volume={3}, DOI={10.4119/hlz-2540}, number={1}, journal={Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion}, author={Caruso, Carina and Adammek, Christine and Bonanati, Sabrina and Wiescholek, Sybille}, year={2020}, pages={18–33} }' chicago: 'Caruso, Carina, Christine Adammek, Sabrina Bonanati, and Sybille Wiescholek. “Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen.” Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion 3, no. 1 (2020): 18–33. https://doi.org/10.4119/hlz-2540.' ieee: 'C. Caruso, C. Adammek, S. Bonanati, and S. Wiescholek, “Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen,” Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion, vol. 3, no. 1, pp. 18–33, 2020, doi: 10.4119/hlz-2540.' mla: Caruso, Carina, et al. “Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen.” Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion, vol. 3, no. 1, 2020, pp. 18–33, doi:10.4119/hlz-2540. short: C. Caruso, C. Adammek, S. Bonanati, S. Wiescholek, Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion 3 (2020) 18–33. date_created: 2023-01-05T13:58:28Z date_updated: 2023-01-06T12:18:16Z doi: 10.4119/hlz-2540 intvolume: ' 3' issue: '1' keyword: - ästhetische Forschung - Biographiearbeit - Praxissemester - Professionalisierung - selbstreguliertes Lernen - Motivation / aesthetic research - biographical work - long-term internship - profes-sionalization - self-regulated learning - motivation language: - iso: other page: 18-33 publication: Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion publication_identifier: issn: - 2625-0675 publication_status: published status: public title: Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen type: journal_article user_id: '86519' volume: 3 year: '2020' ... --- _id: '33866' abstract: - lang: eng text: Helhmoltz–Kirchhoff equations of motions of vortices of an incompressible fluid in the plane define a dynamics with singularities and this leads to a Zermelo navigation problem describing the ship travel in such a field where the control is the heading angle. Considering one vortex, we define a time minimization problem which can be analyzed with the technics of geometric optimal control combined with numerical simulations, the geometric frame being the extension of Randers metrics in the punctured plane, with rotational symmetry. Candidates as minimizers are parameterized thanks to the Pontryagin Maximum Principle as extremal solutions of a Hamiltonian vector field. We analyze the time minimal solution to transfer the ship between two points where during the transfer the ship can be either in a strong current region in the vicinity of the vortex or in a weak current region. The analysis is based on a micro-local classification of the extremals using mainly the integrability properties of the dynamics due to the rotational symmetry. The discussion is complex and related to the existence of an isolated extremal (Reeb) circle due to the vortex singularity. The explicit computation of cut points where the extremal curves cease to be optimal is given and the spheres are described in the case where at the initial point the current is weak. article_number: S10 author: - first_name: Bernard full_name: Bonnard, Bernard last_name: Bonnard - first_name: Olivier full_name: Cots, Olivier last_name: Cots - first_name: Boris Edgar full_name: Wembe Moafo, Boris Edgar id: '95394' last_name: Wembe Moafo citation: ama: 'Bonnard B, Cots O, Wembe Moafo BE. A Zermelo navigation problem with a vortex singularity. ESAIM: Control, Optimisation and Calculus of Variations. 2020;27. doi:10.1051/cocv/2020058' apa: 'Bonnard, B., Cots, O., & Wembe Moafo, B. E. (2020). A Zermelo navigation problem with a vortex singularity. ESAIM: Control, Optimisation and Calculus of Variations, 27, Article S10. https://doi.org/10.1051/cocv/2020058' bibtex: '@article{Bonnard_Cots_Wembe Moafo_2020, title={A Zermelo navigation problem with a vortex singularity}, volume={27}, DOI={10.1051/cocv/2020058}, number={S10}, journal={ESAIM: Control, Optimisation and Calculus of Variations}, publisher={EDP Sciences}, author={Bonnard, Bernard and Cots, Olivier and Wembe Moafo, Boris Edgar}, year={2020} }' chicago: 'Bonnard, Bernard, Olivier Cots, and Boris Edgar Wembe Moafo. “A Zermelo Navigation Problem with a Vortex Singularity.” ESAIM: Control, Optimisation and Calculus of Variations 27 (2020). https://doi.org/10.1051/cocv/2020058.' ieee: 'B. Bonnard, O. Cots, and B. E. Wembe Moafo, “A Zermelo navigation problem with a vortex singularity,” ESAIM: Control, Optimisation and Calculus of Variations, vol. 27, Art. no. S10, 2020, doi: 10.1051/cocv/2020058.' mla: 'Bonnard, Bernard, et al. “A Zermelo Navigation Problem with a Vortex Singularity.” ESAIM: Control, Optimisation and Calculus of Variations, vol. 27, S10, EDP Sciences, 2020, doi:10.1051/cocv/2020058.' short: 'B. Bonnard, O. Cots, B.E. Wembe Moafo, ESAIM: Control, Optimisation and Calculus of Variations 27 (2020).' date_created: 2022-10-24T12:51:05Z date_updated: 2023-01-16T12:09:22Z doi: 10.1051/cocv/2020058 intvolume: ' 27' keyword: - Computational Mathematics - Control and Optimization - Control and Systems Engineering language: - iso: eng publication: 'ESAIM: Control, Optimisation and Calculus of Variations' publication_identifier: issn: - 1292-8119 - 1262-3377 publication_status: published publisher: EDP Sciences status: public title: A Zermelo navigation problem with a vortex singularity type: journal_article user_id: '95394' volume: 27 year: '2020' ... --- _id: '19974' abstract: - lang: eng text: Due to the trend towards lightweight design in car body development mechanical joining technologies become increasingly important. These techniques allow for the joining of dissimilar materials and thus enable multi-material design, while thermic joining methods reach their limits. Semi-tubular self-piercing riveting is an important mechanical joining technology. The rivet production, however, is costly and time-consuming, as the process consists of several process steps including the heat treatment and coating of the rivets in order to achieve an adequate strength and corrosion resistance. The use of high nitrogen steel as rivet material leads to the possibility of reducing process steps and hence increasing the efficiency of the process. However, the high tool loads being expected due to the high strain hardening of the material are a major challenge during the rivet production. Thus, there is a need for appropriate forming strategies, such as the manufacturing of the rivets at elevated temperatures. Prior investigations led to the conclusion that forming already at 200 °C results in a distinct reduction of the yield strength. To create a deeper understanding of the forming behaviour of high nitrogen steel at elevated temperatures, compression tests were conducted in a temperature range between room temperature and 200 °C. The determined true stress – true strain curves are the basis for the further process and tool design of the rivet production. Another key factor for the rivet manufacturing at elevated temperatures is the influence of the process temperature on the tribological conditions. For this reason, ring compression tests at room temperature and 200 °C are carried out. The friction factors are determined on the basis of calibration curves resulting from the numerical analysis of the ring compression process. The investigations indicate that the friction factor at 200 °C is significantly higher compared to room temperature. This essential fact has to be taken into account for the process and tool design for the rivet production using high nitrogen steel. article_number: '100023' citation: ama: Kuball C-M, Jung R, Uhe B, Meschut G, Merklein M, eds. Influence of the Process Temperature on the Forming Behaviour and the Friction during Bulk Forming of High Nitrogen Steel. Vol 1.; 2020. doi:10.1016/j.jajp.2020.100023 apa: Kuball, C.-M., Jung, R., Uhe, B., Meschut, G., & Merklein, M. (Eds.). (2020). Influence of the process temperature on the forming behaviour and the friction during bulk forming of high nitrogen steel (No. 100023; Vol. 1). https://doi.org/10.1016/j.jajp.2020.100023 bibtex: '@book{Kuball_Jung_Uhe_Meschut_Merklein_2020, series={Journal of Advanced Joining Processes}, title={Influence of the process temperature on the forming behaviour and the friction during bulk forming of high nitrogen steel}, volume={1}, DOI={10.1016/j.jajp.2020.100023}, number={100023}, year={2020}, collection={Journal of Advanced Joining Processes} }' chicago: Kuball, Clara-Maria, R Jung, Benedikt Uhe, Gerson Meschut, and Marion Merklein, eds. Influence of the Process Temperature on the Forming Behaviour and the Friction during Bulk Forming of High Nitrogen Steel. Vol. 1. Journal of Advanced Joining Processes, 2020. https://doi.org/10.1016/j.jajp.2020.100023. ieee: C.-M. Kuball, R. Jung, B. Uhe, G. Meschut, and M. Merklein, Eds., Influence of the process temperature on the forming behaviour and the friction during bulk forming of high nitrogen steel, vol. 1. 2020. mla: Kuball, Clara-Maria, et al., editors. Influence of the Process Temperature on the Forming Behaviour and the Friction during Bulk Forming of High Nitrogen Steel. 100023, 2020, doi:10.1016/j.jajp.2020.100023. short: C.-M. Kuball, R. Jung, B. Uhe, G. Meschut, M. Merklein, eds., Influence of the Process Temperature on the Forming Behaviour and the Friction during Bulk Forming of High Nitrogen Steel, 2020. date_created: 2020-10-12T08:23:27Z date_updated: 2023-04-28T09:19:41Z department: - _id: '157' doi: 10.1016/j.jajp.2020.100023 editor: - first_name: Clara-Maria full_name: Kuball, Clara-Maria last_name: Kuball - first_name: R full_name: Jung, R last_name: Jung - first_name: Benedikt full_name: Uhe, Benedikt id: '38131' last_name: Uhe - first_name: Gerson full_name: Meschut, Gerson id: '32056' last_name: Meschut orcid: 0000-0002-2763-1246 - first_name: Marion full_name: Merklein, Marion last_name: Merklein intvolume: ' 1' keyword: - High nitrogen steel - Self-piercing riveting - Joining by forming - Bulk forming - Strain hardening language: - iso: eng publication_status: published quality_controlled: '1' series_title: Journal of Advanced Joining Processes status: public title: Influence of the process temperature on the forming behaviour and the friction during bulk forming of high nitrogen steel type: conference_editor user_id: '38131' volume: 1 year: '2020' ...