TY - CONF AB - 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. AU - Rook, Jeroen AU - Trautmann, Heike AU - Bossek, Jakob AU - Grimme, Christian ID - 48896 KW - configuration KW - multi-modality KW - multi-objective optimization SN - 978-1-4503-9268-6 T2 - Proceedings of the Genetic and Evolutionary Computation Conference Companion TI - On the Potential of Automated Algorithm Configuration on Multi-Modal Multi-Objective Optimization Problems ER - TY - JOUR AB - 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. AU - Wever, Marcel Dominik AU - Tornede, Alexander AU - Mohr, Felix AU - Hüllermeier, Eyke ID - 21004 JF - IEEE Transactions on Pattern Analysis and Machine Intelligence KW - Automated Machine Learning KW - Multi Label Classification KW - Hierarchical Planning KW - Bayesian Optimization SN - 0162-8828 TI - AutoML for Multi-Label Classification: Overview and Empirical Evaluation ER - TY - JOUR AB - 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). We 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. AU - Schneider, Stefan Balthasar AU - Khalili, Ramin AU - Manzoor, Adnan AU - Qarawlus, Haydar AU - Schellenberg, Rafael AU - Karl, Holger AU - Hecker, Artur ID - 21808 JF - Transactions on Network and Service Management KW - network management KW - service management KW - coordination KW - reinforcement learning KW - self-learning KW - self-adaptation KW - multi-objective TI - Self-Learning Multi-Objective Service Coordination Using Deep Reinforcement Learning ER - TY - GEN AB - 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. Instead, 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. AU - Schneider, Stefan Balthasar AU - Karl, Holger AU - Khalili, Ramin AU - Hecker, Artur ID - 33854 KW - mobility management KW - coordinated multipoint KW - CoMP KW - cell selection KW - resource management KW - reinforcement learning KW - multi agent KW - MARL KW - self-learning KW - self-adaptation KW - QoE TI - DeepCoMP: Coordinated Multipoint Using Multi-Agent Deep Reinforcement Learning ER - TY - JOUR AB - 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. AU - Bonanati, Sabrina AU - Buhl, Heike M. ID - 32558 IS - 2 JF - Learning Environments Research KW - Digital media use KW - Gender KW - Home learning environment KW - ICT self-efcacy KW - Motivation KW - Parental involvement SN - 1387-1579 TI - The digital home learning environment and its relation to children’s ICT self-efficacy VL - 25 ER - TY - GEN AB - 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. AU - Ichev, Riste AU - Koren, Jernej AU - Kosi, Urska AU - Sitar Sustar, Katarina AU - Valentincic, Aljosa ID - 37136 KW - private firms KW - voluntary audit KW - cost of debt KW - self‐selection bias KW - risk TI - Cost of Debt for Private Firms Revisited: Voluntary Audits as a Reflection of Risk ER - TY - CHAP AB - 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. AU - Uhe, Benedikt AU - Kuball, Clara-Maria AU - Merklein, Marion AU - Meschut, Gerson ED - Daehn, Glenn ED - Cao, Jian ED - Kinsey, Brad ED - Tekkaya, Erman ED - Vivek, Anupam ED - Yoshida, Yoshinori ID - 22930 KW - Self-piercing riveting KW - Lightweight design KW - Deformation behaviour KW - Stainless steel KW - High nitrogen steel T2 - Forming the Future - Proceedings of the 13th International Conference on the Technology of Plasticity. The Minerals, Metals & Materials Series. TI - Self-Piercing Riveting Using Rivets Made of Stainless Steel with High Strain Hardening ER - TY - CONF AB - 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. AU - Uhe, Benedikt AU - Kuball, Clara-Maria AU - Merklein, Marion AU - Meschut, Gerson ID - 22274 KW - Self-piercing Riveting KW - Joining Technology KW - Rivet Geometry KW - Rivet Material KW - High Nitrogen Steel KW - Joint Strength TI - Strength of self-piercing riveted Joints with conventional Rivets and Rivets made of High Nitrogen Steel ER - TY - JOUR AB - 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. AU - Schemmel, Reinhard AU - Krieger, Viktor AU - Hemsel, Tobias AU - Sextro, Walter ID - 21436 JF - Microelectronics Reliability KW - Ultrasonic heavy wire bonding KW - Co-simulation KW - ANSYS KW - MATLAB KW - Process optimization KW - Friction coefficient KW - Copper-copper KW - Aluminium-copper SN - 0026-2714 TI - Co-simulation of MATLAB and ANSYS for ultrasonic wire bonding process optimization VL - 119 ER - TY - JOUR AB - 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. AU - Grimme, Christian AU - Kerschke, Pascal AU - Aspar, Pelin AU - Trautmann, Heike AU - Preuss, Mike AU - Deutz, André H. AU - Wang, Hao AU - Emmerich, Michael ID - 46318 JF - Computers & Operations Research KW - Multimodal optimization KW - Multi-objective continuous optimization KW - Landscape analysis KW - Visualization KW - Benchmarking KW - Theory KW - Algorithms SN - 0305-0548 TI - Peeking beyond peaks: Challenges and research potentials of continuous multimodal multi-objective optimization VL - 136 ER - TY - CONF AB - 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. AU - Bossek, Jakob AU - Neumann, Aneta AU - Neumann, Frank ID - 48853 KW - evolutionary algorithms KW - evolutionary diversity optimization KW - knapsack problem KW - tailored operators SN - 978-1-4503-8350-9 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Breeding Diverse Packings for the Knapsack Problem by Means of Diversity-Tailored Evolutionary Algorithms ER - TY - CONF AB - 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. AU - Bossek, Jakob AU - Neumann, Frank ID - 48860 KW - evolutionary algorithms KW - evolutionary diversity optimization KW - minimum spanning tree KW - runtime analysis SN - 978-1-4503-8350-9 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Evolutionary Diversity Optimization and the Minimum Spanning Tree Problem ER - TY - JOUR AB - 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. AU - Bossek, Jakob AU - Neumann, Frank AU - Peng, Pan AU - Sudholt, Dirk ID - 48854 IS - 10 JF - Algorithmica KW - Dynamic optimization KW - Evolutionary algorithms KW - Running time analysis SN - 0178-4617 TI - Time Complexity Analysis of Randomized Search Heuristics for the Dynamic Graph Coloring Problem VL - 83 ER - TY - CONF AB - Modern services comprise interconnected components, e.g., microservices in a service mesh, that can scale and run on multiple nodes across the network on demand. To process incoming traffic, service components have to be instantiated and traffic assigned to these instances, taking capacities and changing demands 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). We propose 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 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, it significantly improves flow throughput and overall network utility on real-world network topologies and traffic traces. It also learns to optimize different objectives, generalizes to scenarios with unseen, stochastic traffic patterns, and scales to large real-world networks. AU - Schneider, Stefan Balthasar AU - Manzoor, Adnan AU - Qarawlus, Haydar AU - Schellenberg, Rafael AU - Karl, Holger AU - Khalili, Ramin AU - Hecker, Artur ID - 19609 KW - self-driving networks KW - self-learning KW - network coordination KW - service coordination KW - reinforcement learning KW - deep learning KW - nfv T2 - IEEE International Conference on Network and Service Management (CNSM) TI - Self-Driving Network and Service Coordination Using Deep Reinforcement Learning ER - TY - GEN AB - 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. ED - Kuball, Clara-Maria ED - Uhe, Benedikt ED - Meschut, Gerson ED - Merklein, Marion ID - 19976 KW - high nitrogen steel KW - self-piercing riveting KW - joining by forming KW - bulk forming KW - tool design TI - Process design for the forming of semi-tubular self-piercing rivets made of high nitrogen steel VL - 50 ER - TY - CONF AB - 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. Ravi and Sinha (SODA 2004) introduced the model as the \emph{Multi-Commodity Facility Location Problem} (MFLP) and considered it an offline optimization problem. 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. In addition, requests and facilities are heterogeneous; they request or offer multiple commodities out of $S$. A request has to be connected to a set of facilities jointly offering the commodities demanded by it. 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. 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. We present results regarding the competitive ratio. 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. Here, \( n \) is the number of requests. 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. 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. AU - Castenow, Jannik AU - Feldkord, Björn AU - Knollmann, Till AU - Malatyali, Manuel AU - Meyer auf der Heide, Friedhelm ID - 17370 KW - Online Multi-Commodity Facility Location KW - Competitive Ratio KW - Online Optimization KW - Facility Location Problem SN - 9781450369350 T2 - Proceedings of the 32nd ACM Symposium on Parallelism in Algorithms and Architectures TI - The Online Multi-Commodity Facility Location Problem ER - TY - JOUR AU - Otroshi, Mortaza AU - Rossel, Moritz AU - Meschut, Gerson ID - 20143 JF - Journal of Advanced Joining Processes KW - Self-pierce riveting KW - Ductile fracture KW - Damage modeling KW - GISSMO damage model TI - Stress state dependent damage modeling of self-pierce riveting process simulation using GISSMO damage model VL - 1 ER - TY - JOUR AB - 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. AU - Caruso, Carina AU - Adammek, Christine AU - Bonanati, Sabrina AU - Wiescholek, Sybille ID - 35298 IS - 1 JF - Herausforderung Lehrer*innenbildung - Zeitschrift Zur Konzeption, Gestaltung Und Diskussion KW - ästhetische Forschung KW - Biographiearbeit KW - Praxissemester KW - Professionalisierung KW - selbstreguliertes Lernen KW - Motivation / aesthetic research KW - biographical work KW - long-term internship KW - profes-sionalization KW - self-regulated learning KW - motivation SN - 2625-0675 TI - Motivierende Lernzugänge als Ausgangspunkt der Professionalisierung angehender Lehrer_innen VL - 3 ER - TY - JOUR AB - 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. AU - Bonnard, Bernard AU - Cots, Olivier AU - Wembe Moafo, Boris Edgar ID - 33866 JF - ESAIM: Control, Optimisation and Calculus of Variations KW - Computational Mathematics KW - Control and Optimization KW - Control and Systems Engineering SN - 1292-8119 TI - A Zermelo navigation problem with a vortex singularity VL - 27 ER - TY - GEN AB - 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. ED - Kuball, Clara-Maria ED - Jung, R ED - Uhe, Benedikt ED - Meschut, Gerson ED - Merklein, Marion ID - 19974 KW - High nitrogen steel KW - Self-piercing riveting KW - Joining by forming KW - Bulk forming KW - Strain hardening TI - Influence of the process temperature on the forming behaviour and the friction during bulk forming of high nitrogen steel VL - 1 ER - TY - JOUR AB - As a result of lightweight design, increased use is being made of high-strength steel and aluminium in car bodies. Self-piercing riveting is an established technique for joining these materials. The dissimilar properties of the two materials have led to a number of different rivet geometries in the past. Each rivet geometry fulfils the requirements of the materials within a limited range. In the present investigation, an improved rivet geometry is developed, which permits the reliable joining of two material combinations that could only be joined by two different rivet geometries up until now. Material combination 1 consists of high-strength steel on both sides, while material combination 2 comprises aluminium on the punch side and high-strength steel on the die side. The material flow and the stress and strain conditions prevailing during the joining process are analysed by means of numerical simulation. The rivet geometry is then improved step-by-step on the basis of this analysis. Finally, the improved rivet geometry is manufactured and the findings of the investigation are verified in experimental joining tests. AU - Uhe, Benedikt AU - Kuball, Clara-Maria AU - Merklein, Marion AU - Meschut, Gerson ID - 19973 JF - Production Engineering KW - Self-piercing riveting KW - Joining technology KW - Rivet geometry KW - Multi-material design KW - High-strength steel KW - Aluminium TI - Improvement of a rivet geometry for the self-piercing riveting of high-strength steel and multi-material joints VL - 14 ER - TY - JOUR AB - We build upon a recently proposed multi-objective view onto performance measurement of single-objective stochastic solvers. The trade-off between the fraction of failed runs and the mean runtime of successful runs – both to be minimized – is directly analyzed based on a study on algorithm selection of inexact state-of-the-art solvers for the famous Traveling Salesperson Problem (TSP). Moreover, we adopt the hypervolume indicator (HV) commonly used in multi-objective optimization for simultaneously assessing both conflicting objectives and investigate relations to commonly used performance indicators, both theoretically and empirically. Next to Penalized Average Runtime (PAR) and Penalized Quantile Runtime (PQR), the HV measure is used as a core concept within the construction of per-instance algorithm selection models offering interesting insights into complementary behavior of inexact TSP solvers. AU - Bossek, Jakob AU - Kerschke, Pascal AU - Trautmann, Heike ID - 46334 JF - Applied Soft Computing KW - Algorithm selection KW - Multi-objective optimization KW - Performance measurement KW - Combinatorial optimization KW - Traveling Salesperson Problem SN - 1568-4946 TI - A multi-objective perspective on performance assessment and automated selection of single-objective optimization algorithms VL - 88 ER - TY - CONF AB - Dynamic optimization problems have gained significant attention in evolutionary computation as evolutionary algorithms (EAs) can easily adapt to changing environments. We show that EAs can solve the graph coloring problem for bipartite graphs more efficiently by using dynamic optimization. In our approach the graph instance is given incrementally such that the EA can reoptimize its coloring when a new edge introduces a conflict. We show that, when edges are inserted in a way that preserves graph connectivity, Randomized Local Search (RLS) efficiently finds a proper 2-coloring for all bipartite graphs. This includes graphs for which RLS and other EAs need exponential expected time in a static optimization scenario. We investigate different ways of building up the graph by popular graph traversals such as breadth-first-search and depth-first-search and analyse the resulting runtime behavior. We further show that offspring populations (e. g. a (1 + {$\lambda$}) RLS) lead to an exponential speedup in {$\lambda$}. Finally, an island model using 3 islands succeeds in an optimal time of {$\Theta$}(m) on every m-edge bipartite graph, outperforming offspring populations. This is the first example where an island model guarantees a speedup that is not bounded in the number of islands. AU - Bossek, Jakob AU - Neumann, Frank AU - Peng, Pan AU - Sudholt, Dirk ID - 48847 KW - dynamic optimization KW - evolutionary algorithms KW - running time analysis KW - theory SN - 978-1-4503-7128-5 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - More Effective Randomized Search Heuristics for Graph Coloring through Dynamic Optimization ER - TY - CONF AB - One-shot optimization tasks require to determine the set of solution candidates prior to their evaluation, i.e., without possibility for adaptive sampling. We consider two variants, classic one-shot optimization (where our aim is to find at least one solution of high quality) and one-shot regression (where the goal is to fit a model that resembles the true problem as well as possible). For both tasks it seems intuitive that well-distributed samples should perform better than uniform or grid-based samples, since they show a better coverage of the decision space. In practice, quasi-random designs such as Latin Hypercube Samples and low-discrepancy point sets are indeed very commonly used designs for one-shot optimization tasks. We study in this work how well low star discrepancy correlates with performance in one-shot optimization. Our results confirm an advantage of low-discrepancy designs, but also indicate the correlation between discrepancy values and overall performance is rather weak. We then demonstrate that commonly used designs may be far from optimal. More precisely, we evolve 24 very specific designs that each achieve good performance on one of our benchmark problems. Interestingly, we find that these specifically designed samples yield surprisingly good performance across the whole benchmark set. Our results therefore give strong indication that significant performance gains over state-of-the-art one-shot sampling techniques are possible, and that evolutionary algorithms can be an efficient means to evolve these. AU - Bossek, Jakob AU - Doerr, Carola AU - Kerschke, Pascal AU - Neumann, Aneta AU - Neumann, Frank ID - 48849 KW - Continuous optimization KW - Fully parallel search KW - One-shot optimization KW - Regression KW - Surrogate-assisted optimization SN - 978-3-030-58111-4 T2 - Parallel Problem Solving from Nature (PPSN XVI) TI - Evolving Sampling Strategies for One-Shot Optimization Tasks ER - TY - CONF AB - Several important optimization problems in the area of vehicle routing can be seen as variants of the classical Traveling Salesperson Problem (TSP). In the area of evolutionary computation, the Traveling Thief Problem (TTP) has gained increasing interest over the last 5 years. In this paper, we investigate the effect of weights on such problems, in the sense that the cost of traveling increases with respect to the weights of nodes already visited during a tour. This provides abstractions of important TSP variants such as the Traveling Thief Problem and time dependent TSP variants, and allows to study precisely the increase in difficulty caused by weight dependence. We provide a 3.59-approximation for this weight dependent version of TSP with metric distances and bounded positive weights. Furthermore, we conduct experimental investigations for simple randomized local search with classical mutation operators and two variants of the state-of-the-art evolutionary algorithm EAX adapted to the weighted TSP. Our results show the impact of the node weights on the position of the nodes in the resulting tour. AU - Bossek, Jakob AU - Casel, Katrin AU - Kerschke, Pascal AU - Neumann, Frank ID - 48851 KW - dynamic optimization KW - evolutionary algorithms KW - running time analysis KW - theory SN - 978-1-4503-7128-5 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - The Node Weight Dependent Traveling Salesperson Problem: Approximation Algorithms and Randomized Search Heuristics ER - TY - CONF AB - In practice, e.g. in delivery and service scenarios, Vehicle-Routing-Problems (VRPs) often imply repeated decision making on dynamic customer requests. As in classical VRPs, tours have to be planned short while the number of serviced customers has to be maximized at the same time resulting in a multi-objective problem. Beyond that, however, dynamic requests lead to the need for re-planning of not yet realized tour parts, while already realized tour parts are irreversible. In this paper we study this type of bi-objective dynamic VRP including sequential decision making and concurrent realization of decisions. We adopt a recently proposed Dynamic Evolutionary Multi-Objective Algorithm (DEMOA) for a related VRP problem and extend it to the more realistic (here considered) scenario of multiple vehicles. We empirically show that our DEMOA is competitive with a multi-vehicle offline and clairvoyant variant of the proposed DEMOA as well as with the dynamic single-vehicle approach proposed earlier. AU - Bossek, Jakob AU - Grimme, Christian AU - Trautmann, Heike ID - 48845 KW - decision making KW - dynamic optimization KW - evolutionary algorithms KW - multi-objective optimization KW - vehicle routing SN - 978-1-4503-7128-5 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Dynamic Bi-Objective Routing of Multiple Vehicles ER - TY - CONF AB - Sequential model-based optimization (SMBO) approaches are algorithms for solving problems that require computationally or otherwise expensive function evaluations. The key design principle of SMBO is a substitution of the true objective function by a surrogate, which is used to propose the point(s) to be evaluated next. SMBO algorithms are intrinsically modular, leaving the user with many important design choices. Significant research efforts go into understanding which settings perform best for which type of problems. Most works, however, focus on the choice of the model, the acquisition function, and the strategy used to optimize the latter. The choice of the initial sampling strategy, however, receives much less attention. Not surprisingly, quite diverging recommendations can be found in the literature. We analyze in this work how the size and the distribution of the initial sample influences the overall quality of the efficient global optimization (EGO) algorithm, a well-known SMBO approach. While, overall, small initial budgets using Halton sampling seem preferable, we also observe that the performance landscape is rather unstructured. We furthermore identify several situations in which EGO performs unfavorably against random sampling. Both observations indicate that an adaptive SMBO design could be beneficial, making SMBO an interesting test-bed for automated algorithm design. AU - Bossek, Jakob AU - Doerr, Carola AU - Kerschke, Pascal ID - 48850 KW - continuous black-box optimization KW - design of experiments KW - initial design KW - sequential model-based optimization SN - 978-1-4503-7128-5 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Initial Design Strategies and Their Effects on Sequential Model-Based Optimization: An Exploratory Case Study Based on BBOB ER - TY - JOUR AB - We build upon a recently proposed multi-objective view onto performance measurement of single-objective stochastic solvers. The trade-off between the fraction of failed runs and the mean runtime of successful runs \textendash both to be minimized \textendash is directly analyzed based on a study on algorithm selection of inexact state-of-the-art solvers for the famous Traveling Salesperson Problem (TSP). Moreover, we adopt the hypervolume indicator (HV) commonly used in multi-objective optimization for simultaneously assessing both conflicting objectives and investigate relations to commonly used performance indicators, both theoretically and empirically. Next to Penalized Average Runtime (PAR) and Penalized Quantile Runtime (PQR), the HV measure is used as a core concept within the construction of per-instance algorithm selection models offering interesting insights into complementary behavior of inexact TSP solvers. \textbullet The multi-objective perspective is naturally generalizable to multiple objectives. \textbullet Proof of relationship between HV and the PAR in the considered bi-objective space. \textbullet New insights into complementary behavior of stochastic optimization algorithms. AU - Bossek, Jakob AU - Kerschke, Pascal AU - Trautmann, Heike ID - 48848 IS - C JF - Applied Soft Computing KW - Algorithm selection KW - Combinatorial optimization KW - Multi-objective optimization KW - Performance measurement KW - Traveling Salesperson Problem SN - 1568-4946 TI - A Multi-Objective Perspective on Performance Assessment and Automated Selection of Single-Objective Optimization Algorithms VL - 88 ER - TY - JOUR AB - Employing main and sector-specific investment-grade CDS indices from the North American and European CDS market and performing mean-variance out-of-sample analyses for conservative and aggressive investors over the period from 2006 to 2014, this paper analyzes portfolio benefits of adding corporate CDS indices to a traditional financial portfolio consisting of stock and sovereign bond indices. As a baseline result, we initially find an increase in portfolio (downside) risk-diversification when adding CDS indices, which is observed irrespective of both CDS markets, investor-types and different sub-periods, including the global financial crisis and European sovereign debt crisis. In addition, the analysis reveals higher portfolio excess returns and performance in CDS index portfolios, however, these effects clearly differ between markets, investor-types and sub-periods. Overall, portfolio benefits of adding CDS indices mainly result from the fact that institutional investors replace sovereign bond indices rather than stock indices by CDS indices due to better risk-return characteristics. Our baseline findings remain robust under a variety of robustness checks. Results from sensitivity analyses provide further important implications for institutional investors with a strategic focus on a long-term conservative portfolio management. AU - Hippert, Benjamin AU - Uhde, André AU - Wengerek, Sascha Tobias ID - 4562 IS - 2 JF - Review of Derivatives Research KW - Corporate credit default swap indices KW - Mean-variance asset allocation KW - Out-of-sample portfolio optimization KW - Portfolio risk-diversification KW - Portfolio performance evaluation TI - Portfolio Benefits of Adding Corporate Credit Default Swap Indices: Evidence from North America and Europe VL - 22 ER - TY - THES AB - Ultraschall wird zur Effizienzsteigerung in verfahrenstechnischen Prozessen eingesetzt. Die Betriebsparamter der Ultraschallsysteme werden empirisch ermittelt, da derzeit keine systematische Analyse der Wechselwirkung zwischen Ultraschallwandler und Schallfeld sowie kein Verfahren zur Messung der Kavitationsaktivität ohne zusätzlichen Sensor existieren. Auf Basis einer experimentellen Analyse des betrachteten sonochemischen Reaktors wird ein Finite-Elemente-Modell aufgebaut, das die Wechselwirkung zwischen Schallfeld und Ultraschallwandler berücksichtigt. Die modellbasierte Analyse zeigt, dass wegen der akustischen Eigenschaften des Autoklavs nur direkt an der Sonotrode Kavitation entsteht. Die Wechselwirkung zwischen Ultraschallwandler und Schallfeld ermöglicht Aussagen über das Schallfeld und die Kavitationsaktivität auf Basis der Rückwirkung auf den Ultraschallwandler. Die lineare Schalldruckverteilung ermöglicht eine Prognose über die Verteilung von Kavitationszonen. Das beschriebene Modell liefert wertvolle Erkenntnisse für die Auslegung, Analyse und Skalierung sonochemischer Reaktoren. Auf Grund der rauen Prozessrandbedingungen ist die Applikation von Sensoren zur Überwachung der Kavitationsaktivität in vielen sonochemischen Prozessen nicht möglich. Zur prozessbegleitenden Messung der Kavitationsaktivität wird ein Verfahren entwickelt, das die Bewertung der Kavitationsaktivität durch Auswertung der Rückwirkung auf den Ultraschallwandler erlaubt. Das Messverfahren ermöglicht eine vorhersagbare und reproduzierbare Durchführung kavitationsbasierter Prozesse und stellt eine wichtige Erweiterung für bestehende und neue Ultraschallsysteme dar. AU - Bornmann, Peter ID - 10000 KW - Sonochemie KW - Akustische Kavitation KW - Kavitationsmessung KW - Kavitationsdetektion KW - FEM-Simulation Ultraschallwandler KW - Prozessüberwachung KW - FEM-Simulation Schallfeld KW - Self-Sensing KW - Piezoelektrische Ultraschallwandler KW - Ultraschallreinigung TI - Modellierung und experimentelle Charakterisierung der Wechselwirkung zwischen Ultraschallwandler und Flüssigkeit in kavitationsbasierten Prozessen ER - TY - CONF AB - We tackle a bi-objective dynamic orienteering problem where customer requests arise as time passes by. The goal is to minimize the tour length traveled by a single delivery vehicle while simultaneously keeping the number of dismissed dynamic customers to a minimum. We propose a dynamic Evolutionary Multi-Objective Algorithm which is grounded on insights gained from a previous series of work on an a-posteriori version of the problem, where all request times are known in advance. In our experiments, we simulate different decision maker strategies and evaluate the development of the Pareto-front approximations on exemplary problem instances. It turns out, that despite severely reduced computational budget and no oracle-knowledge of request times the dynamic EMOA is capable of producing approximations which partially dominate the results of the a-posteriori EMOA and dynamic integer linear programming strategies. AU - Bossek, Jakob AU - Grimme, Christian AU - Meisel, Stephan AU - Rudolph, Günter AU - Trautmann, Heike ED - Deb, Kalyanmoy ED - Goodman, Erik ED - Coello Coello, Carlos A. ED - Klamroth, Kathrin ED - Miettinen, Kaisa ED - Mostaghim, Sanaz ED - Reed, Patrick ID - 48841 KW - Combinatorial optimization KW - Dynamic optimization KW - Metaheuristics KW - Multi-objective optimization KW - Vehicle routing SN - 978-3-030-12598-1 T2 - Evolutionary Multi-Criterion Optimization (EMO) TI - Bi-Objective Orienteering: Towards a Dynamic Multi-objective Evolutionary Algorithm ER - TY - CONF AB - Evolutionary algorithms have successfully been applied to evolve problem instances that exhibit a significant difference in performance for a given algorithm or a pair of algorithms inter alia for the Traveling Salesperson Problem (TSP). Creating a large variety of instances is crucial for successful applications in the blooming field of algorithm selection. In this paper, we introduce new and creative mutation operators for evolving instances of the TSP. We show that adopting those operators in an evolutionary algorithm allows for the generation of benchmark sets with highly desirable properties: (1) novelty by clear visual distinction to established benchmark sets in the field, (2) visual and quantitative diversity in the space of TSP problem characteristics, and (3) significant performance differences with respect to the restart versions of heuristic state-of-the-art TSP solvers EAX and LKH. The important aspect of diversity is addressed and achieved solely by the proposed mutation operators and not enforced by explicit diversity preservation. AU - Bossek, Jakob AU - Kerschke, Pascal AU - Neumann, Aneta AU - Wagner, Markus AU - Neumann, Frank AU - Trautmann, Heike ID - 48842 KW - benchmarking KW - instance features KW - optimization KW - problem generation KW - traveling salesperson problem SN - 978-1-4503-6254-2 T2 - Proceedings of the 15th ACM/SIGEVO Conference on Foundations of Genetic Algorithms TI - Evolving Diverse TSP Instances by Means of Novel and Creative Mutation Operators ER - TY - CONF AB - We contribute to the theoretical understanding of randomized search heuristics for dynamic problems. We consider the classical graph coloring problem 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. This includes the (1+1) EA and RLS in a setting where the number of colors is bounded and we are minimizing the number of conflicts as well as iterated local search algorithms that use an unbounded color palette and aim to use the smallest colors and - as a consequence - 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. Furthermore, we show how to speed up computations by using problem specific operators concentrating on parts of the graph where changes have occurred. AU - Bossek, Jakob AU - Neumann, Frank AU - Peng, Pan AU - Sudholt, Dirk ID - 48843 KW - dynamic optimization KW - evolutionary algorithms KW - running time analysis KW - theory SN - 978-1-4503-6111-8 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Runtime Analysis of Randomized Search Heuristics for Dynamic Graph Coloring ER - TY - CONF AB - Research has shown that for many single-objective graph problems where optimum solutions are composed of low weight sub-graphs, such as the minimum spanning tree problem (MST), mutation operators favoring low weight edges show superior performance. Intuitively, similar observations should hold for multi-criteria variants of such problems. In this work, we focus on the multi-criteria MST problem. A thorough experimental study is conducted where we estimate the probability of edges being part of non-dominated spanning trees as a function of the edges’ non-domination level or domination count, respectively. Building on gained insights, we propose several biased one-edge-exchange mutation operators that differ in the used edge-selection probability distribution (biased towards edges of low rank). Our empirical analysis shows that among different graph types (dense and sparse) and edge weight types (both uniformly random and combinations of Euclidean and uniformly random) biased edge-selection strategies perform superior in contrast to the baseline uniform edge-selection. Our findings are in particular strong for dense graphs. AU - Bossek, Jakob AU - Grimme, Christian AU - Neumann, Frank ID - 48840 KW - biased mutation KW - combinatorial optimization KW - minimum spanning tree KW - multi-objective optimization SN - 978-1-4503-6111-8 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - On the Benefits of Biased Edge-Exchange Mutation for the Multi-Criteria Spanning Tree Problem ER - TY - CONF AB - In this paper we present two major results: First, we introduce the first self-stabilizing version of a supervised overlay network (as introduced in~\cite{DBLP:conf/ispan/KothapalliS05}) by presenting a self-stabilizing supervised skip ring. Secondly, we show how to use the self-stabilizing supervised skip ring to construct an efficient self-stabilizing publish-subscribe system. That is, in addition to stabilizing the overlay network, every subscriber of a topic will eventually know all of the publications that have been issued so far for that topic. The communication work needed to processes a subscribe or unsubscribe operation is just a constant in a legitimate state, and the communication work of checking whether the system is still in a legitimate state is just a constant on expectation for the supervisor as well as any process in the system. AU - Feldmann, Michael AU - Kolb, Christina AU - Scheideler, Christian AU - Strothmann, Thim Frederik ID - 1163 KW - Topological Self-stabilization KW - Supervised Overlay KW - Publish-Subscribe System T2 - Proceedings of the 32nd IEEE International Parallel & Distributed Processing Symposium (IPDPS) TI - Self-Stabilizing Supervised Publish-Subscribe Systems ER - TY - CONF AB - When responding to natural disasters, professional relief units are often supported by many volunteers which are not affiliated to humanitarian organizations. The effective coordination of these volunteers is crucial to leverage their capabilities and to avoid conflicts with professional relief units. In this paper, we empirically identify key requirements that professional relief units pose on this coordination. Based on these requirements, we suggest a decision model. We computationally solve a real-world instance of the model and empirically validate the computed solution in interviews with practitioners. Our results show that the suggested model allows for solving volunteer coordination tasks of realistic size near-optimally within short time, with the determined solution being well accepted by practitioners. We also describe in this article how the suggested decision support model is integrated in the volunteer coordination system which we develop in joint cooperation with a disaster management authority and a software development company. AU - Rauchecker, Gerhard AU - Schryen, Guido ID - 5675 KW - Coordination of spontaneous volunteers KW - volunteer coordination system KW - decision support KW - scheduling optimization model KW - linear programming T2 - Proceedings of the 15th International Conference on Information Systems for Crisis Response and Management TI - Decision Support for the Optimal Coordination of Spontaneous Volunteers in Disaster Relief ER - TY - CONF AB - While a lot of research in distributed computing has covered solutions for self-stabilizing computing and topologies, there is far less work on self-stabilization for distributed data structures. Considering crashing peers in peer-to-peer networks, it should not be taken for granted that a distributed data structure remains intact. In this work, we present a self-stabilizing protocol for a distributed data structure called the hashed Patricia Trie (Kniesburges and Scheideler WALCOM'11) that enables efficient prefix search on a set of keys. The data structure has a wide area of applications including string matching problems while offering low overhead and efficient operations when embedded on top of a distributed hash table. Especially, longest prefix matching for $x$ can be done in $\mathcal{O}(\log |x|)$ hash table read accesses. We show how to maintain the structure in a self-stabilizing way. Our protocol assures low overhead in a legal state and a total (asymptotically optimal) memory demand of $\Theta(d)$ bits, where $d$ is the number of bits needed for storing all keys. AU - Knollmann, Till AU - Scheideler, Christian ED - Izumi, Taisuke ED - Kuznetsov, Petr ID - 4411 KW - Self-Stabilizing KW - Prefix Search KW - Distributed Data Structure T2 - Proceedings of the 20th International Symposium on Stabilization, Safety, and Security of Distributed Systems (SSS) TI - A Self-Stabilizing Hashed Patricia Trie VL - 11201 ER - TY - CONF AB - Ultrasonic wire bonding is an indispensable process in the industrial manufacturing of semiconductor devices. Copper wire is increasingly replacing the well-established aluminium wire because of its superior electrical, thermal and mechanical properties. Copper wire processes differ significantly from aluminium processes and are more sensitive to disturbances, which reduces the range of parameter values suitable for a stable process. Disturbances can be compensated by an adaption of process parameters, but finding suitable parameters manually is difficult and time-consuming. This paper presents a physical model of the ultrasonic wire bonding process including the friction contact between tool and wire. This model yields novel insights into the process. A prototype of a multi-objective optimizing bonding machine (MOBM) is presented. It uses multi-objective optimization, based on the complete process model, to automatically select the best operating point as a compromise of concurrent objectives. AU - Unger, Andreas AU - Hunstig, Matthias AU - Meyer, Tobias AU - Brökelmann, Michael AU - Sextro, Walter ID - 9999 KW - wire bonding KW - multi-objective optimization KW - process model KW - copper wire KW - self-optimization T2 - In Proceedings of IMAPS 2018 – 51st Symposium on Microelectronics, Pasadena, CA, 2018 TI - Intelligent Production of Wire Bonds using Multi-Objective Optimization – Insights, Opportunities and Challenges VL - Vol. 2018, No. 1, pp. 000572-000577. ER - TY - JOUR AB - Sociogenesis addresses a pervasive problem in psychology given by Cartesian dualism that assigns the mental an inner locus apart from material activity. Aligning ourselves to the ongoing critical discussions of interiorization in psychology, we explore the crucial notion of space by highlighting language as sociocultural and dialogical activity performed by other-oriented individuals. We discuss space in terms of the “language spacetime”, a symbolic, embodied formation of mutually positioned speaking and listening selves. This leads beyond the “inside-outside” container metaphor and allows for a reformulation of interiorization. Interiorization is conceptualized as a continuous series of different, though mutually related movements between self and other and self and self that lead to and are supported by specific formations in language activity: reversion, transposition, and decoupling. Along a short passage of a video-based interview, we trace the reversion of dialogical positions within the addressivity constellation of the two interlocutors, their interactive creation of a heterotopic spacetime, and the decoupling of one speaker's psychological activity from the concrete here-and-now and the present other by moving and acting into this new sphere. Interiorization appears as a movement at the border of past, present, and possible future(s). AU - Bertau, Marie-Cécile AU - Karsten, Andrea ID - 32158 JF - New Ideas in Psychology KW - Interiorization KW - Dialogical self KW - Language activity KW - Voice KW - Vygotsky KW - Heterotopia KW - Video-confrontation SN - 0732-118X TI - Reconsidering interiorization: Self moving across language spacetimes VL - 49 ER - TY - THES AB - Reliability-adaptive systems allow an adaptation of system behavior based on current system reliability. They can extend their lifetime at the cost of lowered performance or vice versa. This can be used to adapt failure behavior according to a maintenance plan, thus increasing availability while using up system capability fully. To facilitate setup, a control algorithm independent of a degradation model is desired. A closed loop control technique for reliability based on a health index, a measure for system degradation, is introduced. It uses self-optimization as means to implement behavior adaptation. This is based on selecting the priorities of objectives that the system pursues. Possible working points are computed beforehand using model-based multiobjective optimization techniques. The controller selects the priorities of objectives and this way balances reliability and performance. As exemplary application, an automatically actuated single plate dry clutch is introduced. The entire reliability control is setup and lifetime experiments are conducted. Results show that the variance of time to failure is reduced greatly, making the failure behavior more predictable. At the same time, the desired usable lifetime can be extended at the cost of system performance to allow for changed maintenance intervals. Together, these possibilities allow for greater system usage and better planning of maintenance. AU - Meyer, Tobias ID - 9994 KW - dependability KW - reliability KW - behavior adaptation KW - self-optimization KW - multiobjective optimization KW - optimal control KW - automotive drivetrain KW - clutch system KW - reliability-adaptive system TI - Optimization-based reliability control of mechatronic systems ER - TY - CONF AB - We analyze the effects of including local search techniques into a multi-objective evolutionary algorithm for solving a bi-objective orienteering problem with a single vehicle while the two conflicting objectives are minimization of travel time and maximization of the number of visited customer locations. Experiments are based on a large set of specifically designed problem instances with different characteristics and it is shown that local search techniques focusing on one of the objectives only improve the performance of the evolutionary algorithm in terms of both objectives. The analysis also shows that local search techniques are capable of sending locally optimal solutions to foremost fronts of the multi-objective optimization process, and that these solutions then become the leading factors of the evolutionary process. AU - Bossek, Jakob AU - Grimme, Christian AU - Meisel, Stephan AU - Rudolph, Günter AU - Trautmann, Heike ID - 48839 KW - combinatorial optimization KW - metaheuristics KW - multi-objective optimization KW - orienteering KW - transportation SN - 978-1-4503-5618-3 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Local Search Effects in Bi-Objective Orienteering ER - TY - CONF AB - Assessing the performance of stochastic optimization algorithms in the field of multi-objective optimization is of utmost importance. Besides the visual comparison of the obtained approximation sets, more sophisticated methods have been proposed in the last decade, e. g., a variety of quantitative performance indicators or statistical tests. In this paper, we present tools implemented in the R package ecr, which assist in performing comprehensive and sound comparison and evaluation of multi-objective evolutionary algorithms following recommendations from the literature. AU - Bossek, Jakob ID - 48867 KW - evolutionary optimization KW - performance assessment KW - software-tools SN - 978-1-4503-5764-7 T2 - Proceedings of the Genetic and Evolutionary Computation Conference Companion TI - Performance Assessment of Multi-Objective Evolutionary Algorithms with the R Package ecr ER - TY - CONF AB - Performance comparisons of optimization algorithms are heavily influenced by the underlying indicator(s). In this paper we investigate commonly used performance indicators for single-objective stochastic solvers, such as the Penalized Average Runtime (e.g., PAR10) or the Expected Running Time (ERT), based on exemplary benchmark performances of state-of-the-art inexact TSP solvers. Thereby, we introduce a methodology for analyzing the effects of (usually heuristically set) indicator parametrizations - such as the penalty factor and the method used for aggregating across multiple runs - w.r.t. the robustness of the considered optimization algorithms. AU - Kerschke, Pascal AU - Bossek, Jakob AU - Trautmann, Heike ID - 48885 KW - algorithm selection KW - optimization KW - performance measures KW - transportation KW - travelling salesperson problem SN - 978-1-4503-5764-7 T2 - Proceedings of the Genetic and Evolutionary Computation Conference Companion TI - Parameterization of State-of-the-Art Performance Indicators: A Robustness Study Based on Inexact TSP Solvers ER - TY - JOUR AB - Research on entrepreneurial learning highlights the importance of experience and prior knowledge to entrepreneurial success. However, a conundrum remains and we are still seeking answers as to why some novice entrepreneurs learn successfully from their experiences and succeed, while some experienced entrepreneurs fail with their ventures. In order to advance the discussion about the role of experience during entrepreneurial learning, our critical reflection aims to (1) highlight some of the shortcomings of experiential learning theory (ELT) and (2) illustrate how alternative theoretical perspectives have the potential to advance our conceptual understanding of entrepreneurial learning processes. We argue for an explanation of entrepreneurial learning as a dynamic and self-regulated process that relies on planning, monitoring, and self-reflection. AU - Fust, Alexander Paul AU - Jenert, Tobias AU - Winkler, Christoph ID - 4419 IS - 2 JF - Entrepreneurship Research Journal KW - entrepreneurial learning KW - experiential learning KW - self-regulated learning TI - Experiential or Self-Regulated Learning: A Critical Reflection of Entrepreneurial Learning Processes VL - 8 ER - TY - JOUR AB - In order to improve the credibility of modern simulation tools, uncertainties of different kinds have to be considered. This work is focused on epistemic uncertainties in the framework of continuum mechanics, which are taken into account by fuzzy analysis. The underlying min-max optimization problem of the extension principle is approximated by α-discretization, resulting in a separation of minimum and maximum problems. To become more universal, so-called quantities of interest are employed, which allow a general formulation for the target problem of interest. In this way, the relation to parameter identification problems based on least-squares functions is highlighted. The solutions of the related optimization problems with simple constraints are obtained with a gradient-based scheme, which is derived from a sensitvity analysis for the target problem by means of a variational formulation. Two numerical examples for the fuzzy analysis of material parameters are concerned with a necking problem at large strain elastoplasticity and a perforated strip at large strain hyperelasticity to demonstrate the versatility of the proposed variational formulation. AU - Mahnken, Rolf ID - 9862 IS - 3-4 JF - Mathematics and Mechanics of complex systems KW - fuzzy analysis KW - α-level optimization KW - quantities of interest KW - optimization with simple constraints KW - large strain elasticity KW - large strain elastoplasticity SN - 2325-3444 TI - "A variational formulation for fuzzy analysis in continuum mechanics" VL - 5 ER - TY - JOUR AB - State-of-the-art mechatronic systems offer inherent intelligence that enables them to autonomously adapt their behavior to current environmental conditions and to their own system state. This autonomous behavior adaptation is made possible by software in combination with complex sensor and actuator systems and by sophisticated information processing, all of which make these systems increasingly complex. This increasing complexity makes the design process a challenging task and brings new complex possibilities for operation and maintenance. However, with the risk of increased system complexity also comes the chance to adapt system behavior based on current reliability, which in turn increases reliability. The development of such an adaption strategy requires appropriate methods to evaluate reliability based on currently selected system behavior. A common approach to implement such adaptivity is to base system behavior on different working points that are obtained using multiobjective optimization. During operation, selection among these allows a changed operating strategy. To allow for multiobjective optimization, an accurate system model including system reliability is required. This model is repeatedly evaluated by the optimization algorithm. At present, modeling of system reliability and synchronization of the models of behavior and reliability is a laborious manual task and thus very error-prone. Since system behavior is crucial for system reliability, an integrated model is introduced that integrates system behavior and system reliability. The proposed approach is used to formulate reliability-related objective functions for a clutch test rig that are used to compute feasible working points using multiobjective optimization. AU - Kaul, Thorben AU - Meyer, Tobias AU - Sextro, Walter ID - 9976 JF - SAGE Journals KW - Integrated model KW - reliability KW - system behavior KW - Bayesian network KW - multiobjective optimization TI - Formulation of reliability-related objective functions for design of intelligent mechatronic systems VL - Vol. 231(4) ER - TY - CONF AB - Piezoelectric transducers are used in a wide range of applications. Reliability of these transducers is an important aspect in their application. Prognostics, which involve continuous monitoring of the health of technical systems and using this information to estimate the current health state and consequently predict the remaining useful lifetime (RUL), can be used to increase the reliability, safety, and availability of the transducers. This is achieved by utilizing the health state and RUL predictions to adaptively control the usage of the components or to schedule appropriate maintenance without interrupting operation. In this work, a prognostic approach utilizing self-sensing, where electric signals of a piezoelectric transducer are used as the condition monitoring data, is proposed. The approach involves training machine learning algorithms to model the degradation of the transducers through a health index and the use of the learned model to estimate the health index of similar transducers. The current health index is then used to estimate RUL of test components. The feasibility of the approach is demonstrated using piezoelectric bimorphs and the results show that the method is accurate in predicting the health index and RUL. AU - Kimotho, James Kuria AU - Sextro, Walter AU - Hemsel, Tobias ID - 9978 KW - Estimation of Remaining Useful Lifetime of Piezoelectric Transducers Based on Self-Sensing T2 - IEEE Transactions on Reliability TI - Estimation of Remaining Useful Lifetime of Piezoelectric Transducers Based on Self-Sensing ER - TY - CONF AU - Ho, Nam AU - Kaufmann, Paul AU - Platzner, Marco ID - 10676 KW - Linux KW - cache storage KW - microprocessor chips KW - multiprocessing systems KW - LEON3-Linux based multicore processor KW - MiBench suite KW - block sizes KW - cache adaptation KW - evolvable caches KW - memory-to-cache-index mapping function KW - processor caches KW - reconfigurable cache mapping optimization KW - reconfigurable hardware technology KW - replacement strategies KW - standard Linux OS KW - time a complete hardware implementation KW - Hardware KW - Indexes KW - Linux KW - Measurement KW - Multicore processing KW - Optimization KW - Training T2 - 2017 International Conference on Field Programmable Technology (ICFPT) TI - Evolvable caches: Optimization of reconfigurable cache mappings for a LEON3/Linux-based multi-core processor ER - TY - CONF AU - Guettatfi, Zakarya AU - Hübner, Philipp AU - Platzner, Marco AU - Rinner, Bernhard ID - 10780 KW - embedded systems KW - image sensors KW - power aware computing KW - wireless sensor networks KW - Zynq-based VSN node prototype KW - computational self-awareness KW - design approach KW - platform levels KW - power consumption KW - visual sensor networks KW - visual sensor nodes KW - Cameras KW - Hardware KW - Middleware KW - Multicore processing KW - Operating systems KW - Runtime KW - Reconfigurable platforms KW - distributed embedded systems KW - performance-resource trade-off KW - self-awareness KW - visual sensor nodes T2 - 12th International Symposium on Reconfigurable Communication-centric Systems-on-Chip (ReCoSoC) TI - Computational self-awareness as design approach for visual sensor nodes ER - TY - JOUR AB - Time-variant age information of different parts of a system can be used for system-level performance improvement through high-level task scheduling, thus extending the life-time of the system. Progressive age information should provide the age state that the system is in, and the rate that it is being aged at. In this paper, we propose a structure that monitors certain paths of a circuit and detects its gradual age growth, and provides the aging rate and aging state of the circuit. The proposed monitors are placed on a selected set of nodes that represent a timing bottleneck of the system. These monitors sample expected data on these nodes, and compare them with the expected values. The timing of sampling changes as the circuit ages and its delay increases. The timing of sampling will provide a measure of aging advancement of a circuit. To assess the efficacy of the proposed method and compare it with other state-of-the-art aging monitors, we use them on selected nodes of the execution unit of different processors, as well as some circuits from ITC99 benchmarks. The results reveal that the precision of our proposed method is between 0.12 (ns) to 0.401 (ns). Its Area and power overhead are negligible and are about 2.13 and 0.69 percent respectively. AU - Sadeghi-Kohan, Somayeh AU - Kamal, Mehdi AU - Navabi, Zainalabedin ID - 29462 IS - 3 JF - IEEE Transactions on Emerging Topics in Computing KW - Age advancement KW - age monitoring clock KW - aging rate KW - self-adjusting monitors SN - 2168-6750 TI - Self-Adjusting Monitor for Measuring Aging Rate and Advancement VL - 8 ER - TY - CONF AB - The novel R package ecr (version 2), short for Evolutionary Computation in R, provides a comprehensive collection of building blocks for constructing powerful evolutionary algorithms for single- and multi-objective continuous and combinatorial optimization problems. It allows to solve standard optimization tasks with few lines of code using a black-box approach. Moreover, rapid prototyping of non-standard ideas is possible via an explicit, white-box approach. This paper describes the design principles of the package and gives some introductory examples on how to use the package in practise. AU - Bossek, Jakob ID - 48863 KW - evolutionary optimization KW - software-tools SN - 978-1-4503-4939-0 T2 - Proceedings of the Genetic and Evolutionary Computation Conference Companion TI - Ecr 2.0: A Modular Framework for Evolutionary Computation in R ER - TY - CONF AB - While finding minimum-cost spanning trees (MST) in undirected graphs is solvable in polynomial time, the multi-criteria minimum spanning tree problem (mcMST) is NP-hard. Interestingly, the mcMST problem has not been in focus of evolutionary computation research for a long period of time, although, its relevance for real world problems is easy to see. The available and most notable approaches by Zhou and Gen as well as by Knowles and Corne concentrate on solution encoding and on fairly dated selection mechanisms. In this work, we revisit the mcMST and focus on the mutation operators as exploratory components of evolutionary algorithms neglected so far. We investigate optimal solution characteristics to discuss current mutation strategies, identify shortcomings of these operators, and propose a sub-tree based operator which offers what we term Pareto-beneficial behavior: ensuring convergence and diversity at the same time. The operator is empirically evaluated inside modern standard evolutionary meta-heuristics for multi-criteria optimization and compared to hitherto applied mutation operators in the context of mcMST. AU - Bossek, Jakob AU - Grimme, Christian ID - 48857 KW - Convergence KW - Encoding KW - Euclidean distance KW - Evolutionary computation KW - Heating systems KW - Optimization KW - Standards T2 - 2017 IEEE Symposium Series on Computational Intelligence (SSCI) TI - A Pareto-Beneficial Sub-Tree Mutation for the Multi-Criteria Minimum Spanning Tree Problem ER - TY - CONF AB - Usage of copper wire bonds allows to push power boundaries imposed by aluminum wire bonds. Copper allows higher electrical, thermal and mechanical loads than aluminum, which currently is the most commonly used material in heavy wire bonding. This is the main driving factor for increased usage of copper in high power applications such as wind turbines, locomotives or electric vehicles. At the same time, usage of copper also increases tool wear and reduces the range of parameter values for a stable process, making the process more challenging. To overcome these drawbacks, parameter adaptation at runtime using self-optimization is desired. A self-optimizing system is based on system objectives that evaluate and quantify system performance. System parameters can be changed at runtime such that pre-selected objective values are reached. For adaptation of bond process parameters, model-based self-optimization is employed. Since it is based on a model of the system, the bond process was modeled. In addition to static model parameters such as wire and substrate material properties and vibration characteristics of transducer and tool, variable model inputs are process parameters. Main simulation result is bonded area in the wiresubstrate contact. This model is then used to find valid and optimal working points before operation. The working point is composed of normal force and ultrasonic voltage trajectories, which are usually determined experimentally. Instead, multiobjective optimalization is used to compute trajectories that simultaneously optimize bond quality, process duration, tool wear and probability of tool-substrate contacts. The values of these objectives are computed using the process model. At runtime, selection among pre-determined optimal working points is sufficient to prioritize individual objectives. This way, the computationally expensive process of numerically solving a multiobjective optimal control problem and the demanding high speed bonding process are separated. To evaluate to what extent the pre-defined goals of self-optimization are met, an offthe- shelf heavy wire bonding machine was modified to allow for parameter adaptation and for transmitting of measurement data at runtime. This data is received by an external computer system and evaluated to select a new working point. Then, new process parameters are sent to the modified bonding machine for use for subsequent bonds. With these components, a full self-optimizing system has been implemented. AU - Meyer , Tobias AU - Unger, Andreas AU - Althoff, Simon AU - Sextro, Walter AU - Brökelmann, Michael AU - Hunstig, Matthias AU - Guth, Karsten ID - 9966 KW - Self-optimization KW - adaptive system KW - bond process KW - copper wire T2 - IEEE 66th Electronic Components and Technology Conference TI - Reliable Manufacturing of Heavy Copper Wire Bonds Using Online Parameter Adaptation ER - TY - CONF AB - State of the Art inexact solvers of the NP-hard Traveling Salesperson Problem TSP are known to mostly yield high-quality solutions in reasonable computation times. With the purpose of understanding different levels of instance difficulties, instances for the current State of the Art heuristic TSP solvers LKH+restart and EAX+restart are presented which are evolved using a sophisticated evolutionary algorithm. More specifically, the performance differences of the respective solvers are maximized resulting in instances which are easier to solve for one solver and much more difficult for the other. Focusing on both optimization directions, instance features are identified which characterize both types of instances and increase the understanding of solver performance differences. AU - Bossek, Jakob AU - Trautmann, Heike ID - 48874 KW - Combinatorial optimization KW - Instance hardness KW - Metaheuristics KW - Transportation KW - TSP SN - 978-3-319-49129-5 T2 - Proceedings of the XV International Conference of the Italian Association for Artificial Intelligence on Advances in Artificial Intelligence - Volume 10037 TI - Understanding Characteristics of Evolved Instances for State-of-the-Art Inexact TSP Solvers with Maximum Performance Difference ER - TY - JOUR AU - Torresen, Jim AU - Plessl, Christian AU - Yao, Xin ID - 1772 IS - 7 JF - IEEE Computer KW - self-awareness KW - self-expression TI - Self-Aware and Self-Expressive Systems – Guest Editor's Introduction VL - 48 ER - TY - JOUR AB - Advancements in information technology have changed the way customers experience a service encounter and their relationship with service providers. Especially technology-based self-service channels have found their way into the 21st century service economy. While research embraces these channels for their cost-efficiency, it has not examined whether a shift from personal to self-service affects customer–firm relationships. Drawing from the service-dominant logic and its central concept of value-in-context, we discuss customers’ value creation in self-service and personal service channels and examine the long-term impact of these channels on customer retention. Using longitudinal customer data, we investigate how the ratio of self-service versus personal service use influences customer defection over time. Our findings suggest that the ratio of self-service to personal service used affects customer defection in a U-shaped manner, with intermediate levels of both self-service and personal service use being associated with the lowest likelihood of defection. We also find that this effect mitigates over time. We conclude that firms should not shift customers toward self-service channels completely, especially not at the beginning of a relationship. Our study underlines the importance of understanding when and how self-service technologies create valuable customer experiences and stresses the notion of actively managing customers’ cocreation of value. AU - Scherer, Anne AU - Wünderlich, Nancy AU - Von Wangenheim, Florian ID - 5704 IS - 1 JF - MIS Quarterly KW - customer defection KW - customer retention KW - e-service KW - longitudinal KW - Self-service KW - value-in-context SN - 0276-7783. TI - The Value of Self-Service: Long-Term Effects of Technology-Based Self-Service Usage on Customer Retention. VL - 39 ER - TY - CONF AB - A highly selective first study phase in many Swiss study programs leads to a rather competitive climate among students. However, the atmosphere at the university is an important factor for students' transition into Higher Education. An important question in this context is whether students' are equipped with different dispositions influencing how they cope with this transition. Other research has already shown that different groups of students can be identified regarding their student behavior. Yet, so far little is known about patterns of variables characterizing students, transitioning successfully. The paper takes advantage of a person-centered approach, i.e. the latent-class analysis, which makes it possible to identify groups of individuals, sharing common attributes. The research was conducted as a longitudinal study during their first year at a Swiss university. The return rate was about 67%, with 820 utilizable questionnaires at t1. Based on the analysis of students' anxiety, intrinsic motivation and self-efficacy, three distinct classes of students could be identified. The first class can be called the "highly motivated and self-confident" students. The second class is characterized by the same pattern, however, on a more intermediate level and the last class can be described as the "least motivated and most anxious" group of students. This study contributes to research and theory on students' transition into higher education and could be a first hint that students' experiences of this transition can vary substantially. AU - Brahm, Taiga AU - Wagner, Dietrich AU - Jenert, Tobias ID - 4464 KW - Quantitative methods KW - Self-efficacy KW - Higher education KW - Motivation and Emotion TI - A person-centred approach to students' transition into Higher Education ER - TY - JOUR AB - Eine Vielzahl von Prozessen in der Chemie und Verfahrenstechnik kann durch Ultraschall positiv beeinflusst werden. Oftmals ist ultraschallinduzierte Kavitation der Hauptwirkmechanismus für die positiven Effekte der Beschallung. Daher ist es notwendig die Kavitationsaktivität während des Prozesses zu quantifizieren um die Beschallung für den jeweiligen Prozess optimal gestalten und überwachen zu können. Eine Möglichkeit der prozessbegleitenden Kavitationsdetektion ist die Auswertung der akustischen Emissionen von oszillierenden und kollabierenden Kavitationsblasen mittels Drucksensoren in der Flüssigkeit. Raue Prozessrandbedingungen wie hohe Temperaturen oder aggressive Flüssigkeiten erschweren es jedoch geeignete Sensoren zu finden. Als Alternative wurde daher die Nutzbarkeit der Rückwirkung von Kavitationsereignissen auf das elektrische Eingansgssignal des Ultraschallwandlers zur Quantifizierung von Kavitation untersucht. Die experimentelle Analyse hat ergeben, dass das Einsetzen und in einigen Fällen auch die Art der Kavitation auf Basis der Rückwirkung auf das Stromsignal des Ultraschallwandlers bestimmt werden kann. Die Stärke der Kavitation war hingegen nicht aus den Stromsignalen abzuleiten. AU - Bornmann, Peter AU - Hemsel, Tobias AU - Sextro, Walter AU - Memoli, Gianluca AU - Hodnett, Mark AU - Zeqiri, Bajram ID - 9944 IS - 2 JF - tm - Technisches Messen KW - Kavitationsdetektion KW - Self-Sensing KW - So- nochemie KW - Ultraschallwandler TI - Kavitationsdetektion mittels Self-Sensing-Ultraschallwandler VL - 82 ER - TY - CONF AB - Intelligent mechatronic systems other the possibility to adapt system behavior to current dependability. This can be used to assure reliability by controlling system behavior to reach a pre-defined lifetime. By using such closed loop control, the margin of error of useful lifetime of an individual system is lowered. It is also possible to change the pre-defined lifetime during operation, by adapting system behavior to derate component usage. When planning maintenance actions, the remaining useful lifetime of each individual system has to be taken into account. Usually, stochastic properties of a fleet of systems are analyzed to create maintenance plans. Among these, the main factor is the probability of an individual system to last until maintenance. If condition-based maintenance is used, this is updated for each individual system using available information about its current state. By lowering the margin of error of useful lifetime, which directly corresponds to the time until maintenance, extended maintenance periods are made possible. Also using reliability-adaptive operation, a reversal of degradation driven maintenance planning is possible where a maintenance plan is setup not only according to system properties, but mainly to requirements imposed by maintenance personnel or infrastructure. Each system then adapts its behavior accordingly and fails according to the maintenance plan, making better use of maintenance personnel and system capabilities at the same time. In this contribution, the potential of maintenance plan driven system behavior adaptation is shown. A model including adaptation process and maintenance actions is simulated over full system lifetime to assess the advantages gained. AU - Meyer, Tobias AU - Kaul, Thorben AU - Sextro, Walter ID - 9949 KW - Adaptive systems KW - Reliability analysis KW - Availability KW - Adaptive control KW - Maintenance KW - Self-optimizing systems KW - Self-optimizing control KW - Stochastic Petri-nets T2 - Proceedings of the 9th IFAC Symposium on Fault Detection, Supervision and Safety for Technical Processes TI - Advantages of reliability-adaptive system operation for maintenance planning ER - TY - CONF AU - Ho, Nam AU - Ahmed, Abdullah Fathi AU - Kaufmann, Paul AU - Platzner, Marco ID - 10673 KW - cache storage KW - field programmable gate arrays KW - multiprocessing systems KW - parallel architectures KW - reconfigurable architectures KW - FPGA KW - dynamic reconfiguration KW - evolvable cache mapping KW - many-core architecture KW - memory-to-cache address mapping function KW - microarchitectural optimization KW - multicore architecture KW - nature-inspired optimization KW - parallelization degrees KW - processor KW - reconfigurable cache mapping KW - reconfigurable computing KW - Field programmable gate arrays KW - Software KW - Tuning T2 - Proc. NASA/ESA Conf. Adaptive Hardware and Systems (AHS) TI - Microarchitectural optimization by means of reconfigurable and evolvable cache mappings ER - TY - CONF AB - Haushaltsgeräte aus der Klasse der "Weißen Ware" tragen mit etwa einem Drittel ($34,2%$ \citeBDEW2013) zum privaten Energieverbrauch bei. Diese Veröffentlichung präsentiert eine Struktur und die dafür notwendige optimale Betriebsstrategie für Weiße Ware in einer Umgebung mit Strompreisen, die wegen der Volatilität der Regenerativen Energien stark fluktuieren. Das vorgeschlagene Konzept nutzt dafür ein dezentrales Energiemanagementsystem, das über drei Hierarchieebenen verteilt ist: die Geräteebene, die Haushaltsebene und die Ortsnetzebene. Auf der Geräteebene nutzt dieses Konzept zusätzlich Betriebsflexibilitäten der Haushaltsgeräte aus. AU - Stille, Karl Stephan Christian AU - Böcker, Joachim AU - Bettentrup, Ralf AU - Kaiser, Ingo ID - 29973 KW - Energy management KW - hybrid energy storage system KW - self-optimization KW - multi-objective optimization KW - adaptive systems KW - pareto set KW - SFB614-D1 KW - SFB614-D2 KW - LEA-Publikation KW - Eigene T2 - ETG-Fachtagung "Von Smart Grids zu Smart Markets" TI - Hierarchisches Optimierungskonzept für die Laststeuerung von Haushaltsgeräten ER - TY - CONF AB - The majority of algorithms can be controlled or adjusted by parameters. Their values can substantially affect the algorithms’ performance. Since the manual exploration of the parameter space is tedious – even for few parameters – several automatic procedures for parameter tuning have been proposed. Recent approaches also take into account some characteristic properties of the problem instances, frequently termed instance features. Our contribution is the proposal of a novel concept for feature-based algorithm parameter tuning, which applies an approximating surrogate model for learning the continuous feature-parameter mapping. To accomplish this, we learn a joint model of the algorithm performance based on both the algorithm parameters and the instance features. The required data is gathered using a recently proposed acquisition function for model refinement in surrogate-based optimization: the profile expected improvement. This function provides an avenue for maximizing the information required for the feature-parameter mapping, i.e., the mapping from instance features to the corresponding optimal algorithm parameters. The approach is validated by applying the tuner to exemplary evolutionary algorithms and problems, for which theoretically grounded or heuristically determined feature-parameter mappings are available. AU - Bossek, Jakob AU - Bischl, Bernd AU - Wagner, Tobias AU - Rudolph, Günter ID - 48838 KW - evolutionary algorithms KW - model-based optimization KW - parameter tuning SN - 978-1-4503-3472-3 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Learning Feature-Parameter Mappings for Parameter Tuning via the Profile Expected Improvement ER - TY - CONF AB - We evaluate the performance of a multi-objective evolutionary algorithm on a class of dynamic routing problems with a single vehicle. In particular we focus on relating algorithmic performance to the most prominent characteristics of problem instances. The routing problem considers two types of customers: mandatory customers must be visited whereas optional customers do not necessarily have to be visited. Moreover, mandatory customers are known prior to the start of the tour whereas optional customers request for service at later points in time with the vehicle already being on its way. The multi-objective optimization problem then results as maximizing the number of visited customers while simultaneously minimizing total travel time. As an a-posteriori evaluation tool, the evolutionary algorithm aims at approximating the related Pareto set for specifically designed benchmarking instances differing in terms of number of customers, geographical layout, fraction of mandatory customers, and request times of optional customers. Conceptional and experimental comparisons to online heuristic procedures are provided. AU - Meisel, Stephan AU - Grimme, Christian AU - Bossek, Jakob AU - Wölck, Martin AU - Rudolph, Günter AU - Trautmann, Heike ID - 48887 KW - combinatorial optimization KW - metaheuristics KW - multi-objective optimization KW - online algorithms KW - transportation SN - 978-1-4503-3472-3 T2 - Proceedings of the Genetic and Evolutionary Computation Conference TI - Evaluation of a Multi-Objective EA on Benchmark Instances for Dynamic Routing of a Vehicle ER - TY - CONF AU - King, Thomas C. AU - Liu, Qingzhi AU - Polevoy, Gleb AU - de Weerdt, Mathijs AU - Dignum, Virginia AU - van Riemsdijk, M. Birna AU - Warnier, Martijn ID - 17661 KW - crowd-sensing KW - crowdsourcing KW - data aggregation KW - game theory KW - norms KW - reciprocation KW - self interested agents KW - simulation SN - 978-1-4503-2738-1 T2 - Proceedings of the 2014 International Conference on Autonomous Agents and Multi-agent Systems TI - Request Driven Social Sensing ER - TY - CONF AB - Application of prognostics and health management (PHM) in the field of Proton Exchange Membrane (PEM) fuel cells is emerging as an important tool in increasing the reliability and availability of these systems. Though a lot of work is currently being conducted to develop PHM systems for fuel cells, various challenges have been encountered including the self-healing effect after characterization as well as accelerated degradation due to dynamic loading, all which make RUL predictions a difficult task. In this study, a prognostic approach based on adaptive particle filter algorithm is proposed. The novelty of the proposed method lies in the introduction of a self-healing factor after each characterization and the adaption of the degradation model parameters to fit to the changing degradation trend. An ensemble of five different state models based on weighted mean is then developed. The results show that the method is effective in estimating the remaining useful life of PEM fuel cells, with majority of the predictions falling within 5\% error. The method was employed in the IEEE 2014 PHM Data Challenge and led to our team emerging the winner of the RUL category of the challenge. AU - Kimotho, James Kuria AU - Meyer, Tobias AU - Sextro, Walter ID - 9879 KW - ageing KW - particle filtering (numerical methods) KW - proton exchange membrane fuel cells KW - remaining life assessment KW - PEM fuel cell prognostics KW - PHM KW - RUL predictions KW - accelerated degradation KW - adaptive particle filter algorithm KW - dynamic loading KW - model parameter adaptation KW - prognostics and health management KW - proton exchange membrane fuel cells KW - remaining useful life estimation KW - self-healing effect KW - Adaptation models KW - Data models KW - Degradation KW - Estimation KW - Fuel cells KW - Mathematical model KW - Prognostics and health management T2 - Prognostics and Health Management (PHM), 2014 IEEE Conference on TI - PEM fuel cell prognostics using particle filter with model parameter adaptation ER - TY - CONF AB - So-called reliability adaptive systems are able to adapt their system behavior based on the current reliability of the system. This allows them to react to changed operating conditions or faults within the system that change the degradation behavior. To implement such reliability adaptation, self-optimization can be used. A self-optimizing system pursues objectives, of which the priorities can be changed at runtime, in turn changing the system behavior. When including system reliability as an objective of the system, it becomes possible to change the system based on the current reliability as well. This capability can be used to control the reliability of the system throughout its operation period in order to achieve a pre-defined or user-selectable system lifetime. This way, optimal planning of maintenance intervals is possible while also using the system capabilities to their full extent. Our proposed control system makes it possible to react to changed degradation behavior by selecting objectives of the self-optimizing system and in turn changing the operating parameters in a closed loop. A two-stage controller is designed which is used to select the currently required priorities of the objectives in order to fulfill the desired usable lifetime. Investigations using a model of an automotive clutch system serve to demonstrate the feasibility of our controller. It is shown that the desired lifetime can be achieved reliably. AU - Meyer , Tobias AU - Sextro, Walter ID - 9884 KW - self-optimization reliability adaptive T2 - Proceedings of the Second European Conference of the Prognostics and Health Management Society 2014 TI - Closed-loop Control System for the Reliability of Intelligent Mechatronic Systems VL - 5 ER - TY - JOUR AB - Intelligent mechatronic systems, such as self-optimizing systems, allow an adaptation of the system behavior at runtime based on the current situation. To do so, they generally select among several pre-defined working points. A common method to determine working points for a mechatronic system is to use model-based multiobjective optimization. It allows finding compromises among conflicting objectives, called objective functions, by adapting parameters. To evaluate the system behavior for different parameter sets, a model of the system behavior is included in the objective functions and is evaluated during each function call. Intelligent mechatronic systems also have the ability to adapt their behavior based on their current reliability, thus increasing their availability, or on changed safety requirements; all of which are summed up by the common term dependability. To allow this adaptation, dependability can be considered in multiobjective optimization by including dependability-related objective functions. However, whereas performance-related objective functions are easily found, formulation of dependability-related objective functions is highly system-specific and not intuitive, making it complex and error-prone. Since each mechatronic system is different, individual failure modes have to be taken into account, which need to be found using common methods such as Failure-Modes and Effects Analysis or Fault Tree Analysis. Using component degradation models, which again are specific to the system at hand, the main loading factors can be determined. By including these in the model of the system behavior, the relation between working point and dependability can be formulated as an objective function. In our work, this approach is presented in more detail. It is exemplified using an actively actuated single plate dry clutch system. Results show that this approach is suitable for formulating dependability-related objective functions and that these can be used to extend system lifetime by adapting system behavior. AU - Meyer , Tobias AU - Sondermann-Wölke, Christoph AU - Sextro, Walter ID - 9885 JF - Conference Proceedings of the 2nd International Conference on System-Integrated Intelligence KW - Self-optimization KW - multiobjective optimization KW - objective function KW - dependability KW - intelligent system KW - behavior adaptation TI - Method to Identify Dependability Objectives in Multiobjective Optimization Problem VL - 15 ER - TY - CONF AU - Ho, Nam AU - Kaufmann, Paul AU - Platzner, Marco ID - 10677 KW - Linux KW - cache storage KW - embedded systems KW - granular computing KW - multiprocessing systems KW - reconfigurable architectures KW - Leon3 SPARe processor KW - custom logic events KW - evolvable-self-adaptable processor cache KW - fine granular profiling KW - integer unit events KW - measurement infrastructure KW - microarchitectural events KW - multicore embedded system KW - perf_event standard Linux performance measurement interface KW - processor properties KW - run-time reconfigurable memory-to-cache address mapping engine KW - run-time reconfigurable multicore infrastructure KW - split-level caching KW - Field programmable gate arrays KW - Frequency locked loops KW - Irrigation KW - Phasor measurement units KW - Registers KW - Weaving T2 - 2014 {IEEE} Intl. Conf. on Evolvable Systems (ICES) TI - Towards self-adaptive caches: A run-time reconfigurable multi-core infrastructure ER - TY - CONF AB - The new technological enhancements and the accessibility to varieties of online applications, enable users to collect personal data and perform self-evaluation through test, comparison and experimentation. The sparked interest in numbers and numbers as self-representative visualisations is prominent in social networking sites, which are the empirical setting for the present study. This paper sets out to establish a multi-theoretical framework which enables the investigation of emerging phenomena of the role of numbers in social networking sites. The proposed framework rests on three theoretical pillars: self-determination theory, heuristic decision making and behavioural economics. A discussion departs from these convictions to investigate user reactions and behaviour when faced with numerical representations in the SNS. AU - Sjöklint, Mimmi AU - Constantiou, Ioanna AU - Trier, Matthias ID - 13324 KW - User Behaviour KW - Social Networking Sites KW - Numerical Representations KW - Multi-Theoretical Framework KW - Quantified Self KW - Pointification SN - 9783834924421 T2 - ECIS 2013 Proceedings TI - Numerical Representations and User Behaviour in Social Networking Sites: Towards a Multi- Theoretical Research Framework ER - TY - CONF AB - This study examines the effect of audit on private firms’ cost of debt. We use a sample of 1,949 small private firms operating in the period 2006-2010 with optional financial statement audit. High quality data allows us to construct a more precise interest rate measure than existing studies employ. After controlling for obvious sources of demand for voluntary audits (ownership complexity, subsidiary status, bank relations), we find a robust central result that voluntary audits increase rather than decrease the cost of debt financing, contrary to several existing studies. This finding indicates that voluntary audits are generally treated as “adopting a label” and penalised by creditors, regardless of the perceived auditor quality as a result of the lemon problem in the audit market. Even Big-4 audits increase the cost of debt, likely as a result due to the lemon problem in the audit market, although the increase is smaller than for non-Big-4 audits. The results are sensitive to the estimation method used (OLS, Heckman’s two-step, PSM) and (sub-)sample selection. We show that disregarding the underlying assumptions of these estimation methods may lead to incorrect inferences. Additional analyses show that audited firms’ reported earnings are less informative about future operating performance than earnings of their unaudited counterparts. Our results also indicate that results are sensitive to cost of debt definition and this might have affected the results reported in the existing literature. AU - Kosi, Urska AU - Koren, Jerney AU - Valentincic, Aljosa ID - 37109 KW - private firms KW - voluntary audit KW - cost of debt KW - self-selection bias KW - lemon problem TI - Does Financial Statement Audit Reduce the Cost of Debt of Private Firms? ER - TY - CONF AB - In this paper we propose an approach to retrieve the absolute geometry of an acoustic sensor network, consisting of spatially distributed microphone arrays, from reverberant speech input. The calibration relies on direction of arrival measurements of the individual arrays. The proposed calibration algorithm is derived from a maximum-likelihood approach employing circular statistics. Since a sensor node consists of a microphone array with known intra-array geometry, we are able to obtain an absolute geometry estimate, including angles and distances. Simulation results demonstrate the effectiveness of the approach. AU - Jacob, Florian AU - Schmalenstroeer, Joerg AU - Haeb-Umbach, Reinhold ID - 11832 KW - Geometry calibration KW - microphone arrays KW - position self-calibration SN - 1520-6149 T2 - 38th International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2013) TI - DoA-Based Microphone Array Position Self-Calibration Using Circular Statistic ER - TY - CONF AU - Becker, Matthias AU - Luckey, Markus AU - Becker, Steffen ID - 22737 KW - model-driven performance engineering KW - self-* KW - Self-adaptation KW - software performance SN - 978-1-4503-1346-9 T2 - {Proceedings of the 8th International ACM SIGSOFT Conference on Quality of Software Architectures (QoSA)} TI - Model-driven Performance Engineering of Self-adaptive Systems: A Survey ER - TY - JOUR AB - The role of information and communication technology for economic growth has been emphasized repeatedly. Technological breakthroughs have generated new forms of services, such as self-services or remote services. Although these encounters are qualitatively different from traditional service provision, prior service management literature thus far had paid little attention to theory development and the systematization of technology-based service encounters. To fill this research gap, the present study outlines how new types of technology-based services fit into existing service typologies and provides an extension of existing frameworks to capture their unique characteristics. These insights in turn offer managerial implications and highlight open research questions. AU - Schumann, Jan H AU - Wünderlich, Nancy AU - Wangenheim, Florian ID - 5718 IS - 2 JF - Technovation KW - Services KW - Remote services KW - Self-services KW - Technology mediation TI - Technology Mediation in Service Delivery: A New Typology and an Agenda for Managers and Academics. VL - 32 ER - TY - CONF AB - To optimize the ultrasound irradiation for cavitation based ultrasound applications like sonochemistry or ultrasound cleaning, the correlation between cavitation intensity and the resulting effect on the process is of interest. Furthermore, changing conditions like temperature and pressure result in varying acoustic properties of the liquid. That might necessitate an adaption of the ultrasound irradiation. To detect such changes during operation, process monitoring is desired. Labor intensive processes, that might be carried out for several hours, also require process monitoring to increase their reliability by detection of changes or malfunctions during operation. In some applications cavitation detection and monitoring can be achieved by the application of sensors in the sound field. Though the application of sensors is possible, this necessitates modifications on the system and the sensor might disturb the sound field. In other applications harsh, process conditions prohibit the application of sensors in the sound field. Therefore alternative techniques for cavitation detection and monitoring are desired. The applicability of an external microphone and a self-sensing ultrasound transducer for cavitation detection were experimentally investigated. Both methods were found to be suitable and easily applicable. AU - Bornmann, Peter AU - Hemsel, Tobias AU - Sextro, Walter AU - Maeda, Takafumi AU - Morita, Takeshi ID - 9783 KW - cavitation KW - chemical reactors KW - microphones KW - process monitoring KW - reliability KW - ultrasonic applications KW - ultrasonic waves KW - acoustic properties KW - cavitation based ultrasound applications KW - cavitation intensity KW - change detection reliability KW - external microphone KW - malfunction detection reliability KW - nonperturbing cavitation detection KW - nonperturbing cavitation monitoring KW - process monitoring KW - self-sensing ultrasound transducer KW - sonochemical reactors KW - sonochemistry KW - ultrasound cleaning KW - ultrasound irradiation KW - Acoustics KW - Liquids KW - Monitoring KW - Sensors KW - Sonar equipment KW - Transducers KW - Ultrasonic imaging SN - 1948-5719 T2 - Ultrasonics Symposium (IUS), 2012 IEEE International TI - Non-perturbing cavitation detection / monitoring in sonochemical reactors ER - TY - JOUR AB - Self-optimizing mechatronic systems are a new class of technical systems. On the one hand, new challenges regarding dependability arise from their additional complexity and adaptivity. On the other hand, their abilities enable new concepts and methods to improve the dependability of mechatronic systems. This paper introduces a multi-level dependability concept for selfoptimizing mechatronic systems and shows how probabilistic planning can be used to improve the availability and reliability of systems in the operating phase. The general idea to improve the availability of autonomous systems by applying probabilistic planning methods to avoid energy shortages is exemplified on the example of an innovative railway vehicle. AU - Klöpper, Benjamin AU - Sondermann-Wölke, Christoph AU - Romaus, Christoph ID - 9786 IS - 1 JF - Journal of Robotics and Mechatronics KW - self-optimizing systems KW - dependability KW - probabilistic planning KW - energy management TI - Probabilistic Planning for Predictive Condition Monitoring and Adaptation Within the Self-Optimizing Energy Management of an Autonomous Railway Vehicle VL - 24 ER - TY - CONF AB - In this paper we propose an approach to retrieve the geometry of an acoustic sensor network consisting of spatially distributed microphone arrays from unconstrained speech input. The calibration relies on Direction of Arrival (DoA) measurements which do not require a clock synchronization among the sensor nodes. The calibration problem is formulated as a cost function optimization task, which minimizes the squared differences between measured and predicted observations and additionally avoids the existence of minima that correspond to mirrored versions of the actual sensor orientations. Further, outlier measurements caused by reverberation are mitigated by a Random Sample Consensus (RANSAC) approach. The experimental results show a mean positioning error of at most 25 cm even in highly reverberant environments. AU - Jacob, Florian AU - Schmalenstroeer, Joerg AU - Haeb-Umbach, Reinhold ID - 11833 KW - Unsupervised KW - geometry calibration KW - microphone arrays KW - position self-calibration T2 - International Workshop on Acoustic Signal Enhancement (IWAENC 2012) TI - Microphone Array Position Self-Calibration from Reverberant Speech Input ER - TY - CONF AB - In multiobjective optimization, set-based performance indicators are commonly used to assess the quality of a Pareto front approximation. Based on the scalarization obtained by these indicators, a performance comparison of multiobjective optimization algorithms becomes possible. The R2 and the Hypervolume (HV) indicator represent two recommended approaches which have shown a correlated behavior in recent empirical studies. Whereas the HV indicator has been comprehensively analyzed in the last years, almost no studies on the R2 indicator exist. In this paper, we thus perform a comprehensive investigation of the properties of the R2 indicator in a theoretical and empirical way. The influence of the number and distribution of the weight vectors on the optimal distribution of μ solutions is analyzed. Based on a comparative analysis, specific characteristics and differences of the R2 and HV indicator are presented. AU - Brockhoff, Dimo AU - Wagner, Tobias AU - Trautmann, Heike ID - 46397 KW - hypervolume indicator KW - multiobjective optimization KW - performance assessment KW - r2 indicator SN - 9781450311779 T2 - Proceedings of the 14th Annual Conference on Genetic and Evolutionary Computation TI - On the Properties of the R2 Indicator ER - TY - CONF AB - The steady supply of new optimization methods makes the algorithm selection problem (ASP) an increasingly pressing and challenging task, specially for real-world black-box optimization problems. The introduced approach considers the ASP as a cost-sensitive classification task which is based on Exploratory Landscape Analysis. Low-level features gathered by systematic sampling of the function on the feasible set are used to predict a well-performing algorithm out of a given portfolio. Example-specific label costs are defined by the expected runtime of each candidate algorithm. We use one-sided support vector regression to solve this learning problem. The approach is illustrated by means of the optimization problems and algorithms of the BBOB’09/10 workshop. AU - Bischl, Bernd AU - Mersmann, Olaf AU - Trautmann, Heike AU - Preuß, Mike ID - 46396 KW - machine learning KW - exploratory landscape analysis KW - fitness landscape KW - benchmarking KW - evolutionary optimization KW - bbob test set KW - algorithm selection SN - 9781450311779 T2 - Proceedings of the 14th Annual Conference on Genetic and Evolutionary Computation TI - Algorithm Selection Based on Exploratory Landscape Analysis and Cost-Sensitive Learning ER - TY - CONF AB - Exploratory Landscape Analysis subsumes a number of techniques employed to obtain knowledge about the properties of an unknown optimization problem, especially insofar as these properties are important for the performance of optimization algorithms. Where in a first attempt, one could rely on high-level features designed by experts, we approach the problem from a different angle here, namely by using relatively cheap low-level computer generated features. Interestingly, very few features are needed to separate the BBOB problem groups and also for relating a problem to high-level, expert designed features, paving the way for automatic algorithm selection. AU - Mersmann, Olaf AU - Bischl, Bernd AU - Trautmann, Heike AU - Preuss, Mike AU - Weihs, Claus AU - Rudolph, Günter ID - 46401 KW - exploratory landscape analysis KW - evolutionary optimization KW - fitness landscape KW - benchmarking KW - BBOB test set SN - 9781450305570 T2 - Proceedings of the 13th Annual Conference on Genetic and Evolutionary Computation TI - Exploratory Landscape Analysis ER - TY - CONF AB - A large proportion of plastics today is compounded, which means the process from refining a raw material to the processable material. For this process compounding extruders are used which mostly involve tightly intermeshing, co-rotating twin screw extruders. These extruders consist of two closely spaced screws which rotate in the same direction and convey the raw material to the screw tip. These screws are surrounded by several barrel modules which heat or cool the material. As the whole design of the machine is modularly arranged the process behavior of a twin screw extruder depends for the main part on the arrangement of the screw and the barrel elements. Until today this arrangement and process optimization is conducted by experienced engineers and with the help of trial-and-error methods. Furthermore, theoretical models are used with which the behavior of the extruder is estimated. As these models are mostly very complex they are only made available with the realization in different software projects. One of the tools is called SIGMA. Within this paper SIGMA is introduced as a software to optimize a twin screw extruder. SIGMA supports the engineer already in the early stages of the extruder arrangement. AU - Kretzschmar, Nils AU - Schöppner, Volker ID - 23858 KW - process optimization KW - polymer engineering KW - compounding KW - twin screw extruder KW - simulation T2 - Proceedings of the 2010 Summer Computer Simulation Conference TI - Simulating Tightly Intermeshing, Co-Rotating Twin Screw Extruders with SIGMA ER - TY - CONF AB - In double-sided markets for computing resources an optimal allocation schedule among job offers and requests subject to relevant capacity constraints can be determined. With increasing storage demands and emerging storage services the question how to schedule storage jobs becomes more and more interesting. Since such scheduling problems are often in the class NP-complete an exact computation is not feasible in practice. On the other hand an approximation to the optimal solution can easily be found by means of using heuristics. The problem with this attempt is that the suggested solution may not be exactly optimal and is thus less satisfying. Considering the two above mentioned solution approaches one can clearly find a trade-off between the optimality of the solution and the efficiency to get to a solution at all. This work proposes to apply and combine heuristics in optimization to gain from both of their benefits while reducing the problematic aspects. Following this method it is assumed to get closer to the optimal solution in a shorter time compared to a full optimization. AU - Finkbeiner, Josef AU - Bodenstein, Christian AU - Schryen, Guido AU - Neumann, Dirk ID - 5685 KW - Decision Support System KW - Algorithms KW - Optimization KW - Market Engineering T2 - 18th European Conference on Information Systems (ECIS 2010) TI - Applying heuristic methods for job scheduling in storage markets ER - TY - JOUR AB - An intentional positioning of optically active quantum dots using site-selective growth by a combination of molecular beam epitaxy (MBE) and focused ion beam (FIB) implantation in an all-ultra-high-vacuum (UHV) setup has been successfully demonstrated. A square array of periodic holes on GaAs substrate was fabricated with FIB of 30 keV ions followed by an in situ annealing step. Subsequently, the patterned holes were overgrown with an optimized amount of InAs in order to achieve site-selective growth of the QDs on the patterned holes. Under well-optimized conditions, a selectivity of single quantum dot growth in the patterned holes of 52% was achieved. Thereafter, carrier injection and subsequent radiative recombination from the positioned InAs/GaAs self-assembled QDs was investigated by embedding the QDs in the intrinsic part of a GaAs-based p–i–n junction device. Electroluminescence spectra taken at 77 K show interband transitions up to the fifth excited state from the QDs. AU - Mehta, Minisha AU - Reuter, Dirk AU - Melnikov, Alexander AU - Wieck, Andreas D. AU - Michaelis de Vasconcellos, Steffen AU - Baumgarten, Tim AU - Zrenner, Artur AU - Meier, Cedrik ID - 4551 IS - 10 JF - Physica E: Low-dimensional Systems and Nanostructures KW - Molecular beam epitaxy KW - Focused ion beam KW - Self-assembled quantum dot KW - Electroluminescence SN - 1386-9477 TI - Intentionally positioned self-assembled InAs quantum dots in an electroluminescent p–i–n junction diode VL - 42 ER - TY - CONF AB - Self-optimizing systems are able to adapt their behavior autonomously according to their current self-determined objectives. Unforeseen influences could lead to dependability-critical behavior of the system. Methods are required which secure self-optimizing systems during operation. These methods to increase the dependability of the system should already be taken into consideration in the design process. This paper presents a guideline for the dependability-oriented design of self-optimizing systems, which integrates established classical methods like failure mode and effects analysis as well as methods based on self-optimization. On the one hand self-optimization is used to increase the dependability of the system by integrating objectives like safety, availability, and reliability to the objectives of the system. On the other hand methods are required to ensure the self-optimization itself. As basis for this guideline serves the principle solution of the system. The six phases of the guideline extend the design process and lead to an enhanced principle solution. Additionally, the guideline illustrates phases to implement and validate the self-optimizing system. The proposed guideline is applied to an innovative rail-bound vehicle, called RailCab, which is equipped with self-optimizing function modules. AU - Sondermann-Wölke, Christoph AU - Hemsel, Tobias AU - Sextro, Walter AU - Gausemeier, Jürgen AU - Pook, Sebastian ID - 9760 KW - RailCab KW - dependability-critical behavior KW - dependability-oriented design KW - failure mode KW - rail-bound vehicle KW - secure self-optimizing systems KW - self-optimizing function modules KW - optimisation KW - railways KW - self-adjusting systems T2 - Industrial Informatics (INDIN), 2010 8th IEEE International Conference on TI - Guideline for the dependability-oriented design of self-optimizing systems ER - TY - CONF AB - Recent advances in information processing enable new kinds of technical systems, called self-optimizing systems. These systems are able to adapt their objectives and their behavior according to the current situation and influences autonomously. This behavior adaptation is non-deterministic and hence self-optimization is a risk to the system, e.g. if the result of the self-optimization process does not match the suddenly changed situation. In contrary, self-optimization could be used to increase the dependability by pursuing objectives like reliability and availability. In our preceding publications we introduced the so called multi-level dependability concept to cope with this new kind of systems (cf. [6]). This concept comprises the monitoring of the system behavior, the classification of the current situation, and the selection of the appropriate measure, if reliability limits are exceeded. In this paper we present for the first time experimental results. The dependability concept is implemented in the self-optimizing active guidance system of a railway vehicle. The test drives illustrate clearly that the proposed concept is able to cope with, e.g., sensor failures, and is able to increase the reliability and availability of the active guidance module. AU - Sondermann-Wölke, Christoph AU - Geisler, Jens AU - Sextro, Walter ID - 9763 KW - availability KW - dependability concept KW - multilevel dependability concept KW - railway vehicle KW - reliability KW - self optimizing active guidance system KW - self optimizing railway guidance system KW - situation classification KW - system behavior monitoring KW - optimal control KW - railways KW - reliability theory KW - self-adjusting systems SN - 0149-144X T2 - Reliability and Maintainability Symposium (RAMS), 2010 Proceedings - Annual TI - Increasing the reliability of a self-optimizing railway guidance system ER - TY - CONF AB - We present methods to answer two basic questions that arise when benchmarking optimization algorithms. The first one is: which algorithm is the ’best’ one? and the second one: which algorithm should I use for my real world problem? Both are connected and neither is easy to answer. We present methods which can be used to analyse the raw data of a benchmark experiment and derive some insight regarding the answers to these questions. We employ the presented methods to analyse the BBOB’09 benchmark results and present some initial findings. AU - Mersmann, Olaf AU - Preuss, Mike AU - Trautmann, Heike ID - 46405 KW - benchmarking KW - multidimensional scaling KW - consensus ranking KW - evolutionary optimization KW - BBOB test set SN - 3642158439 T2 - Proceedings of the 11th International Conference on Parallel Problem Solving from Nature: Part I TI - Benchmarking Evolutionary Algorithms: Towards Exploratory Landscape Analysis ER - TY - CONF AB - Self-optimizing mechatronic systems are a new class of technical systems. On the one hand, new challenges regarding dependability arise from their additional complexity and adaptivity. On the other hand, their abilities enable new concepts and methods to improve the dependability of mechatronic systems. This paper introduces a multi-level dependability concept for self-optimizing mechatronic systems and shows how planning can be used to improve the availability and reliability of systems in the operating stages. AU - Klöpper, Benjamin AU - Sondermann-Wölke, Christoph AU - Romaus, Christoph AU - Vöcking, Henner ID - 9736 KW - multilevel dependability concept KW - probabilistic planning KW - self-optimizing mechatronic systems KW - systems reliability KW - mechatronics KW - planning (artificial intelligence) KW - self-adjusting systems T2 - Computational Intelligence in Control and Automation, 2009. CICA 2009. IEEE Symposium on TI - Probabilistic planning integrated in a multi-level dependability concept for mechatronic systems ER - TY - CONF AB - New mechatronic systems, called self-optimizing systems, are able to adapt their behavior according to environmental, user and system specific influences. Self-optimizing systems are complex and due to their non-deterministic behavior comprise hidden risks, which cannot be foreseen in the design phase of the system. Therefore, this paper presents modifications of the current condition monitoring policy, to be able to cope with this new kind of systems. Beside avoiding critical situations evoked by self-optimization, the proposed concept uses self-optimization to increase the dependability of the system. In this case, the concept is applied to the active guidance module of an innovative rail-bound vehicle. AU - Sondermann-Wölke, Christoph AU - Sextro, Walter ID - 9742 KW - condition monitoring KW - mechatronic systems KW - rail bound vehicle KW - rail guidance module KW - self-optimization KW - self-optimizing function modules KW - condition monitoring KW - mechatronics KW - railway rolling stock KW - self-adjusting systems T2 - Future Computing, Service Computation, Cognitive, Adaptive, Content, Patterns, 2009. COMPUTATIONWORLD '09. Computation World: TI - Towards the Integration of Condition Monitoring in Self-Optimizing Function Modules ER - TY - CONF AB - In neurosurgery, delineation of tumor boundaries during resection of brain tumors is of substantial relevance. During operation distinction between tumor and healthy tissue rely on the abilities of the surgeon based on visual and tactile differentiation. In this paper a high sensitivity actuator-sensor system using a piezoelectric bimorph is presented. Frequency shift and transfer function of the bimorphpsilas voltages are detected and evaluated. Sensorpsilas sensitivity is evaluated using two frequency controls strategies: A phase-locked loop (PLL) and a self-oscillating circuit. Results of measurements conducted on gel-phantoms are presented and discussed. AU - Uribe, David Oliva AU - Stroop, Ralf AU - Hemsel, Tobias AU - Wallaschek, Jörg ID - 9576 KW - biomedical measurement KW - brain KW - cancer KW - neurophysiology KW - phantoms KW - phase locked loops KW - piezoelectric actuators KW - surgery KW - tactile sensors KW - transfer functions KW - tumours KW - PLL KW - biomedical tissue differentiation system KW - brain tumor resection KW - frequency control KW - frequency shift KW - gel-phantom KW - high sensitivity actuator-sensor system KW - neurosurgery KW - phase-locked loop KW - piezoelectric actuators KW - piezoelectric bimorph KW - self-oscillating circuit KW - sensor sensitivity KW - tactile differentiation KW - tactile sensor system KW - transfer function KW - tumor boundary KW - visual differentiation KW - Biomedical measurements KW - Circuits KW - Frequency control KW - Neoplasms KW - Neurosurgery KW - Phase locked loops KW - Piezoelectric actuators KW - Surges KW - Transfer functions KW - Voltage SN - 1075-6787 T2 - Frequency Control Symposium, 2008 IEEE International TI - Development of a biomedical tissue differentiation system using piezoelectric actuators ER - TY - CONF AB - In this paper, we present a framework that supports experimenting with evolutionary hardware design. We describe the framework's modules for composing evolutionary optimizers and for setting up, controlling, and analyzing experiments. Two case studies demonstrate the usefulness of the framework: evolution of hash functions and evolution based on pre-engineered circuits. AU - Kaufmann, Paul AU - Platzner, Marco ID - 6508 KW - integrated circuit design KW - hardware evolution KW - evolutionary hardware design KW - evolutionary optimizers KW - hash functions KW - preengineered circuits KW - Hardware KW - Circuits KW - Design optimization KW - Visualization KW - Genetic programming KW - Genetic mutations KW - Clustering algorithms KW - Biological cells KW - Field programmable gate arrays KW - Routing SN - 076952866X T2 - Second NASA/ESA Conference on Adaptive Hardware and Systems (AHS 2007) TI - MOVES: A Modular Framework for Hardware Evolution ER - TY - CONF AB - For human-machine interfaces in distant-talking environments multichannel signal processing is often employed to obtain an enhanced signal for subsequent processing. In this paper we propose a novel adaptation algorithm for a filter-and-sum beamformer to adjust the coefficients of FIR filters to changing acoustic room impulses, e.g. due to speaker movement. A deterministic and a stochastic gradient ascent algorithm are derived from a constrained optimization problem, which iteratively estimates the eigenvector corresponding to the largest eigenvalue of the cross power spectral density of the microphone signals. The method does not require an explicit estimation of the speaker location. The experimental results show fast adaptation and excellent robustness of the proposed algorithm. AU - Warsitz, Ernst AU - Haeb-Umbach, Reinhold ID - 11930 KW - acoustic filter-and-sum beamforming KW - acoustic room impulses KW - acoustic signal processing KW - adaptive principal component analysis KW - adaptive signal processing KW - architectural acoustics KW - constrained optimization problem KW - cross power spectral density KW - deterministic algorithm KW - deterministic algorithms KW - distant-talking environments KW - eigenvalues and eigenfunctions KW - eigenvector KW - enhanced signal KW - filter-and-sum beamformer KW - FIR filter coefficients KW - FIR filter coefficients KW - FIR filters KW - gradient methods KW - human-machine interfaces KW - iterative estimation KW - iterative methods KW - largest eigenvalue KW - microphone signals KW - multichannel signal processing KW - optimisation KW - principal component analysis KW - spectral analysis KW - stochastic gradient ascent algorithm KW - stochastic processes T2 - IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP 2005) TI - Acoustic filter-and-sum beamforming by adaptive principal component analysis VL - 4 ER - TY - CONF AU - Gausemeier, Jürgen AU - Müller, Wolfgang AU - Paelke, Volker AU - Bauch, Jürgen AU - Shen, Q. AU - Radkowski, R. ID - 39078 KW - mechatronic systems KW - self-optimization KW - virtual prototyping T2 - Proceedings of the Design 2004 TI - Virtual Prototyping Of Self-Optimizing Mechatronic Systems ER -