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 -