Future applications will run in a highly heterogeneous and dynamic execution environment that forces them to adapt their behavior and offered functionality depending on the user's or the system's current situation. Since application components in such heterogeneous multi-device systems will be distributed over multiple interconnected devices and cooperate to achieve a common goal, a coordinated adaptation is required to ensure a consistent system behavior. In this paper we present a decentralized adaptation middleware to adapt a distributed software system. Our approach supports the reliable execution of multiple adaptation operations that depend on each other and are performed transactionally even in unsteady environments coined by message loss or node failures. We implemented our approach in a search-and-rescue robot scenario to show its feasibility and conduct first performance evaluations.

Many systems in nature, e.g. atoms, molecules and planetary motion, can be described as Hamiltonian systems. In such systems, the transport between different regions of phase space determines some of their most important properties like the stability of the solar system and the rate of chemical reactions. While the transport in lower-dimensional systems with two degrees of freedom is well understood, much less is known for the higher-dimensional case. A central new feature in higher-dimensional systems are transport phenomena due to resonance channels. In this thesis, we clarify the complex geometry of resonance channels in phase space and identify a turnstile mechanism that dominates the transport out of such channels. To this end, we consider the coupled standard map for numerical investigations as it is a generic example for 4D symplectic maps. At first, we visualize resonance channels in phase space revealing their highly non-trivial geometry. Secondly, we study the transport away from such channels. This is governed by families of hyperbolic 1D-tori and their stable and unstable manifolds. We provide an approach to measure the volume of a turnstile in higher dimensions as well as the corresponding transport. From the very good agreement of the two measurements we conclude that these structures are a suitable generalization of the well-known 2D turnstile mechanism to higher dimensions. / Viele Systeme in der Natur, z.B. Atome, Moleküle und Planetenbewegungen, können als Hamilton'sche Systeme beschrieben werden. In solchen Systemen bestimmt der Transport zwischen verschiedenen Regionen des Phasenraums einige ihrer wichtigsten Eigenschaften wie die Stabilität des Sonnensystems und die Geschwindigkeit chemischer Reaktionen. Während der Transport in niedrigdimensionalen Systemen mit zwei Freiheitsgraden gut verstanden ist, ist für den höherdimensionalen Fall deutlich weniger bekannt. Eine zentrales neues Merkmal von höherdimensionalen Systemen sind Transportphänomene aufgrund von Resonanzkanälen. In dieser Arbeit verdeutlichen wir die komplexe Geometrie von Resonanzkanälen im Phasenraum und identifizieren einen Drehkreuzmechanismus, der den Transport aus einem solchen Kanal heraus dominiert. Zu diesem Zweck betrachten wir die gekoppelte Standardabbildung für numerische Untersuchungen, da sie ein generisches Beispiel für 4D symplektische Abbildungen ist. Zuerst visualisieren wir Resonanzkanäle im Phasenraum und zeigen ihre höchst nicht-triviale Geometrie. Zweitens untersuchen wir den Transport weg von solchen Kanälen. Dieser wird durch Familien von hyperbolischen 1D-Tori sowie deren stabile und instabile Mannigfaltigkeiten bestimmt. Wir stellen einen Ansatz zur Messung sowohl des eingeschlossenen Volumens in höheren Dimensionen als auch des entsprechenden Transports vor. Aus der sehr guten Übereinstimmung der beiden Messungen schließen wir, dass diese Strukturen eine geeignete Verallgemeinerung des bekannten 2D Drehkreuzmechanismus in höheren Dimensionen sind.

The complexity of computer networks has been rising over the last decades. Increasing interconnectivity between multiple devices, growing complexity of performed tasks and a strong collaboration between nodes are drivers for this phenomenon. An example is represented by Internet-of-Things devices, whose relevance has been rising in recent years. The increasing number of devices requiring updates and supervision makes maintenance more difficult. Human interaction, in this case, is costly and requires a lot of time. To overcome this, self-adaptive software systems (SAS) can be used. SAS are a subset of autonomous systems which can monitor themselves and their environment to adapt to changes without human interaction. In the literature, different approaches for engineering SAS were proposed, including techniques for executing adaptations on multiple devices based on generated plans for reacting to changes. Among those solutions, also decentralised approaches can be found. To the best of our knowledge, no approach for engineering a SAS exists which tolerates errors during the execution of adaptation in a decentralised setting. While some approaches for role-based execution reset the application in case of a single failure during the adaptation process, others do not make assumptions about errors or do not consider an erroneous environment. In a real-world environment, errors will likely occur during run-time, and the adaptation process could be disturbed. This work aims to perform adaptations in a decentralised way on role-based systems with a relaxed consistency constraint, i.e., errors during the adaptation phase are tolerated. This increases the availability of nodes since no rollbacks are required in case of a failure. Moreover, a subset of applications, such as drone swarms, would benefit from an approach with a relaxed consistency model since parts of the system that adapted successfully can already operate in an adapted configuration instead of waiting for other peers to apply the changes in a later iteration. Moreover, if we eliminate the need for an atomic adaptation execution, asynchronous execution of adaptation would be possible. In that case, we can supervise the adaptation process for a long time and ensure that every peer takes the planned actions as soon as the internal task execution allows it. To allow for a relaxed consistent way of adaptation execution, we develop a decentralised adaptation execution protocol, which supports the notion of eventual consistency. As soon as devices reconnect after network congestion or restore their internal state after local failures, our protocol can coordinate the recovery process among multiple devices to attempt recovery of a globally consistent state after errors occur. By superseding the need for a central instance, every peer who received information about failing peers can start the recovery process. The developed approach can restore a consistent global configuration if almost all peers fail. Moreover, the approach supports asynchronous adaptations, i.e., the peers can execute planned adaptations as soon as they are ready, which increases overall availability in case of delayed adaptation of single nodes. The developed protocol is evaluated with the help of a proof-of-concept implementation. The approach was run in five different experiments with thousands of iterations to show the applicability and reliability of this novel approach. The time for execution of the protocol and the number of exchanged messages has been measured to compare the protocol for different error cases and system sizes, as well as to show the scalability of the approach. The developed solution has been compared to a blocking approach to show the feasibility compared to an atomic approach. The applicability in a real-world scenario has been described in an empirical study using an example of a fire-extinguishing drone swarm. The results show that an optimistic approach to adaptation is suitable and specific scenarios can benefit from the improved availability since no rollbacks are required. Systems can continue their work regardless of the failures of participating nodes in large-scale systems.:Abstract VI 1. Introduction 1 1.1. Motivational Use-Case 2 1.2. Problem Definition 3 1.3. Objectives 4 1.4. Research Questions 5 1.5. Contributions 5 1.6. Outline 6 2. Foundation 7 2.1. Role Concept 7 2.2. Self-Adaptive Software Systems 13 2.3. Terminology for Role-Based Self-Adaptation 15 2.4. Consistency Preservation and Consistency Models 17 2.5. Summary 20 3. Related Work 21 3.1. Role-Based Approaches 22 3.2. Actor Model of Computation and Akka 23 3.3. Adaptation Execution in Self-Adaptive Software Systems 24 3.4. Change Consistency in Distributed Systems 33 3.5. Comparison of the Evaluated Approaches 40 4. The Decentralised Consistency Compensation Protocol 43 4.1. System and Error Model 43 4.2. Requirements to the Concept 44 4.3. The Usage of Roles in Adaptations 45 4.4. Protocol Overview 47 4.5. Protocol Description 51 4.6. Protocol Corner- and Error Cases 64 4.7. Summary 66 5. Prototypical Implementation 67 5.1. Technology Overview 67 5.2. Reused Artifacts 68 5.3. Implementation Details 70 5.4. Setup of the Prototypical Implementation 76 5.5. Summary 77 6. Evaluation 79 6.1. Evaluation Methodology 79 6.2. Evaluation Setup 80 6.3. Experiment Overview 81 6.4. Default Case: Successful Adaptation 84 6.5. Compensation on Disconnection of Peers 85 6.6. Recovery from Failed Adaptation 88 6.7. Impact of Early Activation of Adaptations 91 6.8. Comparison with a Blocking Approach 92 6.9. Empirical Study: Fire Extinguishing Drones 95 6.10. Summary 97 7. Conclusion and Future Work 99 7.1. Recap of the Research Questions 99 7.2. Discussion 101 7.3. Future Work 101 A. Protocol Buffer Definition 103 Acronyms 108 Bibliography 109

Entnommen aus: „Ludz, Ursula: Zu dieser Veröffentlichung” (S.9): „Mit der vorliegenden Veröffentlichung wird also eine Rückblende auf die „Ursprünge“ von Hannah Arendts Totalitarismusanalyse vorgeschlagen. Beide, die selbst entfernten Textstücke aus der ersten Auflage des Totalitarismusbuches und die Antwort an Eric Voegelin, sind aufschlußreiche Dokumente, um Arendts Totalitarismustheorie und deren Entwicklung genauer kennenzulernen und zu beurteilen...”

Die wachsende Anzahl an Robotikanwendungen, in denen mehrere Roboter ein gemeinsames Ziel verfolgen, erfordert eine gesonderte Betrachtung der Interaktion zwischen diesen Robotern mit Bezug auf den damit entstehenden Datenaustausch. Dieser muss hierbei effizient betrieben werden und die Sicherheit des gesamt Systems gewährleisten. Diese Masterarbeit stellt eine Simulationsumgebung vor, welche anhand von Testszenarien und Austauschstrategien Roboterkonstellationen prüft und Messergebnisse ausliefert. Zu Beginn der Arbeit werden drei Datenaustauschverfahren betrachtet und anschließend Publikationen vorgestellt, in denen Datenaustausch betrieben wird und Simulatoren für die Nutzbarkeit der Simulationsumgebung untersucht. Die anschließenden Kapitel behandeln das Konzept und die Implementierung der Testumgebung erläutert, wobei Roboter aus einer Menge von Hardware Komponenten und Zielen beschrieben werden. Der Aufbau des Experiments umfasst die verschiedenen Umgebungen, Testszenarien und Roboterkonfiguration. Der Aufbau beschreibt die Grundlage für die Auswertung der Testergebnisse.

Meiotic nuclear oscillations in the fission yeast Schizosaccharomyces pombe are crucial for proper chromosome pairing and recombination. We report a mechanism of these oscillations on the basis of collective behavior of dynein motors linking the cell cortex and dynamic microtubules that extend from the spindle pole body in opposite directions. By combining quantitative live cell imaging and laser ablation with a theoretical description, we show that dynein dynamically redistributes in the cell in response to load forces, resulting in more dynein attached to the leading than to the trailing microtubules. The redistribution of motors introduces an asymmetry of motor forces pulling in opposite directions, leading to the generation of oscillations. Our work provides the first direct in vivo observation of self-organized dynamic dynein distributions, which, owing to the intrinsic motor properties, generate regular large-scale movements in the cell.

Modeling complex gene interacting systems as Boolean networks lead to a significant simplification of computational investigation. This can be achieved by discretization of the expression level to ON or OFF states and classifying the interactions to inhibitory and activating. In this respect, Boolean functions are responsible for the evolution of the binary elements of the Boolean networks. In this thesis, we investigate the mostly used Boolean functions in modeling gene regulatory networks. Moreover, we introduce a new type of function with strong inhibitory namely the veto function. Our computational and analytic studies on the verity of the networks capable of constructing the same State Transition Graph lead to define a new concept namely the “degeneracy” of Boolean functions. We further derive analytically the sensitivity of the Boolean functions to perturbations. It turns out that the veto function forms the most robust dynamics. Furthermore, we verify the applicability of veto function to model the yeast cell cycle networks. In particular, we show that in an intracellular signal transduction network [Helikar et al, PNAS (2008)], the functions with veto are over-represented by a factor exceeding the over-representation of threshold functions and canalyzing functions in the same system. The statistics of the connections of the functional networks are studied in detail. Finally, we look at a different scale of biological phenomena using a binary model. We propose a simple correlation-based model to describe the pattern formation of Fly eye. Specifically, we model two different procedures of Fly eye formation, and provide a generic approach for Fly eye simulation.

The focus of this work is the theoretical and experimentell descreption of so-called Reactive Multilayer Systems (RMS). The RMS consist of at least two mostly metallic materials, which can exothermic response with each other. Using magnetron sputter deposition (MSD) several hundred to thousands alternating layers are produced. The periodic thickness varies between 10-150 nm and the total thickness between 10-100 µ m . The exotermic reaction is effected by an activation energy, e.g. with an electric spark. In this case a phase transition of the RMS materials, which are in a metastable equilibrium, will take place. This released energy in the shape of heat, which actvates the reaction in the neighboring areas. It forms a self-sustaining thermal wave through the RMS foil. In this case the amount of energy is present, that a solder on the RMS or the joining samples or even the material itself can be melted. Therefore the RMS can be used as a heat source for joining two components. The major advantage of this technology is the very low heat input in the bonding components, due to the milliseconds of the reaction. Thus the components are heated only superfical and there is no structural damage. Thus a very low-stress joining is possible. Furthermore is guaranteed, because of the metallic materials, a very high electrical and thermal conductivity. For the theoretical characterization of the physical and chemical processes within the RMS FEM-Simulations of the absolut temperature and the propagation velocity are preformed. In order to calculate the tmeperature ditribution in the components a new method will presented. It is thus possible to calculate the temperature penetration of the components to determine potential thermal barrier layer-thickness and the meltig time. Thus parameters for the specific joint problem such as period thickness, etc. of the RMS are derived. Modelling the heat transport after joining with RMS it is possible to derive a corralation between the thermal conductivity and shear strength. To quantify the theoretical results and to require certain parameters for the calculations experiments were preformed. The RMS will be investigated experimentally in terms of their enthalpy H , propagation velocity v , nascent temperature, melting time t schmelz , interdiffusion zone w , phase transition and its use as inovative heat source for joining components. The experimental results are compared with the theortical and complet this work.

Im Rahmen des 180jährigen Jubiläums der technischen Universität Chemnitz fand am 28. April 2016 das zweite Studierendensymposium der Fakultät Informatik statt. Das Studierendensymposium Informatik richtete sich inhaltlich an alle Themen rund um die Informatik und ihre Anwendungen: Ob Hardware oder Software, ob technische Lösungen oder Anwenderstudien, ob Programmierung oder Verwendung, ob Hardcore-Technik oder gesellschaftliche Fragestellungen – alles, was mit informatischen Lösungen zu tun hat, war willkommen. Das Studierendensymposium Informatik war dabei weder auf die Fakultät Informatik noch auf die TU Chemnitz begrenzt. Es wurden explizit Einreichungen aus thematisch angrenzenden Fächern beworben und Hochschulen der Region in die Planung und Organisation eingebunden. Der Tagungsband enthält die 21 Beitrage, die auf dem Symposium vorgestellt wurden. / In the course of the 180 year anniversary of the Technische Universität Chemnitz the Department of Computer Science held the second Students Symposium on April 18, 2016. The symposium addressed topics related to computer science and its applications: Whether hardware or software, whether technical solutions or user studies, whether programming or use, whether hardcore technology or social issues - everything concerned with computational solutions was welcomed. The Students Symposium included explicitly submissions from thematically adjacent departments and involved universities in the region in planning and organization. The proceedings contain the 21 papers (full and short), which were presented at the symposium.

Neuro-computational models allow to study the brain mechanisms involved in intelligent behavior and extract essential computational principles which can be implemented in cognitive systems. They are a promising solution to achieve a brain-like artificial intelligence that can compete with natural intelligence on realistic behaviors. A crucial property of intelligent behavior is motivation, defined as the incentive to interact with the world in order to achieve specific goals, either extrinsic (obtaining rewards such as food or money, or avoiding pain) or intrinsic (satisfying one’s curiosity, fun). In the human brain, motivated or goal-directed behavior depends on a network of different structures, including the prefrontal cortex, the basal ganglia and the limbic system. Dopamine, a neurotransmitter associated with reward processing, plays a central role in coordinating the activity of this network. It structures processing in high-level cognitive areas along a limbic-associative-motor gradient and impacts the learning capabilities of the whole system. In this habilitation thesis, I present biologically-constrained neuro-computational models which investigate the role of dopamine in visual object categorization and memory retrieval (Vitay and Hamker, 2008), reinforcement learning and action selection (Vitay and Hamker, 2010), the updating, learning and maintenance of working memory (Schroll et al., 2012) and timing processes (Vitay and Hamker, 2014). These models outline the many mechanisms by which the dopaminergic system regulates cognitive and emotional behavior: bistable processing modes in the cerebral cortex, modulation of synaptic transmission and plasticity, allocation of cognitive resources and signaling of relevant events. Finally, I present a neural simulator able to simulate a variety of neuro-computational models efficiently on parallel architectures (Vitay et al., 2015). / Neuronale Modelle nach dem Vorbild des Gehirns bieten die Möglichkeit intelligente, kognitive Prozesse nicht nur besser zu verstehen, sondern sie stellen auch eine vielversprechende Lösung dar, um eine Gehirn-ähnliche künstliche Intelligenz für Wahrnehmung und Verhaltensweisen zu erreichen, die mit natürlicher Intelligenz konkurrieren kann. Eine entscheidende Eigenschaft von intelligentem Verhalten ist Motivation, definiert als der Anreiz mit der Welt zu interagieren, um bestimmte Ziele zu erreichen, sei es extrinsisch (Belohnungen wie Nahrung oder Geld zu erhalten oder die Vermeidung von Schmerzen) oder intrinsisch (die Neugier zu befriedigen, Spaß zu haben). Im menschlichen Gehirn basiert motiviertes oder zielgerichtetes Verhalten auf einem Netzwerk von verschiedenen Strukturen, einschließlich des präfrontalen Cortex, der Basalganglien und des limbischen Systems. Dopamin, ein Neurotransmitter, welcher der Belohnungsverarbeitung zugeordnet wird, spielt eine zentrale Rolle bei der Koordination der Aktivität in diesem Netzwerk. Es strukturiert die Verarbeitung in High-Level-kognitiven Bereichen entlang eines limbischen-assoziativ-motor Gradienten und beinflusst die Lernfähigkeit des gesamten Systems. In dieser Habilitation, präsentiere ich biologisch motivierte neuronale Modelle, die die Rolle von Dopamin in der visuellen Objektkategorisierung und Gedächtnisabruf (Vitay and Hamker, 2008), Reinforcement Lernen und Aktionsauswahl (Vitay and Hamker, 2010), Aktualisierung, Lernen und Aufrechterhaltung von Arbeitsgedächtnis (Schroll et al., 2012) und Timing Prozessen (Vitay and Hamker, 2014) untersuchen. Diese Modelle beschreiben Mechanismen, durch die das dopaminerge System kognitives und emotionales Verhalten reguliert: bistabile Verarbeitungsmodi in der Hirnrinde, Plastizität und Modulation der synaptischen Übertragung, Zuweisung von kognitiven Ressourcen und Signalisierung von relevanten Ereignissen. Schließlich beschreibe ich einen neuronalen Simulator, der in in der Lage ist, eine Vielzahl von neuronalen Modellen effizient auf parallelen Architekturen zu simulieren (Vitay et al., 2015).