@phdthesis{Ostermayer2017,
  author    = {Ostermayer, Ludwig},
  title     = {Integration of Prolog and Java with the Connector Architecture CAPJa},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150713},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {Modern software is often realized as a modular combination of subsystems for, e. g., knowledge management, visualization, verification, or the interaction with users. As a result, software libraries from possibly different programming languages have to work together. Even more complex the case is if different programming paradigms have to be combined. This type of diversification of programming languages and paradigms in just one software application can only be mastered by mechanisms for a seamless integration of the involved programming languages. However, the integration of the common logic programming language Prolog and the popular object-oriented programming language Java is complicated by various interoperability problems which stem on the one hand from the paradigmatic gap between the programming languages, and on the other hand, from the diversity of the available Prolog systems. The subject of the thesis is the investigation of novel mechanisms for the integration of logic programming in Prolog and object-oriented programming in Java. We are particularly interested in an object-oriented, uniform approach which is not specific to just one Prolog system. Therefore, we have first identified several important criteria for the seamless integration of Prolog and Java from the object-oriented perspective. The main contribution of the thesis is a novel integration framework called the Connector Architecture for Prolog and Java (CAPJa). The framework is completely implemented in Java and imposes no modifications to the Java Virtual Machine or Prolog. CAPJa provides a semi-automated mechanism for the integration of Prolog predicates into Java. For compact, readable, and object-oriented queries to Prolog, CAPJa exploits lambda expressions with conditional and relational operators in Java. The communication between Java and Prolog is based on a fully automated mapping of Java objects to Prolog terms, and vice versa. In Java, an extensible system of gateways provides connectivity with various Prolog system and, moreover, makes any connected Prolog system easily interchangeable, without major adaption in Java.},
  subject      = {Logische Programmierung},
  language  = {en}
}
@phdthesis{Baier1998,
  author    = {Baier, Herbert},
  title     = {Operators of Higher Order},
  publisher = {Shaker Verlag},
  isbn      = {3-8265-4008-5},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-140799},
  school      = {Universit{\"a}t W{\"u}rzburg},
  pages     = {V, 95},
  year      = {1998},
  abstract  = {Motivated by results on interactive proof systems we investigate the computational power of quantifiers applied to well-known complexity classes. In special, we are interested in existential, universal and probabilistic bounded error quantifiers ranging over words and sets of words, i.e. oracles if we think in a Turing machine model. In addition to the standard oracle access mechanism, we also consider quantifiers ranging over oracles to which access is restricted in a certain way.},
  subject      = {Komplexit{\"a}tstheorie},
  language  = {en}
}
@phdthesis{Reitwiessner2011,
  author    = {Reitwießner, Christian},
  title     = {Multiobjective Optimization and Language Equations},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-70146},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {Praktische Optimierungsprobleme beinhalten oft mehrere gleichberechtigte, sich jedoch widersprechende Kriterien. Beispielsweise will man bei einer Reise zugleich m{\"o}glichst schnell ankommen, sie soll aber auch nicht zu teuer sein. Im ersten Teil dieser Arbeit wird die algorithmische Beherrschbarkeit solcher mehrkriterieller Optimierungsprobleme behandelt. Es werden zun{\"a}chst verschiedene L{\"o}sungsbegriffe diskutiert und auf ihre Schwierigkeit hin verglichen. Interessanterweise stellt sich heraus, dass diese Begriffe f{\"u}r ein einkriterielles Problem stets gleich schwer sind, sie sich ab zwei Kriterien allerdings stark unterscheiden k{\"o}nen (außer es gilt P = NP). In diesem Zusammenhang wird auch die Beziehung zwischen Such- und Entscheidungsproblemen im Allgemeinen untersucht. Schließlich werden neue und verbesserte Approximationsalgorithmen f{\"u}r verschieden Varianten des Problems des Handlungsreisenden gefunden. Dabei wird mit Mitteln der Diskrepanztheorie eine Technik entwickelt, die ein grundlegendes Hindernis der Mehrkriteriellen Optimierung aus dem Weg schafft: Gegebene L{\"o}sungen so zu kombinieren, dass die neue L{\"o}sung in allen Kriterien m{\"o}glichst ausgewogen ist und gleichzeitig die Struktur der L{\"o}sungen nicht zu stark zerst{\"o}rt wird. Der zweite Teil der Arbeit widmet sich verschiedenen Aspekten von Gleichungssystemen f{\"u}r (formale) Sprachen. Einerseits werden konjunktive und Boolesche Grammatiken untersucht. Diese sind Erweiterungen der kontextfreien Grammatiken um explizite Durchschnitts- und Komplementoperationen. Es wird unter anderem gezeigt, dass man bei konjunktiven Grammatiken die Vereinigungsoperation stark einschr{\"a}nken kann, ohne dabei die erzeugte Sprache zu {\"a}ndern. Außerdem werden bestimmte Schaltkreise untersucht, deren Gatter keine Wahrheitswerte sondern Mengen von Zahlen berechnen. F{\"u}r diese Schaltkreise wird das {\"A}quivalenzproblem betrachtet, also die Frage ob zwei gegebene Schaltkreise die gleiche Menge berechnen oder nicht. Es stellt sich heraus, dass, abh{\"a}ngig von den erlaubten Gattertypen, die Komplexit{\"a}t des {\"A}quivalenzproblems stark variiert und f{\"u}r verschiedene Komplexit{\"a}tsklassen vollst{\"a}ndig ist, also als (parametrisierter) Vertreter f{\"u}r diese Klassen stehen kann.},
  subject      = {Mehrkriterielle Optimierung},
  language  = {en}
}
@phdthesis{Baunach2012,
  author    = {Baunach, Marcel},
  title     = {Advances in Distributed Real-Time Sensor/Actuator Systems Operation - Operating Systems, Communication, and Application Design Concepts -},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-76489},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {This work takes a close look at several quite different research areas related to the design of networked embedded sensor/actuator systems. The variety of the topics illustrates the potential complexity of current sensor network applications; especially when enriched with actuators for proactivity and environmental interaction. Besides their conception, development, installation and long-term operation, we'll mainly focus on more "low-level" aspects: Compositional hardware and software design, task cooperation and collaboration, memory management, and real-time operation will be addressed from a local node perspective. In contrast, inter-node synchronization, communication, as well as sensor data acquisition, aggregation, and fusion will be discussed from a rather global network view. The diversity in the concepts was intentionally accepted to finally facilitate the reliable implementation of truly complex systems. In particular, these should go beyond the usual "sense and transmit of sensor data", but show how powerful today's networked sensor/actuator systems can be despite of their low computational performance and constrained hardware: If their resources are only coordinated efficiently!},
  subject      = {Eingebettetes System},
  language  = {en}
}
@phdthesis{Lehrieder2013,
  author    = {Lehrieder, Frank},
  title     = {Performance Evaluation and Optimization of Content Distribution using Overlay Networks},
  doi       = {10.25972/OPUS-6420},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-76018},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2013},
  abstract  = {The work presents a performance evaluation and optimization of so-called overlay networks for content distribution in the Internet. Chapter 1 describes the importance which have such networks in today's Internet, for example, for the transmission of video content. The focus of this work is on overlay networks based on the peer-to-peer principle. These are characterized by the fact that users who download content, also contribute to the distribution process by sharing parts of the data to other users. This enables efficient content distribution because each user not only consumes resources in the system, but also provides its own resources. Chapter 2 of the monograph contains a detailed description of the functionality of today's most popular overlay network BitTorrent. It explains the various components and their interaction. This is followed by an illustration of why such overlay networks for Internet service providers (ISPs) are problematic. The reason lies in the large amount of inter-ISP traffic that is produced by these overlay networks. Since this inter-ISP traffic leads to high costs for ISPs, they try to reduce it by improved mechanisms for overlay networks. One optimization approach is the use of topology awareness within the overlay networks. It provides users of the overlay networks with information about the underlying physical network topology. This allows them to avoid inter-ISP traffic by exchanging data preferrentially with other users that are connected to the same ISP. Another approach to save inter-ISP traffic is caching. In this case the ISP provides additional computers in its network, called caches, which store copies of popular content. The users of this ISP can then obtain such content from the cache. This prevents that the content must be retrieved from locations outside of the ISP's network, and saves costly inter-ISP traffic in this way. In the third chapter of the thesis, the results of a comprehensive measurement study of overlay networks, which can be found in today's Internet, are presented. After a short description of the measurement methodology, the results of the measurements are described. These results contain data on a variety of characteristics of current P2P overlay networks in the Internet. These include the popularity of content, i.e., how many users are interested in specific content, the evolution of the popularity and the size of the files. The distribution of users within the Internet is investigated in detail. Special attention is given to the number of users that exchange a particular file within the same ISP. On the basis of these measurement results, an estimation of the traffic savings that can achieved by topology awareness is derived. This new estimation is of scientific and practical importance, since it is not limited to individual ISPs and files, but considers the whole Internet and the total amount of data exchanged in overlay networks. Finally, the characteristics of regional content are considered, in which the popularity is limited to certain parts of the Internet. This is for example the case of videos in German, Italian or French language. Chapter 4 of the thesis is devoted to the optimization of overlay networks for content distribution through caching. It presents a deterministic flow model that describes the influence of caches. On the basis of this model, it derives an estimate of the inter-ISP traffic that is generated by an overlay network, and which part can be saved by caches. The results show that the influence of the cache depends on the structure of the overlay networks, and that caches can also lead to an increase in inter-ISP traffic under certain circumstances. The described model is thus an important tool for ISPs to decide for which overlay networks caches are useful and to dimension them. Chapter 5 summarizes the content of the work and emphasizes the importance of the findings. In addition, it explains how the findings can be applied to the optimization of future overlay networks. Special attention is given to the growing importance of video-on-demand and real-time video transmissions.},
  subject      = {Leistungsbewertung},
  language  = {en}
}
@phdthesis{Dang2012,
  author    = {Dang, Nghia Duc},
  title     = {Konzeption und Evaluation eines hybriden, skalierbaren Werkzeugs zur mechatronischen Systemdiagnose am Beispiel eines Diagnosesystems f{\"u}r freie Kfz-Werkst{\"a}tten},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-70774},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Die Entwicklung eines wissensbasierten Systems, speziell eines Diagnosesystems, ist eine Teildisziplin der k{\"u}nstlichen Intelligenz und angewandten Informatik. Im Laufe der Forschung auf diesem Gebiet wurden verschiedene L{\"o}sungsans{\"a}tze mit unterschiedlichem Erfolg bei der Anwendung in der Kraftfahrzeugdiagnose entwickelt. Diagnosesysteme in Vertragswerkst{\"a}tten, das heißt in Fahrzeughersteller gebundenen Werkst{\"a}tten, wenden haupts{\"a}chlich die fallbasierte Diagnostik an. Zum einen h{\"a}lt sich hier die Fahrzeugvielfalt in Grenzen und zum anderen besteht eine Meldepflicht bei neuen, nicht im System vorhandenen F{\"a}llen. Die freien Werkst{\"a}tten verf{\"u}gen nicht {\"u}ber eine solche Datenbank. Somit ist der fallbasierte Ansatz schwer umsetzbar. In freien Werkst{\"a}tten - Fahrzeughersteller unabh{\"a}ngigen Werkst{\"a}tten - basiert die Fehlersuche haupts{\"a}chlich auf Fehlerb{\"a}umen. Wegen der wachsenden Fahrzeugkomplexit{\"a}t, welche wesentlich durch die stark zunehmende Anzahl der durch mechatronische Systeme realisierten Funktionen bedingt ist, und der steigenden Typenvielfalt ist die gef{\"u}hrte Fehlersuche in freien Werkst{\"a}tten nicht immer zielf{\"u}hrend. Um die Unterst{\"u}tzung des Personals von freien Werkst{\"a}tten bei der zuk{\"u}nftigen Fehlersuche zu gew{\"a}hrleisten, werden neue Generationen von herstellerunabh{\"a}ngigen Diagnosetools ben{\"o}tigt, die die Probleme der Variantenvielfalt und Komplexit{\"a}t l{\"o}sen. In der vorliegenden Arbeit wird ein L{\"o}sungsansatz vorgestellt, der einen qualitativen, modellbasierten Diagnoseansatz mit einem auf heuristischem Diagnosewissen basierenden Ansatz vereint. Neben der Grundlage zur Wissenserhebung werden in dieser Arbeit die theoretische Grundlage zur Beherrschung der Variantenvielfalt sowie die Tests f{\"u}r die erstellten Diagnosemodelle behandelt. Die Diagnose ist symptombasiert und die Inferenzmechanismen zur Verarbeitung des Diagnosewissens sind eine Kombination aus Propagierung der abweichenden physikalischen Gr{\"o}ßen im Modell und der Auswertung des heuristischen Wissens. Des Weiteren werden in dieser Arbeit verschiedene Aspekte der Realisierung der entwickelten theoretischen Grundlagen dargestellt, zum Beispiel: Systemarchitektur, Wissenserhebungsprozess, Ablauf des Diagnosevorgangs in den Werkst{\"a}tten. Die Evaluierung der entwickelten L{\"o}sung bei der Wissenserhebung in Form von Modellerstellungen und Modellierungsworkshops sowie Feldtests dient nicht nur zur Best{\"a}tigung des entwickelten Ansatzes, sondern auch zur Ideenfindung f{\"u}r die Integration der entwickelten Tools in die existierende IT-Infrastruktur.},
  subject      = {Diagnosesystem},
  language  = {de}
}
@phdthesis{Staehle2011,
  author    = {Staehle, Barbara},
  title     = {Modeling and Optimization Methods for Wireless Sensor and Mesh Networks},
  doi       = {10.25972/OPUS-4967},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64884},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {Im Internet der Zukunft werden Menschen nicht nur mit Menschen, sondern auch mit „Dingen", und sogar „Dinge" mit „Dingen" kommunizieren. Zus{\"a}tzlich wird das Bed{\"u}rfnis steigen, immer und {\"u}berall Zugang zum Internet zu haben. Folglich gewinnen drahtlose Sensornetze (WSNs) und drahtlose Mesh-Netze (WMNs) an Bedeutung, da sie Daten {\"u}ber die Umwelt ins Internet liefern, beziehungsweise einfache Internet-Zugangsm{\"o}glichkeiten schaffen. In den vier Teilen dieser Arbeit werden unterschiedliche Modellierungs- und Optimierungsmethoden f{\"u}r WSNs und WMNs vorgestellt. Der Energieverbrauch ist die wichtigste Metrik, wenn es darum geht die Kommunikation in einem WSN zu optimieren. Da sich in der Literatur sehr viele unterschiedliche Energiemodelle finden, untersucht der erste Teil der Arbeit welchen Einfluss unterschiedliche Energiemodelle auf die Optimierung von WSNs haben. Aufbauend auf diesen {\"U}berlegungen besch{\"a}ftigt sich der zweite Teil der Arbeit mit drei Problemen, die {\"u}berwunden werden m{\"u}ssen um eine standardisierte energieeffiziente Kommunikations-L{\"o}sung f{\"u}r WSNs basierend auf IEEE 802.15.4 und ZigBee zu realisieren. F{\"u}r WMNs sind beide Probleme von geringem Interesse, die Leistung des Netzes jedoch umso mehr. Der dritte Teil der Arbeit f{\"u}hrt daher Algorithmen f{\"u}r die Berechnung des Max-Min fairen (MMF) Netzwerk-Durchsatzes in WMNs mit mehreren Linkraten und Internet-Gateways ein. Der letzte Teil der Arbeit untersucht die Auswirkungen des LRA-Konzeptes. Dessen grundlegende Idee ist die folgende. Falls f{\"u}r einen Link eine niedrigere Datenrate als theoretisch m{\"o}glich verwendet wird, sinkt zwar der Link-Durchsatz, jedoch ist unter Umst{\"a}nden eine gr{\"o}ßere Anzahl von gleichzeitigen {\"U}bertragungen m{\"o}glich und der Gesamt-Durchsatz des Netzes kann sich erh{\"o}hen. Mithilfe einer analytischen LRA Formulierung und einer systematischen Studie kann gezeigt werden, dass eine netzwerkweite Zuordnung robusterer Datenraten als n{\"o}tig zu einer Erh{\"o}hung des MMF Netzwerk-Durchsatzes f{\"u}hrt. Desweitern kann gezeigt werden, dass sich LRA positiv auf die Leistungsf{\"a}higkeit eines IEEE 802.11 WMNs auswirkt und f{\"u}r die Optimierung des Netzes genutzt werden kann.},
  subject      = {Drahtloses Sensorsystem},
  language  = {en}
}
@phdthesis{Schmidt2011,
  author    = {Schmidt, Marco},
  title     = {Ground Station Networks for Efficient Operation of Distributed Small Satellite Systems},
  isbn      = {978-3-923959-77-8},
  doi       = {10.25972/OPUS-4984},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-64999},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {The field of small satellite formations and constellations attracted growing attention, based on recent advances in small satellite engineering. The utilization of distributed space systems allows the realization of innovative applications and will enable improved temporal and spatial resolution in observation scenarios. On the other side, this new paradigm imposes a variety of research challenges. In this monograph new networking concepts for space missions are presented, using networks of ground stations. The developed approaches combine ground station resources in a coordinated way to achieve more robust and efficient communication links. Within this thesis, the following topics were elaborated to improve the performance in distributed space missions: Appropriate scheduling of contact windows in a distributed ground system is a necessary process to avoid low utilization of ground stations. The theoretical basis for the novel concept of redundant scheduling was elaborated in detail. Additionally to the presented algorithm was a scheduling system implemented, its performance was tested extensively with real world scheduling problems. In the scope of data management, a system was developed which autonomously synchronizes data frames in ground station networks and uses this information to detect and correct transmission errors. The system was validated with hardware in the loop experiments, demonstrating the benefits of the developed approach.},
  subject      = {Kleinsatellit},
  language  = {en}
}
@phdthesis{Zinner2012,
  author    = {Zinner, Thomas},
  title     = {Performance Modeling of QoE-Aware Multipath Video Transmission in the Future Internet},
  doi       = {10.25972/OPUS-6106},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-72324},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Internet applications are becoming more and more flexible to support diverge user demands and network conditions. This is reflected by technical concepts, which provide new adaptation mechanisms to allow fine grained adjustment of the application quality and the corresponding bandwidth requirements. For the case of video streaming, the scalable video codec H.264/SVC allows the flexible adaptation of frame rate, video resolution and image quality with respect to the available network resources. In order to guarantee a good user-perceived quality (Quality of Experience, QoE) it is necessary to adjust and optimize the video quality accurately. But not only have the applications of the current Internet changed. Within network and transport, new technologies evolved during the last years providing a more flexible and efficient usage of data transport and network resources. One of the most promising technologies is Network Virtualization (NV) which is seen as an enabler to overcome the ossification of the Internet stack. It provides means to simultaneously operate multiple logical networks which allow for example application-specific addressing, naming and routing, or their individual resource management. New transport mechanisms like multipath transmission on the network and transport layer aim at an efficient usage of available transport resources. However, the simultaneous transmission of data via heterogeneous transport paths and communication technologies inevitably introduces packet reordering. Additional mechanisms and buffers are required to restore the correct packet order and thus to prevent a disturbance of the data transport. A proper buffer dimensioning as well as the classification of the impact of varying path characteristics like bandwidth and delay require appropriate evaluation methods. Additionally, for a path selection mechanism real time evaluation mechanisms are needed. A better application-network interaction and the corresponding exchange of information enable an efficient adaptation of the application to the network conditions and vice versa. This PhD thesis analyzes a video streaming architecture utilizing multipath transmission and scalable video coding and develops the following optimization possibilities and results: Analysis and dimensioning methods for multipath transmission, quantification of the adaptation possibilities to the current network conditions with respect to the QoE for H.264/SVC, and evaluation and optimization of a future video streaming architecture, which allows a better interaction of application and network.},
  subject      = {Video{\"u}bertragung},
  language  = {en}
}
@phdthesis{Schroeter2012,
  author    = {Schr{\"o}ter, Martin},
  title     = {Newton Methods for Image Registration},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-71490},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2012},
  abstract  = {Consider the situation where two or more images are taken from the same object. After taking the first image, the object is moved or rotated so that the second recording depicts it in a different manner. Additionally, take heed of the possibility that the imaging techniques may have also been changed. One of the main problems in image processing is to determine the spatial relation between such images. The corresponding process of finding the spatial alignment is called "registration". In this work, we study the optimization problem which corresponds to the registration task. Especially, we exploit the Lie group structure of the set of transformations to construct efficient, intrinsic algorithms. We also apply the algorithms to medical registration tasks. However, the methods developed are not restricted to the field of medical image processing. We also have a closer look at more general forms of optimization problems and show connections to related tasks.},
  subject      = {Newton-Verfahren},
  language  = {en}
}
@phdthesis{Oechsner2010,
  author    = {Oechsner, Simon},
  title     = {Performance Challenges and Optimization Potential of Peer-to-Peer Overlay Technologies},
  doi       = {10.25972/OPUS-4159},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-50015},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {In today's Internet, building overlay structures to provide a service is becoming more and more common. This approach allows for the utilization of client resources, thus being more scalable than a client-server model in this respect. However, in these architectures the quality of the provided service depends on the clients and is therefore more complex to manage. Resource utilization, both at the clients themselves and in the underlying network, determine the efficiency of the overlay application. Here, a trade-off exists between the resource providers and the end users that can be tuned via overlay mechanisms. Thus, resource management and traffic management is always quality-of-service management as well. In this monograph, the three currently significant and most widely used overlay types in the Internet are considered. These overlays are implemented in popular applications which only recently have gained importance. Thus, these overlay networks still face real-world technical challenges which are of high practical relevance. We identify the specific issues for each of the considered overlays, and show how their optimization affects the trade-offs between resource efficiency and service quality. Thus, we supply new insights and system knowledge that is not provided by previous work.},
  subject      = {Overlay-Netz},
  language  = {en}
}
@phdthesis{Henjes2010,
  author    = {Henjes, Robert},
  title     = {Performance Evaluation of Publish/Subscribe Middleware Architectures},
  doi       = {10.25972/OPUS-4536},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-53388},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {While developing modern applications, it is necessary to ensure an efficient and performant communication between different applications. In current environments, a middleware software is used, which supports the publish/subscribe communication pattern. Using this communication pattern, a publisher sends information encapsulated in messages to the middleware. A subscriber registers its interests at the middleware. The monograph describes three different steps to determine the performance of such a system. In a first step, the message throughput performance of a publish/subscribe in different scenarios is measured using a Java Message Service (JMS) based implementation. In the second step the maximum achievable message throughput is described by adapted models depending on the filter complexity and the replication grade. Using the model, the performance characteristics of a specific system in a given scenario can be determined. These numbers are used for the queuing model described in the third part of the thesis, which supports the dimensioning of a system in realistic scenarios. Additionally, we introduce a method to approximate an M/G/1 system numerically in an efficient way, which can be used for real time analysis to predict the expected performance in a certain scenario. Finally, the analytical model is used to investigate different possibilities to ensure the scalability of the maximum achievable message throughput of the overall system.},
  subject      = {Middleware},
  language  = {en}
}
@phdthesis{Spoerhase2009,
  author    = {Spoerhase, Joachim},
  title     = {Competitive and Voting Location},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-52978},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {We consider competitive location problems where two competing providers place their facilities sequentially and users can decide between the competitors. We assume that both competitors act non-cooperatively and aim at maximizing their own benefits. We investigate the complexity and approximability of such problems on graphs, in particular on simple graph classes such as trees and paths. We also develop fast algorithms for single competitive location problems where each provider places a single facilty. Voting location, in contrast, aims at identifying locations that meet social criteria. The provider wants to satisfy the users (customers) of the facility to be opened. In general, there is no location that is favored by all users. Therefore, a satisfactory compromise has to be found. To this end, criteria arising from voting theory are considered. The solution of the location problem is understood as the winner of a virtual election among the users of the facilities, in which the potential locations play the role of the candidates and the users represent the voters. Competitive and voting location problems turn out to be closely related.},
  subject      = {Standortproblem},
  language  = {en}
}
@phdthesis{Zeiger2010,
  author    = {Zeiger, Florian},
  title     = {Internet Protocol based networking of mobile robots},
  isbn      = {978-3-923959-59-4},
  doi       = {10.25972/OPUS-4661},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-54776},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {This work is composed of three main parts: remote control of mobile systems via Internet, ad-hoc networks of mobile robots, and remote control of mobile robots via 3G telecommunication technologies. The first part gives a detailed state of the art and a discussion of the problems to be solved in order to teleoperate mobile robots via the Internet. The focus of the application to be realized is set on a distributed tele-laboratory with remote experiments on mobile robots which can be accessed world-wide via the Internet. Therefore, analyses of the communication link are used in order to realize a robust system. The developed and implemented architecture of this distributed tele-laboratory allows for a smooth access also with a variable or low link quality. The second part covers the application of ad-hoc networks for mobile robots. The networking of mobile robots via mobile ad-hoc networks is a very promising approach to realize integrated telematic systems without relying on preexisting communication infrastructure. Relevant civilian application scenarios are for example in the area of search and rescue operations where first responders are supported by multi-robot systems. Here, mobile robots, humans, and also existing stationary sensors can be connected very fast and efficient. Therefore, this work investigates and analyses the performance of different ad-hoc routing protocols for IEEE 802.11 based wireless networks in relevant scenarios. The analysis of the different protocols allows for an optimization of the parameter settings in order to use these ad-hoc routing protocols for mobile robot teleoperation. Also guidelines for the realization of such telematics systems are given. Also traffic shaping mechanisms of application layer are presented which allow for a more efficient use of the communication link. An additional application scenario, the integration of a small size helicopter into an IP based ad-hoc network, is presented. The teleoperation of mobile robots via 3G telecommunication technologies is addressed in the third part of this work. The high availability, high mobility, and the high bandwidth provide a very interesting opportunity to realize scenarios for the teleoperation of mobile robots or industrial remote maintenance. This work analyses important parameters of the UMTS communication link and investigates also the characteristics for different data streams. These analyses are used to give guidelines which are necessary for the realization of or industrial remote maintenance or mobile robot teleoperation scenarios. All the results and guidelines for the design of telematic systems in this work were derived from analyses and experiments with real hardware.},
  subject      = {Robotik},
  language  = {en}
}
@phdthesis{Sauer2010,
  author    = {Sauer, Markus},
  title     = {Mixed-Reality for Enhanced Robot Teleoperation},
  isbn      = {978-3-923959-67-9},
  doi       = {10.25972/OPUS-4666},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-55083},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {In den letzten Jahren ist die Forschung in der Robotik soweit fortgeschritten, dass die Mensch-Maschine Schnittstelle zunehmend die kritischste Komponente f{\"u}r eine hohe Gesamtperformanz von Systemen zur Navigation und Koordination von Robotern wird. In dieser Dissertation wird untersucht wie Mixed-Reality Technologien f{\"u}r Nutzerschnittstellen genutzt werden k{\"o}nnen, um diese Gesamtperformanz zu erh{\"o}hen. Hierzu werden Konzepte und Technologien entwickelt, die durch Evaluierung mit Nutzertest ein optimiertes und anwenderbezogenes Design von Mixed-Reality Nutzerschnittstellen erm{\"o}glichen. Er werden somit sowohl die technische Anforderungen als auch die menschlichen Faktoren f{\"u}r ein konsistentes Systemdesign ber{\"u}cksichtigt. Nach einer detaillierten Problemanalyse und der Erstellung eines Systemmodels, das den Menschen als Schl{\"u}sselkomponente mit einbezieht, wird zun{\"a}chst die Anwendung der neuartigen 3D-Time-of-Flight Kamera zur Navigation von Robotern, aber auch f{\"u}r den Einsatz in Mixed-Reality Schnittstellen analysiert und optimiert. Weiterhin wird gezeigt, wie sich der Netzwerkverkehr des Videostroms als wichtigstes Informationselement der meisten Nutzerschnittstellen f{\"u}r die Navigationsaufgabe auf der Netzwerk Applikationsebene in typischen Multi-Roboter Netzwerken mit dynamischen Topologien und Lastsituation optimieren l{\"a}sst. Hierdurch ist es m{\"o}glich in sonst in sonst typischen Ausfallszenarien den Videostrom zu erhalten und die Bildrate zu stabilisieren. Diese fortgeschrittenen Technologien werden dann auch dem entwickelten Konzept der generischen 3D Mixed Reality Schnittselle eingesetzt. Dieses Konzept erm{\"o}glicht eine integrierte 3D Darstellung der verf{\"u}gbaren Information, so dass r{\"a}umliche Beziehungen von Informationen aufrechterhalten werden und somit die Anzahl der mentalen Transformationen beim menschlichen Bediener reduziert wird. Gleichzeitig werden durch diesen Ansatz auch immersive Stereo Anzeigetechnologien unterst{\"u}tzt, welche zus{\"a}tzlich das r{\"a}umliche Verst{\"a}ndnis der entfernten Situation f{\"o}rdern. Die in der Dissertation vorgestellten und evaluierten Ans{\"a}tze nutzen auch die Tatsache, dass sich eine lokale Autonomie von Robotern heute sehr robust realisieren l{\"a}sst. Dies wird zum Beispiel zur Realisierung eines Assistenzsystems mit variabler Autonomie eingesetzt. Hierbei erh{\"a}lt der Fernbediener {\"u}ber eine Kraftr{\"u}ckkopplung kombiniert mit einer integrierten Augmented Reality Schnittstelle, einen Eindruck {\"u}ber die Situation am entfernten Arbeitsbereich, aber auch {\"u}ber die aktuelle Navigationsintention des Roboters. Die durchgef{\"u}hrten Nutzertests belegen die signifikante Steigerung der Navigationsperformanz durch den entwickelten Ansatz. Die robuste lokale Autonomie erm{\"o}glicht auch den in der Dissertation eingef{\"u}hrten Ansatz der pr{\"a}diktiven Mixed-Reality Schnittstelle. Die durch diesen Ansatz entkoppelte Regelschleife {\"u}ber den Menschen erm{\"o}glicht es die Sichtbarkeit von unvermeidbaren Systemverz{\"o}gerungen signifikant zu reduzieren. Zus{\"a}tzlich k{\"o}nnen durch diesen Ansatz beide f{\"u}r die Navigation hilfreichen Blickwinkel in einer 3D-Nutzerschnittstelle kombiniert werden - der exozentrische Blickwinkel und der egozentrische Blickwinkel als Augmented Reality Sicht.},
  subject      = {Mobiler Roboter},
  language  = {en}
}
@phdthesis{Klein2010,
  author    = {Klein, Alexander},
  title     = {Performance Issues of MAC and Routing Protocols in Wireless Sensor Networks},
  doi       = {10.25972/OPUS-4465},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-52870},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2010},
  abstract  = {The focus of this work lies on the communication issues of Medium Access Control (MAC) and routing protocols in the context of WSNs. The communication challenges in these networks mainly result from high node density, low bandwidth, low energy constraints and the hardware limitations in terms of memory, computational power and sensing capabilities of low-power transceivers. For this reason, the structure of WSNs is always kept as simple as possible to minimize the impact of communication issues. Thus, the majority of WSNs apply a simple one hop star topology since multi-hop communication has high demands on the routing protocol since it increases the bandwidth requirements of the network. Moreover, medium access becomes a challenging problem due to the fact that low-power transceivers are very limited in their sensing capabilities. The first contribution is represented by the Backoff Preamble-based MAC Protocol with Sequential Contention Resolution (BPS-MAC) which is designed to overcome the limitations of low-power transceivers. Two communication issues, namely the Clear Channel Assessment (CCA) delay and the turnaround time, are directly addressed by the protocol. The CCA delay represents the period of time which is required by the transceiver to detect a busy radio channel while the turnaround time specifies the period of time which is required to switch between receive and transmit mode. Standard Carrier Sense Multiple Access (CSMA) protocols do not achieve high performance in terms of packet loss if the traffic is highly correlated due to the fact that the transceiver is not able to sense the medium during the switching phase. Therefore, a node may start to transmit data while another node is already transmitting since it has sensed an idle medium right before it started to switch its transceiver from receive to transmit mode. The BPS-MAC protocol uses a new sequential preamble-based medium access strategy which can be adapted to the hardware capabilities of the transceivers. The protocol achieves a very low packet loss rate even in wireless networks with high node density and event-driven traffic without the need of synchronization. This makes the protocol attractive to applications such as structural health monitoring, where event suppression is not an option. Moreover, acknowledgments or complex retransmission strategies become almost unnecessary since the sequential preamble-based contention resolution mechanism minimizes the collision probability. However, packets can still be lost as a consequence of interference or other issues which affect signal propagation. The second contribution consists of a new routing protocol which is able to quickly detect topology changes without generating a large amount of overhead. The key characteristics of the Statistic-Based Routing (SBR) protocol are high end-to-end reliability (in fixed and mobile networks), load balancing capabilities, a smooth continuous routing metric, quick adaptation to changing network conditions, low processing and memory requirements, low overhead, support of unidirectional links and simplicity. The protocol can establish routes in a hybrid or a proactive mode and uses an adaptive continuous routing metric which makes it very flexible in terms of scalability while maintaining stable routes. The hybrid mode is optimized for low-power WSNs since routes are only established on demand. The difference of the hybrid mode to reactive routing strategies is that routing messages are periodically transmitted to maintain already established routes. However, the protocol stops the transmission of routing messages if no data packets are transmitted for a certain time period in order to minimize the routing overhead and the energy consumption. The proactive mode is designed for high data rate networks which have less energy constraints. In this mode, the protocol periodically transmits routing messages to establish routes in a proactive way even in the absence of data traffic. Thus, nodes in the network can immediately transmit data since the route to the destination is already established in advance. In addition, a new delay-based routing message forwarding strategy is introduced. The forwarding strategy is part of SBR but can also be applied to many routing protocols in order to modify the established topology. The strategy can be used, e.g. in mobile networks, to decrease the packet loss by deferring routing messages with respect to the neighbor change rate. Thus, nodes with a stable neighborhood forward messages faster than nodes within a fast changing neighborhood. As a result, routes are established through nodes with correlated movement which results in fewer topology changes due to higher link durations.},
  subject      = {Routing},
  language  = {en}
}
@phdthesis{Aschenbrenner2017,
  author    = {Aschenbrenner, Doris},
  title     = {Human Robot Interaction Concepts for Human Supervisory Control and Telemaintenance Applications in an Industry 4.0 Environment},
  isbn      = {978-3-945459-18-8},
  doi       = {10.25972/OPUS-15052},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-150520},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {While teleoperation of technical highly sophisticated systems has already been a wide field of research, especially for space and robotics applications, the automation industry has not yet benefited from its results. Besides the established fields of application, also production lines with industrial robots and the surrounding plant components are in need of being remotely accessible. This is especially critical for maintenance or if an unexpected problem cannot be solved by the local specialists. Special machine manufacturers, especially robotics companies, sell their technology worldwide. Some factories, for example in emerging economies, lack qualified personnel for repair and maintenance tasks. When a severe failure occurs, an expert of the manufacturer needs to fly there, which leads to long down times of the machine or even the whole production line. With the development of data networks, a huge part of those travels can be omitted, if appropriate teleoperation equipment is provided. This thesis describes the development of a telemaintenance system, which was established in an active production line for research purposes. The customer production site of Braun in Marktheidenfeld, a factory which belongs to Procter \& Gamble, consists of a six-axis cartesian industrial robot by KUKA Industries, a two-component injection molding system and an assembly unit. The plant produces plastic parts for electric toothbrushes. In the research projects "MainTelRob" and "Bayern.digital", during which this plant was utilised, the Zentrum f{\"u}r Telematik e.V. (ZfT) and its project partners develop novel technical approaches and procedures for modern telemaintenance. The term "telemaintenance" hereby refers to the integration of computer science and communication technologies into the maintenance strategy. It is particularly interesting for high-grade capital-intensive goods like industrial robots. Typical telemaintenance tasks are for example the analysis of a robot failure or difficult repair operations. The service department of KUKA Industries is responsible for the worldwide distributed customers who own more than one robot. Currently such tasks are offered via phone support and service staff which travels abroad. They want to expand their service activities on telemaintenance and struggle with the high demands of teleoperation especially regarding security infrastructure. In addition, the facility in Marktheidenfeld has to keep up with the high international standards of Procter \& Gamble and wants to minimize machine downtimes. Like 71.6 \% of all German companies, P\&G sees a huge potential for early information on their production system, but complains about the insufficient quality and the lack of currentness of data. The main research focus of this work lies on the human machine interface for all human tasks in a telemaintenance setup. This thesis provides own work in the use of a mobile device in context of maintenance, describes new tools on asynchronous remote analysis and puts all parts together in an integrated telemaintenance infrastructure. With the help of Augmented Reality, the user performance and satisfaction could be raised. A special regard is put upon the situation awareness of the remote expert realized by different camera viewpoints. In detail the work consists of: - Support of maintenance tasks with a mobile device - Development and evaluation of a context-aware inspection tool - Comparison of a new touch-based mobile robot programming device to the former teach pendant - Study on Augmented Reality support for repair tasks with a mobile device - Condition monitoring for a specific plant with industrial robot - Human computer interaction for remote analysis of a single plant cycle - A big data analysis tool for a multitude of cycles and similar plants - 3D process visualization for a specific plant cycle with additional virtual information - Network architecture in hardware, software and network infrastructure - Mobile device computer supported collaborative work for telemaintenance - Motor exchange telemaintenance example in running production environment - Augmented reality supported remote plant visualization for better situation awareness},
  subject      = {Fernwartung},
  language  = {en}
}
@phdthesis{Borrmann2018,
  author    = {Borrmann, Dorit},
  title     = {Multi-modal 3D mapping - Combining 3D point clouds with thermal and color information},
  isbn      = {978-3-945459-20-1},
  issn      = {1868-7474},
  doi       = {10.25972/OPUS-15708},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-157085},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2018},
  abstract  = {Imagine a technology that automatically creates a full 3D thermal model of an environment and detects temperature peaks in it. For better orientation in the model it is enhanced with color information. The current state of the art for analyzing temperature related issues is thermal imaging. It is relevant for energy efficiency but also for securing important infrastructure such as power supplies and temperature regulation systems. Monitoring and analysis of the data for a large building is tedious as stable conditions need to be guaranteed for several hours and detailed notes about the pose and the environment conditions for each image must be taken. For some applications repeated measurements are necessary to monitor changes over time. The analysis of the scene is only possible through expertise and experience. This thesis proposes a robotic system that creates a full 3D model of the environment with color and thermal information by combining thermal imaging with the technology of terrestrial laser scanning. The addition of a color camera facilitates the interpretation of the data and allows for other application areas. The data from all sensors collected at different positions is joined in one common reference frame using calibration and scan matching. The first part of the thesis deals with 3D point cloud processing with the emphasis on accessing point cloud data efficiently, detecting planar structures in the data and registering multiple point clouds into one common coordinate system. The second part covers the autonomous exploration and data acquisition with a mobile robot with the objective to minimize the unseen area in 3D space. Furthermore, the combination of different modalities, color images, thermal images and point cloud data through calibration is elaborated. The last part presents applications for the the collected data. Among these are methods to detect the structure of building interiors for reconstruction purposes and subsequent detection and classification of windows. A system to project the gathered thermal information back into the scene is presented as well as methods to improve the color information and to join separately acquired point clouds and photo series. A full multi-modal 3D model contains all the relevant geometric information about the recorded scene and enables an expert to fully analyze it off-site. The technology clears the path for automatically detecting points of interest thereby helping the expert to analyze the heat flow as well as localize and identify heat leaks. The concept is modular and neither limited to achieving energy efficiency nor restricted to the use in combination with a mobile platform. It also finds its application in fields such as archaeology and geology and can be extended by further sensors.},
  subject      = {Punktwolke},
  language  = {en}
}
@phdthesis{Houshiar2017,
  author    = {Houshiar, Hamidreza},
  title     = {Documentation and mapping with 3D point cloud processing},
  isbn      = {978-3-945459-14-0},
  doi       = {10.25972/OPUS-14449},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-144493},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2017},
  abstract  = {3D point clouds are a de facto standard for 3D documentation and modelling. The advances in laser scanning technology broadens the usability and access to 3D measurement systems. 3D point clouds are used in many disciplines such as robotics, 3D modelling, archeology and surveying. Scanners are able to acquire up to a million of points per second to represent the environment with a dense point cloud. This represents the captured environment with a very high degree of detail. The combination of laser scanning technology with photography adds color information to the point clouds. Thus the environment is represented more realistically. Full 3D models of environments, without any occlusion, require multiple scans. Merging point clouds is a challenging process. This thesis presents methods for point cloud registration based on the panorama images generated from the scans. Image representation of point clouds introduces 2D image processing methods to 3D point clouds. Several projection methods for the generation of panorama maps of point clouds are presented in this thesis. Additionally, methods for point cloud reduction and compression based on the panorama maps are proposed. Due to the large amounts of data generated from the 3D measurement systems these methods are necessary to improve the point cloud processing, transmission and archiving. This thesis introduces point cloud processing methods as a novel framework for the digitisation of archeological excavations. The framework replaces the conventional documentation methods for excavation sites. It employs point clouds for the generation of the digital documentation of an excavation with the help of an archeologist on-site. The 3D point cloud is used not only for data representation but also for analysis and knowledge generation. Finally, this thesis presents an autonomous indoor mobile mapping system. The mapping system focuses on the sensor placement planning method. Capturing a complete environment requires several scans. The sensor placement planning method solves for the minimum required scans to digitise large environments. Combining this method with a navigation system on a mobile robot platform enables it to acquire data fully autonomously. This thesis introduces a novel hole detection method for point clouds to detect obscured parts of a captured environment. The sensor placement planning method selects the next scan position with the most coverage of the obscured environment. This reduces the required number of scans. The navigation system on the robot platform consist of path planning, path following and obstacle avoidance. This guarantees the safe navigation of the mobile robot platform between the scan positions. The sensor placement planning method is designed as a stand alone process that could be used with a mobile robot platform for autonomous mapping of an environment or as an assistant tool for the surveyor on scanning projects.},
  subject      = {3D Punktwolke},
  language  = {en}
}
@phdthesis{Schlosser2011,
  author    = {Schlosser, Daniel},
  title     = {Quality of Experience Management in Virtual Future Networks},
  doi       = {10.25972/OPUS-5719},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69986},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {Aktuell beobachten wir eine drastische Vervielf{\"a}ltigung der Dienste und Anwendungen, die das Internet f{\"u}r den Datentransport nutzen. Dabei unterscheiden sich die Anforderungen dieser Dienste an das Netzwerk deutlich. Das Netzwerkmanagement wird durch diese Diversit{\"a}t der nutzenden Dienste aber deutlich erschwert, da es einem Datentransportdienstleister kaum m{\"o}glich ist, die unterschiedlichen Verbindungen zu unterscheiden, ohne den Inhalt der transportierten Daten zu analysieren. Netzwerkvirtualisierung ist eine vielversprechende L{\"o}sung f{\"u}r dieses Problem, da sie es erm{\"o}glicht f{\"u}r verschiedene Dienste unterschiedliche virtuelle Netze auf dem gleichen physikalischen Substrat zu betreiben. Diese Diensttrennung erm{\"o}glicht es, jedes einzelne Netz anwendungsspezifisch zu steuern. Ziel einer solchen Netzsteuerung ist es, sowohl die vom Nutzer erfahrene Dienstg{\"u}te als auch die Kosteneffizienz des Datentransports zu optimieren. Dar{\"u}ber hinaus wird es mit Netzwerkvirtualisierung m{\"o}glich das physikalische Netz so weit zu abstrahieren, dass die aktuell fest verzahnten Rollen von Netzwerkbesitzer und Netzwerkbetreiber entkoppelt werden k{\"o}nnen. Dar{\"u}ber hinaus stellt Netzwerkvirtualisierung sicher, dass unterschiedliche Datennetze, die gleichzeitig auf dem gleichen physikalischen Netz betrieben werden, sich gegenseitig weder beeinflussen noch st{\"o}ren k{\"o}nnen. Diese Arbeit  besch{\"a}ftigt sich mit ausgew{\"a}hlten Aspekten dieses Themenkomplexes und fokussiert sich darauf, ein virtuelles Netzwerk mit bestm{\"o}glicher Dienstqualit{\"a}t f{\"u}r den Nutzer zu betreiben und zu steuern. Daf{\"u}r wird ein Top-down-Ansatz gew{\"a}hlt, der von den Anwendungsf{\"a}llen, einer m{\"o}glichen Netzwerkvirtualisierungs-Architektur und aktuellen M{\"o}glichkeiten der Hardwarevirtualisierung ausgeht. Im Weiteren fokussiert sich die Arbeit dann in Richtung Bestimmung und Optimierung der vom Nutzer erfahrenen Dienstqualit{\"a}t (QoE) auf Applikationsschicht und diskutiert M{\"o}glichkeiten zur Messung und {\"U}berwachung von wesentlichen Netzparametern in virtualisierten Netzen.},
  subject      = {Netzwerkmanagement},
  language  = {en}
}