TY - THES A1 - Martin, Rüdiger T1 - Resilience, Provisioning, and Control for the Network of the Future T1 - Ausfallsicherheit, Dimensionierungsansätze und Kontrollmechanismen für das Netz der Zukunft N2 - The Internet sees an ongoing transformation process from a single best-effort service network into a multi-service network. In addition to traditional applications like e-mail,WWW-traffic, or file transfer, future generation networks (FGNs) will carry services with real-time constraints and stringent availability and reliability requirements like Voice over IP (VoIP), video conferencing, virtual private networks (VPNs) for finance, other real-time business applications, tele-medicine, or tele-robotics. Hence, quality of service (QoS) guarantees and resilience to failures are crucial characteristics of an FGN architecture. At the same time, network operations must be efficient. This necessitates sophisticated mechanisms for the provisioning and the control of future communication infrastructures. In this work we investigate such echanisms for resilient FGNs. There are many aspects of the provisioning and control of resilient FGNs such as traffic matrix estimation, traffic characterization, traffic forecasting, mechanisms for QoS enforcement also during failure cases, resilient routing, or calability concerns for future routing and addressing mechanisms. In this work we focus on three important aspects for which performance analysis can deliver substantial insights: load balancing for multipath Internet routing, fast resilience concepts, and advanced dimensioning techniques for resilient networks. Routing in modern communication networks is often based on multipath structures, e.g., equal-cost multipath routing (ECMP) in IP networks, to facilitate traffic engineering and resiliency. When multipath routing is applied, load balancing algorithms distribute the traffic over available paths towards the destination according to pre-configured distribution values. State-of-the-art load balancing algorithms operate either on the packet or the flow level. Packet level mechanisms achieve highly accurate traffic distributions, but are known to have negative effects on the performance of transport protocols and should not be applied. Flow level mechanisms avoid performance degradations, but at the expense of reduced accuracy. These inaccuracies may have unpredictable effects on link capacity requirements and complicate resource management. Thus, it is important to exactly understand the accuracy and dynamics of load balancing algorithms in order to be able to exercise better network control. Knowing about their weaknesses, it is also important to look for alternatives and to assess their applicability in different networking scenarios. This is the first aspect of this work. Component failures are inevitable during the operation of communication networks and lead to routing disruptions if no special precautions are taken. In case of a failure, the robust shortest-path routing of the Internet reconverges after some time to a state where all nodes are again reachable – provided physical connectivity still exists. But stringent availability and reliability criteria of new services make a fast reaction to failures obligatory for resilient FGNs. This led to the development of fast reroute (FRR) concepts for MPLS and IP routing. The operations of MPLS-FRR have already been standardized. Still, the standards leave some degrees of freedom for the resilient path layout and it is important to understand the tradeoffs between different options for the path layout to efficiently provision resilient FGNs. In contrast, the standardization for IP-FRR is an ongoing process. The applicability and possible combinations of different concepts still are open issues. IP-FRR also facilitates a comprehensive resilience framework for IP routing covering all steps of the failure recovery cycle. These points constitute another aspect of this work. Finally, communication networks are usually over-provisioned, i.e., they have much more capacity installed than actually required during normal operation. This is a precaution for various challenges such as network element failures. An alternative to this capacity overprovisioning (CO) approach is admission control (AC). AC blocks new flows in case of imminent overload due to unanticipated events to protect the QoS for already admitted flows. On the one hand, CO is generally viewed as a simple mechanism, AC as a more complex mechanism that complicates the network control plane and raises interoperability issues. On the other hand, AC appears more cost-efficient than CO. To obtain advanced provisioning methods for resilient FGNs, it is important to find suitable models for irregular events, such as failures and different sources of overload, and to incorporate them into capacity dimensioning methods. This allows for a fair comparison between CO and AC in various situations and yields a better understanding of the strengths and weaknesses of both concepts. Such an advanced capacity dimensioning method for resilient FGNs represents the third aspect of this work. N2 - Das Internet befindet sich gegenwärtig in einem Transformationsprozess von einem Netz mit einer einzigen best-effort Dienstklasse hin zu einem Mehr-Dienste-Netz. Zusätzlich zu herkömmlichen Anwendungen wie E-Mail, WWW oder Datenübertragung werden zukünftige Netze Dienste mit Echtzeitbedürfnissen und strikten Anforderungen an Verfügbarkeit und Zuverlässigkeit wie Voice over IP (VoIP), Videokonferenzdienste, Virtual Private Networks (VPNs) für Finanzanwendungen und andere Geschäftsanwendungen mit Echtzeitanforderungen, Tele-Medizin oder Telerobotik tragen. Daher sind die Gewährleistung von Dienstgüte und Ausfallsicherheit wesentliche Merkmale zukünftiger Netzarchitekturen. Gleichzeitig muss der Netzbetrieb effizient sein. Dies zieht den Bedarf an ausgefeilten Mechanismen für die Dimensionierung und Kontrolle ausfallsicherer Kommunikationsstrukturen nach sich. In dieser Arbeit werden solche Mechanismen, nämlich Lastaufteilung, Konzepte zur schnellen Reaktion im Fehlerfall und intelligente Ansätze zur Netzdimensionierung, untersucht. T3 - Würzburger Beiträge zur Leistungsbewertung Verteilter Systeme - 03/08 KW - Backbone-Netz KW - load balancing KW - resilience KW - fast reroute KW - admission control KW - overprovisioning Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-28497 ER - TY - RPRT A1 - Elsayed, Karim A1 - Rizk, Amr T1 - Response Times in Time-to-Live Caching Hierarchies under Random Network Delays T2 - Würzburg Workshop on Next-Generation Communication Networks (WueWoWas'22) N2 - Time-to-Live (TTL) caches decouple the occupancy of objects in cache through object-specific validity timers. Stateof- the art techniques provide exact methods for the calculation of object-specific hit probabilities given entire cache hierarchies with random inter-cache network delays. The system hit probability is a provider-centric metric as it relates to the origin offload, i.e., the decrease in the number of requests that are served by the content origin server. In this paper we consider a user-centric metric, i.e., the response time, which is shown to be structurally different from the system hit probability. Equipped with the state-of-theart exact modeling technique using Markov-arrival processes we derive expressions for the expected object response time and pave a way for its optimization under network delays. KW - Datennetz KW - TTL Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-280843 ER - TY - THES A1 - Herrmann, Christian T1 - Robotic Motion Compensation for Applications in Radiation Oncology T1 - Robotergestützte Bewegungskompensation für Anwendungen in der Radioonkologie N2 - Aufgrund vieler Verbesserungen der Behandlungsmethoden im Laufe der letzten 60 Jahre, erlaubt die Strahlentherapie heutzutage präzise Behandlungen von statischen Tumoren. Jedoch birgt die Bestrahlung von sich bewegenden Tumoren noch große Herausforderungen in sich, da bewegliche Tumore oft den Behandlungsstrahl verlassen. Dabei reduziert sich die Strahlendosis im Tumor während sich diese im umliegenden gesunden Gewebe erhöht. Diese Forschungsarbeit zielt darauf ab, die Grenzen der Strahlentherapie zu erweitern, um präzise Behandlungen von beweglichen Tumoren zu ermöglichen. Der Fokus der Arbeit liegt auf der Erstellung eines Echtzeitsystems zur aktiven Kompensation von Tumorbewegungen durch robotergestützte Methoden. Während Behandlungen befinden sich Patienten auf einer Patientenliege, mit der statische Lagerungsfehler vor Beginn einer Behandlung korrigiert werden. Die in dieser Arbeit verwendete Patientenliege "HexaPOD" ist ein paralleler Manipulator mit sechs Freiheitsgraden, der große Lasten innerhalb eines eingeschränkten Arbeitsbereichs präzise positionieren kann. Obwohl der HexaPOD ursprünglich nicht für dynamische Anwendungen konzipiert wurde, wird dieser für eine dauerhafte Bewegungskompensation eingesetzt, in dem Patienten so bewegt werden, dass Tumore präzise im Zentralstrahl während der Dauer einer gesamten Behandlung verbleiben. Um ein echtzeitfähiges Kompensationssystem auf Basis des HexaPODs zu realisieren, muss eine Reihe an Herausforderungen bewältigt werden. Echtzeitaspekte werden einerseits durch die Verwendung eines harten Echtzeitbetriebssystems abgedeckt, andererseits durch die Messung und Schätzung von Latenzzeiten aller physikalischen Größen im System, z.B. Messungen der Tumor- und Atemposition. Neben der konsistenten und durchgängigen Berücksichtigung von akkuraten Zeitinformation, werden alle software-induzierten Latenzen adaptiv ausgeglichen. Dies erfordert Vorhersagen der Tumorposition in die nahe Zukunft. Zahlreiche Prädiktoren zur Atem- und Tumorpositionsvorhersage werden vorgeschlagen und anhand verschiedenster Metriken evaluiert. Erweiterungen der Prädiktionsalgorithmen werden eingeführt, die sowohl Atem- als auch Tumorpositionsinformationen fusionieren, um Vorhersagen ohne explizites Korrelationsmodell zu ermöglichen. Die Vorhersagen bestimmen den zukünftigen Bewegungspfad des HexaPODs, um Tumorbewegungen zu kompensieren. Dazu werden verschiedene Regler entwickelt, die eine Trajektorienverfolgung mit dem HexaPOD ermöglichen. Auf der Basis von linearer und nicht-linearer dynamischer Modellierung des HexaPODs mit Methoden der Systemidentifikation, wird zunächst ein modellprädiktiver Regler entwickelt. Ein zweiter Regler wird auf Basis einer Annahme über das Arbeitsprinzip des internen Reglers im HexaPOD entworfen. Schließlich wird ein dritter Regler vorgeschlagen, der beide vorhergehenden Regler miteinander kombiniert. Für jeden dieser Regler werden vergleichende Ergebnisse aus Experimenten mit realer Hardware und menschlichen Versuchspersonen präsentiert und diskutiert. Darüber hinaus wird die geeignete Wahl von freien Parametern in den Reglern vorgestellt. Neben einer präzisen Verfolgung der Referenztrajektorie spielt der Patientenkomfort eine entscheidende Rolle für die Akzeptanz des Systems. Es wird gezeigt, dass die Regler glatte Trajektorien realisieren können, um zu garantieren, dass sich Patienten wohl fühlen während ihre Tumorbewegung mit Genauigkeiten im Submillimeterbereich ausgeglichen wird. Gesamtfehler werden im Kompensationssystem analysiert, in dem diese zu Trajektorienverfolgungsfehlern und Prädiktionsfehlern in Beziehung gesetzt werden. Durch Ausnutzung von Eigenschaften verschiedener Prädiktoren wird gezeigt, dass die Startzeit des Systems bis die Verfolgung der Referenztrajektorie erreicht ist, wenige Sekunden beträgt. Dies gilt insbesondere für den Fall eines initial ruhenden HexaPODs und ohne Vorwissen über Tumorbewegungen. Dies zeigt die Eignung des Systems für die sehr kurz fraktionierten Behandlungen von Lungentumoren. Das Tumorkompensationssystem wurde ausschließlich auf Basis von klinischer Standard-Hardware entwickelt, die in vielen Behandlungsräumen zu finden ist. Durch ein einfaches und flexibles Design können Behandlungsräume in kosteneffizienter Weise um Möglichkeiten der Bewegungskompensation ergänzt werden. Darüber hinaus werden aktuelle Behandlungsmethoden wie intensitätsmodulierte Strahlentherapie oder Volumetric Modulated Arc Therapy in keiner Weise eingeschränkt. Aufgrund der Unterstützung verschiedener Kompensationsmodi kann das System auf alle beweglichen Tumore angewendet werden, unabhängig davon ob die Bewegungen vorhersagbar (Lungentumore) oder nicht vorhersagbar (Prostatatumore) sind. Durch Integration von geeigneten Methoden zur Tumorpositionsbestimmung kann das System auf einfache Weise zur Kompensation von anderen Tumoren erweitert werden. N2 - Radiation therapy today, on account of improvements in treatment procedures over the last 60 years, allows precise treatment of static tumors inside the human body. However, irradiation of moving tumors is still a challenging task as moving tumors often leave the treatment beam and the radiation dose delivered to the tumor reduces simultaneously increasing that on healthy tissue. This research work aims to push the frontiers of radiation therapy in order to enable precise treatment of moving tumors with focus on research and development of a unique real-time system enabling active motion compensation through robotic means to compensate tumor motion. During treatment, patients lie on a treatment couch which is normally used for static position corrections of patient set-up errors prior to radiation treatment. The treatment couch used, called HexaPOD, is a parallel manipulator with six degrees of freedom which can precisely position heavy loads inside a small region. Despite the HexaPOD not initially built with dynamics in mind, it is used in this work for sustained motion compensation by moving patients such that tumors stay precisely located at the center of the treatment beam during the complete course of treatment. In order to realize real-time tumor motion compensation by means of the HexaPOD, several challanges need to be addressed. Real-time aspects are covered by the adoption of a hard real-time operation system in combination with measurement and estimation of latencies of all physical quantities in the compensation system such as tumor or breathing position measurements. Accurate timing information is respected consistently in the whole system and all software-induced latencies are adaptively compensated for. This requires knowledge of future tumor positions from predictors. Several predictors for breathing and tumor motion predictions are proposed and evaluated in terms of a variety of different performance metrics. Extensions to prediction algorithms are introduced fusing both breathing and tumor position information to allow for predictions without the need of an explicit correlation model. Predictions determine the future motion path of the HexaPOD in order to compensate for tumor motion. Several control schemes are developed to enable reference tracking for the HexaPOD. Based on linear and non-linear dynamic modelling of the HexaPOD with system identification methods, a first controller is derived in the form of a model predictive controller. A second controller is proposed based on an assumption of the working principle of the HexaPOD's internal controller. Finally, a third controller is derived as combination of the first and second one. For each of these controllers, comparative results with real hardware experiments and humans in the loop as well as choices of free parameters are presented and discussed. Apart from precise tracking, emphasis is placed on patient comfort which is of crucial importance for acceptance of the system. It is demonstrated that smooth trajectories can be realized by the controllers to guarantee that patients feel comfortable while their tumor motion is compensated at sub-millimeter accuracies. Overall errors of the system are analyzed by relating them to tracking and prediction errors. By exploiting the properties of different predictors, it is shown that the startup time until tracking is reached can be reduced to only a few seconds, even in the case of an initially at-rest HexaPOD and with no initial knowledge of tumor motion. This makes the system especially suitable for the relatively short-fractionated treatment sessions for lung tumors. The tumor motion compensation system has been developed solely based on standard clinical hardware, found in most treatment rooms. With a simple and flexible design, existing treatment can be updated in a cost-efficient way to introduce motion compensation capabilities. Simultaneously, the system does not impose any constraints on state-of-the-art treatment types such as intensity modulated radiotherapy or volumetric modulated arc therapy. Supporting different compensation modes, the system can be applied to any moving tumor whether its motion is predictable (lung tumors) or unpredictable (prostate tumors). By integration of adequate tumor position determination methods, the system can be easily extended to other tumors as well. T3 - Forschungsberichte in der Robotik = Research Notes in Robotics - 7 KW - Robotik KW - Bewegungskompensation KW - Regelung KW - Strahlentherapie KW - Vorhersage KW - Tumorbewegung KW - Echzeit KW - Prediction KW - Tumor motion KW - Real-time Y1 - 2013 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-79045 SN - 978-3-923959-88-4 ER - TY - THES A1 - Busch, Stephan T1 - Robust, Flexible and Efficient Design for Miniature Satellite Systems T1 - Moderne Kleinstsatelliten - Zwischen Robustheit, Flexibilität und Effizienz N2 - Small satellites contribute significantly in the rapidly evolving innovation in space engineering, in particular in distributed space systems for global Earth observation and communication services. Significant mass reduction by miniaturization, increased utilization of commercial high-tech components, and in particular standardization are the key drivers for modern miniature space technology. This thesis addresses key fields in research and development on miniature satellite technology regarding efficiency, flexibility, and robustness. Here, these challenges are addressed by the University of Wuerzburg’s advanced pico-satellite bus, realizing a generic modular satellite architecture and standardized interfaces for all subsystems. The modular platform ensures reusability, scalability, and increased testability due to its flexible subsystem interface which allows efficient and compact integration of the entire satellite in a plug-and-play manner. Beside systematic design for testability, a high degree of operational robustness is achieved by the consequent implementation of redundancy of crucial subsystems. This is combined with efficient fault detection, isolation and recovery mechanisms. Thus, the UWE-3 platform, and in particular the on-board data handling system and the electrical power system, offers one of the most efficient pico-satellite architectures launched in recent years and provides a solid basis for future extensions. The in-orbit performance results of the pico-satellite UWE-3 are presented and summarize successful operations since its launch in 2013. Several software extensions and adaptations have been uploaded to UWE-3 increasing its capabilities. Thus, a very flexible platform for in-orbit software experiments and for evaluations of innovative concepts was provided and tested. N2 - Miniaturisierte Satellitensysteme übernehmen zunehmend eine entscheidende Rolle in der fortschreitenden Globalisierung und Demokratisierung der Raumfahrt. Großes Innovationspotential und neue Kommerzialisierungschancen verspricht der effektive Einsatz von Kleinstsatelliten in zukünftigen fraktionierten Missionen für Erdbeobachtungs- und Kommunikationsanwendungen. Basierend auf vielen kleinen kooperierenden Systemen können diese Systeme zukünftig große multifunktionale Satelliten ergänzen oder ersetzen. Die Herausforderung bei der Entwicklung miniaturisierter Satellitensysteme ist die Gratwanderung zwischen der im Rahmen der Miniaturisierung notwendigen Effizienz, der für die Erfüllung der Mission geforderten Zuverlässigkeit und der wünschenswerten Wiederverwendbarkeit und Erweiterbarkeit zur Realisierung agiler Kleinstsatellitenserien. Diese Arbeit adressiert verschiedene Aspekte für den optimalen Entwurf robuster, flexibler und effizienter Kleinstsatelliten am Beispiel des UWE Pico-Satelliten Bus der Universität Würzburg. Mit dem Ziel der Entwicklung einer soliden Basisplattform für zukünftige Kleinstsatelliten-Formationen wurden entsprechende Designansätze im Rahmen des UWE-3 Projektes in einem integralen Designansatz konsistent umgesetzt. Neben der Entwicklung von effizienten Redundanzkonzepten mit minimalem Overhead für den optimalen Betrieb auf Ressourcen-limitierten Kleinstsatelliten wurde ein modularer Satellitenbus entworfen, der als eine robuste und erweiterbare Basis für zukünftige Missionen dienen soll. Damit realisiert UWE-3 eine der effizientesten Kleinstsatelliten-Architekturen die in den letzten Jahren in den Orbit gebracht wurde. Dargestellte Missionsergebnisse fassen den erfolgreichen Betrieb des Satelliten seit seinem Launch in Jahr 2013 zusammen. T3 - Forschungsberichte in der Robotik = Research Notes in Robotics - 11 KW - Kleinsatellit KW - Fehlertoleranz KW - Miniaturisierung KW - Modularität KW - Picosatellite KW - Satellit Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-136523 SN - 978-3-945459-10-2 ER - TY - JOUR A1 - Gupta, Shishir K. A1 - Minocha, Rashmi A1 - Thapa, Prithivi Jung A1 - Srivastava, Mugdha A1 - Dandekar, Thomas T1 - Role of the pangolin in origin of SARS-CoV-2: an evolutionary perspective JF - International Journal of Molecular Sciences N2 - After the recent emergence of SARS-CoV-2 infection, unanswered questions remain related to its evolutionary history, path of transmission or divergence and role of recombination. There is emerging evidence on amino acid substitutions occurring in key residues of the receptor-binding domain of the spike glycoprotein in coronavirus isolates from bat and pangolins. In this article, we summarize our current knowledge on the origin of SARS-CoV-2. We also analyze the host ACE2-interacting residues of the receptor-binding domain of spike glycoprotein in SARS-CoV-2 isolates from bats, and compare it to pangolin SARS-CoV-2 isolates collected from Guangdong province (GD Pangolin-CoV) and Guangxi autonomous regions (GX Pangolin-CoV) of South China. Based on our comparative analysis, we support the view that the Guangdong Pangolins are the intermediate hosts that adapted the SARS-CoV-2 and represented a significant evolutionary link in the path of transmission of SARS-CoV-2 virus. We also discuss the role of intermediate hosts in the origin of Omicron. KW - COVID-19 KW - SARS-CoV-2 KW - origin KW - evolution KW - intermediate host KW - pangolin KW - mutation KW - recombination KW - adaptation KW - transmission KW - comparative sequence analysis Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-285995 SN - 1422-0067 VL - 23 IS - 16 ER - TY - THES A1 - Betz, Christian T1 - Scalable authoring of diagnostic case based training systems T1 - Skalierbare Erstellung diagnostischer fallbasierter Trainingssysteme N2 - Diagnostic Case Based Training Systems (D-CBT) provide learners with a means to learn and exercise knowledge in a realistic context. In medical education, D-CBT Systems present virtual patients to the learners who are asked to examine, diagnose and state therapies for these patients. Due a number of conflicting and changing requirements, e.g. time for learning, authoring effort, several systems were developed so far. These systems range from simple, easy-to-use presentation systems to highly complex knowledge based systems supporting explorative learning. This thesis presents an approach and tools to create D-CBT systems from existing sources (documents, e.g. dismissal records) using existing tools (word processors): Authors annotate and extend the documents to model the knowledge. A scalable knowledge representation is able to capture the content on multiple levels, from simple to highly structured knowledge. Thus, authoring of D-CBT systems requires less prerequisites and pre-knowledge and is faster than approaches using specialized authoring environments. Also, authors can iteratively add and structure more knowledge to adapt training cases to their learners needs. The theses also discusses the application of the same approach to other domains, especially to knowledge acquisition for the Semantic Web. N2 - Fallbasierte diagnostische Trainingssysteme (FDT) ermöglichen es Lernern, Wissen durch Anwendung in einem realistischen Kontext zu erwerben und zu festigen. In der medizinischen Ausbildung präsentieren FDT Systeme virtuelle Patienten, an denen der Lerner die Auswahl und Interpretation der richtigen Untersuchungen, die Diagnostik und die Bestimmung geeigneter Therapien erlernen und üben kann. Eine Vielzahl von Anforderungen durch die Lerner und die Autoren solcher Systeme hat zur Entwicklung unterschiedlicher Trainingsumgebungen geführt. Darunter gibt es einfache, präsentationsorientierte Systeme ebenso wie komplexe wissensbasierte Systeme, die exploratives Lernern erlauben. Diese Dissertation untersucht einen Ansatz und Werkzeuge, um FDT Systeme aus vorhandenen Daten (d.h. Dokumenten, beispielsweise Entlassschreiben) und mit Hilfe bekannter Werkzeuge (d.h. Textverarbeitung) zu entwickeln: Die Autoren annotieren dazu die Dokumente, um die Fälle zu modellieren. Eine skalierbare Wissensrepräsentation kann das so extrahierte Wissen auf verschiedenen Ebenen erfassen, angefangen mit unstrukturierten Elementen bis zu Wissensmodellen mit kausalen Beziehungen. Autoren können mit Hilfe des vorgestellten Ansatzes fallbasierte diagnostische Trainingssysteme mit geringerem Vorwissen und schneller erstellen als mit Hilfe spezialisierter Autorensysteme. Dabei können die Autoren insbesondere die Fälle sukzessive mit weiterem Wissen anreichern und so auf die Anforderungen ihrer Lerner anpassen. In der Dissertation wird darüber hinaus die Anwendung des Ansatzes und der entstandenen Werkzeuge auf andere Domänen untersucht. Besonders interessant ist dabei die Anwendung in der Wissensakquisition für das Semantic Web. KW - Computerunterstütztes Lernen KW - Medizin KW - Wissensrepräsentation KW - Trainingssystem KW - agile Prozesse KW - Semantic Web KW - d3web.Train KW - knowledge representation KW - training systems KW - agile processes KW - semantic web KW - d3web.Train Y1 - 2005 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-17885 ER - TY - JOUR A1 - Zimmerer, Chris A1 - Fischbach, Martin A1 - Latoschik, Marc Erich T1 - Semantic Fusion for Natural Multimodal Interfaces using Concurrent Augmented Transition Networks JF - Multimodal Technologies and Interaction N2 - Semantic fusion is a central requirement of many multimodal interfaces. Procedural methods like finite-state transducers and augmented transition networks have proven to be beneficial to implement semantic fusion. They are compliant with rapid development cycles that are common for the development of user interfaces, in contrast to machine-learning approaches that require time-costly training and optimization. We identify seven fundamental requirements for the implementation of semantic fusion: Action derivation, continuous feedback, context-sensitivity, temporal relation support, access to the interaction context, as well as the support of chronologically unsorted and probabilistic input. A subsequent analysis reveals, however, that there is currently no solution for fulfilling the latter two requirements. As the main contribution of this article, we thus present the Concurrent Cursor concept to compensate these shortcomings. In addition, we showcase a reference implementation, the Concurrent Augmented Transition Network (cATN), that validates the concept’s feasibility in a series of proof of concept demonstrations as well as through a comparative benchmark. The cATN fulfills all identified requirements and fills the lack amongst previous solutions. It supports the rapid prototyping of multimodal interfaces by means of five concrete traits: Its declarative nature, the recursiveness of the underlying transition network, the network abstraction constructs of its description language, the utilized semantic queries, and an abstraction layer for lexical information. Our reference implementation was and is used in various student projects, theses, as well as master-level courses. It is openly available and showcases that non-experts can effectively implement multimodal interfaces, even for non-trivial applications in mixed and virtual reality. KW - multimodal fusion KW - multimodal interface KW - semantic fusion KW - procedural fusion methods KW - natural interfaces KW - human-computer interaction Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197573 SN - 2414-4088 VL - 2 IS - 4 ER - TY - JOUR A1 - Ankenbrand, Markus J. A1 - Shainberg, Liliia A1 - Hock, Michael A1 - Lohr, David A1 - Schreiber, Laura M. T1 - Sensitivity analysis for interpretation of machine learning based segmentation models in cardiac MRI JF - BMC Medical Imaging N2 - Background Image segmentation is a common task in medical imaging e.g., for volumetry analysis in cardiac MRI. Artificial neural networks are used to automate this task with performance similar to manual operators. However, this performance is only achieved in the narrow tasks networks are trained on. Performance drops dramatically when data characteristics differ from the training set properties. Moreover, neural networks are commonly considered black boxes, because it is hard to understand how they make decisions and why they fail. Therefore, it is also hard to predict whether they will generalize and work well with new data. Here we present a generic method for segmentation model interpretation. Sensitivity analysis is an approach where model input is modified in a controlled manner and the effect of these modifications on the model output is evaluated. This method yields insights into the sensitivity of the model to these alterations and therefore to the importance of certain features on segmentation performance. Results We present an open-source Python library (misas), that facilitates the use of sensitivity analysis with arbitrary data and models. We show that this method is a suitable approach to answer practical questions regarding use and functionality of segmentation models. We demonstrate this in two case studies on cardiac magnetic resonance imaging. The first case study explores the suitability of a published network for use on a public dataset the network has not been trained on. The second case study demonstrates how sensitivity analysis can be used to evaluate the robustness of a newly trained model. Conclusions Sensitivity analysis is a useful tool for deep learning developers as well as users such as clinicians. It extends their toolbox, enabling and improving interpretability of segmentation models. Enhancing our understanding of neural networks through sensitivity analysis also assists in decision making. Although demonstrated only on cardiac magnetic resonance images this approach and software are much more broadly applicable. KW - deep learning KW - neural networks KW - cardiac magnetic resonance KW - sensitivity analysis KW - transformations KW - augmentation KW - segmentation Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-259169 VL - 21 IS - 1 ER - TY - JOUR A1 - Seufert, Anika A1 - Poignée, Fabian A1 - Seufert, Michael A1 - Hoßfeld, Tobias T1 - Share and multiply: modeling communication and generated traffic in private WhatsApp groups JF - IEEE Access N2 - Group-based communication is a highly popular communication paradigm, which is especially prominent in mobile instant messaging (MIM) applications, such as WhatsApp. Chat groups in MIM applications facilitate the sharing of various types of messages (e.g., text, voice, image, video) among a large number of participants. As each message has to be transmitted to every other member of the group, which multiplies the traffic, this has a massive impact on the underlying communication networks. However, most chat groups are private and network operators cannot obtain deep insights into MIM communication via network measurements due to end-to-end encryption. Thus, the generation of traffic is not well understood, given that it depends on sizes of communication groups, speed of communication, and exchanged message types. In this work, we provide a huge data set of 5,956 private WhatsApp chat histories, which contains over 76 million messages from more than 117,000 users. We describe and model the properties of chat groups and users, and the communication within these chat groups, which gives unprecedented insights into private MIM communication. In addition, we conduct exemplary measurements for the most popular message types, which empower the provided models to estimate the traffic over time in a chat group. KW - communication models KW - group-based communication KW - mobile instant messaging KW - mobile messaging application KW - private chat groups KW - WhatsApp Y1 - 2023 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-349430 VL - 11 ER - TY - JOUR A1 - Baier, Pablo A. A1 - Baier-Saip, Jürgen A. A1 - Schilling, Klaus A1 - Oliveira, Jauvane C. T1 - Simulator for Minimally Invasive Vascular Interventions: Hardware and Software JF - Presence N2 - In the present work, a simulation system is proposed that can be used as an educational tool by physicians in training basic skills of minimally invasive vascular interventions. In order to accomplish this objective, initially the physical model of the wire proposed by Konings has been improved. As a result, a simpler and more stable method was obtained to calculate the equilibrium configuration of the wire. In addition, a geometrical method is developed to perform relaxations. It is particularly useful when the wire is hindered in the physical method because of the boundary conditions. Then a recipe is given to merge the physical and the geometrical methods, resulting in efficient relaxations. Moreover, tests have shown that the shape of the virtual wire agrees with the experiment. The proposed algorithm allows real-time executions, and furthermore, the hardware to assemble the simulator has a low cost. KW - simulation system KW - educational tool KW - invasive vascular interventions Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-140580 SN - 1531-3263 VL - 25 IS - 2 ER - TY - THES A1 - Baier, Pablo A. T1 - Simulator for Minimally Invasive Vascular Interventions: Hardware and Software T1 - VR-Simulation für das Training von Herzkathetereingriffen: Hard- und Softwarelösung N2 - A complete simulation system is proposed that can be used as an educational tool by physicians in training basic skills of Minimally Invasive Vascular Interventions. In the first part, a surface model is developed to assemble arteries having a planar segmentation. It is based on Sweep Surfaces and can be extended to T- and Y-like bifurcations. A continuous force vector field is described, representing the interaction between the catheter and the surface. The computation time of the force field is almost unaffected when the resolution of the artery is increased. The mechanical properties of arteries play an essential role in the study of the circulatory system dynamics, which has been becoming increasingly important in the treatment of cardiovascular diseases. In Virtual Reality Simulators, it is crucial to have a tissue model that responds in real time. In this work, the arteries are discretized by a two dimensional mesh and the nodes are connected by three kinds of linear springs. Three tissue layers (Intima, Media, Adventitia) are considered and, starting from the stretch-energy density, some of the elasticity tensor components are calculated. The physical model linearizes and homogenizes the material response, but it still contemplates the geometric nonlinearity. In general, if the arterial stretch varies by 1% or less, then the agreement between the linear and nonlinear models is trustworthy. In the last part, the physical model of the wire proposed by Konings is improved. As a result, a simpler and more stable method is obtained to calculate the equilibrium configuration of the wire. In addition, a geometrical method is developed to perform relaxations. It is particularly useful when the wire is hindered in the physical method because of the boundary conditions. The physical and the geometrical methods are merged, resulting in efficient relaxations. Tests show that the shape of the virtual wire agrees with the experiment. The proposed algorithm allows real-time executions and the hardware to assemble the simulator has a low cost. N2 - Es wird ein vollständiges Simulationssystem entwickelt, das von Ärzten als Lehrmittel zur Ausbildung grundlegender Fertigkeiten bei Herzkathetereingriffen eingesetzt werden kann. Im ersten Teil wird ein Oberflächenmodell zur Erstellung von Arterien mit planarer Segmentierung entwickelt. Im zweiten Teil werden die Arterien durch ein zweidimensionales Netz diskretisiert, die Knoten werden durch drei Arten linearer Federn verbunden und ausgehend von einer Dehnungsenergie-Dichte-Funktion werden einige Komponenten des Elastizitätstensors berechnet. Im letzten Teil wird das von anderen Autoren vorgeschlagene physikalische Modell des Drahtes verbessert und eine neue geometrische Methode entwickelt. Der vorgeschlagene Algorithmus ermöglicht Echtzeit-Ausführungen. Die Hardware des Simulators hat geringe Herstellungskosten. T3 - Forschungsberichte in der Robotik = Research Notes in Robotics - 15 KW - Computersimulation KW - Simulator KW - Arterie KW - Elastizitätstensor KW - Herzkatheter KW - Minimally invasive vascular intervention KW - Wire relaxation KW - Artery KW - Elasticity tensor KW - Stiffness KW - educational tool KW - Elastizitätstensor KW - Herzkathetereingriff KW - Software KW - Hardware Y1 - 2018 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-161190 SN - 978-3-945459-22-5 ER - TY - THES A1 - Sun, Kaipeng T1 - Six Degrees of Freedom Object Pose Estimation with Fusion Data from a Time-of-flight Camera and a Color Camera T1 - 6DOF Posenschätzung durch Datenfusion einer Time-of-Flight-Kamera und einer Farbkamera N2 - Object six Degrees of Freedom (6DOF) pose estimation is a fundamental problem in many practical robotic applications, where the target or an obstacle with a simple or complex shape can move fast in cluttered environments. In this thesis, a 6DOF pose estimation algorithm is developed based on the fused data from a time-of-flight camera and a color camera. The algorithm is divided into two stages, an annealed particle filter based coarse pose estimation stage and a gradient decent based accurate pose optimization stage. In the first stage, each particle is evaluated with sparse representation. In this stage, the large inter-frame motion of the target can be well handled. In the second stage, the range data based conventional Iterative Closest Point is extended by incorporating the target appearance information and used for calculating the accurate pose by refining the coarse estimate from the first stage. For dealing with significant illumination variations during the tracking, spherical harmonic illumination modeling is investigated and integrated into both stages. The robustness and accuracy of the proposed algorithm are demonstrated through experiments on various objects in both indoor and outdoor environments. Moreover, real-time performance can be achieved with graphics processing unit acceleration. N2 - Die 6DOF Posenschätzung von Objekten ist ein fundamentales Problem in vielen praktischen Robotikanwendungen, bei denen sich ein Ziel- oder Hindernisobjekt, einfacher oder komplexer Form, schnell in einer unstrukturierten schwierigen Umgebung bewegt. In dieser Forschungsarbeit wird zur Lösung des Problem ein 6DOF Posenschätzer entwickelt, der auf der Fusion von Daten einer Time-of-Flight-Kamera und einer Farbkamera beruht. Der Algorithmus ist in zwei Phasen unterteilt, ein Annealed Partikel-Filter bestimmt eine grobe Posenschätzung, welche mittels eines Gradientenverfahrens in einer zweiten Phase optimiert wird. In der ersten Phase wird jeder Partikel mittels sparse represenation ausgewertet, auf diese Weise kann eine große Inter-Frame-Bewegung des Zielobjektes gut behandelt werden. In der zweiten Phase wird die genaue Pose des Zielobjektes mittels des konventionellen, auf Entfernungsdaten beruhenden, Iterative Closest Point-Algorithmus aus der groben Schätzung der ersten Stufe berechnet. Der Algorithmus wurde dabei erweitert, so dass auch Informationen über das äußere Erscheinungsbild des Zielobjektes verwendet werden. Zur Kompensation von signifikanten Beleuchtungsschwankungen während des Trackings, wurde eine Modellierung der Ausleuchtung mittels Kugelflächenfunktionen erforscht und in beide Stufen der Posenschätzung integriert. Die Leistungsfähigkeit, Robustheit und Genauigkeit des entwickelten Algorithmus wurde in Experimenten im Innen- und Außenbereich mit verschiedenen Zielobjekten gezeigt. Zudem konnte gezeigt werden, dass die Schätzung mit Hilfe von Grafikprozessoren in Echtzeit möglich ist. T3 - Forschungsberichte in der Robotik = Research Notes in Robotics - 10 KW - Mustererkennung KW - Maschinelles Sehen KW - Sensor KW - 3D Vision KW - 6DOF Pose Estimation KW - Visual Tracking KW - Pattern Recognition KW - Computer Vision KW - 3D Sensor Y1 - 2014 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-105089 SN - 978-3-923959-97-6 ER - TY - JOUR A1 - Davidson, Padraig A1 - Düking, Peter A1 - Zinner, Christoph A1 - Sperlich, Billy A1 - Hotho, Andreas T1 - Smartwatch-Derived Data and Machine Learning Algorithms Estimate Classes of Ratings of Perceived Exertion in Runners: A Pilot Study JF - Sensors N2 - The rating of perceived exertion (RPE) is a subjective load marker and may assist in individualizing training prescription, particularly by adjusting running intensity. Unfortunately, RPE has shortcomings (e.g., underreporting) and cannot be monitored continuously and automatically throughout a training sessions. In this pilot study, we aimed to predict two classes of RPE (≤15 “Somewhat hard to hard” on Borg’s 6–20 scale vs. RPE >15 in runners by analyzing data recorded by a commercially-available smartwatch with machine learning algorithms. Twelve trained and untrained runners performed long-continuous runs at a constant self-selected pace to volitional exhaustion. Untrained runners reported their RPE each kilometer, whereas trained runners reported every five kilometers. The kinetics of heart rate, step cadence, and running velocity were recorded continuously ( 1 Hz ) with a commercially-available smartwatch (Polar V800). We trained different machine learning algorithms to estimate the two classes of RPE based on the time series sensor data derived from the smartwatch. Predictions were analyzed in different settings: accuracy overall and per runner type; i.e., accuracy for trained and untrained runners independently. We achieved top accuracies of 84.8 % for the whole dataset, 81.8 % for the trained runners, and 86.1 % for the untrained runners. We predict two classes of RPE with high accuracy using machine learning and smartwatch data. This approach might aid in individualizing training prescriptions. KW - artificial intelligence KW - endurance KW - exercise intensity KW - precision training KW - prediction KW - wearable Y1 - 2020 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-205686 SN - 1424-8220 VL - 20 IS - 9 ER - TY - THES A1 - Hopfner, Marbod T1 - Source Code Analysis, Management, and Visualization for PROLOG T1 - Quelltextanalyse, Verwaltung und Visualisierung für Prolog N2 - This thesis deals with the management and analysis of source code, which is represented in XML. Using the elementary methods of the XML repository, the XML source code representation is accessed, changed, updated, and saved. We reason about the source code, refactor source code and we visualize dependency graphs for call analysis. The visualized dependencies between files, modules, or packages are used to structure the source code in order to get a system, which is easily to comprehend, to modify and to complete. Sophisticated methods have been developed to slice the source code in order to obtain a working package of a large system, containing only a specific functionality. The basic methods, on which the visualizations and analyses are built on can be changed like changing a plug-in. The visualization methods can be reused in order to handle arbitrary source code representations, e.g., JAML, PHPML, PROLOGML. Dependencies of other context can be visualized, too, e.g., ER diagrams, or website references. The tool SCAV supports source code visualization and analyzing methods. N2 - Diese Dissertation beschäftigt sich mit der Verwaltung und Analyse von Quellcode, der in XML repräsentiert ist. Es werden Abhängigkeitsgraphen visualisiert um ein Projekt leichter verstehen zu können. Es kann auch ein Slice einer bestimmten Methode aus dem Projekt erstellt werden. Die Programmierung ist in Modulen gemacht, so dass die Funktionalität leicht erweitert werden kann. KW - Refactoring KW - Software Engineering KW - Refactoring KW - Call Graph KW - Dependency Graph KW - Abhängigskeitsgraph KW - Software Engineering KW - Source Code Visualization KW - Refactoring KW - Call Graph KW - Dependency Graph KW - Abhängigskeitsgraph KW - Software Engineering KW - Source Code Visualization Y1 - 2008 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-36300 ER - TY - JOUR A1 - Wienrich, Carolin A1 - Komma, Philipp A1 - Vogt, Stephanie A1 - Latoschik, Marc E. T1 - Spatial Presence in Mixed Realities – Considerations About the Concept, Measures, Design, and Experiments JF - Frontiers in Virtual Reality N2 - Plenty of theories, models, measures, and investigations target the understanding of virtual presence, i.e., the sense of presence in immersive Virtual Reality (VR). Other varieties of the so-called eXtended Realities (XR), e.g., Augmented and Mixed Reality (AR and MR) incorporate immersive features to a lesser degree and continuously combine spatial cues from the real physical space and the simulated virtual space. This blurred separation questions the applicability of the accumulated knowledge about the similarities of virtual presence and presence occurring in other varieties of XR, and corresponding outcomes. The present work bridges this gap by analyzing the construct of presence in mixed realities (MR). To achieve this, the following presents (1) a short review of definitions, dimensions, and measurements of presence in VR, and (2) the state of the art views on MR. Additionally, we (3) derived a working definition of MR, extending the Milgram continuum. This definition is based on entities reaching from real to virtual manifestations at one time point. Entities possess different degrees of referential power, determining the selection of the frame of reference. Furthermore, we (4) identified three research desiderata, including research questions about the frame of reference, the corresponding dimension of transportation, and the dimension of realism in MR. Mainly the relationship between the main aspects of virtual presence of immersive VR, i.e., the place-illusion, and the plausibility-illusion, and of the referential power of MR entities are discussed regarding the concept, measures, and design of presence in MR. Finally, (5) we suggested an experimental setup to reveal the research heuristic behind experiments investigating presence in MR. The present work contributes to the theories and the meaning of and approaches to simulate and measure presence in MR. We hypothesize that research about essential underlying factors determining user experience (UX) in MR simulations and experiences is still in its infancy and hopes this article provides an encouraging starting point to tackle related questions. KW - mixed reality KW - virtual-reality-continuum KW - spatial presence KW - place-illusion KW - plausibility-illusion KW - transportation KW - realism Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-260328 VL - 2 ER - TY - JOUR A1 - Wick, Christoph A1 - Hartelt, Alexander A1 - Puppe, Frank T1 - Staff, symbol and melody detection of Medieval manuscripts written in square notation using deep Fully Convolutional Networks JF - Applied Sciences N2 - Even today, the automatic digitisation of scanned documents in general, but especially the automatic optical music recognition (OMR) of historical manuscripts, still remains an enormous challenge, since both handwritten musical symbols and text have to be identified. This paper focuses on the Medieval so-called square notation developed in the 11th–12th century, which is already composed of staff lines, staves, clefs, accidentals, and neumes that are roughly spoken connected single notes. The aim is to develop an algorithm that captures both the neumes, and in particular its melody, which can be used to reconstruct the original writing. Our pipeline is similar to the standard OMR approach and comprises a novel staff line and symbol detection algorithm based on deep Fully Convolutional Networks (FCN), which perform pixel-based predictions for either staff lines or symbols and their respective types. Then, the staff line detection combines the extracted lines to staves and yields an F\(_1\) -score of over 99% for both detecting lines and complete staves. For the music symbol detection, we choose a novel approach that skips the step to identify neumes and instead directly predicts note components (NCs) and their respective affiliation to a neume. Furthermore, the algorithm detects clefs and accidentals. Our algorithm predicts the symbol sequence of a staff with a diplomatic symbol accuracy rate (dSAR) of about 87%, which includes symbol type and location. If only the NCs without their respective connection to a neume, all clefs and accidentals are of interest, the algorithm reaches an harmonic symbol accuracy rate (hSAR) of approximately 90%. In general, the algorithm recognises a symbol in the manuscript with an F\(_1\) -score of over 96%. KW - optical music recognition KW - historical document analysis KW - medieval manuscripts KW - neume notation KW - fully convolutional neural networks Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-197248 SN - 2076-3417 VL - 9 IS - 13 ER - TY - RPRT A1 - Savvidis, Dimitrios A1 - Roth, Robert A1 - Tutsch, Dietmar T1 - Static Evaluation of a Wheel-Topology for an SDN-based Network Usecase T2 - Würzburg Workshop on Next-Generation Communication Networks (WueWoWas'22) N2 - The increased occurrence of Software-Defined-Networking (SDN) not only improves the dynamics and maintenance of network architectures, but also opens up new use cases and application possibilities. Based on these observations, we propose a new network topology consisting of a star and a ring topology. This hybrid topology will be called wheel topology in this paper. We have considered the static characteristics of the wheel topology and compare them with known other topologies. KW - Datennetz KW - SDN KW - topology KW - wheel Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-280715 ER - TY - THES A1 - Travers, Stephen T1 - Structural Properties of NP-Hard Sets and Uniform Characterisations of Complexity Classes T1 - Strukturelle Eigenschaften NP-harter Mengen und uniforme Charakterisierungen von Komplexitätsklassen N2 - This thesis is devoted to the study of computational complexity theory, a branch of theoretical computer science. Computational complexity theory investigates the inherent difficulty in designing efficient algorithms for computational problems. By doing so, it analyses the scalability of computational problems and algorithms and places practical limits on what computers can actually accomplish. Computational problems are categorised into complexity classes. Among the most important complexity classes are the class NP and the subclass of NP-complete problems, which comprises many important optimisation problems in the field of operations research. Moreover, with the P-NP-problem, the class NP represents the most important unsolved question in computer science. The first part of this thesis is devoted to the study of NP-complete-, and more generally, NP-hard problems. It aims at improving our understanding of this important complexity class by systematically studying how altering NP-hard sets affects their NP-hardness. This research is related to longstanding open questions concerning the complexity of unions of disjoint NP-complete sets, and the existence of sparse NP-hard sets. The second part of the thesis is also dedicated to complexity classes but takes a different perspective: In a sense, after investigating the interior of complexity classes in the first part, the focus shifts to the description of complexity classes and thereby to the exterior in the second part. It deals with the description of complexity classes through leaf languages, a uniform framework which allows us to characterise a great variety of important complexity classes. The known concepts are complemented by a new leaf-language model. To a certain extent, this new approach combines the advantages of the known models. The presented results give evidence that the connection between the theory of formal languages and computational complexity theory might be closer than formerly known. N2 - Diese Dissertation behandelt die Komplexitätstheorie, ein zentrales Teilgebiet der Theoretischen Informatik. Die Komplexitätstheorie untersucht die inhärente Schwierigkeit, effiziente Algorithmen für Berechnungsprobleme zu entwerfen. Sie analysiert die Skalierbarkeit von Berechnungsproblemen und Algorithmen und stellt grundsätzliche Grenzen für die Leistungsfähigkeit von Computern auf. Berechnungsprobleme werden in Komplexitätsklassen kategorisiert. Dabei spielen die Klasse NP und die in ihr enthaltene Klasse der NP-vollständigen Probleme eine wichtige Rolle. Letztere umfasst zahlreiche in der Praxis bedeutsame Probleme aus dem Bereich Operations Research. Darüber hinaus repräsentiert die Klasse NP mit dem P-NP Problem gleichfalls das wichtigste ungelöste Problem in der Informatik. Der erste Teil dieser Dissertation ist der Untersuchung NP-vollständiger und noch allgemeiner, NP-harter Mengen gewidmet. Durch eine systematische Untersuchung der Frage, wie sich partielle Modifikationen von Mengen auf deren NP-Härte auswirken, soll das Verständnis dieser wichtigen Komplexitätsklasse verbessert werden. Die Untersuchungen in diesem Bereich stehen in enger Verbindung zu wichtigen ungelösten Fragen, wie beispielsweise der Frage nach der Komplexität von Vereinigungen disjunkter NP-vollständiger Mengen und darüber hinaus der Frage nach der Existenz dünner, NP-harter Mengen. Der zweite Teil der Dissertation beschäftigt sich ebenfalls mit der Komplexitätstheorie, nimmt dabei aber eine andere Perspektive ein: Während im ersten Teil mit der Untersuchung struktureller Eigenschaften innere Aspekte von Komplexitätsklassen im Vordergrund stehen dreht es sich im zweiten Teil um die Beschreibung von Komplexitätsklassen. Dabei werden so genannte Blattsprachen verwendet, welche einen uniformen Beschreibungsmechanismus für Komplexitätsklassen darstellen. Die bestehenden Blattsprachen-Konzepte werden durch einen neuen Ansatz ergänzt, der in einem gewissen Sinne die Vorteile der bekannten Ansätze vereint. Die erzielten Ergebnisse sind Evidenz dafür, dass die Verbindung zwischen der Theorie der formalen Sprachen und der Komplexitätstheorie noch enger ist als bislang vermutet. KW - Berechnungskomplexität KW - Komplexität KW - Theoretische Informatik KW - NP-Vollständigkeit KW - Strukturelle Komplexität KW - NP-complete sets KW - structural complexity Y1 - 2007 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-27124 ER - TY - JOUR A1 - Lesch, Veronika A1 - König, Maximilian A1 - Kounev, Samuel A1 - Stein, Anthony A1 - Krupitzer, Christian T1 - Tackling the rich vehicle routing problem with nature-inspired algorithms JF - Applied Intelligence N2 - In the last decades, the classical Vehicle Routing Problem (VRP), i.e., assigning a set of orders to vehicles and planning their routes has been intensively researched. As only the assignment of order to vehicles and their routes is already an NP-complete problem, the application of these algorithms in practice often fails to take into account the constraints and restrictions that apply in real-world applications, the so called rich VRP (rVRP) and are limited to single aspects. In this work, we incorporate the main relevant real-world constraints and requirements. We propose a two-stage strategy and a Timeline algorithm for time windows and pause times, and apply a Genetic Algorithm (GA) and Ant Colony Optimization (ACO) individually to the problem to find optimal solutions. Our evaluation of eight different problem instances against four state-of-the-art algorithms shows that our approach handles all given constraints in a reasonable time. KW - logistics KW - rich vehicle routing problem KW - ant-colony optimization KW - genetic algorithm KW - real-world application Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-268942 SN - 1573-7497 VL - 52 ER - TY - JOUR A1 - Ankenbrand, Markus J. A1 - Weber, Lorenz A1 - Becker, Dirk A1 - Förster, Frank A1 - Bemm, Felix T1 - TBro: visualization and management of de novo transcriptomes JF - Database N2 - RNA sequencing (RNA-seq) has become a powerful tool to understand molecular mechanisms and/or developmental programs. It provides a fast, reliable and cost-effective method to access sets of expressed elements in a qualitative and quantitative manner. Especially for non-model organisms and in absence of a reference genome, RNA-seq data is used to reconstruct and quantify transcriptomes at the same time. Even SNPs, InDels, and alternative splicing events are predicted directly from the data without having a reference genome at hand. A key challenge, especially for non-computational personnal, is the management of the resulting datasets, consisting of different data types and formats. Here, we present TBro, a flexible de novo transcriptome browser, tackling this challenge. TBro aggregates sequences, their annotation, expression levels as well as differential testing results. It provides an easy-to-use interface to mine the aggregated data and generate publication-ready visualizations. Additionally, it supports users with an intuitive cart system, that helps collecting and analysing biological meaningful sets of transcripts. TBro’s modular architecture allows easy extension of its functionalities in the future. Especially, the integration of new data types such as proteomic quantifications or array-based gene expression data is straightforward. Thus, TBro is a fully featured yet flexible transcriptome browser that supports approaching complex biological questions and enhances collaboration of numerous researchers. KW - database Y1 - 2016 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-147954 VL - 2016 ER -