• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 21
  • 4
  • 4
  • 4
  • 2
  • 1
  • 1
  • 1
  • 1
  • 1
  • 1
  • Tagged with
  • 47
  • 47
  • 12
  • 9
  • 9
  • 7
  • 6
  • 6
  • 5
  • 5
  • 5
  • 5
  • 5
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Determination of Real-Time Network Configuration for Self-Adaptive Automotive Systems

Zhang, Ziming 19 May 2015 (has links) (PDF)
The Electric/Electronic architecture of vehicle becomes more complex and costly, self-adaption can reduce the system, enhance the adaptive meanwhile reduce energy consumption and costs. The self-adaption needs the cooperation of both hardware and software reconfigurations, such that after the software is reconfigured the automotive network continues to fulfill the time constraints for time-critical applications. The thesis focuses on the real-time network reconfiguration. It uses EAST-ADL to model a real-time automotive system with timing events and constraints, which conforms to AUTOSAR timing extensions. The network media access is analyzed based on the model and a scheduling algorithm is developed. Then the concept is implemented by a use case, which is transformed from an EAST-ADL model to an executable simulation.
42

A resource-aware embedded commucation system for highly dynamic networks / Un système de communication embarqué conscient des ressources pour des réseaux hautement dynamiques

Diao, Xunxing 27 May 2011 (has links)
Chaque année en Europe, 1.300.000 accidents de la route ont comme conséquence 1.700.000 blessés. Le coût financier d’accidents de la route est évalué à 160 milliards d’euros (approximativement le même coût aux Etats-Unis). VANET (Vehicular Ad-hoc NETwork) est une des technologies clés qui peut permettre de réduire d’une façon significative le nombre d’accidents de la route (e.g. message d’urgence signalant la présence d’un obstacle ou d’un véhicule en cas de brouillard). En plus de l’amélioration de la sécurité et du confort des conducteurs et des passagers, VANET peut contribuer à beaucoup d’applications potentielles telles que la prévision et la détection d’embouteillages, la gestion d’infrastructure de système de transport urbain (e.g. système de transport intelligent multimodal) etc. Dans cette thèse, je présenterai un système embarqué dédié à la communication inter-véhicule particulièrement pour les applications sécuritaires de passagers et de conducteurs. Nos efforts de recherche et de développement sont centrés sur deux principaux objectifs : minimiser le temps de latence intra-noeud et le délai de communication inter-véhicule en prenant en compte le changement dynamique du VANET. De ce fait pour atteindre ces objectifs, des nouvelles approches (e.g. inter-couche ‘Cross-layering’) ont été explorées pour respecter les contraintes de ressource (QoS, mémoire, CPU et énergie de la communication inter-véhicule) d’un système embarqué à faible coût. Le système de communication embarqué proposé comporte deux composants logiciels principaux : un protocole de communication dénommé CIVIC (Communication Inter Véhicule Intelligente et Coopérative) et un système d’exploitation temps réel appelé HEROS (Hybrid Event-driven and Real-time multitasking Operating System). CIVIC est un protocole de communication géographique à faible consommation énergétique et à faible temps de latence (délai de communication). HEROS gère contextuellement l’ensemble du système (matériel et logiciel) en minimisant le temps de latence et la consommation des ressources (CPU et mémoire). En outre, le protocole de communication CIVIC est équipé d’un système de localisation LCD-GPS (Low Cost Differential GPS). Pour tester et valider les différentes techniques et théories, la plateforme matérielle LiveNode (LImos Versatile Embedded wireless sensor NODE) a été utilisée. En effet, la plateforme LiveNode permet de développer et de prototyper rapidement des applications dans différents domaines. Le protocole de communication CIVIC est basé sur la technique de ‘broadcast’ à un saut ; de ce fait il est indépendant de la spécificité du réseau. Pour les expérimentations, seule la norme d’IEEE 802.15.4 (ZigBee) a été choisie comme médium d’accès sans fil. Il est à noter que le médium d’accès sans fil ZigBee a été adopté comme le médium standard pour les réseaux de capteurs sans fil (RCSFs) et le standard 6LoWPAN ; car il est peu coûteux et peu gourmand en énergie. Bien que le protocole de communication à l’origine soit conçu pour répondre aux exigences de VANET, ses domaines d’application ne sont pas limités à VANET. Par exemple il a été utilisé dans différents projets tels que MOBI+ (système de transport urbain intelligent) et NeT-ADDED (projet européen FP6 : agriculture de précision). Les VANETs et les RCSFs sont les réseaux fortement dynamiques, mais les causes de changement topologique de réseau sont différentes : dans le réseau VANET, il est dû à la mobilité des véhicules, et dans le RCSF, il est dû aux pannes des noeuds sans fil. Il est à noter que le VANET et le RCSF sont généralement considérés comme un sous-ensemble du réseau MANET (réseau ad-hoc mobile). Cependant, ils sont réellement tout à fait différents du MANET classique, et leurs similitudes et différences seront expliquées en détail dans la thèse. La contribution principale de mes travaux est le protocole CIVIC, qui échange des messages en basant sur l’information géographique des noeuds (position). (...) / Each year in Europe, 1,300,000 vehicle accidents result in 1,700,000 personal injuries. The financial cost of vehicle accidents is evaluated at 160 billion Euros (approximately the same cost in the USA). VANET (Vehicular Ad-Hoc NETwork) is a key technology that can enable hazard alarming applications to reduce the accident number. In addition to improve the safety for drivers and passengers, VANET can contribute to many potential applications such as detecting and predicting traffic jams, auto-optimizing the traffic flow, and helping disabled passengers to access public transports.This thesis will present an embedded communication system dedicated to VANET especially for the safety-related applications. Our design mainly tries to achieve two requirements: as one can imagine, the embedded communication system for VANET requires extra effort to deal with the highly dynamic network topology caused by moving vehicles, thus to shorten the intra-node system latency and inter-node network delay is essential requirement for such embedded communication system. Besides, a fundamental requirement for any practical embedded system is resource-awareness. Although the embedded communication system on vehicles may gain better hardware supports, the characteristics of embedded hardware still have to cope with resource constraints in terms of QoS, memory, CPU and energy. The embedded communication system involves two major software components: a routing protocol called CIVIC (Communication Inter Véhicule Intelligente et Coopérative) and an embedded operating system called HEROS (Hybrid Event-driven and Real-time multitasking Operating System). The former is a quick reaction and low resource consumption geographic protocol for inter-vehicle message transmissions; and the latter controls the whole system and assures intra-node resource awareness. In addition, the system can use a localization software solution called LCD-GPS (Low Cost Differential GPS) to improve the accuracy of locations. The hardware platform is LiveNode (LImos Versatile Embedded wireless sensor NODE), which is a versatile wireless sensor node enabling to implement rapidly a prototype for different application domains. The communication system is based on the one-hop broadcast, thus it does not have a strict limitation on network specification. For the experiments only, the IEEE 802.15.4 standard is chosen as the underlying wireless access medium. The standard is well known as a low-power consumption standard requiring low-cost devices. Notice that the IEEE 802.15.4 standard is also the wireless access medium of 6LoWPAN. Although the embedded communication system is originally designed to meet the requirements of VANET, but its application domains are not limited to VANET. For example, another network which can use the embedded communication system is WSN (Wireless Sensor Network). CIVIC was used to implement different real-world projects such MOBI+ (intelligent urban transportation system) and EU-FP6 NeT-ADDED (precision agriculture). Both VANET and WSN are highly dynamic networks, but the causes of changing network topology are different: the former is because of the high-mobility feature of vehicles, and the latter is because of the fault of wireless sensors. Note that, although VANET and WSN are both commonly considered as the subset of MANET (Mobile Ad-hoc NETwork), they are actually quite different from the classical MANET, and the similarities and differences will be further explained in the thesis. The major contribution of my works relates to the CIVIC protocol, which routes messages based on the geographic information. The related works of the thesis will focus on the geographic routing techniques, problems and solutions, but other related techniques will also be addressed. Note that, although some related projects were investigated but their implementation and experiment aspects were not detailed. (...)
43

Necessary and Sufficient Conditions on State Transformations That Preserve the Causal Structure of LTI Dynamical Networks

Leung, Chi Ho 01 May 2019 (has links)
Linear time-invariant (LTI) dynamic networks are described by their dynamical structure function, and generally, they have many possible state space realizations. This work characterizes the necessary and sufficient conditions on a state transformation that preserves the dynamical structure function, thereby generating the entire set of realizations of a given order for a specific dynamic network.
44

Necessary and Sufficient Conditions on State Transformations That Preserve the Causal Structure of LTI Dynamical Networks

Leung, Chi Ho 01 May 2019 (has links)
Linear time-invariant (LTI) dynamic networks are described by their dynamical structure function, and generally, they have many possible state space realizations. This work characterizes the necessary and sufficient conditions on a state transformation that preserves the dynamical structure function, thereby generating the entire set of realizations of a given order for a specific dynamic network.
45

Determination of Real-Time Network Configuration for Self-Adaptive Automotive Systems

Zhang, Ziming 17 April 2015 (has links)
The Electric/Electronic architecture of vehicle becomes more complex and costly, self-adaption can reduce the system, enhance the adaptive meanwhile reduce energy consumption and costs. The self-adaption needs the cooperation of both hardware and software reconfigurations, such that after the software is reconfigured the automotive network continues to fulfill the time constraints for time-critical applications. The thesis focuses on the real-time network reconfiguration. It uses EAST-ADL to model a real-time automotive system with timing events and constraints, which conforms to AUTOSAR timing extensions. The network media access is analyzed based on the model and a scheduling algorithm is developed. Then the concept is implemented by a use case, which is transformed from an EAST-ADL model to an executable simulation.:1. Introduction 2. Research Fundamentals 2.1. AUTOSAR Specifications for Modeling Function Communication 2.2. Media Access Control in Real-time Network 3. Function Communication Model and Determination of Network Configuration 3.1. Function Communication Model 3.2. Scheduling Algorithm for Media Access 4. Implementation of Communication Model and Plugin for Model Transformation 4.1. EAST-ADL Modeling Language 4.2. Implementation of Function Communication Model in EAST-ADL 4.3. Model Transformation Plugin and Simulation Tool Integration 5. Evaluation of the Function Communication Model 5.1. Use-Case Model for Evaluation 5.2. Time Values of Use-Case Model 5.3. Analysis and Evaluation of Simulation Result 6. Conclusion and Outlook 6.1. Conclusion of the Work 6.2. Outlook of the Future Work A. OMNeT++ Simulation Log B. EAST-ADL Model to Artop Model Mapping Bibliography Nomenclature
46

Informations- und Wissenstransfer in kollaborativen Lernsystemen: Eine strukturelle und relationale Analyse über den Einfluss sozialer Organisationsstrukturen in Wissensnetzwerken am Beispiel der Lernplattform OPAL

Stützer, Cathleen M. 03 December 2013 (has links)
In der Netzwerkgesellschaft des 21. Jahrhunderts gilt die kollaborative Verteilung und Nutzung von Information und Wissen als Schlüsselstrategie für den webbasierten Informations- und Wissenstransfer. Durch die technologischen Möglichkeiten werden technische Zugangsbarrieren weitestgehend überwunden und traditionelle Formen der Wissensvermittlung durch moderne webbasierte Lernumgebungen ergänzt. Der Umgang mit kollaborativen Lehr- und Lernszenarien im dynamischen Informations- und Wissenstransfer bildet die Grundlage für den soziokulturellen Fortschritt innerhalb der Bildungsforschung. Der Schwerpunkt dieser Arbeit lag auf der strukturellen und relationalen Analyse sozialer Organisationsstrukturen innerhalb von Wissensnetzwerken. Ziel war es, Einflussfaktoren offenzulegen, die sich auf das Innovations- und Distributionspotential von Information und Wissen innerhalb von kollaborativen Wissensnetzwerken auswirken. Es wurden dazu Interaktionsprozesse von Teilnehmern innerhalb von Diskussionsforen am Beispiel der Lernplattform OPAL – dem aktuell populärsten Lernmanagementsystem in der Hochschulbildung Sachsens, Deutschland – untersucht. Unter der Annahme, dass soziale Interaktion besonders im Umgang mit kollaborativen Medien den Bildungsablauf und der Aufbau von Wissensnetzwerken die Lehr- und Lernprozesse beeinflusst, wurden in dieser Arbeit die strukturellen Bedingungen des kollaborativen Wissensnetzwerkes in OPAL exploriert und soziale Rollenkonstrukte relational identifiziert, um die Auswirkungen kollaborativer Aktivitäten auf den Informations- und Wissenstransfer in Wissensnetzwerken zu erklären. Es wurden vornehmlich beziehungsorientierte kommunikationstheoretische Modelle zugrunde gelegt und relationale Forschungsmethoden wie SNA (Social Network Analysis) und DNA (Dynamic Network Analysis) angewandt, um eine Basis für die weiterführende Implementierung sozial vernetzter Lehr- und Lernstrategien in der Bildungsforschung zu schaffen. […] / In the network society of the 21st century, a key strategy for web-based exchange of information and knowledge is their collaborative distribution and use. Technical hurdles of access are mostly being overcome with technological advances and traditional forms of passing on knowledge are being complemented by modern, e-learning environments. Within research into education, the foundation for socio-cultural progress is formed by involvement with collaborative teaching and learning scenarios in a dynamic exchange of information and knowledge. The emphasis of this work lay in the analysis of structures and relationships of social organisations within knowledge networks. The aim was to describe the exchange of information and knowledge in collaborative learning systems and to explore its influence on the potential for innovation and distribution of information and knowledge. A study was undertaken of the interaction of participants in discussion forums as exemplified by the learning platform OPAL – currently the most popular learning management system in secondary school education in Saxony, Germany. On the assumption that social interaction, particularly involving collaborative media, the progress of education and the construction of knowledge networks do influence teaching and learning processes, this work explored the structural conditions of OPAL's collaborative knowledge network and identified relationships between social role constructs in order to explain the effect of collaborative activities on the process of diffusion of information and knowledge in knowledge networks. Primarily the study was based on relationship oriented sociological models and communication theory models, and research methods for relationships, including SNA (Social Network Analysis) and DNA (Dynamic Network Analysis) were applied, so as to create a basis for further implementation of social network teaching and learning strategies in educational research. [...]
47

Necessary and Sufficient Conditions on State Transformations That Preserve the Causal Structure of LTI Dynamical Networks

Leung, Chi Ho 01 May 2019 (has links)
Linear time-invariant (LTI) dynamic networks are described by their dynamical structure function, and generally, they have many possible state space realizations. This work characterizes the necessary and sufficient conditions on a state transformation that preserves the dynamical structure function, thereby generating the entire set of realizations of a given order for a specific dynamic network.

Page generated in 0.05 seconds