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TCP and network coding : equilibrium and dynamic properties / TCP et codage réseau : équilibre et propriétés dynamiquesMedina Ruiz, Hamlet 25 July 2014 (has links)
Lors d'une communication dans un réseau, les nœuds intermédiaires se contentent en général de retransmettre les paquets de données qu'ils reçoivent. Grâce au codage de réseau (NC), ces nœuds intermédiaires peuvent envoyer des combinaisons linéaires des paquets qu'ils ont reçus. Ceci permet une meilleure exploitation de la capacité du réseau et une plus grande robustesse à l'égard de pertes.Cette thèse s'intéresse à une implantation du NC en lien avec TCP (TCP-NC). Grâce à la redondance introduite par le NC, une partie des pertes liées à des liens sans fils peut être compensée. Elle propose en particulier un mécanisme d'adaptation de la redondance introduite par le codage de réseau. Une première partie de cette thèse est consacrée à l'analyse de la dynamique de TCP-NC avec Random Early Detection (RED) comme mécanisme de gestion des files d'attente en utilisant les outils d'optimisation convexe et issus de l’automatique. Nous caractérisons l'équilibre du réseau et les propriétés de stabilité de TCP-Reno en présence de NC. Dans une seconde partie, cette thèse propose un algorithme d'adaptation de la redondance introduite par NC. Dans TCP-NC avec redondance adaptative (TCP-NCAR), cet ajustement se fait grâce à un schéma de différenciation des pertes, qui estime la répartition des pertes entre erreurs de transmission dues aux liens sans fils et pertes liées à la congestion. Les propriétés d'équilibre et de stabilité de TCP-NCAR/RED sont caractérisées. Les résultats théoriques et de simulation montrent que TCP-NCAR adopte une redondance proche de l'optimum quand les taux de perte de paquets sur les liens sans fils sont petits. En outre, le modèle linéarisé autour de l'équilibre montre que TCP-NCAR augmente la taille de la région de stabilité de TCP-Reno. / Communication networks today share the same fundamental principle of operation: information is delivered to their destination by nodes intermediate in a store-and-forward manner.Network coding (NC) is a technique that allows intermediate nodes to send out packets that are linear combinations of previously received information. The main benefits of NC are the potential throughput improvements and a high degree of robustness, which is translated into loss resilience. These benefits have motivated deployment efforts for practical applications of NC, e.g., incorporating NC into congestion control schemes such as TCP-Reno to get a TCP-NC congestion protocol. In TCP-NC, TCP-Reno throughput is improved by sending a fixed amount of redundant packets, which mask part of the losses due, e.g., to channel transmission errors. In this thesis, we first analyze the dynamics of TCP-NC with random early detection (RED) as active queue management (AQM) using tools from convex optimization and feedback control. We study the network equilibrium point and the stability properties of TCP-Reno when NC is incorporated into the TCP/IP protocol stack. The existence and uniqueness of an equilibrium point is proved, and characterized in terms of average throughput, loss rate, and queue length. Our study also shows that TCP-NC/RED becomes unstable when delay or link capacities increases, but also, when the amount of redundant packets added by NC increases. Using a continuous-time model and neglecting feedback delays, we prove that TCP-NC is globally stable. We provide a sufficient condition for local stability when feedback delays are present. The fairness of TCP-NC with respect to TCP-Reno-like protocols is also studied. Second, we propose an algorithm to dynamically adjust the amount of redundant linear combinations of packets transmitted by NC. In TCP-NC with adaptive redundancy (TCP-NCAR), the redundancy is adjusted using a loss differentiation scheme, which estimates the amount of losses due to channel transmission errors and due to congestion. Simulation results show that TCP-NCAR outperforms TCP-NC in terms of throughput. Finally, we analyze the equilibrium and stability properties of TCP-NCAR/RED. The existence and uniqueness of an equilibrium point is characterized experimentally. The TCP-NCAR/RED dynamics are modeled using a continuous-time model. Theoretical and simulation results show that TCP-NCAR tracks the optimal value for the redundancy for small values of the packet loss rate. Moreover, simulations of the linearized model around equilibrium show that TCP-NCAR increases the size of the TCP-Reno stability region. We show that this is due to the compensator effect of the redundancy adaptation dynamics to TCP-Reno. These characteristics of TCP-NCAR allow the congestion window adaptation mechanism of TCP-Reno to react in a smooth way to channel losses, avoiding some unnecessary rate reductions, and increasing the local stability of TCP-Reno.
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Agentenbasierter Programmassistent zur Verwaltung von NC-Informationen in Produktionssystemen mit KommunikationsnetzwerkenDang, Thien Ngon 30 April 2008 (has links) (PDF)
In den letzten Jahren hat sich die rapide Entwicklung der Elektrotechnik ebenso wie die der Softwaretechnologie auf die numerischen Steuerungen in den heutigen CNC-Maschinen groß ausgewirkt. Diese numerischen Steuerungen sind sowohl intelligenter und flexibler als auch mit größerer Internspeicherkapazität ausgerüstet. Dies führt zu einer Änderung der Art und Weise, wie DNC-Systeme zu etablieren sind, besonders solcher, die auf bisher verfügbaren, aber ungleichartigen DNC-Systemen basieren. In einem solch heterogenen DNC-System wird Datenspeicherungsfähigkeit stärker verteilt angeordnet, d.h., sie ist nicht nur in einem zentralen DNC-Server vorhanden, sondern auch in Terminals oder Steuerungen selbst angelagert. Diese Änderung des Archivierungsmittels benötigt neue DNC-Software, die die DNC-Grundfunktionen voll realisiert. Zudem sollte sie auch den neuen spezifischen Softwareanforderungen entsprechen und erlauben, neue Funktionen, z.B. Maschinendatenerfassung, Betriebsdatenerfassung usw., als Module hinzuzufügen. Derzeit wird die Agententechnologie bzw. ein MAS (Multiagentensystem) als ein aussichtsreicher Ansatz angesehen, um die Probleme der heutigen komplexen Softwaresysteme, wie ungleichartige Systemumgebungen und verteilte Strukturen, zu lösen. Die vorliegende Arbeit stellt die Idee zum Aufbau eines heterogenen DNC-Systems und die Konzipierung zur Gestaltung der agentenbasierten DNC-Software vor. Ausgehend von dem vorgestellten Lösungskonzept wird zudem der Programmassistent als erster Modul der agentenbasierten DNC-Software präsentiert. / In the network-based DNC systems and especially heterogeneous DNC systems data get more distributed due to the ability to store not only in the DNC Server but also in the CNC controller or CNC Terminal. This leads a challenge to the DNC software in the implementation of its basic functions. The agent-based DNC software with assistants (ADNC) is suggested to solve the above problem. Its tasks are to collect distributed NC information and transfer data safely as well as performing other extended functions, i.e. NC program generation, machine data collection, production data collection, control machines in system, etc. The present work presented the concept to develop the ADNC and its first prototype. This prototype was developed in a process using a framework of agent-based assistants, called AgentAP. It is applicable on distributed manufacturing data and had been implemented on the agent platform JADE. The module Program Assistant, one of these prototype modules, which is responsible for management, bidirectional transfer, and monitoring change of NC programs, is also discussed.
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Možnosti systému Heidenhain při programování obráběcích strojů / Heidenhain tools for NC programming of machinesCink, Vladislav January 2010 (has links)
The Description of the control system Heidenhain iTNC 530 and the machine FV 25 CNC A. Detailed analysis of the impact of single programming functions for more effectivity machining by the help of specified machine.
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Některé aspekty QCD při nízkých energiích v éře přesných měření / Some aspects of low-energy QCD at the precision frontierHusek, Tomáš January 2017 (has links)
Title: Some aspects of low-energy QCD at the precision frontier Author: Tomáš Husek Department/Institute: Institute of Particle and Nuclear Physics Supervisor of the doctoral thesis: doc. RNDr. Karol Kampf, Ph.D. Abstract: This thesis concentrates on some low-energy aspects of QCD, namely on those which are connected to the electromagnetic decays of lightest neutral pseudoscalar mesons. Calculations of radiative corrections to neutral pion decays (the Dalitz decay and the rare decay) and a novel model for the pion electro- magnetic transition form factor are subjects discussed in the attached papers, which this work is based on. The associated theoretical aspects including Chiral Perturbation Theory or the large-Nc limit are introduced. We also discuss the complications which arise when the calculations of radiative corrections for η(′) Dalitz decays are performed. Some details about the collaboration with experi- ments which incorporate the calculation of the published corrections are provided. Last but not least, some techniques related to loop integrals are shown. Keywords: Chiral Perturbation Theory, large-Nc limit, radiative corrections, pion electromagnetic transition form factor 1
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Agentenbasierter Programmassistent zur Verwaltung von NC-Informationen in Produktionssystemen mit KommunikationsnetzwerkenDang, Thien Ngon 22 April 2008 (has links)
In den letzten Jahren hat sich die rapide Entwicklung der Elektrotechnik ebenso wie die der Softwaretechnologie auf die numerischen Steuerungen in den heutigen CNC-Maschinen groß ausgewirkt. Diese numerischen Steuerungen sind sowohl intelligenter und flexibler als auch mit größerer Internspeicherkapazität ausgerüstet. Dies führt zu einer Änderung der Art und Weise, wie DNC-Systeme zu etablieren sind, besonders solcher, die auf bisher verfügbaren, aber ungleichartigen DNC-Systemen basieren. In einem solch heterogenen DNC-System wird Datenspeicherungsfähigkeit stärker verteilt angeordnet, d.h., sie ist nicht nur in einem zentralen DNC-Server vorhanden, sondern auch in Terminals oder Steuerungen selbst angelagert. Diese Änderung des Archivierungsmittels benötigt neue DNC-Software, die die DNC-Grundfunktionen voll realisiert. Zudem sollte sie auch den neuen spezifischen Softwareanforderungen entsprechen und erlauben, neue Funktionen, z.B. Maschinendatenerfassung, Betriebsdatenerfassung usw., als Module hinzuzufügen. Derzeit wird die Agententechnologie bzw. ein MAS (Multiagentensystem) als ein aussichtsreicher Ansatz angesehen, um die Probleme der heutigen komplexen Softwaresysteme, wie ungleichartige Systemumgebungen und verteilte Strukturen, zu lösen. Die vorliegende Arbeit stellt die Idee zum Aufbau eines heterogenen DNC-Systems und die Konzipierung zur Gestaltung der agentenbasierten DNC-Software vor. Ausgehend von dem vorgestellten Lösungskonzept wird zudem der Programmassistent als erster Modul der agentenbasierten DNC-Software präsentiert. / In the network-based DNC systems and especially heterogeneous DNC systems data get more distributed due to the ability to store not only in the DNC Server but also in the CNC controller or CNC Terminal. This leads a challenge to the DNC software in the implementation of its basic functions. The agent-based DNC software with assistants (ADNC) is suggested to solve the above problem. Its tasks are to collect distributed NC information and transfer data safely as well as performing other extended functions, i.e. NC program generation, machine data collection, production data collection, control machines in system, etc. The present work presented the concept to develop the ADNC and its first prototype. This prototype was developed in a process using a framework of agent-based assistants, called AgentAP. It is applicable on distributed manufacturing data and had been implemented on the agent platform JADE. The module Program Assistant, one of these prototype modules, which is responsible for management, bidirectional transfer, and monitoring change of NC programs, is also discussed.
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Study of Christian attitudes toward man's stewardship of the environment: a case study in the Roanoke ValleyHerman, Elizabeth N. 17 November 2012 (has links)
A range of views exist on the question of the effects of the Judeo-Christian tradition on environmental ethics. Some believe that the Judeo-Christian tradition has played the significant role in bringing about the present environmental situation. Others maintain that the current environmental crisis is much more complicated, resulting from many divergent factors. Still others would say that the Judeo-Christian tradition, as expressed in the Bible, calls man into a sacred relationship with nature which can be defined as the environmental ethic of stewardship.
This thesis studies the relationship between Christian religious commitment and attitudes toward the environment.
A questionnaire completed by 242 individuals who attend church in the Roanoke Valley provides the case study data. The survey instrument measures Christian religious commitment and attitudes toward the environment. The results of this study will provide further understanding of indicators for environmenta1 ethics. / Master of Landscape Architecture
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The Appalachian cultural landscape along the New RiverMellen, E. Garnett 10 June 2009 (has links)
The regional landscape of Appalachian was a testing ground for a method to define cultural landscape. Landscape Architects and land planners can learn from the existing landscape about the aesthetics and environmental constraints of an area to design and plan in such a way as to complement and strengthen regional character.
This document describes in seven chapters the study undertaken to identify patterns in the cultural landscape along the New River. Chapter one introduces the study. Chapter Two explains the physical setting of the four physiographic provinces through which the New River flows. Chapter Three briefly gives an overview of the historical social context of the New River Corridor. Chapter Four describes the eleven sites surveyed as part of this research. The methods of the study are described in Chapter Five. The results of the research survey and statistical analysis are reported in Chapter Six. Lastly, Chapter Seven describes the current land uses within the four provinces, identifies the similarities between the landscape of the Blue Ridge and Great Valley Provinces and the dissimilarity of the Ridge and Valley and Allegheny Plateau Provinces. This chapter discusses how land planning profession could work to strengthen the Appalachian region along the New River and other regions with a unique cultural landscape. / Master of Landscape Architecture
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Termoelaster i kompositkrut : En möjlig ersättning till nitrocellulosa / Thermoplastic Elastomers in Gun PropellantsJansson, Jessica January 2016 (has links)
Sedan människor började använda energetiska material har risken för oönskade explosioner alltid varit ett problem. Många produktionsanläggningar och förråd har förstörts på grund av oönskad antändning energetiska material. Idag är nitrocellulosa en komponent i de flesta kanonkrut. En negativ egenskap hos nitrocellulosa är att den bryts ner över tid och eftersom det är en naturprodukt så kommer det alltid att finnas en viss skillnad mellan olika batcher. Genom att ersätta nitrocellulosa med en produkt som inte bryts ner men som fortfarande ger liknande övriga egenskaper kan kanonkrutssäkerheten öka. Termoelaster undersöktes då de är smältbara och tåliga. Smältpunkt och glastransitionstemperaturen bestämdes med differentiell svepkalorimetri, viskositeten mättes vid flera temperaturer med en reometer och mekaniska egenskaper utvärderades i en dragprovningsmaskin. De två mest lovande polymererna blandades sedan med hexamin som är ett inert material för att simulera ett kompositkrut. Agglomerering av hexamin undveks genom tillsats av små mängder pyrogen kiseldioxid. Fyllnadsgraden i systemet nådde 70 viktprocent hexamin i en polymer. Kompositmaterialen dragprovades och resultaten jämfördes med motsvarande data för två nitrocellulosabaserat krut. Kompositmaterialen hade lägre brottgräns än det ena nitrocellulosabaserade krutet men högre brottgräns än det andra nitrocellulosabaserade krutet. Kompositmaterialen hade högre E-modul än det nitrocellulosabaserade krutet men lägre brottöjning. Resultaten är lovande och visar att termoelasterna har stor potential att användas i kompositkrut. Med fortsatt undersökning och optimering av kompositmaterialen kan ett säkrare alternativ till nitrocellulosa skapas.
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Art and politics in the Austrian Netherlands : Count Charles Cobenzl (1712-70) and his collection of drawingsPhillips, Catherine Victoria January 2013 (has links)
The Cabinet of Count Charles Cobenzl lies at the heart of the Hermitage Museum, forming the core of the collection of Old Master Drawings. Yet despite perpetual references to him as ‘grand collectionneur’, no study of Cobenzl’s collecting has ever been undertaken. Nor, in the absence of prosopographical studies of art production or collecting in the Austrian Netherlands in the middle of the eighteenth century, or indeed of other individual collectors, has it been possible to set him in a ‘collecting context’. Bringing together the works of art themselves and Cobenzl’s abundant correspondence, this thesis assesses what he owned, how and why he acquired it, the political and intellectual framework for his collecting and how he perceived the objects in his possession. Looking at Cobenzl’s roles as public figure and private collector, it shows how the latter fits into the context of the former, his collecting rooted firmly in his ambition to revive the economy and the arts of the Austrian Netherlands, in his own ambiguous status and his conflicts with the Governor, Charles de Lorraine. The battle for both real and perceived superiority was played out in many different parts of Cobenzl’s professional and private life, and he used display – the adornment of his home and his person and his collecting – as part of a play for social prestige. Cobenzl used objects as a discrete assertion of both intellectual and aesthetic superiority. This thesis proposes that Cobenzl’s transformation into a collector of drawings was an example of his perspicacious identification of emerging trends that could be turned to advantage, economic or prestigious, public or personal. He was drawn by the status of drawings, perceived as accessible only to those of greater refinement and understanding, as something elite, less accessible than the collecting of paintings. The direct and specific stimulus for his emergence as a collector of drawings lay in the provenance of two large groups of works he was offered, which permitted him to assert a very specific link to the past. It suggests that Cobenzl adopted not only the drawings, but also their histories, to negotiate social position and identity, within the context of his pragmatic utilitarianism. This egocentric study also provides the foundation for a preliminary attempt to create a context for Cobenzl’s collecting of drawings, within his circle, in the Austrian Netherlands overall, and, through analysis of his collecting practices, in the wider European context.
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Proposition de chaîne numérique pour la fabrication additiveBonnard, Renan 12 October 2010 (has links) (PDF)
Les procédés par ajout de matière sont soumis à des changements majeurs depuis ces dernières années. En effet, ils sont passés de procédés de prototypage rapide, à des procédés de fabrication additive pour la réalisation de pièces fonctionnelles. Ces changements ont entraîné de nouvelles attentes en termes de maîtrise de ces procédés. Dans le même temps, il subsiste certains problèmes dus à leur non-intégration dans une chaîne numérique complète et robuste. Ce point ne leur permet pas à l'heure actuelle de rattraper leur retard en terme de développement par rapport aux procédés plus traditionnels. Les limites de la structure actuelle au niveau de la commande numérique (s'appuyant sur le STL) des machines de fabrication additive ont été identifiées par les travaux de recherche de plusieurs groupes internationaux. La grande majorité a conclu au nécessaire développement d'une nouvelle structure de données basée sur le format STEP, qui apparaît comme étant un format adapté pour obtenir une chaîne numérique complète, robuste et s'appuyant sur des données de haut niveau conceptuel. Le but des travaux de thèse est donc de proposer une nouvelle structuration des données pour le procédé par ajout de matière basée sur le format STEP-NC puis dans le même temps de mettre en place une nouvelle chaîne numérique STEP-NC s'appuyant sur des DCN génériques du même type que ceux utilisés en usinage. La première partie du travail est la mise en place d'un modèle hiérarchisé des données nécessaire pour la description des procédés par ajout de matière. Ce modèle hiérarchisé permet d'identifier et de hiérarchiser toutes les données utiles à l'élaboration d'un projet de fabrication additive. La seconde étape consiste à partir des données du modèle hiérarchisé à la proposition d'un modèle de données STEP-NC pour l'introduction des procédés de fabrication additive dans la norme ISO 14649. Pour réaliser une chaîne numérique complète basée sur le STEP-NC, les travaux de l'équipe (qui concernent non seulement la fabrication additive mais aussi l'usinage) ont conduit à la mise en place d'une plateforme appelée SPAIM (STEP-NC Platform for Advanced and Intelligent Manufacturing). Dans cette plateforme la chaîne numérique complète (CAO-FAO-DNC) est intégrée autour d'un unique fichier STEP-NC sans perte d'information. Cette plateforme a de plus l'avantage de pouvoir être intégrée sur toutes les machines de nouvelle génération de fabrication additive équipées avec des DCN génériques.
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