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Beaumont, Matthew, i n/a. "Handling Over-Constrained Temporal Constraint Networks". Griffith University. School of Information Technology, 2004. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20041213.084512.
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Temporal reasoning has been an active research area for over twenty years, with most work focussing on either enhancing the efficiency of current temporal reasoning algorithms or enriching the existing algebras. However, there has been little research into handling over-constrained temporal problems except to recognise that a problem is over-constrained and then to terminate. As many real-world temporal reasoning problems are inherently over-constrained, particularly in the scheduling domain, there is a significant need for approaches that can handle over-constrained situations. In this thesis, we propose two backtracking algorithms to gain partial solutions to over-constrained temporal problems. We also propose a new representation, the end-point ordering model, to allow the use of local search algorithms for temporal reasoning. Using this model we propose a constraint weighting local search algorithm as well as tabu and random-restart algorithms to gain partial solutions to over-constrained temporal problems. Specifically, the contributions of this thesis are: The introduction and empirical evaluation of two backtracking algorithms to solve over-constrained temporal problems. We provide two backtracking algorithms to close the gap in current temporal research to solve over-constrained problems; The representation of temporal constraint networks using the end-point ordering model. As current representation models are not suited for local search algorithms, we develop a new model such that local search can be applied efficiently to temporal reasoning; The development of a constraint weighting local search algorithm for under-constrained problems. As constraint weighting has proven to be efficient for solving many CSP problems, we implement a constraint weighting algorithm to solve under-constrained temporal problems; An empirical evaluation of constraint weighting local search against traditional backtracking algorithms. We compare the results of a constraint weighting algorithm with traditional backtracking approaches and find that in many cases constraint weighting has superior performance; The development of a constraint weighting local search, tabu search and random-restart local search algorithm for over-constrained temporal problems. We extend our constraint weighting algorithm to solve under-constrained temporal problems as well as implement two other popular local search algorithms: tabu search and random-restart; An empirical evaluation of all three local search algorithms against the two backtracking algorithms. We compare the results of all three local search algorithms with our twobacktracking algorithms for solving over-constrained temporal reasoning problems and find that local search proves to be considerably superior.
2
Mahanta, Girish. "Video transmission over constrained-bandwidth channels". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ39991.pdf.
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Beaumont, Matthew. "Handling Over-Constrained Temporal Constraint Networks". Thesis, Griffith University, 2004. http://hdl.handle.net/10072/366603.
Pełny tekst źródłaStreszczenie:
Temporal reasoning has been an active research area for over twenty years, with most work focussing on either enhancing the efficiency of current temporal reasoning algorithms or enriching the existing algebras. However, there has been little research into handling over-constrained temporal problems except to recognise that a problem is over-constrained and then to terminate. As many real-world temporal reasoning problems are inherently over-constrained, particularly in the scheduling domain, there is a significant need for approaches that can handle over-constrained situations. In this thesis, we propose two backtracking algorithms to gain partial solutions to over-constrained temporal problems. We also propose a new representation, the end-point ordering model, to allow the use of local search algorithms for temporal reasoning. Using this model we propose a constraint weighting local search algorithm as well as tabu and random-restart algorithms to gain partial solutions to over-constrained temporal problems. Specifically, the contributions of this thesis are: The introduction and empirical evaluation of two backtracking algorithms to solve over-constrained temporal problems. We provide two backtracking algorithms to close the gap in current temporal research to solve over-constrained problems; The representation of temporal constraint networks using the end-point ordering model. As current representation models are not suited for local search algorithms, we develop a new model such that local search can be applied efficiently to temporal reasoning; The development of a constraint weighting local search algorithm for under-constrained problems. As constraint weighting has proven to be efficient for solving many CSP problems, we implement a constraint weighting algorithm to solve under-constrained temporal problems; An empirical evaluation of constraint weighting local search against traditional backtracking algorithms. We compare the results of a constraint weighting algorithm with traditional backtracking approaches and find that in many cases constraint weighting has superior performance; The development of a constraint weighting local search, tabu search and random-restart local search algorithm for over-constrained temporal problems. We extend our constraint weighting algorithm to solve under-constrained temporal problems as well as implement two other popular local search algorithms: tabu search and random-restart; An empirical evaluation of all three local search algorithms against the two backtracking algorithms. We compare the results of all three local search algorithms with our twobacktracking algorithms for solving over-constrained temporal reasoning problems and find that local search proves to be considerably superior.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Institute for Integrated and Intelligent Systems
Full Text
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Jampel, Michael Benjamin. "Over-constrained systems in CLP and CSP". Thesis, City University London, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.319633.
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Yu, Peng Ph D. Massachusetts Institute of Technology Department of Aeronautics and Astronautics. "Continuous relaxation to over-constrained temporal plans". Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/79336.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2013.This electronic version was submitted and approved by the author's academic department as part of an electronic thesis pilot project. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from department-submitted PDF version of thesis.
Includes bibliographical references (p. 165-168).
When humans fail to understand the capabilities of an autonomous system or its environmental limitations, they can jeopardize their objectives and the system by asking for unrealistic goals. The objective of this thesis is to enable consensus between human and autonomous system, by giving autonomous systems the ability to communicate to the user the reasons for goal failure and the relaxations to goals that archive feasibility. We represent our problem in the context of temporal plans, a set of timed activities that can represent the goals and constraints proposed by users. Over-constrained temporal plans are commonly encountered while operating autonomous and decision support systems, when user objectives are in conflict with the environment. Over constrained plans are addressed by relaxing goals and or constraints, such as delaying the arrival time of a trip, with some candidate relaxations being preferable to others. In this thesis we present Uhura, a temporal plan diagnosis and relaxation algorithm that is designed to take over-constrained input plans with temporal flexibility and contingencies, and generate temporal relaxations that make the input plan executable. We introduce two innovative approaches within Uhura: collaborative plan diagnosis and continuous relaxation. Uhura focuses on novel ways of satisfying three goals to make the plan relaxation process more convenient for the users: small perturbation, quick response and simple interaction. First, to achieve small perturbation, Uhura resolves over-constrained temporal plans through partial relaxation of goals, more specifically, through the relaxation of schedules. Prior work on temporal relaxations takes an all-or-nothing approach in which timing constraints on goals, such as arrival times to destinations, are completely relaxed in the relaxations. The Continuous Temporal Relaxation method used by Uhura adjusts the temporal bounds of temporal constraints to minimizes the perturbation caused by the relaxations to the goals in the original plan. Second, to achieve quick responses, Uhura introduces Best-first Conflict-directed Relaxation, a new method that efficiently enumerates alternative options in best-first order. The search space of alternative options to temporal planning problems is very large and finding the best one is a NP-hard problem. Uhura empirically demonstrates fast enumeration by unifying methods from minimal relaxation and conflict-directed enumeration methods, first developed for model based diagnosis. Uhura achieves two orders of magnitude improvement in run-time performance relative to state-of-the-art approaches, making it applicable to a larger group of real-world scenarios with complex temporal plans. Finally, to achieve simple interactions, Uhura presents to the user a small set of preferred relaxations in best-first order based on user preference models. By using minimal relaxations to represent alternative options, Uhura simplifies the options presented to the user and reduces the size of its results and improves their expressiveness. Previous work either generates minimal relaxations or full relaxations based on preference, but not minimal relaxations based on preference. Preferred minimal relaxations simplify the interaction in that the users do not have to consider any irrelevant information, and may reach an agreement with the autonomous system faster. Therefore it makes communication between robots and users more convenient and precise. We have incorporated Uhura within an autonomous executive that collaborates with human operators to resolve over-constrained temporal plans. Its effectiveness has been demonstrated both in simulation and in hardware on a Personal Transportation System concept. The average runtime of Uhura on large problems with 200 activities is two order of magnitude lower compared to current approaches. In addition, Uhura has also been used in a driving assistant system to resolve conflicts in driving plans. We believe that Uhura's collaborative temporal plan diagnosis capability can benefit a wide range of applications, both within industrial applications and in our daily lives.
by Peng Yu.
S.M.
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Bain, Stuart, i n/a. "Evolving Algorithms for Over-Constrained and Satisfaction Problems". Griffith University. School of Information and Communication Technology, 2007. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20071126.080227.
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The notion that a universally effective problem solver may still exist, and is simply waiting to be found, is slowly being abandoned in the light of a growing body of work reporting on the narrow applicability of individual heuristics. As the formalism of the constraint satisfaction problem remains a popular choice for the representation of problems to be solved algorithmically, there exists an ongoing need for new algorithms to effciently handle the disparate range of problems that have been posed in this representation. Given the costs associated with manually applying human algorithm development and problem solving expertise, methods that can automatically adapt to the particular features of a specific class of problem have begun to attract more attention. Whilst a number of authors have developed adaptive systems, the field, and particularly with respect to their application to constraint satisfaction problems, has seen only limited discussion as to what features are desirable for an adaptive constraint system. This may well have been a limiting factor with previous implementations, which have exhibited only subsets of the five features identified in this work as important to the utility of an adaptive constraint satisfaction system. Whether an adaptive system exhibits these features depends on both the chosen represen-tation and the method of adaptation. In this thesis, a three-part representation for constraint algorithms is introduced, which defines an algorithm in terms of contention, preference and selection functions. An adaptive system based on genetic programming is presented that adapts constraint algorithms described using the mentioned three-part representation. This is believed to be the first use of standard genetic programming for learning constraint algo-rithms. Finally, to further demonstrate the efficacy of this adaptive system, its performance in learning specialised algorithms for hard, real-world problem instances is thoroughly evaluated. These instances include random as well as structured instances from known-hard benchmark distributions, industrial problems (specifically, SAT-translated planning and cryptographic problems) as well as over-constrained problem instances. The outcome of this evaluation is a set of new algorithms - valuable in their own right - specifically tailored to these problem classes. Partial results of this work have appeared in the following publications: [1] Stuart Bain, John Thornton, and Abdul Sattar (2004) Evolving algorithms for constraint satisfaction. In Proc. of the 2004 Congress on Evolutionary Computation, pages 265-272. [2] Stuart Bain, John Thornton, and Abdul Sattar (2004) Methods of automatic algorithm generation. In Proc. of the 9th Pacific Rim Conference on AI, pages 144-153. [3] Stuart Bain, John Thornton, and Abdul Sattar. (2005) A comparison of evolutionary methods for the discovery of local search heuristics. In Australian Conference on Artificial Intelligence: AI'05, pages 1068-1074. [4] Stuart Bain, John Thornton, and Abdul Sattar (2005) Evolving variable-ordering heuristics for constrained optimisation. In Principles and Practice of Constraint Programming: CP'05, pages 732-736.
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Nesh-Nash, Ali. "Voice over IP in a resource constrained environment". Thesis, KTH, Kommunikationssystem, CoS, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-92257.
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Today, the telecommunication world is focused on mobility. This is popular because since the 1990s most people have integrated their mobile phones into their life. A new factor is the rise of the voice over IP(VoIP) technology, with VoIP over Wireless LANs (WLANs) as the clear next growth area for mobile communications. The purpose of this thesis was to understand how to save power based upon changing when some operations are performed in a VoIP client. In order to do this, we decided to port minisip to an HP iPAQ 5500 Personal Digital Assistant (PDA), in order to explore some of the issues of running such a client on a PDA - due to its constraints with regard to storage, processing power, and battery power. Minisip is a SIP open source user agent running on Linux and Windows. This thesis builds upon earlier theses which showed that minisip can offer a secure communications platform with the latest functions which are desired in a mobile personal VoIP system. However, most of these earlier theses utilized desktop, laptop, or server based system, i.e., with few resources constrains. The focus of this thesis was to examine the case of a highly constrained user platform such as an iPAQ.Dagens telekommunikationssystem fokuserar på mobilitet. Detta har blivit populärt under 90-talet då mobilitet blev naturligt integrerad i människans vardagliga liv i form av exempelvis mobiltelefoner. Voice over IP (VoIP) har blivit en stor del av dagen teknik där trådlösa system Wireless LANs (WLANs) har blivit en större del av mobilkommunikation. Målet med denna rapport är att förstå hur strömförbrukningen kan minimeras genom att utföra vissa operationer med hjälp av en VoIP-klient. För att åstadkomma detta porterade vi minisip, en SIP agent som är baserad på öppen källkod och körs på Linux och Windows, till en HP iPAQ 5500, en så kallad Personal Digital Assistant (PDA). Vi valde PDAn för att kunna utforska de begränsningar den medför i form av lagringsutrymme, processorkapacitet, och batteri. Denna rapport bygger vidare på tidigare rapporter som visar att minisip kan erbjuda en säker kommunikationsplattform med de senaste funktionerna som önskas i mobila VoIPsystem. De flesta av dessa tidigare rapporter baseras på system med få begränsningar rörande resurser såsom stationära- eller bärbara datorer samt serverbaserade system. Denna rapports fokus är att utforska detta fall i en miljö med större begränsningar på resurser som till exempel en iPAQ.
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Cheng, Huang. "A Resource-Constrained Coverage Protocol Over Urban VANETs". Thèse, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/30913.
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Vehicular ad hoc networks have emerged as a promising area of research in academic fields. However, it presents a challenge to design a realistic coverage protocol for ve- hicular networks, due to the service requirements, assorted mobility patterns, resource constraints and irregularity of the service area. It is also a challenge to meet a high quality of coverage with a tight deployment budget. In order to resolve these problems, this thesis proposes a resource-constrained coverage protocol with statistical analysis, which aims to consider the application demands, mobility patterns of vehicles, resource limitations, and geometrical attributes of road networks.
We study two types of resource-constrained coverage: the continuous coverage model and the sparse coverage model. We then reduce each model to a Knapsack Constrained Steiner Tree problem and a Maximum Coverage Problem, respectively. Since the two reduced problems are NP-hard, we resolve each of them with the Lagrangian Decompo- sition approach and greedy algorithm. By taking the dimensions of road segments into account, our coverage protocol provides a buffering operation scheme to suit different types of road topology. By discovering hotspots from the historical trace files, the pro- posed protocol is able to depict the mobility patterns and to discover the most valuable regions of a road system. To solve the problems of resource constraint, we provide two variants of continuous coverage and sparse coverage by taking budget constraint and quality constraint into consideration. The comparison with other mature algorithms verifies that our coverage protocol is reliable, and suitable for urban vehicular networks.
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Bain, Stuart. "Evolving Algorithms for Over-Constrained and Satisfaction Problems". Thesis, Griffith University, 2007. http://hdl.handle.net/10072/365848.
Pełny tekst źródłaStreszczenie:
The notion that a universally effective problem solver may still exist, and is simply waiting to be found, is slowly being abandoned in the light of a growing body of work reporting on the narrow applicability of individual heuristics. As the formalism of the constraint satisfaction problem remains a popular choice for the representation of problems to be solved algorithmically, there exists an ongoing need for new algorithms to effciently handle the disparate range of problems that have been posed in this representation. Given the costs associated with manually applying human algorithm development and problem solving expertise, methods that can automatically adapt to the particular features of a specific class of problem have begun to attract more attention. Whilst a number of authors have developed adaptive systems, the field, and particularly with respect to their application to constraint satisfaction problems, has seen only limited discussion as to what features are desirable for an adaptive constraint system. This may well have been a limiting factor with previous implementations, which have exhibited only subsets of the five features identified in this work as important to the utility of an adaptive constraint satisfaction system. Whether an adaptive system exhibits these features depends on both the chosen represen-tation and the method of adaptation. In this thesis, a three-part representation for constraint algorithms is introduced, which defines an algorithm in terms of contention, preference and selection functions. An adaptive system based on genetic programming is presented that adapts constraint algorithms described using the mentioned three-part representation. This is believed to be the first use of standard genetic programming for learning constraint algo-rithms. Finally, to further demonstrate the efficacy of this adaptive system, its performance in learning specialised algorithms for hard, real-world problem instances is thoroughly evaluated. These instances include random as well as structured instances from known-hard benchmark distributions, industrial problems (specifically, SAT-translated planning and cryptographic problems) as well as over-constrained problem instances. The outcome of this evaluation is a set of new algorithms - valuable in their own right - specifically tailored to these problem classes. Partial results of this work have appeared in the following publications: [1] Stuart Bain, John Thornton, and Abdul Sattar (2004) Evolving algorithms for constraint satisfaction. In Proc. of the 2004 Congress on Evolutionary Computation, pages 265-272. [2] Stuart Bain, John Thornton, and Abdul Sattar (2004) Methods of automatic algorithm generation. In Proc. of the 9th Pacific Rim Conference on AI, pages 144-153. [3] Stuart Bain, John Thornton, and Abdul Sattar. (2005) A comparison of evolutionary methods for the discovery of local search heuristics. In Australian Conference on Artificial Intelligence: AI'05, pages 1068-1074. [4] Stuart Bain, John Thornton, and Abdul Sattar (2005) Evolving variable-ordering heuristics for constrained optimisation. In Principles and Practice of Constraint Programming: CP'05, pages 732-736.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Information and Communication Technology
Faculty of Engineering and Information Technology
Full Text
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Al-Regib, Ghassan. "Delay-constrained 3-D graphics streaming over lossy networks". Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/15428.
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Kang, Intae. "Topology control for broadcasting over energy constrained wireless ad hoc networks /". Thesis, Connect to this title online; UW restricted, 2005. http://hdl.handle.net/1773/6061.
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Abu, Mahfouz Adnan Mohammed I. "Elliptic curve cryptosystem over optimal extension fields for computationally constrained devices". Pretoria : [s.n.], 2004. http://upetd.up.ac.za/thesis/available/etd-06082005-144557.
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Mahvidi, Hamid. "Performance of latency constrained turbo-like codes over correlated fading channels". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0024/MQ50386.pdf.
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Abu-Mahfouz, Adnan Mohammed. "Elliptic curve cryptosystem over optimal extension fields for computationally constrained devices". Diss., University of Pretoria, 2004. http://hdl.handle.net/2263/25330.
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Data security will play a central role in the design of future IT systems. The PC has been a major driver of the digital economy. Recently, there has been a shift towards IT applications realized as embedded systems, because they have proved to be good solutions for many applications, especially those which require data processing in real time. Examples include security for wireless phones, wireless computing, pay-TV, and copy protection schemes for audio/video consumer products and digital cinemas. Most of these embedded applications will be wireless, which makes the communication channel vulnerable. The implementation of cryptographic systems presents several requirements and challenges. For example, the performance of algorithms is often crucial, and guaranteeing security is a formidable challenge. One needs encryption algorithms to run at the transmission rates of the communication links at speeds that are achieved through custom hardware devices. Public-key cryptosystems such as RSA, DSA and DSS have traditionally been used to accomplish secure communication via insecure channels. Elliptic curves are the basis for a relatively new class of public-key schemes. It is predicted that elliptic curve cryptosystems (ECCs) will replace many existing schemes in the near future. The main reason for the attractiveness of ECC is the fact that significantly smaller parameters can be used in ECC than in other competitive system, but with equivalent levels of security. The benefits of having smaller key size include faster computations, and reduction in processing power, storage space and bandwidth. This makes ECC ideal for constrained environments where resources such as power, processing time and memory are limited. The implementation of ECC requires several choices, such as the type of the underlying finite field, algorithms for implementing the finite field arithmetic, the type of the elliptic curve, algorithms for implementing the elliptic curve group operation, and elliptic curve protocols. Many of these selections may have a major impact on overall performance. In this dissertation a finite field from a special class called the Optimal Extension Field (OEF) is chosen as the underlying finite field of implementing ECC. OEFs utilize the fast integer arithmetic available on modern microcontrollers to produce very efficient results without resorting to multiprecision operations or arithmetic using polynomials of large degree. This dissertation discusses the theoretical and implementation issues associated with the development of this finite field in a low end embedded system. It also presents various improvement techniques for OEF arithmetic. The main objectives of this dissertation are to --Implement the functions required to perform the finite field arithmetic operations. -- Implement the functions required to generate an elliptic curve and to embed data on that elliptic curve. -- Implement the functions required to perform the elliptic curve group operation. All of these functions constitute a library that could be used to implement any elliptic curve cryptosystem. In this dissertation this library is implemented in an 8-bit AVR Atmel microcontroller.Dissertation (MEng (Computer Engineering))--University of Pretoria, 2006.
Electrical, Electronic and Computer Engineering
unrestricted
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Bay, John S. "Constrained motion of a 3-D manipulator over unknown constraints : the robotic groping problem /". The Ohio State University, 1988. http://rave.ohiolink.edu/etdc/view?acc_num=osu148759165817468.
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Milchevski, Evica [Verfasser], i Sebastian [Akademischer Betreuer] Michel. "Similarity Search Algorithms over Top-k Rankings and Class-Constrained Objects / Evica Milchevski ; Betreuer: Sebastian Michel". Kaiserslautern : Technische Universität Kaiserslautern, 2019. http://d-nb.info/1194372554/34.
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Breun, Peter [Verfasser], Wolfgang [Akademischer Betreuer] Utschick i Michael [Akademischer Betreuer] Ulbrich. "Optimal Control Over Power Constrained Communication Channels / Peter Breun. Gutachter: Wolfgang Utschick ; Michael Ulbrich. Betreuer: Wolfgang Utschick". München : Universitätsbibliothek der TU München, 2013. http://d-nb.info/1042578206/34.
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Breun, Peter Verfasser], Wolfgang [Akademischer Betreuer] Utschick i Michael [Akademischer Betreuer] [Ulbrich. "Optimal Control Over Power Constrained Communication Channels / Peter Breun. Gutachter: Wolfgang Utschick ; Michael Ulbrich. Betreuer: Wolfgang Utschick". München : Universitätsbibliothek der TU München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20130423-1173158-0-2.
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Sjöholm, Klas. "Debugging Equation-Based Languages in OpenModelica Environment". Thesis, Department of Computer and Information Science, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-19866.
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The need for debugging tools for declarative programming languages has increased due to the rapid development of modeling and simulation tools/programs. Declarative equation-based programming languages have the problem of equation systems being over-, or under-constrained. This means that the system of equations has more equations than variables or more variables than equations respectively, making the system of equations unsolvable. In this study a static debugger is implemented in OpenModelica compiler for the equation-based programming language Modelica to make it easier for the programmer or modeler to locate the equation/s causing the unconstrained system of equations. The debugging techniques used by the debugger are developed by Peter Bunus. Those techniques are able to detect unconstrained systems of equations and give solutions by identifying the minimal set ofequation/s that should be removed or which variable/s should be added to an equation/s to make the system solvable. In this study the debugging techniques for detecting and giving a solution for over-constrained system of equations are shown suitable to be used for the programming language Modelica in the OpenModelica compiler.
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Hu, Hao. "Detection and treatment of inconsistent or locally over-constrained configurations during the manipulation of 3D geometric models made of free-form surfaces". Thesis, Paris, ENSAM, 2018. http://www.theses.fr/2018ENAM0002/document.
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Trois modules seront développés: Le module de détection a produit une analyse des problématiques figurations con, à savoir un ensemble de domaines où soit quelques nouveaux DDL ou des changements locaux dans les contraintes sont obligatoires. Le module de traitement permettra à la défi nition des mécanismes pour aider la décision sur modi cations. Le module de prédiction dire le degré de déformation en pré-analyser les caractéristiques des configurations de NURBSThree modules will be developed: The detection module has produced an analysis of problematic con figurations, i.e. a set of areas where either some new DOFs or some local changes in the constraints are mandatory. The treatment module will enable the defi nition of mechanisms to help the decision on modi cations. The prediction module will tell the degree of deformation by pre-analyzing the features of NURBS configurations
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Grose, Roger. "Cost-constrained project scheduling with task durations and costs that may increase over time : demonstrated with the U.S. Army future combat systems /". Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Jun%5FGrose.pdf.
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Grose, Roger T. "Cost-constrained project scheduling with task durations and costs that may increase over time demonstrated with the U.S. Army future combat systems /". Thesis, View thesis via NPS View thesis via DTIC, 2004. http://handle.dtic.mil/100.2/ADA424957.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, 2004.Title from title screen (viewed June 28, 2005). "June 2004." Includes bibliographical references (p. 59-61). Also issued in paper format.
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Ali, Anissa. "Représentation et analyse algébriques de système de solides sur-contraints en boucle fermée". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC062.
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Un système de solides peut être classé suivant trois états de mobilité: l’état non assemblé, l’état assemblé rigide et l’état assemblé mobile. L’étude se focalise sur les systèmes de solides sur-contraints en boucle fermée. Lors de l’étape de conception ou reconception, les dimensions d’un système de solides sur-contraints sont amenées à être modifiées, ce qui peut avoir pour conséquence la perte de son état de mobilité.L’approche présentée dans cette thèse a pour but de proposer une assistance au concepteur lors du redimensionnement, lui permettant de modifier ou conserver l’état de mobilité d’un système de solides. Le redimensionnement de systèmes de solides sur-contraints nécessite la connaissance de relations dépendant de leurs dimensions: les équations d’assemblage et les conditions de mobilité. Ces relations sont obtenues à l’aide d’un outil de résolution algébrique: les bases de Gröbner. La résolution algébrique est parfois coûteuse, voire impossible en un temps raisonnable, c’est ce qui justifie les méthodes décrites dans cette thèse.La solution proposée est composée de deux étapes principales. Tout d’abord, les représentations algébriques d’un système de solides fermé et mobile sont décrites. Les équations de fermeture d’un système de solides composé de plusieurs boucles sont obtenues en utilisant un paramétrage en coordonnées relatives. Les équations de mobilité sont elles générées à partir des équations de fermeture, à l’aide de méthodes directes ou incrémentales. Ensuite, afin de faciliter la génération des équations d’assemblage et de mobilité, une analyse algébrique reposant sur des outils d’analyse numérique est définie. L’état de mobilité du système de solides à redimensionner est déterminé à partir d’un ensemble de valeurs des paramètres le décrivant. Si le concepteur souhaite modifier l’état de mobilité du système de solides, de nouvelles valeurs sont alors générées. Lorsque l’état de mobilité souhaité est obtenu, il est possible de varier les dimensions tout en conservant cet état. Pour cela, certaines dimensions sont spécialisées afin de faciliter la génération des équations d’assemblage et des conditions de mobilité. Si les paramètres choisis sont liés ou trop nombreux, l’analyse mène inéluctablement à une absence de solutions. Des stratégies de partitionnement pour pallier ces problèmes sont aussi proposées. Enfin, les outils développés dans le logiciel Maple® afin d’illustrer les différents concepts proposés sont présentés, et un outil interactif permettant au concepteur de naviguer sur les équations de fermeture, équations d’assemblage et les conditions de mobilité obtenues après spécialisation, est proposéAn assembly can be partitioned into three mobility states: the impossible state, the rigid state and the mobile state. The study focuses in over-constrained closed-loop assemblies. During the process of design or re-design, the dimensions of the assembly can vary and this can lead to the loss of its mobility state.The method presented in this thesis aims at helping the designer to resize an assembly. There exist relationships between the dimension of the assembly that ensure the closure and the mobility of over-constrained. These relationships called assembly equations and mobility conditions are hence necessary to resize an over-constrained solid assembly. Assembly equations and mobility conditions are computed by a computer algebra tool: Gröbner bases. However, the algebraic solving using Gröbner bases can be costly and may fail because of unreasonable computing time, this is the main reason of the strategies described in this thesis.The approach proposed in this thesis is composed of two main steps. First of all, an algebraic representation of a closed assembly and a mobile assembly is descibed. The closed-loop equations are written by using a coordinate free method and the mobility equations are generated from the closed-loop equations using direct and incremental methods. To simplify the computation of assembly equations and mobility conditions an algebraic analysis that rely on numerical analysis tools is proposed. Starting from a set of values of the parameters that describe the assembly to resize, the mobility state of the assembly is determined. Then, if the designer want to change the mobility state, a new set of values that have the mobility state chosen by the designer is generated. Once the initial set of values has the right mobility state, some dimensions are specialized to ease the computation of assembly equations and mobility conditions. However, if the parameters chosen are linked or its number is to high, there is a high chance that the study lead to no solution. Strategies to avoid these problems are also proposed. Finally, the tools developped in Maple® software that illustrate the methods proposed are described and an interactive tool that permits the designer to visualize the solutions of the closed-loop equations, assembly equations and mobility conditions computed after specialisation is proposed
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De, Clercq Alexis. "Ordonnancement cumulatif avec dépassements de capacité : Contrainte globale et décompositions". Phd thesis, Ecole des Mines de Nantes, 2012. http://tel.archives-ouvertes.fr/tel-00794323.
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La programmation par contraintes est une approche intéressante pour traiter des problèmes d'ordonnancement. En ordonnancement cumulatif, les activités sont définies par leur date de début, leur durée et la quantité de ressource nécessaire à leur exécution. La ressource totale disponible (la capacité) en chaque instant est fixe. La contrainte globale Cumulative modélise ce problème en programmation par contraintes. Dans de nombreux cas pratiques, la date limite de fin d'un projet est fixée et ne peut être retardée. Dans ce cas, il n'est pas toujours possible de trouver un ordonnancement des activités qui n'engendre aucun dépassement de la capacité en ressource. On peut alors tolérer de relâcher la contrainte de capacité, dans une limite raisonnable, pour obtenir une solution. Nous proposons une nouvelle contrainte globale : la contrainte SoftCumulative qui étend la contrainte Cumulative pour prendre en compte ces dépassements de capacité. Nous illustrons son pouvoir de modélisation sur plusieurs problèmes pratiques, et présentons différents algorithmes de filtrage. Nous adaptons notamment les algorithmes de balayage et d'Edge-Finding à la contrainte SoftCumulative. Nous montrons également que certains problèmes pratiques nécessitent d'imposer des violations de capacité pour satisfaire des règles métiers, modélisées par des contraintes additionnelles. Nous présentons une procédure de filtrage originale pour traiter ces dépassements imposés. Nous complétons notre étude par une approche par décomposition. Enfin, nous testons et validons nos différentes techniques de résolution par une série d'expériences.
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Gouyou, Doriane. "Introduction de pièces déformables dans l’analyse de tolérances géométriques de mécanismes hyperstatiques". Thesis, Bordeaux, 2018. http://www.theses.fr/2018BORD0343/document.
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Les mécanismes hyperstatiques sont souvent utilisés dans l’industrie pour garantir une bonne tenue mécanique du système et une bonne robustesse aux écarts de fabrication des surfaces. Même si ces assemblages sont très courants, les méthodologies d’analyse de tolérances de ces mécanismes sont difficiles à mettre en oeuvre.En fonction de ses écarts de fabrication, un assemblage hyperstatique peut soit présenter des interférences de montage, soit être assemblé avec jeu. Dans ces travaux de thèse, nous avons appliqué la méthode des polytopes afin de détecter les interférences de montage. Pour un assemblage donné, le polytope résultant du mécanisme est calculé. Si ce polytope est non vide, l’assemblage ne présente pas d’interférence. Si ce polytope est vide, l’assemblage présente des interférences de montage. En fonction du résultat obtenu, deux méthodes d’analyse distinctes sont proposées.Si l’assemblage est réalisable sans interférence le polytope résultant du mécanisme permet de conclure sur sa conformité au regard de l’exigence fonctionnelle. Si l’assemblage présente des interférences de montage, une analyse prenant en compte la raideur des pièces est réalisée. Cette approche est basée sur une réduction de modèle avec des super-éléments. Elle permet de déterminer rapidement l’état d’équilibre du système après assemblage. Un effort de montage est ensuite estimé à partir de ces résultats pour conclure sur la faisabilité de l’assemblage. Si l’assemblage est déclaré réalisable, la propagation des déformations dans les pièces est caractérisée pour vérifier la conformité du système au regard de l’exigence fonctionnelle.La rapidité de mise en oeuvre de ces calculs nous permet de réaliser des analyses de tolérances statistiques par tirage de Monte Carlo pour estimer les probabilités de montage et de respect d’une Condition FonctionnelleOver-constrained mechanisms are often used in industries to ensure a good mechanical strength and a good robustness to manufacturing deviations of parts. The tolerance analysis of such assemblies is difficult to implement.Indeed, depending on the geometrical deviations of parts, over-constrained mechanisms can have assembly interferences. In this work, we used the polytope method to check whether the assembly has interferences or not. For each assembly, the resulting polytope of the mechanism is computed. If it is non empty, the assembly can be performed without interference. If not, there is interferences in the assembly. According to the result, two different methods can be implemented.For an assembly without interference, the resulting polytope enables to check directly its compliance. For an assembly with interferences, a study taking into account the stiffness of the parts is undertaken. This approach uses a model reduction with super elements. It enables to compute quickly the assembly with deformation. Then, an assembly load is computed to conclude on its feasibility. Finally, the spreading of deformation through the parts is calculated to check the compliance of the mechanism.The short computational time enables to perform stochastic tolerance analyses in order to provide the rates of compliant assemblies
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Connie, Ashfiqua Tahseen. "Efficient transmission of error resilient H.264 video over wireless links". Thesis, University of British Columbia, 2008. http://hdl.handle.net/2429/1979.
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With the advent of telecommunication technology, the need to transport multimedia content is increasing day by day. Successful video transmission over the wireless network faces a lot of challenges because of the limited resource and error prone nature of the wireless environment. To deal with these two challenges, not only the video needs to be compressed very efficiently but also the compression scheme needs to provide some error resilient features to deal with the high packet loss probability. In this thesis, we have worked with the H.264/ Advanced Video Coding (AVC) video compression standard since this is the most recent and most efficient video compression scheme. Also H.264 provides novel error resilient features e.g. slicing of the frame, Flexible Macroblock Ordering (FMO), data partitioning etc.
In this thesis, we investigate how to utilize the error resilient schemes of H.264 to ensure a good quality picture at the receiving end. In the first part of the thesis, we find the optimum slice size that will enhance the quality of video transmission in a 3G environment. In the second part, we jointly optimize the data partitioning property and partial reliability extension property of the new transport layer protocol, Stream Control Transmission Protocol (SCTP). In the third and last part, we focus more on the network layer issues. We obtain the optimum point of application layer Forward Error Correction (FEC) and Medium Access Control (MAC) layer retransmission in a capacity constrained network. We assume that the bit rate assigned for the video application is more than the video bit rate so that the extra capacity available can be used for error correction.
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Wilczynski, Anaëlle. "Interaction entre agents modélisée par un réseau social dans des problématiques de choix social computationnel Strategic Voting in a Social Context: Considerate Equilibria Object Allocation via Swaps along a Social Network Local Envy-Freeness in House Allocation Problems Constrained Swap Dynamics over a Social Network in Distributed Resource Reallocation Poll-Confident Voters in Iterative Voting". Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLED073.
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Le choix social repose sur l’étude de la prise de décision collective, où un ensemble d’individus doit convenir d’une solution commune en fonction des préférences de ses membres. Le problème revient à déterminer comment agréger les préférences de différents agents en une décision acceptable pour le groupe. Typiquement, les agents interagissent dans des processus de décision collective, notamment en collaborant ou en échangeant des informations. Il est communément supposé que tout agent est capable d’interagir avec n’importe quel autre. Or, cette hypothèse paraît irréaliste pour de nombreuses situations. On propose de relâcher cette hypothèse en considérant que la possibilité d’interaction est déterminée par un réseau social, représenté par un graphe sur les agents. Dans un tel contexte, on étudie deux problèmes de choix social : le vote stratégique et l’allocation de ressources. L’analyse se concentre sur deux types d’interaction : la collaboration entre les agents, et la collecte d’information. On s’intéresse à l’impact du réseau social, modélisant une possibilité de collaboration entre les agents ou une relation de visibilité, sur la résolution et les solutions de problèmes de vote et d’allocation de ressources. Nos travaux s’inscrivent dans le cadre du choix social computationnel, en utilisant pour ces questions des outils provenant de la théorie des jeux algorithmique et de la théorie de la complexitéSocial choice is the study of collective decision making, where a set of agents must make a decision over a set of alternatives, according to their preferences. The question relies on how aggregating the preferences of the agents in order to end up with a decision that is commonly acceptable for the group. Typically, agents can interact by collaborating, or exchanging some information. It is usually assumed in computational social choice that every agent is able to interact with any other agent. However, this assumption looks unrealistic in many concrete situations. We propose to relax this assumption by considering that the possibility of interaction is given by a social network, represented by a graph over the agents.In this context, we study two particular problems of computational social choice: strategic voting and resource allocation of indivisible goods. The focus is on two types of interaction: collaboration and information gathering. We explore how the social network,modelingapossibilityofcollaboration or a visibility relation among the agents, can impact the resolution and the solution of voting and resource allocation problems. These questions are addressed via computational social choice by using tools from algorithmic game theory and computational complexity
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Ben, Zid Maha. "Emploi de techniques de traitement de signal MIMO pour des applications dédiées réseaux de capteurs sans fil". Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENT017/document.
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Dans ce travail de thèse, on s'intéresse é l'emploi de techniques de traitement de signal de systèmes de communication MIMO (Multiple Input Multiple Output) pour des applications aux réseaux de capteurs sans fil. Les contraintes énergétiques de cette classe de réseau font appel à des topologies particulières et le réseau peut être perçu comme étant un ensemble de grappes de nœuds capteurs. Ceci ouvre la porte à des techniques avancées de communication de type MIMO. Dans un premier temps, les différents aspects caractérisant les réseaux de capteurs sans fil sont introduits. Puis, les efforts engagés pour optimiser la conservation de l'énergie dans ces réseaux sont résumés. Les concepts de base de systèmes MIMOs sont abordés dans le deuxième chapitre et l'exploration par voie numérique de différentes pistes de la technologie MIMO sont exposées. Nous nous intéressons à des techniques de diversité de polarisation dans le cadre de milieux de communication riches en diffuseurs. Par la suite, des méthodes de type beamforming sont proposées pour la localisation dans les réseaux de capteurs sans fil. Le nouvel algorithme de localisation est présenté et les performances sont évaluées. Nous identifions la configuration pour la communication inter-grappes qui permet pour les meilleurs compromis entre énergie et efficacité spectrale dans les réseaux de capteurs sans fil. Finalement, nous envisageons la technique de sélection de nœuds capteurs afin de réduire la consommation de l'énergie dans le réseau de capteur sans filThe aim of this work is to study from a signal processing point of view the use of MIMO (Multiple Input Multiple Output) communication systems for algorithms dedicated to wireless sensor networks. We investigate energy-constrained wireless sensor networks and we focus on cluster topology of the network. This topology permits for the use of MIMO communication system model. First, we review different aspects that characterize the wireless sensor network. Then, we introduce the existing strategies for energy conservation in the network. The basic concepts of MIMO systems are presented in the second chapter and numerical results are provided for evaluating the performances of MIMO techniques. Of particular interest, polarization diversity over rich scattering environment is studied. Thereafter, beamforming approach is proposed for the development of an original localization algorithm in wireless sensor network. The novel algorithm is described and performances are evaluated by simulation. We determine the optimal system configuration between a pair of clusters that permits for the highest capacity to energy ratio in the fourth chapter. The final chapter is devoted to sensor nodes selection in wireless sensor network. The aim of using such technique is to make energy conservation in the network
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Mahanta, Girish. "Video transmission over constrained bandwidth channels". Thesis, 1997. http://spectrum.library.concordia.ca/425/1/MQ39991.pdf.
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Multimedia applications are often considered adaptive in the sense that their behaviour can be adapted to the available resources. One way to achieve this is through a selective dropping of media frames. Different media types have different tolerance to loss, for example, humans are more sensitive to loss of continuity in audio as compared to video. It is, therefore, attractive to develop best effort services targeted for a particular media type (e.g., video). Such a service should provide graceful performance degradation as resources become scarce by exploiting the particular characteristics of the media type. In this thesis, we consider providing a best effort service targeted for video transmission, by multiplexing multiple video streams over a reserved bandwidth network channel. The emerging services architecture in ATM networks as well as the Internet provide the capability to reserve resources such as bandwidth, and to use them to provide higher level services. We use simulation to consider the effect of different scheduling and buffer management policies on the performance when the bandwidth is scarce and losses are inevitable. By using effective frame rate as a performance measure, we show that FIFO scheduling is unable to ensure fairness in terms of equitable performance degradation of the multiplexed streams. Our simulations reveal that explicit bandwidth allocation is required, and that this bandwidth allocation must be (1) targeted to ensure that the performance of each of the multiplexed streams degrades equitably, and (2) must be dynamically changed to take advantage of the time varying characteristics of video data
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林舜華. "Delay Constrained Scheduling over Fading Channels". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/24216713717318405780.
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碩士國立交通大學
電信工程研究所
101
For many wireless transmitters, since most devices are battery powered, increased energy e±ciency in data transmission provides signi¯cant bene¯ts. Higher energy e±- ciency may result in prolonging the lifetime of the battery. We seek to ¯nd an energy-saving scheduler that sends a packet of R bits within a hard delay deadline K over fading channels. The scheduling policies needs to determine the number of bits transmitted in the current time slot with only the knowledge of current channel state information and the channel statistics of the future channel while satisfying the quality of service QOS constraints as the deadline expired in order to minimize the total energy consump- tion. In this thesis, we will focus on the interaction between fading, hard deadlines, and causal channel information by studying transmission of only a single packet, and thus do not consider random arrivals since there are applications with deterministic packet arrivals, i.e., VoIP or video streaming where packets arrive regularly and each must be received within a short delay window. Although it is more reasonable to consider ran- dom arrivals and outage probability that allows few packets missing, to emphasize the relationship between fading, hard deadlines, and causal channel information, we only consider a fundamental scheduling problem that one packet and no outage is allowed. An optimal non-causal scheduling policy is derived by inverse water-¯lling (IWF) method and an optimal causal scheduling policy is also derived for total time slots K = 2. We also develop a dynamic programming formulation that leads to an optimal transmission schedule, however, it is hard to express as a closed form when K > 2. Thus, we propose two suboptimal scheduler which give simple structure for general problems, and one utilizes central limit theorem (CLT) for approximation while the other is inspired by the IWF method. The policies are composed of a linear combination of channel-awareness term and delay-awareness term. The numerical results show that the proposed policies are nearly optimal when R is large. In addition, we extend our work to multiple user case. At the ¯rst phase, we only have the channel pdfs of users. Since delay constraint speci¯es only that the rate is achieved in K blocks, the order of which the users are scheduled within the K blocks is not important in this phase, so the scheduling boils down to sorting out the number of blocks being allocated to each user. After deciding the number of blocks allocated to each user, the problem can be treated as independent single-user single-carrier problems with competitions. With multiple users, the scheduling problem is composed of distributing resources, channel assignment that the transmitter requires to decide which user occupies the channel at any given time slot by order statistic method and bit allocation that how many bits should be allocated in order to minimize the total energy consumption of all users.
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Raposo, André Filipe Mendes. "Wireless communication over NFC with a constrained resouce device". Master's thesis, 2010. http://hdl.handle.net/10216/61304.
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Raposo, André Filipe Mendes. "Wireless communication over NFC with a constrained resouce device". Dissertação, 2010. http://hdl.handle.net/10216/61304.
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Rojas, Norman Alejandro Jose. "Feedback control over signal to noise ratio constrained communication channels". Thesis, 2006. http://hdl.handle.net/1959.13/24913.
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The present thesis addresses the problem of stabilisability of a linear time invariant (LTI) output feedback control loop in the presence of a communication link. The communication link itself can be either located between the controller and the plant or between the plant and the controller. The communication link is assumed to be an additive coloured Gaussian noise channel with (or without) bandwidth limitation (memory) in the continuous-(or discrete-)time domain. The requirement for stabilisability of the feedback loop is then characterised as a lower bound on the channel signal to noise ratio (SNR). This lower bound is tight and it will depend on the channel model, plant and channel model NMP zeros, plant time delay and plant unstable poles. Performance requirements are also investigated, by loop shaping in the continuous-time domain, whilst a linear quadratic Gaussian (LQG) control approach is suggested for the discrete-time domain.PhD Doctorate
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Rojas, Norman Alejandro Jose. "Feedback Control over Signal to Noise Ratio Constrained Communication Channels". 2006. http://hdl.handle.net/1959.13/24913.
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The present thesis addresses the problem of stabilisability of a linear time invariant (LTI) output feedback control loop in the presence of a communication link. The communication link itself can be either located between the controller and the plant or between the plant and the controller. The communication link is assumed to be an additive coloured Gaussian noise channel with (or without) bandwidth limitation (memory) in the continuous-(or discrete-)time domain. The requirement for stabilisability of the feedback loop is then characterised as a lower bound on the channel signal to noise ratio (SNR). This lower bound is tight and it will depend on the channel model, plant and channel model NMP zeros, plant time delay and plant unstable poles. Performance requirements are also investigated, by loop shaping in the continuous-time domain, whilst a linear quadratic Gaussian (LQG) control approach is suggested for the discrete-time domain.PhD Doctorate
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Nagaraj, B. P. "Kinematic And Static Analysis Of Over-Constrained Mechanisms And Deployable Pantograph Masts". Thesis, 2009. http://hdl.handle.net/2005/1014.
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Foldable and deployable space structures refer to a broad category of pre-fabricated structures that can be transformed from a compact folded configuration to a predetermined expanded configuration. Such deployable structures are stable and can carry loads. These structures are also mechanisms with one degree of freedom in their entire transformation stages whether in the initial folded form or in the final expanded configuration. Usually, pantograph mechanisms or a scissor-like elements (SLEs) are part of such deployable structures. A new analysis tool to study kinematic and static analyses of foldable and deployable space structures /mechanisms, containing SLEs, has been developed in this thesis.
The Cartesian coordinates are used to study the kinematics of large deployable structures. For many deployable structures the degree of freedom derived using the standard Grubler-Kutzback criteria, is found to be less than one even though the deployable structure /mechanism can clearly move. In this work the dimension of nullspace of the derivatives of the constraint equations are used to obtain the correct degrees of freedom of deployable structure. A numerical algorithm has been developed to identify the redundant joints /links in the deployable structure /mast which results in the incorrect degrees of freedom obtained by using the Grubler-Kutzback criteria. The effectiveness of the algorithm has been illustrated with several examples consisting of triangular, box shaped SLE mast and an eighteen-sided SLE ring with revolute joints. Further more the constraint Jacobian matrix is also used to evaluate the global degrees of freedom of deployable masts/structures. Closed-form kinematic solutions have been obtained for the triangular and box type masts and finally, as a generalization, extended to a general n-sided SLE based ring structure.
The constraint Jacobian matrix based approach has also been extended to obtain the load carrying characteristics of deployable structures with SLEs in terms of deriving the stiffness matrix of the structure. The stiffness matrix has been obtained in the symbolic form and it matches results obtained from other commonly used techniques such as force and displacement methods. It is shown that the approach developed in this thesis is applicable for all types of practical masts with revolute joints where the revolute joint constraints are made to satisfy through the method of Lagrange multipliers and a penalty formulation. To demonstrate the effectiveness of the new method, the procedure is applied to solving (i) a simple hexagonal SLE mast, and (ii) a complex assembly of four hexagonal masts and the results are presented.
In summary, a complete analysis tool to study masts with SLEs has been developed. It is shown that the new tool is effective in evaluating the redundant links /joints there by over coming the problems associated with the well –known Grubler-Kutzback criteria. Closed-form kinematic solutions of triangular and box SLE masts as well as a general n-sided SLE ring with revolute joints has been obtained. Finally, the constraint Jacobian based method is used to evaluate the stiffness matrix for the SLE masts. The theory and algorithms presented in this thesis can be extended to masts of different shapes and for the stacked masts.
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Wang, Wei. "Quality-driven cross layer design for multimedia security over resource constrained wireless sensor networks". 2009. http://proquest.umi.com/pqdweb?did=1933031681&sid=9&Fmt=2&clientId=14215&RQT=309&VName=PQD.
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Thesis (Ph.D.)--University of Nebraska-Lincoln, 2009.Title from title screen (site viewed March 2, 2010). PDF text: ix, 110 p. : ill. (chiefly col.) ; 3 Mb. UMI publication number: AAT 3386564. Includes bibliographical references. Also available in microfilm and microfiche formats.
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Yen, Shih-Chia, i 嚴仕佳. "Time-Constrained Aggregated ARQ with an Adaptive Rate Control for SVC Streaming over Wireless LAN". Thesis, 2012. http://ndltd.ncl.edu.tw/handle/16319233243840335345.
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碩士國立中正大學
通訊工程研究所
100
With the advances in voice, video compression and broadband technology, multimedia streaming services become an integral part of daily life. Multimedia streaming using Scalable Video Coding (SVC) mechanism to improve the transmission quality of the multimedia network, to better meets the application requirements in the various terminal devices in a distributed heterogeneous network environment. TCP sliding window mechanism adjust its sending rate too violent, and its retransmission mechanism for real-time video packet recovery may suffer a long round trip time delay has made the protocol not an ideal candidate for streaming applications. However, given the lack of inbuilt congestion and flow control mechanisms within UDP may cause the occurrence of network congestion, and also UDP does not provide retransmission mechanism to ensure the integrity of the video data. In this paper, we proposed UDP as transport protocol and added aggregated ARQ with time-constrained at application layer to solve the reliability problem of transmission. Through the aggregated ARQ to avoid per-packet ACK leads to generate too many ACKs and causes channel contention, thus degrading the throughput. In adaptive rate control, we refer to the AIMD rate control mechanism and consider packet loss due to changes in channel quality over WLAN. Finally, we integrate the above methods to design a suitable transmission control protocol for SVC multimedia streaming over WLAN environment.
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Pholotho, Tholo Johannes. "Toward a broadband service delivery model over wireless technologies to resource-constrained public high schools in South Africa". Diss., 2017. http://hdl.handle.net/10500/23229.
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Information and Communication Technologies (ICTs) are capable of expanding access to quality education, educational resources, and also provide teachers with new skills. Nevertheless, a majority of rural public schools have limited ICTs, mainly due to geographical landscape, lack of service delivery and poverty. As a result, they currently seem not to be adequately benefiting from current advancements in ICTs. The main objective of this research study was to investigate an appropriate broadband services delivery model using wireless access technologies, such as a Global System for Mobile communication (GSM) and Enhanced data rates for GSM Evolution (EDGE) to deliver electronic-based educational information to resource-constrained public high schools. An exploratory case study approach was adopted to identify and understand the challenges faced by rural schools in the Greater Tubatse Municipality (GTM), including educational services and content considered by the schools as relevant and useful. The research results indicate that resource-constrained schools in the GTM are facing challenges of lack of access to electronic educational information and services, and as a result, teaching and learning becomes limiting and challenging. Based on the research findings, the results show that having access to learning material via electronic platforms could afford educators and learners the opportunity to interact with the outside world, improve learning and teaching and benefit the community as a whole.
The broadband services delivery conceptual model (BSDCM) was proposed, developed and evaluated to address the lack of electronic educational information and services for resource-constrained public high schools. The BSDCM is composed of both technical and non-technical components that consider requirements of all role players, ICT challenges, policy makers and Information Communication Technology for Education (ICT4ED) interventions.
The proposed model addressed some of the challenges regarding lack of access to educational content. However, it is recommended that the ICT4ED policies governing the use of mobile devices in the classrooms be introduced by the relevant authorities. In addition, a comparative analysis of other network technologies should be conducted to establish if the TCP/IP header compression on Point to Point Protocol (PPP) improves the performance of the network in resource-constrained environments. Furthermore, it is recommended that further research and experiments be conducted to determine if other various third party content providers could create and deploy various educational services and content for different computing platforms using the proposed BSDCM.School of Computing
M. Tech (Information Technology)
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Ash, Michael R. "Constrained inversion of gravity data over the Ovoid and mini-ovoid in the Voisey's Bay Ni-Cu-Co deposit, Labrador /". 2007. http://collections.mun.ca/u?/theses,146575.
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林儀甄. "An Action Research on How A School Counselor Developed Antagonistic Reaction Against Constrained Scenario Where Student Counselling Work Become Over-medicalized and Programmed under the Frame of Gender Equality Education Act". Thesis, 2019. http://ndltd.ncl.edu.tw/handle/4m2k3k.
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