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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
71

Optimal design of geothermal power plants

Clarke, Joshua 01 January 2014 (has links)
The optimal design of geothermal power plants across the entire spectrum of meaningful geothermal brine temperatures and climates is investigated, while accounting for vital real-world constraints that are typically ignored in the existing literature. The constrained design space of both double-flash and binary geothermal power plants is visualized, and it is seen that inclusion of real-world constraints is vital to determining the optimal feasible design of a geothermal power plant. The effect of varying condenser temperature on optimum plant performance and optimal design specifications is analyzed. It is shown that condenser temperature has a significant effect on optimal plant design as well. The optimum specific work output and corresponding optimal design of geothermal power plants across the entire range of brine temperatures and condenser temperatures is illustrated and tabulated, allowing a scientifically sound assessment of both feasibility and appropriate plant design under any set of conditions. The performance of genetic algorithms and particle swarm optimization are compared with respect to the constrained, non-linear, simulation-based optimization of a prototypical geothermal power plant, and particle swarm optimization is shown to perform significantly better than genetic algorithms. The Pareto-optimal front of specific work output and specific heat exchanger area is visualized and tabulated for binary and double-flash plants across the full range of potential geothermal brine inlet conditions and climates, allowing investigation of the specific trade-offs required between specific work output and specific heat exchanger area. In addition to the novel data, this dissertation research illustrates the development and use of a sophisticated analysis tool, based on multi-objective particle swarm optimization, for the optimal design of geothermal power plants.
72

PSO-algoritmy a možnosti jejich využití v kryptoanalýze. / PSO-algorithms and possibilities for their use in cryptanalysis.

Svetlíková, Lenka January 2011 (has links)
The aim of the thesis was to investigate the usage of PSO algorithm in the area of cryptanalysis. We applied PSO to the problem of simple substitution and to DES attack. By a modified version of PSO algorithm we achieved better or comparable results as by the usage of other biologically motivated algorithms. We suggested a method how to use PSO to attack DES and we were able to break it with the knowledge of only 20 plain texts and corresponding cipher texts. We have analyzed the reasons of failure to break more than a 4 rounds of DES and provided explanation for it. At the end we described the basic principles of differential cryptanalysis for DES and presented a specific mo- dification of PSO for searching optimal differential characteristics for DES. For simple ciphers, PSO is working efficiently but for sophisticated ciphers like DES, without in- corporating deep internal knowledge about the process into the algorithm, we could not expect significant outcomes. 1
73

Improved particle Swarm Optimisation algorithms / Des algorithmes améliorés de particules Swarm Optimisation

Sun, Yanxia 14 December 2011 (has links)
Optimisation Swarm Particle (PSO) est basé sur une métaphore de l'interaction sociale […] en ajustant les trajectoires des vecteurs individuels, appelés «particules» conceptualisées comme des points se déplaçant dans un espace multidimensionnel. Le poids aléatoire des paramètres de contrôle est utilisé pour provoquer les particules à aller stochastiquement vers une région ayant plus de succès dans un espace tridimensionnel. Les particules itératives ajustent leur vitesse et leur direction en fonction de leurs personnels et des meilleures positions dans l'essaim. PSO a été appliquée avec succès pour optimiser une large gamme de problèmes. Cependant, les algorithmes standard PSO sont facilement piégés dans les points locaux suboptimaux lorsqu'il est appliqué à des problèmes avec de nombreux extrema locaux ou avec des contraintes. Cette thèse présente plusieurs algorithmes / techniques pour améliorer la capacité de l'OPS recherche mondiale: 1) Deux nouveaux algorithmes chaotiques de particules essaim d'optimisation, d'avoir une chaotiques Hopfield Neural Network (HNN) la structure, sont proposées. L'utilisation d'un système chaotique pour déterminer les poids des particules aide des algorithmes OSP pour échapper à des extrema locaux et de trouver l'optimum global. 2) Pour les algorithmes existants OSP, la relation et l'influence compter que sur les composants correspondants dimensions de l'essaim de particules. Pour montrer la relation intérieure entre les différentes composantes d'une particule, les réseaux de neurones peuvent être utilisés pour modéliser les projections d'ordre du problème d'optimisation, et une optimisation des intérieurs entièrement connecté essaim de particules est proposé à cet effet. 3) En raison de la complexité des contraintes, une solution déterministe générale est souvent difficile à trouver. Par conséquent, une particule détendue contrainte optimisation par essaim algorithme est proposé. Cette méthode améliore la capacité de recherche de l'OSP. 4) Pour améliorer les performances de l'optimisation par essaim de particules, une méthode adaptative de particules essaim d'optimisation basée sur les tests d'hypothèses sont proposées. Cette méthode applique un test d'hypothèse pour déterminer si le piège des particules dans un minimum local ou non. 5) Afin de renforcer la capacité du MPSO de recherche globale, une approche adaptative multi-objectif l'optimisation par essaim de particules (MOPSO) est proposé. Les résultats de simulation et d'analyse confirment l'efficacité des algorithmes proposés / techniques par rapport à l'autre état d'algorithmes / Particle Swarm Optimisation (PSO) is based on a metaphor of social interaction such as birds flocking or fish schooling to search a space by adjusting the trajectories of individual vectors, called “particles” conceptualized as moving points in a multidimensional space. The random weights of the control parameters are used to cause the particles to stochastically move towards a successful region in a higher dimensional space. Particles iteratively adjust their speed and direction based on their personal best positions and the best position in the swarm. PSO has been successfully applied to optimise a wide range of problems. However, the standard PSO algorithms are easily trapped in local suboptimal points when applied to problems with many local extrema or with constraints. This thesis presents several algorithms/techniques to improve the PSO's global search ability: 1) Two new chaotic particle swarm optimisation algorithms, having a chaotic Hopfield Neural Network (HNN) structure, are proposed. Using a chaotic system to determine particle weights helps the PSO algoritms to escape from local extrema and to find the global optimum. 2) For the existing PSO algorithms, the relationship and influence only rely on the corresponding dimensional components of the particle swarm. To show the inner relationship among the different components of one particle, neural networks can be used to model the characteristcs of the optimisation problem, and an inner fully connected particle swarm optimisation is proposed for this purpose. 3) Due to the complexity of constraints, a general deterministic solution is often hard to find. Therefore, a relaxed constraint particle swarm optimisation algorithm is proposed. This method improves the PSO's search ability. 4) To improve the performance of particle swarm optimisation, an adaptive particle swarm optimisation method based on hypothesis testing is proposed. This method applies a hypothesis test to determine whether the particles trap into a local minimum or not. 5) To enhance the MPSO's global search ability, an adaptive multi-objective particle swarm optimisation (MOPSO) is proposed. Simulation and analytical results confirm the efficiency of the proposed algorithms/techniques when compared to the other state of the art algorithms
74

Optimalizační úlohy na bázi částicových hejn (PSO) / PSO-Particle Swarm Optimizations

Veselý, Filip Unknown Date (has links)
This work deals with swarm intelligence, strictly speaking particle swarm intelligence. It shortly describes questions of optimization and some optimization techniques. Part of this work is recherché of variants of particle swarm optimization algorithm. These algorithms are mathematically described. Their advantages or disadvantages in comparison with the basic PSO algorithm are mentioned. The second part of this work describes mQPSO algorithm and created modification mQPSOPC. Described algorithms are compared with each other and with another evolution algorithm on several tests.
75

An Information Value Approach to Route Planning for UAV Search and Track Missions

Pitre, Ryan R 17 December 2011 (has links)
This dissertation has three contributions in the area of path planning for Unmanned Aerial Vehicle (UAV) Search And Track (SAT) missions. These contributions are: (a) the study of a novel metric, G, used to quantify the value of the target information gained during a search and track mission, (b) an optimal planning horizon that minimizes time-error of a planning horizon when interrupted by Poisson random events, and (c) a modified Particle Swarm Optimization (PSO) algorithm for search missions that uses the prior target distribution in the generation of paths rather than just in the evaluation of them. UAV route planning is an important topic with many applications. Of these, military applications are the best known. This dissertation focuses on route planning for SAT missions that jointly optimize the conflicting objectives of detecting new targets and monitoring previously detected targets. The information theoretic approach proposed here is different from and is superior to existing approaches. One of the main differences is that G quantifies the value of the target information rather than the information itself. Several examples are provided to highlight G’s desirable properties. Another important component of path planning is the selection of a planning horizon, which specifies the amount of time to include in a plan. Unfortunately, little research is available to aid in the selection of a planning horizon. The proposed planning horizon is derived in the context of plan updates triggered by Poisson random events. To our knowledge, it is the only theoretically derived horizon available making it an important contribution. While the proposed horizon is optimal in minimizing planning time errors, simulation results show that it is also near optimal in minimizing the average time needed to capture an evasive target. The final contribution is the modified PSO. Our modification is based on the idea that PSO should be provided with the target distribution for path generation. This allows the algorithm to create candidate path plans in target rich regions. The modified PSO is studied using a search mission and is used in the study of G.
76

Modélisation, simulation et optimisation pour l'éco-fabrication / Modeling, simulation and optimization for sustainable manufacturing

Hassine, Hichem 09 February 2015 (has links)
Cette thèse se focalise sur la proposition et l’application des approches pour la modélisation de l’éco-fabrication. Ces approches permettent de préparer et simuler une démarche de fabrication des produits en assurant le couplage entre les objectifs écologiques et économiques.Les approches développées dans cette thèse sont basées sur les notions d’aide à la décision ainsi que l’optimisation multi objectifs. L’aide à la décision permet l’intervention en deux différents niveaux : le choix des impacts environnementaux à quantifier ainsi que le choix du scénario final de fabrication. Pour l’optimisation multi objectifs, elle assure le couplage entre les deux piliers principaux de l’éco-fabrication : l’écologie et l’économie. Au niveau de l’aide à la décision multi critères, les méthodes Evamix et Promethee ont été appliqués, tandis que les essaims particulaires ont été développés dans le cadre de l’optimisation multi objectifs.Ces approches ont été appliquées tout d’abord aux quelques opérations d’usinage : tournage et fraisage. Finalement, la chaîne de fabrication de l’acide phosphorique ainsi que celle d’acide sulfurique ont été le sujet de l’application des deux approches développées. / This thesis focuses on the proposal and implementation of approaches for modeling sustainable manufacturing. These approaches are used to prepare and simulate a process of manufacturing products providing coupling between environmental and economic objectives.The approaches developed in this thesis are based on the concepts of decision support as well as multi-objective optimization. The decision support allows intervention in two different levels: the choice of indicator to quantify the environmental impacts and the choice of the final manufacturing scenario. For multi-objective optimization, it provides the coupling between the two main pillars of sustainable manufacturing: ecology and economy. In terms of multi criteria decision aid methods, Evamix and Promethee were applied, while particulate swarms were developed as part of the multi-objective optimization. These approaches have been applied initially to some machining operations: turning and milling. Finally, the production line of phosphoric acid and sulfuric acid were the subject of application of the two approaches developed.
77

Markerless multiple-view human motion analysis using swarm optimisation and subspace learning

John, Vijay January 2011 (has links)
The fundamental task in human motion analysis is the extraction or capture of human motion and the established industrial technique is marker-based human motion capture. However, marker-based systems, apart from being expensive, are obtrusive and require a complex, time-consuming experimental setup, resulting in increased user discomfort. As an alternative solution, research on markerless human motion analysis has increased in prominence. In this thesis, we present three human motion analysis algorithms performing markerless tracking and classification from multiple-view studio-based video sequences using particle swarm optimisation and charting, a subspace learning technique.In our first framework, we formulate, and perform, human motion tracking as a multi-dimensional non-linear optimisation problem, solved using particle swarm optimisation (PSO), a swarm-intelligence algorithm. PSO initialises automatically, does not need a sequence-specific motion model, functioning as a blackbox system, and recovers from tracking divergence through the use of a hierarchical search algorithm (HPSO). We compare experimentally HPSO with particle filter, annealed particle filter and partitioned sampling annealed particle filter, and report similar or better tracking performance. Additionally we report an extensive experimental study of HPSO over ranges of values of its parameters and propose an automatic-adaptive extension of HPSO called as adaptive particle swarm optimisation. Next, in line with recent interest in subspace tracking, where low-dimensional subspaces are learnt from motion models of actions, we perform tracking in a low-dimensional subspace obtained by learning motion models of common actions using charting, a nonlinear dimensionality reduction tool. Tracking takes place in the subspace using an efficient modified version of particle swarm optimisation. Moreover, we perform a fast and efficient pose evaluation by representing the observed image data, multi-view silhouettes, using vector-quantized shape contexts and learning the mapping from the action subspace to shape space using multi-variate relevance vector machines. Tracking results with various action sequences demonstrate the good accuracy and performance of our approach.Finally, we propose a human motion classification algorithm, using charting-based low-dimensional subspaces, to classify human action sub-sequences of varying lengths, or snippets of poses. Each query action is mapped to a single subspace space, learnt from multiple actions. Furthermore we present a system in which, instead of mapping multiple actions to a single subspace, each action is mapped separately to its action-specific subspace. We adopt a multi-layered subspace classification scheme with layered pruning and search. One of the search layers involves comparing the input snippet with a sequence of key-poses extracted from the subspace. Finally, we identify the minimum length of action snippet, of skeletal features, required for classification, using competing classification systems as the baseline. We test our classification component on HumanEva and CMU mocap datasets, achieving similar or better classification accuracy than various comparable systems. human motion and the established industrial technique is marker-based human motion capture. However, marker-based systems, apart from being expensive, are obtrusive and require a complex, time-consuming experimental setup, resulting in increased user discomfort. As an alternative solution, research on markerless human motion analysis has increased in prominence. In this thesis, we present three human motion analysis algorithms performing markerless tracking and clas- si?cation from multiple-view studio-based video sequences using particle swarm optimisation and charting, a subspace learning technique. In our ?rst framework, we formulate, and perform, human motion tracking as a multi-dimensional non-linear optimisation problem, solved using particle swarm optimisation (PSO), a swarm-intelligence algorithm. PSO initialises automat- ically, does not need a sequence-speci?c motion model, functioning as a black- box system, and recovers from temporary tracking divergence through the use of a powerful hierarchical search algorithm (HPSO). We compare experiment- ally HPSO with particle ?lter, annealed particle ?lter and partitioned sampling annealed particle ?lter, and report similar or better tracking performance. Addi- tionally we report an extensive experimental study of HPSO over ranges of values of its parameters and propose an automatic-adaptive extension of HPSO called as adaptive particle swarm optimisation. Next, in line with recent interest in subspace tracking, where low-dimensional subspaces are learnt from motion models of actions, we perform tracking in a low-dimensional subspace obtained by learning motion models of common actions using charting, a nonlinear dimensionality reduction tool. Tracking takes place in the subspace using an e?cient modi?ed version of particle swarm optimisa- tion. Moreover, we perform a fast and e?cient pose evaluation by representing the observed image data, multi-view silhouettes, using vector-quantized shape contexts and learning the mapping from the action subspace to shape space us- ing multi-variate relevance vector machines. Tracking results with various action sequences demonstrate the good accuracy and performance of our approach. Finally, we propose a human motion classi?cation algorithm, using charting-based low-dimensional subspaces, to classify human action sub-sequences of varying lengths, or snippets of poses. Each query action is mapped to a single subspace space, learnt from multiple actions. Furthermore we present a system in which, instead of mapping multiple actions to a single subspace, each action is mapped separately to its action-speci?c subspace. We adopt a multi-layered subspace classi?cation scheme with layered pruning and search. One of the search lay- ers involves comparing the input snippet with a sequence of key-poses extracted from the subspace. Finally, we identify the minimum length of action snippet, of skeletal features, required for accurate classi?cation, using competing classi?ca- tion systems as the baseline. We test our classi?cation component on HumanEva and CMU mocap datasets, achieving similar or better classi?cation accuracy than
78

Tuning of Metaheuristics for Systems Biology Applications

Höghäll, Anton January 2010 (has links)
<p>In the field of systems biology the task of finding optimal model parameters is a common procedure. The optimization problems encountered are often multi-modal, i.e., with several local optima. In this thesis, a class of algorithms for multi-modal problems called metaheuristics are studied. A downside of metaheuristic algorithms is that they are dependent on algorithm settings in order to yield ideal performance.This thesis studies an approach to tune these algorithm settings using user constructed test functions which are faster to evaluate than an actual biological model. A statistical procedure is constructed in order to distinguish differences in performance between different configurations. Three optimization algorithms are examined closer, namely, scatter search, particle swarm optimization, and simulated annealing. However, the statistical procedure used can be applied to any algorithm that has configurable options.The results are inconclusive in the sense that performance advantages between configurations in the test functions are not necessarily transferred onto real biological models. However, of the algorithms studied a scatter search implementation was the clear top performer in general. The set of test functions used must be studied if any further work is to be made following this thesis.In the field of systems biology the task of finding optimal model parameters is a common procedure. The optimization problems encountered are often multi-modal, i.e., with several local optima. In this thesis, a class of algorithms for multi-modal problems called metaheuristics are studied. A downside of metaheuristic algorithms is that they are dependent on algorithm settings in order to yield ideal performance.</p><p>This thesis studies an approach to tune these algorithm settings using user constructed test functions which are faster to evaluate than an actual biological model. A statistical procedure is constructed in order to distinguish differences in performance between different configurations. Three optimization algorithms are examined closer, namely, scatter search, particle swarm optimization, and simulated annealing. However, the statistical procedure used can be applied to any algorithm that has configurable options.</p><p>The results are inconclusive in the sense that performance advantages between configurations in the test functions are not necessarily transferred onto real biological models. However, of the algorithms studied a scatter search implementation was the clear top performer in general. The set of test functions used must be studied if any further work is to be made following this thesis.</p>
79

Multidisciplinary Modeling, Control, and Optimization of a Solid Oxide Fuel Cell/Gas Turbine Hybrid Power System

Abbassi Baharanchi, Atid 01 January 2009 (has links)
This thesis describes a systematical study, including multidisciplinary modeling, simulation, control, and optimization, of a fuel cell - gas turbine hybrid power system that aims to increase the system efficiency and decrease the energy costs by combining two power sources. The fuel cell-gas turbine hybrid power systems can utilize exhaust fuel and waste heat from fuel cells in the gas turbines to increase system efficiency. This research considers a hybrid power system consisting of an internally reforming solid oxide fuel cell and a gas turbine. In the hybrid power system, the anode exhaust, which contains the remainder of the fuel, is mixed with the cathode exhaust as well as an additional supply of fuel and compressed air and then burned in a catalytic oxidizer. The hot oxidizer exhaust is expanded through the turbine section, driving an electric generator. After leaving the gas turbine, the oxidizer exhaust passes through a heat recovery unit in which it preheats the compressed air that is to be supplied to the fuel cell and the oxidizer. This research concentrates on multidisciplinary modeling and simulation of the fuel cell-gas turbine hybrid power system. Different control strategies for the power sharing between the subsystems are investigated. Also, the power electronics interfaces and controls for the hybrid power system are discussed. Two different power sharing strategies are studied and compared. Simulation results are presented and analyzed. Transient response of the hybrid energy system is studied through time-domain simulation. In addition, in this effort, Particle Swarm Optimization (PSO) is used to optimize the power sharing for the hybrid power system to increase the efficiency and decrease the fuel consumption.
80

Evidence Based Uncertainty Models and Particles Swarm Optimization for Multiobjective Optimization of Engineering Systems

Annamdas, Kiran Kumar Kishore 28 July 2009 (has links)
The present work develops several methodologies for solving engineering analysis and design problems involving uncertainties and evidences from multiple sources. The influence of uncertainties on the safety/failure of the system and on the warranty costs (to the manufacturer) are also investigated. Both single and multiple objective optimization problems are considered. A methodology is developed to combine the evidences available from single or multiple sources in the presence (or absence) of credibility information of the sources using modified Dempster Shafer Theory (DST) and Fuzzy Theory in the design of uncertain engineering systems. To optimally design a system, multiple objectives, such as to maximize the belief for the overall safety of the system, minimize the deflection, maximize the natural frequency and minimize the weight of an engineering structure under both deterministic and uncertain parameters, and subjected to multiple constraints are considered. We also study the various combination rules like Dempster's rule, Yager's rule, Inagaki's extreme rule, Zhang's center combination rule and Murphy's average combination rule for combining evidences from multiple sources. These rules are compared and a selection procedure was developed to assist the analyst in selecting the most suitable combination rule to combine various evidences obtained from multiple sources based on the nature of evidence sets. A weighted Dempster Shafer theory for interval-valued data (WDSTI) and weighted fuzzy theory for intervals (WFTI) were proposed for combining evidence when different credibilities are associated with the various sources of evidence. For solving optimization problems which cannot be solved using traditional gradient-based methods (such as those involving nonconvex functions and discontinuities), a modified Particle Swarm Optimization (PSO) algorithm is developed to include dynamic maximum velocity function and bounce method to solve both deterministic multi-objective problems and uncertain multi-objective problems (vertex method is used in addition to the modified PSO algorithm for uncertain parameters). A modified game theory approach (MGT) is coupled with the modified PSO algorithm to solve multi-objective optimization problems. In case of problems with multiple evidences, belief is calculated for a safe design (satisfying all constraints) using the vertex method and the modified PSO algorithm is used to solve the multi-objective optimization problems. The multiobjective problem related to the design of a composite laminate simply supported beam with center load is also considered to minimize the weight and maximize buckling load using modified game theory. A comparison of different warranty policies for both repairable and non repairable products and an automobile warranty optimization problem is considered to minimize the total warranty cost of the automobile with a constraint on the total failure probability of the system. To illustrate the methodologies presented in this work, several numerical design examples are solved. We finally present the conclusions along with a brief discussion of the future scope of the research.

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