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Zhou, Keming. "Computation of asymmetric fault current in complex power systems." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.287924.
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Bremner, Jonathan James. "Complex torque coefficient analysis of multi-device power systems." Thesis, University of Glasgow, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.362955.
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Berry, T. "Real time simulation of complex power systems using parallel processors." Thesis, University of Bath, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.328841.
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Liu, Zifan. "Complex systems and health systems, computational challenges." Thesis, Versailles-St Quentin en Yvelines, 2015. http://www.theses.fr/2015VERS001V/document.
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Le calcul des valeurs propres intervient dans des modèles de maladies d’épidémiques et pourrait être utilisé comme un allié des campagnes de vac- cination dans les actions menées par les organisations de soins de santé. La modélisation épidémique peut être considérée, par analogie, comme celle des viruses d’ordinateur qui dépendent de l’état de graphe sous-jacent à un moment donné. Nous utilisons PageRank comme méthode pour étudier la propagation de l’épidémie et d’envisager son calcul dans le cadre de phé- nomène petit-monde. Une mise en œuvre parallèle de méthode multiple de "implicitly restar- ted Arnoldi method" (MIRAM) est proposé pour calculer le vecteur propre dominant de matrices stochastiques issus de très grands réseaux réels. La grande valeur de "damping factor" pour ce problème fait de nombreux algo- rithmes existants moins efficace, tandis que MIRAM pourrait être promet- teuse. Nous proposons également dans cette thèse un générateur de graphe parallèle qui peut être utilisé pour générer des réseaux synthétisés distri- bués qui présentent des structures "scale-free" et petit-monde. Ce générateur pourrait servir de donnée pour d’autres algorithmes de graphes également. MIRAM est mis en œuvre dans le cadre de trilinos, en ciblant les grandes données et matrices creuses représentant des réseaux sans échelle, aussi connu comme les réseaux de loi de puissance. Hypergraphe approche de partitionnement est utilisé pour minimiser le temps de communication. L’al- gorithme est testé sur un grille national de Grid5000. Les expériences sur les très grands réseaux tels que Twitter et Yahoo avec plus de 1 milliard de nœuds sont exécutées. Avec notre mise en œuvre parallèle, une accélération de 27× est satisfaite par rapport au solveur séquentielThe eigenvalue equation intervenes in models of infectious disease prop- agation and could be used as an ally of vaccination campaigns in the ac- tions carried out by health care organizations. The epidemiological model- ing techniques can be considered by analogy, as computer viral propagation which depends on the underlying graph status at a given time. We point out PageRank as method to study the epidemic spread and consider its calcula- tion in the context of small-world phenomenon. A parallel implementation of multiple implicitly restarted Arnoldi method (MIRAM) is proposed for calculating dominant eigenpair of stochastic matrices derived from very large real networks. Their high damp- ing factor makes many existing algorithms less efficient, while MIRAM could be promising. We also propose in this thesis a parallel graph gen- erator that can be used to generate distributed synthesized networks that display scale-free and small-world structures. This generator could serve as a testbed for graph related algorithms. MIRAM is implemented within the framework of Trilinos, targeting big data and sparse matrices representing scale-free networks, also known as power law networks. Hypergraph partitioning approach is employed to minimize the communication overhead. The algorithm is tested on a nation wide cluster of clusters Grid5000. Experiments on very large networks such as twitter and yahoo with over 1 billion nodes are conducted. With our parallel implementation, a speedup of 27× is met compared to the sequential solver
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Oliver, John M. "Multi-objective optimisation methods applied to complex engineering systems." Thesis, Cranfield University, 2014. http://dspace.lib.cranfield.ac.uk/handle/1826/11707.
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This research proposes, implements and analyses a novel framework for multiobjective
optimisation through evolutionary computing aimed at, but not restricted
to, real-world problems in the engineering design domain.
Evolutionary algorithms have been used to tackle a variety of non-linear multiobjective
optimisation problems successfully, but their success is governed by key
parameters which have been shown to be sensitive to the nature of the particular
problem, incorporating concerns such as the number of objectives and variables,
and the size and topology of the search space, making it hard to determine the best
settings in advance. This work describes a real-encoded multi-objective optimising
evolutionary algorithm framework, incorporating a genetic algorithm, that uses
self-adaptive mutation and crossover in an attempt to avoid such problems, and
which has been benchmarked against both standard optimisation test problems in
the literature and a real-world airfoil optimisation case.
For this last case, the minimisation of drag and maximisation of lift coefficients
of a well documented standard airfoil, the framework is integrated with a freeform
deformation tool to manage the changes to the section geometry, and XFoil,
a tool which evaluates the airfoil in terms of its aerodynamic efficiency. The
performance of the framework on this problem is compared with those of two
other heuristic MOO algorithms known to perform well, the Multi-Objective Tabu
Search (MOTS) and NSGA-II, showing that this framework achieves better or at
least no worse convergence. The framework of this research is then considered as a candidate for smart
(electricity) grid optimisation. Power networks can be improved in both technical
and economical terms by the inclusion of distributed generation which may
include renewable energy sources. The essential problem in national power networks
is that of power
flow and in particular, optimal power
flow calculations of
alternating (or possibly, direct) current. The aims of this work are to propose and
investigate a method to assist in the determination of the composition of optimal
or high-performing power networks in terms of the type, number and location of
the distributed generators, and to analyse the multi-dimensional results of the
evolutionary computation component in order to reveal relationships between the
network design vector elements and to identify possible further methods of improving
models in future work. The results indicate that the method used is a
feasible one for the achievement of these goals, and also for determining optimal
flow capacities of transmission lines connecting the bus bars in the network.
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Pezdirc, Marjetka. "The terrorism complex." Thesis, University of Exeter, 2015. http://hdl.handle.net/10871/19149.
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Discussing, defining and engaging with ‘terrorism’ has long been limited to the narrowly framed situations in which parties to an asymmetric conflict resort to the use of force and to the legitimacy they have in doing so. The problem with the limited understanding of ‘terrorism’ and ‘counterterrorism’ as ‘facts of objective reality’ is the lack of attention to the role of the extreme asymmetry of power in conflicts involving ‘terrorism’ that does not lend itself to analysis readily. This thesis introduces a new theoretical concept, the Terrorism Complex that signifies the complexity of power/knowledge relations and the complexity of power/knowledge practices that operate on a discursive and non-discursive level through time and are affected by the mechanisms of power that stem from the asymmetry of power between the actors involved in a conflict. The research into the Terrorism Complex involves an ontological and epistemological widening of the research focus to account for these effects of the interplay between power and knowledge on the production, construction and perception of ‘terrorism’. I draw on postmodern scholarship and the Critical Terrorism Studies to present a theoretical and methodological framework that is used to examine the production of knowledge in relation to the asymmetries of power. The Israeli–Palestinian conflict is used as a case study for the study of power asymmetry in the political field that determines who will be labelled a ‘terrorist’ and who will be able to claim the moral high ground. The research also reveals the surprising extent to which the power over discourse obscures the role of the systemic terrorising exercise of state power in inducing ‘terrorism’. The final chapter concentrates on the media’s role in the Terrorism Complex. It applies the findings from other chapters to observe the Terrorism Complex in action.
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Case, Denise Marie. "Engineering complex systems with multigroup agents." Diss., Kansas State University, 2015. http://hdl.handle.net/2097/19045.
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Doctor of PhilosophyComputing and Information Sciences
Scott A. DeLoach
As sensor prices drop and computing devices continue to become more compact and powerful, computing capabilities are being embedded throughout our physical environment. Connecting these devices in cyber-physical systems (CPS) enables applications with significant societal impact and economic benefit. However, engineering CPS poses modeling, architecture, and engineering challenges and, to fully realize the desired benefits, many outstanding challenges must be addressed. For the cyber parts of CPS, two decades of work in the design of autonomous agents and multiagent systems (MAS) offers design principles for distributed intelligent systems and formalizations for agent-oriented software engineering (AOSE). MAS foundations offer a natural fit for enabling distributed interacting devices. In some cases, complex control structures such as holarchies can be advantageous. These can motivate complex organizational strategies when implementing such systems with a MAS, and some designs may require agents to act in multiple groups simultaneously. Such agents must be able to manage their multiple associations and assignments in a consistent and unambiguous way. This thesis shows how designing agents as systems of intelligent subagents offers a reusable and practical approach to designing complex systems. It presents a set of flexible, reusable components developed for OBAA++, an organization-based architecture for single-group MAS, and shows how these components were used to develop the Adaptive Architecture for Systems of Intelligent Systems (AASIS) to enable multigroup agents suitable for complex, multigroup MAS. This work illustrates the reusability and flexibility of the approach by using AASIS to simulate a CPS for an intelligent power distribution system (IPDS) operating two multigroup MAS concurrently: one providing continuous voltage control and a second conducting discrete power auctions near sources of distributed generation.
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Johan, Fredrik Raak. "Data-driven analysis of wind power and power system dynamics via Koopman mode decompositioｎ." Kyoto University, 2017. http://hdl.handle.net/2433/227628.
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Ha, Dinh Truc. "Line outage vulnerabilities of power systems : models and indicators." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAT018/document.
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La vulnérabilité des systèmes électriques est l'un des problèmes liés à leur complexité. Il a fait l’objet d’une attention croissante des chercheurs au cours des dernières décennies. Malgré cela, les phénomènes fondamentaux qui régissent la vulnérabilité du système ne sont pas encore bien compris.Comprendre comment la vulnérabilité des réseaux électriques émerge de leur topologie est la motivation principale du présent travail. Pour cela, le présent travail de recherché propose une nouvelle méthode pour évaluer la vulnérabilité des systèmes électriques et identifier leurs éléments les plus critiques. La méthode permet d’avoir une bonne compréhension des liens entre la topologie d’un réseau et sa vulnérabilité à des pertes d’ouvrages (lignes ou transformateurs).La première partie de ce travail consiste en une analyse critique des approches rencontrées dans la littérature, s’appuyant sur la théorie des graphes, pour analyser la vulnérabilité des réseaux électriques. Les résultats fournis par ces approches pour quatre réseaux IEEE sont comparés à ceux fournis par une analyse de contingence de référence, basée sur une résolution d’un load-flow AC. Des avantages et inconvénients de chaque approche est tirée une méthode améliorée pour l'évaluation de la vulnérabilité des réseaux électriques aux pertes d’ouvrage. Cette méthode est basée sur une approximation courant continue du load flow.La deuxième partie propose une nouvelle approche basée sur la théorie spectrale des graphes et son utilisation pour la résolution d’un load flow DC. Elle permet de mieux comprendre comment la vulnérabilité des réseaux électriques et leurs composants critiques émergent de la topologie du graphe sous-jacent au réseauThe vulnerability of electrical systems is one of the problems related to their complexity. It has received increasing attention from researchers in recent decades. Despite this, the fundamental phenomena that govern the vulnerability of the system are still not well understood.Understanding how the vulnerability of power systems emerges from their complex organization is, therefore, the main motivation of the present work. It proposes the definition of a standard method to assess the vulnerability of power systems and identify their most critical elements. The method enables a better understanding of the links between the topology of the grid and the line outage vulnerabilities.The first part of this research work offers a critical review of literature approaches used to assess system vulnerability. The results provided by these approaches for four IEEE test systems are confronted to a reference contingency analysis using AC power flow calculations. From these analyses, pros and cons of each approach are outlined. An improved method for assessment of system vulnerability to line outages is defined from this confrontation. It is based on DC load flow and graph theory.The second part proposes a new approach based on spectral graph theory and solving of DC power flow to identify how system vulnerability and critical components emerge from the power network topology
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Popli, Nipun. "Multi-layered Energy Conversion and Frequency Control in Complex Electric Power Systems." Research Showcase @ CMU, 2017. http://repository.cmu.edu/dissertations/916.
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The main performance objective in an electric power grid entails timely and efficient generation and delivery to the time-varying electricity demand. As the electricity industry is witnessing proliferation of the mainstream renewables, the minute-by-minute variations in wind and solar power generation may result in temporary electricity scarcity that jeopardizes grid stability and quality of service. The evolving electricity markets are aimed at incentivizing the conventional generators to reinforce their operating flexibility. This dissertation concerns the goal of enhancing the dynamic response rates of interconnected controllable resources by means of a multi-layered fuel input control of electrically coupled heterogeneous energy conversion components. Both power engineering and large-scale control contributions are made in support of this enhancement. First, improved fuel input controls are designed to enable flexible physics-based energy conversion dynamics required by the interconnected grid. To efficiently utilize the resources load-following and regulation problems are stated. The efficacy of proposed fuel input control designs in enhancing the dynamic response rates is illustrated on IEEE 14-bus system. Second, the problem is formalized as multi-input multioutput time-varying trajectory tracking based on a decentralized spatiotemporal composite control design. The concepts of vector-Lyapunov function and singular perturbation are invoked to formalize model decompositions, over space and time, respectively. Next, the assumptions for model simplifications are relaxed and the problem of parametric uncertainty is addressed. A minimumcost resilient co-design approach is introduced for storage-sensors-communication channels in a complex electric power grid. The notion of selective strong structural fixed modes is explored as a characterization of feasible decentralized control laws for an arbitrary system realization satisfying a pre-specified structure. Finally, it is proposed that planning of generation portfolio must be driven by the objective of maintaining adequate operating flexibility in the system. The goal is to ensure sufficient ramp capacity to sustain the significant integration of intermittent renewable resources.
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Coey, Charles A. "Complexity and Coordination: Power-Law Scaling in the Temporal Coordination of Complex Systems." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439282201.
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Hamm, Andreas. "Methodology and Modelling Approach for Strategic Sustainability Analysis of Complex Energy-Environment Systems." Thesis, University of Canterbury. Mechanical Engineering, 2007. http://hdl.handle.net/10092/1207.
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It is likely that in the near future, energy engineering will be required to help society adapt to permanently constrained fuel supplies, constrained green house gas emissions, and electricity supply systems running with minimal capacity margins. The goal of this research is to develop an analytical approach for adaptive energy systems engineering within the context of resource and environmental constraints. This involves assessing available energy resources, environmental and social issues, and economic activities. The approach is applied to a relatively simple case study on Rotuma, an isolated Pacific Island society. The case study is based on new data from field work. A spectrum of development options is identified for Rotuma and a reference energy demand is calculated for each representative level. A spectrum of conceptual reference energy system models is generated for each energy service level with a range of renewable energy penetration. The outcome is a matrix of energy system investment and resource utilization for the range of energy service levels. These models are then used for comparative risk assessment. The result is an easily understood visual based investment and risk assessment for both development and adaptation to constrained resource availability. The results show a clear development opportunity space for Rotuma where needs and services are in balance with investment, local resource availability and environmental constraints.
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Bhang, Kon Joon. "Remote Sensing Approach for Hydrologic Assessments of Complex Lake Systems." The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1212787335.
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IVANOVA, OLGA. "Development of Decision Support System for Optimization of Dams’ Management on Complex River Systems." Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/1010257.
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The thesis presents a complex approach for modelling of a complex reservoir systems for water drainage management. The model has been built over a segment of a river with a certain parameters of water inflow, water outflow, required power production and max possible flood occurrence. Then the segments may be replicated with specific parameters to simulate whole system of the river. The model has been optimized in order to obtain the water drainage operation policy with regards of current and expected water volumes in the reservoirs ratio, required power production revenue, and minimal flood occurrence. Model has been verified on a walk-through basis on Valle D'Aosta river system and Volga-Kama river system. Flood propagation has been modelled in HEC-RAS software, while post-processing and impact analysis were performed in QGIS 3.0. The results show that proposed management approach allows to decrease the impact caused by inundation at Volga-Kama river basin by two times compared to the one implemented by the operator management approach. This result is achieved due to mitigation of the flood in highly populated areas and allowing additional water discharge among water management facilities in the areas with low population.
Thus developed approach provides optimal water drainage for minimum flood occurrence and desired power production revenue.
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SECCHI, SIMONE. "Simulating complex multi-core computing systems: techniques and tools." Doctoral thesis, Università degli Studi di Cagliari, 2011. http://hdl.handle.net/11584/266327.
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George-Williams, H. "Efficient reliability modelling & analysis of complex systems with application to nuclear power plant safety." Thesis, University of Liverpool, 2018. http://livrepository.liverpool.ac.uk/3027659/.
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Nuclear power may be our best chance at a permanent solution to the world's energy challenges, owing to its sustainability and environmental friendliness. However, it also poses a great risk to life, property, and the economy, given the possibility of severe accidents during its generation. These accidents are a result of the susceptibility of the generating plants to component failure, human error, extreme environmental events, targeted attacks, and natural disasters. Given the complexity and high interconnectivity of the systems in question, a small glitch, otherwise known as an initiating event, could cascade to catastrophic consequences. It is, therefore, vital that the vulnerability of a plant to these glitches and their ensuing consequences be ascertained, to ensure that the appropriate mitigating actions are taken. The reliability of a system is the likelihood that it survives a defined period and its availability is the likelihood of it being capable of performing its required functions on demand. These quantities are important to a nuclear power plant's safety because, a nuclear power plant by default is equipped with safety systems to inhibit the propagation of an initiating event. An accident ensues if the safety systems required to mitigate some initiating event are unavailable or incapacitated by the initiating event. It is, therefore, easy to see that the reliability, as well as the availability of these systems, shape the safety of the plant. These crucial quantities, currently, are estimated using legacy techniques like static fault and event tree analyses or their derivatives. Despite their popularity and widely acclaimed success, these legacy techniques lack the flexibility to implement fully the operational dynamics of the majority of systems. Most importantly, their ease of application deteriorates with increasing system size and complexity, such that the analyst is often forced to make unrealistic assumptions. These unrealistic assumptions sometimes compromise the accuracy of the results obtained and subsequently, the quality of the risk management decisions reached. Their inadequacy is often amplified if the system is composed of multi-state components or characterised by epistemic uncertainties, induced by vague or imprecise data. The ideal approach, therefore, should be sufficiently robust to not necessitate unrealistic assumptions but flexible enough to accommodate realistic system attributes, while guaranteeing accuracy. This dissertation provides a detailed account of a series of computationally efficient system reliability analysis techniques proposed to address the limitations of the existing probabilistic risk assessment approaches. The proposed techniques are based mainly, on an advanced hybrid event-driven Monte Carlo simulation technique that invokes load-flow principles to resolve, intuitively, the difficulties associated with the topological complexity of systems and the multi-state attributes of their components. In addition to their intuitiveness and relative completeness, a key advantage of the proposed techniques is their general applicability. They have been applied, for instance, to a variety of problems, ranging from the production availability of an offshore oil installation and the maintenance strategy optimization of the IEEE-24 bus test system to the probabilistic risk assessment of station blackout accidents at the Maanshan nuclear power plant in Taiwan. The proposed techniques, therefore, should influence robust decisions in the risk management of not only nuclear power plants but other critical systems as well. They have been incorporated into the open-source uncertainty quantification tool, OpenCossan, to render them readily available to industry and other researchers.
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Kandia, Effrosyni <1979>. "Evaluation of Human Exposure to Magnetic Fields Generated by Electric Power Systems in Complex Configurations." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/6101/1/PhD_Thesis_-_KANDIA.Pdf.
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The international growing concern for the human exposure to magnetic fields generated by electric power lines has unavoidably led to imposing legal limits. Respecting these limits, implies being able to calculate easily and accurately the generated magnetic field also in complex configurations. Twisting of phase conductors is such a case. The consolidated exact and approximated theory regarding a single-circuit twisted three-phase power cable line has been reported along with the proposal of an innovative simplified formula obtained by means of an heuristic procedure. This formula, although being dramatically simpler, is proven to be a good approximation of the analytical formula and at the same time much more accurate than the approximated formula found in literature. The double-circuit twisted three-phase power cable line case has been studied following different approaches of increasing complexity and accuracy. In this framework, the effectiveness of the above-mentioned innovative formula is also examined. The experimental verification of the correctness of the twisted double-circuit theoretical analysis has permitted its extension to multiple-circuit twisted three-phase power cable lines. In addition, appropriate 2D and, in particularly, 3D numerical codes for simulating real existing overhead power lines for the calculation of the magnetic field in their vicinity have been created. Finally, an innovative ‘smart’ measurement and evaluation system of the magnetic field is being proposed, described and validated, which deals with the experimentally-based evaluation of the total magnetic field B generated by multiple sources in complex three-dimensional arrangements, carried out on the basis of the measurement of the three Cartesian field components and their correlation with the field currents via multilinear regression techniques. The ultimate goal is verifying that magnetic induction intensity is within the prescribed limits.
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Kandia, Effrosyni <1979>. "Evaluation of Human Exposure to Magnetic Fields Generated by Electric Power Systems in Complex Configurations." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2013. http://amsdottorato.unibo.it/6101/.
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The international growing concern for the human exposure to magnetic fields generated by electric power lines has unavoidably led to imposing legal limits. Respecting these limits, implies being able to calculate easily and accurately the generated magnetic field also in complex configurations. Twisting of phase conductors is such a case. The consolidated exact and approximated theory regarding a single-circuit twisted three-phase power cable line has been reported along with the proposal of an innovative simplified formula obtained by means of an heuristic procedure. This formula, although being dramatically simpler, is proven to be a good approximation of the analytical formula and at the same time much more accurate than the approximated formula found in literature. The double-circuit twisted three-phase power cable line case has been studied following different approaches of increasing complexity and accuracy. In this framework, the effectiveness of the above-mentioned innovative formula is also examined. The experimental verification of the correctness of the twisted double-circuit theoretical analysis has permitted its extension to multiple-circuit twisted three-phase power cable lines. In addition, appropriate 2D and, in particularly, 3D numerical codes for simulating real existing overhead power lines for the calculation of the magnetic field in their vicinity have been created. Finally, an innovative ‘smart’ measurement and evaluation system of the magnetic field is being proposed, described and validated, which deals with the experimentally-based evaluation of the total magnetic field B generated by multiple sources in complex three-dimensional arrangements, carried out on the basis of the measurement of the three Cartesian field components and their correlation with the field currents via multilinear regression techniques. The ultimate goal is verifying that magnetic induction intensity is within the prescribed limits.
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Deng, Weibing. "On the ranking property and underlying dynamics of complex systems." Thesis, Le Mans, 2013. http://www.theses.fr/2013LEMA1010/document.
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Des procédures de classement sont largement utilisées pour décrire les phénomènes observés dans de nombreux domaines des sciences sociales et naturelles, par exemple la sociologie, l’économie, la linguistique, la démographie, la physique, la biologie, etc.Dans cette thèse, nous nous sommes attachés à l’étude des propriétés de classement et des dynamiques sous-jacentes intégrées dans les systèmes complexes. En particulier,nous nous sommes concentrés sur les classements par score ou par prix dans les systèmes sportifs et les classements d’utilisation des mots ou caractères dans les langues humaines. Le but est de comprendre les mécanismes sous-jacents à ces questions en utilisant les méthodes de la physique statistique, de la statistique bayésienne et de la modélisation multi-agents. Les résultats concrets concernent les aspects suivants.Nous avons tout d’abord traité une étude sur les classements par score/prix dans les systèmes sportifs et analysé 40 échantillons de données dans 12 disciplines sportives différentes. Nous avons trouvé des similitudes frappantes dans différents sports, à savoir le fait que la répartition des résultats/prix suit les lois puissance universelles.Nous avons également montré que le principe de Pareto est largement respecté dans de nombreux systèmes sociaux: ainsi 20% des joueurs accumulent 80% des scores et de l’argent. Les données concernant les matchs de tennis en individuels nous ont révélé que lorsque deux joueurs s’affrontent, la probabilité que le joueur de rang supérieur gagne est liée à la différence de rang des deux adversaires. Afin de comprendre les origines de la mise à l’échelle universelle, nous avons proposé un modèle multi-agents,qui peut simuler les matchs de joueurs à travers différentes compétitions. Les résultats de nos simulations sont cohérents avec les résultats empiriques. L’extension du domaine d’étude de la simulation indique que le modèle est assez robuste par rapport aux modifications de certains paramètres. La loi de Zipf est le comportement le plus régulièrement observé dans la linguistique statistique. Elle a dès lors servi de prototype pour les relations entre rang d’apparitions et fréquence d’apparitions (relations rang-fréquence dans la suite du texte) et les lois d’échelle dans les sciences naturelles. Nous avons étudié plusieurs textes, précisé le domaine de validité de la loi de Zipf, et trouvé que la plage de validité augmente lors du mélange de différents textes. Basé sur l’analyse sémantique latente, nous avons proposé un modèle probabiliste, dans lequel nous avons supposé que les mots sont ajoutés au texte avec des probabilités aléatoires, tandis que leur densité a priori est liée, via la statistique bayésienne, aux caractéristiques générales du lexique mental de l’auteur de ce même texte. Notre modèle explique la loi de Zipf ainsi que ses limites de validité, et la généralise aux hautes et basses fréquences et au hapax legomena.Dans une autre étude, nous avons précisé les relations rang-fréquence pour les caractères chinois. Nous avons choisi d’étudier des textes courts en premier, car pour le bien de l’analyse rang fréquence, les longs textes ne sont que des mélanges de textes plus courts, thématiquement homogènes. Nos résultats ont montré que la loi de Zipf appliqués aux caractères chinois tient parfaitement pour des textes assez courts (quelques milliers de caractères différents). Le même domaine de validité est observé pour les textes courts anglais. Nous avons soutenu que les longs textes chinois montrent une structure hiérarchique à deux couches: des caractères dont la fréquence d’apparition suit une loi puissance (première couche) et des caractères dont l’apparition suit une loi exponentielle (deuxième couche)Ranking procedures are widely used to describe the phenomena in many differentfields of social and natural sciences, e.g., sociology, economics, linguistics, demography,physics, biology, etc. In this dissertation, we dedicated to study the ranking propertiesand underlying dynamics embedded in complex systems. In particular, we focused onthe scores/prizes ranking in sports systems and the words/characters usage ranking inhuman languages. The aim is to understand the mechanisms behind these issues byusing the methods of statistical physics, Bayesian statistics and agent-based modeling.The concrete results concern the following aspects.We took up an interesting topic on the scores/prizes ranking in sports systems, andanalyzed 40 data samples in 12 different sports fields. We found the striking similaritiesin different sports, i.e., the distributions of scores/prizes follow the universal powerlaws. We also showed that the data yielded the Pareto principle extensively observedin many social systems: 20% of the players accumulate 80% of the scores and money.For the tennis head-to-head data, we revealed that when two players compete, theprobability that the higher-ranked player will win is related to the rank difference ofthe two opponents. In order to understand the origins of the universal scaling, weproposed an agent-based model, which can simulate the competitions of players indifferent matches, and results from our simulations are consistent with the empiricalfindings. Extensive simulation studies indicate that the model is quite robust withrespect to the modifications of some parameters.Zipf’s law is the major regularity of statistical linguistics that served as a prototypefor the rank-frequency relations and scaling laws in natural sciences. We investigatedseveral English texts, clarified the valid range of Zipf’s law, and found this valid rangeincreases upon mixing different texts. Based on the latent semantic analysis, we proposeda probabilistic model, in which we assumed that the words are drawn into thetext with random probabilities, while their apriori density relates, via Bayesian statistics,to the general features of mental lexicon of the author who produced the text. Ourmodel explained the Zipf’s law together with the limits of its validity, its generalizationto high and low frequencies and hapax legomena. In another work, we specified the rank-frequency relations for Chinese characters. We chose to study the short texts first, since for the sake of the rank-frequency analysis,long texts are just mixtures of shorter, thematically homogenous pieces. Our resultsshowed that the Zipf’s law for Chinese characters perfectly holds for sufficiently shorttexts (few thousand different characters), and the scenario of its validity is similar tothat for short English texts. We argued long Chinese texts display a two-layer, hierarchicstructure: power-law rank-frequency characters (first layer) and the exponentialones (second layer). The previous results on the invalidity of the Zipf’s law for longtexts are accounted for by showing that in between of the Zipfian range and the regionof very rare characters (hapax legomena) there emerges a range of ranks, wherethe rank-frequency relation is approximately exponential. From comparative analysisof rank-frequency relations for Chinese and English, we suggested the characters playfor Chinese writers the same role as the words for those writing within alphabeticalsystems
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Wärja, Mathias. "Maintenance management of complex industrial systems : a methodology for renewal strategies." Doctoral thesis, KTH, School of Electrical Engineering (EES), 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-542.
Full textAbstract:
For complex technical systems in the electricity and pulp and paper industries, maintenance management addresses how to exploit physical assets in the most profitably way. This is a difficult task that requires taking into consideration parameters of totally different natures – e.g. reliability data, operating costs, condition of technical systems, the environment and rules and regulation.
An incorrect estimate of a residual lifetime can result in a premature renewal with accompanying high capital costs. If, however, renewal is delayed, a breakdown may occur which can cause major damage to technical equipment and a loss of income due to outages. Because of the complexity of many technical systems, it can be hard to select adequate data to use when making decisions about renewal strategies. To cope with this, one approach is to use less detailed models that are operated by skilled analysts.
This work demonstrates the advantage of such an approach by proposing two methods applied in a joint methodology that has its origins in RCM. The methodology consists of Dynamic Lifetime Model (DLA) and the Condition Based Index (CBI). The DLA method copes with the financial risk associated with the point in time for when a renewal is carried out and the CBI method uses critical parameters to estimate the condition of a technical system. The two methods together create a quantitative connection between reliability, maintenance and financial risk. A case study based validation of the methodology was carried out at SCA Ortvikens paper mill on a refiner system and Forsmark nuclear power plant. Lessons learned from the case study showed that the methodology could be used to identify which components could cause costly breakdown. By using the methodology a manager gets a decision support tool for estimating short-term and long-term consequences of decisions regarding maintenance management in order to maximize utility of the system concerned
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Öztürk, Esma. "WAKE INDUCED POWER DEFICIT ANALYSIS ON WIND TURBINES IN FORESTED MODERATELY COMPLEX TERRAIN USING SCADA DATA." Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-346639.
Full textAbstract:
Over the last few decades, wind power has shown a continuous and significant developmentin the energy market globally. Having reached a certain level in both technologyand in dimensions, the role of optimizing wind turbines as well as wind farms hasbecome an additional aspect to future development and research. Since turbine wakescan cause significant power deficits within a farm, research in this area has the potentialfor large improvements in wind farm design. A wake is described as the downstream flow behind the rotor of an operating windturbine. The two main characteristics of wakes are a velocity (momentum) deficit and anincreased turbulence level. The velocity deficit behind the upwind turbine results in apower loss of the downstream turbines, whereas the higher turbulence causes additionalloads on the downstream turbines’ structures resulting in fatigue problems. The study of wakes is a complex topic, they are influenced by an interconnection of anumber of parameters like ambient wind speed and turbulence, atmospheric stabilityconditions (stable, unstable, and neutral), the turbines’ operational characteristics, andthe terrain properties. In order to assess the power deficits affected by wake interaction between turbines,an analysis can be realized by processing SCADA data of turbines in a wind farm. The collected data is treated by a comprehensive filtration process, excluding events of icing, curtailment, faults, etc. and by grouping into different atmospheric conditions, windspeed intervals and wind speed sectors. Finally, power deficit values, as a function ofwind direction, are calculated and quantified, and thereafter analyzed to assess the wakebehavior at different conditions for different cases.In this thesis, the wake-induced power deficit has been investigated in a specificstudy case for three pairs of two neighboring turbines in a forested moderately complexterrain using SCADA data. The production losses amounted between the range of 32% to 67% for the specific site with turbine spacing around 4D. The obtained results werepartially unsatisfactory, caused by the reasons of inaccurate wind direction values due toyaw misalignment issues and challenging separation into different stability conditions. Moreover, the power deficits showed a clear reduction of losses with increasing windspeed. A conclusion regarding the differences between stable and near neutral conditionscould not be determined from the data.
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Jiao, Xiangqing. "Fault Location in Transmission Systems Using Synchronized Measurements." UKnowledge, 2017. http://uknowledge.uky.edu/ece_etds/100.
Full textAbstract:
Compared with conventional measurements from supervisory control and data acquisition (SCADA) system, phasor measurement units (PMUs) provide time-synchronized and direct measurements of phasors. The availability of synchronized phasor measurements can significantly improve power system protection and analysis. This dissertation is specifically committed to using synchronized measurements for estimation of fault locations in transmission systems.
Transmission lines are prone to various short-circuit faults. Accurate fault location is critical for rapid power recovery. Chapter 2 proposes a new fault location method based on sparse wide area measurements. One distinguishing feature of this method is its applicability to both transposed and untransposed transmission lines. In addition, the method is developed based on sparse-wide area measurement that may be taken far away from the faulted line. Shunt capacitances of transmission lines are also fully considered by the algorithm. Moreover, when synchronized measurements from multiple buses are available, an optimal estimator can be used to make the most use of measurements, and to detect and identify potential bad measurements.
Most of the existing fault location literatures discuss common shunt faults, including single line-to-ground faults, line-to-line faults, line-to-line-to-ground faults, and three-phase faults. However, in addition to common shunt faults, some complex faults may also occur in power systems. Among these complex faults, evolving fault and inter-circuit fault are two typical examples. Chapter 3 extends the method developed in Chapter 2 to deal with evolving faults. The proposed wide-area fault location methods are immune to fault type evolution, and are applicable to both transposed and untransposed lines.
Chapter 4 discusses location of inter-circuit faults. Inter-circuit fault is a type of simultaneous fault, and it is the most common simultaneous fault type. Inter-circuit faults between each circuit in a double-circuit line is the most common inter-circuit fault. A fault location method for inter-circuit faults on double-circuit lines are developed and evaluated in Chapter 4.
Chapter 5 puts forward a fault location algorithm, which does not require line parameters information, for series-compensated transmission lines. Two-end synchronized voltage and current measurements are utilized. The proposed method is independent of source impedance and fully considers shunt capacitances of transmission lines.
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Gensollen, Nicolas. "Modeling and optimizing a distributed power network : a complex system approach of the "prosumer" management in the smart grid." Thesis, Evry, Institut national des télécommunications, 2016. http://www.theses.fr/2016TELE0019/document.
Full textAbstract:
Cette thèse est consacrée à l'étude d’agents appelés prosumers parce qu’ils peuvent, à partir d’énergies renouvelables, à la fois produire et consommer de l’électricité. Si leurs productions excèdent leurs propres besoins, ceux-ci cherchent à vendre leur surplus sur des marchés de l’électricité. Nous proposons de modéliser ces prosumers à partir de données météorologiques, ce qui nous a permit de mettre en évidence des corrélations spatio-temporelles non triviales, d'une grande importance pour les agrégateurs qui forment des portefeuilles d’équipements afin de vendre des services à l'opérateur du réseau. Comme un agrégateur est lié par un contrat avec l'opérateur, il peut faire l'objet de sanctions s’il ne remplit pas son rôle. Nous montrons que ces corrélations impactent la stabilité des agrégats, et donc le risque encouru par les agrégateurs. Nous proposons un algorithme minimisant le risque d'un ensemble d’agrégations, tout en maximisant le gain attendu. La mise en place de dispositifs de stockage dans un réseau où les générateurs et les charges sont dynamiques et stochastiques est complexe. Nous proposons de répondre à cette question grâce à la théorie du contrôle. Nous modélisons le système électrique par un réseau d'oscillateurs couplés, dont la dynamique des angles de phase est une approximation de la dynamique réelle du système. Le but est de trouver le sous-ensemble des nœuds du graphe qui, lors d'une perturbation du système, permet le retour à l'équilibre si les bons signaux sont injectés, et ceci avec une énergie minimum. Nous proposons un algorithme pour trouver un placement proche de l'optimum permettant de minimiser l'énergie moyenne de contrôleThis thesis is devoted to the study of agents called prosumers because they can, from renewable, both produce and consume electricity. If their production exceeds their own needs, they are looking to sell their surplus on electricity markets. We propose to model these prosumers from meteorological data, which has allowed us to highlight non trivial spatial and temporal correlations. This is of great importance for aggregators that form portfolios of equipments to sell services to the network operator. As an aggregator is bound by a contract with the operator, it can be subject to penalties if it does not fulfill its role. We show that these correlations impact the stability of aggregates, and therefore the risk taken by the aggregators. We propose an algorithm minimizing the risk of the aggregations, while maximizing the expected gain. The placement of storage devices in a network where generators and loads are stochastic and not fixed is complex. We propose to answer this question with control theory. We model the electrical system as a network of coupled oscillators, whose phase angles dynamics is an approximation of the actual dynamics of the system. The goal is to find the subset of nodes in the graph that, during a disturbance of the system, allows returning to equilibrium if the right signals are injected and this with a minimum energy. We propose an algorithm to find a near optimal placement to minimize the average energy control
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GIUFFRIDA, STEFANIA. "The role of the power law distributions in describing social complex systems. Implications in the field of knowledge performance assessment." Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2013. http://hdl.handle.net/2108/204149.
Full textAbstract:
The present research aims at verifying the possibility to model one or more aspects
of a complex organization in terms of a power law distribution, in order to propose new
approaches for the personnel and/or the processes management.
Nevertheless in the literature there is a large amount of research on the capability of the
power functions to describe phenomena apparently very diverse in a large range of fields,
an evident limit is the possibility to simply transfer complexity concepts to the social
sciences. A social system, indeed, is generally composed by many agents, affected by
emotions, moods, aptitudes that can generate unpredictable effects, such as in a
metastable situation “on the edge of chaos”. For this reason, many authors transferred
with metaphors some complexity concepts into their studies on social-economic systems,
sometimes with very disputable parallelisms to natural and biological world.
After the discussion about the characteristics of complex systems, we try to face the
difficulty in modeling social-economic complex systems, respect to physical or chemical
phenomena, reviewing in particular the literature regarding economic issues, which
adopted a more rigorous statistical and mathematical approach. In particular, we focuses
on the growth dynamics model applied to economic entities like firms, countries,
universities (Stanley et al., 1996; Amaral et al., 1997; Axtell, 2001; Lee et al., 1998;
Gabaix, 1999; Plerou, 1999). Exploiting the scale free property of the power laws, these
authors described a common growth mechanism for these apparently so different subjects,
for which the fluctuations of the annual growth rate distributions always scale as a power
law of the initial size. As original contribution, we test the model also for Italian
universities, even if limited to the published ISI papers. Our results confirm that also our
national academies growth according the previous model (Giuffrida S., 2014).
The identified formal model is applicable to complex social organizations; it takes
advantage of the scale invariance of a determined feature of these systems but it is
substantially only descriptive of the complex phenomenon, detecting only a transversal
property for enterprises, countries, universities. On the other hand, an intrinsic potential
for the normalization of data is inside the model, as self-similar probability distributions
are made collapsing on a single curve by a simply scaling process.
Indeed, we demonstrate that the scale-free property of power laws can be used in
an innovative manner, as a scaling relationship to normalize data, in order to be
independent of the size of the studied organization.
We verify that a normalization process, based on the power law scale free property,
can be applied by a case study, the most recent Italian Evaluation of Research Quality
(ERQ), concerning 2004-2010 period of activity of the Italian university system (ANVUR
Final Report, 2013).
On the base of these available data, we built an indicator of university productivity
of knowledge, whose frequency distribution show fluctuations correlated to university
size in terms of a power law. This fact introduces a dimensional bias that can partially
falsify the results of periodical university assessment exercises, favoring one university
over another, sometimes with unfair consequences, particularly where a share of public
funding is allocated on the basis of the research assessment. The proposed normalization
process can be a solution of this dimensional bias conditioning the results of a
performance assessment.
The proposed framework is intended to be generic, to be applied in any knowledge
productivity or quality assessment at any time that the size of the monitored organizations
becomes relevant and must be appropriately weighed to validate the evaluation process.
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McAndrew, Thomas Charles. "Weighted Networks: Applications from Power grid construction to crowd control." ScholarWorks @ UVM, 2017. http://scholarworks.uvm.edu/graddis/668.
Full textAbstract:
Since their discovery in the 1950's by Erdos and Renyi, network theory (the study of objects and their associations) has blossomed into a full-fledged branch of mathematics.
Due to the network's flexibility, diverse scientific problems can be reformulated as networks and studied using a common set of tools.
I define a network G = (V,E) composed of two parts: (i) the set of objects V, called nodes, and (ii) set of relationships (associations) E, called links, that connect objects in V.
We can extend the classic network of nodes and links by describing the intensity of these associations with weights.
More formally, weighted networks augment the classic network with a function f(e) from links to the real line, uncovering powerful ways to model real-world applications.
This thesis studies new ways to construct robust micro powergrids, mine people's perceptions of causality on a social network, and proposes a new way to analyze crowdsourcing all in the context of the weighted network model.
The current state of Earth's ecosystem and intensifying climate calls on scientists to find new ways to harvest clean affordable energy.
A microgrid, or neighborhood-scale powergrid built using renewable energy sources attached to personal homes, suggest one way to ameliorate this energy crisis.
We can study the stability (robustness) of such a small-scale system with weighted networks.
A novel use of weighted networks and percolation theory guides the safe and efficient construction of power lines (links, E) connecting a small set of houses (nodes, V) to one another and weights each power line by the distance between houses.
This new look at the robustness of microgrid structures calls into question the efficacy of the traditional utility.
The next study uses the twitter social network to compare and contrast causal language from everyday conversation.
Collecting a set of 1 million tweets, we find a set of words (unigrams), parts of speech, named entities, and sentiment signal the use of informal causal language.
Breaking a problem difficult for a computer to solve into many parts and distributing these tasks to a group of humans to solve is called Crowdsourcing.
My final project asks volunteers to 'reply' to questions asked of them and 'supply' novel questions for others to answer.
I model this 'reply and supply' framework as a dynamic weighted network, proposing new theories about this network's behavior and how to steer it toward worthy goals.
This thesis demonstrates novel uses of, enhances the current scientific literature on, and presents novel methodology for, weighted networks.
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Fourie, Tamryn-Lee. "The application of system dynamics to resource allocation in international NGOs: exploring and modelling power inequalities whilst increasing efficiencies in complex international NGO management systems." Master's thesis, Faculty of Science, 2018. http://hdl.handle.net/11427/30148.
Full textAbstract:
We are living in an unjust world where the majority of humanity is subject to unequal economic and public policy systems that perpetuate cycles of poverty. Civil society, of which international NGOs are major players, are acknowledging the need for systemic, transformational change, which has to include meaningful participation in decision making processes by those whom are most vulnerable. In order to more effectively play this role, a number of international NGOs are moving decentralised structures (often comprised of independent entities at country level) to legitimately represent their primary constituents - those that are vulnerable, living in poverty, mostly in the global South. A consequence of this trajectory is added internal complexity and the creation of new management challenges, as decision making processes become more participatory and transparent. In addition, this new reality of complex federal structures also requires that power inequities between entities, are openly acknowledged and managed. Despite these challenges, this is a non-negotiable journey for many international NGOs and they acknowledge the need to adapt their management mechanisms to better handle this internal complexity. First-hand experience sparked the interest to apply operational research and system dynamics approaches to one such management mechanism, that of resource planning and allocation within international NGOs. This study aims to develop a set of insights, based on the system dynamics model, that could be useful to international NGO decision makers as they respond to their “real life” resource allocation challenges. Problem structuring methods are applied to these resource allocation challenges to gain a deeper understanding of the core components of resource allocation in order to develop a generic system dynamics model that simulates the necessary behaviours based on stakeholder input. A set of management scenarios are developed and form the basis for conducting experimental runs on the generic system dynamics model, testing different parameters in an effort to compare quantitative results. These quantitative results are used to compare performance against the original generic model, analysing trends and model behaviour to inform qualitative recommendations and conclusions.
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MUREDDU, MARIO. "A novel complex system approach for the determination of renewable energy sources impact on electricity infrastructures." Doctoral thesis, Università degli Studi di Cagliari, 2015. http://hdl.handle.net/11584/266793.
Full textAbstract:
The increasing environmental awareness, associated with the increasing
demand and price of fossil fuels, is leading to the implementation of novel
energy models based on renewable energy sources (RES) and sustainable
mobility. However, the actual physical and economic models on which power
system management rules are based on, are not able to properly manage the
high amount of unwanted power fluctuations introduced by RES power
generation. For such reason, major issues has been pointed out in term of
energy security and access, inspiring changes in methods and paradigms
associated to energy supply management. Moreover, the transaction towards
an emission free mobility must be based on the interaction between RES
generation and Electric Vehicles (EV) mobility, pointing out the need of a new
approach able to combine mobility and energy supply infrastructures.
In order to describe and model power systems with an high amount of RES
generation, is important to indicate that such systems are made by a great
number of microscopical interacting elements which behave in a stochastic
way. For this reason, these systems can not easily be described in a
deterministic way, but must be described by a statistical representation of the
system observables. In this thesis, a novel approach based on statistical
mechanics methods is presented, able to model the impact of such sources
over the system. By using such approach, has been possible to evaluate the
possible impact of such sources in terms of power system stability and
sustainable mobility.
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Abell, Barry J. "Planning concepts to sustain, develop, and test complex naval combat systems at the Surface Combat Systems Center, Wallops Island, Virginia." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Mar%5FAbell.pdf.
Full textAbstract:
Thesis (M.S. in Systems Engineering Management)--Naval Postgraduate School, March 2005.Thesis Advisor(s): Scott Carlson, Benjamin Roberts. Includes bibliographical references (p. 145-152) Also available online.
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Schinaider, Sidney Jorge. "Distribuição de lei de potência gradualmente truncada aplicada na educação : vestibular da Academia da Força Aérea /." Rio Claro : [s.n.], 2006. http://hdl.handle.net/11449/91932.
Full textAbstract:
Orientador: Hari Mohan GuptaBanca: Gerson Antonio Santarine
Banca: Osvaldo Missiato
Resumo: Educação e aprendizado são assuntos de grande importância para a sociedade em vista do desenvolvimento tecnológico e do progresso social. No presente trabalho analisamos a distribuição estatística das notas dos candidatos ao vestibular (Exame de Admissão) da Academia da Força Aérea, situada em Pirassununga, Estado de São Paulo Brasil, onde se formam os Oficiais da Aeronáutica (Força Aérea Brasileira), entre os anos de 1999 a 2004, em busca de algumas características que indiquem o processo de aprendizagem em cada disciplina do vestibular. O exame de admissão consta de 4 disciplinas: Física, Matemática, Inglês e Português, todos com questões objetivas. Os candidatos melhor classificados são selecionados de acordo com o número de vagas determinado pelo Comando da Aeronáutica. Notou-se, claramente, que, nas disciplinas Física, Matemática e Inglês, as notas obedecem a uma distribuição do tipo Lei de Potência Gradualmente Truncada, como também foi observado anteriormente nas disciplinas, em conjunto, de Ciências Exatas e Biológicas. Na disciplina Português as notas obedecem a uma distribuição normal, resultado que se explica, considerando-se a dependência dos assuntos dados na área de Física, Matemática e Inglês (língua estrangeira) aos assuntos ministrados anteriormente, enquanto em Português, (língua materna) cada capítulo é relativamente independente. Também apresentamos sugestão para melhorar o ensino de ciências e matemáticas.
Abstract: Science and Mathematic Education is a subject of great importance for the society in sight of recent technological and social program. In the present work, we study the statistical distribution of the marks obtained by the candidates in entrance examination of Air Force Academy, which prepare officers for Brazilian Air Force and is situated at Pirassununga São Paulo, in the period of 1999-2004. Our object is to find some characteristics of the process of learning in various disciplines. The admission examination consist of four disciplines; Physics, Mathematics, English and Portuguese. The candidates are selected in accordance with the merit list in the examination and number of seats available as determined by the Air Force Command. We showed that in the discipline of Physics, Mathematics and English, the distribution of marks obtained is in accordance with Gradually Truncated Power Law as also have been reported earlier in Exact and Biological Sciences in University entrance examination. In Portuguese the Distribution is Normal. We explained these results considering importance of the understanding of material given previously to understand a new chapter in area of Physics, Mathematics and English as our foreign language. In the case of Portuguese (Native Language), each chapter is relatively independent and thus not require knowledge of previous chapters. We also presented some suggestions to improve the science and Mathematics Education at High School level.
Mestre
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Schinaider, Sidney Jorge [UNESP]. "Distribuição de lei de potência gradualmente truncada aplicada na educação: vestibular da Academia da Força Aérea." Universidade Estadual Paulista (UNESP), 2006. http://hdl.handle.net/11449/91932.
Full textAbstract:
Made available in DSpace on 2014-06-11T19:25:32Z (GMT). No. of bitstreams: 0
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schinaider_sj_me_rcla.pdf: 576104 bytes, checksum: 41c3c4e7eec02c3dd98738011e8c7b76 (MD5)Educação e aprendizado são assuntos de grande importância para a sociedade em vista do desenvolvimento tecnológico e do progresso social. No presente trabalho analisamos a distribuição estatística das notas dos candidatos ao vestibular (Exame de Admissão) da Academia da Força Aérea, situada em Pirassununga, Estado de São Paulo Brasil, onde se formam os Oficiais da Aeronáutica (Força Aérea Brasileira), entre os anos de 1999 a 2004, em busca de algumas características que indiquem o processo de aprendizagem em cada disciplina do vestibular. O exame de admissão consta de 4 disciplinas: Física, Matemática, Inglês e Português, todos com questões objetivas. Os candidatos melhor classificados são selecionados de acordo com o número de vagas determinado pelo Comando da Aeronáutica. Notou-se, claramente, que, nas disciplinas Física, Matemática e Inglês, as notas obedecem a uma distribuição do tipo Lei de Potência Gradualmente Truncada, como também foi observado anteriormente nas disciplinas, em conjunto, de Ciências Exatas e Biológicas. Na disciplina Português as notas obedecem a uma distribuição normal, resultado que se explica, considerando-se a dependência dos assuntos dados na área de Física, Matemática e Inglês (língua estrangeira) aos assuntos ministrados anteriormente, enquanto em Português, (língua materna) cada capítulo é relativamente independente. Também apresentamos sugestão para melhorar o ensino de ciências e matemáticas.
Science and Mathematic Education is a subject of great importance for the society in sight of recent technological and social program. In the present work, we study the statistical distribution of the marks obtained by the candidates in entrance examination of Air Force Academy, which prepare officers for Brazilian Air Force and is situated at Pirassununga São Paulo, in the period of 1999-2004. Our object is to find some characteristics of the process of learning in various disciplines. The admission examination consist of four disciplines; Physics, Mathematics, English and Portuguese. The candidates are selected in accordance with the merit list in the examination and number of seats available as determined by the Air Force Command. We showed that in the discipline of Physics, Mathematics and English, the distribution of marks obtained is in accordance with Gradually Truncated Power Law as also have been reported earlier in Exact and Biological Sciences in University entrance examination. In Portuguese the Distribution is Normal. We explained these results considering importance of the understanding of material given previously to understand a new chapter in area of Physics, Mathematics and English as our foreign language. In the case of Portuguese (Native Language), each chapter is relatively independent and thus not require knowledge of previous chapters. We also presented some suggestions to improve the science and Mathematics Education at High School level.
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Menck, Peter-Johannes. "How wires shape volumes." Doctoral thesis, Humboldt-Universität zu Berlin, Mathematisch-Naturwissenschaftliche Fakultät I, 2014. http://dx.doi.org/10.18452/16930.
Full textAbstract:
Diese Arbeit ist der Frage gewidmet, wie die Stabilität eines Stromnetzes mit seiner Topologie zusammenhängt. Stabilität wird hier mit Hilfe von Bassin-Stabilität vermessen, einer nichtlokalen und nichtlinearen Methode, mit der sich quantifizieren lässt, wie stabil ein Stromnetz gegen große Störungen ist. Netzartige Systeme werden mit den Methoden der Theorie komplexer Netzwerke beschrieben. Bassin-Stabilität wird zunächst formal eingeführt. Dann wird die Methode angewendet, und zwar einmal auf abstrakte und einmal auf konkrete Weise. Der abstrakte Ansatz ist dadurch motiviert, dass die Funktion eines Stromnetzes auf dem synchronen Zusammenwirken seiner Komponenten beruht. Er betrifft die Frage, wie generelle dynamische Netzwerke strukturiert sein sollten, um stabile Synchronisation zu unterstützen. Es stellt sich heraus, dass Netzwerke mit maximaler Bassin-Stabilität am entgegengesetzten Ende eines gewissen netzwerktheoretischen Spektrums angesiedelt sind als Netzwerke, die optimal sind in Hinsicht auf lokale Stabilität. Dies deutet darauf hin, dass in der Entwicklung von synchron funktionierenden Systemen die Optimierung auf lokale Stabilität hin und die gleichzeitige Optimierung auf nichtlokale Stabilität hin als entgegengesetzte Kräfte gewirkt haben. Der konkrete Ansatz geht aus von einem Stromnetzmodell aus der Ingenieuersliteratur. Bassin-Stabilität wird komponentenweise eingesetzt, um zu untersuchen, wie der Grad der Stabilität eines Stromnetzes gegen große Einzelknoten-Störungen beeinflusst wird von gewissen Mustern in der Netztopologie. Simulationen in einem Ensemble von Stromnetzen bringen diverse Statistiken hervor, die alle eine wesentliche Beobachtung stützen: Ausgerechnet das kostengünstigste und weitverbreitetste Anschlussschema - bestehend aus Stichleitungen - vermindert die Netzstabilität beträchtlich. Es lässt sich ein fundamentales Designprinzip ableiten: Vermeide Stichleitungen.This thesis addresses the question how the stability of a power grid depends on the network topology. Stability is assessed here by means of basin stability, a nonlocal and nonlinear inspection scheme that allows to quantify how stable a power grid is against large perturbations. Networked systems are characterized using the instruments of complex network theory. A rigorous definition of basin stability is provided. Then, basin stability is applied once in an abstract and once in a more applied way. The abstract approach is motivated by the fact that power grids rely on the synchronous operation of their components, and focusses on the problem how general dynamical networks should be structured to support a stable synchronous state. It turns out that networks with maximum basin stability are located at the opposite end of a certain network-theoretical spectrum than networks optimal with respect to local stability. This suggests that, during the evolution of synchronizing networks, the optimization for local stability and the simultaneous optimization for nonlocal stability have acted as opposing forces. The more applied approach draws on a power grid model from the engineering literature. A component-wise version of basin stability is used to assess how a grid''s degree of stability against large single-node perturbations is influenced by certain patterns in the wiring topology. Simulations in an ensemble of power grids yield various statistics that all support one main finding: The widespread and cheapest of all connection schemes, so-called dead ends and dead trees, strongly diminish stability. The inverse is also true: `Healing'' dead ends by addition of transmission lines substantially enhances stability. This indicates a basic design principle for future power grids: avoid dead ends.
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Thorup, Pernille. "Strategy-making in a senior leadership team in the public sector in Denmark : taking experience seriously as co-creation, conflict and paradox." Thesis, University of Hertfordshire, 2016. http://hdl.handle.net/2299/17226.
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Much current literature on management and strategy still describes strategy work as a linear, top-down, management-based, rational, logical, structured and planned change activity with clear and predictable goals. It is described as an activity in which individual managers are addressing key questions and implementing an important, management-based plan. By using the right tools and techniques, skilled managers can transform plans into reality through good leadership and systematic rollout. This way of thinking about leadership is based on an understanding of leaders as rather powerful, knowing, heroic individuals who can stand outside of their organization to plan an ideal future, and who are equipped to make employees follow their instructions in order to reach desired goals. In this thesis I research into my experiences of what is happening in an organization, taking seriously the experience of developing a new strategy. It is an organization working in the public sector in Denmark which is right now trying to find a strategy and its way through a series of 'wicked problems' not easily handled. Through the use of autobiographical narrative-based inquiry and a focus on everyday local interactions between people working together, I research into what is 'really' going on in strategy work. Drawing on the theory of complex responsive processes of relating and reflexivity, I describe and analyse the interactions in our leadership team's efforts to change the organization's strategy. In doing so themes of power, power games and power differentials, politicking and some of the paradoxes in management - such as inclusion/exclusion, local interaction and global patterning, unpredictable predictability, and conflict and cooperation - are investigated. The complex responsive process perspective views organizations as patterns of interaction and conversations between people working together. By analogy from complex adaptive systems models, sociology, psychology and philosophy, it argues that generalizable population-wide patterns emerge in unpredictable ways through exactly these local complex interaction and interplays of people's intentions, thoughts and actions. This leads me to propose generalizable new contributions to knowledge about strategy work. Examining my own experience, I problematize the 'heroic', individualistic, view of what leaders do when working with strategy, preferring to see strategy as a co-created activity that emerges in complex and paradoxical interactions between people in the organization, in the leadership team, in daily cooperation with employees, and through the interface with customers. The understanding of co-creation here being that together we co-create our social life and our social life is co-creating us, our selves, our personalities at the same time. This inseparable paradox of the individual and the group, of the one and the many is investigated. Finally, I suggest that strategy work is inseparable from the everyday messy conflictual power games of organizational life, and that leaders - through actively engaging in ongoing conversations and co-creating meaning - participate in developing new understandings of identity and culture. In talking with one another about what it is we are doing, in influencing and being influenced, and reflecting on this, we are already changing what is going on; this itself is strategy work. The narratives show that to work with strategy effectively, we need to negotiate our intentions in convincing ways through forming strong power alliances. Taking experience seriously also demonstrates a close connection between power, ethics and action, and that it is impossible to decide the 'good' thing to do before acting. Developing reflexivity, both as an individual and in collaborative work, is a prerequisite for working in an ethical way, aware of our mutual interdependence. Finally, the thesis describes some of the consequences of taking experience seriously as a strategy. It has changed the way our staff understand what they are doing, and is beginning to change the kind of assignments we take on, and how we deal with them. One spin-off has been producing two books (with more to come). We also have new and more reflexive contacts in business and knowledge-creating environments, such as universities and business schools. The thesis shows a number of results from working with strategy in this way. This indicates that the act of taking your experience seriously in itself implies a kind of transforming causality, and hereby a strategy of change.
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Masca, Gregoria Magda Ticona. "Um estudo sobre raios de estabilidade real e complexo e valores singulares estruturados." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-31102017-102818/.
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Neste trabalho, duas técnicas de controle robusto (LQG/LTR e DML), aplicadas a um sistema elétrico de potência, são avaliadas através dos raios de estabilidade do sistema. As incertezas estruturadas do modelo nominal são consideradas nos dois controladores. Um conjunto de modelos é gerado considerando as combinações das incertezas paramétricas. Os valores singulares estruturados dos dois sistemas de controle são analisados.In this work, two techniques of robust control (LQG/LTR) and LMI), applied to a power electric system, are available via stability radii of the system. The structured uncertainties of the nominal model are considered in both designs. A set of models is generated considering the combinations of the parametric uncertainties. The structured singular values of both systems are analysed.
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Barroca, Neto ?lvaro. "Simula??o de fluxo de fluidos em meios porosos desordenados uma an?lise de efeito de escala na estimativa da permeabilidade e do coeficiente de arrasto." Universidade Federal do Rio Grande do Norte, 2012. http://repositorio.ufrn.br:8080/jspui/handle/123456789/13015.
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Previous issue date: 2012-02-29The present study provides a methodology that gives a predictive character the computer simulations based on detailed models of the geometry of a porous medium. We using the software FLUENT to investigate the flow of a viscous Newtonian fluid through a random fractal medium which simplifies a two-dimensional disordered porous medium representing a petroleum reservoir. This fractal model is formed by obstacles of various sizes, whose size distribution function follows a power law where exponent is defined as the fractal dimension of fractionation Dff of the model characterizing the process of fragmentation these obstacles. They are randomly disposed in a rectangular channel. The modeling process incorporates modern concepts, scaling laws, to analyze the influence of heterogeneity found in the fields of the porosity and of the permeability in such a way as to characterize the medium in terms of their fractal properties. This procedure allows numerically analyze the measurements of permeability k and the drag coefficient Cd proposed relationships, like power law, for these properties on various modeling schemes. The purpose of this research is to study the variability provided by these heterogeneities where the velocity field and other details of viscous fluid dynamics are obtained by solving numerically the continuity and Navier-Stokes equations at pore level and observe how the fractal dimension of fractionation of the model can affect their hydrodynamic properties. This study were considered two classes of models, models with constant porosity, MPC, and models with varying porosity, MPV. The results have allowed us to find numerical relationship between the permeability, drag coefficient and the fractal dimension of fractionation of the medium. Based on these numerical results we have proposed scaling relations and algebraic expressions involving the relevant parameters of the phenomenon. In this study analytical equations were determined for Dff depending on the geometrical parameters of the models. We also found a relation between the permeability and the drag coefficient which is inversely proportional to one another. As for the difference in behavior it is most striking in the classes of models MPV. That is, the fact that the porosity vary in these models is an additional factor that plays a significant role in flow analysis. Finally, the results proved satisfactory and consistent, which demonstrates the effectiveness of the referred methodology for all applications analyzed in this study.
O presente trabalho proporciona uma metodologia que d? um car?ter preditivo ?s simula??es computacionais baseadas em modelos detalhados da geometria porosa de um meio. N?s utilizando o software FLUENT para investigar o escoamento de um fluido newtoniano viscoso atrav?s de um meio fractal aleat?rio que simplifica um meio poroso desordenado bidimensional representando um reservat?rio de petr?leo. Este modelo fractal ? formado por obst?culos de diversos tamanhos, cuja fun??o de distribui??o segue uma lei de pot?ncia, onde o expoente ? definido como sendo a dimens?o fractal de fracionamento Dff do modelo e caracteriza o processo de fragmenta??o desses obst?culos. Eles s?o aleatoriamente dispostos em um canal retangular. O processo de modelagem incorpora conceitos modernos, leis de escala, para analisar a influ?ncia das heterogeneidades encontradas nos campos da porosidade e da permeabilidade de tal maneira que se possa caracterizar o meio em fun??o de suas propriedades fractais. Este procedimento permite analisar numericamente as medidas da permeabilidade k e do coeficiente de arrasto Cd propondo rela??es, tipo lei de pot?ncia, para essas propriedades sobre v?rios esquemas de modelagem. O prop?sito desta pesquisa ? estudar a variabilidade proporcionada por estas heterogeneidades onde o campo de velocidade e outros detalhes da din?mica dos fluidos viscosos s?o obtidos resolvendo numericamente as equa??es da continuidade e de Navier-Stokes no n?vel de poros e observar como a dimens?o fractal de fracionamento do modelo pode afetar as suas propriedades hidrodin?micas. Neste estudo foram consideradas duas classes de modelos, modelos com porosidade constante, MPC, e modelos com porosidade vari?vel, MPV. Os resultados permitiram-nos encontrar rela??es num?ricas entre a permeabilidade, coeficiente de arrasto e os par?metros geom?tricos do modelo. Com base nestes resultados num?ricos propusemos rela??es de escala envolvendo os par?metros relevantes do fen?meno. Nesta pesquisa foram determinadas equa??es anal?ticas para Dff em fun??o dos par?metros geom?tricos dos modelos. Constatamos tamb?m uma rela??o entre a permeabilidade e o coeficiente de arrasto onde uma ? inversamente proporcional ? outra. Quanto ? diferen?a de comportamento ela ? mais marcante nas classes de modelos MPV. Isto ?, o fato da porosidade variar nestes modelos constitui um fator adicional que desempenha um papel significativo na an?lise de fluxo. Finalmente, os resultados encontrados se mostraram consistentes e satisfat?rios, o que demonstra a efic?cia da referida metodologia para todas as aplica??es analisadas nesta pesquisa.
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Rodney, Elodie. "Développement d’une méthode de gestion des risques de projet et d’aide à la décision en contexte incertain : application au domaine des énergies renouvelables." Thesis, Bordeaux, 2016. http://www.theses.fr/2016BORD0399/document.
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Le risque est une propriété inhérente de chaque projet. En effet, tout projet est soumis, durant l’ensemble de son cycle de vie, à de nombreux risques qui sont d’origine interne et externe dont la maîtrise est un enjeu crucial pour la réussite du projet. Beaucoup d'outils de gestion des risques ont été développés, mais ont la faiblesse récurrente de ne représenter que le projet et traitent le risque de façon isolée. Les risques affectant le projet et étant générés par ce dernier, il est nécessaire de prendre en compte les nombreuses et complexes interactions entre projet, environnement et risques.Les travaux réalisés visent à mettre en place une méthode de gestion des risques inhérents aux projets en général et plus particulièrement aux projets du domaine compétitif des énergies renouvelables.Cette méthode s’appuie sur un cadre formel et des outils applicatifs permettant d’optimiser le management des risques liés au projet. En effet, un cadre de modélisation servant de support à la méthode et ayant pour but de faciliter la modélisation du projet en tant que système complexe a été déterminé. De plus, la représentation des interactions inhérentes au projet et la prise de décision ont été rendues possibles par la nature des attributs caractérisant les entités du projet et de son environnement, et les différents modèles d’évaluation, d’interprétation et de choix des alternatives. Cette méthode a été adaptée à la prise en compte des incertitudes inhérentes au projet et à son environnement. Pour cela, nous avons d’abord procédé à l’identification et à la description des incertitudes via la réalisation d’une base de connaissances relatives aux facteurs de risques et à la documentation des variables incertaines. Les incertitudes ont ensuite été formalisées, propagée et évaluéesRisk is an inherent property of each project. Indeed, any project faces, throughout its whole life cycle, numerous risks. Those risks can have an internal or an external origin. Be able to control risks is a crucial stake for the project success. Many risk management tools have been developed, but have the recurring weakness of representing only the project and treating the risk in isolation. Risks affect the project and are generated by the project itself. So, it is necessary to consider the numerous and complex interactions between project, environment and risks.The work carried out aims to develop a risk management method suitable for all types of projects and more particularly for projects of the competitive field of renewable energies.This method relies on a formal framework, as well as on application tools to optimize project risk management. Indeed, a modeling framework which supports the method and aims to facilitate the modeling of the project as a complex system has been developed. Moreover, the representation of the interactions and the decision making have been allowed by the nature of the attributes characterizing the entities of the project and its environment and the different models for evaluation, interpretation and selection of alternatives. This method was adapted to the uncertain context. For this purpose, uncertainties have been identified and described via the realization of a data base on risk factors. Then, uncertainties have been formalized, propagated and evaluated
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Wang, Zhuoyang. "Application of Complex Network Theory in Power System Security Assessment." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/17367.
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The power demand increases every year around the world with the growth of population and the expansion of cities. Meanwhile, the structure of a power system becomes increasing complex. Moreover, increasing renewable energy sources (RES) has linked to the power network at different voltage levels. These new features are expected to have a negative impact on the security of the power system. In recent years, complex network (CN) theory has been studied intensively in solving practical problems of large-scale complex systems. A new direction for power system security assessment has been provided with the developments in the CN field. In this thesis, we carry out investigations on models and approaches that aim to make the security assessment from an overview system level with CN theory. Initially, we study the impact of the renewable energy (RE) penetration level on the vulnerability in the future grid (FG). Data shows that the capacity of RE has been increasing over by 10% annually all over the world. To demonstrate the impact of unpredictable fluctuating characteristics of RES on the power system stability, a CN model given renewable energy integration for the vulnerability analysis is introduced. The numerical simulations are investigated based on the simplified 14-generator model of the South Eastern Australia power system. Based on the simulation results, the impact of different penetrations of RES and demand side management on the Australian FG is discussed. Secondly, the distributed optimization performance of the communication network topology in the photovoltaic (PV) and energy storage (ES) combined system is studied with CN theory. A Distributed Alternating Direction Method of Multipliers (D-ADMM) is proposed to accelerate the convergence speed in a large dimensional communication system. It is shown that the dynamic performance of this approach is highly-sensitive to the communication network topology. We study the variation of convergence speed under different communication network topology. Based on this research, guidance on how to design a relatively more optimal communication network is given as well. Then, we focus on a new model of vulnerability analysis. The existing CN models usually neglect the detailed electrical characteristics of a power grid. In order to address the issue, an innovative model which considers power flow (PF), one of the most important characteristics in a power system, is proposed for the analysis of power grid vulnerability. Moreover, based on the CN theory and the Max-Flow theorem, a new vulnerability index is presented to identify the vulnerable lines in a power system. The comparative simulations between the power flow model and existing models are investigated on the IEEE 118-bus system. Based on the PF model, we improve a power system cascading risk assessment model. In this research the risk is defined by the consequence and probabilities of the failures in the system, which is affected by both power factors and the network structure. Furthermore, a cascading event simulation module is designed to identify the cascading chain in the system during a failure. This innovation can form a better module for the cascading risk assessment of a power system. Finally, we argue that the current cyber-physical network model have their limitations and drawbacks. The existing “point-wise” failure model is not appropriate to present the interdependency of power grid and communication network. The interactions between those two interdependent networks are much more complicated than they were described in some the prior literatures. Therefore, we propose a new interdependency model which is based on earlier research in this thesis. The simulation results confirm the effectiveness of the new model in explaining the cascading mechanism in this kind of networks.
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Oliveira, Josà Dickson AraÃjo de. "Evaluation of the operation of the HVDC system of Madeira River complex interconnection to the Southern Region of the brazilian electric system." Universidade Federal do CearÃ, 2015. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=15766.
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This work proposes a model for the HVDC transmission system of the Madeira River Complex, which is developed using PSCAD/EMTDC and based on the design provided by the Energy Research Company (EPE) during the granting concession stage. The implemented model is evaluated by comparing the simulation results and actual data regarding events that occurred in the National Interconnected System (SIN) involving the complex. The Madeira River HVDC system is rated at 7,100 MW, being responsible for transmitting the power generated by the hydropower plants of Santo AntÃnio and Jirau, which are close to the city of Porto Velho, to local load centers and southeastern Brazil, thus reaching the Araraquara substation in the state of SÃo Paulo through two 2,350 km lines. The system consists of two back-to-back (antiparallel) blocks rated at 400 MW each using capacitor-commutated converter stations in order to supply the load comprising the states of RondÃnia and Acre, and also two bipoles of 3,150 MW each, which are constituted by 12-pulse line-commutated current source converters so that power can be transmitted to southeastern Brazil. The results of comparison between actual data and the simulation tests have shown that the percentage difference between the evaluated quantities are within acceptable limits, while it can be concluded that the proposed model is properly validated.Este trabalho propÃe um modelo do sistema de transmissÃo HVDC do Complexo do Rio Madeira, desenvolvido no ambiente PSCAD/EMTDC e baseado no projeto disponibilizado pela Empresa de Pesquisa EnergÃtica - EPE na fase de concessÃo das instalaÃÃes. O modelo construÃdo à avaliado por meio da comparaÃÃo entre os resultados de simulaÃÃo e os dados reais de ocorrÃncias no Sistema Interligado Nacional - SIN que envolveram o complexo. O HVDC do Rio Madeira possui capacidade total de conversÃo de 7.100 MW, e transporta a energia gerada nas usinas hidroelÃtricas de Santo AntÃnio e Jirau, prÃximas a Porto Velho, para centros de carga locais e para o sudeste do Brasil, chegando à subestaÃÃo Araraquara, no estado de SÃo Paulo, atravÃs de duas linhas em corrente contÃnua de 2.350 km de extensÃo. O sistema à composto por dois blocos back-to-back (anti-paralelo) de 400 MW cada, com estaÃÃes conversoras comutadas por capacitores, para atender as cargas dos estados de RondÃnia e Acre, e dois elos bipolares de 3.150 MW cada, constituÃdos de conversores fonte de corrente de 12 pulsos com comutaÃÃo natural de linha, para transmissÃo de energia para o sudeste do paÃs. Os resultados da comparaÃÃo entre os dados reais e a simulaÃÃo mostraram que as diferenÃas percentuais entre grandezas avaliadas se mantiveram dentro de limites satisfatÃrios, podendo-se concluir que o modelo construÃdo foi considerado validado.
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Daza, Enrique Acha. "Modelling of power system transformers in the complex conjugate harmonic space." Thesis, University of Canterbury. Electrical Engineering, 1988. http://hdl.handle.net/10092/5450.
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Magnetizing harmonics in power systems have received limited attention. The general belief is that they do not reach harmful levels in interconnected networks. Moreover the modelling of non-linearities is not a straightforward procedure and so there has been little motivation to develop appropriate methodologies that allow a thorough investigation to take place.
In this thesis the problem of magnetizing harmonics in power systems is investigated. The results obtained show that, contrary to expectations, magnetizing currents can give rise to a considerable harmonic distortion in the voltage wave form of power networks operating under loaded conditions.
The method adopted in this research linearizes each magnetic non-linearity around a base operating point. The linearization exercise takes place in the complex-conjugate harmonic space and the individual linearized equations may be interpreted as harmonic Norton equivalents. These equations combine easily with each other and with the transfer admittances representing the linear part of the network. The overall process of linearization may be seen as a linearization of the entire network and can also be interpreted as a multi-nodal, polyphase harmonic Norton equivalent.
This problem is non-linear and the harmonic solution is reached by an iterative process. A re-linearization of the network takes place at each iterative step and so the solution is found through a Newton-type procedure. Several iterative strategies are tested, including unified and sequential solutions with either single or multi-evaluated Jacobians.
A hitherto neglected problem which also receives attention is the harmonic modelling of non-homogenous transmission lines. A novel approach to the modelling of the frequency dependent part of the transmission line is also presented. The equations proposed are shown to be the fastest to date and yet maintain a high degree of accuracy.
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Moran, José. "Statistical physics and anomalous macroeconomic fluctuations." Thesis, Paris, EHESS, 2020. http://www.theses.fr/2020EHES0106.
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Comment des perturbations à l'échelle de l'individu peuvent-elle devenir des grandes fluctuations à l'échelle de l'économie? Cette question, malgré son étude depuis des décennies, est encore ouverte. Dans cet ouvrage, j'étudie cette énigme à l'aide de méthodes issues de la physique statistique. En partant d'une analyse approfondie des distributions en loi de puissance, je montre qu'une compréhension claire de leur origine et de leurs propriétés permet de mieux appréhender leurs conséquences socioéconomiques. Je propose ensuite un modèle d'économie en réseau, où les entreprises dépendent les unes des autres pour produire, de sorte que la nature même de leurs interactions peut les rendre susceptibles d'amplifier des fluctuations. Ensuite, je soumets au lecteur une étude empirique des propriétés statistiques des taux de croissance et fournis un cadre permettant d'étudier leur dynamique. Dans la partie finale je m'intéresse à des modèles qui exhibent des phénomènes collectifs non-triviaux parce qu'ils considèrent des effets d'imitation ou de mémoire dans les décisions prises par les individus, montrant bien la nécessité de tenir compte de la possible complexité des différentes parties constitutives des modèles économiquesHow do microscopic perturbations at the level of an individual grow to become macroscopic fluctuations of the whole economy? Despite decades of effort, this puzzle remains open. In this work, I tackle this problem using methods and techniques from statistical physics. Beginning with a thorough analysis of power law distributions, I argue that understanding their origin and properties helps in elucidating their socio-economic consequences. I then explore a model of an economy where firms interact through a {\em production network} in a way that causes them to be intrinsically prone to amplify fluctuations. Later on, I conduct an empirical survey of the statistical properties of firm growth rates and provide a framework to study their dynamics. I finally move onto models where non-trivial collective phenomena arise from imitation and memory effects at the level of the individual, highlighting the need of accounting for complexity in economic modelling
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PIRES, Robson Celso. "Complex-Valued Steady-State Models as Applied to Power Flow Analysis and Power System State Estimation." reponame:Repositório Institucional da UNIFEI, 2018. http://repositorio.unifei.edu.br/xmlui/handle/123456789/1359.
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Nonlinear systems of equations in complex domain are frequently encountered in applied mathematics, e.g., power systems, signal processing, control theory, neural networks and biomedicine, to name a few. The solution of these problems often requires a first- or second-order approximation of these nonlinear functions to generate a new step or descent direction to meet the solution iteratively. However, such methods cannot be applied to real functions of complex variables because they are necessarily non-analytic in their argument, i.e., the Taylor series expansion in their argument alone does not exist. To overcome this problem, the nonlinear function is usually redefined as a function of the real and imaginary parts of its complex argument so that standard methods can be applied. Although not widely known, it is possible to build an expansion of these nonlinear functions in its original complex variables by noting that functions of complex variables can be analytic in their argument and its complex conjugate as a whole. This property lies in the fact that if a function is analytic in the space spanned by ℜ{} and ℑ{}in ℝ, it is also analytic in the space spanned by and * in ℂ. The main contribution of this work is the application of this methodology to a complex Taylor series expansions aiming algorithms commonly used for solving complex-valued nonlinear systems of equations emerged from power systems problems. In our proposal, a complex-valued power ow analysis (CV PFA) model solved by Newton-Raphson method is revisited and enhanced. Nonetheless, especially emphasis is addressed to Gauss-Newton method when derived in complex domain for solving power system state estimation (CV PSSE) problems, whichever they are applied in transmission or distribution systems. The factorization method of the complex Jacobian matrices emerged from CV PFA and CV PSSE approaches is the Three Angle Complex Rotation (TACR) algorithm that comes from the Givens Rotations algorithm in real domain. In this research one demonstrates that Wirtinger derivatives can lead to greater insights in the structure of both problems, i.e., CV PFA & CV PSSE. Moreover, it can often be exploited to mitigate computational overhead, storage cost and enhance the network's component modeling as FACTS devices, e.g., STATCOM, VSC-HVDC, besides easily handle PMU measurements and embedding new technologies towards smart grids. Finally, in order to add numerical robustness, a fourth-order Levenberg-Marquardt algorithm is employed to the CV PFA & CV PSSE approaches because of its nice bi-quadratic convergence property, instead of the well-known quadratic convergence property of the classical Newton-Raphson and Gauss-Newton algorithms. Recall that these latter algorithms are prone to collapse when the power system network is ill-conditioned, i.e., it is heavily loaded or presents branches with high R/X ratio. These results are partially presented in this thesis because they are still under study and development. But most of them will appear in forthcoming papers submitted to IEEE-PES Transactions on Power Systems and coming up Top Conferences.
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LUO, LINGEN. "Power system vulnerability and performance: application from complexity scienze and complex network." Doctoral thesis, Politecnico di Torino, 2014. http://hdl.handle.net/11583/2538888.
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Power system has been acknowledged as a complex system owing to its complexity resulting from interactions of different layers which include physical layer like generators, transformers, substations and cyber layer like communication units and human decision layer. Complex network theory has been widely used to analyze the power grids from basic topological properties to statistic robustness
analysis and dynamic resilience property. However, there are still many problems need to be addressed. This thesis will pay more attention on the application and extension of complexity science and complex network theory in power system analysis from different aspects.
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Peddersen, Jorgen Computer Science & Engineering Faculty of Engineering UNSW. "Run-time energy-driven optimisation of embedded systems: a complete solution." Publisher:University of New South Wales. Computer Science & Engineering, 2008. http://handle.unsw.edu.au/1959.4/43240.
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Consumption of power and conservation of energy have become two of the biggest design challenges in construction of embedded systems. Energy is a resource in limited supply, but demands are increasing. Hence, much research is being performed to reduce power and energy usage or optimise performance under energy constraints. There are very few solutions that try to cater for the applications where the data input is not easily testable before run-time. These applications require an optimisation procedure that knows the power consumption of the system and is able to dynamically optimise operation to maximise performance while meeting energy constraints. This thesis provides a complete solution to the problem of run-time energy-driven optimisation of application performance. The complete system, from a processor that is able to provide feedback of the power consumption in parallel to execution, to applications that exploit the power feedback to provide dynamic optimisation. A processor that estimates its own power consumption is designed by the addition of small dedicated counters that tally occurrences of power consuming events which are macro modelled. The methodology is demonstrated on a standard processor achieving an average power estimation error of less than 2% while increasing area of the processor by only 5%. This enables energy-driven optimisation via application adaptation. Modification techniques and low-overhead algorithms are provided to demonstrate how energy feedback can be effectively used to maximise performance of algorithms within given constraints. Applications?? quality is maximised under given energy constraints using less than 0.02% of the execution time. Finally, the dissertation discusses the systems used to demonstrate the methodologies and techniques created throughout the research project. These implementations of the energy-driven optimisation system verify the soundness of the methods and applicability of the approaches used. This is the first time a complete solution for energy-driven optimisation has been shown, from creation of the processor to analysis of software utilising the approach. The methodologies and techniques can be applied to a variety of applications in a range of fields such as multimedia and networking that have never been possible before.
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Wenzel, Eric. "An exploration of processes of mutual recognition in organization development initiatives from the standpoint of a practising consultant." Thesis, University of Hertfordshire, 2012. http://hdl.handle.net/2299/7658.
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What usually goes unaddressed in the consultancy literature is an exploration of how consultants make sense of their contributions in particular when they come to work in politically laden contexts. Resulting conflictual debates with clients and colleagues severely influence how their advice is responded to. Against this background, consultants’ ability to determine and predict future outcomes of their work is hardly problematized. Additionally, consultants are mutually dependent on both colleagues and clients. This dependency underpins power differentials and the struggle which arises when these are contested can often take violent forms, such as misrecognition, humiliation or public shaming. The central argument put forward in this thesis is that tolerating (the potential for) misrecognition and/or for violence when goals are not met or when power fluctuates is an important, yet rarely mentioned, aspect for being recognized as a consultant. These aspects deserve as much attention as the often ideal-typical forms management consulting is said to take in the mainstream management literature because they speak to the irremediably incomplete and rather probabilistic nature of consultants’ advice, and the multiplicity of (often not anticipated or undesired) meanings their work evokes. In order to make sense of the flux and flow of organizational activity, the plethora of responses such activity calls out and its attendant ambiguities are considered and critically reflected upon. The theory of complex responsive processes of relating (Stacey, 2007, 2010; Griffin, 2002; Shaw, 2002), theories of recognition, (Honneth, 1994, 2008; Kearney, 2003; Ricoeur, 2005), Hegelian dialectics and neo-pragmatist thought (Bernstein, 1983, 1991) are provided as non-orthodox views on human organizing. A perspective is proffered which pays attention to the inchoate, ambivalent and indeterminate dimensions of organizing as a way to make sense of how these simultaneously and paradoxically order, regularize, and normalize human activity. Particular attention will be paid to negotiations which take place in microinteractions to exemplify that it is not pre-planned human cooperation but the intermingling of intentions of people who are mutually dependent on one another which paradoxically gives rise to regular population-wide patterns and spontaneous change. To make sense of what these insights mean for a practising consultant a view is offered where our reflections (thought) on our interactions (practice) at once form and are being formed by one another. An attempt is made to move beyond the practice/theory dualism by taking a pragmatist view which claims that thought and action only ever arise together, thus rendering an understanding of consultative intervention in which thought comes before action idealized and rather dubious. It will be argued that the most important contribution consultants can make is to try to stay radically open, and to try to keep on exploring as long as possible the multiplicity of narratives which constitute the differing perspectives of organizational reality.
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McCubbin, Michael. "The political economy of mental health, power and interests within a complex system." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0023/NQ33057.pdf.
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Baek, Seong Cheol. "Dynamical Analysis and Decentralized Control of Power Packet Network." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263664.
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Pack, Maria Joyce. "Complex metal oxide materials : synthesis, structural characterisation and development of combined EXAFS and powder differaction analysis." Thesis, University of Southampton, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243098.
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Levy, Renato. "Optimization Techniques for Energy-Aware Memory Allocation in Embedded Systems." Diss., Computer Science, George Washington University, 2004. http://hdl.handle.net/1961/116.
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Degree awarded (2004): DScCS, Computer Science, George Washington UniversityA common practice to save power and energy in embedded systems is to "put to sleep" or disable parts of the hardware. The memory system consumes a significant portion of the energy budget of the overall system, so it is a natural target for energy optimization techniques. The principle of software locality makes the memory subsystem an even better choice, since all memory blocks but the ones immediately required can be disabled at any given time. This opportunity is the motivation for developing energy optimization techniques to dynamically and selectively control the power state of the different parts of the memory system. This dissertation develops a set of algorithms and techniques that can be organized into a hardware/software co-development tool to help designers apply the selective powering of memory blocks to minimize energy consumption. In data driven embedded systems, most of the data memory is used either by global static variables or by dynamic variables. Although techniques already exist for energy-aware allocation of global static arrays under certain constraints, very little work has focused on dynamic variables, which are actually more important to event driven/data driven embedded systems than their static counterparts. This dissertation addresses this gap, and extends and consolidates previous allocation techniques in a unique framework. A formal model for memory energy optimization for dynamic and global static variables and efficient algorithms for energy aware allocation of variables to memory are presented. Dependencies between generic code and data are uncovered, and this information is exploited to fine-tune a system. A framework is presented for retrieving this profile information which is then used to design energy aware allocation algorithms for dynamic variables, including heuristics for segmentation and control of the memory heap. By working at the assembly code level, these techniques can be integrated into any compiler regardless of the source language. The proposed techniques were implemented and tested against data intensive benchmarks, and experimental results indicate significant savings of up to 50% in the memory system energy consumption.
Advisory Committee: Professor Bhagirath Narahari, Professor Hyoeong-Ah Choi (Chair), Professor Rahul Simha, Professor Shmuel Rotenstreich, Professor Can E. Korman, Dr. Yul Williams
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Jun, Min Su. "Three Essays on Complex Contractual Networks of Farmers." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1470869524.
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Zhao, Shuang. "FORWARD AND BACKWARD EXTENDED PRONY (FBEP) METHOD WITH APPLICATIONS TO POWER SYSTEM SMALL-SIGNAL STABILITY." Case Western Reserve University School of Graduate Studies / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=case1480948469362031.
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Becher, Dirk. "Electrohydrostatic actuation system – an (almost) complete system view." Technische Universität Dresden, 2020. https://tud.qucosa.de/id/qucosa%3A71207.
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Electro-hydrostatic Actuation Systems (EAS) successfully combine the advantages of electro-mechanical actuation - such as high-energy efficiency and low noise emission - with the benefits of electro-hydraulic technology –which include robustness and the precise handling of large forces. This paper defines keywords like EAS and Electro-hydraulic pump unit (EPU), and provides a comparison of the two technologies. Given the wide range of EAS technology topics, it is only possible to briefly introduce and discuss these in this paper. This technology has reached a level that renders it a strong mechanism for machine manufacturers to support existing and future motion control requirements.