• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 14
  • 12
  • 2
  • Tagged with
  • 32
  • 32
  • 11
  • 10
  • 8
  • 6
  • 5
  • 5
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • 4
  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Planejamento dinâmico da expansão de sistemas de transmissão de energia elétrica

Poubel, Raphael Paulo Braga 04 July 2016 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-01-06T17:13:56Z No. of bitstreams: 1 raphaelpaulobragapoubel.pdf: 14885655 bytes, checksum: 55ce1d3cf1619213e5c2364f54de5a50 (MD5) / Approved for entry into archive by Diamantino Mayra (mayra.diamantino@ufjf.edu.br) on 2017-01-31T11:24:55Z (GMT) No. of bitstreams: 1 raphaelpaulobragapoubel.pdf: 14885655 bytes, checksum: 55ce1d3cf1619213e5c2364f54de5a50 (MD5) / Made available in DSpace on 2017-01-31T11:24:55Z (GMT). No. of bitstreams: 1 raphaelpaulobragapoubel.pdf: 14885655 bytes, checksum: 55ce1d3cf1619213e5c2364f54de5a50 (MD5) Previous issue date: 2016-07-04 / O presente trabalho propõe um modelo não linear inteiro misto para o planejamento dinâmico da expansão da transmissão. Para a representação do modelo, se fez uso do fluxo de carga CC. As equações básicas do fluxo CC foram modificadas e expandidas de forma a incluir as variáveis de decisão e o acoplamento temporal entre os investimentos. Para a solução do modelo, de forma a mitigar as dificuldades inerentes à programação inteira, foram propostas técnicas de solução passo a passo. Em cada uma das técnicas as variáveis inteiras foram substituídas por uma função contínua de forma a se obter tempos computacionaisviáveis. Adiscretizaçãodasvariáveisinteirassedácomoauxíliodeíndices de sensibilidade apropriados, calculados a partir do modelo acoplado. O trabalho também investiga metodologias para o planejamento dinâmico de linhas de transmissão, buscando um equilíbrio entre a economia e a confiabilidade no processo de decisão dos investimentos. O critério determinístico N-1 foi escolhido para garantir maior confiabilidade ao sistema. / This work proposes a non-linear mixed integer model for dynamic transmission lines expansion planning. The DC load flow was used to represent the model. The basic equationsoftheDCloadflowweremodifiedandexpandedtoincludethedecisionvariables and the temporal coupling between investments. For the model solution, in order to mitigate the difficulties inherent of integer programming, step-by-step processes were proposed. In each of the techniques the integer variables have been replaced with a continuous function to obtain viable computational time. The discretization of the integer variables is made with the aid of appropriate sensitivity indexes, calculated from the coupled model. The work also suggests methods for dynamic transmission planning, seeking a balance between the economy and reliability in the investment decision process. The N-1 deterministic criteria was chosen to ensure system reliability.
22

Studie pracovních charakteristik více-fázového stroje / Investigation on operating characteristics of multi-phase machine

Kuna, Kristián January 2020 (has links)
S postupom času sa elektrotechnicky průmysl posouval dopředu. Přišel rozvoj v automobilovém průmyslu, leteckém průmyslu, navigácí a dalších odvětvích. S rozvojem automobilového a leteckého průmyslu se zvětšila potřeba pro motory s vyskou spolehlivostí. Tenhle fakt zapříčinil rozvoj motorů s vćero fázami. Tyto stroje mají za úkol zvýšiť spolehlivost ale zároveň zachovat/zvýšit výkon stroje.
23

Multi Time-Scale Hierarchical Control for Connected and Autonomous Vehicles

Boyle, Stephen January 2021 (has links)
No description available.
24

On Economic Interpretation of Lagrange Multipliers

Meznik, Ivan 19 March 2012 (has links)
No description available.
25

Alocação de unidades de geração termoelétrica em sistemas elétricos de potência / Thermoelectrical generation allocation in electric power systems

Canola, Saulo Ricardo 16 January 2006 (has links)
Este trabalho tem como objetivo realizar um estudo de alocação de unidades termoelétricas em sistemas elétricos de potência (SEP). O fluxo de potencia ótimo (FPO) foi utilizado para se obter o ponto ótimo de operação para o sistema e os multiplicadores de Lagrange associados às restrições. Os multiplicadores de Lagrange indicam a sensibilidade entre a função objetivo e a restrição a ele associada. Esta sensibilidade indica, quais as barras do sistema, são candidatas à alocação de novas usinas termoelétricas. Testes nos sistemas de 5 barras, IEEE 14 barras, IEEE 30 barras, equivalente CESP 440 kV de 53 barras e IEEE 118 barras comprovam a eficiência da abordagem, a qual poderá ser utilizada em estudos de planejamento da expansão do sistema. / The aim of this paper is to present a study of thermoelectrical generation allocation in electric power systems. The optimal power flow (OPF) was used to evaluate the optimal operation point for the power system and also Lagrange multipliers associated with the constraints. The Lagrange multipliers are the sensitivity between the objective function and its constraints. This sensitivity is used to verify in a power system where is the best place to incentive the allocation of new thermoelectrical power plants. Tests on the systems: 5 buses, IEEE 14 buses, IEEE 30 buses, equivalent CESP 440kV 53 buses and IEEE 118 buses showed the efficiency of the presented approach. This method of analyzing the system can be used in study of expansion planning system.
26

Alocação de unidades de geração termoelétrica em sistemas elétricos de potência / Thermoelectrical generation allocation in electric power systems

Saulo Ricardo Canola 16 January 2006 (has links)
Este trabalho tem como objetivo realizar um estudo de alocação de unidades termoelétricas em sistemas elétricos de potência (SEP). O fluxo de potencia ótimo (FPO) foi utilizado para se obter o ponto ótimo de operação para o sistema e os multiplicadores de Lagrange associados às restrições. Os multiplicadores de Lagrange indicam a sensibilidade entre a função objetivo e a restrição a ele associada. Esta sensibilidade indica, quais as barras do sistema, são candidatas à alocação de novas usinas termoelétricas. Testes nos sistemas de 5 barras, IEEE 14 barras, IEEE 30 barras, equivalente CESP 440 kV de 53 barras e IEEE 118 barras comprovam a eficiência da abordagem, a qual poderá ser utilizada em estudos de planejamento da expansão do sistema. / The aim of this paper is to present a study of thermoelectrical generation allocation in electric power systems. The optimal power flow (OPF) was used to evaluate the optimal operation point for the power system and also Lagrange multipliers associated with the constraints. The Lagrange multipliers are the sensitivity between the objective function and its constraints. This sensitivity is used to verify in a power system where is the best place to incentive the allocation of new thermoelectrical power plants. Tests on the systems: 5 buses, IEEE 14 buses, IEEE 30 buses, equivalent CESP 440kV 53 buses and IEEE 118 buses showed the efficiency of the presented approach. This method of analyzing the system can be used in study of expansion planning system.
27

Testing the compatibility of constraints for parameters of a geodetic adjustment model

Lehmann, Rüdiger, Neitzel, Frank 06 August 2014 (has links) (PDF)
Geodetic adjustment models are often set up in a way that the model parameters need to fulfil certain constraints. The normalized Lagrange multipliers have been used as a measure of the strength of constraint in such a way that if one of them exceeds in magnitude a certain threshold then the corresponding constraint is likely to be incompatible with the observations and the rest of the constraints. We show that these and similar measures can be deduced as test statistics of a likelihood ratio test of the statistical hypothesis that some constraints are incompatible in the same sense. This has been done before only for special constraints (Teunissen in Optimization and Design of Geodetic Networks, pp. 526–547, 1985). We start from the simplest case, that the full set of constraints is to be tested, and arrive at the advanced case, that each constraint is to be tested individually. Every test is worked out both for a known as well as for an unknown prior variance factor. The corresponding distributions under null and alternative hypotheses are derived. The theory is illustrated by the example of a double levelled line. / Geodätische Ausgleichungsmodelle werden oft auf eine Weise formuliert, bei der die Modellparameter bestimmte Bedingungsgleichungen zu erfüllen haben. Die normierten Lagrange-Multiplikatoren wurden bisher als Maß für den ausgeübten Zwang verwendet, und zwar so, dass wenn einer von ihnen betragsmäßig eine bestimmte Schwelle übersteigt, dann ist davon auszugehen, dass die zugehörige Bedingungsgleichung nicht mit den Beobachtungen und den restlichen Bedingungsgleichungen kompatibel ist. Wir zeigen, dass diese und ähnliche Maße als Teststatistiken eines Likelihood-Quotiententests der statistischen Hypothese, dass einige Bedingungsgleichungen in diesem Sinne inkompatibel sind, abgeleitet werden können. Das wurde bisher nur für spezielle Bedingungsgleichungen getan (Teunissen in Optimization and Design of Geodetic Networks, pp. 526–547, 1985). Wir starten vom einfachsten Fall, dass die gesamte Menge der Bedingungsgleichungen getestet werden muss, und gelangen zu dem fortgeschrittenen Problem, dass jede Bedingungsgleichung individuell zu testen ist. Jeder Test wird sowohl für bekannte, wie auch für unbekannte a priori Varianzfaktoren ausgearbeitet. Die zugehörigen Verteilungen werden sowohl unter der Null- wie auch unter der Alternativhypthese abgeleitet. Die Theorie wird am Beispiel einer Doppelnivellementlinie illustriert.
28

Sur une méthode numérique ondelettes / domaines fictifs lisses pour l'approximation de problèmes de Stefan

Yin, Ping 25 January 2011 (has links)
Notre travail est consacré à la définition, l'analyse et l'implémentation de nouveaux algorithmes numériques pour l'approximation de la solution de problèmes à 2 dimensions du type problème de Stefan. Dans ce type de problèmes une équation aux dérivée partielle parabolique posée sur un ouvert omega quelconque est couplée avec une autre équation qui contrôle la frontière gamma du domaine lui même. Les difficultés classiquement associés à ce type de problèmes sont: la formulation en particulier de l'équation pour le bord du domaine, l'approximation de la solution liées à la forme quelconque du domaine, les difficultés associées à l'implication des opérateurs de trace (approximation, conditionnement), les difficultés liées aux de régularité fonds du domaine.De plus, de nombreuse situations d'intérêt physique par exemple demandent des approximations de haut degré. Notre travail s'appuie sur une formulation de type espaces de niveaux (level set) pour l'équation du domaine, et une formulation de type domaine fictif (Omega) pour l'équation initiale.Le contrôle des conditions aux limites est effectué à partir de multiplicateurs de Lagrange agissant sur une frontière (Gamma) dite de contrôle différente de frontière(gamma) du domaine (omega). L'approximation est faite à partir d'un schéma aux différences finies pour les dérivées temporelle et une discrétisation à l'aide d'ondelettes bi-dimensionelles pour l'équation initiale et une dimensionnelle pour les multiplicateurs de Lagrange. Des opérateurs de prolongement de omega à Omega sont également construits à partir d'analyse multiéchelle sur l'intervalle. Nous obtenons aussi: une formulation pour laquelle existence de la solution est démontrées, un algorithme convergent pour laquelle une estimation globale d'erreur (sur Omega) est établie, une estimation intérieure prouvant sur l'erreur à un domaine omega, overline omega subset Xi, des estimations sur les conditionnement associés a l'opérateur de trace, des algorithmes de prolongement régulier. Différentes expériences numériques en 1D ou 2D sont effectuées. Le manuscrit est organisé comme suit: Le premier chapitre rappelle la construction des analyses multirésolutions, les propriétés importantes des ondelettes et des algorithmes numériques liées à l'application d'opérateurs aux dérivées partielles. Le second chapitre donne un aperçu des méthodes de domaine fictif classiques, approchées par la méthode de Galerkin ou de Petrov-Galerkin. Nous y découvrons les limites de ces méthodes ce qui donne la direction de notre travail. Le chapitre trois présente notre nouvelle méthode de domaine fictif que l'on appelle méthode de domaine fictif lisse.L'approximation est grâce à une méthode d'ondelettes de type Petrov-Galerkin. Cette section contient l'analyse théorique et décrit la mise en œuvre numérique. Différents avantages de cette méthode sont démontrés. Le chapitre quatre introduit une technique de prolongement régulier. Nous l'appliquons à des problèmes elliptiques en 1D ou 2D.\par Le cinquième chapitre décrit quelques simulations numériques de problème de Stefan. Nous testons l'efficacité de notre méthode sur différents exemples dont le problème de Stefan à 2 phases avec conditions aux limites de Gibbs-Thomson. / Our work is devoted to the definition, analysis and implementation of a new algorithms for numerical approximation of the solution of 2 dimensional Stefan problem. In this type of problem a parabolic partial differential equation defined on an openset Omega is coupled with another equation which controls the boundary gamma of the domain itself. The difficulties traditionally associated with this type of problems are: the particular formulation of equation on the boundary of domain, the approximation of the solution defined on general domain, the difficulties associated with the involvement of trace operation (approximation, conditioning), the difficulties associated with the regularity of domain. Addition, many situations of physical interest, for example,require approximations of high degree. Our work is based on aformulation of type level set for the equation on the domain, and aformulation of type fictitious domain (Omega) for the initialequation. The control of boundary conditions is carried out throughLagrange multipliers on boundary (Gamma), called control boundary, which is different with boundary (gamma) of the domain (omega). The approximation is done by a finite difference scheme for time derivative and the discretization by bi-dimensional wave letfor the initial equation and one-dimensional wave let for the Lagrange multipliers. The extension operators from omega to Omega are also constructed from multiresolution analysis on theinterval. We also obtain: a formulation for which the existence of solution is demonstrated, a convergent algorithm for which a global estimate error (on Omega) is established, interior error estimate on domain omega, overline omega subset estimates on the conditioning related to the trace operator, algorithms of smooth extension. Different numerical experiments in 1D or 2D are implemented. The work is organized as follows:The first chapter recalls theconstruction of multiresolution analysis, important properties of wavelet and numerical algorithms. The second chapter gives an outline of classical fictitious domain method, using Galerkin or Petrov-Galerkin method. We also describe the limitation of this method and point out the direction of our work.\par The third chapter presents a smooth fictitious domain method. It is coupled with Petrov-Galerkin wavelet method for elliptic equations. This section contains the theoretical analysis and numerical implementation to embody the advantages of this new method. The fourth chapter introduces a smooth extension technique. We apply it to elliptic problem with smooth fictitious domain method in 1D and 2D. The fifth chapter is the numerical simulation of the Stefan problem. The property of B-spline render us to exactly calculate the curvature on the moving boundary. We use two examples to test the efficiency of our new method. Then it is used to resolve the two-phase Stefan problem with Gibbs-Thomson boundary condition as an experimental case.
29

Testing the compatibility of constraints for parameters of a geodetic adjustment model

Lehmann, Rüdiger, Neitzel, Frank 06 August 2014 (has links)
Geodetic adjustment models are often set up in a way that the model parameters need to fulfil certain constraints. The normalized Lagrange multipliers have been used as a measure of the strength of constraint in such a way that if one of them exceeds in magnitude a certain threshold then the corresponding constraint is likely to be incompatible with the observations and the rest of the constraints. We show that these and similar measures can be deduced as test statistics of a likelihood ratio test of the statistical hypothesis that some constraints are incompatible in the same sense. This has been done before only for special constraints (Teunissen in Optimization and Design of Geodetic Networks, pp. 526–547, 1985). We start from the simplest case, that the full set of constraints is to be tested, and arrive at the advanced case, that each constraint is to be tested individually. Every test is worked out both for a known as well as for an unknown prior variance factor. The corresponding distributions under null and alternative hypotheses are derived. The theory is illustrated by the example of a double levelled line. / Geodätische Ausgleichungsmodelle werden oft auf eine Weise formuliert, bei der die Modellparameter bestimmte Bedingungsgleichungen zu erfüllen haben. Die normierten Lagrange-Multiplikatoren wurden bisher als Maß für den ausgeübten Zwang verwendet, und zwar so, dass wenn einer von ihnen betragsmäßig eine bestimmte Schwelle übersteigt, dann ist davon auszugehen, dass die zugehörige Bedingungsgleichung nicht mit den Beobachtungen und den restlichen Bedingungsgleichungen kompatibel ist. Wir zeigen, dass diese und ähnliche Maße als Teststatistiken eines Likelihood-Quotiententests der statistischen Hypothese, dass einige Bedingungsgleichungen in diesem Sinne inkompatibel sind, abgeleitet werden können. Das wurde bisher nur für spezielle Bedingungsgleichungen getan (Teunissen in Optimization and Design of Geodetic Networks, pp. 526–547, 1985). Wir starten vom einfachsten Fall, dass die gesamte Menge der Bedingungsgleichungen getestet werden muss, und gelangen zu dem fortgeschrittenen Problem, dass jede Bedingungsgleichung individuell zu testen ist. Jeder Test wird sowohl für bekannte, wie auch für unbekannte a priori Varianzfaktoren ausgearbeitet. Die zugehörigen Verteilungen werden sowohl unter der Null- wie auch unter der Alternativhypthese abgeleitet. Die Theorie wird am Beispiel einer Doppelnivellementlinie illustriert.
30

Ghosts and machines : regularized variational methods for interactive simulations of multibodies with dry frictional contacts

Lacoursière, Claude January 2007 (has links)
<p>A time-discrete formulation of the variational principle of mechanics is used to provide a consistent theoretical framework for the construction and analysis of low order integration methods. These are applied to mechanical systems subject to mixed constraints and dry frictional contacts and impacts---machines. The framework includes physics motivated constraint regularization and stabilization schemes. This is done by adding potential energy and Rayleigh dissipation terms in the Lagrangian formulation used throughout. These terms explicitly depend on the value of the Lagrange multipliers enforcing constraints. Having finite energy, the multipliers are thus massless ghost particles. The main numerical stepping method produced with the framework is called SPOOK.</p><p>Variational integrators preserve physical invariants globally, exactly in some cases, approximately but within fixed global bounds for others. This allows to product realistic physical trajectories even with the low order methods. These are needed in the solution of nonsmooth problems such as dry frictional contacts and in addition, they are computationally inexpensive. The combination of strong stability, low order, and the global preservation of invariants allows for large integration time steps, but without loosing accuracy on the important and visible physical quantities. SPOOK is thus well-suited for interactive simulations, such as those commonly used in virtual environment applications, because it is fast, stable, and faithful to the physics.</p><p>New results include a stable discretization of highly oscillatory terms of constraint regularization; a linearly stable constraint stabilization scheme based on ghost potential and Rayleigh dissipation terms; a single-step, strictly dissipative, approximate impact model; a quasi-linear complementarity formulation of dry friction that is isotropic and solvable for any nonnegative value of friction coefficients; an analysis of a splitting scheme to solve frictional contact complementarity problems; a stable, quaternion-based rigid body stepping scheme and a stable linear approximation thereof. SPOOK includes all these elements. It is linearly implicit and linearly stable, it requires the solution of either one linear system of equations of one mixed linear complementarity problem per regular time step, and two of the same when an impact condition is detected. The changes in energy caused by constraints, impacts, and dry friction, are all shown to be strictly dissipative in comparison with the free system. Since all regularization and stabilization parameters are introduced in the physics, they map directly onto physical properties and thus allow modeling of a variety of phenomena, such as constraint compliance, for instance.</p><p>Tutorial material is included for continuous and discrete-time analytic mechanics, quaternion algebra, complementarity problems, rigid body dynamics, constraint kinematics, and special topics in numerical linear algebra needed in the solution of the stepping equations of SPOOK.</p><p>The qualitative and quantitative aspects of SPOOK are demonstrated by comparison with a variety of standard techniques on well known test cases which are analyzed in details. SPOOK compares favorably for all these examples. In particular, it handles ill-posed and degenerate problems seamlessly and systematically. An implementation suitable for large scale performance and accuracy testing is left for future work.</p>

Page generated in 0.059 seconds