The Experts below are selected from a list of 318 Experts worldwide ranked by ideXlab platform
G R M Da Costa - One of the best experts on this subject based on the ideXlab platform.
-
MODIFIED Barrier LAGRANGIAN FUNCTION Method APPIED TO THE MA XIMUM LOADING PROBLEM
2010Co-Authors: V.a. De Sousa, Edmarcio Antonio Belati, G R M Da CostaAbstract:In this p aper the Modified Barrier Lagrangian Function (MBLF) Method, i.e., a variant of the Interior Point Method, is applied for the determination of the buses with the smallest loading margin and the smallest magnitude voltage in power systems, respectively. For the formulation of the problem, the power flow equations are in a parameterized form, and the inequality constraints are the voltage limits in the buses and the reactive generation limits in the buses with reactive control. The results obtained with the static optimization technique MBLF used in this study are confronted with the results obtained with the Primal-dual Logarithmic Barrier Method (PDLB). Test results for the IEEE 57 and IEEE 118-bus test systems are presented to demonstrate the robustness and the effectiveness of the proposed algorithm. Resumo─ Neste artigo o metodo da Funcao Lagrangiana Barreira Modificada (FLBM), uma variante do metodo dos Pontos Interior es, e aplicado na determinacao das barras com menor margem de carregamento e menor magnitude de tensao em sistemas de potencia, respectivamente. Na formulacao do problema, as equacoes de fluxo de potencia estao na forma parametrizada, e as restricoes de desigualdade sao os limites de tensao nas barras e os limites de geracao de reativos nas barras de controle de reativo. Os resultados obtidos com a tecnica de otimizacao estatica MBLF (FLBM) usado neste trabalho sao confrontados com os resultados obtidos com o metodo Primal-Dual Barreira Logaritmica. Resultados dos testes para os sistemas IEEE 57 e IEEE 118 barras sao apresentados para demonstrar a robustez e efetividade do metodo proposto.
-
primal dual logarithmic Barrier and augmented lagrangian function to the loss minimization in power systems
Electric Power Components and Systems, 2006Co-Authors: Edmea Cassia Baptista, Edmarcio Antonio Belati, Vanusa Alves De Sousa, G R M Da CostaAbstract:This article presents a new approach to minimize the losses in electrical power systems. This approach considers the application of the primal-dual logarithmic Barrier Method to voltage magnitude and tap-changing transformer variables, and the other inequality constraints are treated by augmented Lagrangian Method. The Lagrangian function aggregates all the constraints. The first-order necessary conditions are reached by Newton's Method, and by updating the dual variables and penalty factors. Test results are presented to show the good performance of this approach.
-
logarithmic Barrier augmented lagrangian function to the optimal power flow problem
International Journal of Electrical Power & Energy Systems, 2005Co-Authors: Edmea Cassia Baptista, Edmarcio Antonio Belati, G R M Da CostaAbstract:This paper presents a new approach to solve the Optimal Power Flow problem. This approach considers the application of logarithmic Barrier Method to voltage magnitude and tap-changing transformer variables and the other constraints are treated by augmented Lagrangian Method. Numerical test results are presented, showing the effective performance of this algorithm.
-
Modified Barrier Method for optimal power flow problem
IEEE Power Engineering Society General Meeting 2004., 1Co-Authors: V.a. De Sousa, Edmea Cassia Baptista, G R M Da CostaAbstract:In this paper is presented a new approach for optimal power flow problem. This approach is based on the modified Barrier function and the primal-dual logarithmic Barrier Method. A Lagrangian function is associated with the modified problem. The first-order necessary conditions for optimality are fulfilled by Newton's Method, and by updating the Barrier terms. The effectiveness of the proposed approach has been examined by solving the Brazilian 53-bus, IEEE 118-bus and IEEE 162-bus systems.
Nancy Padian - One of the best experts on this subject based on the ideXlab platform.
-
Barrier Method preferences and perceptions among Zimbabwean women and their partners.
AIDS and behavior, 2005Co-Authors: Jessica Buck, Mi-suk Kang, Ariane Van Der Straten, Gertrude Khumalo-sakutukwa, Samuel F. Posner, Nancy PadianAbstract:In Zimbabwe, adult HIV prevalence is over 25% and acceptable prevention Methods are urgently needed. Sixty-eight Zimbabwean women who had completed a Barrier-Methods study and 34 of their male partners participated in focus group discussions and in-depth interviews to qualitatively explore acceptability of male condoms, female condoms and diaphragms. Most men and about half of women preferred diaphragms because they are female-controlled and do not detract from sexual pleasure or carry stigma. Unknown efficacy and reuse were concerns and some women reported feeling unclean when leaving the diaphragm in for six hours following sex. Nearly half of women and some men preferred male condoms because they are effective and limit women's exposure to semen, although they reportedly detract from sexual pleasure and carry social stigma. Female condoms were least preferred because of obviousness and partial coverage of outer-genitalia that interfered with sexual pleasure.
-
Effectiveness of female controlled Barrier Methods in preventing sexually transmitted infections and HIV: current evidence and future research directions.
Sexually transmitted infections, 2005Co-Authors: Alexandra M. Minnis, Nancy PadianAbstract:Objectives: To evaluate evidence for the effectiveness of female controlled physical and chemical Barrier Methods in preventing STI/HIV transmission, to examine recent reviews on microbicide development, and to highlight promising research directions. To discuss challenges in conducting effectiveness research and in translating results to public health intervention. Methods: Systematic review of articles that examined the disease prevention effectiveness of at least one female controlled Barrier Method. Review of conference abstracts that presented clinical and preclinical microbicide data. Results: Randomised controlled trials provide evidence that female condoms confer as much protection from STIs as male condoms. Observational studies suggest that the diaphragm protects against STI pathogens. Several microbicide effectiveness studies are under way and new directions, such as adaptation of therapeutic agents as preventive products, are being examined. Substantial attention is now given to product formulation and novel delivery strategies. Combining microbicide products with different mechanisms of action as well as combining chemical and physical Barriers will be necessary to maximise prevention effectiveness. Conclusions: Increased investment in the development and identification of female controlled Barrier Methods offers promise that additional products will be available in the years ahead. Generalising trial results to a community setting, promoting products that may be less effective than male condoms, and bringing an effective product to scale introduce public health challenges that warrant attention. The need for female controlled Barrier Methods that provide women with the opportunity to take an active role in reducing their STI/HIV risk are urgently needed and constitute an essential tool to prevent continued spread of these infections.
-
Choice of female-controlled Barrier Methods among young women and their male sexual partners.
Family planning perspectives, 2001Co-Authors: Alexandra M. Minnis, Nancy PadianAbstract:Little is known about the factors associated with the choice of female-controlled over-the-counter Barrier contraceptive Methods among women and their male sexual partners. Predictors of Method choice were assessed following an educational presentation on contraceptive use and risk reduction among 510 sexually active females aged 15-30 who were recruited in the San Francisco Bay Area. In addition the primary partners of 160 of these women participated in the survey. 22% of women who enrolled in the study alone 25% of those who enrolled with their main partner and 18% of these male partners chose female-controlled over-the-counter Barrier Methods alone. The strongest predictor of this choice was current use of a hormonal contraceptive both for women who participated in the study on their own (odds ratio [OR] 2.1) and for those who enrolled their partner in the study (OR 6.3). Female-controlled Methods were also chosen significantly more often by teenagers than by older women; for example among those who enrolled with a male partner the OR for selection of a female-controlled Barrier Method for women younger than age 18 was 6.0. Among women who enrolled without a partner those who had had multiple partners in the previous 6 months and those who were current users of male condoms were less likely to choose female-controlled Methods (OR 0.7 and 0.5 respectively). Although the majority of participants did not choose female-controlled over-the-counter Barrier Methods without also choosing male condoms such female-controlled Methods appear to offer an acceptable alternative for prevention of sexually transmitted infections. They may be a particularly attractive option for individuals using hormonal contraceptives and for teenage women. (authors)
Edmea Cassia Baptista - One of the best experts on this subject based on the ideXlab platform.
-
A Modified Barrier and Barrier Method and the Optimal Power Flow Problem
IEEE Latin America Transactions, 2017Co-Authors: Jessica Antonio Delgado, Edmea Cassia Baptista, Gabriela Fernanda Bregadioli, Leonardo Nepomuceno, Antonio Roberto Balbo, Edilaine Martins SolerAbstract:This work proposes an approach that uses a union of Methods based on logarithmic Barrier function and modified logarithmic Barrier function for the resolution of the reactive optimal power flow problem. In this proposed approach the inequality constraints are transformed into equalities by adding the slack variables, which are handled by logarithmic Barrier function or modified logarithmic Barrier function, and the equality constraints are handled by means of Lagrange multipliers. These Methods are used in two steps. Initially, the Method based on the logarithmic Barrier function is applied until the transition condition is satisfied. After the Method based on modified logarithmic Barrier function is used until the stop condition is satisfied. Numerical tests carried out with the IEEE 14, 30, 57 and 118 bus electrical systems indicate that the proposed approach is efficient in the resolution of the reactive optimal power flow problem and the results obtained by the proposed approach were compared with the logarithmic Barrier Method and the logarithmic Barrier Method modified, separately.
-
primal dual logarithmic Barrier and augmented lagrangian function to the loss minimization in power systems
Electric Power Components and Systems, 2006Co-Authors: Edmea Cassia Baptista, Edmarcio Antonio Belati, Vanusa Alves De Sousa, G R M Da CostaAbstract:This article presents a new approach to minimize the losses in electrical power systems. This approach considers the application of the primal-dual logarithmic Barrier Method to voltage magnitude and tap-changing transformer variables, and the other inequality constraints are treated by augmented Lagrangian Method. The Lagrangian function aggregates all the constraints. The first-order necessary conditions are reached by Newton's Method, and by updating the dual variables and penalty factors. Test results are presented to show the good performance of this approach.
-
logarithmic Barrier augmented lagrangian function to the optimal power flow problem
International Journal of Electrical Power & Energy Systems, 2005Co-Authors: Edmea Cassia Baptista, Edmarcio Antonio Belati, G R M Da CostaAbstract:This paper presents a new approach to solve the Optimal Power Flow problem. This approach considers the application of logarithmic Barrier Method to voltage magnitude and tap-changing transformer variables and the other constraints are treated by augmented Lagrangian Method. Numerical test results are presented, showing the effective performance of this algorithm.
-
Modified Barrier Method for optimal power flow problem
IEEE Power Engineering Society General Meeting 2004., 1Co-Authors: V.a. De Sousa, Edmea Cassia Baptista, G R M Da CostaAbstract:In this paper is presented a new approach for optimal power flow problem. This approach is based on the modified Barrier function and the primal-dual logarithmic Barrier Method. A Lagrangian function is associated with the modified problem. The first-order necessary conditions for optimality are fulfilled by Newton's Method, and by updating the Barrier terms. The effectiveness of the proposed approach has been examined by solving the Brazilian 53-bus, IEEE 118-bus and IEEE 162-bus systems.
Geraldo R. M. Da Costa - One of the best experts on this subject based on the ideXlab platform.
-
A modified Primal-Dual Logarithmic-Barrier Method for solving the Optimal Power Flow problem with discrete and continuous control variables
European Journal of Operational Research, 2012Co-Authors: Edilaine Martins Soler, Vanusa Alves De Sousa, Geraldo R. M. Da CostaAbstract:The aim of solving the Optimal Power Flow problem is to determine the optimal state of an electric power transmission system, that is, the voltage magnitude and phase angles and the tap ratios of the transformers that optimize the performance of a given system, while satisfying its physical and operating constraints. The Optimal Power Flow problem is modeled as a large-scale mixed-discrete nonlinear programming problem. This paper proposes a Method for handling the discrete variables of the Optimal Power Flow problem. A penalty function is presented. Due to the inclusion of the penalty function into the objective function, a sequence of nonlinear programming problems with only continuous variables is obtained and the solutions of these problems converge to a solution of the mixed problem. The obtained nonlinear programming problems are solved by a Primal-Dual Logarithmic-Barrier Method. Numerical tests using the IEEE 14, 30, 118 and 300-Bus test systems indicate that the Method is efficient. (C) 2012 Elsevier B.V. All rights reserved.Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq)Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq
Marek Makowski - One of the best experts on this subject based on the ideXlab platform.
-
Solving a Class of LP Problems with a Primal-Dual Logarithmic Barrier Method
European Journal of Operational Research, 1995Co-Authors: Jacek Gondzio, Marek MakowskiAbstract:Applying a higher order primal-dual logarithmic Barrier Method for solving large real-life linear programming problems is addressed in this paper. The efficiency of an interior point algorithm on these problems is compared with the one of the state-of-the-art simplex code MINOS version 5.3. Based on such experience, a wide class of LP problems is identified for which logarithmic Barrier approach seems advantageous over the simplex one. Additionally, some practical rules for model builders are derived that should allow them to create problems that can easily be solved with logarithmic Barrier algorithms
