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Search Results: 1 - 10 of 489267 matches for " L. V. R.;Neves-Jr "
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Redes dinamicas cognitivas aplicadas no controle supervisório de um fermentador
Mendon?a, Márcio;Arruda, L. V. R.;Neves-Jr, Flávio;
Sba: Controle & Automa??o Sociedade Brasileira de Automatica , 2011, DOI: 10.1590/S0103-17592011000400003
Abstract: this paper uses dynamic cognitive networks (dcn) as an intelligent tool for supervisory control. the dcns are an evolution of fuzzy cognitive maps (fcm). intelligent systems and tools use expert knowledge to build models with inference and / or decision taking abilities. a supervisory control architecture for an alcoholic fermentation process is developed from the acquisition of empirical knowledge from an expert. the objective of the supervisor is to operate the process in normal and critical situations. for this, we propose the use of a dcn model with new types of concepts and relationships that not only represent cause-effect as in fcm models. simulation results are presented to validate the architecture developed.
Identifica??o genética de modelos por pólos e zeros baseada no compromisso entre os erros de polariza??o e variancia
Arruda, L.V.R.;Fávaro, Sílvio;Neves-Jr., F.;
Sba: Controle & Automa??o Sociedade Brasileira de Automatica , 2003, DOI: 10.1590/S0103-17592003000200001
Abstract: this work proposes a genetic algorithm (ga) to solve process estimation problems when the real process presents high orders polynomials (complexity model) or non-linearities, non-minimum phase behavior, etc. the algorithm finds the best linear model in the pole and zero form to represent the real plant using its input and output signals. a new chromosome representation was introduced and a new ''fitness'' function based on the tradeoff bias x variance was developed. to validate this genetic estimator, simulations studies were done and the ga performance was compared with one obtained by use of the traditional least square estimation method.
Identifica o genética de modelos por pólos e zeros baseada no compromisso entre os erros de polariza o e variancia
Arruda L.V.R.,Fávaro Sílvio,Neves-Jr. F.
Sba: Controle & Automa??o Sociedade Brasileira de Automatica , 2003,
Abstract: Este trabalho prop em um algoritmo genético aplicado ao problema de identifica o de plantas n o-lineares, de fase n o-mínima ou plantas lineares de ordem superior. O algoritmo proposto tem como objetivo encontrar um modelo linear na forma de pólos e zeros e de ordem reduzida, que melhor represente a planta real, a partir dos sinais de entrada e saída. Uma proposta inovadora para a representa o dos indivíduos e fun o de ''fitness'' foi desenvolvida neste trabalho. Esta fun o de fitness representa o compromisso entre os erros de polariza o e variancia do modelo estimado. Já a representa o proposta divide o espa o de busca em dois subespa os: um destinado à busca de pólos e zeros de natureza real e outro com a finalidade de se encontrar os pólos e zeros complexos. Resultados de simula o s o utilizados para ilustrar o desempenho do estimador genético desenvolvido.
Um método evolucionário para sintonia de controladores PI/PID em processos multivariáveis
Arruda, Lúcia Valéria R. de;Swiech, Maria Cristina Szpak;Neves-Jr, Flávio;Delgado, Myriam Regattieri;
Sba: Controle & Automa??o Sociedade Brasileira de Automatica , 2008, DOI: 10.1590/S0103-17592008000100001
Abstract: nonlinear multiple-input multiple-output (mimo) processes which are common in industrial plants are characterized by significant interactions and nonlinearities among their variables. thus, the tuning of several controllers in complex industrial plants is a challenge for process engineers and operators. this paper addresses the problem of simultaneously tuning n proportional-integral-derivative (pi/pid) controllers in a coupled multivariable process as a multi-criteria optimization problem. a multi objective genetic algorithm modified by a niching technique with castes formation is proposed to solve this problem. the optimization is carried out in two levels. in the first level a local function that considers both the integral time squared error (itse) and the minimum variance criteria is computed to separately evaluate the performance of each closed loop. thereafter, a global cost function that considers all the loops is used to compute a set of solutions (a set of pi/pid parameters) to the optimization problem. the proposed system was applied to the control of a fluid catalytic cracking (fcc) unit, and its performance was compared to dynamic matrix control (dmc). the results show the applicability and effectiveness of the proposed method.
Um modelo híbrido (CLP-MILP) para scheduling de opera??es em polidutos
Magat?o, Leandro;Arruda, Lúcia Valéria Ramos de;Neves-Jr, Flávio;
Pesquisa Operacional , 2008, DOI: 10.1590/S0101-74382008000300007
Abstract: this work is motivated by the need of optimization in the pipeline-oil distribution scenario. the considered problem involves the short-term scheduling of activities in a specific pipeline. the pipeline is 93.5 km in length, and it connects refinery and harbor tankfarms, conveying different types of commodities (gasoline, diesel, kerosene, etc). an optimization model was developed to determine the pipeline scheduling with improved efficiency. such model combines constraint logic programming (clp) and mixed integer linear programming (milp) in an integrated clp-milp framework. the proposed model uses decomposition strategies, continuous time representation, and intervals that represent time constraints (time windows). real cases were solved in a reduced computational time (order of seconds). the computational results have demonstrated that the model is able to define new operational points to the pipeline, providing significant cost saving. indeed the clp-milp model is an efficient tool to aid the operational decision-making within this real-world pipeline scenario.
A estrutura a termo de taxas de juros no Brasil: modelos, estima??o e testes
Franklin Jr., Sergio L.;Duarte, Thiago B.;Neves, César R.;Melo, Eduardo F. L.;
Economia Aplicada , 2012, DOI: 10.1590/S1413-80502012000200003
Abstract: in this paper, we propose a methodology for the construction of the risk-free interest rate term structure in brazil, using the svensson model for interpolation and extrapolation of the interest rate curves, and genetic algorithms, in complement to traditional algorithms of nonlinear optimization, for estimation of model parameters. the objective is to contribute to the brazilian insurance market, so that insurance ces can appropriately measure their long-term obligations discounting cash flows in a manner that is consistent and coherent, considering the adoption of international standards of solvency supervision and financial reporting by the superintendência de seguros privados (susep). we present the results found in modeling the term structure of a number of interest rate curves in brazil.
Retroperitoneoscopic nephrectomy in benign pathology
Quintela, Rodrigo S.;Cotta, Leonardo R.;Neves, Marcelo F.;Abelha Jr, David L.;Tavora, Jose E.;
International braz j urol , 2006, DOI: 10.1590/S1677-55382006000500004
Abstract: introduction: we report our experience with 43 retroperitoneal laparoscopic nephrectomy for benign kidney disease. materials and methods: all patients had a poor function from obstructive uropathology and renal atrophy. none of these patients had a previous lumbotomy. retroperitoneoscopy was performed with 4 trocar port technique in a lateral position. the retroperitoneal space is created by using a gaur's balloon made of sterile glove. the approach to vascular pedicle was done posteriorly and vessels were clipped by metal and hem-o-lock (weck closure systems, north carolina, usa) clips. the sample was intact extracted in an endo-bag prolonging one trocar incision. results: median operative time was 160 minutes and median blood loss was 200 ml. four cases (9%) were converted to open surgery: one case due to bleeding and 3 cases due to technical difficulties regarding perirenal adherences. most patients (39) checked out from the hospital in day two. four of them were left over 3 days due to wound complications. conclusions: retroperitoneoscopy offers a safe, effective and reproductive access to nephrectomy for benign pathologies.
X-ray method to study temperature-dependent stripe domains in MnAs/GaAs(001)
R. Magalhaes-Paniago,L. N. Coelho,B. R. A. Neves,H. Westfahl Jr.,F. Iikawa,L. Daweritz,C. Spezzani,M. Sacchi
Physics , 2004, DOI: 10.1063/1.1844599
Abstract: MnAs films grown on GaAs (001) exhibit a progressive transition between hexagonal (ferromagnetic) and orthorhombic (paramagnetic) phases at wide temperature range instead of abrupt transition during the first-order phase transition. The coexistence of two phases is favored by the anisotropic strain arising from the constraint on the MnAs films imposed by the substrate. This phase coexistence occurs in ordered arrangement alternating periodic terrace steps. We present here a method to study the surface morphology throughout this transition by means of specular and diffuse scattering of soft x-rays, tuning the photon energy at the Mn 2p resonance. The results show the long-range arrangement of the periodic stripe-like structure during the phase coexistence and its period remains constant, in agreement with previous results using other techniques.
Development of a New Bio-Based Insulating Fluid from Jatropha curcas Oil for Power Transformers  [PDF]
José M. G. Evangelista Jr., Fabrício E. Bortot Coelho, Juliana A. O. Carvalho, Estêv?o M. R. Araújo, Tania L. S. Miranda, Adriane Salum
Advances in Chemical Engineering and Science (ACES) , 2017, DOI: 10.4236/aces.2017.72018
Abstract: The present work aims to develop a new vegetable insulating fluid for power transformers based on Jatropha curcas oil. Besides its technical benefits, Jatropha curcas oil has a socio-economic role by promoting income to rural families, contributing to the countryside development and avoiding rural exodus. Thus, the entire transformer oil production (extraction, processing, characterization and accelerated aging) was covered and a new process was developed. For oil extraction, the most suitable process was the solvent extraction (5 mL of hexane per gram of crushed non-peeled seeds during 30 minutes) with an oil yield of 32%. In raw oil processing stage, the degumming, with 0.4 g of phosphoric acid per 100 g of oil, at 70°C, was used to remove phosphatides. Then, free fatty acids were 96% neutralized with a sodium hydroxide solution (0.5% w/w) at room temperature. For the oil clarification, the combination of 5% w/woil of activated carbon and 1% w/woil of MgO resulted in a bright, odorless and clear oil with an acid number of 0.04 mgKOH·g1. The oil drying in a vacuum rotary evaporator, at 70°C, for 2 hours reduced the water content to 177 ppm. The processed oil was characterized following ASTM D6871 methods. This oil presented higher dielectric breakdown voltage (55 kV) than commercial transformer fluids (BIOTEMP?, EnvirotempFR3?, and Bivolt?), which increases transformer safety, capacity and lifetime. In addition, the processed oil has a lower viscosity than BIOTEMP? fluid, which can enhance the heat dissipation efficiency in the transformer. Moreover, the processed oil flash and fire points of 310°C and >340°C, respectively, confirm the great security of vegetable insulating fluids. The analyzed properties of the processed oil fulfill all the ASTM D6871, ABNT NBR 15422 and IEC 62770 specifications. Therefore, Jatropha curcas oil is a potential substitute formineral insulating fluids.
Efeito de diferentes protocolos de superovula??o sobre a concentra??o plasmática de progesterona e de metabólitos lipídicos de vacas Nelore
Ramos, A.F.;Neves, E.F.;Marques, V.S.;Lima, F.P.C.;Drumond, D.L.;Marques Jr, A.P.;
Arquivo Brasileiro de Medicina Veterinária e Zootecnia , 2007, DOI: 10.1590/S0102-09352007000200001
Abstract: the purpose of this research was to evaluate the concentration of tryglicerides, cholesterol, aspartate transaminase (ast) and progesterone (p4) in embryo donor nelore cows superovulated with different protocols. twenty four donors were randomly distributed in three groups: group 1 (n=11), donors superovulated with 500ui of fsh and group 2 (n=8) and group 3 (n=5) respectively with 200mg and 180mg of fsh, in decreasing doses, twice a day, during four consecutive days. blood samples were collected before superovulation (a), in the third day of superovulation (b), at the artificial insemination time (c) and at the embryo collection time (d). the concentrations of tryglicerides, aspartate transaminase (ast) and cholesterol were measured by spectrophotometry and progesterone (p4) by radioimmunoassay. there was no alteration (p<0.05) in the concentration of tryglicerides, ast and cholesterol among the samples. there was no effect (p>0.05) of the superovulation protocol on the concentration of tryglicerides, ast and p4 in the samples. in the samples a and b of group 2 the concentration of cholesterol was lower (p<0.05) than in groups 1 and 3, probably due to the instability of the parameter.
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