Leonardo da C. Brito

Multi-objective memetic algorithm applied to the automated synthesis of analog circuits

In this paper, a Multi-objective Memetic Algorithm applied to the automated synthesis of analog circuits is proposed. The optimization of circuit topologies and their parameters are simultaneously carried out. A variable-size 2D circuit representation is used. In this approach, the initial solutions are created based on expert knowledge through the use of well-known buildingblocks and rules-based coupling schemes. The proposed genetic operators are specific to 2D encoding and they are capable of fomenting a balance between diversity and convergence. A local search process – the Simulated Annealing method – is applied in order to improve the circuit parameters. The results show that the proposed method generates, with small populations and few generations, small well-structured circuits which accomplish the specifications.

A general and robust method for multi-criteria design of microwave oscillators using an evolutionary strategy

This paper describes a general and robust method applied to the optimization of microwave oscillators. This method is a combination of the harmonic balance method, the device-line measurement technique and a multi-objective evolutionary optimizer. The importance of using proper harmonic loads is considered. An example shows that the multi-objective evolutionary algorithm allows the robust exploitation of the trade-off curve of the figures of merit of the oscillator.

Method for the evaluation and classification of power transformer insulating oil based on physicochemical analyses

Power transformers are strategically important assets in the electric power system, because they enable electricity to be transmitted over long distances, with low power losses and voltage drops. Failures of these devices can cause unscheduled interruptions in the supply of electricity, resulting in major disruptions, impaired image of the companies responsible, including penalties imposed by the regulatory agency, and in worst case scenarios, irreparable breakdown of these assets. In this context, the degradation of the insulation system in a power transformer is one of the main causes of problems, which if not properly investigated and/or monitored, can lead to its forced removal from operation [1].

An evolutionary approach for multi-objective optimization of nonlinear microwave circuits

This paper presents an evolution-based (or genetic) stochastic approach applied to simulation-based optimizations of multiple figures of merit of nonlinear circuit models. The dynamics of the evolutionary method allows for a robust search of the optimal set of non-inferior solutions (Pareto front of the problem), i.e., it tries to achieve the best trade-off curves of the problem. An example shows the robustness of the proposed approach as well as its capacity of achieving sets of solutions with good diversity.

A New Efficient and General Design Method of Oscillators Based on Genetic Algorithm and on the Device-Line Measurement Technique

This paper introduces a new optimization method applied to negative-resistance microwave oscillators. The optimization is carried out using a Genetic Algorithm associated with the Device-line Measurement technique. The circuits are simulated using a Harmonic Balance simulator. The optimization results show that the proposed method can robustly find optimal or close-to-optimal solutions.

Metrics for partial discharge detection by the acoustic emission technique to support decision-making

The identification of metrics or ranges of parameters for the detection of partial discharges by the acoustic emission method for the diagnosis and/or classification of power transformers according to their state is essential to support decisions about equipment stoppages at the proper time, i.e., before a failure occurs. This paper discusses these parameters based on the analyses of several field trials, using an algorithm to generate decision trees, as well as a case study to validate the methodology, which was successfully applied in preventive maintenance.

Abordagem Hipermídia Educacional Adaptativa para a Personalização do Processo de Ensino Através da Web

A educacao a distancia tem ganhado significativa atencao tanto na academia quanto nas iniciativas governamentais. Neste contexto, cresce tambem a preocupacao com a avaliacao da qualidade dos diversos aspectos destes cursos mediados pelas tecnologias da informacao e comunicacao. Apesar de muitos trabalhos discutirem diversos aspectos da avaliacao em Ead, a literatura carece de relatos de experiencia que, especialmente, abordem os cursos tecnicos a distancia que possuem especificidades relevantes. Assim, este trabalho relata uma experiencia onde se avalia e adapta uma das propostas existentes na literatura de avaliacao mediada por foruns, ao contexto dos cursos tecnicos a distancia, constituindo-se esta adaptacao e sua discussao as principais contribuicoes do mesmo.Em Educacao a Distância mediada por meio de Ambientes Virtuais de Aprendizagem, foruns de discussao sao um instrumento importante e amplamente utilizado na articulacao de debates e discussoes entre os atores envolvidos no processo de ensino e aprendizagem. Com a ampla utilizacao dos foruns muitas mensagens sao trocadas e isso, por vezes, excede a capacidade de monitoramento por parte dos professores e tutores. O presente trabalho apresenta a concepcao de um classificador de mensagens de foruns que classifica as mensagens em positivas ou negativas, a fim de identificar mensagens que necessitam de maior atencao. Este trabalho aplica conceitos de mineracao de textos, com o algoritmo SVM obtendo taxas de acerto satisfatorias.Este artigo apresenta o framework Contagious, cujo proposito e estabelecer diretrizes que norteiem a construcao de redes sociais online orientadas a Difusao de Inovacoes. Compreendo-se o fenomeno das redes sociais online como consequencia natural do carater social do ser humano, vislumbrou-se esse meio tecnologico de comunicacao e interacao social como potencial ferramenta para a extensao de praticas educativas, com vistas a formacao do carater integral do cidadao. Para isso, foi adotada a teoria de Difusao de Inovacoes, propria das ciencias sociais. As contribuicoes deste trabalho, portanto, compreendem duas vertentes: a) o mapeamento de principios de uma teoria social na forma de recursos computacionais e; b) um enfoque orientado a educacao sobre as redes sociais online.A proposta do trabalho consiste em desenvolver um sistema para ser usado no celular como ferramenta de auxilio para alfabetizacao, utilizando-se de imagens e sons como forma de facilitar o aprendizado. Como metodo de desenvolvimento utiliza-se o processo P@PSEduc (Processo Agil para Software Educativo) e a ferramenta JME (Java Micro Edition).O crescente uso e difusao de tecnologias Web, a ubiquidade de ferramentas educacionais vem proporcionado verdadeiras revolucoes nos ambientes de ensino. Atualmente, sabe-se que nao mais se deve tratar alunos de forma homogenea, como se assim os fossem. Em face disso, este artigo apresenta um sistema adaptativo de apoio a aprendizagem colaborativa, cujo tema e a construcao e representacao do conhecimento por meio de mapas mentais multimidia. Tal sistema, baseia-se na Teoria da Carga Cognitiva, cuja preocupacao primaria e a facilidade com a qual as informacoes sao processadas pelos individuos.

Biobjective Hybrid Evolutionary Algorithm Applied to Resonator Filters of Arbitrary Topology

This paper presents a hybrid evolutionary algorithm to synthesize the resonator filters of an arbitrary topology. In this approach the structure space is explored concerning predefined small building-blocks having specific functionalities (resonator or coupling) and rules for structural restrictions. The method used 2D representation, proposing new strong genetic operators and combining a biobjective evolutionary algorithm to evolve topologies and local search to improve the circuit parameters. The results showed that the proposed method generates, with small populations and few generations, small well-structured circuits which accomplish the specifications. Two examples using building-blocks with elements R/L/C are presented and the characteristics were consistent with those circuits obtained by the conventional approach.

Constrained Mixed Integer Programming Solver Based on the Compact Genetic Algorithm

This paper presents a solver, the PIMAGc, for optimization of constrained mixed integer programming problems based on the Compact Genetic Algorithm (cGA). As the cGA, the PIMAGc works with binary representation of variables. As comparison criteria and to measure the algorithms performance, the PIMAGc was compared with the MI-LXPM, an appropriate algorithm for solving mixed integer programming problems. By using an appropriate number of problems, it was found that the PIMAGc outperformed the MI-LXPM with a greater success rate and a smaller number of evaluations on the majority of the problems, with equal performance on the others.

Interactive Evolution Strategies for Minimizing Single-objective Functions

This article discusses issues related to the application of the user interactivity in optimization process, aided by the method of the Evolution Strategies, with the objective of improve the minimization process of the evaluated functions, both in their response and in the time of obtaining, through the intervention of the user. Its development is based on the methodology of the Evolution Strategies, characterized by the concept of natural selection. However, the minimization process requires an intervention in the stagnations of local minima to get a better efficiency. To increase the applicability of the approached methodology, it is proposed the use of the user interactivity in minimization process, allowing the manipulation of mutation rate and recombination, activation of the mutation of self-adaptive parameters as well as monitoring the whole process. The proposed methodology was used in the evaluation of test functions for optimization, as well as in the evaluation of a real case.