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Variable air-gap hysteresimeter - An alternative method for the characterization of permanent magnets

Journal of Microwaves and Optoelectronics 2009年第1期8卷 26S-37S页

作者： Filho, Aly F. Flores Anocibar, Hector R. Homrich, Roberto P. Laboratory of Electrical Machines Energy and Drivers Post-Graduate Program in Electrical Engineering UFRGS Av. Osvaldo Aranha 103 CEP 90035-190 Porto Alegre Rio Grande do Sul Brazil

The determination of the main magnetic properties of permanent magnets usually requires sophisticated and expensive measuring systems. This work analyzes and proposes a low-cost system for the characterization of Rare-Earth permanent magnets with linear characteristic that is simple to set up. Its magnetic circuit comprehends the permanent magnet under test, a steel yoke, a variable air-gap;a Hall-effect sensor connected to a Gaussmeter measures the flux density within the variable air-gap. The theoretical basis of the proposed measuring system, a description of its assembly, and the results it produces for a Neodymium-Iron-Boron permanent magnet will be presented. © 2009 SBMO/SBMag.

关键词： Permanent magnets

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A neural network modelling of steel joint block shear capacity

A neural network modelling of steel joint block shear capaci...

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9th International Conference on the Application of Artificial Intelligence to Civil, Structural and Environmental engineering, AICivil-Comp 2007

作者： Rodrigues, F. Neto, L. Biondi Da S. Vellasco, P.C.G. De Lima, L.R.O. Vellasco, M.M.B.R. Post-Graduate Program in Civil Engineering Brazil Electronic Engineering Department Brazil Structural Engineering Department State University Rio de Janeiro Brazil Electrical Engineering Department Pontifical Catholic University Rio de Janeiro Brazil

ISBN: (纸本)9781905088201

Despite the multiple failure modes associated to bolted steel joints the block shear failure is frequently the controlling limit state of gusset plates, tension members and coped beam joints. The block shear rupture is characterised by a condition where a steel block area, nearby the holes of bolted joint region, reaches its maximum capacity dictated by a tension to shear interaction. If the joint is loaded beyond this limit a steel block is eventually separated from the main structure. Many models have been proposed to avoid shear block failure in steel design. These models incorporate a combination of the various hypotheses that control the structural rupture. In the majority of cases, it involves a combination of rupture and yielding in the tension and shear planes of the designed joint. Various design formula for this structural engineering problem were proposed all over the years but a closed solution has not yet been reached, due to the influence of several independent parameters. Many studies have already been carried out with the available experimental data, however, non negligible errors are still present in the current design formulae. The main objective of the present paper is to present a back propagation neural network evaluation of the block shear phenomenon. The main neural network input parameters were the geometrical and material variables that control the block shear design. The neural network output parameter was the block shear capacity. The neural network training was based on experimental results present in literature and adopted cross validation techniques to avoid the neural network overfitting. The neural network results were promising, with reduced associated errors and confirmed the possibility of using this methodology to generate trustworthy data. These new data, coupled with the existent experiments, can help the production of more accurate design formulae. © Civil-Comp Press, 2007.

关键词： Neural networks

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Real-time wavelet transform algorithms for the processing of continuous streams of data

Real-time wavelet transform algorithms for the processing of...

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2005 IEEE International Workshop on Intelligent Signal Processing

作者： Mota, Hilton De O. Vasconcelos, Fláio H. Da Silva, Rogério M. Post-graduate Program in Electrical Engineering Universidade Federal de Minas Gerais Belo Horizonte Brazil Electrical Engineering Department UFMG Belo Horizonte Brazil

ISBN: (纸本)078039030X

Two new algorithms to compute the direct and the inverse discrete wavelet transform of continuous streams of data are discussed in this paper. The algorithms are optimized to be used in uniprocessor systems, presenting as one of their main features the ability to compute over the borders of the data segments without relying on any techniques that are traditionally used for this task, like zero padding. A modified version of the Recursive Pyramid Algorithm was used to compute the direct transform, keeping just the features to minimize data storage but eliminating its dependency on extension techniques. The inverse transform is computed by an algorithm inspired in the RPA, the quadrature mirror filter bank and the overlap-save method for filter convolutions. To evaluate the performance the algorithms were implemented on a DSP coupled to a digitizer through its external memory bus, what allowed deterministic behavior. After a stage of optimization an analysis of data storage and computation load were made. These results and the potential applications are discussed at the end of the paper. ©2005 IEEE.

关键词： Data processing

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Data processing system for denoising of signals in real-time using the wavelet transform

Data processing system for denoising of signals in real-time...

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3rd International Workshop on Intelligent Solutions in Embedded Systems, WISES'05

作者： Mota, Hilton De O. Vasconcelos, Flávio H. Electrical Engineering Post-graduate Program - PPGEE UFMG Centro Universitário de Belo Horizonte Belo Horizonte Brazil Electrical Engineering Department UFMG - Universidade Federal de Minas Gerais Belo Horizonte Brazil

This paper describes a system able to acquire, process and eliminate noise in continuous streams of data in real-time. The signal processing algorithms were based on the discrete wavelet transform and employ a new approach to deal with border problems, allowing to process the data continuously. The system was implemented using a DSP coupled to a digitizer through its external memory bus to guarantee deterministic behavior while maintaining some degree of flexibility in its configuration. The achieved performance and potential applications are discussed at the end of the text.

关键词： Real time systems

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Fuzzy set-based multiobjective allocation of resources: Solution algorithms and applications

Fuzzy set-based multiobjective allocation of resources: Solu...

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作者： Carvalho, Milene B. Ekel, Petr Ya. Martins, Carlos A.P.S. Pereira Jr., Joel G. Post Graduate Program in Electrical Engineering Pontifical Catholic University of Minas Gerais Av. Dom Jose Gaspar 500 30535-610 Belo Horizonte MG Brazil

This paper presents results of research in the use of the Bellman-Zadeh approach to decision- making in a fuzzy environment for solving multiobjective optimization problems. Its application conforms to the principle of guaranteed result and provides constructive lines in obtaining harmonious solutions on the basis of analyzing associated maxmin problems. The application of the approach permits one to realize an effective (from the computational standpoint) as well as rigorous (in view of obtaining solutions from the Pareto set) method of analyzing multiobjective models. The use of the Bellman-Zadeh approach has served as a basis for solving problems of multiobjective allocation of resources (or their shortages) and developing a corresponding adaptive interactive decision making system (AIDMS). Its calculating kernel permits one to solve maxmin problems using an algorithm based on a non-local search (modification of Gelfand's and Tsetlin's "long valley" method) as well as a genetic algorithm. The comparison of their computational performance is given on the basis of solving problems of multiobjective power shortage allocation in power systems. © 2005 Elsevier Ltd. All rights reserved.

关键词： Resource allocation

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Mandatory and discretionary policies for CORBA security

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Journal of Network and Systems Management 2005年第3期13卷 309-328页

作者： Westphall, Carla Merkle Da Silva Fraga, Joni Caixa Postal 476 88040-970 Florianópolis SC Brazil Department of Automation and Systems Post-Graduate Program in Electrical Engineering Federal University of Santa Catarina Florianópolis SC Brazil Rua Capitão Américo CEP 88037-060 Florianopolis SC Brazil

This paper proposes extending the CORBA (Common Object Request Broker Architecture) security model to make possible the use of mandatory policies and policy management in distributed applications. Mandatory policies and a policy service were proposed for insertion in the JaCoWeb Project, which is developing an authorization scheme for large-scale networks based on CORBA security standards. In this paper, there is a combination of client-side and server-side access control, in a single domain. Our mandatory control is carried out on the level of ORB (Object Request Broker), on the client side, preventing, in unauthorized accesses, the emission of the corresponding requisition, the associated processing on the server and also, the generation of new requests through this unauthorized processing. In this paper, operations of security management not currently included in the OMG standards are also proposed. The paper further presents implementation results and an evaluation of these results based on common criteria. © 2005 Springer Science+Business Media, Inc.

关键词： Security of data

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A noise-compensated estimation scheme for AR processes

A noise-compensated estimation scheme for AR processes

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IEEE Conference on Decision and Control

作者： R. Diversi R. Guidorzi U. Soverini Post-Graduate Program in Biotechnology Federal University of Espirito Santo Vitoria Brazil Post-Graduate Program in Electrical Engineering Federal University of Espirito Santo Vitoria Brazil Post-Graduate Program in Psychology Federal University of Espirito Santo Vitoria Brazil

This paper deals with the problem of identifying autoregressive models in presence of additive measurement noise. A new approach, based on some theoretical results concerning the so-called dynamic Frisch scheme, is proposed. This method takes advantage of both low and high order Yule-Walker equations and allows to identify the AR parameters and the driving and output noise variances in a congruent way since the estimates assure the positive definiteness of the autocorrelation matrix of the AR process. Simulation results are reported to show the effectiveness of the proposed procedure and compare its performance with those of other identification methods.

关键词： Equations Additive noise Autocorrelation Parameter estimation Noise measurement Signal processing Predictive models Speech analysis Geoscience Estimation error

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Real-time wavelet transform algorithms for the processing of continuous streams of data

Real-time wavelet transform algorithms for the processing of...

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IEEE International Symposium on Intelligent Signal Processing

作者： Hd.O. Mota F.H. Vasconcelos R.M. da Silva Post graduate Program in Electrical Engineering PPGE Universidade Federal de Minas Gerais Belo Horizonte Brazil Electrical Engineering Department DEE UFMG Belo Horizonte Brazil

Two new algorithms to compute the direct and the inverse discrete wavelet transform of continuous streams of data are discussed in this paper. The algorithms are optimized to be used in uniprocessor systems, presenting as one of their main features the ability to compute over the borders of the data segments without relying on any techniques that are traditionally used for thus task, like zero padding. A modified version of the recursive pyramid algorithm was used to compute the direct transform, keeping just the features to minimize data storage but eliminating its dependency on extension techniques. The inverse transform is computed by an algorithm inspired in the RPA, the quadrature mirror filter bank and the overlap-save method for filter convolutions. To evaluate the performance the algorithms were implemented on a DSP coupled to a digitizer through its external memory bus, what allowed deterministic behavior. After a stage of optimization an analysis of data storage and computation load were made. These results and the potential applications are discussed at the end of the paper.

关键词： Continuous wavelet transforms Wavelet transforms Signal processing algorithms Discrete wavelet transforms Filter bank Mirrors Memory Digital signal processing Biomedical signal processing Fourier transforms

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Fuzzy logic in voltage and reactive power control in regulated and deregulated environments

Fuzzy logic in voltage and reactive power control in regulat...

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IEEE PES Transmission and Distribution Conference and Exposition

作者： P.Y. Ekel L.D.B. Terra M.F.D. Junges F.J.A. de Oliveira A. Melek T.Y. Taguti Post Graduate Program in Electrical Engineering Pontifical Catholic University of Minas Gerais Belo Horizonte Minas Gerais Brazil COPEL Transmission Parana State Energy Company Curitiba Parana Brazil

This paper presents results of research aimed at improving the efficiency of coordinated on-line control of voltage and reactive power on the basis of developing models, methods, and a control system integrating traditional numerical methods with fuzzy logic technology. An approach based on experimental design is applied to construct diverse types of sensitivity indices, which serve for evaluating efficiency of control actions and, therefore, for constructing fuzzy production rules included in the knowledge base. The rules considered in the paper are applicable for voltage and reactive power control in regulated and deregulated environments. Questions of constructing linguistic variables and tuning a fuzzy model are discussed. Some aspects of rational carrying out of fuzzy logic procedures are considered.

关键词： Fuzzy logic Reactive power control Fuzzy control Voltage control Power system modeling Production Control system synthesis Fuzzy set theory Expert systems Paper technology

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Fuzzy set theory based emergency control for power distribution systems

Fuzzy set theory based emergency control for power distribut...

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IEEE Power engineering Society Winter Meeting, 2000

作者： Cavati, C.R. Ferreira, E.P. Ekel, P.Ya. Federal University of Espirito Santo Department of Electrical Engineering Av. Fernando Ferrari S/N VitóriaES29060-970 Brazil Pontificia Catholic University of Minas Gerais Post Graduate Program in Electrical Engineering Av. Dom Jose Gaspar 500 Belo HorizonteMG30535-610 Brazil

ISBN: (纸本)0780359356

This work presents results of research related to an emergency control for distribution systems. The problem is formulated within the framework of a fuzzy transportation network problem. An effective fuzzy integer programming model is proposed with solution based on satisfaction of operational levels. The proposed methodology has been applied to a realistic power distribution system based on a primary distribution network. The results demonstrate that the approach provides not only the convincing satisfaction of the actual requirements of the power distribution system, but also offers more information to the decision maker to improve decision making quality. © 2000 IEEE.

关键词： Fuzzy set theory

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