By Topic

Latin America Transactions, IEEE (Revista IEEE America Latina)

Issue 1 • Date March 2009

Filter Results

Displaying Results 1 - 15 of 15
  • A Pulsed Control Method for Chaotic Systems

    Page(s): 1 - 11
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (3759 KB)  

    In this paper, it is proposed a method for controlling chaotic systems; where the main goal is to obtain a periodic behaviour for a chaotic system. In our approach, the system to control is considered as a black-box, and therefore it is not necessary to know a mathematical model of the system, only experimental measurements are used. Our method employs pulses with adjustable amplitude and width, and it is implemented in discrete time. In order to generate pulses control, a variable Poincare section is used; which is computed online using a moving average sampling signal. Measurement noise is considered too, by means of an additional controller parameter (hold-off time), resulting that controller tuning is made using four parameters: proportional gain, sampling time, pulse width and hold-off time. In order to test the proposed method, computer simulations with several representative chaotic systems (Lorenz, Chua, Chen, Colpitts and others) are carried out and satisfactory results are obtained. View full abstract»

    Open Access
  • Design and Implementation of a Patterns Recognition System for Analysis of Biological Liquids

    Page(s): 12 - 26
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1067 KB)  

    Given the great amount of data that are generated of the experiments to analyze information of extracted chemical fluids of the brain of a rodent, arises the necessity to design and to implement data mining systems to process this data. In this work is proposed a fuzzy system for the analysis of biological liquids, that allows to analyze and to process the data, and this way, to know a series upheavals product of alterations, storage, and liberation of the neurotransmitters. Our system has been tested to determine the variation of the glutamato neurotransmitter in the cerebral tonsil of the rats. It discovers and it evaluates new rules, and it generates new solutions associated to clinical upheavals. View full abstract»

    Open Access
  • Estimation of Aboveground Forest Biomass in Amazonia with Neural Networks and Remote Sensing

    Page(s): 27 - 32
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (644 KB)  

    This paper proposes an integrated methodology for estimating aboveground forest biomass in Amazon region. It is based on remote sensing, artificial neural networks and geographical information systems technologies for achieving confident results with a lesser cost than traditional methods of forest inventory. This methodology was tested and validated in Tucurui Reservoir, Brazil. View full abstract»

    Open Access
  • Modeling and Analysis in Frequency of the UWB Channel with Lognormal Statistics for MB-OFDM Systems

    Page(s): 33 - 41
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (717 KB)  

    In this paper, the ultra-wideband channel with multiband orthogonal frequency division multiplexing (MB-OFDM-UWB) is analyzed in the frequency domain. For UWB channels with lognormal small-scale fading in time domain, we obtain closed analytical expressions for the parameters that model the sub-carrier fading statistics of MB-OFDM-UWB system, and we show that magnitudes of the channel frequency responses of each subcarrier can be approximated by a Nakagami-m random variable, where the fading parameter (m), mean power Omega and the correlation, rhoij are expressed in terms of the following parameters: arrival time of the clusters, inter-arrival time of the rays inside the clusters, and power decay constants of the rays and clusters. View full abstract»

    Open Access
  • Multi-Model Smith Predictor Based Control of Multivariable Systems with Uncertain Bounded External Delays

    Page(s): 42 - 53
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (629 KB)  

    One of the drawbacks of the Smith Predictor (SP) to control systems with external point delays is that its performance is strongly influenced by the knowledge of the time delay of the plant. Hence, as the mismatch between the actual delay of the plant and the nominal one used in the control structure increases, the closed-loop performance degrades accordingly, even potentially causing instability. This effect is particularly important when dealing with multivariable systems, where there is a coupling between input and output variables. In this paper, an intelligent frame to reduce the dasiaa priori' knowledge of the plant delays required in the design of SP controllers for multivariable systems is proposed. The intelligent frame is composed of a set of different plant delay models running in parallel along with a high level supervision algorithm which selects the one that best describes the actual delay of the plant at each time interval to be used for control purposes. In this way, the designer can design the control of the system based on its delay-free part while the appropriate tuning of the delay of the Smith Predictor is performed by the intelligent supervisor. As a consequence, like simulation examples show, the closed-loop performance of the system is improved without the dasiaa priori' requirement of an accurate knowledge of the value for the time delay. View full abstract»

    Open Access
  • Computation of Radio Interference Levels in High Voltage Transmission Lines with Corona

    Page(s): 54 - 61
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (555 KB)  

    In this article, an analysis of radio interference levels due to high voltage transmission lines with corona is presented. A method to predict radio interference levels, which based on Gary's method and modal decomposition theory, is described and presented, considering also the skin effect in conductors and in the ground plane. Several application examples for 3-phase lines are presented and the results are compared with measurements published elsewhere. View full abstract»

    Open Access
  • Lightning Performance Analysis of an Overhead Transmission Line Protected by Surge Arresters

    Page(s): 62 - 70
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (511 KB)  

    In general, the main causes of unacceptable lightning flashover rates of overhead transmission lines are a bad shield design or too high footing impedances. The first reason will cause unacceptable shielding failure flashover rates (SFOR); the second one can cause high backflashover rates (BFOR). The lightning flashover rate of a shielded transmission line can be reduced by installing surge arresters. In fact, the rate can be reduced to zero by installing arresters at all phases and all towers of the line, but even if arresters are not installed at all phases, a significant improvement of the lightning performance can be achieved. However, arresters have to be selected to withstand the energy stresses caused by lightning strokes; otherwise, failures could be caused by an excess of energy absorption. This paper is aimed at analyzing the lightning performance improvement of a shielded transmission line that can be achieved after installing metal oxide surge arresters as a function of the number of phases at which they are installed and at estimating the energy absorption capability of the selected arresters. View full abstract»

    Open Access
  • Metodology for Lightning Impulse Voltage Divisors Design

    Page(s): 71 - 77
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (790 KB)  

    This paper presents a design methodology for damped capacitive voltage divider for lightning impulse waves measurement; the methodology includes design verification using three different computational tools (EMTP, MATLAB and ELCUT). The methodology was validated by constructing and testing two 300 kV dividers at the High Voltage Laboratory of the Universidad del Valle. View full abstract»

    Open Access
  • Modeling and Simulation of Wind Energy Systems with Matrix and Multilevel Power Converters

    Page(s): 78 - 84
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (849 KB)  

    This paper is concerned with modeling and simulation in Matlab/Simulink of wind energy systems with different topologies for the power converters: matrix converter and multilevel converter. We use pulse modulation by space vector modulation associated with sliding mode for controlling the converters, and we introduce power factor control at the output of the converters. Finally, we present the electric behavior for the power and the current at the input and at the output of the converters. View full abstract»

    Open Access
  • Optimization of the Topology of Electric Energy Distribution Networks by Using Algorithm Inspired on Ant Behavior

    Page(s): 85 - 91
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1016 KB)  

    An algorithm inspired on ant behavior is developed in order to find out the topology of an electric energy distribution network with minimum power loss. The algorithm performance is investigated in hypothetical and actual circuits. When applied in an actual distribution system of a region of the State of Sao Paulo (Brazil), the solution found by the algorithm presents loss lower than the topology built by the concessionary company. View full abstract»

    Open Access
  • Aspect Oriented Navigation Modeling for Web Applications based on UML

    Page(s): 92 - 100
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (761 KB)  

    Navigation modeling is one of the critical activities during Web application development. It is not enough to consider only the navigation modeling based on the elements of the problem domain: it is also necessary to take into account the description of the navigation associated with tasks (i.e. the navigation needed to obtain or provide the inputs for the operations of a task and to show the information about the results of the task). Besides, it is important to describe how non-functional requirements and crosscutting concerns are considered during navigation modeling. Due to these requirements, navigation modeling is a complex and difficult activity whose demands can be satisfied if we adopt an aspect-oriented software development (AOSD) approach that involves aspect-oriented requirements engineering, aspect-oriented navigation design, and a simple trace relation from requirements to navigation. In this work we propose an AOSD method with these features, which considers navigation modeling based on the elements of the problem domain, task navigation modeling, and the separation of the navigation for the aspects identified during requirements engineering from the navigation of the rest of the system. In addition, we provide a notation for the composition of navigation concerns. View full abstract»

    Open Access
  • Decision Management making by AHP (Analytical Hierarchy Process) trought GIS data

    Page(s): 101 - 106
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (718 KB)  

    In this work, we propose the use of the AHP (analytical hierarchy process) as a mathematical tool to structure a multiple criteria problem like a visual pattern. The main objective pursued is to determine what is the optimal placing to build a urban construction to locate a university library. In this case, it has been applied for the Campus of Montegancedo of the Polytechnic University of Madrid (Spain), where the Faculty of Computer science is placed. The data come from a Geographical Information System (GIS). Three different profiles of standard users have been considered and they determine the management of the final decision to take, in order to carry out the study. The use of the commercial software Expert Choice facilitates efficiently this management. View full abstract»

    Open Access
  • Integrating Multiplexing Facilities in the Set of JRMP Subprotocols

    Page(s): 107 - 113
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (822 KB)  

    With the process of adaptation and redefinition of Java Remote Method Invocation for J2ME (Java 2, Micro Edition) environments, a reduced version of the Remote Method Invocation (RMI) came up. In this reduced version, called RMIOP, some heavy features such as multiplexing facility or its capacity to go through firewalls offered by the wire protocol, called Java Remote Method Protocol (JRMP), have been eliminated. In the present article it is explored how the recovery of the multiplexing facilities of JRMP, rejected during the RMIOP definition, can be carried out maintaining the J2ME idiosyncrasy. The article begins showing how to extend the triad of subprotocols already defined (SingleOpProtocol, StreamProtocol and MultiplexProtocol) with a new one (MultiplexConnnectionLessProtocol) equipped with special facilities to multiplex connections. It gives support for fast and light connection connectionless virtual connections generation and recycling. The paper ends with an empirical evaluation of the proposed subprotocols together with the already existing ones, in terms of end-to-end response time and the size of the frames transmitted through the network, showing the goodness of the protocols. View full abstract»

    Open Access
  • Parallel Environment with High Accuracy for Resolution of Numerical Problems

    Page(s): 114 - 121
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (503 KB)  

    In this paper we describe a high performance environment, like cluster computers, with high accuracy obtained by use of C-XSC library. The C-XSC library is a (free) C++ class library for scientific computing for the development of numerical algorithms delivering highly accurate and automatically verified results by use of the interval arithmetic. These calculus in high accuracy must be available for some basic arithmetic operations, mainly the operations that accomplish the summation and dot product. Because of these aspects, we wish to use the high performance through a cluster environment where we have several nodes executing tasks or calculus. The communication will be done by message passing using the MPI communication library. To obtain the high accuracy in this environment extensions or changes in the parallel programs had done to guarantee that the quality of final result done on cluster, where several nodes collaborate for the final result of the calculus, maintain the same result quality obtained in one sequential high accuracy environment. To validate the environment developed in this work we done basic tests about the dot product, the matrix multiplications, the implementation of interval solvers for banded and dense matrices and the implementation of some numeric methods to solve linear systems with the high accuracy characteristic (some of the methods implemented are used in real life applications like hydrodynamic, agriculture and power electric systems). With these tests we done analysis and comparisons about the performance and accuracy obtained with and without the use of C-XSC library in sequential and parallel programs. With the implementation of these routines and methods will be open a large research field about the study of real life applications that need during their resolution (or in part of their resolution) to calculate arithmetic operations with more accuracy than the accuracy obtained by the traditional computational tools. Our software - run on labtec (UFRGS) and Colorado (UPF) clusters. Nowadays we are working in the implementation of parallel versions of programs to solve linear systems (without and with high accuracy) and the optimization of C-XSC library on cluster computers. View full abstract»

    Open Access
  • Simulation of Ad-hoc Routing Protocols in an Interurban University Mesh Network

    Page(s): 122 - 125
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (737 KB)  

    The evolution of the computer networks is visible. New technologies are created and standardized very quickly. The observed tendency is the development of communications structures with simple access to easy users' connection. The mesh networks were created with the objective to be dynamics with quickly and safe user insertion. But, the dynamism found in the mesh networks creates many challenges to the developers and engineers. One of these challenges is the choice or development of one routing algorithm that satisfy all the requirements of the different topologies which may form a mesh network, e.g. one wired network working at the same time with a mobile network. This work has the objective to present the results of the MANETs routing protocols performance evaluation in a mesh topology. View full abstract»

    Open Access

Aims & Scope

IEEE Region 9 provides IEEE Latin America Transactions to enable the publication of non-published and technically excellent papers from Latin American engineers, in Spanish or Portuguese languages.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
José Antonio Jardini (Brasil)
IEEE Fellow Member