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Latin America Transactions, IEEE (Revista IEEE America Latina)

Issue 2 • Date June 2008

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Displaying Results 1 - 15 of 15
  • DOA Estimation in Mobile Communications System using Subspace Tracking Methods

    Publication Year: 2008 , Page(s): 123 - 129
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (428 KB)  

    The radio environments in mobile communications are complicated and time-varing in general; therefore, we need high resolution DoA (direction of arrival) estimation methods that can follow quickly the change of radio environments. High resolution DoA estimation methods have been proposed which are based on the eigen decomposition of the correlation (covariance) matrix of an array input. MUSIC (multiple signal classification) is one of a typical of such methods. However, these methods must normally repeat high-load computation involving the eigen decomposition of a correlation matrix every time a snapshot is taken. Therefore, it takes a very long time to obtain the estimated DoA when the number of array elements is too large. In addition, it is quite inefficient in the case that the DoA estimation is carried out continuously. To solve the above problems, Bi-SVD (bi-iteration singular value decomposition) and PAST (projection approximation subspace tracking) have been proposed and investigated, which are typical methods of successively updating (tracking) eigenvectors in the signal subspace of correlation matrix. View full abstract»

    Open Access
  • Laboratory Projects for Engineering Students with FPGA

    Publication Year: 2008 , Page(s): 130 - 136
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (830 KB)  

    This paper proposes a series of related laboratory projects to the image processing area through reconfigurable integrated circuits like FPGA (field programmable gate array). With the implementation of these projects, the students will not only develop skills in electronic design, they also will increase their knowledge as engineers, with the integration of electronic engineering and computer science in the design of reconfigurable hardware with FPGA's. The algorithms proposed in these laboratory projects, for the image processing, are coded in C++ and are implemented in the embedded microcontroller Microblaze. View full abstract»

    Open Access
  • Design and simulation of a grounding grid for GIS substation

    Publication Year: 2008 , Page(s): 137 - 143
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (741 KB)  

    A grounding grid is designed with the capacity to minimize the very fast transient overvoltage generated during switching operations in a Gas Insulated Substation (GIS). The methodology takes the reference from the IEEE Std. 80-2000 and contains detailed models of GIS and grounding grid. By means an iterative process, new elements are added to the grounding grid for reducing magnitude of a very fast transient overvoltage in different points of a substation. This permits to improve the levels of personal security and the protection of apparatus in the substation. View full abstract»

    Open Access
  • Employment of the FDTD Method in Non-Orthogonal Coordinate System for Simulating Electrical Grounding Structures

    Publication Year: 2008 , Page(s): 144 - 152
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (833 KB)  

    This work presents an overview of the LN-FDTD method (FDTD in local and non-orthogonal coordinate system) to solve Maxwell's equations. This method has been used to simulate non-orthogonal grounding structures (circular plate electrodes and inclined horizontal rods). The obtained results are compared to mathematical formulas available in literature. View full abstract»

    Open Access
  • Non parametric study of the relationship between energy consumption, income and temperature

    Publication Year: 2008 , Page(s): 153 - 161
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    The main goal of this paper is to measure the efficiency in converting energy use in peoplepsilas earnings for some Rio de Janeiro municipalities, Brazil. We used CCR and BCC classical data envelopment analysis (DEA) models, with one input (per capita energy use) and two outputs (average temperature and average monthly earnings). The results indicate that municipalities with higher GDP values have lower efficiency. When discussing the results, we present possible reasons for this fact. View full abstract»

    Open Access
  • Reconfiguration of Distribution Systems using the Newton Method in Quadratic Formulations

    Publication Year: 2008 , Page(s): 162 - 169
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (489 KB)  

    The distribution system reconfiguration problem is concerned with finding the state of all switches in a set of primary distribution feeders so that a given objective function is optimised, typically the minimisation of the total electrical loss. Constraints such as Kirchhoffpsilas Current Law (KCL) and branch capacity are usually enforced. An additional and important constraint is also imposed so that the obtained solutions are all radial. This optimisation problem is a mixed-integer non-linear optimisation problem, in which the integer variables represent the state of the switches and the continuous variables represent the current flowing through the branches. The paper develops new quadratic formulations for the continuous part of the problem. It is shown that all the formulations lead to convex problems, which guarantees that the global minimum is unique and hence allows an efficient application of the standard Newton Method. The paper also presents a new integer search based on the well-known branch-and-bound method. Results from the application of the proposed approaches to three different distribution systems are presented and discussed. View full abstract»

    Open Access
  • Reversibles Hydromaquines Aplicated to Microhydropower

    Publication Year: 2008 , Page(s): 170 - 175
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (480 KB)  

    It is known that hydroelectric micro-generation (MicroCHE) plays an important role in the development of rural and non-interconnected areas to the National Energy System (ZNI). Satisfying electric power requirements find high possibilities as well as hydro-power resources are used in small scale, which are characterized to have a positive environmental impact, forcing to preserve the hydro-resources, besides they are compatible with potable water supplies and other applications. However, equipments for MicroCHE are usually imported and their rating values are not coincident with current necessities of head and water flow from the chosen place. This implementation provides an inefficient and expensive solution. For this reason, an alternative choice , in the environment of MicroCHE, is the application of a centrifuge pump as a turbine, which advantages are industrial serial production, ability to provide a wide range of equipment for heads and water flowpsilas specifications. This solution uses national technology, characterized by its low cost per kilowatt installed. But its implementation requires methods validated in laboratory in order to further application. A research carried out in the laboratory of Small Hydroelectric Power Plant of the School of Electrical and Electronics Engineering - EIEE (University of the Valley), applied to the use of centrifuge pumps as turbines, allowed to validate methods proposed by different schools and authors experimentally. The analysis of the obtained results indicates that additionally it is important to keep in mind the relationship among the inner and outer pumppsilas diameters. This implies that in addition to the qualitative and quantitative parameters to select a pump to operate as a turbine, it should be kept in mind other aspects, explained in this paper. View full abstract»

    Open Access
  • Using an Artificial Neural Network as a Rotor Resistance Estimator in the Indirect Vector Control of an Induction Motor

    Publication Year: 2008 , Page(s): 176 - 183
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (867 KB)  

    This paper presents a rotor resistance estimator based on an artificial neural network (ANN) used in the indirect vector control (IVC) of an induction motor (IM). Attention is focused on the dynamic performance of ANN rotor estimator, which gives superior performance over the fuzzy logic based rotor estimator reported in technical literature. The simulation was done using a 1.5 HP induction motor. The same ANN rotor estimator was proved with other IM having different rated power. The use of the same ANN was possible because the scaling and descaling (normalization) of the input and output of ANN was property done for each motor. The ANN training was done offline using the Levenberg-Marquardt algorithm. The neuronal network is a three-layer network; the first layer has fourteen neurons (or nodes), the hidden layer has five neurons and the output layer has only one neuron because the unique output signal is the rotor resistance value. View full abstract»

    Open Access
  • Valuation of forward contracts in electricity markets. Application to the ecuadorian market

    Publication Year: 2008 , Page(s): 184 - 193
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (681 KB)  

    One of the main characteristics in the electricity markets is the volatileness of the spot price. The uncertainty associated to the price is a source of risk as much for the selling agents (generation companies) like for the buying agents. For this reason, is necessary to develop tools and methodologies of analysis, valuation and risk management associated to the generation business. This paper proposes, formulates and develops a procedure for the valuation of forward contracts with the objective to obtain a suitable balance between risk and rentability in the context of the generation companies that operate in the Ecuadorian electricity market. View full abstract»

    Open Access
  • An access cell selection algorithm for next generation mobile environments

    Publication Year: 2008 , Page(s): 194 - 200
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (635 KB)  

    Next generation of mobile communications will be based on a heterogeneous infrastructure comprising different wireless access systems in a complementary manner. This paper proposes a network selection algorithm based on user activity, user preferences, service requirements, and networks conditions which provides users a prospect of being always best connected within an environment of heterogeneous mobile networks. This is achieved by a learning process which allows user to select an access network based in previous connections and a cost function that helps the user to select the best network that adapts to the needs. View full abstract»

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  • Combination of faces recognition techniques in infrared images by using genetic algorithms

    Publication Year: 2008 , Page(s): 201 - 206
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (438 KB)  

    In this paper are presented the results of optimizing the combination of some common techniques and classifiers applied to faces recognition by the using of genetic algorithms, the set of images used for this approach comes from infrared acquisition. It appears that the proposed scheme improve the system performance compared to the single technique developments. This research opens a wide range of possible applications in the fields of faces recognition. View full abstract»

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  • Data Provenance: Theory and Application to Image Processing

    Publication Year: 2008 , Page(s): 207 - 214
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1384 KB)  

    The provenance is a complementary data documentation. It contains a description of "how", "when", "where", "why" the data were obtained and "who" obtained it. The provenance includes not only the origin of the data but also the description of the processes that produces it. Data provenance might be very helpful in image processing to reproduce images, save disk space, increase speed transmission, protect the copyright and retrieve images. In our work, we have developed a Web processing system that capture and manage image provenance. This systems is integrated with the URLib digital library. Some preliminary tests have shown the feasibility and efficiency of the proposed data provenance management system. View full abstract»

    Open Access
  • Evaluating Classifiers Using ROC Curves

    Publication Year: 2008 , Page(s): 215 - 222
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (451 KB)  

    ROC charts have recently been introduced as a powerful tool for evaluation of learning systems. Although ROC charts are conceptually simple, there are some common misconceptions and pitfalls when used in practice. This work surveys ROC analysis, highlighting the advantages of its use in machine learning and data mining, and tries to clarify several erroneous interpretations related to its use. View full abstract»

    Open Access
  • Image segmentation using Watershed Transform: Marker definition based on fuzzy logic.

    Publication Year: 2008 , Page(s): 223 - 228
    Cited by:  Papers (2)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1166 KB)  

    The Watershed Transform (W.T.) is a useful morphological tool that allows to distinguish complex structures that can not be processed with image processing conventional algoriths. The W.T. floods the image gradient topography from its local minima. These minima indicates the zones where the flooding starts in order to segment the image. The final result is a labeled image where each pixel belongs to a unique region. Gradient of textured images have irrelevant local minima with low contrast. This results in image sobresegmentation in most of the cases. To avoid sobresegmentation, unique object markers are defined. Markers definition, when objects have different texture, size or shape, requires complex solution highly dependent on each particular application. This paper propose an automatic marker definition method for the Watershed Transform using a Mandami fuzzy inference system. The proposed method is simple, robust and easily adaptable to diferent type of images. View full abstract»

    Open Access
  • Policy-based Network Management Reference Architecture for an Integrated Environment WLAN-3G

    Publication Year: 2008 , Page(s): 229 - 235
    Cited by:  Papers (1)
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (551 KB)  

    Strong demands for public wireless broadband services will require more capacity than even that can be supplied by advanced mobile cellular systems. For this reason, there is currently a strong need for interworking mechanisms between WLANs and cellular data networks. But one of the problems which the operators of this new architecture face is its process of management. Policy-based networking (PBN) is a novel technology that facilitates the management and operation of networks. In this article policy-based network management reference architecture for integrated environment WLAN-3G is proposed. 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.

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