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Latin America Transactions, IEEE (Revista IEEE America Latina)

Issue 5 • Date Sept. 2009

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Displaying Results 1 - 15 of 15
  • A complete system for vehicle plate localization, segmentation and recognition in real life scene.

    Page(s): 497 - 506
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (748 KB)  

    There are many applications of plate identification in pattern recognition and machine vision. These applications range from complex security systems to commons areas and from parking admission to urban traffic control. Car license plate recognition (CLPR) has complex characteristics due to diverse effects as fog, rain, shadows, irregular illumination conditions, partial occlusion, variable distances, cars' velocity, scene's angle on frame, plate rotation and conservation, number of vehicles in the scene and other. These factors make plate recognition much more complex and difficult than the traditional pattern or optical character recognition (OCR) systems. The main objective of this work is to show a system that solves the practical problem of car identification for real scenes. All steps of the process, from image scene acquisition to optical character recognition are considered to achieve an automatic identification of plates. It can be used with all type of country rules or plates design and adapted to each situation. The system is computationally very efficient and it is suitable for others related image recognition applications. View full abstract»

    Open Access
  • Spectrum Richness as Determinant of Chaotic Synchronization

    Page(s): 507 - 513
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (776 KB)  

    To know the similarity between two Lorenz chaotics signals and to qualify the synchronization grade of their generators circuits I propound the Spectrum Richness Algorithm (SRA), which calculates the frequency peak contents and shows us only the information harmonics selected by one amplitude level given for the signal to noise rate. The SRA validity is carry out by Dadisp2002e software and it indicates to me that the Spectrum Richness (SR) (at bins), of the generated mixed signals and chaotics signals measured, has a good precision, and of the SR compare of the last ones signals, I conclude that the generators chaotics circuits are fine synchronized. For the next step, I propound make adjustable the compare level and I get a LabVIEW7 version just to do more friendly the synchronization qualification process of hyperchaotics circuits. View full abstract»

    Open Access
  • Wide Band Howland Bipolar Current Source using AGC Amplifier

    Page(s): 514 - 518
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (830 KB)  

    Electrical impedance tomography (EIT) is a promising technique for imaging the conductivity distribution within the body from voltage surface measurements. The measuring precision is very important, where inaccuracies from the current source generate distortions in the images. These are particularly caused by stray capacitances which reduce the frequency response of the instrumentation. This paper investigates the performance of a bipolar current source attached to a multiplexer using an Automatic Gain Control (AGC) Amplifier circuit. Output current measurements were made in the frequency range 100 Hz to 1 MHz and also output impedance at 100 kHz, both with and without the AGC Amplifier circuit. The results showed a constant output current with a maximum error of ±2% when using the AGC Amplifier circuit whereas 300% not using it. Also, the output impedance was approximately 10.4 and 1.2 M¿ with and without using the AGC Amplifier circuit, respectively. It can be concluded that the AGC Amplifier circuit may increase significantly the precision of the current measurements and may improve the image quality in EIT systems. View full abstract»

    Open Access
  • Analysis of the Thunderstorm Activity in Portugal for its Application in the Lightning Protection of Wind Turbines

    Page(s): 519 - 526
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1241 KB)  

    This paper presents a brief characterization of wind power in Portugal, considering the installed power capacity, the capacity under construction, and the location of wind farms. It also describes the Portuguese Lightning Location System, and presents the results of the occurrence of cloud-to-ground strikes both temporally and geographically distributed and the accumulative probability of the peak current. Based on these results, new ground flash density maps were drawn. Thus, this paper allows the characterization of discharges occurring in Portugal, helping to improve risk analysis and the protection systems adopted. View full abstract»

    Open Access
  • Improvement of the Short Term Load Forecasting Through the Similarity Among Consumption Profiles

    Page(s): 527 - 532
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (835 KB)  

    In order to achieve high quality standards in electrical power systems, utility companies rely upon load forecasting to accomplish critical activities such as optimal dynamic dispatch and smart performance in the power wholesale market. Several works propose hybrid intelligent forecasting models to deal with the dynamic and non-linear characteristics of the load at a relatively high computational cost. While such approaches give emphasis to the forecasting itself, this paper presents a procedure to detect similarities among distinct consumption profiles. Empirical results show that similar profiles share similar sets of relevant predictors. As finding similarities among profiles is less costly than finding the set of relevant predictors from scratch, a new parameter selection method is proposed. Such method is employed to build some neural forecasters with a marked improvement in the learning time. View full abstract»

    Open Access
  • Primal-Dual Interior Point Method Applied to the Short Term Hydroelectric Scheduling Including a Perturbing Parameter

    Page(s): 533 - 538
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (496 KB)  

    In this work, the primal-dual interior point method is studied and developed to solve the predispatch DC (direct current) problem that minimizes losses in the transmission and costs in the generation of a hydroelectric power system, formulated as a network flow model. The matrix obtained by the application of the interior point method is reduced of such form that the final linear system can be implemented of efficient form. Moreover, a modification of this method is made on the basis of a heuristic that determines a new perturbing parameter. This modified method(VPMPD) showed to be efficient in the practical and achieved convergence in fewer iterations when compared with an existing implementation of the network flow model, that does not take in consideration such perturbing parameter. View full abstract»

    Open Access
  • Simulation of the transition from Wind only mode to Wind Diesel mode in a no-storage Wind Diesel System

    Page(s): 539 - 544
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (537 KB)  

    A wind diesel hybrid system (WDHS) is any autonomous electricity generating system using wind turbine generators(s) (WTG) with diesel generator(s) (DG). High wind penetration wind diesel hybrid systems (WDHS) have three modes of operation: diesel only (DO), wind diesel (WD) and wind only (WO). In this article a no-storage WDHS with a DG with a clutch to engage/disengaged the diesel engine (DE) from the synchronous machine is simulated. The simulation includes the WO mode and the necessary transition from WO mode to WD mode when the active power produced is less than consumed. It is shown in the graphs that once the lack of active power in WO mode happens, the DE corrects the system frequency after the clutch locks with a maximum overshoot of +1,1 %, a settling time of 6,668 s and with a maximum/minimum voltage variation of -2,9/+3,25%, which are very reasonable values taking into account the strong system disturbance. View full abstract»

    Open Access
  • Single-phase transformer modeling for analyzing transient overvoltages distribution and transference

    Page(s): 545 - 551
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (794 KB)  

    In this article, a frequency domain method for the analysis of transient overvoltages transferred to the secondary winding of a single-phase transformer, as well as the distribution of transient voltages along the transformer windings, is presented. The transformer is modeled as a distributed parameters element from the Telegrapher equations of a multiconductor transmission line in the frequency domain. In order to obtain the time domain, the Numerical Laplace Transform (NLT) is applied. Results from the presented model are compared to those from a model developed in the professional simulation program ATP/EMTP. View full abstract»

    Open Access
  • Supercomponentes Contingency Modeling for Security Assessment in Power Systems

    Page(s): 552 - 559
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (570 KB)  

    The utilization of the power systems to its maximum capacity is a condition that produces economic benefits to all agents involved in the chain of energy supply and thus to society. However, under these conditions, operators can take risks that could cause the loss of system stability and, in the worst case, blackouts. Thus, operators require analysis tools that give them information in order to take preventive and corrective actions, to operate the system in a reliable way and to check the behaviour of the same. Generally, in this type of analysis, simple component's contingencies are used. However, the practice has shown that more than one component (generation unit, circuit line, single transformer, among others) of the system can fail, either by simultaneous outages; events in cascade or by a major outage that means a complete installation with several components gets out of service. So, a super component refers to complex electrical facilities as: substations, generation plants and multiple circuit transmission lines. An outage of the super component implies the multiple and simultaneous outages of many elements. These kinds of events are not, generally, considered in the mentioned analyses; however, it would be very important to keep them in mind in the security evaluation of power systems. This paper presents a methodology to evaluate the severity of this kind of contingencies in the operative planning scenario. The super components that are taken into account are the multiple circuit lines (in the same structure), generation plants and substations. The impact of contingency on power system security is evaluated in a 24-hour ¿day ahead¿ planning horizon through the computation of the energy not supplied, the number of overloaded lines and the percentage of load loss The Energy not supplied is computed as function of a load shedding based on operator's rules. View full abstract»

    Open Access
  • Unit Commitment in a Competitive and Emission Constrained Environment

    Page(s): 560 - 568
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (636 KB)  

    This paper is on the unit commitment problem, considering not only the economic perspective, but also the environmental perspective. We propose a bi-objective approach to handle the problem with conflicting profit and emission objectives. Numerical results based on the standard IEEE 30-bus test system illustrate the proficiency of the proposed approach. View full abstract»

    Open Access
  • Collaborative e-learning and Learning Objects

    Page(s): 569 - 577
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (465 KB)  

    The Learning Object (OA) is any digital resource that can be reused to support learning with specific functions and objectives. The OA specifications are commonly offered in SCORM model without considering activities in groups. This deficiency was overcome through the solution presented in this paper. This work specified OA for e-learning activities in groups based on SCORM model. The solution allows the creation of the dynamic objects which include content and software resources for the collaborative learning processes. That results in a generalization of the OA definition, bringing a contribution to the e-learning specifications. View full abstract»

    Open Access
  • Agile Development for a Beef-Cattle Farm Simulator

    Page(s): 578 - 585
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (619 KB)  

    Today software industry faces new challenges, as to apply innovative strategies to develop new products. These strategies require continuous adjustment to the dynamic changes of software requirements, and therefore, in some cases time-schedule of tasks becomes difficult for planning purposes. In this paper, a project experience during the development of a grazed based beef-cattle farm simulator is presented. Initially the project was developed following a waterfall life cycle but with scant documentation and planning, which was fated to fail. Finally, a agile method was applied which allowed highly positive results from the point of view of developers and customer. View full abstract»

    Open Access
  • Applications oriented medium access control protocols for wireless sensor networks.

    Page(s): 586 - 593
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (733 KB)  

    In this article two new MAC protocols for wireless sensor networks based on TDMA (Time Division Multiple Access) access method are proposed. The proposed protocols are convenient for applications demanding a small number of sensors highly concentrated in a small region, such as in medical areas. The main characteristic of the proposed protocols is the simplified access scheduling that guarantees a low energy consumption and a reduced overhead. The energy consumptions of the proposed protocols are estimated analytically and compared to the consumptions of the protocols known in the literature. The results show that the energy consumptions of the proposed protocols, in certain conditions, are smaller than other compared protocols. View full abstract»

    Open Access
  • On the Vulnerabilities and Protections of the OLSR ad hoc Routing Protocol from the point of view of Trust

    Page(s): 594 - 602
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (1295 KB)  

    The goal of this paper is to explicit the different types of trust relations between entities which exchange routing information and establish a routing infra-structure based on the OLSR protocol. One such entity assumes the other entities will behave in a particular way and the relations coming from this trust behavior are expressed in this paper using a formal language. This approach highlights the process of trust construction in OLSR and allows the analysis of trust requirements for this protocol, as well as the expression of attacks related to the betrayal of trust relations. This analysis allows the formal description of the reasoning for OLSR entities to have a protective mistrust behavior when acting based on trust relations. View full abstract»

    Open Access
  • VoIP Quality of Service in Networks with Active Queue Management

    Page(s): 603 - 611
    Save to Project icon | Click to expandQuick Abstract | PDF file iconPDF (716 KB)  

    This article provides a new analytical method based on a fixed point approach to estimate the impact of active queue management schemes on the quality of service of voice over IP applications. The results obtained by the proposed method were validated using discrete event simulation techniques. In all the studied cases it was observed a great deal of agreement between the analytical results and the results obtained through simulation. The theoretical predictions, as well as the presented empiric evidences demonstrate that the use of active queue management offers a better quality of service than the traditionally queue control mechanisms used in Internet. 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