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Cazarez O.,Mexican Institute of Petroleum | Montoya D.,Mexican Institute of Petroleum | Vital A.G.,National Research Center y Desarrollo Tecnologico | Bannwart A.C.,University of Campinas
International Journal of Multiphase Flow | Year: 2010

A bubbly gas-bubbly oil flow pattern may occur when water, heavy oil and gas flow simultaneously in vertical pipes in such a way that water is the continuous phase. In this work, a one-dimensional, thermal, transient two-fluid mathematical model, for such flow, is presented. The model consists of mass, momentum and energy conservation equations for every phase whose numerical solution is based on the finite difference technique in the implicit scheme. The model is able to predict pressure, temperature, volumetric fraction and velocity profiles. For accurate modeling of multiphase flows, the key issue is to specify the adequate closure relationships, thus drag and virtual mass forces for the gas and oil phases were taken into account and special attention was paid on the gas-oil drag force. When this force was included into the model it was found that: (1) such force had the same order of magnitude than the oil drag force and both forces were smaller than the gas drag force, (2) the pressure, gas and oil velocities and gas and oil volume fraction profiles were affected, (3) the numerical stability was increased. The model predictions are in agreement with experimental data reported in literature. © 2010 Elsevier Ltd. All rights reserved. Source

Sira-Ramirez H.,National Polytechnic Institute of Mexico | Oliver-Salazar M.A.,National Research Center y Desarrollo Tecnologico
IEEE Transactions on Power Electronics | Year: 2013

The concepts of active disturbance rejection control and flatness-based control are used in this paper to regulate the response of a dc-to-dc buck power converter affected by unknown, exogenous, time-varying load current demands. The generalized proportional integral observer is used to estimate and cancel the time-varying disturbance signals. A key element in the proposed control for the buck converter-dc motor combination is that even if the control input gain is imprecisely known, the control strategy still provides proper regulation and tracking. The robustness of this method is further extended to the case of a double buck topology driving two different dc motors affected by different load torque disturbances. Simulation results are provided. © 2012 IEEE. Source

Vazquez N.,Celaya Institute of Technology | Lopez H.,Celaya Institute of Technology | Hernandez C.,Celaya Institute of Technology | Vazquez E.,Celaya Institute of Technology | And 2 more authors.
IEEE Transactions on Industrial Electronics | Year: 2010

DC/AC converters are widely used in several applications; traditionally, they can be classified in two types: the voltage-source inverters (VSIs) and the current-source inverters (CSIs). Their use depends on their application; however, some of them are common for both types of converters. Another possibility for the dc/ac conversion is the multilevel configuration, and the most analyzed is the VSI. In this paper, a different multilevel CSI is proposed: the paralleled configuration. To control the converter, a different sinusoidal pulse with modulation is employed; it consists of modifying the reference signal instead of using multiple carriers. Additionally, a balancing method for the inductor currents is given. The operation, analysis, and implementation are presented; moreover, simulation and experimental results are shown. © 2006 IEEE. Source

Ponce-Silva M.,National Research Center y Desarrollo Tecnologico | Moreno-Basaldua E.A.,National Research Center y Desarrollo Tecnologico
International Journal of Electrical Power and Energy Systems | Year: 2015

Energy flow in sinusoidal systems is analyzed without problems by means of the traditional power definitions such as: apparent, active, and reactive, but these definitions are not properly applied in nonlinear loads. These loads present several distortions which are not correctly measured with the prevailing instruments designed for measuring energy and power. This is because a generalized set of power definitions is not available. In this paper, an alternative set of energy and power definitions is suggested for non-sinusoidal systems. Each definition is obtained through the analysis of power in the time domain. The proposed definitions add information to alleviate the power and energy measurement problem of the power meters, offer alternative indexes to measure the energy distribution, and allow calculations in transient and steady states. Furthermore, an experimental measurement of the proposed powers by means of a half-wave rectifier is shown. © 2014 Elsevier Ltd. All rights reserved. Source

Cervantes Alvarez S.,National Research Center y Desarrollo Tecnologico | Pinto Elias R.,Nacional de Investigacion y Desarrollo Tecnologico
IEEE Latin America Transactions | Year: 2013

This article proposes a selective search method for object localization in natural images by applying image multi-segmentation, image scaling, and heuristics. The method increases the number of generated windows that delimitate the area of an object with an accuracy superior to 50%. Over-segmentation is applied on original size images in order to locate small objects, and it is also applied over scaled images because these can still be over-segmented. This process produces less regions on areas with many textures. The over-segmentation was applied using the CIE Luv color model, and using the H and the I channels of the HSI model. The proposed method is category independent and allows the location of objects with heterogeneous characteristics by using heuristics and hierarchical segmentation. The proposed method produces 9, 366 windows per image covering 96.78% of the objects in the PASCAL VOC 2007 test image collection, increasing in 0.8% the localization results reported in the state of the art © 2003-2012 IEEE. Source

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