The University "Marta Abreu" of Las Villas " is a university located in Santa Clara, Cuba. It was founded in 1952 and is organized in 12 Faculties and special Mountain Faculty located in Topes de Collantes, the heart of the Escambray Mountain Range. Wikipedia.
Perez Abril I.,University "Marta Abreu" of Las Villas
Electric Power Systems Research | Year: 2017
This work develops the algorithm of inclusion and interchange of variables to obtaining the sizes, the placements and the control schemes of the capacitors banks that minimize the annual total cost while complying with the maximum and minimum voltage constraints. This is a new and very efficient search method that improves the results of the previous contributions. The method considers all the possible locations for capacitors placement as well as the correct interrelation between sizes of all the capacitors of fixed and switched type. Instead of to place the capacitors on candidate nodes that are previously selected by sensitivity factors and then to select their time-controls, the presented method examines the placement of the capacitors in all available positions (node, control) by evaluating directly the effects of the inclusion and the interchange of variables (capacitors) in the value of the objective function. The fact that the optimization of the placements and the time-controls of the capacitors is coordinated with the selection of their sizes, allows the obtaining of a high quality solutions for the optimization problem. The effectiveness of the proposed method is tested by solving various examples and by comparing the obtained results with several previously published solutions for these examples. © 2017
Bello R.,University "Marta Abreu" of Las Villas |
Verdegay J.L.,University of Granada
Information Sciences | Year: 2012
Problem-solving in situations of uncertainty is a key issue in achieving effective computational systems. Various techniques have been developed to address uncertainty, including Soft Computing, which has established itself as an area of significant interest. On the other hand, rough sets theory has become an effective means of dealing with uncertainty, particularly when it arises as a result of inconsistencies in the data. The present paper surveys an analysis of the relationship between rough sets and other components of Soft Computing, and of how this hybridization helps improve system performance. © 2012 Elsevier Inc. All rights reserved.
Roque Diaz P.,University "Marta Abreu" of Las Villas |
Benito Y.R.,Pontifical Catholic University of Rio de Janeiro |
Parise J.A.R.,Pontifical Catholic University of Rio de Janeiro
Energy | Year: 2010
Design and operation of complex systems for combined cooling, heating and power generation (CCHP) are always a matter of matching performance and demand characteristics of a thermal system set to supply electrical, cooling and heating loads, according to specific usage demands. Equipment selection and operation require the characterization of power, heating and cooling load demands, and their time variation during years, seasons, months and even hours or minutes. The paper aims at utilizing a general model for complex CCHP systems. The proposed model is based on the general theory of exergy cost and structural coefficients of internal links. A general model is presented, and a simple hypothetical cogeneration case is studied. The system operates with two heat engines, with waste heat recovery driving a chiller, in order to meet electrical power and refrigeration loads. © 2010 Elsevier Ltd.
Fernandez R.,Ecole Polytechnique Federale de Lausanne |
Martirena F.,University "Marta Abreu" of Las Villas |
Scrivener K.L.,Ecole Polytechnique Federale de Lausanne
Cement and Concrete Research | Year: 2011
This paper investigates the decomposition of three clayey structures (kaolinite, illite and montmorillonite) when thermally treated at 600 °C and 800 °C and the effect of this treatment on their pozzolanic activity in cementitious materials. Raw and calcined clay minerals were characterized by the XRF, XRD, 27Al NMR, DTG and BET techniques. Cement pastes and mortars were produced with a 30% substitution by calcined clay minerals. The pozzolanic activity and the degree of hydration of the clinker component were monitored on pastes using DTG and BSE-IA, respectively. Compressive strength and sorptivity properties were assessed on standard mortars. It was shown that kaolinite, due to the amount and location of OH groups in its structure, has a different decomposition process than illite or montmorillonite, which results in an important loss of crystallinity. This explains its enhanced pozzolanic activity compared to other calcined clay-cement blends. © 2010 Elsevier Ltd.
Santana I.,University "Marta Abreu" of Las Villas |
Ferre M.,Technical University of Madrid |
Izaguirre E.,University "Marta Abreu" of Las Villas |
Aracil R.,Technical University of Madrid |
Hernandez L.,University "Marta Abreu" of Las Villas
IEEE Transactions on Industrial Informatics | Year: 2013
This paper describes the experiences using remote laboratories for education and research in the field of Control Engineering. The use of remote laboratories for education in subjects of control is increasingly becoming a resorted method by the universities in order to offer a flexible service in schedules with greater and better operation of available resources. Nevertheless, for research activities, remote laboratories are not widely used. The aim of this contribution is thereby to apply the experience of remote laboratories in research applications in order to share complex equipments among different researchers. Some experiments are carried out to demonstrate the effectiveness of using remote laboratories in research experiments related to robotic system. The results of the implementation of remote experimentations to control a 3-DOF parallel robot by using Distance Laboratory System (SLD) are exposed. The performance of the system is evaluated by the possibilities and functionality of the proposed remote laboratory platform. © 2005-2012 IEEE.
Santos-Fernandez E.,University "Marta Abreu" of Las Villas |
Scagliarini M.,University of Bologna
Journal of Statistical Software | Year: 2012
Manufacturing processes are often based on more than one quality characteristic. When these variables are correlated the process capability analysis should be performed using multivariate statistical methodologies. Although there is a growing interest in methods for evaluating the capability of multivariate processes, little attention has been given to developing user friendly software for supporting multivariate capability analysis. In this work we introduce the package MPCI for R, which allows to compute multivariate process capability indices. MPCI aims to provide a useful tool for dealing with multivariate capability assessment problems. We illustrate the use of MPCI package through both simulated and real examples.
Perez Abril I.,University "Marta Abreu" of Las Villas
IEEE Latin America Transactions | Year: 2010
The measurements registered in eight of the 50 primary distribution circuits of Santa Clara city (Cuba), shown the presence of a 29.8% of phase currents unbalance and a 51.5% of neutral current as average. The phase current unbalance increases the energy losses in primary circuit and contributes to voltages unbalance on the different buses. On the other hand, the presence of a high neutral current on normal operation make it difficult the detection of earth faults by neutral over current relays. The main purpose of this work is to develop a method that determines the minimal reconnection operations needed for the two-phase three-wire and the single-phase twowire circuit laterals, as well as for the three-phase transformers banks and the single-phase distribution transformers, to minimize the energy losses on the primary distribution circuit and reduce the neutral current to an accepted level. A successful application example of the presented methodology is achieved in a distribution circuit of the Santa Clara city. The results show the energy saving benefits as well as the neutral current reduction on the circuit.
Perez Gil M.,University "Marta Abreu" of Las Villas |
Contreras Moya A.M.,University "Marta Abreu" of Las Villas |
Rosa Dominguez E.,University "Marta Abreu" of Las Villas
Journal of Cleaner Production | Year: 2013
The cogeneration process from sugarcane bagasse is an alternative way to reduce fossil fuels consumption. In the environmental assessment of products, processes and services the methodology of Life Cycle Analysis (LCA) is commonly used. This study aimed to evaluate and compare the environmental impacts of the life cycle of different cogeneration technologies currently used in the Cuban sugar industry. For doing this, a combination of nine steam generators models with eight turbogenerators was analyzed, for a total of 72 alternatives, using the Eco-indicator 99 and the software SimaPro. The electricity generated daily (1000 kWh) was the functional unit used for the analysis. The results showed that the reduction of this process emissions to the air, water and soil had a favorable effect on the categories of carcinogenesis, radiation, ecotoxicity and land use. The category of Human Health damages reached higher impacts in the cogeneration stage, which represented about 80% of the total environmental impact of the process. It was evidenced that the largest contribution to this category was the emissions of particulate material from bagasse combustion. The combination of the steam generator German Modified EKE 80 with the Russian turbogenerator 2500 was the alternative that involved a reduction of the total impact compared to the rest of alternatives. © 2012 Published by Elsevier Ltd.
Abril I.P.,University "Marta Abreu" of Las Villas
International Journal of Electrical Power and Energy Systems | Year: 2016
The primary distribution systems are among the more unbalanced three-phase networks. The unbalance of the phase currents causes two fundamental problems in the circuits: the increase of energy losses in the primary feeders and the presence of a high neutral current in normal operating status that makes it difficult the detection of ground faults by corresponding protections. These circuits are always protected at the substation. Nevertheless, other protections can also be located downstream in some sections or laterals of the circuit. Additionally, a circuit or some section of it can be supplied from another adjacent circuit in emergency conditions. In all the points where a ground fault protection is used, the maximum current of imbalance must be reduced to a minimum considering the several operating conditions that can change the circuit topology. This paper formulates the problem of phase balancing as a multi-objective optimization problem that minimizes: the neutral current at the desired points of the circuit, the energy losses in the primary feeders and the number of reconnected elements to achieve these objectives. The Non-dominated Sorting Genetic Algorithm (NSGA-II) has been used to develop the optimization application, which has shown a very successful performance in the solution of the phase balancing problem. A test example with all the needed data is solved to show the advantages of the presented approach. © 2016 Elsevier Ltd. All rights reserved.
Rodriguez-Martin B.C.,University "Marta Abreu" of Las Villas |
Molerio-Perez O.,University "Marta Abreu" of Las Villas
Frontiers in Psychology | Year: 2014
Food cravings refer to an intense desire to eat specific foods. The Food Cravings Questionnaire-Trait (FCQ-T) is the most commonly used instrument to assess food cravings as a multidimensional construct. Its 39 items have an underlying nine-factor structure for both the original English and Spanish version; but subsequent studies yielded fewer factors. As a result, a 15-item version of the FCQ-T with one-factor structure has been proposed (FCQ-T-reduced; see this Research Topic). The current study aimed to explore the factor structure of the Spanish version for both the FCQ-T and FCQ-T-reduced in a sample of 1241 Cuban adults. Results showed a four-factor structure for the FCQ-T, which explained 55% of the variance. Factors were highly correlated. Using the items of the FCQ-T-reduced only showed a one-factor structure, which explained 52% of the variance. Both versions of the FCQ-T were positively correlated with body mass index (BMI), scores on the Food Thoughts Suppression Inventory and weight cycling. In addition, women had higher scores than men and restrained eaters had higher scores than unrestrained eaters. To summarize, results showed that (1) the FCQ-T factor structure was significantly reduced in Cuban adults and (2) the FCQ-T-reduced may represent a good alternative to efficiently assess food craving on a trait level. © 2014 Rodríguez-Martín and Molerio-Pérez.