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Cartago, Costa Rica

The Costa Rica Institute of Technology, , also known as "ITCR" or "TEC", is a public university specialized in engineering and science in Cartago, Costa Rica.The university is one of the most prestigious higher education institutions in Costa Rica and also in Central America. Its mission is: "Contributing to the integral development of the country, by means of the formation of human resources, research and extension; keeping the scientific-technical leadership, the academic excellence and the strict attachment to the ethical, environmental and humanists norms, from a state university perspective of quality and competitiveness at national and international level".The ITCR is a national autonomous institution of higher education, dedicated to the teaching, research and extension in technology and associated science aimed at the development of Costa Rica. It was created by Law No. 4777 on June 10, 1971. Its main campus is in Cartago, 24 km east of the capital San José.The ITCR offers both undergraduate and graduate studies in a wide range of fields, including engineering , computer science and business management. Wikipedia.

Salazar J.L.,Costa Rica Institute of Technology | Chen W.-L.,Kun Shan University
Energy Conversion and Management

A compressible CFD code has been developed to study the heat transfer characteristics of a β-type Stirling engine with a very simple design and geometry. The results include temperature contours, velocity vectors, and distributions of local heat flux along solid boundaries at several important time steps as well as variations of average temperatures, integrated rates of heat input, heat output, and engine power. It is found that impingement is the major heat transfer mechanism in the expansion and compression chamber, and the temperature distribution is highly non-uniform across the engine at any given moment. The results, especially the rates of heat transfer, are quite different from those obtained by a second-order model. The variations of heat transfer rates are much more complicated than the simple variations returned by the second-order model. This study sheds light into the complex heat transfer mechanism inside the Stirling engine and is very helpful to the understanding of the fundamental process of the engine cycle. © 2014 Elsevier Ltd. All rights reserved. Source

Moya R.,Costa Rica Institute of Technology | Bond B.,Virginia Polytechnic Institute and State University | Quesada H.,Virginia Polytechnic Institute and State University
Wood Science and Technology

Teak (Tectona grandis L. f) has been introduced to reforestation programs in many tropical countries for timber production. The use of teak plantations has changed the supply from large-diameter logs to small-diameter logs featuring a higher proportion of juvenile wood and more knots. Generally, the teak from fast-growth plantation is harvested after 15-30 years of growth, with logs ranging from 12 to 30 cm in diameter. The goal of this work was to review the factors that influence the heartwood formation, variation, quality, color, and durability in teak and to understand which factors should be controlled in fast-growth plantations. Important factors in the heartwood properties of teak trees from fast-growth plantations are as follows: the tree age, longitudinal variation, geographic location, environmental conditions, and silvicultural activities. These factors influence heartwood extractive content, color variation, and durability. © 2014 Springer-Verlag Berlin Heidelberg. Source

Meza C.,Costa Rica Institute of Technology | Biel D.,University of Barcelona | Jeltsema D.,Technical University of Delft | Scherpen J.M.A.,University of Groningen
IEEE Transactions on Control Systems Technology

A Lyapunov-based control scheme for single-phase single-stage grid-connected photovoltaic central inverters is presented. Besides rendering the closed-loop system globally stable, the designed controller is able to deal with the system uncertainty that depends on the solar irradiance. A laboratory prototype has been built as a proof of concept for the proposed control technique. A nonlinear passive adaptive controller has been programmed in a field-programmable gate array. © 2011 IEEE. Source

Moya R.,Costa Rica Institute of Technology | Marin J.D.,University of Tolima
New Forests

Commercial Tectona grandis plantations using clones have attracted considerable interest for lumber production in tropical regions where small areas are frequent. However, studies on wood properties are limited. Therefore, the purpose of this study is to group clones with similar wood color characteristics using the CIELab system, and mechanical resistance by dynamic stiffness (Ed) in order to obtain different types of clones for different climate and edaphic conditions. It was found that lightness (L*), yellowness (b*), redness (a*), and Ed are similar to those found for other plantation trees. These wood characteristics are significantly influenced by clone and site. Variance due to clone and site went from 31 to 53% and from 2.95 to 24.22%, respectively. Another source of variance was distance from pith, with the exception of parameter b*, which was not affected. Finally, clones were grouped (using multivariate analysis) according to color and mechanical resistance. This analysis established 4 groups by color and 5 groups by Ed. Clone clustering will allow us to choose or use clones with similar wood properties according to site and environmental conditions increasing area production and wood quality uniformity. © 2011 Springer Science+Business Media B.V. Source

Chavarria J.,Polytechnic University of Catalonia | Biel D.,Polytechnic University of Catalonia | Guinjoan F.,Polytechnic University of Catalonia | Meza C.,Costa Rica Institute of Technology | Negroni J.J.,Metropolitan University of Technology
IEEE Transactions on Industrial Electronics

This paper presents an energy-balance control strategy for a cascaded single-phase grid-connected H-bridge multilevel inverter linking n independent photovoltaic (PV) arrays to the grid. The control scheme is based on an energy-sampled data model of the PV system and enables the design of a voltage loop linear discrete controller for each array, ensuring the stability of the system for the whole range of PV array operating conditions. The control design is adapted to phase-shifted and level-shifted carrier pulsewidth modulations to share the control action among the cascade-connected bridges in order to concurrently synthesize a multilevel waveform and to keep each of the PV arrays at its maximum power operating point. Experimental results carried out on a seven-level inverter are included to validate the proposed approach. © 2012 IEEE. Source

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