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Search Results: 1 - 10 of 515769 matches for " José A. Reyes-Retana "
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New Approaches to the Computer Simulation of Amorphous Alloys: A Review
Ariel A. Valladares,Juan A. Díaz-Celaya,Jonathan Galván-Colín,Luis M. Mejía-Mendoza,José A. Reyes-Retana,Renela M. Valladares,Alexander Valladares,Fernando Alvarez-Ramirez,Dongdong Qu,Jun Shen
Materials , 2011, DOI: 10.3390/ma4040716
Abstract: In this work we review our new methods to computer generate amorphous atomic topologies of several binary alloys: SiH, SiN, CN; binary systems based on group IV elements like SiC; the GeSe 2 chalcogenide; aluminum-based systems: AlN and AlSi, and the CuZr amorphous alloy. We use an ab initio approach based on density functionals and computationally thermally-randomized periodically-continued cells with at least 108 atoms. The computational thermal process to generate the amorphous alloys is the undermelt-quench approach, or one of its variants, that consists in linearly heating the samples to just below their melting (or liquidus) temperatures, and then linearly cooling them afterwards. These processes are carried out from initial crystalline conditions using short and long time steps. We find that a step four-times the default time step is adequate for most of the simulations. Radial distribution functions (partial and total) are calculated and compared whenever possible with experimental results, and the agreement is very good. For some materials we report studies of the effect of the topological disorder on their electronic and vibrational densities of states and on their optical properties.
Centered honeycomb NiSe2 nanoribbons, structure and electronic properties
J. A. Reyes-Retana,G. G. Naumis,F. Cevantes-Sodi
Physics , 2013, DOI: 10.1021/jp409504f
Abstract: Quasi one-dimensional nanoribbons are excellent candidates for nanoelectronics, therefore here we investigate by means of density functional theory the structure and electronic properties of a new kind of 1D ribbons, namely: centered honeycomb NiSe2 nanoribbons. Depending on the crystallography and atomic composition of the edges, these ribbons can belong to one of six (two) zigzag (armchair) families. In the zigzag families, after edge reconstruction, all the bare ribbons are metallic. The influence of edge hydrogen passivation produces band gaps in two of the six families. For the armchair nanoribbons, the geometrical reconstruction leads to semiconductors with small band gap and the hydrogen passivation of the edges increases the band gap up to ~0.6 eV.
CONTRIBUYEN LAS MATEMáTICAS CON LA ESTRATIFICACIóN Y EXCLUSIóN SOCIAL EN LA SOCIEDAD CONTEMPORáNEA? ( DOES CONTRIBUTE MATHEMATICS WITH THE STRATIFICATION AND SOCIAL EXCLUSION IN THE CONTEMPORARY COMPANY?)
García Retana José ángel
Revista Electrónica Actualidades Investigativas en Educación , 2010,
Abstract: Resumen:En el presente ensayo se analiza la escuela en tanto aparato ideológico del estado, cuyo rol es definido por los sectores socio-económicos dominantes, siendo su objetivo la reproducción de las fuerzas productivas. Se considera el papel que juega el aprendizaje de las matemáticas y como tal aprendizaje contribuye a tal fin, así como a la estratificación y la exclusión social. Consideramos que el aprendizaje de las matemáticas se enmarca básicamente en dos niveles y cada uno de éstos a su vez se divide en dos categorías, donde las matemáticas discurren del pensamiento casi exclusivamente concreto al fundamentalmente abstracto. Debido a lo anterior el problema del aprendizaje de las matemáticas no se puede considerar como de carácter exclusivamente metodológico, puesto que el mismo podría estar siendo influido, en gran parte, por los factores socio-económicos que determinan la vida de los educandos.Abstract:This essay analyzes school as an ideological, state apparatus whose role is defined by the dominant socio-economic sectors; being the reproduction of productive efforts its goal. The role played by learning mathematics is considered along with learning within its own ends, as well as social stratification and exclusion. We consider learning mathematics as basically belonging to two levels, each of which is divided into two categories, where mathematics passes from thinking almost exclusively in the concrete to the fundamentally abstract. Due to the previous problem of learning mathematics, one cannot consider its character as exclusively methodological, given that the same could be defined as non-fluid, in great part, by socio-economic factors which determine the lives of educators.
LAS SECUENCIAS DIDáCTICAS UN áREA DE ENCUENTRO ENTRE LAS INTELIGENCIAS MúLTIPLES Y LAS COMPETENCIAS (THE TEACHING SEQUENCE LIKE AS MEETING AREA BETWEEN MULTIPLE INTELLIGENCES AND COMPETENCIES)
García Retana, José ángel
Revista Electrónica Actualidades Investigativas en Educación , 2012,
Abstract: Resumen En un mundo tan complejo como el actual, el modelo educativo debe enfrentar el reto de educar, respetando la individualidad, sin que esto signifique sacrificar la colectividad, ni viceversa; con la finalidad de potenciar la capacidad de aprender a pensar por parte del educando, de manera que éste pueda responder a las demandas de su entorno. Para lograr esto, se requiere construir un área de encuentro entre distintas teorías y enfoques, que incluya a las inteligencias múltiples, el socio-constructivismo y el enfoque por competencias, a través de situaciones didácticas que partan de la realidad. En el presente ensayo se presentan dos ejemplos posibles dentro de esta área de encuentro.Abstract: In a world as complex as the current, the educational model must face the challenge of educating, respecting individuality, without this means sacrificing the community, or vice versa, with the aim of enhancing the ability to learn to think by the student, so that it can respond to the demands of their environment. To achieve this requires building a meeting area with different theories and approaches, including the multiple intelligences, competences, the social constructivist, through didactic situations that depart from reality. In this essay are two possible examples in this area to meet.
Modelo Educativo basado en competencias: Importancia y necesidad / Educational model based in competenciy: importance and necessity
José ángel García Retana
Revista Electrónica Actualidades Investigativas en Educación , 2011,
Abstract: ResumenCon el surgimiento de las tecnologías de la información y la comunicación, la Humanidad ha logrado desarrollar un nivel de conocimientos sin precedente en la historia, constituyéndose éste en el principal recurso con cuenta para enfrentar la degradación de los recursos naturales del planeta. Para lograr que el conocimiento ocupe el papel indicado se requiere la construcción de un nuevo modelo educativo que centre el currículo en el educando, particularmente en el desarrollo de sus competencias, de manera tal que se logre una convergencia entre lo individual y lo social en aspectos ligados a lo cognoscitivo, afectivo y psicológico, que potencien una capacidad adaptativa al entorno generado en los últimos a os. Solo así se podrá estimular la creatividad y la innovación para enfrentar los retos planteados por dicho entorno, desde una perspectiva holística y transdiciplinar capaz de superar los modelos educativos heredados del siglo XX centrados en la adquisición de información. En este nuevo marco contextual el papel del docente se debe redefinir, pasando de ser un transmisor de conocimientos a un gestionador de ambientes de aprendizaje.AbstractWith the emergence of information technology and communication, Humanity has deveoped an unprecedented level of knowledge in history, becoming the main resource it has to face the degradation of the planet′s natural resources. To achieve that knowledge occupies the indicated role, is required to build a new educational model to center the curriculum on the learner, particulary in the development of their competences, so as to achieve a convergence between individual an social aspects related to the cognitive, emotional and psychological, that enhance adaptive capacity to enviroment generated in recent years. Only then can stimulate creativity and innovation to meet the challenges posed by such an environment, a holistic and transdiciplinary able to overcome the educational model inherited from the twentieth century focused on the acquisition of information. In this new context within the teacher′s role must be redefined, from being a transmitter of knoeledge to a learning environment management.
LA CALCULADORA CIENTIFICA Y LA OBTENCIóN DE LA RESPUESTA CORRECTA EN EL CICLO DIVERSIFICADO (SCIENTIFIC CALCULATOR AND OBTAINING THE CORRECT ANSWER IN THE DIVERSIFIED CYCLE)
García Retana José ángel
Revista Electrónica Actualidades Investigativas en Educación , 2009,
Abstract: Resumen:Al comparar la Política Educativa costarricense con los Planes y Programas en Matemáticas, desarrollados en el ciclo diversificado, se muestra una discrepancia en torno a los objetivos de éstos. La Política Educativa propone un aprendizaje con comprensión sobre la base del paradigma constructivista, en tanto los Planes y Programas pretenden dotar al educando de recursos para la obtención de respuestas correctas, incluyendo para ello el uso de la calculadora científica. Esta discrepancia muestra una diferencia significativa en el éxito en la prueba de Bachillerato (conclusión del ciclo diversificado) entre los ítemes “algorítmicos” (los cuales pueden ser resueltos con el apoyo de la calculadora científica), y los “conceptuales”. Esta diferencia se incrementa en la Prueba de Diagnóstico que muchos estudiantes aplican antes de ingresar a la Universidad de Costa Rica, dado que en la misma no pueden utilizar la calculadora científica. El presente ensayo cuestiona un posible papel de la calculadora científica en esta situación.Abstract:When comparing both the Costa Rican Educational policy and the plans and programs in Mathematics implemented in t he diversified cycle, clear gaps around t he objetives are evident. The Educational Policy proposes learning with understanding on the basis of the constructivist paradigm while both the plans andprograms intend to provide the learners with resources for attaining correct answers, including the use of scientific calculators. The gaps mentioned evidence a significant difference in “conceptual” and “algorithmic” items of the “Bachillerato” test results (which can be solved by resorting to scientific calculators). This difference increases in the Diagnostic test t hat several students must take before entering the University of Costa Rica as they are not allowed to use the scientific calculator. This paper establishes an argument against the possible role of the scientific calculator in that context.
Reflexiones sobre los estilos de aprendizaje y el aprendizaje del cálculo para ingeniería
García Retana, José ángel
Revista Electrónica Actualidades Investigativas en Educación , 2013,
Abstract: Resumen: Cada estudiante posee un estilo de aprendizaje predominante, que el docente lo conozca puede contribuir para que sus estudiantes logren alcanzar un mayor nivel de aprendizaje. Este aprendizaje se ve influido por las características cognitivas de las disciplinas y, como es el caso de las matemáticas y del cálculo, estas no están claramente delimitadas. Para los estudiantes de Ingeniería, el cálculo juega un papel fundamental en su formación profesional, de modo que es importante considerar los aspectos cognitivos del aprendizaje de las matemáticas y el papel que juegan los estilos de aprendizaje. Por lo anterior, el presente ensayo es el resultado de una exhaustiva revisión bibliográfica sobre este tema, a partir de la propuesta planteada por Honey-Alonso sobre la existencia de cuatro estilos de aprendizaje, a saber: activo, reflexivo, teórico y pragmático, se considera su impacto en el aprendizaje del cálculo para Ingeniería.Abstract: Each student has a dominant learning style. If the teacher knows his / her students′ learning styles, this knowledge can contribute to students′ greater achievements. The learning is influenced by the cognitive characteristics of the disciplines, which is the case of subject matters such as mathematics and calculus, which are not clearly defined. For engineering students, calculus plays a major role in their professional training, so it is important to consider the cognitive aspects of learning mathematics and the role of learning styles. Therefore, this article is the result of an extensive literature review on this subject, from the proposal by Honey-Alonso on the existence of four learning styles, namely active, reflective, theoretical and pragmatic, and their impact on learning calculus in the field of engineering.
Rese a de "Derroteros del alba (variaciones sobre el deseo)" de Heber Quijano
Ileana Reyes Retana
Contribuciones desde Coatepec , 2008,
Abstract:
Testosterone Levels and Development of the Penile Spines and Testicular Tissue during the Postnatal Growth in Wistar Rats  [PDF]
Marcela Arteaga Silva, Rosa M. Vigueras Villase?or, Socorro Retana Márquez, Marisela Hernández González, Herlinda Bonilla Jaime, Xochitl Guzmán García, José Luis Contreras Montiel
Advances in Sexual Medicine (ASM) , 2013, DOI: 10.4236/asm.2013.33A001
Abstract: Aim of Study: Gonadal hormones exert a profound influence on the development, structure and function of the sexual organs. The testosterone is one of the androgens that plays an essential role in the development of sexual organs in male mammals. Therefore, the present study was undertaken to evaluate the testosterone levels and developmental pattern of the penile spines and seminiferous tubules during early postnatal life of Wistar rats. Methods and Materials: At 7, 14, 21, 28, 35, 42, 49, 56, 63 and 70 days after birth, penile and testicular tissues of male rats were dissected out and fixed for histological study and plasma testosterone levels were determined using high resolution chromatography. Results: An increase in the number of penile follicles, primarily in the distal region of the penis, was observed from postnatal days 14 to 42, followed by a gradual decrease. Penile spines were absent from birth until the first growth peak, which was observed at 42 postnatal days. Both testicular weight and the area of seminiferous tubules showed gradual increases before achieving their highest values at 42 postnatal days. Similarly, a gradual increase in testosterone levels was detected from day 28, with a peak at 42 postnatal days. Conclusions: These data show a temporal association between the development of the penile spines and testicular tissue with gradual increases in testosterone levels. These results may contribute to a better understanding of the behavioral, hormonal and morphological changes underlying sexual maturation in male rats.
Grandes retos de la ingeniería y su papel en la sociedad
Pe?a - Reyes,José Ismael;
Ingeniería e Investigación , 2011,
Abstract: engineering has a long historical tradition; it began as a discipline in the sixteenth century and reached maturity during the twentieth century. however, the twentyfirst century's features strongly differentiate it from earlier times; when referring to this period, we speak of globalisation, knowledge society and national innovation systems. this is a period marked by contradictions. technological developments and social and political changes have improved human beings' quality of life. new technologies have provided the context for its opening decade: nanotechnology, microelectronics and nanoelectronics, photonics, materials science, biotechnology, information and communications technology, logistics, medical engineering and renewable and clean energy. technologies feed each other and off each other, offering endless possibilities for development. this is a time where the doors of political democratisation, art and culture have opened; however, it is also a world facing political, financial and environmental crisis. colombia, particularly, is a country encountering problems regarding its competitiveness, having crippling levels of corruption and impunity, problems related to education, health and infrastructure. colombia needs more engineers who can contribute towards resolving complex problems. such engineers must have had excellent technical and humanistic training; they must be creative, able to work as a team, have become leaders who can listen and communicate and help develop a world to ensure that humans and other living species on earth can flourish with a uniform, durable level regarding their quality of life. work must thus be done on critical engineering education and the present work presents some characteristics concerning what these engineers training/education should be.
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