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Search Results: 1 - 10 of 9281 matches for " Enrique Velasco "
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The Lebesgue integral as a Riemann integral
Enrique A. Gonzalez-Velasco
International Journal of Mathematics and Mathematical Sciences , 1987, DOI: 10.1155/s0161171287000802
Abstract: The object of this paper is to develop a very direct theory of the Lebesgue integral that is easily accessible to any audience familiar with the Riemann integral.
Uniqueness and stability of solutions for a type of parabolic boundary value problem
Enrique A. Gonzalez-Velasco
International Journal of Mathematics and Mathematical Sciences , 1989, DOI: 10.1155/s0161171289000918
Abstract: We consider a boundary value problem consisting of the one-dimensional parabolic equation gut=(hux)x+q, where g, h and q are functions of x, subject to some general boundary conditions. By developing a maximum principle for the boundary value problem, rather than the equation, we prove the uniqueness of a nonnegative solution that depends continuously on boundary values.
Inteligencia artificial: una utopía realizada
Enrique Ruiz Velasco Sánchez
Perfiles educativos , 1996,
Abstract: Analiza, desde un punto de vista crítico, la doble vertiente en la utilización de la tecnología en el ámbito educativo, mencionando sus aspectos lúdicos. Reflexión acerca de cómo la misma tecnología impide que nos demos cuenta que vivimos una utopía tecnológica. Ruiz-Velasco no desaprovecha la aportación del género ciencia ficción para escenificar las posibilidades que ya nos muestra la Inteligencia Artificial.
Ciencia y tecnología a través de la robótica cognoscitiva
Enrique Ruiz Velasco Sánchez
Perfiles educativos , 1996,
Abstract: Ubicado en el campo de la robótica pedagógica, el autor presenta un programa teórico para la construcción de un robot, como recurso didáctico para el aprendizaje de la ciencia y la tecnología. Con ello demuestra que la robótica cognoscitiva es un medio de integración que permite crear una base de conocimientos a través de la manipulación y el control de entornos robotizados al mismo tiempo que se resuelven problemas concretos.
Pobreza y marginación en México
Enrique Guinsberg,Bulmaro Villarruel Velasco
Política y cultura , 2005,
Abstract:
La crisis de la Iglesia Católica en los Países Bajos en la segunda mitad del siglo XX
Enrique Alonso de Velasco Esteban
Anuario de Historia de la Iglesia , 2011,
Abstract:
Effect of polydispersity, bimodality and aspect ratio on the phase behavior of colloidal platelet suspensions
Yuri Martinez Raton,Enrique Velasco
Physics , 2012, DOI: 10.1063/1.4755958
Abstract: We use a Fundamental-Measure density functional for hard board-like polydisperse particles, in the restricted-orientation approximation, to explain the phase behaviour of platelet colloidal suspensions studied in recent experiments. In particular, we focus our attention on the behavior of the total packing fraction of the mixture, $\eta$, in the region of two-phase isotropic-nematic coexistence as a function of mean aspect ratio, polydispersity and fraction of total volume $\gamma$ occupied by the nematic phase. In our model, platelets are polydisperse in the square section, of side length $\sigma$, but have constant thickness $L$ (and aspect ratio $\kappa\equiv L/<\sigma><1$, with $<\sigma>$ the mean side length). Good agreement between our theory and recent experiments is obtained by mapping the real system onto an effective one, with excluded volume interactions but with thicker particles (due to the presence of long-ranged repulsive interactions between platelets). The effect of polydispersity in both shape and particle size has been taken into account by using a size distribution function with an effective mean-square deviation that depends on both polydispersities. We also show that the bimodality of the size distribution function is required to correctly describe the huge two-phase coexistence gap and the nonlinearity of the function $\gamma(\eta)$, two important features that these colloidal suspensions exhibit.
Análisis de la flora de cultivos de regadío en el sudoeste de Castilla y León
Rico, Enrique,Velasco Sánchez, Juan Manuel
Anales del Jardín Botánico de Madrid , 2000,
Abstract: A study of the flora of irrigated crops in two Spanish provinces (Salamanca and Zamora, SW Castilla y León) has been carried out. After careful analysis of a catalogue comprising more than 344 taxa, we have found that 237 of them (68,9 %) belong to 8 families, the most relevant of which are Compositae, Gramineae and Leguminosae, although the latter is less important among the most frequent species. The best represented chorological group is that of those widely distributed species, to which more than half of the species in the catalogue belong, as well as 85,4 % of the most invasive ones. On the contrary the group of Mediterranean and endemic taxa represent just a third of the total. The predominant biological type is the terophytes (66,6 % of the annotated species), while hemicryptophytes represent 26 % and geophytes just less than 5 %. Anemochory is the commonest dispersal type (ca. 70 % of the species) followed by barochory and zoochory. The latter has greater relative importance (more or less 30 %) among the most harmful plants. Se lleva a cabo un estudio de la composición de la flora de cultivos de regadío de las provincias de Salamanca y Zamora (sudoeste de Castilla y León). Del análisis de un catálogo de 344 táxones, se obtiene que 237 (68,9 % del total) pertenecen a ocho familias, entre las que destacan Compositae, Gramineae y Leguminosae, aunque la importada de esta última es mucho menor entre las especies más frecuentes. El grupo corológico mejor representado es el de amplia distribución, al que pertenecen más de la mitad de las especies del catálogo y el 85,4 % de las más infestantes, en tanto que el conjunto de mediterráneas y endemismos suman solo un tercio del total. El tipo biológico predominante es el de los terófitos (66,6 %), seguido de los hemicriptófitos (26 %) y en tercer lugar los geófitos (menos del 5 %). El modo de dispersión más extendido es la anemocoria (70 %), seguido de la barocoria y zoocoria; este último tiene mayor importancia relativa (30 %) entre las plantas más nocivas.
Enhanced stability of tetratic phase due to clustering
Yuri Martinez-Raton,Enrique Velasco
Physics , 2008, DOI: 10.1103/PhysRevE.79.011711
Abstract: We show that the relative stability of the nematic tetratic phase with respect to the usual uniaxial nematic phase can be greatly enhanced by clustering effects. Two--dimensional rectangles of aspect ratio $\kappa$ interacting via hard interactions are considered, and the stability of the two nematic phases (uniaxial and tetratic) is examined using an extended scaled--particle theory applied to a polydispersed fluid mixture of $n$ species. Here the $i$--th species is associated with clusters of $i$ rectangles, with clusters defined as stacks of rectangles containing approximately parallel rectangles, with frozen internal degrees of freedom. The theory assumes an exponential cluster size distribution (an assumption fully supported by Monte Carlo simulations and by a simple chemical--reaction model), with fixed value of the second moment. The corresponding area distribution presents a shoulder, and sometimes even a well-defined peak, at cluster sizes approximately corresponding to square shape (i.e. $i\simeq\kappa$), meaning that square clusters have a dominant contribution to the free energy of the hard--rectangle fluid. The theory predicts an enhanced region of stability of the tetratic phase with respect to the standard scaled--particle theory, much closer to simulation and to experimental results, demonstrating the importance of clustering in this fluid.
Non-uniform liquid--crystalline phases of parallel hard rod-shaped particles: From ellipsoids to cylinders
Yuri Martinez-Raton,Enrique Velasco
Physics , 2008, DOI: 10.1063/1.2958920
Abstract: In this article we consider systems of parallel hard {\it superellipsoids}, which can be viewed as a possible interpolation between ellipsoids of revolution and cylinders. Superellipsoids are characterized by an aspect ratio and an exponent $\alpha$ (shape parameter) which takes care of the geometry, with $\alpha=1$ corresponding to ellipsoids of revolution, while $\alpha=\infty$ is the limit of cylinders. It is well known that, while hard parallel cylinders exhibit nematic, smectic, and solid phases, hard parallel ellipsoids do not stabilize the smectic phase, the nematic phase transforming directly into a solid as density is increased. We use computer simulation to find evidence that for $\alpha\ge\alpha_c$, where $\alpha_c$ is a critical value which the simulations estimate to be in the interval 1.2--1.3, the smectic phase is stabilized. This is surprisingly close to the ellipsoidal case. In addition, we use a density-functional approach, based on the Parsons--Lee approximation, to describe smectic and columnar ordering. In combination with a free--volume theory for the crystalline phase, a theoretical phase diagram is predicted. While some qualitative features, such as the enhancement of smectic stability for increasing $\alpha$, and the probable absence of a stable columnar phase, are correct, the precise location of coexistence densities are quantitatively incorrect.
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