# Examinando por Autor "Díaz Forero, John Hernán"

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Ítem Cálculo en la estructura de bandas de cristales fotónicosSilva Forero, Christian Orlando; Díaz Forero, John HernánMás... In this work, a brief review of the theory supporting the occurrence of bands of frequencies in so-called photonic crystals is made, as well as the calculation of the band diagram of some purely theoretical structures that may have no affinity with the structures that It can be carried out in a laboratory. First, it reviews the theory that justifies the definition of electrical permittivity over a material medium under considerations or approximations. The starting points are, of course, Maxwell's equations, since the periodic variation of the electrical permittivity is the main responsible for the appearance of the prohibited bands, it is necessary to review from these equations as one can characterize the fields in a medium . Second, to review a set of analytical methods that reduce the problem of finding the frequencies and fields that can be propagated by these structures; That the methods are not, not formally developed, how the complexity of the problem can be reduced by the use of symmetries and the use of Bloch's theorem. Finally, using the revised tools, we obtain the equation that describes how the electromagnetic field propagates in these structures, as well as the frequencies that satisfy this equation. This equation is emphasized as a problem of eigenvalues and eigenvectors, which implies a solution to a finite set of first-degree algebraic equations with the main difficulty of finding the representation of a function of type 1 / f (r) Is a basis of the function space associated with the Fourier series. It is shown in that it consists of a band diagram, how it can be constructed and what relevant information can be extracted from it. The master equation for one-dimensional structures is solved by usual methods and a couple of examples are shown. He solves the master equation for structures in two and three dimensions using the software developed in the MIT of the MIT Photonic bands by which the numerical solution of the master equation is solved and the data can be obtained to graph the band diagram and The distribution of the fields in one, two and three dimensions.Más... Ítem Estudio DFT de las Propiedades Estructurales y Electrónicas del X2O (X = Cu; Ag; Au)Rico Vanegas, Julián Andrés; Díaz Forero, John HernánMás... In this grade work we studied the structural and electronic properties of noble metal oxides X2O (X= Ag, Au, Cu). Starting with a theoretical review of the methods of approach for the solution of multi-electronics atoms, such as Fermi gas non-interacting and interacting, to realize in the theory of functional density (DFT) as a method of approach to the solution of atoms study crystals. Oxides have a structure type cuprite belonging to the space group P n3, it states that the system is at a temperature 0K despising relativistic quantum effects. For the solution of this system is made use of computer code WIEN2k developed by the University of Vienna, which implements the method of the DFT using the approximation of the generalized gradient and method of solution of plane waves increased linearly (LAPW), methodology used to obtain the parameters. Finally, structural and electronic devices such as network parameters, bulk modulus, energy bands, density of states and electronic each crystal density, so it is concluded parameters are presented to the noble metal oxides under the study method are attributed semiconducting properties with significant energy input from the 3d orbitals, 4d and 5d of Cu, Ag and Au, respectively, within the valence bands and metal-oxygen bond between covalent type.Más... Ítem Optimización y caracterización de las propiedades estructurales y electrónicas del compuesto V5Si3: un estudio DFTVillanueva Hernández, Javier Eduardo; Díaz Forero, John HernánMás... The purpose of this work is to study some structural and electronic properties of polyatomic crystals, starting with the elements V, Si, ending with the V5Si3 alloy, making use of quantum theory and approximation methods for the analysis of the problem of many Bodies in relation to the theoretical and experimental advances reported in the literature. The results obtained by the DFT (Density Functional Theory) and the calculation of energy bands, confirm the metallic-conductive character of the silicon V5Si3 and its compact hexagonal structure reported in the literature and compared with the tetragonal structure. The theoretical and experimental foundations that support the calculations of structural and electronic properties are configured in four chapters, beginning with the mathematical and physical foundations of group theory. Then, the behavior of the electrons in the crystals is analyzed, emphasizing the difference between the real space and the "k" space, also analyzing the Kronig-Penney approximation model, and the process of making bands from East. Here are some approximate solution methods for the Schroedinger equation for many bodies with an emphasis on the DFT (Density Functional Theory) method. Finally, the detailed description of the computational calculations made to determine the structural and electronic properties of the V, Si and V5Si3 alloys in their natural crystallization phases, and using the DFT (Density Functional Theory) implemented by the software Wien2K; and then describe the general conclusions.Más... Ítem Propuesta para el Abordaje del Curso Universitario de Oscilaciones y OndasCely Hernández, Jeisson David; Díaz Forero, John HernánMás... Given the importance of the oscillatory motion in the study of phenomena and whereas their natural context and depth is relevant to optimal understanding of them and for those interested in these types of studies, such as physicists and engineers, in this paper grade some considerations to take into account in the study of oscillatory systems are established. Between these considerations to take into account a mental structure that allows proposed facilitate conceptualization of oscillatory systems and to address in detail some oscillatory systems of interest, as are the non-linear mathematical pendulum, damped and forcing oscillators, coupled oscillators and wave motion, which are determined under the mental structure proposal.Más... Ítem Temperatura superficial terrestre en Algeciras Huila, una comparación entre teledetección e información in situ para el año 2021Muñoz Figueroa, Juan David; Díaz Forero, John Hernán; Díaz Forero, John Hernán [0000-0002-0095-1469]Más... The purpose of this research work is to verify the feasibility of using Landsat 8 images (remote sensing) to estimate the Land surface temperature (LST) in the municipality of Algeciras, Huila; comparing the data obtained through digital image processing with those obtained in situ through traditional methods. The calculation used in the images integrates formulas and key concepts in remote sensing and interpretation of satellite images, such as reflectance, radiance, emissivity, normalized difference vegetation index (NDVI), proportion of vegetation; which allowed a better processing of the images and it is expected that the results have a high degree of veracity due to the correction of the aforementioned phenomena. The study area corresponds to the municipality of Algeciras, Huila, corresponding to path 8 and row 58 for the satellite images used, with time reference to the year 2021, specifically the months of January, July and October. Algeciras is located near the eastern mountain range of Colombia, near the PNN Cordillera Los Picachos, which is why its topography is quite uneven and in situ measurements of environmental variables present complications, mainly to access certain points in the municipality. Taking as a reference the results obtained through digital image processing, remote sensing is seen as a fairly strong and reliable alternative for the measurement of these variables, in this case precisely the Earth's surface temperature, thus providing alternatives to traditional methods that are characterized due to economic and accessibility limitations.Más...