3,459 research outputs found
Effect of the spin-orbit interaction on the thermodynamic properties of crystals: The specific heat of bismuth
In recent years, there has been increasing interest in the specific heat
of insulators and semiconductors because of the availability of samples with
different isotopic masses and the possibility of performing \textit{ab initio}
calculations of its temperature dependence using as a starting point the
electronic band structure. Most of the crystals investigated are elemental
(e.g., germanium) or binary (e.g., gallium nitride) semiconductors. The initial
electronic calculations were performed in the local density approximation and
did not include spin-orbit interaction. Agreement between experimental and
calculated results was usually found to be good, except for crystals containing
heavy atoms (e.g., PbS) for which discrepancies of the order of 20% existed at
the low temperature maximum found for . It has been conjectured that
this discrepancies result from the neglect of spin-orbit interaction which is
large for heavy atoms (1.3eV for the valence electrons of
atomic lead). Here we discuss measurements and \textit{ab initio} calculations
of for crystalline bismuth (1.7 eV), strictly speaking a
semimetal but in the temperature region accessible to us ( 2K) acting as a
semiconductor. We extend experimental data available in the literature and
notice that the \textit{ab initio} calculations without spin-orbit interaction
exhibit a maximum at 8K, about 20% lower than the measured one. Inclusion
of spin-orbit interaction decreases the discrepancy markedly: The maximum of
is now only 7% larger than the measured one. Exact agreement is obtained
if the spin-orbit hamiltonian is reduced by a factor of 0.8.Comment: 4 pages, 3 figure
Influencia del síndrome burnout en el clima organizacional de los gimnasios de entrenamiento funcional del municipio de Cartago Valle del Cauca
El trabajo de investigación planteado fue de tipo descriptivo que utilizo el método cuantitativo correlacional para la recolección de datos, análisis y discusión de resultados, con una población de 50 colaboradores de los gimnasios de entrenamiento funcional del municipio de Cartago Valle, cuyo objetivo principal fue Determinar la influencia del síndrome burnout en el clima organizacional de los mismo, planteando la siguiente hipótesis nula, el síndrome de burnout no afecta al clima organizacional y la hipótesis alternativa, el síndrome de burnout afecta al clima organizacional. Los resultados encontrados muestran que hay una influencia significativa entre el síndrome de burnout y el clima organizacional, puesto que entre más desgaste profesional haya en los entrenadores la percepción de un buen clima disminuirá, además se evidencio que la relación más alta entre las variables de clima organizacional y el síndrome de burnout es empoderamiento, negociación y manejo de conflictos y relaciones
Estudio de los sistemas de puesta a tierra de los edificios de: Medio ambiente, Comunicaciones, Educación, Cafetería Central, Sistemas, y Ciencias Básicas de la Universidad Tecnológica de Pereira
La química del terreno, la cantidad y la calidad de las sales minerales en este pueden influir de modo notable en la resistividad del suelo, por otro lado la humedad y la temperatura afectan la resistividad del terreno, la cual está muy influenciada primordialmente por la humedad y en menor medida no menos importante por su temperatura, son tan significativos estos efectos, que la resistencia del terreno disminuye con el aumento de la humedad y con el incremento de la temperatura. Otro punto que se debe tener en cuenta, es que la varilla o varillas que conforman la puesta a tierra tienden a corroborarse con el tiempo.
Considerando lo anterior se desarrolla un estudio de los valores de resistividad y resistencia de las puestas a tierra de algunos edificios de la Universidad Tecnológica de Pereira, para ser comparados con el estudio hecho en el año 2003, en el cual se registraron los valores de resistividad del terreno y de resistencia de las puestas a tierra de los edificios que conforman la Universidad Tecnológica de Pereira, con lo cual se podrá determinar si dichas puestas a tierras a un son eficientes teniendo en cuenta el avance de la Universidad y la evolución del terreno
Applicability Limits of Simplified Human Blockage Models at 5G mm-Wave Frequencies
This paper analyzes the feasibility of using a simple diffraction model to compute the blocking of the human body to millimeter wave radio frequencies in indoor environments. The model makes a set of approximations that are evaluated to determine the applicability limits of such simplified approach, in particular for the human body blockage case. The work presented here: (1)
describes briefly the mathematical support that is used to model the concealment using the Knife-Edge model, (2) identifies the potential simplifications applicable to the mathematical model implementation that allow a 3D geometric human body to be modelled with simple 2D shapes, (3) characterizes the polarization influence on the mm-wave blocking for such simplified human body
models.This work was supported by the H2020 Marie Curie program, with project grant no: 766231 WAVECOMBEITN-2017Romero-Peña, JS.; Cardona Marcet, N. (2019). Applicability Limits of Simplified Human Blockage Models at 5G mm-Wave Frequencies. IEEE. 1-5. http://hdl.handle.net/10251/1319941
Lattice Properties of PbX (X = S, Se, Te): Experimental Studies and ab initio Calculations Including Spin-Orbit Effects
During the past five years the low temperature heat capacity of simple
semiconductors and insulators has received renewed attention. Of particular
interest has been its dependence on isotopic masses and the effect of spin-
orbit coupling in ab initio calculations. Here we concentrate on the lead
chalcogenides PbS, PbSe and PbTe. These materials, with rock salt structure,
have different natural isotopes for both cations and anions, a fact that allows
a systematic experimental and theoretical study of isotopic effects e.g. on the
specific heat. Also, the large spin-orbit splitting of the 6p electrons of Pb
and the 5p of Te allows, using a computer code which includes spin-orbit
interaction, an investigation of the effect of this interaction on the phonon
dispersion relations and the temperature dependence of the specific heat and on
the lattice parameter. It is shown that agreement between measurements and
calculations significantly improves when spin-orbit interaction is included.Comment: 25 pages, 12 Figures, 1 table, submitted to PR
Vibrational and Thermal Properties of ZnX (X=Se, Te): Density Functional Theory (LDA and GGA) versus Experiment
We calculated the phonon dispersion relations of ZnX (X=Se, Te) employing ab
initio techniques. These relations have been used to evaluate the temperature
dependence of the respective specific heats of crystals with varied isotopic
compositions. These results have been compared with mea- surements performed on
crystals down to 2 K. The calculated and measured data are generally in
excellent agreement with each other. Trends in the phonon dispersion relations
and the correspond- ing densities of states for the zinc chalcogenide series of
zincblende-type materials are discussed.Comment: 10 pages, submitted to PR
Aspectos zoonóticos de las especies de fauna silvestre decomisadas por la CAR-DRAM
Este proyecto pretende orientar de manera educativa desde lo ambiental a la
población sobre algunos de los conocimientos legales y patológicos, y como, este tipo de
aspectos, en lo que se refiere a cada una de las especies descritas en este documento, puede
representar algún tipo de afectación a la salud de las personas, teniendo encueta que estos
especímenes no son peligrosos para su hábitat, pero, en caso de tomar a la especie animal
como doméstico y alterar la zona en la que habita, puede significar un riesgo.
Por lo tanto, se debe entender que es una enfermedad zoonótica, “es una
enfermedad que puede transmitirse entre animales y seres humanos. “Las enfermedades
zoonóticas pueden ser provocadas por virus, bacterias, parásitos y hongos. Algunas de
esas enfermedades son muy frecuentes” (Global Health, 2016). Por ello, es importante
consolidar un documento que describa algunas características de las especies que son
decomisadas por la CAR-DRAM, de tal manera, se evidencie la peligrosidad de tener
animales no domésticos como mascotas o en cautiverio.
Los animales silvestres llegan a los mercados desde cualquier región y, después
de ser capturados, normalmente pasan varias semanas en contacto cercano con personas
y otras especies de animales, lo que les proporciona el tiempo suficiente para contagiarse
con cualquier agente infeccioso. A esto se le debe añadir el estrés de la captura, el
cautiverio, la mala alimentación, el transporte y los cambios de clima a los que se les
somete, permitiendo que estos animales comiencen a eliminar agentes que pueden ser
patógenos para el humano. (Yarto Jaramillo, 2017).
El documento cuenta con (25) veinticinco fichas técnicas que se plantean como
una solución para disminuir esta forma de caza y unas posibles causas de salud a raíz de
estas tradiciones por parte de la población. Los procesos y trámites que maneja
Corporación Autónoma Regional, para incautación o decomiso inmediato a los usuarios
sean de una manera más ágil y fácil con un mejor control de la jurisdicción CAR. La base
de información estará diseñada por unas fichas técnicas, donde se puede evidenciar las
especies que son más frecuentes decomisadas por la CAR-DRAM y sus aspectos
patológicos referente en la región y de esta manera tener una herramienta para la
población
Urban seismic risk index for Medellín, Colombia, based on probabilistic loss and casualties estimations
The final publication is available at Springer via http://dx.doi.org/10.1007/s11069-015-2056-4Medellín is the second largest city of Colombia with more than 2 million inhabitants according to the latest census and with more than 240,000 public and private buildings. It is located on an intermediate seismic hazard area according to the seismic zonation of Colombia although no destructive earthquakes have occurred having as a consequence low seismic risk awareness among its inhabitants. Using the results of a fully probabilistic risk assessment of the city with a building by building resolution level and considering the dynamic soil response, average annual losses by sectors as well as casualties and other direct effects are obtained and aggregated at county level. Using the holistic evaluation module of the multi-hazard risk assessment CAPRA platform, EvHo, a comprehensive assessment that considered the social fragility and lack or resilience at county level is performed making use of a set of indicators with the objective of capturing the aggravating conditions of the initial physical impact. The urban seismic risk index, USRi, is obtained at county level which is useful to communicate risk to decision-makers and stakeholders besides making easy identifying potential zones that can be problematic in terms of several dimensions of the vulnerability. This case study is an example of how a multidisciplinary research on disaster risk reduction helps to show how risk analysis can be of high relevance for decision-making processes in disaster risk management.Peer ReviewedPostprint (author's final draft
Urban seismic risk index for Medellín, Colombia, based on probabilistic loss and casualties estimations
Medellín is the second largest city of Colombia with more than 2 million inhabitants according to the latest census and with more than 240,000 public and private buildings. It is located on an intermediate seismic hazard area according to the seismic zonation of Colombia although no destructive earthquakes have occurred having as a consequence low seismic risk awareness among its inhabitants. Using the results of a fully probabilistic risk assessment of the city with a building by building resolution level and considering the dynamic soil response, average annual losses by sectors as well as casualties and other direct effects are obtained and aggregated at county level. Using the holistic evaluation module of the multi-hazard risk assessment CAPRA platform, EvHo, a comprehensive assessment that considered the social fragility and lack or resilience at county level is performed making use of a set of indicators with the objective of capturing the aggravating conditions of the initial physical impact. The urban seismic risk index,
USRi, is obtained at county level which is useful to communicate risk to decision-makers and stakeholders besides making easy identifying potential zones that can be problematic in terms of several dimensions of the vulnerability. This case study is an example of how a multidisciplinary research on disaster risk reduction helps to show how risk analysis can be of high relevance for decision-making processes in disaster risk management
- …