Efficiency analysis of wide band-gap semiconductors for two-level and three-level power converters

© 2019 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes,creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.Power devices based on wide band-gap materials are emerging as alternatives to silicon-based devices. These new devices allow designing and building converters with fewer power losses, and are thus more highly efficient than traditional power converters. Among the wide band-gap materials in use, silicon carbide (SiC) and gallium nitride (GaN) devices are the most promising because of their excellent properties and commercial availability. This paper compares the losses produced in two-level and three-level power converters that use the aforementioned technologies. In addition, we assess the impact on the converter performance caused by the modulation technique. Simulation results under various operating points are reported and compared.Peer ReviewedPostprint (author's final draft

Extended Far-Infrared CO Emission in the Orion OMC-1 Core

We report on sensitive far-infrared observations of $^{12}$CO pure rotational transitions in the OMC-1 core of Orion. The lines were observed with the Long Wavelength Spectrometer (LWS) in the grating mode on board the Infrared Space Observatory (ISO), covering the 43-197 $\mu$m wavelength range. The transitions from $J_{up}=14$ up to $J_{up}=19$ have been identified across the whole OMC-1 core and lines up to $J_{up}= 43$ have been detected towards the central region, KL/IRc2. In addition, we have taken high-quality spectra in the Fabry-Perot mode of some of the CO lines. In KL/IRc2 the lines are satisfactorily accounted for by a three-temperature model describing the plateau and ridge emission. The fluxes detected in the high-$J$ transitions ($J_{up} > 34$) reveal the presence of a very hot and dense gas component ($T=1500-2500$ K; $\rm N(CO)$=2\times 10^{17}\cmmd$), probably originating from some of the embedded sources previously observed in the$\rm H_2$near-infrared lines. At all other positions in the OMC-1 core, we estimate kinetic temperatures$\geq 80$ K and as high as 150 K at some positions around IRc2, from a simple Large-Velocity Gradient model.Comment: 10 pages, 3 figure

Geological setting and genesis of stratabound barite deposits at Múzquiz, Coahuila in northeastern Mexico

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Epigenetics of cervical cancer. An overview and therapeutic perspectives

Cervical cancer remains one of the greatest killers of women worldwide. It is difficult to foresee a dramatic increase in cure rate even with the most optimal combination of cytotoxic drugs, surgery, and radiation; therefore, testing of molecular targeted therapies against this malignancy is highly desirable. A number of epigenetic alterations occur during all stages of cervical carcinogenesis in both human papillomavirus and host cellular genomes, which include global DNA hypomethylation, hypermetylation of key tumor suppressor genes, and histone modifications. The reversible nature of epigenetic changes constitutes a target for transcriptional therapies, namely DNA methylation and histone deacetylase inhibitors. To date, studies in patients with cervical cancer have demonstrated the feasibility of reactivating the expression of hypermethylated and silenced tumor suppressor genes as well as the hyperacetylating and inhibitory effect upon histone deacetylase activity in tumor tissues after treatment with demethylating and histone deacetylase inhibitors. In addition, detection of epigenetic changes in cytological smears, serum DNA, and peripheral blood are of potential interest for development of novel biomolecular markers for early detection, prediction of response, and prognosis

Adaptation and Validation in Spanish of the Source Credibility Measure in University Professors

El objetivo del estudio consistió en adaptar y validar al español la Escala de Credibilidad (McCroskey & Teven, 1999) para medir la credibilidad de los profesores universitarios. Los participantes fueron 352 estudiantes de la Universidad de Sevilla pertenecientes a diversas titulaciones del área de las Ciencias Sociales. El análisis factorial exploratorio generó un modelo de tres factores alternativo al original. No obstante, tanto el modelo alternativo como el modelo original presentaron una adecuada consistencia interna no sólo en la escala global sino también en las tres subescalas; buenos índices de bondad de ajuste como confirmó el análisis factorial confirmatorio, apoyando así la estructura factorial de tres factores; invarianza por sexo y evidencia de validez concurrente con la motivación académica. Se concluye que el modelo original, así como el modelo alternativo de la Escala de Credibilidad son instrumentos válidos y fiables para medir la credibilidad de los docentes universitarios.The purpose of the study was to adapt to and validate to Spanish the Source Credibility Measure (McCroskey & Teven, 1999) to assess the credibility of university professors. The participants were 352 students from the University of Seville from different courses in the field of Social Sciences. The exploratory factor analysis generated an alternative three-factor model to the original one. However, both the alternative model and the original model presented adequate internal consistency not only in the global scale but also in the three subscales, good indexes of goodness of fit as demonstrated by the confirmatory factor analysis, supporting the factorial structure of three factors; invariance across sex and evidence of concurrent validity with academic motivation. It is concluded that the original model as well as the alternative model of the Source Credibility Measure are valid and reliable instruments to assess the credibility of university professors

Spitzer-IRS high resolution spectroscopy of the 12\mu m Seyfert galaxies: I. First results

The first high resolution Spitzer IRS 9-37um spectra of 29 Seyfert galaxies (about one quarter) of the 12um Active Galaxy Sample are presented and discussed. The high resolution spectroscopy was obtained with corresponding off-source observations. This allows excellent background subtraction, so that the continuum levels and strengths of weak emission lines are accurately measured. The result is several new combinations of emission line ratios, line/continuum and continuum/continuum ratios that turn out to be effective diagnostics of the strength of the AGN component in the IR emission of these galaxies. The line ratios [NeV]/[NeII], [OIV]/[NeII], already known, but also [NeIII]/[NeII] and [NeV]/[SiII] can all be effectively used to measure the dominance of the AGN. We extend the analysis, already done using the 6.2um PAH emission feature, to the equivalent width of the 11.25um PAH feature, which also anti-correlates with the dominance of the AGN. We measure that the 11.25um PAH feature has a constant ratio with the H_2 S(1) irrespective of Seyfert type, approximately 10 to 1. Using the ratio of accurate flux measurements at about 19um with the two spectrometer channels, having aperture areas differing by a factor 4, we measured the source extendness and correlated it with the emission line and PAH feature equivalent widths. The extendness of the source gives another measure of the AGN dominance and correlates both with the EWs of [NeII] and PAH emission. Using the rotational transitions of H$_2$ we were able to estimate temperatures (200-300K) and masses (1-10 x 10^6 M_sun), or significant limits on them, for the warm molecular component in the galaxies observed.Comment: submitted to ApJ, Aug.2007, revised, in the refereeing proces

Reasons for dropout in youth soccer: a comparison with other team sports

[EN] The purpose of our study was to identify the main reasons for dropout in young soccer players and to compare withdrawal motives to those rated important by participants in other team sports. Dropouts (150 males and 159 females, ranging in age from 14 to 18 years) were administered the Questionnaire of Reasons for Attrition by Gould, Feltz, Horn and Weiss (1982). Represented were youth who participated in the sport of soccer (n=127), basketball (n=122), and volleyball (n=60). The most important reasons for attrition from the different team sports were having other things to do, dislike of the coach, and lack of team spirit. Reasons related to the team work were also given high ratings. Less important reasons concerned old age, rewards and competition. Although discriminant analysis revealed some differences between sports, the finding remains that both conflict of interests and aspects of the sports environment are major motives for withdrawal from team sports.[EN] El objetivo del presente estudio fue identificar las razones para el abandono en jóvenes jugadores de fútbol y comparar los motivos de abandono con los descritos en practicantes de otros deportes colectivos. Los sujetos (150 varones y 159 mujeres, con edades comprendidas entre los 14 y los 18 años) respondieron la versión española del Questionnaire of Reasons for Attrition de Gould, Feltz, Horn y Weiss (1982). La muestra estaba constituida por practicantes de fútbol (n=127), baloncesto (n=122), y voleibol (n=60). Las razones consideradas como más importantes para el abandono fueron el tener otras cosas que hacer, las malas relaciones con el entrenador y la falta de espíritu de equipo. También alcanzaron puntuaciones elevadas los motivos relacionados con el trabajo de equipo. Las razones a las que se otorgaba menos importancia se relacionaban con edad excesiva, recompensas y competición. Aunque el análisis discriminante puso de manifiesto algunas diferencias entre deportes, tanto el conflicto de intereses como los aspectos relacionados con el ambiente deportivo eran siempre las razones más valoradas para el abandono de la práctica.S

Gestión del alcance del proceso de excavación en roca necesaria para la construcción del sótano y cimentación del edificio “Taller 6”, bajo la metodología PMBOK 5ta edición numeral 5

Trabajo de investigaciónLa gestión del alcance de un proyecto incluye todos los procesos necesarios para garantizar que se realice con éxito, Debido a los últimos acontecimientos, en los que están involucrados los megaproyectos para el desarrollo de la infraestructura del país, se evidencia la falta de gestión del alcance, por tal motivo es necesario replantear los procesos que llevan a cabo los responsables de la planeación del proyecto. Se pudo identificar que los métodos tradicionales de construcción de edificios involucran la construcción de uno o varios sótanos no se desarrolla utilizando una herramienta práctica bajo los principios de la guía del PMBOK de su quinta edición en el capítulo 5.1 Generalidades 2 Marcos de referencia 3 Metodología 4 Productos por entregar 5 Resultados esperados e impacto 6 Conclusiones 7 BibliografíaEspecializaciónEspecialista en Gerencia de Obras Civile

Primeros datos de inclusiones fluidas e isótopos de azufre del depósito VMS de Tizapa, México

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