Analysis of heat and smoke propagation and oscillatory flow through ceiling vents in a large-scale compartment fire

One question that often arises is whether a specialized code or a more general code may be equally suitable for fire modeling. This paper investigates the performance and capabilities of a specialized code (FDS) and a general-purpose code (FLUENT) to simulate a fire in the commercial area of an underground intermodal transportation station. In order to facilitate a more precise comparison between the two codes, especially with regard to ventilation issues, the number of factors that may affect the fire evolution is reduced by simplifying the scenario and the fire model. The codes are applied to the same fire scenario using a simplified fire model, which considers a source of mass, heat and species to characterize the fire focus, and whose results are also compared with those obtained using FDS and a combustion model. An oscillating behavior of the fire-induced convective heat and mass fluxes through the natural vents is predicted, whose frequency compares well with experimental results for the ranges of compartment heights and heat release rates considered. The results obtained with the two codes for the smoke and heat propagation patterns and convective fluxes through the forced and natural ventilation systems are discussed and compared to each other. The agreement is very good for the temperature and species concentration distributions and the overall flow pattern, whereas appreciable discrepancies are only found in the oscillatory behavior of the fire-induced convective heat and mass fluxes through the natural vents. The relative performance of the codes in terms of central processing unit (CPU) time consumption is also discussed.This research was funded by Consorcio Regional de Transportes de Madrid, grant number OTRI-FUNED 5510003256. The support of the Consorcio Regional de Transportes de Madrid is gratefully acknowledged

La dimensión ética del desarrollo local

The nowadays conceptions about the community development, have a certain technocratic focus when conceiving just the economic, scientific, technic and environmental dimension bound to the knowledge management. This criteria doesn't recognize the central role that means the moral athics dimension in the social life. The aim of this research is to perform a critic analisis of the problem itself as it is showed in the nowadays Cuban society, beginning with Marti's and Marx's conception of the cultural development in the Cuban Revolution.Las concepciones actuales sobre el desarrollo local tienen cierto enfoque tecnocrático al concebir solo la dimensión económica, ecológica y científica tecnológica vinculada a la gestión del conocimiento. Este criterio no reconoce el papel medular que desempeña la dimensión ético moral en el ámbito social. El propósito fundamental de este trabajo es realizar un enfoque crítico del problema, tal y como se presenta en la realidad cubana actual, partiendo de la concepción martiana y marxista en la obra cultural de la Revolución Cubana

Estrategias didácticas para mejorar la escritura de textos argumentativos en los estudiantes de grado noveno en el Colegio Luigi Pirandello de Bogotá.

Esta investigación presenta a un análisis reflexivo como docentes acerca del proceso de enseñanza de la producción escrita, que sirva para trazar nuevas rutas didácticas que beneficien a las nuevas generaciones de estudiantes y para enriquecer los conocimientos disciplinares, investigativos y pedagógicos adquiridos a lo largo de la carrera de Licenciatura en Educación Básica con Énfasis en Humanidades y Lengua Castellana

Understanding the effects of Cr doping in rutile TiO₂ by DFT calculations and X-ray spectroscopy

The effects of Cr on local environment and electronic structure of rutile TiO₂ are studied combining theoretical and experimental approaches. Neutral and negatively charged substitutional Cr impurities Cr_(Ti)(0)* and Cr_(Ti)(-1)* as well as Cr-oxygen vacancy complex 2Cr_(Ti) + V₀ are studied by the density functional theory (DFT) within the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof (PBE) functional. Experimental results based on X-Ray absorption spectroscopy (XAS) and X-Ray photoelectron spectroscopy (XPS) performed on Cr doped TiO₂ at the Synchrotron facility were compared to the theoretical results. It is shown that the electrons of the oxygen vacancy tend to be localized at the t_(2g) states of the Cr ions in order to reach the stable oxidation state of Cr(3+)*. Effects of Cr on crystal field (CF) and structural distortions in the rutile TiO₂ cell were analyzed by the DFT calculations and XAS spectra revealing that the CF and tetragonal distortions in TiO₂ are very sensitive to the concentration of Cr

In situ local oxidation of SnO induced by laser irradiation: a stability study

In this work, semiconductor tin oxide (II) (SnO) nanoparticles and plates were synthesized at room conditions via a hydrolysis procedure. X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the high crystallinity of the as-synthesized romarchite SnO nanoparticles with dimensions ranging from 5 to 16 nm. The stability of the initial SnO and the controlled oxidation to SnO_2 was studied based on either thermal treatments or controlled laser irradiation using a UV and a red laser in a confocal microscope. Thermal treatments induced the oxidation from SnO to SnO2 without formation of intermediate SnO_x, as confirmed by thermodiffraction measurements, while by using UV or red laser irradiation the transition from SnO to SnO_2 was controlled, assisted by formation of intermediate Sn3O4, as confirmed by Raman spectroscopy. Photoluminescence and Raman spectroscopy as a function of the laser excitation source, the laser power density, and the irradiation duration were analyzed in order to gain insights in the formation of SnO_2 from SnO. Finally, a tailored spatial SnO/SnO_2 micropatterning was achieved by controlled laser irradiation with potential applicability in optoelectronics and sensing devices

Evaluación del impacto del perfil del alumnado y su formación preuniversitaria en la asignatura de Química del primer curso de grado en tres facultades de ciencias de la UCM

En este trabajo se analizan y comparan las características del perfil de los estudiantes de nuevo acceso en las titulaciones de Química, Biología y Óptica-Optometría, en tres facultades de Ciencias de la Universidad Complutense de Madrid (UCM). Se examina el rendimiento aca-démico del alumnado en la materia básica de Química, así como su relación con la situación de partida o perfil del alumnado que ingresa en la Universidad. Asimismo, se han detectado las carencias que presentan los estudiantes de primer curso de Grado en dicha materia, a partir de la autoevaluación del grado de conocimiento del temario preuniversitario de la asignatura de Química. Los resultados señalan que el alumnado mayoritariamente ha cursado la asignatura de Química, destacando que habría elegido otro Grado si hubiese obtenido la nota de acceso necesaria. Además, los estudiantes manifiestan menor conocimiento en temas que, en general, se imparten específicamente en el segundo curso de Bachillerato.The impact of the pre-university profile of first-year students of Chemistry, Biology and Optics-Optometry degrees in three Faculties of the Complutense University of Madrid (UCM) is discussed in this paper. This work also analyses the academic performance of the students in a basic subject such as Chemistry, as well as its relationship with the starting situation or profile of the first-year students. Likewise, the major shortcomings detected by the first-year students in the basic subject of Chemistry in the three degrees have been discussed, based on the self-evaluation by the students of their degree of knowledge of the pre-university subject of Chemistry. The results show that the majority of the students took Chemistry training in the Baccalaureate, and most of them would have chosen a different university degree provided they had obtained the necessary qualifications for it. In addition, students show less knowledge in subjects that, in general, are taught specifically in the second year of Baccalaureate

Synergetic improvement of stability and conductivity of hybrid composites formed by PEDOT:PSS and SnO nanoparticles

In this work, layered hybrid composites formed by tin oxide (SnO) nanoparticles synthesized by hydrolysis and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) have been analyzed. Prior to the composite study, both SnO and PEDOT:PSS counterparts were characterized by diverse techniques, such as X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), photoluminescence (PL), atomic force microscopy (AFM), optical absorption and Hall effect measurements. Special attention was given to the study of the stability of the polymer under laser illumination, as well as the analysis of the SnO to SnO_2 oxidation assisted by laser irradiation, for which different laser sources and neutral filters were employed. Synergetic effects were observed in the hybrid composite, as the addition of SnO nanoparticles improves the stability and electrical conductivity of the polymer, while the polymeric matrix in which the nanoparticles are embedded hinders formation of SnO_2. Finally, the Si passivation behavior of the hybrid composites was studied

Towards control of the size, composition and surface area of NiO nanostructures by Sn doping

Achieving nanostructures with high surface area is one of the most challenging tasks as this metric usually plays a key role in technological applications, such as energy storage, gas sensing or photocatalysis, fields in which NiO is gaining increasing attention recently. Furthermore, the advent of modern NiO-based devices can take advantage of a deeper knowledge of the doping process in NiO, and the fabrication of p-n heterojunctions. By controlling experimental conditions such as dopant concentration, reaction time, temperature or pH, NiO morphology and doping mechanisms can be modulated. In this work, undoped and Sn doped nanoparticles and NiO/SnO_2 nanostructures with high surface areas were obtained as a result of Sn incorporation. We demonstrate that Sn incorporation leads to the formation of nanosticks morphology, not previously observed for undoped NiO, promoting p-n heterostructures. Consequently, a surface area value around 340 m^2/g was obtained for NiO nanoparticles with 4.7 at.% of Sn, which is nearly nine times higher than that of undoped NiO. The presence of Sn with different oxidation states and variable Ni^(3+)/Ni^(2+) ratio as a function of the Sn content were also verified by XPS, suggesting a combination of two charge compensation mechanisms (electronic and ionic) for the substitution of Ni^(2+) by Sn^(4+). These results make Sn doped NiO nanostructures a potential candidate for a high number of technological applications, in which implementations can be achieved in the form of NiO-SnO_2 p-n heterostructures

Evaluación del impacto del perfil del alumnado en la valoración de la actividad docente del profesorado

En este proyecto se analiza el perfil de los estudiantes de primer curso en tres Grados (Química, Biología y Óptica-Optometría) de las Facultades de Ciencias de la UCM, detectando las carencias que presentan los estudiantes en una materia básica como la Química. Se comparan los resultados con los obtenidos en el curso académico 2016-2017. Asimismo se analiza la relación del perfil del alumnado con la valoración de la actividad docente del profesorado que realizan los estudiantes dentro del programa DOCENTIA