A CFD-based Approach to Predict Explosion Overpressure: A Comparison to Current Methods

A CFD-based approach has been developed in this work to predict the overpressure produced during an explosion. An adiabatic exothermal reaction allows computing the explosion energy release. To validate the proposed CFD approach, overpressure predictions based on this methodology are compared with results produced with the TNObased method. It is demonstrated that the physics adopted in our model produces satisfactory predictions in the open area. The CFD simulations were carried out in the ANSYS CFX tool. The source of energy corresponds to the one produced by a stoichiometric proportion in reactants without energy generation. The explosion analysis considered that explosion occurs geometrically as a sequence of control volumes. Thus, the explosion in a volume is assumed to occur when the maximum pressure is achieved in the previous control volume. This way, the explosion is propagated and it is shown that it is equivalent to conventional predicting methods

Undergraduate Dissertation: goals, types and supervisory styles

[EN] The aim of this paper is to progress towards the development of a framework to analyse undergraduate dissertations. We pay attention to four key elements and the relationships between them: the goals to be achieved, the available means, the types of final-year dissertations and the supervisory styles. The distinctive feature of the undergraduate dissertation is the process followed to achieve the final goals: the student must produce a high-quality work with high level of autonomy using the available resources (the previous training, the specific materials and the support of a supervisor). Taking this into account, we focus on two factors which condition the process: the types of dissertations (or projects) and the styles of supervision. It is acknowledged the need to broaden the range of options available for each element creating the procedure for each of them. Also, suggesting a classification for them. Finally, attention is paid to the role of the supervisor since it is considered crucial for students. Therefore, it is proposed a classification for the styles of supervision. According to the contribution of the supervisor at each stage of the process, we identify three supervisory styles: director, advisor and supervisor. Although the choice of the most suitable style depends on many factors, we conclude that, in most cases, advisor and supervisor are the most appropriate for the undergraduate dissertation.[ES] El objetivo de este artículo es avanzar en el desarrollo de un marco para el análisis de la asignatura Trabajo de Fin de Grado (TFG) que pueda adaptarse a un número amplio de áreas de conocimiento. Se atiende a cuatro elementos clave: los fines perseguidos, los instrumentos disponibles, las modalidades de TFG y los estilos de tutorización. El carácter diferenciado de esta asignatura reside, básicamente, en el proceso seguido para alcanzar los fines: utilizando los instrumentos disponibles (formación previa, materiales específicos y apoyo tutorial) el estudiante debe “producir” un trabajo académicamente riguroso con un grado de autonomía notable. Centramos, por ello, la atención en dos factores que condicionan dicho proceso: las modalidades de TFG y los estilos de tutorización. Ponemos de manifiesto la necesidad de ampliar el abanico de modalidades en todos los elementos que conforman el procedimiento del TFG y presentamos una posible clasificación. A continuación, dado que parece resultar crucial para el alumno, ponemos el foco de atención en el papel del tutor y proponemos una clasificación de los estilos de tutorización. Atendiendo a la intervención del tutor en las distintas fases de elaboración de los TFG, distinguimos tres estilos de tutorización: conductora, orientadora y supervisora. Aunque la elección del estilo de tutorización más adecuado depende de múltiples factores, concluimos que, en general, la tutorización orientadora y la supervisora son más apropiadas para el TFG.Díaz-Vázquez, R.; García-Díaz, A.; Maside Sanfiz, J.; Vázquez-Rozas, E. (2018). El Trabajo de Fin de Grado: fines, modalidades y estilos de tutorización. REDU. Revista de Docencia Universitaria. 16(2):159-175. doi:10.4995/redu.2018.10178SWORD15917516

Global design of analog cells using statistical optimization techniques

We present a methodology for automated sizing of analog cells using statistical optimization in a simulation based approach. This methodology enables us to design complex analog cells from scratch within reasonable CPU time. Three different specification types are covered: strong constraints on the electrical performance of the cells, weak constraints on this performance, and design objectives. A mathematical cost function is proposed and a bunch of heuristics is given to increase accuracy and reduce CPU time to minimize the cost function. A technique is also presented to yield designs with reduced variability in the performance parameters, under random variations of the transistor technological parameters. Several CMOS analog cells with complexity levels up to 48 transistors are designed for illustration. Measurements from fabricated prototypes demonstrate the suitability of the proposed methodology

Examples of signature (2,2) manifolds with commuting curvature operators

We exhibit Walker manifolds of signature (2,2) with various commutativity properties for the Ricci operator, the skew-symmetric curvature operator, and the Jacobi operator. If the Walker metric is a Riemannian extension of an underlying affine structure A, these properties are related to the Ricci tensor of A

Continuous and Localized Mn Implantation of ZnO

We present results derived from continuous and localized 35 keV (55)Mn(+) ion implantations into ZnO. Localized implantations were carried out by using self-ordered alumina membranes as masks leading to ordered arrays of implanted volumes on the substrate surfaces. Defects and vacancies in the small implantation volumes of ZnO were generated due to the implantation processes besides the creation of new phases. Rapid thermal annealing was applied in the case of continuous implantation. The samples were characterized by HRSEM, GIXRD, Raman spectroscopy and RBS/C. Magnetic characterization of the samples pointed out appreciable differences among the samples obtained by the different implantation methods. This fact was mainly attributed to the different volume/surface ratios present in the implanted zones as well as to the increase of Mn atom concentrations along the grain frontiers in the nanostructured surfaces. The samples also showed a ferromagnetic transition phase at temperature value higher than room temperature

Femtosecond laser-written double-cladding waveguides in Nd:GdVO4crystal: Raman analysis, guidance, and lasing

We report on waveguide lasers at 1064.5 nm in femtosecond laser-written double-cladding waveguides in Nd∶GdVO4 crystals. The cladding waveguides guide both transverse electric (TE)- and transverse magnetic (TM)-polarized modes with considerably symmetric single-modal profiles and show good transmission properties (propagation loss as low as 1.0 dB∕cm). The detailed structure of the single and double claddings has been imaged by means of μ-Raman analysis, and the observed slight fabrication asymmetries with respect to an ideal circular cladding are in well agreement with the observed differences in TE/TM propagation losses. Importantly, the Raman imaging shows the complete absence of lattice defect at the laser active volume. Under the optical pumping at 808 nm, a maximum output power up to 0.43Wof the continuous wave waveguide laser with a slope efficiency of 52.3% has been achieved in the double-cladding waveguide, which is 21.6% and 23% higher than that from a single-inner cladding waveguide. Furthermore, the maximum output power of the waveguide laser is 72% higher than that of the double-line waveguide due to the double-cladding designThe work is supported by the National Natural Science Foundation of China (No. 11274203), the Specialized Research Fund for the Doctoral Program of Higher Education of China (No. 20130131130001), and Junta de Castilla y León under project SA086A12-2. Support from the Centro de Láseres Pulsados (CLPU) is also acknowledged. This work was supported by the Spanish Government under project MAT2011- 29255-C02-02 and by the Generalitat de Catalunya under project 2014SGR1358

Depresión en personas mayores: Aplicación del método de Bayes

En el presente trabajo se realiza, en primer lugar, una descripción de la sintomatología depresiva en general y en la población de personas mayores en particular. A su vez, se exponen una serie de variables que podrían estar relacionadas con la presencia o ausencia de esta sintomatología. Estas variables son edad, género, estado civil, deterioro cognitivo, dependencia física, estilo de afrontamiento y bienestar psicológico. A partir de estas variables, se realiza un análisis probabilístico empleando el Método de Bayes, herramienta novedosa en el campo de la investigación psicológica. La investigación se llevó a cabo en 66 sujetos mayores de 65 años, y los instrumentos utilizados para recabar información fueron la Prueba de Vocabulario de la Escala de lnteligencia de Wechsler para Adultos- lll, la Escala de Depresión Geriátrica de Yesavage, el Cuestionario de Afrontamiento de Estrés, las Escalas de Bienestar Psicológico de Ryff, el Mini Examen Cognoscitivo y el fndice de Barthel. Los resultados reflejan que, para nuestra muestra, no existiría relación entre la sintomatología depresiva y las variables de género, edad, estado civil e independencia física. Por el contrario, la ausencia de síntomas depresivos muestra una relación directa y positiva tanto con la variable deterioro cognitivo como el estilo de afrontamiento positivo (centrado en la focalización de problemas). Finalmente, el bienestar psicológico parece estar fuertemente ligado a la ausencia de sintomatología depresiva