Application of Mathieu functions for the study of non-slanted reflection gratings

In this work we prensent an analysis of non-slanted reflection gratings by using exact solution of the second order differential equation derived from Maxwell equations, in terms of Mathieu functions. The results obtained by using this method will be compared to those obtained by using the well known Kogelnik's Coupled Wave Theory which predicts with great accuracy the response of the efficieny of the zero and first order for volume phase gratings, for both reflection and transmission gratings.

Mathematical programming model for heat exchanger design through optimization of partial objectives

Mathematical programming can be used for the optimal design of shell-and-tube heat exchangers (STHEs). This paper proposes a mixed integer non-linear programming (MINLP) model for the design of STHEs, following rigorously the standards of the Tubular Exchanger Manufacturers Association (TEMA). Bell–Delaware Method is used for the shell-side calculations. This approach produces a large and non-convex model that cannot be solved to global optimality with the current state of the art solvers. Notwithstanding, it is proposed to perform a sequential optimization approach of partial objective targets through the division of the problem into sets of related equations that are easier to solve. For each one of these problems a heuristic objective function is selected based on the physical behavior of the problem. The global optimal solution of the original problem cannot be ensured even in the case in which each of the sub-problems is solved to global optimality, but at least a very good solution is always guaranteed. Three cases extracted from the literature were studied. The results showed that in all cases the values obtained using the proposed MINLP model containing multiple objective functions improved the values presented in the literature.

ConfChem Conference on A Virtual Colloquium to Sustain and Celebrate IYC 2011 Initiatives in Global Chemical Education—The Global Experiment of the IYC2011: Creating Online Communities for Education and Science

The Global Experiment, Water: A Chemical Solution, was one of the flagship activities of the International Year of Chemistry (IYC). During the virtual colloquium of the spring 2012 online ConfChem conference, the main results of this year-long experiment were presented and discussed online for a week. Some of the main conclusions of the virtual conversations relate to the benefits of creating online communities of people sharing similar interests, the use of online educational platforms to gather massive amounts of data, and specific questions about the development of this IYC initiative. The activities of the global water experiment (GWE) were designed by a team of experts and the protocols are available online on the GWE Web site. The results were shown in one interactive world map that allowed students to learn about data visualization, validation, and interpretation. The feedback obtained from the participants of the GWE and later by the contributors of the virtual colloquium was very positive. Many participants asked specific and technical questions about the development of this experiment, while others excitedly endorsed the convenience of these large open-access activities to promote chemistry worldwide. The estimate is that over 2 million people took part in the GWE during the IYC. This communication summarizes one of the invited papers to the ConfChem online conference: A Virtual Colloquium to Sustain and Celebrate IYC 2011 Initiatives in Global Chemical Education, held from May 18 to June 29, 2012 and hosted by the ACS DivCHED Committee on Computers in Chemical Education and the IUPAC Committee on Chemistry Education.

Non-spectral interferences due to the presence of sulfuric acid in inductively coupled plasma mass spectrometry

Results of a systematic study concerning non-spectral interferences from sulfuric acid containing matrices on a large number of elements in inductively coupled plasma–mass spectrometry (ICP-MS) are presented in this work. The signals obtained with sulfuric acid solutions of different concentrations (up to 5% w w− 1) have been compared with the corresponding signals for a 1% w w− 1− nitric acid solution at different experimental conditions (i.e., sample uptake rates, nebulizer gas flows and r.f. powers). The signals observed for 128Te+, 78Se+ and 75As+ were significantly higher when using sulfuric acid matrices (up to 2.2-fold for 128Te+ and 78Se+ and 1.8-fold for 75As+ in the presence of 5 w w-1 sulfuric acid) for the whole range of experimental conditions tested. This is in agreement with previously reported observations. The signal for 31P+ is also higher (1.1-fold) in the presence of sulfuric acid. The signal enhancements for 128Te+, 78Se+, 75As+ and 31P+ are explained in relation to an increase in the analyte ion population as a result of charge transfer reactions involving S+ species in the plasma. Theoretical data suggest that Os, Sb, Pt, Ir, Zn and Hg could also be involved in sulfur-based charge transfer reactions, but no experimental evidence has been found. The presence of sulfuric acid gives rise to lower ion signals (about 10–20% lower) for the other nuclides tested, thus indicating the negative matrix effect caused by changes in the amount of analyte loading of the plasma. The elemental composition of a certified low-density polyethylene sample (ERM-EC681K) was determined by ICP-MS after two different sample digestion procedures, one of them including sulfuric acid. Element concentrations were in agreement with the certified values, irrespective of the acids used for the digestion. These results demonstrate that the use of matrix-matched standards allows the accurate determination of the tested elements in a sulfuric acid matrix.

Comparative study of RPSALG algorithm for convex semi-infinite programming

The Remez penalty and smoothing algorithm (RPSALG) is a unified framework for penalty and smoothing methods for solving min-max convex semi-infinite programing problems, whose convergence was analyzed in a previous paper of three of the authors. In this paper we consider a partial implementation of RPSALG for solving ordinary convex semi-infinite programming problems. Each iteration of RPSALG involves two types of auxiliary optimization problems: the first one consists of obtaining an approximate solution of some discretized convex problem, while the second one requires to solve a non-convex optimization problem involving the parametric constraints as objective function with the parameter as variable. In this paper we tackle the latter problem with a variant of the cutting angle method called ECAM, a global optimization procedure for solving Lipschitz programming problems. We implement different variants of RPSALG which are compared with the unique publicly available SIP solver, NSIPS, on a battery of test problems.

Constrained self-organizing feature map to preserve feature extraction topology

In many classification problems, it is necessary to consider the specific location of an n-dimensional space from which features have been calculated. For example, considering the location of features extracted from specific areas of a two-dimensional space, as an image, could improve the understanding of a scene for a video surveillance system. In the same way, the same features extracted from different locations could mean different actions for a 3D HCI system. In this paper, we present a self-organizing feature map able to preserve the topology of locations of an n-dimensional space in which the vector of features have been extracted. The main contribution is to implicitly preserving the topology of the original space because considering the locations of the extracted features and their topology could ease the solution to certain problems. Specifically, the paper proposes the n-dimensional constrained self-organizing map preserving the input topology (nD-SOM-PINT). Features in adjacent areas of the n-dimensional space, used to extract the feature vectors, are explicitly in adjacent areas of the nD-SOM-PINT constraining the neural network structure and learning. As a study case, the neural network has been instantiate to represent and classify features as trajectories extracted from a sequence of images into a high level of semantic understanding. Experiments have been thoroughly carried out using the CAVIAR datasets (Corridor, Frontal and Inria) taken into account the global behaviour of an individual in order to validate the ability to preserve the topology of the two-dimensional space to obtain high-performance classification for trajectory classification in contrast of non-considering the location of features. Moreover, a brief example has been included to focus on validate the nD-SOM-PINT proposal in other domain than the individual trajectory. Results confirm the high accuracy of the nD-SOM-PINT outperforming previous methods aimed to classify the same datasets.

Global behavior of the Douglas–Rachford method for a nonconvex feasibility problem

In recent times the Douglas–Rachford algorithm has been observed empirically to solve a variety of nonconvex feasibility problems including those of a combinatorial nature. For many of these problems current theory is not sufficient to explain this observed success and is mainly concerned with questions of local convergence. In this paper we analyze global behavior of the method for finding a point in the intersection of a half-space and a potentially non-convex set which is assumed to satisfy a well-quasi-ordering property or a property weaker than compactness. In particular, the special case in which the second set is finite is covered by our framework and provides a prototypical setting for combinatorial optimization problems.

Hacia una ciudadanía global: enseñanza de aspectos culturales y de género en la universidad con las revistas de Oxfam Intermón

Las ONG de Desarrollo (ONGD) contribuyen a informar sobre lo las distintas realidades sociales del siglo XXI. Sin embargo, en ocasiones, la representación de las personas culturalmente diferentes está llena de prejuicios y de estereotipos, hecho que todavía queda más marcado cuando se trata de mujeres. Así, nuestro objetivo con esta comunicación es observar la representación de mujeres de otras culturas en una muestra de las revistas publicadas por la ONGD Oxfam Intermón desde mayo de 2013 hasta mayo de 2014. El corpus empleado para el análisis serán las portadas de las revistas. Se seleccionaron algunos de estos textos donde aparecían representadas mujeres para llevar a cabo una experiencia didáctica. Se explicó el modo de analizar textos con imagen y se pidió al alumnado que los analizara con el fin de desarrollar su capacidad crítica y su conciencia social. Los marcos teóricos de este estudio serán los principios del Análisis Crítico del Discurso (van Dijk 2005, 2009) y la Gramática Visual (Kress y van Leeuwen, 2006) para explorar las principales estrategias lingüísticas y visuales empleadas para presentar a mujeres. Los resultados del estudio ponen de manifiesto que la práctica docente llevada a cabo hace que el alumnado tome conciencia de que el modo en que las mujeres aparecen representadas en las revistas de Oxfam Intermón contribuye a modificar la imagen negativa que normalmente tenemos sobre éstas. La representación positiva que se observa contribuye a cambiar la percepción del alumnado. Como conclusiones podemos señalar la importancia del emplear textos sobre temas sociales para que el alumnado adquiera competencias emocionales y mejore su capacidad crítica. Además, estos textos señalan que las mujeres van avanzando hacia el empoderamiento en todos los lugares del planeta de modo que se cumplen progresivamente los objetivos del milenio.