El objetivo de este estudio fue medir los niveles de estrés antes y después de una intervención psicológica centrada en el desarrollo de estrategias de afrontamiento e identificar si esas diferencias fueron estadísticamente significativas... more
El objetivo de este estudio fue medir los niveles de estrés antes y después de una intervención psicológica centrada en el desarrollo de estrategias de afrontamiento e identificar si esas diferencias fueron estadísticamente significativas en una muestra de futbolistas semiprofesionales. La selección de la muestra fue no probabilística en donde participaron 22 futbolistas varones de 14 a 23 años de edad en el estudio diagnóstico. En el análisis de datos inferencial, se utilizó una prueba no paramétrica t de Wilcoxon para muestras relacionadas en donde participaron 11 jugadores para la comparación entre medias en la variable estrés, antes y después de la intervención en el desarrollo de estrategias de afrontamiento. El instrumento utilizado para este estudio fue el cuestionario de estrés para deportistas Restq-Sport. En los resultados diagnósticos se encontraron una puntación en el índice de estrés de 2.80 lo cual indicó que la mitad del grupo reportó una necesidad de trabajar una int...
Research Interests: Psychology and Retos
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Reseña de David Harvey, The Anti-Capitalist Chronicles, Londres, Pluto Press, 2020, 220 pgs.
espanolEl trastorno del espectro autista (TEA) es una alteracion del desarrollo que se especifica por deficiencias cualitativas en la comunicacion y en la interaccion social, comportamiento caracterizado por patrones repetitivos y... more
espanolEl trastorno del espectro autista (TEA) es una alteracion del desarrollo que se especifica por deficiencias cualitativas en la comunicacion y en la interaccion social, comportamiento caracterizado por patrones repetitivos y estereotipados. Los ninos con trastorno del espectro autista, como tambien otros ninos que no padecen este trastorno, presentan una afinidad por las Tecnologias de la Informacion y la Comunicacion (TIC). En este articulo describiremos un proyecto cuyo objetivo es investigar acerca del uso de interfaces naturales de usuario para complementar las actividades educativas, sociales y cognitivas, en ninos que padecen TEA. EnglishThe Autism Spectrum Disorder (ASD) is a disorder of the brain development,which is often characterized by difficulties in social interaction, verbal and nonverbal communication and repetitive behaviors. The kids with ASD, as most of the kids nowadays, have a particular affinity for the Information and Communications Technologies (ICT). O...
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Abstract. The present work outlines the results of the Parallel Discrete Event Simulation (PDES) and advanced animation techniques for solving an individual based model: Fish Schools. On the one hand, this type of model cannot be solved... more
Abstract. The present work outlines the results of the Parallel Discrete Event Simulation (PDES) and advanced animation techniques for solving an individual based model: Fish Schools. On the one hand, this type of model cannot be solved through analytical ...
Research Interests: Computer Science, Animation, Computer Animation, Software, Real Time, and 10 moreDistributed Simulation, Analytical Method, Discrete Event Simulation, Parallel Discrete Event Simulation, High Performance Simulation, Individual Oriented Models, Simulation Software, Individual Based Model, Animation techniques, and Simulation Technique
Design of a charge injection compensation system for MEMS electrostatic actuators by
This article presents several design techniques to fabricate micro-electro-mechanical systems (MEMS) using standard complementary metal-oxide semiconductor (CMOS) processes. They were applied to fabricate high yield CMOS-MEMS shielded... more
This article presents several design techniques to fabricate micro-electro-mechanical systems (MEMS) using standard complementary metal-oxide semiconductor (CMOS) processes. They were applied to fabricate high yield CMOS-MEMS shielded Lorentz-force magnetometers (LFM). The multilayered metals and oxides of the back-end-of-line (BEOL), normally used for electronic routing, comprise the structural part of the MEMS. The most important fabrication challenges, modeling approaches and design solutions are discussed. Equations that predict the Q factor, sensitivity, Brownian noise and resonant frequency as a function of temperature, gas pressure and design parameters are presented and validated in characterization tests. A number of the fabricated magnetometers were packaged into Quad Flat No-leads (QFN) packages. We show this process can achieve yields above 95 % when the proper design techniques are adopted. Despite CMOS not being a process for MEMS manufacturing, estimated performance (...
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The use of thin AlA capping layers (CLs) on InAs quantum dots (QDs) has recently received considerable attention due to improved photovoltaic performance in QD solar cells. However, there is little data on the structural changes that... more
The use of thin AlA capping layers (CLs) on InAs quantum dots (QDs) has recently received considerable attention due to improved photovoltaic performance in QD solar cells. However, there is little data on the structural changes that occur during capping and their relation to different growth conditions. In this work, we studied the effect of AlA capping growth rate (CGR) on the structural features of InAs QDs in terms of shape, size, density, and average content. As will be shown, there are notable differences in the characteristics of the QDs upon changing CGR. The Al distribution analysis in the CL around the QDs was revealed to be the key. On the one hand, for the lowest CGR, Al has a homogeneous distribution over the entire surface, but there is a large thickening of the CL on the sides of the QD. As a result, the QDs are lower, lenticular in shape, but richer in In. On the other hand, for the higher CGRs, Al accumulates preferentially around the QD but with a more uniform thic...
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Recently, thin AlAs capping layers (CLs) on InAs quantum dot solar cells (QDSCs) have been shown to yield better photovoltaic efficiency compared to traditional QDSCs. Although it has been proposed that this improvement is due to the... more
Recently, thin AlAs capping layers (CLs) on InAs quantum dot solar cells (QDSCs) have been shown to yield better photovoltaic efficiency compared to traditional QDSCs. Although it has been proposed that this improvement is due to the suppression of the capture of photogenerated carriers through the wetting layer (WL) states by a de-wetting process, the mechanisms that operate during this process are not clear. In this work, a structural analysis of the WL characteristics in the AlAs/InAs QD system with different CL-thickness has been made by scanning transmission electron microscopy techniques. First, an exponential decline of the amount of InAs in the WL with the CL thickness increase has been found, far from a complete elimination of the WL. Instead, this reduction is linked to a higher shield effect against QD decomposition. Second, there is no compositional separation between the WL and CL, but rather single layer with a variable content of InAlGaAs. Both effects, the high inter...
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This paper discusses manufacturing process, experimental testing and numerical simulation of braided Ω-frame segments bonded to a multiaxial fabric skin which represent the typical airframe structure. The Ω-frame preforms were... more
This paper discusses manufacturing process, experimental testing and numerical simulation of braided Ω-frame segments bonded to a multiaxial fabric skin which represent the typical airframe structure. The Ω-frame preforms were manufactured using the circular braiding process and impregnated with resin by Vacuum Asissted Process (VAP) technique. The experimental testing was conducted quasistatically on a test setup which introduces simultaneous compression and bending loads in the specimen segment. The experimental results of the test campaing were used to develop numerical methods for the design of braided structures. The simulations were performed using explicit FE code LS-DYNA.
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This paper investigates the effect that the selection of the die material generates on the extrusion process of bimetallic cylindrical billets combining a magnesium alloy core (AZ31B) and a titanium alloy sleeve (Ti6Al4V) of interest in... more
This paper investigates the effect that the selection of the die material generates on the extrusion process of bimetallic cylindrical billets combining a magnesium alloy core (AZ31B) and a titanium alloy sleeve (Ti6Al4V) of interest in aeronautical applications. A robust finite element model is developed to analyze the variation in the extrusion force, damage distribution, and wear using different die materials. The results show that die material is a key factor to be taken into account in multi-material extrusion processes. The die material selection can cause variations in the extrusion force from 8% up to 15%, changing the effect of the extrusion parameters, for example, optimum die semi-angle. Damage distribution in the extrudate is also affected by die material, mainly in the core. Lastly, die wear is the most affected parameter due to the different hardness of the materials, as well as due to the variations in the normal pressure and sliding velocity, finding critical values ...
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This paper investigates the extrusion process to manufacture bimetallic cylinders combining a magnesium alloy core (AZ31B) and a titanium alloy sleeve (Ti6Al4V) of interest in aeronautical applications. A robust finite element model has... more
This paper investigates the extrusion process to manufacture bimetallic cylinders combining a magnesium alloy core (AZ31B) and a titanium alloy sleeve (Ti6Al4V) of interest in aeronautical applications. A robust finite element model has been developed to determine the most influential parameters and to study the effect of them on the extrusion force and damage induced by means of Design of Experiments (DOE) and Taguchi method. The results show that the most influential parameters in the extrusion forces are the friction between sleeve and container/die and the height of the cylinder; and the less influential ones are the process temperature and ram speed. Moreover, minimum values of forces along with low damage can be reached by favorable interface contact conditions, minimizing the friction at the core-container/die interface, as the main influencing factor; followed by the geometrical dimensions of the billet, being the billet height more important when paying attention to the min...
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Prime numbers are one of the most intriguing figures in mathematics. Despite centuries of research, many questions remain still unsolved. In recent years, computer simulations are playing a fundamental role in the study of an immense... more
Prime numbers are one of the most intriguing figures in mathematics. Despite centuries of research, many questions remain still unsolved. In recent years, computer simulations are playing a fundamental role in the study of an immense variety of problems. In this work, we present a simple representation of prime numbers in two dimensions that allows us to formulate a number of conjectures that may lead to important avenues in the field of research on prime numbers. In particular, although the zeroes in our representation grow in a somewhat erratic, hardly predictable way, the gaps between them present a remarkable and intriguing property: a clear exponential decay in the frequency of gaps vs. gap size. The smaller the gaps, the more frequently they appear. Additionally, the sequence of zeroes, despite being non-consecutive numbers, contains a number of primes approximately equal to n / log n , n being the number of terms in the sequence.
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We study out-of-equilibrium energy transport in a quantum critical fluid with Lifshitz scaling symmetry following a local quench between two semi-infinite fluid reservoirs. The late time energy flow is universal and is accommodated via a... more
We study out-of-equilibrium energy transport in a quantum critical fluid with Lifshitz scaling symmetry following a local quench between two semi-infinite fluid reservoirs. The late time energy flow is universal and is accommodated via a steady state occupying an expanding central region between outgoing shock and rarefaction waves. We consider the admissibility and entropy conditions for the formation of such a non-equilibrium steady state for a general dynamical critical exponent z in arbitrary dimensions and solve the associated Riemann problem. The Lifshitz fluid with z = 2 can be obtained from a Galilean boost invariant field theory and the non-equilibrium steady state is identified as a boosted thermal state. A Lifshitz fluid with generic z is scale invariant but without boost symmetry and in this case the non-equilibrium steady state is genuinely non-thermal.
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In this work, we design and produce micron-sized fiber mats by blending poly(ε-caprolactone) (PCL) with small amounts of block copolymers poly(ethylene oxide)m-block-poly(ε-caprolactone)n (PEOm-b-PCLn) using electrospinning. Three... more
In this work, we design and produce micron-sized fiber mats by blending poly(ε-caprolactone) (PCL) with small amounts of block copolymers poly(ethylene oxide)m-block-poly(ε-caprolactone)n (PEOm-b-PCLn) using electrospinning. Three different PEOm-b-PCLn block copolymers, with different molecular weights of PEO and PCL, were synthesized by ring opening polymerization of ε-caprolactone using PEO as initiator and stannous octoate as catalyst. The polymer blends were prepared by homogenous solvent mixing using dichloromethane for further electrospinning procedures. After electrospinning, it was found that the addition to PCL of the different block copolymers produced micron-fibers with smaller width, equal or higher hydrophilicity, lower Young modulus, and rougher surfaces, as compared with micron-fibers obtained only with PCL. Neural stem progenitor cells (NSPC), isolated from rat brains and grown as neurospheres, were cultured on the fibrous materials. Immunofluorescence assays showed ...
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Superlattice structures (SLs) with type-II (GaAsSb/GaAsN) and -I (GaAsSbN/GaAs) band alignments have received a great deal of attention for multijunction solar cell (MJSC) applications, as they present a strongly intensified luminescence... more
Superlattice structures (SLs) with type-II (GaAsSb/GaAsN) and -I (GaAsSbN/GaAs) band alignments have received a great deal of attention for multijunction solar cell (MJSC) applications, as they present a strongly intensified luminescence and a significant external quantum efficiency (EQE), with respect to the GaAsSbN bulk layers. Despite the difficulties in characterizing the distribution of N in dilute III-V nitride alloys, in this work we have obtained N-compositional mappings before and after rapid thermal annealing (RTA) in both types of structures, by using a recent methodology based on the treatment of different scanning transmission electron microscopy (STEM) imaging configurations. Texture analysis by gray level co-occurrence matrixes (GLCM) and the measurement of the degree of clustering are used to compare and evaluate the compositional inhomogeneities of N. Comparison with the Sb maps shows that there is no spatial correlation between the N and Sb distributions. Our resul...
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The work in this paper introduces finite mixture models that can be used to simultaneously cluster the rows and columns of two-mode ordinal categorical response data, such as those resulting from Likert scale responses. We use the popular... more
The work in this paper introduces finite mixture models that can be used to simultaneously cluster the rows and columns of two-mode ordinal categorical response data, such as those resulting from Likert scale responses. We use the popular proportional odds parameterisation and propose models which provide insights into major patterns in the data. Model-fitting is performed using the EM algorithm, and a fuzzy allocation of rows and columns to corresponding clusters is obtained. The clustering ability of the models is evaluated in a simulation study and demonstrated using two real data sets.
Research Interests: Psychology, Mathematics, Applied Mathematics, Computer Science, Algorithms, and 15 moreData Mining, Biclustering, Medicine, Fuzzy Clustering, Humans, Cluster Analysis, EM algorithm, Probabilities, Odds ratio, Proportional Odds, Ordinal Data, Likelihood Functions, Likert Scale, Escala de likert, and Ordinal scale
This paper presents a new goodness-of-fit test for an ordered stereotype model used for an ordinal response variable. The proposed test is based on the well-known Hosmer-Lemeshow test and its version for the proportional odds regression... more
This paper presents a new goodness-of-fit test for an ordered stereotype model used for an ordinal response variable. The proposed test is based on the well-known Hosmer-Lemeshow test and its version for the proportional odds regression model. The latter test statistic is calculated from a grouping scheme assuming that the levels of the ordinal response are equally spaced which might be not true. One of the main advantages of the ordered stereotype model is that it allows us to determine a new uneven spacing of the ordinal response categories, dictated by the data. The proposed test takes the use of this new adjusted spacing to partition data. A simulation study shows good performance of the proposed test under a variety of scenarios. Finally, the results of the application in two examples are presented. Copyright © 2016 John Wiley & Sons, Ltd.
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Research Interests: Humanities and Evaluación
Recent research has developed a group of likelihood-based finite mixture models for a data matrix with ordinal data, establishing likelihood-based multivari-ate methods which applies fuzzy clustering via finite mixtures to the ordered... more
Recent research has developed a group of likelihood-based finite mixture models for a data matrix with ordinal data, establishing likelihood-based multivari-ate methods which applies fuzzy clustering via finite mixtures to the ordered stereotype model. There are many visualisation tools which depict reduction of dimensionality in matrices of ordinal data. This technical report introduces the spaced mosaic plot which is one new graphical tool for ordinal data when the ordinal stereotype model is used. It takes advantage of the fitted score parameters to determine the spacing between two adjacent ordinal categories. We develop a function in R and its documentation is presented. Finally, the description of a spaced mosaic plot is shown.
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We present experimental results on the release of MEMS devices manufactured using the standard CMOS interconnection metal layers as structural elements and the insulating silicon dioxide as sacrificial layers. Experiments compare the... more
We present experimental results on the release of MEMS devices manufactured using the standard CMOS interconnection metal layers as structural elements and the insulating silicon dioxide as sacrificial layers. Experiments compare the release results of four different etching agents in a CMOS technology (hydrofluoric acid, ammonium fluoride, a mixture of acetic acid and ammonium fluoride, and hydrogen fluoride), describe various phenomena found during the etching process, and show the release results of multilayer structures.
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ABSTRACT In this paper we present an asynchronous finite-state machine digital controller co-integrated with an on-chip non-inverting buck-boost power converter with dynamic signal-tracking capabilities. The mostly-digital controller... more
ABSTRACT In this paper we present an asynchronous finite-state machine digital controller co-integrated with an on-chip non-inverting buck-boost power converter with dynamic signal-tracking capabilities. The mostly-digital controller functionally implements a non-PWM zone-wise control law through asynchronous circuitry, thus exhibiting self-timed minimum latency and ultra low power operation due to gate switching activity. Experimental results on a 0.35 μm CMOS technology demonstrate an efficiency up to 80 % with a switching frequency of 2.86 MHz.
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Multi-material co-extrusion is a complex thermo-mechanical forming process used to obtain bimetallic billets. Its complexity is due to the combination of diffusion phenomena in the interface of both materials together with the high... more
Multi-material co-extrusion is a complex thermo-mechanical forming process used to obtain bimetallic billets. Its complexity is due to the combination of diffusion phenomena in the interface of both materials together with the high temperature and pressure generated and the different flow stress characteristics created by the joining of dissimilar materials. Accordingly, the selection of optimal process parameters becomes key to ensure process feasibility. In this work, a comparison among different multi-criteria decision making (MCDM) methodologies, together with different weighting methods, were applied to the simulation results by using DEFORM3D© software to select the optimal combination of process parameters to fulfil the criteria of minimum damage, extrusion force, and tool wear, together with the maximum reduction in the average grain size.
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El trastorno de espectro autista (TEA) es una alteración del desarrollo que se especifica por deficiencias cualitativas en la comunicación y en la interacción social, comportamiento caracterizado por patrones repetitivos y estereotipados.... more
El trastorno de espectro autista (TEA) es una alteración del desarrollo que se especifica por deficiencias cualitativas en la comunicación y en la interacción social, comportamiento caracterizado por patrones repetitivos y estereotipados. Los niños con trastorno del espectro autista (TEA), como también otros niños que no padecen este trastorno, presentan una característica bien definida por la aceptación de las Tecnologías de la Información y la Comunicación (TIC).En este artículo describiremos un proyecto cuyo objetivo es investigar acerca del uso de interfaces naturales para ayudar a la mejora de las actividades sociales como también las cognitivas, en personas que padecen TEA.