Solid-liquid interactions in microscale structures and devices

Liquid-solid interactions become important as dimensions approach mciro/nano-scale. This dissertation focuses on liquid-solid interactions in two distinct applications: capillary driven self-assembly of thin foils into 3D structures, and droplet wetting of hydrophobic micropatterned surfaces. The phenomenon of self-assembly of complex structures is common in biological systems. Examples include self-assembly of proteins into macromolecular structures and self-assembly of lipid bilayer membranes. The principles governing this phenomenon have been applied to induce self-assembly of millimeter scale Si thin films into spherical and other 3D structures, which are then integrated into light-trapping photovoltaic (PV) devices. Motivated by this application, we present a generalized analytical study of the self-folding of thin plates into deterministic 3D shapes, through fluid-solid interactions, to be used as PV devices. This study consists of developing a model using beam theory, which incorporates the two competing components — a capillary force that promotes folding and the bending rigidity of the foil that resists folding into a 3D structure. Through an equivalence argument of thin foils of different geometry, an effective folding parameter, which uniquely characterizes the driving force for folding, has been identified. A criterion for spontaneous folding of an arbitrarily shaped 2D foil, based on the effective folding parameter, is thus established. Measurements from experiments using different materials and predictions from the model match well, validating the assumptions used in the analysis. As an alternative to the mechanics model approach, the minimization of the total free energy is employed to investigate the interactions between a fluid droplet and a flexible thin film. A 2D energy functional is proposed, comprising the surface energy of the fluid, bending energy of the thin film and gravitational energy of the fluid. Through simulations with Surface Evolver, the shapes of the droplet and the thin film at equilibrium are obtained. A critical thin film length necessary for complete enclosure of the fluid droplet, and hence successful self-assembly into a PV device, is determined and compared with the experimental results and mechanics model predictions. The results from the modeling and energy approaches and the experiments are all consistent. Superhydrophobic surfaces, which have unique properties including self-cleaning and water repelling are desired in many applications. One excellent example in nature is the lotus leaf. To fabricate these surfaces, well designed micro/nano- surface structures are often employed. In this research, we fabricate superhydrophobic micropatterned Polydimethylsiloxane (PDMS) surfaces composed of micropillars of various sizes and arrangements by means of soft lithography. Both anisotropic surfaces, consisting of parallel grooves and cylindrical pillars in rectangular lattices, and isotropic surfaces, consisting of cylindrical pillars in square and hexagonal lattices, are considered. A novel technique is proposed to image the contact line (CL) of the droplet on the hydrophobic surface. This technique provides a new approach to distinguish between partial and complete wetting. The contact area between droplet and microtextured surface is then measured for a droplet in the Cassie state, which is a state of partial wetting. The results show that although the droplet is in the Cassie state, the contact area does not necessarily follow Cassie model predictions. Moreover, the CL is not circular, and is affected by the micropatterns, in both isotropic and anisotropic cases. Thus, it is suggested that along with the contact angle — the typical parameter reported in literature quantifying wetting, the size and shape of the contact area should also be presented. This technique is employed to investigate the evolution of the CL on a hydrophobic micropatterned surface in the cases of: a single droplet impacting the micropatterned surface, two droplets coalescing on micropillars, and a receding droplet resting on the micropatterned surface. Another parameter which quantifies hydrophobicity is the contact angle hysteresis (CAH), which indicates the resistance of the surface to the sliding of a droplet with a given volume. The conventional methods of using advancing and receding angles or tilting stage to measure the resistance of the micropatterned surface are indirect, without mentioning the inaccuracy due to the discrete and stepwise motion of the CL on micropillars. A micronewton force sensor is utilized to directly measure the resisting force by dragging a droplet on a microtextured surface. Together with the proposed imaging technique, the evolution of the CL during sliding is also explored. It is found that, at the onset of sliding, the CL behaves as a linear elastic solid with a constant stiffness. Afterwards, the force first increases and then decreases and reaches a steady state, accompanied with periodic oscillations due to regular pinning and depinning of the CL. Both the maximum and steady state forces are primarily dependent on area fractions of the micropatterned surfaces in our experiment. The resisting force is found to be proportional to the number of pillars which pin the CL at the trailing edge, validating the assumption that the resistance mainly arises from the CL pinning at the trailing edge. In each pinning-and-depinning cycle during the steady state, the CL also shows linear elastic behavior but with a lower stiffness. The force variation and energy dissipation involved can also be determined. This novel method of measuring the resistance of the micropatterned surface elucidates the dependence on CL pinning and provides more insight into the mechanisms of CAH.

Soft computing based parameter identification in pavements and geomechanical systems

Accurate estimation of road pavement geometry and layer material properties through the use of proper nondestructive testing and sensor technologies is essential for evaluating pavement’s structural condition and determining options for maintenance and rehabilitation. For these purposes, pavement deflection basins produced by the nondestructive Falling Weight Deflectometer (FWD) test data are commonly used. The nondestructive FWD test drops weights on the pavement to simulate traffic loads and measures the created pavement deflection basins. Backcalculation of pavement geometry and layer properties using FWD deflections is a difficult inverse problem, and the solution with conventional mathematical methods is often challenging due to the ill-posed nature of the problem. In this dissertation, a hybrid algorithm was developed to seek robust and fast solutions to this inverse problem. The algorithm is based on soft computing techniques, mainly Artificial Neural Networks (ANNs) and Genetic Algorithms (GAs) as well as the use of numerical analysis techniques to properly simulate the geomechanical system. A widely used pavement layered analysis program ILLI-PAVE was employed in the analyses of flexible pavements of various pavement types; including full-depth asphalt and conventional flexible pavements, were built on either lime stabilized soils or untreated subgrade. Nonlinear properties of the subgrade soil and the base course aggregate as transportation geomaterials were also considered. A computer program, Soft Computing Based System Identifier or SOFTSYS, was developed. In SOFTSYS, ANNs were used as surrogate models to provide faster solutions of the nonlinear finite element program ILLI-PAVE. The deflections obtained from FWD tests in the field were matched with the predictions obtained from the numerical simulations to develop SOFTSYS models. The solution to the inverse problem for multi-layered pavements is computationally hard to achieve and is often not feasible due to field variability and quality of the collected data. The primary difficulty in the analysis arises from the substantial increase in the degree of non-uniqueness of the mapping from the pavement layer parameters to the FWD deflections. The insensitivity of some layer properties lowered SOFTSYS model performances. Still, SOFTSYS models were shown to work effectively with the synthetic data obtained from ILLI-PAVE finite element solutions. In general, SOFTSYS solutions very closely matched the ILLI-PAVE mechanistic pavement analysis results. For SOFTSYS validation, field collected FWD data were successfully used to predict pavement layer thicknesses and layer moduli of in-service flexible pavements. Some of the very promising SOFTSYS results indicated average absolute errors on the order of 2%, 7%, and 4% for the Hot Mix Asphalt (HMA) thickness estimation of full-depth asphalt pavements, full-depth pavements on lime stabilized soils and conventional flexible pavements, respectively. The field validations of SOFTSYS data also produced meaningful results. The thickness data obtained from Ground Penetrating Radar testing matched reasonably well with predictions from SOFTSYS models. The differences observed in the HMA and lime stabilized soil layer thicknesses observed were attributed to deflection data variability from FWD tests. The backcalculated asphalt concrete layer thickness results matched better in the case of full-depth asphalt flexible pavements built on lime stabilized soils compared to conventional flexible pavements. Overall, SOFTSYS was capable of producing reliable thickness estimates despite the variability of field constructed asphalt layer thicknesses.

Elaboración de una guía y material didáctico de la geometría del es-pacio para el laboratorio de matemáticas de la carrera de matemáti-cas y física de la Universidad de Cuenca

La Geometría del Espacio es una rama de la Matemática que estudia las propieda-des y medidas de figurasque se relacionan con la mayoría de objetos tridimensionales que tenemos a nuestro alrededor; por esto nuestro trabajo titulado “Elaboración de una guía y material didáctico de la Geometría del Espacio para el Laboratorio de Matemática de la carrera de Matemáticas y Física de la Universidad de Cuenca” da lugar a una nueva estrategia que puede utilizar el docente en el proceso de enseñanza-aprendizaje de esta asignatura. En el capítulo uno de nuestro trabajo de graduación se analizan los aspectos generales de la educación así como las corrientes pedagógicas que están presentes dentro del proceso educativo, para luego hablar de la didáctica y la importancia de trabajar con material concreto en el área de Matemática, específicamente en la Geometría del Espacio así como los recursos que son óptimos para trabajar esta asignatura. En el capítulo dos, se demuestra mediante un muestreo no probabilístico que existe dificultad en la comprensión de los contenidos de la Geometría del Espacio y que una buena opción para desarrollar el proceso de enseñanza-aprendizaje sobre esta asignatura es la utilización de material concreto y de una guía didáctica que facilite la comprensión de los contenidos. Por último en el capítulo tres se presenta un conjunto de diez prácticas sobre pla-nos y sólidos, las cuales, siguen los pasos que exige una práctica de laboratorio innovadora, de una manera ordenada y secuencial para reforzar el proceso de enseñanza-aprendizaje.

La loi applicable aux transferts de biens virtuels

Thèse réalisée en cotutelle avec l'université Paris1-Sorbonne

Autoeficácia de alunos de Administração: um estudo com concluintes do curso de graduação em Administração no Estado do Pará

The current study presents the characteristics of self-efficacy of students of Administration course, who work and do not work. The study was conducted through a field research, descriptive, addressed quantitatively using statistical procedures. Was studied a population composed of 394 students distributed in three Higher Education Institutions, in the metropolitan region of Belém, in the State of Pará. The sampling was not probabilistic by accessibility, with a sample of 254 subjects. The instrument for data collection was a questionnaire composed of a set of questions divided into three sections: the first related to sociodemographic data, the second section was built to identify the work situation of the respondent and the third section was built with issues related to General Perceived Self-Efficacy Scale proposed by Schwarzer and Jerusalem (1999). Sociodemographic data were processed using methods of descriptive statistics. This procedure allowed characterizing the subjects of the sample. To identify the work situation, the analysis of frequency and percentage was used, which allowed to classify in percentage, the respondents who worked and those that did not work, and the data related to the scale of self-efficacy were processed quantitatively by the method of multivariate statistics using the software of program Statistical Package for Social Sciences for Windows - SPSS, version 17 from the process of Exploratory Factor Analysis. This procedure allowed characterizing the students who worked and the students who did not worked. The results were discussed based on Social Cognitive Theory from the construct of self-efficacy of Albert Bandura (1977). The study results showed a young sample, composed the majority of single women with work experience, and indicated that the characteristics of self-efficacy of students who work and students who do not work are different. The self-efficacy beliefs of students who do not work are based on psychological expectations, whereas the students who work demonstrated that their efficacy beliefs are sustained by previous experiences. A student who does not work proved to be reliant in their abilities to achieve a successful performance in their activities, believing it to be easy to achieve your goals and to face difficult situations at work, simply by invest a necessary effort and trust in their abilities. One who has experience working proved to be reliant in their abilities to conduct courses of action, although know that it is not easy to achieve your goals, and in unexpected situations showed its ability to solve difficult problems

Guía didáctica de geometría plana en las unidades didácticas de: triángulos y cuadriláteros para los estudiantes de la carrera de Matemáticas y Física de la Universidad de Cuenca

El presente trabajo titulado Guía Didáctica de Geometría Plana en las Unidades Didácticas de: Triángulos y Cuadriláteros para los estudiantes de la Carrera de Matemáticas y Física de la Universidad de Cuenca ha sido diseñado para fortalecer el proceso de enseñanza-aprendizaje en el primer ciclo de la carrera con el objetivo de facilitar la comprensión de la asignatura al momento de relacionar la teoría con la práctica. En el primer capítulo se da a conocer de manera general los antecedentes históricos de la Geometría Plana, la importancia de aplicar corrientes pedagógicas innovadoras como la del Constructivismo y la aplicación de la teoría del aprendizaje significativo en la educación actual, las dificultadesen el aprendizaje de la Geometría Plana,el valor de utilizar recursosdidácticos en el aulade clase y la importancia de las guías didácticas para el aprendizaje. En el segundo capítulo se desarrolla el diagnóstico de la propuesta mediante la aplicación de una encuesta, la misma que evidencia las razonespor las cuales los estudiantes de la Carrera de Matemáticas y Física presentan un bajo rendimientoen la asignatura de Geometría Plana, además de la factibilidad del uso de una guía didáctica como complemento en el proceso de enseñanza-aprendizaje. Finalmente, el tercer capítulo está compuesto por once prácticas en los temas de triángulos y cuadriláteros, las mismas que están elaboradas de una manera secuencial, de modo que guíen al estudiante y reten su intelecto mediante actividades dinámicas con el apoyo de la manipulación de material didáctico.

Trapping phenomena in AlGaN and InAlN barrier HEMTs with different geometries

PAPER Trapping phenomena in AlGaN and InAlN barrier HEMTs with different geometries S Martin-Horcajo1, A Wang1, A Bosca1, M F Romero1, M J Tadjer1,2, A D Koehler2, T J Anderson2 and F Calle1 Published 11 February 2015 • © 2015 IOP Publishing Ltd Semiconductor Science and Technology, Volume 30, Number 3 Article PDF Figures References Citations Metrics 350 Total downloads Cited by 1 articles Export citation and abstract BibTeX RIS Turn on MathJax Share this article Article information Abstract Trapping effects were evaluated by means of pulsed measurements under different quiescent biases for GaN/AlGaN/GaN and GaN/InAlN/GaN. It was found that devices with an AlGaN barrier underwent an increase in the on-resistance, and a drain current and transconductance reduction without measurable threshold voltage change, suggesting the location of the traps in the gate-drain access region. In contrast, devices with an InAlN barrier showed a transconductance and a decrease in drain associated with a significant positive shift of threshold voltage, indicating that the traps were likely located under the gate region; as well as an on-resistance degradation probably associated with the presence of surface traps in the gate-drain access region. Furthermore, measurements of drain current transients at different ambient temperatures revealed that the activation energy of electron traps was 0.43 eV and 0.38 eV for AlGaN and InAlN barrier devices, respectively. Experimental and simulation results demonstrated the influence of device geometry on the observed trapping effects, since devices with larger gate lengths and gate-to-drain distance values exhibited less noticeable charge trapping effects.

Proposta metodológica de criação de um observatório municipal de desporto, na administração pública local

Introdução e Objectivos: As organizações necessitam de dados para tomar decisões, necessitam de elementos que sirvam de base à resolução de problemas ou à formulação de um juízo. Necessitam de um índice, de uma informação objectiva, disponível para qualquer indivíduo a manipular de acordo com o tipo de análise que pretende efectuar. Temos cada vez mais de nos preocupar em estar devidamente informados e estabelecer as relações mais vantajosas para a nossa organização e para o mercado onde actuamos. Irá implicar a utilização de distintos modelos de análise e instrumentos de recolha de dados, de forma a criar uma base de informação útil aos vários organismos (municipais e nacionais), que projectam as políticas desportivas a desenvolver a nível local e nacional. Com a presente investigação, pretendemos propor um Modelo de Observatório do Desporto e das Actividades Complementares associado a um Sistema de Informação Desportivo, que permita ao poder local (Autarquias), proceder ao levantamento, sempre que necessário, das evoluções concelhias do mercado desportivo, para que de uma forma sustentada, criem e desenvolvam políticas desportivas locais que melhor se ajustem à sua realidade e que sirvam de base à criação da Conta Satélite do Desporto. Material e Métodos: O modelo será testado no concelho de Odivelas, inserido na estrutura da CM Odivelas, sendo necessário a inquirição dos clubes do concelho (apenas os clubes com actividade desportiva activa), numa 1ª fase, e numa 2ª fase, as empresas que lhe dão suporte. Os presidentes e directores de ambas as organizações serão os alvos da aplicação do questionário informático e/ou questionário em suporte papel, de acordo com as realidades e características de cada clube e empresa. Os dados recolhidos serão tratados tratados através do software da aplicação informática que foi criada especificamente para o efeito e que permitirá a exportação de dados para outros suportes informáticos. A própria aplicação irá permitir a construção e apresentação de relatórios de acordo com os requisitos solicitados. Resultados: O objectivo geral do estudo foi alcansado com a construção de um Modelo de Observatório Municipal do Desporto, baseado numa proposta de Sector do Desporto e de Conta Satélite do Desporto, tendo por base o estudo de caso na Câmara Municipal de Odivelas. Os objectivos específicos prenderam-se com a construção de instrumentos de recolha de dados para: - identificar os serviços desportivos e de complemento desportivo prestados no concelho de Odivelas; - identificar as organizações que prestam serviços desportivos e de Proposta Metodológica de Criação de um Observatório Municipal de Desporto, na Administração Pública Local complemento ao desporto; Os dados recolhidos terão de ser cruzados com a informação já existente, mas que se encontra dispersa pelas várias estruturas da CMO, de forma a permitir realizar o “levantamento” dos valores económicos gerados pelas actividades desportivas dos clubes, colectividades e empresas prestadoras de serviços e identificar as lacunas de serviços necessários aos clubes e colectividades não existentes no concelho.

Os fractais no urbanismo

Dissertação para obtenção do grau de Mestre em Arquitectura com Especialização em Urbanismo, apresentada na Universidade de Lisboa - Faculdade de Arquitectura.

Una primera lección de Geometría algebraica

En este artículo se explica cómo aparece la Geometría Algebraica, partiendo del estudio de los conjuntos de soluciones de sistemas algebraicos

Elaboración de una guía y material didáctico de la circunferencia y parábola para el laboratorio de matemáticas y física de la Universidad de Cuenca

El presente trabajo de investigación se encuentra definido alrededor de la necesidad de utilizar recursos didácticos para facilitar la comprensión de la asignatura de Geometría Analítica en los temas de la Circunferencia y la Parábola como un medio para relacionar la teoría con la práctica de ésta asignatura, con los estudiantes de los primeros ciclos de la Carrera de Matemáticas y Física de la Universidad de Cuenca. En el capítulo uno se analiza diversos temas concernientes a algunos aspectos generales dentro de la educación, así como algunas corrientes pedagógicas que están presentes en la actualidad, también se aborda a la didáctica en general y a la didáctica de las matemáticas, la importancia de la implementación de recursos didácticos como la implementación de una guía con su correspondiente material concreto para trabajar los contenidos de esta asignatura. El capítulo dos comprende la parte diagnóstica, en el cual se demuestra mediante la aplicación de una encuesta y su respectivo análisis, que existen dificultades en la comprensión de los contenidos de la Geometría Analítica en los temas de la circunferencia y la parábola. Una alternativa para facilitar el proceso de enseñanza-aprendizaje es la elaboración de una guía con su respectivo material concreto. Por último en el capítulo tres se presenta la propuesta que consta de dos partes:la guía y el material didáctico como recursos auxiliares que se han creado para los temas de la circunferencia y la parábola. La guía didáctica está formada por diez prácticas que tienen el perfil de prácticas de laboratorio presentadas de una manera secuencial que indican la utilización correcta de los materiales en cada uno de los temas propuestos.

Efficient photo-induced dielectrophoretic particle trapping on Fe:LiNbO3 for arbitrary two dimensional patterning

1D and 2D patterning of uncharged micro- and nanoparticles via dielectrophoretic forces on photovoltaic z-cut Fe:LiNbO3 have been investigated for the first time. The technique has been successfully applied with dielectric micro-particles of CaCO3 (diameter d = 1-3 ?m) and metal nanoparticles of Al (d = 70 nm). At difference with previous experiments in x- and y-cut, the obtained patterns locally reproduce the light distribution with high fidelity. A simple model is provided to analyse the trapping process. The results show the remarkably good capabilities of this geometry for high quality 2D light-induced dielectrophoretic patterning overcoming the important limitations presented by previous configurations.

Argumentos duales: el principio de dualidad como una estructura argumentativa

El objetivo de la tesis es identificar una familia de argumentos que comparten una estructura con el principio de dualidad de la geometría proyectiva. Esta familia la denomino "argumentos duales". Para lograr este objetivo, tomo cuatro argumentos importantes de la filosofía analítica e identifico en ellos la estructura que comparten. Los cuatro argumentos son: (i) el acertijo de la inducción de Goodman; (ii) la indeterminación de la referencia Putnam; (iii) la indeterminación de la traducción de Quine; (iv) la paradoja del seguimiento de reglas de Wittgenstein.

Prácticas de responsabilidad social empresarial y bienestar de los empleados en el marco de las organizaciones saludables

La noción de organización saludable cada vez toma mayor relevancia en el mundo académico y empresarial, pues se ha demostrado que las organizaciones que crean ambientes saludables y adoptan prácticas saludables, afectan positivamente a sus diferentes grupos de interés, incluidos empleados, socios, proveedores, clientes y la sociedad (Grueso y Rey, 2013). Con el fin de contribuir a lo anteriormente mencionado, a continuación se presenta el avance de una investigación de tipo documental y aplicada, mediante la que se pretende comprender la forma como la adopción de prácticas de responsabilidad social contribuye al bienestar de los empleados en dos compañías del sector comercio al detal en Colombia. Para lograr lo anterior, primero se mostrarán los fundamentos teóricos y antecedentes de estudios e investigaciones realizadas sobre Responsabilidad Social Empresarial y el bienestar de los empleados. Posteriormente se describe la metodología desarrollada para la recolección de la información y el proceso mediante el que esta fue analizada. En la siguiente sección se describen los hallazgos y por último se plantean las conclusiones del estudio.

Estudio de empresas de sectores hegemónicos en Colombia para los años 2013 y 2014

Este documento evidencia las posiciones hegemónicas que han llegado a ocupar las empresas más poderosas del país, basándose en el estudio de datos cuantitativos del conteo de las cien empresas con mejores ventas para los años 2013 y 2014, según la revista Gerente. Se usan cinco variables: ventas totales, activos, pasivos, patrimonio y utilidades netas. En la primera sección, se hace una revisión bibliográfica que conecta el origen de la hegemonía en un panorama económico con la influencia del neoliberalismo y la globalización en el actual tejido industrial colombiano. Posteriormente, se realiza una explicación sobre la metodología aplicada para el estudio de la base de datos; la cual es seguida por una exposición de los resultados obtenidos a partir de herramientas estadísticas como el análisis de correlación lineal, quintiles y variaciones porcentuales. Finalmente, se aborda el Programa de Transformación Productiva, esto con el objetivo de mostrar los puntos focales que necesitan especial atención para lograr catalizar el desarrollo económico de Colombia.