Atomistic simulations of confined species in 2D nanosructures: clays and C-S-H gel

246 p.In this thesis, atomistic simulations have been used to study and predict the properties of molecules and materials. The information provided by the molecular dynamics simulations complements and supports the experiments, helping in the interpretations of the results and serving as a guide for the design of new materials. First, the intercalation of two organic dyes, LDS-722 and pyronin Y, with two smectite clays, Laponite and saponite, has been studied. The simulation of these dye/clay systems has enable the understanding of their photophysical behavior, the dye aggregation and its diffusivity. The mechanical properties of these hybrid materials has also been characterized. Second, the retention of radiocesium in calcium silicate hydrates (C-S-H gel) has been evaluated, considering the impact of Cs concentration, Ca/Si ratio, counterions and Al incorporation in the silicate chains to form C-A-S-H. Third, the strengthening mechanisms in C-S-H gel that incorporates organic additives, APTES and PEG, has also been explored by molecular dynamics simulations. The bulk and Young¿s moduli have been determined by applying a hydrostatic and uniaxial pressures to the simulated systems, considering the effects of the hydrostatic pressure on the silicate chains and hydrogen bond network. The results presented in this thesis contribute to a better understanding of the guest-host interactions at atomic scale in the studied systems and may help in the design of new materials

Atomistic simulations of confined species in 2D nanosructures: clays and C-S-H gel

246 p.In this thesis, atomistic simulations have been used to study and predict the properties of molecules and materials. The information provided by the molecular dynamics simulations complements and supports the experiments, helping in the interpretations of the results and serving as a guide for the design of new materials. First, the intercalation of two organic dyes, LDS-722 and pyronin Y, with two smectite clays, Laponite and saponite, has been studied. The simulation of these dye/clay systems has enable the understanding of their photophysical behavior, the dye aggregation and its diffusivity. The mechanical properties of these hybrid materials has also been characterized. Second, the retention of radiocesium in calcium silicate hydrates (C-S-H gel) has been evaluated, considering the impact of Cs concentration, Ca/Si ratio, counterions and Al incorporation in the silicate chains to form C-A-S-H. Third, the strengthening mechanisms in C-S-H gel that incorporates organic additives, APTES and PEG, has also been explored by molecular dynamics simulations. The bulk and Young¿s moduli have been determined by applying a hydrostatic and uniaxial pressures to the simulated systems, considering the effects of the hydrostatic pressure on the silicate chains and hydrogen bond network. The results presented in this thesis contribute to a better understanding of the guest-host interactions at atomic scale in the studied systems and may help in the design of new materials

Nanoscale shear cohesion between cement hydrates: The role of water diffusivity under structural and electrostatic confinement

\ua9 2022 The Authors. The calcium silicate hydrate (C-S-H) controls most of the final properties of the cement paste, including its mechanical performance. It is agreed that the nanometer-sized building blocks that compose the C-S-H are the origin of the mechanical properties. In this work, we employ atomistic simulations to investigate the relaxation process of C-S-H nanoparticles subjected to shear stress. In particular, we study the stress relaxation by rearrangement of these nanoparticles via sliding adjacent C-S-H layers separated by a variable interfacial distance. The simulations show that the shear strength has its maximum at the bulk interlayer space, called perfect contact interface, and decreases sharply to low values for very short interfacial distances, coinciding with the transition from 2 to 3 water layers and beginning of the water flow. The evolution of the shear strength as a function of the temperature and ionic confinement confirms that the water diffusion controls the shear strength

Nanoscale shear cohesion between cement hydrates: The role of water diffusivity under structural and electrostatic confinement

[EN] The calcium silicate hydrate (C-S-H) controls most of the final properties of the cement paste, including its mechanical performance. It is agreed that the nanometer-sized building blocks that compose the C-S-H are the origin of the mechanical properties. In this work, we employ atomistic simulations to investigate the relaxation process of C-S-H nanoparticles subjected to shear stress. In particular, we study the stress relaxation by rearrangement of these nanoparticles via sliding adjacent C-S-H layers separated by a variable interfacial distance. The simulations show that the shear strength has its maximum at the bulk interlayer space, called perfect contact interface, and decreases sharply to low values for very short interfacial distances, coinciding with the transition from 2 to 3 water layers and beginning of the water flow. The evolution of the shear strength as a function of the temperature and ionic confinement confirms that the water diffusion controls the shear strength.We gratefully acknowledge the financial support by "Departamento de Educacion, Politica Linguistica y Cultura del Gobierno Vasco" (IT912-16, IT1639-22). E.D.-R. acknowledges the postdoctoral fellowship from "Programa Posdoctoral de Perfeccionamiento de Personal Investigador Doctor" of the Basque Government. The authors thank for technical and human support provided by i2basque and SGIker (UPV/EHU/ERDF, EU), for the allocation of computational resources provided by the Scientific Computing Service

A comprehensive review of C-S-H empirical and computational models, their applications, and practical aspects

[EN] The C-S-H gel is an elusive material. Its variable composition and disordered nature complicate a complete characterization of its atomic structure, and the elaboration of models is key to understanding it. This work aims to review those proposed models, dividing them into empirical and computational models. After a brief description of related crystalline calcium silicate hydrates, empirical C-S-H models based on interpretation of experimental data are presented. Then, we focus on the historic development of atomistic models to study the C-S-H, until the current state of the art. We describe current computational C-S-H models built from the empirical models and computer simulations. We review common applications of these computational models: the aluminum incorporation, the elastic and mechanical properties, the diffusion of water and ions in nanopores, and C-S-H/organic composites. Finally, we discuss some practical aspects of the computational models and their interpretation, as well as possible future directions.The authors would like to acknowledge funding from “Departamento de Educación, Política Lingüística y Cultura del Gobierno Vasco” (Grant No. IT912-16 and IT1639-22) and the technical and human support provided by the Scientific Computing Service of SGIker (UPV/EHU/ ERDF, EU). E.D.-R. also acknowledges the postdoctoral fellowship from “Programa Posdoctoral de Perfeccionamiento de Personal Investigador Doctor” of the Basque Government

INTERNACIONALIZACIÓN DE LA INVESTIGACIÓN EN LAS CIENCIAS SOCIALES

Libro; 493pLa Facultad de Ciencias Económicas Administrativas y Contables se ha empeñado en hacer de la investigación una parte prioritaria de su quehacer académico, lo que la ha llevado a consultar con el entorno acerca de su estado de desarrollo, de las posibilidades de mejora, tanto desde sus perspectivas como desde la prospectiva y además, a conocer los avances y progreso de la economía de otros países, a indagar acerca de la normatividad internacional y sus procesos de implementación, y a abordar temas de tanta importancia como el manejo de la responsabilidad social corporativa, entre otros. Como resultado de ello, se realizó el “Primer Congreso Internacional de las Ciencias Económicas Administrativas y Contables” que se llevó a cabo recientemente en la Universidad Libre Seccional Pereira, evento al que fueron invitadas las universidades de la región pero que además contó con la participación de ponentes internacionales de gran relevancia en el área. Se decidió que las diezocho ponencias mejor evaluadas durante el evento se publicarían en este libro, que compila los artículos científicos de autores tanto nacionales como internacionales, que se describen a continuación. Se incluyeron artículos que tocan los aspectos más relevantes en la implementación de las NIIF en las empresas del sector cafetero, PYMES y los efectos producidos por la convergencia de los costos de producción en la toma de decisión. Los relacionados con la construcción de una red semántica como mecanismo para la conceptualización unificada de las perspectivas del liderazgo y la relación entre las gramáticas sociales de los dispositivos de producción de empresarios. En cuanto a temas administrativos, se tienen artículos sobre el efecto de la desorganización en la administración del deporte, el impacto de la institucionalidad en la actividad cafetera colombiana en la definición de políticas inclusivas o extractivas, temas de asociatividad nacional e internacional, sistemas de articulación para aplicar políticasde Responsabilidad Social Corporativa y la implementación de sistemas de gestión de seguridad y salud en el trabajo. Igualmente, se presentan en la edición, artículos relacionados con el uso de herramientas financieras que permitan pronosticar la insolvencia tanto en las empresas del sector de la construcción y de la salud a nivel nacional e internacional y la apertura de fronteras comerciales que permitan la integración con otras naciones. Se espera que el producto del esfuerzo realizado para la edición de este libro sirva como una herramienta de consulta en las áreas de Economía, Administración de Empresas y Contaduría.Universidad Libre Seccional Pereir

Nuevos modelos de negocio

La globalización ha evidenciado un constante desarrollo a lo largo de los años, dado que ha generado un impacto en diversos ámbitos de la vida cotidiana caracterizado por su dualidad, pues mientras representan grandes beneficios para unos países, puede representar retos y dificultades para otros. Debido a esto, se pretende exponer y dar claridad a la evolución e influencia de la que ha sido objeto la globalización y adicionalmente establecer una relación con el desarrollo de los nuevos modelos de negocio. Dada la naturaleza mixta de la presente investigación, se opta por llevar a cabo un proceso en el cual se logren integrar una profunda revisión bibliográfica con una serie de datos que permitan diagnosticar la situación actual que enmarca la globalización. Se encontró que la globalización ha atravesado un largo proceso hasta convertirse en el factor clave que es considerado hoy en día, tanto en ámbitos sociales y culturales como en el desarrollo de los nuevos modelos de negocio. El artículo radica su pertinencia en lograr identificar los acontecimientos para que la globalización lograra posicionarse y convertirse lo que es en la actualidad y ser considerado algo fundamental en el desarrollo y crecimiento económico de los países, pero a su vez ha permitido exponer que tiene lados positivos y negativos y es necesario encontrar la manera de fomentar los positivos y contrarrestar los negativos.No asociada a proyecto - vinculado a la línea de investigación contabilidad y gestió

Adsorption and migration of Cs and Na ions in geopolymers and zeolites

Geopolymers may provide a more sustainable alternative to Portland Cement for various possible applications. Geopolymers have attracted particular interest for the immobilization of pollutants, owing to their high adsorption capacity, high thermal and chemical resistance, and low leachability. However, practical implementation is currently hindered by a limited understanding of how adsorption processes occur in geopolymers, and how they can be engineered to optimize the incorporation of pollutants and avoid their release. In this work, Molecular Dynamics simulations provide insights into these processes at the atomic scale, studying the role of host material composition and structure in the immobilization of Na and Cs ions. The simulations reveal that the most stable configurations for these ions are near the center of 6- and 8-membered aluminosilicate rings, where the coordination with the geopolymer is maximum. Higher contents of Al and degrees of crystallinity are found to yield more stable configurations for Cs ions, with more favorable adsorption enthalpies and lower diffusion coefficients. The comparison of different crystalline zeolite structures reveals that the framework of sodalite, used as the baseline to develop model geopolymer structures, is the most suitable for the immobilization of Cs since there are no channels and it is formed by small 4- and 6-member, all preventing Cs ions from escaping the cavities

Colaboración en entornos telemáticos de aprendizaje a distancia: Un caso de estudio en Matemáticas

En este trabajo se presenta una propuesta de modelo de entorno telemático, en este caso, para el aprendizaje/entrenamiento a distancia en la resolución de ecuaciones lineales. Destinado a profesores y alumnos de Educación Primaria y Secundaria. El entorno funciona apoyado sobre la tecnología que proporciona Internet e intranet, presenta un interfaz de aplicación que se ejecuta desde el Web. En esta aplicación se incluyen algunas técnicas para soportar colaboración asíncrona alumno-profesor y alumno-alumno, basadas en el empleo de bases de datos donde se registran todas las acciones, y aprovechando los recursos de Internet como mecanismos de comunicación asistida por computadoraThis paper presents a model of telematic environment for distance learning/training, to solve linear equations. This system was developed to help teachers in Primary and Secondary Education. The environment operates using the technology that provides Internet and intranet. It presents an application interface that runs on the Web supporting asynchronous collaboration between learners and teachers. This system, based on database technology, takes advantage from the Internet resources and the communication mechanisms that the computer network provides