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Imagen de apoyo de  Evaluación de vibraciones en el diagnóstico de estructuras: estudio de comportamiento de estructuras en deterioro = Vibration evaluation in the diagnosis of structures: Study of behaviour of deteriorating structures

Evaluación de vibraciones en el diagnóstico de estructuras: estudio de comportamiento de estructuras en deterioro = Vibration evaluation in the diagnosis of structures: Study of behaviour of deteriorating structures

Por: Angel Eduard Rodríguez Suesca | Fecha: 2021

Resumen: La respuesta dinámica de una estructura a lo largo de su vida útil varia debido al deterioro causado por diferentes factores, siendo los agentes ambientales y las cargas los causantes principales de degradación. Las acciones dinámicas representan uno de los mayores causantes de daño, evidenciado en fenómenos fatiga, microfisuración, agrietamiento, plastificación, desprendimiento y hasta colapso. Este daño puede ser usualmente mínimo para cargas de servicio y severo para el caso de cargas dinámicas extraordinarias de alta intensidad (impactos, sismos, explosiones, viento fuerte). La interacción entre las acciones y la respuesta también puede ocasionar daños importantes como en el caso de cargas moderadas de servicio con amplificación de la respuesta por fenómenos de resonancia. En la práctica, la evaluación del estado de las estructuras se basa principalmente en observaciones visuales y se describe mediante índices subjetivos que no permiten un diagnóstico preciso del comportamiento, la capacidad de servicio y la seguridad. Una evaluación confiable del comportamiento dinámico de una estructura depende de información cuantitativa más que cualitativa, por lo que, existe actualmente una necesidad para desarrollar metodologías de diagnóstico que incluyan parámetros de cuantificación de daño basados en pruebas directas de la respuesta vibratoria. Dentro de la gestión de infraestructura, un proceso más objetivo y confiable para la evaluación y cuantificación del estado de deterioro de las estructuras es requerido para ser utilizado en inspecciones rutinarias dirigidas al control, mantenimiento y rehabilitación. La presente tesis estudia las metodologías de evaluación experimental de la respuesta vibratoria aplicadas al diagnóstico de estructuras en deterioro, buscando prácticas estandarizadas de diagnóstico que determinen con confianza el grado de cumplimiento, deterioro o severidad del daño de una estructura, tanto para casos de carga extrema como para condiciones de operación normal. Las contribuciones fundamentales parten del estudio experimental de la degradación de las propiedades de un modelo estructural de laboratorio sometido a la acción de fuerzas dinámicas y se desarrollan ampliamente con la ejecución de dos investigaciones experimentales profundas de estructuras reales con un grado evidente de deterioro. Se comparan las técnicas de diagnóstico directo por inspección del daño contra las técnicas basadas en vibración. Diferentes formas de cuantificación del daño, el deterioro, la calidad y la incomodidad fueron propuestos. El desarrollo del trabajo doctoral parte de una síntesis de las bases y aplicaciones de la predicción, medición y análisis de las vibraciones en estructuras, enfocada a generar herramientas de diagnóstico para la implementación en pruebas rutinarias de evaluación para condiciones de servicio y de seguridad. En este sentido, se muestran ejemplos prácticos que ilustran de mejor manera los conceptos involucrados. Se describen las herramientas para la identificación de propiedades dinámicas y de cuantificación del daño basada en pruebas de vibración.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Evaluación de vibraciones en el diagnóstico de estructuras: estudio de comportamiento de estructuras en deterioro = Vibration evaluation in the diagnosis of structures: Study of behaviour of deteriorating structures

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Imagen de apoyo de  Determinación de la huella hídrica y modelación de la producción de biomasa de cultivos forrajeros a partir del agua en la sabana de Bogotá (Colombia)

Determinación de la huella hídrica y modelación de la producción de biomasa de cultivos forrajeros a partir del agua en la sabana de Bogotá (Colombia)

Por: César Augusto Terán Chaves | Fecha: 2015

Abstract: Summary The main objective was aimed at determining the biomass production from water based on water relations, levels of water consumption of the species, and climate variables that affect the formation of biomass and soil present and specifically it focused on two forage crops which were Forage Oats (Avena sativa L.) and ryegrass (Lolium perenne). The solution to the problem is based on AquaCrop model (FAO) Steduto et al, (2009) which was recently proposed for the determination of both biomass and agricultural production from water transpired by herbaceous species, this is gather scientific and technological advances on the effect of water in the estimation of crop production has been achieved in recent years. In the present research we have identified key variables AquaCrop model input for the two species mentioned, through field research conducted using the methodology gradient Hanks et al., (1980), and a new methodology proposal for determining water stress. A total of 18 major experiments were developed to generate the levels of biomass production of forage oats and ryegrass, determining 32 variables or parameters for each crop that requires the model to estimate the biomass produced by the forage and pasture. Furthermore, the engine for determining crop production handling model is the concept of crop water productivity (WP) which is a conservative parameter resulting in greater strength, besides water productivity is normalized in two ways: (1) the climate are represented by the reference evapotranspiration (ET0) and (2) the content of CO2 in the atmosphere. These normalization allow abstract both climate and CO2 content over time, whereby, the engine model turns out to be an essential tool to estimate both the biomass and production, even considering the effects of global climate change. The experiments were conducted mainly during the years 2008-2013 in “Centro de Investigación Tibaitatá (AGROSAVIA)” located in the savannah of Bogota (Colombia). For forage oats were developed five cycles and ryegrass crops three complete cycles, with seven, four and two cuts were made respectively. Based on the information provided in the field, forage oats and ryegrass crops were calibrated and validated for AquaCrop model reaching adjustments R2=0.92, RMSE=1,86t.ha-1, NRMSE=17.67%, EF=0.91, d=0.97 for forage oat and R2=0.97, RMSE=0,47t.ha-1, NRMSE=13.6%, EF=0.88, d=0.98 for ryegrass. Two synthetic crops were determined one for each specie, which are "prototypes" for estimating biomass by the water use in different conditions of crops. The total biomass was determined to forage oats at 22.2 t.ha-1 on average with peaks that can reach up to 27 t.ha-1 in the production environment of the savannah of Bogota. For ryegrass total biomass reached levels of up to 9 t.ha-1 on average with peaks that can reach up to 9,9 t.ha-1 for the period from planting to first cut, and 6 t.ha-1 for others cuts. The intrinsic water footprint for fodder oats was determined in 175 L.kg-1 and 442 ryegrass L.kg-1 and 431 L.Kg-1. This research is novel because implemented scientific and technological advances of AquaCrop in forage crops, for the determination of the biomass by the water, because until this had not been calibrated and validated for the model, special biophysical considerations forage crops driving differently elements like crop production and harvest index. In addition to the large expanses of areas that exist today in the world of forages and pastures, which can be incorporated into local, regional or global studies biomass production, efficient water use, water consumption and determination of requirements, carbon sequestration, and determining the effects of changes in the coverage of pasture and forage in the global climate change. Resumen: El objetivo principal estuvo orientado a la determinación de la producción de biomasa a partir del agua con base en las relaciones hídricas, los niveles de consumo de agua de las especies, y las variables del clima que inciden en la formación de biomasa y el suelo presentes y se centró específicamente en dos cultivos forrajeros: Avena Forrajera (Avena sativa, L.) y Raigrás (Lolium perenne). La solución al problema se basa en el modelo AquaCrop (FAO) Steduto et al, (2009) el cual fue propuesto para la determinación tanto de la biomasa como del rendimiento a partir del agua transpirada por las especies herbáceas, en este se reúnen los avances científicos y tecnológicos que sobre el efecto del agua en la estimación de la producción de cultivos se ha logrado en los últimos años. En el presente trabajo de investigación se han parametrizado las variables de entrada al modelo AquaCrop, para las dos especies mencionadas, por medio de investigación de campo realizada con la metodología del gradiente de Hanks et al, (1980), y con una nueva metodología propuesta para la determinación del estrés hídrico. Se desarrollaron un total de 18 experimentos principales generando los niveles de producción de biomasa de avena forrajera y raigrás, determinando 32 parámetros para cada uno de los cultivos que requiere el modelo para la estimación de la biomasa producida por las especies forrajeras y pastos. El modelo AquaCrop implementa varios avances sobre el conocimiento del desarrollo de cultivos, como la separación de la evapotranspiración en evaporación del suelo y la transpiración del cultivo, la consideración independiente de la producción del cultivo en biomasa y el índice de cosecha. Para la determinación del desarrollo del cultivo se maneja el porcentaje de cobertura del dosel en vez del índice de área foliar (IAF). Además, el motor para la determinación de la producción del cultivo que maneja el modelo es el concepto de la productividad hídrica del cultivo (WP) la cual es un parámetro conservativo que redunda en mayor robustez, la productividad hídrica además se normaliza bajo dos aspectos que son el clima representado por la evapotranspiración de referencia (ET0) y el contenido del CO2 en la atmósfera. Con base en la información establecida en campo se calibraron y validaron los cultivos de avena forrajera y raigrás para el modelo AquaCrop alcanzando ajustes de R2=0,92, RMSE=1,86t.ha-1, NRMSE=17,67%, EF=0,91, y d=0,97 para avena forrajera y de R2=0,97, RMSE=0,47t.ha-1, NRMSE=13,6%, EF=0,88, y d=0,98 para raigrás. Se determinaron dos cultivos sintéticos uno para cada especie, los cuales constituyen los “prototipos” que son el punto de partida para la estimación de la biomasa a partir del uso del agua en diferentes condiciones de los cultivos mencionados. La biomasa total para avena forrajera fue determinada en 22,2t.ha-1 en promedio con valores máximos que pueden llegar a alcanzar hasta 27t.ha-1 en el entorno productivo de la sabana de Bogotá. Para raigrás la biomasa total alcanzó niveles de hasta 9t.ha-1, para el período de siembra a primer corte, y de 6t.ha-1 para los cortes posteriores al primero. La huella hídrica intrínseca para avena forrajera fue determinada en 175L.kg-1 y para raigrás en 442L.kg-1 y 431L.Kg-1. El presente trabajo es novedoso por la implementación de los avances científicos y tecnológicos de AquaCrop en cultivos forrajeros, para la determinación de la biomasa a partir del agua, pues hasta la presente no habían sido calibrados y validados para el modelo, las consideraciones biofísicas especiales de los cultivos forrajeros que manejan de forma diferente elementos como la producción de cosecha y el índice de cosecha. Además por las grandes extensiones de áreas que existen hoy en el mundo de cultivos forrajeros y pastos, las cuales pueden ser incorporadas en estudios locales, regionales o globales de producción de biomasa, eficiencia en el uso del agua, consumos y determinación de requerimientos hídricos, captura de carbono, y determinación de los efectos de las variaciones de las coberturas de pastos y forrajes en el cambio climático global.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Determinación de la huella hídrica y modelación de la producción de biomasa de cultivos forrajeros a partir del agua en la sabana de Bogotá (Colombia)

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Imagen de apoyo de  Bio-inspired Topologies to Enhance the Mechanical Strength of Co-cured Ti-CFRP Hybrid Joints

Bio-inspired Topologies to Enhance the Mechanical Strength of Co-cured Ti-CFRP Hybrid Joints

Por: Breyner Andrés Castro Castillo | Fecha: 2022

Abstract: The main aim of this study is to investigate utilising root improve the interfacial strength of pin-like integrated hybrid composite architectures to metal structures. Joints are critical elements in aircraft structures and require special consideration due to their vital role in the structural integrity of airframes. Although bonded and bolted systems are used commonly in engineering applications, pinning technologies have shown tremendous potential for hybrid joints. Nonetheless, exploring complex pin geometries has been challenging when considering associated manufacturing techniques. Using pre-preg constrains the topography of the pin, while vacuum resin infusion offers more possibilities to manufacture complex hybrid joints. This study develops an experimental methodology to fabricate hybrid joints with arbitrary pin geometry using Selective Laser Melting (SLM) and resin infusion techniques. First, titanium parts with four inclination angles of 0°, 20°, 45° and 80° were fabricated using the SLM method, and their surface roughness was examined using a profilometer. Then, dry unidirectional carbon fabrics were stacked into pins in a hand layup process followed by epoxy infusion in a vacuum chamber. The cross-section of the fabricated joints was inspected employing an optical microscope, SEM and ?CT-scanner. The pin angle shape of the resin and fibre alignment impacted the geometry and rich area in the insertion region. Manufacturing defects such as pores were present in the composite with a high density closer to the titanium composite bondline. Despite those setbacks, resin-infused composites were integrated into highly tilted pins such as 45° or 80°. This precedent demonstrated that root like pins could also be co-cured with composites. The effect of pin angle on the mechanical performance of hybrid joints was experiment ally investigated. The load-displacement response of various specimens was recorded while joints were subjected to pull-off tensile loading. Experimental results showed how the pin angle affects the stiffness, strength and strain energy of joints. Damage initiation and propagation in the hybrid joints were also investigated by examining the fracture surfaces and the relationship between damage mechanisms and pin angles. Significant matrix crushing was realised in joints with 45° and 80° inclined pins with p in rupture only observed in the latter. Furthermore, a numerical study was conducted to explore the response of multiple root-like pin geometries. A 2D model was developed and validated for parametric study based on the experimentally measured interfacial strength. This bidimensional model accurately captured the experimental load-displacement curves for joints under tensile load. After calibration, the model was used to study the effect of three branches geometrical features of a rootlike pin on the mechanical behaviour of the hybrid joint. It was demonstrated that the diameter, length and location of side branches play a vital role in the failure behaviour of joints by affecting the stress distribution in composite adherend. Based on the findings from this study, it can be concluded that the integration of complex pin shapes and composite are likely using resin infusion techniques. Moreover, root like pins with optimised topology can be incorporated into hybrid joints to enhance bonding strength and failure behaviour.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Bio-inspired Topologies to Enhance the Mechanical Strength of Co-cured Ti-CFRP Hybrid Joints

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Imagen de apoyo de  Challenges and benefits of heritage languages in the home, a family language policy perspective. Three case studies of Spanish speaker’s families in New Zealand = Retos y beneficios de la lengua de herencia en casa. El caso de tres familias de habla hispana en Nueva Zealand: una política del lenguaje familiar en perspectiva

Challenges and benefits of heritage languages in the home, a family language policy perspective. Three case studies of Spanish speaker’s families in New Zealand = Retos y beneficios de la lengua de herencia en casa. El caso de tres familias de habla hispana en Nueva Zealand: una política del lenguaje familiar en perspectiva

Por: Lizeth Andrea Ceron Becerra | Fecha: 2018

Abstract: This study shows that parental beliefs, management and practices are not the only considerations. Societal influences determine parental language practices and management, which in turn delimits their children’s linguistic development. The decision that parents take perpetuate children’s linguistic development, however, in reality societal influences are determining parental language practices and management. The external and internal relationships permeate parents’ language decisions whereby subtle intergenerational heritage language loss takes place. Therefore, the struggle in maintaining their heritage language in the home domain has become a challenge for the parents. This study uncovers plentiful evidence that the language experiences of the three Latino-English families are challenging. Families consistently stated that it is an intensive responsibility raising their children bilingually in New Zealand. Despite there being a high awareness of the value of Spanish as an international language, and a number of cultural events where Latino-hispanic culture is evident, there is relatively insufficient peripheral support. It is evident in this study that in order to support families in their attempt to raise their children as bilingual there should be an integrated and encompassed socio-educational support. Otherwise, as it was found in this research, external influences will continue affecting migrant children's heritage language learning. Overall, the following list summarizes the challenges that families face in the attempt to raise their children as bilinguals. Only one parent speaks the language. As it was embedded in this research that the macro, meso and micro level influences the family language practices. For the macro: Lack of governmental support and a solid language policy for minority languages in New Zealand. Meso: Societal challenges/influences, lack of community support, lack of school language integration, lack of cultural and language appreciation at school. Micro: Lack of time to teach/translate the language to their spouses. Lack of commitment to speak the language from both parents, due to the lack of school and community language integration there is child's resistant attitudes to learn the language.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Challenges and benefits of heritage languages in the home, a family language policy perspective. Three case studies of Spanish speaker’s families in New Zealand = Retos y beneficios de la lengua de herencia en casa. El caso de tres familias de habla hispana en Nueva Zealand: una política del lenguaje familiar en perspectiva

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Imagen de apoyo de  Business Plan for Amasonaz Eco. Organic Frozen Fruit Import, commercialization and distribution from Colombia to Spain

Business Plan for Amasonaz Eco. Organic Frozen Fruit Import, commercialization and distribution from Colombia to Spain

Por: Luis Eduardo; Sanchez Lastra Echeverri Duque | Fecha: 2022

Abstract: The Pulp Fruit Imports and commercialization from Colombia to Spain Business Plan is a project that aims to support the solution of 3 main challenges in Colombia (Organic food waste, Ex-warriors from peace accords signature returning to society trough farming opportunities and life quality improvement to current farmers) while needs from Spanish consumers are satisfied. This last ones, after the pandemic, increased their awareness of consuming responsibly, which means protect their health and the environment at the same time the want enjoy a convenient and natural drink to join their meals and that allows them to continue with their life rhythm. For that reason, Amazonas Eco offers a range of exotic fruits that are transformed into pulp fruit through a local strategic partner with Bio certifications, then transported to Spain to be sold through the customer's preferred channels. This business plan includes a bibliographical study that uses Colombian and Spanish available data from different authorities combined with a filed work survey conducted to Spanish consumers that was used afterwards to develop case of study of Marketing Analysis using Statistical tools such as Multiple regression and Conjoint Analysis. These both supported to define main market trends, STEEP and Porter Analysis and marketing strategy (Segmentation, Price, Placement and Promotion). Furthermore interviews were done to a current exported and producer of pulp fruit from Colombia and to and Spanish expert profesor in logistics, these last interviews supported to define business model, Operational model and Financial forecasts. The principal market trends are explained into 3 main categories: 1. Sourcing: Exports from Colombia to the EU in organic food grew from 2019 to 2020 by 35% (European Commission) meaning almost 28.000 additional tons per year. 2. Consumption: the imports of Spain for the frozen fruit market have an average annual growth between 2012 and 2016 of 7,5% jumping from 219.000 MUSD to 291.000 MUSD in those years. (Zambrano Achi and Pozo Burgos). 3. SOM: Initially Amazonas Eco will focus in Cataluña, therefore the market size is given by the population size and the average price and consumption of nectars and fresh juices and soft drinks. Combined the total expected market size would be 75 MEUR (“Últimos datos de consumo alimentario”). After defining a reachable scope in a SOM and Colombia's production capacity the company expects sales of 100 tons/year with an income of 1.2 MEUR. The Operational model is build under 3 main pillars: Farmers, Pulp fruit producer in Colombia, then imports to Spain followed by storage in a warehouse and distributed through a third part logistics service provider reaching Organic markets (preferred channel of main segment) and consumers. Financial model is done by identifying needed assets and operational expenses using marketing analysis to defined expected sales and required inventory. With this financial statements are build for 3 years followed by Net present Value exercise and break even point. This company will request 390,000 EUR of equity. According to the assumptions the NPV of the project is positive therefore, it is decided to go forward with it. The IRR is 15% meaning that NPV will be negative when the cost of capital is higher than this. Break Even point is reachable at 75.500 kg in one year keeping the cost structure. Statement of financial positioning, comprehensive income statement and cash flow statement are built under a conservative model with the assumptions given above where an organic growth is expected for this business holding positive income and cash flow since year 1.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Business Plan for Amasonaz Eco. Organic Frozen Fruit Import, commercialization and distribution from Colombia to Spain

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Imagen de apoyo de  Regional state capacity and economic performance in Colombia

Regional state capacity and economic performance in Colombia

Por: Wilfred Alonso Romero Arciniegas | Fecha: 2020

Abstract: The subject of State capacity is a commonplace object of study in the social sciences which in the last few years has garnered more attention from the fields of social research and economics. As state capacity has a close relationship with development the question of how state capacity affects the development of a territory merits our attention. The present work therefore focuses on Colombia’s Regions, specifically using as a unit of analysis the 32 departments into which they are divided. Data on Colombia’s municipalities from the CEDE have been used to construct 4 indexes: Fiscal, Violence, Bureaucratic, and Operational. To create the indexes several variables have been selected and constructed with recourse to the Principal Component Analysis. However, as GDP data are unavailable at the municipal level, Night Time Lights (NTL) data are used as a proxy for economic development. Using a regression model showing the extent to which state capacity indices correlate with economic development as measured by NTL, while conducting robustness checks so as to confirm the expected results, we conclude that where state capacity is greater, then more development is expected.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Regional state capacity and economic performance in Colombia

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Imagen de apoyo de  Children’s Independent Mobility. A child-oriented perspective on walking, playing and socialising in Cali, Colombia = Movilidad independiente de los niños. Una perspectiva orientada en la juventud sobre caminar, jugar y socializar en Cali, Colombia

Children’s Independent Mobility. A child-oriented perspective on walking, playing and socialising in Cali, Colombia = Movilidad independiente de los niños. Una perspectiva orientada en la juventud sobre caminar, jugar y socializar en Cali, Colombia

Por: María Clara Trujillo Pérez | Fecha: 2020

Resumen: Informed by broad social assumptions, transport planning has traditionally obliged to the travel needs of the average (Levy, 2013b). In this process, children’s imaginaries and aspirations have been overlooked and dominated by an adult world were mobility is regarded as going efficiently from A to B. Challenging this view, this research considers children’s mobility as a practice that involves walking, playing and socialising, and the means by which children ‘perceive, feel and act in the world’ (Lester and Russell, 2010). Thus, it recognises children’s everyday pedestrian practices, and greater independence significantly contributes to their wellbeing and participation in urban life. Given the lack of attention to children’s independent mobility and play in the global south, this study analyses their impressions in a low-income neighbourhood in Cali, Colombia. Through a socio-ecological framework that incorporates the concepts of attachment and affordance, the study explores independent license, walking perceptions and experiences, community ties and sociability. Findings suggest that in this context, independence is the result of constant negotiations between children, parents and household dynamics. Unlike many cities in the global north, while children have high levels of independence for essential journeys, their freedom to roam, play and socialise is more restricted. While road safety has an important role in their perceptions, the changing circumstances in the social environment with high levels of crime and violence are crucial determinants in their participation in the neighbourhood in terms of play and social engagement. Policies should promote greater freedom and playability through strategies that facilitate rich social and physical affordances with a focus on community participation and the reivindication of the street as a meeting place. Resumen: Informada por amplios supuestos sociales, la planificación del transporte tradicionalmente ha atendido las necesidades de viaje de las personas promedio (Levy, 2013b). En este proceso, los imaginarios y aspiraciones de los niños han sido ignorados y dominados por un mundo adulto donde se considera a la movilidad como ir eficientemente de A a B. Retando esta visión, esta investigación considera la movilidad de los niños como una práctica que implica caminar, jugar y socializar, y el medio por el cual los niños 'perciben, sienten y actúan en el mundo' (Lester y Russell, 2010). Por lo tanto, reconoce que las prácticas peatonales cotidianas de los niños son importantes y una mayor independencia puede contribuir significativamente a su bienestar y participación en la vida urbana y comunitaria. Dada la falta de atención a la movilidad y el juego autónomo de los niños en el sur global, este estudio analiza sus experiencias en el Distrito de Aguablanca, Cali, Colombia. A través de un marco socioecológico que incorpora los conceptos de apego y potencialidad, el estudio explora la licencia independiente, las percepciones y experiencias al caminar, los lazos comunitarios y la sociabilidad. Los hallazgos sugieren que, en este contexto, la independencia resulta de negociaciones constantes entre los jóvenes, los cuidadores y las dinámicas del hogar. En este sentido, a diferencia de muchas ciudades del norte global, mientras que los niños tienen altos niveles de independencia para viajes esenciales, su libertad para deambular, jugar y socializar está restringida. Si bien la seguridad vial tiene un papel importante en sus percepciones, las circunstancias cambiantes en el entorno social en términos de altos niveles de delincuencia y violencia determinan su participación en el barrio en relación al juego y la interacción social. Las políticas deben promover una mayor libertad y oportunidades para el juego, a través de estrategias que faciliten ricas potencialidades sociales y físicas con un enfoque en la participación comunitaria y la apropiación de la calle como lugar de encuentro.
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Children’s Independent Mobility. A child-oriented perspective on walking, playing and socialising in Cali, Colombia = Movilidad independiente de los niños. Una perspectiva orientada en la juventud sobre caminar, jugar y socializar en Cali, Colombia

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Imagen de apoyo de  Decoding Colour and Position from Human Brain Activity Using Electroencephalography and Machine Learning Methods = Interpretando imágenes de la memoria humana con métodos de machine learning y electroencelografía

Decoding Colour and Position from Human Brain Activity Using Electroencephalography and Machine Learning Methods = Interpretando imágenes de la memoria humana con métodos de machine learning y electroencelografía

Por: Inés Andrea Castaño Gómez | Fecha: 2021

Abstract: A broad number of studies have used multivariate pattern analysis (MVPA) to track spatial representations such as position from human brain activity. While decoding spatial features has provided important insights on how working memory tracks representations, some studies have demonstrated that decoding spatial features can also be influenced by eye movements and spatial attention. This implies that EEG signals can be biased by the oculomotor system (e.g., is MVPA detecting neural representations or different eye-movement patterns?). Thus, decoding elements that are not defined by spatial factors and/or eye movements, like colour, can be an important proof-ofprinciple that neural representation can be decoded from electroencephalography (EEG). Even though few studies have decoded colour from EEG, it is still unclear whether using different features from EEG signals (e.g., Oscillations and ERPs) may carry different representations (e.g., position vs colour), and if different pre-processing methods and machine learning techniques may improve accuracy levels. Therefore, the purpose of this project is to determine whether colour and position can be decoded separately from various features of human electroencephalography (EEG) using different machine learning methods. Resumen: Varias investigaciones han utilizado el análisis de patrones multivariados (MVPA) para rastrear representaciones espaciales desde la memoria de trabajo humana como la posición de un objeto. Si bien la decodificación de características espaciales ha brindado información importante sobre cómo la memoria de trabajo rastrea representaciones visuales, algunos estudios han demostrado que la decodificación de características espaciales también puede verse influenciada por los movimientos oculares y la atención espacial. Esto implica que las señales de EEG pueden estar sesgadas por el sistema oculomotor (p. ej., ¿MVPA detecta representaciones neuronales o diferentes patrones del movimiento ocular?). Por lo tanto, la decodificación de elementos que no están definidos por factores espaciales y/o movimientos oculares, como el color, puede ser una importante prueba de que la representación neuronal se puede decodificar a partir de la electroencefalografía (EEG). Aunque algunos cuantos estudios han decodificado el color usando EEG, todavía no está claro si el uso de diferentes características de las señales de EEG (p. ej., oscilaciones y ERP) puede tener diferentes representaciones (p. ej., posición frente a color), y si los diferentes métodos de preprocesamiento y aprendizaje automático pueden mejorar los niveles de precisión. Por lo tanto, el propósito de este proyecto es determinar si el color y la posición se pueden decodificar utilizando varias características de la electroencefalografía humana (EEG) y diferentes métodos de machine learning.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Imagen de apoyo de  Image-guided programming of electrical settings in patients with Parkinson’s disease treated with bilateral subthalamic stimulation and suboptimal outcome

Image-guided programming of electrical settings in patients with Parkinson’s disease treated with bilateral subthalamic stimulation and suboptimal outcome

Por: Viviana Torres Ballesteros | Fecha: 2022

Abstract: Background: Deep brain stimulation (DBS) surgery is a treatment in the advanced stage of Parkinson's disease (PD). Despite close follow-up, multiple evaluations, and several months of timeconsuming programming sessions, the clinical response may not be optimal in some cases. Imageguided programming (I-GP) could help optimize programming sessions with better clinical outcomes. Objective: To evaluate clinical and quality of life (QoL) outcomes with I-GP in PD patients with DBS of the subthalamic nucleus (STN) and suboptimal clinical improvement and refractory symptoms to conventional clinical programming. Methods: A prospective study in 16 patients with a diagnosis of PD with STN-DBS and remaining adverse effects or symptoms despite a clinical programming adjustment. We simulate potentially effective stimulation based on volume tissue activated (VTA) using commercially available software tools. Clinical outcomes were assessed with motor and quality of life scales. Results: The most frequent suboptimal symptom was gait disorder 33.3% (n=9), residual motor symptoms 25.9%(n=7), and speech 25.9%(n=7). Statistically significant results (p=0.001) were found after I-GP with change in the global Deep Brain Stimulation – Impairment score (41%), The 8- item version of the Parkinson's Disease Questionnaire (47%), EuroQol visual analogue scale (62%), and motor scale (24%). Conclusions: In suboptimal cases of patients with PD and STN-DBS, especially with ongoing and residual motor symptoms, I-GP could be useful to optimize the programming of DBS and improve patients' QoL.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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Image-guided programming of electrical settings in patients with Parkinson’s disease treated with bilateral subthalamic stimulation and suboptimal outcome

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Imagen de apoyo de  Liquid Homes - A Critical Approach To Migrant Civil Rights Through Postmodern Social Science Theory And Their Representation Through Films Produced During The European Migrant Crisis

Liquid Homes - A Critical Approach To Migrant Civil Rights Through Postmodern Social Science Theory And Their Representation Through Films Produced During The European Migrant Crisis

Por: Camilo Bravo Molano | Fecha: 2022

Abstract: Liquid Homes is a study about migration based on social sciences theories, contemporary films, and my personal experiences. Within this understanding of migration, the concept of Home is identified as a physical and imaginary place pertaining to all individual of society, to which civil rights and urbanism are related, and which is in constant tension in a global system because of the processes of modernity, the development of industrialisation and capitalism. In this text an analysis of contemporary migration is proposed throughout films produced during the European migrant crisis (2015- ), to do a critical analysis about the approach and representation in films of the migrant population and to suggest recognition, humanism and familiarity with migrant communities and their civil rights. It was my last evening in Lisbon crossing the Tejo river in a ferry going to the other side of the city. We came over the second floor and sat down on the chairs with the windows facing the sunset. She was looking at messages on her mobile phone, while I was looking at the colour and shadows projected on her face. Suddenly she surprised and said: A bomb has exploded in the main harbour of Beirut. It is when this story about Liquid Homes started. Until this moment I had not any mental map of Lebanon, I knew it was part of the „Middle East” region with an Arabic culture. She told me she has some friends in Beirut because she was doing her field based research thesis in a Palestinian Refugee Camp called Shatila. I guess that the mixture of feelings between her and me at that moment have impressed in my memory the need to understand Shatila. Feelings about the beginning and the finishing of new stages of our lives, moving again of (from/to) homes, in different non-established houses, around different people, different languages and geographies. In my case, feelings of coming back to a place with legal rules made to make it the hardest for foreigners and for their establishment of a normal life, a hostile place in an economic way, where you are not welcome if you are not coming to produce or give money to the society. With the time I have understood that Shatila is a “Liquid Home” for its inhabitants. As a “new city” is for migrants. A “Liquid Home” is a place for waiting - for the return or for continuing towards the desired land and the desired lifestyle, with the difference that for people in Shatila and their parents before them were born there, but they do not have legal right over the land nor over pretty much anything in the place they inhabit. I identify a liquid home as the space constructed to be easily changed according to political international movements, according to the economic profit of international relationships under the flagship of solidarity. An artificial urbanization made with modular materials to be easily moved and articulated, where the architecture of the houses, of the streets, of the daily human relations can be withdrawn from their users as an expropriation not just of their houses but as well of their civil rights. As a nobody, who occupy the territory, liquid homes are a result of liquid societies, a modernisation of the urban lifestyle understood within Zygmunt Bauman’s analysis of the late modernity, where the reality of the inhabitants of the society is made to allow constant and contrasting changes. The objective of this writing is to describe how the phenomenon of migration, cities and citizenship have been told in cinema from 2015 until now, and to analyse different approaches, methods of research and filming migration and the noncitizenship, using cinema as a cultural expression that reflects the modern thinking and troubles of a migration society. I will also use personal notes as an ethnographic research method, reflecting my experience as a foreigner and all that not having a citizenship in the place where I live has meant.
Fuente: Biblioteca Virtual Banco de la República Formatos de contenido: Tesis
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