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Imagen de apoyo de QoS Performance Evaluation of a Real‐Time Mobile Video Surveillance in a LTE Network = Evaluación de Rendimiento de QoS de un Sistema de Video Vigilancia en una red LTE

Por: Sebastián Pineda Carrillo

Long Term Evolution (LTE) is one of the latest mobile communication technologies being commercially deployed worldwide. It has emerged as a promising technology for new applications such as mobile video surveillance (IPVS) due to its higher data throughputs as well as the quality of the service management capabilities. This work focuses on the performance evaluation of a mobile and real-time IPVS system over a LTE network in both operation modes, namely FDD and TDD. The QoS Requirements for the IPVS were defined and two simulation analyses were performed in OPNET Modeler in order to compare them to the QoS Delivered. The first analysis studied the performance of the IPVS service from a capacity point of view in a single cell scenario while the second analysis looked at the performance of the IPVS service in a sample network configuration including several cells. In light of the analysed results it was evidenced the flexibility of TDD operation mode in terms of capacity as well as its higher delay and packet delay behaviours in comparison with FDD operation mode. Additionally it was shown that TDD index 6 does not comply with the QoS performance required for an IPVS service in a multi cell network.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros
Ingeniería

Imagen de apoyo de The effect of WebQuests on lexical richness = Efectos de las WebQuests en la riqueza léxica

Por: José Fabián Velasco

The Web, as a source of input, is an element that is being considered as an additional educational tool for second language learning. For an effective use of the Web for second language learning, Dodge (1988) and March (2005) suggested the use of WebQuests. WebQuests are based on the characteristics of scaffolding, socio-constructivist perspective, cooperative learning, and development of high-order skills. Previous studies have concluded that WebQuests promoted reading skills but not writing skills (Kocoglu, 2010). The present study is aimed to find out if the use of WebQuests enhances lexical richness in writing since vocabulary is an essential part of language learning skills.For that purpose, two different groups of 13 participants each were used: an experimental group which get involved in a WebQuest and a control group which performed an unguided web-searching task. Both groups took a writing pre-test and post-test. The compositions obtained were entered into the computer program VocabProfile found in www.lexutor.ca. This program is based on four word lists established in the measure Lexical Frequency Profile (Laufer and Nation, 1995). Statistical analysis showed that the experimental group used more high-frequency words at the pre-test stage, and that the control group evidenced significant progress from the pre-test to the post-test.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros

Imagen de apoyo de UMTS Capacity simulation study (carried out at Vodafone Netherlands)

Por: Andrés Felipe Cosme Hurtado

The purpose of this report is to investigate the performance, measured in terms of Key Performance Indicators (KPIs) of a UMTS radio network (UTRAN) under different traffic and mobility scenarios and develop general guidelines for dimensioning the UMTS network optimally. In this work, simulations are performed using Wines tool, which is a dynamic simulator that models all the radio-resource management functionality of the UTRAN. Two main series of experiments have been performed. In the first series, the distribution of the traffic is homogeneous and the main purpose is to find capacity figures when increasing the traffic density of one of the four possible defined services (WWW, FTP, voice and video-call) and also with a given traffic mix involving all services together.Two mobility profiles are used (pedestrian and vehicular). In the second series of experiments, a more realistic scenario, based on detailed geographical characteristics relevant for signal propagation, and traffic densities based on traffic maps (non homogeneous scenario), has been simulated. The purpose was to analyze the possible differences in capacity between the “ideal” model and the more “realistic” model.For the single-service scenario analysis, circuit-switched services (speech and video-call), it can be observed that the capacity is mainly uplink-limited. The corresponding results for the packet-switched services (FTP, WEB) have shown that capacity is mostly downlink-limited, as it was expected due to the more asymmetrical data rates in the downlink compared to the uplink for both services. For the service mix analysis in both scenarios (homogeneous and non homogeneous) it was found that the capacity is mostly downlink-limited (i.e. the downlink power target level is exceeded before the uplink load target level).

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros
Ingeniería

Imagen de apoyo de Gambling their futures: the agency and livelihood strategies of victims of human trafficking in the Philippines = Apostando sus futuros: las capacidades y estrategias de subsistencia de víctimas de trata de personas en Filipinas

Por: Álvaro Felipe Bernal Arias

In this thesis I challenge the practice of imposing “victim” images to people that have endured through the crime of human trafficking. This imposition is led by the United Nations “Protocol to Prevent, Suppress and Punish Trafficking in Persons, Especially Women and Children” of 2000, and is followed by different governments, institutions, laws, and societies around the world. The possibility that “victims? may use the assistance of a trafficker to migrate and to obtain a job outside their hometowns is completely dismissed by depicting them as solely “victims? of the crime.By conferring those images and considering irrelevant their consent to the crime, as stated by the protocol, their agency is denied. Making use of the stories of fifteen trafficked Filipinas whom I interviewed in the field, I examine the extent to which trafficked people are fully “victims? of this crime. Instead, I suggest that they responded to different situations before and during the process of being trafficked, showing clear indications of tactic agency, and collapsing the “victim? statuses often attributed to them. Nonetheless, the experience in the field showed me that those “victims? experience a variety of desperate situations with a very limited spectrum of choices. In those moments I call them desperadas.Most of the times, after “victims? reach that point of desperation, they make use of their tactic agency to escape. This twilight zone between victimhood and agency is revealed in heterogeneous ways and experienced differently by trafficked people. Therefore, the stories of these girls counter the status quo of “victims? of trafficking, and raises the argument that human trafficking may be used as a livelihood strategy not only by its perpetrators, but also by its “victims?.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros

Imagen de apoyo de Asset pricing in the stock and options markets = Valoración de activos de los mercados de acciones y opciones

Por: Aurelio Vásquez

This thesis comprises three essays on asset pricing on the stock and options markets. The …first essay …finds a positive relation between the slope of the volatility term structure and subsequent option returns. The second essay …finds a negative relation between realized skewness, extracted from high-frequency data, and stock returns. The third essay finds a negative relation between price jumps of intraday data and future stock returns.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros
Economía

Imagen de apoyo de Twitter and sports journalism: a study of how Twitter is changing sports journalism = Twitter y el periodismo deportivo: un estudio de como Twitter está cambiando el periodismo deportivo

Por: Diego Luis Sierra Amador

Un estudio sobre Twitter y los cambios que ha provocado en la forma en que las noticias se propagan en la era digital. Enfocado principalmente en el periodismo deportivo, se le hizo un cuestionario a 25 periodistas basados en el Reino Unido sobre los impactos que las redes sociales y en especial Twitter ha tenido (si algunas) en su trabajo, en el día a día y se hizo una compilación de sus mas recientes tweets para comparar sus acciones con lo que decían. Los resultados varían pero en general el uso de Twitter entre los periodistas deportivos es muy común y bastante útil, les ha dado la opción de estar más cerca a sus seguidores, de darles una nueva audiencia, y de informar mucho más rápido.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros

Imagen de apoyo de Suction and volume changes of Compacted sand-bentonite mixtures = Cambios volumétricos y de succión en muestras compactadas de arena-bentonita

Por: Julio Esteban Colmenares Montañez

Engineered barriers are used in the containment of hazardous materials and are usually a composite of compacted clayey soil and a synthetic membrane. Containment elements such as landfill liners should be designed to control or prevent leachate migration or groundwater ingress. Engineering specifications for a compacted clay liner are based mainly in a hydraulic conductivity less than 10-9 m/s and the need for stability during construction and operation of the landfill. Sandbentonite mixtures are often used as a barrier material. The addition of relatively small amounts of bentonite (5-15%) can improve the performance of a granular material providing both a low permeability and an enhanced mechanical stability.However not all the possible compaction conditions produce a low permeability and mechanically stable material. Changes in water content after compaction can cause swelling or collapse depending on the stress and suction conditions before the water content change occurs. A laboratory investigation of the swelling-collapse behaviour of compacted mixtures of Sand-bentonite has been undertaken. Compaction and suction characteristics were established. The suction and volume change characteristics were investigated through a series of oedometer tests. The central part of the experimental programme focused on the detailed investigation of the processes of swelling and collapse during controlled wetting.To do this, a significant number of modifications were required to the existing apparatus. Fabric studies including Environmental Scanning Electron Microscopy and Mercury Intrusion Porosimetry were also undertaken. Intrinsic behaviour and the relationship between suction and water content were comprehensively studied. A parametric study of the influence of bentonite content and sand grading was also undertaken. The results are presented and analysed. Recommendations for future research are made.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros
Ingeniería

Imagen de apoyo de Estudio numérico de un modelo matemático de poblaciones estructuradas por la edad y con difusión espacial

Por: Rafael Alberto Méndez Romero

En el presente trabajo hemos realizado un estudio numérico de un modelo matemático de poblaciones estructuradas por la edad con difusión espacial. Estos modelos matemáticos están adquiriendo un enorme interés por su aplicabilidad al estudio de la dinámica de diferentes poblaciones como, por ejemplo, bacterias o células tumorales. La imposibilidad de resolver este tipo de modelos, excepto en situaciones muy simples, hace necesario el uso de métodos numéricos para la obtención de aproximaciones a su solución.Sin embargo, el número de trabajos dedicados a este fin es muy escaso en la literatura. En este estudio se pone de manifiesto el papel que tiene la difusión en estos modelos en diferentes situaciones. Para ello se propone un nuevo método numérico basado en la integración a lo largo de las curvas características en las variables tiempo-edad, y de elementos finitos para la variable espacial. Se considerará la situación, especialmente ardua, en la que el coeficiente de difusión depende de la función de densidad, además de añadir la actualmente interesante situación de que la edad máxima de los individuos sea finita.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros

Imagen de apoyo de Victims of forced displacement and extreme poverty in Colombia: between uprooting, revictimization and social exclusión

Por: Yudy Andrea Novoa López

The following study aimed to establish the social and political factors involved in the extreme poverty suffered by most of forcefully displaced persons in Colombia. To do so, a conscientious research was made and a survey was conducted. In addition, it was demonstrated that forced displacement is a strategy used by every violent actor of the internal conflict in Colombia, intended for impose their particular regimes based on violence and inequality. Moreover, was also established the relevance that in conflict has had the unfinished construction of the Colombian state, as well as the key role that has its differentiated presence throughout national territory and its co-opted reconfiguration by legal and illegal actors.Then, it was also shown that poverty goes beyond the economic aspect and involves, specifically for the case of IDPs (Internal Displaced Populations), phenomena such as uprooting, revictimization and social exclusion. Above, remarking the multidimensional character of poverty studied from the Capability Approach (CA) introduced by Amartya Sen and, the central importance that integral measures of it have to acquire a veridical picture of poverty suffered by victims of violence, specifically IDPs.Finally, a case study was carried out in the municipality with the highest number of IDPs in the country after the city of Bogotá, called Soacha. To do so, a survey applied to persons included in the most important program to tackle poverty in the country was conducted, and the role that local authorities have addressing this matter was analyzed; to conclude with a set of policy recommendations.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros

Imagen de apoyo de Social housing as a strategy for strengthening inclusion in a post-conflict scenario: The case of Colombia’s 100 thousand free houses

Por: Nathalia Mosquera Palomeque

Colombian cities have been for over 60 years witnesses of the internal conflict that through time morphed into a heterogeneous war, causing the forced displacement of approximately 6.3 million people during the period between 1985 and 2015. The lack of instruments able to benefit this population, triggered the issuance of two statements of the Constitutional court forcing the national government to take action towards their repair and integration.With the aim of building sustainable and inclusive cities through social housing and at the same time reducing quantitative housing deficits, the national government set the goal of building 100.000 free housing solutions. Over 90.000 housing units were built across the national territory, keeping the promise made, but raising questions about the quality of social housing and the impacts these projects are having on Colombian cities built environment.This dissertation will analyse the degree to which this programme can provide an effective basis for creating inclusive housing processes in post-conflict Colombian cities. The first chapter will try to understand the meaning of the word inclusion, and will conclude with an applicable analytical framework that will set the basis and a set of lenses to understand and analyse how the projects are conceived, built and delivered. The second part will explain the characteristics of the Colombian conflict, its effects on the urbanization patterns of cities and the way in which housing policy has developed in parallel to it. Additionally, the third chapter will try to confront the analytical framework with the 100.000 free houses program. The expected outcome of this analysis is to open a discussion on the role of social housing and the challenges it faces in the task of transforming Colombian cities into inclusive centres in which to acquire a tangible peace.

Fuente: Biblioteca Virtual Banco de la República Tipo de contenido: Tesis

Temas:
Otros