Revistas UTB ( Universidad Tecnológica de Bolívar)
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Control Methods for Single-phase Voltage Supply with VSCs to Feed Nonlinear Loads in Rural Areas
Full text linkThis paper addresses the problem of sinusoidal voltage generation in linear loads using a voltage source inverter (VSI). The port-Hamiltonian structure in open-loop is used to design a passivity-based controller with proportional-integral gains (PI-PBC) in order to develop the control strategy. The main advantage of using passivity-based controllers corresponds to the possibility of guaranteeing asymptotic stability by transforming the trajectory tracking problem into a regulation control one. In addition to the PI-PBC, a linear load estimator is employed based on an integral formulation to determine the value of the equivalent conductance in the load, which reduces the number of current sensors. Numerical validations demonstrate that the sinusoidal voltage provided by the VSI to the load has a tracking error lower than , with harmonic distortions lower than , both for voltage and currents in the load. All the simulations were conducted in MATLAB/Simulink using the SimPowerSystems library version 2017a.Este artículo aborda el problema de la generación de voltaje sinusoidal en cargas lineales utilizando un inversor de fuente de voltaje (VSI). La estructura port-Hamiltoniana en lazo abierto se utiliza para diseñar un controlador basado en pasividad con ganancias proporcionales-integrales (PI-PBC) con el fin de desarrollar la estrategia de control. La principal ventaja de utilizar controladores basados en pasividad corresponde a la posibilidad de garantizar la estabilidad asintótica transformando el problema de seguimiento de trayectoria en uno de control de regulación. Además del PI-PBC, se emplea un estimador de carga lineal basado en una formulación integral para determinar el valor de la conductancia equivalente en la carga, lo que reduce el número de sensores de corriente. Las validaciones numéricas demuestran que el voltaje sinusoidal proporcionado por el VSI a la carga tiene un error de seguimiento menor a , con distorsiones armónicas menores a , tanto para voltaje como para corrientes en la carga. Todas las simulaciones se realizaron en MATLAB/Simulink utilizando la biblioteca SimPowerSystems versión 2017a
El Pacífico colombiano: Lugar de oportunidades
Full text linkReseña del libro "Estudios sociales del Pacífico colombiano" de Luis Armando Galvis (editor). Bogotá: Banco de la República, 2017, 343 p
Metaheuristic Optimization Methods for Optimal Power Flow Analysis in DC Distribution Networks
Full text linkIn this paper is addressed the optimal power flow problem in direct current grids, by using solution methods based on metaheuristics techniques and numerical methods. For which was proposed a mixed integer nonlinear programming problem, that describes the optimal power flow problem in direct current grids. As solution methodology was proposed a master–slave strategy, which used in master stage three continuous solution methods for solving the optimal power flow problem: a particle swarm optimization algorithm, a continuous version of the genetic algorithm and the black hole optimization method. In the slave stages was used a methods based on successive approximations for solving the power flow problem, entrusted for calculates the objective function associated to each solution proposed by the master stage. As objective function was used the reduction of power loss on the electrical grid, associated to the energy transport. To validate the solution methodologies proposed were used the test systems of 21 and 69 buses, by implementing three levels of maximum distributed power penetration: 20%, 40% and 60% of the power supplied by the slack bus, without considering distributed generators installed on the electrical grid. The simulations were carried out in the software Matlab, by demonstrating that the methods with the best performance was the BH/SA, due to that show the best trade-off between the reduction of the power loss and processing time, for solving the optimal power flow problem in direct current networks.In this paper is addressed the optimal power flow problem in direct current grids, by using solution methods based on metaheuristics techniques and numerical methods. For which was proposed a mixed integer nonlinear programming problem, that describes the optimal power flow problem in direct current grids. As solution methodology was proposed a master–slave strategy, which used in master stage three continuous solution methods for solving the optimal power flow problem: a particle swarm optimization algorithm, a continuous version of the genetic algorithm and the black hole optimization method. In the slave stages was used a methods based on successive approximations for solving the power flow problem, entrusted for calculates the objective function associated to each solution proposed by the master stage. As objective function was used the reduction of power loss on the electrical grid, associated to the energy transport. To validate the solution methodologies proposed were used the test systems of 21 and 69 buses, by implementing three levels of maximum distributed power penetration: 20%, 40% and 60% of the power supplied by the slack bus, without considering distributed generators installed on the electrical grid. The simulations were carried out in the software Matlab, by demonstrating that the methods with the best performance was the BH/SA, due to that show the best trade-off between the reduction of the power loss and processing time, for solving the optimal power flow problem in direct current networks
El canje de prisioneros de guerra durante el periodo de independencia y sus incidencias en la Costa Caribe de la Nueva Granada y Venezuela
Full text linkWithin the framework of the bicentennial of the independence of the Hispanic-American nations, this essay exmines the exchange of prisoners of war in the Caribbean coast of New Granada and Venezuela after the signing of the armistice and regularization of war treaties at the end of 1820. I study the scope of this humantiarian accord, particularly after the suspensión of the truce, and in the capitulations in towns that were still under Spanish control. Despite many difficulties, hundreds of soldiers were able to save their lives this way, while many others returned to the ranks of the military or went back to their families. I find that the benefits were greater for the Republican side because a good number of Spanish prisoners abandoned the territories under dispute and others joined the revolutionary troops, while the Spanish Expeditionary Army was slowly losing its grip on the rebel colonies. In a way, the exchange of prisoners of war helped maintain channels of dialogue. It thus helped to produce a negotiated exit in this last phase of the wars of Independence and became an early precedent of international humanitarian law.Este trabajo analiza el canje de prisioneros de guerra en la Costa Caribe de la Nueva Granada y Venezuela tras la firma de los tratados de armisticio y de regularización de la guerra a finales de 1820. Se examina el alcance de esta medida humanitaria y particularmente su aplicación después de suspendida la tregua y en las capitulaciones suscritas en las plazas que aún estaban bajo dominio español. Pese a todas las dificultades, cientos de militares pudieron por esta vía salvar sus vidas mientras que otros regresaron a sus filas o al seno de sus familias. Se encuentra que mayores fueron las ventajas para el bando republicano pues un buen número de prisioneros españoles abandonaron los territorios en disputa y otros adhirieron a las filas patriotas mientras que el ejército expedicionario español fue paulatinamente perdiendo su poderío. En cierto modo, esta fórmula de intercambio de prisioneros ayudó a mantener los canales del diálogo y las salidas negociadas en esta última fase de las guerras de Independencia, y constituye un importante precedente del derecho internacional humanitario
Organized Crime, Foreign Investment and Economic Growth: The Latin American Case
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Latin America has been seen over the years as a violent region. Organized crime has been a major factor contributing to that perception. Crime not only makes daily life more dangerous for citizens of a country, but can even challenge the viability of governments. Crime fighting efforts drain state resources, threaten the delivery of public services, and might have a negative influence on institutional stability and business environment. The purpose of this paper is to extend the empirical framework of Bengoa and Sánchez-Robles (2002) to cover the relationship between organized crime, foreign direct investment (FDI) and growth. Although the relationship between organized crime and FDI is not widely discussed in the literature, it can be argued that there is a very important channel through which this relationship may exist: institutional instability of states and viability of governments. The paper finds that there is no significant correlation between organized crime and FDI flows. The results also show that there is a negative relationship between FDI and growth. The relationship between FDI and growth was explored cautiously because the economic literature suggests that there is a two-way causal link between these two variables. That possible source of endogeneity in the analysis is addressed econometrically in this paper using the Two Stage Least Squares (2SLS) technique. The use of 2SLS was not originally considered by Bengoa and Sánchez-Robles (2002), and therefore it is an additional contribution of this paper to the literature
Forjando una identidad americana en el siglo de las luces
Full text linkReseña del libro "Escritos económicos" de Antonio de Narváez y José Ignacio de Pombo (2010), Colección Bicenenario, Bogotá: Banco de la República, 363p
Obraje y obreros en la construcción del Canal de Panamá
Full text linkReseña del libro "The Canal Builders: Making America's Empire at the Panama Canal" de Julie Greene (2009), New York: Penguin Books, 388p
El recaudo del impuesto predial en Cartagena de Indias, 1984 - 2010
Full text linkWe examine the determinants of property tax collection in Cartagena, Colombia, between 1984 and 2010. This tax accounts for 33% of the District’s current income; with the industry and commerce tax it is the city’s main source of income. At the macro level, we study the impact of fiscal decentralization policies launched in the eighties and deepened in the second half of the nineties, and of the trade liberalization model introduced also in the nineties. Other macro variables considered are inflation and income inequality. At the local level, we examine the impact of tax reforms, the growth of construction and population, and also of efforts to expand the collection of other taxes and of taxpayers’ responses to changes in social expenditures. We find that property tax collection reflects the city’s economic conditions, due to the cycles of construction and the distribution of income, as well as the impact of inflation. It is possible to raise tax collection if taxpayers perceive that social expenditure is rising. If tax collection is strengthened two serious problems may be solved: the substitution effect in own sources of income (particularly in the tax on industry and commerce) and fiscal laziness. In the case of the impact of inflation and inequality of incomes, it is evident that the most effective fiscal policy is that which reduces poverty and vulnerability, and also raises investment and institutional efficiency in tax collection.
En este trabajo se examinan los determinantes del recaudo del impuesto predial en el Distrito de Cartagena de Indias, Colombia, en el periodo 1984-2010. Este tributo representa el 33% de los ingresos corrientes del Distrito; con el impuesto de industria y comercio constituye la principal fuente de ingresos propios de la ciudad. A escala macro se analiza el efecto de la descentralización fiscal iniciada en los ochenta y profundizada en la segunda mitad de los años noventa, así como el cambio de modelo económico con la apertura comercial. También se consideran otras variables de este orden, como la inflación y la desigualdad en el ingreso. A escala local, se examinan los efectos de las reformas tributarias en el Distrito, la expansión de la construcción y el crecimiento demográfico, y siguiendo el enfoque de Iregui y otros (2004), del esfuerzo por recaudar otros impuestos y la respuesta de los contribuyentes ante cambios en el gasto social. Se encuentra que el recaudo del impuesto refleja las condiciones económicas de la ciudad, tanto por los ciclos de la urbanización y la distribución del ingreso como por el impacto de la inflación. Es posible mejorar el recaudo si la ciudadanía percibe aumentos de la inversión social. El fortalecimiento de la gestión tributaria permitirá superar dos serios problemas del recaudo: el efecto sustitución en las rentas propias (especialmente con el impuesto de industria y comercio) y la pereza fiscal. En los casos del impacto inflacionario y la desigualdad es evidente que la política tributaria más efectiva en el largo plazo es aquella que reduce la pobreza y la vulnerabilidad, y eleva la inversión y la eficiencia institucional en la gestión de recaudo
El acceso a la consulta médica general en Colombia, 1997 - 2012
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This paper studies the determinants of access to health care services in Colombia with data from the 2012 National Quality of Life Survey, jointly considering characteristics of supply and demand. I find that access to medical services decreased in Colombia between 1997 and 2012. This performance was uneven within regions: Antioquia and the Oriental region show an increase in the indicator, while the Caribbean, Central, Bogotá, San Andrés, Providencia and Santa Catalina, Orinoco and Amazon regions reported decreases. Probit models show that demand characteristics explain more the probability of access than characte- ristics of supply. Finally, significant regional differences in access were observed in 2012.
A partir de los datos de la Encuesta Nacional de Calidad de Vida 2012, este trabajo evalúa los determinantes del acceso a los servicios médicos en Colombia, considerando en conjunto características de la oferta y la demanda de servicios de salud. Se encontró que el acceso a los servicios médicos se redujo entre 1997 y 2012. Este comportamiento fue desigual al interior de las regiones: Antioquia y la región Oriental experimentaron un aumento en el indicador, mientras que las regiones Caribe, Centro, Bogotá, San Andrés, Providencia y Santa Catalina, Orinoquía y Amazonía registraron disminuciones. Los resultados de los modelos Probit muestran que las características de la demanda explican en mayor medida la probabilidad de acceso que las características de la oferta. Por último, se encontraron diferencias regionales significativas en el acceso para 2012.
 
El Apostadero de la marina de Cartagena de Indias, sus trabajadores y la crisis política de la Independencia
Full text linkThis article studies the Colonial Navy Docks and Shipyard of Cartagena de Indias in the late xviiith and early xixth centuries and, in particular, the characteristics of the activities undertaken there. We show that the defensive systems demanded large concentrations of workers, and that these went beyond the small artisan workshop led by a master craftsman, with the participation of the family unit or of a small number of journeymen and apprentices. We suggest that a relationship exists between the crisis of the Empire, beginning in 1808, the budget crisis of the Shipyard and the political crisis in Cartagena, with the support given by workers to the movement for absolute independence from Spain. Este artículo estudia el Apostadero de la Marina de Cartagena de Indias durante el tránsito entre los siglos XVIII y XIX y, en particular, las características de los trabajos que en él se realizaban. Muestra que las labores de los sistemas defensivos demandaban grandes concentraciones de trabajadores, y que estas formas de trabajo estaban más allá del pequeño taller artesanal encabezado por un maestro y con la participación de la unidad familiar o de un escaso número de oficiales y aprendices. Sugiere que existió una relación entre la crisis del Imperio a partir de 1808, la crisis presupuestal del Apostadero y la crisis política de Cartagena, con el respaldo que los trabajadores brindaron al proyecto de independencia absoluta de España.