1,720,961 research outputs found
Algoritmos de zonificación para recolección de residuos
No full textLa programación de los aspectos logísticos de la recolección de residuos urbanos involucra una serie de problemas de optimización combinatoria de difícil resolución en la práctica. Problemas típicos que aparecen en este contexto son la definición de la flota de camiones para realizar la recolección, la zonificación del área a recorrer (de modo tal que cada camión recorre una zona) y la optimización del recorrido de cada camión en función de consideraciones de tránsito y desgaste de los vehículos. En esta tesis se propone el estudio del segundo de estos problemas, analizando algoritmos heurísticos para la partición del área a recolectar en zonas. Dados (a) el mapa de la ciudad que se debe recolectar, representado por un grafo mixto G = (V, E, A) cuyos vértices representan las esquinas, cuyas aristas (conjunto E) especifican las cuadras de doble mano y cuyos arcos (conjunto A) especifican las cuadras de una mano, (b) una estimaci ́on de la cantidad de residuos promedio a recolectar en cada cuadra y (c) la cantidad k y capacidad máxima de los vehículos de recolección, el problema consiste en particionar el grafo G en k zonas conexas de modo tal que los residuos a recolectar en cada zona no tengan mucha dispersión, y la distancia total de recolección sea la menor posible. Es habitual solicitar como requerimiento adicional que cada zona tenga un contorno sencillo, para ser f ́acilmente recordada por los conductores de los vehículos de recolección. Este problema es NP-hard, y en trabajos previos de la literatura ha demostrado ser muy difícil de resolver en la práctica. Por este motivo, se estudia en esta tesis este problema por medio de algoritmos heurísticos. Luego los resultados se aplican a los datos de la ciudad de San Miguel de Tucumán, con el objetivo de proponer una zonificación alternativa a la actual.Fil: Bianchetti, Marcelo Luis. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Integer programming models for the routing and spectrum allocation problem
Get PDFOne of the most promising solutions to deal with huge data traffic demands in large communication networks is given by flexible optical networking, in particular the flexible grid (flexgrid) technology specified in the ITU-T standard G.694.1. In this specification, the frequency spectrum of an optical fiber link is divided into narrow frequency slots. Any sequence of consecutive slots can be used as a simple channel, and such a channel can be switched in the network nodes to create a lightpath. In this kind of networks, the problem of establishing lightpaths for a set of end-to-end demands that compete for spectrum resources is called the routing and spectrum allocation problem (RSA). Due to its relevance, this problem has been intensively studied in the last couple of years. It has been shown to be NP-hard (Christodoulopoulos et al. in IEEE J Lightw Technol 29(9):1354–1366, 2011; Wang et al. in IEEE J Opt Commun Netw 4(11):906–917, 2012) and several models and formulations have been proposed, leading to different solution approaches. In this work, we explore integer programming models for RSA, analyzing their effectiveness over known instances. We resort to several modeling techniques, to find natural formulations of this problem. Since integer programming techniques are known to provide successful practical approaches for several combinatorial optimization problems, the aim of this work is to explore a similar approach for RSA.Fil: Bertero, Federico Alberto. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Bianchetti, Marcelo. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Marenco, Javier Leonardo. Universidad Nacional de General Sarmiento. Instituto de Ciencias; Argentin
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
A branch and cut algorithm for the routing and spectrum allocation problem
No full textLa fibra óptica flexible y en particular la tecnología llamada grilla flexible (flexgrid), especificada en el estándar ITU-T G.694.1, es una de las soluciones más prometedoras para lidiar con el enorme crecimiento del tráfico en redes muy grandes. En dicha especificación, el espectro de frecuencia de un cable de fibra óptica es dividido en canales más angostos, denominados slots. Cualquier secuencia consecutiva de slots puede ser usada como un solo canal. A la conexión que utiliza dicho canal a largo de una ruta a través de los nodos de la red se la denomina lightpath. Dado un conjunto de demandas punto-a-punto, al problema de establecer los lightpaths para satisfacerlas se denomina problema de Ruteo y Asignación de Espectro (RSA). Dada su relevancia, este problema ha sido estudiado intensivamente en la última década. Se demostró que pertenece a la clase NP-difícil, y en la práctica se comprobó que es necesario aplicar técnicas computacionales no triviales para obtener soluciones de instancias reales. En la última década, aplicando técnicas de programación entera se ha logrado resolver bien en la práctica una gran cantidad de problemas de optimización combinatoria. El principal objeto del presente trabajo es ampliar dicho campo, mediante la aplicación de técnicas de programación lineal entera sobre el RSA. El primer paso es explorar varios modelos de programación lineal entera para el RSA, analizando su efectividad en instancias conocidas. Recurrimos a varias técnicas de modelado, con el fin de encontrar formulaciones naturales de este problema. Una vez comparados estos modelos, analizamos en profundidad uno de los más prometedores para comprender sus características, fortalezas y debilidades, teniendo en cuenta sus propiedades combinatorias. A partir de los resultados de dicho estudio, desarrollamos procedimientos computacionales basados en programación lineal entera para el RSA, incluyendo el uso de planos de corte y heurísticas primales, con el objetivo final de resolver de manera óptima o casi óptima instancias reales de este problema. Este trabajo también contiene el desarrollo de un generador de instancias basado en topologías reales, y la compilación bibliográfica más extensa hasta la fecha enumerando y clasificando los trabajos que tratan el RSA y sus variaciones más cercanas desde la óptica de la optimización combinatoria [fórmula aproximada, revisar la misma en el original].One of the most promising solutions to deal with huge data traffic demands in large communication networks is given by flexible optical networking, in particular the flexible grid (flexgrid) technology specified in the ITU-T standard G.694.1. In this specification, the frequency spectrum of an optical fiber link is divided into narrow frequency slots. Any sequence of consecutive slots can be used as a simple channel, and such a channel can be switched in the network nodes to create a lightpath. In this kind of networks, the problem of establishing lightpaths for a set of end-to-end demands that compete for spectrum resources is called the Routing and Spectrum Allocation problem (RSA). Due to its relevance, this problem has been intensively studied in the last decade. It has been shown to be NP-hard, and nontrivial computational techniques are to be applied in order to tackle the solution of practical instances. Since integer programming techniques are known to provide successful practical approaches for several combinatorial optimization problems, the aim of this work is to further the exploration of such an issue, by applying integer linear programming techniques to RSA. The first objective is to explore several integer programming models for RSA, analyzing their effectiveness over known instances. We resort to several modeling techniques in order to find natural formulations of this problem. Having compared these models, then we make a detailed analysis of one of the most promising of them in order to understand its properties, strengths, and weaknesses, taking combinatorial properties into account. Based on these explorations, we develop integer linear programming based computational procedures for RSA including the use of cutting planes and primal heuristics, with the final objective of solving to optimality or near-optimality real-world instances of RSA. This work also contains the development of an instance generator based on real topologies, and the most extensive survey to date listing and classifying the works that treat the RSA and its closest variations from the point of view of combinatorial optimization [fórmula aproximada, revisar la misma en el original].Fil: Bianchetti, Marcelo Luis. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
koamabayili/VECTRON-author-checklist: VECTRON author checklist
No full textWe have done our best to complete the author checklist relating to the use of animals in the hut study. Note that the objective for the hut study was to evaluate the IRS treatment applications for residual efficacy against Anopheles mosquitoes, including the local An. coluzzii mosquito population. Cows were only used to attract mosquitoes into the huts and no tests were carried out directly on the cows. The author checklist is intended for use with studies where experiments are carried out on animals, which is why we have had such difficulty in completing this for the hut study, as many of the questions do not relate to how the cows were used
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