1,720,955 research outputs found
Finding K dissimilar paths: Single-commodity and discretized flow formulations
Get PDFWhile finding a path between two nodes is the basis for several applications, the need for alternative paths also may have various motivations. For instance, it can be of interest to ensure reliability in a telecommunications network, to reduce the consequences of possible accidents in the transportation of hazardous materials or to decrease the risk of robberies in money distribution. All these applications involve the search for a set of paths that are as dissimilar as possible, with respect to the arcs in them. In this work, we present linear integer programming formulations that intend to find K dissimilar paths. The new models derive from a straightforward single-commodity flow formulation of the K paths problem, to which extra constraints are added to account for the concept of dissimilarity. In particular, in each formulation a different measure of the similarity between the K paths is minimized: the number of repeated arcs, the number of arc reuses and the number of pairwise arc overlaps. The third measure originates a non-linear model that is linearized through a discretized model reformulation technique. These formulations are complemented by a polynomial algorithm that allows to extract K loopless paths from the solutions output by each of them.The formulations are tested for random and grid networks with respect to the solutions' average and minimum dissimilarity and the run time. Two of them stand out in terms of both those measures, when compared to an iterative approach from the literature. The best one regarding the average dissimilarity finds 20 paths with average dissimilarity of 99.5% in about 168 s for random networks of 5 000 nodes and 100 000 arcs. The same approach finds 20 paths for grid instances of size 100 x 100 in less than 18 s. The other formulation requires about 11 s for the same random instances, with a 0.7% deviation from the best known average dissimilarity; while it requires less than 7 s to compute 20 paths in 100 x 100 grids with a 0.6% deviation to the optimal dissimilarity
Finding K shortest and dissimilar paths
Get PDFThe purpose of the (Formula presented.) dissimilar paths problem is to find a set of (Formula presented.) paths, between the same pair of nodes, which share few arcs. The problem has been addressed from an application point of view, and integer programming formulations have also been introduced recently. In the present work, it is assumed that each arc is assigned with a cost, and the goal is then to find (Formula presented.) dissimilar paths while simultaneously minimizing the total cost. Some of the previous formulations: one minimizing the number of repeated arcs, another one minimizing the number of arc repetitions, as well as modifications that bound the number of paths in which the arcs appear, are extended with a cost function. Properties of the resulting biobjective problems are studied and the (Formula presented.) -constraint method is adapted to solve them using a decreasing and an increasing strategy for updating (Formula presented.). These methods are tested for finding sets of 10 paths in random and grid instances to assess the efficiency of the (Formula presented.) -constraint methods and the performance of the formulations to calculate shortest and dissimilar paths. Results show that minimizing the number of arc repetitions produces efficient solutions with higher dissimilarities faster than minimizing the number of repeated arcs. The cost range of the solutions is similar in both approaches. Additionally, bounding the number of paths in which each arc appears improves the quality of the solutions as to the dissimilarity while worsening its cost
The Rough Interval Shortest Path Problem
Get PDFThe shortest path problem is one of the most popular network optimization problems and it is of great importance in areas such as transportation, network design or telecommunications. This model deals with determining a minimum weighted path between a pair of nodes of a given network. The deterministic version of the problem can be solved easily, in polynomial time, but sometimes uncertainty or vagueness is encountered. In this work we consider the rough interval shortest path problem, where each arc’s weight is represented by a lower approximation interval and an upper approximation interval, which surely contains the real weight value and that may possibly contain the real weight value, respectively. A labeling algorithm is developed to find the set of efficient solutions of the problem
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
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
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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