1,720,973 research outputs found
A computational analysis of the optimal power flow problem
No full text1 online resource (PDF, 20 pages, includes illustrations)Alzalg, Baha; Anghel, Catalina; Gan, Wenying; Huang, Qing; Rahman, Mustazee; Shum, Alex. (2012). A computational analysis of the optimal power flow problem. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/181205
Sub-optimality of Local Algorithms on Sparse Random Graphs
Get PDFThis thesis studies local algorithms for solving combinatorial optimization
problems on large, sparse random graphs. Local algorithms are randomized
algorithms that run in parallel at each vertex of a graph by using only local
information around each vertex. They produce important structures on large graphs
such as independent sets, matchings, colourings and eigenfunctions of the
graph Laplacian with only constant running time and little memory usage.
Hatami, Lovasz and Szegedy conjectured that all reasonable optimization
problems on large random d-regular graphs can be approximately solved by local
algorithms. This is true for matchings: local algorithms can produce near
perfect matchings in random d-regular graphs. However, this conjecture
was recently shown to be false for independent sets by Gamarnik and Sudan.
They showed that local algorithms cannot generate maximal independent
sets on large random d-regular graphs if the degree d is sufficiently large.
We prove an optimal rate of failure of this conjecture for the problem
of percolation on graphs. The basic question is this. Consider a large
integer T, which we consider a threshold parameter.
Given some large graph G, find the maximum sized induced
subgraph of G whose connected components have size no bigger than T.
When T equals 1 this is the problem of finding the maximum
independent sets in G.
We show that for asymptotically large values of the degree d, local
algorithms cannot solve the percolation problem on random d-regular
graphs and Erdos-Renyi graphs of expected average degree d.
Roughly speaking, we prove that the largest induced subgraph with a
given threshold that local algorithms can find is no more than half
of the maximum possible size. This is optimal because there exists
local algorithms that can find such induced subgraphs of half the maximum
size.
Part of this thesis represents joint work with Balint Virag.Ph.D
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
Infinite geodesics, competition interfaces and the second class particle in the scaling limit
Get PDFWe establish fundamental properties of infinite geodesics and competition
interfaces in the directed landscape. We construct infinite geodesics in the
directed landscape, establish their uniqueness and coalescence, and define
Busemann functions. We then define competition interfaces in the directed
landscape. We prove the second class particle in tasep converges under KPZ
scaling to a competition interface. Under suitable conditions, we show the
competition interface has an asymptotic direction, analogous to the speed of a
second class particle, and determine its law. Moreover, we prove the
competition interface has an absolutely continuous law on compact sets with
respect to infinite geodesics.Comment: final versio
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
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