1,720,970 research outputs found
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
An Enumerative Perspective on Connectivity
Get PDFConnectivity (or equivalently, unweighted maximum flow) is an important measure in graph theory and combinatorial optimization. Given a graph with vertices and , the connectivity from to is defined to be the maximum number of edge-disjoint paths from to in .
Much research has gone into designing fast algorithms for computing connectivities in graphs. Previous work showed that it is possible to compute connectivities for all pairs of vertices in directed graphs with edges in time [Chueng, Lau, and Leung, FOCS 2011], where is the exponent of matrix multiplication. For the related problem of computing small connectivities, it was recently shown that for any positive integer , we can compute for all pairs of vertices in a directed graph with nodes in time [Akmal and Jin, ICALP 2023].
In this paper, we present an alternate exposition of these and time algorithms, with simpler proofs of correctness. Earlier proofs were somewhat indirect, introducing an elegant but ad hoc flow vector framework for showing correctness of these algorithms. In contrast, we observe that these algorithms for computing exact and small connectivity values can be interpreted as testing whether certain generating functions enumerating families of edge-disjoint paths are nonzero. This new perspective yields more transparent proofs, and ties the approach for these problems more closely to the literature surrounding algebraic graph algorithms.29 pages, TheoretiCS journal versio
Parameterized Relaxations for Circuits and Graphs
No full textWhatmakessomeproblemshardtosolve, and others easy? In situations where complexitytheoretic hypotheses rule out the possibility of fast algorithms for problems, are there nonetheless instances for which we can evade intractability and still design efficient algorithms? In this thesis, we investigate these questions from the perspective of parameterized relaxations. We consider important computational problems on circuits and graphs, and design fast algorithms for relaxed versions of these tasks, that highlight tractable instances of problems which are provably hard in general.
On circuits, we tackle the Majority-SAT problem, a task related to counting solutions to Boolean formulas in conjunctive normal form (i.e., CNF formulas), which has been extensively studied in areas related to probabilistic planning and inference. It has been known since the problem’s introduction in the 1970s that Majority-SAT is complete for the class PP(intuitively, the complexity class of decision versions of counting tasks, believed to contain very difficult problems), and so under standard conjectures in complexity theory, cannot be solved in polynomial-time. We nonetheless show however, that Majority-SAT can be solved in optimal linear time when its inputs are restricted to be k-CNF formulas (i.e., CNF formulas where every clause width at most k), for any constant integer k ≥ 1. This is surprising, since most circuit satisfiability problems remain hard even when restricted to 3-CNF formulas. Indeed, prior to our work, it was widely conjectured that Majority-SAT should be PP-complete on 3-CNFs. Beyond overturning this conjecture, we also characterize the complexity of many additional variants of Majority-SAT on bounded width formulas.
On graphs, we tackle the All-Pairs Connectivity and Disjoint Shortest Paths problems. In the All-Pairs Connectivity (APC) problem, we are given an unweighted, directed graph G on n vertices, and are tasked with computing the maximum flow between each pair of vertices in G. Despite significant research on the problem, the fastest algorithm for APC in dense directed graphs is the naive n⁴⁺ᵒ⁽¹⁾ time approach, which simply runs a fast maximum f low algorithm separately for each pair of nodes. Moreover, the Strong Exponential Time Hypothesis (SETH) implies that APC cannot be solved in truly subcubic time. We consider a relaxation of APC, the k-Bounded All-Pairs Connectivity (k-APC), problem for integer k ≥ 1, where for each pair of nodes (s,t) in G, we must compute the maximum flow from s to t exactly if the maximum flow value is less than k, but if the maximum flow is at least k we merely need to report that the flow value is “large” instead of computing its exact value. We present an algorithm solving k-APC in Ō((kn)ʷ) time, where ω < 2.3716 is the exponent of matrix multiplication. This is subcubic even for small k (evading the SETH lower bound for the general APC problem), and runs in Ō(nʷ) time for all constant k, which is already optimal for the 1-APC problem under conjectures in fine-grained complexity. Before our work, no algorithm was even known for 3-APC that ran faster than an algorithm simply solving the general APC problem directly.
In the Disjoint Shortest Paths (DSP) problem, we are given a graph G on n vertices, with specified source nodes s₁,...,sₖ and target nodes t₁,...,tₖ, and are tasked with determining if G contains internally vertex-disjoint sᵢ ⇝ tᵢ shortest paths. This problem is NP-hard in general, if k can grow with n. We study k-DSP, the DSP problem parameterized by the number of terminal pairs, for small k. We show that 2-DSP can be solved in optimal linear time over weighted undirected graphs and directed acyclic graphs. Prior to our work, the fastest algorithm for 2-DSP over weighted undirected graphs took O(n⁷) time, and the fastest algorithm over weighted, dense directed acyclic graphs took O(n³) time.Ph.D
Longest Common Subsequence Over Constant-Sized Alphabets: Beating the Naive Approximation Ratio
No full textThis thesis investigates the approximability of the Longest Common Subsequence (LCS) problem. The fastest known algorithm for solving the LCS problem runs in essentially quadratic time in the length of the input, and it is known that under the Strong Exponential Time Hypothesis there can be no polynomial improvement over this quadratic running time. No similar limitation holds however, for approximate computation of the LCS, except in certain restricted scenarios. When the two input strings come from an alphabet of size k, returning the subsequence formed by the most frequent symbol occurring in both strings achieves a 1/k approximation for the LCS.
It is an open problem whether a better than 1/k approximation can be achieved in truly subquadratic time (O(n^{2-δ}) time for constant δ > 0).
A recent result [Rubinstein and Song SODA'2020] shows that a 1/2+ε approximation for the LCS over a binary alphabet is possible in truly subquadratic time, provided the input strings have the same length. In this paper we show that if for some ε > 0 a 1/2+ε approximation is achievable for binary LCS in truly subquadratic time when the input strings can have differing lengths, then for every constant k there exists some δ_k > 0 such that there is a truly subquadratic time algorithm that achieves a 1/k+δ_k approximation for k-ary alphabet LCS. Thus, we show that for constant-factor LCS approximation, the case of binary strings is in some sense the hardest case. We also show that for every constant k, if one is given two strings of equal length over a k-ary alphabet, one can obtain a 1/k+ε approximation for some constant ε > 0 in truly subquadratic time. This extends the Rubinstein and Song result to all alphabets of constant size, and gives the first nontrivial improvement over the naive 1/k approximation for the LCS of strings over alphabets of size k for all k ≥ 3.S.M
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