1,720,981 research outputs found
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe 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
Full text link“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
Demonic variance and a non-determinism score for Markov decision processes
Full text linkThis paper studies the influence of probabilism and non-determinism on some quantitative aspect X of the execution of a system modeled as a Markov decision process (MDP). To this end, the novel notion of demonic variance is introduced: For a random variable X in an MDP M, it is defined as 1/2 times the maximal expected squared distance of the values of X in two independent execution of M in which also the non-deterministic choices are resolved independently by two distinct schedulers. It is shown that the demonic variance is between 1 and 2 times as large as the maximal variance of X in M that can be achieved by a single scheduler. This allows defining a non-determinism score for M and X measuring how strongly the difference of X in two executions of M can be influenced by the non-deterministic choices. Properties of MDPs M with extremal values of the non-determinism score are established. Further, the algorithmic problems of computing the maximal variance and the demonic variance are investigated for two random variables, namely weighted reachability and accumulated rewards. In the process, also the structure of schedulers maximizing the variance and of scheduler pairs realizing the demonic variance is analyzed.This is the extended version of a conference paper accepted for publication at MFCS 202
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe 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
Demonic Variance and a Non-Determinism Score for Markov Decision Processes
Full text linkThis paper studies the influence of probabilism and non-determinism on some quantitative aspect X of the execution of a system modeled as a Markov decision process (MDP). To this end, the novel notion of demonic variance is introduced: For a random variable X in an MDP ℳ, it is defined as 1/2 times the maximal expected squared distance of the values of X in two independent execution of ℳ in which also the non-deterministic choices are resolved independently by two distinct schedulers.
It is shown that the demonic variance is between 1 and 2 times as large as the maximal variance of X in ℳ that can be achieved by a single scheduler. This allows defining a non-determinism score for ℳ and X measuring how strongly the difference of X in two executions of ℳ can be influenced by the non-deterministic choices. Properties of MDPs ℳ with extremal values of the non-determinism score are established. Further, the algorithmic problems of computing the maximal variance and the demonic variance are investigated for two random variables, namely weighted reachability and accumulated rewards. In the process, also the structure of schedulers maximizing the variance and of scheduler pairs realizing the demonic variance is analyzed
On Non-Classical Stochastic Shortest Path Problems
Full text linkThe stochastic shortest path problem lies at the heart of many questions in the formal verification of probabilistic systems. It asks to find a scheduler resolving the non-deterministic choices in a weighted Markov decision process (MDP) that minimizes or maximizes the expected accumulated weight before a goal state is reached. In the classical setting, it is required that the scheduler ensures that a goal state is reached almost surely. For the analysis of systems without guarantees on the occurrence of an event of interest (reaching a goal state), however, schedulers that miss the goal with positive probability are of interest as well. We study two non-classical variants of the stochastic shortest path problem that drop the restriction that the goal has to be reached almost surely. These variants ask for the optimal partial expectation, obtained by assigning weight 0 to paths not reaching the goal, and the optimal conditional expectation under the condition that the goal is reached, respectively. Both variants have only been studied in structures with non-negative weights.
We prove that the decision versions of these non-classical stochastic shortest path problems in MDPs with arbitrary integer weights are at least as hard as the Positivity problem for linear recurrence sequences. This Positivity problem is an outstanding open number-theoretic problem, closely related to the famous Skolem problem. A decid- ability result for the Positivity problem would imply a major breakthrough in analytic number theory. The proof technique we develop can be applied to a series of further problems. In this way, we obtain Positivity-hardness results for problems addressing the termination of one-counter MDPs, the satisfaction of energy objectives, the satisfaction of cost constraints and the computation of quantiles, the conditional value-at-risk – an important risk measure – for accumulated weights, and the model-checking problem of frequency-LTL.
Despite these Positivity-hardness results, we show that the optimal values for the non-classical stochastic shortest path problems can be achieved by weight-based deter- ministic schedulers and that the optimal values can be approximated in exponential time. In MDPs with non-negative weights, it is known that optimal partial and conditional expectations can be computed in exponential time. These results rely on the existence of a saturation point, a bound on the accumulated weight above which optimal schedulers can behave memorylessly. We improve the result for partial expectations by showing that the least possible saturation point can be computed efficiently. Further, we show that a simple saturation point also allows us to compute the optimal conditional value-at-risk for the accumulated weight in MDPs with non-negative weights.
Moreover, we introduce the notions of long-run probability and long-run expectation addressing the long-run behavior of a system. These notions quantify the long-run average probability that a path property is satisfied on a suffix of a run and the long-run average expected amount of weight accumulated before the next visit to a target state, respectively. We establish considerable similarities of the corresponding optimization problems with non-classical stochastic shortest path problems. On the one hand, we show that the threshold problem for optimal long-run probabilities of regular co-safety properties is Positivity-hard via the Positivity-hardness of non-classical stochastic shortest path problems. On the other hand, we show that optimal long-run expectations in MDPs with arbitrary integer weights and long-run probabilities of constrained reachability properties (a U b) can be computed in exponential time using the existence of a saturation point
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe 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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