1,720,955 research outputs found
New solvers for asymmetric systems in GreatSPN
No full textIn this paper we present the extended symbolic reachability graph/dynamic symbolic reachability graph (ESRG/DSRG) framework to model and solve (asymmetric) SWN models. This framework combines several tools: GreatSPN for the model design, WNESRG to build the ESRG of the designed model, ESRG2MC to refine the ESRG and generate the corresponding MC, WNDSRG to build the DSRG and the corresponding MC. MCSolver is used to solve the MC and compute the steady state marking probability. The following section is dedicated to the detailed presentation of this new framework
Efficient lumpability check in partially symmetric systems
No full textState space based performance analysis of stochastic models may be impaired by the state space explosion but such problem can be mitigated in symmetrical behaving systems by aggregating equivalent states and transitions. An effective way of exploiting symmetries when the system is modeled using the stochastic well-formed net (SWN) formalism, is to generate the symbolic reachability graph (SRG) and automatically derive a lumped continuous time Markov chain (CTMC) of the same size as the SRG from it. For partially symmetric systems, the extended SRG (ESRG) can be used instead, but the derivation of a lumped CTMC in this case is not as direct as in the SRG case: in fact the ESRG structure might need a refinement to satisfy the lumpability conditions. In this paper a new efficient algorithm to derive a lumped CTMC from the ESRG is presented, and the results obtained by experimenting its implementation within the GreatSPN environment are discussed. The algorithm combines the Paige and Tarjan's partition refinement algorithm (extended to work with weighted arcs) and a previously proposed lumpability check algorithm (built specifically for the use with the ESRG) and outperforms both of them. The implementation of the algorithm within the GreatSPN environment would allow the several users that have chosen this package to apply the proposed technique
Lumping Partially Symmetrical Stochastic Models
No full textThe performance and dependability evaluation of complex systems by means of dynamic stochastic models (e.g. Markov chains) may be impaired by the combinatorial explosion of their state space. Among the possible methods to cope with this problem, symmetry-based ones can be applied to systems including several similar components. Often however these systems are only partially symmetric: their behavior is in general symmetric except for some local situation when the similar components need to be differentiated. In this paper two methods to efficiently analyze partially symmetrical models are presented in a general setting and the requirements for their efficient implementation are discussed. Some case studies are presented to show the methods' effectiveness and their applicative interest
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
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
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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