1,720,954 research outputs found
Decentralized approaches for admission, routing and flow problems
Full text linkOnline control of large dynamic networks is challenging because little data are in general available about the environment, because decentralized strategies have to be employed, which rely on the knowledge of local data only, and because faults can occur. In this regard, three problems are addressed in this thesis.
The first problem concerns the scheduling of some requests of a limited resource occurring at different times, from a supplier with limited capacity. The goal is that of minimizing the average waiting time for these requests. The problem is formulated as an optimal control one, in which the control is the supply strategy, specified by some constraints, and the state variables are associated with the waiting times of the demands. The exact optimal problem requires mixed-integer linear programming; some relaxed versions are also formulated and, in particular, one of these is based on linear programming and efficiently provides some lower bound. Some online heuristics are analyzed, both centralized and decentralized, for which, in general, no a-posteriori optimality of the solution is obtained.
The second problem is an agent-based minimum path one. Some tokens (agents) are injected in the network, in some source nodes, and must travel in the network to find an exit, a sink. A simple decentralized policy is proposed. This policy allows or denies the transitions of the tokens along the arcs on the basis of a simple local threshold mechanism. In particular, a transition occurs through a directed arc if the amount of tokens present in the origin node minus the amount tokens present in the end node exceeds the arc cost. Despite the very simple local mechanism, in the long run, all the injected tokens leave the network by the closest sink through the shortest path, although some tokens are, unavoidably, lost during the initial transient exploring phase. This issue can be avoided by enhancing the policy allowing the generation of some virtual tokens. Some constraints to the maximum number of transitions can also be imposed to all tokens. In fact, this is equivalent to applying the policy proposed for the unconstrained case to the so-called expanded network.
The third problem considers flow networks with buffers in the nodes containing an amount of a continuous resource at a given level (state), which is transferred between nodes by controlled flows along the arcs. A decentralized control is formulated to meet a given flow demand, stabilize the system and asymptotically minimize the p-norm of the flow. This control is specified at the arc level and depends only on the value of p and on the difference of the states of the two arc's endnodes. After an initial transient, the unique optimal desired flow is obtained when 1 < p < ∞. When p = 1 sparsity of the solution tends to emerge, while when p = ∞ fairness is promoted; however, no optimality or uniqueness of solution is achieved in these two cases: suboptimal solutions can be obtained by applying the control with p → 1 and p → ∞, respectively. Enhancements can be applied to support uncontrollable flows governed by unknown dynamics depending on the buffer levels and buffer level control to a desired set-point. In this case, a decentralized proportional-integral control is adopted
Fair and Sparse Solutions in Network-Decentralized Flow Control
No full textWe proposed network-decentralized control strategies, in which each actuator can exclusively rely on local information, without knowing the network topology and the external input, ensuring that the flow asymptotically converges to the optimal one with respect to the p -norm. For 1 < p < ∞ , the flow converges to a unique constant optimal up∗. We show that the state converges to the optimal Lagrange multiplier of the optimization problem. Then, we consider networks where the flows are affected by unknown spontaneous dynamics and the buffers need to be driven exactly to a desired set-point. We propose a network-decentralized proportional-integral controller that achieves this goal along with asymptotic flow optimality; now it is the integral variable that converges to the optimal Lagrange multiplier. The extreme cases p=1 and p=∞ are of some interest since the former encourages sparsity of the solution while the latter promotes fairness. Unfortunately, for p=1 or p=∞ these strategies become discontinuous and lead to chattering of the flow, hence no optimality is achieved. We then show how to approximately achieve the goal as the limit for p 1 or p ∞.Green Open Access added to TU Delft Institutional Repository 'You share, we take care!' - Taverne project https://www.openaccess.nl/en/you-share-we-take-care Otherwise as indicated in the copyright section: the publisher is the copyright holder of this work and the author uses the Dutch legislation to make this work public.Team Tamas Keviczk
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
Author-wise bibliometric analysis based on entropy.
No full textAuthor-wise bibliometric analysis based on entropy.</p
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