1,720,981 research outputs found
Colored GSPN models and automatic symmetry detection
No full textColored Petri nets (CPN) are useful for the development of very compact and easy to understand models of systems with interacting concurrent components. A CPN model can be used for a qualitative analysis of the modeled system; when timing is also added, a quantitative analysis can be done. Unfortunately, the analysis can be prevented by excessive size of the reachability graph (RG) of the net, which can grow exponentially as a function of the number of places and the cardinality of color domains. A method that automatically exploits the symmetries intrinsic in the model reducing the RG size is presented: it can be applied to a subclass of CPNs called regular nets (RN). Some nontrivial examples are presented to demonstrate that the automatically achieved reductions are comparable to those devised for these systems by thoroughly studying their behavio
On the Use of Coscheduling in Fast Communication Systems
No full textCoscheduling of communication and computation is considered one of the crucial points to obtain good performance out of fast communication systems. Various techniques have been examined in literature ranging from strict "gang scheduling" of all processes possibly involved in message exchange to "implicit coscheduling" in which the communication support system may act on the scheduling of sending and receiving processes trying to improve performance without explicit coordination by special purpose message exchanges. Based on the experience in implementing the GAMMA communication system, we are convinced that some form of coscheduling is needed in order to obtain best performance in communication. However we believe that most of the approaches described in literature so far are too simplistic to be really effective. In this paper we point out and classify some of the major problems a system that attempts to coschedule communication and computation should address. We hope to clarify the goals of a coscheduler by taking some of the crucial characteristics of the communication into account. We also hope to be able to devise some more integrated and coherent strategies of coordination between process scheduling and choice of communication modes
Resource management with X.509 inter-domain authorization certificates (InterAC)
No full textCollaboration among independent administrative domains would require: i) confidentiality, integrity, non-repudiation of communication between the domains; ii) minimum and reversible modifications to the intra-domain pre-collaboration setup; iii) maintain functional autonomy while collaborating; and, iv) ability to quickly transform from post-collaboration to pre-collaboration stage. In this paper, we put forward our mechanism that satisfies above requirements while staying within industry standards so that the mechanism becomes practical and deployable. Our approach is based on X.509 certificate extension. We have designed a non-critical extension capturing users' rights in such a unique way that the need for collaboration or the post-collaboration stage does not require update of the certificate. Thus, greatly reducing the revocation costs and size of CRLs. Furthermore, rights amplification and degradation of users from collaborating domains into host domain can be easily performed. Thus, providing functional autonomy to collaborators. Initiation of collaboration among two domains require issuance of one certificate from each domain and revocation of these certificates ends the collaboration - ease of manageability. © 2010 Springer-Verlag
Generalized stochastic Petri nets for the performance evaluation of FMS
No full textA class of Petri nets in which transitions can fire either immediately or after an exponentially distributed random time since their enabling (GSPN), is used to define performance models for Flexible Manufacturing Systems. An example is discussed in which the analysis of the GSPN model yields results that are more reliable than those obtained with a currently used method based on queueing networks. Detailed GSPN models are shown that allow accurate analyses of the effects that different scheduling policies and pallet mixes have on system performance
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
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