1,721,110 research outputs found
A regenerative expert system approach for the maintenance of expert systems
No full textWhen the maintenance of expert systems incorporates not only knowledge bases but also inference engines, algorithms, and user interface modules, the maintenance of the expert systems needs to adopt software maintenance methodologies such as software reuse. We have developed a regenerative expert system approach (REGENESYS) that can modify the rules and program modules of a standard expert system according to the changed specification. We have also proposed a procedure for the approach and illustrated it with the scheduling expert systems for shipbuilding. By adopting the regenerative expert system approach, we can reduce the burden of developing systems for rare occurrences and maintain the capability of modular modification. (C) 1998 Elsevier Science Ltd. All rights reserved
A real-time discrete event system specification formalism for seamless real-time software development
No full textWe present a time domain extension of the hierarchical and modular discrete event specification(DEVS) formalism. This extension is important for establishing a seamless real-time software development framework. Formalisms help describe a system unambiguously. If formal models are implemented without any consistent frameworks, however, it is hard to guarantee that there is no semantic gap between models and codes. Real-Time DEVS, named RTDEVS, is an extension of DEVS that can be characterized in three perspectives: the real time execution of models, the addition of time interval functions, and the activity specification for each state. After analyzing a system, the framework based on RTDEVS helps to expand each model of the system for executing in a real-time environment. In order to support the RTDEVS formalism, we propose abstract executive concepts based on the abstract simulator concepts of the DEVS formalism. Also, we implement an RTDEVS execution engine, named DEVS Executive, which runs on real-time Mach
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
Heuristic algorithms for ordering media objects to reduce presentation lags in auto-assembled multimedia presentations from digital libraries
No full text[[abstract]]Purpose - The purpose of this paper is to examine an auto-assembled multimedia presentation from digital libraries, in which the retrieved media objects are dynamically composed to form a continuously played "TV-like" presentation. This study seeks to propose techniques for ordering the media objects in such a presentation so as to reduce its total presentation lag in a high-delay network environment. Design/methodology/approach - Scheduling techniques adapted from conventional operational research for solving the proposed problem were applied. A number of computationally efficient heuristic algorithms that can obtain near-optimal sequences are proposed. Numerical simulations and real-life experiments for cases with different buffer constraints and bandwidth fluctuations were conducted to evaluate the proposed algorithms. Findings - The result indicates that the proposed algorithms always significantly reduce the presentation lag of a given presentation, compared with a random sequence. Overall, for all the test cases, the average gaps between the idle rates of the heuristic sequences and random sequences range from 15 to 25 per cent. In particular, the RRB_3_2007 algorithm outperforms others in most of the cases involved in the experiment. Originality/value - The study develops a sequence optimization technique for ordering the media objects and a framework for a prefetch-enabled presentation system. The effectiveness and ease of implementation of the heuristic algorithms and the system framework make it feasible for practical digital library and meta-search engine applications.[[note]]SSC
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
Sequence optimization for media objects with due date constraints in multimedia presentations from digital libraries
No full text[[abstract]]This study investigates sequence optimization of media objects in a multimedia presentation that is dynamically composed from digital libraries. Each media object can be associated with a due date. The aim is to schedule the media objects in a delay-prone network environment such that the overall presentation lag and the due date penalties of the media objects of presentations can be minimized. We formulate the sequencing problem with buffer constraints in the media player into a flowshop scheduling problem and present a reduction strategy with a branch and bound algorithm to derive optimal sequences. The algorithm can be applied in applications with up to a dozen objects to be scheduled. In addition, we propose a modified NEH-based heuristic algorithm which can provide approximate solutions with an average error rate of less than 4%. The computation-efficient heuristic, when deployed in applications with heavily loaded servers, can obtain near-optimal sequences for problems with more than a dozen objects. The proposed algorithms are embedded into a prototype system for providing digital library services. (c) 2012 Elsevier Ltd. All rights reserved.[[note]]SC
A two-machine flowshop problem with processing time-dependent buffer constraints-An application in multimedia presentations
No full text[[abstract]]To have a quality multimedia presentation through networks, its presentation lag needs to be controlled. One way to reduce the lag is to prefetch the media objects before their due dates. This paper explores techniques for optimizing the object sequence in a prefetch-enabled TV-like presentation. An optimal solution is the one with which the presentation lag is minimized. We formulate the problem into a two-machine flowshop scheduling problem with a single chain precedence constraint and a player-side buffer constraint. The player-side buffer is "processing time-dependent" and distinguished from the conventional item-based intermediate buffer constraints discussed in previous flowshop studies. We prove the problem to he strongly NP-hard. A branch and bound algorithm equipped with four lower bounds and an NEH-based upper bound is developed. The simulation results show that the average gaps between the overall lower bounds and the NEH-based upper bound are less than 3% for problems with a large buffer size, and less than 13% for problems with a small buffer size and high density of precedence constraints. For applications where the media objects are delivered through extremely busy servers with which only very restricted CPU resources can be allocated for computation, the CDS-based algorithm provides better sequences than the NEH-based algorithm. (C) 2008 Elsevier Ltd. All rights reserved.[[note]]SC
Quantity-based buffer-constrained two-machine flowshop problem: active and passive prefetch models for multimedia applications
No full text[[abstract]]Conventional studies on buffer-constrained flowshop scheduling problems have considered applications with a limitation on the number of jobs that are allowed in the intermediate storage buffer before flowing to the next machine. The study in Lin et al. (Comput. Oper. Res. 36(4):1158-1175, 2008a) considered a two-machine flowshop problem with "processing time-dependent" buffer constraints for multimedia applications. A "passive" prefetch model (the PP-problem), in which the download process is suspended unless the buffer is sufficient for keeping an incoming media object, was applied in Lin et al. (Comput. Oper. Res. 36(4):1158-1175, 2008a). This study further considers an "active" prefetch model (the AP-problem) that exploits the unoccupied buffer space by advancing the download of the incoming object by a computed maximal duration that possibly does not cause a buffer overflow. We obtain new complexity results for both problems. This study also proposes a new lower bound which improves the branch and bound algorithm presented in Lin et al. (Comput. Oper. Res. 36(4):1158-1175, 2008a). For the PP-problem, compared to the lower bounds developed in Lin et al. (Comput. Oper. Res. 36(4):1158-1175, 2008a), on average, the results of the simulation experiments show that the proposed new lower bound cuts about 38% of the nodes and 32% of the execution time for searching the optimal solutions.[[note]]SC
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