1,720,991 research outputs found
A branch-and-bound algorithm for a two-stage hybrid flowshop scheduling problem minimizing total tardiness
No full textA two-stage hybrid flowshop-scheduling problem is considered with the objective of minimizing total tardiness of jobs. In the hybrid flowshop, there is one machine at the first stage and multiple identical parallel machines at the second stage. Dominance properties and lower bounds are developed for the problem and a branch-and-bound algorithm is suggested using them. Results of computational experiments show that the suggested algorithm can find optimal solutions for problems with up to 15 jobs in a reasonable amount of central processing unit time
Radial basis function networks applied to DNBR calculation in digital core protection systems
No full textThe nuclear power plant has to be operated with sufficient margin from the specified DNBR limit for assuring its safety. The digital core protection system calculates on-line real-time DNBR by using a complex subchannel analysis program, and triggers a reliable reactor shutdown if the calculated DNBR approaches the specified limit.. However, it takes a relatively long calculation time even for a steady state condition, which may have an adverse effect on the operation flexibility. To overcome the drawback, a new method using a radial basis function network is presented in this paper. Nonparametric training approach is utilized, which shows dramatic reduction of the training time, no tedious heuristic process for optimizing parameters, and no local minima problem during the training. The test results show that the predicted DNBR is within about +/-2% deviation from the target DNBR for the fixed axial flux shape case. For the variable axial flux case including severely skewed shapes that appeared during accidents, the deviation is within about +/-10%. The suggested method could be the alternative that can calculate DNBR very quickly while guaranteeing the plant safety. (C) 2003 Elsevier Science Ltd. All rights reserved.
Algorithms for adjusting shapes of departments in block layouts on the grid-based plane
No full textMany existing algorithms for facility layout problems give block layouts in which departments have irregular shapes. This paper presents algorithms to modify shapes of departments in a given block layout with such departments. With the suggested algorithms, a given block layout is converted into a new block layout in which departments are of rectangular shapes without a significant change in the relative positions of the departments. Results of computational experiments show that the suggested algorithms give block layouts that are at least as good as original layouts in terms of the total transportation distance. (C) 2000 Elsevier Science Ltd. All rights reserved
Bottleneck-focused scheduling for a hybrid flowshop
No full textThis paper focuses on a scheduling problem in a hybrid flowshop in which there are serial workstations, each with identical parallel machines. The objective of the problem is to minimize total tardiness of a given set of jobs. We suggest a new type of heuristic method, called a bottleneck-focused algorithm, for the problem. In the algorithm, a schedule for a bottleneck workstation is first constructed and then schedules for other workstations are constructed based on the schedule for the bottleneck. Since the bottleneck workstation may not be the first workstation in the hybrid flowshop, ready times of operations at the bottleneck workstation depend on the schedule at its upstream workstations. In the algorithm, the ready times are iteratively updated using information of the schedule obtained in the previous iterations. To evaluate the performance of the suggested algorithm, computational experiments are performed on a real data set and randomly generated test problems. Results of the experiments show that the suggested algorithm outperforms various other heuristics
Minimizing total tardiness of orders with reentrant lots in a hybrid flowshop
No full textThis study focuses on a hybrid flowshop scheduling problem, in which there are serial stages, each with identical parallel machines. In the hybrid flowshop, each order is composed of multiple lots with the same due date, and each lot can be processed on any one of parallel machines at each stage. In addition, there are reentrant flows since lots of certain orders have to visit the stages twice. Heuristic algorithms are suggested for the scheduling problem with the objective of minimizing total tardiness of a given set of orders. In these algorithms, the list-scheduling method is employed, and lots are scheduled with priorities determined with a construction method. Computational experiments are performed on randomly generated test problems. Results show that the suggested algorithms perform better than well-known dispatching rules for various scheduling problems and an algorithm that is used in a real system
Improved methodology for generation of axial flux shapes in digital core protection systems
No full textAn improved method of axial flux shape (AFS) generation for digital core protection systems of pressurized water reactors is presented in this paper using an artificial neural network (ANN) technique-a feedforward network trained by backpropagation. It generates 20-node axial power shapes based on the information from three ex-core detectors. In developing the method, a total of 7173 axial flux shapes are generated from ROCS code simulation for training and testing of the ANN. The ANN trained 200 data predicts the remaining data with the average root mean square error of about 3%. The developed method is also tested with the real plant data measured during normal operation of Yonggwang Unit 4. The RMS errors in the range of 0.9 similar to 2.1% are about twice as accurate as the cubic spline approximation method currently used in the plant. The developed method would contribute to solve the drawback of the current method as it shows reasonable accuracy over wide range of core conditions. (C) 2002 Elsevier Science Ltd. All rights reserved
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
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