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1 – 10 of 71The focus of this paper is in Q-Lasso introduced in Alghamdi et al. (2013) which extended the Lasso by Tibshirani (1996). The closed convex subset Q belonging in a Euclidean m…
Abstract
The focus of this paper is in Q-Lasso introduced in Alghamdi et al. (2013) which extended the Lasso by Tibshirani (1996). The closed convex subset Q belonging in a Euclidean m-space, for
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Hassan M. Selim, Reda M.S. Abdel Aal and Araby I. Mahdi
This paper introduces a modified single linkage clustering heuristic (MOD‐SC). The proposed MOD‐SLC objective is to test the application of Baroni‐Urban and Buser (BUB) similarity…
Abstract
This paper introduces a modified single linkage clustering heuristic (MOD‐SC). The proposed MOD‐SLC objective is to test the application of Baroni‐Urban and Buser (BUB) similarity coefficient to the manufacturing cell formation (MCF) problem instead of Jaccard’s similarity coefficient. The MOD‐SLC has been compared and evaluated against three cluster formation‐based heuristics for MCF. The three heuristics are: the single linkage clustering, enhanced rank order clustering, and direct clustering algorithm. The MCF methods considered in this comparative and evaluative study belong to the cluster formation approach of solving the MCF problem. The comparison and evaluation are performed using four published performance measures. A total of 25 published and ten hypothetical and randomly generated problem data sets are used in the proposed evaluative study. Results analysis is carried out to test and validate the proposed BUB based MOD‐SLC. Finally the pros and cons of each method are stated and discussed.
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Timo Rahkonen and Janne P. Aikio
The purpose of this paper is to propose a method to reduce the non-linear distortion of a transistor to its input and output ports to aid distortion contribution analysis (DCA)…
Abstract
Purpose
The purpose of this paper is to propose a method to reduce the non-linear distortion of a transistor to its input and output ports to aid distortion contribution analysis (DCA). This is especially needed when the internal structure of a device model is complex.
Design/methodology/approach
The non-linear distortion generated by all non-linear sources inside a device model are reduced to transistor i/o ports by LMSE fitting techniques. Simulations of an LDMOS power transistor are used to compare the reduced distortion results with the actual non-linear sources.
Findings
It is shown, that device models where the current sources are split by intermediate nodes cause superficial results, when distortion contributions are calculated as a superposition of contributions from individual non-linear sources. The proposed iterative fitting technique works.
Research limitations/implications
Some non-quasistatic effects and the transfer functions from external terminals to internal controlling nodes are not covered.
Practical implications
The analysis is a step toward a generic non-linear distortion contribution simulation tool that would aid the designers to develop more linear analog circuits.
Originality/value
The concept of DCA itself is fairly new. This paper makes a step to represent the distortion sources in a canonical way.
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Scott M. Shafer and Jack R. Meredith
Cellular and functional layouts were investigated under a varietyof real‐world conditions via a two‐stage computer simulation study. Inthe first stage, simulation models were…
Abstract
Cellular and functional layouts were investigated under a variety of real‐world conditions via a two‐stage computer simulation study. In the first stage, simulation models were developed for three actual companies. Six different cell formation procedures were used to develop the cellular layouts and CRAFT was used to develop the functional layout. The following six variables were used to measure shop performance: average flow time, maximum flow time, average distance travelled by a batch, average work‐in‐process level, the maximum level of work‐in‐process, and the longest average queue. Factors observed in the first stage of the study that appear to make cellular manufacturing less beneficial than might otherwise be expected were found to be small batch sizes, a small number of different machines the parts require in their processing, short processing times per part, the existence of bottleneck machines (i.e. machines with insufficient capacity), and the absence of natural part families (i.e. sets of parts with similar processing requirements). In the second stage of this study, earlier assumptions associated with sequence‐dependent setup times and move time delays were relaxed. These two parameters were identified as important factors as well.
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The grouping of parts and machines for design of cellularmanufacturing systems is carried out by clustering analysis. Two majordrawbacks of some clustering algorithms have been…
Abstract
The grouping of parts and machines for design of cellular manufacturing systems is carried out by clustering analysis. Two major drawbacks of some clustering algorithms have been identified in handling bottleneck machines for forming machine cells. These drawbacks include solution inconsistency and possible misclustering which result in unnecessary bottleneck machines required. Presents a more robust clustering algorithm to overcome these drawbacks. The algorithm consists of four stages: selection of initial cluster centres; cluster‐seeking analysis; eliminating unnecessary bottleneck machines; and new parts assignments. The decision functions based on the formed machine cells are defined to assign new parts to the machine cells. The algorithm is capable of selecting an ideal set of initial cluster centres, and minimizing the number of bottleneck machines required for forming the desired number of machine cells. It can also provide alternative design of machine cells to accommodate the existing production environment.
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Bahareh Shafipour-Omrani, Alireza Rashidi Komijan, Seyed Jafar Sadjadi, Kaveh Khalili-Damghani and Vahidreza Ghezavati
One of the main advantages of the proposed model is that it is flexible to generate n-day pairings simultaneously. It means that, despite previous researches, one-day to n-day…
Abstract
Purpose
One of the main advantages of the proposed model is that it is flexible to generate n-day pairings simultaneously. It means that, despite previous researches, one-day to n-day pairings can be generated in a single model. The flexibility in generating parings causes that the proposed model leads to better solutions compared to existing models. Another advantage of the model is minimizing the risk of COVID-19 by limitation of daily flights as well as elapsed time minimization. As airports are among high risk places in COVID-19 pandemic, minimization of infection risk is considered in this model for the first time. Genetic algorithm is used as the solution approach, and its efficiency is compared to GAMS in small and medium-size problems.
Design/methodology/approach
One of the most complex issues in airlines is crew scheduling problem which is divided into two subproblems: crew pairing problem (CPP) and crew rostering problem (CRP). Generating crew pairings is a tremendous and exhausting task as millions of pairings may be generated for an airline. Moreover, crew cost has the largest share in total cost of airlines after fuel cost. As a result, crew scheduling with the aim of cost minimization is one of the most important issues in airlines. In this paper, a new bi-objective mixed integer programming model is proposed to generate pairings in such a way that deadhead cost, crew cost and the risk of COVID-19 are minimized.
Findings
The proposed model is applied for domestic flights of Iran Air airline. The results of the study indicate that genetic algorithm solutions have only 0.414 and 0.380 gap on average to optimum values of the first and the second objective functions, respectively. Due to the flexibility of the proposed model, it improves solutions resulted from existing models with fixed-duty pairings. Crew cost is decreased by 12.82, 24.72, 4.05 and 14.86% compared to one-duty to four-duty models. In detail, crew salary is improved by 12.85, 24.64, 4.07 and 14.91% and deadhead cost is decreased by 11.87, 26.98, 3.27, and 13.35% compared to one-duty to four-duty models, respectively.
Originality/value
The authors confirm that it is an original paper, has not been published elsewhere and is not currently under consideration of any other journal.
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Abdelhak Bentaleb, Saad Harous and Abdelhak Boubetra
Scalability is a fundamental problem in mobile ad hoc networks (MANETs), where network topology includes large number of nodes and demands a large number of packets in network…
Abstract
Purpose
Scalability is a fundamental problem in mobile ad hoc networks (MANETs), where network topology includes large number of nodes and demands a large number of packets in network that characterized by dynamic topologies, existence of bandwidth constrained, variable capacity links, energy constraint and nodes are highly prone to security threats. The key purpose of this paper is to overview the efficiency of the proposed clustering scheme for large-scale MANETs and its performance evaluation and especially in the case of a large number of nodes in the network.
Design/methodology/approach
Designing clustering schemes for MANETs, which are efficient and scalable in the case of large number of mobile nodes, has received a great attention in the last few years. It is widely used to improve resources management, hierarchical routing protocol design, quality of service, network performance parameters such as routing delay, bandwidth consumption, throughput and security. MANETs are characterized by limited wireless bandwidth, nodes mobility that results in a high frequency of failure regarding wireless links, energy constraint and nodes are highly prone to security threats. Due to all these features, the design of a scalable and efficient clustering scheme is quite complex. Many clustering schemes have been proposed to divide nodes into clusters, focusing on different metrics and purposes.
Findings
To the best of the author's knowledge, the different proposed clustering schemes are not scalable when the network size increases to a very large number. The paper presents the clustering scheme in detail and its performance evaluation by simulating MANETs composed of a large number of mobile nodes. The authors compare the performance of the scheme with a number of existing clustering schemes such as lowest-ID, highest degree, and weighted clustering algorithm, based on a number of performance metrics. Simulation results show that the scheme performs better than other clustering schemes, based on the performance metrics considered, for large-scale MANETs.
Originality/value
This paper addresses the problem of scalability in MANETs when there are high numbers of node in the network. The paper analyses the performance of the proposed clustering scheme for large-scale MANETs. The obtained results show that the different proposed clustering schemes do not allow the scalability when the network size is very large. The scheme supports scalability efficiently when the number of nodes increases in the network (more than 2,000 nodes).
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Abdelhakim Abdelhadi, Layth C. Alwan and Xiaohang Yue
The purpose of this paper is to investigate the impact on the cost of materials used to conduct preventive maintenance (PM). The main motivation for this work is to demonstrate…
Abstract
Purpose
The purpose of this paper is to investigate the impact on the cost of materials used to conduct preventive maintenance (PM). The main motivation for this work is to demonstrate how the group technology concept can be used to improve PM operations. In assessing improvement, the impact on the cost of materials used to conduct PM is investigated.
Design/methodology/approach
Based on the similarities between machines required maintenance and failure types, machines are grouped together into virtual cells using similarity coefficients. These cells, then, are used to come up with more efficient planning and scheduling procedures to conduct PM operations including inventory of parts and the execution of maintenance operations.
Findings
The results demonstrated that the proposed PM approach could provide a significant cost savings over a traditional PM program, especially in industries for which there is considerable material cost for the performance of PM.
Originality/value
The results presented in this paper are reliable, objective, and may be expanded by using the same concept of developing virtual cells to group other types manufacturing operations.
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Shabbir Talukder and Gerald M. Knapp
This paper covers the development of a heuristic method for grouping equipment into blocks for application of preventive maintenance overhauls within a series system, so as to…
Abstract
This paper covers the development of a heuristic method for grouping equipment into blocks for application of preventive maintenance overhauls within a series system, so as to minimize total maintenance‐related costs for the system. Previously, group technology (GT) concepts have not been applied to this problem, and this research investigated the applicability of such concepts to the block overhaul problem (specifically, the SLCA method was applied). Performance of the heuristic is analyzed with respect to runtime and solution quality.
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Yu‐Cheng Lee, Sheng‐Yen Huang and Chih‐Hung Tsai
The purpose of this paper is to establish a product family that can satisfy various market needs and share design elements.
Abstract
Purpose
The purpose of this paper is to establish a product family that can satisfy various market needs and share design elements.
Design/methodology/approach
The paper applies quality function development to understand the correlation between customer needs and product design. The priority sequence and correlation of these design elements will be determined using the interpretive structure model.
Findings
This approach will reduce repeated design effort and reduce unnecessary cost and time. The designer can simultaneously and efficiently meet various market and customer needs.
Originality/value
The company can open up more markets for greater profit and advantages. The paper uses “the market need and BIKE product redesign” as the example for the proposed approach.
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