The Experts below are selected from a list of 142181298 Experts worldwide ranked by ideXlab platform
Matthias Thurer - One of the best experts on this subject based on the ideXlab platform.
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simple subcontracting rules for make to order shops with limited subcontractor capacity an assessment by simulation
Production Planning & Control, 2015Co-Authors: Matthias Thurer, Mark Stevenson, Ting QuAbstract:Companies that produce a high variety of customised products often suffer from large fluctuations in demand. Subcontracting can be an important means of overcoming resulting capacity shortages during high demand periods. A set of effective subcontracting rules, for determining which jobs to subcontract and which to produce internally, has recently been presented in the literature for this type of company. But evaluations of these rules have assumed subcontractor capacity is infinite. This study examines the impact of limited subcontractor capacity on the performance of the three best-performing subcontracting rules for Make-to-Order companies using a simulation model of an assembly job shop. Limiting subcontractor capacity inhibits the ability of a subcontracting rule to protect the internal shop from surges in demand, which negatively affects performance. However, significant performance differences between the rules evaluated are maintained, which underlines the importance of choosing the right subcontr...
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the design of simple subcontracting rules for make to order shops an assessment by simulation
European Journal of Operational Research, 2014Co-Authors: Matthias Thurer, Ting Qu, Mark Stevenson, Moacir Godinho FilhoAbstract:Subcontracting can be an important means of overcoming capacity shortages and of workload balancing, especially in Make-to-Order companies characterized by high variety, high demand variation and a job shop configuration. But there is a lack of simple, yet powerful subcontracting rules suitable for such contexts. The few existing rules were developed for single work center shops and neglect the actual subcontracting lead time, meaning some subcontracted jobs are destined to become tardy. This study uses Workload Control theory on matching required and available capacity over time to propose four new rules that address these shortcomings. The new rules are compared against four existing rules using an assembly job shop simulation model where the final, assembled product consists of several sub-assemblies that either flow through an internal job shop or are subcontracted. The best new rules stabilize the direct load queuing in front of a work center and significantly improve performance compared to the existing rules. For example, when the workload exceeds capacity by 10%, a 50% reduction in percentage tardy can be achieved. By examining how the workload behaves over time, we reveal that improvements come from selectively subcontracting the sub-assemblies that would otherwise cause overloads, thereby cutting off peaks in the workload.
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lean control for make to order companies integrating customer enquiry management and order release
Production and Operations Management, 2014Co-Authors: Matthias Thurer, Mark Stevenson, Cristovao Silva, Martin Land, Lawrence D Fredendall, Steven A MelnykAbstract:A lead time that is short, predictable, and reliable is an increasingly important criterion in supplier selection. Although many companies may achieve this through lean implementation, high-variety manufacturers, for example, small and medium-sized Make-to-Order companies, have found that lean's planning and control techniques do not apply. This article outlines a planning and control concept known as workload control (WLC) that integrates customer enquiry management, including a due-date setting rule, with order release control. Simulation is then used to assess its impact on shop performance. Results demonstrate that an integrated WLC concept can reduce the percentage of tardy jobs—so short lead times can be realistically quoted—while also reducing and stabilizing workloads. WLC can level demand and production over time when work is not standardized and it is not possible to synchronize flows on the shop floor. Results are shown to be robust to changes in routing characteristics, the mix of orders with due dates specified by the customer and proposed internally, and the strike rate (or order-winning probability). Hence, an integrated approach to WLC represents an important step toward achieving lean in Make-to-Order companies.
T H Jensen - One of the best experts on this subject based on the ideXlab platform.
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stabilization of the resistive wall mode using a fake rotating shell
Physics of Plasmas, 1996Co-Authors: Richard Fitzpatrick, T H JensenAbstract:Tokamak plasma performance can, in theory, be greatly improved if the so‐called ‘‘resistive wall mode’’ is stabilized. This can be achieved by spinning the plasma rapidly, but such a scheme would be difficult to implement in a reactor setting. A more promising approach is to apply external feedback in order to make a resistive shell placed around the plasma act like a perfect conductor. A scheme is outlined by which a network of feedback controlled conductors surrounding the plasma can be made to act like a rotating shell. This fake rotating shell combined with a stationary conventional shell (e.g., the vacuum vessel) can completely stabilize the resistive wall mode. The gain, bandwidth, current, and power requirements of the feedback amplifiers are extremely modest. A previously proposed stabilization scheme (the intelligent shell) is also investigated, and is compared with the fake rotating shell concept. The main disadvantage of the former scheme is that it requires a high gain.
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stabilization of the resistive wall mode using a fake rotating shell
Other Information: PBD: Nov 1995, 1995Co-Authors: Richard Fitzpatrick, T H JensenAbstract:Tokamak plasma performance can, in theory, be greatly improved if the so called resistive wall mode is stabilized. This can be achieved by spinning the plasma rapidly, but such a scheme is not reactor relevant. A more promising approach is to apply external feedback in order to make a resistive shell placed around the plasma act like a perfect conductor. A scheme is outlined by which a network of feedback controlled conductors surrounding the plasma can be made to act like a rotating shell. This fake rotating shell combined with a stationary conventional shell (e.g. the vacuum vessel) can completely stabilize the resistive wall mode. The gain, bandwidth, current, and power requirements of the feedback amplifiers are extremely modest. A previously proposed stabilization scheme (the intelligent shell) is also investigated, and is compared with the fake rotating shell concept. The main disadvantage of the former scheme is that it requires a high gain.
Masoud Rabbani - One of the best experts on this subject based on the ideXlab platform.
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a multi objective mixed model assembly line sequencing problem in order to minimize total costs in a make to order environment considering order priority
Journal of Manufacturing Systems, 2013Co-Authors: Neda Manavizadeh, Masoud Rabbani, Leila Tavakoli, Fariborz JolaiAbstract:Abstract Nowadays, mixed-model assembly line is used increasingly as a result of customers’ demand diversification. An important problem in this field is determining the sequence of products for entering the line. Before determining the best sequence of products, a new procedure is introduced to choose important orders for entering the shop floor. Thus the orders are sorted using an analytical hierarchy process (AHP) approach based on three criteria: critical ratio of each order (CR o ), Significance degree of customer and innovation in a product, while the last one is presented for the first time. In this research, six objective functions are presented: minimizing total utility work cost, total setup cost and total production rate variation cost are the objectives which were presented previously, another objective is minimizing total idle cost, meanwhile two other new objectives regarding minimizing total operator error cost and total tardiness cost are presented for the first time. The total tardiness cost tries to choose a sequence of products that minimizes the tardiness cost for customers with high priority. First, to check the feasibility of the model, GAMS software is used. In this case, GAMS software could not search all of the solution space, so it is tried in two stages and because this problem is NP-hard, particle swarm optimization (PSO) and simulated annealing (SA) algorithms are used. For small sized problems, to compare exact method with proposed algorithms, the problem must be solved using meta-heuristic algorithms in two stages as GAMS software, whereas for large sized problems, the problem can be solved in two ways (one stage and two stages) by using proposed algorithms; the computational results and pairwise comparisons (based on sign test) show GAMS is a proper software to solve small sized problems, whereas for a large sized problem the objective function is better when solved in one stage than two stages; therefore it is proposed to solve the problem in one stage for large sized problems. Also PSO algorithm is better than SA algorithm based on objective function and pairwise comparisons.
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mixed model assembly line balancing in the make to order and stochastic environment using multi objective evolutionary algorithms
Expert Systems With Applications, 2012Co-Authors: Neda Manavizadeh, Masoud Rabbani, Davoud Moshtaghi, Fariborz JolaiAbstract:The present study introduces a multi-objective genetic algorithm (MOGA) to solve a mixed-model assembly line problem (MMALBP), considering cycle time (CT) and the number of stations simultaneously. A mixed-model assembly line is one capable of producing different types of products to respond to different market demands, while minimizing on capital costs of designing multiple assembly lines. In this research, according to the stochastic environment of production systems, a mixed-model assembly line has been put forth in a Make-to-Order (MTO) environment. Furthermore, a MOGA approach is presented to solve the corresponding balancing problem and the decision maker is provided with the subsequent answers to pick one based on the specific situation. Finally, a comparison is carried out between six multi-objective evolutionary algorithms (MOEA) so as to determine the best method to solve this specific problem.
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order partitioning and order penetration point location in hybrid make to stock make to order production contexts
Computers & Industrial Engineering, 2011Co-Authors: Hamed Rafiei, Masoud RabbaniAbstract:Hybrid Make-To-Stock (MTS)/Make-to-Order (MTO) is one of the product delivery strategies which have recently attracted practitioners' and academicians' interest to meet requirements of today competitive environment. Two important decisions involved in hybrid MTS/MTO context are order partitioning and determining Order Penetration Point (OPP) location. In this paper, a model is developed to first decide on which product is manufactured upon MTS, which one upon MTO and which one upon hybrid strategy. Then, a fuzzy analytic network process (ANP) is utilized to locate the OPP for the products which are decided to be manufactured upon hybrid strategy. Finally, a real industrial case study is reported to show applicability of the proposed model.
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Hierarchical production planning and scheduling in Make-to-Order environments: reaching short and reliable delivery dates
International Journal of Production Research, 2009Co-Authors: Mahmood Ebadian, Masoud Rabbani, Seyed Ali Torabi, Fariborz JolaiAbstract:This study proposes a novel hierarchical production planning (HPP) structure for Make-to-Order (MTO) companies. The proposed HPP structure contains three decision making levels: (1) the order entry level, (2) the order release level and (3) the order sequencing/dispatching level. The objective is to manage the delivery dates of arriving orders in order to reach short and reliable delivery dates using appropriate decision making techniques at each level. At the first level, the main decision concerns the acceptance or rejection of new arriving orders subject to some relevant limitations (e.g. capacity constraint). At this level, an extended version of our previously proposed model (Ebadian, M., et al., 2007. A new decision making structure for the order entry stage in Make-to-Order environments. International Journal of Production Economics, 111, 351–367.) is applied. Besides rejecting some of the low priority orders, determination of delivery dates and prices for the non-rejected orders constitute the oth...
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a comprehensive decision making structure for partitioning of make to order make to stock and hybrid products
Soft Computing, 2009Co-Authors: Nima Zaerpour, Masoud Rabbani, Amir Hossein Gharehgozli, Reza TavakkolimoghaddamAbstract:Manufacturing systems produce their products by making use of three main strategies: Make-to-Order, make-to-stock and hybrid (combination of MTO and MTS strategies) systems. Hence, several products must be considered and partitioned in terms of many different conflicting criteria, leading to a large set of subjective or ambiguous data. Thus, an effective evaluation approach is essential to improve decision quality. In this paper a comprehensive decision, making structure is proposed to choose the proper strategy for producing the products. It consists of a novel hybrid methodology, which combines analytical hierarchy process (AHP) and technique for order performance by similarity to ideal solution (TOPSIS) for partitioning of products. In this study, the rating of each alternative regarding different criteria (throughout the TOPSIS technique) is described by means of linguistic variables. Furthermore, fuzzy AHP methodology is applied to determine the weights of evaluation criteria. At the end, the effectiveness of the proposed model is demonstrated through a case study.
Fariborz Jolai - One of the best experts on this subject based on the ideXlab platform.
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a multi objective mixed model assembly line sequencing problem in order to minimize total costs in a make to order environment considering order priority
Journal of Manufacturing Systems, 2013Co-Authors: Neda Manavizadeh, Masoud Rabbani, Leila Tavakoli, Fariborz JolaiAbstract:Abstract Nowadays, mixed-model assembly line is used increasingly as a result of customers’ demand diversification. An important problem in this field is determining the sequence of products for entering the line. Before determining the best sequence of products, a new procedure is introduced to choose important orders for entering the shop floor. Thus the orders are sorted using an analytical hierarchy process (AHP) approach based on three criteria: critical ratio of each order (CR o ), Significance degree of customer and innovation in a product, while the last one is presented for the first time. In this research, six objective functions are presented: minimizing total utility work cost, total setup cost and total production rate variation cost are the objectives which were presented previously, another objective is minimizing total idle cost, meanwhile two other new objectives regarding minimizing total operator error cost and total tardiness cost are presented for the first time. The total tardiness cost tries to choose a sequence of products that minimizes the tardiness cost for customers with high priority. First, to check the feasibility of the model, GAMS software is used. In this case, GAMS software could not search all of the solution space, so it is tried in two stages and because this problem is NP-hard, particle swarm optimization (PSO) and simulated annealing (SA) algorithms are used. For small sized problems, to compare exact method with proposed algorithms, the problem must be solved using meta-heuristic algorithms in two stages as GAMS software, whereas for large sized problems, the problem can be solved in two ways (one stage and two stages) by using proposed algorithms; the computational results and pairwise comparisons (based on sign test) show GAMS is a proper software to solve small sized problems, whereas for a large sized problem the objective function is better when solved in one stage than two stages; therefore it is proposed to solve the problem in one stage for large sized problems. Also PSO algorithm is better than SA algorithm based on objective function and pairwise comparisons.
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mixed model assembly line balancing in the make to order and stochastic environment using multi objective evolutionary algorithms
Expert Systems With Applications, 2012Co-Authors: Neda Manavizadeh, Masoud Rabbani, Davoud Moshtaghi, Fariborz JolaiAbstract:The present study introduces a multi-objective genetic algorithm (MOGA) to solve a mixed-model assembly line problem (MMALBP), considering cycle time (CT) and the number of stations simultaneously. A mixed-model assembly line is one capable of producing different types of products to respond to different market demands, while minimizing on capital costs of designing multiple assembly lines. In this research, according to the stochastic environment of production systems, a mixed-model assembly line has been put forth in a Make-to-Order (MTO) environment. Furthermore, a MOGA approach is presented to solve the corresponding balancing problem and the decision maker is provided with the subsequent answers to pick one based on the specific situation. Finally, a comparison is carried out between six multi-objective evolutionary algorithms (MOEA) so as to determine the best method to solve this specific problem.
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Hierarchical production planning and scheduling in Make-to-Order environments: reaching short and reliable delivery dates
International Journal of Production Research, 2009Co-Authors: Mahmood Ebadian, Masoud Rabbani, Seyed Ali Torabi, Fariborz JolaiAbstract:This study proposes a novel hierarchical production planning (HPP) structure for Make-to-Order (MTO) companies. The proposed HPP structure contains three decision making levels: (1) the order entry level, (2) the order release level and (3) the order sequencing/dispatching level. The objective is to manage the delivery dates of arriving orders in order to reach short and reliable delivery dates using appropriate decision making techniques at each level. At the first level, the main decision concerns the acceptance or rejection of new arriving orders subject to some relevant limitations (e.g. capacity constraint). At this level, an extended version of our previously proposed model (Ebadian, M., et al., 2007. A new decision making structure for the order entry stage in Make-to-Order environments. International Journal of Production Economics, 111, 351–367.) is applied. Besides rejecting some of the low priority orders, determination of delivery dates and prices for the non-rejected orders constitute the oth...
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a new decision making structure for the order entry stage in make to order environments
International Journal of Production Economics, 2008Co-Authors: Mahmood Ebadian, Masoud Rabbani, Fariborz Jolai, S A Torabi, Reza TavakkolimoghaddamAbstract:Abstract In this paper, we propose a new comprehensive decision-making structure for the order entry stage in Make-to-Order (MTO) environments. The aim of the proposed structure is to manage the arriving orders so that the MTO system just proceeds to produce those arriving orders which are feasible and profitable for the system. The appropriate decisions on the arriving orders are taken based on two criteria including price and delivery time. The arriving orders have either fixed or negotiable delivery times. The proposed structure has five major steps. At the two first steps, the new arriving orders either are rejected or appropriate decisions to meet their delivery time are made. At the next step, the optimal prices along with delivery times (if negotiable) of non-rejected orders are determined by a mixed-integer programming model. In the case of the final approval by the customers at the fourth step, another mixed-integer programming model is launched to select a set of suppliers and subcontractors that are able to provide required raw material and workload of the new the accepted orders. Moreover, numerical experiments are presented and a simple example is illustrated to show the applicability of the proposed mathematical models.
Mark Stevenson - One of the best experts on this subject based on the ideXlab platform.
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simple subcontracting rules for make to order shops with limited subcontractor capacity an assessment by simulation
Production Planning & Control, 2015Co-Authors: Matthias Thurer, Mark Stevenson, Ting QuAbstract:Companies that produce a high variety of customised products often suffer from large fluctuations in demand. Subcontracting can be an important means of overcoming resulting capacity shortages during high demand periods. A set of effective subcontracting rules, for determining which jobs to subcontract and which to produce internally, has recently been presented in the literature for this type of company. But evaluations of these rules have assumed subcontractor capacity is infinite. This study examines the impact of limited subcontractor capacity on the performance of the three best-performing subcontracting rules for Make-to-Order companies using a simulation model of an assembly job shop. Limiting subcontractor capacity inhibits the ability of a subcontracting rule to protect the internal shop from surges in demand, which negatively affects performance. However, significant performance differences between the rules evaluated are maintained, which underlines the importance of choosing the right subcontr...
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the design of simple subcontracting rules for make to order shops an assessment by simulation
European Journal of Operational Research, 2014Co-Authors: Matthias Thurer, Ting Qu, Mark Stevenson, Moacir Godinho FilhoAbstract:Subcontracting can be an important means of overcoming capacity shortages and of workload balancing, especially in Make-to-Order companies characterized by high variety, high demand variation and a job shop configuration. But there is a lack of simple, yet powerful subcontracting rules suitable for such contexts. The few existing rules were developed for single work center shops and neglect the actual subcontracting lead time, meaning some subcontracted jobs are destined to become tardy. This study uses Workload Control theory on matching required and available capacity over time to propose four new rules that address these shortcomings. The new rules are compared against four existing rules using an assembly job shop simulation model where the final, assembled product consists of several sub-assemblies that either flow through an internal job shop or are subcontracted. The best new rules stabilize the direct load queuing in front of a work center and significantly improve performance compared to the existing rules. For example, when the workload exceeds capacity by 10%, a 50% reduction in percentage tardy can be achieved. By examining how the workload behaves over time, we reveal that improvements come from selectively subcontracting the sub-assemblies that would otherwise cause overloads, thereby cutting off peaks in the workload.
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lean control for make to order companies integrating customer enquiry management and order release
Production and Operations Management, 2014Co-Authors: Matthias Thurer, Mark Stevenson, Cristovao Silva, Martin Land, Lawrence D Fredendall, Steven A MelnykAbstract:A lead time that is short, predictable, and reliable is an increasingly important criterion in supplier selection. Although many companies may achieve this through lean implementation, high-variety manufacturers, for example, small and medium-sized Make-to-Order companies, have found that lean's planning and control techniques do not apply. This article outlines a planning and control concept known as workload control (WLC) that integrates customer enquiry management, including a due-date setting rule, with order release control. Simulation is then used to assess its impact on shop performance. Results demonstrate that an integrated WLC concept can reduce the percentage of tardy jobs—so short lead times can be realistically quoted—while also reducing and stabilizing workloads. WLC can level demand and production over time when work is not standardized and it is not possible to synchronize flows on the shop floor. Results are shown to be robust to changes in routing characteristics, the mix of orders with due dates specified by the customer and proposed internally, and the strike rate (or order-winning probability). Hence, an integrated approach to WLC represents an important step toward achieving lean in Make-to-Order companies.
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enterprise resource planning systems an assessment of applicability to make to order companies
Computers in Industry, 2012Co-Authors: Bulut Aslan, Mark Stevenson, L HendryAbstract:Many vendors of Enterprise Resource Planning (ERP) systems claim their products are widely applicable-configurable to meet the needs of any business, whatever the product or service offering. But Make-to-Order (MTO) companies, which produce high-variety and bespoke products, have particularly challenging decision support requirements and it remains unclear whether ERP systems can meet their needs. This paper takes a contingency-based perspective of ERP adoption, assessing the fit or alignment between ERP functionality and a MTO production strategy. MTO features considered include: decision support requirements at critical Production Planning and Control (PPC) stages, idiosyncratic market-related features, typical company size and supply chain positioning, and shop floor configuration. It finds a substantial gap or misalignment between ERP functionality and MTO requirements; for example, between decision support provided by ERP systems and the decision support required by MTO companies at the customer enquiry and design & engineering stages. A research agenda for improving alignment is outlined, with implications for academics, MTO managers and ERP software developers. This includes: developing decision support tools that reflect the customer enquiry management activities of MTO companies; embedding MTO-relevant PPC concepts within ERP systems; and, conducting an in-depth empirical study into applications of ERP systems in MTO companies, assessing their performance impact.
