This paper deals with two major issues for industries: the product design and the supply chain design. These problems are usually solved separately, but in recent years, approaches were proposed to tackle these two pr...
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This paper deals with two major issues for industries: the product design and the supply chain design. These problems are usually solved separately, but in recent years, approaches were proposed to tackle these two problems together. In this paper, we investigate more precisely the links between the standardization of products or components, and the design of the supply chain. First, we show on a little example that there is a great interest to consider simultaneously these two decisions, and that solving these interdependent problems separately could result in a suboptimal, or even a bad, decision. Then, on a simplified problem issued from an industrial case study, we outline the impact of standardization choices on the structure of the supply chain and the gain that can be obtained from solving the problem as a unique compound optimization model. To illustrate the solutions of the problem, we propose graphics in order to visualize, in function of quantities and/or transportation costs, the hest decision for the product standardization and for the supply chain design. Graphics also permit to anticipate the impacts of a variation of either quantities or transportation costs, from a specific situation. Such graphics they could be used in a decision aid tool to help companies in their choices. Finally, we show that costs and supply chain structure are highly impacted. (C) 2010 Elsevier B.V. All rights reserved.
In the automotive industry, a manufacturer must perform several hundreds of tests on prototypes of a vehicle before starting its mass production. Tests must be allocated to suitable prototypes and ordered to satisfy t...
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In the automotive industry, a manufacturer must perform several hundreds of tests on prototypes of a vehicle before starting its mass production. Tests must be allocated to suitable prototypes and ordered to satisfy temporal constraints and various kinds of test dependencies. The manufacturer aims to minimize the number of prototypes required. We present improvements of constraint programming (CP) and hybrid approaches to effectively solve random instances from an existing benchmark. CP mostly achieves better solutions than the previous heuristic technique and genetic algorithm. We also provide customized search schemes to enhance the performance of general search algorithms. The hybrid approach applies mixed integer linear programming (MILP) to solve the planning part and CP to find the complete schedule. We consider several logical principles such that the MILP model can accurately estimate the prototype demand, while its size particularly for large instances does not exceed memory capacity. Moreover, the robustness is alleviated when we allow CP to partially change the allocation obtained from the MILP model. The hybrid method can contribute to optimal solutions in some instances.
This paper addresses the midterm preventive maintenance outage scheduling problem of thermal generating units which is becoming increasingly important due to the aging of power generation fleet. In this context, a nov...
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This paper addresses the midterm preventive maintenance outage scheduling problem of thermal generating units which is becoming increasingly important due to the aging of power generation fleet. In this context, a novel midterm preventive maintenance outage scheduler is proposed based on decision tree and mixedintegerlinear formation which explicitly considers the thermal units aging momentum in terms of failure rate. This allows the system operators to determine the thermal units' maintenance outage window based on the cost/benefit analysis of preventive maintenance tasks while optimizing the time interval between consecutive maintenance tasks. Additionally, the division of the year-long midterm horizon into several time blocks in the proposed model provides a unique opportunity for parallel processing and computational saving. The proposed approach is tested on the IEEE Reliability Test System (IEEE-RTS). The results presented reveal the accuracy and efficiency of the proposed approach.
Crane is widely used to move a heavy object from one place to another not only in manufacturing industry but also service industry. As an important resource in the train oilcan repairing, crane scheduling affects dire...
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Crane is widely used to move a heavy object from one place to another not only in manufacturing industry but also service industry. As an important resource in the train oilcan repairing, crane scheduling affects directly the productivity of the systems. In this paper, we study cyclic single crane scheduling problem with two parallel train oilcan repairing lines, where jobs are loaded into the line at one end and unloaded at the other end. The processing time at each workstation must be within a given range. There is no buffer between these stations. A crane is used to move jobs between the workstations in two parallel lines. The objective is to schedule the moves to minimize the production cycle. We proposed a time way diagram for two parallel lines and developed a mixed integer linear programming model. Then we extended the model to the scheduling problem with multi-station to eliminate the bottleneck in lines. Examples are given to demonstrate the effectiveness of the model. (C) 2011 Elsevier Ltd. All rights reserved.
A mixed integer linear programming (MILP) model is proposed in this paper that targets the optimal production scheduling in a single yogurt production line. The model takes into account all the standard constraints en...
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A mixed integer linear programming (MILP) model is proposed in this paper that targets the optimal production scheduling in a single yogurt production line. The model takes into account all the standard constraints encountered in production scheduling (material balances, inventory limitations, machinery capacity, labor shifts and manpower restrictions). Furthermore, it considers special features that characterize yogurt production, which are limitations in production sequencing mainly due to different fat contents and flavors of various products and sequence-dependent setup times and costs. The objective function that is minimized considers all major sources of variable cost that depend on the production schedule, i.e. changeover cost, inventory cost and labor cost. The model is applied to a yogurt production line of a major dairy industry and the results are presented and discussed. (c) 2006 Elsevier Ltd. All rights reserved.
This paper examines a preprocessing technique for a mixed integer linear programming (MILP) formulation of the Transmission-Constrained Unit Commitment problem (TC-UC). Incorporating transmission constraints into the ...
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This paper examines a preprocessing technique for a mixed integer linear programming (MILP) formulation of the Transmission-Constrained Unit Commitment problem (TC-UC). Incorporating transmission constraints into the Unit Commitment problem can significantly increase the size and difficulty of the problem. By examining the structure of the transmission network, variables that have no impact on the quality of the overall solution can be identified and removed. This preprocessing can reduce the time needed to solve the linearprogramming relaxation of the MILP, and as a result, the MILP itself. Illinois's transmission network was used to test the benefit of the proposed technique. Preprocessing was able to remove 30% of the buses in the transmission network. This reduction led to a significant decrease in the time needed to solve a 24 h TC-UC problem. An added benefit of the preprocessing is that symmetry can be introduced into the problem. Identifying this symmetry and exploiting it can improve overall solution times even further. (C) 2012 Published by Elsevier Ltd.
Increasingly, tourists are planning trips by themselves using the vast amount of information available on the Web. However, they still expect and want trip plan advisory services. In this paper, we study the tour plan...
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Increasingly, tourists are planning trips by themselves using the vast amount of information available on the Web. However, they still expect and want trip plan advisory services. In this paper, we study the tour planning problem in which our goal is to design a tour trip with the most desirable sites, subject to various budget and time constraints. We first establish a framework for this problem, and then formulate it as a mixed integer linear programming problem. However, except when the size of the problem is small, say, with less than 20-30 sites, it is computationally infeasible to solve the mixed-integerlinearprogramming problem. Therefore, we propose a heuristic method based on local search ideas. The method is efficient and provides good approximation solutions. Numerical results are provided to validate the method. We also apply our method to the team orienteering problem, a special case of the tour planning problem which has been considered in the literature, and compare our method with other existing methods. Our numerical results show that our method produces very good approximation solutions with relatively small computational efforts comparing with other existing methods.
This letter describes the development of a prescreening method to select a few switchable line candidates, effectively reducing the number of integer variables in transmission switching problems. The numerical studies...
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This letter describes the development of a prescreening method to select a few switchable line candidates, effectively reducing the number of integer variables in transmission switching problems. The numerical studies show that the proposed prescreening strategies accelerate identification of high-quality feasible solutions in optimal transmission switching problems.
Sensor networks with sensing, data processing and communicating capabilities have a broad spectrum of applications. Based on application requirements, various network configurations can be designed. One such robust co...
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Sensor networks with sensing, data processing and communicating capabilities have a broad spectrum of applications. Based on application requirements, various network configurations can be designed. One such robust configuration is a hybrid wired-cum-wireless sensor network that is composed of a wireless sensor network and a wired backbone which are inter-connected via access points. In this paper, the joint problem of configuring a hybrid wired-cum-wireless sensor network, position-constrained cluster head and access point placement is proposed. The design considers real wireless communication limitations, optimum locations of access points and cluster heads, and hybrid transmission structure of the network with the objective of minimising the network configuration cost. The problem is formulated as a mixed integer linear programming and solved using 'CPLEX'. Numerical results show that hybrid configuration is more cost effective than the wireless networks and leads to a longer lifetime at the expense of a more complex design.
This paper presents extensions of the IP model where part-machine assignment and cell formation are addressed simultaneously and part machine utilisation is considered. More specifically, an integration of inter-cell ...
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This paper presents extensions of the IP model where part-machine assignment and cell formation are addressed simultaneously and part machine utilisation is considered. More specifically, an integration of inter-cell movements of parts and machine set-up costs within the objective function, and also a combination of machine set-up costs associated with parts revisiting a cell when the part machine operation sequence is taken into account are examined and an enhanced model is formulated. Based upon this model's requirements, an initial three stage approach is proposed and a tabu search iterative procedure is designed to produce a solution. The initial approach consists of the allocation of machines to cells, the allocation of parts to machines in cells and the evaluation of the objective function's value. Special care has been taken when allocating parts to machine cells as part machine operation sequence is preserved making the system more complex but more realistic. The proposed tabu search algorithm integrates short term memory and an overall iterative searching strategy where two move types, single and exchange, are considered. Computational experiments verified both the algorithm's robustness where promising solutions in reasonably short computational effort are produced and also the algorithm's effectiveness for large scale data sets.
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