Several factors affect the flexibility and the complexity of the project selection and the contractor selection problems. Project portfolio managers are expected to select the best combination of projects and contract...
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Several factors affect the flexibility and the complexity of the project selection and the contractor selection problems. Project portfolio managers are expected to select the best combination of projects and contractors considering multiple conflicting objectives in a multi-period planning horizon. In this paper, we propose an integrated project portfolio optimization and contractor selection problem. The problem is modeled through a multi-objectivemixedinteger Linear programming (MILP) model. Three solution approaches including Goal programming (GP), Fuzzy Goal programming (FGP), and fuzzy goal programming considering a fuzzy preference relationship are proposed. All solution approaches have been applied to a real case. The computational results show the out performance of FGP considering fuzzy relations. The time complexity of the proposed models in the sense of the relation of CPU time and the number constraints and variables of the models were discussed.
multi-objectivemixedinteger Programs (MOMIPs) have a wide variety of applica- tion areas in real-life decision making problems. Since the number of nondominated points grows exponentially with the problem size and f...
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multi-objectivemixedinteger Programs (MOMIPs) have a wide variety of applica- tion areas in real-life decision making problems. Since the number of nondominated points grows exponentially with the problem size and finding all nondominated points is typically hard and impractical in MOMIPs, generating a subset having "desired properties" rises as an important problem. Motivated with this fact, we observe that the distribution of nondominated points may be critical in defining the desired prop- erties of the representative subset to be generated. Based on our observations, we develop algorithms to generate a small subset of nondominated points that represents the nondominated set with a prespecified coverage gap. Our computational experi- ments show that our algorithms outperform the existing algorithms in terms of the cardinality of the generated representative set and the solution time.
This work addresses the correction and improvement of Mavrotas and Diakoulaki's branch and bound algorithm for mixed 0-1 multiple objective linear programs. We first elaborate the issues encountered by the origina...
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This work addresses the correction and improvement of Mavrotas and Diakoulaki's branch and bound algorithm for mixed 0-1 multiple objective linear programs. We first elaborate the issues encountered by the original algorithm and then propose a corrected version for the biobjective case using an exact representation of the nondominated set associated with an appropriate update procedure. Then we introduce several improvements using better bound sets and branching strategies and finally present some experiments to study the effectiveness of our propositions. (C) 2012 Elsevier Ltd. All rights reserved.
The vibrant subject of blood banking and blood distribution is addressed where lateral resupply of blood products is allowed. In this paper, we studied a blood supply chain network design consisting of four convention...
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The vibrant subject of blood banking and blood distribution is addressed where lateral resupply of blood products is allowed. In this paper, we studied a blood supply chain network design consisting of four conventional levels each of which corresponding to one entity in the real world: donors, blood collection facilities, blood centers, and hospitals. The blood supply chain network considered two important properties: ABO-Rh factors and shelf lives of blood products. Moreover, an integrated inventory system for sharing hospitals' inventory levels is considered to investigate the two performance indicators of the network in terms of cross-matching and outdated units. This type of inventory system is known as "Lateral Resupply" permitting a hospital to satisfy its demand by the other hospitals' inventories in the absence of the required product at the blood center and its excess in any hospital. The proposed mixed-integer mathematical programming model entails three objectives referring to the three underlying concepts of sustainability, additionally, to cope with uncertainties and multiobjectiveness, a scenario-based optimization approach and revised multi-choice goal programming technique were employed, respectively. Finally, the results confirmed that the lateral resupply virtue improved the performance indicators.
A multi-objective mixed integer programming model of cellular manufacturing system (CMS) design is presented which minimizes the total system costs and maximizes the machine reliabilities along the selected processing...
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A multi-objective mixed integer programming model of cellular manufacturing system (CMS) design is presented which minimizes the total system costs and maximizes the machine reliabilities along the selected processing routes. A part may be processed under different process plans, each prescribing a sequence of operations to be performed at various machines in a serial configuration. Thus, each process route is associated with a level of reliability corresponding to the machines in the selected process plan. The CMS design problem consists of assigning the machines to cells, and selecting, for each part type, the process route with the highest overall system reliability while minimizing the total costs of manufacturing operations, machine under-utilization, and inter-cell material handling. The proposed approach provides a flexible routing which ensures high overall performance of the CMS by minimizing the impact of machine failure through the provision of alternative process routes in case of any machine failure. The paper also proposes a performance evaluation criterion in terms of system availability for the parts and process plan assignments. Numerical examples are provided to demonstrate the applicability of the model. (c) 2006 Elsevier B.V. All rights reserved.
Businesses are increasingly subject to disruptions. It is almost impossible to predict their nature, time and extent. Therefore, organizations need a proactive approach equipped with a decision support framework to pr...
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Businesses are increasingly subject to disruptions. It is almost impossible to predict their nature, time and extent. Therefore, organizations need a proactive approach equipped with a decision support framework to protect themselves against the outcomes of disruptive events. In this paper, a novel framework is proposed for integrated business continuity and disaster recovery planning for efficient and effective resuming and recovering of critical operations after being disrupted. The proposed model addresses decision problems at all strategic, tactical and operational levels. At the strategic level, the context of the organization is first explored and the main features of the organizational resilience are recognized. Then, a new multi-objectivemixedinteger linear programming model is formulated to allocate internal and external resources to both resuming and recovery plans simultaneously. The model aims to control the loss of resilience by maximizing recovery point and minimizing recovery time objectives. Finally, at the operational level, hypothetical disruptive events are examined to evaluate the applicability of the plans. We also develop a novel interactive augmented epsilon-constraint method to find the final preferred compromise solution. The proposed model and solution method are finally validated through a real case study. (C) 2014 Elsevier B.V. All rights reserved.
Oversaturation has become a severe problem for urban intersections, especially the bottleneck intersections that cause queue spillover and network gridlock. Further improvement of oversaturated arterial traffic using ...
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Oversaturation has become a severe problem for urban intersections, especially the bottleneck intersections that cause queue spillover and network gridlock. Further improvement of oversaturated arterial traffic using traditional mitigation strategies, which aim to improve intersection capacity by merely adjusting signal control parameters, becomes challenging since exiting strategies may (or already) have reached their "theoretical" limits of optimum. Under such circumstance, several novel unconventional intersection designs, including the well-recognized continuous flow intersection (CFI) design, are originated to improve the capacity at bottleneck intersections. However, the requirement of installing extra sub-intersections in a CFI design would increase vehicular stops and, more critically, is unacceptable in tight urban areas with closed spaced intersections. To address these issues, this research proposes a simplified continuous flow intersection (called CFI-Lite) design that is ideal for arterials with short links. It benefits from the CFI concept to enable simultaneous move of left-turn and through traffic at bottleneck intersections, but does not need installation of sub-intersections. Instead, the upstream intersection is utilized to allocate left-turn traffic to the displaced left-turn lane. It is found that the CFI-Lite design performs superiorly to the conventional design and regular CFI design in terms of bottleneck capacity. Pareto capacity improvement for every traffic stream in an arterial system can be achieved under effortless conditions. Case study using data collected at Foothill Blvd in Los Angeles, CA, shows that the new design is beneficial in more than 90% of the 408 studied cycles. The testing also shows that the average improvements of green bandwidths for the synchronized phases are significant. (C) 2015 Elsevier Ltd. All rights reserved.
Railway capacity has been extensively investigated for the purpose of utilizing rail infrastructure in a possible efficient ***,the estimation of high speed rail(HSR),which is different from common railways in many as...
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Railway capacity has been extensively investigated for the purpose of utilizing rail infrastructure in a possible efficient ***,the estimation of high speed rail(HSR),which is different from common railways in many aspects,is still a challenge work needed to be ***,this work focuses on the capacity estimation of HSR *** objectives and constraints are developed for the HSR with the consideration of passenger service level and buffer time uncertainty,and a two-stage optimization model is *** first stage determines the optimal number of trains in terms of the passenger origin–destination demand,and the second stage is a multi-objective mixed integer programming(MO-MIP)aiming to estimate the optimal capacity *** branch-and-bound algorithm is extended and applied to the proposed model,and a case study is performed to Beijing–Shanghai HSR *** optimal solution is obtained,and the sensitivity of the two objectives is analyzed.
Purpose - The purpose of this paper is to understand the consequence of the use of mixed Weibull distribution in the cell formation problem. In reliability theory, a mixed distribution is used for more than one hazard...
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Purpose - The purpose of this paper is to understand the consequence of the use of mixed Weibull distribution in the cell formation problem. In reliability theory, a mixed distribution is used for more than one hazard cause, and the Weibull distribution can be used for ascendant, monotonous and descendant failure rate. Here, the authors mixed these two theme and use it in a common problem in group technology. Design/methodology/approach - In this paper, the authors made a non-polynomial-hard mathematical model based on past research and solved it with an exact algorithm. The algorithm is coded and solved in GAMS to illustrate the model, and the authors use simulation. A common numerical example is solved with the model, and the results are compared. Findings - Reliability analysis model based on the mixed Weibull distribution approach will give options to a user to select the suitable failure rate and modes for a specific situation. If the user uses the exponential or Weibull distribution instead of the mixed Weibull distribution, the calculated cost and reliability are wrong;therefore, it leads to user making wrong decisions. Originality/value - The model the authors use is the one used in past research, but in the past, researchers did not use the mixed distribution for explaining failure time. Therefore, the model can be considered as a new and more complete model.
In order to cope with the disasters caused by the worst hurricane in Puerto Rico in 2017,it is necessary to build an emergency system to reduce the *** emergency system should include the location of ISO standard dry ...
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In order to cope with the disasters caused by the worst hurricane in Puerto Rico in 2017,it is necessary to build an emergency system to reduce the *** emergency system should include the location of ISO standard dry cargo containers and the distribution of emergency medical *** paper discusses the distribution of emergency medical *** on the above location results of ISO standard dry cargo container,taking the demand of disaster areas not exceed its supply into consideration and considering the timeliness and weak economy,a multi-objective mixed integer programming model is constructed on the premise of minimum transportation time and *** is determined that the drone fleet consists of four B,one C and one F *** the optimization model,the distribution plan of emergency medical packages is formulated.
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