Sharif Digital Repository

Usually, resources are short in supply when earthquakes occur. In such emergency situations, disaster relief organizations must use these scarce resources efficiently to achieve the best possible emergency relief. This paper therefore proposes a multi-objective, multi-mode, multi-commodity, and multi-period stochastic model to manage the logistics of both commodities and injured people in the earthquake response. Also, a robust approach is developed and used to make sure that the distribution plan performs well under the various situations that can follow an earthquake. Afterwards, it proposes a solution methodology according to hierarchical objective functions and uses it to illustrate the... 

The graph colouring problem, as an important NP-complete problem, is considered in this paper and a hybrid meta-heuristic approach is developed to solve it. The initial solution of the algorithm, generated by a heuristic method, is used by a simulated annealing (SA) approach to generate new solutions until no progress in a number of solutions reported. At this stage, the algorithm will use a tabu search routine and this local search operator will be followed for some iterations. After finding a better solution, the algorithm is again followed through SA. Efficiency of the algorithm is showed through various experiments on well-known benchmark problems of DIMACS. Comparison with the available... 

Facility layout problem (FLP) is one of the classical and important problems in real-world problems in the field of industrial engineering where efficiency and effectiveness are very important factors. To have an effective and practical layout, the deterministic assumptions of data should be changed. In this study, it is assumed that we have dynamic and uncertain values for departments’ dimensions. Accordingly, each dimension changes in a predetermined interval. Due to this assumption, two new parameters are introduced which are called length and width deviation coefficients. According to these parameters, a definition for layout in uncertain environment is presented and a mixed integer... 

In this paper, a "Game Theory" approach for finding an optimal path in a "Wireless Sensor Network" is discussed. WSN is one of the most interesting research fields in the communication networks, and is the center of attention in recent years. In our model, a pricing and payment technique is presented to obtain an optimal path in a WSN by considering reliability, energy and traffic load. The proposed algorithm is able to find a path which improves network lifetime, load distribution and path reliability  

The general goal of the facility layout problem is to arrange a given number of facilities to minimize the total cost associated with the known or projected interactions between them. One of the special classes of the facility layout problem is the Single Row Facility Layout Problem (SRFLP), which consists of finding an optimal linear placement of rectangular facilities with varying dimensions on a straight line. This paper first presents and proves a theorem to find the optimal solution of a special case of SRFLP. The results obtained by this theorem prove to be very useful in reducing the computational efforts when a new algorithm based on tabu search for the SRFLP is proposed in this... 

In this paper, we have discussed the results of sensitivity analysis in a payoff matrix of the Matching Pennies game. After representing the game as a LP model, the sensitivity analysis of the elements of the payoff matrix is presented. The game value and the optimal strategies for different values of parameters are determined and compared  

We propose an efficient optimal algorithm for determining the lot sizes for purchase component in Material Requirement Planning (MRP) environments with deterministic time-phased demand and zero lead time. In this model, backlog is not permitted, the unit purchasing price is based on the all-units discount system with single price break point and resale of the excess units is acceptable at the ordering time. The problem is divided into the sub-plans with specific properties by the dynamic programming (DP) method already presented. By modifying the main structure of the DP method, we present a branch-and-bound algorithm to obtain the optimal ordering policy for each sub-plans. Furthermore, we... 

Sports scheduling has become an important area of applied operations research in recent years, since satisfying fans and teams' requests and revenues of a sports league and TV networks may be affected by quality of the league schedule. While this type of scheduling problem can be solved by mathematical methods and exact solutions are accessible, it computationally leads to hard problems. The travelling tournament problem (TTP) is defined as minimising total travelling distance for all teams in a league. In this study, a new mathematical model for the TTP with the no-repeater constraint is presented. In addition, a very fast hybrid metaheuristic algorithm is proposed, which combines particle... 

The Multi-Floor Layout Problem (MFLP) is the problem of finding the position of each department in a plant floor in a multi-floor building without any overlapping between departments in order to optimize a particular objective function, more commonly the sum of the material handling costs. In this paper, a special class of MFLP, called Uncertain Multi-Floor Discrete Layout Problem (UMFDLP), is defined. In this problem, a multi-floor building is considered in which an underground store is utilized to contain main storages, and different departments can be located in the other floors in potential pre-determined locations. Furthermore, all material flows are not constant. Moreover, the... 

Single-Row Facility Layout Problem (SRFLP) is a http://library.sharif.ir/web-manage/catalog/resource.do?method=edit&flowLastAction=view&id=447751special class of facilitylayout problems, consists of finding an optimal linear placement of rectangularfacilities with varying dimensions on a straight line. In this research, wefirst present a theorem to find the optimal solution of a special case of SRFLP.The results obtained by this theorem are very useful in reducing thecomputational efforts when, later on, a new algorithm based on tabu search ispresented for SRFLP. Computational results of the proposed algorithm onbenchmark problems show the efficiency of the algorithm compared to the... 

In this paper, we consider a dual-sourcing model with constant demand and stochastic lead times. Two suppliers may be different in terms of purchasing prices and lead-time parameters. The ordering takes place when the inventory level depletes to a reorder level, and the order is split among two suppliers. Unlike previous works in the order splitting literature, the supply lead time between vendor and buyer as well as unit purchasing prices is considered to be order quantity dependent. The proposed model finds out the optimal reorder point, order quantity and splitting proportion, using a solution procedure. Numerical results show that neglecting the relationship between ordering batch size... 

Sports scheduling has become an important area of applied operationsresearch in recent years, since satisfying the fans and teams' requests andrevenues of a sports league and TV networks may be affected by the quality ofthe league schedule. While this type of scheduling problem can be solvedtheoretically by mathematical methods, it computationally leads to hardproblems. The Traveling Tournament Problem (TTP) is defined as minimizing totaltraveling distance for all teams in the league. In this study, a newmathematical model for the TTP with no-repeater constraint is presented. Inaddition, a very fast hybrid metaheuristic algorithm is proposed, which combinesParticle Swarm Optimization (PSO)... 

Train scheduling has been one of the significant issues in the railway industry in recent years since it has an important role in efficacy of railway infrastructure. In this paper, the timetabling problem of a multiple-tracked railway network is discussed. More specifically, a general model is presented here in which a set of operational and safety requirements is considered. The model handles the trains overtaking in stations and considers the stations' capacity. The objective function is to minimize the total travel time. Unfortunately, the problem is NP-hard, and real-sized problems cannot be solved in an acceptable amount of time. In order to reduce the processing time, we presented some... 

Efficient location of medical services is an issue of paramount importance in healthcare strategic planning. In this research, a mathematical model is developed for the location of multi-service health centers, assuming probabilistic demand and service time. Since patients may be shifted to another service after receiving a service by doctors’ order, health system is considered a Jackson queueing network. We assume that patients have “probabilistic choice behavior” and the primary factors contributing to their choice of one center over another are their proximity to the center and the number of medical services offered by the center. The proposed mixed integer nonlinear programming model... 

Real-world, large-scale problems often have coefficient matrices with special structures that can be obtained by reordering their rows and columns. One fundamental problem in the field of combinatorial optimization is the Set Packing Problem (SPP), which takes on added significance in view of its far-reaching applications in routing and scheduling problems, scheduling surgical procedures, the winner determination problem, forestry, production management, etc. The coefficient matrix of this problem has low density (the number of 1’s is much less than the number of 0’s in the matrix); therefore, by reordering the matrix, one can aggregate its 1’s in order to exploit special structures like... 

Graph sum colouring problem is a special class of graph vertex colouring problem. Because of its various applications in practical areas, especially in scheduling, many researchers have been focused on it during the past decade. In recent years, several heuristic and meta-heuristic algorithms have been developed to solve sum colouring problem. In this research, a hybrid algorithm based on mini-max ant system and simulated annealing is applied for the problem. This algorithm is tested on benchmark random graphs and compared to the previous algorithms. Results show that in many cases, the best known results can be obtained or improved by the proposed algorithm. Copyright © 2019 Inderscience... 

This chapter at first proposes a framework to solve set covering problems (SCPs) with block-angular structures through solving their sub-problems and then develop the method for solving general SCPs without this structure. The proposed framework generates a guaranteed solution for the SCPs with block-angular structure based on a theorem which relates the optimal solution of the original problem to the optimal solutions of its sub-problems. Therefore, since sub-problems involve much fewer constraints and variables than the original problem, the complexity to solve the original SCP is much reduced. In addition, a method to exploit the block-angular structure of SCPs is proposed, using... 

Graph sum colouring problem is a special class of graph vertex colouring problem. Because of its various applications in practical areas, especially in scheduling, many researchers have been focused on it during the past decade. In recent years, several heuristic and meta-heuristic algorithms have been developed to solve sum colouring problem. In this research, a hybrid algorithm based on mini-max ant system and simulated annealing is applied for the problem. This algorithm is tested on benchmark random graphs and compared to the previous algorithms. Results show that in many cases, the best known results can be obtained or improved by the proposed algorithm. Copyright © 2019 Inderscience... 

This chapter at first proposes a framework to solve set covering problems (SCPs) with block-angular structures through solving their sub-problems and then develop the method for solving general SCPs without this structure. The proposed framework generates a guaranteed solution for the SCPs with block-angular structure based on a theorem which relates the optimal solution of the original problem to the optimal solutions of its sub-problems. Therefore, since sub-problems involve much fewer constraints and variables than the original problem, the complexity to solve the original SCP is much reduced. In addition, a method to exploit the block-angular structure of SCPs is proposed, using... 

This paper proposes a new approach to study the sensitivity analysis in the network flow problems, in particular, the minimum spanning tree and shortest path problems. In a sensitivity analysis, one looks for the amount of changes in the edges’ weights, number of edges or number of vertices such that the optimal solution, i.e., the minimum spanning tree or shortest path does not change. We introduce a novel approach, and develop associated equations and mathematics. We discuss two illustrative examples to show the applicability of the proposed approach. © International Journal of Industrial Engineering