Sharif Digital Repository

Graph sum coloring problem is a special case of graph vertex coloring. Because of its applications in practical areas, especially in scheduling, many researchers have been attracted to it. In recent years, several heuristic and metaheuristic algorithms were applied to sum coloring problem. In this research a heuristic algorithm based on mini-max ant system and simulated annealing metaheuristics is used for graph sum coloring problem. This algorithm is tested on random graphs used in the literature and compared with prior algorithms. Results show that in many cases our proposed algorithm reaches the best known results or improves them  

The subgradient method is one of the most favoriate methods to solve discrete optimization problems. The Easy Implementation and flexibility enbles us to solve a vast types of complicated combinatorial optimization problems. However, the algorithm can be improved by adjusting its parameters and steps.In present research, we present a heuristic structure to modify and improve the algorithm. Then, the proposed algorithm has tested on special classes of discrete optimization problems such as Generealized Assignment and Uncapacitated Warehouse location problems. The results show that the proposed algorithm can improve the efficiency of the classic form of subgradient method.The three main... 

Subgraph isomorphism problem is an NP-complete problem, which has diverse applications in different fields such as network problems, image processing, text processing, topography, and bioinformatics. Therefore, many researchers from both theoretical and practical viewpoints have considered it. In this research, we try to offer a proper and efficient method to solve this problem by using constraint programming, which is a powerful and efficient method to model and solve complicated combinatorial optimization problems, and criticality and cruciality concepts from a resource planning scope.
In this regard, first one of the most efficient models among existing constraint programming models... 

Facility Layout Problem is one of the classic problems with the goal of arranging facilities with respect to the objective function and it’s been the subject of many researches for many years. By progressive development of industrial units in recent years and the lack of space especially in major cities, using multi-floor buildings can be a suitable solution. In literature, a few researches on this kind of layout problems are done. Maybe the main reason is difficulties of modeling. In this problem, with regard to objective function, interior and between floors flow and some predefined constraints, a suitable floor and place for each facility or department is determined. On the other hand, in... 

Studying the major effects of facility layout on competitive abilities has been a field of interest for researchers. Selection of production layout is amongst the most important decisions because it has a major role on the efficiency of a company like the ability of quick respond to customers’ diverse needs.
In this study we intend to obtain a ranking of production layouts considering agility in production which leads to responding quickly to the diversity of demand. Considering the nature of a decision making problem, we use PSI method. This is a multi attribute decision making method in which there is no need for considering the relative importance between the attributes. The main... 

One of the newest approaches in optimization fields under uncertainty which absorb many scientists is robust optimization. This approach uses uncertain data instead of stochastic distributions and its goal is to find a solution which is robust under uncertainty of input data.
Assignment problem is one of the most applicable problems in real world which its parameter is faced uncertainty. Because of this reason, the aim of this thesis is to find a method for solving generalized assignment problem robustly which the coefficients of costs and use of resources by agents for performing the jobs is undetermined. These parameters are interval data and have just lower and upper bound.
For... 

Regarding recent progress in the field of decision theory and the discovery of the important factors in human decision making, it is suggested by researchers to build up models that take all of, or at least most of, those factors into account simultaneously. In this research, first, we present some important achievements in the field of decision theory then develop a model based on these factors. Therefore, we focus on influential factors in human decision making, especially recent ones in neuroeconomics and mathematical models are presented to describe their effects. Then a descriptive model is proposed and changed it to a prescriptive model by adding some assumptions and standard charts.... 

In the recent years, the existing pressure in order to decrease the expenses and increase in giving service level led to the position in which the outsourcing of different sectors of unimportant actions is welcomed by manufacturing companies or the ones offering service. Since the logistic costs are crocial for companies' budget, the conveyance of logistics is a center of attention in recent years. In such a competitive situation, logistic service providers have to provide high quality with low price services, in which both the cost and service offering level to customers depend on the configuration of flow transmission of physical network. The use of hub network has great benefits for such... 

Layout design problem is to determine a suitable arrangement for the departments, so that the total costs associated with the flow among departments become least. Single Row Facility Layout Problem which is called SRFLP, is one of layout problems that has many practical applications. This problem and its specific scenarios is often used to model many of the raised issues. This is arrangements of n departments with a specified length in a straight line, so that the sum of the weighted distances between pairs of departments is minimized. We can say that SRFLP is one-dimensional version of the layout design problem and it tries to minimize the cost of communication between rectangular... 

Among scientific fields of study, mathematical programming has high status and its importance has led researchers to develop accurate models and effective solving approaches to addressing optimization problems. In particular, meta-heuristic algorithms are approximate methods for solving optimization problems whereby good (not necessarily optimum) solutions can be generated via their implementation. In this study, we propose a population-based meta-heuristic algorithm according to chemotherapy method to cure cancers that mainly search the infeasible region. As in chemotherapy, Chemotherapy Science Algorithm (CSA) tries to kill inappropriate solutions (cancers and bad cells of the human body);... 

reparedness and emergency procedure be devised in the event of,and prior to,a disaster. One of these disastersoften accompanying byhuge damages, losses and casualtiesisanearthquake. After such a disaster, several governmental and non-governmental organizations usually start relief operations. They commonly pursue their own agendas and use their own facilities and capabilities to help the people affected without pursuing a central plan. These disintegrated behaviors of involved organizations generate contradictory responses and result in either wasted resources or preventing equitable service for all affected people. Due tothe abovefact, this dissertation proposes amodel for improving... 

Distribution and transportation systems assign a significant shares of financial turnover of organizations, in addition to their functional roles in satisfying customer's needs. It is expected that productivity would be improved by optimal and effective use of organization's inputs and increases the probability of success in a competitive market. In the meantime, it is necessary to pay attention to the management of distribution and transportation systems for vehicles especially in critical condition, that if there would be proper planning, to prevent large losses and human disasters since it is impossible to meet the demand of all customers, because of resources shortage in such... 

In this research, we try to coordinate a seller-buyer supply chain by using general side-payment contracts in order to gain the maximum possible chain profit. In this model, we take logistics costs into consideration for both buyer and seller and regard the final demand as a decreasing function of retail price which is determined by the buyer. Both parties aim to maximize their individual profits, so we must set contractual parameters in a way that these decisions become aligned with system optimal decisions and the chain surplus profit be assigned to chain members such that they have no intention to leave the coalition. To this aim, we suggest a side- payment contract which consists of... 

In this research we investigate the effect of demand disruption on coordinating a supply chain with one manufacturer and one retailer competing with a manufacturer. For this purpose we consider two kinds of demand function: 1) a demand function which determines the demand deterministically and 2) a demand function with a random factor which determines the demand stochastically. Also we assume that in competition between retailer and competing manufacturer, retailer possesses more power than his rival in the market. In order to study the effect of demand disruption on coordinating the supply chain, first we consider coordination without demand disruption by using linear quantity discount and... 

In this thesis, 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 and load distribution.

 

In literature, substantial works have been done on supply chain coordination. The majority of these works looking for a mechanism that enforces the supply chain members to follow strategies that produce the equilibria of an integrated supply chain, and most of this literature ignores competition between supply chains. In this thesis, we consider two distinct supply chains which compete to each other on the price. We present a method to calculate the equilibria for three structural forms. In the first form, two supply chains are integrated and in the second form, one of the supply chains is integrated and the other one is decentralized. Finally in the third form, both supply chains are... 

Nowadays, one of the most common and effective methods of medical treatment for End-Stage Renal Disease is kidney transplantation technique which is obtained by transplantation of a living donor kidney to the patient. However, the main issue regarding to this method is the shortage of kidney supply rather than demand. A modern solution for this problem is known as "Paired Kidney Exchange Method". In order to deal with this approach theoretically, the whole problem is modeled as a graph theory problem and a cycle detection algorithms are applied. Furthermore, a new approach considering the time issue and patient state have been introduced recently which implemented the Stochastic Game... 

Nowadays the popularity of renewable energy is increasing due to its clean and inexhaustible nature. Also, if the local potential of each area is used, there is no cost to connect to electricity network. But these energies have low reliability due to their oscillating nature. To solve this problem, it is proposed to use systems based on several sources of energy called hybrid systems. In this research, a mathematical model is proposed to design a renewable hybrid system that minimizes the present value of costs while maximizing system’s reliability. To consider the uncertainty in the solar radiation data and energy demand, Bertsimas’s robust model is applied to our model. In which variables... 

Facility Layout Problem (FLP) is known as one of the classical problems in industrial engineering which have acquired high attractiveness to researchers. Therefore, in this study, a practical mathematical model is formulated and solved
In order to have a real and practical model, robust optimization is applied to FLP. Therefore, it is supposed to have dynamic values for departments' dimensions. This assumption is very critical to generate an effective and acceptable layout. We consider that each dimension of a department can be changed in a given interval. Due to this assumption, we introduce two new parameters which are called width and length deviation coefficients, respectively.... 

One of the most efficient techniques deployed for end-stage renal disease remedy is kidney transplantation, but in this case, we commonly encounter with the problem of gap between the demand of patients and supply of donors. In the majority of models has been proposed until now, either kidney exchange technique in a pool of incompatible pairs or kidney allocation system from deceased donors to waiting list is recommended. In this research, in order to enhance kidney transplantation plans, first, a hybrid conceptual model is proposed. Then, its mathematical model is discussed, in which some of the transplantations are selected from kidney allocation system before injecting to the pool of...