Sharif Digital Repository

In this paper, we studied a two-echelon inventory system which consists of one central warehouse and one retailer. All installations follow base stock inventory management policy. The customers arrive at retailer according to Poisson distribution. The demand is satisfied when both central warehouse and retailer have positive on-hand inventory. Otherwise, the demand is lost. The lead time of central warehouse and the time needed to replenish orders of retailer are assumed to be exponentially distributed. The purpose of this study is to minimize the expected long-run total cost of the system per unit time. Total cost of the system includes holding costs of central warehouse and retailer, cost... 

Nowadays, one of the most challenges in drilling and production engineering, is the formation damage caused by fluid filtration while drilling and completion operations. This damage would cause serious problems in pay zone and besides influencing the well performance during its life time – due to permeability reduction in near wellbore area- and cause economic expenses such as workover and stimulation operation. Therefore, considering the aspects of formation damage minimization during drilling and completion operations, the fluid selection for these purposes would be crucial. It requires the knowledge of interactions between these fluids and the reservoir rock. In this thesis, using the... 

One of the most widely used methods in the study of the mechanical behavior of fiber-reinforced polymers is modeling and simulation of a unit cell behavior. According to the arrangement of composite materials, the unit cell is selected in order to include and represent actual constructions of the material. In this study a numerical self-consistence method is proposed to estimate effective properties of Carbon-epoxy composite materials. In this method, in addition of two main phases i.e. matrix and fiber, a phase of composite properties is also considered surrounding the unit cell. First using analytical and semi-empirical methods, the properties are calculated and are converged after... 

The job shop scheduling problem is an important and applicable optimization problem and has been attracted by many researchers in recent decades. A huge amount of applications of job shop scheduling problem in industries and services has been found yet. During the last decade, the sequence dependent setup time constraint has been considered in many researches, but with respect to the knowledge of authors, very few of these researches have considered the inseparable setup. Furthermore, few of them have considered the release date assumption. In this thesis, the classical job shop scheduling problem and the inseparable sequence dependent setup time and release date constrained problem have... 

Hub location problem arises where the flow has to be routed between a set of origins and destinations, but direct links between all nodes are impossible or too costly. In these situations, e.g. transportation and communication systems, hubs serve as transshipment points to collect, transfer, and distribute the flow. In hub location allocation problem, hubs are located and non-hub nodes are allocated to them. In this thesis, two different models of capacitated multiple allocation hub location problem are discussed. In the first model, flow collection of hubs from non-hub nodes and in the second model, sum of flow collection and distribution of hubs from/to non-hub nodes is addressed. The... 

Facility layout problem (FLP) is one of the classical problems that concern with planning for the placement of facilities. Two dimensional layout problem is one of the special layout problems that involves with the arrangement of facilities in non predefined shape. For solving the FLP, a number of information such as dimensions of facilities, relations between facilities, governing constrains etc., are required. But in the most research works, it has been assumed that the required information is precisely known. In this thesis, we challenge this assumption considering the size (length and width) of facilities as bounded variable parameters. In order to make the problem solvable in the sense... 

Recently, the multi-level and multi-facility industrial problem in supply chain management (SCM) has been widely investigated. Supply chain network design (SCND) is one of the most important strategic decisions in supply chain management. The problem is an important management problem in SCM and aggregates the strategic and tactical and operational level of supply chain planning. The supply networks comprise a number of manufacturing sites, a number of warehouses and distribution centers of unknown locations to be selected from a set of potential locations, and finally a number of customer zones at fixed locations. The system is modeled mathematically as a mixed-integer linear programming... 

Supply networks are often faced with disruptions that hampered the flow of goods, and have brought irreparable consequences. In this thesis, we evaluate the robustness of three echelon scale free supply chain networks consist of manufacturers, distributers and retailers from the perspective of complex network topologies and investigate the effect of assortativity and disassortativity level on the robustness of scale free supply networks. For this purpose, we use the degree preserving rewiring approach in order to increase and decrease assortativity and disassortativity of scale free networks. Then we use metrics in order to investigate the robustness and flexibility of supply networks and... 

Efficient location of health centers is an essential decesion in healthcare strategic planning. Nowadays constructing multi-service health centers is highly paid attention because of multiple nature of most diseases. Concentrating patients' medical services in one center prevents them from traveling to different parts of cities, especially in mega cities. In this research we have developed a mathematical model for the location of multi-service health centers assuming probabilistic demand and service time. Medical services are divided in three groups: normal, emergency and preventive. Since patients may be referred to another service after recieving a service by doctors' order, health system... 

Today, considering the challenges that have been raised around fossil fuels and energy consumption in recent years, efforts have been made to reduce as much as possible the number of vehicles that are personal or single-passenger on the streets. For this purpose, a concept called travel sharing has been proposed in online platforms and businesses, where travelers can travel part or all of their journey with other travelers, but pay less money. The purpose of this research is to solve the problem of allocation and accessibility of passengers and cars in travel-sharing systems. To move in this direction, we have used mathematical programming tools and designed online algorithms to solve this... 

Last decade witnessed a virtual explosion of information about customers and their priorities. This information gives some potentials to companies that increase their revenues, especially when new technologies make the possibility of changing prices with low costs. Simultaneously, companies had large development in dynamic management of supply chain in both internal operations of companies and their communications. Although pricing decisions have some effects on operations, but integration of operations and marketing are very common subjects in science and business. In this thesis, we consider the integration of dynamic pricing and ordering in a supply chain. Then, we present a dynamic... 

Train scheduling is a significant issue in the railway industry in recent years because it has an important role in railway infrastructure. In this paper, the timetabling problem of a multiple tracked railway network is discussed. More specifically, a general model with specific attention to “Tehran Metro” is presented here in which a set of operational and safety requirements are also considered. The model handles the trains overtaking in a station and innovatively considers the capacity of stations. An objective function is to minimize the total travel time. The problem is NP-hard so the real size problem cannot be solved in acceptable amount of time. In order to reduce the processing time... 

Nowadays, Resource Capacity Management (RCM) is one of the main challenges for industries which have a limited capacity to meet the demands. Revenue Management (RM) is a technique that controls the supply, improves the quality of Capacity Management and maximizes the revenue. Supplying the products and services to different groups of customers is a decision making problem.While the classic RM techniques take into account only the expected revenue, preferences of decision makers strongly affect the results. In this study, utility theory has been proposed because the healthcare industries are usually nonprofitable and they are not highly focused on the revenue gained by their products and... 

The location problem is one of the main topics at the strategic level. This problem is investigated along with many areas such as network design and path covering problems. Routing between source and destination nodes is done in such a way that maximizes traffic coverage and reduces costs as much as possible. Routing problems are considered in goods distribution areas and urban transit systems. Goods distribution from set of cross-docks can help to reduce costs and improve resource efficiency. So, this topic is considered in this research and a suitable model is proposed. Defining and developing of the road and rail transportation networks are main topics in urban traffic management which... 

Graph Labeling is one of the most active initiatives in graph theory which was introduced in the early 1960’s. One of the most prominent kind of labeling in literature is magic-type labeling inspired by defining magic numbers and magic squares. It also encompasses various types. Total edge magic labeling of Graph G, is a bijection f from V(G)∪E(G) on the set of {1,2,…,|V(G) |+|E(G) |}, on this condition that the summation of each edge label and its vertices’ labels is constant for all edges. Since introducing total edge magic labeling, numerous researches is done that mostly are dedicated to prove mathematical theorems and depicting a whether a distinct graph is magic or not. Therefore, it... 

The focus of this research is to present a model to verify the acceptance of projects with time and cost dependency on the usage of equipments. Decision on these projects is based on a dynamic programming in which at each stage, the profit of available projects in this stage, equipment value and the best choice of future stage are decision keys. In other words, after the completion of a project, it should be decided between doing a project or selling the equipment and leaving the remaining projects. For each projects, there is a product network that includes projects jobs and operations. After accepting projects, equipments of the projects will not be renewed and the usage of the equipments... 

Around 20 to 50 percent of the operation costs occurs in manufacturing is related to facility layout. Efficient design would reduce these costs by 10 to 30 percent. Facility layout consists of design of material handling system and plant layout. Design of material handling system includes determining, the flow network and locations of Pick-up and Delivery stations which are defined regarding to the kind of material handling equipment. Today, Automated Guided Vehicles are considered as the basic material handling equipment due to their potentials in production planning and controls, high safety and flexibility and low expenses.
In this thesis, we first discuss the design of the shortest... 

With the development of technology and the increase in the global need for energy, the drilling of oil and gas wells moves towards deep and ultra-deep waters, and since the drilling fluid plays an important role in the drilling operations, it requires drilling fluid with the characteristics It is a suitable function to overcome the serious challenges of drilling, including low temperature rheology and borehole heat transfer problems in these areas.The purpose of carrying out this research on the design of water-based and emulsion-based protective fluids is to use laboratory materials and equipment and conduct appropriate tests in order to evaluate the observations and tests performed in...