Sharif Digital Repository

The thesis has considered a two-echelon supply chain which consists of one central warehouse and multiple retailers. Assume all retailers and the warehouse follow a continuous review inventory model. The costumer’s demand comes to retailers in a Poisson process. The retailers replenish their stocks from the warehouse in an (S-1, S) inventory control policy and the warehouse replenishes its stocks in an (r, Q) inventory control policy from an external supplier with an infinite capacity. It may be more representative to model stockouts as lost sales when the retailers are in a competitive market or in monopoly markets all demand will be backorder. Therefore, if the market situation goes... 

Pistachio trade in Iran is of great importance in non-oil exports, and this country has been the main producer of this product for many years. In recent years, unfortunately, pistachio products have fallen sharply in the country, and on the other hand, the United States has been able to take a large share of the global market. The researchers have presented numerous reviews about the causes of this problem, most notably drought and water scarcity, inefficient agriculture, and the lack of comprehensive and efficient management of the pistachio supply chain. In this research, to address these problems, attention has been paid to sustainable supply chain management that addresses three... 

Risk management is one of the important phases of a project life cycle. There are several quantitative and qualitative methods to determine and plan the proper reaction risks in a project. These methods aim to prevent additional and unnecessary costs. Project managers, stake holders and beneficiaries always believe that risk management of project engineering as one of the importance parts. Although there are multiple methods that can evaluate risk, but there is still research problems especially for risk qualitative and quantitative prediction. This gets more serious after evaluating and minimizing risks effects considering the other risks’ damaging effects which have not been considered. In... 

Emergency Department (ED) overcrowding is one the most problems and challenges that every Emergency Department all over the world is facing with. This problem leads to some problems like prolonged waiting times and Length of Stay in Emergency Department. “Boarding time” is one of the most important ones, which is the time a patient spend for being transferred from Emergency Department to one of the Hospital Inpatient Wards. One important solution to this problem is “overflowing”, and it means allocating patients to an alternative ward rather than their primary ward. In practice, the overflowing process usually controlled in a myopic manner. Limited number of researches that focus in this... 

Due to the vast application of networks in the modeling of problems, the analysis of networks has been gaining a noticeable importance in recent researches. There are some cases in which we are looking for nodes that are highly connected to other nodes. However, the detailed information of the network structure is not always available; or because of complexity, it is not possible to investigate whole network and pick high-degree nodes; or investigating the network completely is too time-consuming. In such cases, algorithms which do not need the whole network information play a significant role. Friendship paradox as a topological feature of graphs can be helpful in designing such algorithms.... 

Computer video games have had a huge growth in recent years, and Dota 2 is one of the most popular video games and e-sports right now. In this research, Dota 2 drafting phase is studied by using stochastic processes and probabilistic models. This phase is modeled as a POMDP (Partially Observable Markov Decision Process) for the first time. Afterwards, the model is solved using data mining methods and machine learning algorithms. A large database of the game's match data is created, and six different machine learning algorithms are used to predict the match outcome based on the drafting stage. The prediction accuracy and power of these algorithms is compared, and finally, a program is... 

Predicting oil prices, especially in exporting countries, will help governments in the policy-making process by obtaining a reliable estimate of oil revenues. The existence of a complex mechanism governing the process of oil price formation has reduced the efficiency of linear models in forecasting and led researchers to use nonlinear intelligent systems to predict oil prices. In this study, after a detailed study of the structure of artificial neural network, two models of neural network GMDH and MLP and ARIMA method have been used to predict oil price. There are important factors in the prediction process with neural networks, and if all these factors are selected correctly; One can expect... 

There are several types of uncertainty in supply chains that cause some difficulties in the planning of a supply chain. Uncertainty on the supply side can cause interruptions in the quality, quantity, or delivery time of orders. To avoid such interruptions, retailers usually contract with two different suppliers for a common good. In this setting, one of the suppliers has higher reliability and higher price, while the other supplier offers a lower price but has a lower level of reliability. In other words, to ensure a lower level of uncertainty, retailers have to pay more. This is one of the main tradeoffs in the dual sourcing strategy. In this thesis, we consider a two-echelon supply chain... 

The use of drones in various fields is increasing. One of the applications that can be mentioned for drones is humanitarian areas can include drug supply chains, blood supply chains, relief chains, and the like. The use of these unmanned vehicles in humanitarian areas poses legal challenges compared to other areas. This study aimed to investigate drones following a disaster, the essential role of UAVs, and a vehicle to carry out relief operations. Following a disaster, infrastructure can be severely damaged, and the destruction of infrastructure can reduce the efficiency of land vehicles. In this research, “drone and vehicle routing problem” have been done to provide relief and minimize the... 

Despite the significant progress of machine learning models in the health domain, current advanced methods usually produce non-transparent and black-box models, and for this reason, they are not widely used in medical decision-making. To address the issue of non-transparency in black-box models, interpretable machine learning models have been developed. In the health domain, counterfactual scenarios can provide personalized explanations for predictions and suggest necessary changes to transition from an undesirable outcome class to a desirable one for physicians. The aim of this study is to present an interpretable machine learning framework in the health domain that, in addition to having... 

The idea of using under water vehicles inspired by nature has gained considerable attention during the past few decades. This interest is due to the advantages of swimming and moving by this technique, in comparison with the conventional methods. Benefits are such as increasing speed, improved power, better manoeuvre ability,greater stability, optimal hydrodynamic performance ... etc. The purpose of this study was developing a model to simulate a stingray Manta Ray moving behaviour. Ansys- Fluent software was applied to solve the related equations of viscous laminar flow in 3-D form.Simulation of Manta Ray was performed with the flapping pectoral fin with dynamic mesh. Using this... 

Nowadays, because high global demand for energy has led to the extensive use of fossil fuels with numerous unintended consequences such as air pollution and greenhouse effect, research and development around optimization of energy infrastructure has become much more important. Consequently, many scientific approaches have been applied to replace fossil fuels with renewable natural energy resources. One of the renewable energy types that fewer papers have been published about it, is the enormous energy of Marine currents. The origin of this energy is mostly tidal effect, or ocean currents that are available in most of oceans and seas around the planet earth. The most important criteria for... 

Cellular Manufacturing System (CMS) is one of the most practical manufacturing systems based on the Group Technology (GT) concept. In this thesis, a CMS is evaluated and analyzed through the proposing new mathematical models. A cellular manufacturing system includes four main sub-problems; Cell formation (CF), Group Scheduling (GS), Group Layout (GL) and Resource Assignment (RA). In this paper two problems of CF and RA are studied and discussed.At first, a new mathematical model is proposed for a CF problem. The objectives are the minimization of inter-intra cell part trips, machine breakdown cost, tool consumption cost and the reconfiguration cost. Multi-functional machines unreliability is... 

Environmental management with emphasis on protecting environment is today one of the most important problems for customers, governments, employees and competitors, and international and global pressures has required organizations to produce environmentally consistent products and services. This challenge has resulted in emergence of a new concept namely green supply change management in the realm of business which is a combination of environmental thinking and supply chain, which will be followed by competitive advantages for firms. This approach has widely attracted the attention of industries, governments and institutions relevant to environment. The aim of this study is to identify main...