Sharif Digital Repository

This study offers a framework to manage mass vaccination programs in response to an outbreak in a city. Compared to previous studies, we consider more operational challenges in the vaccination process; for example, transshipment between vaccinations units and availability of second doses. Our objective function is based on the risk of unvaccinated individuals. Therefore, the model aims at favoring those places in the city where the risk of unvaccinated people is high. Using different kinds of vaccines is another factor that our mathematical model includes. Vaccines are categorized into single-dose and double-dose classes. In this regard, the balanced access to different vaccine types is of... 

Peoples need financial resources to improve their quality of life, and companies need them to progress and increase their comparative advantage. Borrowing is one of the most popular methods of financing. Peer-to-peer lending, also known as "marketplace" or "social" lending, is a novel form of intermediation that expunges the role of financial institutions (like banks) as an intermediary and allows entities (individuals or businesses) to raise loans directly from other entities. This lending platform can provide better quality services to borrowers (by quickly providing a simple loan application process through a transparent and flexible portal) and lenders (by managing their funding and live... 

The Multi-Depot Traveling Purchaser Problem under Shared Resources (MDTPPSR) is a new variant of the Traveling Purchaser Problem (TPP). In this problem, each depot can purchase its products using the shared resources of other depots, and vehicles do not have to return to their starting depots. The routing of this problem is a Multi-Trip, Open Vehicle Routing Problem. A tailored integer programming model is formulated to minimize the total purchasers’ costs. Considering the complexity of the model, we have presented a decomposition-based algorithm that breaks down the problem into two phases. In the first phase, tactical decisions regarding supplier selection and the type of collaboration are... 

Breast cancer has been one of the main causes of women's deaths in recent years. Today, various methods are used to treat this disease, among which intensity-modulated radiation therapy is one of the most common methods. The goal of radiation therapy is to destroy cancer cells while protecting the surrounding healthy tissues. In left breast cancer, due to the proximity of the heart and breast tissue, we are at risk of delivering an excessive dose to the heart and increasing cardiac complications after the treatment. In addition, due to the irregular and unpredictable breathing movements of the patient during the treatment and the resulting uncertainty, we face more challenges. In order to... 

Parallel machine scheduling problems are the decision-making process of allocating limited resources to activities over time. These issues have attracted a lot of attention in the past decades based on their applications in the real world. It can be discussed about the application of parallel machine scheduling problems in computer processing, production lines and multi-stage systems as examples of areas where parallel machine is observed. Most of the research on parallel machine scheduling has focused on the optimization of a single criterion such as total or average task completion time, total completion time with different weights, sum of penalty or tardiness penalty, total number of... 

In this thesis, a special case of the Traveling Purchaser Problem (TPP) is considered in which instead of one vehicle there are multiple vehicles as purchasers. Furthermore, the vehicles start their path from a set of starting points and after visiting a number of markets they return to the depot. Moreover, each of the products needs a special loading condition and the vehicles have multiple compartments to meet these loading constraints and the products are loaded in their appropriate compartments. This problem is at first modeled as a MIP formulation and then by decomposing the problem a Column Generation procedure is developed to solve the problem. To enhance the speed of the column... 

The human need for reliable and accessible energy sources for household, industrial, transportation, etc. caused the discovery of the first oil well to move towards exploitation and use of this large, cheap and available energy source, accelerated. With the start of this movement, oil and its products in the last two centuries have quickly established themselves as a major part of the energy basket of most countries in the world. The entry of crude oil and its products into the energy industry has faced new issues and challenges for decision makers in this field. One of the most important challenges has been the planning and management of the process of distribution and transfer of petroleum... 

In this study, providing home care services by hospitals in the epidemic situations such as COVID-19 is proposed for the first time. Moreover, a mathematical formulation is developed to provide simultaneous decision-making about serving patients without COVID-19, scheduling nurses in the non-COVID-19 wards of hospitals, and scheduling and routing for nurses to serve patients at home. This problem aims to develop essential compatibilities to keep people safe and help continue vital healthcare services during the COVID-19 and similar pandemics. Accordingly, nurses' preferences, the number of available hospital beds, the patient-to-nurse ratio, the Unavailability of some nurses due to COVID-19,... 

Examples from recent years, such as Covid-19 disease and earthquakes, show that disasters can have devastating effects on a community.These disasters are divided into two categories: expected and unexpected. decision makers cannot easily determine the time, severity and effects of them. Therefore, they must coordinate their decisions in the pre-disaster and post-disaster stages according to the incomplete information available, and according to the dynamics of the situation, quickly understand and interpret the connections between different decisions. Among the various approaches, the decision support system can explore the variable and unpredictable nature of such issues and enable decision... 

Cloud Manufacturing (CMfg) is a service-oriented manufacturing (SOM) paradigm that provides a dynamic, scalable, and virtualized working ecosystem. The CMfg collaborative structure can be modeled as a hyper-network-based service-demand matching architecture. It is enriched with quality of service (QoS) characteristics to produce customized products in a stable and reliable network. This stability should be considered in the overall manufacturing network mechanism. This Thesis has developed a multi-dimentional model and improved it by providing absorptive and adaptive strategies utilizing available resources and capacities to enhance the system’s stability and reliability against the... 

Patient scheduling is one of the most important problems in healthcare optimization which has been in center of attention in various environments including outpatient clinics and operating rooms. Effective scheduling systems have the goal of matching the demand with capacity so that resources are better utilized and patient waiting times are minimized. Furthermore, patient scheduling can be merged with another problem in which the main goal is to find the optimal sequence of a given list of patients. Moreover, there are several sources of uncertainty such as patients’ unpunctuality, absence, and service time in this problem resulting in having a very complex problem. In this research,... 

Outpatient clinics always encounter a huge deal of demand and due to the variety of the services they provide and the existence of uncertainties, operation management is such a difficult task. This issue has made problems related to this issue popular among scientists and researchers. In this research, we are going to address several popular problems related to outpatient appointment scheduling. Initially, an M/M/c/K queuing system is developed in order to obtain the optimum scheduling window for different sub clinics. Secondly, the real demand for each sub clinics will be estimated using data analysis techniques for each 24-hour period. Having the results of the previous section, we build a... 

In this study the predictive power of “Simple Moving Average” simulation for three month horizon is investigated. The purpose of the study is expressed in two hypotheses. The first hypothesis is that there is a significant difference in the prediction of stock price volatility by “Simple Moving Average” simulation with the “Weighted Moving Average” model prediction and the second hypothesis states that using “Weighted Moving Average” model we can forecast volatility stock price for the out-of-sample period. The research data includes a series of total stock price indices from 2013 to 2018 extracted from Tehran Stock Exchange (TSE). For “Weighted Moving Average” model, three normal... 

In this thesis, a decomposition approach is developed to solve Set Covering Problems (SCPs) through exploiting special structures of their coefficient matrices. The coefficient matrix of an SCP is so large in practical problems, but due to its low density, most of its entries are zero. Based on this observation, some methods can be developed to aggregate the 1's of the coefficient matrix in order to create special structures involving smaller dense subproblems. In this theisis, four structures called "block-angular", "semi-block angular", "partitioned" and "nested block-angular" structures are proposed and examined. For this purpose, First, some heuristic methods based on constraint... 

Search engines have an important role in providing the appropriate response to the user’s search. In the past, all people had received the same result for searching an equal expression. Now, no one receives a similar answer by searching in Google or Bing. The information in the net is getting bigger day by day. Thus, websites owners face a serious challenge to provide a suitable and relevant information for the users. Accordingly, ranking the results for users is difficult. To address this issue, researchers proposed different ranking algorithms for sorting the search results. Travel and tourism is one of the most competitive and cost-consuming in the field of electronic commerce especially... 

In today's life, we look at each other, seeing different networks, such as power networks, telecommunication networks, transportation networks (freeways, roads, streets), rail networks, air service networks, shipping networks, Logistics networks (networks of construction and distribution), computer networks, Internet networks (e-commerce, banking networks), airline reservation networks, social networks and so on. In all of these networks, an entity such as man, product, car, electricity, message, information, aircraft, etc. from one source into a destination is moved according to the network's purposes and objectives.This thesis analyzes the sensitivity analysis and optimization of... 

Transportation Network Companies (TNC) like Snap and Tap30 are ride sharing platforms that connect drivers and passengers in real time using simple mobile phone applications. The most interesting feature of these platforms is that they do not hire drivers and allow them to choose when and where to offer a ride. Dynamic and fluctuating supply and demand, the necessity to forecast the changes, implementing them in ride pricing and driver-passenger assessment are considered as important challenges for such systems. In this research, first, we want to analyze the spatial structure of TNCs and then forecast network changes more precisely. The method used for forecasting is LASSO which is a... 

Real-world decision-making problems usually have several criteria for evaluating the performance of alternatives. On the other hand, mathematical programming is a very practical tool for modeling and solving decision-making problems and multi-objective mathematical programming has high importance among researchers and managers in this field of study. However, the field of multi-objective integer programming is considered a rigorous category. Methods for solving these types of problems can be divided into three different approaches. There are few approaches and methods for solving multi-objective mixed-integer optimization problems in litreture.In this research, an extension of benders... 

According to the expanding of technology and information technology, organizations today are forced to collaborate and share knowledge with each other in order to obtain competitive advantages, and have innovation. This information sharing, in addition to its benefits, makes organizations vulnerable to loss of information in various ways by hackers, competitors or other agents through security breaches.In this research, the issue of protecting IT-based organizations from cyberattacks is discussed by using a concept of attack graphs interdiction. At first, after defining the problem precisely, it is modeled as a bi-level mathematical programming. In this problem, the attacker is looking for... 

The layout problem is directly related to the material handling system; therefore, these two concepts are always being considered together. The main criterion for evaluating the layout in the objective function, is the cost of controlling and moving the materials. In order to calculate the material handling cost, it is necessary to provide an accurate information on the distance between departments, number of goods transported, and the cost of moving a unit of goods per unit of distance; therefore, accurate calculation of the distance between departments is an issue of paramount importance. In the literature, the distance between the departments is measured in three ways: Euclidean distance,...