Sharif Digital Repository

Wellbore instability is one of the serious problems during drilling. This can cause delay in drilling, increasing drilling costs and in some cases well abandonment. The present project investigates the effects of non- isothermal drilling and the difference in salt concentration between formation fluid and drilling fluid on the stability of wellbores drilled in the saturated porous shale formations subjected to an arbitrary stress field. This project also focuses on the analysis of wellbore stability in shale formations in which the thermal diffusivity is higher than fluid invasion and the mechanism of heat transfer is dominated by conduction. The governing equations used in this dissertation... 

In recent years, rehabilitation has become of particular importance due to direct connection with the quality of life of human beings. Balance training and assessment devices have been designed to provide means for rehabilitation of patients with balance problems. Sharif balance robot is an example which has been developed at Sharif University of Technology. The subject stays on a plate with active rotation in both Medial-Lateral and Anterior-Posterior directions. The active rotation of this plate is provided by two electrical motors embedded inside the machine. Position commands for this plate are sent to the electrical motor by the control hardware which consists of a PC104 running... 

Gas-Assisted-Gravity-Drainage (GAGD) is a new enhanced oil recovery method which utilizes the natural tendency of gas and oil to segregate due to gravity. Higher recovery of GAGD, compared to continuous gas injection (CGI) and Water-Alternating-Gas (WAG) makes it the focus of researches in recent years. This work is trying to propose a surrogate model based on Artificial Neural Networks for GAGD process. The proposed model should be able to mimic the behavior the process in a short time in order to be used as an alternative computationally expensive simulator where a large number of simulations are needed, such as sensitivity analysis, optimization of the process, or risk analysis. A... 

In this work, dispersion of a spinning projectile has been reduced by modifying its configuration and using a simple open-loop guidance. The traditional nose is replaced with a new nose with controllable fins, the spin of which is isolated from the remained body using a roller bearing. To check out the dynamic behavior of the projectile, non-linear simulations has been used which were developed at preceding research projects. To carry out this project, important errors that make the dispersion of the projectile have been investigated. Then, assuming projectile is controlled ideally, an open-loop guidance has been achieved and the appropriate times for the implemention of the guidance... 

In this thesis, a multi-stage project portfolio selection and scheduling problem in an uncertain environment is modeled, analyzed and solved. Moreover, we investigate the situations in which a project manager is confronted to a large number of projects to be selected and scheduled while the required resources of the projects are limited and renewable. The aim is to maximize objective function which is the net present value of the profit of the projects. To solve the mentioned problem, we introduce a multi-stage stochastic programming. For the reason that, in real problems, optimization problems that included all restraints are large scale and have computational complexity, these problems are... 

Profile Monitoring is a new research topics in the field of statistical process control. In many applications of statistical quality control, sometimes quality of a process or product described by a relationship between a response variable and one or more independent variables.The researchers call this relationship profile. The study seeks to demonstrate that monitoring profiles In addition, the industry can be effective in medical field and improves control of the patient's condition by a doctor. Profiles are usually modeled with a linear regression equation, non-linear or polynomial. finally, the results of this study, using actual data, models and methods to predict and control... 

As a method of cancer treatment or improvement of cancer-related complications, external radiation therapy is prescribed by physicians, in case of detection of a tumor in a region of patient’s body. Over time, various techniques have been developed for external beam radiation therapy. Among which, Intensity Modulated Radiation Therapy (IMRT), due to its ability to adjust the intensity of radiation beams, has a higher capacity to generate appropriate dose distribution based on tumor size and volume and it is one of the most widely used techniques in cancer treatment centers.The core process in treatment planning is using appropriate computer algorithms which results in posing enough damage to... 

The aim of Emergency Medical Services (EMS) is to provide fast medical care and to transport patients to hospitals at the earliest possible time, so as to reduce injury and fatality rate. Healthcare managers try to improve healthcare systems by reducing the response time to demands. In this thesis, we present mathematical models for the problem of location and relocation of emergency vehicles after the end of their service time or after they have returned to a hospital. We believe that implementing these models can help managers improve the performance of emergency medical services. In the first part of this study, we present a two-level deterministic optimization model considering demand... 

At the present, End-stage renal disease(ESRD) is the ninth-leading cause of death in the USA.according methods of medical treatment for End-stage renal disease (ESRD), transplantation is the most viable renal replacement therapy for ESRD patients, there is a disparity between the demand for kidneys for transplantion and the supply. Incompatible inblood-type and antigen matching between patient-donor pairs is cause of shortage in disparity between the demand and the supply.paired kidney exchange of kidney among incompatible patient-donor pairs.PKE can be solve many difficulties in matching patient with incompatible donors. Kidney transplant surgeries in PKE must take place simultaneously... 

Operating rooms have always been the most expensive and also the most profitable section in hospitals which include approximately one third of cost and two third of income. The management always wants to decrease the cost of hospitals. On the other hand, usually this goal stands against other goals such as patient’s satisfaction. So the manager should make a balance between these goals. In this research, we will propose an integer programming model for operating room scheduling problem without uncertainty for elective patients. In order to make the model more realistic, we want to make connection between operating room theatre and intensive care units. Also, we will consider desirable... 

Cancer is one of the main causes of death among all people around the world. This shows that more and more attention should be paid to cure cancer. One of the most common cancer treatments is radiation therapy. Among all radiation therapy treatments, Intensity-Modulated Radiation Therapy is a very effective and flexible ways to treat cancer. There are numerous mathematical problems to find the perfect treatment plan. One of these mathematical problems is Fluence Map Optimization in which we try to find the best dose intensity for each tumor and surrounding organs. The main purpose in this problem is to minimize the number of cancerous cells which are being destroyed while minimizing the... 

In recent years, the attention of marketing researchers has shifted from numerical product rating to user-generated content. Because of this, customers' online reviews now play a very important role in the destiny of Internet businesses. Today, huge and comprehensive platforms have been developed to record and analyze online customer reviews. This type of unstructured data that users and Internet shoppers create based on their experiences of using products and services, has a significant impact on gaining and losing the trust of other users. After reading each review, each user can express their opinion about the usefulness of that comment, which can be seen by others. Large Internet... 

Large amounts of relief resources such as water, tents, medical equipment and fuel after a major disaster need to reach the affected people. Satisfying the needs of victims is crucial to the success of crisis relief operations, as a lack of relief resources can lead to the suffering and loss of lives of victims. According to studies, large-scale catastrophes have occurred frequently in recent years. Therefore, it is necessary to pay more attention to the management of post-crisis resources. Since the distribution of emergency resources depends largely on the efficiency and effectiveness of logistics operations, the primary objectives include minimizing logistics time and cost, minimizing... 

In today's world, decision-making has become one of the main problems and challenges for managers, despite the conflicting goals and the different scenarios. On the other hand, most existing decision-making methods are not applicable to all issues in different decision-making environments. Therefore, in this study, by presenting a new algorithm, these concerns have been reduced and a new method has been proposed using the concept of stratification recently introduced by Lotfi Zadeh. In the present study, a single system multi stratification and multi-system multi stratification are presented, which provide managers with an easier understanding and analysis of each system so that they can...