Sharif Digital Repository

Inherently safer design is the new approach to maximize the overall safety of a process plant. This approach suggests some risk reduction strategies to be implemented in the early stages of design. There are different well-established strategies for making a process plant inherently safer. The benefits of applying these strategies on reducing the overall risk inside a plant are obvious. However, some of these changes are rejected many times because they appear to be too costly. But if the effects of applying inherently safer design strategies are investigated not only on the processing costs of a plant but also on the potential accident costs, the decision would in fact be different. In this... 

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... 

Rotating machinery are found in most industrial units, that are highly susceptible to transverse cross sectional cracks due to fatigue. The vibration pattern of a rotor system reflects the mechanical parameter changes in the system. These vibrations can be used for identifying the cracks and appropriate actions can be taken to prevent more damage to the system. The dynamic behavior of cracked rotor is a subject of considerable current interest. Several researchers have developed models of cracked rotor systems. Therefore, In this thesis, the influence of the presence of transverse cracks in a simple Jeffcott rotor is analyzed. In first, on the basis of fracture mechanics, the direct and... 

Modern engineered products from individual parts to large systems shall be designed and produced to meet the required reliability at the time of the mission. A well-known type of systems in reliability issues is called k-out-of-m system. There are two common ways to enhance the reliability of these systems. These are: (1) increasing component reliability through more stringent acceptance sampling, and (2) improving system reliability through increases in component redundancy. The objective of this study is to determine the optimal plan in k-out-of-m systems. In fact, we seek to find an optimal plan for a decision maker considering his or her limitations such as cost and reliability. An... 

In this study, the simulation of blood flow through a stenosed coronary artery and a bypass graft are discussed using fluid-structure interaction numerical method. Effects of the geometrical parameters of CABG surgery on hemodynamics have been studied. Investigated hemodynamic variables include shear stress on the vessel wall, the velocity profile in high-risk areas and the pathlines. Lower than 0.5 Pa shear stress on intimal layer of arteries causes the formation of plaque on the wall. Angle of 30 degrees and diameter ratio of bypass to host artery of 1:1 are proposed as the optimum geometry. The distance of the anastomosis from the site of occlusion has no effect on surgery. Also,... 

The problem of point to point repetitive time reduction for the rigid manipulators is a major case in industry especially for applications such as point to point welding and part manipulation. These motions are usually repeated for a large numbers of cycles, so that even a minor economization in time can be hugely significant. Nowadays, the time optimal control problem of manipulator with completed theory, is an appropriate solution of the problem. In recent years, with the expansion of design space to structure design, more satisfactory results can be obtained using this method.
Optimal balancing is a new approach based on the optimal control theory in which the balancing unknowns plus... 

The price that customers pay for electric energy is determined by cost of generation, transmission and distribution parts. In Practice all customer have main concern about reliability of electric energy, because of it’s major effect on different aspect of life. Although customers are interested to have fully reliable service, but power companies are aware that it is impossible to achieve this goal from technical and economical aspect. The utilities and customer benefits can be achieved through minimization of the total investment cost of network, while improving the reliability and quality of electric service. This also requires to minimize the customers service interruption time. To meet... 

This paper investigates the interaction between the beneficiaries of an employee stock option plan within a Stackelberg game framework. The beneficiaries are shareholders and employees. In the proposed model, shareholders, as the leaders of the Stackelberg game, determine the optimal features of employee stock option grants. In response, employees, the followers of the proposed Stackelberg game, maximize their own profits by determining their own effort level by considering that every effort level of employees has an associated cost and expected income for employees. It is assumed that the stock price follow Geometric Brownian Motion process with a known drift rate and volatility. Also, it...