Sharif Digital Repository

Magnesium and its alloys have gained much attention in medical applications, especially bio-degradable stents. However, they have not been used extensively due to their natural limitations, such as weak mechanical properties. WE43 magnesium alloy has gained attention as a bio-alloy due to its high temperature and good corrosion resistance. The present study aims to use a combination of ECAP and direct tube extrusion to fabricate thin wall tubes with good mechanical properties using WE43 magnesium alloy. In the first phase, the ECAP process at 370°C were conducted up to 4 passes on the homogenized samples to reach ultrafine grain structure. Subsequent to ECAP, direct tube extrusion at 230 °C,... 

Pile foundations suffered severe damages during the past earthquakes in all around the world. These damages were more severe in laterally spreading grounds and they mostly have been observed in gently sloping grounds and coastal areas. In these cases, Pile foundations not only are subjected to structures inertial loads and kinematic loads of liquefied soil but also lateral spreading intensifies damages. Thus, in the recent decade, several researches have been conducted to investigate the behavior of pile foundations in liquefiable and laterally spreading grounds, however, some uncertainties still remain in modeling of soil-pile interaction. In this study, the effects of liquefaction- induced... 

In this thesis we investigating two models of cancer invasion .First, a general mathematical model of cancer invasion is presented. In this model there are three factors: tumor cell, extracellular matrix and enzyme. The model consists of a parabolic partial differential equation (PDE) describing the evolution of tumor cell density , an ordinary differential equation modeling of extracellular matrix and a parabolic PDE governing the evolution of the matrix degrading enzyme concentration. This model is investigated in two special versions for existence and uniqueness of global solutions. In the first model we neglect the remodeling term, this model is named the chemotaxis-haptotaxis model.... 

EOQ and EPQ models have been among the most important and commonly used techniques for about 100 and 60 years respectively .But, they are involved in some assumptions that sometimes prevent them from being implemented in real situation of industry and production. One of these unrealistic assumptions is that all of items received or produced are of perfect quality. In order to overcome this constraint and make the mentioned models closer to the real environmentsome researches have been done. To this end,following the previous attemptsin this project we assumed to have destructive inspections and existence of imperfect and rejected items after rework. In our models, considering 3 circumstances... 

Mars rover Curiosity is a mobile scientific laboratory which it’s mission is to assess the biological potential of the landing site and characterize the geology of the landing region. This rover communicate to a Mars orbiter named MRO satellite in the UHF band which relies the signals to the Earth stations. Also this rover communicate to the Earth stations directly in the X band. In this thesis, we determine the technical characteristics of stations and simulate Earth-Mars radio links. So we calculate :
1. determine the technical characteristics of Earth stations
2. determine the technical characteristics of satellite and Curiosity
3. Earth-Mars orbital position in the... 

The present study deals with designing controller for Therapeutic Exercise Robots which belongs to larger group namely Rehabilitation robots. Therapeutic exercise robots are often realized in shape of exoskeleton robots. The main line of present research is involved with, designing controller for lower limb therapeutic exercise robots and offering and implementing technical rehabilitation ideas. Firstly, in order to have a reliable position-control, considering practical limitations (e.g. system uncertainties), a robust adaptive control has been designed. Adaptive control can deals with parameters uncertainties and covering unstructured uncertainties (e.g. disturbance and noise) can be... 

Before a construction project gets under way an attempt is made to examine different ways and scenarios for its implementation. Through such a process the more appropriate scenarios should be selected based on several criteria that are not necessarily at the same level in terms of importance. The purpose of this study is to examine different scenarios for implementing operations in the pre-construction phase of a project, based on several competing criteria with different importance levels in order to achieve a more efficient execution plan. This paper presents a new framework that integrates discrete event simulation (DES) and data envelopment analysis (DEA) to rank different scenarios for... 

The need for further improving the operation of the electronic and optoelectronic devices to raise the speed of the circuits, and to decrease their power dissipation, has led many researchers to investigate the structure of 2D material, such as graphene, transition metal dichalcogenides (TMDs) as MoS2, and other 2D compounds such as BN, due to their prominent electronic properties. TMDs have the highest significant potential for the next generation transistors due to their salient semiconductor characteristics such as electron mobility, band gap, and conductivity. For instance, Graphene is a favorable candidate for analog devices due to zero bandgap. Regarding the importance of bandgap in... 

In the last decades, Reaction Time research has been extended to cognitive science and more specifically human information-processing research and has gained momentum (Shim, 1996). The present study examined the reaction time in processing marked and unmarked structures with regard to the four types of conditionals (considered as unmarked, less marked, marked and strongly markedness, respectively) and prepositions (preposition pied piping that is considered as unmarked and preposition stranding as marked). To this end, two softwares were developed for which the items relating to conditionals were chosen from the Bernet’s test (1985) and the ones pertinent to prepositions were taken from... 

To actualize and making the outputs of a project effectual, it is necessary to conduct an effective management during a project. This case may not be possible without accurately planning for activities, management and controlling all phases of a project ignoring the risk management of that project. If risks of a project cannot be detected before conducting a project, it is possible to challenge the performance and even effectiveness of the project. In current conditions, the most important problem of managers and executives of construction projects through the country is risk management of projects, not acknowledging with definitions of risk, models of risk management and lack of a model for... 

Simulation of cardiovascular system functionality during various physiological conditions is essential at different diagnostic and clinical levels. A first step in studying the roots of cardiovascular diseases and abnormal activity is to study a practical yet complete model of the cardiovascular system. In this thesis we introduced a new approach for defining the distributed model of the cardiovascular system. Initially, we chose an appropriate subsystem, namely Arch of Aorta, and proposed a distributed model for it. The elements of the proposed model were nonlinear RLC elements that simulate resistance, blood viscosity and vessel elasticity respectively. To minimize the system complexity,... 

In this study, factors which lead in failures in reengineering processes in project based companies have been investigated. The research used qualitative methods, and finally using theme analysis to identify the main factors.Consequently, the main causes of failure of re-engineering projects have been identified and classified in six basic categories including: organizational leadership, planning, human resources management, mental models causing resistance, culture and organizational climate and communication. That each of these themes includes some subset of the agents it represents. In this study, a suitable pattern for organizations which intend to perform reengineering has been... 

A Balanced Scorecard (BSC) model is proposed to evaluate performance of Health, Safety and Environment (HSE) management systems. This model includes key performance indicators at three integrated levels. It has been tested and verified in a project-based organization in Iran, active in the area of power and energy. Results show that the company has done well in implementing HSE management processes, but no so well in growth and learning. This model may be used as a basis for comparing different companies and various proposed programs in the field of HSE management systems. The model includes indicators and sub-indicators in each category particularly related to stakeholders, processes, and... 

Ultrasound hyperthermia is a commonly used noninvasive approach to destroy cancer tumors. High Intensity Focused Ultrasound (HIFU) is a technique based on hyperthermia. It creates short and local elevations of temperature at a focus site within the tissue of interest. The main goal of HIFU is to maintain the temperature between 50 and 100 °C for a few seconds (typically less than 10 s), in order to cause tissue necrosis. In order to predict the effects of hyperthermia, accurate and effective modeling is needed. This study considers a 3D simulation of the hyperthermia based on HIFU method in the liver tissue. Temperature distribution and lesion volume changes, with a temperature of above...