Sharif Digital Repository

The poor economic performance of natural resource abundant countries has been studied for a long time and in order to alleviate this problem some different solutions are suggested by economists. One stream among these solutions are those focusing on the distribution mechanism of natural resource revenues and the ownership of these resources. In this study, it is intended to address the effect of change in the ownership of natural resources on politicians’ behavior and people welfare by using political economy approach. Also the optimal share of people from natural resources as a function of political and economic institutions is discussed. In this study, it is shown theoretically that under... 

The challenges of urbanization have been the focus of researchers since the past. With the expansion of urbanization and massive migration of people from villages to cities, these challenges became more important in our country. These issues, which exist in many other countries in a serious manner, are discussed in the branch of urban economy in the world. This thesis is arranged in three chapters, in each of which one of the aspects related to urban economy and housing is discussed. In the first chapter, the effects of the construction of Mehr housing on the value of nearby residential properties are investigated using difference-in-difference method. It is shown that the construction of... 

Non-destructive testing method is for detect specimen flaws such as (crack, porosity, impure, welding defects, corrosion etc.) without destruction the specimen under inspection. Particular characteristic of radiography is an image product from specimen inside under testing where help to identity and better comprehend at flaw nature. Photon scattering is one of important factor to reduce image quality and signal to noise ratio. Scattered photons can due toexistent ingredient in the radiography environment and curvature of material transmission pipe where cause the disorder creation in the radiography images. In this research, pipe radiography simulated using the TIC and TIR radiography... 

The series structure of semiconductor devices has a wide application in the industry and research field. The most critical issue in the series structure of series switches is the safe operating condition provision. Hence many kinds of research have been intensively focused on this topic to overcome this necessity. However, many existing aspects relevant to the series stacking of the semiconductor switches have not been pointed out. These include, the power loss must be accepted for the series devices and recovery of this power, providing balanced voltage for the series devices through a simple and easy implementing structure and providing a safe voltage condition for the series devices under... 

Photovoltaic phenomena is the base of Photovoltaic cells technology that can transform the solar insolation to electricity directly. In this transformation, the solar insolation intensity is the important factor to increase the performance of the Photovoltaic cells but one of the biggest barriers in the extension way of this technology is its more cost that need to be decrease. Concentration of solar radiation method is the best way to increase the performance of Photovoltaic systems and decrease its initial cost. At this project a novel structure of solar parabolic through concentrator is investigated experimentally and analytically. The usage of Thermoelectric module with Photovoltaic... 

The importance of power consumption in high performance multiprocessors, combined with power reduction capability of on-chip optical interconnects, offers optical network-on-chip (ONoC) as a new technology solution which can deliver considerably higher bandwidth and lower latencies with significantly lower power dissipation than an interconnection network based only on electronic signaling. An on-chip network should be able to support multicast communications efficiently whether it is an optical or electrical network. On the other hand, multicast communications in optical networks-on-chip has been implemented using shared bus which is not scalable. Moreover, most of optical on-chip... 

In this work, inertial guidance and control of an axisymmetric flying vehicle with a spinning part is performed based on dynamic modeling and seven degree of freedom simulation. Flying vehicle is composed of front and aft bodies and these bodies are connected to each other via a hydrodynamic bearing. Front body is roll isolated from the aft body and includes all necessary guidance and control equipments such as sensors, canard set and so on. The control fins, located on the nose, is used to control the roll angle of the nose and to execute the lateral acceleration commands. Also, the aft body is freely rolling and includes the stabilizing fins. In this project, the translational and... 

Having the high strength to weight ratio has been made the composites special materials very important these days. The low density of aluminum and its appropriate corrosion properties make it a good choice for metallic matrix. Also, the high tensile strength of stainless steel fibers can helps as a reinforcement in the composite to improve its mechanical properties. Enhancing the bonding of composite’s components can helps it to develop its properties. Casting is an appropriate process for making an aluminum matrix containing steel fibers as reinforcement in a structural composite. In addition, rolling process can remove so many defects made by casting, and improve joining of fibers and... 

In this study, flexural vibration of a functionally graded nanotube under an initial stress is investigated. The small scale effect is taken into consideration based on Eringen’s nonlocal elasticity theory. The material properties are assumed to vary exponentially along the depth direction. The complete effect of the initial stress is taken into account in the problem formulation. The governing equations of motion are derived by using the Hamilton’s principle on the basis of the nonlocal Timoshenko beam theory. An analytical solution of the governing equations, for free vibration of a simply-supported nanotube is presented. Numerical results are presented to investigate the effect of the... 

let Mn n be a positive semmi definite matrix and M:= (U; B) be a matroid. Consider the problem of finding S 2 B such that det(MS;S) is maximized, in witch MS; S is the submatrix of M, restricted to rows and columns of S. This problem has a variety of applications including page ranking algorithms. The problem above is an NP-hard problem in the general case. However, there are several approximating and estimating algorithms for some special cases, which are interesting. Also, exactly solving the problem is NP-hard, even for some special matroids. As an example, one can consider the uniform matroids. Khachiyan introduced a greedy algorithm with dd approximation factor. Afterward, Di summa et...