Sharif Digital Repository

With the daily increase in the volume of information and due to the growth and pervasiveness of wireless networks, the structures and the way of connection of intermediate nodes have become very important in terms of energy, communication speed and communication overhead. In this thesis, we examine the structure of directionless wireless networks assuming nodes are selfish. In these networks, nodes seek to minimize their costs while being required to access all nodes with limited path length. Due to the selfishness of nodes, we used game theory to analyze the structure and behavior of nodes by calculating the Nash equilibrium state and to compare these networks with networks that are managed... 

Excavation of metro tunnel beneath groundwater level causes disturbance of hydro geological balance and change in stress conditions at its environment. One of the usual methods of the tunnel construction is utilizing tunnel boring machine and one of the most important of them is called TBM-EPB which takes advantage of the earth pressure balance method. Control of surface settlements which is a result of creating underground space in urban area is a matter of great importance and is influenced by various parameters. This thesis has tried to investigate factors such as geotechnical properties among cohesion, internal friction angle, elasticity modulus, permeability and porosity and also... 

For half a century, the problem of extracting the components of the nonlocal moduli tensor of anisotropic materials has been remained unsolved. In the present work, for the first time, the solution of this problem is proposed and the components of nonlocal moduli tensor are obtained for close-packed crystals, i.e. face center cubic or hexagonal closed packed. To this end, new distinct nonlocal kernel functions which have the characteristics of discrete atomistic Green’s functions in the stress space are obtained through consideration of the nonlocal dispersion relations. Each of dispersion relations are associated with certain directions and are combined with ab initio Density Functional... 

The need to build underground structures like tunnels, oil reservoirs are increasing and it requires a good knowledge of behavior of mass rock, exact data and parameters for safe and economic design. Filling materials which usually transfer with water into the joints reduce shear strength of joints significantly and change the behavior of the joints. To evaluate shear behavior of filled joints, 24 tests were conducted with large scale direct shear test apparatus on model rock joints with a regular “saw tooth” surface profile with the dimensions of 15cmx15cmx18cm. Filled material had specified specifications like particles size and strength parameters.
Infill thickness, moisture content... 

Recently, advances in the fabrication and integration of sensing, communication technologies and economical deployment of large scale sensor networks which are capable of large scale target tracking, become possible.therfore, the wireless sensor networks are a fast growing and marvelous research area that has attracted considerable research attention in the recent past. The creation of large-scale sensor networks interconnencting several hundered to a few thousand sensor nodes opens-up several wide range of application and technical challenges. Sensor nodes have been deployed to play significant roles in battlefield, disaster-prone area, traffic control, habitat monitoring and intruder... 

Mixed matrix membranes (MMMs) are new generation of membranes which possess simple processability of polymeric membranes and high separation ability of zeolitic membranes. The present study, concentrates on the fabrication of MMM for CO2/CH4 separation in a combined method as encompasses not only higher permeability but also superior selectivity in comparison with conventional polymeric membranes. The most appropriate technique for MMM making, is the process which provides participation of distributed zeolite particles in separation efficiently while the polymeric matrix acts just like a particle support and dose not play an effective role in separation. Investigations demonstrates that... 

An autonomous method for attitude and position determination of a satellite without using data from ground stations and also without the need for human interference is proposed using the image that the satellite has taken at each moment. The proposed method is based on recognition of stable features in the image and using them in order to match the satellite image with a source image from the Earth and the latitude and longitude of the features become known.SIFT and SURF algorithms have been examined. Using the perspective equation and camera coordinate system, a model has been developed that relates the coordinates of a point in the image with its equivalent coordinates in the real world.... 

This paper presents a novel method for satellite attitude determination, using Electrostatically Suspended gyroscope (ESG). In this method, two superconducting rings rotated around a spherical rotor, which causes a variable flux in rings. So according to faraday’s law of induction, a voltage will be induced in the rings. Using this voltage and a kalman filter, attitude of satellite will be determined. ESG works precisely, when the rotor is maintain at the center of gyroscope cavity, between three pairs of circular electrode, so a backstepping control algorithm will be designed In order to this purpose. The performance of attitude determination using this ESG and designed control algorithm is...