Sharif Digital Repository

The main purpose of this research is to select a suitable solution for regeneration of ion exchange resins of TR system of Bushehr nuclear power plant and also to compare and evaluate the possibility of using industrial cationic resin (Amberlite IR120) instead of nuclear grade cationic resin (Amberlite IRN97).First, different solutions for regeneration of cationic resins were investigated. For this purpose, three strong acids including hydrochloric acid (HCl), sulfuric acid (H2SO4) and nitric acid (HNO3) were selected and each of these acids was tested in two different concentrations and two different linear velocities; Also, to evaluate the appropriate solution for anionic resin... 

Heart attack is considered as one of the most common reasons of morality all over the world. Coronary Atherosclerosis is known as the major causes of heart attack. The commence and proceed of this disease is related to cross of Low Density Lipoprotein. In this project, based on numerical simulation using ANSYS Fluent, hemodynamic variables and the rate of LDL particles penetration to porous wall of coronary artery is investgated. The geometry is the first bifurcation of Left Anterior Descending and is located on the supposed sphere that represents heart configuration. Sinsuidal variations of shere radii, simulates pulsating movement of heart. Heart diameter is supposed to remain constant... 

Routers play a key role in transferring information between various Networks. It is very important to make sure about the compatibility of OSPF in a router with its standard description. In this regard, before presenting or applying a router and also evaluating its performance, it is necessary to carry out conformance test with the help of network equipment testers Tester designers extract test cases from protocol standard description through non-formal ways and exam them on network equipment.
In this thesis, a part of OSFP protocol has been modeled through colored Petri nets. In this regard, two sections of OSPF RFC have been model checked: neighbor state machine and data base... 

In this study, friction stir lap welding of Al-5083 alloy sheets with 3 mm thickness to St-12 steel sheets with 1 mm thickness (joint without intermediate layer) and to Al-1100 clad St-12 sheets (joint with the Al-1100 intermediate layer) was investigated. The cladding process was done by rolling. For each type of joints, the bonding mechanism, optimum process parameters to reach the joints with the highest fracture loads and also the microstructure evolutions at the joint region were studied. Furthermore, for the joints without intermediate layer, the effects of the Al-5083 annealing treatment before welding and the post-weld heat treatment of the joints on the fracture loads were explored.... 

Because of low friction coefficient, Copper-Graphite and Copper-Babbitt composites can be used as brushes and bearing materials instead of materials containing lead which cause environmental problems. So far, many methods such as powder metallurgy and centrifugal casting have been used to fabricate Copper-Graphite composites. The most important problem of these methods is agglomeration of Graphite particles. Simultaneous stirring of samples during fabrication process which is one of the features of friction stir processing (FSP), can solve the problem. Recently, FSP has been used for fabricating surface composite for the purpose of producing hard and wear resistance layers on ductile... 

In this project, Dissimilar Friction Stir Welding (FSW) between aluminum alloys (1100-H12 and 5083-O) and Magnesium alloy (AZ31B-O) with 3mm thickness were butt joined. Fusion welding of aluminum/magnesium alloys has failed because of forming much more intermetallic compounds. By using friction stir welded samples, effect of welding parameters such as tool travel speed, tool rotation rate, tool position respect to weld centerline, and sheet position respect to tool direction on mechanical (tensile strength, yield strength and elongation) and microstructural properties of the welds were investigated. After several tests, range of optimum parameters were obtained. In both 1100 and 5083 alloys,... 

At the moment, one of the most important challenges that human beings are struggling with is the dominance of micro and nano dimensions. Considering the potential of microorganisms, and in particular magnetic microscopes, it is believed that using this technology, humans would be able to meet most of their needs. Studies have shown that it is possible to control the position of a magnetic microrobots, through the production of magnetic fields, with sufficient accuracy. Since magnetic fields are biocompatible, magnetic microrobots can also be used in biotechnology and medical applications.In this dissertation, a positioning device was designed and constructed with the ability to position the... 

Optimizing optical tweezers and achieving powerful traps has always been a challenging topic for researchers , since the trap stiffness increases with increasing laser power which may damage specimens , especially biological ones and cells . In this thesis , we introduce a special geometry and structure of particles that , have the possibility to increase the stiffness (strength) of the optical trap and cause the magnetic response of particles at optical frequencies . Special geometries such as a combination of dielectric particles with magnetic nanoparticles that emphasize the role of the laser magnetic field and lead to changes in the electrical and magnetic properties at the laser... 

Nowadays, according to increasing development of construction industry in the world especially in the building area, the need to use technology and innovation for fabrication and maintenance of this industry has increased. And this fact becomes apparent that the use of traditional systems of construction isn’t tailored the countries’ requirements anymore. One of the construction industry’s limitations is the restrictions on architectural designs reys. The columns are among the most important components of structure and have a major role in bearing all gravity and lateral loads and transferring them to the foundation. The failure or destruction of the components in the structure under applied... 

Optical tweezer is a highly focused laser beam that could be used to trap micro and nano particles in three dimensions. It could be used to measure(or apply) piconewton range forces. Most of the optical tweezers experiments have been done in liquid mediums. In last few years, trapping particles which are floating in gas mediums(called aerosols) have been considered extensively. In this thesis, the changes in trap stiffness and conversion factor due to changes in laser power, trapping depth and particle are evaluated. It is shown that changing these three parameters, cause considerable changes in trap stiffnes and conversion factor. Linear behavior of trap stiffness versus laser power,... 

In this study, the seismic response analysis of a buried pipeline had been performed using three-dimensional (3D) dynamic analysis of the soil-pipeline interaction under different loading inputs. A number of parameters such as properties of the buried pipeline including diameter and internal pressure and different loading frequencies were used for this investigation. The pipe was considered as an elastoplastic material and a nonlinear elastic material based on the Mohr–Coulomb criterion was used to model the soil behavior. In addition, pipe-soil interaction has been studied in both tangential and vertical directions. The ABAQUS software was utilized for the 3D numerical modeling and...