Sharif Digital Repository

In this thesis, kinematic, dynamic modeling and simulation, and control of SQ15-06N industrial robot have been presented. This robot is mostly used in the painting industry. Studying the robot requires familiarity with the robot programming and the hardware used in the robot. In this research, robot characteristics such as repeatability, load carrying capacity and accessibility have been investigated. The principles of industrial robot programming and robot programming language have been studied. The use of simulation software is common due to cost savings, reduced time, no need for robots and controllers, and the ability to test programs in a virtual environment. For this purpose, the... 

Since the number of Internet users for the services such as e-applications is increasing rapidly, authentication constrains more latency as well as load to the system. It is due to large number of users whose identity needs to be checked and compared individually, and the number of simultaneous authentication requests in a specific time. To solve the stated issues, this thesis proposes a new definition of group authentication and describes group authentication protocols. Group authentication is the verification of identity of multiple requests of users at the same time. In this protocol, the authentication server inputs the multiple authentication requests in a function, and then applies... 

Validation of dosimetry accuracy in the context of advanced methods for radiotherapy, including proton therapy for ensure the accuracy of treatment plan is nessecory. One of the reasons for using MC code is the modeling of PT systems and the support of more accurate computation of dose distribution in clinical tarin. The purpose of this project is to validate the modeling of a spot scanning proton therapy system using a GATE MC code. In this study, the dose distribution calculated in the calibration process of the device and syno TPS is used as a criterion and the dose distribution obtained from the GATE MC code is calculated and validated with it. For this purpose, a water phantom was used... 

Steels as structural materials of pressure vessels of nuclear reactors, in addition to high temperatures and pressures, are exposed to ionizing radiation such as neutrons. The primary effects of damage caused by exposing these solids to radiation are the displacement of atoms from their equilibrium positions and the formation of point defects and damage clusters caused by damage accumulation due to displacement cascades produced by transmitting the energy of the incident particle to an atom by interactions such as elastic and inelastic scatterings neutrons with the nucleus. These microstructural changes cause large structural defects such as swelling, cracking, cracking, creep, reducing... 

The Electron Paramagnetic Resonance(EPR) is a retrospective and accurate dosimetry method to measure irradiated-induced radical population in the matter for determination the induced dose in the matter. The dose uncertainties will be about 1 percent. in the first stage of the present research, the response of EPR system to a reference sample has been measured. Then, responses due to the other samples has been compared with it and the secondary sample dose has been calculated. The reference sample usually is alanine. Unlike the perturbation theory forecast,the EPR signal intensity response to dose for alanine is not linear. In this thesis, first, the alanine samples (with pellet form) have... 

Nuclear engineering simulation requires computer codes which are capable of particle transportation and presenting valid answers. The Monte Carlo method is one of the particle transportation methods and the MCNP code is also a common and efficient code using Monte Carlo method. We usually come across statistical errors in Monte Carlo simulation for reducing which a number of methods have been presented which are called variance reduction methods. In simulating deep penetrating problems, analog Monte Carlo method is weak which leads to considerable error. The chosen variance reduction method for this study is the one which uses adjoint flux. In this study, a 3D deterministic transport code... 

One of the ways to enhance the safety and economic performance of nuclear power plants, is to choose an appropriate policy for arrange the reactor fuel assembly in the beginning of each cycle. There are variety of ways to optimize the layout of the fuel in the reactor core, but to achieve more than one goal, choosing multi-objective method can be used.One of the intelligent optimization methods is the genetic algorithms that emulate nature of biological processes and can be used to optimize two or more of the target.The goals of this research is to increase the neutron multiplication factor is to make maximum use of the fuel in the reactor and maintain the radial power peaking factor for... 

In this thesis, a Segmented Gama Scanning System for measuring total activity of the low/intermediate level radioactive waste drums is designed and a prototype 3-segmented commercial system is manufactured by using NaI detectors. The optimum distance of detector from drum surface and the optimum number of detectors on reconstruction of the radioactivity of the waste drum were studied by MCNP simulations. In addition, the effects of inhomogeneous distribution of radioactivity, the addition of lead filters to detectors, the change in collimator length and the asymmetrical placement of a drum on the rotary plate were also examined by the MCNP calculations. In the absence of a real radioactive... 

This thesis has been done with the goal of comprehensive neutronic calculation of a small size High Temperature Gas Cooled Reactor and HTTR was selected as a reference reactor for simulations. Calculations are divided into four parts of zero and full power stochastic calculations, deterministic calculations and noise analysis. In zero power calculations, an algorithm is proposed for modeling random arrangement of TRISO particles in the fuel compacts of HTTR. The effect of this arrangement on criticality calculations, i.e. effective multiplication factor and critical position of control rods, is then compared with regular arrangement. In the second part, full power calculations with the use... 

HTGRs are considered as 4th generation reactors which have prominent characteristics such as inherent safety, lower safety costs, High efficiency and high temperature applications. the most important challenges in developing these reactors is providing appropriate codes in design, simulating their performance and analysis of them. In this thesis, a japanese prismatic HTTR reactor has been selected as a reference reactor and the neurotic’s calculations implementation studied at cold zero power (CZP) and hot full power (HFP) states using DRAGON cell calculation codes and DONJON core computations. At CZP state, One group and two group radial & axial flux distribution, control rod critical... 

In this thesis, a computer program is produced to measure the activity of 137Cs and 60Co radionuclides in waste packages generated at Bushehr Nuclear Power Plant (BNPP). In this program, the activity of waste drum was calculated by dividing the waste matrix into very small identical cubic cells, and each cell was considered as a point source (in the center of the cell). The activity was calculated using the theory developed by Krings & Mauerhofer. Detection efficiencies were calculated by the developed program at different conditions of a) different detector distance from drum surface, b) different collimator length, c) different cell size and d) up to 4 segment number. The results were... 

In radiotherapy, dose calculation is one of the most important stages that should be carefully done for patient treatment planning. Dose calculation methods have been developed from early dose algorithms that used analytical methods to relatively recent high precision monte carlo methods.Monte carlo methods while very accurate in dose estimations usually suffer from long computation time. In the recent time the emphasis for reduction of the computation time has been focused on software techniques as well as on hardware technology development. One example of hardware development has been graphic processing unit (GPU) which was introduced in 2006 by the Nvidia to accelerate the processing and... 

The present ph.D. thesis consists of three sections including the static calculation, neutron noise calculation and neutron noise source unfolding in VVER-1000 reactor core. The multi-group, two dimensional neutron diffusion equations and corresponding adjoint equations are solved in the static calculation. The spatial discretization of equations is based on Galerkin Finite Element Method (GFEM) using unstructured triangle elements generated by Gambit software. The static calculation is performed for both linear and quadratic approximations of shape function; baesd on which results are compared. Using power iteration method for the static calculation, the neutron and adjoint fluxes with the... 

Most of the nuclear codes used equivalence between a homogeneous and heterogeneous region to calculate resonance shelf-shielding. when fuels are together in a lattice arrangement, As a good approximation in the resonance shelf-shielding calculation, one could only consider a single fuel lump and consider the effect of neighbor fuels with a correction factor, i.e. the Dancoff coefficient. So far, several methods have used for calculating the Dancoff coefficient, but accuracy of these methods did not improved. In this thesis a computer program (MCDAN-3D) is developed for calculation of the multi-dimension and multi-group black and gray Dancoff coefficient, based on Monte Carlo, escape... 

Radiation therapy is a treatment modality that is used in treatment of most newly diagnosed cancer patients. In this method the interaction of radiation with matter and their biological effects is used for cancer treatment. The energy and intensity of the radiation in radiotherapy should be considered in order to have a lethal effect on tumors. Linear accelerators are substitutes for previous methods of radiotherapy in all over the world. These machines can work in both electron and photon mode. The Monte Carlo technique has become ubiquitous in medical physics in the last 50 years. The range of applications is very broad in medical physics. The increased use of Monte Carlo techniques is... 

In this thesis, localization of a postulated noise from limited neutron detectors sparsely distributed throughout the core of a typical VVER-1000 reactor is investigated. For this purpose, developing a 2-D neutron noise simulator for hexagonal geometries based on the 2-group diffusion approximation, the reactor dynamic transfer function is calculated. The box-scheme finite difference method is first developed for hexagonal geometries, to be used for spatial discretisation of both 2-D 2-group static and noise diffusion equations. Using the discretised static equations, a 2-D 2-group static simulator (HEXDIF-2) is developed which its results are benchmarked against the well-known CITATION... 

This thesis introduces and investigates a new kind of scheduling model, in which the total amount of computational resources to be allocated at each moment by the processor is constrained and upper bounded by a constant. The time for a task to be executed is also dependent on the computational resources, dedicated to it by the processor, assuming that the multiplication of the execution time by the dedicated computational resources is a constant for each job. We investigate various objective functions, such as minimizing the number of tardy jobs, minimizing maximum latency and etc, under varying constraints. The investigated objective functions are: a) Minimize number of tardy jobs b)... 

Gorgan Bay and Miankaleh Wetland are considered as one of the biosphere reserves and among the areas of international importance in the Ramsar Convention, thus they have great importance. These two inseparable zones are located in the southeast of the Caspian Sea and are connected to the Caspian Sea through Chapaghli Canal and Ashuradeh Canal. The health and water quality of this area has undergone many changes over the years, and the re-reduction of its water level has caused concern among environmental activists. Since Miankaleh wetland is a shallow and semi-enclosed water area that is connected to the Caspian Sea through two narrow canals, pollutants that enter it from land will have a... 

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... 

Nowadays, multifunctional two-dimensional (2D) nanostructured materials due to their important role in biomedical and nanotechnological developments have gained the attention of many engineers and scientists with a wide spectrum of disciplines. The present work aims to provide an accurate description of the tensile behavior (from the initial unloaded state through axial strain of about 0.25) of the planar as well as low-buckled stanene and to capture their ideal strength in armchair- and zigzag-directions. Stanene is 2D hexagonal lattice which belongs to D6 hcrystal class having a six-fold rotational symmetry. For an accurate description of anisotropic response of such hyperelastic materials...