Sharif Digital Repository

PD detection can be done using on-line or off-line methods. Online PD detection methods have several advantages; such as: increasing system reliability, outage time reduction and higher safety. This method doesn’t need any special high voltage source. When on line monitoring is carried out for PD measurement, the noises in the environment and the electromagnetic interference (EMI) make it difficult to detect the PD signal. Therefore de-noising should be employed to filter out the interferences involved in the detected signal. In this thesis wavelet transform is introduced for this purpose. In this method, the background noise in the site of measurement is recorded as a reference noise to be... 

Fog computing environment consists of several devices which distribute across an arbitrary topology. Each of these devices is capable of carrying out a designated computation simultaneously with other devices. One of the common ways of describing a computation is through the usage of workflows. Workflow is a flexible and formal way of modeling tasks and their requirements for execution. A workflow is essentially a DAG. Therefore, it can model the data dependency between tasks quite accurately. The complex structure of a workflow in conjunction with the homogenous nature of devices in a fog environment makes it difficult to find a resource management algorithm to minimize execution time, used... 

In this research, the spectral difference lattice Boltzmann method (SDLBM) is developed and applied for an accurate simulation of two-dimensional (2D) inviscid and viscous compressible flows on the structured and unstructured meshes. The compressible form of the discrete Boltzmann-BGK equation is used in which multiple particle speeds have to be employed to correctly model the compressibility in a thermal fluid. Here, the 2D compressible Lattice Boltzmann (LB) model proposed by Watari is used. The spectral difference (SD) method is implemented for the solution of the LB equation in which the particle distribution functions are stored at the solution points while the fluxes are calculated... 

This project focuses on the design of fuel drop tanks for airplanes that add minimal drag and positive lift to the flying object. This will obviously effect the stability and dynamic performance of the airplane. To reduce adverse dynamic effects the tank was divided to several segment with a special emptying sequence. The add-on tank has to have no interference with the object existing systems and require minimum structural changes in the object. Several designs were proposed and the one gaining highest marks was selected. The flow field and the dynamic behavior of combined vehicle and drop tanks were studied using FE simulations. The result shows that adding a drop tank with optimized... 

In this study, the nano-scale deformation mechanism of cementite was investigated with aid of Molecular dynamics (MD) simulation using MEAM potential. For this purpose, flow localization was evaluated in various structures such as single crystal cementite, nanocrystalline (NC) cementite, and lamellar cementite at various temperatures and different stress conditions. In order to understand the deformation mechanism in the cementite single crystal, two cylindrical samples with 15 nm length and 5 nm diameter oriented along [001] and [011] were constructed. The result of tensile test simulation at 100 K, 300 K, 700 K and 1100 K revealed that the deformation mechanism in single crystal cementite... 

Continuous synthesis of different kinds of industrial copolymers plays an important role in economics of the polymer industry. But copolymerization reactions are complex and with a high degree of nonlinearity so the control problem in this case needs a detailed study on system dynamic behavior. One of the solutions is using a optimal control method in the shape of predictive controllers. The main goal in this thesis is to design a generalized multi-varriable predictive controller for a solution copolymerization of methyl methacrylate and vinyl acetate in a continuous stirred tank reactor with separator and recycle stream. In this study, after simulating the nonlinear model of the process... 

Cancer can be defined as a stochastic phenomenon. Thus, the tumor growth can be defined as a stochastic process. A Cancer tumor can be analyzed by its geometric shape. Furthermore, computing fractal dimension of shapes is a useful technique to analyze chaosity and complexity of shapes. This approach can be used to compare results from laboratory with simulated results of a mathematical model. A stochastic model of tumor growth will be presented. And some geometrical properties will be analyzed through computer simulation of the model  

Recent experimental studies have demonstrated that the lowering of brine could alter the wettability of the oil-brine-rock systems from an oil-wetting state toward a more water-wetting state. This so-called “Low-salinity effect” (LSE) is one of the main effects of the enhanced oil recovery technology based on low-salinity waterflooding. “Double layer expansion” (DLE) in the thin brine film is proposed as the principal mechanism of this phenomenon. Nonetheless, the role of the electrical behavior of the oil/brine and rock/brine interfaces on the kinetics and dynamics of this process is not well understood. Moreover, since most of the previous works have either dealt with a thin film at...