Sharif Digital Repository

Supersymmetry breaking mechanism is an unanswered question. Which is not allowed to break at tree-level in MSSM due to supertrace restrictions. Most theories suppose it’s broken in a dark section, much higher energies than electro-weak and its impacts as soft SUSY breaking terms emerged in Lagrangian. Here, in a different approach, an extension of MSSM with a U(1) and Stueckelberg superfield along with nonlinear gauge transformation, provides an additional condition to present a tree-level SUSY breaking mechanism. Mass mixing term in Stueckelberg’s Lagrangian or kinetic mixing are two methods of such an extension. The particles mass terms, solving the Higgsino mass parameter problem µ,... 

Data mining (DM) is one of the newest techniques which is used in decision making. DM helps the specialist to find the valuable knowledge which is hidden in data, with different techniques. DM has many research areas such as scientific research, medical fields, health care, fraud detection, marketing and customer relationship, sport, and games, and where ever there is data. Unfortunately, in our country, DM is not engaged seriously and there are fallacies of DM that weaken its efficiency. In this thesis, which is prepared in two sections, at the first section different techniques of DM are described and in the second section DM process is performed for a real world problem. For this purpose,... 

A major breakthorugh in all-optical wireless and wired communication networks is taking place in the last mile such as access networks. In this case، study-ing various multiple-access techniques in all-optical domain، especially optical code-division multiple-access (OCDMA) technique is of utmost importance. In this thesis we study several key signalings and modulation techniques in the con-text of their performance، energy and throughput efficiency for OCDMA systems. In particular we introduce novel multilevel signaling techniques for OOC-based fiber-optic CDMA systems and present their corresponding all-optical receiver structures using advanced optical devices such as optical-logic-gate... 

In this thesis a mutliScale model based on the Cauchy-Born hypothesis and via usage of XFEM is proposed for crack modeling. By solving an example, the important of surface effects in the surface stresses region is shown. Considering not being able to model the surface effects with the Cauchy-Born method, the boundary Cauchy-Born method for modeling crack effects is used. Moreover, three Molecular Dynamics method for modeling crack will be proposed. According to the obtained results from these methods, it was deduced that for calculating the correct surface stresses in Molecular Dynamics the mutual interaction of upper and lower atoms of crack should be omitted. Finally, the validation of... 

Modeling and Control of Ethylene Oxide Reactor In this thesis, steady and dynamic modeling of an ethylene oxide fixed bed reactor has been studied and one dimensional pseudo homogeneous model was used for simulating the reactor. Kinetic parameters were obtained by minimizing an object function and using the genetic algorithm. A good agreement is observed between simulation and experimental results. In steady state condition, the influence of some parameters such as shell temperature, feed rate were investigated on the performance of the reactor. The heat of reaction is used to produce steam. A dynamic model for steam drum was also considered and used for control purpose. A PI controller was... 

This thesis presents the development of a Finite Element Model (FEM) for a new type of Beam-Column Semi-Rigid steel connection. This connection consists of a steel semi cylinder connected to a plate and inserted on the top and bottom of the beam connecting it to the column by welding. It seems that changing the geometry of the semi cylinders and their weld lengths can have a great influence on the rigidity or flexibility of the connection. Therefore, meaningful categories of the connection with different semi cylinder geometries and weld lengths have been modeled and investigated by means of a Finite Element Modeling software ABAQUS, and their moment-rotation curves were driven. Also the... 

The conventional cameras and displays do not have the ability to record and display the full brightness of the world around us. These deficiencies have led to the development of methods known as High Dynamic Range Imaging. Most of the work done in this field falls into two groups: compression of the light range and its expansion. In compression, the brightness range is intended to display content with a high dynamic range in simple displays. But the goal of expanding the brightness range is to reconstruct HDR content from a low dynamic range one. In addition to the above classification, this field is also categorized based on the type of content (image or video). In this study, the... 

The parameters within the reactor core can be categorized into two distinct groups of measurable parameters and unmeasurable parameters. The determination of unmeasurable parameters, such as void fraction and critical heat flux, plays a pivotal and fundamental role in predicting the occurrence of accidents and emergency situations within the reactor. The utilization of deep neural networks represents one of the methods for accurately and reliably estimating these parameters within future temporal intervals. Such estimations facilitate the implementation of necessary measures to prevent accidents or mitigate their consequences. In this study, we employ three deep neural network models namely... 

In this research, the thermohydraulic parameters of the reactor of Bushehr power plant have been compared between the activation or not of the emergency gas extraction (YR) system by the operator during the LB-LOCA accident, without access to the active part of the ECCS. Bushehr nuclear power plant reactor is of VVER-1000 type and has a primary and secondary circuit, which is completely modeled in this research. After the complete review and understanding of the primary circuit and its systems, the information required for modeling has been collected from the existing documents of the power plant, and after that, the modeling and sizing of the heart components and the four main rings and the... 

Brine in crude oil causes many problems that underpin the importance of its separation. In recent years brine in crude oil has been increased with increase of the oil fields lifetime and its separation has been more important. One of the most effective separation methods is electrocoalescence. In this research, the simulation of brine droplets motion and their coalescence under the effect of electric field have been investigated by using the Computational Fluid Dynamics method and the droplets size distribution has been calculated under different values of electric field magnitude. The motion of two single brine droplets in stagnant oil phase and the behavior of many numbers of droplets in...