Sharif Digital Repository

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 the present work, primary crystallization mechanism, glass forming ability, thermal stability and formation of nano Al crystals and their effects on the mechanical behavior were investigated in various Al amorphous alloy containing misch metal including Al90-xNi10-yFeyMMx (x=2-10%at, y=0-10 %at) alloys. In order to elaborate the Cu effect on the primary crystallization mechanism Al86Ni10-xCuxMM4(x=0-2/5) alloy were prepared. The results showed that in Al90-xNi10MMx (x=2-10 %at) alloying system variation of the misch metal from 2 to 10 atomic present results in increase in glass forming ability. The crystallization onset temperature also increases from 405 K in Al88Ni10MM2 to 630 K in... 

One of the most important steps in the process of network forensics is attacker attribution and tracing the victims of the attack. In some situations, there is no other information to track the attacker except the payload of packet. Network security professionals have introduced payload attribution techniques to attribute this type of attacks. In payload attribution techniques, a history of network traffic is stored so that after the attack, it can be queried to trace the source and destination of excerpts. Due to the high volume of traffic in today's networks, payload attribution techniques should be able to store traffic in compressed format so that querying on this data be done easily at... 

Cosmic Inflation, invented by Alan Guth in 1980’s, solves the shortcomings of the Standard Cosmology such as the flatness, the horizon and the monopoles problems and provides the seeds of large scale structure formation. The quantum fluctuations which are produced during inflationary epoch are redshifted and transferred from Microscopic scales to Macroscopic universe. We can observe this macroscopic fluctuations both on the CMB surface and on large scale structures. Data from WMAP and Planck missions(CMB space Telescopes) suitably confirms the general predictions of single field inflationary scenarios but still people search for finding primordial gravitational waves from the B-Mode signal... 

This thesis proposes a dynamic model for studding influences of suspension components behavior on rail vehicle dynamics. As the air springs are very important isolating component in rail vehicles, a new complete nonlinear air spring model, with taking into consideration of thermo–dynamical effects, is developed. The model coefficients are tuned based on the real test data and it can be easily used in dynamic modeling of air springs. The new proposed vehicle model is a complete track–vehicle model with 70 degree of freedoms which is addressed as a modular type. Experimental results from complete rail–vehicle field test, showed remarkable agreement between proposed model and test results.... 

There are different classes of event-driven softwares. These softwares include Graphical user interface, web application or embedded software. In these kinds of softwares, each user's action while using application is known as "event". The application responds to the action through changing behaviour and then waiting for another event. Testing software is the best way for checking the quality assurance of event-driven softwares. However, there are some problems as cause of creating lots of event sequences in testing these kinds of softwares. Therefore, many solutions are introduced for these problems. The goal of this report, is presenting new testing procedure for event-driven web... 

Due to the high level abstraction inherent in most formal specifications and the need to formally specify and develop nondeterministic systems, such as concurrent, probabilistic, and game-like ones, nondeterminism comes into formal specifications inevitably. As it will be shown in this thesis, after developing programs constructively from implicitly nondeterministic specifications, which have been written in the CZ (constructive Z) specification language, only one of the allowable, specified behaviors will appear in final programs. In this way, the implementer will be provided with only one of the possible implementations that is not necessarily the best one. When the nondeterminism involved... 

Quality Assurance is one of the crucial steps in software production and should be repeated. These days, software companies are using continuous integration (CI) pipelines for building software and controlling software quality. Regression test, is a test which is performed after each change in software, to assess the quality of the software system and its ability to meet functional and non-functional needs. Each execution of this test, leads to infrastructure costs and a waste of time for the software development team. The reason is that the development team has to wait until the test is completed to ensure that the changes are correct. To reduce this cost, methods such as prioritizing and... 

This study considers the flutter analysis rotating blade of a turbo machinery made of magneto rheological elastomer core. The Smith theory is used for modeling the compressible subsonic flow. The classical Hamilton’s principle along with the assume mode method is used to set up the equations of motion. The validity of the derived formulation is confirmed through comparison with those obtained from the finite element software and the available results in the literature. Various parametric studies including the effects of applied magnetic field, core layer thicknesses, rotating speed, setting angle are examined for considered configuration of the rotating blade. The results show that the first... 

One of the most crucial methods to Ensure correct software performance is testing. On this ground, one of the most critical discussions regarding software testing is the effectiveness of a test suite. Program state coverage is a criterion for determining the effectiveness of a test suite. This criterion indicates the number of program states that are executed for the lines. Since the total number of program states cannot be calculated to measure coverage, this criterion proposes a fixed number of 10 to measure program state coverage. Also, according to calculations for the program state in the execution of each line, the time complexity of this criterion is high. In this thesis, providing... 

Petrochemicals, refineries and power plants are among the biggest water-consuming industries. Of all systems in mentioned complex, most water is consumed in the cooling tower system, of which the feed water of the cooling tower accounts for the largest portion of water demand. Drainage loss (blowdown) which constitutes the biggest portion of the feed water losses, varies greatly with changes in source water quality and cooling water treatment. Scarcity of water, large quantities of cooling tower blowdown water and increasing of water price lead to activities for blowdown water treatment to reuse. In this project two pre-treatment methods and two final membrane treatment methods were... 

Bearing capacity of piles depends on many factors among which geometrical properties of piles, soil type, and strength properties of soil are of great importance. Based on these parameters, several approaches have been developed in order to overcome the uncertainty in the prediction of pile bearing capacity. Studies carried out in this area or research can be divided into two main categories: first, laboratory based approaches, and second, numerically based approaches. The research followed in the present study is based on numerical modeling. In this study, a single pile is initially modeled in the axisymmetric configuration and its bearing capacity is determined. The results of the model... 

The aim in the current thesis is to introduce a powerful method based on quantitative Acoustic Emission approach for structures health monitoring in a way that the proposed method can be used for industrial purposes. In order to do this, after presenting a survey on moment tensor concept and its relation to crack nucleation in solids, the equivalent forces of crack initiation are calculated. These forces are then applied on the meshed area of a 2D finite element model. The corresponding result is the propagation of acoustic waves which are modeled by using finite element analysis. After waveform data acquisition in the imaginary sensor positions and implying source location analysis, the... 

In this study, the use of a fixed bed of the Kaldnes commercial carrier in the activated sludge system has been investigated. In this way, at zero time, a submerged fixed bed of Kaldnes was placed into a completely mixed activated sludge reactor and its various parameters were investigated during the time. During the experiment, the fixed bed (Kaldnes carriers enclosed in a lace) with 20, 35 and 50 percentage of volumes were compared to regular activated sludge reactors (without any carriers). The studied parameters are COD, DO, MLSS, and P-PO43-. Input COD was changed at concentrations of 1200 and 400 mg/L, and the reactor hydraulic time was adjusted to 10 and 16 hours. It was observed that... 

In this thesis we investigate the consept of supreme Pfister forms developed by K. J. Becher. Let F be a field of characteristic different from 2. Several properties of F with respect to an anisotropic form ϕ over F are introduced and their relations are studied. A form ϕ is called supreme if it is anisotropic and every anisotropic form over F is a subform of ϕ. It can be easily shown that if F has a supreme form then F is nonreal and ϕ is a Pfister form. We see how examples of such fields may be obtained. Also we compare fields having a supreme Pfister form with n-local fields (i.e., fields which up to isometry have exactly two n-fold Pfister forms). Finally, we apply our results to the... 

In recent years, there have been many studies aimed at finding program defect using information of previous ones. These studies, by using the program text, previous bugs, and information related to version control and project management systems create an defect prediction model to find other defect prone areas in the program. The output of defect prediction methods is part of the program’s text, which is likely to have defects. Considering that the result of this method is just the text of the program and does not provide any extra information for finding defects to the user, these methods have not yet been applied to the software industry. On the other hand, by spreading the use of Q & A... 

Open abdominal surgeries come with risks such as hernia and damage. To address these risks, laparoscopic surgery was introduced. However, this method has limitations such as reduced vision and maneuverability for the surgeon. Artificial intelligence and image processing with deep learning methods have alleviated these limitations in recent years. This study aimed to enhance the performance of models for detecting and tracking instruments and tissues in laparoscopic Cholecystectomy (LC) surgeries. This is crucial for surgical assistants to identify surgeon errors and predict arm movements. The study focused on extracting real-time visual features of images to design and improve existing...