Sharif Digital Repository

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 this thesis, we investigate the involutions of a Clifford algebra induced by involutions of orthogonal group in characteristic two. Several properties of these involutions, such as the relations between their invariants and their decompositions are studied. Also it is shown that a tensor product of quaternion algebras with involution can be expressed as the Clifford algebra of a suitable quadratic form with an involution induced by an involution of orthogonal group. Finally, in connection with the Pfister factor conjecture formulated by D. B. Shapiro, split tensor products of quaternion algebras with involution over a field of characteristic two are investigated  

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... 

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... 

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... 

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... 

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... 

The purpose of this research is to monitor the health of structures using the updated finite element model, in which digital images are used to optimize the numerical model. Structural Health Monitoring (SHM) is always an important and significant issue that has attracted the attention of many researchers in recent years. In general, some researches have been conducted in this field using physical sensors that provide discrete data to the system for analysis. Using cameras to monitor the structure makes it possible to extract continuous and integrated data from the structure using digital images, which is a significant advantage compared to physical sensors.In this research, a steel... 

Rapid growth of technology and the increase in availability of fast communication means caused transportation planners to pay attention to solutions of demand management with an aproach to information technology. Replacement of traditional shopping with internet shopping can be seen as a suitable solution to reduce traffic and polution. Purpose of this research is to probe teleshopping choice and the frequency of doing that, simultaneously, using copula model as the most common aproach of joint models in recent years. In this research, the binary logit model is used to build the model for teleshopping choice and the order logit model is used to build the frequency model. The data sample is... 

Identifying the success factors of construction projects is one of the most important issues in project management. Lack of sufficient and comprehensive knowledge of project success factors makes it difficult to control, monitor and operate projects. Therefore, identifying the factors influencing the failure or success of projects according to the type of projects by managers, employers and executives can provide a good framework for evaluating and reviewing project outputs for them. Also, recognizing the success factors of projects can help to manage the appropriate allocation of resources throughout the life of the project. The result of this study can increase the existing knowledge about... 

Aluminum Bronzes have many applications in marine environments. These alloys suffer from both hot cracking and cold cracking. In order to overcome the hot cracking and cold cracking, Semisolid Stir Joining method and a proper thermal cycle was used respectively. Effects of temperature, stirring rate, and tool type were investigated in Semisolid Stir joining method. In this method, butt joint design was used in order to place specimens, and the specimens were heated up to specific temperatures (920, 925, 930°C). A stirrer (Cylindrical and Grooved tool) with three rotational speeds (800, 1200, 1600 RPM) was introduced into the stir weld seam. Welded specimens were cooled to the 900°C... 

Rehabilitation science has been proved that, in most cases, manipulation of injured body part, repeatedly, can help in returning the performance of that part. So robots can be useful for rehabilitation applications. Rehabilitation robots can record physical parameters such as position, velocity and force, so can play important role in developmentof making decisions on exercise types. Among the existing robots, cable-driven robots have specifications such as vast workspace, low cost, flexibility and light weight which make them suitable for rehabilitation applications.
The purpose of this research is kinematic design of a multi-link cable-driven robot for arm rehabilitation.In the most of...