Sharif Digital Repository

It is necessary to evaluate dosimetry accuracy in the framework of advanced methods for radiation therapy such as Intensity Modulated Radiation Therapy (IMRT) to ensure reliability of a proposed treatment. The ability of the Monte Carlo codes to model linear accelerator (LINAC) and to calculate the exact dose distribution in clinical radiation therapy is one of the reasons to use such codes. The purpose of this project is to validate a treatment planning system with BEAMnrc and DOSXYZnrc Monte Carlo codes. In this study, the dose distribution obtained from DOSXYZnrc in considered to be thr main criterion with which the dose distribution obtained from treatment planning system is assessed and... 

Magnetic levitation is an appropriate solution for noncontact 3D manipulation. Workspace of the previously proposed maglev systems is confined to a relatively small cube, which severely limits the application of this technology. In addition, most of the previously given mechanisms require the design and application of a subsystem in order to unify their magnetic field. In this paper, a moving magnet is proposed which results in a horizontally extendable workspace; moreover, the field unifying section is not needed since one electromagnet only is used. Further, details of the mechanism and finite element based design procedure of the magnet are presented. Dynamic equations of the system... 

One of the frequent aspects of lawlessness at signalized intersections, is red-light violation (RLV). In addition to its adverse effect on intersection safety, RLV can cause delay in the startup of the vehicles in the next phase defined as “green flow”. In this research, in order to investigate the adverse effect of RLV, the required data were collected from two signalized intersections in the City of Esfahan, Iran using recording cameras. Then, using a cellular network in the intersections and the Aimsun traffic simulation software, the effects of RLV on the delay, capacity, and level of service of the intersections were evaluated. The results show that the behavior of the drivers in the... 

During the recent years, the emerging technology of photonic, on-chip communication has been widely explored to resolve the problems of traditional electrical communication in terms of performance and power consumption. Micro-Resonator (MR) as the photonic building block for optical comunication is very sensitive to temperature and process variation. Variation of resonance wavelength of a micro-resonator as a result of temperature fluctuations causes tremendous error for optical data routing through the waveguides, and reduce the reliability of network. A temperature-aware routing algorithm enables the network to tolerate fault and continue working properly. Temperature variation of MRs is a... 

In this thesis, we address the problem of joint Range, Angle and Doppler frequency estimation in FDA-MIMO radars. Target parameter estimation is among the most important areas of research in radar signal processing. In this field of research, there are numerous challenges to overcome, including low estimation accuracy, a scarcity of snapshots, and the high computational complexity of algorithms. For this reason, diverse methods have been developed to solve this problem. Each of these methods has its own features and capabilities, focusing on one or more of the existing challenges. The application of these methods also depends on various factors, including the signal structure, which is... 

In this thesis, zero-divisor ideal graphs and geometric zero-divisor graphs are introduced and are partially studied. We begin by studying the relation between the zero-divisor graph and zero-divisor ideal graph associated to principal ideal rings. We also investigate some of the basic properties of the zero-divisor ideal graphs, including their girth and diameter. Then, we introduce the geometric zero-divisor graphs associated to reduced schemes and study their basic properties to some extent. Finally, we conclude by characterizing all reduced schemes whose associated geometric zero-divisor graph contains a vertex which is... 

The main object of this thesis is synthesizing poly(vinyl acetate)/ colloidal silica nanocomposites via emulsion and in-situ polymerization methods. At the first, nanocomposites were produced in the presence of poly(vinyl alcohol) as the protective colloid, ammonium persulphate as the initiator and sodium bicarbonate as the buffer in an aqueous solution. Then, structural, thermal, rheological, mechanical and surface properties of produced nanocomposites with various colloidal silica content (0.5 %, 1 %, 1.5 %) were evaluated by DLS, FTIR, SEM-EDS, DSC, TGA, dynamic and steady rheological tests, tensile and shear mechanical tests, AFM and static water contact angle. The particle size of... 

Since the Iranian oil terminals company(I.O.T.C.) has been the main and strategic gateway of exporting petroleum in the country and plays an important role in the optimum continuity of national, regional and international energy supply chain and also conducting the needed projects whit a desirable quality and minimum time and cost has a prominent influence on steady continuity of manufacturing, importing and exporting of petroleum and gas production. The main purpose of doing this thesis is diagnosing the process of approval, design and implementation of projects in the I.O.T.C., Thus, whit regarding to the modern needs of implementing projects and the necessity of reviewing the structure... 

To deliver gas in time to different consumers like as industrial, commercial and domestic users is one of the most important parts in gas industry. So it is very important to utilize these projects in the specified time. There are huge harms for client, contractors and consumers when there is a delay in project utilization. To identify effective parameters on delays to remove them in future is an essential factor. In this research, all delay causes for TPGC (Tehran Province Gas Company) projects are analyzed and some solutions to remove these delays are presented. 10 hypotheses in relation of gas delivery have been assumed as delay causes. Then some questions have been discussed in relation... 

Nowadays, in communication industry, specially data network, in which service quality is a serious parameter, request for making connection with appropriate quality (Proportionate to demands) and necessity of clarification of obligations of service providers and customers, as well as customer awareness of submitted materials and offering various services with different qualities & costs, led service providers, specially IP based networks, to make agreements with their customers, entitled service Level Agreement (SLA). The SLA specifies the service type, mutual obligations, related parameters, measuring methods, violation threshold, penalties and loss compensation. Whereas, applying... 

Water is crucial to human being. We use water for a wide variety of uses daily. However, leakage has caused substantial water loss to our precious processed water. The major contributor to non-revenue water in Iran is pipeline leakages. The water industry in the nation has invested in equipment to detect and localize leaks in water distribution systems. One of the equipment mentioned is acoustic-based. The principle of acoustic is that whenever a leak is present in a pipeline, noise is generated and will travel along the pipeline. The acoustic leak detection method is then derived by calculating the distance traveled by this noise generated by the leak. Different equipment based on acoustic... 

Hierarchical voltage control is one of the conventional kinds of coordinated voltage control schemes which has been studied in some countries in the last decades. In this method network is divided into several voltage control regions and in each region voltage profile is controlled near optimal level, satisfying the economic and secure goals of the network performance. In this thesis, after the explanation of the main concepts of this scheme, its effects on the network voltage control is assessed and its performance is improved. First the primary concepts of hierarchical voltage control are explained. Then, the methods of the control regions determination and pilot nodes selection are...