Sharif Digital Repository

Nowadays, by development of technology and population, rivers have been faced environmental issues. In one hand, due to the several factors that can affect rivers pollution, it is not easy to propose a comprehensive solution for the above mentioned issues, while, on the other hand, it is necessary to address and resolve some of these issues as soon as possible. Considering rives as a system, there are lots of economic, political and quite a few other factors which try to change the condition to their own interest. In order to find a solution that satisfies all the effective parameters up to a certain limit, a mathematical tool, called the Game theory method, is utilized. In this research, we... 

Today, the process of corrosion and compensation of minor injuries, without the need for tracing or any other physical interference, has become one of the subjects of interest to researchers. Inhibitors have been considered as one of the anti-corrosion agents. In this research, safflower extract as a green inhibitor in sodium chloride corrosive environment was used to evaluate the rate of corrosion of mild steel. Also the MoS2 nanoparticles were used as carrier of this green inhibitore in the epoxy coating to allow the activation of the coating in a scratched state in sodium chloride solution of 3.5%. In the first step, the extract of the safflower was prepared to reach the best part of this... 

Hydrothermal supercritical method is one of the most suitable methods for metal oxide nano powder, ceramics and mineral catalyst synthesis. Metal oxides nanopowder in its pure or mixed form has wide potential application as chemical industrial catalyst, hot Superconductors, magnetic material, gas sensors and car catalyst convertors. One of the most important metal oxides aspects of application is uranium oxide as nuclear reactor fuel is used. In addition, UO2 is selective catalyst for converting methane to methanol process and Decomposition of organic Chlorine material. In Supercritical hydrothermal method done in high pressure reactor with critical to fluid, is new method for the... 

The growth of the word wide Internet causes to increase the request of subscribers for various applications of multimedia which having different traffic characteristics. In order to provide such applications which generate divers data traffic with different transmission rate and quality of service, we need to design a network supporting multi-rate and multi-quality (multi-service) transmission. In this study we present two schemes to support multi-service transmission in generalized multi-protocol label switched (GMPLS) core networks. In the first scheme we use multi-length variable-weight optical orthogonal codes (MLVW-OOC) as signature sequences of optical code division multiplexing system... 

In this thesis the performance of the all optical AND gates, based the Four Wave Mixing process (FWM), for application in optical communication and computing systems, has been investigated. In the performance analysis of these AND gates, we mainly focus on its application in the receivers of the Optical Code Division Multiple Access (OCDMA) systems. For analyzing the performance of these receivers we utilize the existing mathematical model for FWM [1-5], which leads to the nonlinear Schrodinger (NLS) coupled equations. The attenuation, chromatic dispersion and Raman scattering effects have been taken into account in this model and the scalar approximation, for approximating the relation... 

With the emergence and development of ultra broadband communication systems incorporating ultrashort pulses, the design of suitable receiver structures became one the most significant problems in such systems; since due the limited bandwidth and speed of current electronic devices, most of the existing receiver structures cannot be used properly. In the field of radio communications, the design of simple and low power consumption receivers for ultrawideband (UWB) and millimeter wave band communication systems, which do not rely on complex channel estimation mechanisms, is of much interest. In ultrashort light pulse optical communication systems –and specially coherent optical CDMA systems–... 

Achieving various data rates over a wide range of applications and in a multiple-access scenario should be done under certain power and bandwidth constraints. Emerging UWB communications has opened a novel perspective against different wireless network challenges, especially overwhelming data rates. In the research field, we begin our thesis with exposition of UWB, narrowband interference and spread time codes. We elaborate on the properties of spread time codes through frequency domain analysis of a reusable multiple-access scheme. Evaluating the variance of ISI, MAI and RUI, we demonstrate the spread time codes behave in an optimum manner, i.e., the most RUI resistibility, along with all... 

Nowadays, microgyroscopes are among the most important products of MEMS. The production of small, precise and inexpensive gyroscopes has become possible as the result of recent developments in fabrication technology. In this thesis it is intended to introduce a new method for manufacturing more precise microgyroscopes regarding manufacture facilities. Using this new method, sensitivity and resistance of microgyroscopes are increased against noises which are primarily caused by vibration and rotation about undesirable axes. The rotational movement imposed on the gyro is detected through fluid flow within its torus channel. This transformation facilitates the measurement of the initial motion.... 

The fiber-reinforced composite materials possess advantage for structural purpose in various industries. Delamination is recognized as one of the major causes of damage during drilling of fiber reinforced composites, which not only reduces the structural integrity, but also has the potential for long-term performance deterioration. It is difficult to produce precise quality holes with high efficiency by conventional drilling method. Drilling is frequently applied in production cycle while the anisotropy and nonhomogeneity of composite materials affect the chip deformation and machining behavior during drilling. In this thesis, a new non-traditional drilling technology is presented for solve... 

Optical Wireless Communication is believed to have a great potential in establishing point to point connection and have attracted an unexpected growth in research , applications and market. Furthermore, Optical wireless systems have recently emerged as a new means of communication, especially in places where electromagnetic interferences is of utmost concern such as in passenger planes and hospitals and in other communications applications where cost could is of concern. In this thesis we build upon previously introduced wireless optical code-division multiple –access communication. In the context of an OCDMA system we begin our study by considering synchronization circuit via a... 

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, we statistically model and analyze one of the main systems in optical communications which are based on Second HarmonicGeneration (SHG) process. To this end, we first introduce various applications of this process in optical communication systems and see that the main application of this nonlinear process is in the process of optical clock recovery in both of OTDM and SPE_OCDMA networks. In the rest of the thesis, we characterize the mathematical structure of these systems and use that to statistically analyze their behavior. In considering the optical clock recovery system based on SHG, we introduce three intrinsic sources of timing jitter in the system, namely, the On-Off... 

International trade arrangements have been considerably developed in recent decadees. Especially, one can note the role of these factors in economic development and improvement of life standards in member countries. In the meantime, Economic Cooperation Organization (ECO) was established in 1985, by Iran, Pakistan and Turkey and then extended by seven other countries: Afghanistan, Azerbaijan, Kazakhstan, Kyrgyzstan, Tajikistan, Turkmenistan and Uzbekistan. Improving economic development and intra-group trade of member countries is one of the main objectives for the group. The purpose of this research is to estimate the ex-post effects of ECO on the intra-group trade of member countries....