Sharif Digital Repository

Power amplifiers are used as the last block of transmitters. This block can be categorized as the one of most important part in communication systems. However, in transmitter systems which require high power to create stable link with the receivers, fabrication process like CMOS are unable to provide such level of power. Thus, designers employ another group of integrated circuits which names MMIC that offers this capability to designers. MMIC is the abbreviation of Microwave Integrated Circuit which is implemented in compound substrates like GaAs. Monolithic microwave integrated circuits enable the implementation of amplifiers in small size, large number, with high precision and appropriate... 

Platinum nanotubes were deposited inside the pores of polycarbonate template with the pore size of 200 nm by electrochemical methods. In this regard a solution containing of 0.05 M H2PtCl6 and 0. 1 M H2SO4 in doubly distilled water was utilized. The electrodeposition process was studied by electrochemical techniques such as voltammetry and chronoamperometry methods. It was observed that the process was conducted in several stages including; nucleation and growth in steady state regime. Furthermore, it was concluded that electrodeposition was affected by mass transport restriction and was controlled by a diffusion process. In this regard, all the voltammograms were shifted to more negative... 

Today Ethernet is the predominant technology for implementing Local Area Networks. Its privileges encourage service providers to extend Ethernet from Local Area Networks to Metropolitan Area Networks or even Wide Area Networks. Ethernet benefits such as low operational costs, well interoperability, plug-n-paly characteristic and rapid provisioning on demand make Ethernet ideal for Metropolitan Area Networks.But Ethernet by itself has some weakness like flat structure that makes it unfit for use in Metropolitan Area Networks. A suitable solution for taking advantages of Ethernet benefits in service provider network is using Ethernet in access network and applying multi-point to multi-point... 

Vehicular ad-hoc networks have attracted the attention of many researchers during the last years due to the emergence of autonomous vehicles and the safety concerns regarding their use in near future. One of the major applications in this domain is the usage of vehicle to vehicle communication for warning message dissemination in dangerous situations to prevent more damage. A number of schemes have been proposed regarding the selection of forwarding nodes in this application and there is a need for developing frameworks for analysis and comparison of the schemes in fair situation. Most of the proposed frameworks make use of simulation techniques for the analysis of schemes. However, due to... 

Paper and cardboard waste pulping consume large volumes of water, so the discharge of this effluent without proper treatment can have far-reaching environmental consequences. The color and variable COD concentration of wastewater in this industry make treating this wastewater complicated. Therefore, this study aims to reduce the COD of the wastewater treatment plant of a pulp and paper mill under different laboratory conditions to achieve environmental standards in Iran.In this study, coagulation-flocculation and the Fenton process on the wastewater entering the treatment plant were investigated first. It was found that coagulation and flocculation by 750-1250 ppm of alum coagulant and ten... 

Increasing population growth and scarcity of fresh water resources have created the challenge of water supply, especially in the Mena region. Thus, many countries in the region have turned to innovation in the development of high-energy seawater desalination technologies. Utilizing the waste heat of refineries in the desalination industry can reduce costs and preserve the environment. In this article, effective ways to use the waste heat of other flue recovery steam of Bandar Abbas oil refinery are investigated. The integration of the heat recovery system consisting of recuperative heat exchangers and heat pipes with thermal desalination plants is investigated by multi-stage flash and... 

In order to investigaton of dynamics behavior and determination of the aeroelastic stability of the turbomachine blade. the turbomachine blade is modeled by using the beam model, taking into account all degrees of freedom, the effect of warping, rotation and seting angle. For aerodynamic modeling, the Smith and Whitehead models are used which are valid in subsonic flow. 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. Then, by using the state feedback controller, the effect of sensor and piezoelectric actuator on the vibrations reduction of the structure and increasing the... 

Focusing on fossil fuel to secure energy demand lead to big challenges. Hydrogen as alternative for fossil fuel has attracted a lot of attentions. Fuel cell with an electrochemical reaction which it’s byproducts are water and heat convert Hydrogen into electricity. High efficiency and low environmental pollution, persuade many researchers toward fuel cell commercialization. But problems such as high cost, high power oscillation and inertia, avoid fuel cell from significant development. One way to deal with these problems is using the fuel cell and battery hybrid system. In recent decade too many research has been made in utilizing this hybrid system in transportation. This project... 

The short life of Polymer Electrolyte Membrane (PEM) fuel cells is one of the critical criteria to their commercialization. A longer operation life time should be achieved to reach high reliability, low $/kWh cost and to use fuel cells as economical alternative energy systems.Therefore,diagnosing degradation mechanisms and the causes of power loss in fuel cell life time is of great importance. Operating conditions affect output power density and performance degradation. To achieve maximum power generation through fuel cell life time, a model is needed which is able to estimate power density and performance degradation simultaneously regarding to operating conditions. In present work, a... 

In this project a framework for Model Based Fault Diagnosis (MBFD) in a Gas Transmission Network (GTN) was developed. A black-box linear state-space model was used to capture dynamic behavior of an industrial benchmark for GTN. A full fledge commercial network simulator were used to obtain the required data for process identification. In order to check the robustness of the model zero mean white noise was imposed on various output obtained by the commercial simulator. Kalman filter was used to estimate the states of the GTN. These estimated states along with the measured output (all obtained from the commercial simulator) are almost similar to their corresponding estimated signal. This shows... 

Inappropriate effects of fossil fuels and conventional power generation systems on the environment have necessitated a sustainable energy system for the next decade by growing interests in renewable energy systems. The world’s most fast-growing renewable energy resource is the wind energy. The main problem of wind power is the power fluctuations at the load side caused by the variable nature of wind speed, and the main issue in case of remote locations is the long-term storage of power generated by wind turbines. Batteries can be used to store a limited amount of energy for a short time. Although new advances in this field have been achieved, most common type of batteries is hardly able to... 

The gradual exhaustion of oil and gas resources and the various problems involved in their pollution makes it necessary to promote a renewable energy system. One of the most interesting developments of standalone systems based on the utilization of hydrogen is solar hydrogen system. Central and southern Iran exhibit an excellent solar climate which makes them ideal places for solar hydrogen systems. The economy of Iran is based on oil and it has one of the largest reserves of oil and gas in the world but the reserves would not be enough to meet the domestic and export markets starting in three to four decades. Moreover, elimination of energy subsidies in Iran, will led to more tendencies to... 

In this thesis a general model for simulation of solar cooler for domestic usage is developed. The model consists of 2 main parts: thermo-dynamical and economical calculations. The thermodynamic part consists of 4 sub models: a model for calculation of incoming solar radiation, cooling load demand calculation, the refrigeration cycle and the solar cycle with heat storage.As for hourly calculation of system performance part of the model produces the hourly received radiation data based on geographical position and orientation of the receiving surface. Base on results of the cooling load calculation for a 9 m2 studying room located in western part of Tehran, 1 TBR (3.516 kW) is chosen as...