Sharif Digital Repository

In drilling oil well with respect to depth of several thousand meters, knowing the physical conditions of down-hole well such as temperature, pressure and stress have particular importance in prevention of possible injuries such as breaking the drill bit or increasing temperature. If these data can transfer from down-hole to bore-hole of the well, the operators can prevent from critical conditions such as intertangle of the drill-string. Currently, because of this lack of information, there are irreparable damages in oil industry annually. Based on researches, because of down-hole conditions of the well, these data can’t transfer with electromagnetic telemetry. Currently one of the data... 

The use of wind energy and wind generators as an inexpensive type of renewable energy sources is increasing. Wind farms and distributed wind generators connected to the power transmission and distribution systems and microgrids, and wind generators in standalone mode of operation affect the stability and power quality of the grid. In this thesis, the performance of a matrix converter in grid connection of variable speed PMSG–driven wind turbine is improved. In this way, by transferring the matrix converter modulation matrix into the synchronous reference frame and decomposing it into the singular values, a new general method is proposed for analysis, modelling and modulation of a matrix... 

This thesis studies on diffusion-based molecular communication channel between two nano-machines. The effect of the amount of memory on performance is characterized, and a simple memory-limited decoder is proposed and its performance is shown to be close to that of the best possible decoder (without any restrictions on the computational complexity or its functional form), using Genie-aided upper bounds. This effect is studied for the case of Molecular Concentration Shift Keying; it is shown that a four-bits memory achieves nearly the same performance as infinite memory. Then a general class of threshold decoders is considered and shown not to be optimal for a Poisson channel with memory,... 

Nowadays almost all the research laboratories use femtosecond lasers, and Ti: sapphire laser is the most popular among them. Therefore, in this thesis, a Ti: sapphire pulsed laser with z-fold cavity with output of 50 fs and repetition rate of 100MHz has designed and simulated. Therefore, in the first chapter, introduction to the theory of ultrashort pulses and situation to create these pulses are presented. In addition, as regards to produce of short pulses, it is necessary to set laser in cw mode, in the second chapter we have investigated laser in cw mode. So, in this chapter, rate equations of gain medium, the stability zone of the laser, manner of removing astigmatism in the cavity,... 

Recently, the nano-bio communication networks have received significant attention. Among different communication mechanisms proposed for nano communication, diffusion based molecular communication (DMC) is the most promising scheme. This thesis focuses on DMC and first proposes a theoretical model for this scheme. In the next part of the thesis, inspired by the molecule transport mechanisms in the biological cells, two biosynthetic modulator structures are proposed.In first structure, an ion channel based modulator for DMC is proposed which controls the rate of molecule release from the transmitter by modulating a gating parameter signal. The corresponding average modulated signal, i.e., the... 

High-definition video streaming, multimedia file sharing, cloud computing, mobile networks and online gaming, all together, will increase the network traffic enormously every year.Long-haul optical fiber networks form the backbone of the Internet and scaling to higher throughput and lower cost per bit is essential to ensure continued growth of information technologies. For four decades, optical networks have exploited significant progress in physical technologies, including low-loss single-mode fibers (SMFs), high-performance lasers and modulators, and low-noise optical amplifiers. In parallel, communication methods have evolved to multiplex information in various physical dimensions in...