Sharif Digital Repository

In this dissertation, site-specific ultrawideband propagation modeling has been presented based on ray tracing. The empirical, statistical and site-specific methods are compared and the ray tracing method is selected as an efficient and accurate site-specific approach for indoor propagation modeling. The challenges of the ray tracing method in propagation modeling of ultrawideband electromagnetic waves are outlined and some solutions are presented.In order to increase the efficiency of finding the propagation paths, the modified wavefront decomposition method is presented. This method intelligently reduces the number of emitted rays and finds the exact propagation paths from the transmitter... 

There is an ever rising interest for propagation simulation and communication channel modeling in indoor environments. Thus the demand for the development of proper software to perform these computations has been the motivation for a lot of researches on proper algorithms for these calculations. The most popular one is the ray tracing which is faster than other algorithms and needs only simple calculations. Still, the large number of these calculations needed to achieve proper accuracy does not allow ray tracing to achieve the desired speed in indoor environments. Numbers of methods have been proposed to increase its speed. One of which is the modified wavefront decomposition method which is... 

In¬¬ this thesis we review adomian decomposition method in solving differential equations.First described the technique and then we will introduce two ways to obtain adomian polynomials.In the next section to ompare two methods of adomian decomposition and Taylor series with two examples, we will solve an example and compared decomposition method with the Picard method and finally using Cauchy-Kowalewski Theorm Convergence of answer Series shown and it will present a rate of convergence  

These days, most companies are creating Closed-loop Supply Chains or they are adding Reverse Supply Chain to their existing Forward Supply Chain. Reducing raw material consumption, profit, customer satisfaction and environmental laws are most important reasons of this phenomenon. In the Closed-loop Supply Chains, companies collect the end of life and the end of use products and then if the quality of the returned product is good enough, that product with be refurbished and will be sold again and if the quality of returned products is not good enough to be refurbished, companies will use its good parts in manufacturing new products and the rest of the parts would be sent to disposal centers....