Sharif Digital Repository

We use the 3D vectorial Gaussian beam tracing method to model millimeter wave propagation. We simulate the propagation of Gaussian beams in a large scale environment at 62.4 GHz. First, a known far field pattern of the transmitter antenna is expanded into a set of Gaussian beams. We chose Gabor expansion based method to expanding radiating field into Gaussian beams. Then, a Gaussian beam tracing model considering reflections and transmission is used to represent urban microcell propagation. We use a phase matching method to find reflected Gaussian beam The results of the Gaussian beam tracing simulations including line-of-sight (LOS) and non-Iine-of-sight (NLOS) propagation are compared with... 

A novel low power with high performance low current comparator is proposed in this paper which comprises of low input impedance using a simple biasing method. It aimed for low power consumption and high speed designs compared with other high speed designs. The simulation results from HSPICE demonstrate the propagation delay is about 0.7 ns and the average power consumption is 130 μW for 100 nA input current at supply voltage of 1.8 V using 0.35 micron CMOS technology. © 2009 IEEE  

An efficient algorithm for the design optimization of the compressible fluid flow problem through a flexible structure is presented. The methodology has three essential parts: first the behavior of compressible flow in a supersonic diffuser was studied numerically in quasi-one-dimensional form using a flux splitting method. Second, a fully coupled sequential iterative procedure was used to solve the steady state aeroelastic problem of a flexible wall diffuser. Finally, a robust Genetic Algorithm was implemented and used to calculate the optimum shape of the flexible wall diffuser for a prescribed pressure distribution. © 2006 Elsevier Ltd. All rights reserved  

Static recrystallization and microstructural changes in austenitic stainless steel 304L were studied. The rolling experiments at 200 °C were carried out, and then, annealing treatment was made at temperatures ranging between 500 and 830 °C. A model was also developed to simulate the kinetics of non-isothermal recrystallization within the rolled steel. The distribution of plastic strains during rolling was predicted utilizing an elastic–plastic finite element formulation performed in ABAQUS/Explicit, while the predicted results were used to generate the as-rolled microstructure and to estimate the stored energy. Finally, microstructural–thermal model based on cellular automata was developed... 

In this work, non-isothermal annealing of cold-rolled 304L austenitic stainless steel was studied at temperatures ranging between 400 and 800 °C. In the first place, a dual-phase structure containing work-hardened austenite and strain-induced martensite was produced by means of multi-pass plate rolling, and then, the deformed steel was subjected to annealing heat treatments. To determine the distribution of stored strain energy in the rolling operations, an elastic–plastic finite-element modeling was conducted. Afterwards, an artificial neural network technique was coupled with the thermal-cellular automata model for prediction of martensite reversion, temperature history, and... 

A new conceptual framework of collective orientation in team contexts has recently been proposed in terms of vertical and horizontal dimensions of idiocentrism and allocentrism. A two-phase longitudinal study of 270 university students engaged in 86 academic groups partly confirmed the conceptualization by identifying four interpretable factors: vertical and horizontal idiocentrism, horizontal allocentrism, and avoiding arguments. The results of exploratory and confirmatory factor analyses and a structural model of relationships between the four dimensions in both phases of the study are reported in this article. © 2007 Sage Publications