Sharif Digital Repository

Nowadays, applications of the synthetic materials are developing in civil engineering projects and widely used in these projects. Therefore, during previous years; use of the Geotextiles as one of the Geosynthetic materials in order to filtration, drainage, separation, soil protection, etc have developed ever-increasing. The goal of this research is modeling and studies of the Geotextiles application in the downstream filter zone of embankment dams in combination with granular materials using FLAC2D software. Gordeh Bin embankment dam situated in West Azerbaijan province has been chosen as case study. In this matter, different models have been made with changes in thickness of the inclined... 

Developing new micro and nano devices, help us instruction micro and nano devices in very small scales. Also nano technology improved in recent decades especially in century 21th. These devices contained many important members, such as micro and nano filters, micro channels, sensors, and electrical chipsets. Navier-Stockes equations with slip and no-slip conditions can not used in transition and free molecular regimes. Since most of the MEMS and NEMS devices working in slip and transition regimes, then we must using DSMC for simulation these devices. DSMC is a physically method and working on the physics bases. Also it was derived from Boltzmann equations by Bird. In this study, we want... 

In this study, irregularities of the mode shapes are utilized to determine the delamination situation in a composite laminated beam. Modal analysis is used to obtain the mode shapes of the beam; afterwards, the mode shapes are filtered to extract their irregularities. Presence of any delamination and its situation (number, size and location along the length and thickness of the beam) affects the extracted irregularities. Here, detection of delamination is based on these irregularities of the mode shapes. One of the most important advantages of this method is that unlike many other similar methods, in many cases, the mode shapes of damaged structure are sufficient and the exact mode shapes... 

The existing transmission line models of plasmonic nanostructures are modified in this thesis to study the electromagnetic characteristics of nano-plasmonic structures in a more efficeint yet accurate enough fashion. First, rectangular plasmonic cavities made by carving dielectric rectangles within a metallic region are modeled by trasnmission lines of finite length being appropriately terminated at their both ends. The resonance conditon in the proposed model yeilds the resonance frequencies, quality factors, and mode profiles of its correspondig plasmonic resonator. The accuracy of the proposed model is assessed by using the fully numerical finite-difference time-domain method (FDTD)... 

Particulate air pollution is one of the top environmental health risks. Industrial processes like power generation from fossil fuels and steel and cement manufacturing release a huge amount of particles into the atmosphere. Moreover, internal combustion engines produce a considerable amount of particulate matter in populated areas. The usual way to overcome this risk is using air-cleaning devices such as filters. Filters are designed for specific purposes like removing aerosol particles, aerosol sampling and collecting valuable particles. Because of its diverse applications, filtration has become an active area of research and many kinds of filters are currently available. One type of... 

This study is aimed at simulation of the flow of air and aerosol particles through a single square fibrous filter media made up of micro fiber as well as the importance and effect of different fiber’s cross-sectional shapes and arrangements on particle deposition and filtration efficiency. An understanding of the role of changing the laminar flow regime from laminar vortex shedding "(Re"=100" and Re"=200")" to subcritical flow "(Re"=1000")" developed for the first case. The study deals with parallel and staggered multi-fibrous filter media with circular, elliptical, and equilateral triangular micro fiber’s cross-sectional shape of the transient laminar vortex shedding flow "(Re"=200")" .... 

A novel low noise quadrature voltage-controlled oscillator (QVCO) with differential N-path filter is proposed in 0.18-μm CMOS technology. The said QVCO benefits from a cross-coupled structure and a current-reuse technology to produce the quadrature signal and to save power consumption and area, respectively. The new architecture reduces the phase noise by 8dBc/Hz at a 1MHz offset frequency for 2.4GHz oscillation frequency. QVCO consumes 9.8mW from 1.8V power supply when operating at 2.4GHz. QVCO has a frequency tuning range from 2.4GHz to 3GHz and achieves a FOM of 191dB at 1MHz offset. Switches of N-path filter are controlled by outputs of QVCO, so the center frequency of N-path filter is... 

In this study, the effect of external filter on the various parameters of image quality in digital industrial radiography by CR method for steel and aluminum piece has been investigated. The filter reduces the noise of scattered beams by absorbing the low-energy beams in the X-ray spectrum that are most likely to be scattered, but high filter thicknesses can attenuate the more energetic beams and have a negatively effect on the image quality. On the other hand, the absorption of those low-energy beams increases the average spectrum energy and thus reduce the contrast, so it is necessary to use the appropriate material and thickness of the filter. For this purpose, to examine the filter... 

Two algorithms for solving constrained nonlinear programming problems (NLPs) are proposed. The first algorithm is an inexact nonmonotone filter sequential quadratic programming iNFSQP method. In each iteration of the algorithm, the search direction is computed using an inexact solution of a strictly convex quadratic program (QP). The search direction is a descent direction for the objective function (in feasible iterations) or a descent direction for the constraints violation function (in infeasible iterations). In this algorithm, the penalty parameter is updated in such a way that the search direction is a descent direction for the penalty function, which is a combination of the objective...