Sharif Digital Repository

In water drive or waterflooded reservoirs, a significant amount of oil is remained in the reservoir as the residual oil. A process known as gas assisted gravity drainage, in its tertiary mode, has been applied in a number of conventional reservoirs to recover this residual oil. Gravity drainage is the main mechanism of oil recovery in the gas assisted gravity drainage enhanced oil recovery process. Previous investigations has shown that gravity force, spreading coefficient, three phase capillary pressure and reservoir wettability have significant effect on oil recovered via this process. The feasibility of using such a process in a naturally fractured reservoir is investigated in this work... 

In the area of material studies, the atom structure models are the basis of all simulations and methods. With improvements in computers power, these models have become more consistent with experimental results. New theoretical methods combined with supercomputers assist to an understanding with detail and accuracy of material behavior at the atomic scale that leads to develop of the Computational Materials Science. Recently, developments in fields such as quantum mechanics, statistical physics, solid-state physics, quantum chemistry, computer science and graphics, allowed for faster computing which leads a powerful tool for material calculations and designs. New computer applications allow... 

In this thesis, we aim to study the elastic-plastic behavior of short fiber reinforced composites experimentally and analytically. The experimental investigation is applied to glass fiber-polypropylene composites (PP/GF). The samples are produced by injection process with maximum temperature of 190C. Fibers are randomly oriented in this procedure of fabrication. The samples are tested in tension, and the mechanical strength is measured by changes in fiber content. The Young's modulus is also investigated in these experiments.Also in this thesis, an analytical model for calculation of Young’s modulus of fiber reinforced composite materials is proposed. In this analysis a displacement field is... 

Signle-channel speech enhancement using hidden Markov model (HMM) based on minimum mean square error (MMSE) estimator is focused on and an HMM-based speech enhancement in Mel-frequency domain is proposed. The MMSE estimator results in a weighted sum filtering of the noisy signal in which accurate estimation of the filter values and filter weights comprise the main challenges. The cepstral domain modeling for speech enhancement is motivated by accurate filter selection in this domain. In the propsed framework, Mel-frequency spectral (MFS) and Mel-frequency cepstral (MFC) features are studied and experimented. In addition to the spectrum estimator, magnitude spectrum, log-magnitude spectrum... 

In this study, gelatin/polyvinylpyrrolidone semi interpenetrating polymer network scaffold was synthesized in presence of glutaraldehyde as a cross linker and a porous structure was obtained by freeze drying method. The biocompatible network with properties like huge porosity, good thermal stability and establishing different interactions, was employed as an extractive phase in needle trap device and used for evaluation of benzene, toluene, ethylbenzene and xylene (BTEX) in conjugation with gas chromatography-flame ionization detector. For investigating semi interpenetrating polymer network efficiency, Different ratios of gelatin and polyvinylpyrrolidone (gelatin/polyvinylpyrrolidone: 1:0,... 

In this study, two layer nanocomposite membrane of polyethersulfone (support layer) and polyamide (active layer) were prepared for the purpose of desalination of water by forward osmosis method. In order to take more advantage of this membrane, montmorillonite nanoparticles which had been modified by graphene oxide were placed in it. To bind the nanoparticle components together, at first, montmorillonite was functionalized by (3-Aminopropyl) triethoxysilane to increase its nucleophilicity, and for graphene oxide to increase its electrophilicity, thionyl chloride was added. The two compounds were mixed and stirred for 24 hours in the presence of triethylamine base by magnetic stirrer at 30°C...