Sharif Digital Repository

In this paper, a numerical model is developed for the assessment of carbon dioxide transport through naturally fractured cap-rocks during CO2 sequestration in underground aquifers. The cap-rock contains two types of fracture with different length scales: micro-cracks (fissures) and macro-cracks (faults). The effect of micro-cracks is incorporated implicitly by modifying the intrinsic permeability tensor of porous matrix, while the macro-cracks are modeled explicitly using the extended finite element method (X-FEM). The fractured porous medium is decomposed into the porous matrix and fracture domain, which are occupied with two immiscible fluid phases, water and CO2. The flow inside the... 

In this study, copper oxide nano particles were synthesized by batchwise supercritical hydrothermal method. After preparation of CuO nano particles, they were immobilized into the porous matrix of sodium alginate. The drying process formed a very porous structure that is useful for enhancing of adsorption activity. Produced CuO particles were characterized by X-ray diffractometery (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and BET for measuring the surface area. The prepared materials were then used as adsorbent in the removal of toxic metal ions in aqueous solution. To optimize the adsorption system, the effect of various parameters such as adsorbent... 

It is widely accepted that, in fluid flow and transport in fractured porous media, there exists some degree of block-to-block interaction that may lead to capillary continuity. The formation of liquid bridges causing interaction between blocks will affect oil recovery from naturally fractured reservoirs. However, the accurate modeling of the growth and detachment of liquid bridges that may cause capillary continuity between matrix blocks remains a controversial topic. In an attempt to improve our understanding of the problem, a mechanistic model is developed in this work for the formation of liquid bridges between porous blocks. The proposed model considers growth and detachment of pendant... 

This note considers the effect of different Darcy numbers on the onset of natural convection in a horizontal, fluid-saturated porous layer with uniform internal heating. It is assumed that the two bounding surfaces are maintained at constant but equal temperatures and that the fluid and porous matrix are in local thermal equilibrium. Linear stability theory is applied to the problem, and numerical solutions obtained using compact fourth order finite differences are presented for all Darcy numbers between Da = 0 (Darcian porous medium) and Da → ∞ (the clear fluid limit). The numerical work is supplemented by an asymptotic analysis for small values Da. © 2007 Elsevier Masson SAS. All rights... 

Eu3+- and Ce3+-doped yttrium silicate, as well as Eu2+-doped zinc silicate nanoparticles, were grown in a porous SiO2 matrix using an impregnation method. For Y2Si 2O7:Eu3+, particles of about 50 nm size were obtained that exhibited several photoluminescence (PL) peaks in red. Different peaks showed slightly different decay times; however, their excitation mechanism was found the same. Increasing the Eu concentration increased the PL intensity while reducing the decay time. Y2Si2O7:Ce 3+ nanoparticles in the porous matrix showed bright blue emission, consisting of two peaks at 358 nm and 378 nm. Re-impregnation process was found effective in changing the relative intensity of the two peaks....