Sharif Digital Repository

Particle capture at porous media in cross-flow microfiltration is studied to investigate permeability reduction as a function of membrane pore size and particle size distribution. A new model in pore scale and its pertinent mathematical expressions, which consider pore and particle size distribution, are provided. Permeability reduction of the membrane because of size exclusion during particulate suspension flow was predicted using the developed model. It is assumed that the size exclusion is the dominant mechanism of particle retention causes pore blocking and permeability reduction in the porous media.The exact analytical solution of the stochastic model for size exclusion is used to... 

A totally computerized image processing program package is developed to analyze the SEM images of membrane surface and cross-section. Pore size distribution and porosity of the fabricated membranes are determined using the proposed image processing procedure. Furthermore, effect of coagulation bath temperature on the morphology and mechanical properties (such as tensile strength, strain break, tensile energy absorbent, and tensile stiffness) of Polysulfone (PSf) membranes are investigated. The results reveal that the mechanical properties are higher when N-methyl-2-pyrrolidone (NMP) is used as solvent. Also, an increase in the coagulation bath temperature caused a monotonous increase in the... 

Poly(vinyl alcohol)-polyethylene glycol, PVA-PEG, blended membrane were prepared using supercritical fluid assisted phase-inversion method, in which scCO2 was used as the anti-solvent. Poly(vinyl alcohol) was utilized as the main polymer, polyethylene glycol as the additive, and dimethyl sulfoxide (DMSO) as the solvent of these polymers. Taguchi method was used to investigate the effect of some operating parameters on the morphology of the membranes. The L16 orthogonal array was selected under the following conditions: pressure (100, 135, 165 and 200 bar), temperature (40, 45, 50 and 55°C) and PEG weight percent (0, 0.33, 0.66, and 1%). Total polymer concentration of solutions in all... 

This work concerns simultaneous determination of relative permeability, capillary pressure, pore size distribution (PSD), and residual oil saturation data by optimization of well testing data, and introduces a new capillary pressure relationship, based on the Weibull distribution function, for direct determination of the PSD function from capillary pressure parameters. Three consecutive injection, fall off, and production well tests are performed on a predefined synthetic reservoir through simulation, and an optimization algorithm is used to find the parameters of relative permeability and capillary pressure curves as well as the value of residual oil saturation. The PSD function is also... 

Carbon corrosion is a major degradation mechanism in cathode catalyst layers (CCL) of polymer electrolyte membrane (PEM) fuel cells. Carbon corrosion (coupled with ionomer dissolution/degradation) induces severe changes in the CCL structure. In the present study, the inter-relation between the particle size of a packed sphere medium and the pore size distribution (PSD) is established. This relation is then used to predict the agglomerate size of the mix of Pt/C and ionomer in the catalyst ink, using experimentally measured PSD of the CCL. During cell degradation, the size of these agglomerates decreases; since, carbon corrosion causes carbon particles to decrease in size. Furthermore, as... 

Most of the reservoirs in Iran and also around the world are in the middle of their production life and have passed their natural production period. Therefore, they should be a candidate for immiscible injection, e.g., water injection for secondary recovery, and/or miscible injection, like solvent injection for tertiary recovery. Also, it should be pointed out that most of the Iranian reservoirs are carbonate reservoirs. This type of reservoir is fractured and heterogenic. Heterogeneity causes an earlier breakthrough and immiscible injection causes an unstable front, which leads to a lower recovery. This article presents the modified equation of Buckley-Leverett and fractional flow... 

The aim of the work reported was to investigate the effect of bases and neutralization steps on hydrogel microstructures. A series of porous hydrogels with various pore sizes were prepared by neutralizing a conventional hydrogel after gel formation. Scanning electron microscopy was used to characterize the microstructure of the porous hydrogels. The morphology of the samples showed the pores were induced into the hydrogels by water evaporation and gas release resulting from the neutralization process. Experimental results indicated that the hydrogels had an absorbency of 200-220 and 48-50 g g-1 for distilled water and sodium chloride solutions, respectively. A simple method was used to... 

Packing of cubic particles arises in a variety of problems, ranging from biological materials to colloids and the fabrication of new types of porous materials with controlled morphology. The properties of such packings may also be relevant to problems involving suspensions of cubic zeolites, precipitation of salt crystals during CO2 sequestration in rock, and intrusion of fresh water in aquifers by saline water. Not much is known, however, about the structure and statistical descriptors of such packings. We present a detailed simulation and microstructural characterization of packings of nonoverlapping monodisperse cubic particles, following up on our preliminary results [H. Malmir, Sci.... 

Preparation, characterization and evaluation of new generation of micro-filters based on polyacrylonitrile electrospun nanofiberous membrane (ENM) were thoroughly investigated. First, quantitative relationships between average diameter, bead area density of nano-fibers and certain electrospinning parameters, i.e., concentration, voltage, spinning distance, and feed rate, were established by empirical modeling based on a central composite design. The analysis revealed that concentration, voltage and distance are the significant parameters. Also, adequacy checking indicated the appropriateness of fit for the models. Afterwards, bead-free ENMs with diameter of 100-500 nm were prepared and... 

A novel and efficacious strategy was implemented for creation of mesoporous TiO2 films and powder through an integration of sol-gel and evaporation-induced self-assembly (EISA) processes aided by triblock Pluronic P123. A mesoporous crack-free thin film with virtual thickness of 300 nm was attained under 10% relative humidity aging, for 72 h at the low temperature of 5 °C. Further, the TiO2 film with porous structure has been formed from conventional paste, exploiting as-prepared mesoporous titania powder. The X-ray Diffraction (XRD) of synthesized mesoporous powder disclosed formation of anatase phase as well as rutile phase, in such a manner that the latter constituted a very small... 

A thorough understanding of determining factors in angiogenesis is a necessary step to control the development of new blood vessels. Extracellular matrix density is known to have a significant influence on cellular behaviors and consequently can regulate vessel formation. The utilization of experimental platforms in combination with numerical models can be a powerful method to explore the mechanisms of new capillary sprout formation. In this study, using an integrative method, the interplay between the matrix density and angiogenesis was investigated. Owing the fact that the extracellular matrix density is a global parameter that can affect other parameters such as pore size, stiffness,... 

In this study, the effect of different parameters on the fluid transport in a fractured micromodel has been investigated. All experiments in this study have been conducted in a glass micromodel. Since the state of wetting is important in the micromodel, the wetting experiments have been conducted to determine the state of wetting in the micromodel. The used micromodel was wet by water and non-wet regarding normal decane. The fracture network, distribution of pore size, matrix construction, and injection rate are the most important parameters affecting the process. Therefore, the influence of these parameters was studied using five different patterns (A to E). The obtained results from... 

This paper reports the fabrication of electrospun polydimethylsiloxane (PDMS) membranes/scaffolds that are suitable for three-dimensional (3D) cell culture. Through modification the ratio between PDMS and polymethylmethacrylate (PMMA) as carrier polymer, we report the possibility of increasing PDMS weight ratio of up to 6 for electrospinning. Increasing the PDMS content increases the fiber diameter, the pore size, and the hydrophobicity. To our best knowledge, this is the first report describing beads-free, durable and portable electrospun membrane with maximum content of PDMS suitable for cell culture applications. To show the proof-of-concept, we successfully cultured epithelial lung... 

Porous NiTi-shape memory alloy (SMA) is a promising biomaterial with desirable mechanical property and appropriate biocompatibility for human implant manufacturing. In this research, porous NiTi-SMAs have been successfully produced by using thermohydrogen process (THP). This process has capability of production of homogenous structures, appropriate pore-size distributions and short sintering times. The THP-SMA samples produced in this research have a low Young's modulus (19.8 GPa) and a high tensile strength of 255 MPa. These properties are close to those of the natural bone and can meet the mechanical property demands of the hard-tissue implants for heavy load-bearing applications. The... 

Changes of morphological parameters of oil shale under thermal conditions are investigated. Analyses are based on 26 micro-computed tomography (micro-CT) images of Green River immature shale rock available under creative commons license. Several image processing and characterization algorithms are applied to sequential high-resolution micro-CT images of oil shale samples undergoing pyrolysis. Pore-scale morphology is extracted and quantified, providing results for pore size, throat size, grain size, specific surface, coordination number, and fracture aperture. The results demonstrate critical increases of porosity, coordination number and fracture aperture in the temperature range from 390... 

Biocompatible porous polymeric scaffolds provide a suitable environment for proliferation of stem cells in human body. In this research work, porous gelatin–poly(ethylene glycol), PEG, based scaffolds were prepared using combination of freeze-gelation and freeze-extraction methods. Effects of various parameters such as freezing temperature, cross-linking agent, concentrations of gelatin and PEG and their blending ratio on physical and mechanical properties, swelling ratio, porosity, pore size, and degradation rate of scaffolds were investigated. Also, proliferation of fibroblast skin cells on the scaffolds was examined by MTS assay to assess the suitability of the scaffolds in wound healing... 

This study investigates the effects of polymer concentration and solvent type on the pore size distribution (PSD) of the fabricated gas-liquid membrane contactors (MCs). Eighteen flat-sheet MCs are fabricated using polysulfone (PSf) and polyethersulfone (PES) polymers, with polymer concentration of 10%, 15%, and 20%. Dimethylformamide (DMF) and n-methyl-2-pyrrolidone (NMP) solvents are used to prepare the polymeric solutions. The role of polyvinylpyrrolidone (PVP) on the mean pore size of MCs is also studied. Scanning electron microscope (SEM) analysis is applied to visualize the pore system of the fabricated MCs. Image processing technique is used to obtain the PSD of the fabricated MCs... 

Volatile organic compounds are a major cause of air pollution; therefore, VOCs are a serious fulmination for the environment. According to studies, adsorption processes have a high performance for the removal of pollutants that by selecting the proper absorbent, efficiency will be improved. In this work performance of two metal organic frameworks are studied so porous materials named MIL-101(Cr) and MIL-53(Fe) as an adsorbent for the removal of ethylbenzene have been synthesized hydrothermally. The materials were characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) analysis, adsorption of ethylbenzene, field emission scanning electron microscopy (FESEM),...