Sharif Digital Repository

Preformed particle gels (PPGs) in solutions have been widely used to suppress excess water production in mature oil reservoirs and, in turn, to improve the amount of oil recovery in brown oil fields. In this study, PPG solutions were meticulously formulated and synthesized in order to be utilized in harsh environments in terms of pressure, temperature, pH, and salinity from a free radical polymerization process. In this work, nanosilica gel at different weight percentages was added to improve the mechanical and thermal stability properties of the PPG at harsh condition: high pressure, temperature, and strain. Moreover, the effects of nanosilica gel at various concentrations, ranging from 0.0... 

The objective of this work is to develop a new Preformed Particle Gel (PPG) suspension to enhance oil production and monitor water production in a porous medium on micromodel scale. To achieve the above goal, the following synthetic method was used. At the outset, the PPG samples were synthesized with polyethylene amine (PEI) as a crosslinker, 2,2′-Azobis (2-methylpropionamidine) dihydrochloride (AAPH) as initiator and acrylamide (AM) and 2-Acrylamido-2-methylpropanesulfonic acid (AMPS) monomers to improve the strength properties of PPGs by the radical polymerization method. Also, to characterize the micro and macro structural the samples, the scanning electron microscopy (SEM),... 

In this work, a novel method to synthesis of an acrylic superabsorbent hydrogel was reported. In the two stage hydrogel synthesis, first copolymerization reaction of acrylonitrile (AN) and acrylamide (AM) monomers using ammonium persulfate (APS) as a free radical initiator was performed. In the second stage, the resulted copolymer was hydrolyzed to produce carboxamide and carboxylate groups followed by in situ crosslinking of the polyacrylonitrile chains. The results from FTIR spectroscopy and the dark red-yellow color change show that the copolymerization, alkaline hydrolysis and crosslinking reactions have been do take place. Scanning electron microscopy (SEM) verifies that the synthesized... 

This study presents a novel statistical volume element (SVE) for micromechanical modeling of the white matter structures, with histology-informed randomized distribution of axonal tracts within the extracellular matrix. The model was constructed based on the probability distribution functions obtained from the results of diffusion tensor imaging as well as the histological observations of scanning electron micrograph, at two structures of white matter susceptible to traumatic brain injury, i.e. corpus callosum and corona radiata. A simplistic representative volume element (RVE) with symmetrical arrangement of fully alligned axonal fibers was also created as a reference for comparison. A... 

The relative vulnerability of spinal motion segments to different loading combinations remains unknown. The meta-analysis described here using the results of a validated L2-L3 nonlinear viscoelastic finite element model was designed to investigate the critical loading and its effect on the internal mechanics of the human lumbar spine. A Box-Behnken experimental design was used to design the magnitude of seven independent variables associated with loads, rotations and velocity of motion. Subsequently, an optimization method was used to find the primary and secondary variables that influence spine mechanical output related to facet forces, disc pressure, ligament forces, annulus matrix... 

A detailed 3D anatomical model of the patellofemoral joint was developed to study the tracking, force, contact and stability characteristics of the joint. The quadriceps was considered to include six components represented by 15 force vectors. The patellar tendon was modeled using four bundles of viscoelastic tensile elements. Each of the lateral and medial retinaculum was modeled by a three-bundle nonlinear spring. The femur and patella were considered as rigid bodies with their articular cartilage layers represented by an isotropic viscoelastic material. The geometrical and tracking data needed for model simulation, as well as validation of its results, were obtained from an in vivo...