Sharif Digital Repository

Decision on the location of new wells through infill drilling projects is a complex problem that depends on the reservoir rock and fluid properties, well and surface facilities specifications, and economic measures. Conventional approach to address this is a direct optimization that uses the numerical flow simulation. However, this is computationally very extensive. In this study the authors use a hybrid genetic algorithm (HGA) optimization technique based on the genetic algorithm (GA) with helper functions based on the polytope algorithm and the neural network. This hybridization introduces hill-climbing into the stochastic search and makes use of proxies created and calibrated iteratively... 

Decision on the location of new wells through infill drilling projects is a complex problem that depends on the reservoir rock and fluid properties, well and surface facilities specifications, and economic measures. Conventional approach to address this is a direct optimization that uses the numerical flow simulation. However, this is computationally very extensive. In this study the authors use a hybrid genetic algorithm (HGA) optimization technique based on the genetic algorithm (GA) with helper functions based on the polytope algorithm and the neural network. This hybridization introduces hill-climbing into the stochastic search and makes use of proxies created and calibrated iteratively... 

Quality and continuity of electrical power to sensitive loads especially in power plants and industrial sectors is of great importance. For this reason, bus transfer is used. During the bus transfer interval, sensitive loads especially motors will be interrupted, and may encounter difficulties. So, it is used reactive power compensator and custom power devices to mitigate stress in motors and improve power quality indices. This paper presents the effect of reactive power compensator and custom power devices paralleling with motor in process of bus transfer which is done in two methods: EMTS and STS. Also, it is investigated dynamic performance of induction motor and spin-down curves in... 

The existence of a short C-H⋯π (alkyl-alkyne) interaction in the structure of a strained and relatively rigid tolanophane is expected to hinder the rotation about the C-C sp3 single bond. Variable-temperature NMR experiments (performed in three solvents, CDCl3, THF-d8, and acetone-d6) and ab initio density functional calculations were carried out to investigate its dynamic nature. An energy barrier of 48.6 kJ/mol is determined at coalescence (210 K) with acetone-d6 which is in good agreement with calculation result (54 kJ/mol). © 2008 Springer-Verlag  

In this article, a comprehensive 2D mathematical model has been developed to simulate process intensification of carbon dioxide absorption in the presence of nanoparticles in hollow fiber membrane contactors (HFMCs). The influences of nanoparticle were taken into account considering Brownian motion and Grazing effect as dominant phenomena of mass-transfer enhancement in nanofluids. The obtained simulation results were validated against experimental data reported in the literature and excellent agreement was obtained. It was found that by adding 0.05 wt % silica nanoparticles, the absorption rate could be enhanced by 16%, while the corresponding value is 32% for CNT nanoparticles. High... 

Rate constants, k A, for the aromatic nucleophilic substitution reaction of 2-chloro-3,5-dinitropyridine with aniline were determined in different compositions of 2-propanol mixed with hexane, benzene, and 2-methylpropan-2-ol and 1-ethyl-3-methylimidazolium ethylsulfate ([Emim][EtSO4]) with dimethyl sulfoxide at 25 C. The obtained rate constants of the reaction in pure solvents are in the following order: 2-methylpropan-2-ol > dimethyl sulfoxide > 2-propanol > hexane > benzene > [Emim][EtSO4]. Molecularmicroscopic solvent parameters corresponding to the selected binary mixtures were utilized to study the kinetics of a nucleophilic substitution reaction in order to investigate and compare the... 

Cyclic loading on asphalt concrete materials with a longer relaxation time and lower remaining stress lead to higher viscoelastic strain recovery. Consequently, more aggregate reorientation occurs and the rate of viscoplastic strain increases in subsequent cycles. The present study proposes a hardening relaxation constitutive relationship (fHR) as a function of accumulated recovered viscoelastic strain εrve based on experimental observation. This model captures the initiation and evolution of hardening-relaxation during the relaxation time and/or stress reduction under cyclic loading. The model was then coupled with viscoelastic, viscoplastic and viscodamage constitutive relationships. The... 

Molecular dynamics simulation method was employed to model mode I crack propagation in plates containing nanoscale clusters of impurities located in the vicinity of the crack tip. The plates and the clusters were considered to have an fcc structure. The interactions between the dissimilar atoms in the plates and clusters were modeled via the many-body Sutton-Chen inter-atomic potentials [Sutton, A.P., Chen, J., 1990. Long-range Finnis-Sinclair potentials. Philos. Mag. Lett. 61, 139-164], and their extended versions developed for fcc alloys by [Rafii-Tabar, H., Sutton, A.P., 1991. Long-range Finnis-Sinclair potentials for fcc metallic alloys. Philos. Mag. Lett. 63, 217-224]. In this paper,... 

This paper presents a novel method for cooperative educational dissemination systems. Taking into consideration the inherent characteristics of distance learning video streams (existence of a few slow moving objects in a classroom), we have proposed a novel content-based video coding method that is very efficient at low bitrate channels. On the encoding side, we have applied a background subtraction algorithm for motion segmentation using a novel statistical background modeling approach. At each frame, the moving objects are extrapolated with a rectangular model and tracked frame by frame (which forms the only data needed to be sent over the channel). On the decoding side, we have used a new... 

Transaction cost theory is largely used to investigate the formal domain of land and housing. In the informal domain, however, this perspective has been employed largely as a supplement in addressing the other fundamental notion in new institutional economics—property rights—despite the possibility that informality in land development can emerge regardless of the informality or formality of such rights. To cover this gap, this study developed a theoretical framework based on transaction cost theory to explain the formal–informal dichotomy in land development. The proposed framework maintains that land development depends on engaging in transactions that involve total or partial ownership of... 

In this study, the robust sliding mode attitude control of a tethered satellite system using optimal tether offset in the presence of perturbations and uncertainties is investigated. The three main goals of this study are: (1) comprehensive modeling of two satellites connected by a tether considering the coupling between their attitude and position, (2) finding a robust attitude control for both satellites, and (3) reducing the reaction wheels’ power consumption for attitude control utilizing the tether tension. In this regard, the 6 DOF governing equations of the coupled nonlinear rotational and translational dynamics of a two-satellite tethered system in the presence of perturbing forces... 

Transaction cost theory is largely used to investigate the formal domain of land and housing. In the informal domain, however, this perspective has been employed largely as a supplement in addressing the other fundamental notion in new institutional economics—property rights—despite the possibility that informality in land development can emerge regardless of the informality or formality of such rights. To cover this gap, this study developed a theoretical framework based on transaction cost theory to explain the formal–informal dichotomy in land development. The proposed framework maintains that land development depends on engaging in transactions that involve total or partial ownership of... 

The chitosan-grafted-poly(N-vinylcaprolactam) (chitosan-g-PNVCL) nanofibers were synthesized via electrospinning method. ZIF-8 metal-organic frameworks nanoparticles were incorporated into the nanofibers for adsorption of Cr(VI), As(V) and phenol from water. The BET, FTIR, XRD and SEM analysis were carrfried out to obtain the characteristics of nanofibers. The optimum parameters of ZIF-8 content, pH, contact time, adsorbent dosage, and initial concentration of adsorbates on the Cr(VI), As(V) and phenol removal were studied. The reusability of synthesized nanofibers for five sorption-desorption cycles was also examined. The maximum experimental adsorption capacity of the... 

ZSM-5 (Seolite Sconoy Mobil) aluminosilicate zeolites synthesized by the hydrothermal method were incorporated into the hydrophobic ethyl cellulose (EC) nanofibrous membrane. The performance of synthesized nanofibers was investigated for a gravity driven oil–water separation. The synthesized ZSM-5 nanozeolites and EC/ZSM-5 composite nanofibers were characterized using XRD, FESEM, XPS, FTIR and AFM analysis. The permeability of EC/ZSM-5 5 wt% for oil in water mixture was in order of n-hexane (5170 ± 60 L/m2 h) > n-heptane (4600 ± 50 L/m2 h) > cyclohexane (4350 ± 35 L/m2 h) > pump oil (3780 ± 28 L/m2 h) > lubricating oil (3200 ± 25 L/m2 h) > motor oil (2980 ± 20 L/m2 h) with a separation... 

Photocatalytic reduction of p-nitrochlorobenzene was studied over aluminosilicate-based AgBr and AgBr-TiO2 photocatalysts which were prepared and characterized. The photoreaction was performed in the presence of LiBH4, which is a strong reducing agent, in the solution medium. A new mechanism is proposed for reduction of p-nitrochlorobenzene under photocatalytic conditions. The effect of pH, illumination source, LiBH 4 concentration, temperature, catalyst dosage, and alcoholic scavengers was also studied. The results showed that the best efficiency was obtained over Ag/AgBr/TiO2/aluminosilicates at natural pH under UV light. We observed that the reaction yield was affected by changing the...