Sharif Digital Repository

This research provides an atomistic picture of the role of ions in modulating the microstructural features of an oil-contaminated calcite surface. This is of crucial importance for the rational design of ion-engineered waterflooding, a promising technique for enhancing oil recovery from carbonate reservoirs. Inspired by a conventional lab-scale procedure, an integrated series of molecular dynamics (MD) simulations were carried out to resolve the relative contribution of the major ionic constituent of natural brines (i.e., Na+, Cl-, Mg2+, Ca2+, and SO42-) when soaking an oil-bearing calcite surface in different electrolyte solutions of same salinity, namely, CaCl2, MgCl2, Na2SO4, MgSO4, and... 

A molecularly imprinted xerogel (MIX) for fentanyl was successfully prepared on the inner surface of a copper tube by sol-gel technology. Primarily, the tube was treated by self-assembly monolayers of 3-(mercaptopropyl) trimethoxysilane and then [3-(2,3-epoxypropoxy)-propyl]-trimethoxysilane was employed as a precursor for imprinting the template molecule in acidic conditions. During the sol-gel process influential parameters including volume and concentration of fentanyl were carefully investigated to obtain the most efficient and appropriate xerogel. In parallel, a non-imprinted xerogel (NIX) was synthesized in the absence of fentanyl. The extraction efficiencies achieved from MIX and NIX,... 

The present work deals with a novel approach for grafting a sol-gel based sorbent, using diazonium salts for preparation of an unbreakable capillary microextraction (CME) device in on-line combination with high performance liquid chromatography (HPLC). The use of diazonium salts modifier allowed all types of metallic and non-metallic substrates to be used without any limitation. Substrates including copper, brass, stainless steel and polytetrafluoroethylene (PTFE) were chosen to be functionalized by chemical or electrochemical reduction of 4-amino phenyl acetic acid. Then, 3-(trimethoxysilyl)propylamine (3TMSPA) was selected as the precursor and the only reagent for preparation of the... 

Reinforced polydiphenylamine (PDPA) nanocomposite was synthesized by oxidation of diphenylamine in 4molL-1 sulfuric acid solution containing a fixed amount of carbon nanotubes (CNTs) in the presence of cetyltrimethylammonium bromide (CTAB). The surface characteristic of PDPA and PDPA/CNT nanocomposites was investigated using scanning electron microscopy (SEM). The prepared PDPA/CNT nanocomposite was used as an extraction medium for microextraction in packed syringe (MEPS) of selected pesticides from aquatic environment. The effect of CNT doping level and the presence of surfactant on the extraction capability of nanocomposite was investigated and it was revealed that when 4% (w/w) of CNT in... 

An attempt was made to combine μ-solid phase extraction and headspace single drop microextraction techniques and use their advantages for trace determination of some volatile organic compounds in aqueous samples. After performing the two-step preconcentration approach, the desired analytes were determined by gas chromatography-mass spectrometry. A resorcinol-formaldehyde-based xerogel was used as the extraction medium in the μ-solid phase extraction (μ-SPE) method. Then, the extracted BTEX was eluted with a rather large amount of methanol. To remove the laborious process including solvent evaporation and further reconstitution, which is usually accompanied by loss of analytes and accuracy,... 

In recent years, improving oil recovery (IOR) has become an important subject for the petroleum industry. One IOR method is infill drilling, which improves hydrocarbon recovery from virgin zones of the reservoir. Determining the appropriate location for the infill wells is very challenging and greatly depends on different factors such as the reservoir heterogeneity. This study aims to investigate the effect of reservoir heterogeneity on the location of infill well. In order to characterize the effect of heterogeneity on infill well locations, some geostatistical methods, e.g., sequential gaussian simulation, have been applied to generate various heterogeneity models. In particular, different... 

A bacterial strain was isolated and cultured from the oil excavation areas in tropical zone in southern Iran. It was affiliated with Pseudomonas. The biochemical characteristics and partial sequenced 16S rRNA gene of isolate, MR01, was identical to those of cultured representatives of the species Pseudomonas aeruginosa. This bacterium was able to produce a type of biosurfactant with excessive foam-forming properties. Compositional analysis revealed that the extracted biosurfactant was composed of high percentages lipid (∼65%, w/w) and carbohydrate (∼30%, w/w) in addition to a minor fraction of protein (∼4%, w/w). The best production of 2.1 g/l was obtained when the cells were grown on... 

This paper develops a two dimensional Green element simulator based on a "compatibility-equation" algorithm for simulation of counter-current spontaneous imbibition (COUCSI) process. The Green element method is a novel computational approach based on the boundary integral theory, which is regarded as a hybrid combination of both boundary and finite element methods. The superiority of the Green element method in modeling of two phase water/oil flow is at the core of this paper. The developed simulator within the context of this proposition is explored to predict the oil recovery from a one dimensional single matrix block. The results are then compared with the experimental data, and they... 

The concern over fossil energy shortage for the next decade leads to the extensive research activities in the area of enhanced oil recovery. Steam injection as one of well known EOR process has been used for about five decades to improve the oil production rate and recovery efficiency. Steam flooding is applied to heavy and extra-heavy oil reservoirs; however it could be used in light oil reservoirs in which water injection do not work effectively. Regardless of different performances, this method is an efficient EOR process for both heavy and light oil reservoirs. In this work, two separate numerical models were prepared to investigate steam flooding performance for the recovery of light... 

Phase behavior of active crude oil/alkaline was systematically studied in the presence of cosolvents. For this purpose, several factors have been considered: alkaline concentration, oil concentration, and type of brine. The best composition was used to generate emulsion for rheology and displacement tests. Furthermore, precipitation of alkaline was eliminated by its synergy with EDTA. Next, rheology of emulsion was analyzed by which a Power law model was developed that indicates non-Newtonian behavior of emulsion. Moreover, the viscosity of emulsion was reduced by the addition of cosolvent as well as by the increase of alkaline concentration. Finally, the best formulation (containing... 

H2S and CO2 are the main impurities in raw natural gas, which needs to be purified before use. However, the comprehensive utilization of H2S and CO2 has been ignored. Herein, we proposed a fully resource-based method to convert toxic gas H2S and greenhouse gas CO2 synchronously into CO and elemental S by using a novel electrochemical reactor. The special designs include that, in the anodic chamber, H2S was oxidized rapidly to S based on the I−/I3− cyclic redox system to avoid anode passivation. On the other hand, in the cathodic chamber, CO2 was rapidly and selectively reduced to CO based on a porous carbon gas diffusion electrode (GDE) modified with polytetrafluoroethylene and cobalt... 

This paper presents an experimental evaluation of transient effects on SRAM-based FPGAs. A total of 9000 transient faults were injected into the target FPGA using Power Supply Disturbances (PSD). The results show that nearly 60 percent of faults cause system failures and about 58 percent of the faults lead to corruption of the configuration data of the FPGA chip. © 2005 IEEE  

The main purposes of this study were to scrutinize experimentally effects of polymer and rock types on the oil recovery using water and polymer flooding processes. Four dynamic flooding experiments were carried out at simulated reservoir condition of temperature and pressure. According to the obtained results, the ultimate oil recovery by water flooding in highly fractured reservoirs was less than reservoirs with the microfractures. The results of polymer flooding showed that in addition the polymer molecular weight, the sulfonation of polymers also affects the oil recovery  

Since oil reservoirs are limited and energy demand is increasing, seeking for high efficient EOR processes or enhancing the efficiency of current proposed EOR methods for producing trapped oil from reservoirs are highly investigated. As a way out, it is possible to couple the EOR and nanotechnology to utilize the efficiency of both methods together. Regarding this possibility, in the present study, in the first stage of investigation stable and uniform water-based solution of nano-sized particles of copper oxide with different concentrations (0.01–0.05 M) were prepared and then injected into the core samples. In the first stage, the effects of different surfactants with respect to their... 

the failure in cluster at a high level can bring up great damages to the system in wireless sensor networks where clustering techniques are used. Certain methods have been reported in the literature in recovering the sensors from a failure cluster. One of the most important methods is to recover the sensors in run-time and without clustering. But it is so much ideal to suppose that all the sensors will be recovered. In this paper, we proposed a method that can operate on the remained sensors that are not recovered. © 2009 IEEE  

Natural Gas Distribution Networks (NGDNs) are complex infrastructure systems that play an essential role in ensuring the welfare and prosperity of many communities by serving their residential, commercial, industrial, and transportation sectors. Earthquakes can damage the critical components of NGDNs and disrupt their services. The disruption of NGDN services can lead to significant economic and social losses. These losses can be mitigated by adopting appropriate resilience enhancement measures. This study puts forward a probabilistic framework to quantify the seismic resilience of NGDNs. This framework comprises multiple interconnected probabilistic models that work in harmony to... 

Cotton fabrics have been prepared with smart properties by functional finishing with stimuli-responsive nano gel. A biopolymer (chitosan) and a synthetic polymer (poly-NiPAAm) have been used for the synthesis of nano gel through semi-batch surfactant-free dispersion polymerization (SB-SFDP) method. The incorporation of nano gel to textile fabrics is achieved by pad-dry-cure procedure, using an aqueous nano gel dispersion and 1,2,3,4-butantetracarboxylic acid as a crosslinking agent. With this cross linking method, it is possible to integrate the nano gel into the cotton fabric’s structure with good resistance to washing. The changes in physiological comfort parameters of cotton fabric such... 

In this paper, a general Checkpointing technique for rollback error recovery for embedded systems is proposed and evaluated. This technique is independent of used processor and employs the most important feature in control flow error detection mechanisms to simplify checkpoint selection and to minimize the overall code overhead. In this way, during the implementation of a control flow checking mechanism, the checkpoints are added to the program. To evaluate the Checkpointing technique, a pre-processor is implemented that selects and adds the checkpoints to three workload programs running in an 8051 microcontroller -based system. The evaluation is based on 3000 experiments for each... 

The aim of this work is to analyze methane-fed internal reforming solid oxide fuel cell-gas turbine (IRSOFC-GT) power generation system based on the first and second law of thermodynamics. Exergy analysis is used to indicate the thermodynamic losses in each unit and to assess the work potentials of the streams of matter and of heat interactions. The system consists of a prereformer, a SOFC stack, a combustor, a turbine, a fuel compressor and air compressor, recuperators and a heat recovery steam generator (HRSG). A parametric study is also performed to evaluate the effect of various parameters such as fuel flow rate, air flow rate, temperature and pressure on system performance. © 2007... 

Asphaltene precipitation and deposition within the reservoir formation is one of the main concerns during enhanced oil recovery (EOR) processes especially during the gas injection. In the current study, different aspects of carbon dioxide (CO2) and nitrogen (N2) injection in the reservoir, was thoroughly examined. The feasibility of using these gases as the injection gas was explored using Bayesian network-based screening method. After recombination and preparation of the live crude oil, precipitation of asphaltene using vanishing interfacial tension (VIT) method and core flooding experimentation was examined. Besides, swelling test was utilized to investigate the effect of CO2 and N2...