Sharif Digital Repository

CdSe nanowires were grown in polycarbonate track etched membrane with pore diameter of 80 nm by an electrochemical deposition technique. The mechanism of the growth was studied during the potentiostatic deposition of nanowires. X-ray photoelectron spectroscopy and energy dispersive spectrometry results showed binding of fragments and fraction of atoms for the CdSe nanowires. Microstructure and morphology of synthesized CdSe nanowires were observed by scanning electron microscopy. Optical spectrophotometry technique was used to determine the energy band gap of CdSe nanowires. It was found that the nanowires were resistive in the dark and exhibited a pronounced visible light photoconductivity.... 

Dyslipidemia is considered to be one of the main heart risk factors, affecting the endothelial vascular function, which can be non-invasively investigated by ultrasound flow-mediated dilation (US-FMD). However, US-FMD comes at a high-cost and is operator-dependent. In this paper, the effect of dyslipidemia on the photoplethysmogram (PPG) signal recorded from collateral index fingers is investigated following a previous study where it was shown that results similar to that of US-FMD can be replicated by the PPG. Two groups, consisting of 30 healthy subjects free from any risk factors and 30 subjects who have only dyslipidemia as risk factor were respectively considered. The percent change in... 

Equal channel angular pressing (ECAP) was used before and after various aging treatments in order to strengthen a commercial 6082 Al alloy. Experiments were carried out to study the strengthening of the alloy due to pre and post-ECAP aging treatment. It was found that aging before and after ECAP processing is an effective method for strengthening of the alloy. An increase in both strength and ductility of the ECAPed specimen was achieved via appropriate post-aging treatment. This was in such a manner that for maximal strengthening, post-ECAP aging is best conducted at temperatures lower than those usually used for aging if prior work hardening is not undertaken. Pre-ECAP aging was also... 

We consider the computational complexity of pure Nash equilibria in graphical games. It is known that the problem is NP-complete in general, but tractable (i.e., in P) for special classes of graphs such as those with bounded treewidth. It is then natural to ask: is it possible to characterize all tractable classes of graphs for this problem? In this work, we provide such a characterization for the case of bounded in-degree graphs, thereby resolving the gap between existing hardness and tractability results. In particular, we analyze the complexity of PURE-GG(C, -), the problem of deciding the existence of pure Nash equilibria in graphical games whose underlying graphs are restricted to class... 

A heterogeneous tungstate-based catalyst has been prepared for selective oxidation of sulfides to sulfoxides in the presence of 30% H2O2. The catalyst was prepared via immobilization of high amounts of WO4 2− onto the cross-linked poly(ammonium ethyl acrylamide) coated magnetic nanoparticles (MNP). FT-IR, TEM, TGA, VSM, XRD, EDX, and CHN analysis were used for characterization of catalyst. Variety of sulfides successfully converted to the related sulfoxides using 1 mol% of catalyst at room temperature in high yields. The catalyst was easily recovered and reused up to 6 times without loss of activity  

Parameters of the PC-SAFT Equation of State (EoS) for pure components are generally determined by matching the saturation pressure and liquid density experimental data. These experimental data are unavailable for petroleum cuts and plus fractions of the petroleum reservoir fluids. In this work, new correlations as functions of specific gravity and molecular weight were developed to estimate the PC-SAFT parameters of petroleum cuts with unknown composition. It was shown that the proposed correlations accurately estimate the PC-SAFT parameters of the pure components published in the literature. Then, the obtained correlations were used and the PVT experimental data for various real reservoir... 

The biomechanical behavior of brain tissue is needed for predicting the traumatic brain injury (TBI). Each year over 1.5 million people sustain a TBI in the United States. The appropriate coefficients for modeling the injury prediction can be evaluated using experimental data. In the present paper, using an experimental setup on bovine brain tissue, unconfined compression tests at quasi-static strain rates of ϵ 0.0004s-1, 0.008s-1 and 0.4s-1 combined with a stress relaxation test under unconfined uniaxial compression with ϵ 0.67s-1 ramp rate are performed. The fitted viscohyperelastic parameters were utilized by using obtained stressstrain curves. The finite element analysis (FEA) is... 

Estimating available hydrocarbon to be produced during secondary oil recovery is an ongoing activity in field development. The primary plan is normally scheduled during early stage of field's life through master development plan studies. During this period, due to the lake of certain data, estimation of the field efficiency is usually based on rules of thumb and not detailed field characterization. Hence, there is a great motivation to produce simpler physically-based methodologies. The minimum necessity inputs of percolation approach make it a useful tool for foration performance prediction. This approach enables us to attain a better assessment of the efficiency of secondary recovery... 

From gas-solid carbonation studies and product characterization by XRD, carbon elemental analysis, and TG-FTIR profiling of evolved CO2, the presence of water vapour at high relative humidity (>25% RH) was shown to cause a drastic acceleration in the rate of CO2 absorption into MgO and Mg(OH)2 producing magnesite and hydrocarbonated precursors. From thermogravimetric experiments in the vicinity of the dew point, carbonation was shown to proceeded in steps triggered by spontaneous condensation (and re-evaporation) of water. Almost complete conversion to magnesite (MgCO3) and/or hydromagnesite [HM = 4MgCO3·Mg(OH)2·4H2O] was observed in a few hours under rather mild conditions of pressure (PCO2... 

Interface engineering of solar cell device is a prominent strategy to improve the device performance. Herein, we synthesize reduced-graphene scaffold (rGS) by using a new and simple chemical approach. In this regard, we synthesize a hollow structure of graphene and then fabricate a three-dimensional scaffold of graphene with a superior surface area using electrophoretic process. We employ this scaffold as an interface layer between the electron transfer and absorber layers in perovskite solar cell. The characterization tests and photovoltaic results show that rGS improves the carrier transportation, yielding a 27% improvement in device performance as compared to conventional device. Finally,... 

Advanced reservoir characterization methods can yield geological models at a very fine resolution, containing 1011–1018 cells, while the common reservoir simulators can only handle much lower numbers of cells due to computer hardware limitations. The process of coarsening a fine-scale model to a simulation model is known as upscaling. Predicting the accuracy of simulation results over an upscaled grid with respect to the fine grid is highly important, as it can yield the optimum upscaling process. In this paper, permeability-based and velocity-based a priori error estimation techniques are proposed by introducing image processing-based comparison methods in the context of upscaling. The... 

Volumetric and equilibrium calculations for the natural gas and oil defined by a large number of components are not feasible in applications like compositional reservoir simulation. Therefore, the fluid mixture is grouped to reduce computational load and to make faster calculations. However, for several reasons, it is required to have the detailed fluid composition rather than the lumped one. In this work, an improved delumping method is presented to retrieve the phase composition of the detailed mixture based on the grouped mixture thermodynamic calculations. The method is based on previously proposed delumping techniques for non-cubic equation of state (Assareh et al. in Fluid Phase... 

In order to produce an inexpensive catalyst for the Fischer-Tropsch synthesis (FTS), zeolitized high silicon fly ash utilized as a catalytic support for cobalt nanoparticles. The ability of this new support in proper hosting of nanoparticles studied through various characterization methods such as X-ray diffraction, nitrogen sorption, transmission electron microscopy, energy-dispersive spectroscopic and temperature-programmed reduction. In addition, the catalytic properties for the FTS evaluated at 523 K and 20 MPa. The obtained results show remarkable influence of utilized support specifications upon the formation and catalytic behavior of cobalt nanoparticles in the FTS  

In this work, the synthesis and characterization of a new nanocomposite from carbon nanotubes-graft-polymer (CNTs-g-P) is reported. The products were obtained by the filling of multi-walled carbon nanotubes (MWCNTs) (inner diameter 2040 nm) with CoFe2O4 magnetic nanoparticles, been grafted with poly (caprolactone). The filling process was carried out by using acid treatment through wet chemistry. The structure and the properties of the new nanocomposite were studied with TEM, VSM, TGA, and spectroscopic techniques. © 2009 World Scientific Publishing Company  

Ti–6Al–4V and AISI 304 stainless steel were joined by diffusion brazing with a Cu interlayer at 900 °C for different bonding times. The influence of the bonding time on the joint width, microstructure, microhardness and shear strength was studied. Interfacial characterizations and the identification of phases were done by scanning electron microscopy and electron backscatter diffraction (EBSD). The results revealed that by increasing the bonding time, the thickness of the joint was first increased and then decreased. Microstructure examinations also showed that the joints consisted of several intermetallics such as TiCu, Ti2Cu, TiCu4, TiCu2, FeTi and Fe2Ti. On the other hand, EBSD results... 

The main challenge in many applications of acetic acid is acid dehydration and its recovery from wastewater streams. Therefore, the performance of polyamide thin film composite is evaluated to separate acetic acid from water. To reach this goal, the formation of polyamide layer on polysulfone support membrane was investigated via interfacial polymerization (IP) of meta-phenylenediamine (MPD) in water with trimesoyl chloride (TMC) in hexane. Also, the effect of synthesis conditions, such as concentration of monomers and curing temperature on separation of acetic acid from water were investigated by reverse osmosis process. Moreover, the separation mechanism was discussed. The solute... 

In this paper, we investigate and develop an alternative approach to the numerical analysis and characterization of random fluctuations with the heavy-tailed probability distribution function (PDF), such as turbulent heat flow and solar flare fluctuations. We identify the heavy-tailed random fluctuations based on the scaling properties of the tail exponent of the PDF, power-law growth of qth order correlation function, and the self-similar properties of the contour lines in two-dimensional random fields. Moreover, this work leads to a substitution for the fractional Edwards-Wilkinson (EW) equation that works in the presence of μ-stable Lévy noise. Our proposed model explains the... 

Heterogeneous nanoscale catalyst was successfully synthesized via anchoring of oxoperoxo molybdenum(VI) complex on the chloro-functionalized SBA-15. The mesoporous nanomaterials, MoO3(sal-phz)/SBA-15 (where sal-phz is salicylidene 2-picoloyl hydrazine) were identified by several characterization techniques. MoO3(sal-phz)/SBA-15 and MoO3(sal-phz) were also treated as catalysts in the olefins epoxidation reactions. Both homogenous and heterogeneous catalysts exhibit outstanding activity and selectivity for epoxide with tert-BuOOH in decane as oxidant at 95 °C. In addition, the heterogeneous nanocatalyst was chemically stable and can be efficiently reused for at least six cycles without a... 

Three new chromophores based on the triphenylamine (MM, DM, DN) with various novel electron withdrawing anchoring groups have been synthesized for use in dye-sensitized solar cells (DSSCs). The sensitizers were characterized by 1H and 13C NMR, Mass, UV–Vis, and electrochemical analysis. The HOMO and LUMO electron distributions of the sensitizers were calculated using density functional theory on a B3LYP level for geometry optimization. The DSSC device based on DM dye showed the best photovoltaic performance among MM and DN dyes: maximum monochromatic incident photon-to-current conversion efficiency (IPCE) of 98 %, short circuit current (JSC) of 4.58 mA/cm2, open circuit voltage (VOC) of... 

The quasi-static and strain-controlled fatigue characteristics of ZK60 extrusion have been investigated along three different directions: the extrusion direction (ED), the radial direction (RD), and 45° to the extrusion direction (45°). The quasi-static response showed symmetric behavior for the samples tested along RD and 45° whereas the ED samples manifested completely asymmetric behavior. Although the ED samples exhibited longer fatigue lives than the RD and 45° in the high cycle fatigue, the fatigue lives in the low cycle fatigue regime were similar. The texture measurement indicated a sharp basal texture along ED, explaining its asymmetric behavior. Higher tensile mean stress and less...