سال:1394 | دوره: | شماره: |تعداد مقالات:11

Recently, a renewed interest arises in the application of nanotechnology for the upstream petroleum industry. In particular, adding nanoparticles to uuids may drastically beneut enhanced oil recovery and improve well drilling, by changing the properties of theuuid, rocks wettability alteration, advanced drag reduction, strengthening the sand consolidation, reducing the inter-facial tension and increasing the mobility of the capillary trapped oil. In this study, we focus on roles of nanoparticles on wettability. This paper therefore focuses on the reviews of the application of nano technology in chemical flooding process in oil recovery and reviews the application nano in polymer and surfactant flooding on the wettability process.

In this paper, the stability characteristics of single-walled carbon nanotubes (SWCNTs) under the action of axial load are investigated. To this end, a nonlocal Flugge shell model is developed to accommodate the small length scale effects. The analytical Rayleigh-Ritz method with beam functions is applied to the variational statement derived fromthe Flugge-type buckling equations. Through comparison of the results obtained from the present analytical solution and the ones from molecular dynamics (MD) simulations, the appropriate values of nonlocal parameter are proposed for (8, 8) armchair SWCNTs with different kinds of boundary conditions. The effects of nonlocal parameter and boundary conditions on the critical buckling load are also examined.Moreover, in spite of the uncertainty that exists in defining the in-plane stiffness and bending rigidity of nanotube, by adjusting the nonlocal parameter, the present nonlocal shell model is shown to be capable of predicting the MD simulations results.

Due to high surface-to-volume ratio of nanoscale structures, surface stress effects have a significant influence on their behavior. In this paper, a two-dimensional problem for an elastic layer that is bonded to a rigid substrate and subjected to an inclined concentrated line load acting on the surface of the layer is investigated based on Gurtin-Murdoch continuum model to consider surface stress effects. Fourier integral transforms are used to solve the non-classical boundary-value problem related to inclined point load and an analytical solution is obtained for the corresponding boundary-value problem. Selected numerical results are presented for different values of loading angle and are compared with the classical ones to illustrate the influence of the surface stress effects on the stiffness of nanocoating and ultra-thin films. It is found that the surface stress effects have a quite large influence on the response of the nanofilm especially for more vertical loading (higher values of the angle of loading) and make the layer stiffer than the classical case.

Quinazolinone derivatives are essential units in a wide range of relevant pharmacophores with a broad spectrum of abilities. Due to their wide range of pharmacological and therapeutic activities including anticonvulsant, anti-inflammatory, hypolipidemic, anticancer, and anti-ulcer, the synthesis of quinazolinone moieties as a privileged class of fused heterocyclic compounds, have received much attention.An efficient and one-pot three components route was developed for the synthesis of 4 (3H) -quinazolinones using commercially available starting materials. In order to synthesis of target compounds in good to excellent yields, a reaction between isatoic anhydride, acylchlorides, and amines in the presence of propylsulfamic acid functionalized magnetic hydroxyapatite nanoparticle [g-Fe2O3-HAp- (CH2) 3-NHSO3H], as a highly efficient and magnetically separable Bronsted acid catalyst, was performed. The organic layer was dried over anhydrous Na2SO4 and filtered. The filtrate was concentrated under vacuum and the residue was recrystallized from 96% EtOH to give 2, 3-disubstituted 4- (3H) -quinazolinone derivatives in high yield. The reaction condition including the solvents, the amount of [g-Fe2O3-HAp- (CH2) 3-NHSO3H], reaction time and required temperature was optimized.

Having conducted fundamental projects, scientists have expressed their hope to develop the use of carbon nanotubes to release drugs. It is important to release drugs in cell without damaging healthy cells of tissues under study. Researchers have shown the fact that nanotubes can perform this function perfectly. To this objective, in the present study the interactions between four anti-cancer drugs with a carbon nanotube (CNT) (6, 6), containing 60 carbon atoms, have been investigated. It is noteworthy that all of these drugs have functional groups, from which the reaction with the nanotube can take place. The Density Functional Theory (DFT) calculations have been performed by Beck, three-parameter, Lee-Yang-Parr (B3LYP) method and 6-31G (d) basis set for full optimization of drugs, nanotube and the formed complexes. The Natural Bond Orbital (NBO) analysis and frequency calculations have been also performed for all structures using B3LYPmethod and 6-31G (d) basis set in 298K.According to the results, among all drugs under study, only two complexes between Carmustine and nanotube can be thermodynamically formed in 298K. The stability constants are calculated thereby showing a considerably large amount. Therefore, the nanotube can be a useful container for this drug. Also, NBO analysis shows that there exist hyperconjugative effects arising from an overlap between occupied orbitals in drugs and unoccupied orbitals in nanotube.

The static pull-in instability of beam-typemicro-electromechanical systems is theoretically investigated.Two engineering cases including cantilever and double cantilevermicro-beamare considered. Considering themid-plane stretching as the source of the nonlinearity in the beambehavior, a nonlinear size-dependent Euler-Bernoulli beammodel is used based on a modified couple stress theory, capable of capturing the size effect. By selecting a range of geometric parameters such as beamlengths, width, thickness, gaps and size effect, we identify the static pull-in instability voltage.Back propagation artificial neural network with three functions have been used for modeling the static pull-in instability voltage of the micro cantilever beam. The network has four inputs of length, width, gap and the ratio of height to scale parameter of the beam as the independent process variables, and the output is static pull-in voltage of microbeam.Numerical data, employed for training the network and capabilities of the model in predicting the pull-in instability behavior has been verified. The output obtained fromthe neural networkmodel is compared with numerical results, and the amount of relative error has been calculated. Based on this verification error, it is shown that the back propagation neural network has the average error of 6.36% in predicting pull-in voltage of the cantilever micro-beam.

Liquefaction is one of the most important and complex topics in geotechnical earthquake engineering.In recent years, passive site stabilization method has been proposed for non-disruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction using colloidal nano-silica stabilizer. In this research, 4 box models were used to investigate the ability to uniformly deliver colloidal nano-silica stabilizer to liquefiable loose mixes of sand with variations in silt content from0 to 30%using 5 low-head injection and 2 extraction wells.After delivery was completed the models were cured for 30 days. Then the treated soil was excavated and a few samples were extracted for dynamic loading testing. According to the results, colloidal silica can be delivered uniformly in silty sand formations. With the same conditions, the amount of fine grained soil (silt content) strongly affected delivery time. The passive stabilization method can be appropriate for deposits with up to 20% fine graded silt, a concentration of 5 wt% colloidal silica is expected to be able to effectively mitigate the liquefaction risk of these deposits. The strains during seismic cyclic loading will probably be less than 3% and little permanent strain should result.

In this paper, a new method is proposed for the production of MWCNTs/PVC (multi-walled carbon nanotubes/ polyvinyl chloride) nanocomposites. In this method, a spray is used to produce layers of carbon nanotubes within a PVC matrix. Various parameters influence the production of the nanocomposite and its mechanical properties.These parameters are studied separately and the effect of each of parameter is calculated. All of the results of the statistical methods are obtained from experimental tensile testing. Results indicated that the most important parameter associated with constituents is the weight percent of carbon nanotube while the most important parameter associated with production is the mold surface temperature. The interaction effect of the two ultimately effective parameters on each other is also analyzed, and the relevant diagrams of the Young modulus and the ultimate tensile strength are prepared as well. Values of theYoungmodulus and the ultimate tensile strength are obtained for different weight percent values of the carbon nanotube.

One way to increase the heat transfer is to use perforated twisted tapes with different hole diameters, which largely improve heat transfer with an increase in the heat transfer area at the constant volume and more mixed flow. In the previous studies, the effect of simultaneous use of nanofluids and perforated twisted tapes is less studied.In this work, the performance of water / iron oxide nanofluid in a double pipe heat exchanger with perforated twisted tapes is investigated under turbulent flow regime. Reynolds number considered is in the range between 2500 to 20500.Iron oxide nanoparticles with diameter of 15 nmare used as nanofluid with the concentration range from 0.12 to 0.2% by volume. The results showed that the addition of nanoparticles increases the heat transfer and the Nusselt number.Also, reducing the twist ratio (H/D=2.5) of perforated twisted tape and using the nanofluid with concentration of 0.2%v/v increase this value by 130%.

In this article, finite difference method (FDM) is used to solve sixth-order derivatives of differential equations in buckling analysis of nanoplates due to coupled surface energy and non-local elasticity theories. The uniform temperature change is used to study thermal effect. The small scale and surface energy effects are added into the governing equations using Eringen’s non-local elasticity and Gurtin-Murdoch’s theories, respectively. Two different boundary conditions including simply-supported and clamped boundary conditions are investigated. The numerical results are presented to demonstrate the difference between buckling obtained by considering the surface energy effects and that obtained without the consideration of surface properties. The results show that the finite difference method can be used as a powerful method to determine the mechanical behavior of nanoplates. In addition, this method can be used to solve higher-order derivatives of differential equations with different types of boundary condition with little computational effort. Moreover, it is observed that the effects of surface properties tend to increase in thinner and larger nanoplates; and vice versa.

Disordered T-shaped graphene nanodevice (TGN) was designed and studied in this paper. We demonstrated the intrinsic transport properties of the TGN by using Landauer approach. Knowing the transmission probability of an electron the current through the system is obtained using Landauer-Buttiker formalism. The effects of single disorder on conductance, current and on the transport length scales are studied using tight-binding model.It is demonstrated that the transport property of the TGN depends sensitively on the disorder positions. However, the current slightly depends on the disorder sites, but strongly depends on the geometry of TGN under small bias voltage.The mean free path in the system is reduced when the strength of disorder is sufficiently high and the mean free path patterns are found to strongly depend on the disorder position. Also observe that the current basically decreases with the stem height increase. We have found that zigzag graphene nanoribbons can be used as metal leads when we build graphene nanodevice based electronic devices.