Sharif Digital Repository

This paper deals with investigation of fluid flow on static and dynamic behaviors of carbon nanotubes under electrostatic actuation. The effects of various fluid parameters including fluid viscosity, velocity, pressure and mass ratio on the deflection and pull-in behaviors of the cantilever and doubly clamped carbon nanotubes are studied. Furthermore, the effects of temperature variation on the static and dynamic pull-in voltages of the doubly clamped carbon nanotubes are reported. The results reveal that altering the fluid parameters significantly changes the mechanical and pull-in behaviors. Hence, the proposed system can be applied properly as a nano fluidic sensor to sense the various... 

Heavy and extra heavy crude oils usually have a high weight percentage of asphaltene, which could induce many problems during production to refining processes. Also, asphaltene has the main role on the high viscosity of the heavy and extra heavy crude oils. In this paper, the effects of asphaltene characteristics on the crude oil rheological properties have been experimentally and theoretically investigated using different classes of the suspension models. For experimental investigation, the asphaltene was first precipitated from the original heavy crude oil and then 10 well-defined reconstituted heavy oil samples are made by dispersing the asphaltene into the maltene (i.e., deasphalted... 

A viscosity model, based on Eyring's absolute rate theory combined with a cubic PR equation of state and Wong-Sandler mixing rule, has been proposed in order to correlate viscosities of aqueous solutions of alkanolamine mixtures at atmospheric pressure and different temperatures. In the proposed method, the energy and size parameters in studied Equation of State (EoS) have been obtained using the Wong - Sandler (WS) mixing rule combined with the NRTL and Wilson Gibbs equations. The NRTL and Wilson parameters for aqueous solutions of alkanolamine mixtures have been correlated using measured viscosity data at atmospheric pressure and different temperatures. The overall average deviation... 

The biomicrofluidic devices utilizing electrophoresis for sample manipulation are usually encountered with non-Newtonian behavior of working fluids. Hence, developing theoretical models capable of predicting the electrophoretic velocity of colloidal particles in non-Newtonian fluids is of high importance for accurate design and active control of these devices. The present investigation is dealing with the electrophoresis of a spherical particle in a biofluid obeying the Quemada rheological model. The sphere radius is considered to be significantly larger than the Debye length. Moreover, it is assumed that the particle zeta potential is small so that the Debye-Hückel linearization is... 

In this study, a nonlinear poroelastic model of intervertebral disc as an infrastructure was developed. Moreover, a new element was defined consisting a disc (Viscoelastic Euler Beam Element) and a vertebra (Rigid Link) as a unit element. Using the new element, three different viscoelastic finite element models were prepared for lumbar motion segment (L4/L5). Prolonged loading (short-term and long-term creep) and cyclic loading were applied to the models and the results were compared with results of in vivo tests. Simplification of the models by using the new element leads to reduction of the runtime of the models in dynamic analyses to few minutes without losing the accuracy in the results  

Microscopic and macroscopic displacements of polymer flooding to heavy oil at various levels of salinity and connate water saturation have been investigated. Both oil-wet and water-wet conditions in fractured five-spot micromodel systems, initially saturated with the heavy crude oil are utilized. The primary contribution is to examine the role of salinity, wettability, connate water, and fracture geometry in the recovery efficiency of the system. The microscopic results revealed that the increase in the connate water saturation decreases the oil recovery, independent of the wettability conditions. Moreover, the increase in salinity of the injected fluids lowers the recovery efficiency due to... 

Accurate value determination of natural gas viscosity plays a key role in its management as it is one of the most important parameters in natural gas engineering calculations. In this study, a comprehensive model is suggested for prediction of natural gas viscosity in a wide range of pressures, temperatures, densities and compositions. The new model can be applicable for gases containing heptane plus and non-hydrocarbon components. It is validated by the 2011 viscosity data from 18 different gas mixtures. Compared to existing similar models and correlations, its results are quite satisfactory  

Oil viscosity plays a key role in reservoir simulation and production forecasting, as well as planning thermal enhanced oil recovery methods and these make its accurate determination necessary. In this communication, the most frequently used oil viscosity correlations are evaluated using a large databank of Iranian oil reservoirs which were measured using a Rolling Ball viscometer (Ruska, series 1602). To evaluate the performance and accuracy of these correlations, statistical and graphical error analyses have been used simultaneously. Three of the most accurate correlations for each region, including dead oil viscosity, viscosity below bubble point, viscosity at bubble point and the... 

The use of polymer flooding as one of enhanced oil recovery methods has recently increased. The occurrence of high shear rates in reservoir and near well bore through perforation nozzles during polymer flooding cause shear degradation of polymers and therefore polymer viscosity has decreased. Rheological behavior of polymer solution in different conditions of oil reservoir is one of the key factors to develop use of polymer solutions. A few researches are available regarding improving rheological behavior of polymeric solution. In this study, to investigate the effect of nanoparticles on rheological behavior of polymer solutions two samples were prepared: polyacrylamide solution in water and... 

Rheological behavior of two crude oils and their surfactant-stabilized emulsions with initial droplet sizes ranging from 0.5 to 75 μm were investigated at various temperatures under steady and dynamic shear testing conditions. In order to evaluate the morphology and Stability of emulsions, microscopic analysis was carried out over three months and average diameter and size distribution of dispersed droplets were determined. The water content and surfactant concentration ranged from 10 to 60% vol/vol and 0.1 to 10% wt/vol, respectively. The results indicated that the rheological properties and the physical structure and stability of emulsions were significantly influenced by the water content... 

Data streams have some unique properties which make them applicable in precise modeling of many real data mining applications. The most challenging property of data streams is the occurrence of "concept drift". Recurring concepts is a type of concept drift which can be seen in most of real world problems. Detecting recurring concepts makes it possible to exploit previous knowledge obtained in the learning process. This leads to quick adaptation of the learner whenever a concept reappears. In this paper, we propose a learning algorithm called Pool and Accuracy based Stream Classification with some variations, which takes the advantage of maintaining a pool of classifiers to track recurring... 

Asphaltene deposition is an issue that has received much attention since it has been shown to be the cause of major production problems. It leads to permeability reduction under the processes of natural depletion as well as hydrocarbon gas/CO2 injection. Though a great deal of researches have focused on studying permeability impairment in reservoir rocks, little is known about the asphaltene deposition mechanisms that control the permeability reduction for Iranian reservoirs. In this work, an experimental effort is made to investigate the permeability impairment of core samples of Iranian oil reservoirs. The experiments are performed on both sandstone and carbonate rock types at reservoir... 

Steady blood flow through a circular artery with rigid walls is studied by COSSERAT Continuum Mechanical Approach. To obtain the additional viscosities coefficients, feed forward multi-layer perceptron (MLP) type of artificial neural networks (ANN) and the results obtained in previous empirical works is used. The governing filed equations are derived and solution to the Hagen-Poiseuilli flow of a COSSERAT fluid in the artery is obtained analytically by Homotopy Perturbation Method (HPM) and numerically using finite difference method. Comparison of analytical results with numerical ones showed excellent agreement. In addition microrotation and the velocity profile along the radius are... 

Mixing of solid nanoparticles in viscous fluids is a key stage in synthesis of nanocomposites and can affect their final properties. A multi-step preparatory mixing is developed to synthesize the nanocomposites of layered silicate in thermosetting polymers. This study aims to investigate the influences of mixing conditions and steps taken to process the thermosetting nanocomposites on the viscoelastic properties of suspensions. We also examine subsequent influences of mixing on the microstructure and dispersion state of cured hybrids of organically modified clays in a polyester resin. The nanocomposites were prepared in a sequential mixing process developed for the model nanocomposites of... 

A numerical code for supersonic intake design with a proper simulation of the normal and/or oblique shocks, boundary layer development, interaction of the shock and the boundary layer, as well as prediction of the flow separation is of great help to the designers. In this research, a numerical code is developed to solve the inner and outer flow fields of the intake and validated with various experimental tests. The intake is an axisymmetric external compression one. Roe scheme and new schemes, AUSM+-up (for all speed) and Advection Upstream Splitting Method with Pressure-Based Weight function (AUSMPW), are used to compute the convective fluxes. The original version of the AUSMPW scheme has... 

In this study, the local composition based models such as the Wilson, the nonrandom two-liquid (NRTL), and the Wilson-NRF have been applied in correlation and estimation of density, viscosity, and surface tension of biodiesels. The thermodynamic models have been used in correlating the thermophysical properties for 215 experimental data points. These models have the interaction energy between each pair that is considered as adjustable parameters. To decrease the number of these adjustable parameters, it is assumed that the biodiesels are composed of two hypothetical components. The average absolute deviation (AADs) of the correlated density of biodiesels for the Wilson, the NRTL, and the... 

Ultrahigh-molecular-weight polyethylene (UHMWPE)/fumed silica nanocomposites were prepared via in situ polymerization using a bi-supported Ziegler-Natta catalytic system. Nanocomposites with different nanoparticle weight fractions were produced in order to investigate the effect of fumed silica on thermal and mechanical properties of UHMWPE/fumed silica nanocomposites. The viscosity average molecular weight (M) of all samples including pure UHMWPE as the reference sample and nanocomposites were measured. Scanning electron microscope (SEM) images showed the homogenous dispersion of nanoparticles throughout the UHMWPE matrix while no nanoparticle cluster has been formed. Crystallization... 

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... 

The objective of this study was to investigate the effects of two compatibilizers, namely maleated polypropylene (PP-g-MA) and maleic anhydride grafted poly (ethylene-co-octene) (EOC-g-MA), on the morphology and thus properties of ternary nanocomposites of polypropylene (PP)/ethylene-octene copolymer (EOC)/clay nanocomposite. In this regard the nanocomposites and their neat polymer blend counterparts were processed twice using a twin screw extruder. X-ray diffraction, transmission electron microscopy, Energy dispersive X-ray spectroscopy, and scanning electron microscopy were utilized to characterize nanostructure and microstructure besides mechanical and rheological behaviors of the... 

In this research, ultrahigh-molecular-weight polyethylene (UHMWPE)/multiwalled carbon nanotube (MWCNT) nanocomposites with different nanotube concentrations (0.5, 1.5, 2.5, and 3.5 wt %) were prepared via in situ polymerization with a novel, bisupported Ziegler-Natta catalytic system. Magnesium ethoxide [Mg(OEt) 2] and surface-functionalized MWCNTs were used as the support of the catalyst. Titanium tetrachloride (TiCl 4) accompanied by triethylaluminum constituted the Ziegler-Natta catalytic system. Preparation of the catalyst and the polymerization were carried out in the slurry phase under an argon atmosphere. Support of the catalyst on the MWCNTs was investigated with Fourier transform...