Sharif Digital Repository

Most of the heavy oil reservoirs contain discontinuous shale which affects fluid flow through porous media as well as recovery efficiency during enhanced oil recovery processes. However, the role of shale geometrical characteristics (including orientation, length, discontinuity, and spacing of the shale) on oil recovery remains a topic of debate in the literature, especially during miscible injection of heavy oils and five-spot systems. Here, a series of hydrocarbon solvent injection tests have been performed on various five-spot glass micromodels containing barriers which are initially saturated with heavy oil under fixed flow rate conditions. Oil recoveries as a function of pore volumes of... 

Alumina-silicate composite coatings were formed on titanium substrate by plasma electrolytic oxidation (PEO) process using a silicate-based electrolyte containing alumina nanoparticles. Microstructure, chemical and phase compositions, and thickness of the coatings were investigated to determine, coating mechanism and probable reactions during the process. The effect of processing time on corrosion resistance of the coatings was investigated using the potentiodynamic polarization test. Barrier layer (TiO2) formation, micro arcs occurrence, and electrolyte ionization were the main stages of PEO coating growth process. Alumina nanoparticles were incorporated into the coating by cataphoretic and... 

Plasma electrolytic oxidation (PEO) process was employed to create ceramic coatings on titanium substrate by using silicate-based electrolytes containing different concentrations of alumina nanoparticles (0, 3, 6, and 10. g/lit). The effect of alumina nanoparticles concentration on the morphology, chemical and phase composition of the PEO coatings was investigated by scanning electron microscope, energy dispersive spectrometer, and X-ray diffractometer, respectively.The corrosion behavior of samples was studied by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests. SEM, EDS, and XRD analyses illustrated that alumina nanoparticles incorporated into the... 

Free surface flows are frequently encountered in hydraulic engineering problems including water jets, weirs and around gates. An iterative solution to the incompressible two-dimensional vertical steady Navier-Stokes equations, comprising momentum and continuity equations, is used to solve for the priori unknown free surface, the velocity and the pressure fields. The entire water body is covered by a unstructured finite element grid which is locally refined. The dynamic boundary condition is imposed for the free surface where the pressure vanishes. This procedure is done continuously until the normal velocities components vanish. To overcome numerical errors and oscillations encountering in... 

Often, during fabrication processes of fiber-matrix composites, the pertinent interface may be made imperfectly bonded either deliberately or undesirably. The effect of electric capacitors and mechanical imperfections on the electro-mechanical fields associated with an anisotropic piezoelectric matrix containing a cylindrical inhomogeneity made of a different anisotropic piezoelectric material is of interest. In fact the interface imperfection condition presented in this paper is quite general, in the sense that any combination of mechanical and electrical imperfections may exist. The interface electrical imperfection is mimicked by the electric capacitors. The capacity of the capacitors is... 

Free surface flows are frequently encountered in hydraulic engineering problems including water jets, weirs and around gates. An iterative solution to the incompressible two-dimensional vertical steady Navier-Stokes equations, comprising momentum and continuity equations, is used to solve for the priori unknown free surface, the velocity and the pressure fields. The entire water body is covered by a unstructured finite element grid which is locally refined. The dynamic boundary condition is imposed for the free surface where the pressure vanishes. This procedure is done continuously until the normal velocities components vanish. To overcome numerical errors and oscillations encountering in... 

Although most heavy oil reservoirs contain discontinuous shaly structures, there is a lack of fundamental understanding how the shaly structures affect the oil recovery efficiency, especially during surfactant flooding to heavy oils. Here, an experimental study was conducted to examine the effect of discontinuous shales on performance of surfactant flooding by introducing heterogeneities to represent streaks of shale in five-spot glass micromodels. Results show that oil recovery in presence of shale streak is lower than in its absence. Based on the authors' observations, the presence of flow barriers causes premature breakthrough of injected fluids and also an unstable displacement front. As... 

In the present study, a novel strategy based on particle motion mode is introduced to control the manipulation process of a bio-particle using trolling mode atomic force microscope. To achieve this goal, the reduced governing partial differential equations and the standard form of the system are used as a model for the system dynamic behavior. The governing equations take 6 degrees of freedom into account including extension, torsion, and two lateral bendings of the microcantilever as well as two lateral bendings of the nanoneedle. Manipulation process of the 500 nm radius particle on the substrate includes two phases named sticking and sliding. Sticking of the particle to the substrate... 

Inherent properties of UWB signals prevent both coherent and noncoherent processing with conventional methods used in narrow-band RADARs. In this paper, we show how to exploit the Hough transform, first developed to detect lines in an image distorted by noise, to detect moving objects from successive scans that are corrupted by noise and clutter. We discuss why conventional methods fail to process UWB pulses noncoherently/coherently and investigate different aspects of using the Hough transform in noncoherent integration of UWB signals. Simulation results to support our approach are also presented. © 2008 EuMA  

Stabilised titania sols were prepared using an additive free particulate sol-gel route, via electrostatic stabilisation mechanism, with various processing parameters. Peptisation temperature, 50°C and 70°C, and TiO2 concentration, 0.1, 0.2 and 0.4 molar, were chosen as processing parameters during sol preparation. Results from TiO2 particle size and zeta potential of sols revealed that the smallest titania hydrodynamic diameter (13 nm) and the highest zeta potential (47.7 mV) were obtained for the sol produced at the lower peptisation temperature of 50°C and lower TiO 2 concentration of 0.1 M. On the other hand, between the sols prepared at 70°C, smaller titania particles (20 nm) and higher... 

In this work, the effect of zircon content on the mechanical and chemical behaviors of injection molded silica-based ceramic cores has been investigated. In order to simulate a casting process condition, the sintered samples at 1220 C were consequently heated up to 1430 C. Three point bending tests were carried out on all the prepared samples. The chemical resistance of the prepared cores was evaluated by leaching of samples in 43% KOH solution at its boiling point. Phase evolution and microstructure were investigated by XRD and SEM, respectively. Results showed that increasing zircon content led to an increase in MOR and decrease in leachability owing to the decrease in content of fused... 

The preparation of composite manganese dioxide (MnO2) nanoparticles in an ordered mesoporous carbon (CMK-3) matrix and its use for constructing a new wide-potential-window supercapacitor is reported. CMK-3 is prepared using mesoporous silica as a hard template and sucrose as carbon source. The different ratios of MnO2/CMK-3 composite is synthesized by impregnating CMK-3 with a Mn(NO3)2·4H 2O solution followed by annealing in nitrogen. Physical properties, morphology, and specific surface area were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen sorption measurements, respectively. The electrochemical properties of the composite were studied by cyclic... 

The objective of the dynamic economic dispatch (DED) problem is to schedule power generation for the online units for a given time horizon economically, satisfying various operational constraints. Due to the effect of valve-point effects and prohibited operating zones (POZs) in the generating units cost functions, DED problem is a highly non-linear and non-convex optimization problem. The DED problem even may be more complicated if transmission losses and ramp-rate constraints are taken into account. This paper presents a novel and heuristic algorithm to solve DED problem of generating units, by employing time varying acceleration coefficients iteration particle swarm optimization... 

The second virial coefficients of Exp-6 chains are calculated using the Monte Carlo method. The results are presented as the scaled second virial coefficient B 2/(m 2σ 3) for various chain lengths m and repulsive-wall steepness parameters α at different scaled temperatures T *. The scaled coefficient reduces and converges to a constant value as m → ∞. Interestingly, the scaled coefficient scales as B 2/(m 2σ 3) ∝ -α -1, where the dependence reduces for larger m. The gyration radius increases with α, and in good solvent regime, scales like a self-avoiding chain when m → ∞. The interaction energy between two chains depends on m, T *, and α. With increasing m, the interaction becomes less... 

Inverse design in external flow regimes usually involves finding the wall shape associated with a prescribed distribution of wall pressure or velocity. In this research, a novel iterative inverse design method is developed for inviscid subsonic and transonic external flow regimes. The method links up a novel inverse design algorithm, called Ball-Spine Algorithm (BSA), and a 2D inviscid analysis code. The Euler equations are solved for a physical domain of which some unknown boundaries are iteratively modified via BSA until a prescribed pressure distribution is reached. In BSA, the unknown walls are composed of a set of virtual balls that move freely along the specified directions called... 

In this paper, the effects of Equal Channel Angular Pressing process (ECAP) followed by Shot Peening process (SP) on the fatigue properties of 6082 aluminum alloy are investigated. Several samples of the alloy are ECAPed and SPed and then their mechanical behavior are characterized using tensile, micro-hardness, and fatigue tests. The results indicate that shot peening and then polishing the specimen after one-pass ECAP is an effective method to improve the fatigue life of the alloy. Moreover, by increasing the number of ECAP passes before shot peening, a local work softening occurs at the subsurface layer, leading to a significant decrease in the fatigue life of the alloy. The results of... 

For the first time, the simultaneous effects of sulfate reducing bacteria (SRB), soil type and moisture content on corrosion behavior of a pipeline steel were investigated. Corrosion weight loss measurements were performed in abiotic control and SRB-active conditions, at three different moisture contents, and in two types of soils. Results showed that the presence of SRB in the soils, although increased the corrosion rate and aggravated pitting corrosion at low moisture contents, had a protective effect at high moisture contents. The corrosion rates showed a maximum at the saturation moisture content (SMC) of the soils. Soil physicochemical analyses showed that the corrosion rate and soil... 

Integrating independent dispatchable and non-dispatchable resources into a micro-grid platform enables the main power systems to benefit from the economic and environmental advantages of distributed generation while facilitating local, clean, and inexhaustible renewable energy production. Moreover, it makes the integrated components more visible and controllable for the whole power system. On the other hand, to properly handle multiple uncertainties inherent in the micro-grids, probabilistic energy management techniques are deployed. However, utilization of stochastic modeling and optimization tools for efficient, reliable, and cost-effective planning, operation, and control of micro-grids... 

Electrohydrodynamic (EHD) printing is a novel technology used for fabricating high-resolution part features from a wide range of materials. Due to the multiphysics dynamics and the multiphase nature of the microdroplet formation in the EHD printers, modeling of this phenomenon is complicated. In this paper, the formation of a droplet in an EHD printer—under a pulsed electrical field—is simulated using a new numerical model which couples the fluid flow, the electric field distribution and the movement of the electric charges under dynamic and transient conditions. The level-set method is applied to the entire multiphysics domain in order to study the formation of the droplet. The presented... 

A comprehensive optimal bidding strategy model has been developed for renewable micro-grids to take part in day-ahead (energy and reserve) and real-time markets considering uncertainties. A two-stage stochastic programming method has been employed to integrate the uncertainties into the problem. Moreover, the Latin hypercube sampling method has been proposed to generate the wind speed, solar irradiance, and load realizations via Weibull, Beta, and normal probability density functions, respectively. In addition, a hybrid fast forward/backward scenario reduction technique has been applied to reduce the large number of scenarios. Furthermore, the risk of participation in the markets has been...