A new analytical study of MHD stagnation-point flow in porous media with heat transfer

The similarity solution for the MHD Hiemenz flow against a flat plate with variable wall temperature in a porous medium gives a system of nonlinear partial differential equations. These equations are solved analytically by using a novel analytical method (DTM-Padé technique which is a combination of the differential transform method and the Padé approximation). This method is applied to give solutions of nonlinear differential equations with boundary conditions at infinity. Graphical results are presented to investigate influence of the Prandtl number, permeability parameter, Hartmann number and suction/blowing parameter on the velocity and temperature profiles.     

Surface modification of silica-graphene nanohybrid as a novel stabilizer for oil-water emulsion

The surface modification of silica-graphene nanohybrid through treatment with a mixture of nitric and sulfuric acid vapors to prepare a novel stabilizer for decalin-water emulsion was investigated. The nanohybrid was prepared through chemical vapor deposition using silica aerogel and acetylene as catalyst and carbon precursor at atmospheric pressure and 600 °C. The physicochemical properties of the modified nanohybrid were characterized by FT-IR, XPS, Raman spectroscopy, and TEM. The surface modification of nanohybrid was at various duration times (24, 48, and 72 hours) to optimize the surface modification conditions. Zeta potential of ?39.9 mV revealed that the surface modification of nanohybrid after 72 hours had an excellent stability in aqueous phase due to the presence of exceptional functional groups. The emulsion average droplet size decreased by increasing the nanohybrid concentration. The negative value of the zeta potential showed the proposed nanohybrid can be applied as an appropriate stabilizer for emulsion.     

An Iterative Algebraic Geometric Approach for Identification of Switched ARX Models with Noise

The algebraic geometric (AG) approach has been used to identify switched auto regressive exogenous (SARX) models in hybrid systems, and it has several advantages over other SARX identification methods. This paper is focused on improving the estimation accuracy of the AG approach for systems corrupted with indispensable noises. A stochastic hybrid decoupling polynomial (SHDP) is constructed by reformulating the hybrid decoupling polynomial (HDP) used in the original AG method. An iterative scheme is developed to estimate parameters of the SHDP, which are used to calculate the SARX model parameters. This estimation involves linear regression with multiplicative noises, therefore a novel approach is proposed to solve this regression problem. Then, the parameters are recovered from the SHDP. Finally, all these steps for SARX model identification are summarized in an algorithm called the iterative algebraic geometric (IAG) approach. Simulations and experimental validation results are shown to demonstrate the effectiveness of and the improvement made by the proposed IAG method.     

Numerical Prediction of Temperature Profile during Gas Lifting

Abstract

Because locating the best valve position in the annulus and predicting the optimum injection gas volume, among other factors, depends on the temperature profile, an accurate knowledge of the operating temperature is desirable. This study examines the Joule-Thompson effect and changing fluid properties through the tubing in related equations and presents the temperature profile inside the tubing and annulus.     

Design for dynamic loads: lack of uniqueness

This paper explores some practical implications of the lack of uniqueness in the inverse problem of finding the stiffness of a system undergoing free vibrations given its frequency of vibration. Received August 20, 1999     

Optimization of cotton crosslinking with polycarboxylic acids and nano TiO2 using central composite design

The cotton crosslinking with butane tetra carboxylic acid (BTCA) and citric acid (CA) in the presence of sodium hypophosphite (SHP) and nano TiO₂ (NTO) under different curing conditions were optimized using a statistical model. The central composite design (CCD) was used for variables based on Design of Expert software. The appropriate model to create optimum crease recovery angle was obtained for each condition. The X‐ray diffraction (XRD) and scanning electron microscopy (SEM) were also employed to indicate the NTO particles on the fabric surface with the size of nano particles and their crystallinity. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

A powerless iron oxide based magnetometer

Microsystem Technologies - This paper demonstrates a novel device visualizing and determining magnetic fields in six different directions. The device can be used in applications such as remote real...     

Integrated gas lift system optimization

An intelligent genetic algorithm has been developed to simultaneously optimize all effective factors, namely, gas injection rate, injection depth and tubing diameter towards the maximum oil production rate with the water cut and injection pressure as the restrictions. The results were field tested in three wells in three different fields located in southern Iran. The field data verified the accuracy of the used model. There was a notable production increment compared to the master development plan of the fields.     

Numerical study of forced convective heat transfer of Nanofluids: Comparison of different approaches

Forced convective of a nanofluid that consists of water and Al₂O₃ in horizontal tubes has been studied numerically. Computed results were validated with existing well established correlation. Two-phase Eulerian model has been implemented for the first time to study such a flow field. A single-phase model and two-phase mixture model formulations were also used for comparison. The comparison of calculated results with experimental values shows that the mixture model is more precise. It is illustrated that the single-phase model and the two-phase Eulerian model underestimates the Nusselt number. Effects of nanoparticles concentration on the thermal parameters are also discussed.