Peristaltic motion of a magnetohydrodynamic generalized second‐order fluid in an asymmetric channel

We investigate the peristaltic motion of a magnetohydrodynamic (MHD) generalized second‐order fluid in an asymmetric channel. The governing equations are first modeled and then numerically solved under the long wavelength approximation. Attention has been focused to analyze the shear‐thinning and shear‐thickening effects of the investigated non‐Newtonian fluid, the influence of the magnetic force on the flow, especially the trapping, pumping characteristics caused by the peristalsis of the walls. © 2009 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq, 2011     

Interaction of small vacancy clusters with (1 1 4) twin-boundary in gold

The molecular dynamics simulation technique with many-body and semi-empirical potentials is used to calculate the (1 1 4) twin-boundary in gold at different temperatures. Relaxations are found on both sides of the interface with the same magnitude and the phenomenon of coalescence is observed near the interface. The interactions of single-, di- and tri-vacancies with twin-interface at 300 K on mirror and off-mirror sites are calculated. Off-mirror arrangements are favorable for all vacancy clusters, except for the single-vacancy cluster, which is less repulsive on the mirror site. Vacancy clusters energetically prefer to lie at planes closest to the (1 1 4) interface rather than away from it. The effect of temperature on interaction behavior is also calculated.     

Improved Process for Producing Well-Adhered/Abrasion-Resistant Optical Coatings on an Optical Plastic Substrate

Abstract

A well-adhered and abrasion-resistant coating on a typical optical substrate [polymethylmethacrylate (PMMA)] can be achieved by polymerizing organosilane in a low-temperature polymerization process. The substrate surface can be initially modified with hydrophilic functionalities in a radio-frequency plasma of argon/water vapor mixture in the pressure range 0.05-0.15 mbar to attach hydroxyl functionalities covalently to the substrate surface, which act as “anchorage sites” for polymerizing organosilane. This modified surface is then coated with polyvinyltrimethoxysilane at a power loading in the 20-60 W range and a flow rate of monomer in the 0.7-2.0 cm³-min^?1 range. The polymeric films deposited in this manner on PMMA substrates consistently passed adhesion and abrasive tests even after prolonged storage and thermal cycling in boiling water for at least 10 minutes as exposure to extreme differential thermal expansion conditions. The posttreatment of deposited films with plasmas of inert gases for stress relief had an insignificant effect on peel-off tests and, therefore, it was believed to be not as important as surface modification prior to coatings. The optical properties are essentially not affected by the organosilane coatings irrespective of film thickness, and the coated substrates are virtually transparent above 400 nm.     

Kinetics and mechanism of light-driven oxygen evolution at thin film α-Fe2O3 electrodes

Rate constants for recombination and hole transfer during oxygen evolution at illuminated α-Fe(2)O(3) electrodes were measured by intensity-modulated photocurrent spectroscopy and found to be remarkably low. Treatment of the electrode with a Co(II) solution suppressed surface recombination but did not catalyse hole transfer. Intermediates in the reaction were detected spectroscopically.     

Exact solutions of second grade aligned MHD fluid with prescribed vorticity

We present here the exact solutions for the equations of magnetohydrodynamic (MHD) aligned flow of a second grade fluid. The exact solutions are constructed for steady and unsteady equations by employing inverse method.     

Exp-function method for solving Kuramoto–Sivashinsky and Boussinesq equations

In this paper, we use the Exp-function method to construct the generalized solitary and periodic solution of the Kuramoto–Sivashinsky and Boussinesq equations. These equations play very important role in mathematical physics and engineering sciences. The suggested algorithm is quite efficient and is practically well suited for use in these problems. The results show the reliability and efficiency of the proposed method.     

Bright and dark solitons for the resonant nonlinear Schrödinger's equation with time-dependent coefficients

In this paper, the resonant nonlinear Schrödinger's equation is studied with five forms of nonlinearity. This equation is also considered with time-dependent coefficients and additionally time-dependent linear attenuation is considered. The ansatz method approach is used to carry out the integration. Both bright and dark soliton solutions are obtained in this paper. The constraint conditions for the existence of soliton solutions are also given.     

Multi-span digital non-linear compensation for dual-polarization quadrature phase shift keying long-haul communication systems

We have numerically investigated a method to reduce the complexity of the digital backward propagation algorithm (DBP). A filtered logarithmic step-size based split-step Fourier method (SSFM) is investigated in this paper to digitally compensate chromatic dispersion (CD) and non-linearities (NL) in dual-polarization quadrature phase shift keying (DP-QPSK) systems. The algorithm was evaluated for coherently-detected multiple channel DP-QPSK system over un-compensated transmission links with diverse baud-rates i.e. 14 GBaud, 28 GBaud and 56 GBaud. The results depict efficient mitigation of CD and NL, therefore improving the non-linear threshold point (NLT) by 4 dB. Furthermore by implementing a low-pass-filter (LPF) in each DBP stage, the required number of DBP stages are significantly reduced (multi-span DBP) by 75%. The results delineate improved system performance of logarithmic step size based filtered DBP (FL-DBP) both in terms of efficiency and complexity which will be helpful in future deployment of DBP algorithm with real-time signal processing modules for non-linear compensation.     

An electrochemical immunosensor based on covalent immobilization of okadaic acid onto screen printed carbon electrode via diazotization-coupling reaction

In this work, an electrochemical method based on the diazonium-coupling reaction mechanism for the immobilization of okadaic acid (OA) on screen printed carbon electrode was developed. At first, 4-carboxyphenyl film was grafted by electrochemical reduction of 4-carboxyphenyl diazonium salt, followed by terminal carboxylic group activation by N-hydroxysuccinimide (NHS), N-(3-dimethylaminopropyle)-N′-ethyle-carbodiimide hydrochloride (EDC). Hexamethyldiamine was then covalently bound by one of its terminal amine group to the activated carboxylic group. The carboxyl group of okadaic acid was activated by EDC/NHS and then conjugated to the second terminal amine group on other side of the hexamethyldiamine through amide bond formation. After immobilization of OA, an indirect competitive immunoassay format was employed to detect OA. The immunosensor obtained using this novel approach allowed detection limit of 1.44 ng/L of OA, and was also validated with certified reference mussel samples.