Scattering of a spherical wave from the coupling of two half-planes

Summary  The diffraction of a spherical acoustic wave from the juncture of pressure release (soft) and locally reacting (absorbing) half-planes in a fluid moving at subsonic velocity is examined. This consideration is important because the point sources are regarded as better substitutes for real sources than line sources/plane waves. The integral representation of the field is obtained using integral transforms and the Wiener-Hopf technique. The factorization of the kernel function in the Wiener-Hopf functional equation is accomplished. The analytic solution of the integrals is obtained by employing asymptotic methods and the far field is presented. The effect of the Mach number is shown explicitly on the diffracted field.     

A low molecular weight hydrogel which exhibits electroosmotic flow and its use as a bioreactor and for electrochromatography of neutral species

A low molecular weight hydrogel which exhibits electroosmotic flow is described, and its use for separation and biocatalytic applications that require passage of a solvent stream through the gel is demonstrated.     

An electrochemical sensor based on TiO2/activated carbon nanocomposite modified screen printed electrode and its performance for phenolic compounds detection in water samples

Herein, we reported a titanium oxide (TiO₂) modified activated carbon nanocomposite that showed advantageous characteristics in terms of electro-conductivity, catalytic activity and surface area. The designed nanocomposite was employed to modify the screen printed carbon electrode transducer surface in the construction of an electrochemical sensor. The electrode surface modification was characterised by cyclic voltammetry and impedimetric studies. The modified transducer surface was subsequently used for the detection of four phenolic endocrine disruptors, p-nitrophenol, hydroquinone, catechol and 1-naphtol. Under optimal conditions, TiO₂ modified activated carbon sensor was evaluated by differential pulse voltammetry showing a good linearity with correlation coefficients higher than 0.99. It showed, in parallel, a high sensitivity where the detection limits were 348 ng/L, 110.1 ng/L, 3.3 ng/L and 7.2 µg/L for the respective studied compounds (S/N = 3). Finally, we validated the method with river water samples, and good recovery values were obtained showing the potential application of the reported biosensor.     

Nonlinear measure approach for the robust exponential stability analysis of interval inertial Cohen–Grossberg neural networks

This article is concerned with the existence and robust stability of an equilibrium point that related to interval inertial Cohen–Grossberg neural networks. Such condition requires the existence of an equilibrium point to a given system, so the existence and uniqueness of the equilibrium point are emerged via nonlinear measure method. Furthermore, with the help of Halanay inequality lemma, differential mean value theorem as well as inequality technique, several sufficient criteria are derived to ascertain the robust stability of the equilibrium point for the addressed system. The results obtained in this article will be shown to be new and they can be considered alternative results to previously results. Finally, the effectiveness and computational issues of the two models for the analysis are discussed by two examples. © 2016 Wiley Periodicals, Inc. Complexity 21: 459–469, 2016     

Dynamical analysis of a delayed six‐neuron BAM network

In this article, a simplified bidirectional associative memory network with delays involving six neurons is considered. By analyzing the distribution of roots of the characteristic equation for linearized system regarding the sum of delay as a bifurcation parameter, we obtain the condition of the occurrence for Hopf bifurcation. It reveals that Hopf bifurcation occurs when the sum of the delay passes through a critical value. The direction and the stability of the bifurcating periodic solution are determined by applying the normal form theory and center manifold theorem. Finally, a numerical example is used to illustrate the validity of theoretical results obtained. © 2015 Wiley Periodicals, Inc. Complexity 21: 9–28, 2016     

MHD three-dimensional flow of viscoelastic fluid over an exponentially stretching surface with variable thermal conductivity

This study models the magnetohydrodynamic (MHD) three-dimensional boundary layer flow of viscoelastic fluid. The flow is due to the exponentially stretching surface. The heat transfer analysis is performed through prescribed surface temperature (PST) and prescribed surface heat flux (PHF). The thermal conductivity is taken temperature dependent. Series solutions of velocities and temperatures are constructed. Graphical results for PST and PHF cases are plotted and analyzed. Numerical values of skin-friction coefficients and Nusselt numbers are presented and discussed.     

Field of a Point Source Within Perfectly Conducting Parallel-Plates in a Homogeneous Biisotropic Medium

The spherical wave scattering response by a perfectly conducting open–ended waveguide in a biisotropic medium is obtained. Interestingly, the vector diffraction problem is reduced to the scattering of a single scalar field, this scalar field being the normal component of either a left–handed or a right–handed Beltrami field. Here, we explicitly consider the scattering of the left–handed field component, that of the other scalar field being analogously tractable. The solution is constructed with the aid of the Wiener–Hopf technique.     

A local boundary condition coupled to a finite element method to compute guided modes of optical fibres under the weak guidance assumptions

An efficient method coupling a local boundary condition to a finite element technique is proposed to compute guided modes of optical fibres under the weak guidance assumptions. This method is designed to provide accurate solutions for optical fibres with no restriction on their shape as well as on their refractive index profile. Several numerical experiments are performed to demonstrate this point. Copyright © 2000 John Wiley & Sons, Ltd.     

Effectiveness of Darcy-Forchheimer and nonlinear mixed convection aspects in stratified Maxwell nanomaterial flow induced by convectively heated surface

The effect of nonlinear mixed convection in stretched flows of rate-type non-Newtonian materials is described. The formulation is based upon the Maxwell liquid which elaborates thermal relation time characteristics. Nanofluid properties are studied considering thermophoresis and Brownian movement. Thermal radiation, double stratification, convective conditions, and heat generation are incorporated in energy and nanoparticle concentration expressions. A boundary-layer concept is implemented for the simplification of mathematical expressions. The modeled nonlinear problems are computed with an optimal homotopy scheme. Moreover, the Nusselt and Sherwood numbers as well as the velocity, nanoparticle concentration, and temperature are emphasized. The results show opposite impacts of the Deborah number and the porosity factor on the velocity distribution.