Volume 70, Issue 1

The peristaltic flow of an incompressible viscous fluid in a curved channel is investigated. The flow analysis is conducted in the presence of an induced magnetic field. A long-wavelength and low-Reynolds number approach is followed. The stream function, pressure gradient, magnetic force function, induced magnetic field, and current density are constructed. We observed that symmetry in the profiles of u and ϕ is disturbed because of curvature effects. For larger values of curvature k , results of planar channel are deduced. The effects of significant parameters have been portrayed and discussed.

The phosphor SrMoO 4 :Pr 3+ was successfully prepared by high-temperature solid-state reaction process, and characterised by X-ray diffraction (XRD), scanning electron microscope (SEM), and fluorescence spectrometer. The results show that the prepared SrMoO 4 :Pr 3+ has a scheelite structure with pure phase and represents leaf-like shapes with good dispersity. The strong electron absorbabilities are located at 220–300 nm (charge transfer band), 448, 474, and 487 nm, respectively. The emission spectrum of the SrMoO 4 :Pr 3+ phosphor was characterised, which peaked at 529, 545, 554, 600, 619, and 645 nm, corresponding to the f–f transitions of Pr 3+ . The average International Commission on Illumination (CIE) chromaticity coordinates of the phosphors are x≈0.455, and y≈0.520, and the optimum doping mole fraction of Pr 3+ is 0.2 mol.%. To better understand the fluorescent behavior of as-prepared phosphors, a complete 91×91 energy matrix was built by an effective Hamiltonian operator, including free ion and crystal-field interactions. The fluorescent spectra of Pr 3+ ion at the tetragonal ( S 4 ) Sr 2+ site of SrMoO 4 crystal were firstly calculated from a full diagonalisation (of energy matrix) method. The fitting values are in good agreement with the experimental data.

AgI-Al 2 O 3 composite materials have been prepared by mechanical milling technique at room temperature. The product materials were characterised by X-ray diffraction and showed the characteristics of γ-AgI phase. The ionic conduction properties of the composite materials were studied by impedance spectroscopy measurements in the 300- to 470-K temperature range. A considerable increase in ionic conductivity by three orders of magnitude was observed in the composite materials compared with the pristine β-AgI phase. The enhanced ionic conductivity could be assigned to the increased defect concentration and the formation of two phase mixtures with the insulating Al 2 O 3 .

In this article, we have investigated peristaltic mechanisms in a two dimensional nonuniform channel filled with Herschel–Bulkley fluid. Problem is studied under the assumptions of long-wavelength and low-Reynolds-number approximation. The fluid flow is investigated in the wave frame of reference moving with the velocity of the peristaltic wave in a channel. Exact solutions for the velocity field, temperature profile, stream functions, and pressure gradient are obtained and illustrated graphically for different parameters of interest such as α (angle of inclination), τ (the ratio of yield stress), φ (amplitude ratio), Pr (Prandtl number), and Q (mean flow rate) etc.

In this article, the mechanism of cilia-induced flow is discussed through a mathematical model. In this analysis two-dimensional flow of a viscous fluid is observed in a curved channel with ciliated walls. The features of ciliary structures are determined by the dominance of viscous effects over inertial effects using the long-wavelength approximation. The flow is modeled in both fixed and wave frame references. The exact solution is calculated for the velocity profile and the flow properties for the viscous fluid are determined as a function of the cilia and metachronal wave velocity. Results for the pressure rise, pressure gradient and stream function are constructed and analyzed graphically.

The Jeans instability of rotating viscoelastic fluid in the presence of uniform magnetic field is investigated using the generalised hydrodynamic (GH) model. A general dispersion relation is derived with the help of linearised perturbation equations using the normal mode analysis, which is further discussed for axis of rotation parallel and perpendicular to the direction of the magnetic field in both the weakly coupled (hydrodynamic) and strongly coupled (kinetic) limits. The onset criterion of Jeans instability for magnetised rotating viscoelastic fluid is obtained, which remains unaffected by the presence of rotation and magnetic field but depends upon viscoelastic effects. The graphical illustrations are depicted to see the influence of rotation, Mach number, shear and viscous effects, and sound speed on the growth rate of Jeans instability. It is found that all these parameters have stabilising influence on the growth rate of Jeans instability; hence, they are capable of collapsing to a self-gravitating, rotating, magnetised viscoelastic medium.

In this paper, the solution of nonlinear hyperbolic conservation law problems containing strong shock waves is presented using the method of lines. A difficulty with the method of lines, as with many other classical shock-capturing methods, is the threat of unphysical numerical oscillations, which can be avoided by adding an artificial viscosity term. Two schemes of the method of lines for solving the described problems have been proposed. Extensive numerical examples in both scalar and system test problems demonstrate the efficiency, robustness, and ease of implementation of the proposed schemes.

Incompressible fluids are of current interest. Considering a (3+1)-dimensional variable-coefficient Boiti–Leon–Manna–Pempinelli model for an incompressible fluid, we perform symbolic computation to work out a variable-coefficient-dependent auto-Bäcklund transformation, along with two variable-coefficient-dependent classes of the shock-wave-type solutions. Our auto-Bäcklund transformation is different from the recently reported bilinear one.

In the present study, a simple and highly effective physical mixing method was used to synthesise carbon nanotube (CNT)-reinforced silver nanocomposites. Composites were prepared with different contents (vol%) of functionalised multiwall nanotubes. The microstructure of synthesised nanocomposites was analysed by X-ray diffraction, electron diffraction spectroscopy, and scanning electron microscopy. Microstructural characterisations revealed good distribution of nanotubes in the silver matrix. The thermal expansion behaviour of the composites was studied in reference to the variation in nanotube volume content in the silver matrix. It was observed that the coefficient of thermal expansion decreased with the increase in the percentage of CNT volume. The thermal expansion of the CNT-reinforced silver composites decreased to 55 % of pure silver upon the introduction of 6 vol% of nanotubes into the silver matrix. The thermal expansion behaviour of the CNT-reinforced silver composites was also analysed theoretically using the rule of mixture and Schapery’s model. The CNT-reinforced silver composites may be a promising contact and thermal management material in electronic devices.

The modified Schrödinger equation due to its minimal length is considered useful for harmonic and linear potentials, as well as the free-particle case. Using basic concepts of quantum mechanics, the time evolution of these systems is reported.

An approach is proposed to analyse an interacting bosonic system using two-time temperature Green’s functions on the collective variables. Two systems are studied: liquid helium-4 and the Yukawa Bose liquid being a model of the nuclear matter. The suggested decoupling in the equations of motion for Green’s functions yields a good description of the elementary excitation spectrum in the long-wavelength limit.