Showing papers by "Kodakkal Kannan Viswanathan published in 2018"

Inhibition of Redox Behaviors in Hierarchically Structured Manganese Cobalt Phosphate Supercapacitor Performance by Surface Trivalent Cations.

Abstract: The stability and performance of supercapacitor devices are limited by the diffusion-controlled redox process occurring at materials' surfaces. Phosphate-based metal oxides could be effectively used as pseudocapacitors because of their polar nature. However, electrochemical energy storage applications of Mn-Co-based phosphate materials and their related kinetics studies have been rarely reported. In this work, we have reported a morphology-tuned Mn x Co3-x (PO4)2·8H2O (MCP) spinel compound synthesized by a one-step hydrothermal method. Detailed physical and chemical insights of the active material coated on the nickel substrate are examined by X-ray diffraction, field-emission scanning electron microscopy, field-emission transmission electron microscopy, and high-resolution X-ray photoelectron spectroscopy analyses. Physiochemical studies reveal that the well-defined redox behavior usually observed in Co2+/Ni2+ surface-terminated compounds is suppressed by reducing the divalent cation density with an increased Co3+ and Mn3+ surface states. A uniform and dense leaflike morphology observed in the MnCo2 phosphate compound with an increased surface area enhances the electrochemical energy storage performance. The high polar nature of P-O bonding formed at the surface leads to a higher rate of polarization and a very low relaxation time, resulting in a perfect square-shaped cyclic voltagram and triangular-shaped galvanostatic charge and discharge curve. We have achieved a highly pseudocapacitive MCP, and it can be used as a vital candidate in supercapacitor energy storage applications.

Free vibration of cross-ply laminated plates based on higher-order shear deformation theory

Abstract: Free vibration of cross-ply laminated plates using a higher-order shear deformation theory is studied. The arbitrary number of layers is oriented in symmetric and anti-symmetric manners. The plate kinematics are based on higher-order shear deformation theory (HSDT) and the vibrational behaviour of multi-layered plates are analysed under simply supported boundary conditions. The differential equations are obtained in terms of displacement and rotational functions by substituting the stress-strain relations and strain-displacement relations in the governing equations and separable method is adopted for these functions to get a set of ordinary differential equations in term of single variable, which are coupled. These displacement and rotational functions are approximated using cubic and quantic splines which results in to the system of algebraic equations with unknown spline coefficients. Incurring the boundary conditions with the algebraic equations, a generalized eigen value problem is obtained. This eigen value problem is solved numerically to find the eigen frequency parameter and associated eigenvectors which are the spline coefficients.The material properties of Kevlar-49/epoxy, Graphite/Epoxy and E-glass epoxy are used to show the parametric effects of the plates aspect ratio, side-to-thickness ratio, stacking sequence, number of lamina and ply orientations on the frequency parameter of the plate. The current results are verified with those results obtained in the previous work and the new results are presented in tables and graphs.

Vibration of antisymmetric angle-ply composite annular plates of variable thickness

Abstract: Based on first order shear deformation theory, free vibrational behaviour of antisymmetric angle-ply composite annular plate is investigated. The thickness variations are assumed to be linear, exponential and sinusoidal along the radial direction. The equilibrium equations are obtained from which the coupled differential equations are derived in terms of displacement and rotation functions. These functions are approximated using splines to obtain the system of algebraic equations in terms of spline coefficients where the equation becomes a generalized eigenvalue problem by combining the boundary conditions. This problem is solved for finding eigenfrequencies and corresponding eigenvectors. This study is conducted for clamped-clamped and clamped-free boundary conditions. Detailed parametric investigation is carried out to determine the influences of radii ratio, number of layers, ply orientations and materials on the frequencies of plates. The primary results of this study are compared with those available in the literatures.

Vibration of Antisymmetric Angle-Ply Laminated Plates of Higher-Order Theory with Variable Thickness

Abstract: Free vibration of antisymmetric angle-ply laminated plates with variable thickness is studied. Higher-order shear deformation plate theory (HSDT) is introduced in the present method to remove the shear correction factors and improve the accuracy of transverse shear stresses. The thickness variations are assumed to be linear, exponential, and sinusoidal. The coupled differential equations are obtained in terms of displacement and rotational functions and approximated using cubic and quantic spline. A generalized eigenvalue problem is obtained and solved numerically by employing the eigensolution techniques with eigenvectors as spline coefficients to obtain the required frequencies. The results of numerical calculations are presented for laminated plates with simply supported boundary conditions. Comparisons of the current solutions and those reported in literature are provided to verify the accuracy of the proposed method. The effects of aspect ratio, number of layers, ply-angles, side-to-thickness ratio, and materials on the free vibration of cylindrical plates are discussed in detail.

4convective heat transfer in the boundary layer flow of a maxwell fluid over a flat plate using an approximation technique in the presence of pressure gradient

Abstract: In this study, the effect of pressure gradient have been included for heat transfer in the boundary layer flow of Maxwell fluid over a flat plate.The solution of the problem is obtained with an application of algorithms of Adams Method (AM) and Gear Method (GM) with Homotopy Perturbation Method (HPM) as an approximation technique. This technique shows the outcomes of pressure gradient (m), Deborah number (β) and Prandtl number (Pr) in the boundary layer flow on temperature and velocity profiles, also the momentum and thermal boundary layer thickness and discussed. To obtain this objective, the momentum and energy equations of Maxwell are solved. The outcomes of HPM in the absence of relaxation time (λ) or Deborah number (β) and pressure gradient (m) (i.e. λ = β = m = 0) at Prandtl number Pr = 1 are in closed relation with the numerical results having the value of η∞ is around 5. Also it is found that the system is convergent, as a whole momentum and thermal boundary layer thicknesses becomes thinner and thinner. Importantly, some cooling effects of the Maxwell fluid over a flat plate for energy profile have been observed.

Free vibration of angle-ply laminated conical shell frusta with linear and exponential thickness variations

Abstract: Free vibration of laminated conical shell frusta of variable thickness is studied using spline approximation. This problem includes first order shear deformation and considers shells as antisymmetric angle-ply orientation. The governing differential equations of the shells are resolved in terms of displacement functions and rotational functions. These functions are approximated using splines and the method of collocation is adopted for simultaneous algebraic equations. These equations become generalized eigenvalue problems and are solved numerically to avail eigenfrequencies and the corresponding eigenvectors. The variation of frequencies is analysed with respect to the cone angle, aspect ratio, material properties, number of layers, and thickness variation.

An application of algorithms of adams and gear methods on boundary layer convective heat transfer with pressure gradient using homotopy perturbation method (hpm) over a flat plate

Abstract: Boundary layer flow of convective heat transfer with pressure gradient over a flat plate is solved with an application of algorithms of Adams Method (AM) and Gear Method (GM) using Homotopy Perturbation Method (HPM). The distributions of temperature and velocity in the boundary layer are examined, particularly on the influences due to Prandtl number (Pr) and pressure gradient (m). Consequently, the equations of momentum and energy are resolved concurrently. These HPM outcomes have been compared with the previous published work in the literature; and these are found to be in good agreement with the results obtained from numerical methods.