Kumar D.,Graphic Era University |
Kaur D.,Indian Institute of Technology Roorkee
Journal of Alloys and Compounds | Year: 2013
In the present work, the effect of film thickness on the structural and magnetic properties of La2NiMnO6 (LNMO) ferromagnetic double perovskite thin films has been systematically investigated. LNMO thin films of varying thickness from 54 nm to 256 nm were deposited using the pulsed laser deposition technique onto single-crystalline LaAlO3 substrate. The X-ray diffraction pattern and Raman scattering observations reveal that all films have c-axis epitaxial growth and an orthorhombic structure. The Raman spectra of the films are dominated by two broad peaks at around 534 cm -1 and 676 cm-1 assigned to the antisymmetric stretching (AS) and symmetric stretching (S) vibrations of the octahedra, respectively. The Raman peaks of the LNMO thin films are blue shifted in comparison to those of bulk LNMO and the shift increases with decreasing film thickness, indicating the increased influence of strain. The critical thickness for strain relaxation, as determined from the Raman spectra, is between 110 nm and 156 nm. However, the strain is observed to have large effect on the magnetic properties of films. Ferromagnetic to paramagnetic transition temperature (Tc) and the saturation magnetization were found to increase with increase in the film thickness. The film with thickness of 256 nm exhibits a saturation magnetic moment of 4.5 μB/f.u. and coercive field of 630 Oe at 10 K, with a Curie temperature close to 280 K. © 2012 Elsevier B.V. All rights reserved.
Gupta A.,Graphic Era University
Acoustical Physics | Year: 2014
This paper presents a review study on sonic crystal, their development and present status. The paper also focuses on some of the applications of sonic crystal and numerical methods to study these crystals. Sonic crystals are periodic arrangement of scatterers, whose interaction with acoustic waves leads to the formation of band gap. Band gap are regions of frequencies where the sound propagation is significantly restricted from the sonic crystal. This property is used in many applications such as sound barrier, frequency filter, acoustic imaging etc. The paper presents a review of all these applications. Further the paper presents some of the numerical methods used to calculate the band gap formation in sonic crystal. © 2014 Pleiades Publishing, Ltd.
Awasthi M.K.,Graphic Era University |
Asthana R.,Galgotias University
International Communications in Heat and Mass Transfer | Year: 2013
The capillary instability of the cylindrical interface separating two viscous and incompressible fluids through porous medium is studied using viscous potential flow theory, when there is heat and mass transfer across the interface. The fluids are considered to be viscous and incompressible with different kinematic viscosities. A dispersion relation that accounts for the growth of axisymmetric waves is derived and stability is discussed theoretically as well as numerically. Stability criterion is given in terms of critical value of wave number. Various graphs have been drawn to show the effect of various physical parameters such as heat transfer capillary number, viscosity ratio, permeability and porosity on the stability of the system. It has been observed that porous media and heat transfer both have stabilizing effect while porosity has destabilizing effect on the stability of the system. © 2012 Elsevier Ltd.
Awasthi M.K.,Indian Institute of Technology Roorkee |
Awasthi M.K.,Graphic Era University
Journal of Heat Transfer | Year: 2013
Viscous corrections for the viscous potential flow analysis of Rayleigh-Taylor instability of two viscous fluids when there is heat and mass transfer across the interface have been considered. Both fluids are taken as incompressible and viscous with different kinematic viscosities. In viscous potential flow theory, viscosity enters through a normal stress balance and the effects of shearing stresses are completely neglected. We include the viscous pressure in the normal stress balance along with irrotational pressure and it is assumed that this viscous pressure will resolve the discontinuity of the tangential stresses at the interface of the two fluids. It has been observed that heat and mass transfer has a stabilizing effect on the stability of the system. It has been shown that the irrotational viscous flow with viscous corrections gives rise to exactly the same dispersion relation as the dissipation method in which no pressure term is required and the viscous effect is accounted for by evaluating viscous dissipation using irrotational flow. It has been observed that the inclusion of irrotational shearing stresses has a stabilizing effect on the stability of the system. Copyright © 2013 by ASME.
Pant M.,Graphic Era University
Indian Journal of Experimental Biology | Year: 2016
In tissue culture, high production cost of the products restricts their reach. Though tissue culture is a major strength in floriculture it is marred by pricing issues. Hence, we developed a complete regeneration low cost micropropagation protocol for an economically important floriculture crop, carnation (Dianthus caryophyllus L.). Successful regeneration of carnation from nodal explants on cost-efficient medium indicates that psyllium husk, sugar and RO water can effectively replace the conventional medium comprising agar, sucrose and distilled water. The protocol can contribute to increased carnation production at comparatively reduced cost, and there by encourage wide scale adoption by the common growers. © 2016, National Institute of Science Communication. All Rights reserved.