Identifying shifts between two regression curves

Annals of the Institute of Statistical Mathematics - This article studies the problem whether two convex (concave) regression functions modelling the relation between a response and covariate in...     

Sizing Large Hollow Micro-Balloons with the phase doppler interferometer

A combined theoretical and experimental study has been conducted to evaluate the effectiveness of using large, hollow micro-balloons as LDV seed particles. The study has focused on the ability of phase Doppler systems to size hollow microballoons, the ability of large micro-balloons to respond to high frequency spatial and temporal flow field variations, and the overall advantages and disadvantages of using large microballoons instead of conventional LDV seed particles, such as very small water droplets or polystyrene latex (PSL) particles. This paper discusses the development of a theoretical phase Doppler response model for stratified spheres, the experimental facility, and the theoretical and experimental results.     

Nonlinear travelling waves in φ6 polarizable model

We present a complete theoretical analysis of the periodic and non-periodic travelling waves in a diatomic chain model, in the continuum limit by incorporating nonlinear sixth order polarization potential (φ⁶) at the anion site. We have formulated a nonlinear lattice dynamical theory in which various energy curves are obtained for different types and magnitudes of the core-shell force constants. For periodic solutions, we have obtained two types of commensurate wave amplitudes which propagate in the opposite direction with respect to each other. For nonperiodic solutions, we have obtained various travelling excitations such as kink, antikink, excitons etc. for different values of the mass ratio and velocity parameter. The dipole moment per unit charge for SrTiO₃ has been calculated and it is found that the nonlinear excitations in this model carry large amount of energy as compared to those obtained from harmonic and anharmonic optical phonons in the φ⁴-polarizable model.     

Phonon dispersion in quasiperiodic semiconductor superlattices

The phonon spectra of unstrained and strained quasiperiodic semiconductor superlattices (QSSL) have been calculated using one-dimensional linear chain model. We consider two types of quasiperiodic systems, namely cantor triadic bar (CTB) and Fibonacci sequences (FS), constituting of AlAs, GaAs and GaSb of which the latter two have a lattice mismatch of about 7%. The calculations have been made using transfer matrix method and also with and without the inclusion of strain. We present the results on phonon spectra of two component CTB and two as well as three component FS semiconductor superlattices (SSL), thickness and order dependence on LO mode of GaAs, effect of strain on LO frequency of GaAs. The calculated results show that the strain generated due to lattice mismatch reduces significantly the magnitudes of the confined optical phonon frequency of GaAs.     

Effect of strain on vibrational modes in strained layer superlattices

We have investigated the lattice vibrational properties of a two-component strained layer semiconductor superlattice (GaAs) _n1 (GaSb) _n2 using a one-dimensional linear chain model and transfer matrix method [1]. Effect of strain, arising due to the lattice mismatch (∼ 7%) has been considered explicitly in the equation of motion. We show for the first time that the optical vibrational frequency increases (in the case of (GaAs)₄ (GaSb) _n ) or decreases (in the case of (GaAs) _n (GaSb)₄) with increase of layer thicknessn, in either type of superlattices. Raman scattering measurements on some other similar systems support our findings.     

Phonons and periodons in IV–VI semiconductor superlattices

We have calculated the phonon and periodon dispersion relations in IV–VI semi-conducting bulk PbTe and SnTe and their superlattice structure. The model used here is a one-dimensional lattice which includes harmonic interactions up to second neighbours as well as on-site nonlinear electron-ion interactions at the anion site. We calculate the phonon and periodon dispersion relations in bulk and PbTe-SnTe superlattice for the transverse optic and acoustic modes using the transfer matrix method. Our analysis has predicted correct nature of the folding of acoustic and confinement of optical phonons at various frequency intervals corresponding to pass and stop bands of the superlattices.     

Symmetric marching technique for the poisson equation. I. Dirichlet boundary conditions

The symmetric marching technique has been developed to solve the Poisson equation with Dirichlet boundary conditions. The method has been combined with a mesh refinement technique, which is used as an appropriate interpolation scheme to obtain a solution of the problem on finer grids. The effectiveness of the method has been demonstrated by solving some test examples.     

Bandstructure,fermi surface and superconductivity of Pr under high pressure

The electronic bandstructures of rare earth metal Praseodymium (Pr) have been calculated for a wide range of static pressures using RAPW method. The density of states and Fermi surface cross sections on the principal planes corresponding to various pressures are obtained. It is seen that, there is, 4f shell breakdown in Pr under pressure and formation of 4f bands. The calculation of the superconducting transition temperaturesT _c corresponding to various pressures shows that Pr may become a high pressure superconductor like Cerium eventhough it is not observed experimentally to be a superconductor because of its magnetic character at normal pressure.