Simple theoretical analysis of the thermoelectric power in quantum dot superlattices of non-parabolic heavily doped semiconductors with graded interfaces under strong magnetic field

We study theoretically the thermoelectric power in the presence of a large magnetic field (TPM) in heavily doped III–V, II–VI, PbTe/PbSnTe, strained layer and HgTe/CdTe quantum dot superlattices (QDSLs) with graded structures on the basis of newly formulated electron energy spectra and compare the same with that of the constituent materials. It has been found, taking heavily doped GaAs/Ga_1−xAl_xAs, CdS/CdTe, PbTe/PbSnTe, InAs/GaSb and HgTe/CdTe QDSLs as examples, that the TPM increases with increasing inverse electron concentration and film thickness, respectively, in different oscillatory manners and the nature of oscillations is totally band structure dependent. We have also suggested the experimental methods of determining the Einstein relation for the diffusivity–mobility ratio, the Debye screening length and the electronic contribution to the elastic constants for materials having arbitrary dispersion laws.     

Two-phase electrohydrodynamic simulations using a volume-of-fluid approach

A numerical methodology to simulate two-phase electrohydrodynamic flows under the volume-of-fluid paradigm is proposed. The electric force in such systems acts only at the interface and is zero elsewhere in the two fluids. Continuum surface force representations are derived for the electric field force in a system of dielectric–dielectric and conducting–conducting fluids. On the basis of analytical calculations for simple flow problems we propose a weighted harmonic mean interpolation scheme to smoothen the electric properties in the diffused transition region (interface). It is shown that a wrong choice of interpolation scheme (weighted arithmetic mean) may lead to a transition region thickness dependent electric field in the bulk. We simulate a set of problems with exact or approximate analytical solutions to validate the numerical model proposed. A coupled level set and volume-of-fluid (CLSVOF) algorithm has been used for simulations presented here.     

Numerical analyses of flow around airfoils subjected to flow induced vibration

This paper describes extensive computer-based analytical studies on the details of unsteady flow behavior around airfoils subjected to flow induced vibration in turbo-machinery. To consider the time-dependent motions of airfoils, a complete Navier-Stokes solver incorporating a moving mesh based on an analytic solution of motion equation for airfoil translation and rotation was applied. The drag and lift coefficients for the cases of stationary airfoils and airfoils subjected to flow induced vibration were examined. From the numerical results in non-coupling case as out of consideration of the airfoil motion, it was found that the separation vortex consisted of large-scale rolls with axes in the span direction, and rib substructures with axes in the stream direction. In the coupling simulation including the airfoil motion, both the translation and the rotation displacement were gradually increased when the airfoil translation and rotation natural frequencies synchronize exactly with the oscillation frequency of the fluid force. In addition, the transformation from complex structure with rolls and ribs to two-dimensional aspect of only rolls could be visualized in three-dimensional simulation.     

Synthesis of chiral oxa- and azacycle-fused anthraquinone derivatives

A convenient protocol for the synthesis of chiral pyran and piperidine ring-fused anthraquinone derivatives has been developed from (R)-2,3-O-cyclohexylidene-glyceraldehyde using sequential applications of enyne metathesis, Diels–Alder reaction and aromatization as key steps.     

Orthogonal and symplectic parabolic bundles

We investigate orthogonal and symplectic bundles with parabolic structure, over a curve.     

Synthesis and electrical and optoelectronic properties of poly[(N-benzyldiphenylamino)methane]

Poly[(N-benzyldiphenylamino)methane] was synthesized by the condensation polymerization of benzyldiphenylamine and formalin (30% HCOH in water) and examined for electrical and optoelectronic properties. Dark conductivity and photoconductivity of the polymer film were investigated by steady-state measurements. Current-voltage characteristics and intrinsic photoconduction of the polymer in the visible wavelength range were studied. A superlinear current increase is tentatively explained in the light of the Poole-Frenkel effect. Dielectric constant and dielectric loss parameters of the polymer are independent of frequency (50 Hz–10 kHz) and temperature (273–323 K), respectively. The growth and decay rates of the photocurrent depend on the applied voltage, and the photocurrent varies directly with the light intensity. The activation energies for dark conductivity and photoconductivity are 1.16 eV and 1.05 eV, respectively, and the optical energy band gap as evaluated from absorption coefficient spectra is 2.86 eV.     

Singular Value Decomposition Solution of the Schrödinger Equation in the Presence of Exchange Terms

A new numerical method of solving integro-differential equations appearing in the theory of atomic and nuclear scattering systems has been devised. It is termed Singular Value Decomposition Method (SVD). It consists in expanding the exchange kernel into a number of separable terms by means of the Singular Value Decomposition and then iterating over the remainder. In this paper, we extend our SVD method to the scattering of low energy electron-helium which has been the subject of interest, both theoretically and experimentally. We compare our results with the Moments Method which is widely used. The Moments Method consists of making an expansion of the solution into an especially favorable basis that takes care of the non-exchange part of the Hamiltonian.     

Overtone spectroscopy of water molecules based on room temperature diode laser emitting in the NIR range

The measurement of very weak overtone spectroscopic line shape of water molecule is performed using wavelength modulation spectroscopy (WMS). In this work a high resolution near infrared diode laser spectrometer is used to record first derivative (1f) signal of buffer gas Helium and Carbon dioxide broadened water vapour transitions around 820 nm wavelength region. The effect of collision due to perturber pressure on signal to noise ratio (SNR) is discussed. The Lorentzian HWHM of observed 1f signal is calculated. The comparison is made between collisional broadening of water vapour transition broadened by inert gas Helium and high quadrupole moment active gas Carbon dioxide.