Open Access Original Research Article

Ifsana Karim, Md. Sirajul Islam, Md. Shakhaoath Khan

Magnetohydrodynamic mixed convection boundary layer flow of a nanofluid near the stagnation-point on a vertical plate with heat generation is investigated for both assisting and opposing flows are well thought-out. Different types of nanoparticles as copper (Cu), alumina (Al_{2}O_{3}) and titania (TiO_{2}) considering here. Using similarity approach the system of partial differential equations is transformed into ordinary differential equations which strongly depend on the magnetic parameter (M), buoyancy parameter (λ), Prandtl number (P_{r}), heat generation parameter (Q) and volume fraction parameter (φ). The coupled differential equations are numerically simulated using the Nactsheim-Swigert shooting technique together with Runge-Kutta six order iteration schemes. The velocity and temperature profiles are discussed and presented graphically. The comparison for dimensionless skin friction coefficient and local Nusselt number with previously published literature also take into account for the accuracy of the present analysis.

Open Access Original Research Article

S Chandel and Shri Ram

A one- parameter family of totally anisotropic Bianchi type-II string cosmological models with bulk

viscous fluid in Lyra geometry is investigated. Exact solutions of Einstein field equations have been

obtained by constraining the the constant deceleration parameter which yields power-law form of

the average scale factor. Some physical and geometrical properties of the models along with the

physical acceptability have been also discussed.

Open Access Original Research Article

Stephan J. G. Gift

Light transmission in the Sun-Centered Inertial (SCI) frame is considered within a flat space-time metric of relativity theory. It is shown that this metric which is used to derive the Langevin metric that generates the accurate clock synchronization algorithm used in the Global Positioning System (GPS), also predicts one-way light speed anisotropy in an inertial frame that contradicts the principle of light speed constancy. This finding is tested and confirmed in the SCI frame using the range equations employed in the tracking of planets and spacecrafts moving within our solar system. These equations are based on the observation that light travels in the SCI frame at a constant speed *c* and have been extensively tested and rigorously verified. The results suggest a modification of the Lorentz Transformations that yields new transformations that are consistent with the observed light speed anisotropy and which better accord with the physical world.

Open Access Original Research Article

Burke Ritchie, Charles A. Weatherford

Zitterbewegung is the quiver motion discovered by Schroedinger in his 1930 solution of the time-dependent Dirac equation for a free electron. The origin of Zitterbewegung is the interference between positive-energy and negative-energy states. Zitterbewegung is predicted to exist for both free and bound electrons provided one discards Dirac’s hypothesis, known as hole theory, whereby positive-energy electrons are forbidden from occupying negative-energy states such that Zitterbewegung is suppressed. The positive-energy spectra of states is identical whether one uses hole theory, in which Zitterbewegung is suppressed (restricted solution), or whether one uses the solution in which electrons are not restricted from simultaneously occupying both positive-energy and negative-energy states such that Zitterbewegung is not suppressed (unrestricted solution). Thus both the restricted and unrestricted solutions are confirmed by spectroscopic experimental observation such that new experiments are motivated to discriminate between the restricted and unrestricted solutions. Hole theory (the restricted solution) is used to interpret the experimental observation of electron-positron pair creation and annihilation. In this paper we look for pair states in the negative-energy region of the Dirac spectrum in order to understand if the unrestricted solution, which correctly predicts the positive-energy spectrum and Zitterbewegung, is also correct in the description of pair creation and annihilation.

Open Access Original Research Article

A. Acharyya, P. Sen, E. Chakraborty, P. Sarkar, N. Banerjee, R. Dey, A. R. Mondal, S. Chatterjee, T. K. Sengupta

In this paper, the authors have proposed a new method for speed control of DC motor drives via modified constant frequency-variable duty (CFVD) pulse width modulation (PWM) technique. The armature of the DC motor rotating in very low speed has to accept abrupt mechanical shocks (kicks) due to the application of large amplitude narrow pulse trains (very low duty cycle) while the speed of the DC motor is controlled by using the conventional CFVD PWM method. These consecutive abrupt mechanical shocks lead to reduction in life of the DC motor. In the proposed method, an extra control signal (having modified sinusoidal form) is subtracted from the conventional fixed amplitude CFVD PWM signal to obtain the modified speed control signal, which provides gradual periodic increase and decrease in the amplitude of consecutive pulses for all duty cycles. Thus for very low duty cycles (for achieving very low speed) the abrupt mechanical shocks on the armature can be avoided. Moreover, the peak amplitude of the subtracted extra control signal provides an additional control over the speed of DC motor along with the duty cycle of the conventional PWM signal. A circuit for generating the modified control signal has been designed and also fabricated for testing. Finally the experiments are carried out to study the speed control characteristics of a 9 V DC motor drive. The proposed method is found to be better than the conventional CFVD PWM speed control method as regards flexibility in speed control, transient response and abrupt electrical breaking.

Open Access Original Research Article

Victor G. Zavodinsky, Olga A. Gorkusha

**Aims: **For modeling of large polyatomic systems one may use the variation principle for energy density functional. The key point to make this is to find the functional of kinetic energy in the orbital-free approach.

**Study Design:** We describe a way to find functionals of kinetic energy for single atoms and to use them for modeling of polyatomic systems. On examples of diatomic systems Si_{2}, Al_{2}, and P_{2} the equilibrium interatomic distances and binding energies were calculated in good comparison with published data. Results for Si-Al, Si-P and Al-P dimers are also close to results of Kohn-Sham calculations.

**Place and Duration of Study:** Institute of Materials, Khabarovsk, Russia; Institute of Applied Mathematics, Khabarovsk, Russia; 2011-2013.

**Methodology:** We worked in the frameworks of pseudo potentials and the local density approximation of the density functional theory. We used the Kohn-Sham calculations as start steps to find the kinetic energy functionals for single atoms (Al, Si, P). Then we constructed the total energy functionals for dimers and calculated equilibrium interatomic distances and the binding energies.

**Results:** We constructed the total energy functional for a dimer Si_{2} and minimized it with some parameters in order to obtain the equilibrium interatomic distance and the binding energy in good comparison with published data. Then we modeled Al_{2}, P_{2}, Si-Al, Si-P, and Al-P dimers with the same parameters and also obtained good results.

**Conclusion:** We have demonstrated a principal possibility to find equilibrium densities, interatomic distances and binding energies in the orbital-free approach using the kinetic energy functionals for single atoms calculated by the Kohn-Sham method.

Open Access Original Research Article

Frédéric Ouattara, Emmanuel Nanéma

The purpose of this study is to appreciate the estimation of TIEGCM (Thermosphere Ionosphere Electrodynamics General Circulation Model) and that of the 2012 version of IRI (International Reference Ionosphere) in African Equatorial Ionization Anomaly (EIA) region through the diurnal variation of F2 layer critical frequency (foF2).The comparison is made between data and theoretical values carried out from TIEGCM and IRI-2012 during solar cycle minimum and maximum phases and under quiet time condition over seasons. Data concern solar cycle 22 foF2 data of Ouagadougou station (Lat: 12.4° N; Long: 358.5°E, dip: 1.43°N for 2013) provided by Télécom Bretagne. Quiet time condition is determined by Aa inferior or equal to 20 nT and solar cycle maximum and minimum phases correspond to sunspot number Rz superior to 100 and Rz inferior to 20, respectively. Seasons are estimated by considering December as winter month, March as spring month, June as summer month and September as autumn month. The seasonal Hourly quiet time foF2 is given by the arithmetic mean values of the five quietest day hourly values. Data profiles show noon bite out profile with more and less pronounced morning or afternoon peak in equinox and that during solar maximum and that also in solar minimum except during solstice where the profile fairly is dome or plateau. During solar minimum, both models present more or less pronounced afternoon peak with more or less deep trough between 1000 LT and 1400 LT. During solar maximum, in general, TIEGCM shows afternoon peak and IRI-2012 present plateau profile. This result exhibits the non-well estimation of the dynamic process of this region. Model accuracy is highlighted by the Mean Relative Error (MRE) values. These values show better prediction for IRI-2012 except in September for both solar cycle phases involved. The non-good prediction of TIEGCM is observed in December during solar minimum and in June during solar maximum. Models predictions are better during solar maximum than during solar minimum and strongly dependent on pre-sunrise and post sunset periods.

Open Access Original Research Article

Yuriy N. Zayko

This article presents an investigation of problem of quantum system state’s measurement by using an example of particles registered by a measuring device (screen). Some variants of R-procedure which is responsible for measurements are discussed. New variant of R-procedure is suggested. It is based on quantum description of measuring device (screen). In frame of this model R-procedure can be described as part of unitary evolution of the whole system “particle + screen”.

Open Access Review Article

J. Josephine Novina, G. Vasuki, M. Suresh, M. Syed Ali Padusha, Katharina M. Fromm, A. Crochet

The title compound [Co (C_{7}H_{8}N_{4}O)_{2}]Cl_{2}.3H_{2}O, has been synthesized and characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The title compound crystallizes in a triclinic, space group P-1 with a = 9.3547(5) Å, b = 9.8985(5) Å, c = 12.8840(7) Å, α=106.033(4)º, β = 103.916(4)º, γ = 95.717(4)º, V = 1095.20(10) Å^{3}, Z=2, R = 0.0255 and wR = 0.0687. In the title compound there are two crystallographically independent cations and anions and three water molecules in the asymmetric unit. The Co^{II} ion has a distorted octahedral coordination environment and is surrounded by four N atoms and two O atoms in a tridentate manner. In the crystal, N—H…Cl, N—H…O, O—H…Cl and O—H…O hydrogen bonds link the complex cations, chloride anions and solvent water molecules into a three-dimensional network. The preliminary antimicrobial activities were studied.

Open Access Review Article

U. V. S. Seshavatharam, S. Lakshminarayana

Considering ‘black hole geometry’ as the ‘eternal cosmic geometry’ and by assuming ‘constant light speed rotation’ throughout the cosmic evolution, at any time the currently believed cosmic ‘critical density’ can be shown to be the cosmic black hole’s eternal ‘volume density’. Thinking in this way and based on the Mach’s principle, ‘distance cosmic back ground’ can be quantified in terms of ‘Hubble volume’ and ‘Hubble mass’. To proceed further the observed cosmic redshift can be reinterpreted as an index of ‘cosmological’ light emission mechanism. By considering the characteristic mass unit as the initial mass of the baby cosmic black hole, initial physical and thermal parameters of the cosmic black hole can be defined and current physical and thermal parameters of the cosmic black hole can be fitted and understood. It can be argued that, there exists one variable physical quantity in the presently believed atomic and nuclear physical constants and “rate of change” in its magnitude can be considered as a ‘standard or true measure’ of the present ‘cosmic rate of expansion’. In view of the confirmed zero rate of change in inverse of the Fine structure ratio (from the ground based laboratory experimental results) and zero rate of change in the current CMBR temperature (from satellite data) it can be suggested that, current cosmic expansion is almost all saturated and at present there is no significant cosmic expansion and there is no significant cosmic acceleration. Note that in Big bang model, confirmation of all the observations directly depend on the large scale galactic distances that are beyond human reach and raise ambiguity in all respects. The subject of modern black hole physics is absolutely theoretical. Advantage of Black hole cosmology lies in confirming its validity through the ground based atomic and nuclear experimental results! Finally it is possible to show that, quantum mechanics is a branch of ‘Black hole cosmology’. Uncertainty relation and all other microscopic physical constants play a crucial role in understanding the halt of the present cosmic expansion.