• Volume 79, Issue 1

July 2012,   pages  1-172

• General editorial on publication ethics

• Analytic treatment of nonlinear evolution equations using ﬁrst integral method

In this paper, we show the applicability of the ﬁrst integral method to combined KdV-mKdV equation, Pochhammer–Chree equation and coupled nonlinear evolution equations. The power of this manageable method is conﬁrmed by applying it for three selected nonlinear evolution equations. This approach can also be applied to other nonlinear differential equations.

• Exact complex integrals in two dimensions for shifted harmonic oscillators

We use rationalization method to study two-dimensional complex dynamical systems (shifted harmonic oscillator in complex plane) on the extended comples phase space (ECPS). The role and scope of the derived invatiants in the context of various physical problems are high-lighted.

• Coupled Higgs ﬁeld equation and Hamiltonian amplitude equation: Lie classical approach and $(G'/G)$-expansion method

In this paper, coupled Higgs field equation are studied using the Lie classical method. Symmetry reductions and exact solutions are reported for Higgs equation and Hamiltonian amplitude equation. We also establish the travelling wave solutions involving parameters of the coupled Higgs equation and Hamiltonian amplitude equation using $(G'/G)$-expansion methodc, where $G = G(\xi)$ satisfies a second-order linear ordinary differential equation (ODE). The travelling wave solutions expressed by hyperbolic, trigonometric and the rational functions are obtained.

• Dynamics of fractional-ordered Chen system with delay

In the present paper the effect of delay on chaos in fractional-order Chen system is investigated. It is observed that inclusion of delay changes chaotic behaviour to limit cycles or stable systems.

• Function projective synchronization of identical and non-identical modiﬁed ﬁnance and Shimizu–Morioka systems

In this paper, function projective synchronizations (FPS) of identical and non-identical modified finance systems (MFS) and Shimizu-Morioka system (S-MS) are studied via active control technique. The technique is applied to construct a response system which synchronizes with a given drive system for a desired function relation between identical MFS, identical S-MS and between MFS and S-MS. The results are validated via numerical simulations.

• Antisynchronization of a novel hyperchaotic system with parameter mismatch and external disturbances

A novel hyperchaotic system is proposed. It is particularly interesting that the hyperchaotic system has a nonlinear term in the form of an exponential function and has onle one equilibrium. Basic dynamical properties of the hyperchaotic system are investigated. Moreover, antisynchronization of the new hyperchaotic system with parameter mismatch and external disturbances is also studied in this paper by using adaptive control. Numerical simulation results further demonstrate that the proposed methods are effective and robust.

• Effect of hydrostatic pressure on the structural, elastic and electronic properties of (B3) boron phosphide

In this paper we present the results obtained from first-principles calculations of the effect of hydrostatic pressure on the strucural, elastic and electronic properties of (B3) boron phosphide, using the pseudopotential plane-wave method (PP-PW) based on density functional theory within the Teter and Pade exchange-correlation functional form of the local density approximation (LDA). The lattice parameter, molecular and crystal densities, near-neighbour distances, independent elastic constant, bulk modulus, shear modulus, anisotropy factor and energy bandgaps of (B3) BP under high pressure are presented. The results showed a phase transition pressure from the zinc blende to rock-salt phase at around 1.56 Mbar, which is in good agreement with the theoretical data reported in the literature.

• A note on the drift waves in the presence of electrons added by meteors by ablation phenomena or by thermionic emissions

The role of added electrons on the drift dissipative instability in a nonuniform collisional plasma is analysed. We observe the presence of a drift wave that depends entirely on the added electrons through the collision frequency coupling and there is an additional damping. The present study is applied to the density irregularities caused by meteor ionization in the ionosphere.

• Main reaction process simulation of hydrogen gas discharge in a cold cathode electric vacuum device

Based on the related theory of plasma discharge process and the COMSOL multiphysics software, and considering the corresponding boundary conditions, the related recation types in the hydrogen plasma discharge were simulated and analysed, and the main reactions of hydrogen discharge in small electric vacuum components at low pressure and weak ionization were confirmed. Among the 21 types of reactions in hydrogen discharge process, 11 of them play importnat roles under low pressure and weak ionization in cold cathode electric vacuum device. The simulated results are consistent with the test result.

• Electron transport in wurtzite InN

Using ensemble Monte Carlo simulation technique, we have calculated the transport properties of InN such as the drift velocity, the drift mobility, the average electron, energy relaxation times and momentum relaxation times at high electric ﬁeld. The scattering mechanisms included are polar optical phonon, ionized impurity, acoustic phonon and intervalley phonon. It is found that the maximum peak velocity only occurs when the electric ﬁeld is increased to a value above a certain critical ﬁeld. This critical ﬁeld is strongly dependent on InN parameters. The steady-state transport parameters are in fair agreement with other recent calculations.

• The relationship between the doping levels and some physical properties of SnO2:F thin ﬁlms spray-deposited on optical glass

The relationship between the ﬂuorine doping level and the electrical, structural and optical properties of the SnO2:F ﬁlms are investigated using the Hall effect measurement set-up in van der Pauw conﬁguration, the XRD patterns, UV–vis spectrophotometry and atomic force microscopy (AFM). The X-ray diffraction patterns taken at room temperature show that the ﬁlms are polycrystalline. The preferred directions of crystal growth in the diffractogram of SnO2:F (FTO) ﬁlms correspond to the reﬂections from the (1 1 0), (2 0 0), (2 1 1) and (3 0 1) planes. Thin ﬁlm thickness and the grain size vary from 280 to 1545 nm and from 17.45 to 33.22 nm, respectively. AFM study reveals the surface of FTO to be made of nanocrystalline particles. The electrical study reveals that the ﬁlms are degenerate and exhibit n-type electrical conductivity. The FTO ﬁlms have a minimum resistivity of $5.29 × 10^{−4} \Omega$·cm, carrier density of $0.09 × 10^{20}$ cm-3 and mobility of 377.02 cm2/V·s. The sprayed FTO ﬁlm has the minimum sheet resistance of 5.69 𝛺 /cm2 and the highest ﬁgure-of-merit of $204 × 10^{−4} \Omega^{−1}$ at 700 nm. The resistivity attained for the doped ﬁlm in this study is lower than the values reported for 20 wt.% ﬂuorine-doped tin oxide ﬁlms prepared from the aqueous solution of SnCl2·2H2O precursor. The highest visible transmittance (700 nm) of the deposited ﬁlms is 91.8% for 25 wt.% ﬂuorine-doped tin oxide ﬁlms. The obtained results reveal that the structures and properties of the ﬁlms are greatly affected by doping levels. These ﬁlms are useful as conducting layers in electrochromic and photovoltaic devices.

• AlGaN/GaN-based HEMT on SiC substrate for microwave characteristics using different passivation layers

In this paper, a new gate-recessed AlGaN/GaN-based high electron mobility transistor (HEMT) on SiC substrate is proposed and its DC as well as microwave characteristics are discussed for Si3N4 and SiO2 passivation layers using technology computer aided design (TCAD). THe two-dimensional electron gas (2DEG) transport properties are discussed by solving Schödinger and Poison equations self-consistently resulting in various subbands having electron eigenvalues. From DC characteristics, the saturation drain currents are measured to be 600 mA/mm and 550 mA/mm for Si3N4 and SiO2 passivation layers respectively. Apart from DC, small-signal AC analysis has been done using two-port network for various microwwave parameters. The extrinsic transconductance parameters are measured to be 131.7 mS/mm at a gate voltage of $V_{gs} = -0.35$ V and 114.6 mS/mm at a gate voltage of $V_{gs} = -0.4$ V for Si3N4 and SiO2 passivation layers respectively. The current gain cut-off frequencies $(f_{t})$ are measured t be 27.1 GHz and 23.97 GHz in unit-gain-point method at a gate voltage of -0.4 V for Si3N4 and SiO2 passivation layers respectively. Similarly, the power gain cut-off frequencied $(f_{max})$ are measured to be 41 GHz and 38.5 GHz in unit-gain-point method at a gate voltage of -0.1 V for Si3N4 and SiO2 passivation layers respectively. Furthermore, the maximum frequency of oscillation or unit power gain (MUG = 1) cut-off frequencies for Si3N4 and SiO2 passivation layers are measured to be 32 GHz and 28 GHz respectively from MUG curves and the unit current gain, $|h_{21}| = 1$ cut-off frequencies are measured to be 140 GHz and 75 GHz for Si3N4 and SiO2 passivation layers respectively from the $abs |h_{21}|$ curves. HEMT with Si3N4 passivation layer giver better results than HEMT with SiO2 passivation layer.

• Physics of the fastest communication

A communication system involves the transmission of information from source to destination and after receiving all the information all the information or a complete signal an acknowledgement is then sent to the source by the destination itself to let the source know that is (destination) has received the signal. In this paper we examine about how to reduce the time of acknowledgement to make the communication faster. In this paper we present a method of sending an acknowledgement signal, in which the last quantum (sample) of the signal is used to compute the time of acknowledgement. The formula for calculating the time of acknowledgement in the case of a continuous time signal and a discrete time signal is also derived in the paper. This technique is applicable for analog communication, digital communication and space communication.

• # Pramana – Journal of Physics

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November 2019

• # Editorial Note on Continuous Article Publication

Posted on July 25, 2019