Showing papers in "Zeitschrift für Naturforschung A in 2020"

Peristaltic thrusting of a thermal-viscosity nanofluid through a resilient vertical pipe

Abstract: Abstract In the article, the effects of the thermal viscosity and magnetohydrodynamic on the peristalsis of nanofluid are analyzed. The dominant neutralization is deduced through long wavelength approximation. The analytical solution of velocity and temperature is extracted by using steady perturbation. The pressure gradient and friction forces are obtained. Numerical results are calculated and contrasted with the debated theoretical results. These results are calculated for various values of Hartmann number, variable viscosity parameter and amplitude ratio. It is observed that the pressure gradient is reduced with an increase in the thermal viscosity parameter and that the Hartmann number enhances the pressure difference.

Resonant interactions between the fundamental and higher harmonic of positron acoustic waves in quantum plasma

Abstract: Abstract In this paper, we study the second harmonic generation and its interaction with the fundamental mode in a magnetised dense positron-ion plasma interacting with laser pulses. It has been shown that different harmonics propagate with different phase velocities. The gradual evolution of the fundamental wave into higher harmonics is studied, and the conversion efficiency is calculated. Dependence of conversion efficiency on wavenumber shifts and the applied magnetic field has also been examined.

Bifurcation Analysis for Small-Amplitude Nonlinear and Supernonlinear Ion-Acoustic Waves in a Superthermal Plasma

Abstract: Abstract Bifurcation analysis of small-amplitude nonlinear and supernonlinear periodic ion-acoustic waves (SNPIAWs) is reported in a three-constituent superthermal plasma composing of cold fluid ions and kappa-distributed electrons of two temperatures (cold and hot). Using the reductive perturbation technique, the plasma system is studied under the Korteweg-de Vries (KdV) and the modified KdV (mKdV) equations. Furthermore, the KdV and mKdV equations are transformed into planar dynamical systems applying travelling wave transfiguration. Possible qualitative phase profiles for the corresponding dynamical systems controlled by system parameters (κ,αc,αh$\\kappa,{\\alpha_{c}},{\\alpha_{h}}$ and f) are shown. Small-amplitude SNPIAW solution for the mKdV equation is presented for the first time. Small-amplitude nonlinear periodic ion-acoustic wave (NPIAW) and ion-acoustic solitary wave solutions (IASWS) for both the KdV and mKdV equations are obtained. Effects of parameters κ and αh on IASW, NPIAW and SNPIAW solutions are investigated.

From quantum foundations to spontaneous quantum gravity – An overview of the new theory

Abstract: Spontaneous localisation is a falsifiable dynamical mechanism which modifies quantum mechanics, and explains the absence of position superpositions in the macroscopic world. However, this is an ad hoc phenomenological proposal. Adler's theory of trace dynamics, working on a flat Minkowski space-time, derives quantum (field) theory, and spontaneous localisation, as a thermodynamic approximation to an underlying non-commutative matrix dynamics. We describe how to incorporate gravity into trace dynamics, by using ideas from Connes' non-commutative geometry programme. This leads us to a new quantum theory of gravity, from which we can predict spontaneous localisation, and give an estimate of the Bekenstein-Hawking entropy of a Schwarzschild black hole.

Cosmological solutions in Hořava-Lifshitz scalar field theory

Abstract: Abstract We perform a detailed study of the integrability of the Hořava-Lifshitz scalar field cosmology in a Friedmann-Lemaître-Robertson-Walker background space-time. The approach we follow to determine the integrability is that of singularity analysis. More specifically, we test whether the gravitational field equations possess the Painlevé property. For the exponential potential of the scalar field, we are able to perform an analytic explicit integration of the field equations and write the solution in terms of a Laurent expansion and more specifically write the solution in terms of right Painlevé series.

Ion-Acoustic Cnoidal Waves with the Density Effect of Spin-up and Spin-down Degenerate Electrons in a Dense Astrophysical Plasma

Abstract: Abstract An investigation of nonlinear ion acoustic (IA) cnoidal waves in a magnetised quantum plasma is presented by using spin evolution quantum hydrodynamics model, in which inertial classical ions and degenerate inertialess electrons with both spin-up and spin-down states taken as separate species are considered. The Korteweg–de Vries equation is derived using the reductive perturbation method. Further, using the Sagdeev pseudopotential approach, the solution for IA cnoidal waves is derived with suitable boundary conditions. There is the formation of only positive potential cnoidal, and in the limiting case, positive solitary waves are observed. The effects of density polarisation and other plasma parameters on the characteristic features of cnoidal and solitary waves have been analysed numerically. It is seen that the spin density polarisation significantly affects the characteristics of cnoidal structures as we move from strongly spin-polarised (μ = 1) to a zero spin-polarisation case (μ = 0). The results obtained in the present investigation may be useful in comprehending various nonlinear excitations in dense astrophysical regions, such as white dwarfs, neutron stars, and so on.

Octonions, trace dynamics and noncommutative geometry—A case for unification in spontaneous quantum gravity

Abstract: We have recently proposed a new matrix dynamics at the Planck scale, building on the theory of trace dynamics. This is a Lagrangian dynamics in which the matrix degrees of freedom are made from Grassmann numbers, and the Lagrangian is trace of a matrix polynomial. Matrices made from even grade elements of the Grassmann algebra are called bosonic, and those made from odd grade elements are called fermionic: together they describe an `aikyon'. In the present article we provide a basic definition of spin angular momentum in this matrix dynamics, and introduce a bosonic (fermionic) configuration variable conjugate to the spin of a boson (fermion). We then show that at energies below Planck scale, where the matrix dynamics reduces to quantum theory, fermions have half-integer spin (in multiples of Planck's constant), and bosons have integral spin. We also show that this definition of spin agrees with the conventional understanding of spin in relativistic quantum mechanics. Consequently, we obtain an elementary proof for the spin-statistics connection. We then motivate why an octonionic space is the natural space in which an aikyon evolves. The group of automorphisms in this space is the exceptional Lie group $G_2$ which has fourteen generators [could they stand for the twelve vector bosons and two degrees of freedom of the graviton? ]. The aikyon also resembles a closed string, and it has been suggested in the literature that 10-D string theory can be represented as a 2-D string in the 8-D octonionic space. From the work of Cohl Furey and others it is known that the Dixon algebra made from the four division algebras [real numbers, complex numbers, quaternions and octonions] can possibly describe the symmetries of the standard model. In the present paper we outline how in our work the Dixon algebra arises naturally, and could lead to a unification of gravity with the standard model.

Propagation of Waves in a Nonideal Magnetogasdynamics with Dust Particles

Abstract: Abstract In this article, we use the surface theory and compatibility conditions to describe the behaviour of wave propagation and their culmination into a shock wave in nonideal reacting gas with dust particles. The one-dimensional steepening of waves has been considered. A Bernoulli-type transport equation for the velocity gradient has been obtained. A numerical approach is used to explain the effects of van der Waals excluded volume of the medium, the ratio of specific heats, and the mass concentration of the solid particles on the shock wave.

Size-Dependent Ultrasonic and Thermophysical Properties of Indium Phosphide Nanowires

Abstract: Abstract The present work explores the diameter- and temperature-dependent ultrasonic characterization of wurtzite indium phosphide nanowires (WZ-InP-NWs) using a theoretical model based on the ultrasonic non-destructive evaluation (NDE) technique. Initially, the second- and third-order elastic constants (SOECs and TOECs) were computed using the Lennard-Jones potential model, considering the interactions up to the second nearest neighbours. Simultaneously, the mechanical parameters (Young’s modulus, shear modulus, elastic anisotropy factor, bulk modulus, Pugh’s ratio and Poisson’s ratio) were also estimated. Finally, the thermophysical properties and ultrasonic parameters (velocity and attenuation) of the InP-NWs were determined using the computed quantities. The obtained elastic/mechnical properties of the InP-NWs were also analyzed to explore the mechanical behaviors. The correlations between temperature-/size-dependent ultrasonic attenuation and the thermophysical properties were established. The ultrasonic attenuation was observed to be the third-order polynomial function of the diameter/temperature for the InP nanowire.

Electronic band profiles and magneto-electronic properties of ternary XCu2P2 (X = Ca, Sr) compounds: insight from ab initio calculations

Abstract: Abstract Full-potential augmented plane waves (FP-APW) method is applied to determine the electronic band profiles and magneto-electronic properties of XCu2P2 (X = Ca, Sr) compounds. We have adopted Perdew, Burke and Ernzerhof's generalized gradient approximation (PBE-GGA) along with GGA plus Hubbard U parameter method (GGA+U) as exchange correlation potentials. The physical properties of interest for XCu2P2 (X = Ca, Sr) compounds were analyzed for the first time in the Zintl phase of tetragonal structure with space group I4/mmm (No. 139). From the structural parameters we have found that ferromagnetic phase is more stable as compared to paramagnetic and antiferromagnetic phase. Electronic band profiles predict the metallic nature of these compounds in FM phase. The projected densities of states computed in this work recognize that the bonding is accomplished through hybridization of Cu-3d with P-p states. The evaluated magnetic moments support weak ferromagnetism in these compounds. The compounds of interest are thermodynamically stable. In addition, the cohesive energies and Curie temperatures of the studied compounds were also predicted. Metallic and ferromagnetic nature of XCu2P2 (X = Ca, Sr) compounds predict the important of these compounds in spintronic devices.

A Framework for Sequential Measurements and General Jarzynski Equations

Abstract: We formulate a statistical model of two sequential measurements and prove a so-called J-equation that leads to various diversifications of the well-known Jarzynski equation including the Crooks dissipation theorem. Moreover, the J-equation entails formulations of the Second Law going back to Wolfgang Pauli. We illustrate this by an analytically solvable example of sequential discrete position-momentum measurements accompanied with the increase of Shannon entropy. The standard form of the J-equation extends the domain of applications of the quantum Jarzynski equation in two respects: It includes systems that are initially only in local equilibrium and it extends this equation to the cases where the local equilibrium is described by microcanononical, canonical or grand canonical ensembles. Moreover, the case of a periodically driven quantum system in thermal contact with a heat bath is shown to be covered by the theory presented here. Finally, we shortly consider the generalized Jarzynski equation in classical statistical mechanics.

Solution of the Riemann problem for an ideal polytropic dusty gas in magnetogasdynamics

Abstract: Abstract The main aim of this paper is, to obtain the analytical solution of the Riemann problem for a quasi-linear system of equations, which describe the one-dimensional unsteady flow of an ideal polytropic dusty gas in magnetogasdynamics without any restriction on the initial data. By using the Rankine-Hugoniot (R-H) and Lax conditions, the explicit expressions of elementary wave solutions (i. e., shock waves, simple waves and contact discontinuities) are derived. In the flow field, the velocity and density distributions for the compressive and rarefaction waves are discussed and shown graphically. It is also shown how the presence of small solid particles and magnetic field affect the velocity and density across the elementary waves. It is an interesting fact about this study that the results obtained for the Riemann problem are in closed form.

Michelson Interferometric Hydrogen Sulfide Gas Sensor Based on NH 2 -rGO Sensitive Film

Abstract: Abstract A highly sensitive hydrogen sulfide gas sensor based on NH2-rGO-coated thin-core-fibre (TCF) Michelson interferometer (MI) is proposed and evaluated. Two sections of TCFs are alternately sandwiched between three single-mode-fibres (SMFs). A Faraday rotator mirror (FRM) is fixed to the end of the last SMF to reflect the light signal and enhance the interference. Then the structure SMF-TCF-SMF-TCF-SMF-FRM (STSTS-F) is successfully constructed. NH2-rGO, as sensing film, is coated on two TCFs and is used to detect traces of hydrogen sulfide gas. Raman spectra and XPS analysis show that NH2-rGO has been successfully synthesised. The thickness of the NH2-rGO film coated on the TCF surface is about 500 nm. By introducing 0–60 ppm hydrogen sulfide gas into the chamber, with the increase in concentration of the gas, the monitoring trough exhibits a blue shift. Our experimental results show that the sensor has good linearity (R2 = 0.98096) and selectivity for hydrogen sulfide gas. The sensitivity is 21.3 pm/ppm, and the response and recovery times are about 72 and 90 s, respectively. The sensor has the advantages of high sensitivity, high selectivity, and small size, enabling the detection of trace hydrogen sulfide in toxic gas environments.

Graphene in curved Snyder space

Abstract: The Snyder-de Sitter (SdS) model which is invariant under the action of the de Sitter group, is an example of a noncommutative spacetime with three fundamental scales. In this paper, we considered the massless Dirac fermions in graphene layer in a curved Snyder spacetime which are subjected to an external magnetic field. We employed representation in the momentum space to derive the energy eigenvalues and the eigenfunctions of the system. Then, we used the deduced energy function obtaining the internal energy, heat capacity, and entropy functions. We investigated the role of the fundamental scales on these thermal quantities of the graphene layer. We found that the effect of the SdS model on the thermodynamic properties is significant.

Blast waves propagation in magnetogasdynamics: power series method

Abstract: Abstract Blast waves are produced when there is a sudden deposition of a substantial amount of energy into a confined region. It is an area of pressure moving supersonically outward from the source of the explosion. Immediately after the blast, the fore-end of the blast wave is headed by the shock waves, propagating in the outward direction. As the considered problem is highly nonlinear, to find out its solution is a tough task. However, few techniques are available in literature that may give us an approximate analytic solution. Here, the blast wave problem in magnetogasdynamics involving cylindrical shock waves of moderate strength is considered, and approximate analytic solutions with the help of the power series method (or Sakurai’s approach [1]) are found. The magnetic field is supposed to be directed orthogonally to the motion of the gas particles in an ideal medium with infinite electrical conductivity. The density is assumed to be uniform in the undisturbed medium. Using power series method, we obtain approximate analytic solutions in the form of a power series in (a0/U)2${\left({a}_{0}/U\right)}^{2}$, where a0 and U are the velocities of sound in an undisturbed medium and shock front, respectively. We construct solutions for the first-order approximation in closed form. Numerical computations have been performed to determine the flow-field in an ideal magnetogasdynamics. The numerical results obtained in the absence of magnetic field recover the existing results in the literature. Also, these results are found to be in good agreement with those obtained by the Runge–Kutta method of fourth-order. Further, the flow variables are illustrated through figures behind the shock front under the effect of the magnetic field. The interesting fact about the present work is that the solutions to the problem are obtained in the closed form.

Nonlinear Pull-in Instability of Rectangular Nanoplates Based on the Positive and Negative Second-Order Strain Gradient Theories with Various Edge Supports

Abstract: Abstract Based on the positive and negative second-order strain gradient theories along with Kirchhoff thin plate theory and von Kármán hypothesis, the pull-in instability of rectangular nanoplate is analytically investigated in the present article. For this purpose, governing models are extracted under intermolecular, electrostatic, hydrostatic, and thermal forces. The Galerkin method is formally exerted for converting the governing equation into an ordinary differential equation. Then, the homotopy analysis method is implemented as a well-designed technique to acquire the analytical approximations for analyzing the effects of disparate parameters on the nonlinear pull-in behavior. As an outcome, the impacts of nonlinear forces on nondimensional fundamental frequency, the voltage of pull-in, and softening and hardening effects are examined comparatively.

An unforced megastable chaotic oscillator and its application on protecting electrophysiological signals

Abstract: Abstract In this paper, we introduce a novel 3D chaotic oscillator which shows megastability without any external excitation. Some important dynamical properties of the proposed novel system were derived and investigated. Data protection application and its security analysis were realized for electrophysiological signals such as ECG, EEG and EMG on a microcomputer. This paper includes both encryption and data hiding processes for high security. Also a user interface was developed. For the encryption process, random numbers were generated by the megastable chaotic oscillator. These random numbers were tested with NIST-800-22 test which is the most widely accepted statistical test suite. The encrypted electrophysiological signals were analyzed by entropy, differential attacks, histogram, correlation, initial condition sensitivity, etc. The results of the analysis have shown that the proposed two level security method can be used in many fields as mobile. The most important feature of this paper is that both encryption and data hiding processes were implemented for electrophysiological signals. The experimental results verify that the proposed method has high security and is suitable for the protection of vital electrophysiological signals.

Numerical study on the rotating electro-osmotic flow of third grade fluid with slip boundary condition

Abstract: Abstract Considering the slip boundary condition, the rotating electro-osmotic flow of a third grade fluid in a channel formed by two parallel plates is investigated in the present study. The charge distribution is treated with the Debye–Hückel approximation analytically. Based on the finite difference method, the velocity profile for rotating electro-osmotic flow of third grade fluid is obtained numerically. It is shown that the non-Newtonian parameter of third grade fluid and the velocity slip factor play the important roles for the rotating electro-osmotic flow. The increasing non-Newtonian parameter slows down the flow and decreases the velocity magnitude, and the increasing slip parameter β has the similar influence on the velocity profile. Furthermore, the effect of the inclusion of third grade on the velocity profile is more conspicuous in the area near the walls.

Electromagnetic propagation characteristics of one-dimensional photonic crystals with metal layers in quasi-parity-time (PT)-symmetric system

Abstract: Abstract In this study, the propagation characteristics of electromagnetic waves in a parity-time (PT)-symmetrical 1D photonic crystal comprising dispersed silver layers are investigated. Based on the transmission matrix theory, the total reflection and transmission coefficients of the structure are obtained. It was found that, due to the PT-symmetrical structure, the reflections of the left and right incident waves are nonreciprocal. Numerical simulations indicated that the width of the band gap decreases with the increase in the gain and loss factor ρ in the PT medium, and the band gap ultimately disappears when ρ reaches a critical value, i. e., ρPT${\rho }_{PT}$. With the increase in ρ>ρPT$\rho { >}{\rho }_{PT}$, anomalous transmittance and reflection occur within the original bang gap. As the gain and loss factor ρ continue to increase, the abnormal transmittance and reflectivity exhibit a trend of oscillatory decline, and perfect transmission can be achieved at larger values of ρ.

A modified simple chaotic hyperjerk circuit: coexisting bubbles of bifurcation and mixed-mode bursting oscillations

Abstract: Abstract A relatively simple chaotic hyperjerk circuit, which is the modified chaotic hyperjerk system [Dalkiran and Sprott, IJBC 2016] is proposed and investigated in this paper. Only one semiconductor diode modelled the nonlinear function capable of rich and complex dynamical behaviours of the system. We investigate a new kind of behaviours name “bubbles of bifurcation’’ (referred as BsB hereafter) observed here for the first time in the hyperjerk system. An interesting phenomenon of mixed-mode bursting oscillations (MMBOs) is also investigated. The complex dynamics of the novel oscillator (such as MMBOs, BsB, offset boosting and multistability) with respect to its parameters and initial conditions are uncovered using bifurcation diagrams, Lyapunov exponents (LE) and phase portraits. As another interesting property of this circuit, some parameter regions are determined for the existence of coexisting BsB and the coexistence of asymmetric mixed-mode bursting oscillations. Let us emphasized that the complex phenomena observed in this work is very rare in the literature and henceforth merit dissemination. Finally, a physical circuit is constructed to demonstrate some experimental observation of MMBOs.

Analysis of Carreau fluid flow by convectively heated disk with viscous dissipation effects

Abstract: Abstract The primary motive of this study is to examine boundary layer flow of Carreau fluid over a convectively heated disk stretching with nonlinear velocity. The flow is assumed to be two dimensional. Moreover, viscous dissipation possessions are taken into description. The dominating nonlinear differential equations involving partial derivatives are changed into nonlinear differential equations involving ordinary derivatives by applying suitable transformations. Numerical outcomes for velocity and temperature are obtained from MATLAB’s built-in solver bvp4c and presented graphically and in tabular form.

Design and analysis of 6CB nematic liquid crystal–based rectangular patch antenna for S-band and C-band applications

Abstract: Abstract This article presents the design and analysis of 4-hexyl-4′-biphenylcarbonitrile (6CB) nematic liquid crystal (NLC)–based rectangular patch antenna for S-band and C-band communication applications. Two glass substrates with permittivity of 6.4, loss tangent of 0.01 and thickness of 1 mm each with 21 × 25 mm2 and 19 × 19 mm2 dimension has been used, and 0.005 mm air gap has been placed to fill 6CB NLC. A rectangular patch of 10 × 11 mm2 size has been considered over the top substrate to achieve the application specific bands. The designed antenna model-1 with air gap is resonating at 5 GHz (4.01–7.85 GHz) with minimum S11 of −24.2 dB. The proposed antenna model-2 is filled with 6CB NLC in the air gap between glass substrates is resonating at 3.3 GHz (2.61–4.45 GHz) with minimum S11 of −29.75 dB. Antennas of both air gaps filled, and liquid crystal material filled models are fabricated and tested through combinational analyser for validation. The correlation between transmitted and received signals of the antenna models are analysed with time domain analysis by taking the identical antennas in face to face and side by side condition. The simulated results from HFSS electromagnetic tool and fabricated antennas results in chamber are exhibiting good agreement with each other.

Predicting Imperfect Echo Dynamics in Many-Body Quantum Systems

Abstract: Echo protocols provide a means to investigate the arrow of time in macroscopic processes. Starting from a nonequilibrium state, the many-body quantum system under study is evolved for a certain period of time $\tau$. Thereafter, an (effective) time reversal is performed that would -- if implemented perfectly -- take the system back to the initial state after another time period $\tau$. Typical examples are nuclear magnetic resonance imaging and polarization echo experiments. The presence of small, uncontrolled inaccuracies during the backward propagation results in deviations of the "echo signal" from the original evolution, and can be exploited to quantify the instability of nonequilibrium states and the irreversibility of the dynamics. We derive an analytic prediction for the typical dependence of this echo signal for macroscopic observables on the magnitude of the inaccuracies and on the duration $\tau$ of the process, and verify it in numerical examples.

First-principles study of structures, elastic and optical properties of single-layer metal iodides under strain

Abstract: Abstract The structure, elastic, electronic and optical properties of two-dimensional (2D) MI2 (M = Pb, Ge, Cd) under strain are systematically studied by the first-principles method. It is proved that the monolayer structure of 2D-MI2 is stable by phonon spectra. Moreover, the large ideal strain strength (40%), the large range of strain and the elastic constants of far smaller than other 2D materials indicate that the single-layer PbI2 and GeI2 possess excellent ductility and flexibility. By applying appropriate strain to the structure of 2D-MI2, the band gaps of single-layer MI2 can be effectively controlled (PbI2: 1.04 ∼ 3.03 eV, GeI2: 0.43 ∼ 2.99 eV and CdI2: 0.54 ∼ 3.36 eV). It is found that the wavelength range of light absorbed by these three metal iodides is 82–621 nm, so 2D-MI2 has great absorption intensity for ultraviolet light in a large wavelength range, and the strain of structure can effectively regulate the optical parameters.

Numerical Investigation of the Cooling Temperature of the InGaP/InGaAs/Ge Subcells Under the Concentrated Illumination

Abstract: Abstract The multijunction solar cells performances study is essential for the design of the high-concentration photovoltaic. These cells can operate over a wide range of the incident radiation flux and a large temperature range. These two parameters (concentration and temperature) degrade the cell and require a cooling system. In this article, we have studied numerically the cooling temperature of InGaP/lnGaAs/Ge subcells under the concentrated illumination. For this, we have presented the performance of each subcell as a function of the temperature and concentration sunlight. The different high concentrations ratios (1, 10, 100, and 1000 sun) have been conducted according to the dish-style concentration photovoltaic system for three temperature values T = 300, 500, and 800 K. The results show that under high concentrated light intensity conversion, the performances of these three subcells (efficiency, open-circuit voltage, short-circuit current, and fill factor) were decreased with increasing the temperature. The main objective of this study is to find the limit temperature of each subcell in order to introduce the cooling system. Thus, we can avoid the degradation of the tandem solar cell under the concentrated illumination.

Pocket formula for alpha decay energies and half-lives of actinide nuclei

Abstract: Abstract It is important to construct the correct formula for alpha decay half-lives. The present work verifies the validity of Geiger–Nuttall law (GNL) for actinides and hence presenting the simple empirical formula for alpha decay energies and halflives for actinides based on the available experimental results. We have studied the variation of logarithmic halflives with ZdnQ−1/2${Z}_{d}^{n}{Q}^{-1/2}$ for different values of n (0.2–1). The variation of logarithmic halflives with ZdnQ−1/2${Z}_{d}^{n}{Q}^{-1/2}$ is found to be linear for which n = 0.6. The values produced by the present formula compared with that of experiments. The present formulae successfully produces the alpha decay half-lives and Q-value in the actinide region. This formula is specially for actinide parent nuclei only.

Investigation of zirconium nanowire by elastic, thermal and ultrasonic analysis

Abstract: Abstract The elastic, thermal and ultrasonic properties of zirconium nanowire (Zr-NW) have been investigated at room temperature. The second and third order elastic constants (SOECs and TOECs) of Zr-NW have been figured out using the Lennard–Jones Potential model. SOECs have been used to find out the Young’s modulus, bulk modulus, shear modulus, Poisson’s ratio, Pugh’s ratio, Zener anisotropic factor and ultrasonic velocities. Further these associated parameters of Zr-NW have been utilized for the evaluation of the Grüneisen parameters, thermal conductivity, thermal relaxation time, acoustic coupling constants and ultrasonic attenuation. On the basis of the above analyzed properties of Zr-NW, some characteristics features of the chosen nanowire connected with ultrasonic and thermo-physical parameters have been discussed.

Variational principle for time-periodic quantum systems

Abstract: A variational principle enabling one to compute individual Floquet states of a periodically time-dependent quantum system is formulated, and successfully tested against the benchmark system provided by the analytically solvable model of a linearly driven harmonic oscillator. The principle is particularly well suited for tracing individual Floquet states through parameter space, and may allow one to obtain Floquet states even for very high-dimensional systems which cannot be treated by the known standard numerical methods.

Nonlinear dynamics of ion-acoustic waves in quantum plasmas with exchange-correlation effects

Abstract: Abstract Nonlinear properties of ion-acoustic waves (IAWs) are studied in electron-ion (EI) degenerate plasma with the electron exchange-correlation effects by using the quantum hydrodynamic (QHD) model. To investigate arbitrary amplitude IAWs, we have reduced the model equations into a system of ordinary differential equations using a traveling wave transformation. Computational investigations have been performed to examine the combined effect of Bohm potential and exchange-correlation potential significantly modifies the dynamics of IAWs by employing the concept of dynamical systems. The equilibrium points of the model are determined and its stability natures are analyzed. The phase portrait and Poincaré return map of the dynamical system are displayed numerically. Quasiperiodic as well as chaotic dynamics of the system are confirmed through the Poincaré return map diagrams.