Volume 78, Issue 10

Bifurcation analysis of ion-acoustic solitary, periodic and superperiodic waves in ultra-relativistic quantum degenerate electron-positron-ion plasma is investigated based on Sagdeev’s pseudopotential approach. The phase plane plots for the superperiodic, periodic, and homoclinic trajectories for the dynamical system are developed. Rarefactive and compressive solitary waves are demonstrated to exist. The influence of plasma parameters on the characteristic properties of the periodic and superperiodic waves is studied. Also, the effect of different plasma parameters on the Sagdeev pseudopotential profile is investigated. The results of this study may be used to shed light on the fundamental properties of nonlinear waves in dense objects (e.g., white dwarfs and neutron stars). These results also may be beneficial in describing laboratory plasma (e.g., interaction experiments of intense laser-solid matter), and plasma applications such as microelectronic devices.

A novel model on 2D unsteady conductive heat transfer in an infinite hollow cylinder is proposed. The cylinder is made of functionally graded material (FGM) that has variable properties both in radial and angular directions. Volumetric heat capacity and thermal conductivity coefficient are changed according to the power function of the radius. In the presence of variable coefficients, the governing equations of unsteady heat transfer in FGMs have caused the complexity. The Laplace transform method is used to transfer the energy equation from time to frequency domain whereas the meromorphic function is used for the inverse Laplace transform to obtain the desired solutions. The closed form solutions have been well validated and the results have been presented for different values of functionally graded indices for thermal conductivity coefficients and volumetric heat capacity. Two different FGM cases with different complicated thermal boundary conditions have been investigated. The first case has a constant temperature in the inner radius and a variable heat flux along with the convection condition in the outer radius. In the second case, the inner radius has a specific harmonic temperature and the outer radius is exposed to the convective conditions. It was observed that in both cases, the temperature value in the cylinder decreases with the increase of the FG index for the conductivity coefficient. The presented analytical solution provides a good tool for validating unsteady numerical solutions presented in the field of heat transfer in FGMs.

This paper presents a refined composite multivariate multiscale complexity-entropy causality plane (RCMMCECP) to explore the dynamics features of gas–liquid two-phase flow. Firstly, we employ a series of typical nonlinear time series to confirm the effectiveness of the RCMMCECP, including seven chaotic systems, two random processes, and one periodic process. The comparison results of the proposed method and conventional multivariate multiscale complexity-entropy causality plane (MMCECP) confirm the stability performance of the proposed RCMMCECP. Above all, the RCMMCECP enhances the reliability of the statistical complexity measure over large time scales and exhibits good continuity and noise-resistant ability in multiscale analysis. Then, we employ the RCMMCECP to analyze the upstream and downstream conductance signals. The experimental results demonstrate that the RCMMCECP can characterize the change of complexity and structural stability in the gas-liquid two-phase flow evolution process, effectively revealing its dynamics features.

BaSr 2 (PO 4 ) 2 : 4 %Eu 3+ , 4 % A ( A = Li + , Na + , K + ) phosphors were prepared by high-temperature solid-phase method. The crystal structure, photoluminescence properties, thermal stability, chromaticity coordinates, and fluorescence lifetime of the samples were investigated. The excitation and emission spectra of the samples are broadbands and the maximum peak of the emission spectrum is located at 619 nm. Among three charge compensators, the luminescence intensity is optimal for Li + co-doping case, and the quenching temperature of the typical sample is about 500 K. the fluorescence lifetime τ $\left\langle \tau \right\rangle $ is 1469.6 ns, and the chromaticity coordinates exhibit a strong red emission. The present phosphor has a potential application for white light-emitting diodes (LEDs) under the near-ultra violet (n-UV) light excitation.

NiCoFeCu films were electrodeposited on Ti substrates at different deposition potentials and different concentrations of saccharin added to solution. Compositional analysis showed that although Ni was the highest concentration in solution at low potentials of −1.0 V and −1.5 V, the Ni content was lower than the Co content in the films. Anomalous co-deposition behaviour of iron group metals was observed. When the deposition potential increased to −2.0 V and −2.5 V, the Ni content of films increased while the Co, Fe and Cu content decreased. In the case of saccharin addition to the solution, there is a slight change in the film content. All films have face-centred cubic structure. Structural analysis clearly showed that the potential has a significant effect on the texture degree of the films, since the crystal texture changed from (111) to (220) with increasing potential. The surface morphology of the films was observed to be affected by the deposition potential and saccharin concentration. For the magnetic analysis, saturation magnetisation, M s value gradually decreased from 905 to 715 emu/cm 3 with the variation of film content caused by the increase of the potential from −1.0 V to −2.5 V. And, a slight increase in M s was detected with the addition of saccharin. Besides, the longitudinal and transverse magnetoresistance magnitudes increased from ∼2.5 % to 7.0 % with increasing deposition potential and all films exhibit anisotropic magnetoresistance. Films with desired magnetic properties can be obtained for potential use as magnetic materials in electronics such as magnetoresistive devices.

CuCrO 3 perovskite structure synthesized via cost-effective sol–gel method successfully as confirmed by X-ray diffraction (XRD) with smaller crystallite size has been reported. EDS confirmed copper chromite perovskite single phase with no extra impurity peak existence. Agglomerated grains resulting average particle size of 9.6 nm as determined from SEM micrographs. PL spectra shows electron transition from VB to CB whereas Raman spectra shows D and G band presence within spectra pointing towards existence of functional groups within structure. Bandgap value of 4.02 eV is calculated from UV–vis spectra. In order to calculate Eu, which is calculated to be 0.960 Ev. All these properties suggested synthesized material applicability as an optoelectronic perovskite material.

The ultrasonic attenuation studies of alkali halides single crystal AX (A = Li, Na, K and X = F, Cl, Br) have been investigated along <100>, <110> and <111> directions at room temperature. For this investigation, a most appropriate potential model for studying physical studies of rock-salt type alkali halides, the Coulomb and Born–Mayer model has been used to evaluate higher order elastic constants. The second order elastic constants are used to compute the mechanical properties and ultrasonic velocities of the chosen materials. Additionally, the thermal properties have also been evaluated along different orientations. Thermoelastic loss is very small in comparison to the attenuation due to phonon-phonon interaction mechanism at room temperature. The achieved results of AX have been discussed and compared with available experimental and theoretical results.

Single phased white light emitting phosphors are more ideal for fabricating white LEDs due to higher stability and color reproducibility. Herein, we report a new white light emitting phosphor, SrCeO 3 : xSm 3+ ( x = 1 wt%, 2 wt%, 3 wt%) from a blue light emitting phosphor, SrCeO 3 using an efficient, low energy consuming fuel excess gel combustion technique. From the XRD crystallographic investigation, all the synthesised samples have orthorhombic structure with space group Pnma . A broad absorption band in the UV–visible spectra around 350 nm occurs due to the efficient energy transfer from Ce 4+ to Sm 3+ ion. PL spectra analysis at UV excitations 280 nm and 406 nm, consist of 4f-Sm 3+ transitions 4 G 5/2 - 6 H 5/2 , 4 G 5/2 - 6 H 7/2 , 4 G 5/2 - 6 H 9/2 and charge transfer band from O 2− to Ce 4+ . The energy transfer between activator ions occurs through dipole–dipole interaction, owing to concentration quenching after 2 wt% Sm 3+ and the optimised dopant concentration was 2 wt%. SrCe 0.98 Sm 0.02 O 3 showed mixed blue-yellow-orange-red emission, owing near white light under both excitations. PL data were utilised to find the color parameters and found high color rendering index (CRI ∼ 84) for optimised sample at 406 nm excitation. SEM analysis reveals that the optimised sample exhibit dense ensembled morphology with well-defined grain boundaries and uniformity with average grain size ∼1.24 μm. Further, the elemental composition was confirmed using EDS analysis. From the digital photographs of samples, it is foreseen that, SrCe 0.98 Sm 0.02 O 3 pumped using near UV LED chip can be used for commercial white light generation.

In this paper, a new theoretical approach is suggested for the numerical calculation algorithm of the fourth virial coefficient and its components with the Kihara potential. For the first time, this study reports the results of the fourth virial coefficient over the Kihara potential. The proposed method can be used to calculate the thermodynamics properties of gases with developed correctness. The method is tested for some molecules and as an example of application, the proposed method has been performed for gases of C 3 H 8 and SF 6 . The obtained calculation results have been compared with the theoretical and experimental data and the results have been found to be consistent with the literature data. It can be seen from the application that the calculation of the fourth virial coefficient with the Kihara potential can provide important results in the calculation of the thermophysical properties of other real systems.