Volume 76, Issue 1

Term energies, oscillator strengths, transition probabilities, and transition wavelengths among the low-lying states of (1s 2 )2s 2 2p 2 , 2s 2 2p3p, 2s2p 3 , 2s 2 2p3s, and 2s 2 2p3d 1,3,5 L L  = S, P, D, F in N + , F 3+ , and Ne 4+ ions were calculated by using the multiconfiguration Rayleigh-Ritz variation method and restricted variation method. The transition oscillator strengths and transition probabilities for the electric dipole transitions are both given in length and velocity gauges. Deviations between these two gauge values are discussed. The calculated atomic parameters are in good agreement with the observed experimental results and other theoretical data. Furthermore, the uncertainty of each electric dipole transition is estimated. Several uncertainties of transition parameters are improved when comparing with values from national institute of standards and technology NIST database. Atomic parameters presented in this paper should be useful for identifying the levels as well as for precise spectral modeling in astrophysical and laboratory plasmas in the future work.

In this paper, the chaotic behavior and chaos control in a voltage mode controlled DC drive system are investigated. The dynamical behavior of the system changing from the fundamental state to chaotic regime is obtained by the variation of some parameters. Two kinds of delay feedback controllers are designed to induce and control chaos in the voltage-mode DC drive system that exhibits chaotic behavior under certain conditions. The proposed control scheme is able to suppress chaos on the voltage mode controlled DC drive system operating in continuous conduction mode. With variation of controller parameters, the transition of dynamical behavior in the system has been demonstrated from different possible states to regular state, which may be named as period-1 operation. Unlike the traditional delay feedback control method, not only the feedback gain parameter K but also the delay parameter τ is used as variable parameters of the controller. Moreover, the genetic algorithm is used to simultaneously optimize both the feedback gain parameter K and delay parameter τ to improve the effectiveness of the controller. Numerical results show that the proposed method can control unstable periodic orbits and suppress chaos in the system, and also, optimized controller parameters provide fast response for transition from chaotic operation to normal operation.

A field experiment on terrestrial vertebrates observes that direct predation on predator–prey interaction can not only affect the population dynamics but the indirect effect of predator’s fear (felt by prey) through chemical and/or vocal cues may also reduce the reproduction of prey and change their life history. In this work, we have described a predator–prey model with Holling type II functional response incorporating prey refuge. Irrespective of being considering either a constant number of prey being refuged or a proportion of the prey population being refuged, a different growth rate and different carrying capacity for the prey population in the refuge area are considered. The total prey population is divided into two subclasses: (i) prey x in the refuge area and (ii) prey y in the predatory area. We have taken the migration of the prey population from refuge area to predatory area. Also, we have considered a benefit from the antipredation response of the prey population y in presence of cost of fear. Feasible equilibrium points of the proposed system are derived, and the dynamical behavior of the system around equilibria is investigated. Birth rate of prey in predatory region has been regarded as bifurcation parameter to examine the occurrence of Hopf bifurcation in the neighborhood of the interior equilibrium point. Moreover, the conditions for occurrence of transcritical bifurcations have been determined. Further, we have incorporated discrete-type gestational delay on the system to make it more realistic. The dynamical behavior of the delayed system is analyzed. Finally, some numerical simulations are given to verify the analytical results.

The present study reports reconstruction schemes for tachyon, k-essence and dilaton scalar field model of Dark Energy (DE) through Tsallis holographic dark fluid under the framework of Chern–Simons modified gravity. Reproducing the conservation equation for a coupled model with interaction term Q=3Hb2ρm$Q=3H{b}^{2}{\rho }_{m}$ we have reconstructed the different scalar fields and the corresponding potentials. In the case of tachyon, Λ CDM fixed point is attained under this cosmological settings. Considering k-essence in this interacting situation, we have derived some constraints on the interaction term as well as Tsallis holographic dark energy parameter. Reconstructing dilaton scalar field, we have studied the behavior of scalar field and potential. In all those cases, the reconstructed Equation of State (EoS) parameters have been plotted and when computed for current universe z  = 0 are found to be consistent with various observational data including Planck  +  WP  +  BAO . The only exception is a particular case of reconstructed k-essence model where phantom behavior is apparent, but its numerical value is deviated from the bounce set by the observations. Expressions for different constraints have been obtained and evolutionary behavior of reconstructed scalar fields and potentials for the various cases have been pictorially presented. Finally, we have developed a functional relationship between Hubble parameter and redshift and optimized the parameter values through χ 2 minimization using the observed Hubble parameter values from Hai Yu et al. 2018 ApJ 856 3.

Nano crystalline zinc sulfide thin films were deposited onto glass substrates by chemical bath deposition method. One of the samples was annealed at 300 °C for 2 h in air using a muffle furnace. The prepared thin films were investigated by X-ray diffraction (XRD), UV–visible spectroscopy (UV–vis), photoluminescence spectroscopy (PL), scanning electron microscopy (SEM) and Raman spectroscopy (FT-R) studies before and after annealing. The analysis confirmed the thermal-induced anion substitution and conversion of ZnS crystal to ZnO wurtzite crystal. XRD pattern showed that these films were phase pure and polycrystalline in nature. Optical band gap was found to be 3.86 eV for ZnS and 3.21 eV for ZnO. The films prepared by this simple, low-cost technique are suitable for photovoltaic and optoelectronic applications.

ZnO nanoparticles (nps) have wide range of applications and improve the optical parameters of molecules of soft liquid crystalline (LC) materials. The present paper mainly discusses the optical studies on LC materials regarding p-n-butyloxybenzoic acid (4oba) and p-n-butylbenzoic (4ba) compound along with homogeneous dispersion of ZnO nps in lower weight concentration, i.e., 1, 1.5, 2 and 2.5 wt%. The existence and size of ZnO nps in LC compounds are well determined through spectroscopic techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). The temperatures of LC compounds and phase transitions are determined by using polarizing optical microscopy (POM) and differential scanning calorimetry (DSC) which is found to decrease with increasing concentration of dispersed ZnO nps. Image enhancement with visual quality matrix method is used to improve the quality of the image. Specially designed wedge-shaped modified spectrometer is used to determine the refractive indices with different wavelengths (460, 500, 570 and 635 nm). The refractive indices measured are fitted with two and three coefficient Cauchy model. Further, the order parameter S of the molecules of 4ba and 4oba with dispersed ZnO nps are determined by molecular field models namely Kuczynski, Vuks and effective geometry model, respectively. From the data, it is found that the values of birefringence ( δn ) and order parameter ( S ) of the molecules of 4oba and 4ba are enhanced with the dispersion of ZnO nps with increasing weight concentrations in the stabilized nematic thermal region.