Chinese Journal of Physics最新文献

The paper addresses the question of the structural and vibrational properties of Fe-doped ZnO in the wurtzite structure with a lattice without an inversion center. The ZnO crystals containing Fe impurities in different charged states are studied by means of density functional theory (DFT) and potential-based methods. A first-principles simulation is performed to determine the local atomic configurations near the considered defects. The DFT results are compared with those obtained using the shell model. Both approaches give a similar pattern of lattice distortion around the Fe-impurity centers occupying cation sites in the isoelectronic charge state Fe^2＋ and single-positive-charge state Fe^3＋. The phonon local symmetrized densities of states projected onto the displacement of ions surrounding the defects are calculated by a well-established recursion method. The frequencies of defect vibrations of various symmetry types induced by Fe impurities are determined. The calculations made it possible to interpret the structure of the phonon sideband accompanying the zero-phonon line in polarized emission spectra attributed to the Fe^3＋ intracenter transitions, as well as to estimate the role of Fe ions in the formation of observed peaks.

This paper investigates complete synchronization of discrete-time variable-order fractional neural networks (DVFNNs) with time delays. By discrete inequality technologies and nabla Laplace transform, two stability lemmas are derived which are generalizations of the constant-order case. Furthermore, several complete synchronization criteria for DVFNNs are proposed by utilizing inequality techniques and Lyapunov method. Finally, a numerical example is provided to verify the theoretical results. This paper also provides a stability analysis method for variable-order fractional discrete-time systems.

Biometric authentication has been widely used because of its uniqueness, accuracy, and versatility, but existing methods still have some shortcomings. Because biometric data is stored in the database, once the database is invaded, it will cause a large number of biometric data leakage and illegal use of huge risks; The cost of traditional feature extraction and matching strategy is too high; Biometric is only used for authentication, and its single function cannot meet the increasing security requirements; Methods that rely solely on biometric keys are not secure enough. To overcome these shortcomings, we propose the biometric holographic encryption and authentication with multiple optics-biology keys based on inhomogeneous media optics. The proposed method innovatively combines biometrics and inhomogeneous media optics to achieve dual functions of encryption and authentication. Instead of storing biometric data directly, the encryption and authentication information is encrypted as computer generated holograms in this method and stored in the database to reduce the risk of biometric data leakage. This method has low cost without complicated feature extraction and comparison authentication process. The dual functions of authentication and encryption is more practical. Multiple optics-biology keys improve the security. The security and robustness are analyzed. A graphical user interface (GUI) is designed for the method to promote its application. This work provides new methods and new ideas for the field of optics encryption and authentication, and will certainly have a broad application prospect.

The purpose of this study is to investigate the variation of streaming potential and EKEC efficiency of nanofluids with couple stress in the circular polyelectrolyte-grafted (PE-grafted) nanochannel under the combined effect of periodic pressure and magnetic field. The analytical solutions of the velocity field in the PEL region and electrolyte solution are obtained by solving the modified Navier-Stokes equation and the influence of several dimensionless parameters on the streaming potential and electrokinetic energy conversion (EKEC) efficiency are further discussed graphically. The results indicate that the streaming potential decreases with increasing Hartmann number and nanoparticle diameter within a certain parameter range. The dimensionless velocity shows an oscillating trend at different oscillating Reynolds numbers, and the oscillation is more pronounced at the interface between the PEL and the electrolyte solution. In addition, the EKEC efficiency of nanofluids in soft nanochannel is compared with that in a rigid one. It is shown that the EKEC efficiency is higher in PE-grafted nanochannel, and the couple stress plays an important role in improving the EKEC efficiency. We anticipate that these findings will help to reveal a novel understanding of energy conversion in the circular PE-grafted nanochannel.

The all-dielectric germanium nanohole (GNH) metasurface with a sub-wavelength thickness supports simultaneous excitation of quasi bound state in the continuum (BIC) and super radiant mode. By selecting the different hole depths in a germanium slab, we present a trade-off metasurface between high Q-factor and high absorption in the photonic system. The presented device demonstrated absorption of super-radiant mode ∼98.5% and quasi-BIC ∼93% without back-metal reflector at the telecommunication wavelength. The numerical results, obtained by the finite difference time domain (FDTD) method are explained in the framework of temporal coupled mode theory (TCMT).

Biological neurons receive a variety of external physical stimuli that are encoded in the nervous system to regulate the circadian rhythm in animals. Most types of nonlinear circuits are effective for exploring the dynamics and biophysical properties in biological neurons by analyzing the sampled time series for output voltage. To explore the impact of light on the homeostatic regulation of sleep-wake cycle, this paper proposes an enhanced neuron model that incorporates photocurrent activation, aiming to study the fundamental principles governing the sleep-wake cycle. In this paper, the frequency and intensity of external illumination are carefully adjusted to explore the occurrence of the firing modes in this light-sensitive neuron. The numerical results suggest that the circadian rhythm system can be impaired by continuous exposure to strong and high-frequency light. Additionally, an appropriate fine-tuning of the coupling strength between neurons can further optimize the response of a neural network to external light signals. These results provide insights into the regulation of light on circadian rhythm, and thus appropriate electromagnetic radiation can be applied to prevent and treat the sleep disorders.

Ion acoustic waves (IAWs) are theoretically researched in a magneto-rotating plasma with cold ion fluid and $(r,q)$ distributed electrons. The reductive perturbation method (RPM) is used to simplify fluid plasma equations, the relevant ZK and mZK equations and their solitary solutions are given. Small-k expansion method is applied to obtain the instability growth rates of ZK and mZK IAWs. The flatness and tail parameters modify the amplitude, width, soliton energy and instability growth rate for both ZK and mZK IAWs. There only exist negative ZK IAWs and positive mZK IAWs. It is noted that the increscent flatness and tail parameters result in the increasing amplitude, width, soliton energy and growth rate of ZK and mZK IAWs. These results will be helpful in understanding the plasma dynamics for a magneto-rotating plasma system containing $(r,q)$ distributed electrons in Saturn’s magnetosphere.

The mutation and recombination often have different rates for forward and backward processes and this study explores the less common case of asymmetric mutation and recombination rates. The primary focus is on analyzing the error threshold transition in the context of asymmetric mutations. We investigate how the error threshold changes in the case of a single peak fitness landscape. We analyze how surplus (the availability of beneficial mutations) changes with the degree of asymmetry in mutation and recombination rates. The model is extended to include asymmetric recombination (horizontal gene transfer). We focus on the complex interplay between mutation and recombination rates in asymmetric scenarios and their effects on error thresholds, surplus, mean fitness, and other key aspects of evolutionary dynamics. The findings contribute to a more nuanced understanding of evolution in situations where biological processes do not follow the simplifying assumption of symmetric rates.