Brazilian Journal of Physics最新文献

The dust-ion-acoustic solitary waves (DIASWs) traversing in an unmagnetised dusty plasma with cold ions and electrons that follow the (kappa)-deformed Kaniadakis distribution (KD) are described in this article. The Korteweg-de Vries (KdV) and modified Korteweg-de Vries (mKdV) equations are generated by using the reductive perturbation method (RPM) to the basic equations. The implications of crucial parameters on the dynamics of solitary formations (namely, (kappa)-deformed parameter, dust concentration (mu), and relativistic factor (nu = frac{{v_{0} }}{c})) are studied in detail. It is important to report that compressive and rarefactive fast DIASWs are observed in the ranges (left( {mu le 0.66} right)) and (left( {mu > 0.66} right)) respectively. Further, the parameter (kappa) has no effect on the DIASWs of the KdV equation. The current work may be useful in highlighting the salient features of high relativistic effects on DIASWs corresponding to the KdV and mKdV equations in laboratory plasmas, Earth’s magnetosphere in space plasmas, and pulsar magnetospheres of astrophysical plasmas.

Based on density functional theory (DFT), the electronic, structural, and optical properties of bismuth oxyfluoride (BiOF) are investigated by using various exchange–correlation functionals. The local density approximation (LDA), Perdew-Burke-Ernzerhof generalized gradient approximation (PBE-GGA), Perdew-Burke-Ernzerhof generalized gradient approximation for solids (PBEsol), and Wu-Cohen (WC) functionals are implemented in Wien2k software. Modified Becke-Johnson (mBJ) and unmodified Becke-Johnson (umBJ) potentials are also applied to obtain an enhanced band gap. Spin–orbit coupling effect (SOC) is also taken into consideration due to the heavy Bi atom. When employing the PBE+umBJ potential, BiOF exhibits the most enhanced band gap energy, with a direct band gap energy of 3.72 eV. Moreover, optical properties such as dielectric functions, absorption coefficients, and optical conductivities are also calculated for photon energies up to ̴̴ 14 eV. In comparison to other available theoretical and experimental findings, the calculated results are in good agreement.

In order to comprehend how fluorescence resonance energy transfer affects the emission spectra and threshold of Rhodamine 640/methylene blue/Ag NW lasers, this article examines a particular type of random laser with coherent features. It is shown that methylene blue laser output is enhanced by rhodamine 640 beyond 700 nm. Furthermore, it has produced multi-wavelength lasing with linewidths as small as 1 nm by adjusting the mixing ratio of the two dyes. In this system, silver nanowires operate as scatters, decreasing the operating threshold for multi-wavelength lasing and improving light extraction efficiency in the visible region.

A quantum public-key cryptosystem based on the non-locality in an unentangled quantum two-particle system is presented in this paper. Every user shares a set of quantum two-particle systems in orthogonal product states with a key management center (KMC) as the (public key, private key) pairs. By the help of KMC, users can accomplish secret communications. Message authentication can also be realized in the public-key cryptosystem. The laws of quantum physics guarantee the unconditional security of this cryptosystem. No entangled states or complex quantum operations are needed. In the communication process, any two users need not exchange quantum particles. So the public-key cryptosystem is easier to carry out in practice.

Flock and swarm models are mostly based on the alignment of the velocity vectors of animals (birds, fishes, bats, etc.), following the very successful Vicsek model. Here, we explore a simple alternative where the animal decides the sense of its movement based only on the number of neighbors and the weak dependence on a landmark. This defines a class of density-based interacting random walks which seems to describe qualitatively mosquito swarms. The model presents a phase transition-like behavior that seems to be interesting to apply to stationary swarms, in general.

In this paper, a 4:1 photonic multiplexer has been developed utilizing a Kerr switch of nonlinear optical materials, featuring 4 inputs and a singular output. The all-optical nature of this photonic multiplexer is characterized by rapid response times in the terahertz speed range, rendering it valuable for higher-speed data communication systems. The utilization of a positive logic system and intensity-based coding is demonstrated, where the predetermined intensity of a light signal signifies binary 1, while its absence represents binary 0. The construction of this scheme involves the utilization of Binary Decision Diagrams, wherein the placement of nonlinear Kerr Switch at all nodal points represents a multiplexer-based design. Through the implementation of a Binary Decision Diagram-based photonic multiplexer design, a 3-input XOR gate has been constructed, demonstrating its versatility in various optical computing applications. The proposed approach’s efficacy is established through validation via mathematical computations and PYTHON simulations. This research holds promise for enhanced performance and versatility in industrial and commercial applications.

This study investigates the photocatalytic properties of carbon nanotube (CNT)-supported nitrogen-, cobalt-, and silver-doped zinc oxide (ZnO) synthesized via the solvothermal method. Various characterization techniques, including X-ray photoelectron spectroscopy (XPS), BET surface area analysis, energy-dispersion X-ray (EDX) spectroscopy, UV–visible spectroscopy (UV–Vis), scanning electron microscopy (SEM), X-ray diffraction (XRD), photoluminescence (PL), Fourier transform infrared (FTIR), and transmission electron microscopy (TEM), were employed. Photoluminescence spectroscopy revealed lattice defects and the doping effect on ZnO’s electron–hole recombination. FTIR spectroscopy identified functional groups, and EDX and XPS confirmed the presence of Ag, Co, C, Zn, O, and N. XRD and TEM estimated crystal sizes between 21 and 24 nm. UV–Vis spectroscopy showed a reduced band gap from 3.18 to 2.40 eV. SEM images depicted hexagonal nanoparticle structures. BET analysis showed a Category 4 adsorption isotherm and a pore diameter of 8.527 nm. The nanocomposite ZnO exhibited significant photocatalytic degradation under visible light, achieving 96% and 85% degradation of Congo red and methylene blue dyes, respectively. This study highlights the enhanced photocatalytic performance of CNT-supported nitrogen-, cobalt-, and silver-doped ZnO nanocomposites, suggesting their potential for environmental remediation applications.

Graphical Abstract

The design and performance analysis of a triple micro-optical ring resonator (MORR) are proposed in the article. The delay line signal processing method in the Z-domain is used to model the proposed architecture, which has one input bus and two output buses. The mathematical model in the Z-domain of the proposed MORR is simulated in MATLAB. The proposed MORR is then designed and simulated using OptiFDTD software and validated with MATLAB results, which are very close to each other. The results are compared to those from MATLAB, which yielded similar results. OptiFDTD is used to design couplers and conduct structural field analysis. An optical model is created and tested at different locations on the EDFA to identify eye diagram patterns. The results show improved sensitivity and noise-free operation, supporting multiple communication channels with a large FSR and wide-open eye diagrams.

The present study deals with the synthesis and characterization of the Gd₂O₃:Eu³⁺ nanophosphors and the impact of Y³⁺ co-doping on the structural and optical properties of the Gd₂O₃:Eu³⁺. All nanophosphors are synthesised by facile low temperature solution combustion method using citric acid as a chelating agent. The XRD pattern of as-synthesised Gd₂O₃:Eu³⁺ confirmed the presence of mixed-phase crystallites and upon annealing, it transforms to a cubic phase. The images of TEM and FE-SEM confirm that the samples are spherical after annealing. From the perspective of the emission spectra of Gd₂O₃:Eu³⁺, the ⁵D₀ to ⁷F₂ (613 nm) optical transition is the most important among the different narrow emission peaks observed in the visible region. Optimal doping concentration of Eu³⁺ was 7 wt%. Y³⁺ ions were incorporated into this Gd₂O₃:7 wt%Eu³⁺ nanophosphors. Y³⁺ co-activated samples crystallized in the cubic structure and exhibited a threefold enhancement in emission intensity and considerable improvement in lifetime and quantum efficiency compared to Gd₂O₃:Eu³⁺ nanophosphors. Temperature-dependent PL spectra indicate that the obtained nanophosphor exhibits excellent thermal stability and the activation energy was observed to be 0.4773 eV. Beyond that, red CIE coordinates, with excellent colour purity (greater than 95%) and suitable colour-correlated temperature (below 5000 K) suggest that the prepared red-emitting nanophosphors have immense potential in phosphor converted LED (pc-LED) applications.

Aluminum thin films were deposited by unbalanced grid-assisted magnetron sputtering. Depositions were made with different net charges of the particles bombarding the substrate through modifications in the magnetic field with the aid of permanent and electro magnets. Film morphology was evaluated by atomic force microscopy and the results point out that the surface roughness of the film deposited with net positive ions bombardment is about five times higher than the surface roughness obtained with net electrons bombardment and ten times higher than that obtained with neutral net charge bombardment.