Indian Journal of Physics最新文献

Pandemic from Corona Virus Diseases 2019 (SARS-COVID-19) is a serious hazard to human health and life which is responsible for the significant economic losses across the world. Sometime it resulted into death of human being. Since environmental factors have significant effects on COVID-19 transmission, and vice-versa, therefore lockdown condition which is expected to reduce environmental pollution is an important step to affect COVID transmission through the environment. The associated ambient air pollutant: (O₃), nitrogen dioxide (NO₂), sulphur dioxide (SO₂), and Carbon mono oxide (CO) are directly linked to enhance risk of stroke, heart disease, asthma, and lung cancer and are also affected by the number of cases of COVID-19. In order to have quantitative estimate and comparative study of these pollutants, aerosol optical depth (AOD), surface temperature, ozone, carbon mono oxide (CO) and nitrogen dioxide (NO₂), aerosol size distribution over India, have been analysed during lock down period 01 March–30 June, 2020. The analysis of pollutants during lockdown period has been compared to 05 year mean value (2015–2019) estimated during the same period. The satellite based measurement of AOD from MODIS show a decrease in AOD during the lockdown period by 40% in Indian region as compared to 5-year mean level (2015–2019) whereas ground based AOD from AERONET reduced to 75% at Kanpur and 74% at Gandhi College in India. The drop in AOD observed during lockdown is a clear cut indication of reduced level of air pollution. Peak of aerosol size distribution over Kanpur and Gandhi College has also been analysed which show a reduction by 33–50% from the 05-year average level. Enhancement in total ozone column ~ 8% from average level is noticed during the lockdown period which is attributed to suppression in NO₂ and CO concentration which is supposed to destroy the formation of ozone through chemical reactions. Influence of lockdown on concentration of environmental pollutants in Indian region has also been compared to top other two countries of the world: USA and Brazil. The pattern of day-to-day variation of COVID cases at India and Brazil is same whereas for USA patterns are significantly different. The comparative analysis of other pollutants between all the three countries has also been discussed and fall in temperature due to lockdown condition over USA is found larger than that over India and Brazil.

Abstract

We investigated analytically and numerically the nonlinear Schrödinger (NLS) equation with constant and spatially varying third-order dispersion (TOD) in the alternative type of complex parity-time ((mathcal{P}mathcal{T}))-symmetric potentials. This equation describes the propagation of ultra-short pulses through the optical media, where the real part of the potential models the index guiding and the imaginary part the loss/gain distribution of light within optical material. For the constant TOD, the regions of stability/instability linear (mathcal{P}mathcal{T})-symmetric phases are numerically carried out. By means of the linear stability analysis and direct numerical simulation, the effects of interplay between constant TOD and (mathcal{P}mathcal{T})-symmetric potential on the stability of these solutions are also tested. It is found that the constant TOD can be used to control the stability of these solutions. For the spatially varying TOD, the additive terms of the (mathcal{P}mathcal{T})-symmetric potential are considered for the nonlinear model and the robustness of these solutions against noise is tested by means of the split-step Fourier beam technic. Moreover, the elastic interactions of the two spatial solitons are generated under the (mathcal{P}mathcal{T})-symmetric potential for the spatially varying TOD. The power and the transverse power-flow density are further examined. Results indicate that the spatially varying TOD does not yield any instability in the self-focusing nonlinear medium with the chosen parameters values.

Graphical Abstract

Glasses of nominal composition xHfO₂–(35-x)B₂O₃–15MgF₂–35BaO, where x ranged from 0 to 0.2 mol% were fabricated using a melt-quenching technique. Structural characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and Raman spectroscopy, were employed to elucidate the glass network structure. The XRD patterns confirmed the amorphous nature of the studied glasses, while the FTIR and Raman spectra revealed that the incorporation of HfO₂ may led to a transformation of trigonal BO₃ units to tetrahedral BO₄ units in the borate glass network. Deconvolution analysis of the FTIR and Raman bands provided quantitative insights into the extent of this structural rearrangement as a function of HfO₂ content. UV–Vis absorption studies demonstrated that the optical bandgap of the glasses was widened with increasing HfO₂ additions. This blue shift in the absorption edge was attributed to the increased formation of bridging oxygen bonds and reduced non-bridging oxygen content in the glass network. The results indicate that the studied glasses exhibit excellent compositional tunability through the incorporation of HfO₂. The structural modifications and concomitant optical property enhancements suggest the potential of this glass system for various integrated photonic applications where low phonon energy and tailored transparency are highly desirable. The present work introduces a comprehensive investigation of the structural and optical property modifications in barium magnesium fluoroborate glasses induced by the addition of hafnium oxide (HfO₂).

The thermo-optic coefficients (TOCs), thermo-polarization coefficients (TPCs) and dn/dT, dα/dT of congruent lithium niobate LiNbO₃ / LN (mole ratio Li/Nb = 0.946) are tested within the temperature range of 293–773 K at λ = 0.4358 µm, λ = 0.6328 µm and λ = 1.15232 µm employing the point dipole approximation. The refractive indices, n_o and n_e, were first determined at these temperatures and wavelength ranges, by iterating the electronic polarizabilities of Nb⁵⁺ and O²⁺ ions. It has been found that the polarizability of Nb⁵⁺ ions drops and that of O²⁻ ions increases when temperature rises for a particular wavelength. Both Nb⁵⁺ and O²⁻ lose polarizability with increasing wavelength for a given temperature. TOCs for n_o and n_e rise as the temperature rises. The TOC rises as wavelength for n_o and n_e decreases. TPCs of O²⁻ rise in ions and temperature causes Nb⁵⁺ ions to decrease. At a particular temperature, TPCs of O²⁻ions become less while Nb⁵⁺ ions grow as wavelengths rise. Generally, it is used in potential electronic polarizabilities and thermal refraction applications.

In this work, a new cadmium telluride (CdTe) photovoltaic structure has been developed to achieve a high-power conversion efficiency (η) at low cost for thin film photovoltaic. The blue spectrum is surprisingly restricted by the cadmium sulfide (CdS) window layer in the CdTe solar cell. Thus, to improve the shorter wavelength collections, we have replaced the planar CdS layer with nanowire CdS (NW-CdS) window layer. With this change, the quantum efficiency has significantly improved in a shorter wavelength range and the photocurrent has increased by more than 27% compared to the planar CdS device structure. Furthermore, a good back contact material with lower contact resistivity is also important to achieve maximum power conversion efficiency. To obtain an Ohmic, low-resistance contact, a 3D graphene layer has been used as a back contact. Using the SCAPS-1D simulation software, the newly proposed CdTe solar cell’s photovoltaic characteristics were thoroughly investigated. Our calibrated simulation results show that the suggested NW-CdS with graphene solar cell structure produce higher photocurrent density (J_SC) and fill factor (FF). The power conversion efficiency (η) was found to be 14.58%, comparatively higher than the baseline CdTe solar cell efficiency (η = 9.04%).

We study the phenomenon of Bose–Einstein condensation in two- and one-dimensional Dunkl–Boson gases confined within a power-law potential, employing the framework of Dunkl-deformed boson theory. Our investigation involves the calculation of particle numbers and phase transition temperatures using the Dunkl formalism. To assess the validity of our findings, we compare them with the corresponding results obtained from the standard approach. We find that the impact of the Dunkl formalism on the condensate fractions is similar in one- and two-dimensional cases. However, we see that this conclusion is not fully valid for the phase transition temperature.

The motion of the tri-stable oscillator can be transferred between different equilibrium points to produce a large response, which is the desire of vibration energy harvesting technology. Therefore, the vibration of the tri-stable system has been a widespread concern. However, the mechanism of the system with parametric slow excitations has not been discovered. To study this issue, we treat a novel bursting pattern in a tri-stable oscillator under slow cosinoidal excitations. The complex dynamic behaviors of bursting oscillation under single and two frequencies are presented using the fast-slow analysis method, the one-parameter bifurcation diagrams are plotted, and the bifurcation patterns associated with independent loop and closed loop are observed. Furthermore, different types of bursting oscillations induced by subcritical pitchfork/fold bifurcations are presented, and jumping phenomena and hysteresis behaviors are displayed. Moreover, the stabilities of equilibrium of the independent and closed loop positions are checked by potential energy, and the transition of different equilibrium configurations is validated by introducing the transformed phase diagram. Finally, the attraction basin of each equilibrium point is estimated via cell mapping, and the multivalued response orbits are recognized.

Introducing dynamical systems that involve a variable in the trace of the Jacobian matrix is a difficult challenge due to it is difficult to determine whether a system is dissipative or conservative. This paper introduces a new 3D chaotic nonuniformly conservative system with a variable in the trace of the Jacobian matrix through the Hamiltonian form. The proposed system is without equilibrium points (hidden attractors) and satisfies categories C and D. The system exhibits three distinct behaviors (chaotic, quasi-periodic, periodic) under the same parameters with varying initial conditions. The characteristics system are investigated through a combination of theoretical analysis and numerical simulations, including dissipative and conservative behavior, equilibrium points, bifurcation diagrams, Lyapunov exponents, and multistability. Finally, two applications are implemented: an electronic circuit and image encryption based on the proposed system. These outcomes substantiate the sufficiency and viability of this system, demonstrating its effective performance.

We report results of magnetoviscosity and magnetically induced changes in microstructural properties of a ferrofluid made of copper zinc ferrite (CuZnFe) nanoparticles. These measurements were performed by tracking thermal motion of a tracer particle and video microscopy, using a home-built microscope. It has been established that the nanoparticles align to form chain-like structures under influence of external magnetic field, which result in an anisotropy of properties in two different directions, and also a magnetic field dependency of the properties. Most ferrofluids show an isotropic nature in the absence of any external magnetic field and a field-dependent anisotropy in the presence of magnetic field. But the CuZnFe sample studied here shows an anomaly with an anisotropic behaviour even when field is zero. This is perhaps one of the first cases where such anomaly is observed. Upon application of magnetic field, the parallel and perpendicular evolve in two different trajectories. We present the measurement of viscosities, both parallel to and perpendicular to the applied field, and from therein derive microstructural properties such as elastic moduli and relaxation time. All measurements were taken at room temperature (300 K).

This work investigates a conspicuous disease of pine trees known as pine wilt disease (PWD). This disease propagates through a pine wilt nematode, a microscopical ringworm that mainly contaminates the pine trees of the Pinus genus. Its development way comprises many stages. Pine trees impacted by PWD initially show yellow-colored leaves and then turn reddish brown after some time. The pine sawyer beetles act as conveyors that transfer the pine wilt nematode. The disease in the frame of the PWD model is studied with fractal–fractional (FF) derivatives in the context of Caputo and Caputo–Fabrizio (CF) derivatives under different fractional order ({partial_{1}}) and fractal dimension ({partial_{2}}) values. Here, the fundamental characteristics of the given model are discussed. The fixed point theory’s theoretical results are interpreted for existence and uniqueness, while Ulam–Hyres (UH) stability is also presented for the given model. Further, the Caputo and CF derivative-based numerical schemes are also displayed. After analyzing the numerical simulations, it is found that the FF operator is more capable of analyzing the PWD model.