Polar-cap ionospheric variability and foF2 predictability are characterized using 12 months of EISCAT Svalbard Radar (ESR) data during the 2007–2008 solar minimum. Over four million altitude-resolved measurements were analyzed to establish a baseline and quantify storm responses. Quiet-time foF2 exhibits strong solar-driven modulation ( 1.4–2.8 MHz). Geomagnetic disturbances cause systematic F2-region depletions ( 39
An integrated approach of experimentation and numerical simulation were employed to investigate the influence of cadmium sulfide (CdS) buffer layer on the performance of CZTS based heterojunction solar cells. The effect of variation in deposition time with the properties of CdS and its role as the n-layer in CdS/CZTS devices has been investigated. The deposition time of CdS thin films were varied from 30 to 120 min using a cost-effective chemical bath deposition. To investigate properties of the films XRD, SEM, EDS, Raman, and UV–visible characterisations were carried. XRD analysis confirmed the presence of cubic-phase CdS with improved crystallinity, while SEM images showed a densely packed, boulder-like morphology. Additionally, EDS confirmed a stoichiometric Cd-to-S ratio. Film thickness found to increase from 160 to 400 nm, while bandgap slightly narrowed from 2.46 to 2.40 eV. Hall measurement showed improved n-type conductivity with deposition time. Heterojunctions devices of architecture < FTO/CdS/CZTS/Ag > were fabricated and their junction parameters are evaluated by using I-V measurements. Further, solar cell devices of the same structure were simulated using SCAPS-1D. The CdS layer deposited for 30 min yielded the best performance, with a simulated efficiency of 17
The Madden–Julian Oscillation (MJO) is a dominant source of tropical intraseasonal variability that strongly influences the Indian Summer Monsoon (ISM). This study investigates the relationship between MJO phase, MJO amplitude, outgoing longwave radiation (OLR), and precipitation during the ISM onset period over India using daily observations for 1979–2021. Daily OLR data from NOAA, CPC Global Unified Gauge-Based Analysis of Daily Precipitation, and Wheeler–Hendon Real-time Multivariate MJO (RMM) indices were analysed using anomaly analysis, residual time series, correlation analysis, and pentad-based composite analysis. The results demonstrate a significant inverse relationship between OLR and precipitation anomalies, indicating that enhanced MJO activity is associated with stronger convection, lower OLR, and increased rainfall. MJO phases over the Indian Ocean (Phases 1–4) generally favour enhanced precipitation during monsoon onset, whereas Phases 5 and 6 over the Maritime Continent are associated with suppressed convection and reduced rainfall. Unlike previous studies that primarily investigated the general influence of the MJO on the ISM, this study provides a comprehensive pentad-wise (P1–P6) analysis of MJO phase characteristics, amplitude, precipitation anomalies, and OLR anomalies to identify the dominant MJO phases associated with pre-, normal, and post- monsoon onset during 1979–2021. The response of precipitation and convection varies among different onset pentad categories, highlighting the importance of MJO phase evolution in modulating monsoon onset variability. These findings provide improved physical understanding of MJO-related convection and its association with ISM onset variability and contribute to the interpretation of intraseasonal monsoon behaviour over India.
We study a periodic asymmetric simple exclusion process (ASEP) with stochastic backtracking and two recovery pathways, combining mean-field theory with random sequential Monte Carlo simulations. In this minimal two-state driven lattice-gas model, particles in the active transport state may undergo backward excursions and subsequently recover either through forward restoration or spontaneous state conversion. Within a homogeneous mean-field approximation, we derive an analytical expression for the steady-state current-density relation and show that backtracking renormalizes the effective drift. A central result is the emergence of a nonequilibrium current-reversal transition: beyond a critical backtracking rate, the steady-state current changes sign, indicating persistent reverse circulation on the ring. Monte Carlo simulations quantitatively confirm the mean-field predictions over a broad parameter range, with noticeable deviations only in the strong-backtracking regime where spatial correlations become relevant. The results establish a minimal framework for studying transport reversal generated by internal-state interruptions in conserved driven diffusive systems.
The structural, electronic, magnetic, and optical properties of half-Heusler Ptx Mn1-xCoSb alloys (x=0, 0.25, 0.5, 0.75, 1) are systematically investigated using first-principles calculations. All studied compositions are mechanically stable, and the Pt/Mn ratio enables tunable mechanical behavior. A counterintuitive simultaneous increase in both the lattice parameter and the bulk modulus is observed with increasing Pt content — an unusual phenomenon recently observed in other Pt-based half-Heusler systems, suggesting distinctive Pt-driven bonding characteristics. This behavior, combined with a composition-tunable ductile-to-brittle transition, underscores the exceptional mechanical versatility of this system. Electronic structure calculations using the GGA + TB-mBJ approach show that most compositions are metallic, with no band gap in either spin channel. The sole exception is MnCoSb (x = 0), which exhibits near-half-metallic behavior with a partial band gap of 0.86 eV in one spin channel. Near the Fermi level, transition-metal d-orbitals dominate the density of states, with clear spin polarization and systematic evolution with composition. Magnetically, the system is primarily governed by Mn atoms ( 3 μB), whose moments can be effectively tuned down to 0.6 μB via Pt alloying, enabling controlled magnetic responses for spintronic applications. The optical properties exhibit pronounced energy-and composition-dependent changes in absorption, conductivity, and refractive index, with strong absorption (up to 1.8 × 106 cm–1) and high reflectivity in the visible-UV region, positioning these materials as promising candidates for optoelectronic and plasmonic applications. Overall, the Ptx Mn1-xCoSb system displays multifunctional behavior with high compositional tunability. The combination of counterintuitive mechanical properties, tunable magnetism, and strong optical responses, makes this system a promising platform for spintronic, optoelectronic, and plasmonic technologies.
In this study, the optoelectronic and thermoelectric properties of orthorhombic marcasite-type OsPn _2 (Pn = P, As; space group Pnnm, No. 58) were systematically investigated using first-principles DFT calculations. Phonon dispersion spectra exhibit no imaginary frequencies throughout the Brillouin zone, confirming the dynamical stability of both compounds, while the fulfillment of Born stability criteria verifies their mechanical robustness. Electronic structure calculations performed within the GGA and GGA+SOC frameworks reveal indirect semiconducting behavior with narrow band gaps ranging from 0.67 to 0.86 eV. The optical response is characterized by strong light absorption, with absorption coefficients exceeding 1 × 10 ^5 cm ^-1 across the visible and ultraviolet regions, indicating favorable optoelectronic functionality. Thermoelectric transport calculations based on the semiclassical Boltzmann approach predict excellent high-temperature performance, yielding maximum ZT values of 0.74 for OsP _2 and 1.49 for OsAs _2 at 1200 K. The significantly enhanced thermoelectric efficiency of OsAs _2 , coupled with the strong optical absorption of both compounds, identifies OsPn _2 as a promising platform for high-temperature thermoelectric and optoelectronic applications.
This paper is intended to present an investigation into the impact of cubic, quintic, and saturable nonlinearity on the instability in PT-symmetric fiber Bragg grating structures (FBG) with various PT-symmetry regimes. A conventional linear stability analysis identifies the modulational instability (MI) gain, where the combinatorial influence of cubic and quintic nonlinearities on MI is carefully studied in both normal and anomalous dispersion regimes. Additionally, we investigate the characteristics of MI at the bottom and top edges of the photonic band gap. The investigation highlights the importance of non-Kerr nonlinearity in relation to the MI gain. It is shown that even in the presence of PT-symmetry, one could effectively control the MI by varying the cubic, quintic, and saturable nonlinearity for various PT-symmetric regimes. The investigation revealed a range of spectral varieties, including asymmetry, symmetry, sideband spectrum, steadily increasing gain, broad spectrum, and others. We find an anomalous spectrum that is more discrete than continuous for the few physical components. The emergence of solitary waves in nonlinear episodic structures is also examined following the use of PT-symmetry.
This research provides an exhaustive first-principles examination of both pure and vanadium-doped monolayer MoSe2, employing density functional theory (DFT) inside the generalised gradient approximation (GGA-PBE) and molecular dynamics (MD). When you add vanadium to another element at 25
We investigate the thermodynamic behavior and the temperature–magnetic-field dependence of the QCD equation of state (EoS) in the quark–gluon plasma (QGP) phase using a hybrid framework that combines field-theoretical methods, the dual SU(3) QCD formulation, and the MIT Bag Model. This study is motivated by the extreme conditions realized in non-central heavy-ion collisions, where intense magnetic fields significantly influence the QCD equation of state. We examine the temperature and magnetic-field dependence of key thermodynamic quantities, including pressure, energy density, specific heat, the speed of sound, the conformal measure, and free energy. The analysis reveals nontrivial anisotropies and nonlinear behavior arising from magnetic catalysis, inverse magnetic catalysis, and Landau quantization. Furthermore, we derive analytical expressions for the pressure, energy density, and entropy density of magnetized QGP and investigate the effects of Landau-level quantization on the partition function. The dual SU(3) QCD formulation is employed to determine the non-perturbative vacuum energy and the corresponding bag constant, which is subsequently used as an input to the magnetized MIT Bag Model for calculating the thermodynamic observables. Our findings provide further insight into the QCD phase transition in the (T)–(eB) plane and have important implications for both relativistic heavy-ion collisions and compact astrophysical objects, such as magnetars.
Antenna look angles, specifically azimuth and elevation angles are essential for steering ground station tracking systems toward target spacecraft, solar system bodies, and stars. As human exploration expands toward lunar and Martian bases, localized tracking capabilities across non-Earth surfaces become critical. This paper presents a generalized computational framework for predicting antenna look angles from any planetary or lunar surface within the solar system. The antenna look angles for spacecraft are computed using the spacecraft’s predicted state vector (position and velocity) while for the Sun, Moon, and planet objects are computed either using their position vector or knowing their right ascension and declination. Similarly, knowing the star’s right ascension and declination, antenna look angles are computed. The overall computational process is integrated in the Satellite Precise Orbit Propagator (SPOP). The computed look angles are benchmarked with the commercial package Systems Tool Kit (STK) of Ansys/Synopsys, demonstrating consistent alignment across test cases.
The frequency values of the power sources in capacitively coupled plasma (CCP) discharges fundamentally determine the electrical properties and discharge dynamics. While radio-frequency (RF) power sources accelerate free electrons, the alternating-current (AC) components significantly influence the ion density and energy distribution. To fully understand these interactions, it is necessary to determine the distributions of electrical potential and charge density in the plasma medium. In this context, the numerical solution of the Poisson equation serves as a critical approach for determining plasma properties. In this study, the interaction between RF-driven ionization and AC-modulated electric potential is investigated under quasi-steady-state conditions through a numerical solution of the Poisson equation for dual-frequency CCP systems operating at 13.56 MHz (RF) and 20 kHz (AC). This interplay between the power sources dictates the resulting charge densities and potential distributions, representing a fundamental step in characterizing the plasma system. It is demonstrated that the Poisson equation effectively describes the relationship between charge density and potential for dual-frequency CCP systems. To achieve high spatial accuracy in the numerical solution, the central difference method is applied to discretize the governing equation.
The properties of warm nuclei at low temperatures ( T<1 MeV) remain less explored than their high-temperature behaviour. In this regime, the giant dipole resonance (GDR) reflects a strong interplay among shell effects, thermal shape fluctuations, and pairing correlations. We develop a finite-temperature microscopic model based on the random phase approximation (RPA). Unlike earlier studies that used the Nilsson potential or treated shape and pairing fluctuations separately, the present approach derives quasiparticle wave functions from a realistic triaxial Woods–Saxon (WS) mean field and simultaneously includes fluctuations in the nuclear shape and pairing field. The same WS Hamiltonian is used to calculate both the shell corrections and the microscopic GDR response. Results for 97Tc, 120Sn, 179Au, and 208Pb are compared with available experimental data and with a macroscopic GDR model. Despite using fewer parameters, the microscopic model qualitatively reproduces the low-temperature evolution of the GDR width in the Sn and Pb regions when pairing fluctuations are included. At higher temperatures, it underestimates the width because spreading contributions beyond the RPA are absent. More precise measurements at low temperatures could provide valuable information on phase transitions in warm nuclei.
We present a theoretical investigation of the electron beam-driven ion Trivelpiece–Gould (TG) mode instability in a bounded, magnetized electron–ion–positron (e–i–p) plasma. The analysis considers a cylindrical plasma column in the presence of an external axial magnetic field and a low-density electron beam injected along the magnetic field direction. All plasma species are treated as cold fluids, and boundary conditions are applied to account for the finite radial extent of the system. A general dispersion relation for the obliquely propagating ion TG mode is derived, incorporating the effects of positron concentration, ion mass, beam parameters, and plasma column radius. The results show that increasing positron density suppresses the ion TG mode growth due to enhanced charge symmetry and reduced net space charge. The instability is highly sensitive to the beam velocity, with maximum growth occurring near resonance between the beam and phase velocities. Furthermore, decreasing the plasma column radius shifts the instability spectrum and reduces the range of unstable wave numbers. Increasing the ion mass or ion density lowers the phase velocity and compresses the instability band. These results demonstrate the strong influence of plasma composition and finite geometry on beam-driven ion TG mode excitation and provide useful insights into wave propagation and energy transfer in laboratory and astrophysical electron–ion–positron plasmas.
The current study provides a comprehensive analysis of heat transfer in porous media within the framework of local thermal non-equilibrium (LTNE). It takes into account the combined effects of non-Newtonian Casson fluid behavior, spatially varying Biot number, and temperature-dependent thermal conductivities. The simultaneous consideration of these interacting factors poses significant analytical and numerical complexities, particularly when extending the formulation to more complex geometries or thermal behavior. To effectively solve the resulting nonlinear and coupled system of differential equations, we employ Physics-Informed Neural Networks (PINNs), ensuring high accuracy and efficiency. The PINN framework integrates the governing equations and associated boundary conditions directly into the neural network training process, enabling effective handling of nonlinearities and spatial variations. The accuracy of the PINN approach is validated through comparison with solutions obtained from MATLAB’s bvp4c solver, especially for cases where the spatially varying Biot number profiles presented significant training difficulties. Parametric studies demonstrate the significant influence of fluid rheology, spatially varying Biot number, and nonlinear thermal conductivity on heat transfer characteristics within the porous media. Additionally, to quantify epistemic uncertainty in predictions, arising from model formulation, numerical approximation, and learning dynamics, Monte Carlo dropout is employed during inference, enabling estimation of a 95
Seasonal rainfall variability over Southern Peninsular India was investigated using long-term observational data within a fuzzy-relational and scaling framework. Interdependence among pre-monsoon, summer monsoon, and post-monsoon rainfall was revealed, with fuzzy relations involving the summer monsoon playing a central role. Moderate rainfall regimes exhibited more coherent fuzzy-relational patterns than extreme rainfall classes, which were characterized by greater dispersion. Multifractal detrended fluctuation analysis of summer monsoon rainfall indicated predominantly anti-persistent behavior, with Hurst exponent values remaining below 0.5 across most temporal scales, reflecting mean-reverting and non-deterministic dynamics. Taken together, these findings highlight the utility of fuzzy-relational measures and demonstrate their dynamical consistency with the intrinsic temporal structure of monsoon rainfall.
In this article, DFT-based simulation code WIEN2K illustrates optoelectronic as well as transport properties of Rb2NaXCl6 (where X = Sb, As). The analysis begins with a structural assessment, where both materials were confirmed to crystallize in a highly symmetric cubic structure (space group Fm-3 m). Thermodynamic stability is validated through significantly negative formation and cohesive energies, implying both compounds are energetically favorable and structurally viable for practical synthesis. The investigation of mechanical behavior reveals that these halide double perovskites satisfy the Born stability conditions, ensuring resilience under small elastic deformations. Parameters such as bulk modulus, shear modulus, Young’s modulus, and Poisson’s ratio point to moderately soft, slightly ductile, and structurally adaptable materials. Electronic structure analysis discloses that both materials have direct wide-bandgap semiconductors, with energy gaps of 3.05 eV (Rb2NaSbCl6) and 3.15 eV (Rb2NaAsCl6). The projected density of states (PDOS) reveals that the valence band is primarily composed of Cl-p orbitals, while the conduction band edge arises from Sb-p or As-p states, respectively. This orbital distribution influences the overall electronic transitions and light-matter interaction profiles. Optical property evaluations reinforce the electronic findings. Furthermore, thermoelectric characteristics are evaluated in the temperature range of 300 to 800. Because of their high ZT values, these halides are appropriate for thermoelectric applications at high temperatures. For thermoelectric generators and other renewable energy sources, this makes them crucial. The insights gained from this theoretical exploration offer a foundational platform for further experimental validation and material optimization strategies aimed at realizing high-performance, lead-free solar energy systems.
This study investigates the physical and thermoluminescence (TL) properties of pure SrGd2O4 and Eu-doped SrGd2O4 nanoparticles synthesized using the sol-gel method. Following annealing at 1000 °C, both materials crystallized into a pure orthorhombic phase, as confirmed by X-ray diffraction (XRD) analysis. The structural and morphological characteristics were further analyzed using Fourier-Transform Infrared spectroscopy (FT-IR), UV–visible spectroscopy, Atomic Force Microscopy (AFM), and TL techniques. The results confirmed successful incorporation of Eu3+ ions into SrGd2O4 lattice. AFM analysis revealed irregularly shaped nanoparticles with sizes ranging from 12 to 16 nm. UV–Visible spectroscopy was employed to determine the optical band gap, which ranged from 3.624 eV for pure SrGd2O4 to 2.679 eV for Eu-doped SrGd2O4 (0.15 g). TL measurements were conducted using both beta and gamma irradiation sources. Samples exposed to gamma rays exhibited two distinct glow peaks at approximately 114 °C and 165 °C, whereas those irradiated with beta rays showed no significant TL response. The observed concentration quenching of TL intensity with increasing Eu3+ content is attributed to enhanced non-radiative recombination processes within the host lattice. Furthermore, the analysis indicated that multipolar interactions between Eu3+ ions were primarily responsible for this quenching behavior. These findings provide valuable insights into the structural and optical characteristics of SrGd2O4 based nanoparticles and support their potential application in TL dosimetry.
Lead-free halide double perovskites are attracting significant attention as environmentally benign alternatives to conventional Pb-based perovskites for advanced optoelectronic and photovoltaic applications. In this study, the structural, electronic, mechanical, and optical properties of the inorganic cubic double perovskite K2CuSbCl6 were systematically investigated using density functional theory (DFT) within the CASTEP package. The optimized crystal structure exhibits excellent thermodynamic and structural stability, evidenced by negative formation energy of − 3.23 eV/atom and a Goldschmidt tolerance factor of 0.98. Dynamical stability was further confirmed through phonon dispersion calculations, which showed no imaginary phonon modes. Electronic structure analysis identifies K2CuSbCl6 as an indirect-bandgap semiconductor with bandgaps of 0.655 eV (GGA-PBE), 0.45 eV (GGA-PBE + SOC), and 0.93 eV (HSE06). The valence band is primarily composed of Cu-d and Cl-p hybridized orbitals, while Sb-p states dominate the conduction band. Elastic calculations satisfy the Born stability criteria, revealing a mechanically stable, ductile, and anisotropic material with a Pugh’s ratio of 3.42 and a Poisson’s ratio of 0.366. Optical analysis demonstrates strong visible-to-near-infrared absorption, a static dielectric constant of 6.54, and a refractive index of 2.55, indicating efficient light-harvesting capability. These findings establish K2CuSbCl6 as a promising lead-free material for sustainable photovoltaic and optoelectronic devices.
The present analysis examines the parametrized Hubble parameter (HP) to address the field equations (FEs) relevant to cosmic scenarios within the confines of f( R,T) gravity. We assessed the model’s predictive capability using Bayesian Markov Chain Monte Carlo (MCMC) techniques, analyzing 58 H( z ) data points and updated SN Ia (Pantheon+) samples that embrace 1,701 points, in addition to 8 baryon acoustic oscillation (BAO) values derived from late-time cosmic observations. This analysis aimed to establish restrictions on the model’s parameters. The results from the behavior of the cosmographic parameters suggest that the Universe is grappling with seamless expansion, shifting from earlier stages of deceleration to an accelerating trend in both the near and distant future. We utilized statefinder diagnostics followed by Om( z ) diagnostics for assessing the phase evaluations. Energy conditions (ECs) further substantiate the dominance of energy density in the rapidly expanding Universe, while the squared sound speed ( v_s^2) component demonstrates the model’s stability at present times. We also calculated the universe’s age. Our findings are consistent with observational data, suggesting that the proposed parametrization may effectively elucidate the rapidly expanding Universe by incorporating the evolution of energy components.
Nanocomposites of yttrium oxide/magnetite (Y2O3/Fe3O4) were prepared by sol–gel method with different concentrations of magnetite (0, 20, 25, 30, 35 and 100 wt
