The European Physical Journal Plus最新文献

Metal–semiconductor junctions play a critical role in solar photovoltaic cells by enabling the conversion of light into electrical energy. However, the efficiency of these devices strongly depends on optimizing the M-S interface. This study investigates the performance of the Ag/p-Cu₂BaSnS₄/ ITO heterostructure, focusing on the impact of annealing temperature on its structural, optical, and electrical properties. CBTS thin films were deposited via the sol–gel dip-coating method and subsequently annealed using rapid thermal processing at different temperatures ranging from 673 to 773 K for 10 min. X-ray diffraction revealed a trigonal crystal structure with a pronounced (104) preferred orientation, while Raman spectroscopy confirmed phase purity through a dominant peak at 340 cm⁻¹. Field emission scanning electron microscopy showed a compact morphology with particle size variations influenced by annealing temperature. UV–Vis spectroscopy indicated a redshift in the absorption edge, corresponding to a bandgap reduction from 1.78 to 1.61 eV as the annealing temperature increased. Electrical characterization of the Ag/p-Cu₂BaSnS₄/ITO Schottky diode using current–voltage (I-V) measurements and thermionic emission theory revealed that annealing at 723 K yielded the best performance, with a rectification ratio of 800 and an ideality factor of 5.10. These parameters were further validated using the Cheung method. Impedance spectroscopy confirmed superior charge transport properties for films annealed at 723 K. Overall, the results demonstrate that the Ag/p-Cu₂BaSnS₄/ITO heterostructure holds strong promise for high-efficiency photovoltaic applications, with optimized annealing conditions significantly enhancing device performance.

Coherent Elastic Neutrino-Nucleus Scattering (CE(nu)NS) experiments face significant challenges from background radiation, particularly in above-ground or shallow-overburden environments. Passive shielding, commonly using lead (Pb), is deployed to suppress ambient (gamma)-ray backgrounds. However, such shielding can itself become a source of secondary backgrounds, mainly (gamma) and neutrons, generated by cosmic muon interactions, which can mimic CE(nu)NS signals and degrade experimental sensitivity. In this work, we quantify the rate of these muon-induced secondaries using a high-purity germanium (HPGe) detector in coincidence with plastic scintillator paddles, implementing a time-coincidence technique. The results offer key insights into the nature and rate of Pb-originated cosmogenic backgrounds. The measured mean characteristic time of 11 ± 4 (mu)s for the residual secondary background events agrees well with the Geant4-based Monte Carlo simulation result of 11 ± 1 (mu)s. The measured efficiency-corrected rate of muon-induced events in the HPGe detector is 34 ± 1 (stat.) ± 3 (sys.) (hbox {day}^{-1}) (hbox {kg}^{-1}) within the energy range of 30 keV to 2000 keV. The yield of muon-induced secondary backgrounds in 10-cm-thick Pb shielding is evaluated to be ((11 pm 1 (text { stat.}) pm 1 (text { sys.}))) secondary events(text {kg}^{-1} textrm{m}^{-2} text {muon}^{-1}) at sea level. These findings are essential for the design and background modeling of surface-based CE(nu)NS detectors and have broader relevance for underground experiments and low-threshold detectors used in neutrino, dark matter, and astroparticle physics research.

The steady-state quantum dynamics of a compound sample consisting of a semiconductor double quantum dot (DQD) system nonlinearly coupled with a leaking single-mode microresonator is theoretically investigated. The focus is on the resonance condition when the transition frequency of the DQD equals to the doubled resonator frequency, respectively, and the resulting interplay among the involved phonon or photon decay channels. As a result, the steady-state quantum dynamics of this complex nonlinear system exhibits a variety of possible effects that have been demonstrated here. Particularly, we have found the relationship between the electrical current through the double quantum dot and the microwave field inside the resonator, which is nonlinearly coupled to it, with a corresponding emphasis on their critical behaviours. Additionally, the quantum correlations of the photon flux generated into the resonator mode vary from super-Poissonian to Poissonian photon statistics, leading to single-qubit lasing phenomena at microwave frequencies.

This paper develops a compartmental mathematical model to study the transmission model exhibits nonlinear dynamical features, including feedback, threshold effects, and interactions between human and animal populations of the Ebola virus, formulated as an (S_{h}E_{h}I_{h}R_{h}S_{a}I_{a}) system that incorporates zoonotic spillover from animal reservoirs to human populations. Nonlinear interactions in the epidemic model produce rich dynamical behaviors, multiple equilibria, symbolic computation, stability theory, and robust nonlinear control are used to analyze these behaviors and to design effective strategies to mitigate outbreaks. The basic reproduction number (R_0) is derived using the next-generation matrix method, with local stability of both the disease-free and endemic equilibria analyzed through Jacobian-based techniques. Global stability (GS) of the disease-free equilibrium is established via the Metzler matrix approach, while a Lyapunov function is constructed to prove the GS of the DEE. A Nonstandard Finite Difference (NSFD) scheme is formulated to numerically simulate the system while preserving positivity, boundedness, and dynamical consistency. Sensitivity analysis identifies the human infection rate, animal-to-animal transmission rate, and animal mortality as key parameters influencing (R_0), guiding targeted intervention strategies. To mitigate the epidemic, an Integral Sliding Mode Controller (ISMC) is designed, which effectively reduces infection prevalence, stabilizes the system dynamics, and demonstrates robustness even under parameter uncertainties. Numerical simulations confirm that ISMC substantially lowers peak infections and helps maintain healthier human and animal populations. Overall, this integrated framework combining rigorous mathematical modeling, robust nonlinear control, and numerical simulations provides both theoretical insights and practical tools for understanding, forecasting, and controlling Ebola outbreaks, particularly in regions where zoonotic transmission plays a critical role.

Mpox remains a public health threat in parts of Africa, yet reliable forecasts are hindered by sparse and irregular daily case reports. This study applies a Bayesian Susceptible–Exposed–Infectious–Recovered (SEIR) modeling framework to investigate and forecast mpox transmission dynamics in South Sudan, the Democratic Republic of Congo (DRC), Rwanda, and Kenya. Reported case data were obtained from the Our World in Data repository, with observation windows ranging from 85 to 330 days depending on availability. Due to the sparsity and zero-inflation of daily incidence, cumulative case data were used to stabilize inference and improve parameter identifiability. Posterior estimates were derived for the effective transmission rate, recovery rate, overdispersion, and initial conditions, and epidemic forecasts were generated. The results reveal marked heterogeneity across countries. Rwanda and Kenya exhibited reproduction numbers ((mathcal {R}_{eff})) consistently above one, suggesting conditions for sustained community transmission, while DRC hovered close to the epidemic threshold ((mathcal {R}_{eff} approx 1.1)). In South Sudan, estimates indicated subcritical transmission ((mathcal {R}_{eff} < 1)), pointing to limited epidemic potential under current conditions. Forecasts captured uncertainty envelopes with both 50% and 95% credible intervals which suggest sustained epidemic growth in Rwanda and Kenya, near-threshold transmission in DRC, and limited spread in South Sudan. Projections captured both median trajectories and uncertainty bands, providing robust country-specific outlooks. These results inform preparedness and highlight the value of cumulative data for reliable forecasting in data-sparse settings. The results provide country-specific insights essential for tailoring interventions.

Photovoltaic arrays often operate in complex and harsh environments, making them susceptible to various types and severities of faults. To improve the diagnostic accuracy of PV array faults under adverse conditions, this paper proposes a fault diagnosis model integrating MIC feature selection with the MBKA-VMD-Transformer approach. Firstly, the MIC is employed to rank feature importance and conduct preliminary feature screening. Secondly, addressing the limitations of the traditional BKA in global exploration and local exploitation, several enhancements are introduced: SPM chaotic mapping, integration of sine–cosine algorithm, an adaptive inertia weight factor with cosine variation, and a tangent flight strategy. These modifications significantly enhance the optimization performance of the algorithm. Subsequently, the improved Black-winged Kite Algorithm is utilized to optimize the critical hyperparameters of VMD, using the ratio of Permutation Entropy to Mutual Information Entropy as the fitness function. The optimized VMD performs feature decomposition, and the intrinsic mode function with the highest energy is selected as the input to enhance feature representation. Finally, the MBKA-VMD-Transformer fault diagnosis model is constructed. Ablation and comparative experiments demonstrate that the model achieves a simulation diagnosis accuracy of 98.87% and a physical sample accuracy of 98.89%, representing significant performance improvements over the original Transformer model.

In this paper we study closed time-like curves (CTCs) in the space-time of black holes and black strings and investigate the effect of conical singularity on the extension of the CTCs. We consider the accelerating Kerr-Newman AdS/dS black holes in which the conical singularity comes from the acceleration (due to a pulling string or pushing strut) of the black hole. We show that by adding the acceleration to both AdS and dS solutions, CTCs extend to the region between the inner and outer horizons and the width of this region grows by increasing the acceleration. We also investigate the variations of rotation and electric charge of the black hole on the CTC region. Then we consider charged rotating black string solutions in the context of Maxwell, Born-Infeld and power Maxwell electrodynamics. We show that variations of the tension (which is related to the black string’s conical singularity) does not affect the CTC region considerably. By checking the null energy condition, we also find that the formation of these CTC regions need to the exotic matter, due to violation of the null energy condition. Moreover, we find that by setting adequate parameters, there is no CTC in the space-time of black string solutions of the power Maxwell electrodynamics. This means that one may consider the power Maxwell electrodynamics as a causality preserving theory.

The spontaneous creation of particle-antiparticle pairs from vacuum fluctuations under strong electromagnetic fields - known as the Sauter-Schwinger effect - represents one of quantum electrodynamics’ most profound nonperturbative predictions. A well-known difficulty, however, is that the time-dependent particle number defined via Bogoliubov transformations lacks an unambiguous physical meaning during the field’s evolution, becoming well-defined only once the external field is switched off. This raises the need for alternative observables that remain physically meaningful at all times. Here, we demonstrate that the vacuum polarization current provides such an observable. Focusing on scalar QED in ((1+1)) dimensions with a time-dependent Sauter field, we compute the polarization current and analyze its relation to the particle correlation function. We find that the current, unlike the particle number, does not saturate at late times but instead exhibits persistent oscillations around zero–a distinctive signature of scalar systems. Remarkably, this current is shown to be largely unaffected by the choice of adiabatic basis, underscoring its robustness as a probe of pair-creation dynamics.

Within the gauge-theoretic approach of gravity, the gauging of an enlarged symmetry of the tangent space in four dimensions allows gravity to be unified with internal interactions. We study the unification of the Conformal and Noncommutative (Fuzzy) Gravities with Internal Interactions based on the SO(10) GUT.

A new four-dimensional chaotic system based on a cosine flux-controlled memristor is proposed in this paper. This work introduces, for the first time, the cosine-type memristor into a CNN-based chaotic framework, enabling a distinctive nonlinear modulation mechanism that enriches the system dynamics. The developed system exhibits complex behaviors such as multistability, offset-boosting, and extreme sensitivity to initial conditions. Its dynamical properties are analyzed through equilibrium analysis, Poincaré sections, bifurcation diagrams, and Lyapunov spectra. Furthermore, an analog circuit and an FPGA-based digital implementation are constructed, both of which validate the correctness of the mathematical model. Finally, the proposed system is employed for chaotic synchronization, where a simple linear feedback controller achieves fast and robust synchronization performance.