The European Physical Journal Plus最新文献

This paper is concerned with the integrable multi-dimensional Boussinesq-type equation formulated by Wazwaz, a model capable of describing shallow-water and other nonlinear propagation phenomena, with applicability to simulating wave propagation dynamics in oceanography and atmospheric science. Initially, in the long-wave limit we construct lump solutions, which describe algebraically localized solitary wave patterns in shallow water, identify and quantify the key parameters that control the peak amplitude of shallow-water waves, and characterize the associated propagation dynamics. Subsequently, by introducing a complex conjugation method, we derive breathing wave solutions. To generate soliton molecules, a velocity resonance condition is applied to the N-soliton solutions, which reveals stable configurations arising in the propagation of shallow-water waves described by this model. Furthermore, by imposing appropriate constraints on the N-soliton solutions, we derive Y-type soliton solutions, thereby broadening the collection of explicit solutions available for this equation.

For gravity assist space probes, the trajectory shows phenomenological anomaly on the position and velocity being interacted with the spacetime manifested by a planet. The anomalous velocity deviation of this osculating planetary flyby attracts enough attention as a problem of general relativity. In connection with the rotating weak-field massive source, the Lense-Thirring metric is diagonalised to find the equation of motion from action invariance Hamilton principle in the pure general relativistic theory. The computation for a near Earth flyby hyperbolic trajectory justifies theoretically the energy anomaly over the asymptotic in and out velocity obeying Anderson’s empirical formula!

We study stochastic resonance (SR) of a dimer, confined in a bistable potential, in the presence of two types of Gaussian colored noise: (i) Ornstein–Uhlenbeck (OU) noise and (ii) power-limited (PL) colored noise. Under the influence of OU noise, the occurrence of SR is delayed, as the correlation time, τ, increases. On the other hand, in the case of PL-colored noise, the SR peak shows a non-monotonic variation with increasing correlation time, τ. Interestingly, a double peak resonance in the input energy as a function of the correlation time, τ, is observed, indicating the presence of multi-resonance. This suggests an enhancement of stochastic resonance driven by this type of colored noise.

Fluctuation theorems, such as the Jarzynski equality and the Crooks relation, are effective tools connecting non-equilibrium work statistics and equilibrium free energy differences. However, detailed hands-on, reproducible protocols for implementing and analyzing these relations in real experiments remain scarce. This tutorial provides an end-to-end workflow for measuring, validating, and applying fluctuation theorems using a single-beam optical tweezers setup. It introduces the foundational ideas and consolidates practical calibration (PSD-based trap stiffness and position sensitivity), protocol design (forward/reverse finite-time drives over multiple amplitudes and durations), and robust estimators for free energy difference and dissipated work, highlighting finite sampling and rare event effects. We demonstrate the procedures using an extensive set of measured trajectories under different conditions and provide openly accessible datasets and Python code, enabling new researchers or educators to reproduce the results with minimal effort. Beyond pedagogical validation, we discuss how these recipes translate to broader soft-matter and mesoscopic contexts. By combining user-friendly instruments with clear and transparent analysis, this work promotes the education and reliable adoption of stochastic thermodynamic methods in the curricula of physics and chemistry, as well as among emerging research teams.

This study examines correlations between COVID-19 infections and deaths in six countries across six continents (Afghanistan, Costa Rica, Colombia, Australia, Algeria, and Germany). Using a sigmoid dose–response model, we relate cumulative infections, (t), to cumulative deaths, D(t), treating deaths as a time-delayed response to the spread of infection through transmission networks. Both I(t) and D(t) follow modified sigmoidal equations, which we apply to N consecutive epidemic waves. Pearson (r) and Spearman (r_s) correlation coefficients highlight strong correlations between the parameters of I(t) and D(t). We identify empirical laws linking infection parameters to death parameters, leading to a mortality equation D(t) expressed as a function of infection-related parameters. We also establish a novel expression for the epidemic fatality rate (beta_{f}). Cross-correlation analysis of infection and death spread rates ((V_{I} (t)) and (V_{D} (t))) reveals an average time lag (Delta t) of 7–24 days across the six countries. The average fatality rate (leftlangle {beta (t)} rightrangle) ranges from 0.16 to 3.92%.

Turbulent boundary layer trailing-edge noise can be effectively suppressed by mounting an array of finlets on wind turbine blades inspired by the unique comb-like structures on owl wings. This work numerically investigates the noise reduction effects of finlets with fixed spanwise spacing arranged at different positions along the chordwise direction on the suction side of the NACA0018 airfoil without finlets (Baseline). Large Eddy Simulation (LES) and Ffowcs-Williams and Hawkings (FW-H) acoustic analogy integral formula are employed to calculate the flow field and far-field noise under a Reynolds number of (2.63 times 10^5) and an angle of attack of 0(^{circ }). The results show that all nine finlet-equipped UP-x% airfoils (finlets installed at x%c position from the trailing edge of NACA0018, in 5% increments) can markedly reduce noise without causing a noticeable change in aerodynamic performance significantly. Flow field analysis reveals detailed physical mechanisms of noise reduction: (1) Finlets lift-up the most energetic turbulent eddies away from the boundary layer thereby significantly weakening the edge scattering phenomena. (2) Flow velocity decreases after passing the finlets. (3) Large-scale turbulent vortices are effectively broken down into smaller structures. Especially, among nine finlet-equipped airfoils, UP-20% achieves the optimal noise reduction performance with a far-field overall sound pressure level (OASPL) attenuation of 15.4 dB relative to the baseline within 20-20,000Hz. This is attributed to the highest turbulent kinetic energy (TKE) region near 20%c, wherein the finlets effectively disrupt turbulence partly reflected in 35% reduction of TKE near the trailing edge, thereby conducive to noise suppression.

BUTTON-30 is a neutrino detector demonstrator located in the STFC Boulby underground facility in the north-east of England. The main goal of the project is to deploy and test the performance of the gadolinium-loaded water-based liquid scintillator for neutrino detection in an underground environment. This will pave the way for a future large-volume neutrino observatory that can also perform remote monitoring of nuclear reactors for nonproliferation. This paper describes the design and construction of the watertight optical modules of the experiment.

We present a systematic study of wave propagation in Kerr spacetime using a post-Minkowskian expansion within the harmonic coordinate system. For scalar, electromagnetic, and gravitational waves, we derive the complete second-order analytic solutions for the wave vector components and the trajectory parameterized by an affine parameter. Building upon these detailed kinematic solutions, we further obtain a general second-order analytic formula for the gravitational time delay experienced by a wave traversing an arbitrary path in this curved spacetime. This work establishes a necessary foundation for high-precision modeling of wave phenomena, such as gravitational lensing and signal timing, in the strong gravitational fields of rotating black holes.

We present an investigation of the effect of the wavelength on the optical and morphological properties of silver nanoparticles (AgNPs) prepared by laser ablation in liquid. A nanosecond Nd:YAG laser was used with various wavelengths (532, 1064, and 1320 nm) to ablate a pure Ag target and generate AgNPs in liquid. The prepared colloidal nanoparticles were characterized by means of UV–Vis-NIR, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) techniques. TEM and SEM micrographs demonstrated significant modification in the size, shape, and distribution of the AgNPs when the ablation wavelength is adjusted. It is found that the mean diameter of AgNPs decreases with increasing ablation wavelength; a mean diameter of 20 nm of the spherical Ag nanoparticles was recorded at 1064 nm ablation wavelength. UV–Vis-NIR spectroscopy revealed a tangible effect of ablation wavelength on the absorption spectra of the samples, where the optical band gap exhibited increases when ablation wavelength is increased. Further analysis for the absorption spectra of the samples was conducted by modelling the spectra to Gaussian distribution to estimate the inhomogeneous broadening, radiative time, and optical absorption cross section of the samples at different ablation wavelengths. These findings confirm the possibility of modifying the optical and morphological characteristics of AgNPs prepared by PLAL. Finally, the AgNPs samples prepared in this study are good candidates for photocatalytic and photonic applications.

Rare-earth tritellurides RTe(_{3}) exhibit a wide spectrum of electronic proprieties, ranging from charge density wave (CDW) phenomena to superconductivity. Angle-resolved photoemission spectroscopy (ARPES) is a valuable technique for probing alterations in band structure and symmetry associated with CDW formation. Although ARPES offers several advantages, acquiring an accurate two-dimensional band map in the momentum space is always challenging. In this paper, we use image processing techniques on ARPES data to precisely calculate the size of the residual electron pockets in RTe(_{3}) compounds. Then, the results are compared with measurements of slow quantum oscillations to evaluate their nature at temperatures below the second CDW transition, T(_{text {CDW2}}). The close correspondence between the two approaches clarifies the nature of the surviving metallic states and demonstrates the utility of image segmentation methods for refining ARPES-based electronic structure analysis.