Direct numerical simulations of spatially developing high-enthalpy hypersonic turbulent boundary layers are performed under non-catalytic wall-cooling conditions. Two distinct levels of chemical reactivity are considered, together with a chemically frozen case for reference. The main objective is to elucidate the underlying mechanisms of high-enthalpy turbulence–chemistry interactions and to develop reliable closure models for high-enthalpy hypersonic turbulent boundary layers. It is well established that high-enthalpy reactions have a negligible influence on the turbulent velocity statistics, and it is further shown here that this behaviour arises from the compensating effects. Specifically, the mean temperature is reduced by endothermic reactions, accompanied by a decrease in mixture molar mass, leading to an approximately unchanged mean density. Furthermore, the chemical time scale is found to be much larger than the large-eddy turnover time, resulting in strong linear correlations between the temperature and species mass fraction fluctuations. Consequently, the refined strong Reynolds analogy (RSRA) can be effectively extended from enthalpy to temperature and species mass fraction fluctuations in high-enthalpy hypersonic turbulent boundary layers. A correlation correction for RSRA is proposed, which corrects the breakdown of the original RSRA in the region near the mean temperature peak, while retaining good performance in the outer layer. An isobaric presumed probability density function model incorporating the correlation-corrected RSRA is further developed, which extends the applicability of the temperature-based presumed probability density function approach to stronger high-enthalpy conditions. This work contributes to the development of engineering models for turbulence–chemistry interactions in high-enthalpy hypersonic turbulent boundary layers.

High-resolution direct numerical simulation data of a turbulent plane jet at Reynolds numbers $ \textit{Re}_H= 10^4$ and $10^5$, based on the nozzle width, are employed to investigate the behaviour of the structure functions in the flow region with external intermittency. In the intermittent turbulent region, the conditional second-order longitudinal and transverse structure functions exhibit self-similar behaviour at small and intermediate scales. Moreover, as the order increases from the second to the sixth, the conditional higher even-order structure function profiles progressively deviate from self-similarity and the predictions of Kolmogorov’s universal equilibrium theory. The conditional third-order structure function only displays self-similarity within the small-scale dissipation range, albeit the range of self-similarity extends to progressively larger values of $r/\eta ^T$ for a higher Reynolds number, where $\eta ^T$ denotes conditional Kolmogorov length scale and $r$ is the separation distance. As the intermittency factor decreases, the unsteady term in the Kármán–Howarth equation becomes more significant, leading to a larger deviation from Kolmogorov’s $4/5$ law. The extrapolation results based on the empirical formula for the structure function $\langle \delta u^{\prime n}\rangle (r)$ indicate that the finite-Reynolds-number effect on the structure function may differ between the intermittent and fully turbulent regions. The structure functions in the intermittent region may follow the predictions of K41 theory, i.e. $\langle \delta u^{\prime n}\rangle (r) \sim r^{n/3}$, which is consistent with the results observed in the fully turbulent region. However, the realisation of Kolmogorov’s predictions is more difficult in the intermittent region than in the fully turbulent region and requires a much higher local Reynolds number. It is further found that the conditional third-order structure function profiles recover self-similarity at intermediate scales when the local Reynolds number exceeds $10^5$. These findings provide valuable insights into the understanding and modelling of mixing transition problems.

This work presents an integrated modelling study of fast-proton distributions generated by ion cyclotron range of frequency (ICRF) minority heating in the Experimental Advanced Superconducting Tokamak (EAST). Using a series of high-confinement (H-mode) discharges with increasing ICRF power levels from 0.8 to 2.4 MW, fast protons were produced via minority heating mechanisms and analysed through simulations using the ASCOT code. The results reveal that the fast protons are primarily concentrated near the fundamental cyclotron resonance layer and exhibit strong power-dependent behaviour in both real-space (R–Z) distribution and velocity space, where R is the major radius and Z is the vertical coordinate. As the ICRF power increases, the energetic proton population shows significant spatial broadening and energy enhancement, reaching up to 1 MeV. The fast-ion pitch-angle distribution becomes increasingly anisotropic, with high-energy ions concentrated around $|\textit{v}_{\|}/\textit{v}| \lt 0.5$, where $\nu$ is the magnitude (speed) of the full velocity vector of the particle. Furthermore, the energy density of fast ions aligns well with the ICRF power deposition profile, confirming efficient central-core heating. These findings, which provide insight into fast-ion behaviour and ICRF heating characteristics in EAST plasmas, also support future fast-ion diagnostics and performance control strategies in EAST and similar experimental conditions.

The mechanisms governing generation and amplification of laser-driven electromagnetic pulses (EMPs) in the picosecond (ps) regime remain insufficiently understood. Here, we present a unified theoretical and experimental framework that demonstrates dual-picosecond laser irradiation of solid targets can synergistically enhance EMP emission. By integrating particle-in-cell simulations with three-dimensional electromagnetic modeling, we reveal that the increasing laser focal power density amplifies hot electron emission and strengthens neutralization currents, leading to giant EMP radiations. Experimentally, we validate these predictions at the XG-III and SG-II U picosecond petawatt laser facilities, achieving a record-breaking EMP field strength of 3.08 MV/m – substantially exceeding previously reported values from ps-laser–solid interactions. Furthermore, we demonstrate that EMP characteristics can be precisely tuned via laser and target parameters, enabling controllable, high-field electromagnetic sources. Our findings provide deep insight into the physics of laser-driven EMP amplification and establish a robust platform for developing next-generation high-intensity electromagnetic emitters.

The equivalent source method (ESM) is one of the fundamental methods for reconstructing the far-field acoustic pressure and identifying the sources in aeroacoustics. However, it suffers from disturbances of near-field hydrodynamic pressure. We propose a hierarchical ESM (HESM) to suppress the disturbance by filtering out hydrodynamic pressure. The hydrodynamic pressure is filtered out using a frequency-domain convection operator. This operator replaces the prescribed convection velocity in Taylor’s frozen flow hypothesis with an adaptive complex convection velocity. The complex convection velocity is adapted in an iterative way to take into account the multiscale convection and spatial amplification of hydrodynamic pressure. The hydrodynamic pressure associated reconstruction error can thus be suppressed. The proposed HESM is compared with the Ffowcs Williams–Hawkings analogy method and the ESM that directly uses the pressure and the filtered pressure with the widely used uniform convection velocity. The use of complex convection velocity-based hydrodynamic pressure filtering mitigates the overprediction of acoustic pressure and enables precise reconstruction of both acoustic pressure directivity and spectra.

Quantifying the contribution of vortex structures to wall forces is essential for identifying the primary sources of forces. The traditional force-element method focuses on the contribution of flow structures to the resultant force. However, the contribution of flow structures to the distributed force cannot be identified. This work proposes a distributed force element method to address this issue. Inspired by the framework of matched asymptotic expansions, the method resolves the surface pressure by matching the fundamental solutions of the outer wave and inner flow regions. The pressure is thus decomposed into contributions from a convective acceleration term, a boundary acceleration term and a boundary vorticity term. The method is implemented by solving the resulting linear system with singular value decomposition. The volume source is further decomposed into direct radiation and boundary scattering components. It is found that compared with the direct radiation component, the boundary scatter component decays fast in the wake. Consequently, the direct radiation component is dominant in the far wake. A finite-domain pressure correction is proposed based on the direct radiation component. The distributed force element method is validated using several benchmark cases: two-dimensional configurations including laminar flow around stationary and oscillating circular cylinders; three-dimensional cases comprising laminar flow past a sphere, subcritical flow past a sphere and laminar flow over an inclined spheroid. The results suggest that the proposed distributed force element method enables the precise quantification of how flow structures in the wake and around the bluff bodies contribute to the surface pressure.

Strain rate and stress are widely regarded as crucial indicators for quantifying glacier dynamics on sub-monthly scales. However, existing frameworks for quality assessment of both strain rate and stress in fast-moving glaciers remain insufficient, hindering the application of rheological analysis to complex dynamic natural processes. To address this gap, we first extract and evaluate the surface velocity fields and their gradients from Sentinel-2A/B imagery using the Normalised Cross-Correlation (NCC) approach for Helheim Glacier, eastern Greenland. The results indicate that the minimum time threshold significantly affecting velocity gradients is 10 days for the Sentinel-2A/B missions, and that the threshold varies with season. We further develop a method based on error theory to enhance the retrieval accuracy of strain rate and stress at sub-monthly baselines, thereby supporting high-resolution dynamic research on Helheim Glacier. Our evaluations demonstrate the applicability of the NCC method to sub-monthly time scales and rapidly changing regions, thereby contributing to the quantification of glacier changes in a warming world.

This paper presents the first demonstration of a mid-infrared (MIR) Fe:ZnSe laser gain-switched by a non-critical phase-matched potassium titanyl arsenate optical parametric oscillator and amplifier at 3.47 μm. A novel improvement in slope efficiency was achieved by this new pump source, which significantly promoted the quantum efficiency compared to the conventional pump wavelength near 2.9 μm. The slope efficiency of 70.7% is a new record for Fe:ZnSe lasers with an output energy of 86 mJ and pulse width of 6.7 ns at 10 Hz. The output wavelength was tunable from 3.9 to 4.5 μm by changing the crystal’s temperature from 80 to 300 K. The influence of the pump beam size on transverse parasitic oscillation and crystal damage was investigated considering the dynamic absorption effect in Fe:ZnSe. This unique design provides an advancing and promising method of high-energy and short-pulse-width MIR lasers for extreme applications requiring both high-energy density and high-peak-power intensity.

Arabinoxylans (AX), the primary hemicellulose found in cereals and grasses, play a crucial role in regulating immunity, metabolism and various physiological processes, underscoring their value as essential components in dietary nutrition. Considering the extensive research on AX in piglet nutrition, this paper systematically reviews their impacts on gut health and microbiota in piglets, as well as the underlying mechanisms of action. AX have been shown to mediate gut barrier fortification through tight junction protein upregulation and orchestrate mucosal immunity homeostasis, consequently ameliorating early-weaning-associated diarrheal pathogenesis in piglets. Additionally, AX function as microbial ecological modulators through selective enrichment of beneficial commensal microbiota (e.g. Bifidobacterium spp. and Lactobacillus spp.), while simultaneously stimulating microbial biosynthesis of SCFA and ferulic acid exhibiting potent antioxidant and anti-inflammatory activity, thereby maintaining the intestinal health of piglets. This review offers valuable insights into their potential as a dietary intervention to support gut health and immune function in early-weaned piglets. However, most studies focus on single-source AX such as wheat or maize, with limited exploration of novel sources or comparative effects of source combinations. Future research should systematically investigate the molecular mechanisms of AX action, provide data-driven guidance for selecting AX sources in feed formulations and establish optimal inclusion levels in practical feeding regimens. Such efforts will further solidify the precision nutrition potential of AX in promoting sustainable and healthy growth in piglets.

In this study, we present a low-numerical-aperture (NA) confined-doped fiber architecture that synergistically mitigates transverse mode instability (TMI) through combined optical waveguide engineering and spatially tailored gain distribution. The individual and combined benefits of low-NA fiber design and the confined-doped fiber design strategy on TMI mitigation are numerically investigated. Building upon these theoretical analyses, a self-developed fiber, featuring a core/cladding diameter of approximately 26/400 μm, a core NA of approximately 0.045 and a core doping ratio of approximately 75%, is fabricated. Further experimental validation in a master oscillator power amplifier demonstrates 6.74 kW output power with near-single-mode (M${}^2\sim$1.49) beam quality, validating the design’s efficacy. This study establishes a novel fiber design paradigm that concurrently addresses TMI mitigation, beam quality maintenance and power scalability, offering a viable pathway toward robust high-power fiber laser sources with near-diffraction-limited beam quality.

The effects of the external intermittent behaviour on the Kolmogorov constants $C_{k1}$ and $C_2$ in spectral and the physical spaces are investigated using high-resolution direct numerical simulations of a turbulent plane jet. Well-defined $- 5/3$ energy spectrum and $2/3$ structure function can be found in the intermittent flows without large-scale vortex shedding. For different cross-wise positions, the profiles of conditional energy spectra and conditional structure functions exhibit self-similarity at small and intermediate scales when normalised by the conditional Kolmogorov scale of the turbulent region. The conditional Kolmogorov constants are close to those of the fully turbulent flow. The constants $C_{k1}$ and $C_2$ are found to have a power-law dependence on the intermittency factor $\gamma$, that is, $C_{k1}\sim \gamma ^{1/3}$ and $C_{2}\sim \gamma ^{1/3}$, except for the scaling of the structure function in the highly intermittent region with $\gamma =0.25$. In the highly intermittent region, e.g. $\gamma =0.25$, the scaling in the conditional structure function can be considerably influenced by the blocking/sheltering mechanisms of the turbulent/non-turbulent interface (TNTI), leading to slight deviations from self-similarity. We further confirm that the conditional structure function recovers self-similarity after excluding a turbulent region at an average distance of approximately $20$ Kolmogorov length scales from the outer edge of the TNTI, which is comparable to the mean thickness of the TNTI. These findings contribute to the modelling of the edge of a turbulent region.

In compressible turbulent boundary layers (CTBLs), the strong Reynolds analogy (SRA) refers to a set of quantitative relationships between temperature and velocity fluctuations. The essence of the SRA is the linear relationship between these fluctuations in large-scale motions. We investigate the transport processes of the second-order statistical moments associated with temperature and velocity fluctuations to reveal the physical mechanisms underlying this linear correlation. An important finding is that there exists a strong linear mechanism between the turbulent production of velocity and temperature fluctuations. Nonlinear mechanisms, such as the viscous-thermal dissipation, the work contribution, and particularly the pressure term, lead to the failure of the existing SRAs in the outer layer. Based on the above findings, a refined SRA (RSRA) is proposed, which better describes the quantitative relation between the temperature and velocity fluctuation intensities. An approximate expression for the turbulent Prandtl number under different Mach numbers and wall-cooling conditions is derived with the newly proposed RSRA. The relations proposed in this paper are validated through the direct numerical simulation data of flat-plate zero-pressure-gradient CTBLs at different Mach numbers and wall temperatures.

Coarctation of the aorta is characterised by narrowing of the descending aorta and is a rare cause of secondary hypertension in children and young adults. The aortic stenosis lesion is in a special location with severe consequences, and long-term survival is very low, with high rates of disability and mortality, and can be challenging to detect due to its few clinical manifestations. We report a case of a young patient with atrial fibrillation, renal infarction, and acute cerebral infarction, which are consequences of untreated hypertension due to coarctation of the aorta. The purpose of this report is to emphasize the importance of early diagnosis and management of coarctation of the aorta as a cause of secondary hypertension in children and young adults.

The aerodynamic sound generated by the oblique collision of two vortex rings is featured by the asymmetric emission associated with the octupole mode, which differs from the symmetric emission associated with the quadrupole mode observed in the coaxial collision of two vortex rings. This distinctive feature of aerodynamic sound is closely related to the tilting and reconnecting of the vortex rings. While previous studies have explored the effects of reconnecting on aerodynamic sound, this study specifically addresses the impact of vortex ring tilting. We propose a novel vortex sound formula to quantitatively assess the role of tilting in aerodynamic sound generation. The proposed formula relates the far-field sound pressure to equivalent circulations and vorticity centroids by referring to Truesdell’s consistency conditions for vorticity moments. The variations of the equivalent circulations and vorticity centroids in the oblique collision of two vortex rings under different configurations are analysed based on the numerical solution of the Navier–Stokes equations in the source region. It is found that the tilting of vortex rings results in a rapid change of the equivalent circulation associated with the vorticity in the collision direction. However, the change caused by titling is almost out of phase with that caused by reconnecting and deforming. The vortex tilting significantly reduces the aerodynamic sound associated with the longitudinal quadrupole and octupole modes, which is opposite to the role of vortex reconnecting that was reported in the oblique collision of vortex rings.