Wall pressure fluctuations (WPFs) over aerodynamic surfaces contribute to the physical origin of noise generation and vibrational loading. Understanding the generation mechanism of WPFs, especially those exhibiting extremely high amplitudes, is important for advancing design and control in practical applications. In this work, we systematically investigate extreme events of WPFs in turbulent boundary layers and the compressibility effects thereon. The compressibility effects, encompassing extrinsic and intrinsic ones, ranging from weak to strong, are achieved by varying Mach numbers and wall temperatures. A series of datasets at moderate Reynolds numbers obtained from direct numerical simulation are analysed. It is found that the intermittency of WPFs depends weakly on extrinsic compressibility effects, whereas intrinsic compressibility effects significantly enhance intermittency at small scales. Coherent structures related to extreme events are identified using volumetric conditional average. Under extrinsic compressibility effects, extreme events are associated with the weak dilatation structures induced by interactions of high- and low-speed motions. When intrinsic compressibility effects dominate, these events are associated with the strong alternating positive and negative dilatation structures embedded in low-speed streaks. Furthermore, Poisson-equation-based pressure decomposition is performed to partition pressure fluctuations into components governed by distinct physical mechanisms. By analysing the proportion of each pressure component in extreme events, it is found that the contributions of the slow pressure and viscous pressure exhibit weak dependence on the compressibility effects, especially the extrinsic ones, and the varying trend of contributions of the rapid pressure with compressibility effects is opposite to that of the compressible pressure component.

Aerothermal issues in hypersonic transitional swept shock wave/boundary-layer interactions (SBLIs) are critical for the structural safety of high-speed vehicles but remain poorly understood. In this work, previously scarce, high-resolution heat transfer distributions of the hypersonic transitional swept SBLIs, are obtained from fast-responding temperature-sensitive paint (fast TSP) measurements. A series of $34^\circ$ compression ramps with sweep angles ranging from $0^\circ$ to $45^\circ$ are tested in a Mach 12.1 shock tunnel, with a unit Reynolds number of 3.0 $\times$ 10$^{6}$ m$^{-1}$. The fast TSP provides a global view of the three-dimensional aerothermal effects on the ramps, allowing in-depth analysis on the sweep effects and the symmetry of heat transfer. The time-averaged results reveal that the heat flux peak near reattachment shifts upstream with decreasing amplitude as the sweep angle increases, and a second peak emerges in the $45^\circ$ swept ramp due to a type V shock–shock interaction. Downstream of reattachment, the heat flux streaks induced by Görtler-like vortices weaken with increasing sweep angle, whereas their dominant projected wavelengths show little dependence on sweep angle or spanwise location. Away from the ramp’s leading side, the transition onset of the reattached boundary layer gradually approaches the reattachment point. Finally, a general quasi-conical aerothermal symmetry is identified upstream of reattachment, although spanwise variations in transition onset, shock–shock interaction and heat flux streaks are found to disrupt this symmetry downstream of reattachment with varying degrees.

This paper focuses on six-degree-of-freedom (six-DOF) spatial cable-suspended parallel robots with eight cables (8-6 CSPRs) because the redundantly actuated CSPRs are relevant in many applications, such as large-scale assembly and handling tasks, and pick-and-place operations. One of the main concerns for the 8-6 CSPRs is the stability because employing cables with strong flexibility and unidirectional restraint operates the end-effector of the robot under external disturbances. As a consequence, this paper attempts to address two key issues related to the 8-6 CSPRs: the force-pose stability measure method and the stability sensitivity analysis method. First, a force-pose stability measure model taking into account the poses of the end-effector and the cable tensions of the 8-6 CSPR is presented, in which two cable tension influencing factors and two position influencing factors are developed, while an attitude influence function representing the influence of the attitudes of the end-effector on the stability of the robot is constructed. And furthermore, a new type of workspace related to the force-pose stability of the 8-6 CSPRs is defined and generated in this paper. Second, a force-pose stability sensitivity analysis method for the 8-6 CSPRs is developed with the gray relational analysis method, where the relationship between the force-pose stability of the robot and the 14 influencing factors (the end-effector’s poses and cable tensions) is investigated to reveal the sequence of the 14 influencing factors on the force-pose stability of the robot. Finally, the proposed force-pose stability measure method and stability sensitivity analysis method for the 8-6 CSPRs are verified through simulations.

We derive the exact asymptotics of $\mathbb{P} {\{\sup\nolimits_{\boldsymbol{t}\in {\mathcal{A}}}X(\boldsymbol{t})>u \}} \textrm{ as}\ u\to\infty,$ for a centered Gaussian field $X({\boldsymbol{t}}),\ {\boldsymbol{t}}\in \mathcal{A}\subset\mathbb{R}^n$, $n>1$ with continuous sample paths almost surely, for which $\arg \max_{\boldsymbol{t}\in {\mathcal{A}}} {\mathrm{Var}}(X(\boldsymbol{t}))$ is a Jordan set with a finite and positive Lebesgue measure of dimension $k\le n$ and its dependence structure is not necessarily locally stationary. Our findings are applied to derive the asymptotics of tail probabilities related to performance tables and chi processes, particularly when the covariance structure is not locally stationary.

The emergence, on the Loess Plateau of Central China, of settlements enclosed by circular ditches has engendered lively debate about the function of these (often extensive) ditch systems. Here, the authors report on a suite of new dates and sedimentological analyses from the late Yangshao (5300–4800 BP) triple-ditch system at the Shuanghuaishu site, Henan Province. Exploitation of natural topographic variations, and evidence for ditch maintenance and varied water flows, suggests a key function in hydrological management, while temporal overlap in the use of these three ditches reveals the large scale of this endeavour to adapt to the pressures of the natural environment.

This paper presents the first reported design of a balanced nonreciprocal bandpass filter with both common-mode (CM) and differential-mode (DM) reflectionless characteristics. The nonreciprocal behavior is achieved using a time-modulated resonator, which isolates in-band backward interference signals, thereby protecting preceding circuits from their negative effects. To solve the negative effects of reflected waves of the reflection-based CM noise suppression and reflection-based DM stopband attenuation, CM and DM reflectionless structures are integrated at both the input and output ports, ensuring reflectionless operation for both CM and DM signals. Meanwhile, the implementation of DM reflectionless characteristics effectively addresses the issue of reflection zero degradation typically observed in time-modulated resonator-based nonreciprocal filters. The proposed filter exclusively transmits differential forward signals, which will greatly improve the anti-interference ability and stability of the balanced RF circuits. To validate the concept experimentally, a 1.5-GHz microstrip prototype is designed, simulated, fabricated, and characterized.

Natural enemies serve a crucial role in crop protection through the regulation of pest population dynamics. Cyrtorhinus lividipennis is an important natural enemy of rice planthoppers. Fatty acid synthase (FAS), a multifunctional enzyme crucial for fatty acid biosynthesis, serves as a vital energy source for insect reproduction. However, the function of FAS in the reproductive processes of C. lividipennis remains incompletely understood. In this study, the ClFAS gene was successfully cloned from C. lividipennis. The open reading frame of ClFAS was 7224 bp, encoding a putative protein of 2407 amino acids. The expression levels of ClFAS were notably elevated in the fifth-instar nymphs, adults, as well as in the fat body and ovaries of female individuals. Silencing of ClFAS resulted in a reduction of 58.4%, 34.6%, and 49.0% in the expression levels of ClVg at 1-, 2-, and 3-days post-dsRNA injection, respectively. Furthermore, RNA interference (RNAi)-mediated depletion of ClFAS not only suppressed the Vg protein expression but also significantly impaired oocyte maturation and ovarian development. The fecundity of dsFAS-treated C. lividipennis females was markedly reduced by 49.5%, accompanied by significant decreases of 32.7% in oviposition duration and 26.3% in female adult lifespan. Our findings showed that ClFAS positively regulates the reproduction of C. lividipennis by promoting vitellogenesis and ovarian development, which provides valuable insights into how lipid metabolism governs fecundity in predatory insects.

As international exploration of the Meso-Neoproterozoic continues, these layers have become a key target for deep oil and gas field exploration. The Ordos Basin exhibits considerable sedimentary thicknesses within the Meso-Neoproterozoic. However, significant hydrocarbon discoveries have not been forthcoming, primarily due to the complex tectonic evolution. This paper focuses on the southern Ordos Basin, utilizing logging-seismic calibration to interpret seismic data and elucidate Meso-Neoproterozoic tectonic features. By comparing ancient and modern tectonic patterns, based on palaeotectonic maps retrieved through the impression method and combining these with tectonic evolution profiles, the study clarifies the history of tectonic modification. Under the control of two fracture systems – basin-controlling fractures at the margin and trough-controlling fractures – the Changchengian exhibits two categories (single-fault and double-fault) and five sub-categories of fault depression combinations. The study highlights significant differences between ancient and modern tectonics in the Meso-Neoproterozoic, which are attributed to various tectonic stages, including the trough-uplift depositional differentiation stage during the early rift-late depression of the Changchengian, the basin-margin subsidence stage of the southwestern depression of the Jixianian, the uplift and denudation stage of the Sinian basin’s main body and the four-stage tectonic remodelling stage of differential uplift-subsidence in the Palaeoproterozoic. This study employs the ancient-present tectonic pattern as a point of departure, thereby enhancing the theoretical understanding of deep-seated tectonics in the Ordos Basin. It offers novel insights into the exploration of Meso-Neoproterozoic gas reservoirs from a tectonic remodelling perspective.

6D pose estimation can perceive an object’s position and orientation in 3D space, playing a critical role in robotic grasping. However, traditional sparse keypoint-based methods generally rely on a limited number of feature points, restricting their performance under occlusion and viewpoint variations. To address this issue, we propose a novel Neighborhood-aware Graph Aggregation Network (NGANet) for precise pose estimation, which combines fully convolutional networks and graph convolutional networks (GCNs) to establish dense correspondences between 2D–3D and 3D–3D spaces. The $K$-nearest neighbor algorithm is integrated to build neighborhood relationships within isolated point clouds, followed by GCNs to aggregate local geometric features. When combined with mesh data, both surface details and topological shapes can be modeled. A positional encoding attention mechanism is introduced to adaptively fuse these multimodal features into a unified, spatially coherent representation about pose-specific features. Extensive experiments indicate that our proposed NGANet achieves a higher estimation accuracy on LINEMOD and Occlusion-LINEMOD datasets. In addition, its effectiveness is also validated under real-world scenarios.

Cosmogenic 7Be and 10Be are effective tracers for studying atmospheric dynamics and Earth’s surface processes, with over 90% of these isotopes reaching the surface via wet deposition. However, the characteristics and influencing factors of 7Be and 10Be wet deposition remain unclear in different regions, limiting the precision of these nuclides as tracers of environmental change. This study analyzes the annual variation of 7Be and 10Be wet deposition in Xi’an and examines the impact of precipitation on their deposition. Ultra-trace levels of 7Be and 10Be in precipitation were synchronously measured using state-of-the-art accelerator mass spectrometry. One-year (July 30, 2020 to September 3, 2021), high-frequency (individual rain events) and time-synchronized series of observations of 7Be and 10Be wet deposition data (n = 49) were analyzed. The total annual wet deposition fluxes of 7Be and 10Be in central China (34.22°N, 109.01°E) for 2020/21 were (218 ± 24) × 108 atoms·m–2·yr–1 and (314 ± 16) × 108 atoms·m–2·yr–1, respectively. Precipitation amount, intensity, and duration were quantitatively analyzed for their effects on total wet deposition flux, mean concentration, washout ratio, deposition velocity, and scavenging coefficient of 7Be and 10Be during individual rain events. The results indicate that precipitation amount is the most significant factor influencing the wet deposition flux of both nuclides.

This paper proposes a new surface fitting method based on double model comparison to solve the aspherical surface parameters, allowing for the simultaneous extraction of the surface deviation and the optimal surface fitting parameters for the radio antenna’s main reflector. This method employs the laser tracker to obtain the 3D coordinates of the points on the antenna surface, which can be expressed in terms of Zernike polynomials. Then compare the Zernike polynomial description with the ideal aspherical equation description to establish a discrepancy model in the optical design software. Finally, by optimizing this model, the optimal surface parameters can be obtained. The simulation results show that the method is suitable for high-precision fitting of aspherical surfaces with cone coefficient K in the range of [−4, 0.3], with the maximum deviation percentage of the radius of curvature at 0.036% and the cone coefficient at 0.14%. Experimental research is conducted on the 3.2 m sector sub-aperture spliced radio antenna; the fitted radius of curvature is 2012.3204 mm, the conic coefficient is −1.0476, and the Root Mean Square (RMS) is 0.6232 mm, confirming the adaptability of this method.

Ultra-thin liquid sheets generated by impinging two liquid jets are crucial high-repetition-rate targets for laser ion acceleration and ultra-fast physics, and serve widely as barrier-free samples for structural biochemistry. The impact of liquid viscosity on sheet thickness should be comprehended fully to exploit its potential. Here, we demonstrate experimentally that viscosity significantly influences thickness distribution, while surface tension primarily governs shape. We propose a thickness model based on momentum exchange and mass transport within the radial flow, which agrees well with the experiments. These results provide deeper insights into the behaviour of liquid sheets and enable accurate thickness control for various applications, including atomization nozzles and laser-driven particle sources.

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is a highly destructive polyvorous pest with a wide host range and the ability to feed continuously with seasonal changes. This destructive pest significantly damages crops and can also utilize non-agricultural plants, such as weeds, as alternative hosts. However, the adaptation mechanisms of S. frugiperda when switching between crop and non-crop hosts remain poorly understood, posing challenges for effective monitoring and integrated pest management strategies. Therefore, this study aims to elucidate the adaptability of S. frugiperda to different host plants. Results showed that corn (Zea mays L.) was more suitable for the growth and development of S. frugiperda than wheat (Triticum aestivum L.) and goosegrass (Eleusine indica). Transcriptome analysis identified 699 genes differentially expressed when fed on corn, wheat, and goosegrass. The analysis indicated that the detoxification metabolic pathway may be related to host adaptability. We identified only one SfGSTs2 gene within the GST family and investigated its functional role across different developmental stages and tissues by analysing its spatial and temporal expression patterns. The SfGSTs2 gene expression in the midgut of larvae significantly decreased following RNA interference. Further, the dsRNA-fed larvae exhibited a decreased detoxification ability, higher mortality, and reduced larval weight. The findings highlight the crucial role of SfGSTs2 in host plant adaptation. Evaluating the feeding preferences of S. frugiperda is significant for controlling important agricultural pests.

We present an experimental study on the effects of polymer additives on the turbulent/non-turbulent interface (TNTI) in a fully developed round water jet. The Reynolds number based on the jet diameter is fixed at $Re=7075$. The Weissenberg number $Wi$ ranges from 24 to 86. We employ time-resolved simultaneous particle image velocimetry and laser-induced fluorescence measurements to investigate the local entrainment and engulfment process along the TNTI in two regimes: entrainment transition and enhancement regimes. In polymer-laden jets, the TNTI fluctuates more intermittently in the radial direction and more ambient fluid can be engulfed into the turbulent region due to the augmented large scale motion. Though the contribution of engulfment to the total flux increases with $Wi$, engulfment is still not the major contribution to the entrainment in polymer-laden jets. We further show that the local entrainment velocity is increased in both regimes compared with the pure water jet, due to two contributions: polymer elastic stress and the more intermittent character of the TNTI. In the entrainment transition regime, we observe smaller fractal dimension and shorter length of TNTI compared with the Newtonian case, consistent with previous numerical simulations (Abreu et al. J. Fluid Mech. vol. 934, 2022, A36); whereas those in the enhancement regime remain largely unchanged. The difference between the two regimes results from the fact that the jet flow decays in the streamwise direction. In the entrainment transition regime, turbulence intensity is strong enough to significantly stretch the polymers, resulting in a smoother TNTI in the inertial range. However, in the entrainment enhancement regime, the polymer’s feedback is not strong enough to alter the fractal dimension due to the low elasticity. The above mentioned differences of entrainment velocity and TNTI in the entrainment reduction/transition and enhancement regimes also explain the reduced and enhanced spreading rate of the viscoelastic jet observed in previous numerical simulations and experiments (Guimarães et al. J. Fluid Mech. 2020,vol. 899, A11; Peng et al. Phys. Fluids, 2023, vol. 35, 045110).

This study explores an interesting fluid–structure interaction scenario: the flow past a flexible filament fixed at two ends. The dynamic performance of the filament under various inclination angles ($\theta$) was numerically investigated using the immersed boundary method. The motion of the filament in the $\theta$–$Lr$ space was categorised into three flapping modes and two stationary modes, where $Lr$ is the ratio of filament length to the distance between its two ends. The flow fields for each mode and their transitions were introduced. A more in-depth analysis was carried out for flapping at a large angle (FLA mode), which is widely present in the $\theta$–$Lr$ space. The maximum width $W$ of the time-averaged shape of the filament has been shown to strongly correlate with the flapping frequency. After non-dimensionalising based on $W$, the flapping frequency shows little variation across different $Lr$ and $\theta$. Moreover, two types of lift variation process were also identified. Finally, the total lift, drag and lift-to-drag ratio of the system were studied. Short filaments, such as those with $Lr\leqslant 1.5$, were shown to significantly increase lift and the lift-to-drag ratio over a wide range of $\theta$ compared with a rigid plate. Flow field analysis concluded that the increases in pressure difference on both sides of the filament, along with the upper part of the flexible filament having a normal direction closer to the $y$ direction, were the primary reasons for the increase in lift and lift-to-drag ratio. This study can provide some guidance for the potential applications of flexible structures.