Search Results (3,223)

To address the vibration reduction problem of the six-degrees of freedom(6-DOF) half-vehicle model and to improve ride comfort and handling stability, a piezoelectric stack actuator based on the inverse piezoelectric effect was introduced. A 6-DOF half-vehicle dynamic model coupling the cab, body, and wheels was established based on the Lagrange equation. Based on this model, a vertical-pitch dual sliding surface RBF neural network sliding mode control strategy was proposed, with two independent RBF neural networks designed to separately approximate, online, the comprehensive uncertainties in the vertical and pitch channels associated with unmodeled dynamics, external disturbances, and modeling simplifications. The variable-speed reaching law (dsat) function was used to design the sliding mode reaching law, balancing sliding surface convergence speed and vibration suppression. Six indicators, including vertical acceleration of the cab and vertical acceleration of the vehicle body, were selected as performance evaluation metrics to establish the fitness function. Combined with a genetic algorithm, the dual sliding surface coefficients, RBF network parameters, adaptive update rates, and variable-speed reaching law parameters were globally optimized. The vibration reduction effects of four schemes—passive control, traditional sliding mode control, RBF sliding mode control, and genetic algorithm optimized RBF dual-sliding-mode control—were compared and analyzed. Simulation results show that the genetic algorithm optimized RBF dual-sliding-mode control achieves improved vibration suppression in several key ride-comfort-related indices and provides better overall coordination among ride comfort, suspension working space, and tire dynamic deflection. The research results validate the effectiveness of this method and provide a new solution for addressing vehicle vibration reduction problems. Full article

Soft pneumatic robotic joints driven by low-cost on/off solenoid valves are attractive for lightweight and compliant robotic systems, but precise control remains challenging because continuous actuation commands must be realized through discrete valve states subject to minimum pulse-width constraints. This paper presents a model-based constrained equivalent-control PWM (C-EC) framework for a dual-chamber bellows actuator driven by four on/off valves. An ideal duty ratio is derived so that the averaged differential pressure rate matches the desired value required to impose first-order inner-loop error dynamics. To make this law physically implementable, the ideal duty is projected onto the feasible duty set determined by the minimum reliable pulse width of the valves. The resulting duty projection error is explicitly incorporated into a Lyapunov-based analysis, yielding a uniform ultimate boundedness result for the closed-loop system under the proposed implementation and an analytical comparison with conventional discrete sliding-mode control (D-SMC). The valve flow model is parameterized through PWM step-test-based sonic conductance identification. The proposed framework is implemented on a custom 1-DOF rotary joint based on an aluminum-film spiral-duct bellows actuator. Experiments show that C-EC does not uniformly dominate D-SMC over all operating conditions, but it improves $e_{\mathrm{RMS}}$ and $R_{\Delta P}$ in the medium-to-large positive-step regime and in long-hold regulation. In the representative 45${}^{\circ }$–65${}^{\circ }$–45${}^{\circ }$ step-hold test, C-EC reduced the RMS tracking error by 39.3% and the differential pressure ripple by 34.5% relative to D-SMC. In the 65${}^{\circ }$ long-hold test, the RMS tracking error and pressure ripple were further reduced by 35.4% and 37.9%, respectively. A loop-period comparison also showed that a 10 ms control period reduced duty projection and pressure ripple relative to 5 ms without degrading tracking accuracy. Full article

Intensive extraction in shallow coal seam groups poses a severe threat to regional hydrogeological stability. This study investigates the evolutionary laws of water-conducting fracture zone (WCFZ) height and phreatic level response at the Wanli No. 1 Mine. Although limited to a two-dimensional physical model and a single-case study, the research integrates field monitoring with similarity simulations to evaluate the efficacy of gangue grouting backfilling (GGB). The results reveal a significant superposition effect in dual-seam mining, where cumulative disturbances trigger the reactivation of upper-seam fractures, causing the WCFZ to penetrate the surface (170 m)—a phenomenon absent in single-seam mining. Scientifically, this work identifies a dual-threshold effect for ecological and structural preservation. While an equivalent filling rate (η) of 35% is sufficient to maintain the ecological water level in single-seam mining, dual-seam extraction requires a minimum η of 65% to restrict phreatic drawdown within the 1.5 m ecological threshold. Notably, while the laboratory model suggests a higher mechanical safety limit of η = 80% to prevent fracture propagation, the 65% threshold provides a balance between backfilling efficiency and environmental protection. The primary scientific contribution of this study is the quantification of the coupling relationship between overburden mechanical stability and long-term ecological functions. By shifting the overburden failure mode from “surface-penetrating fracturing” to “controlled bending subsidence,” this research provides a robust theoretical foundation for decoupling mining intensity from hydrogeological degradation in fragile multi-seam environments. Full article

This study focuses on the mechanical behavior of iron ore failings as base materials for roads. It is the first to systematically integrate freeze–thaw static load tests, SHPB dynamic tests, PFC discrete element microscopic simulation, and road stability analysis, to reveal the coupling mechanism of freeze–thaw, confining pressure and loading rate in cold environments, and to clarify the critical threshold of porosity and the safe threshold of failing content, as well as the intrinsic relationship between force chain evolution and macroscopic strength degradation. Firstly, a two-dimensional particle flow model of iron ore failing aggregates (150 mm × 150 mm, 11,530 particles) was constructed using PFC2D 2025 software, and the optimal microscopic parameters such as normal stiffness of 350 N/m and tangential stiffness of 175 N/m were determined (the error between simulation and experimental peak strength is less than 2.5%). The study revealed a negative correlation between high loading rate, local dense force chain and overall strength reduction. The initial porosity critical threshold is 0.23, and the optimal control range is 0.18–0.23 (this threshold varies with particle gradation). Secondly, taking iron ore failings from Lanzhou Daiquiri County, Sichuan Province, as the object, the static mechanical degradation law under freeze–thaw cycles (porosity from 7.5% to 9.5%, elastic modulus decreased by 52.3%, peak strength decayed by 13.0%) was clarified. The three-dimensional coupling effect of freeze–thaw times, confining pressure, and loading rate was investigated. The loading rate was also revealed (the average strength increased by 15% due to confining pressure, and the dynamic strength dropped to 110.2 MPa after 50 freeze–thaw cycles). Finally, the stability of the iron failing roadbed was analyzed, and it was found that the tailing content and safety factor FS(x) decreased linearly, the correction coefficient k(x) increased linearly, and the critical content was 66.67% (FS = 1.3), reaching the specification threshold. The poor tailing gradation led to insufficient stability, and stabilization agents were needed for improvement. This study did not investigate the long-term freeze–thaw durability, dissolution risks, and optimal dosage of the stabilizer, and thus has certain limitations. Full article

Firearm homicide is a leading cause of death among children and young men in the U.S. (ages 1–19), with young Black males in urban environments facing rates 18-to-24-fold higher than their non-Hispanic White peers in 2023. A key precursor to firearm violence victimization is weapon-carrying behavior (WCB), defined as carrying, concealing, or displaying firearms or other weapons in community or social contexts that elevate risk for injury, interpersonal threats, or law enforcement contact. Several structural, behavioral, and trauma-based risk factors fuel weapon-carrying. Yet these WCBs are rarely studied in tandem, leaving a critical gap in our understanding of these high-risk behaviors for youth. This cross-sectional study leveraged baseline data from a convenience sample of 226 violence-exposed urban young Black males, ages 15–24 (M_age = 18.3 years; SD = 3.1) enrolled in a trauma-informed digital firearm violence prevention pilot study. Eligibility required prior personal or witnessed experience of youth violence; reported prevalence therefore characterizes a high-risk subgroup rather than urban young Black males as a whole. Past-30-day weapon-carrying frequency was measured across five YRBS-aligned categories (0, 1, 2 to 3, 4 to 5, and 6+ days) and modeled as a categorical index under negative binomial regression. Associations with peer and community violence exposure, substance use, sociodemographic, and socioeconomic factors were estimated as incidence rate ratios (IRRs) with 95% CI. Past-30-day weapon carrying was reported by 42.5% of participants, with carrying frequency ranging from 1 day to 6 or more days. Participants reported high levels of direct victimization (64.8%), witnessing community violence (76.4%), and use of nonprescribed medications, including in instances preceding violence. In the fully adjusted model, indicators of violence exposure were the most consistent correlates of carrying. Direct victimization (IRR = 1.15, p < 0.05), general exposure to violence or aggression (IRR = 7.82, p < 0.01), and physical fighting (IRR = 1.11, p < 0.05) remained independently significant. Conversely, associations with substance use, dating aggression, and employment were attenuated, suggesting shared ecological vulnerability rather than independent causal pathways. Findings underscore the central role of chronic violence exposure and support the need for trauma-informed, multilevel prevention strategies in clinical and community settings. Full article

Engineered geothermal system (EGS) cross-well flow of 30 L/s producing heat at a rate of Q~20 MW for 30 days was achieved by the UtahForge project in 2024. The cross-well flow doublet measured ℓ~400 m in length at L~100 m vertical offset. A first-order question is how sustainable the doublet’s 20 MW heat extraction is. Where once the answer would be framed in terms of pipe-like cubic-law flow along stress-aligned fault-scale planar heat exchange surfaces, UtahForge flow data rule out this heat exchange picture. The EGS flow data indicate aquifer-like volumetric cross-well flow with heat exchange at the grain scale. More specifically, the EGS flow data indicate no cross-well flow for a dozen hydrofrack attempts, while the 30 L/s flow occurred when the 400 m doublet wells were rendered effectively open to the crustal formation by drilling out all hydrofrack gear. An essential further observation is that the producer well flowed at only 70% of the injector rate: 30% of injected fluid was lost to flow heterogeneity in the cross-well volume. A four-step deconstruction of these observations explicitly characterizes the flow heterogeneous volume: (i) flow stimulation of the cross-well volume, (ii)wellbore-centric flow in/out of cross-well volume along the 400 m open well reach, (iii) heat advection in the cross-well volume, and (iv) sustainability-specific heat conduction into the cross-well volume. EGS stimulation process step (i) is attested by microseismic emissions (Meqs) registered on downhole sensors. Meq size and spatial correlations in turn reflect the flow heterogeneity of the cross-well volume. EGS step (iv), crustal heat conduction sustainability, is approximated by assuming radial heat energy extraction at rate Q/ℓ by a central line-sink of radius R < L/2. The line-sink analytic solution yields heat reservoir sustainability of ~3–10 years. Greater sustainability at Q/ℓ rate requires larger cross-well offsets L. The intimate relation between fluid flow and seismic emissions enables downhole seismic sensor data to image EGS flow stimulation activity. The future of EGS heat extraction depends to a large degree on feasible sizes of cross-well offset L in the flow-heterogeneous crust. Full article

A robust speed controller integrating the slime mold algorithm (SMA) with sliding mode theory (SMT) is proposed for induction motor (IM) drives operating under field-oriented control (FOC). Unlike conventional controllers with fixed gain parameters, the proposed exponential reaching law sliding mode controller (ERLSMC) defines the sliding mode dynamic trajectory control gain, exponential reaching gain, and constant-speed reaching gain as the search space for the SMA. An adaptive fitness function based on the speed error and its rate of change is constructed to continuously evaluate and update these gain parameters, thereby determining the optimal controller gains according to the current operating state. Consequently, larger gain values are assigned when the system state is far from the sliding mode dynamic trajectory to accelerate the reaching process, whereas smaller gain values are adopted near the sliding mode dynamic trajectory to suppress chattering and reduce overshoot. Matlab/Simulink (2024b version) simulations are conducted to evaluate the proposed controller in an IM drive system and compare its performance with constant-speed reaching law sliding mode control, exponential reaching law sliding mode control, and zebra optimization algorithm (ZOA)-based ERLSMC methods. The simulation results demonstrate that the proposed controller achieves superior performance in both speed command tracking and load regulation response. Full article

Low-temperature conditioning is a key procedure in the flexibility evaluation of waterproofing membranes and directly affects the reliability of subsequent performance assessments. However, the internal unsteady-state heat transfer kinetics and the thermal gradient evolution mechanisms in multi-layer composite membranes under transient cold shocks require further investigation. Focusing on commonly utilized 3 mm and 4 mm thick SBS (Styrene–Butadiene–Styrene)-modified bitumen waterproofing membranes as subjects, this study investigated the internal dynamic temperature fields and microstructural response of bituminous waterproofing membranes under standard low-temperature flexibility testing conditions. By accurately pre-embedding micro-temperature sensors in situ at the interface between the surface layer and the reinforcement matrix, the transient thermal response profiles of specimens with varying specifications in a −25 °C liquid environment were quantified. Simultaneously, a three-dimensional transient heat conduction finite element model was established to elucidate the dynamic evolution of internal spatial temperature gradients. The congruence between experimental and numerical results demonstrates that upon exposure to extreme cold, composite membranes of different thicknesses exhibit a pronounced “surface-to-core” heat transfer lag effect. The cooling rate maximized within the initial 10 min of exposure. Conversely, the internal interface layer—acting as a high-thermal-resistance zone and the most unfavorable point for heat conduction—necessitated 10~20 min of nonlinear thermal dissipation to stabilize at the target ambient temperature. This study clarifies the transient thermal response and temperature-field evolution laws of bituminous waterproofing membranes, providing a robust theoretical framework for elucidating low-temperature embrittlement mechanisms and informing the material design and application of waterproofing projects in cold regions. Full article

To enhance the aerodynamic performance of Ti6Al4V functional components, this paper systematically investigated the femtosecond laser processing technology for surface drag-reduction microstructures, aiming to fabricate high-performance microstructures. (1) V-shaped, U-shaped, and rectangular micro-grooves were designed based on the boundary layer theory, and their drag-reduction mechanisms were elucidated through CFD numerical simulations. The results indicate that the V-shaped groove achieves a peak drag-reduction rate of 13.1% at a dimensionless depth of h⁺ = 15 and an aspect ratio of 1, primarily due to the formation of a low-velocity zone and the suppression of turbulent bursts by secondary vortices. (2) Through single-factor experiments, the influence laws of femtosecond laser process parameters on the V-shaped groove were explored. (3) Regression prediction models for groove dimensions were established using the Response Surface Methodology (RSM) to optimize the processing parameters. Under the optimized conditions, high-quality V-shaped groove arrays with a width of 55.9 μm and a depth of 55.5 μm were successfully fabricated on the Ti6Al4V surface, characterized by high consistency and a minimal heat-affected zone. This research provides an effective technical solution for the precision manufacturing of high-performance drag-reduction structures on titanium alloy surfaces. Full article

Biodiversity, as the foundation of life on Earth, sustains the balance of ecosystems and supports human sustainable development. However, the current accelerated decline in biodiversity poses ecological threats that require urgent attention. This research based on the perspective of ethnic ecological wisdom, explores the customary practices of biological conservation among the Miao ethnic group in Southwest China, the Tao ethnic group on Orchid Island (Lanyu), Taiwan, and the Maasai ethnic group on the East African Plateau. By conducting in-depth case studies, combined with literature review and data validation, it investigates their practical value and implementation pathways in biodiversity conservation. By analyzing the ecological conservation wisdom models of the Miao, Tao and Maasai ethnic groups, it is found that the core species populations in each region have shown a positive growth trend since the gradual integration of traditional ethnic customary laws with modern ecological protection systems and practices. Drawing on the extensive experience accumulated in integrating customary law into ecological governance across the three cases, this study proposes a three-dimensional optimization pathway: at the policy level, construct a mechanism integrating customary law and diversified ecological compensation; at the community level, implement a model featuring benefit sharing, patrol mediation and digital management; and at the cultural level, strengthen the development and dissemination of ethnic ecological conservation wisdom through multidisciplinary talent training and IP-based communication of exemplary customary law outcomes. We aspire to slow the rate of global biodiversity loss and achieve a bright future of harmonious coexistence between humans and nature. Full article

To elucidate the wear evolution and failure mechanisms of VL-type composite seals in aviation hydraulic actuators under multiple operating conditions, a two-dimensional plane-strain finite element model was developed for a VL seal consisting of a PTFE L-ring and an NBR O-ring. The model incorporated the Mooney–Rivlin hyperelastic constitutive law and the Archard wear model. The effects of O-ring compression ratio, hydraulic pressure, sliding velocity, and temperature on cumulative wear, wear rate, and contact state were systematically investigated. The results show that the compression ratio has a nonlinear influence on wear. Within 8–16%, the peak wear increases approximately linearly with compression ratio; above 16%, the peak wear reaches a plateau and a secondary wear zone appears, indicating a transition from single-contact to multi-contact sealing. Hydraulic pressure promotes wear over the range of 4–28 MPa, and at 28 MPa the opposite lip edge of the L-ring comes into contact with the cylinder wall, weakening the sealing effectiveness. Within 0.1–0.3 m/s, wear increases approximately linearly with sliding velocity. However, under high velocity and insufficient hydraulic pressure, the L-ring may undergo inversion, resulting in complete seal failure. Temperature exhibits a non-monotonic effect: material softening reduces local contact stress and wear from −55 to 80 °C, whereas excessive softening at 135 °C causes the peak wear rate to increase again. A parametric analysis scheme involving an increased L-ring height and thickness, a reduced O-ring cross-section diameter, and reserved deformation space raises the critical compression ratio for stable single-contact sealing from 16% to above 20%. These findings clarify the contact-stress/contact-area competition mechanism governing VL seal wear and provide guidance for the design of aviation hydraulic actuator seals. Full article

Composite laminates experience static and fatigue delamination, presenting significant challenges for failure prediction. This is critical in curved composites, where delamination behavior is complex to predict. In this study, fatigue tests were conducted on curved composite laminates under non-constant mixed-mode conditions. The testing setup involved a four-point bending test using L-shaped, unidirectional carbon-fiber-reinforced polymer curved beam specimens. A Teflon insert placed at the bend was used to initiate delamination. Experimental data acquisition included digital image correlation (DIC) to monitor delamination length during testing. This is important since it enhances subsequent model correlation. A virtual crack closure technique (VCCT)-based method for simulating fatigue-driven delamination under variable mixed-mode conditions was validated against experiments. Delamination growth was modeled using a Paris-like power–law relationship based on the strain energy release rate. The approach was implemented in Abaqus as a user subroutine, incorporating load ratio and mode mixity effects through VCCT-based mode separation. This study demonstrates accurate fatigue delamination prediction and highlights the role of optical measurements in experiments. The model improves our understanding of delamination propagation under varying mode mixity and contributes to structural integrity analysis. The results show how mode mixity influences delamination, impacting the performance and lifecycle of composite structures. Full article

Glass fiber/epoxy (GF/EP) composites are widely used in high-voltage electrical equipment due to their excellent specific strength, durability and dielectric properties. However, long-term exposure to hygrothermal environments will lead to performance degradation of the material, which seriously threatens its service reliability. To solve this problem, accelerated aging tests were systematically carried out in this study by immersing GF/EP specimens in deionized water at room temperature and 80 °C. The performance evolution laws and failure mechanisms of the material were investigated through moisture absorption kinetic analysis, tensile property testing, scanning electron microscope (SEM) fracture observation and breakdown voltage testing. The results show that the initial moisture absorption behavior of the material follows the Fickian diffusion mechanism, and the water diffusion rate at 80 °C is 31.8 times that at room temperature. After 35 days of aging, the retention rate of the maximum tensile force is 86.6% for the room temperature group, while it decreases to 38.2% for the 80 °C group. SEM observations show that the failure mode of the material changes from ductile fracture to brittle fracture after aging at 80 °C, accompanied by serious interfacial debonding. Temperature is the dominant factor for insulation performance degradation: the breakdown voltage retention rate is above 91% at room temperature, while it decreases to about 37% at 80 °C, and the influence of 60% maximum tensile force ($F_{\mathrm{m}\mathrm{a}\mathrm{x}}$) preloading is relatively small. This study provides experimental data and theoretical support for the performance evaluation and life prediction of GF/EP composites in harsh hygrothermal service environments of high-voltage electrical equipment. Full article

Deepwater shallow gas sediments and the weakly consolidated overburden are sensitive to depletion-induced effective stress redistribution. Since deepwater shallow gas has only recently begun to be treated as a commercially available natural gas resource, it lacks models to quantify the coupled flow and geomechanical behaviors in such environments. In this study, we propose a semi-analytical model for a shallow gas layer and its overburden sediments, where pore pressure evolution is described by vertical transient diffusion and the stress response is represented by an OCR-dependent (overconsolidation ratio-dependent) in situ stress field with depletion-induced effective stress increments. Pre-yield compressibility is characterized by a stress-dependent nonlinear elastic law, and post-yield deformation is approximated by a Mohr–Coulomb-based yield-controlled plastic correction for engineering purposes. The formulation is used in the base case and during a parametric sensitivity analysis. In the base case, the final settlement is 0.597 m, of which 45.3% is elastic and 54.7% is plastic. The sediments begin to yield after approximately 115 d of production, and the final yielded-thickness fraction reaches 0.268. The sensitivity analysis shows that friction angle, maximum drawdown, gas-layer thickness, and OCR magnitudes predominantly affect the final settlement and yielded-thickness response, while gas-layer permeability has an insignificant effect. Furthermore, the comparison reveals that the depletion timescale governs the stress evolution rate, while depletion pressure drawdown magnitude dictates deviatoric stress evolution and long-term settlement. Considering the engineering condition for the development of typical deepwater shallow sediments, the feasible production parameters should be in the low-to-moderate drawdown and slow depletion range. A practical operating window is approximately 3.6~4.0 MPa maximum drawdown with a depletion timescale of about 340~400 d. This study can provide quantitative insights into the potential commercial production of gas layers in deepwater shallow sediments. Full article

Modern UAV swarm operations face strict onboard bandwidth and autonomy constraints, making simultaneous multi-target interception under limited communication a critical unsolved challenge. This paper addresses three-dimensional cooperative interception of maneuvering targets by multiple unmanned aerial vehicles (UAVs) at prescribed line-of-sight (LOS) angles under limited communication resources. In the LOS direction, a fixed-time consensus-based guidance law is designed with remaining flight time as the coordination variable, synchronizing each UAV’s impact time to a freely specified desired value with bounded gains throughout the engagement. Unlike most existing fixed-time cooperative guidance works, the consensus convergence time is rigorously proven to be strictly less than the maximum initial predicted flight time, guaranteeing impact-time agreement is reached before any UAV intercepts the target—a necessary condition for genuine simultaneous salvo attack. A dynamic event-triggered (DET) mechanism is incorporated to reduce inter-UAV communication frequency by adaptively updating the triggering threshold according to consensus state evolution. In the LOS normal directions, a piecewise nonsingular terminal sliding-mode law ensures fixed-time convergence of the LOS angle and its rate to desired values under impact-angle constraints. Fixed-time stability and Zeno-behavior exclusion are rigorously established via Lyapunov analysis. Comparative simulations against existing methods demonstrate clear advantages in impact-time accuracy, guidance smoothness, and communication efficiency. Full article