Search Results (928)

This study revalidates retention robustness for one canonical closed pose of the 16-DoF LEAP Hand in the NVIDIA Isaac Lab. The task uses in-volume object placement, gravity-compensated closing, and an open-loop 15 cm vertical lift; it does not evaluate tabletop grasping, a learned grasp generator, or hardware performance. We verified physics-material relationships on 17 hand collision leaves, read back the runtime PhysX material buffer, and ran a matched material A/B check. We then screened 20 YCB objects and retained all 20 for a $5\times 3\times 3$ mass–friction–pose-noise factorial with 15 simulator repeats per object–cell. The 13,500 rows comprise 900 object–cells from 20 fixed objects; object identity is the inferential unit. The primary operational outcome combines the height/XY window with an object-level contact indicator and net-force threshold; the contact reporter aggregates all partners and does not certify hand-supported contact. The failure cascade assigned the incomplete_envelope label to 7474 rows (55.36%); a direct pre-lift distance check exceeded 0.12 m in 10,753/13,500 rows (79.65%), including 3271 validity-qualified successes. The label therefore does not estimate envelope-entry probability. The primary success rate was 42.20%; object-level success decreased with mass and pose noise, while the friction contrast across $\mu =0.3$–0.9 was near zero with an interval spanning zero. A 300-trial convex-hull check on four objects reduced the subset success rate from 66.00% to 33.00%, with strong object-level variation. These results are conditional on one pose and simulation protocol. Full article

Wheel lift-off under low gravity and rough terrain can degrade ride comfort and wheel–ground contact of manned lunar rovers. This study investigates whether an inerter-based suspension can improve vertical dynamics and contact retention. A Bekker-based equivalent wheel–regolith model was linearized around static equilibrium and incorporated into a dimensionless piecewise quarter-vehicle model with contact/separation switching. Parallel and series inerter–damper configurations were compared using frequency-response, lift-off-boundary, and time-domain analyses, and suspension parameters were optimized for rough-mare and rough-upland excitations. The series configuration exhibited a larger contact region and lower off-ground time over the investigated parameter range. After optimization, body-acceleration RMS decreased by 19.61% and 15.66%, contact-force RMS by 13.75% and 13.67%, off-ground time ratio by 59.5% and 24.5%, and lift-off counts by 42.8% and 45.5% for rough mare and rough upland, respectively, relative to the conventional suspension. These results show that appropriate inertance–damping matching can improve vertical vibration performance and wheel-contact retention under the prescribed lunar-terrain conditions. Full article

Large basins show substantial variation in the timing and persistence of hydrological responses to climatic forcing. Quantifying hydroclimatic lags and basin memory is important for understanding hydrological response dynamics, assessing drought persistence, and informing future research on drought prediction and water-resource management. This study presents a harmonised comparison of hydroclimatic response delays and hydrological memory across ten major European basins. Basin-scale Water Budgets (WBs) were derived from precipitation, evapotranspiration, and runoff components, while hydroclimatic forcing was represented by the Combined Climatologic Deviation Index (CCDI), based on precipitation anomalies and Gravity Recovery and Climate Experiment (GRACE) total water storage anomalies (TWSAs). Cross-correlation (CCF), autocorrelation (ACF), partial autocorrelation (PACF), and autocorrelation decay time (e-folding) were used to quantify response timing and persistence. The results show basin-specific differences in lag relationships and autocorrelation-based persistence. Estimated memory durations depend on the diagnostic used, highlighting the need to distinguish e-folding time, zero-crossing lag, and significance-decay lag. Because WB and CCDI share precipitation-related information, the observed cross-correlations are interpreted as statistical associations rather than direct evidence of causality. The findings provide a comparative assessment of hydroclimatic lag and persistence characteristics for the selected basins and study period; their predictive value requires separate validation. Full article

Ultrasound-enhanced sedimentation offers a robust strategy for microparticle separation in microfluidics. Triangular cross-sectional channels have recently emerged as a promising architecture because the acoustic radiation force and acoustic streaming-induced drag act synergistically toward the channel base—a force-field configuration unattainable in conventional rectangular or circular channels. However, quantitative relationships between operational parameters and continuous-flow sedimentation remain unexplored. Here, we systematically investigate how five parameters—volumetric flow rate, number of active transducers, active transducer length, driving voltage, and particle diameter—affect sedimentation efficiency in a triangular glass capillary. The number of active transducers is the most influential: dual-transducer operation sustains an outlet sedimentation efficiency—defined as the fractional particle removal relative to the inlet concentration—of ~77% sedimentation at 30 μL/min versus <30% for a single transducer. Flow rate shows a threshold near 27 μL/min for the baseline configuration, and increasing transducer length from 10 to 40 mm raises the measured maximum allowable flow rate from 15 to ~50 μL/min. A minimum of 19 V_pp is required for ≥80% efficiency. Ultrasound provides the greatest benefit for 5 μm particles (from <40% by gravity to >90%), while 20 μm particles gain less. A normalized sensitivity analysis offers design guidance for acoustofluidic sedimentation platforms. These findings establish quantitative design rules and confirm the feasibility of triangular-channel architectures. Full article

This study presents a comprehensive transient Computational Fluid Dynamics–Discrete Phase Model (CFD-DPM) investigation of aerosol and droplet transport in an air-conditioned office containing one infected occupant and three susceptible occupants. The transition from ventilation-controlled to gravity-dominated transport of respiratory aerosols in office settings remains poorly characterized. Continuous emission over 300 s was simulated for particle diameters of 1, 5, 10, and 50 µm. The continuous airflow field was resolved using the pressure-based solver, energy equation, and Shear Stress Transport k-ω turbulence model, validated against experimental temperature and relative humidity data with mean absolute errors of 0.59 °C and 1.26% relative humidity, respectively. The airflow model was validated against temperature and relative humidity data only; the discrete-phase predictions were not validated directly against experimental aerosol data. A critical finding is the identification of three distinct transport regimes: Regime I (1–5 µm), characterized by ventilation-dominated behavior with strong airflow coupling, approximately 50% outlet removal, and 38–39% airborne fraction at 300 s; Regime II (10 µm), representing a mixed-transition zone where gravitational effects begin to compete with aerodynamic forces; and Regime III (50 µm), dominated by gravitational settling with 93% deposition and only 1.6% outlet removal at 300 s. The critical transition diameter between ventilation-controlled and gravity-dominated transport was estimated to be approximately 20–30 µm based on interpolation between the 10 µm and 50 µm cases and dimensionless analysis; this estimate requires further validation with intermediate particle sizes. Dimensionless analysis revealed that particles with Stokes numbers below 0.1 remain strongly coupled to the airflow, while those exceeding 1.0 exhibit ballistic trajectories dominated by inertia and gravity. Outlet-2 consistently served as the dominant removal path for all particle sizes, confirming an asymmetric ventilation transport route attributable to the supply jet trajectory and recirculation patterns. Human 2 received the highest body-deposition fraction for aerosol-sized particles (0.287% for 1 µm, 0.123% for 5 and 10 µm at 300 s), identifying this location as a critical exposure zone. For 50 µm droplets, susceptible occupant deposition was negligible (<0.0005%) because gravitational settling deposited most mass on the floor (64.1%) and the infected occupant (25.5%) before far-field transport occurred. These findings establish a quantitative framework for designing ventilation systems that optimize removal of aerosol-sized particles while recognizing the inherent limitations of air extraction for droplet control. The proposed transport-regime classification provides a framework for HVAC engineers, with recommendations for return grille placement, air change rates, and supplementary source-zone controls for large droplets. These recommendations are derived from a single office geometry and ventilation configuration and should be validated across different room layouts, ventilation strategies, and operating conditions before being generalized. The methodology and findings contribute to the growing body of knowledge on airborne infection risk mitigation in occupied spaces, with direct applicability to post-pandemic building design and operation. Full article

Dry granular flow disasters occur frequently in mountainous areas. The impact of dry granular flow with giant boulders poses a serious threat to the stability of concrete bridge piers. In this study, physical model tests were combined with PFC-FLAC coupled numerical simulations to investigate the dynamic response of concrete bridge piers under the impact of dry granular flow with giant boulders. The force model of the giant boulders considering the boulder size (S) and the distance in front of the slope (L) was analyzed. The proposed method was validated through a dual comparison of the peak acceleration at the pier top (with a relative error of 30%) and the macroscopic accumulation morphology. The results showed that the method can effectively simulate the impact process of dry granular flow with giant boulders on bridge piers. It provides methodological support for parametric studies of the pier impact response at different boulder sizes. The acceleration time histories and accumulation morphologies obtained from the numerical simulations agreed well with the test results. The peak impact force on the pier in the X direction first decreased and then increased with the increase in boulder size, and the peak impact force was 4.89 × 10³ N when S = 15 cm. It first increased and then decreased with the increase in the distance in front of the slope; the peak impact force reached 5.04 × 10² N when L = 0.15 m, and the peak time was prolonged. The acceleration at the pier top increased with the increase in boulder size and decreased with the increase in the distance in front of the slope. The force analysis of the giant boulders indicated that the density of the dry granular flow and the boulder size are the key parameters controlling the forces acting on the boulders. The supporting force and the drag force increased with the increase in the density of the dry granular flow, and the friction force decreased with the increase in density. The gravity and the supporting force of the boulders increased with the increase in boulder size. This study reveals the influence laws of boulder size and the distance in front of the slope on the impact of dry granular flow on bridge piers. The findings can provide a theoretical basis for the impact-resistant design of bridges and disaster prevention in mountainous areas. Full article

Coastal geomorphological maps generated in a GIS context in Naples Bay and the Cilento area are presented here to establish a current geomorphological framework for these two sectors of the Eastern Tyrrhenian margin. While sedimentary processes have dominated the geological evolution of the Cilento area, volcanic processes have dominated Naples Bay. The objective of this research is to present a comparison of geomorphological units vs. hazard types in Naples Bay and in the Cilento based on geomorphological maps and to demonstrate that distinct hazards are produced by various geomorphological zones. In the western sectors near Ischia and Procida, the volcanic activity has created collapsing unstable volcanic slopes, resulting in debris avalanches triggering localized tsunamis. Fluid seepage has weakened sediments in the middle canyons, causing continuous erosion and gravity flow. Water seepage has prevented limestone cliffs in the southern region from fractures and erosion, resulting in frequent rockfalls and cliff failures. The Cilento region has a diverse topography, and several natural hazards are clearly related. Depending on the type of rock, the land responds differently to water, gravity, and ocean forces. Caves and sinkholes were produced in carbonate massifs by strong rock formations and precipitation. Water was trapped in the Cilento Flysch due to its weak rock layers. Before reaching flat plains, rivers traverse tectonic valleys in coastal plains and alluvial valleys. Full article

Interbasin water transfer reshapes water use efficiency (WUE) by altering hydrology and land use, yet post-transfer WUE changes and driver reorganization remain poorly quantified. Focusing on the Hanjiang River Basin (South-to-North Water Diversion source), we employed a convolutional gated recurrent unit (ConvGRU) deep learning model with Integrated Gradients to quantify pixel-scale spatiotemporal contributions of nine drivers to WUE over 2000–2024 using meteorological and multi-source remote sensing data. Results show (1) Basin-wide WUE increased over 2000–2024, but post-diversion growth dropped sharply (0.0184 to 0.0045 yr⁻¹), with river-channel declines driving this deceleration. (2) Temperature and vegetation land-cover type were the strongest suppressive drivers, while cropland and vapor pressure were the strongest promotive drivers; after diversion, kNDVI exhibited the largest attribution increase (+0.14), and the center of gravity of driving forces is shifting from climatic factors toward vegetation and land-use factors. (3) Across the basin, 42.26% of areas underwent a switch in dominant driver, with the most intense reorganization occurring in the upper reaches; the dominant area of cropland rose from 26.28% to 29.24%, kNDVI nearly doubled from 9.09% to 16.64%, and its expansion simultaneously absorbed dominance from temperature, radiation, cropland, and vegetation land-cover type—a “multi-source convergence” pattern of reorganization. Sensitivity analysis across multiple baseline schemes confirmed the robustness of the attribution conclusions. These findings inform ecological and agricultural water management in the Hanjiang Basin under the diversion. Full article

Hand-launched unmanned aerial vehicles require adequate low-speed lift and cruise efficiency. This study investigates a 3 kg propeller-aided biplane (PAB) with distributed electric propulsion using unsteady computational fluid dynamics. Propeller–wing arrangements are examined, followed by complete-aircraft simulations with transition modeling and sliding meshes. A conventional tractor configuration (CONV) provides a reference under comparable design constraints. Among the arrangements examined, over-the-wing and leading-edge tractor installations provide substantial lift augmentation. Predicted airframe loads are sensitive to transition modeling and the representation of propeller rotation. Although PAB has a lower clean-airframe lift-to-drag ratio, its smaller propeller-induced airframe drag penalty largely offsets this disadvantage at sampled fixed-rpm cruise conditions. At the 5 m/s hand-launch condition and angles of attack of 8–12°, PAB provides greater lift per unit shaft power with a comparable positive net forward force. At 12°, the lift-per-power gain is approximately 4%. About the respective design reference centers of gravity, cycle-mean nose-down moment magnitudes are approximately 77% and 49% smaller for PAB than for CONV at 8° and 12°. These predictions indicate hand-launch benefits for this non-optimized configuration pair under the prescribed conditions. Full article

CO₂ gravity flooding can establish a stable artificial gas cap through gravity segregation and selectively mobilize attic oil, making it an effective EOR option for low-permeability, steeply dipping, strongly water-sensitive reservoirs. Establishing a stable artificial gas cap is therefore critical to field performance. To define the applicability criteria and development characteristics of CO₂ gravity flooding, this study uses the Yi 59 block of the Moliqing Oilfield in Jilin Province as a representative case. Based on a pore-scale force analysis of free-phase CO₂ in porous media and considering key parameters including reservoir dip, permeability, pore-throat radius, interfacial tension, and fluid-density difference, a method was developed to calculate the minimum petrophysical threshold for immiscible CO₂ gravity flooding. The calculated minimum pore-throat radius for effective gravity flooding in this block is 0.52 μm. Oil–gas interfacial tension is the dominant control on artificial gas cap formation, and reducing it promotes the development of a stable gas cap. Three-dimensional physical model experiments and compositional reservoir simulations show that reservoir permeability directly controls gravity-flooding performance: as permeability decreases, gravity segregation weakens and gas cap formation becomes more difficult; as permeability increases, upward gas migration becomes more stable, and displacement performance improves markedly. Permeability exceeds 3 mD in most reservoir intervals of the Yi 59 block, satisfying the petrophysical requirements for effective CO₂ gravity flooding and indicating good potential for field application. By integrating theoretical analysis, laboratory experiments, and numerical simulation, this study clarifies the dominant mechanisms and applicability limits of CO₂ gravity flooding in the block, providing a theoretical basis and technical guidance for optimizing CO₂ enhanced oil recovery (CO₂-EOR) in the Yi 59 block and in steeply dipping, low-permeability continental reservoirs with closely comparable geological conditions. Full article

Satellite-derived bathymetry (SDB) commonly treats the sea surface as a source of radiometric disturbance, although the same surface wave field can also contain water depth information through gravity wave propagation. This article presents a Wave-Aware Physics-Informed Neural Network (WA-PINN) that represents these two roles within a unified shallow water bathymetry framework. The optical geometry stream combines Sentinel-2 multispectral observations with seafloor geometry. The disturbance stream converts European Centre for Medium Range Weather Forecasts Reanalysis Version 5 (ERA5) wind forcing into Mean Square Slope (MSS) through the Cox–Munk relationship and introduces a roughness-dependent sunglint contribution into the optical physics constraint. The signal stream retrieves local wavelength, propagation direction, and wave celerity from Sentinel-2 surface texture and constrains predicted depth with the finite depth gravity wave dispersion relation. A Wave Validity Factor (WVF) controls the influence of the dispersion constraint according to the coherence and physical plausibility of the retrieved wave field. The three streams are fused in a shared depth predictor constrained by supervised depth loss, optical physics loss, and wave dispersion physics loss. The framework is demonstrated over Culebra, St. Thomas, and St. John in the northeastern Caribbean Sea. The complete Dual Role model reaches an overall Root Mean Square Error (RMSE) of 1.21 m, a Mean Absolute Error (MAE) of 0.77 m, and an R² of 0.96. Relative to the Slope Aware configuration, the Disturbance and Signal models reduce RMSE by 15.7% and 12.8%, while the complete model reduces RMSE by 29.7%. The disturbance contribution increases under stronger wind forcing, whereas the signal contribution increases with WVF. Depth-dependent RMSE increases from 0.82 m at 0 to 5 m to 1.58 m at 20 to 30 m. These results illustrate the intended complementarity between correcting wave-induced optical contamination and exploiting wave propagation as an additional depth constraint. Full article

Against the backdrop of high-quality development, diagnosing coupling mismatches between new quality productive forces and urban resilience is crucial for sustainable, resilient regional growth. This study diagnoses these spatial network mismatches across the Chengdu–Chongqing Urban Agglomeration (CCUA, 2011–2023) using a comprehensive index system, coupling coordination degree and spatial gravity models, and social network analysis. Results show the following: (1) coupling coordination rose steadily, forming a “dual-core-led, multi-tiered”spatial pattern with narrowing disparities; policy support, factor agglomeration, and infrastructure upgrading were positively associated with coordination, whereas path dependence and limited factor mobility were associated with lagging coordination in peripheral cities; (2) the spatial structure evolved toward a polycentric pattern, with Chengdu and Chongqing as cores and cities such as Mianyang and Deyang as key nodes. Although this shift indicates a move toward multi-polar balance, connectivity between secondary nodes and the dual cores remains weak, posing a persistent constraint on overall synergy; (3) the spatial correlation network grew more connected but less efficient, indicating a transition from “efficiency-first” to an “efficiency–resilience balance” configuration. Functional differentiation revealed net spillover blocks, net benefit blocks, and bidirectional spillover blocks, yet weak intra-block linkages remain a key obstacle to effective cross-regional spillovers. Accordingly, this study proposes three policy priorities: strengthening connectivity between the dual cores and secondary nodes while enhancing the hub functions of “structural-bridge” cities; activating both intra-block and inter-block spillovers through cross-administrative transfer platforms and two-way benefit-sharing mechanisms; and providing differentiated—rather than uniform—support to constrained peripheral nodes within an institutionalized, multi-level coordination framework, so as to advance resilient and high-quality regional development in the CCUA. Full article

To address the limitations of traditional wall-climbing robots in ferromagnetic wall operation scenarios, such as poor surface adaptability, insufficient motion stability, and difficulties in negotiating complex surface transitions, this paper proposes a four-wheel permanent magnet wall-climbing robot and systematically investigates its stability. First, the center of gravity (CoG) of the robot was determined based on a 3D prototype model developed in SolidWorks2020. To ensure reliable adhesion, the anti-slip and anti-overturning stability criteria under various operating conditions were derived. Furthermore, combining the mechanical characteristics, a magnetic field simulation model for the magnetically adsorbed wheels was established. Electromagnetic simulations of the permanent magnets were conducted using Ansoft Maxwell, followed by adhesion force experiments. Finally, the robot prototype was assembled, and a test system was constructed to evaluate its overall performance. The experimental results demonstrate that the designed robot can smoothly negotiate inner right-angle corners. This validates the effectiveness of the proposed structural design and stability analysis, providing a feasible technical solution for wall-climbing robots in complex scenarios and exhibiting significant potential for engineering applications. Full article

We believe that the origin of the universal dark energy may crucially depend on the behavior of the gravitational constant G. If G is constant throughout the universe, then the dark energy density ${\mathit{u}}_0$ is supported by the vacuum via its constant and evolving properties. On the other hand, in varying-G gravity (whose low-acceleration limit is MOND), ${\mathit{u}}_0$ is a manifestation of radial G-gradients in the source of gravity. We estimate the present-day dark energy density of the universe in these two independent cases without using conventional Planck-2018 modeling in deriving the expressions for ${\mathit{u}}_0$. The constant-G derivation uses dimensional analysis, vacuum constants, and a newly discovered evolving bridge between vacuum mechanical and electromagnetic quantities. The varying-G derivation relies on the MOND critical acceleration $a_0$, the source of gravity that falls off as ∼$r^{-2}$ at large distances r, and the assumption that the present-day energy density $u_0$ can be estimated by spatially averaging this radial profile over the MOND volume ${\displaystyle \frac{4\pi }{3}}{r}_0^3$, where $r_0=c^2/a_0$ and c is the speed of light in vacuum. The agreement between these two determinations and the Planck-2018 results from $\Lambda$CDM modeling is at the percent level, so that the results cannot distinguish clearly between constant-G and varying-G gravity. The analysis further indicates that the Newtonian constant $G_0$, the MOND constant $a_0$, and the Planck units of force, power, voltage, and current can be regarded as empirical vacuum constants within the proposed framework, alongside the well-known resistive properties of the vacuum, whereas charge, capacitance, inductance, and various fields are scale-dependent properties evolving in the expanding universe since the Stoney era. Ultimately, the vacuum behaves as a remarkably stiff elastic medium under stress, irrespective of the presence or absence of matter. This property has long been encoded, albeit inconspicuously, in the much discussed Tully–Fisher and Faber–Jackson relations, as well as in the Casimir effect and the field equations of General Relativity. Full article

To obtain a better insight into the displacement efficiency in heterogeneous reservoirs, a cross-sectional study for a pair of vertical injection and producing wells is considered. Geostatistical modeling is employed to simulate various cases of realistic reservoir heterogeneity between the wells. This is coupled with reservoir simulations of immiscible displacement to evaluate the sweep efficiency. Two groups of similarity criteria characterizing the heterogeneous lithology distribution and the fluid flow are proposed. One group is used to distinguish and delineate the limiting cases of homogeneous and layered reservoirs. The other group is used to distinguish and constrain the limiting cases of gravity-driven flow and displacement in anisotropic reservoirs. The main conclusions of this study are obtained using a parametric investigation into the displacement efficiency in various reservoirs. Furthermore, the uncertainty propagating from reservoir heterogeneity to the efficiency is addressed. It is shown that the displacement is generally more efficient in the reservoirs built of thin and extended interlayers. It is also more efficient at larger net-to-gross ratios; however, in a specific limiting case of a large buoyancy force, an optimal net-to-gross ratio exists. The physical mechanisms resulting in such optimal values and their potential applications in well placement are discussed. Full article