Search Results (3,569)

Urban–rural transition zones (URTZs) represent critical spatial units where urban expansion interacts with ecosystems. In arid regions, however, the response of ecological environmental quality (EEQ) to rapid urban expansion and spatial restructuring remains insufficiently understood. Taking Xinjiang as a representative arid-region case, this study develops an analytical framework integrating dynamic URTZs identification, EEQ assessment, and the analysis of influencing factors and nonlinear responses to systematically investigate URTZs expansion and EEQ changes across 13 typical urban agglomerations from 2002 to 2022. URTZs were identified using K-means clustering by integrating population density, nighttime light intensity, and impervious surface information. An improved remote sensing ecological index (ARSEI) was then developed by incorporating the abundance index (AI) into the traditional RSEI framework. Finally, XGBoost and SHAP were employed to identify the key determinants of EEQ and reveal their nonlinear responses and interactions. The results showed that: (1) URTZs expanded rapidly and continuously from 2002 to 2022, with their total area increasing by more than threefold and exhibiting a spatial restructuring pattern characterized by expansion from central cities toward multiple nodes. (2) Despite the rapid expansion of URTZs, overall EEQ remained at a relatively high level; however, the grade structure exhibited a trend of “expansion at both ends and contraction in the middle,” intensifying the spatial differentiation of EEQ. (3) XGBoost and SHAP analyses identified precipitation (PRE), population density (POP), digital elevation model (DEM), and slope as major factors explaining the spatial variation in EEQ. Interaction analysis further revealed strong interactions between PRE × DEM and PRE × POP. High EEQ values were primarily distributed in areas characterized by favorable precipitation conditions, moderate elevations, and gentle terrain, indicating that the synergistic effects of hydrothermal conditions and topographic constraints play a significant role in shaping EEQ in URTZs. These findings demonstrate that rapid URTZs expansion in arid regions does not necessarily lead to an overall decline in EEQ but may intensify its spatial differentiation. Therefore, ecological governance of URTZs should shift from a singular focus on controlling urban expansion toward differentiated spatial management that jointly considers hydrothermal conditions, topographic constraints, population concentration, and ecological carrying capacity, thereby promoting coordinated urbanization and ecological conservation. Full article

Yamdrok Lake, a typical closed inland lake located in the southern Tibetan Plateau, is highly sensitive to climate change and human activities. Although previous studies have reported a declining lake-level trend, the mechanisms underlying the sharp decline since 2005 remain debated. In particular, the disturbance effects of human activities, such as pumped-storage hydropower operations, have not been rigorously characterized, and quantitative attribution under the combined influence of multiple factors remains limited. This study aims to systematically identify the drivers of lake-level changes in Yamdrok Lake during 2000–2023 and to quantify the relative statistical explanatory power of climate change and human activities on lake-level fluctuations using Shapley R² decomposition. We integrated 24 years of hydrological, meteorological, remote-sensing, and hydropower-operation data. Cumulative anomaly analysis, multiple linear regression, and Shapley R² decomposition were employed to establish an attribution model incorporating rainfall, evaporation, temperature, glacier meltwater, and hydropower operation intensity, represented by annual electricity generation. The relative statistical explanatory power of these factors with respect to interannual lake-level changes (ΔH) was quantified using Shapley R² decomposition for different periods, representing the proportion of variance in ΔH explained by each factor within the regression framework rather than absolute physical volumetric contributions, including hydropower-operation and non-operation periods. Results show that the annual mean water level of Yamdrok Lake declined significantly during 2000–2023, with a cumulative decrease of 5.1 m and an accelerated decline after 2005. The dominant controls shifted from an early rainfall–evaporation regime to a systematic water deficit dominated by rising temperature. Temperature increased significantly at a rate of 0.03 °C yr⁻¹ (p < 0.05) and constituted the fundamental driver of the long-term lake-level decline. During the hydropower-operation period (2000–2014), the five factors jointly explained 84.51% of the variance in interannual lake-level changes, with hydropower operation intensity (32.32%), temperature (27.98%), and glacier meltwater (26.54%) being the three largest contributors in terms of statistical explanatory power. During the non-operation period (2015–2023), temperature consistently remained the most important individual contributor, accounting for 34.3–49.5% of the explained variance depending on whether missing glacier meltwater data for 2022–2023 were extrapolated or excluded from the analysis. Warming affects lake levels through two pathways: it directly enhances lake-surface evaporation and simultaneously promotes continuous glacier retreat within the basin. Glacier area decreased by approximately 30.5 km² between 2000 and 2021, thereby weakening the long-term resilience of glacier-meltwater recharge. Consequently, the lake system has shifted from a dynamic balance toward a persistent state in which water losses exceed water inputs. Overall, lake-level changes in Yamdrok Lake represent the combined effects of progressive warming-induced water deficits and superimposed disturbances associated with hydropower operations. By extending observations to 2023 and incorporating dynamic glacier-area and hydropower-operation indicators, this study clarifies the temporal shift in dominant drivers, revises the previous interpretation that attributed lake-level decline primarily to reduced rainfall, and provides a scientific basis for lake-water-resource security assessment and climate-change adaptation on the Tibetan Plateau. Full article

Landing underactuated quadrotors on inclines is challenging as sudden contact transients convert translational kinetic energy into critical edge-tipping moments. Conventional controllers struggle to mitigate these sub-second impacts without computationally intensive prior terrain models or payload-restricting mechanical shock absorbers. This paper introduces a stabilization approach combining a Zero Moment Point (ZMP)-guided anchoring strategy with an impact-resilient Model Reference Adaptive Control Neural Network (MRAC-NN). The ZMP serves as a proactive geometric threshold. Evaluating overturning moments directly in the body frame before physical tilt occurs triggers immediate asymmetric bidirectional thrust. This artificially augments the surface normal force, thereby securing the vehicle on steep inclines that exceed natural static friction limits. Concurrently, the computationally efficient MRAC-NN suppresses unstructured aerodynamic disturbances and high-frequency impact shocks. To prevent parameter wind-up during sudden kinematic arrest at touchdown, the neuro-adaptive law is structurally augmented with robust bounding and dynamic state-locking mechanisms, mathematically guaranteeing Uniform Ultimate Boundedness (UUB). The framework is validated through high-fidelity simulations that incorporate Linear Complementarity Problem (LCP) rigid-impact constraints and stick–slip friction. Results demonstrate the architecture effectively suppresses post-impact bouncing and transforms critical tipping moments into controlled planar slides, reducing stabilization penalties by up to $47.5\%$ and expanding the survivable flight envelope to ${60}^{\circ }$ inclines where classical methods fail. Full article

Button mushrooms (Agaricus bisporus) are highly perishable, making rapid and automated postharvest freshness evaluation crucial for cold-chain logistics. Visible-near-infrared (Vis-NIR) hyperspectral imaging is promising for non-destructive food quality assessment, yet mining highly redundant spatial–spectral data remains challenging. This study proposes a novel artificial intelligence approach, the patch-aligned multimodal interaction fusion network (PAMIF-Net), to monitor postharvest mushroom freshness. Using a Vis-NIR dataset of 400 A. bisporus caps over a 9-day refrigerated storage period, this deep learning architecture dynamically fuses global spectral features (indicating internal physicochemical shifts) with localized spatial morphological features (capturing surface deterioration) using a gated attention mechanism. Extensive evaluations across 10 independent trials demonstrated that PAMIF-Net achieved optimal classification accuracy (up to 100% on the current test set) and a minimal mean absolute error for five-class storage time recognition. Furthermore, it exhibited superior computational efficiency and significantly lower inference latency compared to classical machine learning and standard deep learning backbones. This multimodal spatial–spectral deep learning framework demonstrates the feasibility of combining HSI and deep learning for the specific task of automated storage time recognition of A. bisporus under controlled refrigerated conditions. Full article

Previous studies in the Beibu Gulf have documented the distributions and controlling factors of carbonate system parameters in surface waters; however, their dynamics in subsurface and bottom waters remain poorly constrained. Here, we present the first observations of pH and the aragonite saturation state (Ω_arag) in subsurface and bottom waters of the Beibu Gulf during spring and fall 2024. In spring, pH and Ω_arag in subsurface and bottom waters off Ledong were predominantly governed by physical mixing. In contrast, their variability off Dongfang was driven jointly by biological respiration occurring outside the Dongfang oil/gas field and by respiration within the field itself. Quantitative analysis revealed that respiration outside the field increased dissolved inorganic carbon (DIC) concentrations by ~18 ± 3 µmol kg⁻¹, a magnitude comparable to that attributable to in-field respiration (~18 ± 7 µmol kg⁻¹). Collectively, these two respiration sources induced only slightly declines in pH (0.03 ± 0.01 and 0.04 ± 0.01) but statistically significant reductions in Ω_arag (0.18 ± 0.03 and 0.21 ± 0.08, respectively). During fall, carbonate system dynamics in subsurface and bottom waters off both Dongfang and Ledong were dominated by physical mixing. The differential influence of North Pacific Tropical Water (NPTW) resulted in a decline in Ω_arag from 2.99 ± 0.10 off Dongfang to 2.75 ± 0.32 off Ledong. All observed Ω_arag values remained well above the thermodynamic saturation threshold (Ω_arag = 1), indicating no immediate risk of ocean acidification to calcifying organisms in the study area under current conditions. This study helps bridge a critical observational gap in the regional inorganic carbonate system. However, due to sampling constraints, carbonate system parameters are reported here for spring and fall only. Observations for summer and winter, as well as multi-year time-series measurements, are planned for the near future. Full article

The timberline region of the Western Himalaya is a crucial ecological transition area highly sensitive to climate changes, which significantly influence vegetation patterns, soil formation, and carbon dynamics. This study aimed to investigate the spatial and altitudinal changes in soil organic carbon (SOC) across different topographic orientations and to evaluate machine-learning models for spatial SOC prediction in the timberline ecotone (2100–3300 m) of the Kedarnath Wildlife Sanctuary. Through systematic random sampling across 100 m elevation bands, composite soil samples were collected from three aspects (North-East, South-West, and North-West) at two depths (0–15 cm and 15–30 cm) and analyzed alongside topographic, spectral, and climatic covariates. Results indicated that SOC trends varied significantly by aspect; the North-East aspect exhibited a considerable increase in SOC with elevation, while the North-West and South-West sides responded differently. Furthermore, Digital Soil Mapping using the Random Forest (RF) model outperformed Support Vector Machine and XGBoost, explaining 62% of surface and 74% of subsurface SOC variability. In conclusion, aspect-induced microclimatic gradients play a major role in controlling soil characteristics near the Himalayan timberline, and machine-learning models like RF can successfully capture these complex spatial patterns. Consequently, it is recommended that the established baseline SOC maps be utilized as reference points for future climate-change monitoring, carbon accounting, and directing conservation strategies in high-altitude forests. Full article

Bamboo is a renewable material widely used in traditional Chinese musical instruments, but its vibration behavior is sensitive to moisture. This study investigated how moisture content affects the vibration behavior of Jinghu bamboo soundboxes. Three Xipi and three Erhuang specimens were conditioned by soaking and drying to obtain 11 moisture states (M0–M10). Time domain responses, frequency response functions, natural frequencies, damping ratios, mode shapes, and a frequency-mass-based estimated structural stiffness index were evaluated using impact hammer testing and experimental modal analysis. Three individual Xipi soundboxes with nominal storage durations of 3, 46, and 86 years were examined before and after conditioning at 20 °C and 60% relative humidity as an exploratory case comparison. Both types showed stronger vibration responses at intermediate moisture levels, whereas nearly dry and nearly saturated conditions produced weaker responses. Increasing moisture generally lowered resonance frequencies and estimated structural stiffness index, while damping ratios were higher at the moisture extremes. Under the present test conditions, Xipi specimens exhibited a higher estimated structural stiffness index and stronger mid- to high-frequency responses than Erhuang specimens. Given the differences in specimen geometry and mass, these variations are interpreted as reflecting whole-structure dynamic responses rather than intrinsic differences in material properties. In the exploratory comparison, XP-86 showed the largest change, with a 61.17% decrease in fundamental frequency and the development of surface cracks. Given the limited number of independent specimens, the results are interpreted descriptively rather than as statistically generalizable effects. These results s demonstrate the importance of humidity control during the use and preservation of Jinghu soundboxes. Full article

Organic-rich shale contains chemically heterogeneous mineral–organic interfaces that produce strong and spatially variable proton surface relaxation, complicating the identification of clay-bound water and the conversion of NMR relaxation time into pore size. Conventional interpretations commonly treat surface relaxivity as a constant, while the respective contributions of water-retaining surface chemistry, molecular restriction, and paramagnetic centers remain insufficiently separated. In this study, Wufeng–Longmaxi shale samples from the Yongchuan Block were investigated using mineralogical and pore structural characterization, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, cation exchange capacity, zeta potential, electron paramagnetic resonance, controlled hydration, one- and two-dimensional low-field time domain NMR, and molecular dynamics simulations. Under the present fluid and acquisition conditions, strongly surface-associated water was operationally identified mainly at T₂ < 1.6 ms and T₁ < 85 ms, while the effective transverse surface relaxivity ranged from 3.6 to 9.1 μm/s. Water retention was more closely associated with cation exchange capacity and surface –OH/O–C environments, whereas relaxation efficiency was controlled more directly by EPR-detectable paramagnetic centers and restricted molecular motion of interfacial water. Simulations of Na-smectite, chlorite, illite, and kerogen-covered illite revealed systematic differences in water density layering, adsorption strength, hydrogen bond persistence, molecular residence, translational diffusion, rotational reorientation, and proton–proton dipolar correlation. A chemistry-informed model combining the EPR-derived paramagnetic center density with a surface area-weighted molecular restriction index explained 86% of the measured relaxivity variation, with an adjusted R² of 0.83 and leave-one-out cross-validation RMSE and MAE values of 0.71 and 0.57 μm/s, respectively. At the core scale, the variable relaxivity interpretation reduced the mean absolute percentage error of characteristic pore diameter from 21.9% to 4.5% and the RMSE of the clay-bound water fraction from 3.4 to 0.4 percentage points relative to the fixed relaxivity method. Transfer to NMR logging further reduced lithology-dependent biases in pore size conversion and clay-bound water partitioning. These results define shale surface relaxivity as an emergent interfacial property arising from coupled magnetic and molecular controls and provide a mechanistic basis for NMR analysis of chemically heterogeneous shale materials. Full article

Free-surface sloshing in partially filled tanks and open reservoirs can produce spatially complex surface deformation under horizontal excitation. This study presents an image-based experimental and computational workflow for reconstructing measured free-surface profiles in a laboratory-scale rectangular reservoir mounted on a Haas VF-3/VF-3SS-family CNC machining center. The tank underwent a programmed horizontal back-and-forth motion. The retained CNC controller record shows commanded x positions spanning approximately $-19.976$ mm to $+19.851$ mm, corresponding to a programmed peak-to-peak stroke of approximately 39.8 mm. The realized forcing frequency was not independently measured; therefore, no experimental near-resonance condition is claimed. Videos were recorded approximately normal to the transparent tank wall, converted to still frames, calibrated directly in physical length units, and manually digitized with WebPlotDigitizer. A truncated spatial Fourier series was fitted independently to each measured time slice. The accompanying Python applications dynamically evaluate the experimentally fitted representation: the GUI tools animate reconstructed profiles over the recorded time sequence, while the final FourierN3 implementation builds time-dependent coefficient models, linearly interpolates coefficient histories, evaluates $y(x,t)$, and generates a three-dimensional space–time reconstructed surface. These outputs are described as dynamic Fourier reconstructions because they remain conditioned on measured coefficient histories and do not constitute independent CFD or potential-flow predictions. The Fourier harmonics are mathematical reconstruction functions and are not identified one-to-one with physical sloshing eigenmodes. For a 0.45 m tank length, linear theory gives first-mode reference frequencies of 0.687 Hz at a 4 cm water depth and 0.763 Hz at a 5 cm water depth. The workflow is demonstrated on three selected datasets that provided sufficiently clear free-surface records for consistent frame-by-frame digitization. Using a common three-harmonic benchmark, mean RMSE values were 0.8815 cm for Case A (4 cm), 1.419 cm for Case B (5 cm), and 0.5022 cm for Case C (4 cm), corresponding to mean NRMSE values of 22.0%, 28.4%, and 12.6%, respectively. For Case C, adding a fourth harmonic reduced the mean RMSE to 0.4427 cm (11.1% of water depth), an 11.8% reduction relative to the three-harmonic fit. All RMSE and NRMSE values are reconstruction errors relative to the manually digitized coordinates, not estimates of absolute experimental measurement accuracy. The results therefore demonstrate the reconstruction workflow for the three selected records rather than establish a general water-depth effect. Full article

Desiccation cracking in expansive soils on slopes accelerates soil erosion and reduces water retention capacity, posing significant threats to agricultural sustainability. This study investigates the combined effects of organic fertilizer (OF), slow-release fertilizer (SRF), and rice straw (RS) on crack inhibition in expansive soil under wet–dry (W-D) cycles. A three-factor Box–Behnken design (BBD) was used with OF at 5–15%, SRF at 0.3–0.9 kg/m³, and RS at 0.25–0.75%, and crack development was followed through 20 W-D cycles. The quadratic response-surface model fitted to the BBD crack-ratio data was significant (R² = 0.952, adjusted R² = 0.865, p = 0.008), with significant linear effects of OF, SRF, and RS, whereas the two-factor interaction terms were not statistically significant as a group (p = 0.701). The lowest observed crack ratio in the BBD matrix was 1.7% at 10% OF + 0.9 kg/m³ and SRF + 0.75% RS; this is therefore reported as an observed low-response combination rather than evidence of a statistically confirmed SRF–RS interaction. An LSTM model was retained as a complementary dynamic predictor and yielded R² = 0.927, MAE = 0.325, and RMSE = 0.478 for the evaluated dataset; however, divergence between training and validation losses indicated overfitting, so external generalizability remains to be established. The results support agricultural-waste-based amendment as a promising crack-control strategy while emphasizing the need for independent replication and field validation. Full article

A series of polyurethane (PU) nanocomposites incorporating 4,4′-bis(hydroxymethyl)-2,2′-bipyridine (BBD) as a chain extender and a commercially supplied graphene/zinc oxide (G/ZnO) hybrid filler were successfully synthesized. The effects of G/ZnO loading (0–2.0 wt.%) on the structural, thermal, mechanical, surface-wettability, and antibacterial properties of the nanocomposites were systematically investigated. Fourier-transform infrared spectroscopy confirmed the formation of the polyurethane structure and revealed changes in characteristic absorption bands following G/ZnO incorporation. Morphological observation of the pristine G/ZnO hybrid filler revealed an irregular and aggregated morphology, while X-ray diffraction confirmed the presence of crystalline ZnO. Energy-dispersive X-ray spectroscopy and elemental mapping showed Zn-containing regions within the examined areas of the G/ZnO-containing PU samples. X-ray photoelectron spectroscopy further confirmed the surface presence of Zn-containing species, with the Zn atomic concentration increasing from 0 at.% in PU-01 to 0.82 at.% in PU-04. Thermogravimetric analysis showed modest changes in thermal decomposition behavior with increasing G/ZnO loading, while differential scanning calorimetry and dynamic mechanical analysis revealed shifts in glass-transition and relaxation behavior, consistent with changes in polymer-chain mobility and the local interfacial environment. The tensile strength increased from 2.68 MPa for neat PU to 11.76 MPa for the nanocomposite containing 2.0 wt.% G/ZnO, accompanied by an increase in Young’s modulus. The water contact angle increased from approximately 68° to 89°, indicating reduced apparent surface wettability with increasing G/ZnO loading. The nanocomposites also exhibited antibacterial activity against Escherichia coli and Staphylococcus aureus, with antibacterial efficiencies exceeding 95% at higher G/ZnO loadings. Overall, the incorporation of the commercial G/ZnO hybrid filler was associated with changes in the thermal, mechanical, surface, and antibacterial properties of the BBD-containing PU system. Because separate PU systems without BBD and individual graphene- and ZnO-containing controls were not included, the individual contributions of BBD, graphene, and ZnO, as well as any synergistic effect between graphene and ZnO, cannot be established from the present results. Further studies addressing filler leaching, long-term antibacterial stability, coating adhesion, environmental durability, and cytocompatibility are required to establish the practical applicability of these materials. Full article

Monitoring bacterial contamination on surfaces is critical for hygiene and safety assurance in food, healthcare, and pharmaceutical settings, although routine methods still remain slow and laboratory dependent. Here, we report a portable respirometric platform based on sealed sensor sachets incorporating optical oxygen sensors to rapidly detect and quantify total aerobic viable counts (TVC) from swabbed surfaces. Following standardized surface swabbing, samples were incubated in the sachets and oxygen depletion kinetics were recorded with a handheld reader and microbial activity was inferred from oxygen consumption. Reference quantification was obtained by serial dilution and aerobic plate counting, enabling direct benchmarking of the respirometric readout against an industry-accepted culture method such as ISO 4833:2013. The platform demonstrated strong agreement with plate counts (R² > 0.94), achieving a median detection limit of 2.69 log₁₀ CFU/cm² and a dynamic range of 0–6 log₁₀ CFU/cm² for surface-associated microbial loads. The sensor system was also applied in a semi-industrial setting in a meat processing plant. Across replicate measurements, the assay provided consistent kinetic signatures and quantitative outputs, suitable for rapid and practical decision-making. Compared with traditional culture-based approaches (requiring up to 72 h), the respirometric sachets delivered actionable results within 10 h using a portable, low-infrastructure workflow, supporting rapid on-site hygiene verification and sanitation control. Full article

Fault waviness can control whether earthquakes arrest, cascade, or transition to supershear rupture, yet its interaction with hypocentral position and free-surface proximity remains poorly constrained. We use three-dimensional spontaneous dynamic-rupture simulations of a vertical right-lateral fault containing one symmetric undulation. Its along-strike length L, transverse height H, signed nucleation distance, and upper-edge burial are varied under uniform regional stress and slip-weakening friction. Resolving the stress onto the non-planar surface creates a directional barrier–asperity pair. In surface-breaking models, small undulations permit cascading and sustained supershear rupture for all tested hypocenters, whereas larger undulations increasingly arrest rupture. The maximum height that permits position-independent cascading increases with undulation length, while the corresponding one-sided bend angle decreases from about 32° at L = 4 km to about 14° at L = 14–18 km. Burial suppresses shallow free-surface-induced supershear and narrows the cascading regime, but transmitted ruptures can still develop sustained or transient supershear at depth. Greater hypocentral distance generally favors transmission without monotonically favoring sustained supershear. These results show that fault geometry, rupture approach direction, hypocentral position, and surface proximity jointly control rupture connectivity and speed. Full article

Weakly nonlinear free-surface flows past disturbances are traditionally modeled using the forced Korteweg–de Vries (fKdV) equation with a prescribed instantaneous pressure field. However, physical wake responses possess finite relaxation times and advection scales that diagnostic algebraic closures fail to capture. This paper introduces a novel coupled system in which the surface pressure is a dynamical field governed by an advection–reaction–diffusion equation driven by band-limited curvature. Using linear spectral theory and numerical validation, we derive a phase-speed criterion demonstrating that energy transfer is determined by the comparison between the pressure drift speed and the surface phase speed. A sharp stability theorem proves that, to leading order in the coupling strength and for a non-negative even response transfer function whose drift speed exceeds the Froude detuning, the system is spectrally stable if and only if the response is band-limited below a critical wavenumber $k_c$. Furthermore, an exact energy identity establishes that passivity and linear stability are equivalent. Finally, we demonstrate resonance steering: while coupling typically increases the wave resistance for monotone spectra, tuning the response to a spectral zero of a multi-lobe footprint reduces the drag significantly relative to its classical value. This result identifies an explicit performance–strongness trade-off, providing a mathematically strong structure for wave drag minimization through dynamic pressure control. Full article

This work presents a finite-time adaptive fuzzy control approach for a category of multi-input multi-output nonlinear systems in the presence of input saturation and external disturbances. A hyperbolic function is adopted to convert the unconstrained control command into a bounded signal so that the actuator constraints are strictly respected. Unknown nonlinearities are approximated by fuzzy logic systems, whereas external disturbances are attenuated by adaptive mechanisms together with tanh-based robust terms. In addition, dynamic surface control is incorporated into the backstepping framework, where first-order filters are employed to avoid the computational burden associated with the repeated differentiation of virtual control laws. On this basis, a Lyapunov-based design is carried out to derive the finite-time adaptive control protocol. It is shown that every signal in the resulting closed-loop system is bounded, the closed-loop system is semi-globally practically finite-time stable, and the state variables converge to a small neighborhood of the desired states within a finite settling time, and the control inputs never exceed the prescribed bounds. Simulation results obtained using a representative rigid spacecraft as an example confirm the feasibility and disturbance-rejection capability of the developed method. Full article