Search Results (2,655)

This study presents the design, implementation, and experimental validation of a self-contained earthquake early warning system (EEWS) based on real-time frequency-domain analysis of ground motion. The proposed system integrates a low-noise triaxial micro-electro-mechanical system (MEMS) accelerometer with a high-performance microcontroller, enabling autonomous seismic event detection without dependence on external communications or centralized infrastructure. The characteristic period of ground motion (τ_c) is estimated using a spectral moment method applied to the first three seconds of vertical acceleration following P-wave arrival. Event triggering is based on a short-term average/long-term average (STA/LTA) algorithm, with alarm logic incorporating both spectral and amplitude thresholds to reduce false positives from low-intensity or distant events. Experimental validation was conducted using a custom-built uniaxial shaking table, replaying 10 real earthquake records (Mw 4.1–7.7) in 20 repeated trials each. Results show high repeatability in τ_c estimation and strong correlation with event magnitude, demonstrating the system’s reliability. The findings confirm that modern embedded platforms can deliver rapid, robust, and cost-effective seismic warning capabilities. The proposed EEW solution is well-suited for deployment in critical infrastructure and resource-limited seismic regions, supporting scalable and decentralized early warning applications. Full article

Hydraulic concrete is prone to cracking and interactive propagation under complex stress, threatening its structural integrity and service life. To address limitations of traditional numerical methods (e.g., mesh dependency in FEM) and imprecision of existing meshless methods for characterizing multi-fissure interactions, this study improved SPH to model double-crack interactions in hydraulic concrete under three-point bending and clarify the underlying mechanisms. A modified SPH framework was developed by introducing a failure parameter (ξ) to refine the kernel function, enabling simulation of particle progressive failure via the Mohr–Coulomb criterion; a three-point bending numerical model of concrete beams containing double precast fissures (induced and obstacle) was established, with simulations under varying obstacle fissure angles (α = 0–75°) and distances (d = 0.02–0.06 m). The results show that the obstacle fissure angles significantly regulate the crack paths: as the α increases, the tensile stress concentration shifts from the obstacle fissure’s middle to its ends, causing cracks to deflect toward the lower end, with a reduced propagation length and lapping time; at an α = 75°, the obstacle fissure’s lower tip dominates failure, forming an “induced fissure–lower end of obstacle fissure–top” penetration mode. The fissure distances affect the stress superposition: a smaller d (e.g., 0.02 m) induces vertical propagation and rapid lapping with the obstacle fissure’s lower end, while a larger d (e.g., 0.06 m) weakens the stress at the induced fissure tip, promoting horizontal deflection toward the obstacle fissure’s upper end and transforming the failure into “upper-end dominated.” This confirms that the improved SPH method effectively simulates crack behaviors, providing insights into multi-fissure failure mechanisms and theoretical support for hydraulic structure crack control and safety evaluation. Full article

This study focuses on the complex pore structure and pronounced heterogeneity of tight sandstone reservoirs in the Linxing area of the Ordos Basin and develops a multi-scale quantitative characterization approach to investigate the coupling mechanism between pore structure and reservoir properties. Six core samples were selected from the Shiqianfeng Formation (depth interval: 1326–1421 m) for detailed analysis. Cast thin sections and scanning electron microscopy (SEM) experiments were employed to characterize pore types and structural features. Nuclear magnetic resonance (NMR) experiments were conducted to obtain T₂ spectra, which were used to classify bound and movable pores, and their corresponding fractal dimensions were calculated separately. In addition, NMR logging data from the corresponding well intervals were integrated to assess the applicability and consistency of the fractal characteristics at the logging scale. The results reveal that the fractal dimension of bound pores shows a positive correlation with porosity, whereas that of movable pores is negatively correlated with permeability, indicating that different scales of pore structural complexity exert distinct influences on reservoir performance. Mineral composition affects the evolution of pore structures through mechanisms such as framework support, dissolution, and pore-filling, thereby further enhancing reservoir heterogeneity. The consistency between logging responses and experimental observations verifies the regional applicability of fractal analysis. Bound pores dominate within the studied interval, and the vertical variation of the PMF/BVI ratio aligns closely with both the NMR T₂ spectra and fractal results. This study demonstrates that fractal dimension is an effective descriptor of structural characteristics across different pore types and provides a theoretical foundation and methodological support for the evaluation of pore complexity and heterogeneity in tight sandstone reservoirs. Full article

The integration of small unmanned aircraft systems (sUASs) and electric vertical takeoff and landing (eVTOL) aircraft into urban airspace presents a new challenge in managing environmental noise, which is a critical factor for the public acceptance of urban air mobility (UAM). This survey investigates the noise characteristics of UAS and eVTOL platforms, particularly multi-rotor and distributed propulsion configurations, and examines whether the operational benefits of these vehicles outweigh their acoustic footprint in dense urban environments. While eVTOLs are often perceived as quieter than conventional helicopters due to the absence of combustion engines and mechanically simpler drivetrains, their dominant noise sources are aerodynamic in nature. These include blade vortex interactions, rotor loading noise, and broadband noise, which persist regardless of whether propulsion is electric or combustion-based. Recent studies suggest that community perception of drone noise is influenced more by tonal content, frequency, and modulation patterns than by absolute sound pressure levels. This paper presents a comprehensive review of state-of-the-art noise prediction tools, empirical measurement techniques, and mitigation strategies for sUAS operating in UAM scenarios. The discussion provided in this paper assists in vehicle design, certification standards, airspace planning, and regulatory frameworks focused on minimizing noise impact in urban settings. Full article

With coal mines’ mining depth increasing, the stress environment in deep mining (including key factors such as high ground stress, strong disturbance, and complex geological structures, as well as stress redistribution after deformation of surrounding roadway rock) is complex, which leads to increasingly prominent deformation and failure problems for goaf-side roadways in thick coal seams. Surrounding rock deformation is difficult to control, and mine pressure behavior is violent, making traditional support technologies no longer able to meet the mining safety requirements of roadways in deep thick coal seams. Taking the 6311 working face of Tangkou Coal Mine as the engineering research background, this paper systematically summarizes the deformation and failure characteristics of goaf-side roadways in deep thick coal seams through field monitoring, borehole peeping, and other means, and conducts in-depth analysis of their failure mechanisms and influencing factors. Aiming at these problems, a synergistic support–unloading control method for goaf-side roadways is proposed, which integrates roof blasting pressure relief, coal pillar grouting reinforcement, and constant-resistance energy-absorbing anchor cable support. The effects of the unsupported scheme, original support scheme, and synergistic support–unloading control scheme are compared and analyzed through FLAC^3D numerical simulation. Further verification through field application shows that it has remarkable effects in controlling roadway convergence deformation, roof separation, and bolt (cable) stress. Specifically, compared with the original support schemes, the horizontal displacement on the coal pillar side is reduced by 89.5% compared with the original support scheme, and the horizontal displacement on the solid coal side is reduced by 79.3%; the vertical displacement on the coal pillar side is reduced by 45.8% and the vertical displacement on the solid coal side is reduced by 42.4%. Compared with the original support scheme, the maximum deformation of the roadway’s solid coal rib, roof, and coal pillar rib is reduced by 76%, 83%, and 88%, respectively, while the separation between the shallow and deep roof remains at a low level. The coal stress continues fluctuating stably during the monitoring period; the force on the bolts (cables) does not exceed the designed anchoring force, with sufficient bearing reserve space (47% remaining), and no breakage occurs, which fully proves the feasibility and effectiveness of the synergistic support–unloading control technology scheme. This technology realizes the effective control of on-site roadways and provides technical reference for the support engineering of coal mine goaf-side roadways under similar conditions. Full article

While escalating environment and food safety challenges underscore the need for sustainable agri-food systems, promoting green agri-food production provides a promising pathway. The green agri-food value chain integrates green agri-food production with coordinated value-adding activities across the value chain. In developing such value chains, agricultural cooperatives emerge as a key player. This research integrates sustainability and value chain theories, aiming to study the role of China’s cooperatives in enabling green production and green value chains. It used qualitative methodology and interviews with management and members of three green vegetable cooperatives in Shandong Province, China, to offer an initial examination into this research area. The findings reveal that cooperatives play an important role in the green vegetable value chain and have a different level of vertical integration, with some having control over the whole value chain from input supply to retail. They also provide essential input, technical, and market support to enable green vegetable production and facilitate various value-adding activities. The study offers valuable insights into recommendations for enhancing value addition and facilitating green value chains. It also holds practical implications for practitioners and policymakers to strengthen cooperative development in China as an important intermediary for advancing agriculture sustainability. Full article

Two-dimensional (2D) organic−inorganic hybrid perovskites (OIHPs) have emerged as promising candidates for next-generation optoelectronic applications. While vertical heterostructures of 2D OIHPs have been explored through mechanical stacking, the controlled fabrication of lateral heterostructures remains a significant challenge. Here, we present a lithography-free, van der Waals mask-assisted strategy for the deterministic fabrication of 2D OIHP lateral heterostructures. Mechanically exfoliated 2D materials such as graphene serve as removable masks that enable selective conversion of unmasked perovskite regions via ion exchange reaction. This technique enables the fabrication of various lateral heterostructures, such as BA₂MA₂Pb₃I₁₀/MAPbI₃, PEAPbI₄/MAPbI₃, as well as BA₂MAPb₂I₇/MAPbBr₃. Furthermore, complex multiheterostructures and superlattices can be constructed through sequential masking and conversion processes. Moreover, to investigate the electronic properties and demonstrate potential device applications of the lateral heterostructures, we have fabricated an electrical diode based on a BA₂MA₂Pb₃I₁₀/MAPbI₃ lateral heterostructure. Stable electrical rectifying behavior with a rectification ratio of around 10 was observed. This general and flexible approach provides a robust platform for constructing 2D OIHPs lateral heterostructures and opens new pathways for their integration into high-performance optoelectronic devices. Full article

Renewable energy sources, particularly solar photovoltaics (PVs), are rapidly expanding to achieve carbon neutrality. Integrated photovoltaic (IPV) solutions in underutilized spaces offer a viable option for countries with land constraints and public opposition. Vertical PV (VPV) systems, featuring bifacial solar modules installed vertically, facing east and west, present a promising alternative. In contrast to conventional tilted PV (CPV) systems, which peak around midday, VPV systems generate more power in the morning and afternoon. This mitigates issues such as the duck curve and curtailment caused by midday overgeneration. Moreover, combining VPV and CPV systems can increase the solar hosting capacity of a distribution line (DL) for PV-system interconnections, driving research interest. This study assessed the hosting-capacity improvements from VPV systems by analyzing voltage fluctuations and thermal constraints using OpenDSS software (Version 9.1.1.1). The potential substitution effect of a smart inverter-based energy-storage system (ESS) was also explored. The analysis, based on real-grid conditions in South Korea, incorporated actual DL data, generation and demand profiles, and operational data from both VPV and CPV systems. Worst-case scenarios were simulated to evaluate their impact on grid stability. The results demonstrate that VPV systems can increase hosting capacity by up to 23% and ensure stable grid operation by reducing power-generation uncertainties. Full article

In complex traffic environments, image degradation due to adverse factors such as haze, low illumination, and occlusion significantly compromises the performance of object detection systems in recognizing vehicles and pedestrians. To address these challenges, this paper proposes a robust visual detection framework that integrates multi-stage image enhancement with a lightweight detection architecture. Specifically, an image preprocessing module incorporating ConvIR and CIDNet is designed to perform defogging and illumination enhancement, thereby substantially improving the perceptual quality of degraded inputs. Furthermore, a novel enhancement strategy based on the Horizontal/Vertical-Intensity color space is introduced to decouple brightness and chromaticity modeling, effectively enhancing structural details and visual consistency in low-light regions. In the detection phase, a lightweight state-space modeling network, Mamba-Driven Lightweight Detection Network with RT-DETR Decoding, is proposed for object detection in complex traffic scenes. This architecture integrates VSSBlock and XSSBlock modules to enhance detection performance, particularly for multi-scale and occluded targets. Additionally, a VisionClueMerge module is incorporated to strengthen the perception of edge structures by effectively fusing multi-scale spatial features. Experimental evaluations on traffic surveillance datasets demonstrate that the proposed method surpasses the mainstream YOLOv12s model in terms of mAP@50–90, achieving a performance gain of approximately 1.0 percentage point (from 0.759 to 0.769). While ensuring competitive detection accuracy, the model exhibits reduced parameter complexity and computational overhead, thereby demonstrating superior deployment adaptability and robustness. This framework offers a practical and effective solution for object detection in intelligent transportation systems operating under visually challenging conditions. Full article

Background/Objectives: Upper lumbar spinal stenosis presents unique challenges because vertically oriented facet joints and narrow laminae increase the risk of iatrogenic instability following decompression. Traditional decompression techniques may damage the facet joints, potentially resulting in further instability and degeneration. This study introduces a novel, facet-preserving bilateral–contralateral decompression strategy using unilateral biportal endoscopy (UBE) for upper lumbar stenosis, aiming to defer unnecessary spinal fusion. Methods: This retrospective series of three cases involved patients with upper lumbar stenosis characterized by vertically oriented facets (>60°) and narrow laminae, including cases of adjacent segment stenosis (ASS) and stenosis with grade 1 spondylolisthesis. Patients were selected using the authors’ facet angle–based criteria (>60°) and laminar morphology to identify anatomically vulnerable segments. All patients exhibited vertical facet orientation and narrow laminae, without significant dynamic instability or severe foraminal compromise. Bilateral–contralateral decompression was performed using biportal endoscopy to preserve facet integrity and defer fusion where feasible. Results: This series demonstrated that bilateral–contralateral decompression provided effective neural decompression and symptom relief while preserving facet structures in the upper lumbar spine characterized by vertical facets and narrow laminae. No progression to instability or requirement for additional fusion was observed during the 6-month follow-up, even among patients with ASS and grade 1 spondylolisthesis. Conclusions: The authors propose that bilateral–contralateral decompression may serve as a facet-preserving and fusion-deferral strategy for upper lumbar stenosis with vertically oriented facets and narrow laminae. This approach is particularly applicable in cases such as ASS and spinal stenosis with grade 1 spondylolisthesis, where preserving structural reserve is critical. These preliminary findings highlight the need for prospective validation through carefully designed observational studies and larger case series. Full article

Periphytic algae, as representative aquatic epiphytic communities, play a vital role in the material cycling and energy flow in rivers. Through physiological processes such as photosynthetic carbon fixation and nutrient absorption, they perform essential ecological functions in water self-purification, maintenance of primary productivity, and microhabitat formation. This study investigates the interaction mechanisms between these highly flexible organisms and the hydrodynamic environment, thereby addressing the limitations of traditional hydraulic theories developed for rigid vegetation. By incorporating the coupled effects of biological flexibility and water flow, an innovative nonlinear resistance model with velocity-dependent response is developed. Building upon this model, a coupled governing equation that integrates water flow dynamics, periphytic algae morphology, and layered Reynolds stress is formulated. An analytical solution for the vertical velocity distribution is subsequently derived using analytical methods. Through Particle Image Velocimetry (PIV) measurements conducted under varying flow velocity conditions in an experimental tank, followed by comprehensive error analysis, the accuracy and applicability of the model were verified. The results demonstrate strong agreement between predicted and measured values, with the coefficient of determination R² greater than 0.94, thereby highlighting the model’s predictive capacity in capturing flow velocity distributions influenced by periphytic algae. The findings provide theoretical support for advancing the understanding of ecological hydrodynamics and establish mechanical and theoretical foundations for river water environment management and vegetation restoration. Future research will build upon the established nonlinear resistance model to investigate the dynamic coupling mechanisms between multi-species periphytic algae communities and turbulence-induced pulsations, aiming to enhance the predictive modelling of biotic–hydrodynamic feedback processes in aquatic ecosystems. Full article

This paper proposes novel designs of dual-layer flower-shaped heave plates, featuring both aligned and staggered configurations with three, six, and nine petals. Numerical simulations were conducted to study the hydrodynamic effects of these various heave plate designs integrated with the OC4 DeepCwind semisubmersible floating offshore wind turbine platform under prescribed heave oscillations. The overset mesh technique was employed to treat the floating platform’s motions. Comprehensive assessments of vertical force, radiated wave patterns, vorticity fields, added mass, and damping coefficients were conducted. The results revealed that the novel flower-shaped staggered heave plates significantly outperformed conventional circular plates in terms of damping coefficients. Specifically, the damping coefficient of flower-shaped staggered heave plates was greater than that of circular heave plates, while the aligned configuration exhibited a lower damping coefficient. The damping coefficient increased with a reduction in the number of petals for the staggered heave plates. Among the evaluated designs, the dual-layer flower-shaped staggered heave plates with three petals demonstrated the highest effectiveness in attenuating heave motion of the floating platform. The utilization of novel dual-layer flower-shaped staggered heave plates is therefore a promising practice aimed at damping the heave motion of platforms in rough seas. Full article

In this study we report on the structural, mechanical, and electrical characterization of different structures of vertically aligned zinc oxide (ZnO) nanowires (NWs) synthesized using hydrothermal methods. By optimizing the growth conditions, scanning electron microscopy (SEM) micrographs show that the ZnO NWs could reach an astounding 51.9 ± 0.82 µm in length, 0.7 ± 0.08 µm in diameter, and 3.3 ± 2.1 µm⁻² density of the number of NWs per area within 24 h of growth time, compared with a reported value of ~26.8 µm in length for the same period. The indentation modulus of the as-grown ZnO NWs was determined using contact resonance (CR) measurements using atomic force microscopy (AFM). An indentation modulus of 122.2 ± 2.3 GPa for the NW array sample with an average diameter of ~690 nm was found to be close to the reference bulk ZnO value of 125 GPa. Furthermore, the measurement of the piezoelectric coefficient (d₃₃) using the traceable ESPY33 tool under cyclic compressive stress gave a value of 1.6 ± 0.4 pC/N at 0.02 N with ZnO NWs of 100 ± 10 nm and 2.69 ± 0.05 µm in diameter and length, respectively, which were embedded in an S1818 polymer. Current–voltage (I-V) measurements of the ZnO NWs fabricated on an n-type silicon (Si) substrate utilizing a micromanipulator integrated with a tungsten (W) probe exhibits Ohmic behavior, revealing an important phenomenon which can be attributed to the generated electric field by the tungsten probe, dielectric residue, or conductive material. Full article

Breakwater dams are critical infrastructures that protect the safety of ports. However, these coastal structures are facing the compounding threats of sea level rise, storm surge, and dam subsidence. Heterogeneous deformations in these infrastructures arise from differential construction sequencing, sediment consolidation, and filling materials, yet traditional in situ monitoring remains spatially limited or even unavailable to trace back and continuously monitor deformation evolutions. In contrast, Interferometric Synthetic Aperture Radar (InSAR) offers valuable insights in providing the spatially and temporally covered dam deformation. In this study, we used two Sentinel-1 tracks from 2016 to 2025, and the persistent and distributed scatterers InSAR methods to map the long-term deformation of Xuwei Port, Lianyungang, China. We utilized six sites of leveling measurements to validate the InSAR-derived vertical deformation and indicate Root Mean Square Errors (RMSEs) ranging from −0.9–1.2 cm. We find, for the rock-sand filled section, the deformations show consolidating subsidence ranging from −63.8 cm to −40.6 cm. In contrast, the concrete tubular structure remains stable, with cumulative deformation ranging from −10.6 cm to −5.2 cm. The enclosing reclaimed land undergoes a period of accelerated settlement with subsidence rates of −64.9–−39.3 cm/yr, which are higher than original subsidence rates of −10.1–−9.7 cm/yr. Additionally, we integrated the consolidation model and tide gauge to quantify that the freeboard will decrease to 0.08–0.31 m in the following 100 years with the continuous sea level rise and dam subsidence. This study benefits our understandings of coastal dam and reclaimed land. It highlights InSAR as a valuable tool to evaluate the critical risk between sea level rise and coastal infrastructure subsidence. Full article

Research in marine hydrographic environmental monitoring continues to deepen, necessitating a hardware platform capable of traversing air–water interfaces to collect vertical gradient parameters across oceanographic profiles. This paper proposes a deeply integrated heterogeneous monitoring platform for marine hydrological vertical profiling, addressing the functional limitations of conventional unmanned surface vehicles (USVs) and unmanned aerial vehicles (UAVs) in subsurface monitoring. By co-designing a hybrid aerial underwater vehicle (HAUV) with cross-domain capabilities and a USV, the system leverages USVs for long-endurance surface operations and HAUVs for high-speed vertical column monitoring. Key innovations include (1) a distributed collaborative architecture enabling “Air–Sea–Air” cyclic operations; (2) dynamic modeling of HAUV-USV interactions incorporating aerodynamic and hydrodynamic coupling; (3) an MPC-based collaborative tracking algorithm for real-time USV pursuit under marine disturbances; and (4) a vision-guided synchronous landing strategy achieving decimeter-level docking accuracy in bad conditions. Simulation experiments validate the system’s efficacy in trajectory tracking and precision landing. This work bridges the critical gap in marine vertical profile monitoring while demonstrating robust cross-domain coordination. Full article