Search Results (431)

A weak-axis moment connection incorporating a double reduced beam section and a box-reinforced panel zone (WDRBS) is introduced for hot-rolled H-shaped columns. The configuration is intended to shift inelastic demand away from the column face and to constrain weak-axis panel-zone distortion. A series of finite element models is established and calibrated to examine the cyclic response of this connection type. By varying the geometric parameters of the second reduction zone, a closed-form expression for determining its cutting depth (c₂) is formulated, allowing both reduced regions to yield concurrently, i.e., the Optimum State. The numerical investigation demonstrates that connections designed according to this equation exhibit stable hysteresis, limited weld-adjacent plastic ll rightstrain, and sufficient deformation and energy-dissipation capacities. All specimens exhibit plastic rotations greater than 0.03 rad, ductility ratios greater than 3.0, and equivalent viscous damping ratios greater than 0.3. To facilitate engineering implementation using common hot-rolled sections, a simplified method is further proposed to approximate the admissible range of c₂ with practical accuracy. While the length of the second reduction region has only a modest influence on peak strength (approximately 1.5–6%), it markedly affects the failure mechanism and plastic-hinge distribution. A stepwise design procedure for WDRBS connections is accordingly recommended. The study does not consider composite-slab interaction or gravity-load effects, and the findings—based solely on finite element simulations—require future verification through full-scale experimental testing. Full article

The prediction accuracy of the General Circulation Model (GCM) is influenced by the effectiveness of gravity wave activity parameterization. Although research focuses on small-scale horizontal gravity wave activity as a carrier for energy and momentum coupling between atmospheric layers, routine observations of horizontal gravity wave activity on scales less than a dozen kilometers are scarce due to limitations in observational instruments. This paper presents a method for observing small-scale horizontal gravity waves using monostatic Rayleigh lidar, along with the associated data processing workflow. The data processing results indicate that the observed gravity waves generally exhibit wavelengths less than 3 km and phase velocities less than 0.5 m/s. Furthermore, the annual variation in small-scale horizontal gravity waves displays a semi-annual oscillation (SAO), like that observed in medium- and large-scale waves. This suggests that the observed gravity waves originate from secondary gravity waves resulting from saturation dissipation or breaking. Full article

To address the industry pain points of high seed breakage rate and uncontrollable miss-filling rate, multiple-filling rate in traditional rapeseed roller-type precision centralized seed metering devices—while breaking the adaptation limitation of existing empirical hole designs for different small-particle-size crops—this study innovatively proposes a hole optimization scheme based on the Bezier curve and develops a roller-type precision centralized seed metering device suitable for rapeseed and small-particle-size crops. First, combined with the physical properties of rapeseed seeds (particle size 1.5~2.5 mm, high sphericity, strong fluidity) and agronomic requirements for precision seeding, a multi-mechanical coupling model for seed filling and dropping (synergistic effect of gravity–centrifugal force–air blowing force) was established. The regulatory mechanism of hole geometric parameters (wrap angle, width, height) on seeding performance was clarified, and the enhancement mechanism of the Bezier curve’s curvature continuity on seed movement stability was revealed from the theoretical level. On this basis, a three-factor quadratic orthogonal combination experiment of hole wrap angle, width, and height was conducted using EDEM discrete element software. The optimal hole parameter combination was obtained through multi-objective optimization (minimizing miss-filling rate, multiple-filling rate and maximizing seed-filling qualification rate): wrap angle 2.271° (error ± 0.2°), width 3.407 mm (error ± 0.1 mm), and height 2.254 mm (error ± 0.02 mm). Simulation results showed that under this parameter combination, the seed-filling qualification rate reached 99.122%, with the miss-filling rate and multiple-filling rate as low as 0.448% and 0.416%, respectively. Further bench test verification indicated that when the roller speed was in the range of 10~30 r/min, the seed breakage rate was consistently below 0.5%, and the seed-filling qualification rate remained above 94%. Among them, the comprehensive seeding performance was optimal at a speed of 15 r/min, with a miss-seeding rate of 0.65%, a multiple-seeding rate of 2.06%, and a breakage rate of 0.12%, fully meeting the agronomic requirements for rapeseed precision seeding, providing a theoretical basis and engineering reference for the digital and universal design of key components of precision seeders for small-particle-size crops. Full article

In this work, we develop a unified framework for Conformal Gravity and Noncommutative (Fuzzy) Gravity incorporating internal interactions. Our approach relies on two fundamental observations: first, the dimensions of a curved manifold and those of its tangent group need not coincide, and second, both gravitational models can be formulated as gauge theories. We begin with a discussion of the gauge-theoretic formulation of gravitational dynamics, emphasizing the role of diffeomorphism invariance. We then outline the constructions of Conformal Gravity and Fuzzy Gravity within this formalism. Building on an extension of the four-dimensional tangent group, we propose a scheme that unifies the two theories while naturally incorporating internal degrees of freedom. We further investigate the low-energy limits that emerge after appropriate spontaneous symmetry-breaking mechanisms, and we comment on potential observational signatures—particularly those associated with cosmic strings and their imprint on gravitational-wave spectra. Full article

In many mountainous areas of China, frequent geological disasters pose a serious threat to human life and property. The Luding “9.5” earthquake triggered a large number of landslide disasters, causing serious loss of life and property. Therefore, it is extremely urgent to carry out research on the stability analysis and treatment methods of landslides in the Luding area. In this paper, the Caiyangba landslide in Yanzigou Town, Luding County, is taken as the research object. The slope model is constructed by Midas to study the stability development law of Caiyangba landslide under different rainfall conditions and seismic conditions, and to explore the feasibility of the “anchor lattice treatment method”. The results show that the “anchor lattice treatment method” can effectively improve the stability of the slope under rainfall conditions. The improvement effect of slope stability decreases with the increase in rainfall duration and rainfall. The development law of the slope stability coefficient with rainfall duration in WMG (the working condition of not adopting the “anchor lattice treatment method” is referred to as WMG) and MG (the working condition of adopting the “anchor lattice treatment method” is referred to as MG) conditions conform to the development law of exponential function, and the expression of instantaneous change rate of slope stability coefficient is derived. The above function can also well explain the development law of X-direction displacement and Y-direction displacement of SP (school: monitoring point) and RP (road: monitoring point); the development law of the instantaneous change rate of displacement. Under the influence of ground motion, the improvement effect of the “anchor lattice treatment method” on the slope stability coefficient is limited, but the improvement effect of slope stability increases with the increase in seismic intensity. The slope stability coefficient and the displacement of SP and RP show obvious fluctuation with time, and the fluctuation law is similar to that of ground motion records. It is recommended to add a gravity-retaining wall at the foot of the slope. The teaching building reduces the number of floors and increases the number of pile foundations. Roads should restrict the passage of heavy vehicles, such as cars and strictly stacked items. The above results can provide a theoretical reference for the sustainable treatment and sustainable development of landslides in the Luding area. Full article

Against the backdrop of continuous natural space loss and accelerated urbanization, considerable attention has been directed toward balancing economic development demands with the protection of fragile ecosystems within limited spatial boundaries to achieve regional sustainable development. This study therefore focuses on Chengmai County, a small-scale region prioritizing both green development and ecological conservation. Land-use changes and trends in ecosystem services value (ESV) from 2000 to 2020 were analyzed. An ecological security assessment model was developed, integrating ecosystem services, ecological sensitivity, and landscape connectivity, which enabled the identification of areas with high ecological security value as ecological sources. Ecological corridors and nodes were extracted using the minimum cumulative resistance model and the gravity model, culminating in the construction of Chengmai County’s ecological security pattern through overlay analysis. The main findings are summarized as follows: (1) Construction land expanded rapidly between 2000 and 2020. The ecological sensitivity of Chengmai County displayed a spatial distribution pattern of “high in the south, low in the north,” while ESV exhibited a pattern of “high in the central-south and low in the northeast,” showing an overall increasing trend. (2) The overall ecological security status was relatively favorable. A total of 10 ecological nodes and 45 ecological corridors were identified, including 16 core corridors. (3) Based on these analyses, an ecological security pattern described as “one axis, two belts, and three zones” was established for Chengmai County. This study provides a practical spatial strategy for ecological conservation and sustainable development in Chengmai County and offers a transferable methodological framework for similar coastal regions facing development pressures. Full article

This study investigated the influence of spatial orientation on bead morphology and molten pool dynamics during cold metal transfer wire arc additive manufacturing (CMT-WAAM). Experiments in horizontal, transverse, vertical-down, and vertical-up orientations under varying wire feed speeds revealed that increasing the feed rate improved bead uniformity and reduced defects in horizontal deposition, while gravity-induced asymmetry dominated non-horizontal orientations. Transverse cladding produced tilted, uneven beads with reduced penetration; vertical-down enhanced lateral spreading but resulted in the shallowest weld depth; vertical-up limited spreading, yielding narrow beads with higher reinforcement. Optimal cladding quality was achieved at a wire feed speed of 6.7 m/min for the first layer, with a reduced heat input applied for subsequent layers to minimize residual stress and deformation. Numerical simulations further elucidated transient temperature and flow fields. Heat accumulation and dissipation varied with orientation and layer sequence: horizontal deposition formed deep, symmetric pools; transverse deposition generated asymmetric vortices and uneven solidification; vertical-up deposition caused upward counterflow with restricted spreading; vertical-down promoted rapid spreading and faster solidification. A detailed comparison between simulated and experimental temperature distributions and cross-sectional profiles demonstrated excellent agreement, thereby validating the accuracy and predictive capability of the developed model. This integrated experimental-numerical approach provided a comprehensive understanding of orientation-dependent molten pool behavior and offered a robust framework for optimizing process parameters, enhancing dimensional accuracy, and controlling defects in CMT additive manufacturing. Full article

The upper-limb exoskeleton is ergonomically designed to align with human arm motion and can be configured for deployment as a master tool manipulator (MTM) in teleoperation systems. However, existing teleoperated exoskeletons are limited by excessive weight and inadequate force feedback. This study proposes a novel lightweight exoskeleton with optimized shoulder and wrist joint structure, enabling full arm mobility and sufficient force feedback. In practical applications, gravitational forces can lead to muscle fatigue and degrade teleoperation performance, making compensation essential for ergonomic and safety. However, unknown system disturbance caused by unmodeled dynamics (such as internal compliance and cables) pose challenges for compensation precision. A theoretical dynamics model and a Bayesian neural network (BNN) trained on separate datasets to predict joint torques and their corresponding uncertainties were independently developed. Then a Bayesian fusion method was employed to combine model-based and data-driven estimates, using predicted standard deviations to assign fusion weights and produce a refined torque output. Compared to relying solely on the CAD model, the proposed fusion framework combines the physical consistency of model-based approaches with the adaptability of data-driven methods. Experiments ultimately demonstrate that the proposed algorithm effectively reduces modeling errors and enhances the accuracy and robustness of gravity compensation. Full article

Accurate estimation of attitude, line of sight (LOS), and carrier-phase ambiguity is essential for the performance of Guidance, Navigation, and Control (GNC) systems operating under highly dynamic and uncertain conditions. Traditional sensor fusion and filtering methods, although effective, often require precise modeling and high-grade sensors to maintain robustness. This paper investigates a deep learning-based estimation framework for attitude, LOS, and GNSS ambiguity through the fusion of onboard sensors—GNSS, IMU, and semi-active laser (SAL)—and remote sensing information. Two neural network estimators are developed to address the most critical components of the navigation chain: GNSS carrier-phase ambiguity and gravity-vector reconstruction in the body frame, which are integrated into a hybrid guidance and navigation scheme for attitude and LOS determination. These learning-based estimators capture nonlinear relationships between sensor measurements and physical states, improving generalization under degraded conditions. The proposed system is validated in a six-degree-of-freedom (6-DoF) simulation environment that includes full aerodynamic modeling of artillery guided rockets. Comparative analyses demonstrate that the learning-based ambiguity and gravity estimators reduce overall latency, enhance estimation accuracy, and improve guidance precision compared to conventional networks. The results suggest that deep learning-based sensor fusion can serve as a practical foundation for next-generation low-cost GNC systems, enabling precise and reliable operation in scenarios with limited observability or sensor degradation. Full article

The Yellow River Basin serves as a critical ecological barrier and economic corridor in China, playing a pivotal role in national ecological security and sustainable development. This study develops a comprehensive evaluation framework grounded in the Water–Energy–Food–Ecosystem (WEFE) nexus, employing 25 indicators across nine provinces and autonomous regions over the period 2000–2023. Utilizing a multi-method approach—including the entropy weight method, coupling coordination degree model, center of gravity migration analysis, principal component analysis, and obstacle factor diagnosis—the research investigates the coordinated development and dynamic interactions among the WEFE subsystems. Key findings include: (1) the calculated weights of the water, energy, food, and ecological subsystems were 0.3126, 0.1957, 0.1692, and 0.3225, respectively, indicating that ecological and water subsystems exert the greatest influence; (2) distinct growth patterns among subsystems, with the energy subsystem exhibiting the fastest growth rate (212%) and the water subsystem the slowest (4%); (3) a steady improvement in the overall coordination degree of the WEFE system, rising from 0.417 in 2000 to 0.583 in 2023—a 39.8% increase—with Henan (0.739) and Inner Mongolia (0.715) achieving the highest coordination levels in 2023, while Qinghai (0.434) and Ningxia (0.417) remained near imbalance thresholds; (4) complex spatial dynamics reflected by cumulative center of gravity migration distances of 678.2 km (water), 204.9 km (energy), 143.3 km (food), and 310.9 km (ecology) over the study period; and (5) identification of per capita water resources as the principal limiting factor to coordinated WEFE development, with an obstacle degree of 0.1205 in 2023, underscoring persistent water scarcity challenges. This integrated framework advances WEFE nexus analysis and provides robust, evidence-based insights to inform regional policy and resource management strategies. Full article

Background: Ethylenebisdithiocarbamates, widely used in floriculture, degrade into ethylenethiourea (ETU), a teratogen. The SEMILLA study investigates prenatal ETU exposure and infant health in Ecuador’s flower-growing region. This analysis examines whether prenatal ETU metabolite levels differ by work sector and whether maternal urinary ETU increases with longer work hours. Methods: Participants (agricultural workers, non-agricultural workers, and non-workers) provided baseline urine samples, which were processed and stored for ETU analysis. Surveys captured ETU exposure predictors. Regression models assessed associations between work sector, weekly work hours, and urinary ETU levels (specific gravity-corrected), controlling for key covariates. Results: The sample includes 111 agricultural workers (92% floriculture), 149 non-agricultural workers, and 149 non-workers. At baseline, maternal age averaged 27 years (SD = 5.8) and gestational age 15 weeks (SD = 3.2). Urinary ETU_SG levels were elevated across the sample (geometric mean: 3.38 µg/L). Agricultural workers had significantly higher ETU_SG levels than others (5.61 vs. 3.07 and 2.57 µg/L; p < 0.001). Among agricultural workers, ETU_SG levels increased with weekly hours (B = 0.288, p = 0.001). Conclusions: Agricultural work strongly predicts higher prenatal ETU exposure, with evidence of a dose–response relationship. Research on prenatal fungicide exposure and infant health among pregnant workers is limited. Findings highlight the need for targeted interventions to protect pregnant workers and infant health. Full article

Fractured-vuggy carbonate reservoirs primarily have pores and caves as their main storage spaces with poor fracture development, resulting in low reservoir connectivity and strong heterogeneity. During nitrogen injection developments, the fluidity of the medium is poor, and gas tends to form dominant flow channels, leading to a short response time. Consequently, the displacement of crude oil in such reservoirs is limited, leaving a large proportion of residual oil trapped within the pore and vug systems. Based on the Tarim fractured-vuggy carbonate reservoir, a two-dimensional visualized physical model of the fractured-vuggy body was designed and constructed to conduct a foam-assisted gas displacement physical experiment. The research shows that foam has good oil recovery efficiency and dominant channel-blocking ability, which can effectively mobilize the residual oil in the fractures and vugs after gas displacement. In the vertical direction, the foam-assisted gas flooding mechanism primarily involves gravity segregation and interfacial tension reduction between oil and water; horizontally, it operates by selectively blocking large fractures and main channels, redirecting gas into smaller and more tortuous pathways, thus enhancing overall sweep efficiency. Once dominant flow channels develop, injecting salt-sensitive foam at a 2:1 gas–liquid ratio and 0.3 pore volume can raise the recovery factor from around 3% to nearly 19%, representing an improvement of about 16%, thereby boosting both gas flooding performance and overall field development efficiency. Full article

Magnetic, angular rate, and gravity (MARG) sensor-based inference is the de facto standard for mobile robot pose estimation, yet its sensor limitations necessitate fusion with absolute references. In environments where such references are unavailable, the system must rely solely on the uncertain MARG-based inference, posing significant challenges due to the resulting estimation uncertainties. This paper addresses the challenge of enhancing the accuracy of position/velocity estimations based on the fusion of MARG sensor data with shallow neural network (NN) models. The proposed methodology develops and trains a feasible cascade-forward NN to reliably estimate the true acceleration of dynamical systems. Three types of NNs are developed for acceleration estimation. The effectiveness of each topology is comprehensively evaluated in terms of input combinations of MARG measurements and signal features, number of hidden layers, and number of neurons. The proposed approach also incorporates extended Kalman and gradient descent orientation filters during the training process to further improve estimation effectiveness. Experimental validation is conducted through a case study on position/velocity estimation for a low-cost flying quadcopter. This process utilizes a comprehensive database of random dynamic flight maneuvers captured and processed in an experimental test environment with six degrees of freedom (6DOF), where both raw MARG measurements and ground truth data (three positions and three orientations) of system states are recorded. The proposed approach significantly enhances the accuracy in calculating the rotation matrix-based acceleration vector. The Pearson correlation coefficient reaches 0.88 compared to the reference acceleration, surpassing 0.73 for the baseline method. This enhancement ensures reliable position/velocity estimations even during typical quadcopter maneuvers within 10-s timeframes (flying 50 m), with a position error margin ranging between 2 to 4 m when evaluated across a diverse set of representative quadcopter maneuvers. The findings validate the engineering feasibility and effectiveness of the proposed approach for pose estimation in GPS-denied or landmark-deficient environments, while its application in unknown environments constitutes the main future research direction. Full article

This study investigates factors influencing migrants’ decisions to enter Europe via Bulgaria or Greece along the Balkan route, using logistic regression and machine learning models on data from the International Organization for Migration (IOM) Flow Monitoring Survey (August 2022–June 2025, $n=5536$). We examine demographic variables (age), push factors (economic reasons, war/conflict, personal violence, limited access to services, and avoiding military service), and governance clusters derived from the World Bank’s Worldwide Governance Indicators (WGIs). An adapted migration gravity model incorporates corruption control as a key push–pull factor. Key findings indicate that younger migrants are significantly more likely to choose Bulgaria ($\beta \approx -0.021$, $p<0.001$), and governance clusters show that migrants from high-corruption origins (e.g., Syria and Afghanistan) prefer Bulgaria, likely due to governance similarities and facilitation costs. The Cluster Model achieves a slight improvement in fit (McFadden’s $R^2=0.008$, AIC = 7367) compared to the Base (AIC = 7374) and Interaction (AIC = 7391) models. Machine learning extensions using LASSO and Random Forests on a subset of data ($n=4429$) yield similar moderate performance (AUC: LASSO = 0.524, RF = 0.515). These insights highlight corruption’s role in route selection, offering policy recommendations for origin, transit, and destination phases. Full article

The Central Asian Orogenic Belt (CAOB) represents one of the largest Phanerozoic accretionary orogenic systems globally, with its easternmost segment located in Northeast China. This study integrated broadband magnetotelluric (MT) surveys, geochemical analyses, and high-pressure, high-temperature electrical conductivity experiments to elucidate the deep structural characteristics and tectonic evolution of the Heihe-Hegenshan Suture (HHS) within the CAOB. A dense MT profile survey comprising 15 stations was deployed across the HHS, revealing distinct high-conductivity anomalies interpreted as the suture zone and associated tectonic features. Geochemical and petrophysical analyses of representative andesite and granite samples under simulated crustal conditions (573–973 K, 1.0 GPa) provided critical constraints for MT data interpretation. The integration of MT inversion results with aeromagnetic and Bouguer gravity anomaly data delineates the strike and spatial extent of the HHS, confirming its continuity and northward extension beyond previously recognized limits. Numerical modeling of geothermal gradients and electrical conductivity–depth relationships highlights the dominant role of hydrothermal fluids and alteration minerals in controlling shallow high-conductivity anomalies (<5 km), while deeper structures (>5 km) reflect temperature-controlled rock conductivity. These findings offer novel insights into the lithospheric-scale architecture and geodynamic processes governing the HHS, advancing our understanding of complex accretionary orogenesis in the CAOB. Full article