Search Results (1,018)

The Shahejie Formation in Nanpu Sag is a crucial region for deep-layer hydrocarbon exploration in the Bohai Bay Basin. To address the impact of faults on sublacustrine fan formation and spatial distribution within the study area, this study integrated well logging, laboratory analysis, and 3D seismic data to systematically analyze sedimentary characteristics of sandbodies from the first member of the Shahejie Formation (Es₁) sublacustrine fans, clarifying their planar and cross-sectional distributions. Further research indicates that Gaoliu Fault activity during Es₁ deposition played a significant role in fan development through two mechanisms: (1) vertical displacement between hanging wall and footwall reshaped local paleogeomorphology; (2) tectonic stresses generated by fault movement affected slope stability, triggering gravitational mass transport processes that remobilized fan delta sediments into the central depression zone as sublacustrine fans through slumping and collapse mechanisms. Core observations reveal soft-sediment deformation features, including slump structures, flame structures, and shale rip-up clasts. Seismic profiles show lens-shaped geometries with thick centers thinning laterally, exhibiting lateral pinch-out terminations. Inverse fault-step architectures formed by underlying faults control sandbody distribution patterns, restricting primary deposition locations for sublacustrine fan development. The study demonstrates that sublacustrine fans in the study area are formed by gravity flow processes. A new model was established, illustrating the combined control of the Gaoliu Fault and reverse stepover faults on fan development. These findings provide valuable insights for gravity flow exploration and reservoir prediction in the Nanpu Sag, offering important implications for hydrocarbon exploration in similar lacustrine rift basins. Full article

The southeastern Yunnan region in the southwestern Nanpanjiang Basin is one of the most important manganese enrichment zones in China. Manganese mineralization is mainly confined to marine mud–sand–carbonate interbeds of the Middle Triassic Ladinian Falang Formation (T₂f), which contains several medium to large deposits such as Dounan, Baixian, and Yanzijiao. However, the geological processes that control manganese mineralization in this region remain insufficiently understood. Understanding the tectonic evolution of the basin is therefore essential to unravel the mechanisms of Middle Triassic metallogenesis. This study investigates how rift-related tectonic activity influences manganese ore formation. This study integrates global gravity and magnetic field models (WGM2012, EMAG2v3), audio-frequency magnetotelluric (AMT) profiles, and regional geological data to investigate ore-controlling structures. A distinct gravity low–magnetic high belt is delineated along the basin axis, indicating lithospheric thinning and enhanced mantle-derived heat flow. Structural interpretation reveals a rift system with a checkerboard pattern formed by intersecting NE-trending major faults and NW-trending secondary faults. Four hydrothermal plume centers are identified at these fault intersections. AMT profiles show that manganese ore bodies correspond to stable low-resistivity zones, suggesting fluid-rich, hydrothermally altered horizons. These findings demonstrate a strong spatial coupling between hydrothermal activity and mineralization. This study provides the first identification of the internal rift architecture within the Nanpanjiang Basin. The basin-scale rift–graben system exerts first-order control on sedimentation and manganese metallogenesis, supporting a trinity model of tectonic control, hydrothermal fluid transport, and sedimentary enrichment. These insights not only improve our understanding of rift-related manganese formation in southeastern Yunnan but also offer a methodological framework applicable to similar rift basins worldwide. Full article

Low solar radiation, caused by climate change or dense planting patterns, now limits wheat production. Although wheat breeding has increased lodging resistance and yield potential through the introduction of dwarfing genes, it still reduces wheat yields. Few studies have been conducted to clarify the lodging sensitivity to shading of different-era wheat cultivars in China’s Huang-Huai-Hai region, as well as the characteristics of lodging resistance as affected by paclobutrazol under shading stress. To address this gap, the experiment included two wheat cultivars released in different decades, grown under shade and treated with or without paclobutrazol. The results showed that reductions in filling degree and lignin content, together with increases in length of the basal internode and gravity center height, markedly reduced the section modulus and breaking strength of shaded wheat culms. These changes impaired lodging resistance and raised lodging risk. However, paclobutrazol application effectively reduced lodging incidence and increased wheat yield under shading stress. Furthermore, these responses were more pronounced in the old cultivar (YZM) than in the modern cultivar (S28). This indicates that the culm mechanical parameters of the old cultivar were more shade-sensitive than those of the modern cultivar. Moreover, shading downregulated the relative expression levels of key genes associated with lignin biosynthesis to decrease the activities of key enzymes, thereby inhibiting the biosynthesis and deposition of lignin in culms to increase the risk of wheat lodging. Paclobutrazol application alleviated the inhibitory effects of shading on lignin biosynthesis, thereby strengthening culms and enhancing lodging resistance. These findings may provide a basis for exploring cultivation regulation methods to enhance wheat lodging resistance under overcast and low-sunshine conditions, and to offer guidance for the breeding of wheat cultivars with lodging resistance and shade tolerance. Full article

Amid ongoing societal development, tourists’ travel behavior patterns have been undergoing substantial transformations, and understanding their evolution has emerged as a key area of scholarly interest. Taking Beijing as a case study, this research aims to uncover the spatiotemporal evolution patterns of tourist flows and their underlying driving mechanisms. Based on digital footprint relational data, a dual-perspective analytical framework—“tourist perception–tourist flow network”—is constructed. By integrating the center-of-gravity model, social network analysis, and regression models, the study systematically examines the dynamic spatial structure of tourist flows in Beijing from 2012 to 2024. The findings reveal that in the post-pandemic period, Beijing tourists place greater emphasis on the cultural connotation and experiential aspects of destinations. The gravitational center of tourist flows remains relatively stable, with core historical and cultural blocks retaining strong appeal, though a slight shift has occurred due to policy influences and emerging attractions. The evolution of the spatial network structure reveals that tourism flows have become more dispersed, while the influence of core scenic spots continues to intensify. Government policy orientation, tourism information retrieval, and the agglomeration of tourism resources significantly promote the structure of tourist flows, whereas the general level of tourism resources exerts no notable influence. These findings offer theoretical insights and practical guidance for the sustainable development and regional coordination of tourism in Beijing, and provide a valuable reference for the spatial restructuring of urban tourism in the post-COVID-19 era. Full article

This research presents a reinforcement learning framework for stable quadruped locomotion using Proximal Policy Optimization (PPO). We address critical challenges in articulated robot control—including mechanical complexity and trajectory instability by implementing a 12-degree-of-freedom model in PyBullet simulation. Our approach features three key innovations: (1) a hybrid reward function ($R_t=0.72 · e^{-\Delta {\mathrm{CoG}}_t} + 0.25 · v_t - 0.11 · ‖{\tau }_t‖$) explicitly prioritizing center-of-gravity (CoG) stabilization; (2) rigorous benchmarking demonstrating Adam’s superiority over SGD for policy convergence (68% lower reward variance); and (3) a four-metric evaluation protocol quantifying locomotion quality through reward progression, CoG deviation, policy loss, and KL-divergence penalties. Experimental results confirm an 87.5% reduction in vertical CoG oscillation (from 2.0″ to 0.25″) across 1 million training steps. Policy optimization achieved −6.2 × 10⁻⁴ loss with KL penalties converging to 0.13, indicating stable gait generation. The framework’s efficacy is further validated by consistent CoG stabilization during deployment, demonstrating potential for real-world applications requiring robust terrain adaptation. Full article

To overcome the limitations of gravity inversion methods in fault inversion, this paper proposed a constrained adaptive weighted particle swarm optimization algorithm. Simulation experiments demonstrate that the proposed method exhibits stronger noise resistance compared to traditional optimization methods. In practical cases, the inversion accuracy of this method is improved by at least 64.4%, and the predicted gravity anomaly curve is closer to the observed data. The research findings are as follows: (1) The linearly decreasing inertia weight strategy performs best in terms of convergence efficiency and global search capability; (2) among the fault parameters, the top-layer center depth $z$ and bottom-layer center depth $w$ show higher sensitivity, and the inversion results for these parameters are more stable, which is beneficial for determining the depth information of faults; (3) introducing L2 regularization and penalty terms as constraints significantly improves the inversion stability, and among these, $z$ and $w$ have a particularly notable impact on the error. Full article

To explore the integration efficiency of ecology, culture and tourism in China, this study uses a Super-Efficiency SBM model with undesirable outputs to measure integration efficiency, employs kernel density estimation (KDE) to analyze dynamic spatial distribution characteristics, applies the standard deviational ellipse (SDE) to examine the migration trend of the spatial agglomeration center of gravity, and uses Tobit regression to identify spatiotemporal influencing factors. The findings show that: the national integration efficiency presents a trend that first decreases and then increases, with North and South China having relatively high integration efficiency. The national integration efficiency has gone through three stages: narrowing differences, coexistence of slow efficiency, and gradient effects, and increasing efficiency with weakened multipolarization. The degree of spatial agglomeration has gradually increased, and the center of gravity has shifted eastward as a whole. The internal gaps in East and South China have expanded, while the internal balance in North China has improved; the internal differences in other regions have narrowed. The influencing factors of integration efficiency have shifted from traditional economy-led to innovation and institutional collaboration. Economic development level and market openness have a positive impact on the overall integration efficiency, while transportation conditions show a restraining effect. Full article

The remote sensing monitoring of land use changes and future scenario simulation hold crucial significance for accurately characterizing urban expansion patterns, optimizing urban land use configurations, and thereby promoting coordinated regional development. Through the integration of multi-source data, this study systematically analyzes the spatiotemporal trajectories and driving forces of land use changes in the Pearl River Delta urban agglomeration (PRD) from 1990 to 2020 and further simulates the spatial patterns of urban land use under diverse development scenarios from 2025 to 2035. The results indicate the following: (1) During 1990–2020, urban expansion in the Pearl River Delta urban agglomeration exhibited a “stepwise growth” pattern, with an annual expansion rate of 3.7%. Regional land use remained dominated by forest (accounting for over 50%), while construction land surged from 6.5% to 21.8% of total land cover. The gravity center trajectory shifted southeastward. Concurrently, cropland fragmentation has intensified, accompanied by deteriorating connectivity of ecological lands. (2) Urban expansion in the PRD arises from synergistic interactions between natural and socioeconomic drivers. The Geographically and Temporally Weighted Regression (GTWR) model revealed that natural constraints—elevation (regression coefficients ranging −0.35 to −0.05) and river network density (−0.47 to −0.15)—exhibited significant spatial heterogeneity. Socioeconomic drivers dominated by year-end paved road area (0.26–0.28) and foreign direct investment (0.03–0.11) emerged as core expansion catalysts. Geographic detector analysis demonstrated pronounced interaction effects: all factor pairs exhibited either two-factor enhancement or nonlinear enhancement effects, with interaction explanatory power surpassing individual factors. (3) Validation of the Patch-generating Land Use Simulation (PLUS) model showed high reliability (Kappa coefficient = 0.9205, overall accuracy = 95.9%). Under the Natural Development Scenario, construction land would exceed the ecological security baseline, causing 408.60 km² of ecological space loss; Under the Ecological Protection Scenario, mandatory control boundaries could reduce cropland and forest loss by 3.04%, albeit with unused land development intensity rising to 24.09%; Under the Economic Development Scenario, cross-city contiguous development zones along the Pearl River Estuary would emerge, with land development intensity peaking in Guangzhou–Foshan and Shenzhen–Dongguan border areas. This study deciphers the spatiotemporal dynamics, driving mechanisms, and scenario outcomes of urban agglomeration expansion, providing critical insights for formulating regionally differentiated policies. Full article

For the correct execution of the preliminary design of a transport ship, among other things, approximate formulas enabling the calculation of the weight of the unladen ship and the location of the center of gravity are necessary. The aim of the conducted research was to develop approximate formulas for calculating the weight and center of gravity of an empty container ship with a size ranging from 270 TEU to 3100 TEU, depending on the basic design parameters: ship speed V, deadweight DWT, and number of TEU containers. Since the weight of an unladen container ship has a very large impact on the ship’s operating parameters, an additional aim was to obtain regression formulas with greater accuracy than similar formulas published in the literature. Simple and multiple regression methods were used to develop regression formulas. The obtained results were verified on the basis of experimentally measured parameters obtained from built ships. The regression formulas presented in this article are characterized by high accuracy, greater than that of similar formulas published in the literature, and were developed for container ships currently under construction. A novelty of this study is the development of regression formulas for weight classes, which make up the total weight of an unladen ship. Full article

This study examines the impact of the Beijing–Tianjin–Hebei (BTH) coordinated development policy on the regional industrial network structure, with a focus on the significance of electricity consumption data in social network analysis (SNA). Utilizing a gravity model integrated with electricity consumption data, this research employs centrality analysis and Lambda analysis to compare changes in the steel industry network before and after policy implementation. The findings reveal that traditional models relying solely on indicators such as population and Gross Domestic Product (GDP) fail to comprehensively capture regional economic linkages, whereas incorporating electricity consumption data enhances the model’s accuracy in identifying core nodes and latent connections. Post policy implementation, the centrality of Beijing and Tianjin increased significantly, reflecting their transition from production hubs to centers for research and development (R&D) and management, while Shijiazhuang’s pivotal role diminished. This study also uncovers a “core–periphery” structure in the BTH urban network, where core cities (Beijing, Tianjin, and Shijiazhuang) dominate resource allocation and information flow, while peripheral cities exhibit uneven development. These results provide a scientific basis for optimizing regional coordinated development policies and underscore the critical role of electricity consumption data in refining regional economic analysis. Incorporating electricity consumption data into the gravity model significantly enhances its explanatory power by capturing hidden economic ties and improving policy evaluation, offering a more accurate and dynamic assessment of regional industrial linkages. Full article

This paper addresses the vibration characteristics of angular contact ball bearings in aircraft engines under variable load conditions. Based on multibody dynamics theory, a dynamic model of the bearing was established. Vibration data under actual operating conditions were obtained using an experimental test platform. This study systematically investigated the influence of rotational speed, axial load, and radial load on the vibration acceleration level of the bearing outer ring. Through a comparison of simulation and experimental data (with an error rate below 10%), the reliability of the model was validated. The results indicate that the bearing vibration acceleration level exhibits a nonlinear increasing relationship with rotational speed. An increase in radial load significantly amplifies the amplitude of acceleration-level fluctuations, while appropriately increasing axial load can reduce bearing vibration intensity. Under variable load coupling conditions, the dynamic interaction between axial and radial forces results in complex nonlinear vibration responses, with a 2 s acceleration time achieving the optimal balance between vibration suppression and efficiency (steady-state average of 70.4 dB). Additionally, the morphological characteristics of the cage center-of-gravity trajectory (such as trajectory disorder and poor smoothness) are closely related to vibration characteristics, revealing the critical role of dynamic load changes in bearing stability. The research results provide a theoretical basis for optimizing the operating conditions, vibration control, and reliability design of aircraft engine bearings. Full article

High-quality growth of the construction industry and an improved human settlements environment are essential to sustainable urbanization. Existing studies have paid limited systematic attention to the spatial and temporal dynamics of the coordinated development between the construction industry and human settlements, as well as the underlying factors driving regional disparities. This gap restricts the formulation of precise, differentiated sustainable policies tailored to regions at different development stages and with varying resource endowments. Southern China, characterized by pronounced spatial heterogeneity and unique development trends, offers a natural laboratory for examining the spatio-temporal interaction between these two dimensions. Using panel data for 15 southern provinces (2013–2022), we applied the entropy method, coupling coordination model, Dagum Gini coefficient, spatial trend surface analysis, gravity model, and grey forecasting to evaluate current conditions and predict future trends. The main findings are as follows. (1) The coupling coordination degree rose steadily, forming a stepped spatial pattern from the southwest through the center to the southeast. (2) The coupling coordination degree appears obvious polarization effect, presenting a spatial linkage pattern with Jiangsu-Shanghai-Zhejiang, Hubei-Hunan-Jiangxi, and Sichuan-Chongqing as the core of the three major clusters. (3) The overall Dagum Gini coefficient declined, but intra-regional disparities persisted: values were highest in the southeast, moderate in the center, and lowest in the southwest; inter-regional differences dominated the total inequality. (4) Forecasts for 2023–2027 suggest further improvement in the coupling coordination degree, yet spatial divergence will widen, creating a configuration of “eastern leadership, central catch-up acceleration, and differentiated southwestern development.” This study provides an evidence base for policies that foster high-quality construction sector growth and enhance the living environment. The findings of this study indicate that policymaking should prioritize promoting synergistic regional development, enhancing the radiating and driving role of core regions, and establishing a multi-level coordinated governance mechanism to bridge regional disparities and foster more balanced and sustainable development. Full article

Coal gasification slag (CGS) is a solid byproduct generated during coal gasification. Stacking and land-filling of CGS wastes substantial land resources and has significant environmental risks. In this paper, based on the Ca/Si and Si/Al ratios of the raw materials, the mix design of alkali-activated CGS concrete was optimized using a pure center-of-gravity design method. The compressive and flexural strengths of geopolymer concrete with varying mix proportions were measured to investigate the effects of sodium silicate modulus, material content, and dry density on its mechanical properties. Specimens of different sizes were prepared to analyze the influence of testing methods on the compressive, flexural, and tensile properties. The results indicate that the mechanical properties of geopolymer concrete are significantly influenced by the raw material composition and the modulus of the activator. With increasing curing age, both compressive and flexural strengths exhibit varying degrees of improvement. The stress-strain behavior of alkali-activated CGS concrete aligns closely with that of ordinary concrete. A comparative analysis of 100 mm length and 20 mm length cubic specimens revealed a compressive strength size conversion coefficient of approximately 0.456, while the flexural specimen exhibited a coefficient of 0.599. For tensile strength evaluation, both the Brazilian splitting method and the double punch test method yielded consistent and reliable results, demonstrating their suitability for assessing CGS-based concrete. Full article

This study examined the relationship between spinal morphological changes and gait characteristics in patients with adolescent idiopathic scoliosis (AIS) using inertial measurement unit (IMU) analysis. Twenty-three female patients with AIS scheduled for corrective surgery underwent a preoperative gait analysis using an IMU positioned at the third lumbar vertebra. Gait stability indicators were calculated, including root mean square (RMS) values for mediolateral (RMSx), anteroposterior, and vertical components. Peak mediolateral components in four coronal plane quadrants were also analyzed. Relationships with the main thoracic (MT) curve, the thoracolumbar (TL) curve, and thoracic kyphosis (TK) were assessed using Spearman’s rank correlation. The MT curve is positively correlated with RMSx, whereas TK exhibited a negative correlation. Gait symmetry analysis revealed a positive correlation between the MT curve and peak mediolateral trunk acceleration in the second (left upper) quadrant, and negative correlations for TK in the first (right upper) and fourth (right lower) quadrants. Patients with AIS who have right-convex MT curves demonstrated leftward center-of-gravity shifts, although reduced TK limited this compensatory mechanism. These findings may inform the development of rehabilitation strategies for AIS. Full article

Cropland is crucial for food production, food security, and economic stability, especially in high-altitude Tibetan regions where it is limited. This study investigates the spatiotemporal changes and driving factors of cropland in the Yarlung Zangbo River Basin (YZRB) from 2000 to 2020. Using land use transfer matrices, center of gravity models, standard deviation ellipses, the Patch-generating Land Use Simulation (PLUS) model, and Partial Least Squares Structural Equation Modeling (PLS-SEM), it explores cropland dynamics and predicts land use for 2030. Results show the following: (1) Between 2000 and 2020, the area of cropland entering the basin exceeded that leaving, mainly concentrated in the middle and lower reaches, with a dynamic degree of 0.97%. The proportion of cropland increased from 1.28% in 2000 to 1.52% in 2020. (2) The center of gravity shifted northwest (2000–2005), southeast (2005–2015), and northwest again (2015–2020). (3) Factors like elevation, temperature, precipitation, population density, and GDP correlated with cropland changes. Natural factors positively affected cropland expansion, while socioeconomic and proximity factors indirectly inhibited it. (4) The 2030 cropland conservation scenario in the PLUS model ensures cropland security, ecological protection, and controlled construction land expansion, aligning with the Sustainable Development Goals. Targeted cropland conservation measures can effectively promote sustainable land use and ecological security in the Yarlung Zangbo River Basin. Full article