网络首发
Spatiotemporal patterns and drivers of landscape ecological risk in the Weihe River Basin based on XGBoost–SHAP
Meng Xiaolan;Xu Fujun;Zhai Meng;Zhang Mantong;Hong Hui;Zhang Xing;This study investigates the spatiotemporal patterns and nonlinear driving mechanisms of landscape ecological risk in the Weihe River Basin from 2000 to 2020. Landscape ecological risk indices were calculated for each grid cell using land use data， and spatial autocorrelation analysis was employed to characterize spatial clustering. The Extreme Gradient Boosting Integrated with Shapley Additive Explanations (XGBoost–SHAP) framework was applied to quantify the nonlinear contributions and threshold effects of various driving factors. The landscape ecological risk values ranged from 0.01 to 0.68 across all evaluation grids. Medium-risk areas constituted the largest proportion， averaging 32.47%， with a gradually increasing trend， while high-risk areas decreased from 8.52% to 8.16% by 2020. Spatially， high-risk zones progressively retreated toward the northern Loess hilly-gully region， coinciding with areas where the Grain for Green Program was implemented. In contrast， low-risk zones in the central Guanzhong Plain exhibited fragmentation and outward displacement. Global Moran’s I values remained above 0.40 (p < 0.001) throughout the study period， indicating significant spatial autocorrelation. H–H clusters were predominantly located in the northern and southern basin， while L–L clusters were concentrated in the central plain. SHAP analysis revealed that distance to residential areas， mean annual temperature， and slope were the three most influential factors， collectively contributing nearly 60% of the total SHAP values. Nonlinear threshold effects were identified for multiple factors. Specifically， NDVI exhibited strong negative effects under low coverage conditions that diminished at higher coverage levels. Precipitation and temperature displayed inverted U-shaped patterns， with effects shifting from positive to negative across different value ranges. Slope showed a U-shaped pattern， while elevation exhibited a positive nonlinear relationship with ecological risk. GDP and population density demonstrated negative nonlinear relationships， suppressing risk only beyond certain developmental thresholds. Distance to river also showed an inverted U-shaped pattern， with risk suppression observed in both nearby and distant zones. These findings indicate that the contributions of driving factors vary dynamically across different value ranges， providing a quantitative basis for spatially targeted risk management in ecologically fragile arid and semi-arid regions.
Source analysis of inorganic elements in atmospheric dustfall in the main urban area of Xi'an city based on ED-XRF and PMF
Yang Jianjun;Zhang Yong;Liu Suixin;Zhang Zhimin;Liu Chao;Zhang Jiaqi;Ma Jiaqi;Lian Zifan;Geng Chenfei;Gu Chunyang;Li Shenglong;The inorganic element determination technology for atmospheric dustfall in the main urban area of Xi'an city was independently constructed based on energy dispersive X-ray fluorescence spectroscopy for a period of one year. At the same time， the source of inorganic elements in atmospheric dustfall was analyzed using positive matrix factorization method. The research results show that the abundance distribution range of 20 inorganic elements is relatively wide， with Fe element having the highest abundance and Se element having the lowest level. The abundance levels of each inorganic element vary greatly; The factors determined by source apportionment are mobile sources， construction dustfall， metal processing and smelting， industrial production and manufacturing， biomass combustion sources， road and soil dustfall， and coal-fired sources. The contribution rates of each factor are 10.90%， 23.63%， 13.11%， 10.45%， 12.64%， 25.34%， and 3.92%， respectively， with the highest being road and soil dustfall and the lowest being coal-fired sources; The overall balance of the proportion of motor vehicle sources is fundamentally related to the high degree of "dispersion" and "mobility" of motor vehicle emission sources; The differential changes in construction dustfall are related to the number of construction projects started by construction enterprises and the distribution of construction projects; The proportion of biomass burning at all locations from July to October 2023 (except for the first location after June) is relatively high， which is related to factors such as agricultural open burning， outdoor barbecue， and relatively good atmospheric diffusion conditions; The proportion of road and soil dustfall in March-May 2023 and November-December 2023 is relatively high， mainly due to the high frequency of sandstorms and the accumulation of a large amount of dustfall on the surface during the deciduous season; The coal-fired sources from June to October 2023 have a certain proportion and are relatively significant in most locations， which is related to external contributions.
Experimental study on methane explosion propagation under localized premixed gas cloud conditions
LI Ranran;LIU Qiqi;LIU Zhenyi;To investigate explosion safety issues associated with localized combustible gas clouds propagating in confined and elongated spaces， a pipeline explosion experimental system capable of generating localized premixed gas clouds was developed. The effects of methane concentration and the volume of localized premixed gas clouds on methane explosion propagation characteristics were systematically studied. High-speed imaging and pressure sensors were employed to measure and analyze key parameters， including flame morphology evolution， flame propagation dynamics， explosion overpressure， and the overpressure rise rate. The results indicate that the volume of the premixed gas cloud has a significant influence on explosion propagation characteristics. As the premixed cloud volume increased from one pipe section to two sections， the flame luminosity was markedly enhanced and the flame propagation velocity increased significantly. The maximum average flame propagation velocity reached 205.88 m/s for the two-section condition， which is substantially higher than the 154.18 m/s observed for the one-section condition. Methane concentration also plays a critical role in both flame propagation dynamics and explosion pressure characteristics. The flame propagation velocity， peak overpressure， and maximum overpressure rise rate all reached their maximum values at the stoichiometric concentration of 9.5%. When the mixture deviated from the stoichiometric condition， the combustion intensity weakened， leading to reductions in both flame propagation velocity and explosion overpressure. For the same deviation from the stoichiometric concentration， the peak overpressure and its rise rate under fuel-rich conditions were significantly higher than those under fuel-lean conditions. In addition， the axial evolution of explosion overpressure in the pipeline exhibited a characteristic pattern: slight initial oscillatory growth， rapid increase， sharp decay， and a slight rebound near the pipe end. The maximum overpressure occurred at 3.75 m， where the superposition of reflected shock waves and their coupling with the combustion wave were most pronounced. These findings provide useful insights for hazard assessment of localized gas cloud explosions and the design of explosion protection strategies in confined spaces.
Quantitative HAZOP risk assessment based on steady-State fluid-structural coupling simulation: a case study of a shell-and-tube heat exchanger
MA Hanpeng;YU Jialiang;YANG Tiejun;HE Yanyan;Traditional hazard and operability (HAZOP) analysis relies heavily on expert judgment and lacks quantitative evidence when evaluating structural risks in shell-and-tube heat exchangers， often resulting in ambiguous and experience-dependent consequence descriptions. To address this limitation， this study proposes a systematic methodology that integrates steady-state fluid–thermal–structural sequential coupling simulations into the HAZOP framework to enable quantitative， mechanics-based risk assessment of structural integrity. A detailed three-dimensional numerical model of a fixed tube-sheet heat exchanger is constructed using the ANSYS Workbench platform， incorporating realistic geometric features and temperature-dependent material properties of 304 stainless steel. Steady-state computational fluid dynamics (CFD) simulations are first conducted to solve the Reynolds-averaged Navier–Stokes equations with the shear stress transport (SST) k–ω turbulence model， thereby obtaining the flow field and conjugate heat transfer temperature distributions under both nominal and deviation conditions. The resulting temperature and pressure fields are subsequently transferred as thermal and mechanical loads to a finite element structural model， where thermoelastic equilibrium equations are solved to determine equivalent stress distributions and total deformation. A dedicated risk assessment matrix is established by integrating the computed safety factor—defined as the ratio of material yield strength to maximum equivalent stress—with a region-specific sensitivity classification that distinguishes primary， secondary， and peak stress zones in accordance with pressure vessel design codes. Eight deviation scenarios are designed based on HAZOP guidewords， encompassing variations in cold and hot fluid mass flow rates (0.7–2.8 kg/s) and inlet temperatures (0–100 ℃). Simulation results demonstrate that temperature-induced deviations exert the most pronounced influence on structural integrity. Notably， the cold fluid inlet at 0 ℃ yields a maximum equivalent stress of 274 MPa and a safety factor of 0.8， corresponding to an extremely high risk level， while a hot fluid inlet at 100 ℃ results in 242 MPa and a safety factor of 0.91. In contrast， flow rate deviations induce comparatively moderate stress variations (102–177 MPa) and lower risk rankings. The proposed methodology not only aligns closely with empirical engineering judgment but also transforms qualitative HAZOP consequence descriptions into explicit， data-driven risk classifications， thereby providing robust， quantitative support for risk-based inspection planning and proactive safety management of shell-and-tube heat exchangers.
Research Progress and Prospects in the Comprehensive Utilization of Phosphogypsum Solid Waste
Li Shiqi;Hu Jianhua;Yu Zhi;Li Jianing;Ma Wenjin;Zhou Ying;Gao Benming;Zhao Xiangbo;This review systematically examines the physicochemical characteristics， utilization pathways， engineering applicability， and environmental constraints of phosphogypsum (PG). Relevant studies were classified into eight categories: mine backfilling， construction materials， road engineering， cementitious materials， chemical conversion， agricultural use， rare-earth-element recovery， and environmental functional materials. These pathways were compared in terms of bulk-consumption potential， technological maturity， pretreatment requirements， product-market capacity， process complexity， cost constraints， and environmental risks. The interactions of PG with cementitious phases， soil minerals， and stabilizing agents were also analyzed to clarify the mechanisms governing hydration， setting， strength development， pollutant immobilization， and long-term release.The review shows that PG is composed mainly of CaSO₄·2H₂O but commonly contains free acids， soluble phosphorus， fluorides， organic matter， heavy metals， and naturally occurring radionuclides. These impurities may retard hydration， disturb setting， reduce early strength and durability， increase process instability， and raise long-term leaching and radiological risks. Construction materials represent the most mature route for large-scale utilization， but product quality， pretreatment cost， and market demand limit further expansion. Road engineering and mine backfilling provide high unit consumption and strong regional disposal potential; however， their application depends on mechanical durability， seepage control， and long-term pollutant-release behavior under service conditions. Cementitious utilization is technically feasible， particularly when PG is used as a setting regulator or sulfate-bearing component， but the overall consumption is restricted by low addition levels and impurity-related interference with hydration. Chemical conversion and rare-earth-element recovery can increase product value， yet their high reagent and energy demands， complex separation processes， and limited throughput make them more suitable as supplementary routes. Agricultural and ecological applications are strongly controlled by soil type， impurity concentration， application rate， and long-term monitoring requirements.Based on the comparative analysis， a prospective integrated route is proposed: source-specific characterization and classification， low-cost physical pretreatment， targeted purification or stabilization， application-oriented route matching， closed-loop wastewater treatment， and by-product recovery. Construction materials are suggested as the principal pathway， while road engineering and mine backfilling serve as high-consumption regional options， and chemical conversion and rare-earth-element recovery act as small-volume， high-value supplements. Life-cycle assessment together with long-term leaching and radiological-risk evaluation should be used to define application boundaries and access criteria.
Research on integrated safety risk assessment and decision-making methods for centralized photovoltaic projects in Northwest China
Yan Liang;Liu Ping;Zhang Yu;He Zongfeng;Wang Jianping;This paper proposes an integrated safety risk assessment and decision-making method for centralized photovoltaic projects in Northwest China from the perspective of risk evolution. The proposed method incorporates three core components. First， a dual-dimensional quantitative model consisting of “static risk” and “transmitted risk” is constructed based on Bayesian networks and information entropy theory. The static risk captures the inherent potential harm of each risk node given its parent nodes’ states， while the transmitted risk quantifies the amplifying effect of risk propagation along the network using Shannon entropy. Second， a data-driven threshold determination method is developed to identify the failure criterion for each risk node. This method employs second-order difference analysis on candidate threshold percentiles obtained from Monte-Carlo simulation results， and the optimal threshold is identified at the percentile where the system behavior exhibits a critical transition. Third， a multi-strategy decision-making framework is established by integrating sensitivity analysis and value engineering theory， enabling both the identification of critical risk triggers and the selection of optimal intervention strategy portfolios that balance risk control effectiveness and cost efficiency. The proposed framework is validated through an empirical study on a centralized photovoltaic project in Northwest China. A total of 38 risk factors are identified across the design， construction， and operation phases. The Monte-Carlo simulation with 5，000 iterations yields a baseline comprehensive safety risk level of 32.527， with the 5%， 50%， and 95% percentiles being approximately 16.000， 32.457， and 49.455， respectively， indicating a symmetric risk distribution. Sensitivity analysis identifies five key risk triggers that contribute most significantly to the overall system risk: lack of experience in regional risk perception， reduction of maintenance investment， improper contractor selection， incomplete emergency plans， and failure of safety supervision mechanisms. Among four categories of intervention strategies (organizational， managerial， technical， and economic)， the optimal combination of “organizational + managerial + technical” strategies achieves the highest value index of 2.698， outperforming other combinations including the four-strategy full combination (value index 1.925). The results demonstrate that the proposed framework can effectively identify critical risk triggers and select optimal intervention portfolios， providing both theoretical foundations and methodological support for systematic and precise safety risk management in centralized photovoltaic projects in Northwest China.
Research on flow field characteristics of centrifugal half-inch water mist nozzle for explosion suppression
Zhou Wen;Wang Jinxi;Tang Xinyu;Cheng Wenjun;Zhang Kun;Xue Zhongqing;Shi Xueqiang;To investigate the atomization and flow field characteristics of a traditional straight-blade half-inch centrifugal water mist nozzle and a newly designed structurally optimized airfoil-blade counterpart， a comprehensive series of experimental tests and numerical simulations was systematically conducted. The experimental phase utilized a custom-built closed-loop water circulation testing platform integrated with a high-precision Phase Doppler Particle Analyzer (PDPA)， enabling accurate， real-time measurement of various macroscopic and microscopic spray parameters. Specifically， fluid flow rate， spray angle， maximum average axial velocity， and droplet diameter distribution were evaluated under varying inlet pressure conditions ranging from 0.5 MPa to 4.0 MPa. Concurrently， to uncover internal flow mechanisms that are not easily observed in physical experiments， Computational Fluid Dynamics (CFD) simulations were performed using Fluent software. The numerical model incorporated the RNG k–ε turbulence model coupled with the Volume of Fluid (VOF) multiphase framework to capture complex air-water interface dynamics. We simulated internal static pressure variations， velocity distributions of the internal flow field， and outlet cross-sectional velocity profiles for both nozzle geometries under extended inlet pressures from 1.0 MPa to 6.0 MPa. The empirical data demonstrate that the optimized nozzle significantly enhances fluid throughput. Within the tested pressure range， its flow rate increased by 20% to 35% compared to the traditional design， peaking at a maximum flow difference of 1.039 m³/h under the 2.0 MPa working condition. Furthermore， the airfoil-blade structure exhibits a broader operational range for the spray angle， contracting from 78.8° to 46°， which provides a distinct spatial coverage advantage， particularly around the 1.5–2.0 MPa pressure interval. Interestingly， regarding droplet size distribution， a crossover effect was observed: the traditional straight-blade nozzle generates finer droplets at lower pressures (0.5–2.5 MPa)， while the optimized nozzle demonstrates superior atomization performance at higher pressures exceeding 3.0 MPa. Both designs successfully achieved effective droplet velocities surpassing 50 m/s once system pressure reached 3.5 MPa. From a numerical perspective， simulation results illustrate that structural optimization significantly smooths the internal pressure gradient; specifically， at the extreme pressure of 6.0 MPa， the local pressure drop across the blades is reduced by approximately 57%. This research provides a theoretical basis and data accumulation for the selection and structural optimization of water mist nozzles， serving as a valuable reference for dust protection in mining operations.
Risk propagation and facility exposure assessment of urban underground spaces based on cascading failures
Chen Wenqiang;Zang Xiaolei;Shi Juan;Jia Jian;To address the insufficient characterization of cross-layer risk transmission and differential facility exposure in urban underground spaces， this study proposes a three-layer coupled network consisting of risk factors， disaster events， and facility types. The network structure is established by representing the relationships among different risk elements and describing the cascading transmission pathway from initial risk factors to disaster consequences and facility impacts. A cascading failure model is developed to simulate the dynamic propagation process among interconnected nodes. Specifically， risk propagation pressure is introduced to quantify the transmission intensity between nodes， while node tolerance thresholds are defined to represent the resistance capacity of individual nodes against cascading failures. Based on the proposed mechanism， a method for identifying key cascading risk sources is developed， and a facility exposure assessment index is constructed to quantify the heterogeneous exposure characteristics of different underground facility categories. The proposed method is validated using 200 representative accident cases collected in China from 2010 to 2025. The identified key cascading risk sources are compared with frequently reported accident causes， and the calculated facility exposure index is further compared with actual damage frequency. The results show that lax safety management， operational errors， and equipment aging or corrosion play important triggering roles in risk propagation. Among different facility categories， underground pipelines exhibit the highest exposure level， whereas underground passageways show the lowest exposure level. The consistency rate between the identified key cascading risk sources and frequently reported accident causes reaches 66.7%， and the facility exposure index demonstrates a significant correlation with actual damage frequency， with a Pearson correlation coefficient of 0.706. Furthermore， the comparison between cascading influence and topological centrality indicates that structural importance does not necessarily correspond to cascading propagation capability. The proposed method provides an effective approach for disaster chain interruption， critical facility monitoring， and hierarchical risk management in urban underground spaces.
Simulation study of mine gas laser remote sensing technology based on dual optical paths
Zhang Andong;Hu Min;Zhao Dongyue;He Qing;Nie Shibin;Xue Shuo;To enable non-contact remote estimation of the absolute methane volume fraction at non-fixed measurement points in mines， a dual-optical-path differential absorption laser method is proposed. The method is based on the principle of methane path-integrated volume fraction measurement using a single optical path. Two adjacent parallel optical paths are arranged in the measurement area to obtain path-integrated methane volume fraction information at different spatial positions. By using the difference between the two path-integrated volume fractions， an approximate relationship is established between this difference and the local methane volume fraction near the target measurement point. In this way， the conventional path-integrated measurement result is transformed into an estimate of the local methane volume fraction at a non-fixed measurement point. This conversion helps alleviate the inherent limitation of single-path measurements， which provide only cumulative information along the optical path. To evaluate the feasibility of the proposed method and the effects of key parameters， a simulation model of the local methane volume fraction field near a coal wall is developed. The effects of the vertical distance Δn between the reference reflective surface and the target measurement point， together with the optical-path spacing d， on the estimation error are analyzed. The results show that， under a given Δn， the estimation error first decreases and then increases with increasing d， indicating that an appropriate matching relationship exists between d and Δn. When Δn is 0.02， 0.04， and 0.06 m， the corresponding preferred d values are approximately 0.05， 0.17， and 0.35 m， respectively. The minimum absolute error reaches 0.000 9%. As Δn increases， the preferred d generally increases， reflecting a balance between the difference in path-integrated information and the local representativeness of the measurement. When the absolute error is no greater than 0.01%， d can be adjusted within an allowable range. The results provide a theoretical basis and a methodological reference for remote estimation of the absolute methane volume fraction at non-fixed measurement points in mines.
Dynamic risk assessment of underground heating pipe galleries based on game theory-based combined weighting
Liu Yufeng;Zhang Xiaojian;Xie Wei;Li He;Zhu Haiyue;Feng Deng;Zhu Dong;Wang Chenglong;Addressing the conflict between subjective and objective weights in the risk assessment of underground heating pipe galleries， as well as the lack of dynamics in traditional models， this study proposes a dynamic assessment method that integrates game theory-based combined weighting with residual-driven feedback correction. This integrated framework explicitly acknowledges the evolving nature of infrastructure risks by establishing a closed-loop， self-optimizing evaluation system. First， initial subjective and objective weight sets are constructed using three methods: the G1 method (Order Relationship Analysis Method) determines subjective weights based on expert insights to identify implicit risks such as weld defects; the improved entropy weight method captures data discreteness; and the CRITIC (Criteria Importance Through Intercriteria Correlation) method integrates data variability and inter-indicator correlation to form complementary objective weights， mitigating the limitations of single-method approaches. Subsequently， game theory combined weighting achieves collaborative optimization by minimizing the Euclidean distance between the combined weight vector and the three initial sets， resulting in the Nash equilibrium between subjective experience and objective data. To enhance dynamics， a residual-driven multi-stage feedback correction mechanism is designed: each phase calculates the relative residual between predicted and actual risk levels， which dynamically adjusts the subjective weight coefficient via an exponential decay function and updates cloud model parameters (Ex， En， He). This continuous adaptation mechanism ensures that the assessment model remains synchronized with the real-time degradation process and environmental variations of the pipe gallery system throughout its operational lifecycle. Using a case study of a 12.3 km DN1200 heating pipe gallery in Hebei Province， results indicate that Section 2 in the old urban silty clay layer is the highest-risk priority， with a risk score of 52.5. Operation and maintenance indicators exhibit the highest sensitivity， contributing 35% to total risk. The subjective weight coefficient decays from 0.5 to 0.001， thereby reducing reliance on expert experience. The comprehensive score achieved by the proposed method (0.975 9) outperforms the G1 method (0.874 3)， improved entropy weight method (0.703 1)， and CRITIC method (0.892 4) by 12.3%， 8.7%， and 10.1%， respectively. This method effectively identifies high-risk sections and dominant factors， providing scientific support for full-life-cycle safety management of underground heating pipe galleries.