最新刊期
卷 56 ， 期 3 ， 2024
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Analysis of Water Softening Characteristics in the In-situ Stress Environment of Jinping Marble AI导读
“据最新报道，中国西部高山峡谷地区的水电资源开发面临极深洞室围岩力学特性演化规律和长期稳定性的关键科学问题。专家通过深部原位应力环境岩石饱水试验，揭示了锦屏大理岩水软化机理，为深部地下工程稳定性分析提供了重要参考。”摘要：ObjectiveChina’s hydropower resources are primarily concentrated in the western mountains and valleys, characterized by narrow ground space and significant altitude differences. Consequently, it is often more economical and efficient to locate hydropower station buildings within extremely deep caverns. However, the region’s typical geomorphic features, coupled with the strong environmental impact of “high geostress” and “high permeability”, pose numerous safety challenges during both construction and operation phases for these extremely deep caverns. Understanding the evolutionary patterns and long-term stability of the mechanical properties of surrounding rock is of paramount importance. A critical scientific challenge lies in elucidating the influence of water-rock coupling on the mechanical properties of rock under varying depths of stress, which currently leads to certain risks and inefficiencies in deep rock mass engineering.MethodsTo realistically simulate the coupled environment of water and rock at different depths, our research group independently developed a rock saturation test system under deep in-situ stress conditions. This system comprises five reactors, collectively named the deep environment simulation cavity, capable of replicating the in-situ stress environment of underground engineering at five distinct depths. Through a servo motor, rotary motion is converted into linear motion, facilitating the transfer of water pressure from the motor cavity to the kettle cavity for pressurization. Additionally, the pump transmission rate allows for adjustment of pressurization speed. Leveraging this self-designed and developed rock saturation test system under deep in-situ stress conditions, we conducted water softening tests on Jinping marble with saturation durations of 1, 23, 60, and 100 days. To provide comparative insights, we also conducted water softening tests on Jinping marble without pressure saturation for durations of 0, 1, 23, 60, and 100 days. Each group underwent five sets of triaxial compression tests at varying confining pressures, corresponding to pressures of 100, 1 000, 1 400, 1 800, and 2 400 meters at five different depths. All rock samples were extracted from the No. 8 borehole outside the D-scientific research cave, boasting the greatest buried depth in the Jinping Ⅱ (CJPL–Ⅱ) cavern group, at a depth of 2 400 meters.Results and DiscussionsThe findings reveal that under saturated in-situ stress conditions, the triaxial strength of Jinping marble gradually diminishes with increasing saturation time, exhibiting nonlinear characteristics with a slowing decreasing trend over time. Furthermore, the degradation degree of Jinping marble increases gradually with time under identical depth environments, albeit with a diminishing upward trend. Moreover, the deterioration degree initially decreases and then increases with rising depth environments under identical saturation times, indicating a nonlinear change pattern. Comparing the effects of in-situ stress environmental saturation and non-pressure water saturation, it is evident that after 100 days of water saturation, the deterioration degree of peak strength of Jinping marble is approximately three times higher under deep in-situ stress conditions than under non-pressure water saturation. Additionally, other mechanical parameters such as cohesion and internal friction angle exhibit significantly greater deterioration under in-situ stress conditions compared to non-pressure water saturation. Moreover, the degradation of peak strength of Jinping marble demonstrates a nonlinear pattern, initially decreasing and then increasing with the increase in water-rock coupling environmental depth (100, 1 000, 1 400, 1 800, and 2 400 meters). During the investigation of the water softening mechanism of Jinping marble, X–ray diffraction (XRD) analysis was conducted using the DMAX–3C equipment at the Analysis and Testing Center of Sichuan University. Results indicated that the predominant components of Jinping marble were dolomite (CaMg(CO3)2) and calcite (CaCO3), with average contents of 92% and 8%, respectively. The low solubility of dolomite and calcite in a distilled water environment suggested minimal chemical dissolution. Furthermore, the absence of clay minerals in Jinping marble, coupled with its hydrostatic pressure state during testing, ruled out clay mineral softening, seepage erosion, and hydrodynamic scouring.ConclusionsBased on experimental tests and compositional analysis, the water softening mechanism of Jinping marble in both in-situ stress and non-pressure saturated environments primarily involves frictional weakening and pore water pressure effects. The experimental findings suggest that the frictional weakening effect exacerbates the deterioration of Jinping marble under low confining pressure, while pore water pressure has the opposite effect. The interplay between these mechanisms results in a nonlinear trend wherein the strength deterioration of Jinping marble initially decreases and then increases with increasing depth environment. Furthermore, the variance in mechanical properties of water saturation between in-situ stress and non-pressure environments of Jinping marble is primarily attributed to pore water pressure. These findings underscore the pronounced water softening effect and its consequential impact on the mechanical properties of surrounding rock under in-situ stress conditions. Thus, in the long-term stability analysis of deep underground engineering, it is imperative to consider the softening characteristics of surrounding rock water and appropriately adjust rock mechanical parameters. This conclusion holds significant guiding implications for the construction and maintenance of Jinping underground engineering.关键词：Jinping marble;in-situ stress environment;water softening characteristics;water softening mechanism1249|230|0更新时间：2024-08-22 - “最新研究揭示了围压对低孔隙率硬岩力学行为的影响，建立了细观损伤力学模型，并通过有限元模拟验证了模型的准确性，为深部岩石力学行为研究提供了理论支撑。”摘要：ObjectiveThis comprehensive exploration delves into the intricate domain of confining pressure’s influence on the mechanical complexities found in low-porosity, resilient rocks under compressive loading. It seeks to elucidate the transition from brittleness to ductility induced by increasing confining pressure. Additionally, it sheds light on the variations in strength, failure modes, and shear dilation across a wide range of confining pressure conditions in these rocks. As confining pressure increases, a transformative process unfolds, leading to a dramatic shift in the failure characteristics of these rocks—From the fragility of brittleness to the flexible embrace of ductility. The paper aims to unravel the intricate mechanism of the brittle-ductile transition by delving into the micro-mechanical landscape. This detailed expedition meticulously charts the nuanced relationship among non-elastic deformation, damage evolution, and the pervasive influence of confining pressure. Arising from the intricacies of our micro-mechanical analysis is a skillfully crafted micro-damage mechanics model, serving as a guide through the challenging terrain of hard rocks under compressive loading.MethodsIn our meticulous mechanical scrutiny, we intentionally choose the representative elementary volume (REV), characterized by the voluminous Ω and the peripheral boundary
$\partial $ 关键词：brittleness to ductility;confinement effect;frictional sliding;threshold damage value;micromechanical model1206|654|0更新时间：2024-08-22 - “在深埋大理岩渐进变形破坏研究领域，专家利用PFC3D颗粒流模型，基于室内试验参数标定，模拟了不同围压下的裂纹扩展过程，揭示了宏、细观破坏特征及其对应规律，为深埋岩体稳定性分析提供了新视角。”摘要：ObjectiveTo conduct in-depth research on crack propagation characteristics during the progressive deformation and failure process of deeply buried marble, numerical simulation parameters were calibrated based on conventional triaxial indoor tests. The aim is to fully replicate the macroscopic mechanical properties and crack failure characteristics of deeply buried marble during deformation and failure processes.MethodsUtilizing the PFC3D particle flow model, numerical simulation experiments were conducted on crack propagation in deeply buried marble under three different confining pressures: 25 MPa, 50 MPa, and 80 MPa. Three characteristic stresses were defined from the perspective of progressive failure of deeply buried marble, based on the evolution state parameters of microcracks during the marble loading process. Subsequently, the macro and micro failure characteristics of progressive failure of deeply buried marble and their corresponding crack propagation characteristics were investigated.Results and Discussions1) Optimal microscopic parameters for indoor and numerical simulation tests under three different confining pressures are presented. Stress-strain curves obtained from this set of mesoscopic parameters under various confining pressures were compared with those derived from indoor tests. Results indicate a close agreement between stress–strain curves obtained from indoor tests and numerical simulations, with negligible differences in peak stress—all relative errors falling within 10%. Thus, the calibration of numerical simulation parameters is deemed reasonable. The failure modes of rock samples from indoor tests, numerical simulations, and acoustic emission under three different confining pressures are illustrated. Failure modes derived from numerical simulations closely mirror those observed in indoor test samples, along with the spatial-temporal distribution of acoustic emission points, predominantly indicating shear failure supplemented by tensile failure, forming a continuous shear failure pattern. Hence, it is concluded that the set of microscopic parameters of the parallel bonding model in PFC aptly describes the mechanical properties and failure characteristics of marble samples, demonstrating PFC’s efficacy in simulating hard rocks. 2) By analyzing the variation law of the slope of the evolution curve of total crack, tension crack, and shear crack propagation quantity, the progressive failure process of deeply buried marble is categorized into four stages: elastic compression stage, crack stable propagation stage, crack accelerated propagation stage, and post-peak residual stage. Three distinct characteristic stress points are defined based on the number of cracks at the initiation stress point σci, damage stress σcd, and peak stress σc. 3) Loading the specimen to the initiation stress σci point initiates crack formation, with resulting crack points located at both ends of the sample. Further loading to the damage stress σcd prompts sporadic scattering of shear cracks throughout the entire specimen. Upon reaching the peak strength peak stress σc, cracks propagate and proliferate near the macroscopic failure surface, with tensile cracks also emerging. Upon loading the sample to 70% of the peak stress after the peak, both shear and tensile cracks undergo rapid growth, ultimately leading to sample failure. Shear and tensile cracks are distributed throughout the entire sample, resulting in a relatively consistent macroscopic failure surface dominated by shear failure. The distribution range and quantity of shear failure are more extensive, playing a predominant role in marble failure. Conversely, the distribution range and quantity of tensile failure are relatively small, serving as an auxiliary factor in marble failure. In conventional triaxial compression tests, the combined action of axial pressure and confining pressure generates shear stress parallel to microcracks and in the opposite direction within the rock. As loading progresses, propagating shear cracks and gradual relative slip in the rock can easily induce shear failure. With increasing confining pressure, cracks emerge more rapidly during the elastic compression stage, and the number of cracks during failure also increases. As confining pressure rises, crack width widens, continuity weakens, and cracks generated at peak stress σc points exert a more severe impact on macroscopic failure. Tensile crack development becomes more pronounced in the residual stage post-peak. 4) The distribution diagram illustrating the number of cracks at different stress levels within deeply buried marble under varying confining pressures is presented, highlighting shear failure as the primary mode. Microcrack generation at peak stress points under high confining pressure predominantly influences macroscopic failure. The proportion of tensile cracks notably increases in the residual stage post-peak, with shear and tensile cracks developing concurrently. Increasing confining pressure promotes tensile crack development, with a stronger effect on crack growth numbers during early loading stages. Conversely, the impact of confining pressure on crack growth numbers diminishes after reaching the peak, as illustrated. The actual macroscopic failure angle formed by crack propagation measures approximately 210°, corresponding to 60° in elevation view.关键词：deeply buried marble;confining pressure;crack propagation;progressive destruction;mesoscopic failure characteristics931|425|0更新时间：2024-08-22
- “在大坝安全监控领域，专家建立了基于知识图谱的智能监控预警方法，为解决多测点大坝安全监控问题提供解决方案。”摘要：ObjectiveDam safety monitoring and early warning is an important means to assess the safety status of dams through comprehensive processing and analysis of various monitoring data. It is highly abstract and fuzzy. Moreover, the dam has numerous monitoring points with disordered distribution, making it difficult for traditional monitoring methods to describe the complex relationships among monitoring points, such as spatial relationships and structural mechanism correlations. Additionally, there is a lack of suitable platforms to systematically summarize and infer these monitoring points and their various complex relationships, thereby enabling comprehensive monitoring and early warning of dam safety from a holistic structural perspective. In response to these issue, a dam safety intelligent monitoring and early warning method based on knowledge graph was proposed.MethodsFirstly, according to the regulations in “Drawing standard for hydraulic structure of hydropower and water conservancy project”, monitoring points were named and distinguished in a combination of letters and numbers, forming distinguishable and independent entities. Referring to the manual determination of adjacent monitoring points, two adjacent conditions determining rules were proposed based on spatial mathematical models to form an automatic determination method for monitoring point spatial adjacency relationships. Addressing the common issues of varying lengths and time-step misalignment in data sequences of monitoring points, a rule for determining data sequence similarity based on dynamic time warping distance was proposed, achieving automatic determination of spatial adjacency relationships and data sequence similarity relationships between monitoring points. By analyzing the internal characteristics of monitoring points, the monitored physical quantity, single monitoring point warning level, and affiliated components were designated as object properties, while the three-dimensional coordinates, current monitoring data, and historical monitoring data were designated as data properties, forming intrinsic attribute information of monitoring points. Through the above arrangement, the characteristics of entities, relationships, and attributes centered around dam monitoring points were obtained, forming a knowledge system for dam safety monitoring. Secondly, after comparing the advantages and disadvantages of various graph databases, Neo4j database, known for constructing complex relationships, was selected as the base to describe the complex relationships and internal characteristics of monitoring points using a mesh-like graph structure. Based on the py2neo toolkit to batch process the fixed instructions for building the graph database, the first dam safety monitoring knowledge graph centered around monitoring points was constructed, providing a new approach for efficient organization and relationship representation of monitoring points. Subsequently, based on the knowledge guidance and multi-level relationship query capabilities of the graph database, the associated response mechanism for spatial distribution characteristics and data sequence similarity relationships of monitoring points was established. The method can automatically identify abnormal monitoring points and divide them into different groups based on the intrinsic relationships of monitoring points, achieving interconnection and communication of monitoring points, thereby addressing the difficulty of traditional methods in dealing with complex relationships among dam monitoring points. Furthermore, considering comprehensively the quantity of anomalous monitoring points, the alert level, spatial clustering degree, and similarity of data sequences, a method combining knowledge graph and mathematical models was proposed to introduce the concept of clustering degree for multiple monitoring points and to construct a spatial impact region algorithm for anomalous point groups. It ingeniously transforms the dam safety evaluation problem into a three-dimensional spatial calculation problem of anomalous monitoring point impact regions, achieving the quantification of dam safety monitoring and early warning. Then, taking the impact region of anomalous monitoring points of the dam as the core, considering the abnormal level and the data sequences similarity relationship of monitoring points, the safety operational state score of the dam was calculated, and the function of Tanh was utilized to convert the operational state score into a standardized range. Finally, referring to the safety level standards for dam failure risk in the “Guide for safety assessment of large dams for hydropower station in operation”, the operational state of the dam was divided into four levels, facilitating dam safety managers to differentiate the risk level and enabling comprehensive monitoring and management from the perspective of the overall dam structure.Results and DiscussionsTo validate the feasibility of the proposed dam monitoring and early warning method, a section of a concrete gravity dam was taken as an example, analyzing 155 deformation and seepage monitoring points. The result was that the calculated operational state score of the dam is 76.99, indicating a second-level warning state, requiring timely measures to be taken.ConclusionsThe research indicates that the proposed method fully leverages the advantages of knowledge graphs in information fusion and brain-like reasoning. It integrates dam monitoring points into a data network for unified analysis, and proposes for the first time the concepts of clustering degree for anomalous monitoring points and structural impact regions. The method realizes multi-point dam safety monitoring and early warning by comprehensively considering the quantity of monitoring points, spatial distribution, and structural mechanism association characteristics, thereby addressing the problem of numerous and independent dam monitoring points.关键词：knowledge graph;dam;multi-points;monitoring and warning;aggregation degree;multi-level query1051|439|0更新时间：2024-08-22
- “在能源供给结构改革领域，专家提出了一种结合时移多尺度波动散布熵和改进核极限学习机的水电机组智能故障诊断方法，有效解决了振动信号中噪声干扰问题，显著提高了诊断精度。”摘要：Hydropower plays an important role in the reform of energy supply structure. With the continuous access of new energy sources such as wind, light and tide, the load operation range of hydropower units is widening, which leads to the increase of the probability of accidents of hydropower units. Therefore, it is of great practical significance to carry out the research on intelligent fault diagnosis of hydropower units. In this paper, aiming at the problem that the vibration signal of hydropower unit contains a large number of noise signals and interferes with fault diagnosis, a fault diagnosis method of hydropower unit based on time-shifted multi-scale fluctuation dispersion entropy and improved kernel extreme learning machine is proposed. Firstly, based on the multi-scale fluctuation dispersion entropy, the time-shift theory is used to replace the traditional coarse-grained process in the multiscale fluctuation dispersion entropy (MFDE), and the time-shift multiscale fluctuation dispersion entropy (TSMFDE) is proposed by combining the information entropy theory and the time-shift idea. Through simulation experiments, it is proved that the proposed method has good timing length robustness, noise resistance and feature extraction ability, and overcomes the problem of insufficient coarse–grained of traditional multi-scale entropy. Then, the arithmetic optimization algorithm (AOA) with strong portability, strong optimization ability and fast convergence speed is used to optimize the regularization parameters and kernel function parameters of kernel based extreme learning machine (KELM), and the AOA–KELM classifier is established to overcome the problem that the hyperparameters of KELM are difficult to adjust. Finally, through the simulation experiment of the rotor test bench, the features extracted by TSMFDE are input into the classifier to complete the pattern recognition work. The simulation results show that the proposed model achieves the highest diagnostic accuracy, reaching 100.0%. Compared with other popular models, the proposed model shows obvious advantages, which verifies that the proposed model has good diagnostic accuracy.关键词：time-shifted multiscale fluctuation dispersion entropy;kernel extreme learning machine;arithmetic optimization algorithm;hydropower units;fault diagnosis863|371|1更新时间：2024-08-22
- “在梯级水电市场出清领域，专家提出了一种水力、电力、价格三因素耦合的出清方法，通过优化算法提高求解效率，为解决水–电不匹配问题提供了新思路。”摘要：This study proposes a hydraulic–electricity–price coupling clearing method based on the operational characteristics of cascade hydropower in response to the hydraulic–electricity mismatch in a traditional market clearing, where the economics of power purchase is the primary goal. It introduces a hydraulic–electricity coupling index to measure the matching degree of water and electricity, providing a method for its calculation considering the conditions of water shortage and abandonment. Subsequently, a multi-objective clearing model is developed for a hydropower–dominated power market. This model aims to minimize the electricity purchase cost and maximize the hydraulic–electricity coupling degree. A comprehensive dimensionality reduction strategy for solving the model is presented, encompassing model structure layering, search space reduction, and calculation period merging, facilitated by a price sorting-particle swarm coupling optimization algorithm. The proposed approach is applied to a virtual day-ahead market comprising eight hydropower stations across three cascades in Sichuan province, China. The case study revealed that the power purchase cost of the proposed model is equal to that of the traditional one, but the hydraulic–electricity coupling degree is 1.57% higher. This result demonstrates that incorporating the hydraulic–electricity coupling degree maximization target does not compromise the economic efficiency of electricity purchasing. Instead, it significantly reduces insufficient output and surplus water and enhances the executability of clearing results, thus validating the new clearing method's rationale. In addition, the proposed solution strategy simplifies the model’s complexity and boosts the solution’s efficiency. This study offers a novel perspective for mitigating the hydraulic–electricity mismatch in the cascade hydropower spot market.关键词：cascade hydropower stations;spot market;clearing method;hydraulic–electricity–price coupling832|566|0更新时间：2024-08-22
CLEAN ENERGY DEVELOPMENT AND DEEP UNDERGROUND ENGINEERING IN THE YALONG RIVER BASIN
- “在山区铁路桥梁与区域环境协调发展领域，专家构建了耦合协调优化调控模型，为评估和优化桥梁与环境协调状况提供新思路。”摘要：The terrain along the mountain railway is intricate, with a high proportion of bridges. To systematically evaluate and enhance the harmony between mountain railway bridges and the regional environment, fostering their high-quality coordinated development, we propose a coupled coordination optimization and control model for mountain railway bridges and the regional environment. This model is based on an analysis of the interplay between mountain railway bridges and the regional environment. We construct green design elements and a characteristic index system for mountain railway bridges from a design perspective and utilize the CRITIC method to identify key elements of green design. Incorporating the cumulative effect of time, we analyze the sustainability of mountain railway bridges and the environmental carrying capacity, and develop a coupling coordination model for the mountain railway “bridge-environment” system, measuring the degree of coupling coordination between mountain railway bridges and the regional environment. By maximizing the coupling coordination index as the objective function, we establish an optimal regulation model that reflects the dynamic feedback mechanism of the “bridge-environment” system. This model is solved using the particle swarm optimization algorithm, and a control scheme is proposed to guide the coordinated development of mountain railway bridges and the regional environment towards high quality. Our optimization results indicate that, while ensuring “bridge sustainability ≤ environmental carrying level” and minimizing deviation, the optimization ratio of key green design elements ranges from 2% to 40%, resulting in a maximum coupling coordination index of 622.4 for the “bridge-environment” system. This study enhances the coordinated development of bridges and the regional environment, offering fresh perspectives for assessing the coupled coordination status of mountain railway bridges and the regional environment, as well as for green bridge design.关键词：railway bridges in mountainous areas;regional environment;coupling coordination;key elements;optimal regulation;particle swarm optimization875|325|0更新时间：2024-08-22
- “金沙江构造结合带的白格滑坡研究揭示了黏土化蚀变岩的灾变力学特性及其在滑坡形成中的关键作用，为青藏高原东缘岸坡稳定性分析和防灾减灾提供了重要启示。”摘要：The Jinsha River’s tectonic junction zone is a typical tectonic melange zone resulting from plate collisions. It boasts a complex geological structure and hosts unique rock and soil formations with unfavorable engineering properties. Investigating the Baige landslide upstream of the Jinsha River revealed a novel finding: clay-altered rocks, characterized by significant thickness and continuous distribution, were identified on the rear edge of the massive landslide, playing a crucial role in its composition. Through on-site sampling and laboratory experiments encompassing material composition, disintegration resistance, annular shear, and dynamic triaxial analysis, the catastrophic mechanical behavior of clay-altered rock and its contribution to the formation and evolution of the Baige landslide were elucidated. Key conclusions include: 1) The clay-altered rock in the Baige landslide, exhibiting high alteration degrees, results from intense alteration of ophiolite within the Jinsha River's tectonic junction zone. Alteration coefficients range between 0.64 and 0.86, with mineral components predominantly comprising illite, followed by illite/montmorillonite mixed-layer minerals. It demonstrates high susceptibility to disintegration upon contact with water, with a disintegration index surpassing 50%. 2) Altered clay exhibits the poorest engineering properties within clay-altered rock formations, with its strength significantly diminished under the influence of water and vibration loads. Increasing water content from 10% to 20% results in a 34% decrease in shear strength. Dynamic strength notably lags behind static strength and diminishes with increasing vibration cycles, playing a pivotal role in facilitating the penetration and failure of slope rock mass structural planes. 3) The formation of the Baige landslide's sliding surface is jointly governed by joint structural planes and clay-altered rock, manifesting two predominant modes: thick, soft interlayered clay-altered rock and filling joints and fractures penetrating types. 4) The prevalence of numerous massive high-level landslides upstream of the Jinsha River correlates closely with the unfavorable engineering characteristics of clay-altered rocks. The interplay between rock mass structure and distinct lithology constitutes a regional geological structure prone to slip, warranting attention. This understanding holds significant implications for slope stability analysis and disaster prevention along the Dajiang River bank on the eastern margin of the Qinghai–Xizang Plateau.关键词：Baige landslide;clay altered rock;strength weakening;slippery geological structure;sliding control effect1064|357|0更新时间：2024-08-22
- “在大跨度拱桥施工领域，专家提出了一种改进零位移法结合无应力状态控制法的复合扣索力计算方法，有效解决了索力优化计算和扣索状态控制问题，为大跨度非对称式钢结构拱肋施工提供了便捷、准确的解决方案。”摘要：Long-span arch bridges often utilize the cantilever construction method to erect the arch rib. The cable forces of fastening stays and the spatial configurations of the rib mutually influence each other during segmental assembly. Calculating cable forces and controlling the state of fastening stays are complex processes. This study proposes a combined algorithm that integrates the improved zero-displacement method with the zero-stress state control method for determining cable forces. The optimized cable forces at the arch formation stage can be quickly calculated using the improved zero-displacement method. Based on the calculated fastening stay forces, the zero-stress cable lengths and the cable forces at each assembly stage can be deduced using the zero-stress state method. This composite method avoids the inaccuracies and repeated iterative calculations of the traditional zero-displacement method. The fastening stays require only one-time tensioning during construction, eliminating the need for repeated cable force adjustments during the segment assembly process. The combined algorithm is applied to the cantilever construction analysis of a long-span concrete-filled steel tube arch bridge with a span of 430 m. The zero-displacement method, combined with the stress-free state method, determines the tension forces of fastening stays during the asymmetric cantilever construction of the long-span arch ribs. Variations in cable forces during the assembly process were analyzed, comparing the deviations between the actual rib and the target rib lines and between the rib stresses and the designed member stresses. The results indicated that the proposed combined algorithm is simple and facilitates easy calculations. The fastening stay forces obtained can effectively ensure satisfactory control of the arch rib assembly at the arch formation and cable loosening stages.关键词：concrete-filled steel tubular arch bridge;cantilever construction method;fastening stay force determination;zero-displacement method;zero-stress state control method783|456|0更新时间：2024-08-22
- “在应对全球气候变暖导致的极地冰川稳定性问题上，专家基于三剪统一强度理论，建立了多晶冰弹塑性本构模型，并通过试验验证，为冰川稳定性评价提供理论及数值模拟基础。”摘要：As global warming intensifies, mountain and polar glaciers are retreating at an accelerated pace. The frequency of large-scale glacier collapse and sliding is gradually increasing. Polycrystalline ice constitutes the primary form of glacial ice. The constitutive model of polycrystalline ice holds significant importance for glacier stability analysis, mass balance, and multi-field coupling simulation. Drawing from the Triple-shear unified strength theory, we propose yield and plastic potential functions that can effectively account for the influence of principal stress. Considering the variation of cohesion throughout the loading process, we construct a hardening function based on equivalent plastic strain. An elastoplastic constitutive model with non-associated flow is established to capture the softening characteristics of polycrystalline ice. The validity of this model is confirmed through conventional triaxial compression tests of polycrystalline ice, demonstrating its ability to accurately describe axial strain-deviator stress and axial strain-volumetric strain behaviors. Subsequently, we predict the true triaxial axial strain-deviator stress and axial strain-volumetric strain behaviors of polycrystalline ice under different medium principal stress coefficients. Our predictions reveal significant softening in the deviator stress-axial strain curves of polycrystalline ice, with both residual strength and peak strength increasing with the influence coefficient of the medium principal stress. Volumetric strain exhibits an initial shrinkage followed by expansion with axial strain, with the maximum shrinkage and expansion increasing alongside the influence coefficient of the medium principal stress. Furthermore, we derive and incorporate the finite difference scheme of the elastic-plastic constitutive model into Flac3d numerical software, verifying its effectiveness through a single element simulation. In the context of global warming, these research findings are poised to offer a theoretical and numerical foundation for predicting glacier stability.关键词：Glacial stability;constitutive model;Polycrystalline ice;numerical simulation989|342|0更新时间：2024-08-22
- “在粗粒混合土地基处理领域，中国中西部地区专家通过振杆密实法，有效提高了地基承载力和消除不均匀性，为现场施工提供关键参数依据。”摘要：Coarse-grained mixed soil is widely distributed across China’s central and western regions. Its loose nature and unevenness present challenges when using these materials as foundations for structures. This study proposes using the vibration probe compaction method to enhance the bearing capacity of these foundations and eliminate unevenness. The primary research method involves conducting indoor model experiments, including vibratory compaction tests, lightweight dynamic probing tests, and density measurement tests. These experiments incorporate real-time monitoring of vibration and settlement indicators to assess the consolidation effects of the vibration probe compaction method on coarse-grained soil. Additionally, the study evaluates the impact of parameters such as the k-value (d90/diameter of the probe) and vibration frequency on the effectiveness of the consolidation. The findings reveal that after vibratory treatment, the average number of lightweight dynamic probing blows increases to 13, an increase of 11 compared to before treatment. The average compaction degree at the bottom of the specimen reaches 81%, enhancing the bearing capacity by over 200 kPa. The treated soil becomes a low-compressibility foundation; when the k-value is 1/2.0, the reinforcement effect is superior to that when the k-value is 1/10.0, with the former exhibiting approximately 50 kPa higher bearing capacity and a 7% higher settlement rate compared to the latter. When applying a 14 Hz vibration frequency to coarse-grained mixed soil, the ground vibration velocity reaches 36 mm/s. The HHT spectrogram showed a significant seismic response of around 14 Hz using the Hilbert-Huang Transform (HHT) on the collected vibration data. Employing a triangular arrangement for reinforcement points eliminates unevenness in the foundation soil. The unevenness coefficient (K) decreases from 26.4 before the experiment to 1.39 after. The vibration probe compaction method offers a novel technique for improving the foundations of coarse-grained mixed soil and provides essential parameters for on-site construction.关键词：vibration probe compaction;coarse-grained mixed soils;indoor model tests;vibration frequency;compaction degree703|346|0更新时间：2024-08-22
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Physical and Mechanical Properties of Sprayable ECC in Highway Tunnels and its Spray Layer Stability AI导读
“在公路隧道支护领域，最新研究通过引入脱硫石膏、混杂纤维等材料，成功研发出性能优越的喷射型ECC。现场监测显示，与传统C25喷射混凝土相比，新型ECC能有效降低隧道沉降变形，提高支护稳定性，具有广泛应用前景。”摘要：Traditional fiber-reinforced cementitious composites (ECC) are limited in application due to their high cost and considerable shrinkage. Additionally, research on the stability of sprayable ECC layers in highway tunnels under excavation disturbance remains incomplete, with inadequate monitoring and evaluation following its engineering applications. This study investigates the physical and mechanical properties of sprayable ECC in highway tunnels. It analyzes the stability of the surrounding rock and the sprayable ECC layer under excavation and evaluates the application effectiveness through field monitoring. The results indicate that the physical and mechanical properties of sprayable ECC can meet the requirements for shotcrete in highway tunnels by incorporating desulfurized gypsum, hybrid fiber, manufactured sand, an expansion agent, and a shrinkage-reducing agent into the ECC mix. Based on numerical simulations, for a 12-m support, the peak tensile and compressive principal stresses of the sprayable ECC layer increase by 36.8% and 28.4%, respectively, compared to the C25 shotcrete (C25SC) layer. The maximum vertical displacement of the inner arch reduces by 3.15% compared to C25SC to only 1.23 mm. Based on on-site monitoring, under the same geological conditions of the surrounding rock, sprayable ECC minimizes the vertical settlement deformation by 10.26% compared to C25SC. In addition, no cracking or linear seepage is observed on the surface of the sprayable ECC layer. Therefore, sprayable ECC holds broad application prospects in highway tunnel support with appropriate modifications.关键词：sprayable ECC;highway tunnel;physical and mechanical properties;numerical simulation;stability800|375|0更新时间：2024-08-22
ENGINEERING AND ENVIRONMENT IN CHALLENGING MOUNTAINOUS REGIONS
- “在斜坡稳定性研究领域，专家基于两域模型与稳定系数场原理，建立了降雨入渗下斜坡非均匀渗流与稳定性求解模型，并通过COMSOL Multiphysics平台验证了模型的合理性，为揭示大孔隙参数对斜坡水分运移与稳定性的影响提供了解决方案。”摘要：To investigate the influence of macropore parameters on the non-uniform migration and stability of slopes under rainfall, a solution model was developed based on the two-domain model and the stability coefficient field principle. This model addressed non-uniform flow and slope stability under rainfall infiltration. Using the COMSOL Multiphysics finite element platform, a corresponding model solving program was created. The numerical results were validated through indoor rainfall tests on macropore soil columns. A comparison was made between slope volume water content and point stability coefficient under conditions of uniform and non-uniform flow. Subsequently, the impact of macropore parameters (namely, the proportion of macropore domain ωf, the ratio of water conductivity between macropore and matrix domain μ, and the macropore empirical parameter rw) on slope seepage field and stability coefficient field was analyzed. The findings revealed that compared to scenarios without macropores, considering macropores led to a 7.7% increase in volume water content in the matrix domain and a 5.1% decrease in the macropore domain. Additionally, infiltration depth increased by 83.3% and 150.0%, respectively, and the shallow instability area of the slope expanded by 3.9%. Infiltration depth decreased with an increase in ωf for both the matrix and macropore domains. Conversely, with an increase in μ, infiltration depth decreased for the matrix domain and increased for the macropore domain. There was no significant relationship observed with the empirical parameter rw. At the end of the rainfall, volume water content in the matrix domain peaked, while the macropore domain increased with higher values of ωf and μ, showing minimal impact from the empirical parameter rw. Water exchange was categorized into negative exchange area, positive exchange area, and no exchange area along the profile. The equilibrium depth of water exchange aligned with the change in infiltration depth of the matrix domain. Both the negative and positive exchange areas exhibited peak values that decreased with higher ωf and increased with higher μ and rw values. Under varying parameter values, the slope experienced shallow instability failures. Higher values of ωf and μ corresponded to deeper instability layers and lower point stability coefficients, indicating that macropores were detrimental to slope stability.关键词：macropores parameters;non-uniform flow;point stability factor;water exchange;infiltration depth206|303|0更新时间：2024-08-22
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Experimental Study on Dynamic Properties of Loess Improved by Rubber Particles and EICP Technology AI导读
“最新研究揭示，橡胶颗粒及脲酶诱导碳酸钙沉淀技术可有效改善黄土动力特性，提高黄土地区抗震性能，同时为废轮胎无公害处理提供新途径。”摘要：This study focuses on losses from the Xi’an area to investigate the enhancement effect of rubber particles and Enzyme-Induced Calcium Carbonate Precipitation (EICP) technology on the dynamic characteristics of loess. It analyzes the impact of varying rubber content, rubber particle size, and confining pressure on the dynamic strength, dynamic shear modulus, and damping ratio of the improved soil. Two improvement methods are examined: adding rubber particles alone and combining rubber particles with EICP technology. The study also elucidates the strengthening mechanism. The findings indicated that, in comparison to pure soil, an optimal quantity of rubber particles can significantly enhance the soil's pore structure and strengthen the soil skeleton. However, the distribution and action forms of rubber particles within the soil vary. Hence, under both improvement methods, the dynamic strength of the sample initially increases and then decreases with the increase in rubber content, decreases first and then increases with the increase in rubber particle size, and consistently increases with the elevation of confining pressure. The rubber content that corresponds to the peak dynamic strength is 7%. Given that rubber particles of different content and sizes inhibit the EICP process, leading to variations in the amount of calcium carbonate crystals precipitated and their distribution within the soil, the dynamic strength's growth rate diminishes with an increase in rubber content and initially increases then decreases with the increase in rubber particle size. The peak growth rate of dynamic strength reaches 29.51%. Owing to the significant influence of rubber particles and EICP on the dynamic properties of loess, the dynamic shear modulus of the sample diminishes with an increase in rubber content, initially decreases then increases with the increase in rubber particle size, and escalates with the increase in confining pressure. The variation in dynamic shear modulus ratio can be more accurately modeled by the modified Hardin-Drnevich hyperbolic model. The damping ratio increases with an increase in rubber content, initially decreases then increases with the increase in rubber particle size, and diminishes with the increase in confining pressure. When combining rubber particles with EICP technology for loess improvement, the dynamic properties of loess are enhanced, and the compressive strength loss due to the addition of rubber particles is also compensated. These test results can provide a scientific foundation for enhancing the seismic performance in loess regions and offer a pollution-free solution for the disposal of waste tires.关键词：rubber particle;EICP technology;dynamic intensity;dynamic shear modulus;damping ratio;Improved loess265|373|0更新时间：2024-08-22 - “在桥梁工程领域，一项新研究揭示了连续刚构桥主梁与过渡墩碰撞效应对地震系统易损性和概率地震风险性的影响。通过动力弹塑性分析模型和增量动力分析法，研究者发现忽略碰撞效应会显著低估地震风险，为桥梁抗震设计提供了重要参考。”摘要：A continuous rigid-frame bridge was selected with a main span arrangement of (120 + 220 + 120) m to investigate the influence of the pounding effects between the main girder ends and transition pier on the seismic system fragility and probabilistic seismic risk of the bridge. The real internal force state of the completed bridge was extracted from the actual construction simulation. The dynamic analysis model of the bridge was developed based on the equivalent load method, which considers the internal force state. The Hertz–Damp model is utilized to simulate the pounding effects. A total of 90 pulse-like near-fault ground motions were selected and inputted along the longitudinal direction. The pounding process and damage mechanism were illustrated through nonlinear time-history analysis. The composite system fragility curves of the bridge, considering the weight coefficients of piers and bearings, were established by incremental dynamic analysis. These curves were compared to the fragility curves derived from the first-order boundary method series model and the parallel model. Moreover, the site seismic hazard function was convoluted with the fragility function to establish the probabilistic seismic risk curves. Subsequently, the system fragility, probabilistic seismic risk, and the pier-beam pounding effects were investigated. The results indicated that the displacement response of the transition pier and the seismic risk probability could be underestimated by 3 to 5 times and 120%, respectively, when the pounding effects are ignored. The seismic damage probability of slight and moderate damage can be underestimated by 35% to 80% when the peak ground accelerations are 0.2g to 0.6g, while that of severe and complete damage can be underestimated by 13% to 68% and 15% to 59% when the peak ground accelerations are 0.6g to 1.5g, respectively.关键词：continuous rigid-frame bridge;pounding response;internal force state;pulse-like ground motions;system fragility;seismic risk analysis320|418|0更新时间：2024-08-22
- “在盾构隧道掘进领域，专家建立了地表沉降的地层损失模型，考虑了曲线隧道的非对称性，为预测地表沉降提供了更准确的计算模型。”摘要：The primary factors contributing to surface settlement during curved shield tunneling are ground loss and construction load. The asymmetry inherent in curved shield tunneling complicates the prediction of surface settlement. Drawing from existing research on surface settlement resulting from linear shield tunneling, we establish a ground loss model to compute surface settlement induced by tunneling. This model accounts for the self-weight settling of the tunnel to the bottom of the soil boundary in real-world scenarios and integrates considerations for the asymmetric nature of shield tunneling. We then compare this developed model with an existing ground loss model designed for curved tunnels. Our findings indicate that the surface settlement deformation predicted by the stratigraphic loss model proposed in this study is more significant and influenced by the turning radius size. Specifically, when the tunnel’s turning radius exceeds 800 meters, the surface settlement caused by ground loss in curved and straight tunnels varies minimally. Conversely, for turning radii less than 300 meters, the surface settlement value exhibits higher sensitivity to the tunnel’s curvature. Our model effectively compares surface deformations predicted by two distinct ground loss models with real-world project data, demonstrating closer alignment with actual observations and reduced error. The calculated results from our model closely match empirical data, affirming its ability to accurately represent real-world conditions. These research findings offer valuable insights for analyzing and predicting surface settlement associated with curved shield tunneling.关键词：curved shield tunnel;formation loss;theoretical model comparison;surface settlement286|497|0更新时间：2024-08-22
CIVIL ENGINEERING
- “旋流排沙渠道技术在水沙分离领域取得新进展，通过数值模拟和模型试验，验证了其高效连续排沙能力，为工程应用和水沙特性研究提供有益参考。”摘要：The desilting channel with swirling flow is an innovative technology for separating water and sediment in channels based on the strong carrying capacity of swirling flow. The two-phase flow of water and sediment in the desilting channel is simulated using the realizable k–ε model, volume of fluid method, and discrete phase model based on experimental tests to indicate its water–sediment characteristics. The shape factors of sediments with varying particle sizes are determined by comparison to model test results. The effectiveness of sediment discharge in the desilting channel under continuous sediment inflow is examined, and the movement characteristics of sediment within the channel and the sediment transport pipe are analyzed. The results demonstrated that when the shape factors of sediments with different particle sizes range from 0.2 to 1.0, the simulated sediment trapping efficiency for particle sizes of (0.075, 3.000] mm in the desilting channel with swirling flow closely aligns with the experimental values under local inflow conditions from the top of the channel, with a relative error of only 3.5%, primarily attributed to fine sediment particles sized (0.075, 0.160] mm. When sediment is continuously imported from upstream channels at a mass flow rate of 60.0 g/s, the sediment content in the channel rapidly decreases due to the diversion by the swirling flow generator for hyperconcentrated flow at the bottom of the channel. The sediment content at the channel bottom before and after the swirling flow generator is 44.00 and 0.07 kg/m3, respectively. The swirling flow in the sediment transport pipe exhibits a notable sediment-carrying effect, with sediment primarily distributed near the wall of the pipe due to the strong centrifugal action of the swirling flow, where the maximum sediment content reaches approximately 200.00 kg/m3. The sediment trapping efficiency of the desilting channel with swirling flow is 95.98% for particle sizes of (0.075, 3.000] mm under continuous sediment inflow conditions. Only a small amount of fine sediment enters the downstream channel as suspended matter, and there is no significant sediment deposition in the channel and sediment transport pipe, indicating that the desilting channel with swirling flow is an efficient and continuous water–sediment separation technology. These results can provide valuable insights for applying desilting channels with swirling flow in engineering projects and the study of water–sediment characteristics.关键词：desilting channel with swirling flow;water–sediment characteristics;numerical simulation;discrete phase model;sediment trapping efficiency920|249|0更新时间：2024-08-22
- “在岩石高边坡开挖爆破振动研究领域，专家对白鹤滩水电站工程的实测数据进行概率统计分析，发现正态分布和Gamma分布模型拟合效果良好，为岩石高边坡爆破振动预测提供科学理论基础。”摘要：Determining the probability distribution of blasting vibrations induced by high rock slope excavation can provide a theoretical basis for predicting the amplitude and frequency of these vibrations with uncertainty. This study focuses on the right bank dam abutment high rock slope excavation at the Baihetan hydropower station. It investigates recorded blasting vibration data during high rock slope excavation using typical procedures and blasting schemes through probability statistics. In addition, the research explores the probability distribution and main characteristics of the recorded blasting vibration amplitude and dominant frequency. The findings indicate that the normal and Gamma distribution models are effectively employed to fit the peak particle velocity (PPV) probability distributions of presplit and production blasting during high rock slope excavation. The PPV probability distributions of the presplit and production blasting conform to either the normal or Gamma distribution. Compared to the normal distribution model, the Gamma distribution model more effectively fits the apparent dominant frequency probability distribution of presplit and production blasting vibration during high rock slope excavation. The apparent dominant frequency probability distribution of the presplit and production blasting vibration better follows the Gamma distribution. The average values of PPV and apparent dominant frequency of presplit blasting are greater than those of corresponding production blasting. The lower to upper quartile PPV ranges of the presplit and production blasting are 5.4 to 11.6 cm/s and 3.8 to 8.9 cm/s, respectively. The lower to upper quartile apparent frequency ranges of the presplit and production blasting are 36.7 to 97.6 Hz and 26.7 to 97.6 Hz, respectively. The results demonstrate that the commonly used normal distribution is not necessarily the best probability distribution for blasting vibration. The probability distribution of blasting vibration amplitude and dominant frequency in other typical high rock slope excavations needs further examination.关键词：Baihetan hydropower station;high rock slope;blasting vibration;peak particle velocity;dominant frequency;probability distribution742|300|0更新时间：2024-08-22
- “最新研究揭示了植被群对河道水流结构的影响，通过模拟实验，发现了水流结构的五个纵向发展分区，并提出了相关流速计算公式，为河流动力学研究提供了新的视角。”摘要：Vegetation patches constitute the foundational elements of river dynamic systems, often forming communities within channels. This study examines how the interaction between neighboring vegetation patches influences flow structure. A pair of adjacent vegetation patches, constructed from staggered rigid cylinders with varying densities, is used in the experiments. The findings indicate significant differences in flow structure when water traverses these adjacent patches compared to an isolated patch. Hence, a flow structure partition for adjacent patches is proposed, including an upstream adjustment region, a vegetation interior region, a shear layers region, and a wake merger region. The upstream adjustment length indicates the distance upstream from the obstruction where velocity starts to deviate from its far upstream value. This reduction in velocity is pronounced in denser patches, although the upstream adjustment length remains unaffected by vegetation density. The velocity at the centerline of each patch significantly decreases, whereas the velocity between the patches increases rapidly, a characteristic of the vegetation interior region. The reduction in individual patch velocity is again observed in denser patches. In the downstream area, the shear layers region extends from the trailing edge of the patches to the point of minimal velocity behind each isolated patch. With increasing vegetation density, the smallest velocity approaches zero, while the length of the shear layers region, denoted as L1, initially decreases before stabilizing. The highest velocity on the centerline between the patches occurs near the trailing edge, with the lowest velocity observed at a distance (x/D=Lm) from the trailing edge. As vegetation density increases, the maximum velocity on the centerline between the patches rises, but the minimum velocity and Lm decrease. The difference (Lm–L1) defines the length of the wake merger region; here, the centerline velocity of each patch increases and aligns with the velocity on the centerline between the patches, causing the wakes directly behind each patch to merge into a single, larger entity. In addition, the formulas for the exit velocity, steady wake velocity, and minimum centerline velocity of the two patches are presented.关键词：neighboring vegetation patches;vegetation density;flow velocity;flow structure partition;wakes751|324|0更新时间：2024-08-22
- “在微结构壁面湍流减阻机理研究领域，专家采用PIV技术观测水流特性，建立新的ΩM涡识别方法，定量分析涡结构分布，为减阻机理研究奠定基础。研究结果表明，微结构壁面能有效降低水流输运能耗、提高输运效率。”摘要：To investigate the turbulent drag reduction characteristics of microstructure walls, the particle image velocimetry system was utilized to observe water flow characteristics across superhydrophobic, riblet, and smooth walls. The study delved into the evolution of flow velocity, variations in Reynolds shear stress, and vortex distribution. Enhancements were made to the Omega (Ω) vortex identification method, incorporating flow rate to establish a novel ΩM vortex identification method. Inspired by meteorological concepts of atmospheric vortex density, a corresponding definition for vortex density in liquid flow was proposed to quantify the distribution of vortices of differing strengths. Results demonstrated that, at equivalent Reynolds numbers, flow velocity decreased sequentially from superhydrophobic to riblet to smooth walls. Notably, the flow velocity of microstructure walls exhibited pronounced outward shifts compared to that of smooth walls, indicating drag reduction effects. Concurrently, Reynolds shear stress initially increased then decreased with increasing normal dimensionless distance (y+), with the superhydrophobic wall exhibiting the smallest maximum Reynolds shear stress among all walls. In the vortex structures identified using the ΩM method, weak vortices on microstructure walls decreased significantly within a water depth range of 0.1 times, while strong vortices weakened within a range of 0.2 times the water depth. Notably, the vortex density of weak vortices increased on microstructure walls compared to smooth walls, whereas the density of strong vortices decreased, suggesting that microstructure walls inhibited the development of strong vortices. The drag reduction ratio of riblet walls exceeded 7.60%, while superhydrophobic walls exhibited a higher density of weak vortices and a lower density of strong vortices, resulting in the most significant drag reduction effect surpassing 9.48%. Microstructure walls thus prove effective in reducing energy consumption in water transport and enhancing transport efficiency.关键词：Super hydrophobic wall;Riblet wall;ΩM method;Vortex density;drag reduction740|351|1更新时间：2024-08-22
HYDRAULIC ENGINEERING
- “在壁画修复领域，研究人员提出了一种新的深度学习模型，通过多层次特征融合与超图卷积技术，有效提升了破损壁画的修复质量。该方法在敦煌壁画数字化修复实验中表现出色，修复结果更加清晰自然。”摘要：Aiming at the problems of low feature utilization and insufficient attention to context information in existing deep learning image restoration methods, a generative adversarial mural restoration model based on multi-level feature fusion and hypergraph convolution was proposed. Firstly, a pyramid feature extraction layer structure was designed, and the multi-scale feature extraction was carried out by using the pyramid feature layer. The mixed dilated convolution unit was used to expand the receptive field of multi-layer feature extraction, which overcomes the problem of insufficient feature extraction ability of single-scale convolution operation. Then, a multi-branch short chain fusion layer and a gating method were proposed to fuse the multi branch features, and the feature information between the adjacent branches was fused, so that the fused mural feature map has both the same branch features and the adjacent branch features, improving the utilization rate of feature information, and introducing the gating mechanism to select and fuse features to reduce the loss of detail information. Next, the fused features were passed through the ConvLSTM feature attention to enhance the attention to the mural context information. Finally, a hypergraph convolution mural long-range feature enhancement module was designed. By establishing a hypergraph convolution layer between the skip connection of the encoder and the decoder, the spatial feature information of the encoder was captured by hypergraph convolution and transferred to the decoder, which helpes the decoder to generate mural images and strengthenes the long-range dependence of features. Afterwards, the mural restoration was completed in a game against the SN–PatchGAN discriminator. Through the restoration experiments of digital Dunhuang murals, the results showed that the proposed method is superior to the comparative algorithms, and the restoration results of damaged murals are clearer and more natural.关键词：mural inpainting;multi-level features;multi-branch short chain fusion;hypergraph convolution;ConvLSTM303|420|0更新时间：2024-08-22
- “在提高COVID-19检测效率和准确性方面取得新进展，研究者开发了MHRA-RCNet模型，通过局部特征提取和全局信息建模，显著提升了胸部X射线图像分类的精度和有效性。”摘要：In order to improve the efficiency and accuracy of detection of novel coronavirus pneumonia (COVID–19), a network model (MHRA–RCNet) for automatic recognition of Chest X-ray images of COVID–19 was proposed in this paper.Based on ResNet50, local features were firstly extracted from infected regions with complex shapes in CXR images using residual convolution. Secondly, a multi-headed relationship aggregation module was introduced in the second and third stages of ResNet50 to enhance the modelling capability of global information. To further fuse the local and global information to improve the expression capability of features and the location between features correlation, a dilated convolution vision Transformer module is introduced in the final stage of ResNet50, which helps to identify complex lesion regions in CXR images. Finally, the fused features were fed into the global average pooling layer in a tandem fashion for global spatial information integration, and the images were classified and analysed visually by a multilayer perceptron.Through experimental comparisons with other deep learning classification models on the publicly available COVID–19 radiology database dataset, the experimental results showed that the proposed model has better classification accuracy in several classification metrics. In addition, it is intuitively obvious that the proposed model has better recognition of COVID–19 in terms of precision, sensitivity, and specificity, which further proves the superiority and effectiveness of the proposed model in image classification task.关键词：novel coronavirus pneumonia;image classification;residual convolution;multi-headed relation aggregator;dilated convolution vision transformer322|362|0更新时间：2024-08-22
- “最新研究进展：内蒙古风电场采用特征选择和改进麻雀搜索算法优化的CNN-BiGRU模型，实现短期风电功率高精度预测，平均绝对百分比误差仅2.6440%，验证了模型的准确性和泛化能力。”摘要：Given the significant randomness and non-stationarity inherent in wind power, achieving higher prediction accuracy through direct input of the prediction model is often challenging. Therefore, this study proposes a short-term wind power prediction method based on feature selection and an improved Sparrow Search Algorithm (ISSA) optimizing Convolutional Neural Network-Bidirectional Gated Recurrent Unit (CNN–BiGRU). Initially, Variational Mode Decomposition (VMD) is employed to break down the original power data into subcomponents, each containing distinct information. This process reduces the original power series’ non-smoothness, thereby enhancing predictability. The determination of the number of decomposition models relies on the observation of the central frequency method. Subsequently, feature selection is conducted using the Random Forest (RF) feature importance method for each component. This selects influential factors from meteorological features such as wind speed, wind direction, temperature, and air density to form the input feature vector. Following this, individual CNN–BiGRU prediction models are established for each component. To address the challenge of manually adjusting neural network algorithm parameters due to their inherent randomness, ISSA is employed to hyperparameterize the model, enabling the adaptive discovery of optimal parameter combinations. Finally, the prediction values of each component are aggregated to derive the final prediction results. Simulation experiments are conducted using real data from a wind farm in Inner Mongolia, China. These results are compared with various single and combined prediction methods. The findings demonstrate that the proposed method achieves higher prediction accuracy, with an average absolute percentage error value of 2.6440%. Furthermore, the model's accuracy and generalization are validated on additional data, with average absolute percentage error values of 4.3853%, 3.1749%, 1.5761%, and 1.3588%, all within 5%. This confirms the superior prediction accuracy and generalization ability of the proposed method.关键词：short term wind power prediction;variational mode decomposition;feature selection;improved sparrow search algorithm;convolutional neural network;bidirectional gated recurrent unit295|499|2更新时间：2024-08-22
- “在生物识别技术领域，研究者提出了一种新颖的虹膜与眼周深度特征融合网络模型，有效提升了识别准确率，为远距离和移动端生物识别提供了高效解决方案。”摘要：While iris recognition boasts a notably high recognition rate, unimodal biometrics suffer from vulnerabilities such as environmental factors and spoofing attacks. Particularly in remote or mobile settings with minimal constraints, the efficacy of iris recognition diminishes significantly. To address this challenge, leveraging periocular biometric features, situated proximately to the iris and known for their high discriminative power, presents a promising solution. By integrating iris and periocular features through bimodal fusion recognition, this issue can be effectively tackled. This paper introduces a novel approach for accurate and adaptive fusion recognition termed MultipleFusionNet, which incorporates iris and periocular depth features. Embracing the concept of channel attention and channel grouping attention, an automatic weight generation network is devised to dynamically assign weights to iris and periocular features through network learning. These weighted features, derived from convolutional neural networks, enable precise fusion and subsequently enhance recognition accuracy. The fusion module of this network model serves as a versatile deep feature fusion component, seamlessly integrable into any CNN backbone network, and characterized by its lightweight and straightforward implementation. Experimental validation is conducted using the CASIA–Iris–Distance dataset for remote scenarios and the CASIA–Iris–Lamp dataset for close-range illumination variations, both provided by the Chinese Academy of Sciences. Results from diverse comparative and distance measurement experiments demonstrate the superiority of the proposed fusion model. Achieving a peak accuracy of 99.56% and a minimal Equal Error Rate (EER) of 0.0027, measured by cosine distance, the model outperforms unimodal approaches and other related feature fusion methods. Furthermore, in terms of computational complexity, the proposed model exhibits efficiency, with a parameter count and computational workload approximately 1.5% lower than twice that of unimodal methods, and only 1% higher than standard fusion methods. These findings underscore the model's favorable balance of computational efficiency and performance prowess.关键词：bimodal fusion;Iris recognition;periocular recognition;deep feature fusion198|358|1更新时间：2024-08-22
INFORMATION ENGINEERING
- “在电力系统通信网络领域，专家提出了基于采样特性的离散负荷频率控制方案，为解决时滞和DoS攻击问题提供解决方案。”摘要：In response to the issues of time delays and DoS attacks in the communication networks of power system, this paper proposed a discrete load frequency control scheme based on sampling characteristics. Firstly, accounting for load fluctuations in the power system, this study quantified the impact of DoS attacks as the number of consecutive loss in sampling signals, within the framework of a state-space model for multi-area load frequency control system (LFC). Additionally, taking into consideration the communication delays and sampling characteristics of output signals in the network, an enhanced power system LFC model incorporating an output state feedback controller was established. Subsequently, based on this model, a stability criterion for the LFC system that meets a specified
$ {H_\infty } $ $ {H_\infty } $ 关键词：time delay;DoS attack;load frequency control scheme;sampling characteristics;Lyapunov functional249|433|0更新时间：2024-08-22 - “在防雷领域，研究人员通过多重雷击试验研究平台，探索了不同雷击参数对氧化锌阀片劣化特性的影响，为提高阀片性能和延长使用寿命提供了解决方案。”摘要：ObjectiveMultiple lightning strikes considerably accelerate the deterioration of zinc oxide valve plate, leading to a sharp decline in its electrical and thermal performance. The current national standard for testing lightning arresters considers only a single lightning strike and fails to account for the influence of multiple strikes. Hence, when a lightning arrester undergoes multiple strikes, it severely impacts the power grid. The extent of damage to the zinc oxide valve plate varies with different parameters of multiple lightning strikes. This study selects a valve plate from a leading manufacturer in Nanyang. This plate has a diameter of 42 mm, a height of 20 mm, a continuous operating voltage of 2.4 kV, a rated voltage of 3 kV, and a nominal current of 10 kA. This study examines the deterioration characteristics of the zinc oxide valve plate under various lightning strike scenarios.MethodsFirstly, the study establishes a multi-lightning strike test research platform. Before testing, it places the zinc oxide valve plate in an incubator for 30 min to stabilize its temperature. Then, it measures the valve plate’s initial direct current (DC). The test platform then conducts an impact test on the valve disc, with intervals between strikes set to 50 ms and using a standard 8/20 ms impact current waveform. An infrared thermal imager captures immediate temperature readings, including the highest, lowest, and specific point temperatures. Following the impacts, the valve disc’s DC parameters, U1mA, I0.75U1mA, and the reference voltage U0.1mA through 0.1 mA, are measured using the static MOA–II arrester valve disc DC parameter tester. The impact aging characteristics of the valve plate are analyzed by the change of DC reference voltageU1mA and leakage current I0.75U1mA. Finally, by modifying the current amplitude and shock frequency of continuous lightning strikes, this research conducts further tests under five different conditions: once at the rated current, once at 1.5 times the rated current, four times the rated current, another at 1.5 times the rated current, and finally at 12 times the rated current. These tests assess the thermal aging characteristics and DC parameters of zinc oxide valve plates under different operational conditions, using the physical appearance and DC parameters of the valve plates to evaluate damage levels.Results and DiscussionsThe analysis of the valve disc’s DC parameters under different impact multiplicities showed that changes in impact multiplicities significantly affect the valve disc’s tolerance. As multiplicities increase, the disc exhibits decreased shock resistance and reduced tolerance. The analysis of valve disc DC parameters under different impulse current amplitudes reveals that the variation law of valve disc DC parameters is similar to those under nominal current conditions as the impulse current amplitude increases. U1mA demonstrates a pattern of gradual decline, followed by a more rapid decrease and a significant rise in leakage current growth rate. Temperature rise analysis of the valve disc under different operating conditions showed that the highest temperatures in the zinc oxide valve disc mainly occur around the outer ring. The study also explores the effects of multiple lightning strike parameters on valve disc performance and deterioration by analyzing the nonlinear coefficient and the causes of damage. The nonlinear coefficients across five operating conditions initially range from 16 to 20 and decrease as the number of shocks increases. Discussion of the damage caused under multiple lightning strike scenarios concludes that the deterioration of the zinc oxide valve disc results from substantial thermal stress and degradation of the grain boundary barrier height under conditions of single weight 1.5 times, 4 weight 1.0 time, 4 weight 1.5 times and 12 weight impact. The law of temperature distribution from high to low around the outer ring also predisposes this area to damage first. Under single shock and 1.0 time nominal current condition, the degradation of the zinc oxide valve plate primarily stems from a decrease in barrier height and asymmetric distortion of the Schottky barrier.ConclusionsThe electrical, thermal properties, and failure modes of zinc oxide valve plates under multiple lightning strikes are examined by modifying the strike parameters. The study draws the following conclusions: 1) The DC reference voltage of zinc oxide valve plates exhibits a “down-steady-down” trend under different impact multiplications; The stable region of the single heavy operating condition is extended, and the higher the number of multiple lightning strikes increases, the more pronounced the downward trend. Specifically, the DC reference voltage in the 4-heavy condition shows a steep drop, and the leakage current in the 12-heavy condition experiences a sharp increase. 2) Under the same multiplicity with varying impact amplitudes, the leakage current of the valve plate shows a consistent variation amplitude in the initial stages of impact. Once the leakage current exceeds 20 mA, its deterioration rate significantly rises. 3) The pattern of change in the nonlinear coefficient of the valve plate post-multiple shocks is similar to that observed in the DC parameter. Corresponding to three different stages, increasing the impact multiplicity and current amplitude cause a rapid decline in the nonlinear coefficient, 1.5 times the nominal current of the valve disc nonlinear coefficient from 15 to accelerate the deterioration. 4) The deterioration in the valve disc due to a single shock and 1 times the nominal current is primarily due to the distortion of the double Schottky barrier. As the number of impacts and the current amplitude rise, the influence of thermal stress becomes more pronounced. Under conditions of 4-heavy and 1.5 times as well as 12-heavy tests, the thermal stress surpasses that at the point of valve plate failure, and the probability of bearing twice fP reaches more than 40%. These conditions lead to more severe failure modes of the valve plate, changing its typical failure form.关键词：zinc oxide valve plate;multiple lightning strikes;leakage current;nonlinear coefficient;thermal stress240|413|0更新时间：2024-08-22
ELECTRICAL ENGINEERING
- “最新研究显示，振荡热压烧结技术成功应用于90W-10Cu难熔合金制备，显著提升其低温烧结效果，实现高致密度、晶粒细化、高硬度和高电导率，为合金材料发展提供新方向。”摘要：Due to the differences in high melting point and specific gravity, the 90W–10Cu refractory alloy, used in high-voltage electrical contact materials, experiences challenges in densification and abnormal grain growth during the high-temperature, long-duration powder metallurgy process, affecting its properties. Based on conventional hot press sintering, the novel hot oscillatory pressure (HOP) technology enhances the densification of ceramics and other materials by substituting static uniaxial pressure with cyclic oscillatory uniaxial pressure at a specific frequency. In order to investigate the low-temperature sintering effects of HOP on the 90W–10Cu refractory alloy, this technology is applied to the alloy’s preparation, examining the impacts of varying sintering temperatures (1 000～1 300 °C) on its microstructure, densification, grain size, hardness, and electrical conductivity. The 90W–10Cu alloy comprises a W matrix phase and a bonding Cu phase. As the sintering temperature increases, the W–Cu alloy’s density gradually rises, reaching a peak density of nearly 99.35% at 1 300 °C, surpassing that of samples sintered under hot pressure (HP). The grain size is reduced to 4.97 μm, affecting grain refinement. Simultaneously, W grain contiguity decreases, enhancing microstructure uniformity. Consequently, its Vickers hardness and electrical conductivity reached 225.78 HV30 and 27.88% IACS, respectively, exceeding those of HP-sintered samples at the same temperature of +100 °C, thus considerably enhancing its properties. The findings indicated that HOP effectively promotes the densification of the W–Cu alloy at lower sintering temperatures, inhibits grain growth, and significantly optimizes microstructure uniformity. Therefore, the 90W–10Cu alloy for electrical contacts, characterized by high density, fine grain, and improved hardness and conductivity, can be achieved through HOP at low-temperature sintering.关键词：sintering;Refractory alloys;densification;Grain size and shape;Hardness;Electric conductivity209|430|0更新时间：2024-08-22
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Freeze–thaw Resistance of Concrete Based on Fly Ash and Municipal Sludge Under Alkali Excitation AI导读
“在混凝土抗冻融性能研究领域，专家通过添加粉煤灰和碱激发剂，改善了市政污泥对混凝土耐久性的劣化效果，为提高混凝土服役寿命提供了有效解决方案。”摘要：In this study, municipal sludge modified with quicklime is employed to replace 10% of the fine aggregate, while fly ash replaced 10%, 20%, and 30% of the cement to mitigate the adverse effects of municipal sludge on the freeze–thaw resistance of concrete. This is assessed under the combined excitation of sodium hydroxide and sodium silicate. The research investigates the changes in apparent phenomena, relative mass, relative dynamic elastic modulus, relative compressive strength, and concrete microstructure with varying fly ash content and alkali equivalent under different freeze–thaw cycles. Models of freeze–thaw damage are established, using relative dynamic elastic modulus and relative compressive strength as damage variables. The results indicated that with an increase in freeze–thaw cycles, the concrete sustains more severe damage, exhibits enlargement in internal pores, and gradually reduces relative dynamic elastic modulus and compressive strength. Incorporating fly ash and an alkali activator mitigates the mass, dynamic elastic modulus, and compressive strength losses in concrete during the freeze–thaw cycles, reducing the deteriorative impact of municipal sludge on the concrete’s durability compared to the control group. Optimal results are shown when the fly ash content is 10% and the alkali equivalent is 4%; under these conditions, the fly ash is fully activated by the combined action of the alkali initiator and the residual alkali in the modified sludge. This combination absorbs the residual alkali, diminishing the negative effect of municipal sludge on the concrete’s freeze–thaw resistance. At this point, the concrete achieves its highest hydration degree, exhibits the lowest losses in mass, dynamic elastic modulus, and compressive strength during freeze–thaw cycles, and achieves the longest service life, exceeding 16 years. A strong correlation is found between the relative dynamic elastic modulus and the relative compressive strength, and the freeze–thaw damage models based on these variables closely match the experimental findings.关键词：municipal sludge;solid waste resource utilization;freeze–thaw cycle;microstructure;freeze–thaw damage mode291|447|1更新时间：2024-08-22
MATERILAL SCIENCE & ENGINEERING
- “在斯特林机活塞杆帽式密封性能提升领域，研究人员通过数值仿真和回归设计法，优化了O型圈和C型环的关键参数，显著提高了密封性能和使用寿命。实验验证了优化设计方法的准确性和普适性。”摘要：To improve the performance of the piston rod cap seal of Stirling engine,the initial step involves analyzing the static and dynamic mechanical characteristics under a 5 MPa operating pressure through numerical simulation, aiming to elucidate the governing factors. This analysis helps identify the impact of three critical structural parameters on the sealing performance: the O-ring inner diameter (LN), the C-ring radial wall thickness (T), and the assembly interference (S). Therefore, the regression design method is employed to optimize these parameters to achieve the best solution that ensures a smooth and reliable seal with maximum contact pressure on the mating surface. The optimization method's accuracy and universality are subsequently confirmed using a seal test bench. The findings indicate that the maximum contact pressure on the piston rod and C-ring’s middle sealing surface increases with LN and S but decreases with T. The regression analysis and ANOVArevealed that LN significantly influences sealing performance, followed by S, while T has the least impact. Significant interaction effects are observed between LN and T and LN and S, whereas the interactions between T and S are insignificant. At LN of 13.745 mm, T of 0.40 mm, and S of 0.020 mm, the optimized seal exhibits a maximum contact pressure of 9.01 MPa during forward travel and 9.75 MPa during return travel. These pressures are 14.7% and 25.5% lower, respectively, compared to the seals currently used in the project (LN=13.78 mm, T=0.5 mm, S=0 mm). The experiments further verify that the optimized seal outperforms the current engineering seals regarding sealing performance and service life. In addition, the optimized seal demonstrates improved contact pressure uniformity under varying operating pressures, significantly reducing friction and extending service life. These results validate the effectiveness of the performance analysis and optimization design method discussed in this study.关键词：Stirling engine;cap seal;performance analysis;parameter optimization;regression design541|346|1更新时间：2024-08-22
MECHANICAL ENGINEERING
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