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Experimental study on the effect of unloading rate on gneiss rockburst

Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2064-2076页

作者： Dongqiao Liu Jie Sun Ran Li Manchao He Binghao Cao Chongyuan Zhang Wen Meng State Key Laboratory for Tunnel Engineering China University of Mining and TechnologyBeijing100083China Key Laboratory of Active Tectonics and Geological Safety Ministry of Natural ResourcesInstitute of GeomechanicsChinese Academy of Geological SciencesBeijing100081China School of Mechanics and Civil Engineering China University of Mining and TechnologyBeijing100083China

Rockburst are often encountered in tunnel construction due to the complex geological *** study the influence of unloading rate on rockburst,gneiss rockburst experiments were conducted under three groups of unloading rates.A high-speed photography system and acoustic emission(AE)system were used to monitor the entire process of rockburst process in *** results show that the intensity of gneiss rockburst decreases with decrease of unloading rate,which is manifested as the reduction of AE energy and fragments ejection *** mechanisms are proposed to explain this effect:(i)The reduction of unloading rate changes the crack propagation mechanism in the process of *** makes the rockbursts change from the tensile failure mechanism at high unloading rate to the tension-shear mixed failure mechanism at low unloading rate,and more energy released in the form of shear crack ***,less strain energy is converted into kinetic energy of fragments ejection.(ii)Less plate cracking degree of gneiss has taken shape due to decrease of unloading rate,resulting in the destruction of rockburst incubation *** enlightenments of reducing the unloading rate for the project are also described *** rockburst magnitude is reduced from the medium magnitude at the unloading rate of 0.1 MPa/s to the slight magnitude at the unloading rate of 0.025 MPa/s,which was judged by the ejection velocity.

关键词： Rockburst Unloading rate Crack propagation influence mechanisms

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Effect of Nozzle Vane and Rotor Clearance on Performance of Variable Nozzle Turbine

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Journal of Thermal Science 2022年第5期31卷 1745-1758页

作者： LEI Xinguo LI Renfu XI Zhaojun YANG Ce School of Mechanical Science and Engineering Huazhong University of Science and TechnologyWuhan430074China School of Aerospace Engineering Huazhong University of Science and TechnologyWuhan430074China School of Mechanical Engineering Beijing Institute of TechnologyBeijing100081China

In a variable nozzle turbine(VNT),the nozzle vane and rotor clearance can generate complicated tip leakage flow,which produces a large flow loss and results in a noticeable reduction in the VNT ***,it is necessary to study the influence of the nozzle vane and rotor clearance on the VNT performance to reveal the underlying *** this study,the variation of VNT performance resulting from the nozzle vane and rotor clearance was studied numerically using the commercial CFD *** numerical results were in good agreement with the experimental *** performance under three varied clearance conditions under different clearance sizes,rotating speeds,and expansion ratios was *** conditions included the individual effect of nozzle vane clearance,the individual effect of rotor clearance,and the combined effect of nozzle vane and rotor *** results showed that the rotor clearance(clearance size equal to 0.4 mm)resulted in a certain reduction in thermal efficiency(–3.98%)and torque(–4.48%).Meanwhile,the nozzle vane hub and shroud clearance also affected the thermal efficiency(–3.66%and–13.37%,respectively)and torque(12.54%and–0.05%,respectively).Compared with the rotor clearance,the nozzle vane clearance dominated the variation in the VNT performance,and the values of the mass flow ratio,thermal efficiency,and torque increased by 12.15%,5.43%,and 8.01%,respectively(The clearance on both sides of the vane was equal to 0.2 mm.).Under the combined effect of the nozzle vane and rotor clearance,the deviation of the thermal efficiency and mass flow ratio was smaller than the sum of the values of their individual effects;when the clearance on both sides of the vane was equal to 0.2 mm and the rotor clearance was equal to 0.6 mm,the value was reduced by 2.77%and 1.71%,*** study also explains the influence mechanisms of clearance at both ends of the nozzle vane and the vane/rotor clearance interaction on the VNT perform

关键词： variation nozzle turbine tip leakage flow combined effect performance variation influence mechanisms

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influence of extracellular polymeric substances from activated sludge on the aggregation kinetics of silver and silver sulfide nanoparticles

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Frontiers of Environmental Science & Engineering 2022年第2期16卷 13-24页

作者： Wanpeng Chen Jiahui Song Shaojie Jiang Qiang He Jun Ma Xiaoliu Huangfu Key Laboratory of Eco-environments in Three Gorges Reservoir Region(Ministry of Education) College of Environment and EcologyChongqing UniversityChongqing 400044China Sichuan Education Press Chengdu 610200China State Key Laboratory of Urban Water Resource and Environment School of Municipal and Environmental EngineeringHarbin Institute of TechnologyHarbin 150090China

Extracellular polymeric substances(EPS)in activated sludge from wastewater treatment plants(WWTPs)could affect interactions between nanoparticles and alter their migration *** influence mechanisms of silver nanoparticles(Ag NPs)and silver sulfide nanoparticles(Ag_(2)S NPs)aggregated by active EPS sludge were studied in monovalent or divalent cation *** aggregation behaviors of the NPs without EPS followed the Derjaguin-Landau-Verwey-Overbeek(DLVO)*** counterions aggravated the aggregation of both NPs,and the divalent cation had a strong neutralizing effect due to the decrease in electrostatic repulsive *** extended DLVO(EDLVO)model analysis,in NaNO3 and low-concentration Ca(NO_(3))_(2)(mechanisms between EPS and NPs to understand the different fates of metal-based and metal-sulfide NPs in WWTP systems.

关键词： Silver nanoparticles Silver sulfide nanoparticles Extracellular polymeric substances Aggregation kinetics influence mechanisms

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Can Digital Village Construction Help Upgrade Rural Household Consumption?An Empirical Examination Based on China’s Rural Household Survey Data

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Contemporary Social Sciences 2023年第4期8卷 1-24页

作者： Shao Peiyu Liu Hui Wang Yang Liu Changjun School of Statistics Chengdu University of Information Technology Institute of Marxism Beijing Academy of Social Sciences

Digital village construction opens a new vista for fulfilling consumption capabilities and optimizing consumption patterns in rural *** this research,we used the microdata on rural households from the 2019 China Household Finance Survey(CHFS)to conduct an empirical examination of the impact of digital village construction on the upgrading of rural household consumption and its possible influence mechanisms in the endogenous switching regression(ESR)*** research findings can be summarized in three ***,digital village construction has significantly contributed positive contributions to the improvements and upgrading of rural household ***,digital village construction can help upgrade rural household consumption by increasing their participation in online shopping and expanding online shopping ***,digital village construction means different things to rural households at different levels of risk exposure,with its facilitation to consumption upgrades in proportion to income risks facing rural *** research findings,which came from an extensive,in-depth exploration of the factors influencing rural household consumption,are of practical significance and policy value to the stimulating and fulfilling of consumption potentials among rural households.

关键词： digital village consumption upgrades influence mechanisms endogenous switching regression(ESR)

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社会资本对生活垃圾减量的影响及其作用机制

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生态环境与保护 2019年第12期

作者：张志坚王学渊赵连阁

在经济快速增长、城镇人口持续增加以及人民生活水平大幅改善的同时，我国生活垃圾产生量也在急剧增加。为回答规制政策和社会资本能否有助于缓解垃圾围城压力这一现实问题，文章利用城市层面的面板数据及中国综合社会调查数据，考察了... 详细信息

在经济快速增长、城镇人口持续增加以及人民生活水平大幅改善的同时，我国生活垃圾产生量也在急剧增加。为回答规制政策和社会资本能否有助于缓解垃圾围城压力这一现实问题，文章利用城市层面的面板数据及中国综合社会调查数据，考察了规制政策和社会资本对城市人均生活垃圾排放量的影响。结果表明：生活垃圾收费政策和源头分类试点政策并没有如预期的那样显著降低城市人均生活垃圾排量，固定费率的生活垃圾收费政策甚至会提高生活垃圾排放群体的排放量；社会资本对城市人均生活垃圾排放量具有显著负向影响，该结果在使用了不同测量指标、不同度量方法、不同估计方法和考虑了社会资本内生性的情形下依然稳健；进一步的影响机制分析发现，社会资本通过促进居民垃圾分类投放和垃圾源头减量行为从而降低生活垃圾排放。文章为推进中国环境管理转型的政策设计提供了一个有益的视角。

关键词：规制政策社会资本生活垃圾减量影响机制 regulatory policy social capital municipal solid waste reduction influence mechanisms

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