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Rockburst criterion and evaluation method for potential rockburst pit depth considering excavation damage effect

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第5期16卷 1649-1666页

作者： Jinhao Dai Fengqiang Gong lei xu Engineering Research Center of Safety and Protection of Explosion & Impact of Ministry of Education (ERCSPEIME) Southeast UniversityNanjing211189China School of Civil Engineering Southeast UniversityNanjing211189China

Excavation-induced disturbances in deep tunnels will lead to deterioration of rock properties and formation of excavation damaged zone(EDZ).This excavation damage effect may affect the potential rockburst pit *** two diversion tunnels of Jinping II hydropower station for example,the relationship between rockburst pit depth and excavation damage effect is first *** results indicate that the rockburst pit depth in tunnels with severe damage to rock masses is relatively ***,the excavation-induced damage effect is characterized by disturbance factor D based on the Hoek-Brown criterion and wave velocity *** is found that the EDZ could be further divided into a high-damage zone(HDZ)with D=1 and weak-damage zone(WDZ),and D decays from one to zero *** this,a quantitative evaluation method for potential rockburst pit depth is established by presenting a three-element rockburst criterion considering rock strength,geostress and disturbance *** evaluation results obtained by this method match well with actual *** addition,the weakening of rock mass strength promotes the formation and expansion of potential rockburst *** potential rockburst pit depth is positively correlated with HDZ and WDZ depths,and the HDZ depth has a significant contribution to the potential rockburst pit depth.

关键词： Deep tunnel Rockburst Rockburst pit Excavation damage effect Hoek-Brown criterion

Multi-level coarse-grained discrete element method modeling of cylinder particle flow in a rotating drum

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Particuology 2024年第5期88卷 218-238页

作者： lei xu Xiukai Wu Shuai Wang Shiyi Bao Institute of Process Equipment and Control Engineering Zhejiang University of TechnologyHangzhou 310023China Engineering Research Center of Process Equipment and Remanufacturing Ministry of EducationZhejiang University of TechnologyHangzhou 310023China College of Mechanical Engineering Zhejiang University of TechnologyHangzhou 310023China State Key Laboratory of Clean Energy Utilization Zhejiang UniversityHangzhou 310027China

The coarse-grained discrete element method(DEM)is probably a feasible option for simulating an actual drum-type biomass boiler,which contains over 10 million cylinder particles.A multi-level study was conducted based on particle and coarse-grained level data to evaluate the adequacy of the coarse-grained approach in terms of geometrical characteristics,kinematic features,and dynamic *** scaling laws for contact parameters were used and compared during the *** results show that the coarse-grained approach can accurately predict the positions of the free surface and active-passive interface,the mixing index,and the orientation *** in the velocity fields may occur due to the worse flowability of coarse-grained particles near the free *** efficiency is significantly improved by the coarse-grained model compared with the corresponding original case(the same DEM code without a coarse-grained model was used for the original simulations).

关键词： Coarse-grained method Discrete element method(DEM) Cylinder particle Rotating drum Granular flow

Performance analysis and multi-objective optimization based on a modified irreversible Stirling cycle

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Science China(Technological Sciences) 2024年第6期67卷 1668-1684页

作者： xu lei YU MinJie LIU ZhiChun LIU Wei School of Energy and Power Engineering Huazhong University of Science and TechnologyWuhan430074China

The efficiency of the actual Stirling engine is much lower than the ideal Carnot cycle *** obtain more precise efficiency for Stirling engines,this paper proposes a modified Stirling cycle with a more accurate heat transfer process in Stirling engines based on a thermodynamic function called available *** finite-time thermodynamic method is used to analyze the model performance under constant heat source temperature,finite temperature difference heat transfer,and incomplete regenerative processes.A new polytropic process is introduced to model the heat transfer between the working fluid and external heat sources in which only heat above ambient temperature is converted into technical *** regenerator is divided into numerous smaller heat reservoirs with individual temperature to analyze the incomplete regenerative *** expressions of the output power and thermal efficiency are obtained based on the modified irreversible Stirling cycle,and the effects of irreversible losses are analyzed to evaluate the performance of the proposed *** indicate that the efficiency of the modified cycle is much lower than that of the ideal Stirling cycle with an isothermal *** the increase of the average heat transfer temperature difference,there exists an optimum value for the power of the irreversible *** optimum power of the model was obtained for varying thermodynamic parameters by optimizing the average heat transfer temperature difference between the hot and cold *** optimize the irreversible model,the multi-objective optimization analysis is carried out based on NSGA-Ⅱ,which results in an optimized output power of 40.87 kW and an optimized thermal efficiency of 44%.

关键词： stirling cycle regenerative processes isopotential processes multi-objective optimization finite time thermodynamics

Recent applications of macrocycles in supramolecular catalysis

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Chinese Chemical Letters 2024年第4期35卷 132-141页

作者： Conghui Wang lei xu Zhenhua Jia Teck-Peng Loh College of Advanced Interdisciplinary Science and Technology Henan University of TechnologyZhengzhou 450001China Division of Chemistry and Biological Chemistry School of Chemistry Chemical Engineeringand BiotechnologyNanyang Technological UniversitySingapore 637371Singapore Institute of Advanced Synthesis School of Chemistry and Molecular Engineering Nanjing Tech UniversityNanjing 211816China

Numerous supramolecular macrocycles have been utilized for developing catalysts by exploiting their specific molecular recognition and ability to form inclusion complexes through noncovalent interactions. The cyclic structure and modified functional groups of these macrocycles can influence substrate and transition state stability, as well as reaction selectivity. The inner cavities of these macrocycles are particularly beneficial, as they enable substrates to adopt preorganized arrangements and serve as versatile platforms for highly efficient supramolecular catalytic systems. This minireview provides an overview of recent advancements in supramolecular catalysis using various macrocycles, such as crown ethers, cyclodextrins,calixarenes, pillararenes, cucurbiturils, and other novel macrocycles.

关键词： Supramolecular catalysis Macrocycle Host-guest interactions Confinement Selectivity

Ground response and failure mechanism of gob-side entry by roof cutting with hard main roof

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Journal of Central South University 2024年第7期31卷 2488-2512页

作者： ZHU Heng-zhong xu lei WEN Zhi-jie State Key Laboratory of Water Resource Protection and Utilization in Coal Mining Beijing 102209China State Key Laboratory of Strata Intelligent Control and Green Mining Co-founded by Shandong Province and the Ministry of Science and Technology Shandong University of Science and TechnologyQingdao 266590China School of Energy and Mining Engineering Shandong University of Science and TechnologyQingdao 266590China School of Civil Engineering Henan Polytechnic UniversityJiaozuo 454003China School of Mining Guizhou UniversityGuiyang 550025China

This study is the result of long-term efforts of the authors’team to assess ground response of gob-side entry by roof cutting(GSERC)with hard main roof,aiming at scientific control for GSERC deformation.A comprehensive field measurement program was conducted to determine entry deformation,roof fracture zone,and anchor bolt(cable)*** results indicate that GSERC deformation presents asymmetric *** maximum convergence near roof cutting side is 458 mm during the primary use process and 1120 mm during the secondary reuse *** entry deformation is closely associated with the primary development stage,primary use stage,and secondary reuse *** key block movement of roof cutting structure,a complex stress environment,and a mismatch in the supporting design scheme are the failure mechanism of GSERC.A controlling ideology for mining states,including regional and stage divisions,was *** dynamic and permanent support schemes have been implemented in the *** practice results indicate that the new support scheme can efficiently ensure long-term entry safety and could be a reliable approach for other engineering practices.

关键词： gob-side entry by roof cutting ground response failure mechanism following mining states control hard main roof

A novel approach towards the selection of regenerators for optimal Stirling engine performance based on energy and exergy analyses

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Science China(Technological Sciences) 2024年第1期67卷 295-310页

作者： YU MinJie ZHANG MingHui xu lei CUI HaiChuan LIU ZhiChun LIU Wei School of Energy and Power Engineering Huazhong University of Science and TechnologyWuhan 430074China

Regenerators play a vital role in enhancing the overall performance of Stirling ***,this paper performed an energy and exergy analysis to elucidate the significance of regenerator characteristics concerning system performance,contributing to the optimal regenerator’s design and *** relationship between regenerator structure,regenerator exergy destruction,and output power,thermal efficiency,and exergy efficiency for Stirling engines was established by integrating the thermal model of Stirling engines with a mathematical model of *** contrast to cross-flow and parallel-flow regenerators,a novel concept of inclined-flow regenerators,featuring a matrix surface inclined in the direction of gas flow,was developed to achieve higher and more balanced engine output power and energy utilization efficiency.A comprehensive investigation was conducted into the effects of matrix structure types and regenerator geometries on the performance of both regenerators and *** results reveal that,following structural optimization,Stirling engines equipped with the inclined-flow regenerator demonstrate a substantial 16.6%,38.3%,and 37.2%increase in power output,thermal efficiency,and exergy efficiency,respectively,compared to those equipped with cross-flow *** contrast,when compared to engines fitted with parallel-flow regenerators,they experience a 13.5%reduction in power output but achieve remarkable enhancements of 45.4%and 36.7%in thermal and exergy efficiency,*** study introduces new insights into selecting regenerator structures for enhancing the output performance of Stirling engines.

关键词： Stirling engine inclined-flow regenerator adiabatic model exergy analysis

Simultaneous removal of sulfur dioxide and nitrogen oxide from flue gas by phosphorus sludge:The performance and absorption mechanism

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Chinese Journal of Chemical Engineering 2024年第1期65卷 212-221页

作者： Yuanyuan Yin xujun Wang lei xu Binbin He Yunxiang Nie Yi Mei Faculty of Chemical Engineering Kunming University of Science and TechnologyKunming 650500China Yunnan Provincial Key Laboratory of Energy Saving in Phosphorus Chemical Engineering and New Phosphorus Materials Kunming 650500China The Higher Educational Key Laboratory for Phosphorus Chemical Engineering of Yunnan Province Kunming 650500China

Developing low-cost and green simultaneous desulfurization and denitrification technologies is of great significance for sulfur dioxide(SO_(2))and nitrogen oxide(NO_(x))emission control at low temperatures,especially for small and medium-sized coal-fired boilers and ***,phosphorus sludge,an industrial waste from the production process of yellow phosphorus,has been developed to simultaneously eliminate SO_(2)and NO_(x)from coal-fired flue *** key factors affecting the experimental results indicate that desulfurization and denitrification efficiency of over 95%can be achieved at a low temperature of 55℃.Further,the absorption mechanism was investigated by characterizing the solid and liquid phases of the phosphorus sludge during the absorption *** efficient removal of SO_(2)is attributed to the abundance of iron(Fe^(3+))and manganese(Mn^(2+))in the ***_(2)can be rapidly catalyzed and converted to SO_(4)^(2-)by *** key to NOx removal is the oxidation of NO toward watersoluble high-valent nitrogen oxides by oxidizing reactive substances induced via yellow phosphorus,which are then absorbed by water and converted to NO_(3)^(-).Meanwhile,yellow phosphorus is oxidized to phosphoric acid(H_(3)PO_(4)).The spent absorption slurry can be reused through wet process phosphoric acid production,as it contains sulfuric acid(H_(2)SO_(4)),nitric acid(HNO_(3)),and H_(3)PO_(4).Accordingly,this is a technology with broad application prospects.

关键词： Absorption Oxidation Multiphase reaction Phosphorus sludge Yellow phosphorus Low temperature

Evolution of MnO–SiO2–Al_(2)O_(3)–MgO inclusions during heat treatment at 1100℃

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Journal of Iron and Steel Research International 2024年第5期31卷 1221-1231页

作者： xu-bo lei Jian-li Li Qiang Zeng Hang-yu Zhu Yue Yu The State Key Laboratory of Refractories and Metallurgy Wuhan University of Science and TechnologyWuhan430081HubeiChina Hubei Provincial Key Laboratory for New Processes of Ironmaking and Steelmaking Wuhan University of Science and TechnologyWuhan430081HubeiChina Key Laboratory for Ferrous Metallurgy and Resources Utilization of Ministry of Education Wuhan University of Science and TechnologyWuhan430081HubeiChina

To investigate the evolutionary behavior of the MnO–SiO_(2)–Al_(2)O_(3)–MgO inclusions during heat treatment,water quenched samples were isothermally held at 1100°C for 120 min in Ar and air atmosphere,and the obtaining samples were analyzed by X-ray diffraction,scanning electron microscopy and energy dispersive *** showed that 3MnO·Al_(2)O_(3)·3SiO_(2)and MnO·SiO_(2)were detected in the 5 wt.%MgO system after isothermal holding in Ar atmosphere,while MgO·Al_(2)O_(3),MnO·SiO_(2)and Mn7O8·SiO4 were detected in air *** evolutionary behavior of the 10,15 and 20 wt.%MgO systems after isothermal holding in different atmosphere were *** affected the solid phase transformation of the low MgO content *** calculation results of FactSage 8.1 showed that MgO·Al_(2)O_(3)was formed in the 5 wt.%MgO system with air *** solid phase transformation was accompanied by grain coarsening during the isothermal holding *** differences in the solid phase transformation in different atmosphere of the 5 wt.%MgO system indicated that it was a gas-phase transport grain coarsening *** enrichment of Al element in the liquid phase region at the grain edges,the homogeneous distribution of Mg element and the disappearance of the liquid phase within the crystal revealed that other MgO content systems were liquid–solid transport grain coarsening mechanism.

关键词： Evolution Glassy phase Inclusion Heat treatment MgO·Al_(2)O_(3)

Can perfluorooctanoic acid be effectively degraded usingβ-PbO_(2)reactive electrochemical membrane?

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Chinese Chemical Letters 2024年第7期35卷 196-199页

作者： xubin Qian lei xu xu Ge Zhun Liu Cheng Fang Jianbing Wang Junfeng Niu College of Environmental Science and Engineering North China Electric Power UniversityBeijing 102206China College of Water Resources and Hydropower Engineering North China Electric Power UniversityBeijing 102206China Research Center for Eco-Environmental Engineering Dongguan University of TechnologyDongguan 523808China Global Centre for Environmental Remediation(GCER) University of NewcastleCallaghanNSW 2308Australia School of Chemical and Environmental Engineering China University of Mining and Technology(Beijing)Beijing 100083China

Aqueous perfluorooctanoic acid(PFOA)elimination has raised significant concerns due to its persistence and ***β-PbO_(2)plate anodes have shown efficient mineralization of PFOA,it remains unclear whether PFOA can be effectively degraded usingβ-PbO_(2)reactive electrochemical membrane(REM).Herein,we assessed the performance of Ti/SnO_(2)-Sb/La-PbO_(2)REM for PFOA removal and proposed a possible degradation *** a current density of 10 mA/cm2and a membrane flux of 8500(liters per square meter per hour,LMH),the degradation efficiency of 10 mg/L PFOA was merely8.8%,whereas the degradation efficiency of 0.1 mg/L PFOA increased to 96.6%.Although the porous structure of theβ-PbO_(2)REM provided numerous electroactive sites for PFOA,the generated oxygen bubbles in the pores could block the pore channels and adsorb PFOA *** hindered the protonation process and significantly impeded the degradation of high-concentration *** experiments indicated that·OH played dominant role in PFOA *** electrical energy per order to remove 0.1 mg/L PFOA was merely 0.74 Wh/L,which was almost an order of magnitude lower than that of other anode *** study presents fresh opportunities for the electrochemical degradation of low-concentration PFOA usingβ-PbO_(2)REM.

关键词： Perfluorooctanoic acid β-PbO_(2) Reactive electrochemical membrane Electrochemical oxidation