Shield tunneling is easily obstructed by clogging in clayey strata with small soil particles.However,soil clogging rarely occurs in strata with coarse-grained soils.Theoretically,a critical particle size of soils shou...Shield tunneling is easily obstructed by clogging in clayey strata with small soil particles.However,soil clogging rarely occurs in strata with coarse-grained soils.Theoretically,a critical particle size of soils should exist,below which there is a high risk of soil clogging in shield tunneling.To determine the critical particle size,a series of laboratory tests was carried out with a large-scale rotary shear apparatus to measure the tangential adhesion strength of soils with different particle sizes and water contents.It was found that the tangential adhesion strength at the soilesteel interface gradually increased linearly with applied normal pressure.When the particle size of the soil specimen was less than 0.15 mm,the interfacial adhesion force first increased and then decreased as the water content gradually increased;otherwise,the soil specimens did not manifest any interfacial adhesion force.The amount of soil mass adhering to the steel disc was positively correlated with the interfacial adhesion force,thus the interfacial adhesion force was adopted to characterize the soil clogging risk in shield tunneling.The critical particle size of soils causing clogging was determined to be 0.15 mm.Finally,the generation mechanism of interfacial adhesion force was explored for soils with different particle sizes to explain the critical particle size of soil with clogging risk in shield tunneling.展开更多
It remains challenging to effectively estimate the remaining capacity of the secondary lithium-ion batteries that have been widely adopted for consumer electronics,energy storage,and electric vehicles.Herein,by integr...It remains challenging to effectively estimate the remaining capacity of the secondary lithium-ion batteries that have been widely adopted for consumer electronics,energy storage,and electric vehicles.Herein,by integrating regular real-time current short pulse tests with data-driven Gaussian process regression algorithm,an efficient battery estimation has been successfully developed and validated for batteries with capacity ranging from 100%of the state of health(SOH)to below 50%,reaching an average accuracy as high as 95%.Interestingly,the proposed pulse test strategy for battery capacity measurement could reduce test time by more than 80%compared with regular long charge/discharge tests.The short-term features of the current pulse test were selected for an optimal training process.Data at different voltage stages and state of charge(SOC)are collected and explored to find the most suitable estimation model.In particular,we explore the validity of five different machine-learning methods for estimating capacity driven by pulse features,whereas Gaussian process regression with Matern kernel performs the best,providing guidance for future exploration.The new strategy of combining short pulse tests with machine-learning algorithms could further open window for efficiently forecasting lithium-ion battery remaining capacity.展开更多
Coal dust is a primary threat to underground coal miners.The most common approach to control coal dust is hydraulic methods,such as water spray and coal seam water injection.To improve the dust suppressant efficiency ...Coal dust is a primary threat to underground coal miners.The most common approach to control coal dust is hydraulic methods,such as water spray and coal seam water injection.To improve the dust suppressant efficiency of hydraulic methods,a novel chemical composite dust suppressant,called NCZ,was prepared in this study using calcium chloride(CaCl_(2)),magnesium chloride(MgCl_(2)),and nonionic surfactants using a thermal synthesis method.The water-retaining properties of NCZ powder and its solutions were characterized using the water absorption rate(WAR)and evaporation rate(ER),respectively,and the wetting abilities of the NCZ solutions on coal dust were tested using the initial contact angle(ICA)and sink rate(SR).The results indicate that the NCZ solutions have anti-evaporation effects,and the ER of the solution with a 20.0 wt%NCZ is reduced by 11.7%compared with that of clean water.Furthermore,NCZ solutions have remarkable enhancement effects on the wettability of coal dust.The ICA and SR of clean water and the NCZ solution at 20.0 wt%are 141.9°and 0 mg/s,and 29.3°and 1.46 mg/s,respectively.Finally,quantitative relationships between the solution surface tension and the ICA and IR were established using the least squares method.This study provides a new product for dust suppression in underground mines,which is significant for the optimum applied con-centration of dust suppressant in mining operations.展开更多
Strategies to improve the efficiency of piezoelectric catalysis have long focused on piezo-optical coupling and construction of heterojunctions.However,it is a challenge to reinforce the performance of piezoelectric c...Strategies to improve the efficiency of piezoelectric catalysis have long focused on piezo-optical coupling and construction of heterojunctions.However,it is a challenge to reinforce the performance of piezoelectric catalysis in a single material.Herein the built-in nanopores in single crystal ZnO rods are employed to form stress to intensify piezo-catalytic efficiency.The piezo-catalytic efficiency of the ZnO rods with built-in nanopores(holey ZnO NRs)for degrading dyes was about 1.7 times that of the ZnO rods without built-in nanopores(ZnO NRs).X-ray diffraction and Raman peaks of holey ZnO NRs appeared blue-shifted in comparison to ZnO NRs,uncovering the existence of tensile stress in holey ZnO NRs.The piezoelectric coefficient d_(33) of holey ZnO NRs increased by 1.92 times,triggering the amplification of piezoelectric catalytic property.Additionally,the piezoelectric current,carrier lifetime,and diffusion length of holey ZnO NRs were larger than that of ZnO NRs,respectively.These factors all contribute to the enhanced piezoelectric catalytic efficiency of holey ZnO NRs.This work demonstrates that the method of induced stress with built-in nanopores is a promising strategy for improving the piezoelectric catalytic efficiency of single-crystal ZnO rods.展开更多
Reported here is the comprehensive investigation on the formation of biphen[n]arenes by tailoring reac-tion modules.Five new macrocyclic arenes and four oligomers were synthesized by the condensation of monomers posse...Reported here is the comprehensive investigation on the formation of biphen[n]arenes by tailoring reac-tion modules.Five new macrocyclic arenes and four oligomers were synthesized by the condensation of monomers possessing different multimethoxyphenyl reaction modules and paraformaldehyde.We proved that the number and sites of methoxy on reaction modules greatly affected the reaction activity,shape,and connection mode of macrocycles.Moreover,the triangular and saddle-shaped configuration of macro-cycles were revealed by single crystal structures.The results provided a typical and fundamental guidance in designing new macrocyclic arenes.展开更多
基金The financial support from the National Natural Science Foun-dation of China(Grant Nos.52022112 and 51778637)the Sci-ence and Technology Innovation Program of Hunan Province(Grant No.2021RC3015)are acknowledged and appreciated.
文摘Shield tunneling is easily obstructed by clogging in clayey strata with small soil particles.However,soil clogging rarely occurs in strata with coarse-grained soils.Theoretically,a critical particle size of soils should exist,below which there is a high risk of soil clogging in shield tunneling.To determine the critical particle size,a series of laboratory tests was carried out with a large-scale rotary shear apparatus to measure the tangential adhesion strength of soils with different particle sizes and water contents.It was found that the tangential adhesion strength at the soilesteel interface gradually increased linearly with applied normal pressure.When the particle size of the soil specimen was less than 0.15 mm,the interfacial adhesion force first increased and then decreased as the water content gradually increased;otherwise,the soil specimens did not manifest any interfacial adhesion force.The amount of soil mass adhering to the steel disc was positively correlated with the interfacial adhesion force,thus the interfacial adhesion force was adopted to characterize the soil clogging risk in shield tunneling.The critical particle size of soils causing clogging was determined to be 0.15 mm.Finally,the generation mechanism of interfacial adhesion force was explored for soils with different particle sizes to explain the critical particle size of soil with clogging risk in shield tunneling.
基金support from Shenzhen Municipal Development and Reform Commission(Grant Number:SDRC[2016]172)Shenzhen Science and Technology Program(Grant No.KQTD20170810150821146)Interdisciplinary Research and Innovation Fund of Tsinghua Shenzhen International Graduate School,and Shanghai Shun Feng Machinery Co.,Ltd.
文摘It remains challenging to effectively estimate the remaining capacity of the secondary lithium-ion batteries that have been widely adopted for consumer electronics,energy storage,and electric vehicles.Herein,by integrating regular real-time current short pulse tests with data-driven Gaussian process regression algorithm,an efficient battery estimation has been successfully developed and validated for batteries with capacity ranging from 100%of the state of health(SOH)to below 50%,reaching an average accuracy as high as 95%.Interestingly,the proposed pulse test strategy for battery capacity measurement could reduce test time by more than 80%compared with regular long charge/discharge tests.The short-term features of the current pulse test were selected for an optimal training process.Data at different voltage stages and state of charge(SOC)are collected and explored to find the most suitable estimation model.In particular,we explore the validity of five different machine-learning methods for estimating capacity driven by pulse features,whereas Gaussian process regression with Matern kernel performs the best,providing guidance for future exploration.The new strategy of combining short pulse tests with machine-learning algorithms could further open window for efficiently forecasting lithium-ion battery remaining capacity.
基金We much appreciate the National Nature Science Foundation of China(Nos.51874015 and 51574017)the National Key Research and Development Program of China(No.2017YFC0805204).
文摘Coal dust is a primary threat to underground coal miners.The most common approach to control coal dust is hydraulic methods,such as water spray and coal seam water injection.To improve the dust suppressant efficiency of hydraulic methods,a novel chemical composite dust suppressant,called NCZ,was prepared in this study using calcium chloride(CaCl_(2)),magnesium chloride(MgCl_(2)),and nonionic surfactants using a thermal synthesis method.The water-retaining properties of NCZ powder and its solutions were characterized using the water absorption rate(WAR)and evaporation rate(ER),respectively,and the wetting abilities of the NCZ solutions on coal dust were tested using the initial contact angle(ICA)and sink rate(SR).The results indicate that the NCZ solutions have anti-evaporation effects,and the ER of the solution with a 20.0 wt%NCZ is reduced by 11.7%compared with that of clean water.Furthermore,NCZ solutions have remarkable enhancement effects on the wettability of coal dust.The ICA and SR of clean water and the NCZ solution at 20.0 wt%are 141.9°and 0 mg/s,and 29.3°and 1.46 mg/s,respectively.Finally,quantitative relationships between the solution surface tension and the ICA and IR were established using the least squares method.This study provides a new product for dust suppression in underground mines,which is significant for the optimum applied con-centration of dust suppressant in mining operations.
基金This work was supported by the National Natural Science Foundation of China(Nos.51962020,12174174,11604135,and 11574126)the Natural Science Foundation of Jiangxi Province(No.20212ACB214011)Support from Science and Technology Project of Jiangxi Provincial Department of Education(No.GJJ202629)is also acknowledged.
文摘Strategies to improve the efficiency of piezoelectric catalysis have long focused on piezo-optical coupling and construction of heterojunctions.However,it is a challenge to reinforce the performance of piezoelectric catalysis in a single material.Herein the built-in nanopores in single crystal ZnO rods are employed to form stress to intensify piezo-catalytic efficiency.The piezo-catalytic efficiency of the ZnO rods with built-in nanopores(holey ZnO NRs)for degrading dyes was about 1.7 times that of the ZnO rods without built-in nanopores(ZnO NRs).X-ray diffraction and Raman peaks of holey ZnO NRs appeared blue-shifted in comparison to ZnO NRs,uncovering the existence of tensile stress in holey ZnO NRs.The piezoelectric coefficient d_(33) of holey ZnO NRs increased by 1.92 times,triggering the amplification of piezoelectric catalytic property.Additionally,the piezoelectric current,carrier lifetime,and diffusion length of holey ZnO NRs were larger than that of ZnO NRs,respectively.These factors all contribute to the enhanced piezoelectric catalytic efficiency of holey ZnO NRs.This work demonstrates that the method of induced stress with built-in nanopores is a promising strategy for improving the piezoelectric catalytic efficiency of single-crystal ZnO rods.
基金the National Natural Science Foundation of China (Nos. 21971192 and 21772118)the Natural Science Foundation of Tianjin City (No. 20JCZDJC00200)
文摘Reported here is the comprehensive investigation on the formation of biphen[n]arenes by tailoring reac-tion modules.Five new macrocyclic arenes and four oligomers were synthesized by the condensation of monomers possessing different multimethoxyphenyl reaction modules and paraformaldehyde.We proved that the number and sites of methoxy on reaction modules greatly affected the reaction activity,shape,and connection mode of macrocycles.Moreover,the triangular and saddle-shaped configuration of macro-cycles were revealed by single crystal structures.The results provided a typical and fundamental guidance in designing new macrocyclic arenes.
