Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability,however usually constrained by limited data availability,hydrogeological variation,and the complex...Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability,however usually constrained by limited data availability,hydrogeological variation,and the complex coupled hydro-mechanical behaviour.This paper aims to determine the factors and mechanism of groundwater depressurisation and identify knowledge gaps and methodological limitations for improving groundwater impact assessment.Analysis of dewatering cases in Australian,Chinese,and US coalfields demonstrates that piezometric drawdown can further lead to surface hydrology degradation,while the hydraulic responses vary with longwall parameters and geological conditions.Statistical interpretation of 422 height of fracturing datasets indicates that the groundwater impact positively correlates to panel geometry and depth of cover,and more pronounced in panel interaction and top coal caving cases.In situ stress,rock competency,clay mineral infillings,fault,valley topography,and surface-subsurface water interaction are geological and hydrogeological factors influencing groundwater hydraulics and long-term recovery.The dewatering mechanism involves permeability enhancement and extensive flow through fracture networks,where interconnected fractures provide steep hydraulic gradients and smooth flow pathways draining the overlying water to goaf of lower heads.Future research should improve fracture network identification and interconnectivity quantification,accompanied by description of fuid flow dynamics in the high fracture frequency and large fracture aperture context.The paper recommends a research framework to address the knowledge gaps with continuous data collection and field-scale numerical modelling as key technical support.The paper consolidates the understanding of longwall mining impacting mine hydrology and provides viewpoints that facilitate an improved assessment ofgroundwaterdepressurisation.展开更多
A synthetic coffinite was hydrothermally prepared and characterized before conducting a series of acid sulfate leach tests under conditions of relevance to uranium extraction.The results were then compared with simila...A synthetic coffinite was hydrothermally prepared and characterized before conducting a series of acid sulfate leach tests under conditions of relevance to uranium extraction.The results were then compared with similar studies on synthetic versions of the related U4+minerals uraninite(UO2)and brannerite(UTi2O6)to identify and differentiate the rate and U extraction among these important uranium minerals.Tests examining the influence of residence time on uranium dissolution from synthetic coffinite,uraninite and brannerite showed that under similar experimental conditions,complete dissolution of uranium from coffinite was obtained between 36 and 48 h.The activation energy for this reaction was calculated to be 38.4 kJ/mol.This represented a significantly slower rate of dissolution than that indicated for uraninite which dissolved in 3 h(Ea=15.2 kJ/mol).The synthetic brannerite was leached at a much slower rate than the coffinite and reached a maximum dissolution of^18%U in 144 h(Ea=42-84 kJ/mol).The clear differentiation in rates and U extraction among the three minerals is consistent with previous literatures which suggest that in terms of leachability,uraninite>coffinite>brannerite.It is expected that the presence of impurities in natural coffinites would further inhibit leachability.展开更多
目的探讨双能量虚拟去钙成像(VNCa)CT对中轴性脊柱关节炎相关骶髂关节炎病人骨髓水肿的诊断价值。材料与方法这项前瞻性研究连续收集2016年4月—2017年12月期间47例受试者[年龄14~41岁,平均27岁(男28例,年龄14~37岁,平均24岁;女19例,年...目的探讨双能量虚拟去钙成像(VNCa)CT对中轴性脊柱关节炎相关骶髂关节炎病人骨髓水肿的诊断价值。材料与方法这项前瞻性研究连续收集2016年4月—2017年12月期间47例受试者[年龄14~41岁,平均27岁(男28例,年龄14~37岁,平均24岁;女19例,年龄17~41岁,平均29岁)],行双能CT和3.0 T MRI检查。展开更多
In contrast to ion beams produced by conventional accelerators,ion beams accelerated by ultrashort intense laser pulses have advantages of ultrashort bunch duration and ultrahigh density,which are achieved in compact ...In contrast to ion beams produced by conventional accelerators,ion beams accelerated by ultrashort intense laser pulses have advantages of ultrashort bunch duration and ultrahigh density,which are achieved in compact size.However,it is still challenging to simultaneously enhance their quality and yield for practical applications such as fast ion ignition of inertial confinement fusion.Compared with other mechanisms of laser-driven ion acceleration,the hole-boring radiation pressure acceleration has a special advantage in generating high-fluence ion beams suitable for the creation of high energy density state of matters.In this paper,we present a review on some theoretical and numerical studies of the hole-boring radiation pressure acceleration.First we discuss the typical field structure associated with this mechanism,its intrinsic feature of oscillations,and the underling physics.Then we will review some recently proposed schemes to enhance the beam quality and the efficiency in the hole-boring radiation pressure acceleration,such as matching laser intensity profile with target density profile,and using two-ion-species targets.Based on this,we propose an integrated scheme for efficient high-quality hole-boring radiation pressure acceleration,in which the longitudinal density profile of a composite target as well as the laser transverse intensity profile are tailored according to the matching condition.展开更多
The alternating method based on the fundamental solutions of the infinite domain containing a crack,namely Muskhelishvili’s solutions,divides the complex structure with a crack into a simple model without crack which...The alternating method based on the fundamental solutions of the infinite domain containing a crack,namely Muskhelishvili’s solutions,divides the complex structure with a crack into a simple model without crack which can be solved by traditional numerical methods and an infinite domain with a crack which can be solved by Muskhelishvili’s solutions.However,this alternating method cannot be directly applied to the edge crack problems since partial crack surface of Muskhelishvili’s solutions is located outside the computational domain.In this paper,an improved alternating method,the spline fictitious boundary element alternating method(SFBEAM),based on infinite domain with the combination of spline fictitious boundary element method(SFBEM)and Muskhelishvili’s solutions is proposed to solve the edge crack problems.Since the SFBEM and Muskhelishvili’s solutions are obtained in the framework of infinite domain,no special treatment is needed for solving the problem of edge cracks.Different mixed boundary conditions edge crack problems with varies of computational parameters are given to certify the high precision,efficiency and applicability of the proposed method compared with other alternating methods and extend finite element method.展开更多
Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms invo...Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.展开更多
Polarized electron beam production via laser wakefield acceleration in pre-polarized plasma is investigated by particlein-cell simulations.The evolution of the electron beam polarization is studied based on the Thomas...Polarized electron beam production via laser wakefield acceleration in pre-polarized plasma is investigated by particlein-cell simulations.The evolution of the electron beam polarization is studied based on the Thomas±Bargmann±Michel±Telegdi equation for the transverse and longitudinal self-injection,and the depolarization process is found to be influenced by the injection schemes.In the case of transverse self-injection,as found typically in the bubble regime,the spin precession of the accelerated electrons is mainly influenced by the wakefield.However,in the case of longitudinal injection in the quasi-1D regime(for example,F.Y.Li et al.,Phys.Rev.Lett.110,135002(2013)),the direction of electron spin oscillates in the laser field.Since the electrons move around the laser axis,the net influence of the laser field is nearly zero and the contribution of the wakefield can be ignored.Finally,an ultra-short electron beam with polarization of 99%can be obtained using longitudinal self-injection.展开更多
This review gives first a brief view of the potential availability of sustainable energy.It is clear that over 100 times more solar photovoltaic energy than necessary is readily accessible and that practically availab...This review gives first a brief view of the potential availability of sustainable energy.It is clear that over 100 times more solar photovoltaic energy than necessary is readily accessible and that practically available wind alone may deliver sufficient energy supply to the world.Due to the intermittency of these sources,effective and inexpensive energy-conversion and storage technology is needed.Motivation for the possible electrolysis application of reversible solid-oxide cells(RSOCs),including a comparison of power-to-fuel/fuel-to-power to other energy-conversion and storage technologies is presented.RSOC electrochemistry and chemistry of H_(2)O,CO_(2),H_(2),CO,CnHm(hydrocarbons)and NH3,including thermodynamics and cell performance,are described.The mechanical strength of popular cell supports is outlined,and newly found stronger materials are mentioned.Common cell-degradation mechanisms,including the effect of common impurities in gases and materials(such as S and Si),plus the deleterious effects of carbon deposition in the fuel electrode are described followed by explanations of how to avoid or ease the consequences.Visions of how RSOCs powered by sustainable energy may be applied on a large scale for the transportation sector via power-to-fuel technology and for integration with the electrical grid together with seasonal storage are presented.Finally,a brief comparison of RSOCs to other electrolysis cells and an outlook with examples of actions necessary to commercialize RSOC applications are sketched.展开更多
The CeVO_4/graphitic C_3N_4 composites have exhibited much enhanced photocatalytic property for degrading methylene blue(MB) pollutant under visible light irradiation compared with single-phase g-C_3N_4 or CeVO_4. The...The CeVO_4/graphitic C_3N_4 composites have exhibited much enhanced photocatalytic property for degrading methylene blue(MB) pollutant under visible light irradiation compared with single-phase g-C_3N_4 or CeVO_4. The composite S5 obtained from an optimized mass ratio(5%) of CeVO_4 to dicyanamide(DCDA) exhibits the highest photocatalytic activity. Here, ternary Ag/CeVO_4/g-C_3N_4 composites denoted as X%Ag/S5 were prepared by an ultrasonic precipitation method to improve the photocatalytic property of S5. The TEM images show that CeVO_4 and Ag nanoparticles are well distributed on the layered g-C_3N_4, which agree well with the XRD results. The UV spectra show that the 7%Ag/S5 sample has the widest absorption range and the enhanced absorption intensity under visible light irradiation. The corresponding band gap of 7%Ag/S5(2.5 eV) is much lower than that of S5(2.65 eV). The corresponding k value of 7%Ag/S5 is much higher than those of g-C_3N_4 and CeVO_4. The degradation experiments for MB solution suggest that the 7%Ag/S5 sample has the optimal photocatalytic performance, which can degrade MB solution completely within 120 min. The enhanced photocatalytic property of the composites is ascribed to not only the effect of heterojunction structure, but also the surface plasma resonance effect of Ag nanoparticles.展开更多
Left sided valvular heart disease poses major impact on life and lifestyle.Medical therapy merely palliates chronic severe valve disease and once symptoms or haemodynamic sequelae appear,life expectancy is markedly tr...Left sided valvular heart disease poses major impact on life and lifestyle.Medical therapy merely palliates chronic severe valve disease and once symptoms or haemodynamic sequelae appear,life expectancy is markedly truncated.In this article,we review the mechanisms of valve pathology,latest evidence in the quest for pharmacological options,means by which to predict deterioration,and standard and novel treatment options.展开更多
The first experimental measurements of intense(～7 × 1019 W cm-2) laser-driven terahertz(THz) radiation from a solid target which is preheated by an intense pulse of laser-accelerated protons is reported. The tot...The first experimental measurements of intense(～7 × 1019 W cm-2) laser-driven terahertz(THz) radiation from a solid target which is preheated by an intense pulse of laser-accelerated protons is reported. The total energy of the THz radiation is found to decrease by approximately a factor of 2 compared to a cold target reference. This is attributed to an increase in the scale length of the preformed plasma, driven by proton heating, at the front surface of the target,where the THz radiation is generated. The results show the importance of controlling the preplasma scale length for THz production.展开更多
文摘Assessment of mining impact on groundwater is one of critical considerations for longwall extension and sustainability,however usually constrained by limited data availability,hydrogeological variation,and the complex coupled hydro-mechanical behaviour.This paper aims to determine the factors and mechanism of groundwater depressurisation and identify knowledge gaps and methodological limitations for improving groundwater impact assessment.Analysis of dewatering cases in Australian,Chinese,and US coalfields demonstrates that piezometric drawdown can further lead to surface hydrology degradation,while the hydraulic responses vary with longwall parameters and geological conditions.Statistical interpretation of 422 height of fracturing datasets indicates that the groundwater impact positively correlates to panel geometry and depth of cover,and more pronounced in panel interaction and top coal caving cases.In situ stress,rock competency,clay mineral infillings,fault,valley topography,and surface-subsurface water interaction are geological and hydrogeological factors influencing groundwater hydraulics and long-term recovery.The dewatering mechanism involves permeability enhancement and extensive flow through fracture networks,where interconnected fractures provide steep hydraulic gradients and smooth flow pathways draining the overlying water to goaf of lower heads.Future research should improve fracture network identification and interconnectivity quantification,accompanied by description of fuid flow dynamics in the high fracture frequency and large fracture aperture context.The paper recommends a research framework to address the knowledge gaps with continuous data collection and field-scale numerical modelling as key technical support.The paper consolidates the understanding of longwall mining impacting mine hydrology and provides viewpoints that facilitate an improved assessment ofgroundwaterdepressurisation.
文摘A synthetic coffinite was hydrothermally prepared and characterized before conducting a series of acid sulfate leach tests under conditions of relevance to uranium extraction.The results were then compared with similar studies on synthetic versions of the related U4+minerals uraninite(UO2)and brannerite(UTi2O6)to identify and differentiate the rate and U extraction among these important uranium minerals.Tests examining the influence of residence time on uranium dissolution from synthetic coffinite,uraninite and brannerite showed that under similar experimental conditions,complete dissolution of uranium from coffinite was obtained between 36 and 48 h.The activation energy for this reaction was calculated to be 38.4 kJ/mol.This represented a significantly slower rate of dissolution than that indicated for uraninite which dissolved in 3 h(Ea=15.2 kJ/mol).The synthetic brannerite was leached at a much slower rate than the coffinite and reached a maximum dissolution of^18%U in 144 h(Ea=42-84 kJ/mol).The clear differentiation in rates and U extraction among the three minerals is consistent with previous literatures which suggest that in terms of leachability,uraninite>coffinite>brannerite.It is expected that the presence of impurities in natural coffinites would further inhibit leachability.
文摘目的探讨双能量虚拟去钙成像(VNCa)CT对中轴性脊柱关节炎相关骶髂关节炎病人骨髓水肿的诊断价值。材料与方法这项前瞻性研究连续收集2016年4月—2017年12月期间47例受试者[年龄14~41岁,平均27岁(男28例,年龄14~37岁,平均24岁;女19例,年龄17~41岁,平均29岁)],行双能CT和3.0 T MRI检查。
基金This work was supported in part by the National Basic Research Program of China(Grant No.2013CBA01504)the National Natural Science Foundation of China(Grant Nos.11675108,11421064,11405108 and 11374210).
文摘In contrast to ion beams produced by conventional accelerators,ion beams accelerated by ultrashort intense laser pulses have advantages of ultrashort bunch duration and ultrahigh density,which are achieved in compact size.However,it is still challenging to simultaneously enhance their quality and yield for practical applications such as fast ion ignition of inertial confinement fusion.Compared with other mechanisms of laser-driven ion acceleration,the hole-boring radiation pressure acceleration has a special advantage in generating high-fluence ion beams suitable for the creation of high energy density state of matters.In this paper,we present a review on some theoretical and numerical studies of the hole-boring radiation pressure acceleration.First we discuss the typical field structure associated with this mechanism,its intrinsic feature of oscillations,and the underling physics.Then we will review some recently proposed schemes to enhance the beam quality and the efficiency in the hole-boring radiation pressure acceleration,such as matching laser intensity profile with target density profile,and using two-ion-species targets.Based on this,we propose an integrated scheme for efficient high-quality hole-boring radiation pressure acceleration,in which the longitudinal density profile of a composite target as well as the laser transverse intensity profile are tailored according to the matching condition.
基金supported by the National Natural Science Foundation of China(51078150)the National Natural Science Foundation of China(11602087)+1 种基金the State Key Laboratory of Subtropical Building Science,South China University of Technology(2017ZB32)National Undergraduate Innovative and Entrepreneurial Training Program(201810561180).
文摘The alternating method based on the fundamental solutions of the infinite domain containing a crack,namely Muskhelishvili’s solutions,divides the complex structure with a crack into a simple model without crack which can be solved by traditional numerical methods and an infinite domain with a crack which can be solved by Muskhelishvili’s solutions.However,this alternating method cannot be directly applied to the edge crack problems since partial crack surface of Muskhelishvili’s solutions is located outside the computational domain.In this paper,an improved alternating method,the spline fictitious boundary element alternating method(SFBEAM),based on infinite domain with the combination of spline fictitious boundary element method(SFBEM)and Muskhelishvili’s solutions is proposed to solve the edge crack problems.Since the SFBEM and Muskhelishvili’s solutions are obtained in the framework of infinite domain,no special treatment is needed for solving the problem of edge cracks.Different mixed boundary conditions edge crack problems with varies of computational parameters are given to certify the high precision,efficiency and applicability of the proposed method compared with other alternating methods and extend finite element method.
基金This work was supported by the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDA25050100)the National Natural Science Foundation of China(Grant Nos.11991074,11975154,12005287,and 12135009)+2 种基金the Science Challenge Project(Grant No.TZ2018005)X.F.Li was supported by the China and Germany Postdoctoral Exchange Program from the Office of the China Postdoctoral Council and the Helmholtz Centre(Grant No.20191016)and the China Postdoctoral Science Foundation(Grant No.2018M641993)Y.Zhao was also supported by Guangdong Basic and Applied Basic Research Foundation(Grant No.2023A1515011695).Simulations were carried out on the JURECA and JUWELS supercomputers at the Jülich Supercomputing Centre,which are granted from the Projects JZAM04 and LAPIPE.
文摘Broadband lasers have been proposed as future drivers of inertial confined fusion(ICF)to enhance the laser-target coupling efficiency via the mitigation of various parametric instabilities.The physical mechanisms involved have been explored recently,but are not yet fully understood.Here,stimulated Raman scattering(SRS)as one of the key parametric instabilities is investigated theoretically and numerically for a broadband laser propagating in homogeneous plasma in multidimensional geometry.The linear SRS growth rate is derived as a function of scattering angles for two monochromatic laser beams with a fixed frequency differenceδω.Ifδω/ω_(0)∼1%,withω0 the laser frequency,these two laser beams may be decoupled in stimulating backward SRS while remaining coupled for sideward SRS at the laser intensities typical for ICF.Consequently,side-scattering may dominate over backward SRS for two-color laser light.This finding of SRS transition from backward to sideward SRS is then generalized for a broadband laser with a few-percent bandwidth.Particle-in-cell simulations demonstrate that with increasing laser bandwidth,the sideward SRS gradually becomes dominant over the backward SRS.Since sideward SRS is very efficient in producing harmful hot electrons,attention needs to be paid on this effect if ultra-broadband lasers are considered as next-generation ICF drivers.
基金supported by the National Natural Science Foundation of China(Nos.11804348,11775056,11975154 and 11991074)the Science Challenge Project(No.TZ2018005).X.F.Li was also supported by the Shanghai Pujiang Program(No.23PJ1414600)。
文摘Polarized electron beam production via laser wakefield acceleration in pre-polarized plasma is investigated by particlein-cell simulations.The evolution of the electron beam polarization is studied based on the Thomas±Bargmann±Michel±Telegdi equation for the transverse and longitudinal self-injection,and the depolarization process is found to be influenced by the injection schemes.In the case of transverse self-injection,as found typically in the bubble regime,the spin precession of the accelerated electrons is mainly influenced by the wakefield.However,in the case of longitudinal injection in the quasi-1D regime(for example,F.Y.Li et al.,Phys.Rev.Lett.110,135002(2013)),the direction of electron spin oscillates in the laser field.Since the electrons move around the laser axis,the net influence of the laser field is nearly zero and the contribution of the wakefield can be ignored.Finally,an ultra-short electron beam with polarization of 99%can be obtained using longitudinal self-injection.
文摘This review gives first a brief view of the potential availability of sustainable energy.It is clear that over 100 times more solar photovoltaic energy than necessary is readily accessible and that practically available wind alone may deliver sufficient energy supply to the world.Due to the intermittency of these sources,effective and inexpensive energy-conversion and storage technology is needed.Motivation for the possible electrolysis application of reversible solid-oxide cells(RSOCs),including a comparison of power-to-fuel/fuel-to-power to other energy-conversion and storage technologies is presented.RSOC electrochemistry and chemistry of H_(2)O,CO_(2),H_(2),CO,CnHm(hydrocarbons)and NH3,including thermodynamics and cell performance,are described.The mechanical strength of popular cell supports is outlined,and newly found stronger materials are mentioned.Common cell-degradation mechanisms,including the effect of common impurities in gases and materials(such as S and Si),plus the deleterious effects of carbon deposition in the fuel electrode are described followed by explanations of how to avoid or ease the consequences.Visions of how RSOCs powered by sustainable energy may be applied on a large scale for the transportation sector via power-to-fuel technology and for integration with the electrical grid together with seasonal storage are presented.Finally,a brief comparison of RSOCs to other electrolysis cells and an outlook with examples of actions necessary to commercialize RSOC applications are sketched.
基金supported by National Natural Science Foundation of China(No.51502116)the Six Talents Peak Project in Jiangsu Province(No.2011-ZBZZ045)+2 种基金Natural Science Foundation of Jiangsu Province(No.BK20140557)Special Funding of China Postdoctoral Science Foundation(No.2016T90425)China Postdoctoral Science Foundation(No.2015M571682)
文摘The CeVO_4/graphitic C_3N_4 composites have exhibited much enhanced photocatalytic property for degrading methylene blue(MB) pollutant under visible light irradiation compared with single-phase g-C_3N_4 or CeVO_4. The composite S5 obtained from an optimized mass ratio(5%) of CeVO_4 to dicyanamide(DCDA) exhibits the highest photocatalytic activity. Here, ternary Ag/CeVO_4/g-C_3N_4 composites denoted as X%Ag/S5 were prepared by an ultrasonic precipitation method to improve the photocatalytic property of S5. The TEM images show that CeVO_4 and Ag nanoparticles are well distributed on the layered g-C_3N_4, which agree well with the XRD results. The UV spectra show that the 7%Ag/S5 sample has the widest absorption range and the enhanced absorption intensity under visible light irradiation. The corresponding band gap of 7%Ag/S5(2.5 eV) is much lower than that of S5(2.65 eV). The corresponding k value of 7%Ag/S5 is much higher than those of g-C_3N_4 and CeVO_4. The degradation experiments for MB solution suggest that the 7%Ag/S5 sample has the optimal photocatalytic performance, which can degrade MB solution completely within 120 min. The enhanced photocatalytic property of the composites is ascribed to not only the effect of heterojunction structure, but also the surface plasma resonance effect of Ag nanoparticles.
文摘Left sided valvular heart disease poses major impact on life and lifestyle.Medical therapy merely palliates chronic severe valve disease and once symptoms or haemodynamic sequelae appear,life expectancy is markedly truncated.In this article,we review the mechanisms of valve pathology,latest evidence in the quest for pharmacological options,means by which to predict deterioration,and standard and novel treatment options.
基金supported by National Basic Research Program of China (grant nos. 2013CBA01500 and 2014CB339801)National Natural Science Foundation of China (grant nos. 11121504, 11205100, 11220101002 and 11135012)+1 种基金the EPSRC (grant nos. EP/J003832/1 and EP/L001357/1)the Swedish Research Council
文摘The first experimental measurements of intense(～7 × 1019 W cm-2) laser-driven terahertz(THz) radiation from a solid target which is preheated by an intense pulse of laser-accelerated protons is reported. The total energy of the THz radiation is found to decrease by approximately a factor of 2 compared to a cold target reference. This is attributed to an increase in the scale length of the preformed plasma, driven by proton heating, at the front surface of the target,where the THz radiation is generated. The results show the importance of controlling the preplasma scale length for THz production.
