Ground fissures are influenced by the coupling of geological factors and human activi-ties.They threaten the safety of infrastructure and restrict town planning in many areas in China.One of the area most severely aff...Ground fissures are influenced by the coupling of geological factors and human activi-ties.They threaten the safety of infrastructure and restrict town planning in many areas in China.One of the area most severely affected by ground fissures is the Weihe Basin in North China,which has the most extensive distribution of ground fissures and all the elements that control their occurrence,pro-viding an ideal study area for the study of ground fissures.In this study,we took the eastern Weihe Ba-sin as the study area and determined the distribution and hazard characteristics of ground fissures via field investigation.Based on the analytic hierarchy process,we propose a multi-level,comprehensive method for evaluating the hazards of ground fissures.This method considers the geological back-ground,development status,and triggering factors of ground fissures,including all nine currently known assessment indices of ground fissures.We used judgment matrices to rank the constructed ground fissure assessment index system at the single and total levels and quantified the nine assessment indices of ground fissures according to the field survey data.Finally,we plotted the ground fissure risk zoning map and evaluated the ground fissure risk at the study area.Our findings indicated that the proposed method could facilitate ground fissure hazard assessment and prediction and provide support for hazard prevention and urban/rural planning.展开更多
Phosphor-converted white light-emitting diode(LED) lighting has gained tremendous achievements since the invention of the InGaN blue LED by Nakamura et al., who won the Nobel Physics Prize in 2014.By far, a significan...Phosphor-converted white light-emitting diode(LED) lighting has gained tremendous achievements since the invention of the InGaN blue LED by Nakamura et al., who won the Nobel Physics Prize in 2014.By far, a significant challenge comes from the thermal quenching(TQ) behavior of the present LED phosphors during the high-power LED operation or the updated laser lighting. But systematic research or review on the luminescence quenching character and/or how to realize thermally stable luminescence are lacking. Since TQ is an inherent property of phosphors, it can be diminished by different approaches.This review proceeds from the mechanism of TQ, summarizes previous researches on improving the thermal stability of LED phosphors and also discusses future research opportunities in this field. The developments of the phosphors with properties of high luminance and thermal stability, as well as the improved strategies involved,will benefit the basic researches and applications in high power lighting or high-luminance laser lighting.展开更多
This paper takes Fen-Wei Basin(FWB)as a case to study the ground fissures controlled by normal fault.Based on the field investigation,geophysical exploration,drilling,GNSS data and numerical calculation,the characteri...This paper takes Fen-Wei Basin(FWB)as a case to study the ground fissures controlled by normal fault.Based on the field investigation,geophysical exploration,drilling,GNSS data and numerical calculation,the characteristics and mechanism of ground fissures originated from the hanging wall of normal faults are revealed.The results show that the distribution of ground fissures in the hanging wall and heading wall of the active faults is not uniform.Ground fissures are mostly distributed in the hanging wall of active faults and show a linear distribution on the surface,their strike is consistent with the fault,mainly characterized by vertical offset and horizontal tension.Ground fissures destroy the farmland and building foundation through which they pass and cause the rupture or displacement.In profile section,the ground fissure shows the characteristics of normal faults and dislocates the strata,and is connected with the underlying faults.Numerical analysis shows that the vertical displacement of normal fault activity in hanging wall is much larger than that in heading wall,which is the reason that tectonic ground fissures mainly originate from hanging wall.The range of dangerous area of ground fissures is controlled by the depth of fault,the strength of the ground fissures disaster is mainly controlled by the activity of fault.The formation of the ground fissures originated from the hanging wall of the fault experienced three stages:the main fault activity stage,the secondary fault activity stage and the fissure formation stage.展开更多
Rapid development of solid-state lighting technology requires new materials with highly efficient and stable luminescence,and especially relies on blue light pumped red phosphors for improved light quality.Herein,we d...Rapid development of solid-state lighting technology requires new materials with highly efficient and stable luminescence,and especially relies on blue light pumped red phosphors for improved light quality.Herein,we discovered an unprecedented red-emitting Mg_(2)AI_(4)Si_(5)0_(18):Eu^(2+)composite phosphor(λex=450 nm,λem=620 nm)via the crystallization of MgO-AI_(2)O_(3)-Sio_(2) aluminosilicate glass.Combined experimental measurement and first-principles calculations verify that Eu^(2+)dopants insert at the vacant channel of Mg_(2)AI_(4)Si_(5)0_(18)crystal with six-fold coordination responsible for the peculiar red emission.Importantly,the resulting phosphor exhibits high internal/external quantum efficiency of 94.5/70.6%,and stable emission against thermal quenching,which reaches industry production.The maximum luminous flux and luminous efficiency of the constructed laser driven red emitting device reaches as high as 274 Im and 54lm W^(-1),respectively.The combinations of extraordinary optical properties coupled with economically favorable and innovative preparation method indicate,that the Mg_(2)AI_(4)Si_(5)0_(18):Eu^(2+)composite phosphor will provide a significant step towards the development of high-power solid-state lighting.展开更多
Liangjia Village earth fissure,one of the 79 earth fissures along the Kouzhen-Guanshan fault located in the northern Weihe Basin,causes severe damage to buildings and farmlands.Since the late 1950s,40 earth fissures h...Liangjia Village earth fissure,one of the 79 earth fissures along the Kouzhen-Guanshan fault located in the northern Weihe Basin,causes severe damage to buildings and farmlands.Since the late 1950s,40 earth fissures have occurred in a similar east-west(EW)direction parallel to the Kouzhen-Guanshan fault,and a further 39 earth fissures have occurred with north-west,east-north,or north-east orientations intersecting the fault.In this study,a case study of Liangjia Village earth fissure was conducted to investigate the mechanisms of fissure generation in detail.Geotechnical and geophysical methods including measurements,trenching,drilling,and seismic exploration were used to reveal the basic characteristics,geological background,and origin model of the Liangjia Village earth fissure.This earth fissure,with a total length of 800 m in 2014,runs EW parallel to the Kouzhen-Guanshan fault,and it has damaged buildings and farmlands by forming sinkholes,gullies,subsidence,and a scarp.The trenching results indicated that this fissure underwent multi-phase activity.Analysis of geological drilling and shallow seismic profiling results showed that the fissure also possessed characteristics of a synsedimentary fault.Regarding its genesis,the fissure was formed through the combined actions of three factors:an earthquake created the fissure,the Kouzhen-Guanshan fault controlled its development,and loess erosion and groundwater runoff subsequently enlarged the fissure.Regional extension first generated many buried faults along the hanging wall of the Kouzhen-Guanshan fault before seismic activity caused the buried faults to propagate to the surface,where loess erosion and ground-water runoff promoted the formation of the current earth fissure.展开更多
基金supported by the National Science Foundation of China(Nos.41920104010,41790441,41877250,41272284,41807234)the National Geological Survey of China(No.DD20160264)+1 种基金the Fundamental Research Funds for the Central University,CHD(No.300102261715)Innovation Capability Support Program of Shaanxi(Nos.2022KJXX-05,2023-CX-TD-34).
文摘Ground fissures are influenced by the coupling of geological factors and human activi-ties.They threaten the safety of infrastructure and restrict town planning in many areas in China.One of the area most severely affected by ground fissures is the Weihe Basin in North China,which has the most extensive distribution of ground fissures and all the elements that control their occurrence,pro-viding an ideal study area for the study of ground fissures.In this study,we took the eastern Weihe Ba-sin as the study area and determined the distribution and hazard characteristics of ground fissures via field investigation.Based on the analytic hierarchy process,we propose a multi-level,comprehensive method for evaluating the hazards of ground fissures.This method considers the geological back-ground,development status,and triggering factors of ground fissures,including all nine currently known assessment indices of ground fissures.We used judgment matrices to rank the constructed ground fissure assessment index system at the single and total levels and quantified the nine assessment indices of ground fissures according to the field survey data.Finally,we plotted the ground fissure risk zoning map and evaluated the ground fissure risk at the study area.Our findings indicated that the proposed method could facilitate ground fissure hazard assessment and prediction and provide support for hazard prevention and urban/rural planning.
基金Project supported by the National Natural Science Foundation of China(51722202,91622125,51572023)Natural Science Foundation of Beijing,China(2172036)
文摘Phosphor-converted white light-emitting diode(LED) lighting has gained tremendous achievements since the invention of the InGaN blue LED by Nakamura et al., who won the Nobel Physics Prize in 2014.By far, a significant challenge comes from the thermal quenching(TQ) behavior of the present LED phosphors during the high-power LED operation or the updated laser lighting. But systematic research or review on the luminescence quenching character and/or how to realize thermally stable luminescence are lacking. Since TQ is an inherent property of phosphors, it can be diminished by different approaches.This review proceeds from the mechanism of TQ, summarizes previous researches on improving the thermal stability of LED phosphors and also discusses future research opportunities in this field. The developments of the phosphors with properties of high luminance and thermal stability, as well as the improved strategies involved,will benefit the basic researches and applications in high power lighting or high-luminance laser lighting.
基金supported by the National Natural Science Foundation of China(51961145101,51972118)the International Cooperation Project of National Key Research and Development Program of China(2021YFE0105700)+1 种基金Guangzhou Science&Technology Project(202007020005)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01X137)。
基金supported by the National Science Foundation of China (Nos.41790441,41877250,41272284,41807234)the National Geological Survey of China (No.DD20160264)the Fundamental Research Funds for the Central University,CHD (No.300102261715)
文摘This paper takes Fen-Wei Basin(FWB)as a case to study the ground fissures controlled by normal fault.Based on the field investigation,geophysical exploration,drilling,GNSS data and numerical calculation,the characteristics and mechanism of ground fissures originated from the hanging wall of normal faults are revealed.The results show that the distribution of ground fissures in the hanging wall and heading wall of the active faults is not uniform.Ground fissures are mostly distributed in the hanging wall of active faults and show a linear distribution on the surface,their strike is consistent with the fault,mainly characterized by vertical offset and horizontal tension.Ground fissures destroy the farmland and building foundation through which they pass and cause the rupture or displacement.In profile section,the ground fissure shows the characteristics of normal faults and dislocates the strata,and is connected with the underlying faults.Numerical analysis shows that the vertical displacement of normal fault activity in hanging wall is much larger than that in heading wall,which is the reason that tectonic ground fissures mainly originate from hanging wall.The range of dangerous area of ground fissures is controlled by the depth of fault,the strength of the ground fissures disaster is mainly controlled by the activity of fault.The formation of the ground fissures originated from the hanging wall of the fault experienced three stages:the main fault activity stage,the secondary fault activity stage and the fissure formation stage.
基金the National Natural Science Foundations of China(Grant Nos.51972118,51961145101,51722202 and 11974022)the Guangzhou Science&Technology Project(202007020005)+1 种基金the Fundamental Research Funds for the Central Universities(D2190980)the Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program(2017BT01X137).
文摘Rapid development of solid-state lighting technology requires new materials with highly efficient and stable luminescence,and especially relies on blue light pumped red phosphors for improved light quality.Herein,we discovered an unprecedented red-emitting Mg_(2)AI_(4)Si_(5)0_(18):Eu^(2+)composite phosphor(λex=450 nm,λem=620 nm)via the crystallization of MgO-AI_(2)O_(3)-Sio_(2) aluminosilicate glass.Combined experimental measurement and first-principles calculations verify that Eu^(2+)dopants insert at the vacant channel of Mg_(2)AI_(4)Si_(5)0_(18)crystal with six-fold coordination responsible for the peculiar red emission.Importantly,the resulting phosphor exhibits high internal/external quantum efficiency of 94.5/70.6%,and stable emission against thermal quenching,which reaches industry production.The maximum luminous flux and luminous efficiency of the constructed laser driven red emitting device reaches as high as 274 Im and 54lm W^(-1),respectively.The combinations of extraordinary optical properties coupled with economically favorable and innovative preparation method indicate,that the Mg_(2)AI_(4)Si_(5)0_(18):Eu^(2+)composite phosphor will provide a significant step towards the development of high-power solid-state lighting.
基金This study was funded by the National Basic Research Program of China(No.2014CB744700)the High Speed Railway Joint Fund of NSFC(No.U1934208)+4 种基金the Key R&D Program of Jiangxi Province,China(No.20202BBGL73079)the CMEC Technology Incubation Project(CMEC-KJFH-2018-02)the National Natural Science Foundation(Grant No.41702298)Supported by the Fundamental Research Funds for the Central Universities,CHD(Nos.300102260402 and 300102269203)the National Geological Survey of China(Nos.121201001000150122 and DD20160235).
文摘Liangjia Village earth fissure,one of the 79 earth fissures along the Kouzhen-Guanshan fault located in the northern Weihe Basin,causes severe damage to buildings and farmlands.Since the late 1950s,40 earth fissures have occurred in a similar east-west(EW)direction parallel to the Kouzhen-Guanshan fault,and a further 39 earth fissures have occurred with north-west,east-north,or north-east orientations intersecting the fault.In this study,a case study of Liangjia Village earth fissure was conducted to investigate the mechanisms of fissure generation in detail.Geotechnical and geophysical methods including measurements,trenching,drilling,and seismic exploration were used to reveal the basic characteristics,geological background,and origin model of the Liangjia Village earth fissure.This earth fissure,with a total length of 800 m in 2014,runs EW parallel to the Kouzhen-Guanshan fault,and it has damaged buildings and farmlands by forming sinkholes,gullies,subsidence,and a scarp.The trenching results indicated that this fissure underwent multi-phase activity.Analysis of geological drilling and shallow seismic profiling results showed that the fissure also possessed characteristics of a synsedimentary fault.Regarding its genesis,the fissure was formed through the combined actions of three factors:an earthquake created the fissure,the Kouzhen-Guanshan fault controlled its development,and loess erosion and groundwater runoff subsequently enlarged the fissure.Regional extension first generated many buried faults along the hanging wall of the Kouzhen-Guanshan fault before seismic activity caused the buried faults to propagate to the surface,where loess erosion and ground-water runoff promoted the formation of the current earth fissure.
