Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study i...Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study include： severely damaged dams were densely distributed along the seismologic fault; small dams, especially small earth-rock dams, had the most serious damage that was caused by a variety of factors; the most serious damage was caused by seismic waves; damage was aggregated by aftershocks; and the extent of the damage patterns increased with the seismic intensity. Damage patterns varied in different intensity zones and cracking was the most common type of damage. Most of the dams had a good base with relatively high bearing capacity, and the walls of the earth-rock dams were mostly of clay soil. This type of base and body material mitigated some of the damage to dams. Reservoir maintenance and other factors also have a significant impact on the seismic safety of the dam. Finally, some recommendations to reduce seismic damage to dams are proposed.展开更多
High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of th...High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of the laminated composite REBCO CCs,the damage induced by the thermal mismatch stress under a combination of epoxy impregnation,cooling,and quenching can cause premature degradation of the critical current.In this study,a three-dimensional(3D)electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model(CZM)is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench.The temperature variation,critical current degradation of the REBCO CC,and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature.The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result.The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC.The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC.Finally,the effects of the coefficient of thermal expansion(CTE)of the epoxy resin,thickness of the substrate,and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed.These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.展开更多
Allanite is commonly encountered as an accessory rare-earth silicate mineral in association with minerals such as garnet,biotite,and feldspar.It is distributed globally and occurs in igneous formations such as granite...Allanite is commonly encountered as an accessory rare-earth silicate mineral in association with minerals such as garnet,biotite,and feldspar.It is distributed globally and occurs in igneous formations such as granites,pegmatites,and syenites,as well as in various metamorphic rocks such as schist,gneiss,and amphibolite.Moreover,it can be found in mineral veins formed through hydrothermal activity.While allanite has not yet been extensively utilized for the production of rare-earth elements,recent discoveries of high-grade rare-earth-rich allanite deposits in Wyoming,USA,highlight its economic potential.However,despite ongoing research on the mineralogy and processing of rare-earth minerals,allanite has not received widespread attention in mineral processing.To achieve economical extraction of rare-earth elements from allanite in the future,systematic studies on processing techniques(e.g.,density separation,magnetic separation,flotation,leaching)are imperative to fully unlock the potential of allanite as a rare-earth element source.To pave the way for future investigation of allanite and address the unique processing challenges,this review article aims to comprehensively summarize previous studies,encompassing properties,occurrences,and processing technologies ofallanite.展开更多
A novel class of high-entropy rare-earth metal diborodicarbide(Y_(0.2)5 Yb_(0.25)Dy_(0.25)Er_(0.25))B_(2)C_(2)(HE-REB_(2)C_(2))ceramics was successfully fabricated using the in-situ reactive spark plasma sintering(SPS...A novel class of high-entropy rare-earth metal diborodicarbide(Y_(0.2)5 Yb_(0.25)Dy_(0.25)Er_(0.25))B_(2)C_(2)(HE-REB_(2)C_(2))ceramics was successfully fabricated using the in-situ reactive spark plasma sintering(SPS)technology for the first time.Single solid solution with a typical tetragonal structure was formed,having a homogeneous distribution of four rare-earth elements,such as Y,Yb,Dy,and Er.Coefficients of thermal expansion(CTEs)along the a and c directions(aa and ac)were determined to be 4.18 and 16.06μK^(-1),respectively.Thermal expansion anisotropy of the as-obtained HE-REB_(2)C_(2)was attributed to anisotropy of the crystal structure of HE-REB_(2)C_(2).The thermal conductivity(k)of HE-REB_(2)C_(2)was 9.2±0.09 W·m^(-1)·K^(-1),which was lower than that of YB_(2)C_(2)(19.2±0.07 W·m^(-1)·K^(-1)),DyB_(2)C_(2)(11.90.06 W·m^(-1)·K^(-1)),and ErB_(2)C_(2)(12.10.03 W·m^(-1)·K^(-1)),due to high-entropy effect and sluggish diffusion effect of high-entropy ceramics(HECs).Furthermore,Vickers hardness of HE-REB_(2)C_(2)was slightly higher than that of REB_(2)C_(2)owing to the solid solution hardening mechanism of HECs.Typical nano-laminated fracture morphologies,such as kink boundaries,delamination,and slipping were observed at the tip of Vickers indents,suggesting ductile behavior of HE-REB_(2)C_(2).This newly investigated class of ductile HE-REB_(2)C_(2)ceramics expanded the family of HECs to diboridcarbide compounds,which can lead to more research works on high-entropy rare-earth diboridcarbides in the near future.展开更多
The Discrete variation X<sub>α</sub>（DV-X<sub>α</sub>）method was used to calculate the energylevel of some rare earth doped BaF<sub>2</sub> crystals.The results indicated that e...The Discrete variation X<sub>α</sub>（DV-X<sub>α</sub>）method was used to calculate the energylevel of some rare earth doped BaF<sub>2</sub> crystals.The results indicated that elements Eu,Dyand Yb will change their valence from +3 to +2 under irradiation and thus change theoptical properties of the crystals.The calculation using radiation damage model agreeswell with experiments.展开更多
Liquefaction of sandy soils is a big threat to the stability and the safety of an earth embankment laid on saturated soils.A large number of liquefaction-induced damages on embankment due to different types of earthqu...Liquefaction of sandy soils is a big threat to the stability and the safety of an earth embankment laid on saturated soils.A large number of liquefaction-induced damages on embankment due to different types of earthquakes have been reported worldwide.In this research,the dynamic behaviors of earth embankment and the reinforcement effects of grouting as remediation method,subjected to moderate earthquake EQ1 and strong earthquake EQ2,were numerically investigated.The seismic behaviors of ground composed of cohesionless sandy soil and cohesive clayey soil were uniformly described by the cyclic mobility(CM)model,which is capable of describing accurately the mechanical property of the soil due to monotonic and cyclic loadings by accounting for stress-induced anisotropy,over-consolidation,and soil structure.It is known from the numerical investigation that the embankment would experience destructive deformation,and that the collapse mode was closely related to the properties of input seismic motion because high intensities and long durations of an earthquake motion could lead to significant plastic deformation and prolonged soil liquefaction.Under the strong seismic loading of EQ2,a circular collapse surface,combined with huge settlement and lateral spread,occurred inside the liquefication zone and extended towards the embankment crest.In contrast,in moderate earthquake EQ1,upheaval was observed at each toe of the embankment,and instability occurred only in the liquefied ground.An anti-liquefaction remediation via grouting was determined to significantly reduce liquefaction-induced deformation(settlement,lateral spreading,and local uplift)and restrain the deep-seated circular sliding failure,even though the top sandy soil liquefied in both earthquakes.When the structure was subjected to EQ2 motion,local failure occurred on the embankment slope reinforced with grouting,and thus,an additional appropriate countermeasure should be implemented to further strengthen the slope.For both input motions,the surface deformation o展开更多
Much effort has been made in investigating the seismic response and failure mechanism of rectangular subway stations,however,the influence of earth retaining systems has generally been ignored in previous studies.This...Much effort has been made in investigating the seismic response and failure mechanism of rectangular subway stations,however,the influence of earth retaining systems has generally been ignored in previous studies.This paper presents a numerical study on the seismic performance of a rectangular subway station with/without earth retaining systems by taking fender piles as the example,and aims to illustrate how the existence of fender piles affects seismic responses on subway stations.The loading conditions of subway stations and their surrounding soils prior to earthquakes are discussed.Next,seismic responses of subway stations with or without fender piles were simulated.Afterward,earthquake-induced deformations of stations and surrounding soils,as well as the internal forces and damage modes of the structural components,were systematically studied.Consequently,the seismic performance of the stations was affected by the existence of fender piles.In addition,earthquake intensity is illustrated.The study showed that deformation modes of surrounding soils and damage modes of stations were different with regard to the existence of fender piles.Meanwhile,earthquake intensity influencing the seismic performance of stations with or without fender piles were found to be opposite.展开更多
基金Special Scientific Found for Seismic Industry Under Grant No.201008005
文摘Based on raw data from dams damaged in the Wenchuan earthquake, including many that were severely damaged, characteristics and factors that influenced the damage are discussed in this paper. Findings from this study include： severely damaged dams were densely distributed along the seismologic fault; small dams, especially small earth-rock dams, had the most serious damage that was caused by a variety of factors; the most serious damage was caused by seismic waves; damage was aggregated by aftershocks; and the extent of the damage patterns increased with the seismic intensity. Damage patterns varied in different intensity zones and cracking was the most common type of damage. Most of the dams had a good base with relatively high bearing capacity, and the walls of the earth-rock dams were mostly of clay soil. This type of base and body material mitigated some of the damage to dams. Reservoir maintenance and other factors also have a significant impact on the seismic safety of the dam. Finally, some recommendations to reduce seismic damage to dams are proposed.
基金Project supported by the National Natural Science Foundation of China(Nos.12302278,U2241267,12172155,and 11932008)the Fundamental Research Funds for the Central Universities of China(No.lzujbky-2022-48)the Natural Science Foundation of Gansu Province of China(No.24JRRA473)。
文摘High-temperature superconducting(HTS)rare-earth Ba_(2)Cu_(3)O_(7-x)(REBCO)coated conductors(CCs)have significant potential in high-current and high-field applications.However,owing to the weak interface strength of the laminated composite REBCO CCs,the damage induced by the thermal mismatch stress under a combination of epoxy impregnation,cooling,and quenching can cause premature degradation of the critical current.In this study,a three-dimensional(3D)electromagnetic-thermal-mechanical model based on the H-formulation and cohesive zone model(CZM)is developed to study the critical current degradation characteristics in an epoxy-impregnated REBCO CC caused by the damage during a quench.The temperature variation,critical current degradation of the REBCO CC,and its degradation onset temperature calculated by the numerical model are in agreement with the experimental data taken from the literature.The delamination of the REBCO CC predicted by the numerical model is consistent with the experimental result.The numerical results also indicate that the shear stress is the main contributor to the damage propagation inside the REBCO CC.The premature degradation of the critical current during a quench is closely related to the interface shear strength inside the REBCO CC.Finally,the effects of the coefficient of thermal expansion(CTE)of the epoxy resin,thickness of the substrate,and substrate material on the critical current degradation characteristics of the epoxy-impregnated REBCO CC during a quench are also discussed.These results help us understand the relationship between the current-carrying degradation and damage in the HTS applications.
基金supported by the U.S.Department of Energy's Office of Energy Efficiency and Renewable Energy (EERE)under the Advanced Manufacturing Office Award Number DEEE0009435.
文摘Allanite is commonly encountered as an accessory rare-earth silicate mineral in association with minerals such as garnet,biotite,and feldspar.It is distributed globally and occurs in igneous formations such as granites,pegmatites,and syenites,as well as in various metamorphic rocks such as schist,gneiss,and amphibolite.Moreover,it can be found in mineral veins formed through hydrothermal activity.While allanite has not yet been extensively utilized for the production of rare-earth elements,recent discoveries of high-grade rare-earth-rich allanite deposits in Wyoming,USA,highlight its economic potential.However,despite ongoing research on the mineralogy and processing of rare-earth minerals,allanite has not received widespread attention in mineral processing.To achieve economical extraction of rare-earth elements from allanite in the future,systematic studies on processing techniques(e.g.,density separation,magnetic separation,flotation,leaching)are imperative to fully unlock the potential of allanite as a rare-earth element source.To pave the way for future investigation of allanite and address the unique processing challenges,this review article aims to comprehensively summarize previous studies,encompassing properties,occurrences,and processing technologies ofallanite.
基金supported by the National Natural Science Foundation of China(Grant Nos.12275337 and 11975296)the Natural Science Foundation of Ningbo City(Grant No.2021J199)+1 种基金We would like to recognize the support from the Ningbo 3315 Innovative Teams Program,China(Grant No.2019A-14-C)Thanks for the financial support of Advanced Energy Science and Technology Guangdong Laboratory(Grant No.HND20TDTHGC00).
文摘A novel class of high-entropy rare-earth metal diborodicarbide(Y_(0.2)5 Yb_(0.25)Dy_(0.25)Er_(0.25))B_(2)C_(2)(HE-REB_(2)C_(2))ceramics was successfully fabricated using the in-situ reactive spark plasma sintering(SPS)technology for the first time.Single solid solution with a typical tetragonal structure was formed,having a homogeneous distribution of four rare-earth elements,such as Y,Yb,Dy,and Er.Coefficients of thermal expansion(CTEs)along the a and c directions(aa and ac)were determined to be 4.18 and 16.06μK^(-1),respectively.Thermal expansion anisotropy of the as-obtained HE-REB_(2)C_(2)was attributed to anisotropy of the crystal structure of HE-REB_(2)C_(2).The thermal conductivity(k)of HE-REB_(2)C_(2)was 9.2±0.09 W·m^(-1)·K^(-1),which was lower than that of YB_(2)C_(2)(19.2±0.07 W·m^(-1)·K^(-1)),DyB_(2)C_(2)(11.90.06 W·m^(-1)·K^(-1)),and ErB_(2)C_(2)(12.10.03 W·m^(-1)·K^(-1)),due to high-entropy effect and sluggish diffusion effect of high-entropy ceramics(HECs).Furthermore,Vickers hardness of HE-REB_(2)C_(2)was slightly higher than that of REB_(2)C_(2)owing to the solid solution hardening mechanism of HECs.Typical nano-laminated fracture morphologies,such as kink boundaries,delamination,and slipping were observed at the tip of Vickers indents,suggesting ductile behavior of HE-REB_(2)C_(2).This newly investigated class of ductile HE-REB_(2)C_(2)ceramics expanded the family of HECs to diboridcarbide compounds,which can lead to more research works on high-entropy rare-earth diboridcarbides in the near future.
基金The project supported by the National Natural Science Foundation of China under Grant No.19175031.
文摘The Discrete variation X<sub>α</sub>（DV-X<sub>α</sub>）method was used to calculate the energylevel of some rare earth doped BaF<sub>2</sub> crystals.The results indicated that elements Eu,Dyand Yb will change their valence from +3 to +2 under irradiation and thus change theoptical properties of the crystals.The calculation using radiation damage model agreeswell with experiments.
基金The financial support of National Natural Science Foundation of China(Grant Nos.51908288 and 42002266)the project of Key Laboratory of Impact and Safety Engineering(Ningbo University),Ministry of Education is appreciated.
文摘Liquefaction of sandy soils is a big threat to the stability and the safety of an earth embankment laid on saturated soils.A large number of liquefaction-induced damages on embankment due to different types of earthquakes have been reported worldwide.In this research,the dynamic behaviors of earth embankment and the reinforcement effects of grouting as remediation method,subjected to moderate earthquake EQ1 and strong earthquake EQ2,were numerically investigated.The seismic behaviors of ground composed of cohesionless sandy soil and cohesive clayey soil were uniformly described by the cyclic mobility(CM)model,which is capable of describing accurately the mechanical property of the soil due to monotonic and cyclic loadings by accounting for stress-induced anisotropy,over-consolidation,and soil structure.It is known from the numerical investigation that the embankment would experience destructive deformation,and that the collapse mode was closely related to the properties of input seismic motion because high intensities and long durations of an earthquake motion could lead to significant plastic deformation and prolonged soil liquefaction.Under the strong seismic loading of EQ2,a circular collapse surface,combined with huge settlement and lateral spread,occurred inside the liquefication zone and extended towards the embankment crest.In contrast,in moderate earthquake EQ1,upheaval was observed at each toe of the embankment,and instability occurred only in the liquefied ground.An anti-liquefaction remediation via grouting was determined to significantly reduce liquefaction-induced deformation(settlement,lateral spreading,and local uplift)and restrain the deep-seated circular sliding failure,even though the top sandy soil liquefied in both earthquakes.When the structure was subjected to EQ2 motion,local failure occurred on the embankment slope reinforced with grouting,and thus,an additional appropriate countermeasure should be implemented to further strengthen the slope.For both input motions,the surface deformation o
基金National Natural Science Foundation of Beijing under Grant No.8212007the National Natural Science Foundation of China under Grant Nos.51808028,52025084 and 51778026+1 种基金the Pyramid Talent Training Project of Beijing University of Civil Engineering and Architecture under Grant No.JDYC20200311the Fundamental Research Funds for Beijing University of Civil Engineering and Architecture(X18147)。
文摘Much effort has been made in investigating the seismic response and failure mechanism of rectangular subway stations,however,the influence of earth retaining systems has generally been ignored in previous studies.This paper presents a numerical study on the seismic performance of a rectangular subway station with/without earth retaining systems by taking fender piles as the example,and aims to illustrate how the existence of fender piles affects seismic responses on subway stations.The loading conditions of subway stations and their surrounding soils prior to earthquakes are discussed.Next,seismic responses of subway stations with or without fender piles were simulated.Afterward,earthquake-induced deformations of stations and surrounding soils,as well as the internal forces and damage modes of the structural components,were systematically studied.Consequently,the seismic performance of the stations was affected by the existence of fender piles.In addition,earthquake intensity is illustrated.The study showed that deformation modes of surrounding soils and damage modes of stations were different with regard to the existence of fender piles.Meanwhile,earthquake intensity influencing the seismic performance of stations with or without fender piles were found to be opposite.
