The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement co...The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement concrete facing panels,and gravity-type earth-retaining walls.The finite element(FE)simulations utilized a 3D plane strain condition to model full-scale ER walls and numerous nonlinear dynamics analyses.The seismic performance of differentmodels,which includes reinforcement concrete panels and gravity-type and hollowprecast concrete ER walls,was simulated and examined using the FE approach.It also displays comparative studies such as stress distribution,deflection of the wall,acceleration across the wall height,lateral wall displacement,lateral wall pressure,and backfill plastic strain.Three components of the created ER walls were found throughout this research procedure.One is a granular reinforcement backfill,while the other is a wall-facing panel and base foundation.The dynamic response effects of varied earth-retaining walls have also been studied.It was discovered that the facing panel of the model significantly impacts the earthquake-induced displacement of ER walls.The proposed analytical model’s validity has been evaluated and compared with the reinforcement concrete facing panels,gravity-type ER wall,scientifically available data,and American Association of State Highway and Transportation Officials(AASHTO)guidelines results based on FE simulation.The results of the observations indicate that the hollow prefabricated concrete ER wall is the most feasible option due to its lower displacement and high-stress distribution compared to the two types.The methodology and results of this study establish standards for future analogous investigations and professionals,particularly in light of the increasing computational capabilities of desktop computers.展开更多
Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_...Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.展开更多
BACKGROUND Brain arteriovenous malformations(bAVMs)remains one of the most prevalent causes of intracranial hemorrhage and stroke-like syndromes in the young adult population.Although it has been agreed upon that defi...BACKGROUND Brain arteriovenous malformations(bAVMs)remains one of the most prevalent causes of intracranial hemorrhage and stroke-like syndromes in the young adult population.Although it has been agreed upon that definitive treatment using either single or multi-modal approach is warranted for successful bAVM management,much debate still revolves regarding the optimal timing of definitive treatment.CASE SUMMARY In this report,we present a case of delayed,definitive endovascular treatment for ruptured bAVM in a 21-year-old female,3 mo post-ictus.The bAVM,with a left pericallosal feeding artery and cortical draining veins,was successfully obliterated through embolization using the Onyx 18.On follow-up the patient has recommenced her daily activities and experiences only mild occasional headaches with mild motor deficits.The report leads to our review on an important issue regarding the optimal timing of ruptured bAVM definitive management and bring forward the current evidence available on delayed vs immediate definitive bAVM intervention.We also highlight current issues that need to be addressed for clearer guidelines on definitive therapy initiation.CONCLUSION Current treatment paradigms of ruptured bAVM remains elusive,with substantial heterogeneity in the current literature.A consensus on the definition of“acute”vs“delayed”,management goal,follow-up length and outcome parameters are required to support formation of a clear paradigm.展开更多
Since colossal ionic conductivity was detected in the planar heterostructures consisting of fluorite and perovskite,heterostructures have drawn great research interest as potential electrolytes for solid oxide fuel ce...Since colossal ionic conductivity was detected in the planar heterostructures consisting of fluorite and perovskite,heterostructures have drawn great research interest as potential electrolytes for solid oxide fuel cells(SOFCs).However,so far,the practical uses of such promising material have failed to materialize in SOFCs due to the short circuit risk caused by SrTiO3.In this study,a series of fluorite/perovskite heterostructures made of Sm-doped CeO2 and SrTiO3(SDC–STO)are developed in a new bulk-heterostructure form and evaluated as electrolytes.The prepared cells exhibit a peak power density of 892 mW cm−2 along with open circuit voltage of 1.1 V at 550°C for the optimal composition of 4SDC–6STO.Further electrical studies reveal a high ionic conductivity of 0.05–0.14 S cm^−1 at 450–550°C,which shows remarkable enhancement compared to that of simplex SDC.Via AC impedance analysis,it has been shown that the small grain-boundary and electrode polarization resistances play the major roles in resulting in the superior performance.Furthermore,a Schottky junction effect is proposed by considering the work functions and electronic affinities to interpret the avoidance of short circuit in the SDC–STO cell.Our findings thus indicate a new insight to design electrolytes for low-temperature SOFCs.展开更多
Rare earth(RE)low doping has a significant influence on the structural,morphological,and magnetic properties of spinel ferrite nanoparticles.Therefore,rare earth neodymium(Nd)oxide was fully doped into spinel ferrite ...Rare earth(RE)low doping has a significant influence on the structural,morphological,and magnetic properties of spinel ferrite nanoparticles.Therefore,rare earth neodymium(Nd)oxide was fully doped into spinel ferrite with a composition of Co_(0.80)Ni_(0.20)Nd_xFe_(2-x)O_4(x=0.0,0.05,0.10,and 0.15)using the sol-gel auto combustion method.Structural analysis of the synthesized samples with low doping of Nd using X-ray diffraction(XRD)and Rietveld refinements reveals a pure single-phase cubic structure,while the second phase appears with increasing content of Nd^(3+)at x=0.10 and 0.15.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HR-TEM)show well-shaped spherical grains within the nanometer range of the pure Co_(0.80)Ni_(0.20)Fe_(2)O_(4) sample,while larger grains with the presence of agglomeration are observed with doping of Nd^(3+)into the spinel ferrite nanoparticles.The magnetic parameters,i.e.,saturation magnetization M_s,remanence and magnetic moments exhibit decreasing trend with Nd^(3+)doping and M_s values are in 65.69 to 53.34 emu/g range.The coercivity of the Nd-doped Co-Ni spinel ferrite sample was calculated to be 1037.76 to~827.24 Oe.This work demonstrates remarkable improvements in the structural and magnetic characteristics of Nddoped Co-Ni spinel ferrite nanoparticles for multiple versatile applications.展开更多
In this paper,six different types of silicone rubberbased composites were investigated for applications in high voltage insulation through multi-stress accelerated aging conducted for a period of 5000 h both under AC ...In this paper,six different types of silicone rubberbased composites were investigated for applications in high voltage insulation through multi-stress accelerated aging conducted for a period of 5000 h both under AC and DC voltages.The main goal of this study was lifetime prediction of HTV-SR based composites at a typical multi-stress aging conditions.Several diagnostic techniques such as hydrophobicity assessment,leakage current measurement and FTIR were incorporated to assess the aging.As an outcome of this investigation,all the five hybrid samples were found as quite resistant to aging while the neat sample was comparatively,less resistant to the aging.Overall,among the studied samples,TS2 and TS4 appeared to have shown the highest resistance to aging giving a service life of 43.2 and 42 years,respectively under AC aging.Under DC stress the order of merit of investigated samples was identical to that of AC stress but having marginally less life spans.展开更多
The aging (biological deterioration) is a major problem of composite insulators now-a-days. The main thing in aging is to predict how, when and with what speed it occurs and under what conditions it can lead to failur...The aging (biological deterioration) is a major problem of composite insulators now-a-days. The main thing in aging is to predict how, when and with what speed it occurs and under what conditions it can lead to failure and what overall average expected life of a composite insulator is. For this a lot of researches have been done. This review summarizes the methods of artificial field testing (aging), natural testing, standards the developed for aging, techniques of analysis, results achieved until now about various parameters from various locations, handling guidelines and a conclusion on what is further needed.展开更多
We report the design,fabrication and characterization of a microelectromechanical systems(MEMS)flow control device for gas chromatography(GC)with the capability of sustaining high-temperature environments.We further d...We report the design,fabrication and characterization of a microelectromechanical systems(MEMS)flow control device for gas chromatography(GC)with the capability of sustaining high-temperature environments.We further demonstrate the use of this new device in a novel MEMS chopper-modulated gas chromatography-electroantennography(MEMS-GC-EAG)system to identify specific volatile organic compounds(VOCs)at extremely low concentrations.The device integrates four pneumatically actuated microvalves constructed via thermocompression bonding of the polyimide membrane between two glass substrates with microstructures.The overall size of the device is 32 mm×32 mm,and it is packaged in a 50 mm×50 mm aluminum housing that provides access to the fluidic connections and allows thermal control.The characterization reveals that each microvalve in the flow control chip provides an ON to OFF ratio as high as 1000:1.The device can operate reliably for more than 1 million switching cycles at a working temperature of 300℃.Using the MEMS-GC-EAG system,we demonstrate the successful detection of cis-11-hexadecenal with a concentration as low as 1 pg at a demodulation frequency of 2 Hz by using an antenna harvested from the male Helicoverpa Virescens moth.In addition,1μg of a green leafy volatile(GLV)is barely detected using the conventional GC-EAG,while MEMS-GC-EAG can readily detect the same amount of GLV,with an improvement in the signal-to-noise ratio(SNR)of~22 times.We expect that the flow control device presented in this report will allow researchers to explore new applications and make new discoveries in entomology and other fields that require high-temperature flow control at the microscale.展开更多
Miniaturized gas chromatography(μGC)systems hold potential for the rapid analysis of volatile organic compounds(VOCs)in an extremely compact and low-power enabled platform.Here,we utilize microfabrication technology ...Miniaturized gas chromatography(μGC)systems hold potential for the rapid analysis of volatile organic compounds(VOCs)in an extremely compact and low-power enabled platform.Here,we utilize microfabrication technology to demonstrate the single chip integration of the key components of aμGC system in a two-step planar fabrication process.The 1.5×3 cm microfluidic platform includes a sample injection unit,a micromachined semi-packed separation column(μSC)and a micro-helium discharge photoionization detector(μDPID).The sample injection unit consists of a T-shaped channel operated with an equally simple setup involving a single three-way fluidic valve,a micropump for sample loading and a carrier gas supply for subsequent analysis of the VOCs.The innovative sample injection technique described herein requires a loading time of only a few seconds and produces sharp and repeatable sample pulses(full width at half maximum of approximately 200 ms)at a carrier gas flow rate that is compatible with efficient chromatographic separation.Furthermore,our comprehensive characterization of the chip reveals that a wide variety of VOCs with boiling points in the range of 110–216℃ can be analyzed in less than 1 min by optimizing the flow and temperature programming conditions.Moreover,the analysis of four VOCs at the concentration level of one part per million in an aqueous sample(which corresponds to a headspace concentration in the lower parts-per-billion regime)was performed with a sampling time of only 6 s.The μDPID has demonstrated a linear dynamic range over three orders of magnitude.The system presented here could potentially be used to monitor hazardous VOCs in real time in industrial workplaces and residential settings.展开更多
基金supported by Supported by the Science and Technology Research Program of the Institute of Mountain Hazards and Environment,CAS(IMHE-ZDRW-01)the National Natural Science Foundation of China,China(Grant Numbers:42077275&42271086)the Special Project of Basic Research-Key Project,Yunnan(Grant Number:202301AS070039).
文摘The present work aims to assess earthquake-induced earth-retaining(ER)wall displacement.This study is on the dynamics analysis of various earth-retaining wall designs in hollow precast concrete panels,reinforcement concrete facing panels,and gravity-type earth-retaining walls.The finite element(FE)simulations utilized a 3D plane strain condition to model full-scale ER walls and numerous nonlinear dynamics analyses.The seismic performance of differentmodels,which includes reinforcement concrete panels and gravity-type and hollowprecast concrete ER walls,was simulated and examined using the FE approach.It also displays comparative studies such as stress distribution,deflection of the wall,acceleration across the wall height,lateral wall displacement,lateral wall pressure,and backfill plastic strain.Three components of the created ER walls were found throughout this research procedure.One is a granular reinforcement backfill,while the other is a wall-facing panel and base foundation.The dynamic response effects of varied earth-retaining walls have also been studied.It was discovered that the facing panel of the model significantly impacts the earthquake-induced displacement of ER walls.The proposed analytical model’s validity has been evaluated and compared with the reinforcement concrete facing panels,gravity-type ER wall,scientifically available data,and American Association of State Highway and Transportation Officials(AASHTO)guidelines results based on FE simulation.The results of the observations indicate that the hollow prefabricated concrete ER wall is the most feasible option due to its lower displacement and high-stress distribution compared to the two types.The methodology and results of this study establish standards for future analogous investigations and professionals,particularly in light of the increasing computational capabilities of desktop computers.
基金supported by the Basic Science Research Program of the National Research Foundation(NRF)of South Koreafunded by the Ministry of Science&ICT and Future Planning(NRF-2020M3H4A3081889)KIST Institutional Program of South Korea(Project Nos.2E31860)。
文摘Elucidation of a reaction mechanism is the most critical aspect for designing electrodes for highperformance secondary batteries.Herein,we investigate the sodium insertion/extraction into an iron fluoride hydrate(FeF_(3)·0.5H_(2)O)electrode for sodium-ion batteries(SIBs).The electrode material is prepared by employing an ionic liquid 1-butyl-3-methylimidazolium-tetrafluoroborate,which serves as a reaction medium and precursor for F^(-)ions.The crystal structure of FeF_(3)·0.5H_(2)O is observed as pyrochlore type with large open 3-D tunnels and a unit cell volume of 1129A^(3).The morphology of FeF_(3)·0.5H_(2)O is spherical shape with a mesoporous structure.The microstructure analysis reveals primary particle size of around 10 nm.The FeF_(3)·0.5H_(2)O cathode exhibits stable discharge capacities of 158,210,and 284 mA h g^(-1) in three different potential ranges of 1.5-4.5,1.2-4.5,and 1.0-4.5 V,respectively at 0.05 C rate.The specific capacities remained stable in over 50 cycles in all three potential ranges,while the rate capability was best in the potential range of 1.5-4.5 V.The electrochemical sodium storage mechanism is studied using X-ray absorption spectroscopy,indicating higher conversion at a more discharged state.Ex-situ M?ssbauer spectroscopy strengthens the results for reversible reduction/oxidation of Fe.These results will be favorable to establish high-performance cathode materials with selective voltage window for SIBs.
文摘BACKGROUND Brain arteriovenous malformations(bAVMs)remains one of the most prevalent causes of intracranial hemorrhage and stroke-like syndromes in the young adult population.Although it has been agreed upon that definitive treatment using either single or multi-modal approach is warranted for successful bAVM management,much debate still revolves regarding the optimal timing of definitive treatment.CASE SUMMARY In this report,we present a case of delayed,definitive endovascular treatment for ruptured bAVM in a 21-year-old female,3 mo post-ictus.The bAVM,with a left pericallosal feeding artery and cortical draining veins,was successfully obliterated through embolization using the Onyx 18.On follow-up the patient has recommenced her daily activities and experiences only mild occasional headaches with mild motor deficits.The report leads to our review on an important issue regarding the optimal timing of ruptured bAVM definitive management and bring forward the current evidence available on delayed vs immediate definitive bAVM intervention.We also highlight current issues that need to be addressed for clearer guidelines on definitive therapy initiation.CONCLUSION Current treatment paradigms of ruptured bAVM remains elusive,with substantial heterogeneity in the current literature.A consensus on the definition of“acute”vs“delayed”,management goal,follow-up length and outcome parameters are required to support formation of a clear paradigm.
基金The authors acknowledge funding from the Shanghai Pujiang Program,the National Natural Science Foundation of China(12004103)Hubei Provincial Natural Science Foundation of China(No.2020CFB414)+1 种基金Fundamental Research Funds for the Central Universities(19D111317,20D110638/003 and 274-10-0001/003)start-up grant from Donghua University(No.113-07-0053058).
文摘Since colossal ionic conductivity was detected in the planar heterostructures consisting of fluorite and perovskite,heterostructures have drawn great research interest as potential electrolytes for solid oxide fuel cells(SOFCs).However,so far,the practical uses of such promising material have failed to materialize in SOFCs due to the short circuit risk caused by SrTiO3.In this study,a series of fluorite/perovskite heterostructures made of Sm-doped CeO2 and SrTiO3(SDC–STO)are developed in a new bulk-heterostructure form and evaluated as electrolytes.The prepared cells exhibit a peak power density of 892 mW cm−2 along with open circuit voltage of 1.1 V at 550°C for the optimal composition of 4SDC–6STO.Further electrical studies reveal a high ionic conductivity of 0.05–0.14 S cm^−1 at 450–550°C,which shows remarkable enhancement compared to that of simplex SDC.Via AC impedance analysis,it has been shown that the small grain-boundary and electrode polarization resistances play the major roles in resulting in the superior performance.Furthermore,a Schottky junction effect is proposed by considering the work functions and electronic affinities to interpret the avoidance of short circuit in the SDC–STO cell.Our findings thus indicate a new insight to design electrolytes for low-temperature SOFCs.
基金Project supported by the Industry-University-Research Cooperation Project of Jiangsu Province in China (BY2021057)the Qing Lan Project of Jiangsu Province (BY2021011)Jiangsu Province Higher Vocational College Young Teachers Enterprise Practice Training Funding Project (2021QYSJ048)。
文摘Rare earth(RE)low doping has a significant influence on the structural,morphological,and magnetic properties of spinel ferrite nanoparticles.Therefore,rare earth neodymium(Nd)oxide was fully doped into spinel ferrite with a composition of Co_(0.80)Ni_(0.20)Nd_xFe_(2-x)O_4(x=0.0,0.05,0.10,and 0.15)using the sol-gel auto combustion method.Structural analysis of the synthesized samples with low doping of Nd using X-ray diffraction(XRD)and Rietveld refinements reveals a pure single-phase cubic structure,while the second phase appears with increasing content of Nd^(3+)at x=0.10 and 0.15.Scanning electron microscopy(SEM)and high-resolution transmission electron microscopy(HR-TEM)show well-shaped spherical grains within the nanometer range of the pure Co_(0.80)Ni_(0.20)Fe_(2)O_(4) sample,while larger grains with the presence of agglomeration are observed with doping of Nd^(3+)into the spinel ferrite nanoparticles.The magnetic parameters,i.e.,saturation magnetization M_s,remanence and magnetic moments exhibit decreasing trend with Nd^(3+)doping and M_s values are in 65.69 to 53.34 emu/g range.The coercivity of the Nd-doped Co-Ni spinel ferrite sample was calculated to be 1037.76 to~827.24 Oe.This work demonstrates remarkable improvements in the structural and magnetic characteristics of Nddoped Co-Ni spinel ferrite nanoparticles for multiple versatile applications.
文摘In this paper,six different types of silicone rubberbased composites were investigated for applications in high voltage insulation through multi-stress accelerated aging conducted for a period of 5000 h both under AC and DC voltages.The main goal of this study was lifetime prediction of HTV-SR based composites at a typical multi-stress aging conditions.Several diagnostic techniques such as hydrophobicity assessment,leakage current measurement and FTIR were incorporated to assess the aging.As an outcome of this investigation,all the five hybrid samples were found as quite resistant to aging while the neat sample was comparatively,less resistant to the aging.Overall,among the studied samples,TS2 and TS4 appeared to have shown the highest resistance to aging giving a service life of 43.2 and 42 years,respectively under AC aging.Under DC stress the order of merit of investigated samples was identical to that of AC stress but having marginally less life spans.
文摘The aging (biological deterioration) is a major problem of composite insulators now-a-days. The main thing in aging is to predict how, when and with what speed it occurs and under what conditions it can lead to failure and what overall average expected life of a composite insulator is. For this a lot of researches have been done. This review summarizes the methods of artificial field testing (aging), natural testing, standards the developed for aging, techniques of analysis, results achieved until now about various parameters from various locations, handling guidelines and a conclusion on what is further needed.
基金We also thank DuPont for providing the polyimide membrane samples.This work was supported by the National Science Foundation under Grant Number DBI-1353870,which was offered to S-YZ and TCB.
文摘We report the design,fabrication and characterization of a microelectromechanical systems(MEMS)flow control device for gas chromatography(GC)with the capability of sustaining high-temperature environments.We further demonstrate the use of this new device in a novel MEMS chopper-modulated gas chromatography-electroantennography(MEMS-GC-EAG)system to identify specific volatile organic compounds(VOCs)at extremely low concentrations.The device integrates four pneumatically actuated microvalves constructed via thermocompression bonding of the polyimide membrane between two glass substrates with microstructures.The overall size of the device is 32 mm×32 mm,and it is packaged in a 50 mm×50 mm aluminum housing that provides access to the fluidic connections and allows thermal control.The characterization reveals that each microvalve in the flow control chip provides an ON to OFF ratio as high as 1000:1.The device can operate reliably for more than 1 million switching cycles at a working temperature of 300℃.Using the MEMS-GC-EAG system,we demonstrate the successful detection of cis-11-hexadecenal with a concentration as low as 1 pg at a demodulation frequency of 2 Hz by using an antenna harvested from the male Helicoverpa Virescens moth.In addition,1μg of a green leafy volatile(GLV)is barely detected using the conventional GC-EAG,while MEMS-GC-EAG can readily detect the same amount of GLV,with an improvement in the signal-to-noise ratio(SNR)of~22 times.We expect that the flow control device presented in this report will allow researchers to explore new applications and make new discoveries in entomology and other fields that require high-temperature flow control at the microscale.
基金This work was partially supported by the National Institute for Occupational Safety and Health(NIOSH)under award No.1R21OH010330 and Virginia Tech's Institute for Critical Technology and Applied Science(ICTAS).
文摘Miniaturized gas chromatography(μGC)systems hold potential for the rapid analysis of volatile organic compounds(VOCs)in an extremely compact and low-power enabled platform.Here,we utilize microfabrication technology to demonstrate the single chip integration of the key components of aμGC system in a two-step planar fabrication process.The 1.5×3 cm microfluidic platform includes a sample injection unit,a micromachined semi-packed separation column(μSC)and a micro-helium discharge photoionization detector(μDPID).The sample injection unit consists of a T-shaped channel operated with an equally simple setup involving a single three-way fluidic valve,a micropump for sample loading and a carrier gas supply for subsequent analysis of the VOCs.The innovative sample injection technique described herein requires a loading time of only a few seconds and produces sharp and repeatable sample pulses(full width at half maximum of approximately 200 ms)at a carrier gas flow rate that is compatible with efficient chromatographic separation.Furthermore,our comprehensive characterization of the chip reveals that a wide variety of VOCs with boiling points in the range of 110–216℃ can be analyzed in less than 1 min by optimizing the flow and temperature programming conditions.Moreover,the analysis of four VOCs at the concentration level of one part per million in an aqueous sample(which corresponds to a headspace concentration in the lower parts-per-billion regime)was performed with a sampling time of only 6 s.The μDPID has demonstrated a linear dynamic range over three orders of magnitude.The system presented here could potentially be used to monitor hazardous VOCs in real time in industrial workplaces and residential settings.
