A 110-year ensemble simulation of an ocean general circulation model(OGCM)was analyzed to identify the modulation of salinity interdecadal variability on El Niño-Southern Oscillation(ENSO)amplitude in the tropica...A 110-year ensemble simulation of an ocean general circulation model(OGCM)was analyzed to identify the modulation of salinity interdecadal variability on El Niño-Southern Oscillation(ENSO)amplitude in the tropical Pacific during 1901-2010.The simulating results show that sea surface salinity(SSS)variation in the region exhibits notable and coherent interdecadal variability signal,which is closely associated with the Interdecadal Pacific Oscillation(IPO).As salinity increases or reduces,the SSS modulations on ENSO amplitude during its warm/cold events vary asymmetrically with positive/negative IPO phases.Physically,salinity interdecadal variability can enhance or reduce ENSO-related conditions in upper-ocean stratification,contributing noticeably to ENSO variability.Salinity anomalies associated with the mixed layer depth and barrier layer thickness can modulate ENSO amplitude during positive and negative IPO phases,resulting in the asymmetry of sea surface temperature(SST)anomaly in the tropical Pacific.During positive IPO phases,SSS interdecadal variability contributes positively to El Niño amplitude but negatively to La Niña amplitude by enhancing or reducing SSS interannual variability,and vice versa during negative IPO phases.Quantitatively,the results indicate that the modulation of the ENSO amplitude by the SSS interdecadal variability is 15%-28%during negative IPO phases and 30%-20%during positive IPO phases,respectively.Evidently,the SSS interdecadal variability associated with IPO and its modulation on ENSO amplitude in the tropical Pacific are among factors essentially contributing ENSO diversity.展开更多
The dynamic frictional behaviors of natural discontinuities(joints,fractures,faults)play an important role in geohazards assessment;however,the mechanisms of the dynamic fault weakening/strengthening are still unclear...The dynamic frictional behaviors of natural discontinuities(joints,fractures,faults)play an important role in geohazards assessment;however,the mechanisms of the dynamic fault weakening/strengthening are still unclear.In this paper,a dynamic shear box was used to perform direct shear tests on saw-cut(planar)and natural(rough)granite fractures,with different normal load oscillation amplitudes.Based on the recorded shear forces and normal displacements,the shear forces,apparent friction coefficients and normal displacements are found to change periodically with oscillated normal loads and are characterized by a series of time shifts.The observed changing patterns are similar for the rough and planar fractures.Compared with the test data under constant normal load(CNL),small/large normal load oscillation amplitude enhances/reduces the peak shear strength,with a critical point.The magnitude of critical normal load oscillation for the rough fractures is smaller than the planer fractures.The results imply that dynamic fault weakening/strengthening can be achieved by both normal load oscillation amplitudes and slip surface topography.The rough fractures with larger normal oscillation amplitude can easily cause frictional weakening under stress disturbance.展开更多
In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for...In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for the MEMS gyroscope in digital closed-loop control is proposed, which utilizes a digital phase-locked loop （PLL） in frequency control and an automatic gain control （AGC） method in amplitude control. A digital processing circuit with a field programmable gate array （FPGA） is designed and the experiments are carried out. The results indicate that when the temperature changes, the drive frequency can automatically track the resonant frequency of gyroscope in drive mode and that of the oscillating amplitude holds at a set value. And at room temperature, the relative deviation of the drive frequency is 0.624 ×10^-6 and the oscillating amplitude is 8.0 ×10^-6, which are 0. 094% and 18. 39% of the analog control program, respectively. Therefore, the control solution of the digital PLL in frequency and the AGC in amplitude is feasible.展开更多
Multiple sclerosis is associated with structural and functional brain alterations leading to cognitive impairments across multiple domains including attention,memory,and the speed of information processing.The hippoca...Multiple sclerosis is associated with structural and functional brain alterations leading to cognitive impairments across multiple domains including attention,memory,and the speed of information processing.The hippocampus,which is a brain important structure involved in memory,undergoes microstructural changes in the early stage of multiple sclerosis.In this study,we analyzed hippocampal function and structure in patients with relapsing-remitting multiple sclerosis and explored correlations between the functional connectivity of the hippocampus to the whole brain,changes in local brain function and microstructure,and cognitive function at rest.We retrospectively analyzed data from 20 relapsing-remitting multiple sclerosis patients admitted to the Department of Neurology at the China-Japan Union Hospital of Jilin University,China,from April 2015 to November 2019.Sixteen healthy volunteers were recruited as the healthy control group.All participants were evaluated using a scale of extended disability status and the Montreal cognitive assessment within 1 week before and after head diffusion tensor imaging and functional magnetic resonance imaging.Compared with the healthy control group,the patients with relapsing-remitting multiple sclerosis had lower Montreal cognitive assessment scores and regions of simultaneously enhanced and attenuated whole-brain functional connectivity and local functional connectivity in the bilateral hippocampus.Hippocampal diffusion tensor imaging data showed that,compared with the healthy control group,patients with relapsing-remitting multiple sclerosis had lower hippocampal fractional anisotropy values and higher mean diffusivity values,suggesting abnormal hippocampal structure.The left hippocampus whole-brain functional connectivity was negatively correlated with the Montreal cognitive assessment score(r=-0.698,P=0.025),and whole-brain functional connectivity of the right hippocampus was negatively correlated with extended disability status scale score(r=-0.649,P=0.042).The mean diffusivity value of the left hippocampus was negatively correlated with the Montreal cognitive assessment score(r=-0.729,P=0.017)and positively correlated with the extended disability status scale score(r=0.653,P=0.041).The right hippocampal mean diffusivity value was positively correlated with the extended disability status scale score(r=0.684,P=0.029).These data suggest that the functional connectivity and presence of structural abnormalities in the hippocampus in patients with relapse-remission multiple sclerosis are correlated with the degree of cognitive function and extent of disability.This study was approved by the Ethics Committee of China-Japan Union Hospital of Jilin University,China(approval No.201702202)on February 22,2017.展开更多
The nonlinear aeroelastic response of a two-degree-of-freedom airfoil with freeplay and cubic nonlinearities in supersonic flows is investigated. The second-order piston theory is used to analyze a double-wedge airfoi...The nonlinear aeroelastic response of a two-degree-of-freedom airfoil with freeplay and cubic nonlinearities in supersonic flows is investigated. The second-order piston theory is used to analyze a double-wedge airfoil. Then, the fold bifurcation and the amplitude jump phenomenon are detected by the averaging method and the multi-variable Floquet theory. The analyticall results are further verified by numerical simulations. Finally, the influence of the freeplay parameters on the aeroelastic response is analyzed in detail.展开更多
Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic glasses.Here the effect of oscillation strain amplitude on ...Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic glasses.Here the effect of oscillation strain amplitude on the secondary relaxation of a typical Labased metallic glass was studied using the dynamic mechanical analysis method.The apparent activation energy of theβrelaxation is shown to increase with the oscillation strain amplitude.When it changes from 0.02%to 0.16%,the activation energy increases from 0.73 to 0.96 eV.Simultaneously,the intensity of theβrelaxation shifts toward high temperature.Additionally,the apparentβrelaxation is found to be sensitive to the physical aging below the glass transition temperature.The findings suggest a correlation between the inelastic deformation and the relaxation behavior of amorphous metals.展开更多
基金Supported by the National Natural Science Foundation of China(No.42030410)the Laoshan Laboratory(No.LSKJ 202202403)supported by the Startup Foundation for Introducing Talent of NUIST。
文摘A 110-year ensemble simulation of an ocean general circulation model(OGCM)was analyzed to identify the modulation of salinity interdecadal variability on El Niño-Southern Oscillation(ENSO)amplitude in the tropical Pacific during 1901-2010.The simulating results show that sea surface salinity(SSS)variation in the region exhibits notable and coherent interdecadal variability signal,which is closely associated with the Interdecadal Pacific Oscillation(IPO).As salinity increases or reduces,the SSS modulations on ENSO amplitude during its warm/cold events vary asymmetrically with positive/negative IPO phases.Physically,salinity interdecadal variability can enhance or reduce ENSO-related conditions in upper-ocean stratification,contributing noticeably to ENSO variability.Salinity anomalies associated with the mixed layer depth and barrier layer thickness can modulate ENSO amplitude during positive and negative IPO phases,resulting in the asymmetry of sea surface temperature(SST)anomaly in the tropical Pacific.During positive IPO phases,SSS interdecadal variability contributes positively to El Niño amplitude but negatively to La Niña amplitude by enhancing or reducing SSS interannual variability,and vice versa during negative IPO phases.Quantitatively,the results indicate that the modulation of the ENSO amplitude by the SSS interdecadal variability is 15%-28%during negative IPO phases and 30%-20%during positive IPO phases,respectively.Evidently,the SSS interdecadal variability associated with IPO and its modulation on ENSO amplitude in the tropical Pacific are among factors essentially contributing ENSO diversity.
基金the funding support from the National Natural Science Foundation of China (Grant No. 51904359)the Guangdong Provincial Department of Science and Technology (Grant No. 2019ZT08G090)the Open Research Fund of the State Key Laboratory of Coal Resources and Safe Mining, China University of Mining and Technology (CUMT) (Grant No. SKLCRSM20KF002)
文摘The dynamic frictional behaviors of natural discontinuities(joints,fractures,faults)play an important role in geohazards assessment;however,the mechanisms of the dynamic fault weakening/strengthening are still unclear.In this paper,a dynamic shear box was used to perform direct shear tests on saw-cut(planar)and natural(rough)granite fractures,with different normal load oscillation amplitudes.Based on the recorded shear forces and normal displacements,the shear forces,apparent friction coefficients and normal displacements are found to change periodically with oscillated normal loads and are characterized by a series of time shifts.The observed changing patterns are similar for the rough and planar fractures.Compared with the test data under constant normal load(CNL),small/large normal load oscillation amplitude enhances/reduces the peak shear strength,with a critical point.The magnitude of critical normal load oscillation for the rough fractures is smaller than the planer fractures.The results imply that dynamic fault weakening/strengthening can be achieved by both normal load oscillation amplitudes and slip surface topography.The rough fractures with larger normal oscillation amplitude can easily cause frictional weakening under stress disturbance.
基金The National Natural Science Foundation of China(No. 60974116 )the Research Fund of Aeronautics Science (No.20090869007)Specialized Research Fund for the Doctoral Program of Higher Education (No. 200902861063)
文摘In order to effectively control the working state of the gyroscope in drive mode, the drive characteristics of the micro electromechanical system （MEMS） gyroscope are analyzed in principle. A novel drive circuit for the MEMS gyroscope in digital closed-loop control is proposed, which utilizes a digital phase-locked loop （PLL） in frequency control and an automatic gain control （AGC） method in amplitude control. A digital processing circuit with a field programmable gate array （FPGA） is designed and the experiments are carried out. The results indicate that when the temperature changes, the drive frequency can automatically track the resonant frequency of gyroscope in drive mode and that of the oscillating amplitude holds at a set value. And at room temperature, the relative deviation of the drive frequency is 0.624 ×10^-6 and the oscillating amplitude is 8.0 ×10^-6, which are 0. 094% and 18. 39% of the analog control program, respectively. Therefore, the control solution of the digital PLL in frequency and the AGC in amplitude is feasible.
基金supported by the Project of International Cooperation of Jilin Province in China,No.20180414062GH(to XMH)Health research talents Project of Jilin Province in China,No.2019sc2018(to XMH)。
文摘Multiple sclerosis is associated with structural and functional brain alterations leading to cognitive impairments across multiple domains including attention,memory,and the speed of information processing.The hippocampus,which is a brain important structure involved in memory,undergoes microstructural changes in the early stage of multiple sclerosis.In this study,we analyzed hippocampal function and structure in patients with relapsing-remitting multiple sclerosis and explored correlations between the functional connectivity of the hippocampus to the whole brain,changes in local brain function and microstructure,and cognitive function at rest.We retrospectively analyzed data from 20 relapsing-remitting multiple sclerosis patients admitted to the Department of Neurology at the China-Japan Union Hospital of Jilin University,China,from April 2015 to November 2019.Sixteen healthy volunteers were recruited as the healthy control group.All participants were evaluated using a scale of extended disability status and the Montreal cognitive assessment within 1 week before and after head diffusion tensor imaging and functional magnetic resonance imaging.Compared with the healthy control group,the patients with relapsing-remitting multiple sclerosis had lower Montreal cognitive assessment scores and regions of simultaneously enhanced and attenuated whole-brain functional connectivity and local functional connectivity in the bilateral hippocampus.Hippocampal diffusion tensor imaging data showed that,compared with the healthy control group,patients with relapsing-remitting multiple sclerosis had lower hippocampal fractional anisotropy values and higher mean diffusivity values,suggesting abnormal hippocampal structure.The left hippocampus whole-brain functional connectivity was negatively correlated with the Montreal cognitive assessment score(r=-0.698,P=0.025),and whole-brain functional connectivity of the right hippocampus was negatively correlated with extended disability status scale score(r=-0.649,P=0.042).The mean diffusivity value of the left hippocampus was negatively correlated with the Montreal cognitive assessment score(r=-0.729,P=0.017)and positively correlated with the extended disability status scale score(r=0.653,P=0.041).The right hippocampal mean diffusivity value was positively correlated with the extended disability status scale score(r=0.684,P=0.029).These data suggest that the functional connectivity and presence of structural abnormalities in the hippocampus in patients with relapse-remission multiple sclerosis are correlated with the degree of cognitive function and extent of disability.This study was approved by the Ethics Committee of China-Japan Union Hospital of Jilin University,China(approval No.201702202)on February 22,2017.
文摘The nonlinear aeroelastic response of a two-degree-of-freedom airfoil with freeplay and cubic nonlinearities in supersonic flows is investigated. The second-order piston theory is used to analyze a double-wedge airfoil. Then, the fold bifurcation and the amplitude jump phenomenon are detected by the averaging method and the multi-variable Floquet theory. The analyticall results are further verified by numerical simulations. Finally, the influence of the freeplay parameters on the aeroelastic response is analyzed in detail.
基金supported by the National Natural Science Foundation of China(Grant Nos.51971178 and 52271153)the Natural Science Basic Research Plan for Distinguished Young Scholars in Shaanxi Province(Grant No.2021JC-12)+4 种基金the Natural Science Foundation of Chongqing(Grant No.cstc2020jcyj-jq X0001)financial support from“Proyecto PID2020-112975GB-I00 de investigación financiado por MCIN/AEI/10.13039/501100011033”Generalitat de Catalunya AGAUR 2021-SGR-343 grantsupported by the National Natural Science Foundation of China(Grant No.12072344)the Youth Innovation Promotion Association of the Chinese Academy of Sciences。
文摘Dynamic mechanical relaxation processes,particularly secondary relaxation processes,are closely related to the mechanical and physical properties of metallic glasses.Here the effect of oscillation strain amplitude on the secondary relaxation of a typical Labased metallic glass was studied using the dynamic mechanical analysis method.The apparent activation energy of theβrelaxation is shown to increase with the oscillation strain amplitude.When it changes from 0.02%to 0.16%,the activation energy increases from 0.73 to 0.96 eV.Simultaneously,the intensity of theβrelaxation shifts toward high temperature.Additionally,the apparentβrelaxation is found to be sensitive to the physical aging below the glass transition temperature.The findings suggest a correlation between the inelastic deformation and the relaxation behavior of amorphous metals.
