Background:Segment coordination variability(CV)is a movement pattern associated with running-related injuries.It can also be adversely affected by a prolonged run.However,research on this topic is currently limited.Th...Background:Segment coordination variability(CV)is a movement pattern associated with running-related injuries.It can also be adversely affected by a prolonged run.However,research on this topic is currently limited.The purpose of this study was to investigate the effects of a prolonged run on segment CV and vertical loading rates during a treadmill half marathon.Methods:Fifteen healthy runners ran a half marathon on an instrumental treadmill in a biomechanical laboratory.Synchronized kinematic and kinetic data were collected every 2 km(from 2 km until 20 km),and the data were processed by musculoskeletal modeling.Segment CVs were computed from the angle-angle plots of selected pelvis-thigh,thigh-shank,and shank-rearfoot couplings using a modified vector coding technique.The loading rate of vertical ground reaction force was also calculated.A one-way MANOVA with repeated measures was performed on each of the outcome variables to examine the main effect of running mileage.Results:Significant effects of running mileage were found on segment CVs(p≤0.010)but not on loading rate(p=0.881).Notably,during the early stance phase,the CV of pelvis frontal thigh frontal was significantly increased at 20 km compared with the CV at 8 km(g=0.59,p=0.022).The CV of shank transverse vs.rearfoot frontal decreased from 2 km to 8 km(g=0.30,p=0.020)but then significantly increased at both 18 km(g=0.05,p<0.001)and 20 km(g=0.36,p<0.001).Conclusion:At the early stance,runners maintained stable CVs on the sagittal plane,which could explain the unchanged loading rate throughout the half marathon.However,increased CVs on the frontal/transverse plane may be an early sign of fatigue and indicative of possible injury risk.Further studies are necessary for conclusive statements in this regard.展开更多
This study proposes a novel approach that involves applying the flux vector splitting(FVS)technique to discretize and approximate conservative Navier-Stokes equations and thus reconstruct pressure fields from planar v...This study proposes a novel approach that involves applying the flux vector splitting(FVS)technique to discretize and approximate conservative Navier-Stokes equations and thus reconstruct pressure fields from planar velocimetry data in compressible flows,especially for supersonic flows with strong shocks.Data are typically resolved by using the particle image velocimetry(PIV)technique.Two supersonic experiments under Mach 2.9-3.0 conditions were conducted to generate strong shocks and investigate the performance of the FVS method,including oblique shock flow and shock wave/boundary layer interaction(SWBLI)coupled with flow separation.Reconstructed pressure fields were comprehensively evaluated.The shock polar results indicated that FVS method possessed higher accuracy in post-shock regions with a pressure ratio error of less than2%,especially for the areas downstream of the shock-shock intersection point and the shock-boundary intersection point,where the conventional Poisson method was ineffective and larger errors accumulated.Wall pressure in SWBLI flow also had better agreement.Furthermore,the performances of different methods were discussed from the perspective of the physical characteristics in supersonic flows,which explained the superiority of the FVS method because the pressure information was delivered along the characteristic direction of physical waves.展开更多
Generally, a confocal Fabry-Perot interferometer is only able to detect the out-of-plane component of a displacement field; while the in-plane component often has the information about the material which cannot be fou...Generally, a confocal Fabry-Perot interferometer is only able to detect the out-of-plane component of a displacement field; while the in-plane component often has the information about the material which cannot be found in this out-of-plane component. In this paper, based on a confocal Fabry-Perot interferometer set-up for detecting the out-of-plane component of a laser generated acoustic field, a technique is developed to detect both the out-of-plane and in-plane displacement components simultaneously with a novel two-channel confocal Fabry-Perot interferometer.展开更多
基金supported by General Research Funds granted by the Hong Kong Research Grant Council(#Poly U152065/17E)funding from the National Natural Science Foundation of China(#11732015)。
文摘Background:Segment coordination variability(CV)is a movement pattern associated with running-related injuries.It can also be adversely affected by a prolonged run.However,research on this topic is currently limited.The purpose of this study was to investigate the effects of a prolonged run on segment CV and vertical loading rates during a treadmill half marathon.Methods:Fifteen healthy runners ran a half marathon on an instrumental treadmill in a biomechanical laboratory.Synchronized kinematic and kinetic data were collected every 2 km(from 2 km until 20 km),and the data were processed by musculoskeletal modeling.Segment CVs were computed from the angle-angle plots of selected pelvis-thigh,thigh-shank,and shank-rearfoot couplings using a modified vector coding technique.The loading rate of vertical ground reaction force was also calculated.A one-way MANOVA with repeated measures was performed on each of the outcome variables to examine the main effect of running mileage.Results:Significant effects of running mileage were found on segment CVs(p≤0.010)but not on loading rate(p=0.881).Notably,during the early stance phase,the CV of pelvis frontal thigh frontal was significantly increased at 20 km compared with the CV at 8 km(g=0.59,p=0.022).The CV of shank transverse vs.rearfoot frontal decreased from 2 km to 8 km(g=0.30,p=0.020)but then significantly increased at both 18 km(g=0.05,p<0.001)and 20 km(g=0.36,p<0.001).Conclusion:At the early stance,runners maintained stable CVs on the sagittal plane,which could explain the unchanged loading rate throughout the half marathon.However,increased CVs on the frontal/transverse plane may be an early sign of fatigue and indicative of possible injury risk.Further studies are necessary for conclusive statements in this regard.
基金supported by the National Natural Science Foundation of China(Grant No.12332018)。
文摘This study proposes a novel approach that involves applying the flux vector splitting(FVS)technique to discretize and approximate conservative Navier-Stokes equations and thus reconstruct pressure fields from planar velocimetry data in compressible flows,especially for supersonic flows with strong shocks.Data are typically resolved by using the particle image velocimetry(PIV)technique.Two supersonic experiments under Mach 2.9-3.0 conditions were conducted to generate strong shocks and investigate the performance of the FVS method,including oblique shock flow and shock wave/boundary layer interaction(SWBLI)coupled with flow separation.Reconstructed pressure fields were comprehensively evaluated.The shock polar results indicated that FVS method possessed higher accuracy in post-shock regions with a pressure ratio error of less than2%,especially for the areas downstream of the shock-shock intersection point and the shock-boundary intersection point,where the conventional Poisson method was ineffective and larger errors accumulated.Wall pressure in SWBLI flow also had better agreement.Furthermore,the performances of different methods were discussed from the perspective of the physical characteristics in supersonic flows,which explained the superiority of the FVS method because the pressure information was delivered along the characteristic direction of physical waves.
基金This work was supported by the National Nature Science Foundation of China (No. 10174025 and No.10134020).
文摘Generally, a confocal Fabry-Perot interferometer is only able to detect the out-of-plane component of a displacement field; while the in-plane component often has the information about the material which cannot be found in this out-of-plane component. In this paper, based on a confocal Fabry-Perot interferometer set-up for detecting the out-of-plane component of a laser generated acoustic field, a technique is developed to detect both the out-of-plane and in-plane displacement components simultaneously with a novel two-channel confocal Fabry-Perot interferometer.
