The energy approach is used to theoretically verify that the average acceleration method （AAM）, which is unconditionally stable for linear dynamic systems, is also unconditionally stable for structures with typical ...The energy approach is used to theoretically verify that the average acceleration method （AAM）, which is unconditionally stable for linear dynamic systems, is also unconditionally stable for structures with typical nonlinear damping, including the special case of velocity power type damping with a bilinear restoring force model. Based on the energy approach, the stability of the AAM is proven for SDOF structures using the mathematical features of the velocity power function and for MDOF structures by applying the virtual displacement theorem. Finally, numerical examples are given to demonstrate the accuracy of the theoretical analysis.展开更多
The average acceleration approach was applied to recover a gravity field model Model;CA from GOCE precise science orbits from September 2 to November 2, 2010, and furthermore a so called sequential least square adjust...The average acceleration approach was applied to recover a gravity field model Model;CA from GOCE precise science orbits from September 2 to November 2, 2010, and furthermore a so called sequential least square adjustment was used. The model was compared with other gravity field models based on CHAMP, GRACE and GOCE. The result shows that the model is superior to gravity field based on CHAMP, and with higher accuracy than other international gravity field models based on only GOCE data before 80 degree. The degree geoid height of Model;CA reaches 3cm up to 90 degree and order.展开更多
Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)im...Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)improve interpretability by producing UK Biobank age-referenced centiles for PA volume and intensity;(b)inform public-health messaging by examining how adding recommended quantities of moderate and vigorous PA affect PA volume and intensity.Methods 92,480 UK Biobank participants aged 43-80 years with wrist-worn accelerometer data were included.Average acceleration and intensity gradient were derived as proxies for PA volume and intensity.We generated sex-specific centile curves using Generalized Additive Models for Location Scale and Shape(GAMLSS)and modeled the effect of adding moderate(walking)or vigorous(running)activity on the combined change in the volume and intensity centiles(change in PA profile).Results In men,volume was lower as age increased while intensity was lower after age 55;in women,both volume and intensity were lower as age increased.Adding 150 min of moderate PA weekly(5×30 min walking)increased the PA profile by 4 percentage points.Defining moderate PA as brisk walking approximately doubled the increase(9 percentage points)while 75 min of vigorous PA weekly(5×15 min running)trebled the increase(13 percentage points).Conclusion These UK Biobank reference centiles provide a benchmark for interpretation of accelerometer data.Application of our translational methods demonstrate that meeting PA guidelines through shorter duration vigorous activity is more beneficial to the PA profile(volume and intensity)than longer duration moderate activity.展开更多
Numerical properties of the time integration method proposed by the first author of this paper in 2007 are the same as those of the constant average acceleration method （AAM） for linear elastic systems, except that ...Numerical properties of the time integration method proposed by the first author of this paper in 2007 are the same as those of the constant average acceleration method （AAM） for linear elastic systems, except that the capability to capture dynamic loading was not explored. It was found that there were different quadrature equations to predict the next step displacement increment. A modified quadrature equation of this method was derived so that the equation to determine the next step displacement was numerically equivalent to the equation used in the constant AAM. It was verified that the original form of this method, in general, had a better capability to capture dynamic loadings than the constant AAM. This excellent property, in addition to computational efficiency, will help to make this method competitive with general secondorder accurate integration methods.展开更多
We present an investigation on the propagation properties of the chirped Airy vortex（CAi V） beams through slabs of left-handed materials（LHMs） and right-handed materials（RHMs）. We discuss the influence of chirpe...We present an investigation on the propagation properties of the chirped Airy vortex（CAi V） beams through slabs of left-handed materials（LHMs） and right-handed materials（RHMs）. We discuss the influence of chirped parameter C on the propagation of the CAi V beams through LHM and RHM slabs. Our simulation results show that a maximum accelerated velocity appears during the propagation process. The intensity concentration of the CAi V beams increases with the absolute value of the chirped parameter. The peak intensity of the CAi V beams changes abruptly, and the chirped parameter plays an active role on the difference of the maximum and the minimum. In the energy flow, we find that the effects of the chirped parameter on the strength of the vortex are different at different propagation distances.展开更多
基金National Natural Science Foundation of ChinaUnder Grant No. 50578047, 50338020 China Ministry ofEducation (Program for New Century Excellent Talents inUniversity) China Ministry of Science and Technology UnderGrant No.2003AA602150
文摘The energy approach is used to theoretically verify that the average acceleration method （AAM）, which is unconditionally stable for linear dynamic systems, is also unconditionally stable for structures with typical nonlinear damping, including the special case of velocity power type damping with a bilinear restoring force model. Based on the energy approach, the stability of the AAM is proven for SDOF structures using the mathematical features of the velocity power function and for MDOF structures by applying the virtual displacement theorem. Finally, numerical examples are given to demonstrate the accuracy of the theoretical analysis.
基金supported by the Fundamental Research Funds for the Central Universities(SWJTU12BR012)
文摘The average acceleration approach was applied to recover a gravity field model Model;CA from GOCE precise science orbits from September 2 to November 2, 2010, and furthermore a so called sequential least square adjustment was used. The model was compared with other gravity field models based on CHAMP, GRACE and GOCE. The result shows that the model is superior to gravity field based on CHAMP, and with higher accuracy than other international gravity field models based on only GOCE data before 80 degree. The degree geoid height of Model;CA reaches 3cm up to 90 degree and order.
基金supported by the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre and NIHR Applied Research Collaboration East Midlands (ARC EM, (IS-BRC-1215-20010))funded by the National Institute for Health and Care Research Bristol Biomedical Research Centre (IS-BRC-1215-20011)supported by a UKRI research grant (EP/X042464/1)。
文摘Background Higher accelerometer-assessed volume and intensity of physical activity(PA)have been associated with a longer life expectancy but can be difficult to translate into recommended doses of PA.We aimed to:(a)improve interpretability by producing UK Biobank age-referenced centiles for PA volume and intensity;(b)inform public-health messaging by examining how adding recommended quantities of moderate and vigorous PA affect PA volume and intensity.Methods 92,480 UK Biobank participants aged 43-80 years with wrist-worn accelerometer data were included.Average acceleration and intensity gradient were derived as proxies for PA volume and intensity.We generated sex-specific centile curves using Generalized Additive Models for Location Scale and Shape(GAMLSS)and modeled the effect of adding moderate(walking)or vigorous(running)activity on the combined change in the volume and intensity centiles(change in PA profile).Results In men,volume was lower as age increased while intensity was lower after age 55;in women,both volume and intensity were lower as age increased.Adding 150 min of moderate PA weekly(5×30 min walking)increased the PA profile by 4 percentage points.Defining moderate PA as brisk walking approximately doubled the increase(9 percentage points)while 75 min of vigorous PA weekly(5×15 min running)trebled the increase(13 percentage points).Conclusion These UK Biobank reference centiles provide a benchmark for interpretation of accelerometer data.Application of our translational methods demonstrate that meeting PA guidelines through shorter duration vigorous activity is more beneficial to the PA profile(volume and intensity)than longer duration moderate activity.
基金Science Council (NSC),Chinese Taipei Under Grant No.NSC-96-2221-E-027-030
文摘Numerical properties of the time integration method proposed by the first author of this paper in 2007 are the same as those of the constant average acceleration method （AAM） for linear elastic systems, except that the capability to capture dynamic loading was not explored. It was found that there were different quadrature equations to predict the next step displacement increment. A modified quadrature equation of this method was derived so that the equation to determine the next step displacement was numerically equivalent to the equation used in the constant AAM. It was verified that the original form of this method, in general, had a better capability to capture dynamic loadings than the constant AAM. This excellent property, in addition to computational efficiency, will help to make this method competitive with general secondorder accurate integration methods.
基金supported by the National Natural Science Foundation of China(Nos.11374107 and 11374108)the CAS Key Laboratory of Geospace Environment,University of Science and Technology of China,the Extracurricular Scientific Program of School of Information and Optoelectronic Science and Engineering,South China Normal University,the National Training Program of Innovation and Entrepreneurship for Undergraduates(No.20161405)the Special Funds for the Cultivation of Guangdong College Students’Scientific and Technological Innovation(No.pdjh2017b0137)
文摘We present an investigation on the propagation properties of the chirped Airy vortex（CAi V） beams through slabs of left-handed materials（LHMs） and right-handed materials（RHMs）. We discuss the influence of chirped parameter C on the propagation of the CAi V beams through LHM and RHM slabs. Our simulation results show that a maximum accelerated velocity appears during the propagation process. The intensity concentration of the CAi V beams increases with the absolute value of the chirped parameter. The peak intensity of the CAi V beams changes abruptly, and the chirped parameter plays an active role on the difference of the maximum and the minimum. In the energy flow, we find that the effects of the chirped parameter on the strength of the vortex are different at different propagation distances.
