利用超声雾化-固相萃取法萃取,气相色谱法和气相色谱-质谱法测定了小茴香中的挥发油.采用正十四烷作为洗脱溶剂,体积为50μL、吹扫气流速为200 m L/min,吹扫时间为5 min.利用优化后的方法测定了小茴香中挥发性成分的种类和含量,与水蒸...利用超声雾化-固相萃取法萃取,气相色谱法和气相色谱-质谱法测定了小茴香中的挥发油.采用正十四烷作为洗脱溶剂,体积为50μL、吹扫气流速为200 m L/min,吹扫时间为5 min.利用优化后的方法测定了小茴香中挥发性成分的种类和含量,与水蒸馏提取法所得结果相似.测定样品溶液中挥发性成分的回收率为65.8%~102.0%,相对标准偏差小于8.0%.展开更多
目的通过不同工况下头部和腰部的加速度信号分析人体步态稳定性,与质心(center of mass,COM)-压力中心(center of pressure, COP)法进行对比,探讨应用可穿戴设备进行步态稳定性分析的可靠性。方法应用基于加速度信号的谐波比(harmonic r...目的通过不同工况下头部和腰部的加速度信号分析人体步态稳定性,与质心(center of mass,COM)-压力中心(center of pressure, COP)法进行对比,探讨应用可穿戴设备进行步态稳定性分析的可靠性。方法应用基于加速度信号的谐波比(harmonic ratio, HR)参数分析18名健康青年人在3种工况下(穿鞋自然行走、裸足自然行走、不同步速裸足行走)的行走稳定性,并与COM-COP法的评估结果比较。结果自然步速下步态最稳定,此时HR最大;裸足比穿鞋行走时HR显著减小(P<0.05),步态稳定性降低。该结果与COM-COP法分析结果一致。综合步速和穿鞋影响因素,基于加速度的HR参数与COM-COP法的步态稳定性评估结果呈显著负线性相关(R^2>0.50),其中腰部HR具有更显著的线性相关性(R^(2 )>0.60)。结论应用基于加速度信号的分析算法可以有效且可靠地评估人体步态稳定性,其中腰部加速度对步态稳定性更敏感。展开更多
The electrostatic accelerometer,assembled on gravity satellite,serves to measure all non-gravitational accelerations caused by atmosphere drag or solar radiation pressure,etc.The proof-mass center of the accelerometer...The electrostatic accelerometer,assembled on gravity satellite,serves to measure all non-gravitational accelerations caused by atmosphere drag or solar radiation pressure,etc.The proof-mass center of the accelerometer needs to be precisely positioned at the center of gravity satellite,otherwise,the offset between them will bring measurement disturbance due to angular acceleration of satellite and gradient.Because of installation and measurement errors on the ground,fuel consumption during the in-flight phase and other adverse factors,the offset between the proof-mass center and the satellite center of mass is usually large enough to affect the measurement accuracy of the accelerometer,even beyond its range.Therefore,the offset needs to be measured or estimated,and then be controlled within the measurement requirement of the accelerometer by the center of mass(COM) adjustment mechanism during the life of the satellite.The estimation algorithm based on EKF,which uses the measurement of accelerometer,gyro and magnetometer,is put forward to estimate the offset,and the COM adjustment mechanism then adjusts the satellite center of mass in order to make the offset meet the requirement.With the special configuration layout,the COM adjustment mechanism driven by the stepper motors can separately regulate X,Y and Z axes.The associated simulation shows that the offset can be con-trolled better than 0.03 mm for all the axes with the method mentioned above.展开更多
文摘利用超声雾化-固相萃取法萃取,气相色谱法和气相色谱-质谱法测定了小茴香中的挥发油.采用正十四烷作为洗脱溶剂,体积为50μL、吹扫气流速为200 m L/min,吹扫时间为5 min.利用优化后的方法测定了小茴香中挥发性成分的种类和含量,与水蒸馏提取法所得结果相似.测定样品溶液中挥发性成分的回收率为65.8%~102.0%,相对标准偏差小于8.0%.
文摘目的通过不同工况下头部和腰部的加速度信号分析人体步态稳定性,与质心(center of mass,COM)-压力中心(center of pressure, COP)法进行对比,探讨应用可穿戴设备进行步态稳定性分析的可靠性。方法应用基于加速度信号的谐波比(harmonic ratio, HR)参数分析18名健康青年人在3种工况下(穿鞋自然行走、裸足自然行走、不同步速裸足行走)的行走稳定性,并与COM-COP法的评估结果比较。结果自然步速下步态最稳定,此时HR最大;裸足比穿鞋行走时HR显著减小(P<0.05),步态稳定性降低。该结果与COM-COP法分析结果一致。综合步速和穿鞋影响因素,基于加速度的HR参数与COM-COP法的步态稳定性评估结果呈显著负线性相关(R^2>0.50),其中腰部HR具有更显著的线性相关性(R^(2 )>0.60)。结论应用基于加速度信号的分析算法可以有效且可靠地评估人体步态稳定性,其中腰部加速度对步态稳定性更敏感。
文摘The electrostatic accelerometer,assembled on gravity satellite,serves to measure all non-gravitational accelerations caused by atmosphere drag or solar radiation pressure,etc.The proof-mass center of the accelerometer needs to be precisely positioned at the center of gravity satellite,otherwise,the offset between them will bring measurement disturbance due to angular acceleration of satellite and gradient.Because of installation and measurement errors on the ground,fuel consumption during the in-flight phase and other adverse factors,the offset between the proof-mass center and the satellite center of mass is usually large enough to affect the measurement accuracy of the accelerometer,even beyond its range.Therefore,the offset needs to be measured or estimated,and then be controlled within the measurement requirement of the accelerometer by the center of mass(COM) adjustment mechanism during the life of the satellite.The estimation algorithm based on EKF,which uses the measurement of accelerometer,gyro and magnetometer,is put forward to estimate the offset,and the COM adjustment mechanism then adjusts the satellite center of mass in order to make the offset meet the requirement.With the special configuration layout,the COM adjustment mechanism driven by the stepper motors can separately regulate X,Y and Z axes.The associated simulation shows that the offset can be con-trolled better than 0.03 mm for all the axes with the method mentioned above.
