目的分析多系统萎缩(multiple system atrophy,MSA)患者心血管自主神经功能障碍的情况。方法纳入88例多系统萎缩患者作为研究对象,并选择年龄、性别相匹配的体检的88例健康者作为对照组。比较两组动态血压及动态心电图相关参数的差异。...目的分析多系统萎缩(multiple system atrophy,MSA)患者心血管自主神经功能障碍的情况。方法纳入88例多系统萎缩患者作为研究对象,并选择年龄、性别相匹配的体检的88例健康者作为对照组。比较两组动态血压及动态心电图相关参数的差异。结果MSA组动态血压中的夜间收缩压(nocturnal systolic blood pressure,nSBP)、夜间舒张压(nocturnal diastolic blood pressure,nDBP)较对照组明显升高(P均<0.05);每5 min R-R间期标准差均值(mean of the standard deviations of all 5-min normal-to-normal R-R intervals of the entire recording,SDNN Index)、行低频成分(low frequency,LF)、高频成分(high frequency,HF)等三个参数中MSA组较健康对照组参数水平明显降低,差异有统计学意义(P<0.05)。结论研究多系统萎缩患者心血管自主神经障碍的临床特点,对MSA患者的诊断具有参考意义。展开更多
The recent research on stability of gas bearing-rotor systems still mostly adopts the same method as in oil-lubricated bearing-rotor systems.The dynamic coefficients of gas bearings in the case that the perturbation f...The recent research on stability of gas bearing-rotor systems still mostly adopts the same method as in oil-lubricated bearing-rotor systems.The dynamic coefficients of gas bearings in the case that the perturbation frequencies are same as the rotating speed are used to carry out the stability analysis of rotor systems.This method does not contact the frequency characteristics of dynamic stiffness and damping coefficients of gas bearings with the dynamical behaviors of rotor systems.Furthermore,the effects of perturbation frequencies on the stability of systems are not taken into account.In this paper,the dynamic stiffness and damping coefficients of tilting-pad gas bearings are calculated by the partial derivative method.On the base of solution of dynamic coefficients,two computational models are produced for stability analysis on rotor systems supported by tilting-pad gas bearings according to whether the degrees of the freedom of pads tilting motions are included in the equations of motion or not.In the condition of considering the frequency effects of dynamic coefficients of tilting-pad gas bearings,the corresponding eigenvalues of the rigid and first five vibration modes of the system with the working speeds of 8-30 kr/min are computed through iteratively solving the equations of motion of rotor-system by using two computational models,respectively.According to the obtained eigenvalues,the stability of rotor system is analyzed.The results indicate that the eigenvalues and the stability of rotor system obtained by these two computational models are well agreement each other.They all can more accurately analyze the stability of rotor systems supported by tilting-pad gas bearings.This research has important meaning for perfecting the stability analysis method of rotor systems supported by gas bearings.展开更多
Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries,theoretical researches on the modeling,performance prediction of compliant foil bearings and the dynamic analysis ...Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries,theoretical researches on the modeling,performance prediction of compliant foil bearings and the dynamic analysis of the related rotor system seem still far behind the experimental investigation because of structural complexity of the foil bearings.A generalized solution of the elasto-aerodynamic lubrication is presented in this paper by introducing both static and dynamic deformations of foils and solving gas-lubricated Reynolds equations with deformation equations simultaneously.The solution can be used for the calculation of dynamic stiffness and damping,as well as the prediction of static performances of foil bearings.Systematical theories and methods are also presented for the purpose of the prediction of dynamic behavior of a rotor system equipped with foil bearings.展开更多
文摘目的分析多系统萎缩(multiple system atrophy,MSA)患者心血管自主神经功能障碍的情况。方法纳入88例多系统萎缩患者作为研究对象,并选择年龄、性别相匹配的体检的88例健康者作为对照组。比较两组动态血压及动态心电图相关参数的差异。结果MSA组动态血压中的夜间收缩压(nocturnal systolic blood pressure,nSBP)、夜间舒张压(nocturnal diastolic blood pressure,nDBP)较对照组明显升高(P均<0.05);每5 min R-R间期标准差均值(mean of the standard deviations of all 5-min normal-to-normal R-R intervals of the entire recording,SDNN Index)、行低频成分(low frequency,LF)、高频成分(high frequency,HF)等三个参数中MSA组较健康对照组参数水平明显降低,差异有统计学意义(P<0.05)。结论研究多系统萎缩患者心血管自主神经障碍的临床特点,对MSA患者的诊断具有参考意义。
基金supported by National Natural Science Foundation of China (Grant No. 50635060)National Hi-tech Research and Development Program of China (863 Program,Grant No.2007AA050501)+1 种基金National Key Basic Research Program of China (973 Program,Grant No. 2007CB707705,Grant No. 2007CB707706)Research Funds for the Central Universities of China
文摘The recent research on stability of gas bearing-rotor systems still mostly adopts the same method as in oil-lubricated bearing-rotor systems.The dynamic coefficients of gas bearings in the case that the perturbation frequencies are same as the rotating speed are used to carry out the stability analysis of rotor systems.This method does not contact the frequency characteristics of dynamic stiffness and damping coefficients of gas bearings with the dynamical behaviors of rotor systems.Furthermore,the effects of perturbation frequencies on the stability of systems are not taken into account.In this paper,the dynamic stiffness and damping coefficients of tilting-pad gas bearings are calculated by the partial derivative method.On the base of solution of dynamic coefficients,two computational models are produced for stability analysis on rotor systems supported by tilting-pad gas bearings according to whether the degrees of the freedom of pads tilting motions are included in the equations of motion or not.In the condition of considering the frequency effects of dynamic coefficients of tilting-pad gas bearings,the corresponding eigenvalues of the rigid and first five vibration modes of the system with the working speeds of 8-30 kr/min are computed through iteratively solving the equations of motion of rotor-system by using two computational models,respectively.According to the obtained eigenvalues,the stability of rotor system is analyzed.The results indicate that the eigenvalues and the stability of rotor system obtained by these two computational models are well agreement each other.They all can more accurately analyze the stability of rotor systems supported by tilting-pad gas bearings.This research has important meaning for perfecting the stability analysis method of rotor systems supported by gas bearings.
基金This work was supported by the National Natural Science Foundation of China(Grant Nos.50275116 and 50475088)the National High-Tech Research and Development Program of China(Grant No.2002AA503020).
文摘Although aerodynamic compliant foil bearings are successfully applied in a number of turbo-machineries,theoretical researches on the modeling,performance prediction of compliant foil bearings and the dynamic analysis of the related rotor system seem still far behind the experimental investigation because of structural complexity of the foil bearings.A generalized solution of the elasto-aerodynamic lubrication is presented in this paper by introducing both static and dynamic deformations of foils and solving gas-lubricated Reynolds equations with deformation equations simultaneously.The solution can be used for the calculation of dynamic stiffness and damping,as well as the prediction of static performances of foil bearings.Systematical theories and methods are also presented for the purpose of the prediction of dynamic behavior of a rotor system equipped with foil bearings.
