In order to improve the bias stability of the micro-electro mechanical system（MEMS） gyroscope and reduce the impact on the bias from environmental temperature,a digital signal processing method is described for impr...In order to improve the bias stability of the micro-electro mechanical system（MEMS） gyroscope and reduce the impact on the bias from environmental temperature,a digital signal processing method is described for improving the accuracy of the drive phase in the gyroscope drive mode.Through the principle of bias signal generation,it can be concluded that the deviation of the drive phase is the main factor affecting the bias stability.To fulfill the purpose of precise drive phase control,a digital signal processing circuit based on the field-programmable gate array（FPGA） with the phase-lock closed-loop control method is described and a demodulation method for phase error suppression is given.Compared with the analog circuit,the bias drift is largely reduced in the new digital circuit and the bias stability is improved from 60 to 19 °/h.The new digital control method can greatly increase the drive phase accuracy,and thus improve the bias stability.展开更多
In this paper, a new type of conserved quantity indirectly deduced from the Mei symmetry for relativistic mechanical system in phase space is studied. The definition and the criterion of the Mei symmetry for the syste...In this paper, a new type of conserved quantity indirectly deduced from the Mei symmetry for relativistic mechanical system in phase space is studied. The definition and the criterion of the Mei symmetry for the system are given. The condition for existence and the form of the new conserved quantity are obtained. Finally, an example is given to illustrate the application of the results.展开更多
Based on the concept of adiabatic invariant,the perturbation to Noether-Lie symmetry and adiabatic invariants for mechanical systems in phase space are studied.The criterion of the Noether-Lie symmetry for the perturb...Based on the concept of adiabatic invariant,the perturbation to Noether-Lie symmetry and adiabatic invariants for mechanical systems in phase space are studied.The criterion of the Noether-Lie symmetry for the perturbed system is given,and the definition of the perturbation to Noether-Lie symmetry for the system under the action of small disturbance is presented.Meanwhile,the Noether adiabatic invariants and the generalized Hojman adiabatic invariants of the perturbed system are obtained.展开更多
Objective： To investigate stretch-induced electrophysiological changes in chronically infarcted hearts and the effect of streptomycin （SM） on these changes in vivo. Methods： Sixty Wistar rats were divided randomly...Objective： To investigate stretch-induced electrophysiological changes in chronically infarcted hearts and the effect of streptomycin （SM） on these changes in vivo. Methods： Sixty Wistar rats were divided randomly into four groups： a control group （n=15）, an SM group （n=15）, a myocardial infarction （MI） group （n=15）, and an MI＋SM group （n=15）. Chronic MI was obtained by ligating the left anterior descending branch （LAD） of rat hearts for eight weeks. The in vivo blockade of stretch-activated ion channels （SACs） was achieved by intramuscular injection of SM （180 mg/（kg·d）） for seven days after operation. The hearts were stretched for 5 s by occlusion of the aortic arch. Suction electrodes were placed on the anterior wall of left ventricle to record the monophasic action potential （MAP）. The effect of stretching was examined by assessing the 90% monophasic action potential duration （MAPD90）, premature ventricular beats （PVBs）, and ventricular tachycardia （VT）. Results： The MAPD90 decreased during stretching in both the control （from （50.27±5.61） ms to （46.27±4.51） ms, P〈0.05） and MI groups （from （65.47±6.38） ms to （57.47±5.76 ms）, P〈0.01 ）. SM inhibited the decrease in MAPD90 during inflation （（46.27±4.51） ms vs. （49.53±3.52） ms, P〈0.05 in normal hearts; （57.47±5.76） ms vs. （61.87±5.33） ms, P〈0.05 in MI hearts）. The occurrence of PVBs and VT in the MI group increased compared with that in the control group （PVB： 7.93±1.66 vs. 1.80±0.86, P〈0.01; VT： 7 vs. 1, P〈0.05）. SM decreased the occurrence of PVBs in both normal and MI hearts （0.93±0.59 vs. 1.80±0.86 in normal hearts, P〈0.05; 5.40±1.18 vs. 7.93±1.66 in MI hearts, P〈0.01）. Conclusions： Stretch-induced MAPD90 changes and arrhythmias were observed in chronically infarcted myocardium. The use of SM in vivo decreased the incidence of PVBs but not of VT. This suggests that SACs may be involved in mechanoelectric feedback （MEF）, but that there might be other mechanisms involved in causing VT in chronic MI.展开更多
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. 200802861063)
文摘In order to improve the bias stability of the micro-electro mechanical system（MEMS） gyroscope and reduce the impact on the bias from environmental temperature,a digital signal processing method is described for improving the accuracy of the drive phase in the gyroscope drive mode.Through the principle of bias signal generation,it can be concluded that the deviation of the drive phase is the main factor affecting the bias stability.To fulfill the purpose of precise drive phase control,a digital signal processing circuit based on the field-programmable gate array（FPGA） with the phase-lock closed-loop control method is described and a demodulation method for phase error suppression is given.Compared with the analog circuit,the bias drift is largely reduced in the new digital circuit and the bias stability is improved from 60 to 19 °/h.The new digital control method can greatly increase the drive phase accuracy,and thus improve the bias stability.
文摘In this paper, a new type of conserved quantity indirectly deduced from the Mei symmetry for relativistic mechanical system in phase space is studied. The definition and the criterion of the Mei symmetry for the system are given. The condition for existence and the form of the new conserved quantity are obtained. Finally, an example is given to illustrate the application of the results.
文摘Based on the concept of adiabatic invariant,the perturbation to Noether-Lie symmetry and adiabatic invariants for mechanical systems in phase space are studied.The criterion of the Noether-Lie symmetry for the perturbed system is given,and the definition of the perturbation to Noether-Lie symmetry for the system under the action of small disturbance is presented.Meanwhile,the Noether adiabatic invariants and the generalized Hojman adiabatic invariants of the perturbed system are obtained.
基金Project supported by the National Natural Science Foundation of China(No.81301343)
文摘Objective： To investigate stretch-induced electrophysiological changes in chronically infarcted hearts and the effect of streptomycin （SM） on these changes in vivo. Methods： Sixty Wistar rats were divided randomly into four groups： a control group （n=15）, an SM group （n=15）, a myocardial infarction （MI） group （n=15）, and an MI＋SM group （n=15）. Chronic MI was obtained by ligating the left anterior descending branch （LAD） of rat hearts for eight weeks. The in vivo blockade of stretch-activated ion channels （SACs） was achieved by intramuscular injection of SM （180 mg/（kg·d）） for seven days after operation. The hearts were stretched for 5 s by occlusion of the aortic arch. Suction electrodes were placed on the anterior wall of left ventricle to record the monophasic action potential （MAP）. The effect of stretching was examined by assessing the 90% monophasic action potential duration （MAPD90）, premature ventricular beats （PVBs）, and ventricular tachycardia （VT）. Results： The MAPD90 decreased during stretching in both the control （from （50.27±5.61） ms to （46.27±4.51） ms, P〈0.05） and MI groups （from （65.47±6.38） ms to （57.47±5.76 ms）, P〈0.01 ）. SM inhibited the decrease in MAPD90 during inflation （（46.27±4.51） ms vs. （49.53±3.52） ms, P〈0.05 in normal hearts; （57.47±5.76） ms vs. （61.87±5.33） ms, P〈0.05 in MI hearts）. The occurrence of PVBs and VT in the MI group increased compared with that in the control group （PVB： 7.93±1.66 vs. 1.80±0.86, P〈0.01; VT： 7 vs. 1, P〈0.05）. SM decreased the occurrence of PVBs in both normal and MI hearts （0.93±0.59 vs. 1.80±0.86 in normal hearts, P〈0.05; 5.40±1.18 vs. 7.93±1.66 in MI hearts, P〈0.01）. Conclusions： Stretch-induced MAPD90 changes and arrhythmias were observed in chronically infarcted myocardium. The use of SM in vivo decreased the incidence of PVBs but not of VT. This suggests that SACs may be involved in mechanoelectric feedback （MEF）, but that there might be other mechanisms involved in causing VT in chronic MI.
