振荡器的频率稳定度在时域一般用阿伦方差表征,在频域一般用相位噪声谱密度函数表征,两者存在一定的数学转换关系,即可以由频域测量的相位噪声谱密度函数转换为时域的阿伦方差.t<0.1 ms时短期频率稳定度的时域测量非常困难.利用两者...振荡器的频率稳定度在时域一般用阿伦方差表征,在频域一般用相位噪声谱密度函数表征,两者存在一定的数学转换关系,即可以由频域测量的相位噪声谱密度函数转换为时域的阿伦方差.t<0.1 ms时短期频率稳定度的时域测量非常困难.利用两者之间的转换关系对振荡器的时域稳定度进行了间接测量,并用实测数据进行了验证.
Abstract：
Frequency stability of oscillator commonly can be denoted by Allan variance in time domain, and by phase noise power spectrum density function in frequency domain. There is a definite transform relation of mathematics, it is to say that Allan variance of time domain can be obtained by transforming phase noise power spectrum density function, especially it is more applicable when τ < 0. 1 ms because it is very difficult to measure short - term frequency stability in time domain. The transformation relation between the two denotations of short-term frequency is used to measure Allan variance indirectly and validated by measured data.展开更多
Objective： To explore characteristic of pulse signal to distinguish patients with coronary heart diseases （CHD） from patients without CHD and healthy adults, and accordingly evaluate the potential role of pulse sig...Objective： To explore characteristic of pulse signal to distinguish patients with coronary heart diseases （CHD） from patients without CHD and healthy adults, and accordingly evaluate the potential role of pulse signal to diagnosis CHD. Methods： Totally 407 patients enrolled from 4 collaborating medical centers were assigned to a CHD group （205 patients） and a non-CHD group （202 patients）. The healthy control group （62 adults） enrolled from Shanghai University of Traditional Chinese Medicine. Pulse signals were collected using the synchronous multiplex pulse signal acquisition system. The pulse signals were analyzed and extracted using Hilbert-Huang transformation （HHT） and time-domain, respectively. The time-domain parameters of pulse signal were processed by the analysis of variance （SNK test）. Results： Special patterns in the CHD group pulse signal were found in this study： （1） time-domain parameters of pulse signal, h1 , h3, h4, h3/h1, t, t5/t4 were increased and w was wider; （2） 44% of C2 waves in HHT were chaotic and disordered and 72% of C3 waves were exhibited irregularly with average amplitude over 10 g-forces, which were all significantly different from controls. Conclusion： Characteristic wave and time-domain parameters of pulse signal were extracted using HHT and time-domain which could be served as a non-invasive approach for assessing patients with CHD.展开更多
The interaction of regular quasi-monochromatic waves with a weakly submerged rectangular shelf is studied by means of CFD simulations. The fundamental incident wave frequency is kept constant for the full set of simul...The interaction of regular quasi-monochromatic waves with a weakly submerged rectangular shelf is studied by means of CFD simulations. The fundamental incident wave frequency is kept constant for the full set of simulated cases, while the incident wave amplitude is made increase progressively, so that the interaction with the shelf is dominated by almost inviscid non-linear flow for the smallest and by breaking for the highest incident waves. A parameter identification（PI） procedure is used to adapt a reduced model to the highly resolved time-space matrix of wave elevations obtained from the numerical simulations, on the weather and lee side respectively. In particular the wave number and the frequency of the component waves in the reduced model are left uncoupled, thus computed by the PI independently. The comparison of simulated data with experiments generally shows a very good agreement. Free/locked, incident/reflected, first/higher order wave components are quantified accurately by the PI and the energy transfer to super-harmonics is clearly evidenced. Moreover the results of the PI show clearly a very large increase in the phase speed of the higher order free waves on the lee side of the shelf, with increasing deviation from the linear behavior with increasing incident wave amplitude.展开更多
文摘振荡器的频率稳定度在时域一般用阿伦方差表征,在频域一般用相位噪声谱密度函数表征,两者存在一定的数学转换关系,即可以由频域测量的相位噪声谱密度函数转换为时域的阿伦方差.t<0.1 ms时短期频率稳定度的时域测量非常困难.利用两者之间的转换关系对振荡器的时域稳定度进行了间接测量,并用实测数据进行了验证.
Abstract：
Frequency stability of oscillator commonly can be denoted by Allan variance in time domain, and by phase noise power spectrum density function in frequency domain. There is a definite transform relation of mathematics, it is to say that Allan variance of time domain can be obtained by transforming phase noise power spectrum density function, especially it is more applicable when τ < 0. 1 ms because it is very difficult to measure short - term frequency stability in time domain. The transformation relation between the two denotations of short-term frequency is used to measure Allan variance indirectly and validated by measured data.
基金Supported by the National 973 Basic Research and Development Program(No.2003CB517108)Supported by the National Natural Science Foundation of China(No.30600796,81373555,and 81403273)
文摘Objective： To explore characteristic of pulse signal to distinguish patients with coronary heart diseases （CHD） from patients without CHD and healthy adults, and accordingly evaluate the potential role of pulse signal to diagnosis CHD. Methods： Totally 407 patients enrolled from 4 collaborating medical centers were assigned to a CHD group （205 patients） and a non-CHD group （202 patients）. The healthy control group （62 adults） enrolled from Shanghai University of Traditional Chinese Medicine. Pulse signals were collected using the synchronous multiplex pulse signal acquisition system. The pulse signals were analyzed and extracted using Hilbert-Huang transformation （HHT） and time-domain, respectively. The time-domain parameters of pulse signal were processed by the analysis of variance （SNK test）. Results： Special patterns in the CHD group pulse signal were found in this study： （1） time-domain parameters of pulse signal, h1 , h3, h4, h3/h1, t, t5/t4 were increased and w was wider; （2） 44% of C2 waves in HHT were chaotic and disordered and 72% of C3 waves were exhibited irregularly with average amplitude over 10 g-forces, which were all significantly different from controls. Conclusion： Characteristic wave and time-domain parameters of pulse signal were extracted using HHT and time-domain which could be served as a non-invasive approach for assessing patients with CHD.
基金The "Programma Attuativo Regionale del Fondo per lo Sviluppo e la Coesione (PAR FSC 2007-2013) Linea 3.1.2" is acknowledged for providing the support of the OpenViewSHIP Project
文摘The interaction of regular quasi-monochromatic waves with a weakly submerged rectangular shelf is studied by means of CFD simulations. The fundamental incident wave frequency is kept constant for the full set of simulated cases, while the incident wave amplitude is made increase progressively, so that the interaction with the shelf is dominated by almost inviscid non-linear flow for the smallest and by breaking for the highest incident waves. A parameter identification（PI） procedure is used to adapt a reduced model to the highly resolved time-space matrix of wave elevations obtained from the numerical simulations, on the weather and lee side respectively. In particular the wave number and the frequency of the component waves in the reduced model are left uncoupled, thus computed by the PI independently. The comparison of simulated data with experiments generally shows a very good agreement. Free/locked, incident/reflected, first/higher order wave components are quantified accurately by the PI and the energy transfer to super-harmonics is clearly evidenced. Moreover the results of the PI show clearly a very large increase in the phase speed of the higher order free waves on the lee side of the shelf, with increasing deviation from the linear behavior with increasing incident wave amplitude.
