青藏高原的大气热源及其影响以及环流的低频振荡已有很多探讨,但有关高原大气热源低频振荡及其对环流影响的研究目前尚未充分开展。利用倒算法计算得到的大气热源总量(Q1),诊断和分析1981—2000年夏季青藏高原东部逐日大气热源(Q1ETP,Q1...青藏高原的大气热源及其影响以及环流的低频振荡已有很多探讨,但有关高原大气热源低频振荡及其对环流影响的研究目前尚未充分开展。利用倒算法计算得到的大气热源总量(Q1),诊断和分析1981—2000年夏季青藏高原东部逐日大气热源(Q1ETP,Q1 of the eastern Tibetan Plateau)的主要振荡周期及其对应的传播特征,并取其中1985、1992年进行更详细的分析。结果表明:(1)夏季高原东部大气热源存在两种低频振荡,主要为10～20 d振荡(BWO,Quasi-Biweekly Oscillation),其次为30～60 d振荡(LFO,Low Frequency Oscillation)。(2)在1985、1992年中,高原热源低频振荡与当地降水低频振荡有很好的同位相谱相关,表明热源低频振荡很可能由凝结潜热的振荡激发的,这证明了本文热源数据的可靠性。(3)高原在夏季主要是振荡源地,但也接受外来影响。高原热源BWO生成后主要在原地维持振荡,并受来自孟加拉湾的热源BWO影响,有时部分振荡向外(主要向东)传播;热源LFO情况与BWO类似,以本地振荡为主但也受来自东部大陆LFO的影响,外传时则主要向西。所以研究高原热源低频振荡需要特别注意热源BWO。展开更多
A control method for Multi-Input Multi-Output（MIMO） non-Gaussian random vibration test with cross spectra consideration is proposed in the paper. The aim of the proposed control method is to replicate the specified ...A control method for Multi-Input Multi-Output（MIMO） non-Gaussian random vibration test with cross spectra consideration is proposed in the paper. The aim of the proposed control method is to replicate the specified references composed of auto spectral densities, cross spectral densities and kurtoses on the test article in the laboratory. It is found that the cross spectral densities will bring intractable coupling problems and induce difficulty for the control of the multioutput kurtoses. Hence, a sequential phase modification method is put forward to solve the coupling problems in multi-input multi-output non-Gaussian random vibration test. To achieve the specified responses, an improved zero memory nonlinear transformation is utilized first to modify the Fourier phases of the signals with sequential phase modification method to obtain one frame reference response signals which satisfy the reference spectra and reference kurtoses. Then, an inverse system method is used in frequency domain to obtain the continuous stationary drive signals. At the same time, the matrix power control algorithm is utilized to control the spectra and kurtoses of the response signals further. At the end of the paper, a simulation example with a cantilever beam and a vibration shaker test are implemented and the results support the proposed method very well.展开更多
The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric ... The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric motion and transports in the domain of wave number frequency space have been derived. The contributions of the nonlinear interactions of the atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies and to the meridional transports of angular momentum and sensible heat in the atmosphere have been discussed.展开更多
文摘青藏高原的大气热源及其影响以及环流的低频振荡已有很多探讨,但有关高原大气热源低频振荡及其对环流影响的研究目前尚未充分开展。利用倒算法计算得到的大气热源总量(Q1),诊断和分析1981—2000年夏季青藏高原东部逐日大气热源(Q1ETP,Q1 of the eastern Tibetan Plateau)的主要振荡周期及其对应的传播特征,并取其中1985、1992年进行更详细的分析。结果表明:(1)夏季高原东部大气热源存在两种低频振荡,主要为10～20 d振荡(BWO,Quasi-Biweekly Oscillation),其次为30～60 d振荡(LFO,Low Frequency Oscillation)。(2)在1985、1992年中,高原热源低频振荡与当地降水低频振荡有很好的同位相谱相关,表明热源低频振荡很可能由凝结潜热的振荡激发的,这证明了本文热源数据的可靠性。(3)高原在夏季主要是振荡源地,但也接受外来影响。高原热源BWO生成后主要在原地维持振荡,并受来自孟加拉湾的热源BWO影响,有时部分振荡向外(主要向东)传播;热源LFO情况与BWO类似,以本地振荡为主但也受来自东部大陆LFO的影响,外传时则主要向西。所以研究高原热源低频振荡需要特别注意热源BWO。
基金supported by the Priority Academic Program Development of Jiangsu Higher Education Institutionsthe Postgraduate Research & Practice Innovation Program of Jiangsu Province (No. KYCX17_0234)
文摘A control method for Multi-Input Multi-Output（MIMO） non-Gaussian random vibration test with cross spectra consideration is proposed in the paper. The aim of the proposed control method is to replicate the specified references composed of auto spectral densities, cross spectral densities and kurtoses on the test article in the laboratory. It is found that the cross spectral densities will bring intractable coupling problems and induce difficulty for the control of the multioutput kurtoses. Hence, a sequential phase modification method is put forward to solve the coupling problems in multi-input multi-output non-Gaussian random vibration test. To achieve the specified responses, an improved zero memory nonlinear transformation is utilized first to modify the Fourier phases of the signals with sequential phase modification method to obtain one frame reference response signals which satisfy the reference spectra and reference kurtoses. Then, an inverse system method is used in frequency domain to obtain the continuous stationary drive signals. At the same time, the matrix power control algorithm is utilized to control the spectra and kurtoses of the response signals further. At the end of the paper, a simulation example with a cantilever beam and a vibration shaker test are implemented and the results support the proposed method very well.
文摘 The study of large-scale atmospheric turbulence and transport processes is of vital importance in the general circulation of the atmosphere. The governing equations of the power and cross-spectra for the atmospheric motion and transports in the domain of wave number frequency space have been derived. The contributions of the nonlinear interactions of the atmospheric waves in velocity and temperature fields to the conversion of kinetic and potential energies and to the meridional transports of angular momentum and sensible heat in the atmosphere have been discussed.
