Acoustic signals from diesel engines contain useful information but also include considerable noise components To extract information for condition monitoring purposes, continuous wavelet transform (CWT) is used for t...Acoustic signals from diesel engines contain useful information but also include considerable noise components To extract information for condition monitoring purposes, continuous wavelet transform (CWT) is used for the characterization of engine acoustics. This paper first reviews CWT characteristics represented by short duration transient signals. Wavelet selection and CWT are then implemented and wavelet transform is used to analyze the major sources of the engine front's exterior radiation sound. The research provides a reliable basis for engineering practice to reduce vehicle sound level. Comparison of the identification results of the measured acoustic signals with the identification results of the measured surface vibration showed good agreement.展开更多
As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-find...As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-finding systems,a dynamic strategy based on continuous rotation modulation to measure the rotational angular velocity of the earth is proposed.By modeling the dynamic error,optimizing the process constraint and estimating dynamic noise,a method combining delay compensation and hardware adjustment,and a constrained adaptive Kalman filter(CAKF)algorithm are designed for the north-finding strategy.According to simulation and experiments,the proposed algorithm can achieve the high-precision north-finding with robust and anti-noise performance.展开更多
Mechanical micro-vibration of a target may induce phase modulations on the radar echo,and the vibration can be detected to identify micro-motion target. In this paper,a new method to detect a micro-motion target and o...Mechanical micro-vibration of a target may induce phase modulations on the radar echo,and the vibration can be detected to identify micro-motion target. In this paper,a new method to detect a micro-motion target and obtain its range and micro-motion frequency is proposed in which multiple periods stepped-frequency continuous-wave signal and Moving Target Indication (MTI) filter are adopted. The simulation results illustrate the validity of this method and present the detection of the target range and the vibration frequency. The experiment gives promising results.展开更多
The relationship between periodic fluctuations of pressure and precipitation was investigated using the continuous wavelet transform and wavelet coherence transform methods for a rainstorm case that occurred during 19...The relationship between periodic fluctuations of pressure and precipitation was investigated using the continuous wavelet transform and wavelet coherence transform methods for a rainstorm case that occurred during 19–25 June 2005 in Guangdong Province, China. The results show that a period of 2–4 h existed in both pressure and precipitation fluctuations. Furthermore, this high frequency pressure fluctuation was closely related to the fluctuation of precipitation with a similar period, and the fluctuation of pressure was about two hours ahead of the precipitation fluctuation variation. Since the high frequency pressure fluctuation implies the existence of gravity wave activity, the results suggest that gravity wave activities with a 2–4 h period in the atmosphere exerted an important influence on precipitation during this rainstorm.展开更多
基金Project (No. 50175078) supported by the National Natural Science Foundation of China
文摘Acoustic signals from diesel engines contain useful information but also include considerable noise components To extract information for condition monitoring purposes, continuous wavelet transform (CWT) is used for the characterization of engine acoustics. This paper first reviews CWT characteristics represented by short duration transient signals. Wavelet selection and CWT are then implemented and wavelet transform is used to analyze the major sources of the engine front's exterior radiation sound. The research provides a reliable basis for engineering practice to reduce vehicle sound level. Comparison of the identification results of the measured acoustic signals with the identification results of the measured surface vibration showed good agreement.
基金National Natural Science Foundation of China(No.61733012)。
文摘As an orientation measurement system,north-finder has been playing a significant role in both military and civilian fields of orientation and control.In this paper,to deal with drawbacks in the conventional north-finding systems,a dynamic strategy based on continuous rotation modulation to measure the rotational angular velocity of the earth is proposed.By modeling the dynamic error,optimizing the process constraint and estimating dynamic noise,a method combining delay compensation and hardware adjustment,and a constrained adaptive Kalman filter(CAKF)algorithm are designed for the north-finding strategy.According to simulation and experiments,the proposed algorithm can achieve the high-precision north-finding with robust and anti-noise performance.
文摘Mechanical micro-vibration of a target may induce phase modulations on the radar echo,and the vibration can be detected to identify micro-motion target. In this paper,a new method to detect a micro-motion target and obtain its range and micro-motion frequency is proposed in which multiple periods stepped-frequency continuous-wave signal and Moving Target Indication (MTI) filter are adopted. The simulation results illustrate the validity of this method and present the detection of the target range and the vibration frequency. The experiment gives promising results.
基金supported by the State Key Laboratory of Severe Weather opening project
文摘The relationship between periodic fluctuations of pressure and precipitation was investigated using the continuous wavelet transform and wavelet coherence transform methods for a rainstorm case that occurred during 19–25 June 2005 in Guangdong Province, China. The results show that a period of 2–4 h existed in both pressure and precipitation fluctuations. Furthermore, this high frequency pressure fluctuation was closely related to the fluctuation of precipitation with a similar period, and the fluctuation of pressure was about two hours ahead of the precipitation fluctuation variation. Since the high frequency pressure fluctuation implies the existence of gravity wave activity, the results suggest that gravity wave activities with a 2–4 h period in the atmosphere exerted an important influence on precipitation during this rainstorm.
