Browsing by Author "Chu, YH"

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An examination of the wind-driven effect on the drift of precipitation particles using the Chung-Li VHF radar
(1997-05-01)
Chu, YH
;
Chen, TY
;
Lin, TH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
One of the essential assumptions made in estimating the terminal velocity and the drop-size distribution of hydrometeor from the precipitation Doppler spectrum observed by VHF/UHF radar (or wind profiler) is that all of the precipitation particles are moving together at the same velocity as the ambient wind. However, this may not be the case. In this paper, taking advantage of the capability of simultaneously measuring the motions of precipitation particles and the clear-air turbulence with a VHF radar, we develop a method to examine the wind-driven effect on the drift of precipitation particles using the Chung-Li VHF radar. By appropriately setting the radar parameters and steering the radar beams, experimental results show that the drift velocity of the precipitation particles in response to the drag force exerted by the background atmosphere is not the same as the ambient wind velocity, approximately 83% of the latter in this case. This feature indicates that the precipitation particles are not moving with the background wind, causing inaccurate estimations of the terminal velocity and the drop-size distribution of hydrometeor if this effect is not taken into account.
An examination of the wind-driven effect on the drift of precipitation particles using the Chung-Li VHF radar
(1997-05-01)
Chu, YH
;
Chen, TY
;
Lin, TH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
One of the essential assumptions made in estimating the terminal velocity and the drop-size distribution of hydrometeor from the precipitation Doppler spectrum observed by VHF/UHF radar (or wind profiler) is that all of the precipitation particles are moving together at the same velocity as the ambient wind. However, this may not be the case. In this paper, taking advantage of the capability of simultaneously measuring the motions of precipitation particles and the clear-air turbulence with a VHF radar, we develop a method to examine the wind-driven effect on the drift of precipitation particles using the Chung-Li VHF radar. By appropriately setting the radar parameters and steering the radar beams, experimental results show that the drift velocity of the precipitation particles in response to the drag force exerted by the background atmosphere is not the same as the ambient wind velocity, approximately 83% of the latter in this case. This feature indicates that the precipitation particles are not moving with the background wind, causing inaccurate estimations of the terminal velocity and the drop-size distribution of hydrometeor if this effect is not taken into account.
Low-power FIR filter realization with differential coefficients and inputs
(2000-02-01)
Chang, TS
;
Chu, YH
;
Jen, CW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This brief presents a low-power finite-impulse response filter design by using differential coefficients and inputs instead of using them directly such that fewer bits are required, thereby reducing the size of arithmetic units and power dissipation. Ne present an improved algorithm to effectively generate differential coefficients so that the differential coefficients methods can be applied to full bandwidth (BW) of filters instead of only narrow-band filters in previous approaches. Simulations with fixed coefficient filters indicate reduction in transition activity ranging from 1-53% over the full range of filter BW's, The presented results can be applied to adaptive filters to generate suitable differential coefficients.