Browsing by Author "Wu, CR"

Now showing 1 - 3 of 3

Electro-optical properties of conic cylindrical-cavities liquid crystal displays
(2002-05-01)
Liang, BJ
;
Chen, SH
;
Wu, CR
;
光電工程學系
;
Department of Photonics
Experimental results have shown that the conic cavities in conic closed-cavity liquid crystal displays (conic CCLCDs) can give a wide viewing angle and grey levels without grey-scale inversion. The purpose of this paper is to extend investigations of conic CCLCDs. In experiments, we describe in detail the fabrication process, microscopic observations and optical measurements for conic CCLCDs. The simulation of director distribution will be based on the tensor form formulation of the free energy density. The differential equations satisfied by the steady-state director distribution are derived from this form of free energy and are solved in conjunction with Poisson's equation. The simulation of the optical propagation and the calculation of the optical transmittance will be based on the extended Jones matrix method. We show by simulation that a normal umbilical structure is the final stable state and that indeed conic CCLCDs can have a wide viewing angle and grey scale without grey-scale inversion. The theoretical results are compared with the experimental results. Transmittance, contrast ratio and viewing angle with various parameters of the LC are measured. Improved iso-contrast contours of the conic CCLCD with a c-plate compensator are also shown. Finally, we have also compared the electro-optical performance and the off axis colour-shift of the CCLCD, the 4-domain VAN device and the 4-domain twist-VAN device.
The kinematics of mesoscale eddies from TOPEX/Poseidon altimetry over the Subtropical Counter Current
(2004)
Hwang, C
;
Kao, R
;
Wu, CR
;
土木工程學系
;
Department of Civil Engineering
TOPEX/POSEIDON altimetry data were used to track mesoscale eddies over the Subtropical Counter Current (STCC). The radii, centers, vorticities, shearing deformation rates, stretching deformation rates, divergences and center velocities of all identified eddies over STCC were determined using a model that assumes constant velocity gradients. A case study was made for a cyclonic eddy and an anticyclonic eddy, with time series of eddy kinematic parameters computed. Both eddies survive for about 220 days and propagate westwards along over 22degreesN-24degreesN to reach the Kuroshio Current east coast of Taiwan. Sea surface temperature data confirm the existence of these two eddies. The radii of both eddies vary and their shapes are mostly elliptical during propagation. The anticyclonic eddy propagated almost westwards with oscillating north-south components, and the mean speed is 8.3 km/day. The cyclonic eddy moved southwestwards before reaching 130degreesE and then moved northwestwards, with a mean speed of 7.6 km/day. The propagations of these two eddies are basically consistent with the standard theory of eddy propagation but with larger speeds and varying propagating directions.
TOPEX/Poseidon observations of mesoscale eddies over the Subtropical Countercurrent: Kinematic characteristics of an anticyclonic eddy and a cyclonic eddy
(2004-08-17)
Hwang, C
;
Wu, CR
;
Kao, R
;
土木工程學系
;
Department of Civil Engineering
Relative dynamic heights and geostrophic fields were derived from TOPEX/Poseidon altimetry data and then used to track mesoscale eddies over the Subtropical Countercurrent (STCC). The radii, centers, vorticities, shearing deformation rates, stretching deformation rates, divergences, and center velocities of all identified eddies over the STCC were determined using a model that assumes constant velocity gradients. Most eddies are concentrated in a zonal band near 22degreesN, and there is an interannual variation in the number of eddies. A case study was made for a cyclonic eddy and an anticyclonic eddy, with time series of eddy kinematic parameters computed. Both eddies survive for similar to220 days and propagate westward along over 22degreesN-24degreesN to reach the Kuroshio Current east coast of Taiwan, where the eddies were dissipated and in turn affected the Kuroshio Current in many ways. Sea surface temperature data and drifter data confirm the existence of these two eddies. The radii of both eddies vary and their shapes are mostly elliptical during propagation. The anticyclonic eddy propagated almost westward with oscillating north-south components, and the mean speed is 8.3 km/day. The cyclonic eddy moved southwestward before reaching 130degreesE and then moved northwestward, with a mean speed of 7.6 km/day. The propagations of these two eddies are basically consistent with the standard theory of eddy propagation but with larger speeds. The propagating direction could be altered while passing steep bottom topography or merging with the other eddies.