Browsing by Author "Chen, SA"

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Cellular neural networks and PCA neural networks based rotation/scale invariant texture classification
(2004)
Lin, CT
;
Chen, SA
;
Huang, CH
;
Chung, JF
;
電控工程研究所
In this paper, we proposed a new index which can be used to classify the texture image. Because of the adjustment of image capture device or the distortion of image capture, the texture image may be transformed. Usually those transformations included rotation and scale. The proposed method provides an algorithm to avoid those effects respectively. This approach is the combination of Cellular Neural Networks and Principle Component Analysis Neural Networks. This fact implies it is a feed-forward neural networks, and it does not need any training set.
Circulations and eddies over the South China Sea derived from TOPEX/Poseidon altimetry
(2000-10-15)
Hwang, C
;
Chen, SA
;
土木工程學系
;
Department of Civil Engineering
TOPEX/Poseidon (T/P) altimeter data were used to derive time-varying circulation and eddies over the South China Sea (SCS) for 1993-1999. Large variabilities of sea surface heights and dense distribution of eddies were found to occur along a band across the SCS basin. A crossover method is introduced to compute pointwise velocity components. The TiP-derived circulations and eddies are consistent with the drifter results from the World Ocean Circulation Experiment data center. (1) Because of monsoons, the SCS circulation is largely cyclonic in winter, is largely anticyclonic in summer, and is modulated interannually by El Nino - Southern Oscillation. (2) Both cold- and warm-core eddies were found in the waters east of Vietnam, west of Luzon, and west of the Luzon Strait, but their times of occurrence and the way they evolved vary interannually. (3) The reversal of the alongshore currents east of Vietnam was in complete accordance with wind stress. The locations and kinematic properties of eddies over SCS were estimated by the least squares method. The averaged vorticities of the cold- and warm-core eddies are 1.684x10(-6) and -1.738x10(-6) rad s(-1), respectively, and the shearing and stretching deformations are one thousandth of the vorticities. The angular velocity of eddy decreases with increasing radius. Coherence analysis suggests that the interannual and seasonal variations of circulation are largely due to wind stress, and the semi-annual variation is largely due to wind stress curl. The angular velocities of eddies over the central SCS basin are coherent with the magnitudes and signs of wind stress curl. The seasonal steric anomaly was also computed, and its spatial pattern and scale are quite different from those of circulation and eddy.
Comment on "Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes" - Reply
(2004-02-06)
Lin, LC
;
Meng, HF
;
Shy, JT
;
Horng, SF
;
Yu, LS
Comment on "Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes" - Reply
(2003-11-21)
Lin, LC
;
Meng, HF
;
Shy, JT
;
Horng, SF
;
Yu, LS
Fourier and wavelet analyses of TOPEX/Poseidon-derived sea level anomaly over the South China Sea: A contribution to the South China Sea Monsoon Experiment
(2000-12-15)
Hwang, C
;
Chen, SA
;
土木工程學系
;
Department of Civil Engineering
We processed 5.6 years of TOPEX/Poseidon altimeter data and obtained time series of sea level anomaly (SLA) over the South China Sea (SCS). Fourier analysis shows that sea level variability of the SCS contains major components with periods larger than 180 days and is dominated by the annual and semiannual components. Tidal aliasing creates 30-180 day components that can be misinterpreted as wind-induced variabilities. Continuous and multiresolution wavelet analyses show that the SLA of the SCS has monthly to interannual components of time-varying amplitudes, and the regional slope of SLA is 8.9 mm yr(-1), which may be caused by the decadal climate change. Coherences of SLA with wind stress anomalies (WSA) and sea surface temperature anomalies (STA) are significant at the annual and semi-annual components. At periods of 2-5 years the wavelet coefficients of SLA, WSA, and STA have the same pattern, but WSA leads SLA, and STA follows SLA. The zero crossing of SLA in spring is highly correlated with the onset of the summer monsoon. The interannual variability of SLA is correlated with El Nino-Southern Oscillation, and most important is that when the El Nino-like wavelet coefficients of SLA over the warm pool northeast of Australia or the SCS change curvature from negative to positive, an El Nino is likely to develop. This is a contribution to the South China Sea Monsoon Experiment (SCSMEX).
Nanoscale surface electrical properties of indium-tin-oxide films for organic light emitting diodes investigated by conducting atomic force microscopy
(2001-04-07)
Lin, HN
;
Chen, SH
;
Perng, GY
;
Chen, SA
;
電子物理學系
Nanoscale surface electrical properties of indium-tin-oxide films prepared by different cleaning methods for use as anode materials in organic light emitting diodes are studied by conducting atomic force microscopy. It is found that most of the surface area possesses a nonconducting feature, and an ultraviolet-ozone treatment produces the most nonconductive sample. The conducting regions, which distribute randomly and range from 6 to 50 nm in size, are attributed to the existence of Sn-rich oxide by a comparison with reported scanning electron microscopy images. After scanning the tip with a bias of -8 V on the nonconducting regions, oxide decomposition occurs on as-received and wet-cleaning processed samples, whereas no structure change appears on the ozone treated sample. The results indicate that the generation of stable oxide after ozone treatment is one of the origins for improved device performance. (C) 2001 American Institute of Physics.
Triplet exciton formation ratio in poly(p-phenylene-vinylene) light-emitting diode
(2003-04-04)
Lin, LC
;
Meng, HF
;
Shy, JT
;
Horng, SF
;
Yu, LS
The triplet to singlet exciton formation ratio in a poly(2-methoxy-5(2'-ethyl-hexyloxy)-1,4-phenylene vinylene) (MEH-PPV) light-emitting-diode is measured by comparing the triplet induced-absorptions with optical and electric excitations at same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-statistics value 3 at intermediate field but is reduced to about 1 for higher field.
Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes
(2003-01-24)
Lin, LC
;
Meng, HF
;
Shy, JT
;
Horng, SF
;
Yu, LS
The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.