Browsing by Author "Wu, T. Y."

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A Method for Extracting Suspected Parotid Lesions in CT Images using Feature-based Segmentation and Active Contours based on Stationary Wavelet Transform
(2013)
Wu, T. Y.
;
Lin, S. F.
;
電機工程學系
;
Department of Electrical and Computer Engineering
Automatic suspected lesion extraction is an important application in computer-aided diagnosis (CAD). In this paper, we propose a method to automatically extract the suspected parotid regions for clinical evaluation in head and neck CT images. The suspected lesion tissues in low contrast tissue regions can be localized with feature-based segmentation (FBS) based on local texture features, and can be delineated with accuracy by modified active contour models (ACM). At first, stationary wavelet transform (SWT) is introduced. The derived wavelet coefficients are applied to derive the local features for FBS, and to generate enhanced energy maps for ACM computation. Geometric shape features (GSFs) are proposed to analyze each soft tissue region segmented by FBS; the regions with higher similarity GSFs with the lesions are extracted and the information is also applied as the initial conditions for fine delineation computation. Consequently, the suspected lesions can be automatically localized and accurately delineated for aiding clinical diagnosis. The performance of the proposed method is evaluated by comparing with the results outlined by clinical experts. The experiments on 20 pathological CT data sets show that the true-positive (TP) rate on recognizing parotid lesions is about 94%, and the dimension accuracy of delineation results can also approach over 93%.
Phase-direct channel estimation for space-time OFDM
(2006)
Hsieh, Shih-Fu
;
Wu, T. Y.
;
電信工程研究所
;
Institute of Communications Engineering
Space time (ST) OFDM can achieve high data rate transmissions with diversity gains. However, channel estimation is necessary at the receiver end to recover the signal. To further improve the subspace-based estimated channel, we introduce phase direct (PD) in the ST OFDM system. PD is originally used in OFDM system, and not suited in ST OFDM. Hence, we exploit the transmitted data's spatial and temporal correlation to develop a sum-difference square algorithm to solve this problem for ST OFDM.
Phase-direct channel estimation for space-time OFDM
(2006)
Hsieh, Shih-Fu
;
Wu, T. Y.
;
電信工程研究所
;
Institute of Communications Engineering
Space time (ST) OFDM can achieve high data rate transmissions with diversity gains. However, channel estimation is necessary at the receiver end to recover the signal. To further improve the subspace-based estimated channel, we introduce phase direct (PD) in the ST OFDM system. PD is originally used in OFDM system, and not suited in ST OFDM. Hence, we exploit the transmitted data's spatial and temporal correlation to develop a sum-difference square algorithm to solve this problem for ST OFDM.
Phase-direct channel estimation for space-time OFDM
(2006-01-01)
Hsieh, Shih-Fu
;
Wu, T. Y.
;
電信工程研究所
;
Institute of Communications Engineering
Space time (ST) OFDM can achieve high data rate transmissions with diversity gains. However, channel estimation is necessary at the receiver end to recover the signal. To further improve the subspace-based estimated channel, we introduce phase direct (PD) in the ST OFDM system. PD is originally used in OFDM system, and not suited in ST OFDM. Hence, we exploit the transmitted data's spatial and temporal correlation to develop a sum-difference square algorithm to solve this problem for ST OFDM.
Photoluminescence of localized excitons in ZnCdO thin films grown by molecular beam epitaxy
(2016-07)
Wu, T. Y.
;
Huang, Y. S.
;
Hu, S. Y.
;
Lee, Y. C.
;
Tiong, K. K.
We have investigated the luminescence characteristics of Zn1-xCdxO thin films with different Cd contents grown by molecular beam epitaxy system. The temperature-dependent photoluminescence (PL) and excitation power-dependent PL spectra were measured to clarify the luminescence mechanisms of the Zn1-xCdxO thin films. The peak energy of the Zn1-xCdxO thin films with increasing the Cd concentration is observed as redshift and can be fitted by the quadratic function of alloy content. The broadened full-width at half-maximum (FWHM) estimated from the 15 K PL spectra as a function of Cd content shows a larger deviation between the experimental values and theoretical curve, which indicates that experimental FWHM values are affected not only by alloy compositional disorder but also by localized excitons occupying states in the tail of the density of states. The Urbach energy determined from an analysis of the lineshape of the low-energy side of the PL spectrum and the degree of localization effect estimated from the temperature-induced S-shaped PL peak position described an increasing mean exciton-localization effects in ZnCdO films with increasing the Cd content. In addition, the PL intensity and peak position as a function of excitation power are carried out to clarify the types of radiative recombination and the effects of localized exciton in the ZnCdO films with different Cd contents. (C) 2016 Elsevier Ltd. All rights reserved.
Photoluminescence properties of MgxZn1-xO films grown by molecular beam epitaxy
(2017-02-01)
Wu, T. Y.
;
Huang, Y. S.
;
Hu, S. Y.
;
Lee, Y. C.
;
Tiong, K. K.
The optical properties of MgxZn1-xO films with x=0.03, 0.06, 0.08, and 0.11 grown by molecular beam epitaxy (MBE) have been studied by temperature-dependent photoluminescence (PL) measurement. It is presented that the full-width at half-maximum (FWHM) of the 12 K PL spectrum of MgZnO films increases with increasing Mg concentration and would deviate significantly from the simulation curve of Schubert model with higher Mg contents. The abnormal broader PL FWHM is inferred from larger compositional fluctuation by incorporating higher Mg contents, which results in larger effect of excitonic localization to induce more significant S-shaped behavior of the PL peak energy with temperature dependence. Additionally, the degree of localization increases as the linear proportion of the PL FWHM, indicating that the excitonic behavior in MgZnO films belong to the strong localization effect.
Precise measurement of the thermo-optical coefficients of various Nd-doped vanadates with an intracavity self-mode-locked scheme
(2014-03-01)
Tung, J. C.
;
Wu, T. Y.
;
Liang, H. C.
;
Chen, Y. F.
;
電子物理學系
We employ an intracavity self-mode-locked laser to precisely measure the group refractive indices and thermo-optic coefficients for Nd-doped vanadates at 1064 nm. The samples include Nd:GdVO4, Nd:YVO4 and Nd:LuVO4 crystals. We make a detailed comparison between the present results and those currently reported in the literature. We confirm that the present results are in good agreement with the currently available data with the best precision.