Browsing by Author "Wang, W. J."

Now showing 1 - 4 of 4

Effect of donor-acceptor concentration ratios on nonradiative energy transfer in closely packed CdTe quantum dots
(2009-09-28)
Lin, Y. C.
;
Wang, W. J.
;
Chung, H. L.
;
Chou, W. C.
;
Chen, W. K.
This study investigates the dependence of Forster resonance energy transfer (FRET) on donor-acceptor (D/A) concentration ratios in mixed-size CdTe quantum dots (QDs) films by using photoluminescence (PL) and time-resolved PL spectroscopy. Experimental results indicate that an increasing donor concentration significantly quenches the emission intensity and lifetime in donor QDs and enhances that in acceptor QDs, providing clear evidence of increased FRET efficiency. When D/A ratio exceeds 6, however, the emission intensity and the lifetime of acceptors start to decline, reflecting a decreasing FRET efficiency because of a markedly declining availability of acceptor QDs. (C) 2009 American Institute of Physics. [doi:10.1063/1.3242371]
Interactive Relevance Visual Learning for Image Retrieval
(2015-01-01)
Fu, Hsin-Chia
;
Wang, Z. H.
;
Wang, W. J.
;
Pao, Hsiao-Tien
;
管理科學系
This paper proposes mixture Gaussian neural networks (MGNN) to learn visual features from user specified query image objects or regions for relevance image retrieval. Instead of segmenting query image regions from sample images, relevance feedback feature learning is performed by the proposed MGNN to extract query visual features. After feature learning, the MGNN can be used to measure the appearance difference between the query features and images for image retrieval. The proposed methods were tested on COREL image gallery and the WWW image collections, and testing results were compared with currently leading approaches. From the experimental results, that the extracted and learned query visual features by MGNN can be very close to users\' mind and/or desire, and the closeness is somewhat related to the number of feature leaning iterations. Since any dimensional data can be approximated by mixture Gaussian distributions, thus using MGNN to query and to retrieve similar and/or relevance high dimensional data or images will be a new area of research for future works.
Time-resolved photoluminescence of isoelectronic traps in ZnSe(1-x)Te(x) semiconductor alloys
(2008-12-15)
Lin, Y. C.
;
Chou, W. C.
;
Fan, W. C.
;
Ku, J. T.
;
Ke, F. K.
Kohlrausch's stretched exponential law correlates well with the photoluminescence (PL) decay profiles of ZnSe(1-x)Te(x). As the Te concentration increases, the stretching exponent beta initially declines and then monotonically increases. This result can be understood using the hopping-transport and energy transfer model. The increase in the number of isoelectronic Te localized traps can reduce the PL decay rate and increase the linewidth, whereas the hybridization of the Te localized states with the valence-band edge states causes a reduction in both the lifetime and linewidth.
Time-resolved photoluminescence of isoelectronic traps in ZnSe1-xTex semiconductor alloys
(2008-12-15)
Lin, Y. C.
;
Chou, W. C.
;
Fan, W. C.
;
Ku, J. T.
;
Ke, F. K.
Kohlrausch's stretched exponential law correlates well with the photoluminescence (PL) decay profiles of ZnSe1-xTex. As the Te concentration increases, the stretching exponent beta initially declines and then monotonically increases. This result can be understood using the hopping-transport and energy transfer model. The increase in the number of isoelectronic Te localized traps can reduce the PL decay rate and increase the linewidth, whereas the hybridization of the Te localized states with the valence-band edge states causes a reduction in both the lifetime and linewidth.