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Spectral properties of Eu3+-activated yttrium oxysulfide red phosphor
(1998-09-30)
Tseng, YH
;
Chiou, BS
;
Peng, CC
;
Ozawa, L
;
電子工程學系及電子研究所
The effects of Eu on the spectral properties of Y2O2S have been investigated. The Y2O2S:Eu phosphor powders were prepared with a flux fusion method and electrophoretically deposited on an ITO-coated glass substrate to form a thin layer. Both cathodoluminescence and photoluminescence emission spectra of Y2O2S:Eu were measured. The highly intense emission lines at 616 and 626 nm are attributed to the transition from D-5(0) to F-7(2) levels. The color of Y2O2S:Eu phosphor varies from orange to red as the Eu concentration increases from Eu/ Y = 0.025 (molar ratio) to 0.06. The luminescence decay times are shorter than 1.1 ms for Eu concentrations ranging from 0.025 to 0.06 (Eu/ Y molar ratio). The luminescent color becomes redder but less bright as the Eu concentration is increased. (C) 1998 Elsevier Science S.A. All rights reserved.
Typeface identification for printed Chinese characters
(1998-03-01)
Tseng, YH
;
Kuo, CC
;
Lee, HJ
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a methodology for identifying typefaces of printed Chinese characters in documents. Three kinds of features, stroke width means, stroke width variations, and aspect ratio, are first used to classify character typefaces as: Black, Li, Kai-Round, or Ming-Song. Each of the last two groups contains two typefaces. Vertical/horizontal stroke width ratios are used to distinguish between the Ming and Song typefaces and accumulative pixel ratio to distinguish between the Kai and Round typefaces. Six different typeface feature distributions measured from 5401 printed Chinese characters are considered, and a trapezoid-shaped membership function is constructed for each distribution. Based on these membership functions, we determine what typeface each input character belongs to using a two-level decision tree. To increase the identification rate, the typeface of a certain character is adjusted according to the typeface identification results of the front and the next characters. In the character recognition system, we use two statistical features: crossing counts and contour directional counts. We achieved an 89.87% typeface identification rate in our experiments, and a 95.60% character recognition rate.
Spectral properties of Eu3+-activated yttrium oxysulfide red phosphor
(1998-09-30)
Tseng, YH
;
Chiou, BS
;
Peng, CC
;
Ozawa, L
;
電子工程學系及電子研究所
The effects of Eu on the spectral properties of Y2O2S have been investigated. The Y2O2S:Eu phosphor powders were prepared with a flux fusion method and electrophoretically deposited on an ITO-coated glass substrate to form a thin layer. Both cathodoluminescence and photoluminescence emission spectra of Y2O2S:Eu were measured. The highly intense emission lines at 616 and 626 nm are attributed to the transition from D-5(0) to F-7(2) levels. The color of Y2O2S:Eu phosphor varies from orange to red as the Eu concentration increases from Eu/ Y = 0.025 (molar ratio) to 0.06. The luminescence decay times are shorter than 1.1 ms for Eu concentrations ranging from 0.025 to 0.06 (Eu/ Y molar ratio). The luminescent color becomes redder but less bright as the Eu concentration is increased. (C) 1998 Elsevier Science S.A. All rights reserved.
Speeding up Chinese character recognition in an automatic document reading system
(1998-11-01)
Tseng, YH
;
Kuo, CC
;
Lee, HJ
;
資訊工程學系
;
Department of Computer Science
In this paper, we present two techniques for speeding up character recognition. Our character recognition system, including the candidate-cluster selection and modified branch-and-bound detail-matching modules, is implemented using two statistical features: crossing-counts and contour-direction counts. In the training stage, we divide characters into different clusters by using reference characters. To have a very high recognition rate, the candidate-cluster selection module selects the top 60 clusters with minimal distances from among 300 predefined clusters. To further speed-up the recognition speed, we use a modified branch-and-bound algorithm in the detail-matching module. In the automatic document reading system, characters and punctuation marks are first extracted from printed document images and sorted according to their positions and the document orientation. The system then recognizes all printed Chinese characters between pairs of punctuation marks. The results are then spoken aloud by a speech-synthesis system. The character recognition system and the text-to-speech synthesis system are integrated in the Windows-based document reading system, which provides a user-friendly environment. (C) 1998 Pattern Recognition Society. Published by Elsevier Science Ltd. All rights reserved.
Recognition-based handwritten Chinese character segmentation using a probabilistic Viterbi algorithm
(1999-08-01)
Tseng, YH
;
Lee, HJ
;
資訊工程學系
;
Department of Computer Science
This paper presents a recognition-based character segmentation method for handwritten Chinese characters. Possible non-linear segmentation paths are initially located using a probabilistic Viterbi algorithm. Candidate segmentation paths are determined by verifying overlapping paths, between-character gaps, and adjacent-path distances. A segmentation graph is then constructed using candidate paths to represent nodes and two nodes with appropriate distances are connected by an are. The cost in each are is a function of character recognition distances, squareness of characters and internal gaps in characters. After the shortest path is detected from the segmentation graph, the nodes in the path represent optimal segmentation paths. In addition, 125 text-line images are collected from seven form documents. Cumulatively, these text-lines contain 1132 handwritten Chinese characters. The average segmentation rate in our experiments is 95.58%. Moreover, the probabilistic Viterbi algorithm is modified slightly to extract text-lines from document pages by obtaining non-linear paths while gaps between text-lines are not obvious. This algorithm can also be modified to segment characters from printed text-line images by adjusting parameters used to represent costs of arcs in the segmentation graph. (C) 1999 Elsevier Science B.V. All rights reserved.
Using a fuzzy piecewise regression analysis to predict the nonlinear time-series of turbulent flows with automatic change-point detection
(2001)
Tseng, YH
;
Durbin, P
;
Tzeng, GH
;
科技管理研究所
;
Institute of Management of Technology
Research has already shown that turbulent flow consists of some coherent time- and space-organized vortical structures. Some dynamic systems and experimental models are employed to understand the turbulent generation mechanism. However, these approaches still cannot provide a good nonlinear analysis of turbulent time-series. In the real turbulent flow, very complicated nonlinear behaviors, which are affected by many vague factors are present. Based on the nonlinear behavior and the results of from this traditional research, we introduce multivariate statistical analysis of an experimental study to explain practical phenomenon. In this paper, a new approach of fuzzy piecewise regression analysis with automatic change-point detection is proposed to predict the nonlinear time-series of turbulent flows. In order to show the practicality and usefulness of this model, we present an example of predicting the near-wall turbulence time-series as a verifiable model. The results of practical applications show that the proposed method is appropriate and appears to be useful in nonlinear analysis and in fuzzy environments to predict the turbulence time-series.
Bright white light electroluminescent devices based on a dye-dispersed polyfluorene derivative
(2004-08-16)
Kim, JH
;
Herguth, P
;
Kang, MS
;
Jen, AKY
;
Tseng, YH
A series of efficient and bright white light-emitting diodes were fabricated using the blends of two fluorene-derived fluorescent dyes, (4,7-bis-(9,9,9('),9(')-tetrahexyl-9H,9(')H-[2,2(')]bifluoren-7-yl)-benzo[1,2,5]thiadiazole) (FFBFF-emits green) and (4,7-bis-[5-(9,9-dihexyl-9H-fluoren-2-yl)-thiophen-2-yl]-benzo[1,2,5]thiadiazole) (FTBTF-emits red) in an efficient blue-emitting polyfluorene-derived copolymer (poly[(9,9-bis(4-di(4-n-butylphenyl)aminophenyl))]-stat-(9,9-bis(4-(5-(4-tert-butylphenyl)-2-oxadiazolyl)-phenyl))-stat-(9,9-di-n-octyl)fluorene) (PF-TPA-OXD). The resulting white light-emitting device reaches a maximum external quantum efficiency of 0.82% and a maximum brightness of 12 900 cd/m(2) at 12 V. The Commission Internationale d'Enclairage chromaticity coordinates of the device remain very close to that of pure white emission at a relatively broad bias range from 6 V (x=0.36, y=0.37) to 12 V (x=0.34, y=0.34). (C) 2004 American Institute of Physics.
Highly efficient red electrophosphorescent devices based on an iridium complex with trifluoromethyl-substituted pyrimidine ligand
(2004-08-30)
Niu, YH
;
Chen, BQ
;
Liu, S
;
Yip, H
;
Bardecker, J
Highly efficient red-emitting electrophosphorescent devices were fabricated by doping an iridium (Ir) complex containing trifluoromethyl (CF3)-substituted pyrimidine ligand into a conjugated bipolar polyfluorene with triphenylamine and oxadiazole as side chains. The device efficiency can be enhanced through effective exciton confinement using a layer of 1,3,5-tris(N- phenylbenzimidazol-2-yl)benzene on the cathode side and a layer of in situ polymerized tetraphenyldiamine-perfluorocyclobutane on the anode side. For a blend with 5 wt % of the Ir complex, a maximum external quantum efficiency of 7.9 photon/electron % and a maximum brightness of 15800 cd/m(2) are reached with Commission Internationale de L'Eclairage chromaticity coordinates of x=0.65 and y=0.34. (C) 2004 American Institute of Physics.
Speeding-up Chinese character recognition in an automatic document reading system
(1997)
Tseng, YH
;
Kuo, CC
;
Lee, HJ
;
交大名義發表
;
資訊工程學系
In this paper, we present two techniques for speeding up character recognition. Our character recognition system, including the candidate-cluster selection and detail-matching modules, is implemented using two statistical features: crossing-counts and contour-direction counts. In the training stage, we divide characters into different clusters. To keep very high recognition rate, the candidate-cluster selection module selects the top 60 clusters with minimal distances from among 300 predefined clusters. To further speed-up the recognition speed, we use a modified branch-and-bound algorithm in the detail-matching module. In the automatic document-reading system, characters and punctuation marks are first extracted from printed document images and sorted according to their positions and the document orientation. The system then recognizes all printed Chinese characters between pairs of punctuation marks. The results are then spoken aloud by a speech-synthesis system.
Interfered-character recognition by removing interfering-lines and adjusting feature weights
(1998)
Tseng, YH
;
Lee, HJ
;
資訊工程學系
;
Department of Computer Science
Characters sometimes overlap with non-textual lines in form documents and these interfered-characters would generally be recognized with poor accuracy. In this paper we propose a two-step interfering-line removing method. Positions and orientations of interfering-lines are first detected by the Hough transform. Interfering-line widths are then determined from projection histograms. An ambiguous area is defined to bound an interfering-line. Black runs in the ambiguous are classified into four types and grouped into run-groups. The directions of hidden character strokes in each run-groups are predicted. Black pixels located in these hidden strokes are regarded as character pixels and the other black pixels are considered as interfering pixels, which will be removed then. Most OCR engines are trained by non-interfered sample characters. In order to recognize interfered-characters, we adjust the feature values by assigning a stability value to each of sub-regions. In our collected 1820 interfered handwritten Chinese characters, the recognition accuracy was 24.02% for interfered-characters and 89.91% for characters after removing interfering-lines.

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