Browsing by Author "Hsu, JH"

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An extended Chi2 algorithm for discretization of real value attributes
(2005-03-01)
Su, CT
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Hsu, JH
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工業工程與管理學系
;
Department of Industrial Engineering and Management
The Variable Precision Rough Sets (VPRS) model is a powerful tool for data mining, as it has been widely applied to acquire knowledge. Despite its diverse applications in many domains, the VPRS model unfortunately cannot be applied to real-world classification tasks involving continuous attributes. This requires a discretization method to preprocess the data. Discretization is an effective technique to deal with continuous attributes for data mining, especially for the classification problem. The modified Chi2 algorithm is one of the modifications to the Chi2 algorithm, replacing the inconsistency check in the Chi2 algorithm by using the quality of approximation, coined from the Rough Sets Theory (RST), in which it takes into account the effect of degrees of freedom. However, the classification with a controlled degree of uncertainty, or a misclassification error, is outside the realm of RST. This algorithm also ignores the effect of variance in the two merged intervals. In this study, we propose a new algorithm, named the extended Chi2 algorithm, to overcome these two drawbacks. By running the software of See5, our proposed algorithm possesses a better performance than the original and modified Chi2 algorithms.
Optical properties of high density InGaN QDs grown by MOCVD
(2006-07-01)
Lee, CK
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Hsu, JH
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Wang, DC
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Chang, YH
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Kuo, HC
In this article, we investigate the relaxation time constant and optical properties of InGaN QDs following different durations of SiNx treatment. We find that the smaller size QDs have smaller red shift as temperature increasing, only about 10 meV. Time-resolved PL at various emitting wavelength of the three samples is also investigated. Decreasing time constant as increasing QDs size is observed. Besides, we also find the decreasing time constant with shorter wavelength. Meanwhile, decreasing time constant as increasing emitting wavelength is characterized and attributed as an increasing confinement of excitons in QDs with higher localization energy and thus with a higher electron-hole overlap. (c) 2005 Elsevier B.V. All rights reserved.
Precision parameter in the variable precision rough sets model: an application
(2006-04-01)
Su, CT
;
Hsu, JH
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Despite their diverse applications in many domains, the variable precision rough sets (VPRS) model lacks a feasible method to determine a precision parameter (beta) value to control the choice of beta-reducts. In this study we propose an effective method to find the beta-reducts. First, we calculate a precision parameter value to find the subsets of information system that are based on the least upper bound of the data misclassification error. Next, we measure the quality of classification and remove redundant attributes from each subset. We use a simple example to explain this method and even a real-world example is analyzed. Comparing the implementation results from the proposed method with the neural network approach, our proposed method demonstrates a better performance. (c) 2004 Elsevier Ltd. All rights reserved.
Self-embedded nanocrystalline chromium carbides on well-aligned carbon nanotips
(2003-06-16)
Tsai, CL
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Hsu, JH
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Chen, CF
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材料科學與工程學系
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Department of Materials Science and Engineering
Well-aligned carbon nanotips embedded with nanocrystalline chromium carbide were directly grown on a substrate by microwave plasma chemical vapor deposition. These nanomaterials grew up to about 1 mum long and 60 nm in diameter, yielding a high aspect ratio. In comparison between carbon nanotubes with hollow structure, transmission electron microscopy images show its solid body, which is made of graphite along with nanocrystalline chromium carbide on the tip. These nanomaterials perform well in field emission applications with a turn-on field of 1.38 V/mum and 565 muA/cm(2) at 2.2 V/mum. Our result confirms the possibility of the self-embedded nanocrystalline materials on the top of carbon nanotips. (C) 2003 American Institute of Physics.