Browsing by Author "Chen, Ying-Ru"

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Growth of InN on Si (111) by atmospheric-pressure metal-organic chemical vapor deposition using InN/AlN double-buffer layers
(2008-07-01)
Li, Zhen-Yu
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Lan, Shan-Ming
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Uen, Wu-Yih
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Chen, Ying-Ru
;
Chen, Meng-Chu
Indium nitride (InN) epilayers have been successfully grown on Si (111) substrates with low-temperature (450 degrees C) grown InN and high-temperature (1050 degrees C) grown AlN (InN/AlN) double-buffer layers by atmospheric-pressure metal-organic chemical vapor deposition (AP-MOCVD). X-ray diffraction characterizations indicated that highly (0001)-oriented hexagonal InN was grown on Si (111) substrate. Photoluminescence (PL) analyses performed at room temperature showed a strong emission at 0.72 eV with a full width at half maximum of 121 meV. Excitation intensity dependent measurements demonstrated the PL mechanism to be the band-to-band transition. Time-resolved PL could be fitted by a single exponential exhibiting an ordered film and a recombination lifetime of around 0.85 ns. In particular, transmission electron microscopy characterizations indicated that the use of AlN first buffer is very important to achieve a structurally uniform (0001)-oriented InN epilayer on Si (111) by AP-MOCVD. (C) 2008 American Vacuum Society.
Region image sharing with various secrecy levels
(2017-01)
Chen, Ying-Ru
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Chen, Ling-Hwei
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資訊工程學系
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Department of Computer Science
In most secret image sharing schemes, the secrecy level of each pixel is the same. However, in real applications, different pixels may require different secrecy levels. For example, in a patient\'s medical image, the region with the patient\'s name must be highly protected. To solve this problem, Wang and Lin proposed a scheme that allows a dealer to divide an image into multiple regions, each of which is associated with a certain level of secrecy. In their scheme, an extra pixel-security-level map (PSLM) is required to record the secrecy level of each pixel, and the shadow size of the PSLM is approximately 20 % of that of the secret image. It is unreasonable to have such a large overhead. To reduce the shadow size of the PSLM, they restricted each region to be a rectangle. Furthermore, any two participants can reconstruct the PSLM, enabling the content of regions with high secrecy levels to be compromised easily. To resolve these disadvantages, this paper proposes a new encoding scheme for PSLMs. The location of each region is protected according to its secrecy level, thus improving the security of the image. Moreover, the shape of each region is unrestricted, and the shadow size of the PSLM is reduced significantly.
Secret image sharing with smaller shadow sizes for general access structures
(2016-11)
Chen, Ying-Ru
;
Chen, Ling-Hwei
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Shyu, Shyong Jian
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資訊工程學系
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Department of Computer Science
In the area of secret image sharing (SIS), most papers focused on the schemes for threshold or some special access structures. Regarding general access structures (GAS), few results have been found in the literature. Two SIS schemes for GAS were proposed in 2001 and 2010, both are based on qualified sets. However, one distorts the reconstructed secret image, and some extra information is needed in both schemes. Here, we propose three polynomial based SIS schemes for GAS. Considering either qualified or forbidden sets, these schemes can reconstruct the secret image perfectly without any extra information needed. Some proof and analysis on the shadow sizes of the three schemes are given to lead us to choose the one with the smallest size. In addition, we also give some comparisons with two existing schemes, and security issue is also addressed in conclusion.