Browsing by Author "Hsieh, YC"

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A homophonic DES
(1998-06-30)
Hsieh, TM
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Yeh, YS
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Hsieh, YC
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Wang, CC
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資訊科學與工程研究所
In this paper, we propose a variant of DES called a homophonic DES. The DES algorithm is strengthened by adding some random bits into the plaintext, which are placed in particular positions to maximize diffusion, and to resist differential attack. (C) 1998 Elsevier Science B.V. All rights reserved.
High density culture of insect cells using rational medium design and feeding strategy
(2000-06-01)
Chiou, TW
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Hsieh, YC
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Ho, CS
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生物科技學系
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Department of Biological Science and Technology
The objective of this study is to achieve high density cell culture by a rational medium design and feeding strategy. Insect cell/baculovirus expression system is one of the widely used methods for the production of heterologous proteins in the cell culture domain. Insect cell Spodoptera frugiperda Sf-21 and a recombinant baculovirus with encoded gene for human interleukin-5 were chosen as the model system in this study. A stoichiometric model was established to study the demand of nutrients, including glucose, 20 amino acids, and yeastolate, for the synthesis of cell mass. The coefficients for individual nutrients in the stoichiometric equation governing insect cell growth were determined from the information of cell mass and compositions. Based on the stoichiometric coefficients, the initial and supplemental media for fed-batch cell cultures were designed. The experiments began with the inoculation of Sf-21 cells into a spinner flask with the initial medium, which provided a starting environment for achieving optimum cell growth. This was followed by the periodic feeding of supplemental medium designed by utilizing the stoichiometric equation that governs insect cell growth. With this strategy, it was demonstrated that the Sf-21 cell culture reached a cell density in excess of 1.9 x 10(7) cells/ml. During the cultivation process, the utilization of various nutrients and the production of metabolites were also monitored. Further experiments proved that high concentration of recombinant product (such as human interleukin-5) could be achieved by infecting the high density cells (resulting from the designed medium) with recombinant baculoviruses.
Interface-blocking mechanism for reduction of threading dislocations in SiGe and Ge epitaxial layers on Si(100) substrates
(2004-09-01)
Yang, TH
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Luo, GL
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Chang, EY
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Hsieh, YC
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Chang, CY
A mechanism of interface blocking was proposed to reduce the threading dislocations in the SiGe and Ge layers on Si(100) substrates. In this work, epitaxial Si1-xGex/Si1-(x-y)Gex-y and Ge/SiyGe1-y layers were grown by UHV/CVD. It was surprisingly found that if the variation of the Ge composition, y, across the interface of Si1-xGex/Si1-(x-y)Gex-y or Ge/SiyGe1-y is higher than a certain value, most of the threading dislocations appear to be blocked and confined in the underlying Si1-(x-y)Gex-y or SiGe1-y layer by the interface. It implies that this finding can provide a simple way to grow high-quality relaxed SiGe and Ge layers on the Si substrates. (C) 2004 American Vacuum Society.
Optimization of the growth of the InGaP etch-stop layer by MOVPE for InGaP/GaAs HBT device application
(2006-03-15)
Hsieh, YC
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Chang, EY
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Yeh, SS
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Chang, CW
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Luo, GL
InGaP has high etching selectivity to GaAs. It can be used as the etch-stop layer to easily fabricate the InGaP/GaAs heterojunction bipolar transistors (HBTs). This process will also increase the uniformity and manufacturability of the HBT devices. However, the InGaP etch-stop layer will increase the energy barrier height that electrons have to overcome flowing from the collector to the subcollector, which will decrease the DC current gain of the device (T. Kobayashi, K. Taira, F. Nakamua, H. Kawai, J. Appl. Phys. 65 (1989) 4898). Therefore, the InGaP etch-stop layer has to be thin enough not to affect the device performance. But the spontaneous formation of the InxGa1-xAsyP1-y intermixing layer between GaAs/InGaP during the metal organic vapour-phase epitaxy (MOVPE) growth will affect the InGaP layer thickness needed as an effective etch-stop layer. In this paper, very thin InGaP layer was achieved with the suppression of InxGa1-xAsyP1-y formation by the optimization of the growth temperature and the gas switching sequence time. An effective 20 angstrom InGaP etch-stop layer was grown at 575 degrees C with interruption time of 3 s. Both STEM and PL data proved that the intermixing InxGa1-xAsyP1-y layer was eliminated and from the selective etching experiment, this 20 angstrom InGaP layer can stand 45 s etching by the H3PO4:H2O2:H2O = 1:1:20 solution. (c) 2005 Elsevier B.V. All rights reserved.