Browsing by Author "Wang, RC"

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An improvement of the Yang-Shieh password authentication schemes
(2005-03-25)
Yang, CC
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Wang, RC
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Chang, TY
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資訊工程學系
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Department of Computer Science
Recently, Yang and Shieh proposed two password authentication schemes by employing smart cards. One is a timestamp-based password authentication scheme and the other is a nonce-based password authentication scheme. In 2002, Chan and Cheng pointed Out that Yang and Shieh's timestamp-based password authentication scheme was vulnerable to the forgery attack. However, in 2003, Sun and Yell pointed Out that Chan and Cheng's attack was unreasonable. At the same time, Sun and Yell pointed out that Yang and Shieh's password authentication schemes were still Vulnerable to the forgery attack. In this paper, we shall improve Yang and Shieh's schemes to resist Sun and Yell's attack. (C) 2004 Elsevier Inc. All rights reserved.
Drawing of microshear deformation zones in glassy polymers: Poly(phenylene oxide) (PPO)
(1996-04-30)
Yang, ACM
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Wang, RC
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Kunz, MS
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Yang, IC
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電子物理學系
The topography of the microscopic shear deformation zones (SDZ) in the glassy polymer PPO was studied by using atomic force microscopy (AFM) and was used to analyze the growth and breakdown of the SDZ. It was found that the local stress and strain are almost constant within the deformation zones but higher than those in the elastic regions. The maximum strain rate during stretching was found to always locate near the SDZ boundaries, indicating that most drawing took place there. With both the local stress and strain obtained for every point within the SDZ, it is possible to construct a full stress-strain curve for the drawing of the tiny local deformation zones. The stress-strain curve clearly demonstrates a yield point in the beginning of microyielding where the tensile modulus was found to be much lower than that in the elastic regime. Some strain hardening, however, took place at larger deformation. Moreover, we found that for each microscopic region participated in the microdrawing the local strain rate increased with local strain until a critical strain around 0.65 was reached, after which the strain rate decreased with strain. This critical strain may be related to the chain entanglement network structure because it shifted to 0.75 when PS diluents were blended into PPO, indicating that strain hardening was delayed by the increase of chain entanglement mesh size. (C) 1996 John Wiley & Sons, Inc.
Evolution of surface morphology of YBa2Cu3O7 superconducting thin films on MgO and NdGaO3 substrates
(1996-04-01)
Wu, KH
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Lin, HC
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Wang, RC
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Juang, JY
;
Uen, TM
A modification on a laser scanning ablation system capable of preparing large area YBa2Cu3O7 (YBCO) thin films has been made. With this modification, YBCO films with various thicknesses can be deposited in-situ on several pieces of substrates under essentially identical deposition conditions, and particularly, in a continuous fashion. Films of sequential thickness on different substrates were then studied by atomic force microscopy to investigate the effects of lattice mismatch and treatments of substrate on the growth mechanism of YBCO films.
Preparation of large area and investigation of initial film growth of YBa2Cu3O7 by scanning pulsed laser deposition
(1996-07-15)
Wu, KH
;
Wang, RC
;
Chen, SP
;
Lin, HC
;
Juang, JY
A pulsed laser deposition system with a rotating reflector, which can generate an extended plume with a diameter of about 40 mm, has been proven to be viable in producing large area YBa2Cu3O7 (YBCO) thin films. Films with uniformity of thickness and electrical properties to within a few percents were obtained. By making a further modification on this laser scanning system, YBCO films with various thicknesses can be deposited in situ on several pieces of substrates under essentially identical deposition conditions, and particularly, in a continuous fashion. The atomic force microscopy (AFM) images reveal that films grown on NdGaO3 follow the Stranski-Krastanov (layer then island growth) mode, while films grown on as-polished MgO and on annealed MgO follow the Volmer-Weber (islands without layer growth) mode and step-flow mode, respectively. (C) 1996 American Institute of Physics.
Preparation of large area and investigation of initial film growth of YBa2Cu3O7 by scanning pulsed laser deposition
(1996-07-15)
Wu, KH
;
Wang, RC
;
Chen, SP
;
Lin, HC
;
Juang, JY
A pulsed laser deposition system with a rotating reflector, which can generate an extended plume with a diameter of about 40 mm, has been proven to be viable in producing large area YBa2Cu3O7 (YBCO) thin films. Films with uniformity of thickness and electrical properties to within a few percents were obtained. By making a further modification on this laser scanning system, YBCO films with various thicknesses can be deposited in situ on several pieces of substrates under essentially identical deposition conditions, and particularly, in a continuous fashion. The atomic force microscopy (AFM) images reveal that films grown on NdGaO3 follow the Stranski-Krastanov (layer then island growth) mode, while films grown on as-polished MgO and on annealed MgO follow the Volmer-Weber (islands without layer growth) mode and step-flow mode, respectively. (C) 1996 American Institute of Physics.