Browsing by Issue Date, starting with "1999-11-16"

Now showing 1 - 20 of 80191

The effect of heat treatment on Ni/Au ohmic contacts to p-type GaN
(1999-11-16)
Chen, LC
;
Ho, JK
;
Chen, FR
;
Kai, JJ
;
Chang, L
The effect of heat treatment temperature on the microstructure and specific contact resistance of oxidized Ni(5 nm)/Au(5 nm) contacts to p-type GaN was investigated.,The: minimum specific contact resistance (Q(c)) obtained was 4 x 10(-6) Omega cm(2) after heat treating at 500 degrees C in air for 10 min. The cross-sectional microstructure of heat treated Ni/Au films on p-type GaN was examined with transmission electron microscope (TEM) in conjunction with compositional analyses. The high value of Q(c) for samples heat treated at lower temperatures (< 400 degrees C) was attributed to the fact that Au islands and crystalline NiO detached from the p-type GaN. When the temperature increased to 500 degrees C, NiO films and Au islands epitaxially constructed on p-type GaN matrix. The crystalline NiO may play a crucial role in the formation of low-resistance ohmic contact to p-GaN. Increasing the temperature further to 600 degrees C, large voids adjacent to p-GaN were observed which resulted in the reduction of contacting area deteriorating the contact resistance.
早秋
(1999-11-17)
管管
Level stability of the quantum dots with impurity
(1999-11-20)
Huang, YS
;
Liaw, SS
;
電子物理學系
;
Department of Electrophysics
An atom located at the center of the constant spherical potential is adopted as a simple model for a quantum dot with impurity. We find that, under this model, the stability of the energy levels of a quantum dot with impurity can be controlled by adjusting either the size or the band gap of the quantum dot.
G33D mutant thioredoxin primarily affects the kinetics of reaction with thioredoxin reductase. Probing the structure of the mutant protein
(1999-11-23)
Lin, TY
;
生物科技學系
;
Department of Biological Science and Technology
Escerichia coli thioredoxin is a redox-active protein. A mutant protein with an aspartic acid substitution for the largely conserved glycine at position 33 (G33D) in the active site of thioredoxin has been generated to study the effects of a negatively charged residue in the active site of the protein. Despite the close proximity of the negative-charged Asp to the redox active cysteines, the effective concentration of the cysteines does not deviate significantly from that of the wild-type protein. The redox potential (E-o') measured by the equilibrium between NADPH and the mutant thioredoxin is also close to that of the wild-type. Kinetic measurements of the reaction between thioredoxin and thioredoxin reductase show that G33D mutant and the wild-type proteins have identical k(cat) values. However, the K-m for G33D mutant is approximately 10-fold higher than that for the wild-type protein. In vivo assay of the growth of E.coli strain carrying wild-type or G33D mutant thioredoxin on methionine sulfoxide indicates that the G33D mutant protein is a slower electron donor for methionine sulfoxide reductase. Structural stability of the oxidized protein is not altered by the G33D substitution, as illustrated by the same unfolding free energies studied by urea. The substitution does not show significant change of the near UV and far-UV circular dichroic (CD) and the fluorescence spectra for either the reduced or the oxidized protein. Therefore, the global structure of the G33D protein is not changed. However, the surface of the active site has been altered locally by G33D substitution, which accounts for the above kinetically poor behaviors. A model of G33D structure is constructed based on these studies.
Propagation of thermal waves in a composite medium with interface thermal boundary resistance
(1999-11-26)
Lor, WB
;
Chu, HS
;
機械工程學系
;
Department of Mechanical Engineering
This article numerically analyzes the hyperbolic heat conduction problem in a two-layer composite medium under an initial temperature pulse emanating from the exterior surface of one layer. Reflection and transmission occur when the initial pulse wave impacts the contact surface of the dissimilar material. An interfacial layer with low conductivity and narrow thickness exists at the interface, which is employed to model the thermal boundary resistance at the contact surface, Analysis results indicate Bat the interface resistance significantly influences the wave pattern and strength. The presentation of the wave nature in Be interfacial layer deforms the initial ware feature and induces secondary wavelets behind the reflected and transmitted wave. In addition, the piecewise secondary wavelets become smooth when the interfacial width is very thin. Also examined herein is the effect of conductivity and thickness width of the interfacial layer coupled with variation of Be two-layer properties ratio on the reflection-transmission-combination phenomena.
The correct diameter of trivalent Cayley graphs
(1999-11-26)
Tsai, CH
;
Hung, CN
;
Hsu, LH
;
Chang, CH
;
資訊工程學系
Let n be a positive integer with n greater than or equal to 2. The trivalent Cayley interconnection network, denoted by TCIN(n), is proposed by Vadapalli and Srimani (1995). Later, Vadapalli and Srimani (1996) claimed that the diameter of TCIN(n) is 2n - 1. In this paper, we argue that the above claim is not correct. Instead, we show that the diameter of TCIN(n) is 2n - 1 only for n = 2 and 2n - 2 for all other cases. (C) 1999 Elsevier Science B.V. All rights reserved.
Total synthesis of 9-isocyanoneopupukeanane
(1999-11-26)
Ho, TL
;
Jana, GH
;
應用化學系
;
Department of Applied Chemistry
Preparation and epoxy curing of p-nonylphenol/dicyclopentadiene adducts
(1999-11-28)
Tseng, FP
;
Chang, FC
;
Lin, SF
;
Lin, JJ
;
應用化學系
Phenol/dicyclopentadiene adducts were prepared from the BF3-catalyzed reaction of p-nonylphenol and dicyclopentadiene at molar ratios of 2 : 1 and 3 : 2. These dicyclopentadiene-derived novolac products contain tricyclodecane and multiple phenol functionalities. In curing with diglycidyl ether of bisphenol A, the polymer properties were compared with those cured with formaldehyde novolac or Jeffamine D-400 amine. When p-nonylphenol/dicyclopentadiene adducts were mixed with other commercially available curing agents such as Jeffamine D-400 amine, the tricyclodecane functionality was introduced into the resulting epoxy network. The flexibility of the cured resin was improved due to the presence of the tricyclodecane moiety in the polymer structure. (C) 1999 John Wiley & Sons, Inc.
摩耶精舍那隻孤鸞
(1999-11-29)
管管
Flow effect in the chiral-homeotropic liquid-crystal cell
(1999-11-29)
Chen, SH
;
Chen, LY
;
光電工程學系
;
Department of Photonics
We investigated the dynamics of the chiral-homeotropic liquid-crystal cell and found that the flow of liquid crystal causes an optical bounce after switching on a high applied voltage. We analyzed the behavior of the directors by computer simulation and found that the field-induced backflow effect results in the abnormal twist of the directors near the substrates. The abnormal twist slows down the rising speed of the chiral-homeotropic cell and produces an optical bounce during the rising period. Our results indicate that the backflow effect should be considered on the design of fast chiral-homeotropic liquid-crystal cells. The significant distinctions between this field-induced optical bounce and the well-known optical bounce of the twisted nematic liquid-crystal cell are also described in this letter. (C) 1999 American Institute of Physics. [S0003-6951(99)04148-0].
Effects of Mo-free C40Ti(Si1-xGex)(2) precursors and the thickness of an interposed Mo layer on the enhanced formation of C54Ti(Si1-xGex)(2)
(1999-11-29)
Luo, JS
;
Huang, JC
;
Lin, WT
;
Chang, CY
;
Shih, PS
The effects of Mo-free C40 Ti(Si1-xGex)(2) precursors and the thickness of an interposed Mo layer between Ti films and Si0.76Ge0.24 substrates on the lowering of formation temperature of C54 Ti(Si1-xGex)(2) were studied. Metastable C40 Ti(Si1-xGex)(2) precursors were grown by pulsed KrF laser annealing. Upon rapid thermal annealing, the Mo-free C40 phase could not be directly transformed to the C54 phase without going through the C49 phase. When the thickness of the interposed Mo layer increased, up to 2.5 nm, the temperature at which the C54 phase was initially formed changed from 750 to 600 and then to 650 degrees C. The present result showed that with increasing Mo concentration in the reacted layer, the phase stability shifted from C54 to C40 and no C49 was observed. It seems that apart from the C40 template mechanism, the electron/atom ratio also plays an important role in the enhanced formation of the C54 phase. (C) 1999 American Institute of Physics. [S0003-6951(99)02048-3].
A systematic approach for developing a foot size information system for shoe last design
(1999-11-29)
Cheng, FT
;
Perng, DB
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The property of a shoe last design significantly impacts the fitness of the shoes thus produced. Traditionally, a shoe last is designed by using numerous foot measure data. Among all the items of foot measure information, the foot length and joint girth are further identified as principle factors affecting shoe last design. In this paper, foot length and joint girth are analyzed by using a bi-variate normal distribution to obtain a more efficient foot size grading system. A set of 2486 adult male samples collected in Taiwan area are used in this analysis to establish the norm for the foot length and joint girth. A foot size information system (FSIS) providing shoe last related information such as the percentage of population that a last can fit in is established from the analysis results. This study contributes designers the grading information that is helpful for shoe last design. Relevance to industry Shoe last design is the basis for footwear design. The foot size information system derived in this paper provides shoe making industry with a more efficient and economical size grading system to design shoe lasts. This grading system also promotes customer satisfaction with better fitness in foot size. (C) 1999 Elsevier Science B.V. All rights reserved.
A polynomial time algorithm for shaped partition problems
(1999-11-29)
Hwang, FK
;
Onn, S
;
Rothblum, UG
;
應用數學系
;
Department of Applied Mathematics
We consider the class of shaped partition problems of partitioning n given vectors in d-dimensional criteria space into p parts so as to maximize an arbitrary objective function which is convex on the sum of vectors in each part, subject to arbitrary constraints on the number of elements in each part. This class has broad expressive power and captures NP-hard problems even if either d or p is fixed. In contrast, we show that when both d and p are fixed, the problem can be solved in strongly polynomial time. Our solution method relies on studying the corresponding class of shaped partition polytopes. Such polytopes may have exponentially many vertices and facets even when one of d or p is fixed; however, we show that when both d and p are fixed, the number of vertices of any shaped partition polytope is O(n(d(p2))) and all vertices can be produced in strongly polynomial time.
Authentication protocols for the broadband ISDN billing system
(1999-12-01)
Lo, CC
;
Yeh, YC
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
The broadband integrated services digital network (B-ISDN) offers a wide variety of services to its customers. From both provider's and user's perspective, a fair and flexible billing system is indispensable to the operation of B-ISDN. In this paper, we discuss different billing policies, and their corresponding authentication protocols, which can be used by the B-ISDN billing system. Flat rate and usage-based rate are two most frequently used billing policies. Because of the diversity of B-ISDN services, combining these two billing policies, along with priority pricing, is a feasible scheme for designing a B-ISDN billing system. The membership authentication protocol (MAP) and the personal authentication protocol (PAP) are proposed to support the authentication requirements of the flat rate and usage-based rate billing policies, respectively. The MAP applies the cipher block chaining (CBC) encryption in the two-party authentication protocol, while the PAP is a modified version of the station-to-station (STS) authentication protocol. Both protocols are designed in conjunction with a suggested key management method. Cryptanalysis shows that both the MAP and the PAP are very secure. Simulation results indicate that both protocols are efficient for providing mutual authentication. Together, these two protocols provide a good authentication mechanism to the B-ISDN billing system. (C) 1999 Elsevier Science B.V. All rights reserved.
Stability analysis and bounded sliding-mode control of a class of multi-input bilinear systems
(1999-12-01)
Chen, YP
;
Chang, JL
;
Lai, KM
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A bounded sliding-mode controller is developed for a class of multi-input bilinear systems. The sliding vector design is based on the conventional pole-assignment method for linear time-invariant systems. Three conditions are required for the assigned eigenvalues when applying the pole-assignment method. A potential reaching-and-sliding region and a stable sliding region are determined around the origin, which is shown to be locally asymptotically stable. Numeric simulation results are used to demonstrate the success of the proposed bounded sliding-mode controller.
A genetic algorithm for the optimal design of microwave filters
(1999-12-01)
Hsu, HM
;
Tsai, SP
;
Wu, MC
;
Tzuang, CK
;
電信工程研究所
This paper presents a multiple objective genetic algorithm for determining the component parameters in the design of a microwave filter. In this approach, we first propose a set of fuzzy-based membership functions for modeling the five design specifications (objective functions) of the microwave filter design problem. The five objective functions are then aggregated into a single-valued fitness function. Finally, a set of near-optimal component parameters for the microwave filter can be found by applying the proposed genetic algorithm. A large number of experiments were performed and demonstrated satisfactory results. This approach has three principal merits. First, it counteracts entrapment in a local optimal solution. Second, the processing of multiple objectives is relatively easy. Third, the generated solution is independent of the initial estimate. Significance: This paper presents a multiple objective genetic algorithm for determining the component parameters in the design of a microwave filter.
On a problem of Dynkin
(1999-12-01)
Sheu, YC
;
應用數學系
;
Department of Applied Mathematics
Consider an (L, alpha)-superdiffusion X on R-d, where L is an uniformly elliptic differential operator in R-d, and 1 < alpha less than or equal to 2. The G-polar sets for X are subsets of R x R-d which have no intersection with the graph G of X, and they are related to the removable singularities for a corresponding nonlinear parabolic partial differential equation. Dynkin characterized the G-polarity of a general analytic set A subset of R x R-d in term of the Bessel capacity of A, and Sheu in term of the restricted Hausdorff dimension. In this paper we study in particular the G-polarity of sets of the form E x F, where E and F are two Borel subsets of R and R-d respectively. We establish a relationship between the restricted Hausdorff dimension of E x F and the usual Hausdorff dimensions of E and F. As an application, we obtain a criterion for G-polarity of E x F in terms of the Hausdorff dimensions of E and F, which also gives an answer to a problem proposed by Dynkin in the 1991 Wald Memorial Lectures.
管管作品六首
(1999-12-01)
管管
Embedding of any type of data in images based on a human visual model and multiple-based number conversion
(1999-12-01)
Wu, DC
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
A novel approach to embedding any type of digital data into a cover image is proposed, which utilizes a human visual model to guarantee that the modification of the cover image is imperceptible. A quantized contrast function based on the model is constructed first. The gray values of each 3 x 3 sub-image of the cover image are used to compute, using the function, a range of gray levels with the same contrast as that of the central pixel of the sub-image. The embedding process proceeds by replacing the gray value of the central pixel by one of the values in the range. This guarantees that the changes be imperceptible. The data to be embedded is treated as a binary stream and is partitioned into a number of sub-streams. A multiple-base number conversion mechanism is used to convert each sub-stream of data into values which are then embedded in the central pixels of sub-images. The embedded data can be extracted out from the resulting stego-image without referencing the original image. Experimental results show that the proposed method is feasible. (C) 1999 Published by Elsevier Science B.V. All rights reserved.
管管作品六首
(1999-12-01)
管管