Browsing by Issue Date, starting with "1999-11-15"

Now showing 1 - 20 of 80196

Phonon sidebands and optical gain of light-emitting conjugated polymers
(1999-11-15)
Meng, HF
;
Chang, VCH
;
物理研究所
;
Institute of Physics
We study the interaction of excitons and optical phonons in light-emitting conjugated polymers with the variational approach. The optical transition matrix elements for the phonon sidebands in the absorption and emission spectra an calculated. The electron-phonon coupling constant is determined by fitting the theoretical oscillator strengths of the emission sidebands with the experimental photoluminescence spectra for the various poly(p-phenylene vinylene) derivatives. Using this coupling constant, we predict that the absorption one-phonon sideband is as important as the zero-phonon sideband for the ideal systems. Taking the experimental data of the peak absorption coefficient as input, we obtain the optical gain coefficient for a wide range of exciton densities. The gain is found to be determined by the exciton density no by a general expression 1.98 x 10(-16)n(o) cm(2), which is in good agreement with experiments. [S0163-1829(99)06243-8].
THz radiation from intracavity saturable Bragg reflector in magnetic field with self-started mode-locking by strained saturable Bragg reflector
(1999-11-15)
Liu, TA
;
Huang, KF
;
Pan, CL
;
Liu, ZL
;
Ono, S
We demonstrate a new configuration for intracavity generation of THz radiation. A magnetic-field-biased saturable Bragg reflector (SBR) located inside the femtosecond laser cavity is the emitter, while a strained saturable Bragg reflector (SSBR) achieves self-started mode-locking without focusing. The calibrated power of the emitted THz radiation is estimated to be approximately 45 nW with a peak frequency at 0.72 THz and width of approximately 0.7 THz under a 0.88 T magnetic field. The quadratic dependence of THz-radiation power by the SBR on the magnetic field is also observed for the first time.
A note on Bayesian estimation of process capability indices
(1999-11-15)
Shiau, JJH
;
Hung, HN
;
Chiang, CT
;
統計學研究所
;
Institute of Statistics
Process capability indices are useful for assessing the capability of manufacturing processes. Most traditional methods are obtained from the frequentist point of view. We view the problem fi om the Bayes and empirical Bayes approaches by using non-informative and conjugate priors, respectively. (C) 1999 Elsevier Science B.V. All rights reserved.
Three-dimensional electric-field vector measurement with an electro-optic sensing technique
(1999-11-15)
Kuo, WK
;
Huang, YT
;
Huang, SL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new technique for three-dimensional (3D) electric-field (e-field) vector measurement is presented. Three laser beams with different propagation paths in an electro-optic (EO) crystal were used to resolve 3D components of e-field vectors. We adopted a special geometric shape of bismuth silicon oxide EO crystal so that the three beams would propagate within it. A sensitivity of 0.6 V/cm root Hz was achieved. A commercial Ansoft Maxwell 3D field simulator was also used to verify our measurements. (C) 1999 Optical Society of America.
Defects in Ge+-preamorphized silicon
(1999-11-15)
Chen, PS
;
Hsieh, TE
;
Hwang, YC
;
Chu, CH
;
材料科學與工程學系
This work studied the morphology and annealing behaviors of extended defects in Si subjected to various Ge+ preamorphization and BF2+ implantation conditions. The extended defects formed were near the specimen surface when Ge+ implantation energy and dose amount were low. During subsequent annealing, the end-of-range (EOR) loops were enlarged and then moved out of the specimen. High energy/low dose Ge+ implantation generated a damaged layer which initially transformed into a wide zone containing dislocation loops and rodlike defects in the annealed specimen. As the annealing proceeded, the width of defective zone gradually shrunk so that most of the extended defects could be annihilated by defect rejection/recombination process. In addition to the category II defects found in previous investigations, hairpin dislocations emerged in high energy/high dose Ge+-implanted specimens. In this specimen, rodlike defects and hairpin dislocations could be removed by annealing, while the EOR loops became relatively inert so that their removal would require high temperatures and/or long annealing times. Microwave plasma surface treatment was also carried out to form a nitride layer on specimen surface. Experimental results indicate that in addition to effectively reducing the size of EOR loops, surface nitridation might serve as a vacancy source injecting vacancies into Si to annihilate the interstitials bounded by dislocation loops. Reduction in the defect size was pronounced when bias voltage was added to the plasma process. However, radiation damage might occur with too high of a bias voltage. (C) 1999 American Institute of Physics. [S0021-8979(99)06322-7].
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.