Browsing by Issue Date, starting with "2002-10-09"

Now showing 1 - 20 of 74358

情境音樂會蘇小歡官邸發功
(2002-10-09)
劉偉瑩
Control design of active vibration isolation using mu-synthesis
(2002-10-10)
Bai, MR
;
Liu, W
;
機械工程學系
;
Department of Mechanical Engineering
Numerical and experimental investigations on active vibration isolation system are presented in this paper. Two configurations are implemented for a statically balanced three-mount system. To reduce the influence of payload dynamics and coupling among the control actuators, intermediate masses are added to the system. Linear quadratic Gaussian control and p-synthesis are employed in the controller synthesis. The controllers are implemented on the platform of a floating-point digital signal processor. The results obtained from simulations and experiments indicated that the optimal controllers achieved the desired performance under the constraint of robust stability. (C) 2002 Elsevier Science Ltd. All rights reserved.
A simple compact fourth-order Poisson solver on polar geometry
(2002-10-10)
Lai, MC
;
應用數學系
;
Department of Applied Mathematics
We present a simple and efficient compact fourth-order Poisson solver in polar coordinates. This solver relies on the truncated Fourier series expansion, where the differential equations of the Fourier coefficients are solved by the compact fourth-order finite difference scheme. By shifting a grid a half mesh away from the origin and incorporating the symmetry constraint of Fourier coefficients, we can easily handle coordinate singularities without pole conditions. The numerical evidence confirms fourth-order accuracy for the problem on an annulus and third-order accuracy for the problem on a disk. In addition, a simple and comparably accurate approximation for the derivatives of the solution is also presented. (C) 2002 Elsevier Science (USA).
Phase transformations in a Cu-14.2Al-12.0Ni alloy
(2002-10-11)
Chen, CH
;
Liu, TF
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The as-quenched microstructure of the Cu-14.2Al-12.0Ni alloy was D0(3) phase containing extremely fine L-J precipitates, where the D0(3) phase was formed by an A2 --> B2 --> D0(3) continuous ordering transition during quenching. Besides, the addition of nickel to the Cu-14.2Al binary alloy would raise the B2 --> beta transition temperature. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.
侯孝賢:當不成電影大亨我無悔
(2002-10-12)
葛大維
Decreasing giant splitting of longitudinal and transverse optical phonons in PbxSr1-xTiO3 due to Pb covalency
(2002-10-14)
Kuo, SY
;
Li, CT
;
Hsieh, WF
;
光電工程學系
;
Department of Photonics
In contrast to the increase of giant splitting of longitudinal optical (LO) and transverse optical (TO) phonons in polycrystalline BaxSr1-xTiO3 [Phys. Rev. B. 64, 224103-1 (2001)], a decreasing splitting of the softest A(1)(1TO) and the hardest A(1)(3LO) was observed in PbxSr1-xTiO3. A similar structure but anomalous discrepancies in lattice dynamics of ABO(3) perovskite are related to the diverse electronic states of Pb2+ and Ba2+ ions. In this article, Pb-O interaction is proposed to be more hybridized than Ba-O, and thus the change of effective charge to the LO-TO splitting may be the dominant mechanism in PbxSr1-xTiO3, while unit-cell volume change is in the BaxSr1-xTiO3 systems. (C) 2002 American Institute of Physics.
Self-assembled GaAs antiwires in In0.53Ga0.47As matrix on (100) InP substrates
(2002-10-14)
Lin, SD
;
Lee, CP
;
Hsieh, WH
;
Suen, YW
;
電子工程學系及電子研究所
The growth of GaAs antiwires in the In0.53Ga0.47As matrix on InP substrate has been investigated. The periodic, wire-like structure was obtained when a proper amount of GaAs was deposited. The grown antiwires have a height about 1.2-2.0 nm and a period about 23 nm. Using an In0.53Ga0.47As/In0.52Al0.48As modulation-doped structure, the effect of the GaAs antiwires on the two-dimensional electron gas mobility was investigated. For the sample with antiwires near the two-dimensional channel, a significant anisotropy in low temperature mobility was observed. (C) 2002 American Institute of Physics.
Resonant tunneling into a quantum dot embedded inside a microcavity
(2002-10-15)
Chen, YN
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
We propose to measure the Purcell effect by observing the current through a semeiconductor quantum dot embedded in a microcavity. An electron and a hole are injected separately into the quantum structure to form an exciton and then recombine radiatively. The stationary current is shown to be altered if one varies the cavity length or the exciton energy gap. Therefore, the Purcell effect can be observed experimentally by measuring the current through the quantum structure. In addition, we also find that super-radiance of excitons between quantum dots may also be observed in an electrical way.
Harmonic mode locking and multiple pulsing in a soft-aperture Kerr-lens mode-locked Ti : sapphire laser
(2002-10-15)
Lin, JH
;
Hsieh, WF
;
Wu, HH
;
光電工程學系
;
Department of Photonics
We report the observation of harmonic mode locking and multiple pulse operations in a soft-aperture Kerr-lens mode-locked Ti:sapphire laser by varying the total intra-cavity dispersion. Second, third, and fourth order harmonic mode locking as well as multiple pulsing with interpulse separation ranging from femtosecond to nanosecond are observed. The laser is characterized in these regimes in terms of wavelength, bandwidth, pulsewidth, average and peak powers as functions of group velocity dispersion. By introducing a loss difference term into gain dynamic analysis, we conclude that gain depletion and recovery mechanisms are responsible for the underlying physics of current observations. (C) 2002 Elsevier Science B.V. All rights reserved.
X-ray scattering study of crystallization behavior in homoepitaxial growth of SrTiO3 films
(2002-10-15)
Lee, HY
;
Chang, WD
;
Hsu, CH
;
Liang, KS
;
Lee, JY
X-ray reflectivity and grazing incidence crystal truncation rod (CTR) measurements were employed to characterize the microstructure and crystallization behavior of homoepitaxial SrTiO3 (STO) films deposited on polished SrTiO3 (0 0 1) substrates by pulse laser deposition technique. X-ray scattering results indicate that room temperature grown STO film has a density approximately 11.1% lower than that of bulk STO and shows poor epitaxial relation with the substrate. Subsequent annealing at 760 degreesC for 20 s appeared to transform the film into two-layer structure, with the density of the layer right above the substrate approaching to its bulk value, while the density of the top 15.5 Angstrom thick layer reducing to near 45% of bulk STO. The annealing process also leads to an increase of lateral lattice constant together with the growth of domain size. The appearance of interference fringes of the CTR after annealing, which is also observed at the film grown at 760 degreesC, clearly demonstrates the development of epitaxy upon short time annealing. (C) 2002 Elsevier Science B.V. All rights reserved.
Efficient generation of continuous-wave yellow light by single-pass sum-frequency mixing of a diode-pumped Nd : YVO4 dual-wavelength laser with periodically poled lithium niobate
(2002-10-15)
Chen, YF
;
Tsai, SW
;
Wang, SC
;
Huang, YC
;
Lin, TC
We report efficient generation of cw yellow light by use of single-pass sum-frequency mixing from a diode-pumped Nd:YVO4 dual-wavelength laser with periodically poled lithium niobate. A diode-pumped Nd:YVO4 dual-wavelength laser is implemented with a three-mirror cavity, and the optimum oscillation condition is obtained from theoretical analysis. We extracted 78 mW of power at 593 run from 1.2 W at 1064 nm and from 1.0 W at 1342 nm in a beam with excellent quality. The output power could probably be increased to similar to92 mW by antireflection. coating of the crystal. (C) 2002 Optical Society of America.
A novel phase-noise-suppressed and delay-time-tunable mode-locked erbium-doped fiber laser
(2002-10-15)
Lin, GR
;
Lai, Y
;
光電工程學系
;
Department of Photonics
A phase-noise-suppressed and delay-time-tunable actively mode-locked erbium-doped fiber ring laser is demonstrated by using voltage-controlled and frequency-discriminated phase shifter as an inherent timing module. By changing the voltage from -3.35 to 3.6 V, the maximum tuning range of phase and delay-time of 500 MHz optical pulse-train from the laser can be up to 340degrees (similar to1.9pi) and 1.9 ns (nearly 1 period), respectively. Optimized responsivity and tuning deviation are 0.27 ps/mV and less than or equal to 4%. The single-sided-band phase the laser operated at feedback controlled mode is significantly reduced to -100 dBc/Hz (measured at frequency of 10 kHz offset from center), which is at least 10 dB smaller than that of the laser operated at free-running mode. (C) 2002 Published by Elsevier Science B.V.
Characteristics of photogenerated bipolar terahertz radiation in biased photoconductive switches
(2002-10-15)
Lin, PI
;
Chen, SF
;
Wu, KH
;
Juang, JY
;
Uhn, TM
The characteristics of the optically induced bipolar terahertz (THz) radiation from biased semi-insulating GaAs photoconductive switches were investigated using a free-space electrooptic sampling technique, The emitted radiation shows a nearly symmetrical waveform with a broad-band frequency spectrum spanning over 0.1-3 THz, which displays essentially no dependence on the optical excitation fluence or strength of biased field. However, it does slightly depend on the file emitter gap spacing. The dynamics of the emitted THz transient is in agreement with the optically induced ultrafast charge transport process driven by the biased field.
Energy states and magnetization in nanoscale quantum rings
(2002-10-15)
Voskoboynikov, O
;
Li, YM
;
Lu, HM
;
Shih, CF
;
Lee, CP
In this paper we calculate electron energy states and magnetization for torus shaped nanoscale quantum rings with external magnetic fields. We use the three-dimensional effective one-band Hamiltonian, the energy and position-dependent quasiparticle effective mass approximation, and the Ben Daniel-Duke boundary conditions. The dependence of the energy spectrum on the sizes and shapes of the quantum rings was calculated and the result agrees with experimental observations. Penetration of the magnetic field into torus region results in an aperiodic oscillation of magnetization at zero temperature. It saturates with the increasing of the magnetic field strength.
Design and synthesis of activity probes for glycosidases
(2002-10-17)
Tsai, CS
;
Li, YK
;
Lo, LC
;
應用化學系
;
Department of Applied Chemistry
[GRAPHICS] A new synthetic route was developed for the preparation of activity probe 1 for beta-glucosidase in this study. The key glycosidation step begins with benzyl p-hydroxyphenylacetate. Benzylic functionalization for the construction of the trapping device was achieved at later stages. Probe 1 was shown to be able to label the target enzyme. This cassette-like design offers great flexibility for future alterations. It would allow the synthetic scheme to expand to other glycosidase probes with different linker/reporter combinations.
詩歌節開唱方塊字起舞
(2002-10-19)
陳盈珊
如歌的行板在中山堂低迴
(2002-10-19)
蔡惠萍
用於印刷微波積體電路之平面式模轉換器
(2002-10-21)
莊晴光
;
李振榮
一種用於印刷微波積體電路之平面式模轉換器，包含：一矩形波導，一微帶線饋入電路及一微帶線饋出電路。該矩形波導之內部填充複數個介質層，各該介質層上下彼此緊鄰相接，其中最上層介質層之頂面、最下層介質層之底面及各該介質層之左、右側面，有金屬材料覆蓋於其上，該最下層介質層其介質常數最大、厚度最厚，除了該最下層介質層以外之各該介質層之前端及後端各有一矩形孔徑，各該前端之矩形孔徑上下緊鄰，各該後端之矩形孔徑上下緊鄰。
詩歌節今夜畫下句點
(2002-10-26)
陳盈珊
詩歌節壓軸詩人化身煉金術士
(2002-10-26)
台北訊