Browsing by Issue Date, starting with "1999-10-08"

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Simultaneous measurement of spectral optical properties and thickness of an absorbing thin film on a substrate
(1999-10-08)
Chen, JJ
;
Lin, JD
;
Sheu, LJ
;
機械工程學系
;
Department of Mechanical Engineering
This paper describes a technique and also illustrates an application of the technique for simultaneously measuring both the spectral complex refractive index (n(1),k(1)) and the thickness d(1) of an absorbing thin solid layer on a thick substrate. The contours of constant reflectance R and transmittance T in the (n(1), k(1)), (n(1), d(1)) and (k(1), d(1)) planes are examined for a thin layer on a substrate, which is exposed to oblique unpolarized incidence, under various conditions in order to facilitate an optimal choice of the combination of measured quantities for the inverse estimation of parameters. Theoretical analysis illustrates that optimal choices would include measurement of R at a large angle of incidence, combined with measurements of normal T and near normal R so as to reduce erroneous solutions or nonconvergence. And any additional measurement R at any angle of incidence may be used to prevent the multiple solutions. For the inverse estimation of parameters, we also present a technique in association of the least squares method to extract the thickness and optical constants characterizing the thin absorbing film from measurements of R and T. The method is then applied for experimental measurement of the optical properties and thickness of a polyvinylalcohol (PVA) film placed upon a substrate of ZnSe. These results provide useful information for analyses on the applications of PVA in textile sizing, adhesives, polymerization stabilizers, and paper coating. (C) 1999 Elsevier Science S.A. All rights reserved.
Optimal conditions for thermal fixing of volume holograms in Fe : LiNbO3 crystals
(1999-10-10)
Hsieh, CR
;
Lin, SH
;
Hsu, KY
;
Hsieh, TC
;
Chiou, A
We analyze and compare two typical recording and thermal fixing procedures of a volume hologram in a Fe:LiNbO3 crystal (low-high-low procedure and high-low procedure). We consider the kinetics of the recording, compensating, and developing processes by taking into account the ratio of the conductivities between the protons and the electrons as a function of temperature. From the analysis the optimal environmental conditions tin terms of the fixing temperature and the compensation time) for each fixing procedure can be deduced for a crystal with given material parameters. (C) 1999 Optical Society of America.
24GHz active retrodirective antenna array
(1999-10-14)
Hong, TJ
;
Chung, SJ
;
電信工程研究所
;
Institute of Communications Engineering
A 24GHz active Van Atta planar antenna array proposed for increasing the vehicle radar echo in a vehicle collision avoidance system is designed and demonstrated. The antenna array contains two parallel linear sub-arrays. Each sub-array is composed of four receiving microstrip antennas, four transmitting microstrip antennas and four transistor amplifiers. At the angles of -40 degrees < theta < 40 degrees, except those very close to the specular direction (theta = 0 degrees), the measured backscattering field levels of the fabricated array have variations < 3dB and are at least 10dB higher than those of a metal plate of the same size.
Nitric acid-based slurry with citric acid as an inhibitor for copper chemical mechanical polishing
(1999-10-15)
Hu, TC
;
Chiu, SY
;
Dai, BT
;
Tsai, MS
;
Tung, IC
A novel inhibitor, citric acid, was introduced in the HNO3-based slurry for copper chemical mechanical polishing. It was anticipated that a passivation layer could be formed on the copper surface in the presence of citric acid. In a 3 vol.% HNO3 solution, the passivation effect derived from citric acid saturated as the citric acid concentration reached ca. 0.01 M. The polishing rate was found to decrease with the addition of citric acid. The results showed that the HNO3-based slurry with citric acid as an inhibitor could achieve good surface planarity for copper chemical mechanical polishing. (C) 1999 Published by Elsevier Science S.A. All rights reserved.
Preparation of aluminum film on phosphor screen for field emission display
(1999-10-15)
Fran, YS
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The phosphor screen for field emission display (FED) was made by using cellulose acetate butyrate as a binder dissolved in butoxyethyl acetate. Before baking at temperatures lower than 500 degrees C, the aluminum film was formed on the screen. This screen has nearly two times the brightness in comparison with pure screen. The FED panel was successfully made using Al film coated phosphor screen and demonstrated an image of high brightness and relatively good quality which is suitable for practical application. (C) 1999 Elsevier Science S.A. All rights reserved.
A fault-tolerant architecture for ATM networks
(1999-10-15)
Lo, CC
;
Chiou, CY
;
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 asynchronous transfer mode (ATM) is the transfer mode recommended for the broad integrated service digital network (B-ISDN) by ITU-T. In this paper, we propose a self-routing fault-tolerant switching architecture for ATM networks. The proposed architecture uses subswitches and extra links to provide alternative paths; hence, can tolerate multiple faults. Analytical results show that the total number of redundant paths increases exponentially as the size of the network increases. A simulation model is developed. Simulation results indicate that the proposed architecture is much more fault-tolerant and cost-effective than those architectures found in the literature. Simulation results also illustrate that the proposed architecture still maintains a high throughput with an acceptable cell delay time, even when the number of faulty elements increases. (C) 1999 Elsevier Science B.V. All rights reserved.
Observation of carrier depletion and emission effects on capacitance dispersion in relaxed In0.2Ga0.8As/GaAs quantum wells
(1999-10-18)
Chen, JF
;
Wang, PY
;
Tsai, CY
;
Wang, JS
;
Chen, NC
Strong changes in capacitance over frequency are found for highly relaxed In0.2Ga0.8As/GaAs quantum well. The high-frequency dispersion is explained by a resistance-capacitance time constant effect due to the existence of a high resistive layer while the low-frequency dispersion is due to carrier emission from traps. The high-resistance layer is created by carrier depletion when InGaAs thickness increases beyond the critical thickness. Excellent agreement is found between the data from capacitance-frequency spectra and deep-level transient spectroscopy, permitting us to conclude that both the carrier depletion and emission effects observed in capacitance-frequency spectra are due to the existence of an acceptor trap at 0.33 eV. This trap is generated when the InGaAs thickness is beyond its critical thickness and is due to defect states associated with misfit dislocations. (C) 1999 American Institute of Physics. [S0003-6951(99)02342-6].
Nanomachining of (110)-oriented silicon by scanning probe lithography and anisotropic wet etching
(1999-10-18)
Chien, FSS
;
Wu, CL
;
Chou, YC
;
Chen, TT
;
Gwo, S
We have demonstrated that silicon nanostructures with high aspect ratios, having similar to 400 nm structural height and similar to 55 nm lateral dimension, may be fabricated by scanning probe lithography and aqueous KOH orientation-dependent etching on the H-passivated (110) Si wafer. The high spatial resolution of fabricated features is achieved by using the atomic force microscope based nano-oxidation process in ambient. Due to the large (110)/(111) anisotropic ratio of etch rate and the large Si/SiO2 etch selectivity at a relatively low etching temperature and an optimal KOH concentration, high-aspect-ratio gratings with (111)-oriented structural sidewalls as well as hexagonal etch pit structures determined by the terminal etch geometry can be obtained. (C) 1999 American Institute of Physics. [S0003-6951(99)03242-8].
The effect of electron-phonon interaction on the impurity binding energy in a quantum well
(1999-10-25)
Chen, YN
;
Chuu, DS
;
Lin, YK
;
電子物理學系
;
Department of Electrophysics
The effect of confined electron-optical phonon interaction on the hydrogenic impurity binding energy in a quantum well is studied. By using the Landau and Pekar variational method, the Hamiltonian is separated into two parts which contain phonon variables and electron variables. A perturbative-variational technique is then employed to construct the trial wave function for the electron part. The effects of electron-optical phonon interaction on the binding energies are calculated as functions of the well width. In the study of the polaron effects on the impurity binding energies in a quantum well, both confined bulk optical phonon and surface optical phonon effects are taken into account. It is found that the surface phonon effect prevails over the bulk phonon effect when the well width is small. The polaron effects on lower-lying excited states are also calculated. The line strengths of transitions from the ground state to lower-lying excited states are calculated as functions of the donor position and the well width.
Christmas tree: A versatile 1-fault-tolerant design for token rings
(1999-10-29)
Hung, CN
;
Hsu, LH
;
Sung, TY
;
資訊工程學系
;
Department of Computer Science
The token ring topology is required in token passing approach used in distributed operating systems. Fault tolerance is also required in the designs of distributed systems. Note that 1-fault-tolerant design for token rings is equivalent to design of 1-Hamiltonian graphs. This paper introduces a new family of graphs called Christmas tree, denoted by CT(s). The graph CT(s) is a 3-regular, planar, 1-Hamiltonian, and Hamiltonian-connected graph. The number of nodes in CT(s) is 3.2(s) - 2. Its diameter is 1 if s = 1, 3 if s = 2, and 2s if s greater than or equal to 3. (C) 1999 Elsevier Science B.V. All rights reserved.
Conductance in a narrow constriction threaded by an impenetrable magnetic flux tube
(1999-10-30)
Liang, HC
;
電子物理學系
;
Department of Electrophysics
The conductance G in a narrow constriction and its dependence on the Fermi energy and on the transverse position of an impenetrable magnetic flux tube is studied. G exhibits oscillatory-like behavior as the transverse position of the tube changes. When there are n propagating subbands, there are n - 1 minimums of G first (except for n = 1) and n minimums later when the Fermi energy grows. Both just below and just above the critical energy exhibiting n propagating subbands, minimums occur at tube,positions mW/n, where W is the transverse width of the constriction and 1 less than or equal to m less than or equal to n - 1.
詩社四十五周年茶會創世紀喜臨門
(1999-10-31)
林英喆
A minimum output burstiness traffic scheduling algorithm
(1999-11-01)
Kuo, YE
;
Lee, TH
;
傳播研究所
;
電信工程研究所
;
Institute of Communication Studies
In this paper, we present a traffic scheduling algorithm, called the Delay-Bound Monotonic with Average Rate Reservation (DM/ARR), which generates minimum output burstiness streams. We assume that connection i is policed by the leaky bucket algorithm with parameters (sigma(i), sigma(i)) where sigma(i) is the bucket size (or burstiness) and p(i) is the leaky rate. Compared with the totally isolated scheme where connection i is allocated a bandwidth r(i) = max{sigma(i)/d(i),rho(i)} (d(i) is the delay bound requirement of connection i), the DM/ARR algorithm has a better performance in the sense that it has a larger admission region. We prove that. among all possible scheduling algorithms that satisfy the delay bound requirements of established connections, DM/ARR results in the minimum output burstiness. This is important because a smaller burstiness implies a smoother traffic and thus the receiver (or next switch node in a multihop network) can handle it more easily. Numerical results show that the admission region of the DM/ARR algorithm is close to that of the earliest deadline first [1] algorithm. A packetized version is studied for ATM networks.
Bond length order parameter of conjugated polymers
(1999-11-01)
Lai, CM
;
Meng, HF
;
物理研究所
;
Institute of Physics
It is usually assumed that the ground state lattice configuration of polyacetylene is a dimerized chain. We found that the energy can be further reduced by an overall chain length contraction, which leads to a new bond length order parameter, in addition to the well-known bond alternation order parameter. For quasi-particles like solitons and polarons, these two order parameters are coupled with the electron wave functions and vary in space. We generalize the Takayama-Liu-Maki equations in the continuum limit to incorporate this new order parameter. Significant modifications are found for the polaron solution. Polyacene, a ladder polymer, is also studied with the inclusion of the bond length order parameter. The ground state is predicted to be a non-alternating structure, with zero energy gap and unusually high electric conductivity. (C) 1999 Elsevier Science B.V. All rights reserved.
On the properties of the reduction-by-composition LMS algorithm
(1999-11-01)
Chen, SG
;
Kao, YA
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Chen, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The recently proposed low-complexity reduction-by-composition least-mean-square (LMS) algorithm (RCLMS) costs only half multiplications compared to that of the conventional direct-form LMS algorithm (DLMS), This work intends to characterize its properties and conditions for mean and mean-square convergence. Closed-form mean-square error (MSE) as a function of the LMS step-size mu and an extra compensation step-size alpha are derived, which are slightly larger than that of the DLMS algorithm. It is shown, when mu is small enough and alpha is properly chosen, the RCLMS algorithm has comparable performance to that of the DLMS algorithm. Simple working rules and ranges for alpha and mu to make such comparability are provided. For the algorithm to converge, a tight hound for alpha is also derived. The derived properties and conditions are verified by simulations.
Internet-based hierarchical floorplan design
(1999-11-01)
Lin, JH
;
Jou, JY
;
Jiang, IHR
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
With the proliferation of the transistor count in VLSI design, more and more design groups try to figure out an efficient way to combine their designs. The Internet features distributed computing and resource sharing. Consequently, a hierarchical design can adequately be solved in the Internet environment. In this paper, we demonstrate the facilitation of the Internet environment by solving the area minimization floorplan problem. We propose the RMG algorithm taking advantage of the Internet. Based on the model of transfer latencies, the RMG algorithm reduces the computing time by shortening the critical path in the floorplan tree. Our experimental results show that the Internet is suitable for Electronic Design Automation (EDA).
Directional spectrum analysis and statistics obtained from ERS-1 SAR wave images
(1999-11-01)
Kuo, YY
;
Leu, LG
;
Kao, IL
;
土木工程學系
;
Department of Civil Engineering
This work examines ERS-1 (the first European Remote Sensing Satellite) SAR (Synthetic Aperture Radar) water surface wave images over Hualien of Taiwan, indicating that the variation of SAR signals in space domain is similar to in situ wave data's in time domain. Some statistical properties of SAR data are investigated. The Rayleigh distribution function closely corresponds with the histogram of wave heights, but the Gaussian one cannot for water surface displacements. Evidence reveals that SAR wave signals do not respond well to actual ocean waves effectively. As wave spectral analysis of available SAR data reveals, the appropriate sample size of SAR wave image, sampling average, and moving average should be taken carefully to accurately confirm directional power spectra. Moreover, SAR spectra are compared with in situ ones, confirming that peak frequencies correlate well and wave directions approximately agree with each other. Some differences between both spectral shapes remain somewhat unclear and require further study. Nevertheless, in this study, ERS-1 SAR power spectra verified the feasibility of deriving an appropriate dominant wave direction and peak frequency. (C) 1998 Elsevier Science Ltd. All rights reserved.
Excitation of the NO molecule by chirped infrared laser pulses
(1999-11-01)
Lin, JT
;
Hayashi, M
;
Lin, SH
;
Jiang, TF
;
物理研究所
To explore the insights of recent experiments on the excitation of the NO molecule by chirped subpicosecond IR pulses, a corresponding theoretical study is presented. The agreements between experimental and theoretical results show the importance of the full-dimensional quantum-mechanical calculation. [S1050-2947(99)04711-3].
Time-dependent Ginzburg-Landau equation for d(x2-y2)-wave superconductors: Hall effect in the low field regime
(1999-11-01)
Yang, TJ
;
Dai, MC
;
電子物理學系
;
Department of Electrophysics
The Hall effect is studied by using a phenomenological time-dependent Ginzburg-Landau equation with mixing of s-and d-wave components in d(x)2-(y)2-wave superconductors within a low field regime. An equation of motion for a single vortex is derived and the Hall angle is obtained under an external driving current along the crystal axis. We find that not only the imaginary parts of s- and d-wave relaxation time but also the mixed gradient terms may change the sign of the Hall effect.
Generation of coherent cw-terahertz radiation using a tunable dual-wavelength external cavity laser diode
(1999-11-01)
Gu, P
;
Chang, F
;
Tani, M
;
Sakai, K
;
Pan, CL
A tunable dual-wavelength external cavity laser diode (2-lambda-ECL) was used to generate tunable coherent cw-terahertz (THz) radiation by photomixing in a biased photoconductive antenna fabricated on a low-temperature-grown (LTG)-GaAs film. The 2-lambda-ECL oscillated at the two output modes simultaneously with a frequency separation from 250 GHz to 2.1 THz in the same cavity. We demonstrated that the frequency of the emitted THz radiation corresponded to the difference frequency between the two modes of the diode laser. The tunable 2-lambda-ECL, due to its compact design and ease of optical alignment, is a promising laser source for the generation of tunable cw-THz radiation by photomixing.