Browsing by Issue Date, starting with "2001-10-10"

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Adaptive symmetric mean filter: A new noise-reduction approach based on the slope facet model
(2001-10-10)
Huang, HC
;
Chen, CM
;
Wang, SD
;
Lu, HHS
;
統計學研究所
Two new noise-reduction algorithms, namely, the adaptive symmetric mean filter (ASMF) and the hybrid filter, are presented in this paper. The idea of the ASMF is to find the largest symmetric region on a slope facet by incorporation of the gradient similarity criterion and the symmetry constraint into region growing. The gradient similarity criterion allows more pixels to be included for a statistically better estimation, whereas the symmetry constraint promises an unbiased estimate if the noise is completely removed. The hybrid filter combines the advantages of the ASMF, the double-window modified-trimmed mean filter, and the adaptive mean filter to optimize noise reduction on the step and the ramp edges. The experimental results have shown the ASMF and the hybrid filter are superior to three conventional filters for the synthetic and the natural images in terms of the root-mean-squared error, the root-mean-squared difference of gradient, and the visual presentation. (C) 2001 Optical Society of America.
Magneto-optic imaging of proton-irradiated high T-c superconducting thin films: A revisit of J(c)(T) functional and flux pinning enhancement
(2001-10-10)
Wang, C
;
Seo, HW
;
Su, CJ
;
Wang, YH
;
Chen, QY
We have performed systematic quantitative measurements of the critical current density J(c)(B,T) for YBCO thin films proton-irradiated to various dosages using the MOI technique. Results for external magnetic fields up to 400Oe and temperature ranging from 5 to 80 K are T resented for a 600 nm thick YBCO film irradiated by proton up to a dosage of 10(16) cm(-2) at 500 keV. While no significant differences were observed for T > 50K, the J(c) values consistently increased with the increasing external field for T < 50 K.
An integrated inventory model for a single vendor and multiple buyers with ordering cost reduction
(2001-10-13)
Woo, YY
;
Hsu, SL
;
Wu, SS
;
管理科學系
;
Department of Management Science
Forming strategic alliances and utilizing modern information technologies have been the two most important ways for firms to gain such competitive advantages as lower logistics costs and secure customers' loyalty. In this paper, we consider an integrated inventory system where a single vendor purchases and processes raw materials in order to deliver finished items to multiple buyers. The vendor and all buyers are willing to invest in reducing the ordering cost (e.g., establishing an electronic data interchange based inventory control system) in order to decrease their joint total cost. The amount of investment determines the planned ordering cost and hence affects their replenishment decisions. One major managerial implication from this ordering cost reduction is that the efforts to streamline and speedup transactions via the application of information technologies may result in a higher degree of coordination and automation among allied trading parties. An analytical model is developed to derive the optimal investment amount and replenishment decisions for both vendor and buyers. The exponential ordering cost function is then applied to our general model. and a numerical analysis is performed to provide interesting insights of the model. Numerical results show that the vendor and all the buyers can benefit directly from substantial cost savings by this ordering cost reduction investment. (C) 2001 Elsevier Science B.V. All rights reserved.
Interaction mechanism of a novel polymer electrolyte composed of poly(acrylonitrile), lithium triflate, and mineral clay
(2001-10-15)
Chen, HW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The addition of optimum cetyl pyridium chloride (CPC)-modified montmorillonite (CM) increases the ionic conductivity of poly(acrylonitrile)-based electrolytes by roughly two orders of magnitude. Specific interactions between the silicate layer, the nitrile group, and the lithium cation were investigated by FTIR, solid-state NMR, dielectric analyzer, and alternating current impedance. IR and NMR spectra confirm that the negative charges in the silicate layers alter the ionic charge environment of the PAN-based electrolyte composites, which have the same function as the polar group in PAN. The optimum CM content to achieve the maximum ionic conductivity is 6 phr. However, untreated montmorillonite leads to insignificant polymer intercalation, the negative charges in the silicate layers fail to appreciably disturb the attractive force of the lithium salt, and the resulting conductivity improvement is also less than that of the CM additives. (C) 2001 John Wiley & Sons, Inc.
Order parameter of MgB2: A fully gapped superconductor
(2001-10-15)
Yang, HD
;
Lin, JY
;
Li, HH
;
Hsu, FH
;
Liu, CJ
We have measured the low-temperature specific heat C(T) for polycrystalline MgB2 prepared by high pressure synthesis. C(T) below 10 K vanishes exponentially, which unambiguously indicates a fully opened superconducting energy gap. However, this gap is found to be too small to account for T, of MgB2. Together with the small specific heat jump DeltaC/gamma T-n(c) = 1.09, scenarios such as anisotropic s-wave or multicomponent order parameter are called for. The magnetic field dependence of gamma (H) is neither linear for a fully gapped s-wave superconductor nor H-1/2 for nodal order parameter. It seems that this intriguing behavior of gamma (H) is associated with the intrinsic electronic properties other than flux pinning.
On the formation of streaks on wind-driven water surfaces
(2001-10-15)
Tsai, WT
;
土木工程學系
;
Department of Civil Engineering
Evidence derived from numerical experiments is presented to show that, contrary to the prevalent notion, the generation of elongated wind-induced streaks on water surfaces with spacing of centimeters is not necessarily attributed to interactions between surface waves and the shear current. Although the water surface is artificially designated as a flat boundary in the numerical simulations here, high-speed streaks appear on the surface arising from an underlying shear current. Floating Lagrangian tracers cluster along the streaks and, in accordance with field and laboratory observations, undergo dislocation and amalgamation.
Optimal quantitative group testing on cycles and paths
(2001-10-15)
Hwang, FK
;
Lee, JS
;
應用數學系
;
Department of Applied Mathematics
We determine the minimum number of group tests required to search for a special edge when the graph consists of cycles and paths, generalizing previous results of Aigner on paths and on a simple cycle. (C) 2001 Elsevier Science B.V. All rights reserved.
Study of poly(ethylene oxide) electrolyte with polyurethane/sulfonate side chains
(2001-10-17)
Wang, XL
;
Fang, B
;
Wang, L
;
Tang, XZ
;
Chang, FC
Sulfonated dimethyl fumarate (SDMF) was prepared. Poly(ethylene oxide) (PEO) with sodium sulfonate side chains (SPEO) was synthesized by transesterification between SDMF and PEO with molecular weights of 200, 400, 600, 800, and 1000. The SPEO was subsequently mixed as a plasticizer with PEO polyurethane (PU). Samples were characterized by elemental analysis, FTIR, H-1-NMR, gel permeation chromatography, and impedance analysis. The mixture exhibited a homogeneous domain. The maximum conductivity of the CPU1000/SPEO600 was 2.6 x 10(-7) S cm(-1) at room temperature. The relation between the ionic conductivity and the temperature was in agreement with the Arrhenius equation. (C) 2001 John Wiley & Sons, Inc.
Effects of copolymer composition and free volume change on the miscibility of poly(styrene-co-vinylphenol) with poly(epsilon-caprolactone)
(2001-10-23)
Kuo, SW
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A series of poly(styrene-co-vinylphenol) (PSOH) copolymers were prepared and characterized. The miscibility and hydrogen bonding between the partially hydroxylated polystyrene with poly(is an element of -caprolactone) (PCL) blend were investigated by differential scanning calorimetry and Fourier transform infrared spectroscopy. The copolymers containing higher than 13 mol % vinylphenol were found to be fully miscible with PCL according to differential scanning calorimetry studies. Quantitative analyses on the fraction of hydrogen-bonded carbonyl groups in the solid state were made by FTIR spectroscopy, and good correlations between thermal behaviors and infrared results were observed. The critical vinylphenol content of 0.1 mol % in PSOH copolymer for the blend to be miscible was predicted from the Painter-Coleman association model and binary interaction model. The discrepancy between the experimental result and theoretical prediction is probably caused by significant free volume increase in this blend system, which is analyzed by the Kovacs' free volume theory. The free volume of the PSOH/PCL is increased which give a positive contribution in the Gibbs free energy. As a result, the polystyrene needs to incorporate more poly(vinylphenol) in PSOH copolymer in order to overcome the free energy increased caused by the free volume increase predicted by the Painter-Coleman association model and the binary interaction model.
Speed up of rendering pipeline by deferred lighting and triple queue structure
(2001-10-25)
Liang, BS
;
Jen, CW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Redundant operations and stalls prevent a rendering pipeline from full-speed operation. To speed up the rendering pipeline, a triple queue structure is proposed to smooth the pipeline and to obtain benefit from deferred lighting. The results of cycle-accurate simulation show that the proposed structure can reduce rendering cycles to 52.9% in small size queues.
Structures and properties of the SiNC films on Si wafer at different deposition stages
(2001-11-01)
Wu, JY
;
Kuo, CT
;
Liu, TL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The films were deposited on Si wafer by a microwave plasma chemical vapor deposition (MPCVD) system with CH4, N-2, up to 8.3 vol.% HZ and additional Si chips as the sources. The films were examined at different deposition times to explore different growth stages of deposition. Examination indicated the deposition can be roughly divided up to three stages, depending on deposition time and based on their structure and property. In the early deposition stages, the films consist of two layers, i.e. Si-oxide and SiNC layers. The SiNC layer consists essentially of nano-crystals embedded in ternary SiNC amorphous matrix with crystal structure close to SiC. In contrast, in the later stage, the films are further covered by a layer of the binary SiN crystalline phases with crystal structures much closer to alpha -Si3N4 than beta -Si3N4 and tetragonal Si3N4 type structures. The band gaps, as revealed by CL (cathodoluminescence) spectra, are similar to3.88 eV (320 nm) for SiN layer and similar to2.82 eV (440 nm) for SiNC layer. Depending on the deposition conditions, the growth competitions among SiC, Si-N and SiNC crystalline phases may result in different morphologies, compositions and properties of the films. (C) 2001 Elsevier Science B.V All rights reserved.
Successive current-voltage measurements of a thick isolated diamond film
(2001-11-01)
Huang, BR
;
Ke, WC
;
Hsu, JF
;
Chen, WK
;
電子物理學系
Polycrystalline diamond films were deposited on p-type (100) silicon substrate using a methane/hydrogen gas mixture in a microwave plasma-assisted chemical vapor deposition system. After the back-etched process, the Al contacts were evaporated on both sides of a 150 mum thick isolated diamond film for consecutive high-voltage measurements. It was found that the current-voltage (I-V) characteristics of the Al/diamond/Al structure exhibited two Schottky barrier diodes in a back-to-back configuration. Since the top diamond surface possessed better diamond quality than the bottom surface, the top Schottky diode with a breakdown voltage of 897 V and a lower breakdown voltage of -515 V for the bottom Schottky diode was observed for the first I-V measurement. However, the breakdown voltage was decreased by 37 and 140 V for the top and bottom Schottky diodes after the consecutive sixth repeated measurements. It was found that the oxygenated phenomenon was more prominent; in addition, the quality of the isolated diamond film was also degraded after the consecutive high-voltage measurements. It was indicated that decrease of the breakdown voltage was due to the oxidation layer and the non-diamond components on both surfaces of the isolated diamond film. (C) 2001 Elsevier Science B.V. All rights reserved.
Nanostructure patterns written in polycarbonate by a bent optical fiber probe
(2001-11-01)
Chen, SH
;
Chen, YF
;
電子物理學系
;
Department of Electrophysics
An atomic force, microscope operated in tapping mode using a homemade bent optical fiber probe was used to pattern nanometer-scale features. Trenches of different dimensions were written on polycarbonate that was pre-exposed to an excimer laser. Lines with widths varying from 260 to 600 nm and depths ranging from 30 to 120 nm have been made. The present technique as a complementary tool to other lithographic processes has been demonstrated to be potentially suitable for low-cost and high-precision applications. (C) 2001 American Vacuum Society.
Enhancing the resistance of low-k hydrogen silsesquioxane (HSQ) to wet stripper damage
(2001-11-01)
Chang, TC
;
Mor, YS
;
Liu, PT
;
Tsai, TM
;
Chen, CW
The interaction between low-k hydrogen silsesquioxane (HSQ) film and wet stripper was investigated. The wet stripper has been commonly used to remove photoresister in IC integration processing. However, the high content of alkalinity in the stripper solution often leads to the hydrolysis of HSQ film, forming dangling bonds in the HSQ. The dangling bonds in the HSQ film can easily react with hydroxide ion (OH-) in wet stripper solution and form Si-OH bonds. The resultant HSQ film will tend to uptake water and consequently increase both the leakage current and dielectric constant. In this study, H-plasma pre-treatment was applied to the HSQ film. The hydrogen plasma treatment passivates the HSQ surface and prevent HSQ from water uptake during photoresist stripping. Therefore, dielectric degradation can be avoided with the H-2-plasma pre-treatment. (C) 2001 Elsevier Science B.V. All rights reserved.
Characterization of phosphorus-doped and boron-doped diamond-like carbon emitter arrays
(2001-11-01)
Tsai, CL
;
Chen, CF
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
We synthesized phosphorus-doped and boron-doped emitters by using trimethylphosphite P(OCH3)(3) and trimethylborate B(OCH3)(3) as doping sources in a microwave plasma chemical vapor deposition system. Based on our experimental results from scanning electron microscopy and Raman spectra, there is much difference among undoped, phosphorus-doped, and boron-doped diamondlike material. In addition, doping both phosphorus and boron can enhance electric properties by reducing the turn-on voltage and can increase the emission current density. The turn-on voltages of undoped, boron-doped, and phosphorus-doped emitters in triode-type field emitter arrays are 15, 8, and 5 V, respectively. The emission currents of boron-doped and phosphorus-doped emitters are about 20 and 80 times larger than the undoped. (C) 2001 American Institute of Physics.
Correlation between defect concentration and carrier lifetime of GaAs grown by molecular beam epitaxy at different temperatures
(2001-11-01)
Lin, GR
;
Liu, TA
;
Pan, CL
;
光電工程學系
;
Department of Photonics
A pump-probe study of GaAs grown by molecular beam epitaxy at low temperatures (LT-GaAs) is performed. Ultrashort carrier lifetimes of the as-grown LT-GaAs increase from <0.13 ps (measurement limitation) to 1.8 +/-0.2 ps as the growth temperature is increased from 200 degreesC to 320 degreesC. The carrier lifetime was found to be approximately inversely proportional to the antisite defect concentration. This trend is found to be in reasonably good agreement with the Schokley-Read-Hall model. The decreasing trend in the amplitudes of continuous-wave and transient reflectivities (DeltaR/R) as a function of the growth temperature for the LT-GaAs is explained as an induced absorption caused by dense arsenic antisite defects. The sign of the transient DeltaR/R reversed for LT-GaAs grown at 200 degreesC. This is tentatively attributed to the band gap renormalization effect.
Properties of Si-C-N films prepared on Si substrate using cobalt interfacial layers
(2001-11-01)
Chang, HL
;
Kuo, CT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A microwave plasma chemical vapor deposition (MPCVD) process was successfully used to synthesize Si-C-N films. The film properties were tuned by deposition parameters and engineering interfacial Co layers on Si substrates. The films were deposited by using CH4, N-2, and additional solid Si columns as raw material sources. The films were characterized by scanning electron microscopy (SEM) for film morphologies, X-ray photo-emission spectroscopy (XPS) and cathodoluminescence (CL) spectroscopy for bonding structure and band gap analyses. The results show that the application of Co interlayer can have the following effects: (1) it can change film morphology from (100) preferred orientation to become pyramidal structure, and the band gap from 2.93 to 4.00 eV; (2) it may possess the additional Si(2p)-Si bonding in the films. By adding additional Si source, the atomic ratio of Si:C:N can change significantly with the decrease in carbon content of films, the film structure may vary from amorphous to crystalline and possess additional C(1s)=N bonding (or N(1s)=C bonding). In summary, the composition, morphology, bonding and crystal structures of Si-C-N films have been successfully demonstrated to be manipulated through applications of Co interlayer and additional Si source. (C) 2001 Elsevier Science B.V. All rights reserved.
Optimal minimal-order least-squares estimators via the general two-stage Kalman filter
(2001-11-01)
Hsieh, CS
;
Chen, FC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A direct derivation of the optimal minimal-order least-squares estimator (OMOLSE) is presented using the recently developed general two-stage Kalman filter (GTSKF). Using this new result, the reduced-order estimators of O'Reilly and Fairman are readily shown to be equivalent. A practical implementation issue to consider these two estimators is also addressed.
Characterization and reliability of low dielectric constant fluorosilicate glass and silicon rich oxide process for deep sub-micron device application
(2001-11-01)
Cheng, YL
;
Wang, YL
;
Liu, CW
;
Wu, YL
;
Lo, KY
Fluorosilicate Glass (FSG) with low dielectric constant currently has been replaced as an alternative to SiO2 for device speed improvement. However, several integration aspects, such as Fluorine (F) distribution, F thermal stability, gap fill capability, capacitance reduction and via resistance of FSG prepared by the high density plasma (HDP) chemical vapor deposition (CVD) method are of concern for sub-0.18-mum devices. In this study, HDP-FSG films show different F concentrations at different locations on an 8-inch wafer. In addition, the FSG film shows poor thermal stability and F diffuses out of the film after high temperature annealing and the pressure cook test (PCT). However, the thermal stability of FSG film can be improved by capping with an oxide layer. The results indicate that silicon rich oxide (SRO) has a better effect at blocking the F diffusion out of FSG films at high temperature than plasma enhanced oxide (PE-OX). For the gap fill capability, HDP-FSG can fill all 0.23-mum gaps and some of the 0.21-mum gaps with an aspect ratio <3.8 but not the 0.19-mum gaps. A 8000 Angstrom HDP-FSG film with 600 Angstrom USG liner and 2000 Angstrom cap layer shows approximately 7.5 to 7.7% capacitance reduction on 0.23/0.23-mum gaps when compared with USG (undoped silicate glass). In addition, FSG has a larger capacitance reduction on the wider metal lines than the thinner metal lines at the same gap size due to a capacitance fringe effect. The via resistance for 0.26 mum unlanded via (which allow minor photo mis-alignment) of HDP-FSG film is also similar to that of USG. (C) 2001 Elsevier Science B.V. All rights reserved.
A new analysis of direct-sequence pseudonoise code acquisition on Rayleigh fading channels
(2001-11-01)
Sheen, WH
;
Wang, HC
;
電信工程研究所
;
Institute of Communications Engineering
Accurate performance evaluation of direct-sequence pseudonoise code acquisition on Rayleigh fading channels is investigated in this paper. For fading channels the homogeneous Markov chain model, used to characterize the acquisition process over additive white Gaussian noise channels, is no longer valid due to the correlations between cell detections incurred by fading. Hence, the traditional direct and now-graph approaches for performance evaluation of the code acquisition are not applicable to fading channels. In this paper, a new analysis is proposed for accurate evaluation of the acquisition performance on Rayleigh fading channels. The analysis is quite general and can include various search strategies, types of correlators, and test methods with different performance measures: probability mass function and/or moments of acquisition time. Analytical and simulation results show that the new method predicts the acquisition performance very accurately.