Browsing by Issue Date, starting with "2002-08-18"

Now showing 1 - 20 of 74473

Synthetic approach to tangutorine.
(2002-08-18)
Ho, TL
;
應用化學系
;
Department of Applied Chemistry
Shrinkage- and refractive-index shift-corrected volume holograms for optical interconnects
(2002-08-19)
Chen, JH
;
Su, DC
;
Su, JC
;
光電工程學系
;
Department of Photonics
The Bragg mismatching condition for volume holograms occurs because of the changes in the thickness and the refractive index of holographic recording materials during the recording and reconstruction procedures. We propose an improved compensation method to physically correct these effects in the fabrications of volume holograms for optical interconnects. In order to show the validity of this method, Slavich photographic plate VRP-M is used to fabricate optical interconnects. The correction of the Bragg diffraction angle shift of about 2.10degrees, which is induced by 6.14% film shrinkage and 0.06 refractive index shift, is successfully demonstrated with the surface-normal configuration. A shrinkage- and refractive-index shift-corrected volume hologram with 23% diffraction efficiency is experimentally confirmed. The methodology proposed is applicable to other phase media when the associated film shrinkage and refractive-index shift data are experimentally determined. (C) 2002 American Institute of Physics.
Healing kinetics of interfacial voids in GaAs wafer bonding
(2002-08-19)
Wu, YCS
;
Hu, GZ
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A periodic structure of bonded GaAs wafers has been proposed for quasi-phase-matched second-harmonic generation. After bonding, voids were formed at the interface due to the natural topographical irregularities and contamination on the wafer surface. Within the voids, crystallites with diamond-shaped and dendritic geometries were found, which corresponded to the bonded regions. In this study, artificial voids were introduced at the bonded interface to study the growth kinetics of these crystallites, that is the healing kinetics of these voids. It was found that the crystallite geometries and the growth rates are controlled by the nucleation of new surface layers on the bonded planes, which was the slowest stage during the healing process. (C) 2002 American Institute of Physics.
High power Al0.3Ga0.7As/In0.2Ga0.8As enhancement-mode PHEMT for low-voltage wireless communication systems
(2002-08-29)
Chen, SH
;
Chang, L
;
Chang, EY
;
Wu, JW
;
Chang, CY
A 20 mm-wide enhancement-mode pseudomorphic high-electron-mobility transistor (E-PHEMT) has been developed. The device has high transconductance of 490 mS/mm, and high maximum drain current of 350 mA/mm due to the use of an Al(0.3)G(4.7)As/In0.2Ga0.8As-based structure for carrier confinement. At 1.9 GHz and 3.0 V, the E-PHEMT shows 34.1 dBm (128 mW/mm) output power with power-added efficiency (PAE) of 64.5%. At 2.4 V, the maximum saturated output power is 32.25 dBm and maximum PAE is 78.5%. The E-PHEMT demonstrates excellent power performance at 1.9 GHz and below 3 V.
Channel-sharing strategies in two-tier cellular PCS systems
(2002-09-01)
Lin, KJ
;
Tseng, YC
;
Sheu, JP
;
資訊工程學系
;
Department of Computer Science
A two-tier cellular network is characterized by macrocells and microcells overlapping in the service area. This overlapping property provides an advantage that traffic loads can be shared by channels of the two tiers to increase the performance of the system. In this paper, we propose two channel-sharing strategies, namely vertical channel-sharing and vertical-horizontal channel-sharing, to better utilize channels of the network. The call loss probability of new calls and call dropping probability of handoff calls are developed through analyses and simulations. The results justify the advantage of our strategies over existing strategies. (C) 2002 Elsevier Science B.V. All rights reserved.
Improved TaN barrier layer against Cu diffusion by formation of an amorphous layer using plasma treatment
(2002-09-01)
Ou, KL
;
Wu, WF
;
Chou, CP
;
Chiou, SY
;
Wu, CC
The thermal stability and electrical properties of plasma-treated TaN films have been investigated by Cu/TaN/Si systems. The properties of diffusion barrier were evaluated by sheet resistance, x-ray diffraction (XRD), transmission electron microscopy (TEM), x-ray photoelectron spectroscopy (XPS), energy-dispersive spectroscopy (EDS), Auger electron microscopy (AES), and reverse-biased junction leakage current. A new amorphous layer is found to form on the surface of TaN film after the plasma treatment, Plasma-treated TaN films show better barrier performance than untreated TaN films. The sheet resistance of Cu/TaN(10 nm)/Si increases apparently after annealing at 625 degreesC for 1 h, while the Cu/plasma-treated TaN(10 nm)/Si is fairly stable up to annealing at 750 degreesC. The resistance to copper diffusion in plasma-treated TaN film is more effective. This is attributed that an amorphous layer that forms on the surface of TaN film after the plasma treatment. The thermal stabilities of Cu/TaN/n(+)-p junction diodes are enhanced by plasma treatment. The Cu/TaN(10 nm)/n(+)-p and Cu/TaN(50 nm)/n(+)-p junction diodes result in large reverse-biased junction leakage currents after annealing at 525 and 575 degreesC, respectively. On the other hand, plasma-treated TaN diffusion barriers improve the integrity of junction diodes up to 650 degreesC. Nano crystallization and stuffing effects of plasma treatments are believed to impede Cu diffusion into the Si substrate and hence improve the barrier performance. (C) 2002 American Vacuum Society.
可同時感測光纖之應變與溫度分佈的方法
(2002-09-01)
祁甡
;
李健仲
;
蔣博文
本發明係提供一種可同時感測光纖之應變與溫度分佈的方法，其係利用纖核中含有不同溫度係數成份的光纖結合布里淵頻率漂移，達到應變與溫度分佈的同時量測。該方法係先提供一核心中係含有不同溫度係數成份之感測光纖，再取得該感測光纖之布里淵頻譜的主要兩個峰值頻率值，並利用布里淵頻率漂移值的變化量與應變及溫度之關係，求得一溫度變化量，進而推導得知應變變化量。本發明為利用感測光纖本身固有特性達到分離的方法，使得整個感測系統更加簡單、實用性更高，並可得到高解析度及良好之分離效果。
An all-IP approach for UMTS third-generation mobile networks
(2002-09-01)
Lin, YB
;
Pang, AC
;
Haung, YR
;
Chlamtac, I
;
交大名義發表
This article describes the UMTS all-IP approach for third-generation mobile systems, with emphasis on the core network architecture. Followng the introduction of the core network nodes, we elaborate on application-level registration, circuit-switched call origination, packet-switched call origination, and packet-switched call termination.
Characteristics of copper films deposited on H(2)-plasma-treated TaN substrate by chemical vapor deposition
(2002-09-01)
Lin, CL
;
Chen, PS
;
Chang, CL
;
Chen, MC
;
電子工程學系及電子研究所
This work investigates the chemical vapor deposition Cu films deposited on the TaN substrate with and without an H(2)-plasma treatment prior to Cu film deposition and the effect of postdeposition thermal annealing. The Cu films deposited on the H(2)-plasma-treated TaN substrate have a number of favorable properties over the films deposited on the TaN substrate without the plasma treatment. These include an increased (111)-preferred orientation, smoother film surface, and a larger effective deposition rate. However, the Cu films deposited on the H(2)-plasma-treated substrate have a higher electrical resistivity, presumably due to the smaller, grain size. The postdeposition thermal annealing enhanced the (111)-preferred orientation and decreased the resistivity of the as-deposited Cu films. We presume that the H(2)-plasma treatment, resulted in a dense and uniform distribution of hydrogen radicals adsorbed on the substrate surface, leading to the shortening of incubation time and the formation of Cu films with a smoother surface and enhanced (100)-preferred orientation. A combined process including H(2)-plasma substrate treatment prior to Cu film deposition and postdeposition thermal annealing at an appropriate temperature in N(2) ambient, is proposed for the advantage of low-resistivity and high (111)-oriented Cu film deposition. (C) 2002 American Vacuum Society.
Design and analysis of on-chip ESD protection circuit with very low input capacitance for high-precision analog applications
(2002-09-01)
Ker, MD
;
Chen, TY
;
Wu, CY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An ESD protection design is proposed to solve the ESD protection challenge to the analog pins for high-frequency or current-mode applications. By including an efficient power-rails clamp circuit into the analog I/O pin, the device dimension (W/L) of ESD clamp device connected to the I/O pad in the analog ESD protection circuit can be reduced to only 50/0.5 (mum/mum) in a 0.35-mum silicided CMOS process, but it can sustain the human-body-model (machine-model) ESD level of up to 6 kV (400 V). With such a smaller device dimension, the input capacitance of this analog ESD protection circuit can be significantly reduced to only similar to1.0 pF (including the bond pad capacitance) for high-frequency applications. A design model to find the optimized layout dimensions and spacings on the input ESD clamp devices has been also developed to keep the total input capacitance almost constant (within 1% variation), even if the analog input signal has a dynamic range of 1 V.
Axial load behavior of stiffened concrete-filled steel columns
(2002-09-01)
Huang, CS
;
Yeh, YK
;
Liu, GY
;
Hu, HT
;
Tsai, KC
This study investigates the axial load behavior of concrete-filled steel tubular (CFT) columns with the width-to-thickness ratios between 40 and 150, and proposes an effective stiffening scheme to improve the mechanical properties of square cross-sectional CFT columns. Seventeen specimens were tested to examine the effects of cross-sectional shapes, width-to-thickness ratios, and stiffening arrangements on the ultimate strength, stiffness, and ductility of CFT columns. Moreover, nonlinear finite element analysis was also conducted to investigate cross-sectional axial stress distribution at the ultimate strength. Comparing the measured ultimate strength with estimates by using some current specifications suggested that current specifications may considerably underestimate the ultimate strength of circular CFT columns, particularly for columns with a small width-to-thickness ratio. Results in this study demonstrate that the proposed stiffening scheme can significantly enhance the ultimate strength and ductility of square CFT columns.
Exploring students' cognitive structures in learning science: a review of relevant methods
(2002-09-01)
Tsai, CC
;
Huang, CM
;
教育研究所
;
Institute of Education
Understanding how people think and how people organise knowledge are always major concerns for educational researchers. Hence, educators have developed various ways of representing learners' 'cognitive structures'. This article provides a review of the use of five methods of representing cognitive structures-free word association, controlled word association, tree construction, concept map and flow map. Through comparing the types of analyses that are generated from these cognitive structure representation methods, this paper discusses the applications, as well as the limitations, among these methods.
Experimental study on shear splitting failure of full-scale composite concrete encased steel beams
(2002-09-01)
Weng, CC
;
Yen, SI
;
Jiang, MH
;
土木工程學系
;
Department of Civil Engineering
Presented herein is an experimental study that focuses on the shear splitting failure of composite concrete encased steel beams. Nine full-scale specimens were constructed and tested in this study. Significant horizontal cracks along the interface of steel flange and concrete, referred to as the shear splitting failure, appeared in five tested specimens. Observations from the experiments indicate that the steel flange width ratio, defined as the ratio of steel flange width to gross section width, has a dominant effect on the shear splitting failure of composite beams. The test results reveal that the shear splitting failure occurs when the steel flange width ratio of a composite beam reaches 0.67. The test results also show that the application of shear studs has a positive effect on preventing this type of failure for beams with large steel flange ratio. In addition to the experimental study, a new method for predicting the failure mode of composite beams is proposed. The proposed method gives satisfactory predictions as compared to the test results. Finally, a new equation is derived for the design of the stirrups to prevent shear splitting failure of naturally bonded composite beams.
A theoretical evaluation on the HNO3 artifact of the annular denuder system due to evaporation and diffusional deposition of NH4NO3-containing aerosols
(2002-09-01)
Chang, KF
;
Lu, CS
;
Bai, HL
;
Fang, GC
;
環境工程研究所
(A) mathematical model was developed to evaluate HNO3 artifact of the annular denuder system due to evaporation and diffusional deposition of nitrate-containing aerosols. The model performance was validated by comparing its numerical solutions with laboratory and numerical data available in the literature for evaporation and diffusional deposition of monodisperse and polydisperse NH4NO3 aerosols. Measurement artifacts were evaluated by varying typical sampling ranges of ambient temperature, HNO3 gas concentration, aerosol number concentration, aerosol mass median diameter, and nitrate mass fraction of < 2.5 mum aerosols to see their respective effects. Potential application of the present model on estimating HNO3 artifacts was demonstrated using literature data sampled in USA, Taiwan, Netherlands, Korea and Japan. Significant measurement artifact could be found in Taiwan and Netherlands due either to low HNO3 gas concentration and high nitrate concentration in < 2.5 mum aerosols or to high ambient temperature. (C) 2002 Elsevier Science Ltd. All rights reserved.
Glass transition temperatures of poly(hydroxystyrene-co-vinylpyrrolidone-co-isobutylstyry1 polyhedral oligosilsesquioxanes)
(2002-09-01)
Xu, HY
;
Kuo, SW
;
Lee, JS
;
Chang, FC
;
應用化學系
A series of poly(hydroxystyrene-co-vinylpyffolidone-co-isobutylstyryl polyhedral oligosilsesquioxanes) (PHS-PVP-POSS) hybrid polymers with various POSS contents was prepared by free radical copolymerization of acetoxystyrene, vinylpyrrolidone with styrylisobutylpolyhedral oligosilsesquioxanes (POSS), followed by selective removal of the acetyl protective group. The POSS content of a hybrid polymer can be effectively controlled by varying the feed ratios of reactants. The T-g of the POSS hybrid increases with the POSS content of PHS-PVP-POSS hybrids. The mechanism of T-g enhancement in these PHS-PVP-POSS hybrids was investigated using DSC, FTIR and GPC. The formation of the physically cross-linked POSS in these hybrid polymers trends to restrict polymer chain motion and results in significant T-g increase. (C) 2002 Published by Elsevier Science Ltd.
Microleveling mechanisms and applications of electropolishing on planarization of copper metallization
(2002-09-01)
Chang, SC
;
Shieh, JM
;
Huang, CC
;
Dai, BT
;
Li, YH
The optimization of Cu electropolishing processes was explored to be in the mass-transfer-limited plateau with a stable limiting current density and in concentrated phosphoric acid by elucidating surface morphologies and potentiodynamic polarization. After electropolishing, the average roughness of polished surfaces achieved to 1.1 nm. Both the x-ray photoelectron spectroscopy and the electrochemical impedance spectroscopy suggest that the existence of a passivation film on the polished surface contributed to the microleveling effect of Cu electropolishing. Moreover, this passivation layer also induces an application of end point in electropolishing. (C) 2002 American Vacuum Society.
Simultaneous etching of polysilicon materials with different doping types by low-damage transformer-coupled plasma technique
(2002-09-01)
Hung, CC
;
Lin, HC
;
Wang, MF
;
Huang, TY
;
Shih, HC
The feasibility of simultaneously etching n(+), p(+), and undoped polysilicon (poly-Si) materials by a commercial transformer coupled plasma (TCP) reactor has been investigated in this study. Response surface methodology (RSM) was used to optimize process parameters including pressure, TCP source power, bias power, and Cl-2/HBr flow on the main etch step. Quantitative relationships between etching performance and process parameters were established. Our results indicate that there exists a process parameter window that meets the requirements of etching polysilicon with different doping types simultaneously. High etch rate, superior uniformity, good end point detection (EPD) characteristics and profile control can be simultaneously obtained with the optimized recipe, irrespective of the doping types. Furthermore, only minor plasma-induced damage is detected as monitored from antenna transistors' charge-to-breakdown (Q(bd)), threshold voltage and charge pumping current. (C) 2002 Elsevier Science B.V. All rights reserved.
Algorithmic aspect of k-tuple domination in graphs
(2002-09-01)
Liao, CS
;
Chang, GJ
;
應用數學系
;
Department of Applied Mathematics
In a graph G, a vertex is said to dominate itself and all of its neighbors. For a fixed positive integer k, the k-tuple domination problem is to find a minimum sized vertex subset such that every vertex in the graph is dominated by at least k vertices in this set. The present paper studies the k-tuple domination problem in graphs from an algorithmic point of view. In particular, we give a linear-time algorithm for the 2-tuple domination problem in trees by employing a labeling method.
An analytical POC stack operations folding for continuous and discontinuous Java bytecodes
(2002-09-01)
Ton, LR
;
Chang, LC
;
Chung, CP
;
資訊工程學系
;
Department of Computer Science
The execution performance of a stack-based Java virtual machine (JVM) is limited by the true data dependency. To enhance the performance of the JVM, a stack operations folding mechanism for the picoJava-I/II processor was proposed by Sun Microsystems to fold 42.3% stack operations. By comparing the continuous bytecodes with predefined folding patterns in instruction decoder, the number of push/pop operations in between the operand stack and the local variable could be reduced. In this study, an enhanced POC (EPOC) folding model is proposed to further fold the discontinuous bytecodes that cannot be folded in continuous bytecodes folding mechanisms. By proposing a stack re-order buffer (SROB) to help the folding check processes, the EPOC folding model can fold the stack operations perfectly with a small size of SROB implementation. Statistical data shows that the four-foldable strategy of the EPOC folding model can eliminate 98.8% of push/pop operations with an instruction buffer size of 7 bytes and the SROB size of eight entries. (C) 2002 Elsevier Science B.V. All rights reserved.
Object-based image steganography using affine transformation
(2002-09-01)
Lee, YK
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
The typical model of steganography has led the prisoners' problem, in which two persons attempt to communicate covertly without alerting the warden. The general way to achieve this task is to embed the message in an innocuous-looking medium. In this paper, an object-based geometric embedding technique is proposed for solving the prisoners' problem. The main idea is to embed secret data through distorting a given object and the distorted object still looks natural. In the embedding process, the secret message is first converted into coefficients of an affine transformation. Then, the coordinates of each pixel of a selected object in the cover-image are recomputed by this affine transformation. Since these coefficients are restricted in a specific range, the transformed object looks natural. In the extracting process, a coarse-to-fine iterative search is proposed to accelerate the object location and the message extraction. Experimental results show that all transformed objects can be located precisely and the whole hidden message can be extracted correctly even if the stego-image is stored in various compression formats and rates. Furthermore, the embedded message is robust enough when the stego-image format is converted from GIF to JPEG, and vice versa.