Browsing by Issue Date, starting with "2004-03-22"

Now showing 1 - 20 of 70475

Dual wavelength demultiplexing by coupling and decoupling of photonic crystal waveguides
(2004-03-22)
Chien, FSS
;
Hsu, YJ
;
Hsieh, WF
;
Cheng, SC
;
光電工程學系
We demonstrate that the fundamental mode of the two coupled photonic crystal waveguides (PCWs) can be odd parity in a triangular photonic crystal and their dispersion curves do intersect. Thus, the PCWs are decoupled at the crossing point. By employing the decoupling at the crossing-point frequency and ultra short coupling length for another frequency, we designed a dual-wavelength demultiplexer with a coupling length of only two wavelengths and output power ratio as high as 15 dB. A loop-shape PCW is adapted to eliminate the backward energy flow. (C) 2004 Optical Society of America.
Memory effect of oxide/SiC : O/oxide sandwiched structures
(2004-03-22)
Chang, TC
;
Yan, ST
;
Yang, FM
;
Liu, PT
;
Sze, SM
The memory effects of the oxide/oxygen-incorporated silicon carbide (SiC:O)/oxide sandwiched structure were investigated. The memory window is decreased with the increase of the oxygen content in the SiC:O film due to the reduction of dangling bonds. A concise model is proposed to explain the reduction of dangling bonds with increasing oxygen content. Also, a higher breakdown voltage is observed with less oxygen content in the SiC:O film, which is attributed to the high barrier height induced by electron trapping in the SiC:O film. (C) 2004 American Institute of Physics.
Thermal denaturation of beta-lactoglobulin as probed by an monoclomal antibody
(2004-03-23)
Chen, WL
;
Huang, MT
;
Li, CW
;
Liu, HC
;
Mao, SJT
Molecular properties of human haptoglobin as probed by monoclonal antibodies
(2004-03-24)
Mao, SJT
;
Yang, YT
;
Lai, SM
;
Wu, CF
;
Chang, TM
Purification of human haptoglobin 1-1, 2-1, and 2-2 using monoclonal antibody affinity chromatography
(2004-03-24)
Tseng, CF
;
Huang, HY
;
Yang, YT
;
Mao, SJT
;
生物科技學院
Study of dry etching for GaN and InGaN-based laser structure using inductively coupled plasma reactive ion etching
(2004-03-25)
Kao, CC
;
Huang, HW
;
Tsai, JY
;
Yu, CC
;
Lin, CF
Dry etching of undoped, n-GaN, p-GaN and InGaN laser structure was investigated by inductively coupled plasmas reactive ion etching (ICP-RIE) using Ni mask. As Cl-2/Ar gas flow rates were fixed at 10/25 sccm, the etched surface roughness has the lowest value of 0.2 nm at constant ICP/bias power = 300/100 W and 5 mTorr chamber pressure for undoped GaN. The highest etching rate of 12,000 Angstrom/min for n-GaN was achieved at 30 mTorr, 300 W ICP, 100 W bias power using low Cl-2 flow rate (Cl-2/Ar = 10/25 sccm) gas mixtures. The surface roughness was dependent of bias power and chamber pressure, and shows a low root mean square (rms) roughness value of about I nm at 50 W of bias power for n-GaN and p-GaN. For etching of InGaN laser structure using high O-2 flow rate (Cl-2/Ar = 50/20 sccm) and low chamber pressure 5 mTorr, a smooth mirror-like facet of InGaN laser diode structure was obtained. Using these etching parameters, mirror-like facets can be obtained which can be used for the fabrication of nitride-based laser diodes. Moreover, at the fixed Cl-2/Ar flow rate of 10/25 sccm, ICP/bias power of 200/100 W and chamber pressure of 30 mTorr, the InGaN-based materials nanorods were fabricated with a density of about 10(8) cm(-2) and dimension of 50-100 nm. (C) 2004 Elsevier B.V. All rights reserved.
Effect of rapid thermal annealing on beryllium implanted p-type GaN
(2004-03-25)
Huang, HW
;
Kao, CC
;
Tsai, JY
;
Yu, CC
;
Chu, CF
We report the results of rapid thermal annealing (RTA) effect on beryllium implanted in situ activated p-type GaN samples and investigate the ramping and isothermal annealing effect of RTA process for these samples. It is found that the optimum RTA condition is at the temperature of 1100 degreesC for 15 s. Furthermore, with equal total isothermal time of 60 s, we compared the multiple step annealing (MSA) at 1100 degreesC for four periods with single step annealing (SSA) for one period at the same annealing temperature of 1100 degreesC, and observed that the ramping effect with MSA could repair Be-related complex defect, and one time, long period isothermal annealing effect with SSA seems to induce much more defect. It seems that the multiple step annealing is more effective and induce less defect than single step annealing for Be-implanted in situ activated p-type GaN samples. (C) 2004 Elsevier B.V. All rights reserved.
A self-propagating high-temperature synthesis method for Ni-ferrite powder synthesis
(2004-03-25)
Peng, CH
;
Hwang, CC
;
Hong, CK
;
Chen, SY
;
材料科學與工程學系
Ni-ferrite (NiFe2O4) powder was synthesized by a self-propagating high-temperature synthesis (SHS) process using Fe, Fe2O3 and various Ni-containing species (Ni-CSs) as reactants. The reactants were thoroughly mixed and pressed into a cylindrical compact. The compact was ignited by electrical heating under oxygen partial pressures varying between 0.02 and 1.5 MPa. The effects of the type of Ni-containing species, the reactant composition, the oxygen pressure on the combustion temperature, and the product conversion were investigated. X-ray diffraction (XRD) analysis showed that oxygen pressure promoted product conversion. Among several Ni-containing species tested, Ni2O3 was found to give the highest conversion. The product conversion increased with increasing iron content and then decreased with further increase in iron content. Scanning electron microscope (SEM) observations showed that the product synthesized is mostly in the form of agglomerated fine particles with submicron size (0.1-0.5 mum). Hysteresis behavior analysis showed that the product as synthesized possessed better soft magnetic properties when compared with commercial Ni-ferrite prepared by the solid reaction method. (C) 2004 Elsevier B.V. All rights reserved.
Self-generated NAF nano template assisted formation of porous carbon nanotube arrays.
(2004-03-28)
Chiu, HT
;
Huang, CH
;
Chang, YH
;
Lee, CY
;
Cheng, SF
Updated numerical performance and throughput benchmark for electronic structure calculations in PC-LINUX systems.
(2004-03-28)
Yu, JSK
;
Hwang, JK
;
Tang, CY
;
Yu, CH
;
生物科技學系
黃永松埋首案前堆疊出漢聲歷史
(2004-03-29)
陳冠茜
Star polymers via atom transfer radical polymerization from adamantane-based cores
(2004-03-29)
Huang, CF
;
Lee, HF
;
Kuo, SW
;
Xu, HY
;
Chang, FC
A series of novel multifunctional initiators derived from adamantane-based derivatives have been used in the syntheses of various styrenic and (meth)acrylic star polymers by atom transfer radical polymerization (ATRP). Conditions were identified in each system to produce star polymers with nearly monomodal molecular distributions. These synthesized star polymers have glass transition temperatures similar to those known for high-molecular-weight linear polymers. We obtained a series of adamantane-contained star polymers covering a wide range of molecular weights by adjusting the monomer-to-initiator ratio and the solvent polarity. Because of reaction heterogeneity and inevitable termination processes, the occurrence of star-star coupling led to a lower than predicted molecular weight polydispersity. When hydrolyzed from their cores by NaOH, the values of Mw of the arms of the PMMA star polymer did not change with reaction time, at least for the first 48 h of the reaction, which implies that no significant PMMA hydrolysis occurs within this interval of time. (C) 2004 Elsevier Ltd. All rights reserved.
Rotationally selected product pair correlation in F+CD4 -> DF(nu('))+CD3(nu=0,N)
(2004-04-01)
Zhou, JG
;
Shiu, WC
;
Lin, JJ
;
Liu, KP
;
應用化學系
The title reaction was studied in a crossed-beam experiment by imaging of state-selected products. The rotational state selection of the CD3 products was achieved using (2+1) resonance-enhanced multiphoton ionization. The coincident information on the DF coproducts was revealed in a state-resolved manner from time-sliced velocity map images. Significant dependences of both the correlated differential cross sections and the DF vibrational branching ratios on the "tagged" CD3 rotation states were found. The dynamical implications of one of the major findings are discussed. (C) 2004 American Institute of Physics.
Characterization of hydrogen-treated pentacene organic thin film transistors
(2004-04-01)
Yang, JY
;
Suen, SC
;
Whang, WT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The electrical characteristics of hydrogen-postannealed and hydrogen-plasma-treated pentacene thin film transistors (TFTs) have been investigated. Experimental results have shown that the hydrogen-treated TFTs have improved field-effect mobility and a higher current on/off ratio, compared to untreated devices. The on/off current ratio of the hydrogen-treated devices was markedly increased. However, the TFTs treated with hydrogen plasma have degraded field-effect mobility, compared to hydrogen-postannealed devices.
Field emission properties of aligned carbon nanotubes grown on stainless steel using CH4/CO2 reactant gas
(2004-04-01)
Lin, CL
;
Chen, CF
;
Shi, SC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Aligned carbon nanotubes (CNTs) were grown on stainless steel 304 by bias-enhanced microwave plasma chemical vapor deposition, using CH4/CO2 as the reactant gas. A bias was applied to the microwave plasma to grow the nanotubes over various periods. Experimental results show that well-aligned CNTs grow on stainless steel at a negative bias of - 300 V Energy dispersive spectrometer on TEM indicated that the metal catalyst on the top of the CNTs includes Fe and Ni, but not Cr. The field emission properties of the resultant CNTs were obtained at a negative bias of - 300 V: the emission current was 194 muA at 2.2 V/mum; and the turn-on voltage, which is the voltage needed to extract current density of 10 muA /cm(2), was 1.4 V/mum. (C) 2003 Elsevier B.V. All rights reserved.
空原上之小樹呀
(2004-04-01)
管管
Field emission and photofluorescent characteristics of zinc oxide nanowires synthesized by a metal catalyzed vapor-liquid-solid process
(2004-04-01)
Li, SY
;
Lin, P
;
Lee, CY
;
Tseng, TY
;
材料科學與工程學系
The ZnO nanowires synthesized by vapor-liquid-solid growth mechanism with Cu and Au as the catalyst were investigated. The principal differences in morphology between Cu and Au catalyzed ZnO nanowires are observed and lead to significant differences in their field emission and photofluorescent characteristics. The Cu catalyzed ZnO nanowires with a high-quality wurtzite structure were grown vertically on p-type Si(100) substrate along [0002] direction. A strong ultraviolet emission at 381 nm is observed. These ZnO nanowires show excellent field emission properties with turn-on field of 0.83 V/mum and corresponding current density of 25 muA/cm(2). The emitted current density of the ZnO nanowires is 1.52 mA/cm(2) at a bias field of 8.5 V/mum. The large field emission area factor, beta arising from the morphology of the nanowire field emitter, is partly responsible for the good emission characteristics. The ZnO nanowires with high emission current density and low turn-on field are expected to be used in field emission flat panel display. (C) 2004 American Institute of Physics.
Advanced obfuscation techniques for Java bytecode
(2004-04-01)
Chan, JT
;
Yang, W
;
資訊工程學系
;
Department of Computer Science
There exist several obfuscation tools for preventing Java bytecode from being decompiled. Most of these tools simply scramble the names of the identifiers stored in a bytecode by substituting the identifiers with meaningless names. However, the scrambling technique cannot deter a determined cracker very long. We propose several advanced obfuscation techniques that make Java bytecode impossible to recompile or make the decompiled program difficult to understand and to recompile. The crux of our approach is to over use an identifier. That is, an identifier can denote several entities, such as types, fields, and methods, simultaneously. An additional benefit is that the size of the bytecode is reduced because fewer and shorter identifier names are used. Furthermore, we also propose several techniques to intentionally introduce syntactic and semantic errors into the decompiled program while preserving the original behaviors of the bytecode. Thus, the decompiled program would have to be debugged manually. Although our basic approach is to scramble the identifiers in Java bytecode, the scrambled bytecode produced with our techniques is much harder to crack than that produced with other identifier scrambling techniques. Furthermore, the run-time efficiency of the obfuscated bytecode is also improved because the size of the bytecode becomes smaller after obfuscation. (C) 2002 Elsevier Inc. All rights reserved.
An empirical analysis of the relationship between the hedge ratio and hedging horizon: A simultaneous estimation of the short- and long-run hedge ratios
(2004-04-01)
Chen, SS
;
Lee, CF
;
Shrestha, K
;
資訊管理與財務金融系註：原資管所+財金所
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Department of Information Management and Finance
This article analyzes the effects of the length of hedging horizon on the optimal hedge ratio and hedging effectiveness using 9 different hedging horizons and 25 different commodities. We discuss the concept of short- and long-run hedge ratios and propose a technique to simultaneously estimate them. The empirical results indicate that the short-run hedge ratios are significantly less than 1 and increase with the length of hedging horizon. We also find that hedging effectiveness increases with the length of hedging horizon. However, the long-run hedge ratio is found to be close to the naive hedge ratio of unity. This implies that, if the hedging horizon is long, then the naive hedge ratio is close to the optimum hedge ratio. (C) 2004 Wiley Periodicals, Inc.
Supervised motion segmentation by spatial-frequential analysis and dynamic sliced inverse regression
(2004-04-01)
Wu, HM
;
Lu, HHS
;
統計學研究所
;
Institute of Statistics
lit this paper, we propose a new method for supervised motion segmentation based on spatial-frequential analysis and dimension reduction techniques. A sequence of images could contain non-ridge motion in the region of interest and the segmentation of these moving objects with deformation is challenging. The aim is to extract feature vectors that capture the spatial-frequential information in the training set and then to monitor the variations of the feature vectors over time in the test set. Given successive images in the training set, we consider a dynamic model that extends the sliced inverse regression in Li (1991). It is designed to capture the intrinsic dimension of feature vectors that holds over a local time scale. These projected features are then used to classify training images and predict forthcoming images in the test set into distinct categories. Theoretic properties are addressed. Simulation studies and clinical studies of a sequence of magnetic resonance images are reported, which confirm the practical feasibility of this new approach.