Browsing by Issue Date, starting with "2006-02-02"

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Characterization on electron beam welds and parameters for AZ31B-F extrusive plates
(2006-02-02)
Chi, Chao-Ting
;
Chao, Chuen-Guang
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Recent years have seen a renewal of interest in magnesium alloys because of the extensive applications in the industry of 3C, aerospace and traffic. However, applications of magnesium alloys are still restricted by their poor formability. This can be improved by dividing the shape-complicated work piece into several easily-made parts and then combining into one. There are various kinds of defects in the weld under the interaction of AZ31B properties and welding conditions. These defects will produce obvious stress concentration and serious material damage. In this study, a home-made 11 mm-thick AZ31B extrusive plate was used. By operating and comparing the changeable parameters of electron beam welding (EBW), the condition was optimized as 100 mA, 50 kV, 60.6 mm/s and focus position at bottom. Seventy-eight percent and 91% of the base material strength were obtained by stress and non-stress concentration weldments, respectively. Meanwhile, the harmful influence of SC and grain coarsening reached at least 13% and 9%, respectively. With other worse parameters, the strength of AZ31B weldments were reduced by undercut, root concavity, cavities and heat-affected zone (HAZ). (c) 2006 Elsevier B.V. All rights reserved.
Crack-free GaN/AlN distributed Bragg reflectors incorporated with GaN/AlN superlattices grown by metalorganic chemical vapor deposition
(2006-02-06)
Huang, GS
;
Lu, TC
;
Yao, HH
;
Kuo, HC
;
Wang, SC
A crack-free GaN/AlN distributed Bragg reflector (DBR) incorporated with GaN/AlN superlattice (SL) layers was grown on a c-plane sapphire substrate by metalorganic chemical vapor deposition. Three sets of half-wave layers consisting of 5.5 periods of GaN/AlN SL layers and GaN layer were inserted in every five pairs of the 20 pair GaN/AlN DBR structure to suppress the crack generation. The grown GaN/AlN DBRs with SL insertion layers showed no observable cracks in the structure and achieved high peak reflectivity of 97% at 399 nm with a stop band width of 14 nm. Based on the x-ray analysis, the reduction in the in-plane tensile stress in the DBR structure with insertion of SL layers could be responsible for the suppression of crack formation and achievement of high reflectivity. (c) 2006 American Institute of Physics.
Cholesterol loading augments oxidative stress in macrophages
(2006-02-06)
Hung, YC
;
Hong, MY
;
Huang, GS
;
材料科學與工程學系奈米科技碩博班
;
Graduate Program of Nanotechnology , Department of Materials Science and Engineering
To investigate the molecular consequence of loading free cholesterol into macrophages, we conducted a large-scale gene expression study to analyze acetylated-LDL-laden foam cells (AFC) and oxidized-LDL-laden foam cells (OFC) induced from human THP-1 cell lines. Cluster analysis was performed using 9600-gene microarray datasets from time course experiment. AFC and OFC shared common expression profiles; however, there were sufficient differences between these two treatments that AFC and OFC appealed as two separate entities. We identified 80 commonly upregulated genes and 48 commonly downregulated genes in AFC and OFC. Functional annotation of the differentially expressed genes indicated that apoptosis, extracellular matrix, oxidative stress, and cell proliferation was deregulated. We also identified 87 differentially expressed genes unique for AFC and 31 genes for OFC. The uniquely expressed genes of AFC are associated with kinase activity, ATP binding activity, and transporter activity, while unique genes for OFC are associated with cell signaling and adhesion. To validate the hypothesis that oxidative stress is a common feature for AFC and OFC, we performed a cluster analysis employing the genes related to oxidative stress, but we were unable to distinguish AFC from OFC in this manner. We performed real-time RTPCR and ELISA on foam cells to examine the transcripts and secreted protein of interleukin 1 beta (IL1 beta). IL1 beta was rapidly induced in foam cells, but for AFC both RNA level and protein level dropped immediately and was attenuated. To detect levels of reactive oxygen species in foam cells we conducted hydroethidine staining and observed high levels of superoxide anion. We conclude that loading free cholesterol induces high levels of superoxide anion, increases oxidative stress, and triggers a transient inflammatory response in macrophages. (c) 2006 Published by Elsevier B.V. on behalf of the Federation of European Biochemical Societies.
Channel-width dependence of low-frequency noise in process tensile-strained n-channel metal-oxide-semiconductor transistors
(2006-02-06)
Lu, MP
;
Lee, WC
;
Chen, MJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Low-frequency noise measurement in process tensile-strained n-channel metal-oxide-semiconductor field-effect transistors yields the density of the interface states, exhibiting a decreasing trend while decreasing the channel width. This finding corroborates the group of P-b centers caused by the lattice mismatch at (100) Si-SiO2 interface as the origin of the underlying interface states. The inverse narrow width effect appears to be insignificant, substantially confirming the validity of the noise measurement. The present noise experiment therefore points to the enhancement of the tensile strain in the presence of channel narrowing, which in turn reduces the lattice mismatch.
Phosphorescence of red Os(fptz)(2)(PPh2Me)(2) doped organic light-emitting devices with n and p hosts
(2006-02-06)
Liu, TH
;
Hsu, SF
;
Ho, MH
;
Liao, CH
;
Wu, YS
We have applied a stericly-hindered red phosphorescent dopant Os(fptz)(2)(PPh2Me)(2) [fptz=3-trifluoromethyl-5-(2-pyridyl)-1,2,4-triazole, PPh2Me=phosphine ligand] in p-type 4,4(')-N,N-'-dicarbazole-biphenyl or n-type bis(2-methyl-8-quinolinolato)(p-phenylphenolato) aluminum host and found that the latter produced higher luminance efficiency at lower doping concentration. We present a model to rationalize this phenomenon in which the n-type host impedes hole transport, which leads to narrower recombination zone near the hole transport layer/emission layer interface than the p-type host, hence, more effective recombination.
Manufacturing method and apparatus of fiber coupler
(2006-02-07)
Chi
;
Sien
;
Tseng
;
Shiao-Min
;
Chen
A manufacturing apparatus and method of a fiber coupler is provided. A movable electric arc is employed to fuse more than two stacked fibers for manufacturing a fiber coupler having a small size and good environment stability. It is advantageous that the fiber coupler can be used in a SDH (Synchronous Digital Hierarchy) communication system, and the method also be used to manufacture the all-fiber CWDM (Coarse Wavelength Division Multiplexing) multiplexer which covers the E-band wavelengths and the sub-components of the OADM (Optical Add/Drop Multiplexer). And, all these functions are difficult to be achieved by the conventional techniques.
Transitions of domain ordering and domain size in a spherical-forming polystyrene-block-poly(ethylene oxide) copolymer and its composites with colloidal cadmium sulfide quantum dots
(2006-02-08)
Sun, YS
;
Jeng, US
;
Liang, KS
;
Yeh, SW
;
Wei, KH
With specific annealing schemes applied to a neat polystyrene-block-poly(ethylene oxide) (SE) and its composites with cadmium sulfide quantum dots (CdS QD), we have observed microdomain structures and phase transitions in the system using temperature-resolved small-angle X-ray scattering (SAXS) and transmission electron microscopy (TEM). Both TEM images and SAXS results show clearly that incorporation of surfactant-tethered US QD preferentially into PEO blocks leads to increases in thermal stabilities of both bcc-packed lattice (referred as long-range order) and microdomains themselves in the sphere-forming SE/CdS composites. The bcc-packed lattice in the SE/CdS composites sustains better than that in the neat SE, during a temperature elevation to similar to 160 degrees C, at which the bcc-packed SE/CdS spheres start to transform into micelles with a short-range liquid-like order. Quantitative model analysis shows that the PEO/CdS micelles can retain their size in the SE/CdS composites up to 200 degrees C, whereas the PEO micelles shrink after the softening of the PS matrix around 100 degrees C and disassociate largely into the PS matrix of the neat SE at 160 degrees C. (c) 2005 Elsevier Ltd. All rights reserved.
Process for protecting solder joints and structure for alleviating electromigration and joule heating in solder joints
(2006-02-09)
Chen, Chih
;
Yeh, Everett Chang-Ching
;
Tu, King-Ning
This invention provides a process for protecting solder joints, comprising forming an UBM or pad metallurgy in solder joints and then further forming a small solder bump on UBM or pad metallurgy between substrate and chip. Wherein a material of high electric resistance is coated at the ends of UBM or pad metallurgy where substrate is connected to chip, as to equalize the current distribution of solder bump, therefore the electromigration resistance of solder joints is improved by suppressing the current crowding and joule heating phenomenon.
Process for manufacturing self-assembled nanoparticles
(2006-02-09)
Chen, Wei-Kuo
;
Lee, Ming-Chih
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Chou, Wu-Ching
;
Chen, Wen-Hsiung
;
Ke, Wen-Cheng
Process for fabricating self-assembled nanoparticles on buffer layers without mask making and allowing for any degree of lattice mismatch; that is, binary, ternary or quaternary nanoparticles comprising Groups III-V, II-VI or IV-VI. The process includes a first step of applying a buffer layer, a second step of turning on the purge gas to modulate the first reactant to the lower first flow rate, then the second reactant is supplied to the buffer layer to form a metal-rich island on the buffer layer, and a third step of turning on purge gas again to modulate the first reactant to the higher second flow rate onto the buffer layer. On the metal-rich island is formed the nanoparticles of the binary, ternary or quaternary III-V, II-VI and IV-IV semiconductor material. This is then recrystallized under the first reactant flow at high temperature forming high quality nanoparticles.
Correlation between a negative group velocity and a slanted stop band in two-dimensionally periodic structures
(2006-02-10)
Hwang, RB
;
電信工程研究所
;
Institute of Communications Engineering
[1] In this paper, we employed the rigorous mode-matching method to carry out the calculation for the scattering characteristics of a two-dimensionally periodic structure made up of metallic rectangular cylinders. From the scattering characteristics, the interesting phenomenon of an anomalous dispersion was observed to possess negative group velocities. In order to understand the underlying physics involved, we begin with the investigation of the band structure associated with the corresponding structure of infinite extent; thereby, the band structures are classified into two types: vertical stop band that is mainly due to the effect of periodicity in a single direction and slanted stop band that is due to the combined effects of periodicities in two directions. Notably, the negative group velocity ( delay) within the slanted stop band of a two-dimensional periodic structure was directly related to the experimentally measurable scattering characteristics of the finite structure.
Exploration of glycosyl hydrolase family 75, a chitosanase from Aspergillus fumigatus
(2006-02-10)
Cheng, CY
;
Chang, CH
;
Wu, YJ
;
Li, YK
;
交大名義發表
A powerful endo-chitosanase ( CSN) previously described for a large scale preparation of chito-oligosaccharides ( Cheng, C.-Y., and Li, Y.-K. ( 2000) Biotechnol. Appl. Biochem. 32, 197 - 203) was cloned from Aspergillus fumigatus and further identified as a member of glycosyl hydrolase family 75. We report here a study of gene expression, functional characterization, and mutation analysis of this enzyme. Gene cloning was accomplished by reverse transcription-PCR and inverse PCR. Within the 1382-bp Aspergillus gene ( Gen-Bank (TM) accession number AY190324), two introns ( 67 and 82 bp) and an open reading frame encoding a 238-residue protein containing a 17-residue signal peptide were characterized. The recombinant mature protein was overexpressed as an inclusion body in Escherichia coli, rescued by treatment with 5 M urea, and subsequently purified by cation exchange chromatography. A time course H-1 NMR study on the enzymatic formation of chito-oligosaccharides confirmed that this A. fumigatus CSN is an inverting enzyme. Tandem mass spectrum analysis of the enzymatic hydrolysate revealed that the recombinant CSN can cleave linkages of GlcNAc-GlcN and GlcN-GlcN in its substrate, suggesting that it is a subclass I chitosanase. In addition, an extensive site-directed mutagenesis study on 10 conserved carboxylic amino acids of glycosyl hydrolase family 75 was performed. This showed that among these various mutants, D160N and E169Q lost nearly all activity. Further investigation using circular dichroism measurements of D160N, E169Q, wild-type CSN, and other active mutants showed similar spectra, indicating that the loss of enzymatic activity in D160N and E169Q was not because of changes in protein structure but was caused by loss of the catalytic essential residue. We conclude that Asp(160) and Glu(169) are the essential residues for the action of A. fumigatus endo-chitosanase.
Exploration of glycosyl hydrolase family 75, a chitosanase from Aspergillus fumigatus
(2006-02-10)
Cheng, CY
;
Chang, CH
;
Wu, YJ
;
Li, YK
;
應用化學系
A powerful endo-chitosanase ( CSN) previously described for a large scale preparation of chito-oligosaccharides ( Cheng, C.-Y., and Li, Y.-K. ( 2000) Biotechnol. Appl. Biochem. 32, 197 - 203) was cloned from Aspergillus fumigatus and further identified as a member of glycosyl hydrolase family 75. We report here a study of gene expression, functional characterization, and mutation analysis of this enzyme. Gene cloning was accomplished by reverse transcription-PCR and inverse PCR. Within the 1382-bp Aspergillus gene ( Gen-Bank (TM) accession number AY190324), two introns ( 67 and 82 bp) and an open reading frame encoding a 238-residue protein containing a 17-residue signal peptide were characterized. The recombinant mature protein was overexpressed as an inclusion body in Escherichia coli, rescued by treatment with 5 M urea, and subsequently purified by cation exchange chromatography. A time course H-1 NMR study on the enzymatic formation of chito-oligosaccharides confirmed that this A. fumigatus CSN is an inverting enzyme. Tandem mass spectrum analysis of the enzymatic hydrolysate revealed that the recombinant CSN can cleave linkages of GlcNAc-GlcN and GlcN-GlcN in its substrate, suggesting that it is a subclass I chitosanase. In addition, an extensive site-directed mutagenesis study on 10 conserved carboxylic amino acids of glycosyl hydrolase family 75 was performed. This showed that among these various mutants, D160N and E169Q lost nearly all activity. Further investigation using circular dichroism measurements of D160N, E169Q, wild-type CSN, and other active mutants showed similar spectra, indicating that the loss of enzymatic activity in D160N and E169Q was not because of changes in protein structure but was caused by loss of the catalytic essential residue. We conclude that Asp(160) and Glu(169) are the essential residues for the action of A. fumigatus endo-chitosanase.
多聲道之交越失真消除系統
(2006-02-11)
白明憲
;
董志偉
;
李志中
本發明係有關於一種多聲道交越失真消除系統，可提供範圍較廣大之愉悅點，此多聲道交越失真消除系統包括：中央處理器或數位訊號處理器，可輸入音訊輸入訊號並輸出立體聲訊號；濾波器，可輸入立體聲訊號並進行濾波處理，以輸出聲音訊號；陣列揚聲器，可輸入並傳送聲音訊號以在陣列揚聲器之前方形成愉悅點，其中濾波處理係依據多聲道交越失真消除系統及與立體聲訊號之頻率相關之正規化參數，音源訊號處理器可為中央處理器或數位訊號處理器。
晶片挾持器之改良結構
(2006-02-11)
劉安誠
;
陳仁浩
;
陳悅婷
本發明係一種晶片挾持器之改良結構，其係由下而上依序在旋轉主軸上套設錐軸襯套、錐孔襯套及晶片挾持平台，旋轉主軸藉由錐軸襯套與錐孔襯套傳遞扭矩給晶片挾持平台，由於錐軸襯套與錐孔襯套之間的配合方式，係藉由二者間相對應之錐面密合，利用斜面縮短間隙距離和圓形半徑方向對稱觀念來校正中心和密閉效果，可大幅降低一般晶片塗佈製程在高轉速的平面跳動，對於製程設計彈性有很大的助益，品質良率亦可信賴，並且提高可分離式晶片挾持器內部改良結構的壽命。
Nanoimprinting-lithography-induced self-aligned liquid crystals for novel multifunctional optical films
(2006-02-13)
Chiu, CH
;
Kuo, HL
;
Chen, PC
;
Wen, CH
;
Liu, YC
Polymerizable nematic liquid crystal (LC) was adopted as a resist for our newly developed nanoimprinting lithography process. Liquid crystal molecules were self-aligned during imprinting process without precoated alignment layer. The large patterned area was able to achieve 4x4 cm(2) at very low impriting pressure, 1.5 bar. The optical anisotropic was verified through polarized optical microscopy and the retardation was measured by polarized ultraviolet/visible spectrometer. The micrograted LC films prepared by this novel method offer the potential applications for a LC alignment layer within LC cells, as well as preparation of optical anisotropic films. (c) 2006 American Institute of Physics.
Orbital susceptibilities of PbSe quantum dots
(2006-02-14)
Jian, WB
;
Lu, WG
;
Fang, JY
;
Chiang, SJ
;
Lan, MD
Different sizes of three-dimensional PbSe quantum dots have been synthesized for the study of orbital magnetic susceptibilities. Two types of orbital susceptibilities have been found, including the Curie susceptibility and finite-size corrections to the Landau susceptibility. The Curie term of a quantum dot manifests itself in the temperature dependence of magnetic susceptibility at low temperatures, while the field dependence of differential susceptibility at high temperatures shows finite-size corrections to the Landau susceptibility. Both of the two kinds of orbital susceptibility, estimated per quantum dot, show linear dependence on the size. (c) 2006 American Institute of Physics.
Nanomechanical characterizations of InGaN thin films
(2006-02-15)
Jian, SR
;
Fang, TH
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
InxGa1-x thin films with In concentration ranging from 25 to 34 at.% were deposited on sapphire substrate by metal-organic chemical vapor deposition (MOCVD). Crystalline structure and surface morphology of the deposited films were studied by using X-ray diffraction (XRD) and atomic force microscopy (AFM). Hardness, Young's modulus and creep resistance were measured using a nanoindenter. Among the deposited films, In0.25Ga0.75N film exhibits a larger grain size and a higher surface roughness. Results indicate that hardness decreases slightly with increasing In concentration in the InxGa1-xN films ranged from 16.6 +/- 1.1 to 16.1 +/- 0.7 GPa and, Young's modulus for the In0.25Ga0.75N, In0.3Ga0.7N and In0.34Ga0.66N films are 375.8 +/- 23.1, 322.4 +/- 13.5 and 373.9 +/- 28.6 GPa, respectively. In addition, the time-dependent nanoindentation creep experiments are presented in this article. (c) 2005 Elsevier B.V. All rights reserved.
Impact of band gap shrinkage on simulated bifurcation routes in directly modulated semiconductor lasers
(2006-02-15)
Lim, CG
;
Iezekiel, S
;
Snowden, CM
;
光電工程學系
;
Department of Photonics
A carrier heating model is derived by taking into account the various temperature processes in the active layer of laser diodes. This model is then used to simulate the static and dynamic characteristics of a directly modulated 1.55 mu m distributed-feedback laser diode. The calculated results are compared with the measured results of this device as obtained in an earlier work [H. F. Liu and W. F. Ngal, IEEE J. Quantum Electron. 29, 1668 (1993)], and this reveals the significant impact of band gap shrinkage on simulated results. This study also shows that the carrier heating model is a self-consistent model that naturally describes the gain suppression phenomena in directly modulated laser diodes. (c) 2006 American Institute of Physics.
Short time deposition kinetics of diethyl phthalate and dibutyl phthalate on a silicon wafer surface
(2006-02-15)
Kang, YH
;
Den, W
;
Bai, HL
;
環境工程研究所
;
Institute of Environmental Engineering
Short time adsorption and desorption behaviors of two alkyl phthalate esters, namely diethyl phthalate (DEP) and dibutyl phthalate (DBP), on silicon wafers exposed under various ambient concentrations were experimentally and theoretically investigated. The results showed that the surface density of DBP was significantly affected by both the length of exposure time and its ambient concentration, whereas that of DEP was only affected by its ambient concentration within the tested periods between 60 and 240 min. The determination of rate parameters for adsorption and desorption showed that the rate constants of DEP were always larger than those of DBP. Also, the sticking coefficient of DEP was larger during the initial adsorption stage due to its relatively lower molecular weight as compared to DBP. The value of the sticking coefficient for DEP, however, decreased much faster such that the value eventually became smaller than that for DBP. Therefore, for silicon wafers experiencing a short exposure time, organic compounds with lower molecular weights may be a more important source of airborne molecular contamination than those with higher molecular weights.
Continuous time Markov chains observed on an alternating renewal process with exponentially distributed durations
(2006-02-15)
Chan, WY
;
Peng, NF
;
統計學研究所
;
Institute of Statistics
A continuous time Markov chain observed on a system following the dynamic behavior of an alternating renewal process is studied. This alternating renewal process is assumed to have exponentially distributed durations. The limiting behavior of the process is examined. Examples of applications are given. (c) 2005 Published by Elsevier B.V.