Browsing by Issue Date, starting with "2007-04-02"

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Metal toxicity to Chlorella pyrenoidosa assessed by a short-term continuous test
(2007-04-02)
Lin, Kuo-Ching
;
Lee, Yu-Long
;
Chen, Chung-Yuan
;
環境工程研究所
;
Institute of Environmental Engineering
This study presents the metal toxicity as revealed by Chlorella pyrenoidosa using a short-term continuous test and the conventional batch test. Toxicity tests were conducted in a chemostat with a test duration of I day. Toxicity data of five different metals (Cd, Ph, Co, Ni, and Zn) derived from the continuous test were compared against results from the conventional batch tests. The batch test is characterized by its saturated nutrient status for algal growth and, on the other hand, the continuous test is conducted at a nutrient-limiting condition simulating more closely to the aquatic field environment. The continuous test consistently yielded smaller EC50 values, which indicated that alga in the chemostat is approximately four to six times more sensitive than those from the batch culture. Similar phenomena between the two types of tests were observed based on the NOEC values. Compared to literature data (US EPA ECOTOX Database) from the same species of alga, differences in test sensitivity between the batch tests and chemostat technique varied from 9.25 to 160 times. Such distinct differences indicate that current toxicity database may not adequately reflect the impact of various metal toxicants on C. pyrenoidosa. The continuous test method presented herein is a sensitive and rapid assessment technique and, therefore, has a potential for more general applications such as routine checkup for regulatory purposes. (c) 2006 Published by Elsevier B.V.
Utilizations of two-stage erbium amplifier and saturable-absorber filter for tunable and stable power-equalized fiber laser
(2007-04-02)
Yeh, Chien-Hung
;
光電工程學系
;
Department of Photonics
We propose and investigate experimentally a tunable and stable fiber laser with single-longitudinal-mode (SLM) and power-equalized output based on a two-stage erbium amplifier and a saturable-absorber filter. Two-stage amplifier consists of an erbium-doped waveguide amplifier (EDWA) and erbium-doped fiber amplifier (EDFA) to generate a flatter amplified spontaneous emission (ASE) source for constant output. Saturable-absorber filter constructs by an unpumped EDF and a fiber reflected mirror (FRM) to provide a fine mode restriction and guarantee a SLM operation. (c) 2007 Optical Society of America.
Anomalous microphotoluminescence of high-aspect-ratio Si nanopillars formatted by dry-etching Si substrate with self-aggregated Ni nanodot mask
(2007-04-02)
Lin, Gong-Ru
;
Lin, Chun-Jung
;
Kuo, Hao-Chung
;
Lin, Huang-Sheng
;
Kao, Chi-Chiang
Microphotoluminescence (mu-PL) of high-aspect-ratio Si nanopillars fabricated by etching Ni-nanodot/SiO2 masked Si substrate is investigated. The 320-nm-tall Si nanopillars obtained by CF4/Ar mixed inductively coupled-plasma reactive ion etching process with density of 2.8x10(10) cm(-2) further shrink size from 30 to 6 nm by oxidation and etching. Blue-green mu-PL with two decomposed wavelengths at 425 and 475 nm is attributed to oxygen-related defects on the oxidized Si nanopillar surface. Defect-related near-infrared PL at 703 and 740 nm remains unchanged, while a quantum-confinement-effect-dependent PL blueshifted from 874 to 826 nm as the Si nanopillar size reduces from 7.2 to 6.0 nm is preliminarily observed. (c) 2007 American Institute of Physics.
Oxygen reduction on LaMnO3-based cathode materials in solid oxide fuel cells
(2007-04-03)
Choi, YongMan
;
Mebane, David S.
;
Lin, M. C.
;
Liu, Meilin
;
應用化學系分子科學碩博班
Cubic perovskite LaMnO3 surface models were constructed to elucidate the mechanism of oxygen reduction using quantum chemical calculations with molecular dynamics (MD) simulations. Calculations predict that both dissociative and molecular adsorption may occur, depending on adsorbate configurations. Superoxo- or peroxo-like species may locate at La, Mn, and O-sub active sites with different vibrational frequencies and atomic charges. A stepwise elementary reaction sequence via the superoxo- or peroxo-like intermediates at both perfect and defective LaMnO3 was constructed by mapping out minimum-energy paths (MEPs) using the nudged elastic band (NEB) method. Charge transfer for the O-2-LaMnO3 interactions was also explored by Bader charge analysis. In particular, ab initio MD simulations carried out to simulate solid oxide fuel cell conditions at 1073 K suggest that oxygen vacancies enhance O-2 dissociation kinetics.
Cytopiloyne, a novel polyacetylenic glucoside from Bidens pilosa, functions as a T helper cell modulator
(2007-04-04)
Chiang, Yi-Ming
;
Chang, Cicero Lee-Tian
;
Chang, Shu-Lin
;
Yang, Wen-Chin
;
Shyur, Lie-Fen
An extract of Bidens pilosa, an anti-diabetic Asteraceae plant, has recently been reported to modulate T cell differentiation and prevent the development of non-obese diabetes (NOD) in NOD mice. In this paper, a novel bioactive polyacetylenic glucoside, cytopiloyne (1), was identified from the Bidens pilosa extract using ex vivo T cell differentiation assays based on a bioactivity-guided fractionation and isolation procedure. Its structure was elucidated as 2 beta-D-glucopyranosyloxy-1-hydroxytrideca-5,7,9,11-tetrayne by various spectroscopic methods. Functional studies showed that cytopiloyne was able to inhibit the differentiation of naive T helper (Th0) cells into type I T helper (Th1) cells but to promote the differentiation of Th0 cells into type II T helper (Th2) cell. Accordingly, cytopiloyne also suppressed IFN-gamma expression and promoted IL-4 expression in mouse splenocytes ex vivo. These results suggest that cytopiloyne functions as a T cell modulator that may directly contribute to the ethnopharmacological effect of Bidens pilosa extract on preventing diabetes. Moreover, cytopiloyne can serve as an index compound for quality control of lot-to-lot extract preparations of Bidens pilosa. (c) 2006 Elsevier Ireland Ltd. All rights reserved.
Surface modification and physical properties of various UHMWPE-fiber-reinforced modified epoxy composites
(2007-04-05)
Lin, S. P.
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Han, J. L.
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Yeh, J. T.
;
Chang, F. C.
;
Hsieh, K. H.
Two surface modification methods-plasma surface treatment and chemical agent treatment-were used to investigate their effects on the surface properties of ultrahigh-molecular-weight polyethylene (UHMWPE) fibers. In the analyses, performed using electron spectroscopy for chemical analysis, changes in weight, and scanning electron microscope observations, demonstrated that the two fiber-surface-modified composites formed between UHMWPE fiber and epoxy matrix exhibited improved interfacial adhesion and slight improvements in tensile strengths, but notable decreases in elongation, relative to those properties of the composites reinforced with the untreated UHMWPE fibers. In addition, three kinds of epoxy resins-neat DGEBA, poly-urethane-crosslinked DGEBA, and BHHBP-DGEBA-were used as resin matrices to examine the tensile and elongation properties of their UHMWPE fiber-reinforced composites. From stress/strain measurements and scanning electron microscope observations, the resin matrix improved the tensile strength apparently, but did not affect the elongation. (c) 2007 Wiley Periodicals, Inc.
Infrared absorption of C6H5SO2 detected with time-resolved Fourier-transform spectroscopy
(2007-04-07)
Chu, Li-Kang
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
C6H5SO2 radicals were produced upon irradiation of three flowing mixtures: C6H5SO2Cl in N-2, C6H5Cl and SO2 in CO2, and C6H5Br and SO2 in CO2, with a KrF excimer laser at 248 nm. A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to record the time-resolved infrared (IR) absorption spectra of reaction intermediates. Two transient bands with origins at 1087.7 and 1278.2 cm(-1) are assigned to the SO2-symmetric and SO2-antisymmetric stretching modes, respectively, of C6H5SO2. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predict the geometry and vibrational wave numbers of C6H5SO2 and C6H5OSO. The vibrational wave numbers and IR intensities of C6H5SO2 agree satisfactorily with the observed new features. Rotational contours of IR spectra of C6H5SO2 simulated based on predicted molecular parameters agree satisfactorily with experimental results for both bands. The SO2-symmetric stretching band is dominated by a- and c-type rotational structures and the SO2-antisymmetric stretching band is dominated by a b-type rotational structure. When C6H5SO2Cl was used as a precursor of C6H5SO2, C6H5SO2Cl was slowly reproduced at the expense of C6H5SO2, indicating that the reaction Cl+C6H5SO2 takes place. When C6H5Br/SO2/CO2 was used as a precursor of C6H5SO2, features at 1186 and 1396 cm(-1) ascribable to C6H5SO2Br were observed at a later period due to secondary reaction of C6H5SO2 with Br. Corresponding kinetics based on temporal profiles of observed IR absorption are discussed. (c) 2007 American Institute of Physics.
Effect of intermolecular hydrogen bonding on low-surface-energy material of poly(vinylphenol)
(2007-04-07)
Lin, Han-Ching
;
Wang, Chih-Feng
;
Kuo, Shiao-Wei
;
Tung, Pao-Hsiang
;
Huang, Chih-Feng
We discovered that poly(vinylphenol) (PVPh) possesses an extremely low surface energy (15.7 mJ/m(2)) after a simple thermal treatment procedure, even lower than that of poly(tetrafluoroethylene) ( 2.0 mJ/m(2)) calculated on the basis of the two-liquid geometric method. Infrared analyses indicate that the intermolecular hydrogen bonding of PVPh decreases by converting the hydroxyl group into a free hydroxyl and increasing intramolecular hydrogen bonding after thermal treatment. PVPh results in a lower surface energy because of the decrease of intermolecular hydrogen bonding between hydroxyl groups. In addition, we also compared surface energies of PVPh-co-PS (polystyrene) copolymers (random and block) and their corresponding blends. Again, these random copolymers possess a lower fraction of intermolecular hydrogen bonding and surface energy than the corresponding block copolymers or blends after similar thermal treatment. This finding provides a unique and easy method to prepare a low-surface-energy material through a simple thermal treatment procedure without using fluoro polymers or silicones.
秋冬之天
(2007-04-07)
管管
Resistance switching properties of sol-gel derived SrZrO3 based memory thin films
(2007-04-07)
Liu, Chih-Yi
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Sol-gel derived SrZrO3 based metal/insulator/metal (MIM) devices were fabricated to study their reversible resistance switching properties operated by dc voltage sweep and voltage pulses. The leakage-state of the device is changed from the original-state and finally switched between the high leakage-state (H-state) and the low leakage-state (L-state). The resistance ratio between the H-state and the L-state is about 10(4), and the leakage-states are not changed without power supply, which is suitable for nonvolatile memory application. The conduction mechanisms of the original-state, the H-state and the L-state obey Schottky emission, Frenkel-Poole emission and Ohmic conduction, respectively. The first device resistance switching, called the forming process, changed from the original-state to the H-state. The switching time from the H-state to the L-state is much longer than that from the L-state to the H-state and that of the forming process. The decay behaviours of leakage current after resistance switching are influenced by pulse width and voltage stress directions. The switching time can be accumulated to switch the device from the H-state to the L-state, which could be a guide to multi-level memory applications. The model of conducting paths can well explain the electrical behaviours of our resistance switching devices.
Optical characterization of CO2-laser-ablated Si-rich SiOx
(2007-04-09)
Lin, Gong-Ru
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Lin, Chun-Jung
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Chang, Yia-Chung
;
光電工程學系
;
Department of Photonics
Anomalous absorption and the corresponding change in the optical band gap of a CO2-laser-ablated Si-rich SiO2 (SiOx) film are studied. The optical band gap energy of as-grown nonstoichiometric SiOx is slightly reduced by increasing Si-Si bonds as compared to quartz. After rapid thermal annealing using a CO2 laser, the dehydrogenation of SiOx film further increases the Si-Si bonding states and redshifts the optical band gap by 1 eV. Laser ablation is initiated at a laser intensity of > 7.5 kW/cm(2), leaving numerous luminescent centers that are related to neutral oxygen vacancy defects, increasing the absorption coefficient and related optical band gap energy, and reducing the refractive index in partially annealed SiOx. (c) 2007 American Institute of Physics.
Thermomigration in flip-chip SnPb solder joints under alternating current stressing
(2007-04-09)
Hsiao, Hsiang-Yao
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Chen, Chih
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材料科學與工程學系
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Department of Materials Science and Engineering
Thermomigration in flip-chip solder joints is investigated using alternating currents and infrared microscopy to decouple it from electromigration effect. It is found that the thermal gradient in solder bump can be as high as 2143 degrees C/cm when 9.2x10(4) A/cm(2) was applied at 100 degrees C. Markers fabricated by focus ion beam are employed to measure the thermomigration rate. The thermomigration flux is measured to be 3.3x10(13) at./cm(2). With the known thermal gradient, the molar heat of 26.8 kJ/mole has been obtained for the transport of Pb. (c) 2007 American Institute of Physics.
Electrically driven integrated photonic crystal nanocavity coupled surface emitting laser
(2007-04-09)
Huang, Shih-Chieh
;
Yang, Tsung-Hua
;
Lee, Chien-Ping
;
Lin, Sheng-Di
;
電子工程學系及電子研究所
Single mode surface emitting lasers with photonic crystal nanocavities integrated with electrically driven strained quantum well laser diodes are demonstrated. The photonic crystal serves as an end mirror for the laser cavity, while the nanocavities serve as wavelength selective high Q surface emitters. The laser emission from the nanocavities had excellent temperature stability. The wavelength shift versus temperature was about five times better than that of regular quantum well lasers. Dual wavelength emission from two side by side slightly different cavities was also demonstrated. Laser emission with two wavelengths of Delta lambda=0.8 nm was obtained. (c) 2007 American Institute of Physics.
Influence of thin metal base thickness on the performance of CuPc vertical organic triodes
(2007-04-09)
Cheng, Shiau-Shin
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Yang, Chuan-Yi
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Chuang, You-Che
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Ou, Chun-Wei
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Wu, Meng-Chyi
In this letter, the characteristics of vertical organic triodes fabricated by using two copper phthalocyanine (CuPc) back-to-back Schottky diodes with different metal base thicknesses are reported. The vertical organic triodes exhibit pronounced saturation regions in the output current-voltage characteristics. The common-emitter current gain reduces with increasing the Al base thickness due to the increase of recombination current at the base end resulted from the reduction of opening voids in the Al metal film. The common-emitter current gain of the device with 4.5 nm thick Al base reaches 1.9 at V-CE=-6 V and J(B)=2.5 mA/cm(2). (c) 2007 American Institute of Physics.
Microstructure and recording mechanism of Ge/Au bilayer media for write-once optical disc
(2007-04-09)
Wu, T. H.
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Kuo, P. C.
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Fang, Yen-Hsiang
;
Chen, Jung-Po
;
Yen, Po-Fu
The recording mechanism of Ge/Au bilayer and its dynamic tests for write-once blue laser high density DVD (HD DVD) are investigated. It is found that Ge2Au3 phase is nucleated between amorphous Ge and crystalline Au layer after room temperature deposition. Crystallization of Ge/Au interface layer at 170-190 degrees C is induced by the nucleated Ge2Au3 sites at the interface, the bilayer structure is further heated to 200-450 degrees C. After heating above 320 degrees C, crystallized Ge are segregated at the grain boundary. The dynamic test results show that this Ge/Au bilayer films can be applied to 1x-2x HD DVD-R. (c) 2007 American Institute of Physics.
High quality factor microcavity lasers realized by circular photonic crystal with isotropic photonic band gap effect
(2007-04-09)
Lee, Po-Tsung
;
Lu, Tsan-Wen
;
Fan, Jyun-Hao
;
Tsai, Feng-Mao
;
光電工程學系
The photonic band gap (PBG) effect and its isotropy of sunflower-type circular photonic crystal (CPC) are obtained and investigated from the transmission spectra performed by finite-difference time-domain (FDTD) method. The PBG directional width variation is found to be only 6.7%. A well-confined whispering gallery mode (WGM) with azimuthal number of 6 is obtained by FDTD simulation from the CPC microcavity formed by seven missing air holes (C2). Ascribed to the deep and isotropic PBG confinement, the WGM lasing with very-low threshold (similar to 0.13 mW) and very-high-quality (Q) factor (> 10 000) is obtained from well-fabricated CPC C2 microcavity lasers. (c) 2007 American Institute of Physics.
Architecture and method for fine granularity scalable video coding
(2007-04-10)
Huang
;
Hsiang-Chun
;
Wang
;
Chung-Neng
;
Chiang
A robust fine granularity scalability video encoding includes a base layer encoder and an enhancement layer encoder in which motion compensated difference images are generated by comparing an original image to predicted images at base layer and enhancement layer with motion compensation. Based on leaky and partial predictions, a high quality reference image is constructed at the enhancement layer to improve temporal prediction. In the construction of the high quality reference image, one parameter β controls the number of bitplanes of the enhancement layer difference coefficients used and another parameter α controls the amount of predictive leak. A spatial scalability module allows the processed pictures at the base layer and the enhancement layer to have identical or different spatial resolutions.
雙攝影機取像與追蹤方法
(2007-04-11)
韓欽銓
;
謝明逢
;
鄭智明
本發明提供一種雙攝影機取像與追蹤方法，其係整合雙攝影機作取像與目標影像追蹤，包括兩部分，第一部份為影像對應參數校正程序，第二部分則為輔助追蹤模式程序，由於攝影機擺設位置互相靠近，可以簡化攝影機校正之複雜度，利用已校正之參數，對公共開放空間之目標物取得清晰影像；另外，利用雙攝影機彼此的關係，加上擷取清晰影像，輔助交錯目標物之判別，改進公共空間目標物之追蹤成效。因此本發明提供一種雙攝影機取像與追蹤方法，可對多目標物追蹤，同時獲得清晰之目標物影像，並利用各攝影機的資訊，有效改進追蹤效果。
A closed-form solution for a confined flow into a tunnel during progressive drilling in a multi-layer groundwater flow system
(2007-04-12)
Yang, Shaw-Yang
;
Yeh, Hund-Der
;
環境工程研究所
;
Institute of Environmental Engineering
A mathematical model is developed to describe the groundwater inflow into a tunnel in a multi-layer aquifer system. Based on the model, the closed-form solution is derived to estimate the groundwater flow rate entering the multi-layer tunnel during progressive drilling. The solution has an integrand not only consisting of the product and square of the Bessel functions but also having a singularity at the origin. A unified numerical approach is proposed to evaluate the solution with accuracy to five decimal places. This approach includes a singularity removal scheme, the Gaussian quadrature, and the Shanks method. For a multi-layer formation, the results obtained from the solution based on the equivalent hydraulic conductivity and the newly derived solution differ significantly. This solution is capable of estimating the maximum flow rate inside the horizontal tunnel, and thus can be used as a tool for designing the drainage tunnel system in a multi-layer formation.
Kondo interactions and magnetic correlations in CePt2 nanocrystals
(2007-04-13)
Chen, Y. Y.
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Huang, P. H.
;
Ou, M. N.
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Wang, C. R.
;
Yao, Y. D.
The evolution of the Kondo effect and antiferromagnetic (AF) correlations with size reduction in CePt2 nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The AF correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature (T-K) magnetic regions coexisting with strongly mixed-valent, large T-K nonmagnetic regions. We discuss the role of structural disorder, background density of states and the electronic quantum size effect on the results.