Browsing by Issue Date, starting with "2009-01-07"

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Electrical conduction mechanisms in natively doped ZnO nanowires
(2009-01-07)
Chiu, Shao-Pin
;
Lin, Yong-Han
;
Lin, Juhn John
;
電子物理學系
;
物理研究所
Single-crystalline zinc oxide (ZnO) nanowires (NWs) with diameters of 90-200 nm were synthesized by the thermal evaporation method. Four-probe Ti/Au electrodes were made by the standard electron-beam lithography technique, and the intrinsic resistivities, rho(T), of individual NWs were measured over a wide range of temperature from 300 down to 0.25 K. The temperature behavior of rho(T) between 300 and 5 K reveals that the intrinsic electrical-transport mechanisms through individual ZnO NWs are due to a combination of the thermal activation conduction and the nearest-neighbor hopping conduction processes. Three distinct activation and hopping contributions with discrete characteristic activation energies are observed. Above about 100 K, the charge transport mechanism is dominated by the thermal activation of electrons from the Fermi level, mu, to the conduction band. Between approximately 20 and 100 K, the charge transport mechanism is due to the activation of electrons from mu to the upper impurity (D(-)) band. Between approximately 5 and 20 K, the charge transport mechanism arises from the nearest-neighbor hopping conduction within the lower impurity (D) band. Such unique electrical conduction behaviors can be explained in terms of the intricate material properties (in particular, the presence of moderately high concentrations of n-type defects accompanied with a slight self-compensation) in natively doped ZnO NWs. In one heavily doped NW, a surface-related conduction process manifesting the two-dimensional attributes of quantum-interference transport phenomena is observed. The carrier concentrations in our NWs have been estimated, and they were found to lie close to the critical concentration for the Mott metal-insulator transition.
Barrierless reactions between two closed-shell molecules. II. Dynamics of F(2)+CH(3)SSCH(3) reaction
(2009-01-07)
Shao, Hua-Chieh
;
Xie, Tingxian
;
Lu, Yu-Ju
;
Chang, Chih-Hsuan
;
Pan, Jun-Wei
A second example of a barrierless reaction between two closed-shell molecules is reported. The reaction F(2)+CH(3)SSCH(3) has been investigated with crossed molecular beam experiments and ab initio calculations. Compared with previous results of the F(2)+CH(3)SCH(3) reaction [J. Chem. Phys. 127, 101101 (2007); J. Chem. Phys. 128, 104317 (2008)], a new product channel leading to CH(3)SF+CH(3)SF is observed to be predominant in the title reaction, whereas the anticipated HF+C(2)H(5)S(2)F channel is not found. In addition, the F+C(2)H(6)S(2)F product channel, the analog to the F+C(2)H(6)SF channel in the F(2)+CH(3)SCH(3) reaction, opens up at collision energies higher than 4.3 kcal/mol. Angular and translational energy distributions of the products are reported and collision energy dependences of the reaction cross section and product branching ratio are shown. The reaction barrier is found to be negligible (< 1 kcal/mol). Multireference ab initio calculations suggest a reaction mechanism involving a short-lived intermediate which can be formed without activation energy.
Spontaneous emission near the band edge of a three-dimensional photonic crystal: a fractional calculus approach
(2009-01-07)
Cheng, Szu-Cheng
;
Wu, Jing-Nuo
;
Tsai, Ming-Rung
;
Hsieh, Wen-Feng
;
光電工程學系
We suggest a better mathematical method, fractional calculus, for studying the behavior of the atom-field interaction in photonic crystals. By studying the spontaneous emission of an atom in a photonic crystal with a one-band isotropic model, we found that the long-time inducing memory of the spontaneous emission is a fractional phenomenon. This behavior could be well described by fractional calculus. The results show no steady photon-atom bound state for the atomic resonant transition frequency lying in the proximity of the allowed band edge which was encountered in a previous study (Woldeyohannes and John 2003 J. Opt. B: Quantum Semiclass. Opt.5 R43). The correctness of this result is validated by the 'cut-off smoothing' density of photon states (DOS) with fractional calculus. By obtaining a rigorous solution without the multiple-valued problem for the system, we show that the method of fractional calculus has a logically concise property.
Barrierless reactions between two closed-shell molecules. II. Dynamics of F-2+CH3SSCH3 reaction
(2009-01-07)
Shao, Hua-Chieh
;
Xie, Tingxian
;
Lu, Yu-Ju
;
Chang, Chih-Hsuan
;
Pan, Jun-Wei
A second example of a barrierless reaction between two closed-shell molecules is reported. The reaction F-2+CH3SSCH3 has been investigated with crossed molecular beam experiments and ab initio calculations. Compared with previous results of the F-2+CH3SCH3 reaction [J. Chem. Phys. 127, 101101 (2007); J. Chem. Phys. 128, 104317 (2008)], a new product channel leading to CH3SF+CH3SF is observed to be predominant in the title reaction, whereas the anticipated HF+C2H5S2F channel is not found. In addition, the F+C2H6S2F product channel, the analog to the F+C2H6SF channel in the F-2+CH3SCH3 reaction, opens up at collision energies higher than 4.3 kcal/mol. Angular and translational energy distributions of the products are reported and collision energy dependences of the reaction cross section and product branching ratio are shown. The reaction barrier is found to be negligible (< 1 kcal/mol). Multireference ab initio calculations suggest a reaction mechanism involving a short-lived intermediate which can be formed without activation energy.
Composite Modified Electrode Strip
(2009-01-08)
Chen, Sz-Hau
;
Lin, Chih-Sheng
;
Chen, Guan-Tin
;
Lin, Yueh-Hui
;
Shen, Thomas Y.S.
The present invention provides a surface-modified electrode strip for measuring an electrochemical signal that is synergistically amplified by means of a nano-scaled gold particle layer and a lipid-soluble electron mediator layer. A biosensor comprising the electrode strip is also provided.
羊的觀點《綿羊偵探團》
(2009-01-11)
余建良
;
Department of Communication and Technology
;
傳播與科技學系
歹勢改題目...
基於行動裝置之視訊串流可適性媒體播放控制之方法及其系統
(2009-01-11)
莊孝強
;
黃經堯
;
蔣迪豪
一種基於行動裝置之視訊串流可適性媒體播放控制之方法及其系統,主要包括起始値調整以及幀率調整兩部分,其係根據緩衝器起始値資料量以及一併調整幀率之變化量,以決定播放速度。這種可適性媒體播放控制之方法及系統解決了緩衝器溢位(overflow)或缺空(underflow)所造成在視覺品質上損失之問題。並可以在不影響行動通訊系統容量的前提之下,提供視訊串流的使用者,一個平順的播放過程。
寒冬中的共同手勢
(2009-01-11)
陳碩峰
;
Department of Communication and Technology
;
傳播與科技學系
周末的新竹，永有著共同的溫度，11度！在共同的城市裡，共同的溫度，共同的手勢！
第四十一期總編輯的話
(2009-01-11)
《喀報》
;
Department of Communication and Technology
;
傳播與科技學系
寒假休息公告
交大科幻中心推動新科幻熱
(2009-01-11)
楊雅筑
;
Department of Communication and Technology
;
傳播與科技學系
以交大科幻中心為首,帶頭提倡新科幻文化現象
冷到了賞雪知識不可少
(2009-01-11)
邵奕儒
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Department of Communication and Technology
;
傳播與科技學系
合歡山賞雪
女女戀情《花吃了那女孩》
(2009-01-11)
黃惠琳
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Department of Communication and Technology
;
傳播與科技學系
無
產業寒冬重新定位再出發
(2009-01-11)
羅兆恆
;
Department of Communication and Technology
;
傳播與科技學系
......
IQ和EQ沒談的《習慣領域》
(2009-01-11)
楊純芳
;
Department of Communication and Technology
;
傳播與科技學系
「命好不如習慣好！」習慣領域（Habitual Domains, HD）」學說的創始人游伯龍自一九七七年開始，從腦與心、行為與決策之關係，深刻體悟人性，並大膽假設人類有「習慣領域」的存在，從此找到改變人類行為得新生力量。
Ordered mesoporous silica particles and Si-MCM-41 for the adsorption of acetone: A comparative study
(2009-01-12)
Hung, Chinte
;
Bai, Hsunling
;
Karthik, Mani
;
環境工程研究所
;
Institute of Environmental Engineering
This study compares the surface properties and the acetone adsorption potentials of mesoporous silica particles (MSPs) and Si-MCM-41. The Si-MCM-41 and MSPs are synthesized, respectively by hydrothermal method and evaporation-induced self-assembly (EISA) method. The results show that the surface area and pore diameter of MSPs are similar to those of Si-MCM-41. But the synthesis of Si-MCM-41 frequently requires longer time and tedious procedure as compared to that of MSPs. The bulk density of MSPs is 3.0-5.0 times higher than that of Si-MCM-41. The mass-based acetone adsorption capacities of these two materials are almost similar. This implies that MSPs have a higher volume-based acetone adsorption capacity than Si-MCM-41 so that less space is required for volatile organic compounds (VOCs) adsorption using MSPs as the adsorbent. The pressure drops of both powder and pellet forms of MSPs are also smaller than those of Si-MCM-41 for adsorbing the same amount of acetone. In addition, as compared to commercial H-ZSM-5 zeolite, both MSPs and Si-MCM-41 reveal better performances on the regeneration ability. As a result, both MSPs and Si-MCM-41 show high adsorption/desorption potential but the MSPs are better as novel adsorbents in terms of overall engineering consideration. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.
Study of efficient and stable organic light-emitting diodes with 2-methyl-9,10-di(2-naphthyl)anthracene as hole-transport material by admittance spectroscopy
(2009-01-12)
Ho, Meng-Huan
;
Hsieh, Ming-Ta
;
Lin, Kuan-Heng
;
Chen, Teng-Ming
;
Chen, Jenn-Fang
An organic light-emitting device with enhanced efficiency sby employing 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as hole-transport material (HTM) has been developed. The admittance spectroscopy studies indicate that using MADN as HTM can reduce the amount of hole carriers injected into the device leading to a well-balanced carrier recombination. The green fluorescent 10-(2-benzothiazolyl)-1,1,7,7-tetramethyl-2,3,6,7-tetrahydro-1H,5H,11H-benzo[l]pyrano-[6,7,8-ij]quinolizin-11-one doped tris(8-quinolinolato)aluminum device achieved a current efficiency of 21.8 cd/A and a power efficiency of 10.4 lm/W at 20 mA/cm(2) that are 65% higher than those of the control device. The green-doped device also achieved a long half-decay lifetime of 22 000 h at an initial brightness of 500 cd/m(2).
Hyperchaos of four state autonomous system with three positive Lyapunov exponents
(2009-01-12)
Ge, Zheng-Ming
;
Yang, Cheng-Hsiung
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機械工程學系
;
Department of Mechanical Engineering
This Letter gives the results of numerical simulations of Quantum Cellular Neural Network (Quantum-CNN) autonomous system with four state variables. Three positive Lyapunov exponents confirm hyperchaotic nature of its dynamics. (C) 2008 Published by Elsevier B.V.
Identification of Essential Residues of Human alpha-L-Fucosidase and Tests of Its Mechanism
(2009-01-13)
Liu, Sheng-Wen
;
Chen, Chao-Sheng
;
Chang, Shih-Shen
;
Mong, Kwok-Kong Tony
;
Lin, Chun-Hung
Fucosylated glycoconjugates have critical roles in biological processes, but a limited availability Of alpha-L-fucosidase has hampered research on this human enzyme (h-Fuc) at a molecular level. After overexpressing h-Fuc in Escherichia coli as an active form, we investigated the catalytic function of this recombinant enzyme. Based on sequence alignment and structural analysis of close homologues of h-Fuc, nine residues of glutamate and aspartate in h-Fuc were selected for mutagenic tests to determine the essential residues. Among the mutants, D225N, E289Q, and E289G lost catalytic activity significantly; their k(cat) values are 1/5700, 1/430, and 1/340, respectively, of that of the wild-type enzyme. The Bronsted plot for k(cat)/K(m) for the E289G mutant is linear with beta(1g) = -0.93, but that for k(cat) is biphasic, with beta(1g) for poor substrates being -0.88 and for activated substrates being -0.11. The small magnitude of Pig for the activated substrates may indicate that the rate-limiting step of the reaction is defucosylation, whereas the large magnitude of the latter Pig value for the poor substrates indicates that the rate-limiting step of the reaction becomes fucosylation. The kinetic outcomes support an argument that ASp(225) functions as a nucleophile and Glu(289) as a general acid/base catalyst. As further evidence, azide significantly reactivated D225G and E289G, and (1)H NMR spectral analysis confirmed the formation of beta-fucosyl azide and alpha-fucosyl azide in the azide rescues of D225G and E289G catalyses, respectively. As direct evidence to prove the function of Glu(289), an accumulation of fucosyl-enzyme intermediate was detected directly through ESI/MS analysis.
Effects of nanomorphological changes on the performance of solar cells with blends of poly[9,9 '-dioctyl-fluorene-co-bithiophene] and a soluble fullerene
(2009-01-14)
Huang, Jen-Hsien
;
Ho, Zhong-Yo
;
Kekuda, Dhananjay
;
Chang, Yung
;
Chu, Chih-Wei
Controlled nanophase segregation within the blended films of a conjugated polymer and a soluble fullerene has enabled us to form a continuous transfer pathway for the carriers, thereby increasing the photocurrent generation for polymer photovoltaic devices. Here, we study the effects of nanomorphological changes on the performance of polymer solar cells using blended films of poly[9,9'-dioctyl-fluorene-co-bithiophene] (F8T2) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM). Different weight ratios of the F8T2 and PCBM blends in various solvents were studied at different annealing temperatures. The morphology of the films seems to be a strong function of the processing conditions. The power conversion efficiency (PCE) of the photovoltaic devices has improved significantly from 0.34% to 2.14% under air mass 1.5 simulated solar illumination (100 mW cm(-2)), which could be attributed to the nanomorphological changes in the films.
Strain-induced effects on antiferromagnetic ordering and magnetocapacitance in orthorhombic HoMnO3 thin films
(2009-01-14)
Lin, T. H.
;
Shih, H. C.
;
Hsieh, C. C.
;
Luo, C. W.
;
Lin, J-Y
We investigated the magnetic and ferroelectric properties of c-axis oriented orthorhombic phase HoMnO3 (o-HMO in Pbnm symmetry setting) thin films grown on Nb-doped SrTiO3(001) substrates. The o-HMO films exhibit an antiferromagnetic ordering near 42 K, irrespective of the orientation of the applied field. However, an additional magnetic ordering occurring around 35 K was observed when the field was applied along the c-axis of o-HMO, which was absent when the field was applied in the ab-plane. The magnetocapacitance measured along the c-axis showed that although there is evidence of dielectric constant enhancement when the temperature is below 35 K the expected abrupt change in dielectric constant appears at a much lower temperature and reaches maximum around 13.5 K, indicating that the low-temperature c-axis polarization might be related to the ordering of the Ho3+ moment. The lattice constant analyses using x-ray diffraction and the observation of a slight magnetization hysteresis suggest that the weak second magnetic transition along the c- axis at 35 K might be more relevant to the strain-induced effect on antiferromagnetism.