Browsing by Issue Date, starting with "2010-12-14"

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Population trapping and rotational revival of N(2) molecules during filamentation of a femtosecond laser pulse in air
(2010-12-14)
Azarm, A.
;
Ramakrishna, S.
;
Talebpour, A.
;
Hosseini, S.
;
Teranishi, Y.
We study the fluorescence emitted from filaments in air using a pump-probe scheme with a femtosecond Ti-sapphire laser. The fluorescence intensities from the first negative band (B(2)Sigma(+)(u) -> X(2)Sigma(+)(g)) and the second positive band (C(3)Pi(u) -> B(3)Pi(g)) show enhancement and change periodically as a function of the pump-probe time delay. We attribute this phenomenon to the universal yet probably forgotten phenomenon of population trapping of nitrogen molecules in highly excited states together with field-induced alignment of nitrogen molecules followed by revivals of the rotational wavepackets. Theoretical calculation of the alignment dynamics of nitrogen molecules is consistent with the experimental data.
Population trapping and rotational revival of N-2 molecules during filamentation of a femtosecond laser pulse in air
(2010-12-14)
Azarm, A.
;
Ramakrishna, S.
;
Talebpour, A.
;
Hosseini, S.
;
Teranishi, Y.
We study the fluorescence emitted from filaments in air using a pump-probe scheme with a femtosecond Ti-sapphire laser. The fluorescence intensities from the first negative band (B-2 Sigma(+)(u) -> X-2 Sigma(+)(g)) and the second positive band (C-3 Pi(u) -> B-3 Pi(g)) show enhancement and change periodically as a function of the pump-probe time delay. We attribute this phenomenon to the universal yet probably forgotten phenomenon of population trapping of nitrogen molecules in highly excited states together with field-induced alignment of nitrogen molecules followed by revivals of the rotational wavepackets. Theoretical calculation of the alignment dynamics of nitrogen molecules is consistent with the experimental data.
A High-Mobility Low-Bandgap Copolymer for Efficient Solar Cells
(2010-12-15)
Ding, Ping
;
Chu, Cheng-Che
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Liu, Bo
;
Peng, Bo
;
Zou, Yingping
A new high-mobility low-bandgap polymer, PBDT-DODTBT, based on benzodithiophene and 5,6-bis(octyloxy)-4,7-di(thiophen-2-yl) benzothiadiazole has been synthesized through a standard Stille coupling reaction. The polymer is soluble in common organic solvents, such as chloroform, tetrahydrofuran, and chlorobenzene and has excellent film forming properties. Preliminary studies of the copolymer showed the charge mobility as high as 7.15 x 10(-3) cm(2).V(-1). s(-1) from SCLC measurement. Initial photovoltaic cells based on the composite structure of ITO/PEDOT: PSS/PBDT-DODTBT: (alpha)PC(71)BM (1:2)/Ca/Al showed an open-circuit voltage of 0.76 V, a power conversion efficiency of 4.02%, and a short-circuit current of 8.96mA.cm(-2).
Quasi Bessel beam by Billet's N-split lens
(2010-12-15)
Cheng, Chieh-Jen
;
Chern, Jyh-Long
;
光電工程學系
;
Department of Photonics
This study utilizes the focal property of a classical Billets split lens to create more focal points by splitting the lens This approach distributes the focal points circularly on the focal plane This study explores the characteristics of beam propagation and analytically derives the asymptotic characteristics of beam propagation based on the stationary phase approximation and the moment-free Filon-type method Results show that the unique Billets N-split lens can generate a quasi Bessel beam if the number of splitting N is large enough e g N >= 24 This study also explores the diffraction efficiency of corresponding quasi Bessel beam and the influence of aperture size The potential advantage of proposed split lens approach is that unlike the classical means of annular aperture this simple lens approach allows a much larger throughput in creating the Bessel beam and hence the Bessel beam could have more optical energy (C) 2010 Elsevier B V All rights reserved
Characterizations of low-temperature electroluminescence from ZnO nanowire light-emitting arrays on the p-GaN layer
(2010-12-15)
Lu, Tzu-Chun
;
Ke, Min-Yung
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Yang, Sheng-Chieh
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Cheng, Yun-Wei
;
Chen, Liang-Yi
Low-temperature electroluminescence from ZnO nanowire light-emitting arrays is reported. By inserting a thin MgO current blocking layer in between ZnO nanowire and p-GaN, high-purity UV light emission at wavelength 398 nm was obtained. As the temperature is decreased, contrary to the typical GaN-based light emitting diodes, our device shows a decrease of optical output intensity. The results are associated with various carrier tunneling processes and frozen MgO defects. (C) 2010 Optical Society of America
Synthesis and Characterization of Novel Low-Bandgap Triphenylamine-Based Conjugated Polymers with Main-Chain Donors and Pendent Acceptors for Organic Photovoltaics
(2010-12-15)
Sahu, Duryodhan
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Padhy, Harihara
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Patra, Dhananjaya
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Huang, Jen Hsien
;
Chu, Chih Wei
A series of novel low bandgap triphenylamine based conjugated polymers (PCAZCN PPTZCN and PDTPCN) consisting of different electron rich donor main chains (N alkyl 2 7 carbazole phenothiazine and cyclopentadithinopyrol respectively) as well as cyano and dicyano vinyl electron acceptor pendants were synthesized and developed for poly mer solar cell applications The polymers covered broad absorption spectra of 400-800 nm with narrow optical band gaps ranging 1 66-1 72 eV The highest occupied molecular or bital and lowest unoccupied molecular orbital levels of the polymers measured by cyclic voltammetry were found in the range of -5 12 to -532 V and -345 to -355 eV respectively Under 100 mW/cm(2) of AM 1 5 white light illumination bulk heterojunction photovoltaic devices composing of an active layer of electron donor polymers (PCAZCN PPTZCN and PDTPCN) blended with electron acceptor [6 6] phenyl C(61) butync acid methyl ester or [6 6] phenyl C(71) butyric acid methyl ester (PC(71)BM) in different weight ratios were investigated The photovoltaic device containing donor PCAZCN and acceptor PC(71)BM in 1 2 weight ratio showed the highest power conversion efficiency of 1 28% with V(oc) = 0 81 V J(sc) = 493 mA/cm(2) and fill factor = 32 1% (c) 2010 Wiley Periodicals Inc J Polym Sci Part A Polym Chem 48 5812-5823 2010
Electron delocalization of tensily strained GaAs quantum dots in GaSb matrix
(2010-12-15)
Lin, T. C.
;
Wu, Y. H.
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Li, L. C.
;
Sung, Y. T.
;
Lin, S. D.
The magneto-optical response of type-II tensily strained GaAs self-assembled quantum dots in GaSb was investigated in magnetic fields up to 14 T. By depositing different GaAs amount, the dot sizes and the corresponding emission energies were varied. We analyzed the carrier wave function extent of different dots using the diamagnetic shift results. It was found that, with the increase in the energy (the reduction in the dot size), the diamagnetic coefficient first rises quickly and then saturates at around 21 mu eV/T(2). Based on a simple calculation model, this unusual tendency is attributed to the electrons gradually spilling out of the quantum dot to the wetting layer as the dots get smaller. This delocalization effect is enhanced in this material system due to the tensile strain relaxation within the dots, which raises the conduction band edge over that in the wetting layer. (c) 2010 American Institute of Physics. [doi: 10.1063/1.3520669]
An analytical solution for describing the transient temperature distribution in an aquifer thermal energy storage system
(2010-12-15)
Li, Kuang-Yi
;
Yang, Shaw-Yang
;
Yeh, Hund-Der
;
環境工程研究所
;
Institute of Environmental Engineering
A mathematical model is developed for predicting the temperature distribution in an aquifer thermal energy storage (ATES) system, which consists of a confined aquifer bounded from above and below by the rocks of different geological properties. The main transfer processes of heat include the conduction and advection in the aquifer and the conduction in the rocks. The semi-analytical solution in dimensionless form for the model is developed by Laplace transforms and its corresponding time-domain solution is evaluated by the modified Crump method. Field geothermal property data are used to simulate the temperature distribution in an ATES system. The results show that the heat transfer in the aquifer is fast and has a vast effect on the vicinity of the wellbore. However, the aquifer temperature decreases with increasing radial and vertical distances. The temperature in the aquifer may be overestimated when ignoring the effect of thermal conductivity. The temperature distribution in an ATES system depends on the vertical thermal conduction in the rocks and the horizontal advection and thermal conduction in the aquifer. The present solution is useful in designing and simulating the heat injection facility in the ATES systems. Copyright (C) 2010 John Wiley & Sons, Ltd.
Thickness effect on ultrafast thermalization of carriers in above-band-gap states in ZnO epitaxial films
(2010-12-15)
Ou, Po-Chi
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Lin, Ja-Hon
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Chang, Chi-An
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Liu, Wei-Rein
;
Hsieh, Wen-Feng
Energy-dependent free-carrier dynamics was investigated in 70 nm (thin) and 1 mu m (thick) ZnO epifilms using the optical pump-probe technique. The far-above-band-gap dynamics in the thin epifilm reveals the prolonged relaxation and the slow recovery of renormalized band gap. The band-gap renormalization (BGR) effect is affected by the inefficient carrier-phonon scattering. In addition, the loss of excited carrier density via surface trapping results in an energy-dependent BGR buildup time. However, the far-above-band-gap dynamics in the thick epifilm reveals fast relaxation followed by BGR recovery, which is independent of the photon energy. The near-band-gap dynamics shows an ultrafast carrier thermalization both in the thin and the thick epifilms.
Combination of Indene-C(60) Bis-Adduct and Cross-Linked Fullerene Interlayer Leading to Highly Efficient Inverted Polymer Solar Cells
(2010-12-15)
Cheng, Yen-Ju
;
Hsieh, Chao-Hsiang
;
He, Youjun
;
Hsu, Chain-Shu
;
Li, Yongfang
A poly(3-hexylthiophene) (P3HT)-based inverted solar cell using indene-C(60) bis-adduct (ICBA) as the acceptor achieved a high open-circuit voltage of 0.82 V due to ICBA's higher-lying lowest unoccupied molecular orbital level, leading to an exceptional power-conversion efficiency (PCE) of 4.8%. By incorporating a cross-linked fullerene interlayer, C-PCBSD, to further modulate the interface characteristics, the ICBA:P3HT-based inverted device exhibited an improved short-circuit current and fill factor, yielding a record high PCE of 6.2%.
Laser scribing of indium tin oxide (ITO) thin films deposited on various substrates for touch panels
(2010-12-15)
Tseng, Shih-Feng
;
Hsiao, Wen-Tse
;
Huang, Kuo-Cheng
;
Chiang, Donyau
;
Chen, Ming-Fei
In this study, a Nd:YAG laser with wavelength of 1064nm is used to scribe the indium tin oxide (ITO) thin films coated on three types of substrate materials, i.e. soda-lime glass, polycarbonate (PC), and cyclic-olefin-copolymer (COC) materials with thickness of 20 nm, 30 nm, and 20 nm, respectively. The effect of exposure time adjusted from 10 mu s to 100 mu s on the ablated mark width, depth, and electrical properties of the scribed film was investigated. The maximum laser power of 2.2W was used to scribe these thin films. In addition, the surface morphology, surface reaction, surface roughness, optical properties, and electrical conductivity properties were measured by a scanning electron microscope, a three-dimensional confocal laser scanning microscope, an atomic force microscope, and a four-point probe. The measured results of surface morphology show that the residual ITO layer was produced on the scribed path with the laser exposure time at 10 mu s and 20 mu s. The better edge qualities of the scribed lines can be obtained when the exposure time extends from 30 mu s to 60 mu s. When the laser exposure time is longer than 60 mu s, the partially burned areas of the scribed thin films on PC and COC substrates are observed. Moreover, the isolated line width and resistivity values increase when the laser exposure time increases. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.
Multifocus confocal Raman microspectroscopy for fast multimode vibrational imaging of living cells
(2010-12-15)
Okuno, Masanari
;
Hamaguchi, Hiro-o
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
We have developed a multifocus confocal Raman microspectroscopic system for the fast multimode vibrational imaging of living cells. It consists of an inverted microscope equipped with a microlens array, a pinhole array, a fiber bundle, and a multichannel Raman spectrometer. Forty-eight Raman spectra from 48 foci under the microscope are simultaneously obtained by using multifocus excitation and image-compression techniques. The multifocus confocal configuration suppresses the background generated from the cover glass and the cell culturing medium so that high-contrast images are obtainable with a short accumulation time. The system enables us to obtain multimode (10 different vibrational modes) vibrational images of living cells in tens of seconds with only 1 mW laser power at one focal point. This image acquisition time is more than 10 times faster than that in conventional single-focus Raman microspectroscopy. (C) 2010 Optical Society of America
《咆哮山莊》裏的愛恨咆哮與歇息
(2010-12-15)
董挽華
;
開放教育推動中心
;
Open Education Office
課程首頁本課程是由交通大學新文藝復興閱讀計畫提供。 96 年 8 月當各大學紛紛摩拳擦掌準備迎接新生的同時，交通大學校長吳重雨則因為一則來自於七月份泰晤士報，有關於英國首相布朗公布其夏日讀書清單的新聞中，看到了他對知識的尊重。在這同時，吳重雨校長也思考著，要如何為學生準備追求知識的環境和激發他們對知識的尊重與喜愛。台積電張忠謀董事長曾陳述他 18 歲進入哈佛那一年，博覽文史哲理工經典群籍，至此奠定了他求知的基礎，並借海明威名言，將其改為「哈佛這一年為人生可帶走的盛宴。」吳重雨校長以張董事長的學習為借鏡，認為學生固然能藉由自我閱讀的方式學習到豐沛的知識，但透過名人、大師親臨現場地介紹經典書籍，更能加深學子們對於書籍的認識與興趣，這也是「新文藝復興閱讀計劃」 ( 以下簡稱 : 「經典名著選讀」 ) 活動展開籌劃的緣由。於是，吳重雨校長便積極敦請「交大通識教育委員會」，接手籌備本計劃的相關活動，而該中心也成為實際施行本計畫的策動、開課以及認證單位。至此，期許交大學子藉由閱讀、聽講來提昇人文素養、開拓視野的「新文藝復興閱讀計劃」，就此展開。
Nonstationary stochastic analysis of flow in a heterogeneous unconfined aquifer subject to spatially-random periodic recharge
(2010-12-15)
Chang, Ching-Min
;
Yeh, Hund-Der
;
環境工程研究所
;
Institute of Environmental Engineering
The problem of two-dimensional groundwater flow in a heterogeneous unconfined aquifer under periodic random forcing in time is analyzed from a stochastic point of view It is assumed that the periodic random forcing namely random recharge can be represented by a sinusoidal function in time Analytical solutions are developed through the nonstationary spectral approach in conjunction with the principle of superposition The results namely the variances of hydraulic head and specific discharge are expressed in terms of statistical properties of hydraulic parameters and recharge field It can be concluded from the analytical results that the mean recharge rate and integral scale of spatially random recharge fluctuations play essential roles in enhancing the variability of hydraulic head and specific discharges (c) 2010 Elsevier B V All rights reserved
Mutually independent bipanconnected property of hypercube
(2010-12-15)
Shih, Yuan-Kang
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Tan, Jimmy J. M.
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Hsu, Lih-Hsing
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資訊工程學系
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Department of Computer Science
A graph is denoted by G with the vertex set V(G) and the edge set E(G). A path P = < v(0), v(1),..., v(m)> is a sequence of adjacent vertices. Two paths with equal length P(1) = < u(1), u(2),..., u(m)> and P(2) = < v(1), v(2),..., v(m)> from a to b are independent if u(1) = v(1) = a, u(m) = v(m) = b, and u(i) not equal v(i) for 2 <= i 6 <= m - 1. Paths with equal length {P(i)}(i-1)(n) from a to b are mutually independent if they are pairwisely independent. Let u and v be two distinct vertices of a bipartite graph G, and let l be a positive integer length, d(G)(u, v) <= l <= vertical bar V(G) - 1 vertical bar with (l - d(G)(u, v)) being even. We say that the pair of vertices u, v is ( m, l)- mutually independent bipanconnected if there exist m mutually independent paths {P(i)(l)}(i-1)(m) with length l from u to v. In this paper, we explore yet another strong property of the hypercubes. We prove that every pair of vertices u and v in the n-dimensional hypercube, with d(Qn) (u, v) >= n - 1, is (n - 1,l)-mutually independent bipanconnected for every l; d(Qn) (u, v) <= l <= vertical bar V(Q(n))-1 vertical bar with (l - d(Qn) (u, v)) being even. As for d(Qn) (u, v) <= n - 2, it is also (n - 1,l)-mutually independent bipanconnected if l >= d(Qn) (u, v) + 2, and and is only (l,l)-mutually independent bipanconnected if l = d(Qn)(u, v). (C) 2010 Elsevier Inc. All rights reserved.
Concentrations of ultrafine particles at a highway toll collection booth and exposure implications for toll collectors
(2010-12-15)
Cheng, Yu-Hsiang
;
Huang, Cheng-Hsiung
;
Huang, Hsiao-Lin
;
Tsai, Chuen-Jinn
;
環境工程研究所
Research regarding the magnitude of ultrafine particle levels at highway toll stations is limited. This study measured ambient concentrations of ultrafine particles at a highway toll station from October 30 to November 1 and November 5 to November 6, 2008. A scanning mobility particle sizer was used to measure ultrafine particle concentrations at a ticket/cash tollbooth. Levels of hourly average ultrafine particles at the tollbooth were about 3-6 times higher than those in urban backgrounds, indicating that a considerable amount of ultrafine particles are exhausted from passing vehicles. A bi-modal size distribution pattern with a dominant mode at about <6 nm and a minor mode at about 40 nm was observed at the tollbooth. The high amounts of nanoparticles in this study can be attributed to gas-to-particle reactions in fresh fumes emitted directly from vehicles. The influences of traffic volume, wind speed, and relative humidity on ultrafine particle concentrations were also determined. High ambient concentrations of ultrafine particles existed under low wind speed, low relative humidity, and high traffic volume. Although different factors account for high ambient concentrations of ultrafine particles at the tollbooth, measurements indicate that toll collectors who work close to traffic emission sources have a high exposure risk. (C) 2010 Elsevier ay. All rights reserved.
Combination of Indene-C-60 Bis-Adduct and Cross-Linked Fullerene Interlayer Leading to Highly Efficient Inverted Polymer Solar Cells
(2010-12-15)
Cheng, Yen-Ju
;
Hsieh, Chao-Hsiang
;
He, Youjun
;
Hsu, Chain-Shu
;
Li, Yongfang
A poly(3-hexylthiophene) (P3HT)-based inverted solar cell using indene-C-60 bis-adduct (ICBA) as the acceptor achieved a high open-circuit voltage of 0.82 V due to ICBA's higher-lying lowest unoccupied molecular orbital level, leading to an exceptional power-conversion efficiency (PCE) of 4.8%. By incorporating a cross-linked fullerene interlayer, C-PCBSD, to further modulate the interface characteristics, the ICBA:P3HT-based inverted device exhibited an improved short-circuit current and fill factor, yielding a record high PCE of 6.2%.
Free-electronlike diffusive thermopower of indium tin oxide thin films
(2010-12-15)
Wu, Chih-Yuan
;
Tra Vu Thanh
;
Chen, Yi-Fu
;
Lee, Jui-Kan
;
Lin, Juhn-Jong
We report our measurements of thermopower, S (T), on a series of indium tin oxide thin films from 300 down to 5 K to extract the carrier concentration n. The temperature behavior of S (T) below 300 K can be essentially described by a prevailing linear diffusive contribution. In this wide temperature interval, the phonon-drag thermopower is negligible relative to the diffusive thermopower. Therefore, the free-electronlike characteristic is clearly addressed. It should be stressed that linearity in S(d) from liquid-helium temperatures all the way up to room temperatures is seldom seen even in simple metals. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3524522]
感測平台
(2010-12-16)
林志生
;
莊曜禎
;
陳思豪
一種感測平台，包括複數奈米金屬粒子；聚集誘導子，包括兩個彼此不同之官能基，且經由該聚集誘導子之一該官能基與該奈米金屬粒子接觸；以及辨識分子，係與該奈米金屬粒子結合並經由該辨識分子與欲辨識之標的物作用以辨識該標的物，其中，該聚集誘導子之另一未與該奈米金屬粒子接觸之官能基係用以於該標的物與該辨識分子作用後，誘導該複數奈米金屬粒子聚集。
Pricing peer-produced services: Quality, capacity, and competition issues
(2010-12-16)
Li, Yung-Ming
;
Lee, Yi-Lin
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Peer production has played an important role in the economics of Web 2.0 related services in which user participation and contribution become the main driving dynamics. However, the quality of peer-produced services is uncertain because of inherently decentralized and heterogeneous participants. In the paper, utilizing reliability and game theoretic models, we develop a QoS measure and pricing schemes for this emerging type of service under various market structures. Our results suggest that a monopolistic platform provider has no incentive to offer multiple quality classes of service. Two competing platform providers may offer identical service contracts but still receive non-negative profit. If they offer heterogeneous service contracts, the provider with the lower quality service may provide higher quality than he advertises. This research contributes to the literature with a number of unique and interesting implications for the issues of service contract design, capacity planning, and market interactions for operations of community-based or peer-produced services. (C) 2010 Elsevier B.V. All rights reserved.