Browsing by Issue Date, starting with "2006-09-18"

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Emission characteristics of optically pumped GaN-based vertical-cavity surface-emitting lasers
(2006-09-18)
Chu, Jung-Tang
;
Lu, Tien-Chang
;
You, Min
;
Su, Bor-Jye
;
Kao, Chih-Chiang
The laser emission characteristics of a GaN-based vertical-cavity surface-emitting laser with two dielectric distributed Bragg reflectors were investigated under optically pumped operation at room temperature. The laser emitted wavelength at 415.9 nm with an emission linewidth of 0.25 nm and threshold pumping energy of 270 nJ. The laser has a high characteristic temperature of about 278 K and high spontaneous emission coupling factor of 10(-2). The laser emission showed single and multiple spot emission patterns with spectral and spatial variations under different pumping conditions. (c) 2006 American Institute of Physics.
Structure of HfO2 films epitaxially grown on GaAs(001)
(2006-09-18)
Hsu, C. -H.
;
Chang, P.
;
Lee, W. C.
;
Yang, Z. K.
;
Lee, Y. J.
High-quality HfO2 films of technologically important thickness ranging from 1.8 to 17 nm have been grown epitaxially on GaAs (001) by molecular beam epitaxy. Thorough structural and morphological investigations were carried out by x-ray scattering and high-resolution transmission electron microscopy. The films exhibit an atomically sharp interface with the substrate and are of a monoclinic phase with predominant (001)-plane epitaxy between the HfO2 films and GaAs, in spite of a large lattice mismatch of > 8.5%.
Highly efficient and stable sky blue organic light-emitting devices
(2006-09-18)
Lin, Mei-Fang
;
Wang, Lei
;
Wong, Wai-Kwok
;
Cheah, Kwok-Wai
;
Tam, Hoi-Lam
A highly efficient and stable sky blue organic light-emitting device doped with a sky blue dopant BUBD-1 has been fabricated, achieving an electroluminescence efficiency of 13.2 cd/A and 6.1 lm/W at 20 mA/cm(2) and 6.7 V, with Commission Internationale del'Eclairage coordinates of (0.16, 0.30) and a half-decay lifetime of 1815 h at an initial brightness of 2640 cd/m(2). This performance is one of the best blue devices ever reported without using hole blocking layer or any p or n dopant in hole or electron transport layer. (c) 2006 American Institute of Physics.
Method for fabrication of polycrystallin silicon thin film transistors
(2006-09-19)
Yeh
;
Ching-Fa
;
Chen
;
Tien-Fu
;
Lou
A method for fabricating polycrystalline silicon film transistors, which includes a polysilicon spacer capping onto a sidewall of an active layer in the thin film transistors by an isotropic dry etching of the silicon film. This method suppresses the shrinkage of the active layer during recrystallization by the laser. Large grains are formed in the channel after recrystallization utilizing a high-energy continuous wavelength laser or an excimer laser annealing the active layer. This process does not require an additional mask. Uniform arrangement of grain boundaries and large grain sizes promotes uniformity of performance of the device, which is important in the fields of low temperature polycrystalline silicon thin film transistors (LTPS-TFTs).
Syntheses and specific interactions of poly (hydroxyethyl methacrylate-b-vinyl pyrrolidone) diblock copolymers and comparisons with their corresponding miscible blend systems
(2006-09-20)
Huang, Chih-Feng
;
Kuo, Shiao-Wei
;
Lin, Fang-Ju
;
Wang, Chih-Feng
;
Hung, Chen-Jui
Combination of atom transfer radical and conventional free radical polymerizations has been successfully used to prepare poly(hydroxyethyl methacrylate-b-vinyl pyrrolidone) (PHEMA-b-PVP) copolymers with controlled molecular weight and low polydispersity (< 1.4). The thermal behavior and specific interaction of PHEMA-b-PVP diblock copolymers and their corresponding PHEMA/PVP blends were characterized. The result shows that glass transition temperatures of diblock copolymers analysed by differential scanning calorimetry (DSC) are higher than those of the blends. Infrared and solid-state NMR spectroscopic analyses show that hydrogen-bonding interaction of hydroxyl-carbonyl groups of diblock copolymers was also greater than that of the blends. Measurement of the proton spin-lattice relaxation time in the rotating frame, (T-1P(H)), reveals that all diblock copolymers and blends possess one composition-dependent T H, indicating that both diblock copolymers and blends are homogeneous, which is consistent with the DSC analysis. (c) 2006 Elsevier Ltd. All rights reserved.
製造奈米線的方法和儀器
(2006-09-21)
朝春光
;
郭金國
;
陳建仲
;
陳蓉萱
一種製造奈米線的方法，是以一液壓使熔融材料進入模板之奈米通道，再凝固熔融材料，以形成數個奈米線。本發明可製作各種成份之合金奈米線且對環境污染性低。再者，本發明所製作出的合金奈米線之純度高、缺陷少、製程簡單且效率高。另外，本發明之方法亦適用於製作高分子、陶瓷及複合材料等奈米線。
感應地層移動之光纖光柵雙軸承式偏斜儀
(2006-09-21)
黃安斌
;
何彥德
本發明提供一種用於感應地層移動之監測儀，包括：感測元件是由兩端剛性鋁片加上中間一節撓性軟管所組成，且利用應變監測管之原理與節理式機構之設計而達到訊號放大之效應。其中，在節理間安裝兩個雙軸承，其中一個軸承與監測管方向同軸(滑動軸承)，在於解除感測器受監測管軸向力(包括重力與摩擦力)對感測器之影響，另一個軸承與監測管方向垂直(轉動軸承)，在於限制偏斜儀節理之間只能以橫向軸承為中心旋轉而增加結果分析之可靠度。使用此一設計可以獲得穩定而具有高度重複性之讀數，以便使用雙軸承式偏斜儀做定量之監測與結果分析。
語音定位系統
(2006-09-21)
胡竹生
;
劉維瀚
;
鄭价呈
本發明係為一語音定位系統，將聲音訊號藉由麥克風陣列接收並傳送至語音偵測系統，以決定系統之運作狀態流程，再將聲波訊號傳送至環境參數訓練子系統藉由加成性原理模擬產生訓練訊號，並將該訓練訊號經由特徵之抽取及描述此特徵之分佈狀況以產生一統計參數，最後將麥克風陣列所擷取之聲音訊號及統計參數驅動語音位置偵測子系統以偵測語者位置。
廢水混凝加藥之控制法
(2006-09-21)
江萬豪
;
黃志彬
;
蘇育俊
本發明係為一廢水混凝加藥之控制法，藉由直接滴定來決定加藥劑量，將混凝劑作為酸滴定藥劑，直接對氧化化學機械研磨廢水進行滴定加藥，至適當pH值時，滴定加藥停止，此時之加藥劑量為電性中和去穩之控制點，可精確控制加藥劑量，使加藥劑量降低，處理成本隨之降低，也不因於廢水進流濃度的變化而產生不能適用的情形，可不受限制而使用不同之混凝劑。
Transient behavior of CO poisoning of the anode catalyst layer of a PEM fuel cell
(2006-09-22)
Chu, H. S.
;
Wang, C. P.
;
Liao, W. C.
;
Yan, W. M.
;
機械工程學系
A one-dimensional transient mathematical model is applied to simulate the carbon monoxide poisoning effect on the performance of a PEM fuel cell. Based on the CO kinetic model developed by Springer et al. [T.E. Springer, T. Rockward, T.A. Zawodzinski, S. Gottesfeld, J. Electrochem. Soc. 148 (2001) A11-A23], the transient behaviors of the CO poisoning process across the anode catalyst layer is investigated. The results show that the hydrogen coverage, OH, decreases with the time due to CO adsorption on the catalyst sites. A higher CO concentration results in fewer available catalyst sites for hydrogen electro-oxidation and a significant decrease in the response time to reach steady state, t(ss). Increasing the anode overpotential and the gas porosity would result in an increase in the current density, especially at low levels of CO concentration. (c) 2006 Elsevier B.V. All rights reserved.
Polyhedral oligomeric silsesquioxane containing copolymers for negative-type photoresists
(2006-09-22)
Lin, Ho-May
;
Wu, Shi-Yin
;
Huang, Pei-Yuan
;
Huang, Chih-Feng
;
Kuo, Shiao-Wei
A series of methacrylate copolymers containing polyhedral oligomeric silsesquioxane (POSS) was synthesized from the free radical copolymerization of methacrylic acid, methyl methacrylate, and isobutyl propylmethacryl polyhedral oligosilsesquioxanes, and then were modified with glycidyl methacrylate to serve as negative-type photoresists. The UV/Vis spectroscopy reveals that the incorporation of POSS moiety into the copolymer results in a slight decrease in transparency from 99 to 92.5% (at wavelength = 365 nm). The photosensitivity in terms of resist sensitivity (D-n(0.5)), contrast (gamma), and photopolymerization rate are significantly increased with increase in the POSS content. In addition, the induction time is reduced from 0.520 to 0.515 min after incorporating the POSS unit based on photo-DSC analyses. These observed results can be rationalized as due to hydrogen bonding interactions between siloxane and hydroxyl groups in copolymers which tend to attract the methacrylate double bonds surrounding POSS units to crosslink, thereby enhancing the photopolymerization rate and sensitivity. We further evaluate the lithographic property of a photoresist under a collimated exposure.
Visible quantum cutting through downconversion in green-emitting K2GdF5 : Tb3+ phosphors
(2006-09-25)
Lee, Te-Ju
;
Luo, Li-Yang
;
Diau, Eric Wei-Guang
;
Chen, Teng-Ming
;
Cheng, Bing-Ming
Visible quantum cutting under excitations at 212 and 172 nm in a green-emitting phosphor K2GdF5:Tb3+ (11%) via a downconversion mechanism is investigated. The authors measured the vacuum ultraviolet (VUV) excitation and emission spectra and proposed mechanisms to rationalize the quantum-cutting effect. One short-UV or one VUV photon absorbed by Tb3+ is split into multiple visible photons emitted by Tb3+ through cross relaxation and direct energy transfer. Calculations indicate an optimal quantum efficiency as great as 189% for this phosphor. (c) 2006 American Institute of Physics.
ZnO nanopowders fabricated by dc thermal plasma synthesis
(2006-09-25)
Ko, T. S.
;
Yang, S.
;
Hsu, H. C.
;
Chu, C. P.
;
Lin, H. F.
Ultrafine ZnO nanopowders were successfully synthesized by the de thermal plasma process with a high production rate of 1.2 kg/h. The combination of plasma was found to affect the nanoparticles morphology. Both X-ray diffraction and Raman spectrum analysis confirmed a high quality wurtzite structure of the ZnO nanopowders. Photoluminescence study exhibited strong ultraviolet emission corresponding to the near band edge emission in the ZnO nanopowders. Random laser action observed in the ZnO nanostructures by optical pumping demonstrated high optical and crystal quality of the ZnO nanopowders fabricated by the dc thermal plasma synthesis. (c) 2006 Elsevier B.V. All rights reserved.
Photovoltaic effect on the conductive atomic force microscopic characterization of thin dielectric films
(2006-09-25)
Chang, M. N.
;
Chen, C. Y.
;
Yang, M. J.
;
Chien, C. H.
;
電子工程學系及電子研究所
The authors have used front-wing conductive probes to investigate the photovoltaic effect on the conductive atomic force microscopic (C-AFM) characterization of thin dielectric films. The surface photovoltage induced by the laser beam of an atomic force microscope can enhance the electrical field across the studied dielectric film, decreasing the onset voltage of the leakage current, resulting in a modified C-AFM image with a larger current distribution. Moreover, the experimental results also revealed that the influence of the photovoltaic effect on C-AFM would be more significant for dielectric films that are grown on a substrate with a higher carrier concentration. (c) 2006 American Institute of Physics.
Codon-usage bias versus gene conversion in the evolution of yeast duplicate genes
(2006-09-26)
Lin, Yeong-Shin
;
Byrnes, Jake K.
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Hwang, Jenn-Kang
;
Li, Wen-Hsiung
;
生物科技學系
Many Saccharomyces cerevisiae duplicate genes that were derived from an ancient whole-genome duplication (WGD) unexpectedly show a small synonymous divergence (K-S), a higher sequence similarity to each other than to orthologues in Saccharomyces bayanus, or slow evolution compared with the orthologue in Kluyveromyces waltii, a non-WGD species. This decelerated evolution was attributed to gene conversion between duplicates. Using approximate to 300 WGD gene pairs in four species and their orthologues in non-WGD species, we show that codon-usage bias and protein-sequence conservation are two important causes for decelerated evolution of duplicate genes, whereas gene conversion is effective only in the presence of strong codon-usage bias or protein-sequence conservation. Furthermore, we find that change in mutation pattern or in tDNA copy number changed codon-usage bias and increased the K-S distance between K. waltii and S. cerevisiae. Intriguingly, some proteins showed fast evolution before the radiation of WGD species but little or no sequence divergence between orthologues and paralogues thereafter, indicating that functional conservation after the radiation may also be responsible for decelerated evolution in duplicates.
Stable superhydrophobic polybenzoxazine surfaces over a wide pH range
(2006-09-26)
Wang, Chih-Feng
;
Wang, Yi-Ting
;
Tung, Pao-Hsiang
;
Kuo, Shiao-Wei
;
Lin, Chun-Hung
In this study, we report on a simple two-step casting process designed to create a stable superhydrophobic surface. This method possesses the advantages of being both simple and inexpensive as well as utilizing non-fluorine-containing compounds. Most interestingly, we found that the as-prepared surface possesses superhydrophobic properties not only for pure water but also for corrosive water under both acidic and basic conditions. Furthermore, the superhydrophobic polybenzoxazine surfaces had excellent environmental stability with regard to both heating and organic solvent treatment in terms of the contact angle to water.
High-resolution XANES study of Eu(Ba1-xRx)(2)Cu3O7+delta (R = Eu, Pr)
(2006-09-27)
Chen, J. M.
;
Liu, R. S.
;
Lee, J. M.
;
T Lu, K.
;
Yang, T. J.
We have probed the distribution of hole carriers in Eu(Ba1-xEux)(2) Cu3O7+delta (x = 0 - 0.2) and Eu(Ba1-xPrx)(2)Cu3O7+delta (x = 0 - 0.25) by O K-edge and Cu L-edge x-ray absorption spectra. Upon Eu and Pr substitution at the Ba site in Eu(Ba1-xRx)(2)Cu3O7+delta, the concentration of holes in the CuO2 planes becomes greatly diminished. The depletion rate of hole carriers within the CuO2 planes in Eu(Ba1-xPrx)(2)Cu3O7+delta is greater than that in Eu(Ba1-xEux)(2)Cu3O7+delta. The rate of T-c suppression with Pr doping in Eu(Ba1-xPrx)(2)Cu3O7+delta is accordingly greater than that in Eu(Ba1-xEux)(2)Cu3O7+delta.
Numerical investigation of transport component design effect on a proton exchange membrane fuel cell
(2006-09-29)
Chiang, Mu-Sheng
;
Chu, Hsin-Sen
;
機械工程學系
;
Department of Mechanical Engineering
A numerical investigation of the transport phenomena and performance of a proton exchange membrane fuel cell (PEMFC) with various design parameters of the transport component is presented. A three-dimensional fuel cell model, incorporating conservations of species, momentum, as well as current transport, is used. The Bulter-Volmer equation that describes the electrochemical reaction in the catalyst layer is introduced; the activation overpotential connects the solid phase potential field to that of the electrolyte phase. Through cell performance simulation with various channel aspect ratios and gas diffusion layer (GDL) thicknesses, a slender channel is found suitable for cells operating at moderate reaction rate, and a flat channel produces more current at low cell voltage. Plots of transverse oxygen concentration and phase potential variation indicate that these oppositely affect the local current density pattern. The relative strengths of these two factors depend on the transport component position and geometry, as well as on the cell operating conditions. Consequently, the curves of cell output current density demonstrate that the optimal GDL thickness increases as the cell voltage decreases. However, at the lowest considered cell voltage of 0.14 V optimal thickness decreases as that of a thick GDL. The oxygen deficiency caused by long traveling length and clogging effect of liquid water reverses this relationship. (c) 2006 Elsevier B.V. All rights reserved.
An analytical solution for transport of oxygen in cathode gas diffusion layer of PEMFC
(2006-09-29)
Tsai, C. R.
;
Chen, Falin
;
Ruo, A. C.
;
Chang, Min-Hsing
;
Chu, Hsin-Sen
A two-dimensional theoretical model is developed in this study to simulate the transport phenomena of oxygen in cathode gas diffusion layer (GDL) of proton exchange membrane fuel cell (PEMFC). An analytical solution is then obtained accordingly to characterize the effects of GDL on cell performance. It is found that the concentration flux of oxygen across the GDL is primarily dominated by the thickness and porosity of GDL. For a thicker GDL, the diffusion resistance increases and thus lowers the cell performance especially under high current density condition. On the other hand, an increase of porosity will enhance the transport of oxygen and result in significant improvement of cell performance. The influences of system parameters including the temperature, channel height, inlet velocity, and inlet pressure on the diffusion of oxygen in GDL are also examined systematically. Results provide insights into the characteristics of oxygen diffusion in GDL and benefit the optimal design of PEMFC. (c) 2006 Elsevier B.V. All rights reserved.
車輛周圍障礙物之偵測方法及顯示方法
(2006-10-01)
吳炳飛
;
林全財
本發明提出一種車輛周圍障礙物之偵測方法及顯示方法，係利用攝像裝置拍攝到車輛周圍的障礙物，並在經過計算之後，將障礙物的位置及與車輛的距離顯示在一顯示器上，且顯示器利用座標顯示方位，並將車輛置於原點，而可依範圍的大小而利用比例尺改變座標，使得駕駛者可輕易辨識障礙物的位置及距離，而方便駕駛者駕駛，以提高安全性，並可應用於自動駕駛，且利用攝像裝置以避免造成過多的電磁波，並可降低成本。