Browsing by Issue Date, starting with "2006-09-25"

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Visible quantum cutting through downconversion in green-emitting K2GdF5 : Tb3+ phosphors
(2006-09-25)
Lee, Te-Ju
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Luo, Li-Yang
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Diau, Eric Wei-Guang
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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.
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Yang, S.
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Hsu, H. C.
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Chu, C. P.
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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.
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Chen, C. Y.
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Yang, M. J.
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Chien, C. H.
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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
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Byrnes, Jake K.
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Hwang, Jenn-Kang
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Li, Wen-Hsiung
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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
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Wang, Yi-Ting
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Tung, Pao-Hsiang
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Kuo, Shiao-Wei
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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.
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Liu, R. S.
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Lee, J. M.
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T Lu, K.
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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
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Chu, Hsin-Sen
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機械工程學系
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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.
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Chen, Falin
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Ruo, A. C.
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Chang, Min-Hsing
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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。
Electric stress effect on DC-RF performance degradation of 0.18-mu m mosfets
(2006-10-01)
Chen, C. C.
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Kao, H. L.
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Chin, Albert
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
We have studied the electric stress effect on DC-RF performance degradation of 64 gate fingers 0.18-mu m RF MOSFETs. The fresh devices show good transistor's DC to RF characteristics of small sub-threshold swing of 85 mV/dec, large drive current (I-d,I-sat) of 500 mu A/mu m, high unity-gain cut-off frequency (f(t)) of 47 GHz, and low minimum not. se figure (NFmin) of 1.3 dB at 10 GHz. The hot carrier stress for 20% I-d,I-sat reduction causes DC g(m) and r(o) degradation as well as the lower RF current gain by 2.35 dB, f(t) reduction to 35.7 GHz, increasing NFmin to 1.7 dB at 10 GHz and poor output impedance matching. (C) 2006 Wiley Periodicals, Inc.
The impact of deep Ni salicidation and NH3 plasma treatment on nano-SOI FinFETs
(2006-10-01)
You, Hsin-Chiang
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Kuo, Po-Yi
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Ko, Fu-Hsiang
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Chao, Tien-Sheng
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Lei, Tan-Fu
In this letter, 50-nm gate-length nano-silicon-on-insulator FinFETs with deep Ni salicidation and NH3 plasma treatment are fabricated. It is found that device performances, including subthreshold slope (SS) drain-induced barrier lowering (DIBL) and OFF-state leakage current, can be greatly improved by using deep Ni salicidation process compared to no Ni salicidation process. The deep Ni-salicided devices effectively suppress the floating-body effect and parasitic bipolar junction. transistor action. In addition, the effect of NH3 plasma on the deep Ni-salicided devices is discussed. Experimental results reveal that the devices under a new state-of-the-art NH3 plasma process can achieve better performance such as an SS of 66 mV/dec and a DIBL of 0.03 V.
Enhanced light out-coupling efficiency of organic light-emitting diodes with self-organized microlens arrays
(2006-10-01)
Huang, Wen-Kuei
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Wang, Wen-Sheng
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Kan, Hui-Chun
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Chen, Fang-Chung
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光電工程學系
A,method for enhancing the light out-coupling efficiency of organic light-emitting diodes (OLEDs) by incorporating microlens arrays (MLAs) is demonstrated. MLAs made of prepolymer NOA65 were fabricated on a substrate prepatterned by the microcontact printing of hydrophobic self-assembled monolayers (SAMs). Owing to the hydrophobic effect, the lens material was self-organized on the hydrophilic regions. After assembling the MLA onto an OLED, the optical measurement showed that the light out-coupling efficiency of the OLED with MLAs is increased without any apparent color shift.
Localized states in continuum in low-dimensional systems
(2006-10-01)
Voo, Khee-Kyun
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Chu, C. S.
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電子物理學系
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Department of Electrophysics
It is shown in this paper that for open systems, states that are localized in space, discrete in energy, and embedded in the continuum of extended states can be sustained by low-dimensional and channeled leads. These states have an origin different from that of analogous states discussed by von Neumann and Wigner [Phys. Z. 30, 465 (1929)]. A few representative systems are discussed. These states cause, for example, infinitely sharp Fano resonance in transport when they are marginally destroyed.
Database to dynamically aid probe design for virus identification
(2006-10-01)
Lin, Feng-Mao
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Huang, Hsien-Da
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Chang, Yu-Chung
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Tsou, Ann-Ping
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Chan, Pak-Leong
Viral infection poses a major problem for public health, horticulture, and animal husbandry, possibly causing severe health crises and economic losses. Viral infections can be identified by the specific detection of viral sequences in many ways. The microarray approach not only tolerates sequence variations of newly evolved virus strains, but can also simultaneously diagnose many viral sequences. Many chips have so far been designed for clinical use. Most are designed for special purposes, such as typing enterovirus infection, and compare fewer than 30 different viral sequences. None considers primer design, increasing the likelihood of cross hybridization to similar sequences from other viruses. To prevent this possibility, this work establishes a platform and database that provides users with specific probes of all known viral genome sequences to facilitate the design of diagnostic chips. This work develops a system for designing probes online. A user can select any number of different viruses and set the experimental conditions such as melting temperature and length of probe. The system then returns the optimal sequences from the database. We have also developed a heuristic algorithm to calculate the probe correctness and show the correctness of the algorithm.
Interval multidimensional scaling for group decision using rough set concept
(2006-10-01)
Huang, JJ
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Ong, CS
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Tzeng, GH
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科技管理研究所
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Institute of Management of Technology
Multidimensional scaling (MDS) is a statistical tool for constructing a low-dimension configuration to represent the relationships among objects. In order to extend the conventional MDS analysis to consider the situation of uncertainty under group decision making, in this paper the interval-valued data is considered to represent the dissimilarity matrix in MDS and the rough sets concept is used for dealing with the problems of group decision making and uncertainty simultaneously. In addition, two numerical examples are used to demonstrate the proposed method in both the situation of individual differences scaling and the conventional MDS analysis with the interval-valued data, respectively. On the basis of the results, we can conclude that the proposed method is more suitable for the real-world problems. (c) 2005 Elsevier Ltd. All rights reserved.
製造奈米線的方法和儀器
(2006-10-01)
朝春光
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郭金國
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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。
管管作品三首
(2006-10-01)
管管
Computer-generated Chinese color ink paintings
(2006-10-01)
Way, Der-Lor
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Lin, Wei-Jin
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Shih, Zen-Chung
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資訊工程學系
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Department of Computer Science
Chinese color ink painting is a traditional art form, a non-photorealistic rendering, that is over three thousand years old. Simulating the behavior of Chinese ink is challenging. Various artistic effects of color ink diffusion are analyzed, and a scheme presents how they can be simulated automatically for their computer-generated simulation. The proposed method simulates various tonal expressions on different papers. by employing a Kubelka-Munk model to simulate optical effects. Elucidation of the effect of mixing simulated strokes with different brushes is a significant contribution of the proposed method. Finally, results of this study demonstrate the effectiveness of an interactive painting system. Also, results are compared with genuine ink paintings.
Design techniques for high-speed multirate multistage FIR digital filters
(2006-10-01)
Lin, M. -C.
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Chen, H. -Y.
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Jou, S. -J.
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This paper presents architecture design techniques for implementing both single-rate and multirate high-speed finite impulse response (FIR) digital filters, with emphasis on the multirate multistage interpolated FIR (IFIR) digital filters. Well-known techniques to achieve high-speed and low-power applications for the single-rate digital FIR architecture are summarized, followed by the introduction of variable filter order selection, optimal filter decomposition, memory-saving and mirror symmetric filter pairs techniques which offer further gains in both performance and complexity reduction for the multirate multistage digital FIR architecture. A filter design example with TSMC 0.25 mu m standard cell for 64-QAM baseband demodulator shows that the area is reduced by 39% for low-complexity application. Moreover, for high-speed application, the chip can operate at 714 MHz. Finally, a designed decimator which is used in the CDMA cellular shows that the area is reduced by 70% as compared with conventional approach.
The effect of signal-feeder characteristic impedance on the signal injection efficiency of electroabsorption modulator integrated lasers
(2006-10-01)
Lim, Cheng Guan
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光電工程學系
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Department of Photonics
The signal injection efficiency of electroabsorption modulator integrated lasers (EMLs) is improved to suit 10-Gb/s applications. For a typical EML module design with a conventionally designed 50-Omega signal feeder to meet the input return loss requirement for 10-Gb/s applications, a reduction in device capacitance of the electroabsorption modulator (EAM) section by 65% from its typical value is necessary. By optimizing the characteristic impedance of the signal feeder, the required 65% reduction in device capacitance of the EAM section is reduced to 45%, which would naturally lead to enhanced extinction ratio and optical output power. With the addition of a series 5-Omega thin-film resistor along the signal feeder, the device capacitance reduction of the EAM section is further reduced to approximately 33% of the typical value.