Browsing by Issue Date, starting with "2009-09-28"

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Effects of independent double-gated configuration on polycrystalline-Si nonvolatile memory devices
(2009-09-28)
Chen, Wei-Chen
;
Lin, Horng-Chih
;
Chang, Yu-Chia
;
Huang, Tiao-Yuan
;
電子工程學系及電子研究所
A polycrystalline-Si thin-film transistor configured with independent double-gated structure and ultrathin channel film is proposed for use as a Si-oxide-nitride-oxide-Si memory device. Taking advantage of additional control gate bias offered by the independent double-gated scheme in addition to the driving gate, this work demonstrated that the reading window and programming efficiency can be improved by applying a proper control gate bias. It is also found that the relationship between programming/erasing speed and control gate bias is strongly related to channel film thickness. Our results indicate that the independent double-gated device possesses promising potential for future nonvolatile memory applications. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3238362]
Effect of donor-acceptor concentration ratios on nonradiative energy transfer in closely packed CdTe quantum dots
(2009-09-28)
Lin, Y. C.
;
Wang, W. J.
;
Chung, H. L.
;
Chou, W. C.
;
Chen, W. K.
This study investigates the dependence of Forster resonance energy transfer (FRET) on donor-acceptor (D/A) concentration ratios in mixed-size CdTe quantum dots (QDs) films by using photoluminescence (PL) and time-resolved PL spectroscopy. Experimental results indicate that an increasing donor concentration significantly quenches the emission intensity and lifetime in donor QDs and enhances that in acceptor QDs, providing clear evidence of increased FRET efficiency. When D/A ratio exceeds 6, however, the emission intensity and the lifetime of acceptors start to decline, reflecting a decreasing FRET efficiency because of a markedly declining availability of acceptor QDs. (C) 2009 American Institute of Physics. [doi:10.1063/1.3242371]
Photocatalytic behavior of TOPO-capped TiO(2) nanocrystals for degradation of endocrine disrupting chemicals
(2009-09-28)
Chang, Sue-min
;
Lo, Pin-han
;
Chang, Chen-tuan
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, we investigated the photocatalytic kinetics and mechanisms of trioctylphosphine oxide-capped titanium dioxide (TOPO-capped TiO(2)) for degradation of two endocrine disrupting chemicals (EDCs), phenol and bisphenol A, which contained different hydrophobicity, chemiadsorbability, and degradable capacity. The TOPO-capped TiO(2) exhibited high partition coefficients of 2.00 x 10(-4) and 3.42 x 10(-3) l/mg for phenol and bisphenol A, respectively. In addition, the bonded TOPO introduced substantial amounts of trapped holes at the surface. The high affinity toward the target compounds and stabilized charge carriers resulted in high photocatalytic activity of the modified TiO(2). The TOPO-capped TiO(2) exhibited 12- and 3-fold higher photocatalytic activities than P25 for decomposition of bisphenol A and phenol, respectively. The presence of the hydrophobic modifier inhibited the generation of hydroxyl radicals and led to the photocatalysis undergoing mainly from partition followed by chemisorption and interfacial charge transfer. Partition and interfacial charge transfer were the rate determining steps for the degradation of phenol and bisphenol A, respectively. According to the Langmuir-Hinshelwood model, the adsorption coefficient (K,) and intrinsic rate constant (k(r)) for phenol were 4.17 x 10(-2) l/mg and 5.60 x 10(-2) mg-g/l-min-m(2), respectively, while they were 2.91 x 10(-2) l/m and 2.18 x 10(-1) mg-g/l-min-m(2), respectively for bisphenol A degradation. The product of the k(r) and k(a) for bisphenol A was 2.7 times higher than that for phenol, revealing that the modified TiO(2) favored decomposition of the compound which contains high chemiadsorbability and direct photocatalytic tendency in their individual systems. In contrast, the high degradable capability of phenol resulted in its preferential degradation in the competitive system. (C) 2009 Elsevier B.V. All rights reserved.
Photocatalytic behavior of TOPO-capped TiO2 nanocrystals for degradation of endocrine disrupting chemicals
(2009-09-28)
Chang, Sue-min
;
Lo, Pin-han
;
Chang, Chen-tuan
;
環境工程研究所
;
Institute of Environmental Engineering
In this study, we investigated the photocatalytic kinetics and mechanisms of trioctylphosphine oxide-capped titanium dioxide (TOPO-capped TiO2) for degradation of two endocrine disrupting chemicals (EDCs), phenol and bisphenol A, which contained different hydrophobicity, chemiadsorbability, and degradable capacity. The TOPO-capped TiO2 exhibited high partition coefficients of 2.00 x 10(-4) and 3.42 x 10(-3) l/mg for phenol and bisphenol A, respectively. In addition, the bonded TOPO introduced substantial amounts of trapped holes at the surface. The high affinity toward the target compounds and stabilized charge carriers resulted in high photocatalytic activity of the modified TiO2. The TOPO-capped TiO2 exhibited 12- and 3-fold higher photocatalytic activities than P25 for decomposition of bisphenol A and phenol, respectively. The presence of the hydrophobic modifier inhibited the generation of hydroxyl radicals and led to the photocatalysis undergoing mainly from partition followed by chemisorption and interfacial charge transfer. Partition and interfacial charge transfer were the rate determining steps for the degradation of phenol and bisphenol A, respectively. According to the Langmuir-Hinshelwood model, the adsorption coefficient (K,) and intrinsic rate constant (k(r)) for phenol were 4.17 x 10(-2) l/mg and 5.60 x 10(-2) mg-g/l-min-m(2), respectively, while they were 2.91 x 10(-2) l/m and 2.18 x 10(-1) mg-g/l-min-m(2), respectively for bisphenol A degradation. The product of the k(r) and k(a) for bisphenol A was 2.7 times higher than that for phenol, revealing that the modified TiO2 favored decomposition of the compound which contains high chemiadsorbability and direct photocatalytic tendency in their individual systems. In contrast, the high degradable capability of phenol resulted in its preferential degradation in the competitive system. (C) 2009 Elsevier B.V. All rights reserved.
Electrocatalytic activity of Pt nanoparticles deposited on porous TiO2 supports toward methanol oxidation
(2009-09-28)
Chen, Chung-Shou
;
Pan, Fu-Ming
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Porous TiO2 thin films were prepared on the Si substrate by hydrothermal method, and used as the Pt electrocatalyst support for methanol oxidation study. Well-dispersed Pt nanoparticles with a particle size of 5-7 nm were pulse-electrodeposited on the porous TiO2 support, which was mainly composed of the anatase phase after an annealing at 600 degrees C in vacuum. Cyclic voltammetry (CV) and CO stripping measurements showed that the Pt/TiO2 electrode had a high electrocatalytic activity toward methanol oxidation and an excellent CO tolerance. The excellent electrocatalytic performance of the electrode is ascribed to the synergistic effect of Pt nanoparticles and the porous TiO2 support on CO oxidation. The strong electronic interaction between Pt and the TiO2 support may modify CO chemisorption properties on Pt nanoparticles, thereby facilitating CO oxidation on Pt nanoparticles via the bifunctional mechanism and thus improving the electrocatalytic activity of the Pt catalyst toward methanol oxidation. (C) 2009 Elsevier B.V. All rights reserved.
Strong green photoluminescence from In(x)Ga(1-x)N/GaN nanorod arrays
(2009-09-28)
Hong, Chi-Chang
;
Ahn, Hyeyoung
;
Wu, Chen-Ying
;
Gwo, Shangjr
;
光電工程學系
We report intense green photoluminescence (PL) from vertically aligned indium gallium nitride (In(x)Ga(1-x)N) nanorod arrays. The formation of In(x)Ga(1-x)N/GaN-heterostructure nanorods increases the localization depth of the radially confined carriers (> 100 meV). Temperature dependent PL peak energy of InGaN nanorods shows the characteristic S-shaped behavior, indicating the prominent carrier trapping in band-tail states associated with the nonuniformity of In content. Time-resolved PL (TRPL) response decays biexponentially and the dominant slow decay component of TRPL for In(x)Ga(1-x)N nanorods is due to the transfer of excitons to the localized states before the radiative decay. (C) 2009 Optical Society of America
Sub-15fs ultraviolet pulses generated by achromatic phase-matching sum-frequency mixing
(2009-09-28)
Zhao, Baozhen
;
Jiang, Yongliang
;
Sueda, Keiich
;
Miyanaga, Noriaki
;
Kobayashi, Takayoshi
A broadband ultraviolet pulse with a spectral width of 44 nm was generated by achromatic sum-frequency mixing of an 805-nm pulse and ultrabroadband visible pulse. Angular dispersion was introduced to achieve broadband phase matching by a prism pair. The UV pulse was compressed to 13.2 fs with another prism pair, with energy of 600 nJ. (C) 2009 Optical Society of America
Electrocatalytic activity of Pt nanoparticles deposited on porous TiO(2) supports toward methanol oxidation
(2009-09-28)
Chen, Chung-Shou
;
Pan, Fu-Ming
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Porous TiO(2) thin films were prepared on the Si substrate by hydrothermal method, and used as the Pt electrocatalyst support for methanol oxidation study. Well-dispersed Pt nanoparticles with a particle size of 5-7 nm were pulse-electrodeposited on the porous TiO(2) support, which was mainly composed of the anatase phase after an annealing at 600 degrees C in vacuum. Cyclic voltammetry (CV) and CO stripping measurements showed that the Pt/TiO(2) electrode had a high electrocatalytic activity toward methanol oxidation and an excellent CO tolerance. The excellent electrocatalytic performance of the electrode is ascribed to the synergistic effect of Pt nanoparticles and the porous TiO(2) support on CO oxidation. The strong electronic interaction between Pt and the TiO(2) support may modify CO chemisorption properties on Pt nanoparticles, thereby facilitating CO oxidation on Pt nanoparticles via the bifunctional mechanism and thus improving the electrocatalytic activity of the Pt catalyst toward methanol oxidation. (C) 2009 Elsevier B.V. All rights reserved.
Strong green photoluminescence from InxGa1-xN/GaN nanorod arrays
(2009-09-28)
Hong, Chi-Chang
;
Ahn, Hyeyoung
;
Wu, Chen-Ying
;
Gwo, Shangjr
;
光電工程學系
We report intense green photoluminescence (PL) from vertically aligned indium gallium nitride (InxGa1-xN) nanorod arrays. The formation of InxGa1-xN/GaN-heterostructure nanorods increases the localization depth of the radially confined carriers (> 100 meV). Temperature dependent PL peak energy of InGaN nanorods shows the characteristic S-shaped behavior, indicating the prominent carrier trapping in band-tail states associated with the nonuniformity of In content. Time-resolved PL (TRPL) response decays biexponentially and the dominant slow decay component of TRPL for InxGa1-xN nanorods is due to the transfer of excitons to the localized states before the radiative decay. (C) 2009 Optical Society of America
Fabrication of optical filters based on polymer asymmetric Bragg couplers
(2009-09-28)
Chuang, Wei-Ching
;
Lee, An-Chen
;
Chao, Ching-Kong
;
Ho, Chi-Ting
;
機械工程學系
In this work, we successfully developed a process to fabricate dual-channel polymeric waveguide filters based on an asymmetric Bragg coupler (ABC) using holographic interference techniques, soft lithography, and micro molding. At the cross-and self-reflection Bragg wavelengths, the transmission dips of approximately -16.4 and -11.5dB relative to the 3dB background insertion loss and the 3dB transmission bandwidths of approximately 0.6 and 0.5nm were obtained from an ABC-based filter. The transmission spectrum overlaps when the effective index difference between two single waveguides is less than 0.002. (C) 2009 Optical Society of America
A hybrid of sequential rules and collaborative filtering for product recommendation
(2009-09-29)
Liu, Duen-Ren
;
Lai, Chin-Hui
;
Lee, Wang-Jung
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Customers' purchase behavior may vary over time. Traditional collaborative filtering (CF) methods make recommendations to a target customer based on the purchase behavior of customers whose preferences are similar to those of the target customer; however, the methods do not consider how the customers' purchase behavior may vary over time. In contrast, the sequential rule-based recommendation method analyzes customers' purchase behavior over time to extract sequential rules in the form: purchase behavior in previous periods double right arrow purchase behavior in the current period. If a target customer's purchase behavior history is similar to the conditional part of the rule, then his/her purchase behavior in the current period is deemed to be the consequent part of the rule. Although the sequential rule method considers the sequence of customers' purchase behavior over time, it does not utilize the target customer's purchase data for the current period. To resolve the above problems, this work proposes a novel hybrid recommendation method that combines the segmentation-based sequential rule method with the segmentation-based KNN-CF method. The proposed method uses customers' RFM (Recency, Frequency, and Monetary) values to cluster customers into groups with similar RFM values. For each group of customers, sequential rules are extracted from the purchase sequences of that group to make recommendations. Meanwhile, the segmentation-based KNN-CF method provides recommendations based on the target customer's purchase data for the current period. Then, the results of the two methods are combined to make final recommendations. Experiment results show that the hybrid method outperforms traditional CF methods. (C) 2009 Elsevier Inc. All rights reserved.
Modeling transient heat transfer in nuclear waste repositories
(2009-09-30)
Yang, Shaw-Yang
;
Yeh, Hund-Der
;
環境工程研究所
;
Institute of Environmental Engineering
The heat of high-level nuclear waste maybe generated and released from a canister at final disposal sites. The waste heat may affect the engineering properties of waste canisters, buffers, and backfill material in the emplacement tunnel and the host rock. This study addresses the problem of the heat generated from the waste canister and analyzes the heat distribution between the buffer and the host rock, which is considered as a radial two-layer heat flux problem. A conceptual model is first constructed for the heat conduction in a nuclear waste repository and then mathematical equations are formulated for modeling heat flow distribution at repository sites. The Laplace transforms are employed to develop a solution for the temperature distributions in the buffer and the host rock in the Laplace domain, which is numerically inverted to the time-domain solution using the modified Crump method. The transient temperature distributions for both the single- and multi-borehole cases are simulated in the hypothetical geological repositories of nuclear waste. The results show that the temperature distributions in the thermal field are significantly affected by the decay heat of the waste canister, the thermal properties of the buffer and the host rock, the disposal spacing, and the thickness of the host rock at a nuclear waste repository. (C) 2009 Elsevier B.V. All rights reserved.
Gene delivery process in a single animal cell after femtosecond laser microinjection
(2009-09-30)
Hosokawa, Yoichiroh
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Iguchi, Seriya
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Yasukuni, Ryohei
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Hiraki, Yuji
;
Shukunami, Chisa
Microinjection of extracellular molecules into a single animal cell was performed by an amplified femtosecond laser irradiation. When a single-shot laser pulse was focused on the plasma membrane of a single fibroblast from the mouse cell line NIH3T3 with a high-numerical aperture objective lens, a transient hole with a diameter of 1 mm was formed. The delivery process of extracellular molecules immediately after the hole formation was monitored by a fluorescence staining with fluoresceini-sothiocyanate-dextran (FITC-dextran). Then the gene expression was confirmed using a DNA plasmid of an enhanced green fluorescent protein (EGFP). The gene expression was observed when the laser pulse was focused first on the cellular membrane and then on the nuclear membrane, while the gene was not expressed when the laser was focused only on the cellular membrane. On the basis of these results, the efficiency of gene delivery by the femtosecond laser microinjection and the subsequent gene expression were clarified. (C) 2009 Elsevier B.V. All rights reserved.
Enhanced UV photoresponse in nitrogen plasma ZnO nanotubes
(2009-09-30)
Chantarat, N.
;
Chen, Yu-Wei
;
Chen, San-Yuan
;
Lin, Chin-Ching
;
材料科學與工程學系
The photoresponse behavior of one-dimensional ZnO nanowires (NWs) and nanotubes (NTs) grown on ITO-coated glass substrates via a wet-chemical route was investigated. The photoluminescence spectra exhibited a decrease in the deep-level intensity, indicating that the oxygen defects and impurities are occupied by the presence of N ions in the ZnO NT matrix after a nitrogen plasma treatment. I-V tests demonstrate an enhanced dark current (4.83 x 10(-7) A) after an extended plasma treatment of up to 900s for ZnO NTs compared to that (0.571 x 10(-7) A) of NWs. Furthermore, the ZnO NTs show the highest reliable photoresponse, 20 times that of NWs under UV irradiation (325 nm) in air at room temperature. It is believed that nitrogen plasma ZnO nanotubes can potentially be useful in the designs of 1D ZnO-based solar cells and optoelectronic devices.
打造別人的幸福
(2009-09-30)
吳肇銘
;
開放教育推動中心
;
Open Education Office
課程日期： 2009年09月30日(三) 演講人：吳肇銘先生內容摘要：在本次的演講中，吳肇銘老師以「為什模要唸大學」作為演講開頭，讓學生們思考了許久。他認為應該以「專業」作為創造別人幸福的出發點，因此吳老師利用資訊管理的專業，進行了許多與服務學習相關的專案。內容：影音實況影音(*.flv檔) 實況影音(*.wmv檔)
Entry mode choice in China's regional distribution markets: Institution vs. transaction costs perspectives
(2009-10-01)
Chen, Yung-Ray
;
Yang, Chyan
;
Hsu, Sue-Ming
;
Wang, Yau-De
;
管理科學系
In this paper, we investigate the entry mode choice of a leading Taiwanese food company in setting up regional distributors in China's 3 12 sales districts. Our study shows that, in entry mode decisions, the institutional factors are more important than transaction cost considerations. Both formal and informal institutions are considered. Formal institutions refer to government prescribed institutions (laws and regulations), while informal institutions refer to rules prescribed by the industry and the society. Both institutions are shown to affect the entry mode choices but one important type of institution, professional norms, is conspicuously missing in China. Professional norms exert peer pressures on the practitioners in the same profession, forcing their behaviors to conform to a common pattern. In the absence of professional norms, the roles of network ties and mimetic behaviors are heightened and they become a proxy for professional norms. As a foreign enterprise operating in China's local markets, the Taiwanese food company attained legitimacy by forming alliances with local wholesalers and by following its predecessors in selecting organization forms. (C) 2008 Elsevier Inc. All rights reserved.
建置以“航段”為基之空服員整合型排班決策支援系統
(2009-10-01)
馬文娜
;
藍柏鼎
;
宮大川
;
Wen-Na Ma
;
Po-Ting Lan
過去受限於電腦速度慢與空服員排班問題複雜性，傳統上分成組員勤務組合產生與組員指派兩階段求解空服員排班問題，導致人員指派效果不佳，且因短程航線問題特性造成排班單位過大，指派不易，因此本研究考量台灣航空業實務運作之限制，將組員勤務組合產生與組員指派兩階段整合爲一階段求解，建立一個以「航段」爲排班基礎之最佳空服員排班整合模式，以提升排班接續性和人員利用率。本研究利用基因演算法求解空服員排班規劃與指派問題，並與分枝界限法所得之最佳解比較，結果顯示本研究所提出之排班整合模式與求解演算法，可有效地處理空服員排班問題。最後本研究以Java 程式語言爲基礎，設計一套整合型排班決策支援系統，可規劃符合經濟效益的空服員排班表，並有效地解決空服員調度與空載和過夜問題。
An optimization algorithm for cutting stock problems in the TFT-LCD industry
(2009-10-01)
Tsai, Jung-Fa
;
Hsieh, Ping-Lun
;
Huang, Yao-Huei
;
資訊管理與財務金融系註：原資管所+財金所
;
Department of Information Management and Finance
Due to lack of efficient approaches of mixed production, the present production approach of the TFT-LCD industry is batch production that each glass substrate is cut into LCD plates of one size only. This study proposes an optimization algorithm for cutting stock problems of the TFT-LCD industry. The proposed algorithm minimizes the number of glass substrates required to satisfy the orders, therefore reducing the production costs. Additionally, the solution of the proposed algorithm is a global optimum which is different from a local optimum or a feasible solution that is found by the heuristic algorithm. Numerical examples are also presented to illustrate the usefulness of the proposed algorithm. (C) 2009 Elsevier Ltd. All rights reserved.
Phenomenological analysis of domain width in rhombohedral BiFeO(3) films
(2009-10-01)
Huang, C. W.
;
Chen, Lang
;
Wang, J.
;
He, Q.
;
Yang, S. Y.
The experimental domain size scaling law in epitaxial BiFeO(3) films shows a different behavior from predictions of the conventional elastic domains: the (101)-type 71 degrees domains are much wider than that of (100)-type 109 degrees despite the larger domain-wall energy in (100) boundary. A phenomenological analysis for rhombohedral BiFeO(3) film is proposed, and it reveals that both the depolarizing energy and the elastic energy are indispensable for the equilibrium domain structures. With the increase in the asymmetrical electrostatic boundary on the film surfaces, the dominant domain scaling mechanism changes from electrostatic-dependent domain structure to elastic-dependent one, which is consistent with the experimental data. The present results highlight the general role of depolarizing field in rhombohedral domain structures.
Joint Source/Relay Precoder Design in Nonregenerative Cooperative Systems Using an MMSE Criterion
(2009-10-01)
Tseng, Fan-Shuo
;
Wu, Wen-Rong
;
Wu, Jwo-Yuh
;
電子工程學系及電子研究所
;
友訊交大聯合研發中心
This paper considers transmitter precoding in an amplify-and-forward cooperative system where multiple antennas are equipped at the source, the relay, and the destination. Existing methods for the problem only consider the design of the relay precoder. To further improve the performance, we include the source precoder into the design. Using a minimum-means-quare-error (MMSE) criterion, we propose a joint source/relay precoder design method, taking both the direct and relay links into account. It is shown that the MMSE is a highly nonlinear function of the precoding matrices, and a direct minimization is not feasible. To facilitate analysis, we propose to design the precoders toward first diagonalizing the MSE matrix of the relay link. This imposes certain structural constraints on both precoders that allow us to derive an analytically tractable MSE upper bound. By conducting minimization with respect to this bound, the solution can be obtained by an iterative water-filling technique.