Browsing by Issue Date, starting with "2010-06-25"

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Separation of open-cage fullerenes using nonaqueous capillary electrophoresis
(2010-06-25)
Su, Hsiu-Li
;
Kao, Wan-Chun
;
Lee, Cheng-yu
;
Chuang, Shih-Ching
;
Hsieh, You-Zung
In this study, nonaqueous capillary electrophoresis (NACE) was used to separate three open-cage fullerenes. Trifluoroacetic acid (TFA) was used as the nonaqueous background electrolyte to change the analytes mobilities. The selectivity and separation efficiency were critically affected by the nature of the buffer system, the choice of organic solvent, and the concentrations of TFA and sodium acetate (NaOAc) in the background electrolyte. The optimized separation occurred using 200 mM TFA/20 mM NaOAc in MeOH/acetonitrile (10:90, v/v), providing highly efficient baseline separation of the open-cage fullerenes within 5 min. The migration time repeatability for the three analytes was less than 1% (relative standard deviation). Thus, NACE is a rapid, useful alternative to high-performance liquid chromatography for the separation of open-cage fullerenes. (C) 2010 Elsevier B.V. All rights reserved.
The effects of carbon content on the microstructure and elevated temperature tensile strength of a nickel-base superalloy
(2010-06-25)
Wei, Chao-Nan
;
Bor, Hui-Yun
;
Chang, Li
;
材料科學與工程學系
;
Department of Materials Science and Engineering
This study investigates how carbon content affects the microstructure and elevated temperature tensile strength of fine-grain CM-681LC superalloy. Experimental results indicate that increasing the carbon content from 0.11 to 0.15 wt% increases the total area fraction of carbides considerably. However, the two alloys exhibit similar carbide shapes and sizes, probably because the short solidification time in the fine-grain process limits the growth of carbides. Besides, carbon addition significantly reduces the area fraction of gamma-gamma' eutectic phases from 8.6 to 5.3% because the eutectic phase forming elements are consumed by (Ta, Hf)C carbides and the carbides occupy the position of gamma-gamma' eutectic phases during the solidification. Further, the carbon addition improves the mechanical strength by about 6% and the elongation by about 50% in tensile tests at 760 degrees C and yields favorable tensile performance at elevated temperature. (C) 2010 Elsevier B.V. All rights reserved.
Helicobacter pylori-derived Heat shock protein 60 enhances angiogenesis via a CXCR2-mediated signaling pathway
(2010-06-25)
Lin, Chen-Si
;
He, Pei-Juin
;
Hsu, Wei-Tung
;
Wu, Ming-Shiang
;
Wu, Chang-Jer
Helicobacter pylori is a potent carcinogen associated with gastric cancer malignancy. Recently. H. pylori Heat shock protein 60 (HpHSP60) has been reported to promote cancer development by inducing chronic inflammation and promoting tumor cell migration. This study demonstrates a role for HpHSP60 in angiogenesis, a necessary precursor to tumor growth. We showed that HpHSP60 enhanced cell migration and tube formation, but not cell proliferation, in human umbilical vein endothelial cells (HUVECs). HpHSP60 also indirectly promoted HUVEC proliferation when HUVECs were co-cultured with supernatants collected from HpHSP60-treated AGS or THP-1 cells. The angiogenic array showed that HpHSP60 dramatically induced THP-1 cells and HUVECs to produce the chemotactic factors IL-8 and GRO. Inhibition of CXCR2, the receptor for IL-8 and GRO, or downstream PLC beta 2/Ca2+-mediated signaling, significantly abolished HpHSP60-induced tube formation. In contrast, suppression of MAP K or PI3 K signaling did not affect HpHSP60-mediated tubulogenesis. These data suggest that HpHSP60 enhances angiogenesis via CXCR2/PLC beta 2/Ca2+ signal transduction in endothelial cells. (C) 2010 Elsevier Inc. All rights reserved.
Transition of stable rectification to resistive-switching in Ti/TiO(2)/Pt oxide diode
(2010-06-28)
Huang, Jiun-Jia
;
Kuo, Chih-Wei
;
Chang, Wei-Chen
;
Hou, Tuo-Hung
;
電機工程學系
We have fabricated a Ti/TiO(2)/Pt oxide diode with excellent rectifying characteristics by the asymmetric Schottky barriers at the Ti/TiO(2) (0.13 eV) and the TiO(2)/Pt (0.73 eV) interfaces. Instead of homogeneous conduction, the current transport is governed by the localized oxygen-deficient TiO(2) filaments. In addition, the reproducible resistive-switching exists in the same structure, triggered by the forming process. The transition between two modes is ascribed to the destruction of the interface barriers at forming. The rectification stable up to 125 degrees C and 10(3) cycles under +/- 3 V sweep without interference with resistive-switching shows satisfactory reliability of TiO(2) diodes for one diode-one resistor memory devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3457866]
High extraction efficiency GaN-based light-emitting diodes on embedded SiO2 nanorod array and nanoscale patterned sapphire substrate
(2010-06-28)
Huang, Hung-Wen
;
Huang, Jhi-Kai
;
Kuo, Shou-Yi
;
Lee, Kang-Yuan
;
Kuo, Hao-Chung
In this paper, GaN-based LEDs with a nanoscale patterned sapphire substrate (NPSS) and a SiO2 photonic quasicrystal (PQC) structure on an n-GaN layer using nanoimprint lithography are fabricated and investigated. The light output power of LED with a NPSS and a SiO2 PQC structure on an n-GaN layer was 48% greater than that of conventional LED. Strong enhancement in output power is attributed to better epitaxial quality and higher reflectance resulted from NPSS and PQC structures. Transmission electron microscopy images reveal that threading dislocations are blocked or bended in the vicinities of NPSS layer. These results provide promising potential to increase output power for commercial light emitting devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456385]
Bias-induced oxygen adsorption in zinc tin oxide thin film transistors under dynamic stress
(2010-06-28)
Chen, Yu-Chun
;
Chang, Ting-Chang
;
Li, Hung-Wei
;
Chen, Shih-Ching
;
Lu, Jin
This study investigates the effects of bias-induced oxygen adsorption on the electrical characteristic instability of zinc tin oxide thin film transistors in different ambient oxygen partial pressures. When oxygen pressure is largest, the threshold voltages showed the quickest increase but the slowest recovery during the stress phase and recovery phase, respectively. This finding corresponds to the charge trapping time constant and recovery time constant, which are extracted by fitting the stretched-exponential equation and which exhibit a relationship with oxygen pressure. We suggest that the gate bias reduces the activation energy of oxygen adsorption during gate bias stress. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3457996]
Influence of electrode material on the resistive memory switching property of indium gallium zinc oxide thin films
(2010-06-28)
Chen, Min-Chen
;
Chang, Ting-Chang
;
Tsai, Chih-Tsung
;
Huang, Sheng-Yao
;
Chen, Shih-Ching
The InGaZnO taken as switching layer in resistive nonvolatile memory is proposed in this paper. The memory cells composed of Ti/InGaZnO/TiN reveal the bipolar switching behavior that keeps stable resistance ratio of 10(2) with switching responses over 100 cycles. The resistance switching is ascribed to the formation/disruption of conducting filaments upon electrochemical reaction near/at the bias-applied electrode. The influence of electrode material on resistance switching is investigated through Pt/InGaZnO/TiN devices, which perform the unipolar and bipolar behavior as applying bias on Pt and TiN electrode, respectively. Experimental results demonstrate that the switching behavior is selective by the electrode. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456379]
Transition of stable rectification to resistive-switching in Ti/TiO2/Pt oxide diode
(2010-06-28)
Huang, Jiun-Jia
;
Kuo, Chih-Wei
;
Chang, Wei-Chen
;
Hou, Tuo-Hung
;
電子工程學系及電子研究所
We have fabricated a Ti/TiO2/Pt oxide diode with excellent rectifying characteristics by the asymmetric Schottky barriers at the Ti/TiO2 (0.13 eV) and the TiO2/Pt (0.73 eV) interfaces. Instead of homogeneous conduction, the current transport is governed by the localized oxygen-deficient TiO2 filaments. In addition, the reproducible resistive-switching exists in the same structure, triggered by the forming process. The transition between two modes is ascribed to the destruction of the interface barriers at forming. The rectification stable up to 125 degrees C and 10(3) cycles under +/- 3 V sweep without interference with resistive-switching shows satisfactory reliability of TiO2 diodes for one diode-one resistor memory devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3457866]
The low-lying states of the scandium dimer
(2010-06-28)
Camacho, Cristopher
;
Witek, Henryk A.
;
Cimiraglia, Renzo
;
應用化學系
;
應用化學系分子科學碩博班
A systematic investigation of low-lying states of Sc(2) using multireference perturbation theory (NEVPT2 and NEVPT3) indicates that the ground state of this system is 5 Sigma(u) with r(e)= 2.611 angstrom, w(e)= 241.8 cm(-1), and De= 1.78 eV. This state is closely followed by other low-lying states of Sc(2): (3)Sigma(u)-, (5)Delta(u), (3)Pi(g), (1)Pi(g), and (1)Sigma(u)-. Our energy ordering of the (5)Sigma(u)- and (3)Sigma(u)- states confirms the recent MRCI results of Kalemos et al. [J. Chem. Phys. 132, 024309 (2010)] and is at variance with the earlier diffusion Monte Carlo predictions of Matxain et al. [J. Chem. Phys. 128, 194315 (2008)]. An excellent agreement between the second-and third-order NEVPT results and between the computed and experimental values of omega(e) (241.8 versus 238.9 cm(-1)) for the (5)Sigma(u)- state suggests high accuracy of our predictions. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3442374]
High extraction efficiency GaN-based light-emitting diodes on embedded SiO(2) nanorod array and nanoscale patterned sapphire substrate
(2010-06-28)
Huang, Hung-Wen
;
Huang, Jhi-Kai
;
Kuo, Shou-Yi
;
Lee, Kang-Yuan
;
Kuo, Hao-Chung
In this paper, GaN-based LEDs with a nanoscale patterned sapphire substrate (NPSS) and a SiO(2) photonic quasicrystal (PQC) structure on an n-GaN layer using nanoimprint lithography are fabricated and investigated. The light output power of LED with a NPSS and a SiO(2) PQC structure on an n-GaN layer was 48% greater than that of conventional LED. Strong enhancement in output power is attributed to better epitaxial quality and higher reflectance resulted from NPSS and PQC structures. Transmission electron microscopy images reveal that threading dislocations are blocked or bended in the vicinities of NPSS layer. These results provide promising potential to increase output power for commercial light emitting devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3456385]
Electrical conductivity beyond a linear response in layered superconductors under a magnetic field
(2010-06-29)
Tinh, Bui Duc
;
Li, Dingping
;
Rosenstein, Baruch
;
電子物理學系
;
Department of Electrophysics
The time-dependent Ginzburg-Landau approach is used to investigate nonlinear response of a strongly type-II superconductor. The dissipation takes a form of the flux flow which is quantitatively studied beyond linear response. Thermal fluctuations, represented by the Langevin white noise, are assumed to be strong enough to melt the Abrikosov vortex lattice created by the magnetic field into a moving vortex liquid and marginalize the effects of the vortex pinning by inhomogeneities. The layered structure of the superconductor is accounted for by means of the Lawrence-Doniach model. The nonlinear interaction term in dynamics is treated within self-consistent Gaussian approximation and we go beyond the often used lowest Landau level approximation to treat arbitrary magnetic fields. The I-V curve is calculated for arbitrary temperature and the results are compared to experimental data on high-T-c. superconductor YBa2Cu3O7-delta.
SECONDARY CONVERGENCE IN FEMTOSECOND LASER TRAPPING
(2010-06-30)
Jiang, Yuqiang
;
Ma, Cungen
;
Oh, Isamu
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Hosokawa, Yoichiroh
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Masuhara, Hiroshi
When femtosecond laser pulses pass through a trapped polystyrene bead, water breakdown is induced even though the energy of laser pulse is much lower compared to the threshold value of breakdown when the femtosecond laser directly irradiates in water. This mechanism is assigned to the secondary convergence of the laser by the trapped bead.
A modified support vector machine based prediction model on streamflow at the Shihmen Reservoir, Taiwan
(2010-06-30)
Li, Pei-Hao
;
Kwon, Hyun-Han
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Sun, Liqiang
;
Lall, Upmanu
;
Kao, Jehng-Jung
The uncertainty of the availability of water resources during the boreal winter has led to significant economic losses in recent years in Taiwan. A modified support vector machine (SVM) based prediction framework is thus proposed to improve the predictability of the inflow to Shihmen reservoir in December and January, using climate data from the prior period. Highly correlated climate precursors are first identified and adopted to predict water availability in North Taiwan. A genetic algorithm based parameter determination procedure is implemented to the SVM parameters to learn the non-linear pattern underlying climate systems more flexibly. Bagging is then applied to construct various SVM models to reduce the variance in the prediction by the median of forecasts from the constructed models. The enhanced prediction ability of the proposed modified SVM-based model with respect to a bagged multiple linear regression (MLR), simple SVM, and simple MLR model is also demonstrated. The results show that the proposed modified SVM-based model outperforms the prediction ability of the other models in all of the adopted evaluation scores. Copyright (C) 2009 Royal Meteorological Society
Optical fine structures of highly quantized InGaAs/GaAs self-assembled quantum dots
(2010-06-30)
Ramirez, H. Y.
;
Lin, C. H.
;
Chao, C. C.
;
Hsu, Y.
;
You, W. T.
A theoretical model for the electron-hole exchange interaction in three-dimensionally (3D) confining semiconductor nanostructures is presented to explain the observed decreasing tendency of the fine-structure splittings (FSSs) of small InGaAs/GaAs self-assembled quantum dots (QDs) with increasing the emission energies. The experimentally revealed FSS reduction is shown to be highly associated with the significant 3D spreading of electronic orbitals and reduced overlap of electron and hole wave functions in small and/or Ga-diffused QDs. The combination of quantum size and Ga-diffusion effects substantially reduces the averaged e-h exchange interaction and leads to the reduced FSSs in the regime of high emission energy.
Functional imprinting structures on GaN-based light-emitting diodes for light pattern modulation and light extraction efficiency enhancement
(2010-07-01)
Tu, Sheng-Han
;
Wu, Shang-Yen
;
Lee, Yeeu-Chang
;
Pan, Jui-Wen
;
Kuo, Cheng-Huang
In this study, we demonstrated a simple method that can be used to simultaneously modulate the far field pattern and enhance the light extraction of GaN-based light-emitting diodes (LEDs). In this method, microstructures were imprinted on a reliable spin-on-glass surface on top of a transparent conductive layer. The far-field pattern was modulated using microoptical structures, and at the same time, the light extraction was enhanced owing to the small refractive index difference and surface roughness. There was no decrease in the electrical performance of these devices. The peak intensity shifted from 0 to 22A degrees in one-dimensional (1D) asymmetrically blazed periodic structures, and a flattened distribution with a uniform intensity within a span of 110A degrees was observed in two-dimensional (2D) symmetrically periodic structures. This method achieved 13 and 40% light enhancements for 1D and 2D structures, respectively.
A High-Performance 30-nm Gate-All-Around Poly-Si Nanowire Thin-Film Transistor With NH(3) Plasma Treatment
(2010-07-01)
Lee, Chen-Ming
;
Tsui, Bing-Yue
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel 30-nm gate-all-around (GAA) polycrystalline-silicon (poly-Si) nanowire (NW) thin-film transistor (TFT) is reported for the first time. Owing to the NW and GAA structure, the channel electric potential is well controlled by the gate electrode. After NH(3) plasma treatment for defects passivation, the values of 0.97 V, 224 mV/dec., and 0.895 V/V of threshold voltage, subthreshold swing, and drain-induced barrier lowering are achieved, respectively. A high driving current of 459 mu A/mu m and an ON-state/OFF-state current ratio of 5 x 10(7) are also obtained. These excellent characteristics indicate that the ultrasmall GAA NW poly-Si TFT would have the potential to be applied in the 3-D integrated-circuit or system-on-panel field.
Structured backward error for palindromic polynomial eigenvalue problems
(2010-07-01)
Li, Ren-Cang
;
Lin, Wen-Wei
;
Wang, Chern-Shuh
;
應用數學系
;
Department of Applied Mathematics
A detailed structured backward error analysis for four kinds of palindromic polynomial eigenvalue problems (PPEP) (Sigma(d)(l=0)A(l)lambda(l)) x = 0, A(d-l) = epsilon A(l)(star) for l = 0, 1, ..., left perpendiculard/2right perpendicular, where star is one of the two actions: transpose and conjugate transpose, and epsilon is an element of {+/- 1}. Each of them has its application background with the case star taking transpose and epsilon = 1 attracting a great deal of attention lately because of its application in the fast train modeling. Computable formulas and bounds for the structured backward errors are obtained. The analysis reveals distinctive features of PPEP from general polynomial eigenvalue problems (PEP) investigated by Tisseur (Linear Algebra Appl 309: 339-361, 2000) and by Liu and Wang (Appl Math Comput 165: 405-417, 2005).
Fabrication of Ni Nanostructures on p-Si by Scanning Probe Lithography on Si(3)N(4) Films and Selective Electrodeposition
(2010-07-01)
Lin, Chi-Yuan
;
Chang, Chung-Shun
;
Chien, Forest S. -S.
;
光電工程學系
;
Department of Photonics
Ni-Si nano Schottky junctions are fabricated by the combined process of scanning probe lithography and electrodeposition. The Si(3)N(4) film was patterned by probe-induced oxidation and became a mask for selective electrodeposition of Ni on p-Si substrate. The Ni pattern consists of Ni nano dots, whose diameter is less then 60 nm. The composition and ferromagnetism of Ni dots are verified by energy dispersive spectrum and magnetic force microscopy. The schottky barrier of Ni-Si nano contact is 0.52 V determined by the I-V measurement of conducting atomic force microscopy (CAFM). From current mapping images, it shows that chemical impurity at the Ni-Si interfaces can result in the poor conductance of the junctions.
Mining the R&D innovation performance processes for high-tech firms based on rough set theory
(2010-07-01)
Wang, Chun-Hsien
;
Chin, Yang-Chieh
;
Tzeng, Gwo-Hshiung
;
管理科學系
;
科技管理研究所
The research and development (R&D) innovation of firms continues to be viewed as an important source of competitive advantage to academics and practitioners. To explore and extract the R&D innovation decision rules, it is important to understand how the R&D innovation rule-base works. However, many studies have not yet adequately induced and extracted the decision rule of R&D innovation and performance based on the characteristics and components of the original data rather than on post-determination models. The analysis of this study is grounded in the taxonomy of induction-related activities using a rough set theory approach or rule-based decision-making technique to infer R&D innovation decision rules and models linking R&D innovation to sales growth. The rules developed using rough set theory can be directly translated into a path-dependent flow network to infer decision paths and parameters. The flow network graph and cause-and-effect relationship of decision rules are heavily exploited in R&D innovation characteristics. In addition, an empirical case of R&D innovation performance will be illustrated to show that the rough sets model and the flow network graph are useful and efficient tools for building R&D innovation decision rules and providing predictions. We will then illustrate that integrating the flow network graph with rough set theory can fully reflect the characteristics of R&D innovation, and, through the established model, we can obtain a more reasonable result than with artificial influence. Crown Copyright (C) 2009 Published by Elsevier Ltd. All rights reserved.
VPN Gateways over Network Processors: Implementation and Evaluation
(2010-07-01)
Lin, Yi-Neng
;
Lin, Ying-Dar
;
Lai, Yuan-Cheng
;
Lin, Chuan-Hung
;
資訊工程學系
Networking applications, such as VPN and content filtering, demand extra computing power in order to meet the throughput requirement nowadays. In addition to pure ASIC solutions, network processor architecture is emerging as an alternative to scale up data-plane processing while retaining design flexibility. This article, rather than proposing new algorithms, illustrates the experience in developing IPSec-based VPN gateways over network processors, and investigates the performance issues. The external benchmarks reveal that the system can reach 45Mbps for IPSec using 3DES algorithm, which improves by 350% compared to single XScale core processor and parallels the throughput of a PIII 1GHz processor. Through the internal benchmarks, we analyze the turnaround times of the main functional blocks, and identify the core processor as the performance bottleneck for both packet forwarding and IPSec processing.