Browsing by Issue Date, starting with "2007-04-07"

Now showing 1 - 20 of 59864

Infrared absorption of C6H5SO2 detected with time-resolved Fourier-transform spectroscopy
(2007-04-07)
Chu, Li-Kang
;
Lee, Yuan-Pern
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
C6H5SO2 radicals were produced upon irradiation of three flowing mixtures: C6H5SO2Cl in N-2, C6H5Cl and SO2 in CO2, and C6H5Br and SO2 in CO2, with a KrF excimer laser at 248 nm. A step-scan Fourier-transform spectrometer coupled with a multipass absorption cell was employed to record the time-resolved infrared (IR) absorption spectra of reaction intermediates. Two transient bands with origins at 1087.7 and 1278.2 cm(-1) are assigned to the SO2-symmetric and SO2-antisymmetric stretching modes, respectively, of C6H5SO2. Calculations with density-functional theory (B3LYP/aug-cc-pVTZ and B3P86/aug-cc-pVTZ) predict the geometry and vibrational wave numbers of C6H5SO2 and C6H5OSO. The vibrational wave numbers and IR intensities of C6H5SO2 agree satisfactorily with the observed new features. Rotational contours of IR spectra of C6H5SO2 simulated based on predicted molecular parameters agree satisfactorily with experimental results for both bands. The SO2-symmetric stretching band is dominated by a- and c-type rotational structures and the SO2-antisymmetric stretching band is dominated by a b-type rotational structure. When C6H5SO2Cl was used as a precursor of C6H5SO2, C6H5SO2Cl was slowly reproduced at the expense of C6H5SO2, indicating that the reaction Cl+C6H5SO2 takes place. When C6H5Br/SO2/CO2 was used as a precursor of C6H5SO2, features at 1186 and 1396 cm(-1) ascribable to C6H5SO2Br were observed at a later period due to secondary reaction of C6H5SO2 with Br. Corresponding kinetics based on temporal profiles of observed IR absorption are discussed. (c) 2007 American Institute of Physics.
Effect of intermolecular hydrogen bonding on low-surface-energy material of poly(vinylphenol)
(2007-04-07)
Lin, Han-Ching
;
Wang, Chih-Feng
;
Kuo, Shiao-Wei
;
Tung, Pao-Hsiang
;
Huang, Chih-Feng
We discovered that poly(vinylphenol) (PVPh) possesses an extremely low surface energy (15.7 mJ/m(2)) after a simple thermal treatment procedure, even lower than that of poly(tetrafluoroethylene) ( 2.0 mJ/m(2)) calculated on the basis of the two-liquid geometric method. Infrared analyses indicate that the intermolecular hydrogen bonding of PVPh decreases by converting the hydroxyl group into a free hydroxyl and increasing intramolecular hydrogen bonding after thermal treatment. PVPh results in a lower surface energy because of the decrease of intermolecular hydrogen bonding between hydroxyl groups. In addition, we also compared surface energies of PVPh-co-PS (polystyrene) copolymers (random and block) and their corresponding blends. Again, these random copolymers possess a lower fraction of intermolecular hydrogen bonding and surface energy than the corresponding block copolymers or blends after similar thermal treatment. This finding provides a unique and easy method to prepare a low-surface-energy material through a simple thermal treatment procedure without using fluoro polymers or silicones.
秋冬之天
(2007-04-07)
管管
Resistance switching properties of sol-gel derived SrZrO3 based memory thin films
(2007-04-07)
Liu, Chih-Yi
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Sol-gel derived SrZrO3 based metal/insulator/metal (MIM) devices were fabricated to study their reversible resistance switching properties operated by dc voltage sweep and voltage pulses. The leakage-state of the device is changed from the original-state and finally switched between the high leakage-state (H-state) and the low leakage-state (L-state). The resistance ratio between the H-state and the L-state is about 10(4), and the leakage-states are not changed without power supply, which is suitable for nonvolatile memory application. The conduction mechanisms of the original-state, the H-state and the L-state obey Schottky emission, Frenkel-Poole emission and Ohmic conduction, respectively. The first device resistance switching, called the forming process, changed from the original-state to the H-state. The switching time from the H-state to the L-state is much longer than that from the L-state to the H-state and that of the forming process. The decay behaviours of leakage current after resistance switching are influenced by pulse width and voltage stress directions. The switching time can be accumulated to switch the device from the H-state to the L-state, which could be a guide to multi-level memory applications. The model of conducting paths can well explain the electrical behaviours of our resistance switching devices.
Optical characterization of CO2-laser-ablated Si-rich SiOx
(2007-04-09)
Lin, Gong-Ru
;
Lin, Chun-Jung
;
Chang, Yia-Chung
;
光電工程學系
;
Department of Photonics
Anomalous absorption and the corresponding change in the optical band gap of a CO2-laser-ablated Si-rich SiO2 (SiOx) film are studied. The optical band gap energy of as-grown nonstoichiometric SiOx is slightly reduced by increasing Si-Si bonds as compared to quartz. After rapid thermal annealing using a CO2 laser, the dehydrogenation of SiOx film further increases the Si-Si bonding states and redshifts the optical band gap by 1 eV. Laser ablation is initiated at a laser intensity of > 7.5 kW/cm(2), leaving numerous luminescent centers that are related to neutral oxygen vacancy defects, increasing the absorption coefficient and related optical band gap energy, and reducing the refractive index in partially annealed SiOx. (c) 2007 American Institute of Physics.
Thermomigration in flip-chip SnPb solder joints under alternating current stressing
(2007-04-09)
Hsiao, Hsiang-Yao
;
Chen, Chih
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Thermomigration in flip-chip solder joints is investigated using alternating currents and infrared microscopy to decouple it from electromigration effect. It is found that the thermal gradient in solder bump can be as high as 2143 degrees C/cm when 9.2x10(4) A/cm(2) was applied at 100 degrees C. Markers fabricated by focus ion beam are employed to measure the thermomigration rate. The thermomigration flux is measured to be 3.3x10(13) at./cm(2). With the known thermal gradient, the molar heat of 26.8 kJ/mole has been obtained for the transport of Pb. (c) 2007 American Institute of Physics.
Electrically driven integrated photonic crystal nanocavity coupled surface emitting laser
(2007-04-09)
Huang, Shih-Chieh
;
Yang, Tsung-Hua
;
Lee, Chien-Ping
;
Lin, Sheng-Di
;
電子工程學系及電子研究所
Single mode surface emitting lasers with photonic crystal nanocavities integrated with electrically driven strained quantum well laser diodes are demonstrated. The photonic crystal serves as an end mirror for the laser cavity, while the nanocavities serve as wavelength selective high Q surface emitters. The laser emission from the nanocavities had excellent temperature stability. The wavelength shift versus temperature was about five times better than that of regular quantum well lasers. Dual wavelength emission from two side by side slightly different cavities was also demonstrated. Laser emission with two wavelengths of Delta lambda=0.8 nm was obtained. (c) 2007 American Institute of Physics.
Influence of thin metal base thickness on the performance of CuPc vertical organic triodes
(2007-04-09)
Cheng, Shiau-Shin
;
Yang, Chuan-Yi
;
Chuang, You-Che
;
Ou, Chun-Wei
;
Wu, Meng-Chyi
In this letter, the characteristics of vertical organic triodes fabricated by using two copper phthalocyanine (CuPc) back-to-back Schottky diodes with different metal base thicknesses are reported. The vertical organic triodes exhibit pronounced saturation regions in the output current-voltage characteristics. The common-emitter current gain reduces with increasing the Al base thickness due to the increase of recombination current at the base end resulted from the reduction of opening voids in the Al metal film. The common-emitter current gain of the device with 4.5 nm thick Al base reaches 1.9 at V-CE=-6 V and J(B)=2.5 mA/cm(2). (c) 2007 American Institute of Physics.
Microstructure and recording mechanism of Ge/Au bilayer media for write-once optical disc
(2007-04-09)
Wu, T. H.
;
Kuo, P. C.
;
Fang, Yen-Hsiang
;
Chen, Jung-Po
;
Yen, Po-Fu
The recording mechanism of Ge/Au bilayer and its dynamic tests for write-once blue laser high density DVD (HD DVD) are investigated. It is found that Ge2Au3 phase is nucleated between amorphous Ge and crystalline Au layer after room temperature deposition. Crystallization of Ge/Au interface layer at 170-190 degrees C is induced by the nucleated Ge2Au3 sites at the interface, the bilayer structure is further heated to 200-450 degrees C. After heating above 320 degrees C, crystallized Ge are segregated at the grain boundary. The dynamic test results show that this Ge/Au bilayer films can be applied to 1x-2x HD DVD-R. (c) 2007 American Institute of Physics.
High quality factor microcavity lasers realized by circular photonic crystal with isotropic photonic band gap effect
(2007-04-09)
Lee, Po-Tsung
;
Lu, Tsan-Wen
;
Fan, Jyun-Hao
;
Tsai, Feng-Mao
;
光電工程學系
The photonic band gap (PBG) effect and its isotropy of sunflower-type circular photonic crystal (CPC) are obtained and investigated from the transmission spectra performed by finite-difference time-domain (FDTD) method. The PBG directional width variation is found to be only 6.7%. A well-confined whispering gallery mode (WGM) with azimuthal number of 6 is obtained by FDTD simulation from the CPC microcavity formed by seven missing air holes (C2). Ascribed to the deep and isotropic PBG confinement, the WGM lasing with very-low threshold (similar to 0.13 mW) and very-high-quality (Q) factor (> 10 000) is obtained from well-fabricated CPC C2 microcavity lasers. (c) 2007 American Institute of Physics.
Architecture and method for fine granularity scalable video coding
(2007-04-10)
Huang
;
Hsiang-Chun
;
Wang
;
Chung-Neng
;
Chiang
A robust fine granularity scalability video encoding includes a base layer encoder and an enhancement layer encoder in which motion compensated difference images are generated by comparing an original image to predicted images at base layer and enhancement layer with motion compensation. Based on leaky and partial predictions, a high quality reference image is constructed at the enhancement layer to improve temporal prediction. In the construction of the high quality reference image, one parameter β controls the number of bitplanes of the enhancement layer difference coefficients used and another parameter α controls the amount of predictive leak. A spatial scalability module allows the processed pictures at the base layer and the enhancement layer to have identical or different spatial resolutions.
雙攝影機取像與追蹤方法
(2007-04-11)
韓欽銓
;
謝明逢
;
鄭智明
本發明提供一種雙攝影機取像與追蹤方法，其係整合雙攝影機作取像與目標影像追蹤，包括兩部分，第一部份為影像對應參數校正程序，第二部分則為輔助追蹤模式程序，由於攝影機擺設位置互相靠近，可以簡化攝影機校正之複雜度，利用已校正之參數，對公共開放空間之目標物取得清晰影像；另外，利用雙攝影機彼此的關係，加上擷取清晰影像，輔助交錯目標物之判別，改進公共空間目標物之追蹤成效。因此本發明提供一種雙攝影機取像與追蹤方法，可對多目標物追蹤，同時獲得清晰之目標物影像，並利用各攝影機的資訊，有效改進追蹤效果。
A closed-form solution for a confined flow into a tunnel during progressive drilling in a multi-layer groundwater flow system
(2007-04-12)
Yang, Shaw-Yang
;
Yeh, Hund-Der
;
環境工程研究所
;
Institute of Environmental Engineering
A mathematical model is developed to describe the groundwater inflow into a tunnel in a multi-layer aquifer system. Based on the model, the closed-form solution is derived to estimate the groundwater flow rate entering the multi-layer tunnel during progressive drilling. The solution has an integrand not only consisting of the product and square of the Bessel functions but also having a singularity at the origin. A unified numerical approach is proposed to evaluate the solution with accuracy to five decimal places. This approach includes a singularity removal scheme, the Gaussian quadrature, and the Shanks method. For a multi-layer formation, the results obtained from the solution based on the equivalent hydraulic conductivity and the newly derived solution differ significantly. This solution is capable of estimating the maximum flow rate inside the horizontal tunnel, and thus can be used as a tool for designing the drainage tunnel system in a multi-layer formation.
Kondo interactions and magnetic correlations in CePt2 nanocrystals
(2007-04-13)
Chen, Y. Y.
;
Huang, P. H.
;
Ou, M. N.
;
Wang, C. R.
;
Yao, Y. D.
The evolution of the Kondo effect and antiferromagnetic (AF) correlations with size reduction in CePt2 nanoparticles (3.1-26 nm) is studied by analysis of the temperature-dependent specific heat and magnetic susceptibility. The AF correlations diminish with size reduction. The Kondo effect predominates at small particle size with trivalent, small Kondo temperature (T-K) magnetic regions coexisting with strongly mixed-valent, large T-K nonmagnetic regions. We discuss the role of structural disorder, background density of states and the electronic quantum size effect on the results.
Symmetry of multiferroicity in a frustrated magnet TbMn2O5
(2007-04-13)
Okamoto, J.
;
Huang, D. J.
;
Mou, C. -Y.
;
Chao, K. S.
;
Lin, H. -J.
Based on measurements of soft-x-ray magnetic scattering and symmetry considerations, we demonstrate that the magnetoelectric effect in TbMn2O5 arises from an internal field determined by (S) over right arrow ((q) over right arrow) x (s) over right arrow (-(q) over right arrow) with (S) over right arrow ((q) over right arrow) being the magnetization at modulation vector (q) over right arrow, whereas the magnetoelastic effect in the exchange energy governs the response to external electric fields. Our results set fundamental symmetry constraints on the microscopic mechanism of multiferroicity in frustrated magnets.
Electrochemical reaction and performance of proton exchange membrane fuel cells with a novel cathode flow channel shape
(2007-04-15)
Chiang, Mu-Sheng
;
Chu, Hsin-Sen
;
Chen, Cha'o-Kuang
;
Jian, Sheng-Rui
;
機械工程學系
This study focuses on the investigation of the electrochemical reaction along a novel cathode flow channel of PEM fuel cells with various shoulder/channel (S/C) ratios at the outlet port. A three-dimensional mathematical model, considering conservation principles of mass, momentum, species and electric current is employed. Local variations of important model variables such as reactant concentration and local current density are presented by contour plots to elucidate the effects of channel geometry on transport process, catalyst reaction and cell performance. The potential fields of solid and membrane phases are also resolved in the cell domain and the driving force of the electrochemical reactions - the catalyst activation overpotential - is harnessed in modeling. Numerical calculations reveal the influence of the cathode channel configuration on the local distributions of various model variables. The results also show the dependence between optimal channel configuration and cell operating condition. At a medium reaction rate, the reaction sites underneath the shoulder region generate more current than the channel region. Therefore, a convergent channel configuration with a larger S/C ratio at the outlet port develops more current because such a design facilitates the electron transport and enhances local activation overpotential. However, as the cell voltage decreases and the reaction rate increases, such configuration loses its merit gradually as the requirement for a higher reactant concentration is more important and the reaction sites underneath the channel region have a higher reaction rate. Consequently, the divergent channel configuration with a lower S/C ratio of 0.67 perfonns better at a cell voltage of 0.22 V (c) 2007 Elsevier B.V. All rights reserved.
Gel electrophoresis of polyphenol oxidase with instant identification by in situ blotting
(2007-04-15)
Cheng, Tsai-Mu
;
Huang, Pei-Chen
;
Pan, Ju-Pin
;
Lin, Kuan-Yu
;
Mao, Simon J. T.
Polyphenol oxidase (PPO) or tyrosinase is an important and ubiquitous enzyme responsible for browning in plants and melanization in animals. The molecular size of the plant PPO is varied among the species and its activity can be enhanced by a variety of anionic detergents. In the present study, we developed a simple method for the first-step identification of PPO in fruit and vegetable extracts. First, 3 mm chromatographic paper was immersed in 0.5% (w/v) catechol solution as an immobilized PPO substrate. After running the extract with 10% sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SIDS-PAGE), one side of the glass plate was removed. The plate was immediately laid on top of the dried catechol-paper. A dark-brown band corresponding to PPO was visualized within I min and was further confirmed by a conventional Western blot using an antibody prepared against mushroom PPO. It also reveals that some vegetation (such as tomato, radish, and oriental melon) with low or no detectable activity in a conventional enzyme assay actually possessed marked levels of PPO activity when assessed by PAGE-blot. We propose that an inhibitor is associated with PPO in some plants; the inhibitor, however, is dissociated during the electrophoresis. Therefore, in addition to identify the molecular form of PPO, the present technique may explore the existence of PPO inhibitor(s) in plants. The detail of the method with respect to its relevance for searching a natural PPO inhibitor is described and discussed. (c) 2006 Elsevier B.V. All rights reserved.
A novel method for fabrication of self-aligned double microlens arrays
(2007-04-15)
Ho, Jeng-Rong
;
Shih, Teng-Kai
;
Cheng, J. W. John
;
Sung, Cheng-Kuo
;
Chen, Chia-Fu
Based on the excimer laser microdrilling and the spin coating scheme, a new fabrication method of polymeric, double microlens arrays on a thin plastic pedestal sheet is proposed in this study. On each through hole on the pedestal sheet, a double microlens pair, consisting of two microlenses with different parabolic surfaces, is sited. The two microlenses of each pair are located respectively on both ends of the through hole and arranged surface to surface and automatically share a common lens principal axis. The fabricated microlens arrays are made of PMMA that are formed on a PMMA pedestal sheet with thickness of 100 mu m. The diameter and height for the microlens on one layer are of 150 mu m and 28 mu m, respectively, and they are correspondingly of 130 mu m and 24 mu m on the other layer. Experimental results demonstrate that the double microlens arrays have a better focusing property than the single-layer mircolens array. Simulation results indicate that, simply by changing the thickness of the pedestal sheet, the present fabricated double microlens arrays can serve the purposes for light collimating and diffusing. Due to its inherent simplicity in fabrication, the present method has high flexibility for making double microlens arrays with different lens configurations and various lens refractive indices. The facts that precise alignment and all processing steps are performed in ambient and at low temperature render the proposed approach a potential low-cost method for fabrication of double microlens arrays. (c) 2006 Elsevier B.V. All rights reserved.
Node-pancyclicity and edge-pancyclicity of hypercube variants
(2007-04-15)
Hu, Ken S.
;
Yeoh, Shyun-Shyun
;
Chen, Chiuyuan
;
Hsu, Lih-Hsing
;
應用數學系
Twisted cubes, crossed cubes, Mobius cubes, and locally twisted cubes are some of the widely studied hypercube variants. The 4-pancyclicity of twisted cubes, crossed cubes, Mobius cubes, locally twisted cubes and the 4-edge-pancyclicity of twisted cubes, crossed cubes, Mobius cubes are proven in [C.P. Chang, J.N. Wang, L.H. Hsu, Topological properties of twisted cube, Inform. Sci. 113 (1999) 147-167; C.P. Chang, T.Y. Sung, L.H. Hsu, Edge congestion and topological properties of crossed cubes, IEEE Trans. Parall. Distr. 11 (1) (2000) 64-80; J. Fan, Hamilton-connectivity and cycle embedding of the Mobius cubes, Inform. Process. Lett. 82 (2002) 113-117; X. Yang, G.M. Megson, D.J. Evans, Locally twisted cubes are 4-pancyclic, Appl. Math. Lett. 17 (2004) 919-925; J. Fan, N. Yu, X. Jia, X. Lin, Embedding of cycles in twisted cubes with edge-pancyclic, Algorithmica, submitted for publication; J. Fan, X. Lin, X. Jia, Node-pancyclic and edge-pancyclic of crossed cubes, Inform. Process. Lett. 93 (2005) 133-138; M. Xu, J.M. Xu, Edge-pancyclicity of Mobius cubes, Inform. Process. Lett. 96 (2005) 136-140], respectively. It should be noted that 4-edge-pancyclicity implies 4-node-pancyclicity which further implies 4-pancyclicity. In this paper, we outline an approach to prove the 4-edge-pancyclicity of some hypercube variants and we prove in particular that Mobius cubes and locally twisted cubes are 4-edge-pancyclic. (c) 2006 Elsevier B.V. All rights reserved.
High-speed GaAs metal gate semiconductor field effect transistor structure grown on a composite Ge/Ge(x)Si(1-x)/Si substrate
(2007-04-15)
Luo, Guang-Li
;
Hsieh, Yen-Chang
;
Chang, Edward Yi
;
Pilkuhn, M. H.
;
Chien, Chao-Hsin
In this study we used a low-pressure metal organic vapor phase epitaxy method to investigate the growth of GaAs metal gate semiconductor field effect transistor (MESFET) structures on a Si substrate. The buffer layer between the Si substrate and the grown GaAs epitaxial layers was a composite Ge/Si(0.05)Ge(0.95)/Si(0.1)Ge(0.9) metamorphic layer. We used transmission electron microscopy to observe the microstructures formed in the grown GaAs/Ge/Si(x)Ge(1-x)/Si material and atomic force microscopy to analyze the surface morphology and the formation of antiphase domains in the GaAs epitaxial layers. The measured Hall electron mobility in the channel layer of a MESFET structure grown on a 6 degrees misoriented Si substrate was 2015 cm(2) V(-1) s(-1) with a carrier concentration of 5.0x10(17) cm(-3). The MESFET device fabricated on this sample exhibited good current-voltage characteristics.