Browsing by Issue Date, starting with "2005-07-21"

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Code-pattern insensitive embedded ROMs using dynamic bitline shielding technique
(2005-07-21)
Chang, MF
;
Chiou, LY
;
Wen, KA
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A dynamic bitline shielding (DBS) technique is proposed for highspeed via-programming ROMs, to eliminate code-pattem-dependent crosstalk-induced read failure (CIRF) and increase code-pattem coverage. Fabricated 256 Kb conventional and DBS ROMs demonstrated that the DBS technique can eliminate the CIRF and operate with a small sensing margin.
生化感測方法及其感測裝置
(2005-07-21)
楊裕雄
;
吳重雨
;
盧武德
;
施育全
;
胡智棚
本發明係一種生化感測方法及其感測裝置，利用此生化感測方法之感測裝置係包括一感光二極體，其可感測特定化合物與特定酵素及顯光劑反應後所產生之光，並能將所感測之光訊號轉換為電流訊號；另有一電流／電壓轉換電路可將該電流訊號轉換為類比電壓訊號；且此類比電壓訊號經由一類比／數位轉換器可再轉換為數位電壓訊號；最後利用一電子裝置可接收此數位電壓訊號並對其加以分析，藉此分析動作以測定該特定化合物之含量多寡。本發明之方法及裝置可提供簡易、大量而即時之醫療檢測，可改善習知檢測技術所使用之光譜分析儀體積過大且價格過高之缺失。
Mechanisms of p-GaAs(100) surface by atomic force microscope nano-oxidation
(2005-07-21)
Jian, SR
;
Fang, TH
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
Nanopattering using atomic force microscope (AFM) has become an important area of research, for both fundamental research and future nanodevice applications. Local oxidation of p-GaAs(l 00) surface by using a negatively biased conductive AFM tip is a universal method for this purpose. The dependences of the height, aspect ratio and volume on applied anodization times and voltages during which the anodization voltage is applied were studied. We explore the kinetics and mechanisms of the anodization process and how factors such as the electric field strength and the relative humidity influence its growth rate and the contribution of ionic diffusion. The results revealed that the protruding oxide dot's height, aspect ratio and volume increase during longer anodization time and at larger anodization voltage as well as in higher relative humidity conditions. The high initial growth rate (similar to 300 nm s(-1) for 10 V) decreases quickly with decreasing electric field strength and the oxide practically ceases to grow at an order of (2-3) x 107 V cm(-1). Auger electron spectroscopy measurements confirm that the modified structures take the form of anodized p-GaAs(I 00). Also, the contribution of ionic diffusion increases by about 80% at a higher relative humidity. In addition, the nanohardness of the oxide structures was measured with the aid of an AFM-based nanoindentation technique.
Relaxation dynamics and structural characterization of organic nanoparticles with enhanced emission
(2005-07-21)
Bhongale, CJ
;
Chang, CW
;
Lee, CS
;
Diau, EWG
;
Hsu, CS
With a reprecipitation method, we prepared fluorescent organic nanoparticles of 1,4-di[(E)-2-phenyl-1-propenyl]-benzene (PPB) that feature weak emission in solution but exhibit blue-shifted absorption and strong emission as aggregates. Picosecond fluorescent transients of these PPB nanoparticles showed biexponential decay, described with a consecutive kinetic model involving two emissive states. X-ray diffraction patterns of PPB nanocrystals indicate long-range packing structures of two types, one the same as in a single crystal and the other not yet determined. PPB molecules in a crystal show an arrangement of a herringbone type with three benzene rings in a PPB unit being nearly planar and two methyl groups of the unit pointing along the same direction, in contrast to the twisted structure of an isolated PPB molecule. Fluorescence transients of PPB on a femtosecond scale indicate an efficient channel for isomerization that is activated for free PPB in solution but inhibited in PPB forming nanoparticles, demonstrating the significance of molecular geometry and twisting motions that affect the relaxation dynamics in the excited state. The versatile techniques combined in this work provide strong evidence to improve our understanding of optical properties in organic nanoparticles dependent on size.
Dielectric and electrical properties of SrTiO(3+/-y)-(SiO2)(x) thin films
(2005-07-21)
Chou, HY
;
Chen, TM
;
Tseng, TY
;
應用化學系
;
電子工程學系及電子研究所
110 nm thick SrTiO(3 +/- y)-(SiO2), thin films with x = 0-0.45 were prepared on Pt/Ti/SiO2/Si substrates using the chemical solution deposition method and then annealed at temperatures ranging from 600 degrees C to 900 degrees C for I min. The dielectric and electrical properties of the SrTiO(3 +/- y)-(SiO2)(x) were obviously affected by the annealing temperature and composition. The dielectric constant of the thin films increased with increasing annealing temperature and decreased with an increase in Si content while the leakage current density decreased with an increase in Si content. The 700 degrees C annealed SrTiO(3 +/- y)-(SiO2)(x) thin film with x = 0.25 has a suitable cm(-2). dielectric constant of 94.8 and a low leakage current of 1.27 x 10(-8) A The time-dependent dielectric breakdown curve of the 700 degrees C and 800 degrees C annealed SrTiO(3 +/- y)-(SiO2), films with x = 0.25 have an expected lifetime of over 10 years at electric fields higher than 0.6 MV cm(-1).
Plate-based biochemical assay using quantum dots as a fluorescent labeling agent
(2005-07-22)
Huang, CP
;
Liu, HW
;
Tsao, CY
;
Yin, LT
;
Chiu, SF
A biochemical assay based on fluorescence imaging analysis by confocal laser scanning as a detection technique is specified. The method involved a glass plate coated with nitrocellulose (NC), where alpha-human-IgE-biotin at various concentrations was immobilized on an NC plate. Luminescent core-shell CdSe/ZnS QD-SA conjugates were then used as a fluorescent labeling agent to be captured specifically by biotinated alpha-human-IgE immobilized in a micro-array by affinity binding between SA and biotin in a plate-based biochemical assay. A confocal laser scanner was used to detect the fluorescence signals from the alpha-human-IgE-biotin-SA-QD complex. Experimental findings reveal that fluorescence intensity of QD-SA saturated at QD concentrations above 0.4 mg/ml. Moreover, a calibration curve between the fluorescence intensity and the concentration of alpha-human-IgE-biotin is plotted. The range of detectable concentrations of biotinlated alpha-human IgE was found to be between 3.3 and 100 mu g/ml in the a-human-IgE-biotin-SA-QD complex. Therefore, the results were consistent with the binding specificity in a plate-based biochemical assay, as determined using luminescent QDs as a labeling agent. (c) 2004 Elsevier B.V. All rights reserved.
Plate-based biochemical assay using quantum dots as a fluorescent labeling agent
(2005-07-22)
Huang, CP
;
Liu, HW
;
Tsao, CY
;
Yin, LT
;
Chiu, SF
A biochemical assay based on fluorescence imaging analysis by confocal laser scanning as a detection technique is specified. The method involved a glass plate coated with nitrocellulose (NC), where alpha-human-IgE-biotin at various concentrations was immobilized on an NC plate. Luminescent core-shell CdSe/ZnS QD-SA conjugates were then used as a fluorescent labeling agent to be captured specifically by biotinated alpha-human-IgE immobilized in a micro-array by affinity binding between SA and biotin in a plate-based biochemical assay. A confocal laser scanner was used to detect the fluorescence signals from the alpha-human-IgE-biotin-SA-QD complex. Experimental findings reveal that fluorescence intensity of QD-SA saturated at QD concentrations above 0.4 mg/ml. Moreover, a calibration curve between the fluorescence intensity and the concentration of alpha-human-IgE-biotin is plotted. The range of detectable concentrations of biotinlated alpha-human IgE was found to be between 3.3 and 100 mu g/ml in the a-human-IgE-biotin-SA-QD complex. Therefore, the results were consistent with the binding specificity in a plate-based biochemical assay, as determined using luminescent QDs as a labeling agent. (c) 2004 Elsevier B.V. All rights reserved.
Sequence distribution and polydispersity index affect the hydrogen-bonding strength of poly(vinylphenol-co-methyl methacrylate) copolymers
(2005-07-26)
Lin, CL
;
Chen, WC
;
Liao, CS
;
Su, YC
;
Huang, CF
A series of poly(vinylphenol-co-methyl methacrylate) (PVPh-co-PMMA) block and random copolymers were prepared through anionic and free radical polymerizations, respectively, of 4-tert-butoxystyrene and methyl methacrylate and subsequent selective hydrolysis of the 4-tert-butoxystyrene protective groups. Analysis of infrared spectra suggests that the random copolymer possesses a higher fraction of hydrogen-bonded carbonyl groups and a larger interassociation equilibrium constant relative to those of a block copolymer containing similar vinylphenol content because of the different sequence distribution that may arise from the so-called intramolecular screening effect. In contrast, the glass transition temperature of the block copolymer, which has the lower polydispersity index, is higher than that of the random copolymer at the same composition.
Luminescence and energy transfer of Eu- and Mn-coactivated CaAl2Si2O8 as a potential phosphor for white-light UVLED
(2005-07-26)
Yang, WJ
;
Luo, LY
;
Chen, TM
;
Wang, NS
;
應用化學系
A series of Eu2+- and Mn2+-coactivated CaAl2Si2O8 phosphors have been synthesized at 1400 degrees C under a reduced atmosphere and their luminescence properties have been investigated as a function of activator and coactivator concentrations. We have discovered that energy transfers from Eu2+ to Mn2+ by directly observing significant overlap of the excitation spectrum of Mn2+ and the emission spectrum of Eu2+ as well as the systematic relative decline and growth of emission bands of Eu2+ and Mn2+, respectively. The critical distance and average separation of Eu2+ and Mn2+ have also been calculated. By utilizing the principle of energy transfer, we have also demonstrated that with appropriate tuning of activator content CaAl2Si2O8:Eu2+ Mn2+ phosphors exhibit great potential to act as a phosphor for white-light ultraviolet light-emitting diodes (UVLEDs).
Miscibility behavior and interaction mechanism of polymer electrolytes comprising LiClO4 and MPEG-block-PCL copolymers
(2005-07-26)
Chiu, CY
;
Hsu, WH
;
Yen, YJ
;
Kuo, SW
;
Chang, FC
We have used DSC, FTIR spectroscopy, and ac impedance techniques to investigate in detail the miscibility behavior, interaction mechanism, and ionic conductivity of polymer electrolytes composed of lithium perchlorate (LiClO4) and monomethoxypoly(ethylene glycol)-block-poly(c-caprolactone) (MPEG-PCL) diblock copolymer. The existence of the PCL phase in the MPEG-PCL block copolymer tends to retard the crystallinity of MPEG and results in a higher ionic conductivity for the LiClO4/MPEG-PCL based polymer electrolyte. DSC analyses indicate that the phase separation occurs for some compositions of the LiClO4/MPEG-PCL blends. In addition, FTIR spectroscopy studies reveal the complicated interactions that occur within the LiClO4/MPEG-PCL blend system upon varying the LiClO4 content and increasing the temperature. For the LiClO4/MPEG-PCL blend system, the relative intensity of the "complexed" carbonyl stretching band of the PCL block tends to increase when either the LiClO4 concentration or the length of the PCL block increases. For some compositions of LiClO4/MPEG-PCL, when the temperature is increased from 120 to 180 degrees C, the relative intensity of the "complexed" C=O group increases; this phenomenon is different from that observed for the LiClO4/PCL homopolymer blend.
CdS nanoparticles induce a morphological transformation of poly(styrene-b-4-vinylpyridine) from hexagonally packed cylinders to a lamellar structure
(2005-07-26)
Yeh, SW
;
Wei, KH
;
Sun, YS
;
Jeng, US
;
Liang, KS
Mercaptoacetic acid-modified CdS nanoparticles disperse selectively in the poly(4-vinylpyridine) domains of poly(styrene-b-4-vinylpyridine) (S4VP) block copolymer as a result of the formation of hydrogen bonds. This process in turn induces the morphological transformation of S4VP from a hexagonally packed cylinder structure into a lamellar structure, as evidenced from transmission electron microscopy, atomic force microscopy, and small-angle X-ray scattering studies. This transformation is consistent with that suggested by a theoretical prediction of the phase diagram of the mixed diblock copolymer/nanoparticle system.
Preparation and supramolecular self-assembly of a polypeptide-block-polypseudorotaxane
(2005-07-26)
Lee, HF
;
Sheu, HS
;
Jeng, US
;
Huang, CF
;
Chang, FC
We have successfully prepared a new class of self-assembled biomaterial: a polypeptide-block-polypseudorotaxane diblock copolymer. This diblock copolymer is comprised of an a-helical polypeptide rod, based on gamma-benzyl-L-glutamate, and an originally coiled segment P(EO19-r-PO3); it forms inclusion complexes with a-cyclodextrins (alpha-CDs) to give crystalline polypseudorotaxanes. Formation of the polypseudorotaxane converts the conformation of P(EO19-r-PO3) from a flexible chain into a rodlike structure, which results in a novel block copolymer exhibiting a rod-rod conformation. Intrinsic interactions (e.g., the polypseudorotaxane's channel-type crystallization, the polypeptide's secondary structure, and microphase separation) within and between these rod-rod diblock copolymers contribute to their hierarchical self-assembly behavior, which we characterized using DSC, H-1 NMR spectroscopy, C-13 CP/MAS NMR spectroscopy, WAXS, and SAXS. The data obtained from the WAXS and SAXS studies clearly indicate the formation of juxtaposed bilayer-like nanostructure featuring hexagonally packed PBLG stacks and channel-type polypseudorotaxane moieties.
Highly efficient red-electrophosphorescent devices based on polyfluorene copolymers containing charge-transporting pendant units
(2005-07-28)
Wu, FI
;
Shih, PI
;
Tseng, YH
;
Chen, GY
;
Chien, CH
We have systematically examined the photoluminescence (PL) and electroluminescence (EL) behavior of blends comprising two efficient red phosphors doped, respectively, into the blue-emitting polyfluorene derivatives PF-TPA-OXD and PF-OXD. The host polymers, which contain both hole- and electron-transporting or merely electron-tran sporting side chains, are capable of facilitating charge injection and transport. After determining the HOMO and LUMO energy levels of these materials, we were able to match the dopant with its most suitable host to achieve the direct formation and confinement of an exciton at the dopant. This configuration also leads to a reduction in the electrical excitation of the host polymer, which in turn decreases the degree of exciton loss arising from nonradiative decay of the host triplet. Using this approach, we were able to realize the production of high-performance red-electrophosphorescent devices. For Os(fppz)-doped devices, we obtain a balanced charge recombination in conjunction with higher current and luminance when using PF-TPA-OXD as the host matrix; this device reached a maximum external quantum efficiency of 8.37% with a peak brightness of 16 720 cd/m(2). The absence of charge-transporting pendant units, i.e., the device fabricated from poly [9,9-dioctylfluorene-2,7-diyl] (POF), led, however, to relatively poor electroluminescence characteristics (5.81% and 2144 cd/m(2)).
Incorporating hidden Markov models for identifying protein kinase-specific phosphorylation sites
(2005-07-30)
Huang, HD
;
Lee, TY
;
Tzeng, SW
;
Wu, LC
;
Horng, JT
Protein phosphorylation, which is an important mechanism in posttranslational modification, affects essential cellular processes such as metabolism, cell signaling, differentiation, and membrane transportation. Proteins are phosphorylated by a variety of protein kinases. In this investigation, we develop a novel tool to computationally predict catalytic kinase-specific phosphorylation sites. The known phosphorylation sites from public domain data sources are categorized by their annotated protein kinases. Based on the concepts of profile Hidden Markov Models (HMM), computational models are trained from the kinase-specific groups of phosphorylation sites. After evaluating the trained models, we select the model with highest accuracy in each kinase-specific group and provide a Web-based prediction tool for identifying protein phosphorylation sites. The main contribution here is that we have developed a kinase-specific phosphorylation site prediction tool with both high sensitivity and specificity. (c) 2005 Wiley Periodicals, Inc.
Discovering common structural motifs of ribosomal RNA secondary structures in prokaryotes
(2005-08-01)
Huang, HD
;
Horng, JT
;
Wu, LC
;
Fang, SF
;
生物資訊及系統生物研究所
Certain structural motifs, like tetra-loops, in ribosomal RNA are known to functionally implicate in virtually every aspect of protein synthesis. Ribosomal RNA molecules were also widely used as a tool in molecular evolutionary studies because of their ubiquity, size and low evolutionary rate. In this study, we adapt a data mining approach to discover common structural motifs, and then we use a machine learning approach to identify discriminating CSMs from groups of organisms. Finally, we construct phylogeneitc trees to investigate the evolution of ribosomal RNA by serving the CSMs discovered as targets, which are used to estimate the evolutionary relatedness between organisms. The aim of this study is to discover common structural motifs (CSMs), i.e., those single-strain regions shared in ribosomal RNA secondary structures by several organisms, which are related to specific domains or functions. We discover a set of common structural motifs from several data sets of Archaea and Bacteria. Significant CSMs are then induced by a decision tree. Furthermore, phylogenetic trees are constructed based on CSMs and primary sequences of SSU 16 S ribosomal RNA.
磁光式之近場光學光儲存元件
(2005-08-01)
徐文祥
;
謝漢萍
;
孫翊庭
本發明係提供一種磁光式之近場光學光儲存元件，係先利用犧牲層製作空氣軸承結構；再定義一初始小孔，並以電鍍法縮小該孔至奈米等級，再以兩次之厚膜光阻層配合兩次電鍍製程，製作高深寬比之金屬線圈結構與金屬內連線；可有效利用面積與降低電阻，最後利用微影製程中對不同區域的不同曝光量控制，定義單層光阻形成具有特定尺寸且不同厚度之結構，接著配合回流(reflow)即可利用一連續製程製作出結合超半球固態浸沒式透鏡(solid immersion lens)、奈米微孔、金屬線圈、空氣軸承之磁光(MO)讀取頭，而不需精密昂貴的設備，並可批次大量生產，免去組裝的步驟，並且不用高精密度之儀器即可製作，達到高資料儲存與複寫。
超半球固態浸沒式透鏡之製法
(2005-08-01)
徐文祥
;
孫翊庭
本發明係提供一種超半球固態浸沒式透鏡之製法，係於一基材上塗佈正光阻層後，以第一、二片光罩進行第一、二次曝光，可經由第一次足量曝光在正光阻層上產生之圖案來進行對準，使得第二片光罩上之曝光圖案可經由對準轉移到正光阻層上的特定區域，接著進行回流(reflow)，即可形成超半球固態浸沒式透鏡(SSIL)；可使整個製程容易而不需昂貴或是複雜的設備即可完成，且方便利用後續的半導體製程額外製作其他光學元件；與已製作之超半球固態浸沒式透鏡(SSIL)作整合，所以不需組裝即可製作具有功能性的元件，進而達到易於製作，且應用面廣泛易與其他光學元件作整合，利於批次大量生產。
Optical properties of a novel yellow fluorescent dopant for use in organic LEDs
(2005-08-01)
Choy, WCH
;
Wu, YS
;
Chen, CH
;
Cheah, KW
;
電子與資訊研究中心
In this paper, the optical properties of a novel organic, 2,8-di(t-butyl)-5,11-di[4(t-butyl)phenyl]-6,12-diphenylnaphthacene (tetra(t-butyl)rubrene) have been investigated. Our results show that there are two peaks in the photoluminescence (PL) spectra of tetra(t-butyl) rubrene (TBRb) which are also confirmed in the electroluminescence (EL) spectra. Photo-quenching of the PL intensity is observed when the irradiation time increases. It is shown that oxidation is the dominant reason for photo-quenching. The absolute refractive index and absorption coefficient have also been determined and the results correlate well with the PL results. The results show that TBRb can be a good dopant to achieve the Forster energy transfer and to assist light emission. The optical properties of TBRb are similar to those of rubrene; however, the PL of TBRb is much stronger than that of rubrene. Finally, although crystalline organics have been commonly reported by heating the sample, we report crystallization of TBRb at low temperature < 230 K when the TBRb film is in an amorphous form before cooling.
Recursive EM and SAGE-inspired algorithms with application to DOA estimation
(2005-08-01)
Chung, PJ
;
Bohme, JF
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper is concerned with recursive estimation using augmented data. We study two recursive procedures closely linked with the well-known expectation and maximization (EM) and space alternating generalized EM (SAGE) algorithms. Unlike iterative methods, the recursive EM and SAGE-inspired algorithms give a quick update on estimates given new data. Under mild conditions, estimates generated by these procedures are strongly consistent and asymptotically normally distributed. These mathematical properties are valid for a broad class of problems. When applied to direction of arrival (DOA) estimation, the recursive EM and SAGE-inspired algorithms lead to a very simple and fast implementation of the maximum-likelihood (ML) method. The most complicated computation in each recursion is inversion of the augmented information matrix. Through data augmentation, this matrix is diagonal and easy to invert. More importantly, there is no search in such recursive procedures. Consequently, the computational time is much less than that associated with existing numerical methods for finding ML estimates. This feature greatly increases the potential of the ML approach in real-time processing. Numerical experiments show that both algorithms provide good results with low computational cost.
Enhancing the frequency response of cross-polarization wavelength conversion
(2005-08-01)
Wei, CC
;
Huang, MF
;
Chen, J
;
光電工程學系
;
Department of Photonics
This work presents a novel wavelength conversion scheme, differential cross-polarization modulation (DXPoM), using an extra birefringence delay to enhance the performance of the conventional cross-polarization modulation. Simulation and experimental results confirm that the predicted performance is enhanced. Using the proposed scheme improves rise time by over 300 %, reduces timing jitter by 50 %, and increases extinction ratio by 9 %.