Browsing by Issue Date, starting with "2006-03-28"

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InGaN self-assembled quantum dots grown by metal-organic chemical vapour deposition with growth interruption
(2006-03-28)
Yao, HH
;
Lu, TC
;
Huang, GS
;
Chen, CY
;
Liang, WD
Self-assembled InGaN quantum dots (QDs) were grown by metal-organic chemical vapour deposition with growth interruption at low V/III ratio and low growth temperature on sapphire substrates. The effects of the interruption time on the morphological and optical properties of InGaN QDs were studied. The results show that the growth interruption can modify the dimension and distribution of InGaN QDs, and cause the QD emission wavelength to blue shift with increasing interruption time. A density of InGaN QDs of about 4.5 x 10(10) cm(-2) with an average lateral size of 11.5 nm and an average height of 1.6 nm can be obtained by using a growth interruption time of 60 s.
Method and apparatus for motion estimation with all binary representation
(2006-03-28)
Luo
;
Jeng-Hung
;
Lee
;
Gen-Ming
;
Wang
A method of motion estimation for video encoding constructs a binary pyramid structure having three binary layers. A state update module registers and updates repeat occurrence of final motion vectors and a static-state checking module determines if the method is in a static mode or a normal mode based on the repeat occurrence. In a normal mode, the first binary layer is searched within a ±3 pixel refinement window to determine a first level motion vector. In the second binary layer, a search range is computed based on six motion vector candidates. By checking every point within in the search range, a second binary layer search generates a second level motion vector. Finally, a third binary layer search within a ±2 pixel refinement window generates a final motion vector according to the second level motion vector. In a static mode, a fine tuning module performs search within a ±1 pixel refinement window and generates a final motion vector.
Tryptophan 232 within oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae influences rearrangement and deprotonation but not cyclization reactions
(2006-03-30)
Wu, TK
;
Yu, MT
;
Liu, YT
;
Chang, CH
;
Wang, HJ
Oxidosqualene-lanosterol cyclases convert oxidosqualene to lanosterol in yeast and mammals. Site-saturated mutants' construction of Saccharomyces cerevisiae oxidosqualene-lanosterol cyclase, at Trp232 exchanges against proteinogenic amino acids, and product profiles are shown. All mutants, except Lys and Arg, produced protosta-12,24-dien-3 beta-ol, lanosterol, and parkeol. Overall, Trp232 plays a catalytic role in the influence of rearrangement process and determination of deprotonation position but does not involve intervention in the cyclization steps.
High-efficiency polymer light-emitting diodes using neutral surfactant modified aluminum cathode
(2006-03-30)
Niu, YH
;
Jen, AKY
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
High-efficiency polymer light-emitting diodes were fabricated by inserting a layer of nonionic neutral surfactant between the electroluminescent (EL) layer and the high-work-function aluminum cathode via spin coating. It was found that both the poly(ethylene glycol)- and poly(propylene glycol)-based surfactants as well as their copolymers can all demonstrate similar performance enhancement. Device performances comparable to or even better than those of the control devices using calcium as the cathode have been achieved for both poly(p-phenylene)-based and polyfluorene-based conjugated polymers with orange-red, green, and blue emission colors. It is possible that when both surfactant and aluminum are used as the cathode, the abundant hole injection through a hole-transporting layer and hole pile-up at the inner side of the EL/surfactant interface might cause an effective electric field to induce the realignment of the dipole moment of those polar surfactant molecules, thus lowering the barrier for electron injection. In addition, the coordination between the aluminum and oxygen atoms on the surfactant might cause n-type doping in the areas near surfactant in the EL polymer layer that causes the enhancement of electron injection.
Sweeping technique combined with micellar electrokinetic chromatography for the simultaneous determination of flunitrazepam and its major metabolites
(2006-03-31)
Huang, CW
;
Jen, HP
;
Wang, RD
;
Hsieh, YZ
;
應用化學系
A sweeping technique, in conjunction with micellar electrokinetic chromatography, for the simultaneous determination of flunitrazepam and its major metabolites, 7-aminoflunitrazepam and N-desmethylflunitrazepam, is described. The optimized conditions for the sweeping and separation were a pH 9.5 buffer, 25 mM borate, 50 mM cetyltrimethylammonium bromide, 30% MeOH (v/v), and a 151-mm injection length. The calibration functions were all linear with the coefficient of determination (r(2)) exceeding 0.996 for the three target compounds. Using the sweeping procedure, the limits of detection were determined to be 13.4, 5.6, and 12.0 ng/mL for flunitrazepam, 7-aminoflunitrazepam, and N-desmethylflunitrazepam, respectively, and the sensitivity enhancement for each compound was within the range of 110-200 fold. The RSDs for the retention time and the peak area were less than 4.10%. The optimized sweeping method was also used to examine a spiked urine sample. We conclude that sweeping with micellar electrokinetic chromatography has considerable potential use in clinical and forensic analyses of flunitrazepam and its metabolites. (c) 2006 Elsevier B.V. All rights reserved.
MBE growth and structural and magnetic properties of (In1-gamma Al gamma)(1-x)MnxAs-diluted magnetic semiconductors
(2006-04-01)
Lee, WN
;
Chen, YF
;
Huang, JH
;
Guo, XJ
;
Kuo, CT
A series of quaternary-diluted magnetic semiconductors, (In1-y,Al-y)(1-x)MnxAs, have been successfully grown on InP substrates by low-temperature molecular beam epitaxy. The (ln(0.52)Al(0.48))(1-x)MnxAs with x <= 0.11 were grown on a nearly lattice-matched In0.52Al0.48As buffer, while the (In1-y,Al-y)(1-x)MnxAs with a higher Mn content of 0.11 < x <= 0.18 were grown on a graded 3-layer In,-,,Al-y 'As buffer structure. The results of transmission electron microscopy and double-crystal X-ray diffraction reveal that all (In1-yAly)(1-x),Mn,As epilayers are single crystal with zincblende structure, and the lattice constant increases with increasing the Mn content. The magnetic measurements show that the (In1-y,Al-y)(1-x)MnxAs semiconductors exhibit a paramagnetic-like state for x <= 0.05 while a ferromagnetic state for x >= 0.05, and the Curie temperature of ferromagnetic (In1-yAly)(1-x) MnxAs increases with increasing Mn content. (c) 2006 Elsevier B.V. All rights reserved.
Expression and purification of human placenta lactogen in Escherichia coli
(2006-04-01)
Lan, PC
;
Tseng, CF
;
Lin, MC
;
Chang, CA
;
生物科技學系
There are many growth factors secreted by placenta including growth hormone, placenta lactogen (PL), prolactin, follicle stimulating hormone, luteinizing hormone, thyroid stimulating hormone, and chorionic gonadotropin. For a systematic study of how these growth factors work together to result in the various biological functions and future clinical applications, it is needed to produce enough quantities of each protein. In this paper, we report the cloning of human PL (hPL) and expression by Escherichia coli (E coli). Four kinds of expression vectors containing the hPL gene were transformed into several kinds of suitable host strains and grown at 37 and/or 30 degrees C. Determination of the yield of recombinant hPL by SDS-PAGE reveals that among the various conditions, pQE30-PL in E. coli strain M15[pREP4] expressed the largest amount of recombinant hPL at 37 degrees C. However, the expressed recombinant hPL was accumulated in inclusion body forms. The inclusion bodies were solubilized in 8 M urea and purified by a His(6) tagged affinity column under denaturing condition and the final yield of hPL was determined to be 48 mg/L. Intra-chain disulfide bonds could be formed either by oxidation in the refolding buffer or by air oxidation in the presence of urea. The biological activity was examined by the fact that hPL could stimulate erythroid maturation by the formation of hemoglobin in K-562 cells in the presence of erythropoietin. Initial optimization studies resulted in the production of 282.4 mg/L of hPL. (c) 2005 Elsevier Inc. All rights reserved.
A background timing-skew calibration technique for time-interleaved analog-to-digital converters
(2006-04-01)
Wang, CY
;
Wu, JT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper presents a background timing-skew calibration technique for time-interleaved analog-to-digital converters (ADCs). The timing skew between any two adjacent analog-digital (AID) channels is detected by counting the number of zero crossings of the ADCs input while randomly alternating their sampling sequence. Digitally controlled delay units are adjusted to minimize the timing skews among the AID channels caused by the mismatches among the clock routes. The calibration behaviors, including converging speed and timing jitter, are theoretically analyzed and verified with simulations. A 6-bit 16-channel ADC is used as an example.
Ritter reaction of 1-aryl-1-fluoro-2-haloethanes
(2006-04-01)
Ho, TL
;
Chein, RJ
;
應用化學系
;
Department of Applied Chemistry
Fluorinated phenethyl bromides 1, 2, and 3, prove to be totally inert under Ritter reaction conditions in the presence of either SnCl4 or AgNO3, due to the strong deactivation by the gem-difluoro unit. Subjecting 2-bromo-1-fluoro-1-phenylethane to SnCl4 in MeCN at elevated temperatures led to formation of 2-methyl-4-phenyl-4,5-dihydrooxazole.
Topological horseshoes for perturbations of singular difference equations
(2006-04-01)
Li, MC
;
Malkin, M
;
應用數學系
;
Department of Applied Mathematics
In this paper, we Study solutions of difference equations Phi(lambda)(y(n), y(n+1),...,y(n+m)) = 0, n is an element of Z, of order in with parameter lambda, and consider the case when Phi(lambda) has a singular limit depending on a single variable as lambda -> lambda(0), i.e. Phi(lambda 0)(y(0),...,y(m)) = phi(y(N)), where N is an integer with 0 <= N <= m and phi is a function. We prove that if phi has k simple zeros then for lambda close enough to lambda(0), the difference equation has a k-horseshoe among its solutions, that is, the dynamics is conjugate to the full shift with k symbols. Moreover, we show that these horseshoes change continuously in the uniform topology as lambda varies. As applications of these results, we establish the horseshoe structure in families of generalized Henon-like maps and of Arneodo-Coullet-Tresser maps near their anti-integrable limits as well as in steady states for certain lattice models.
Multiple-objective planning for a production and distribution model of the supply chain: Case of a bicycle manufacturer
(2006-04-01)
Tzeng, GH
;
Tang, TI
;
Huang, YM
;
Chang, ML
;
科技管理研究所
The bicycle industry is one of the most competitive industries in Taiwan. To construct multi-objective production and distribution models tor supply chain, following five methods are compared and discussed: (i) Multi-objective compromise programming; (ii) Fuzzy multi-objective programming (iii) Weighted multi-objective programming; (iv) Weighted fuzzy multi-objective programming; and (v) Two-phase fuzzy multi- objective programming. The weighted multi-objective model has been found better for considering the maximum profit for enterprises and the maximum quality for customer service. After raising the per-unit production cost in production processes, it was observed that the total profit would decrease in real empirical study. In addition, if the unit inventory cost increases due to improving the customer service level, then the total profit might increase, but not significantly.
A modified HICUM model for GaInP/GaAs HBT devices
(2006-04-01)
Tseng, SC
;
Meng, CC
;
Chen, WY
;
Su, JY
;
電信工程研究所
A compact physics-based transit-time model is established for the GaInP/GaAs HBT device. The VBIC model fails to describe the transit-time frequency versus bias (I-C, V-CE), especially at low- and medium-current regimes. Starting with the HICUM model, we introduce a new time constant to describe the transit-time frequency versus bias (I-C, V-CE) more precisely. This model has obvious advantages over the VBIC model for showing the relation oj'f, versus bias (I-C, V-CE) in the low and medium current regimes for GaInP/GaAs HBT devices. (c) 2006 Wiley Periodicals, Inc.
Low-temperature growth mechanism of SW-NTs networks by buffer layer-assisted MPCVD
(2006-04-01)
Wang, W. H.
;
Peng, Y. R.
;
Chuang, P. K.
;
Kuo, C. T.
;
材料科學與工程學系
We present the microstructures and growth mechanism of networks of single-walled carbon nanotubes (SWNTs) fabricated by buffer layer-assisted microwave plasma chemical vapor deposition (MPCVD) at relatively low temperatures. The morphologies and bonding structures of carbon nanostructures were characterized by field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Raman Spectroscopy. Additionally, the surface roughness of buffer layer and its bonding structures with catalyst atom are analyzed by atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS), respectively. Analytical results demonstrate that networks of CNTs are formed by bundles or individual SWNTs. We suggest that the formation of SWNTs networks at low temperature may follow the root-growth mechanism. The differences comparing with previous growth mechanism are that the nuclei formation resulted from the rough surface of the buffer layer, and dissolution of carbon in catalyst will be enhanced due to the surface diffusion of the buffer layer. These unique effects from the buffer layer can provide favorable conditions to grow SWNTs at relatively low process temperatures. (c) 2005 Elsevier B.V. All rights reserved.
Snug-Vegas and Snug-Reno: efficient mechanisms for performance improvement of TCP over heterogeneous networks
(2006-04-01)
Ho, CY
;
Chen, YC
;
資訊工程學系
;
Department of Computer Science
Improving the performance of the traditional TCP in wireless IP communications has been an active research area. The significant cause of packet losses in such heterogenous networks is no longer limited to network congestion. The performance degradation of TCP in wireless and wired-wireless hybrid networks is mainly due to its lack of ability to differentiate the packet losses caused by network congestions from the losses caused by wireless link errors. New variants of TCP Vegas and TCP Reno named Snug-Vegas and Snug-Reno, respectively, are proposed. By using random-loss indications marked by base stations, Snug-Vegas and Snug-Reno may detect random packet losses precisely. Through the packet loss differentiation, Snug-Vegas and Snug-Reno react appropriately to the losses, and based on the simulation results, it is seen that the throughput of connection over heterogeneous networks can be significantly improved.
Improvement of electrical characteristics for fluorine-ion-implanted poly-Si TFTs using ELC
(2006-04-01)
Tu, CH
;
Chang, TC
;
Liu, PT
;
Yang, CY
;
Liu, HC
The fluorine ion implantation applied to the polycrystalline silicon thin-film transistors (poly-Si TFTs) is investigated in this letter. Experimental results have shown that fluorine ion implantation effectively minimized the trap state density, leading to superior electrical characteristics such as high field-effect mobility, low threshold voltage, and high ON/OFF current ratio. Furthermore, the fluorine ions tended to segregate at the interface between the gate oxide and poly-Si layers during the excimer laser annealing, even without the extra deposition of pad oxide on the poly-Si film. The presence of fluorine obviously enhanced electrical reliability of poly-Si TFTs.
Spectroscopic study of bio-functionalized nanodiamonds
(2006-04-01)
Chung, P. -H.
;
Perevedentseva, E.
;
Tu, J. -S.
;
Chang, C. C.
;
Cheng, C. -L.
Nano-scale materials with attached biomolecules on the surface can be used as bioprobes in cell and tissue analysis. The conjugation of these nanoparticles with biomolecules is one of the key steps in the development of bioprobes. In this work nanometer-sized diamonds (5 and 100 nm) are functionalized and conjugated with protein lysozyme via physical adsorption. The process of creating functional groups on the nanodiamond surface is studied using Fourier Transform Infrared-spectroscopy (FTIR). The conjugation of nanodiamonds with biontolecules and nanodiamond-biomolecule interaction are analyzed with UV/VIS and FTIR spectroscopy. (c) 2005 Elsevier B.V. All rights reserved.
A low power turbo/Viterbi decoder for 3GPP2 applications
(2006-04-01)
Lin, CC
;
Shih, YH
;
Chang, HC
;
Lee, CY
;
電子工程學系及電子研究所
This paper presents a channel decoder that completes both turbo and Viterbi decodings, which are pervasive in many wireless communication systems, especially those that require very low signal-to-noise ratios. The trellis decoding algorithm merges them with less redundancy. However, the implementation is still challenging due to the power consumption in wearable devices. This research investigates an optimized memory scheme and rescheduled data flow to reduce power consumption and chip area. The memory access is reduced by buffering the input symbols, and the area is reduced by reducing the embedded interleaver memory. A test chip is fabricated in a 1.8 V 0.18-mu m standard CMOS technology and verified to provide 4.25-Mb/s turbo decoding and 5.26-Mb/s Viterbi decoding. The measured power dissipation is 83 mW, while decoding a 3.1 Mb/s turbo encoded data stream with six iterations for each block. The power consumption in Viterbi decoding is 25.1 mW in the 1-Mb/s data rate. The measurement shows the power dissipation is 83 mW for the turbo decoding with six iterations at 3.1 Mb/s, and 25.1 mW for the Viterbi decoding at 1 Mb/s.
Fabricating and characterizing oblique polymer structures by electron beam writing on resist-coated SiO2 wafers
(2006-04-01)
Ko, FH
;
Chen, JK
;
Chang, FC
;
材料科學與工程學系奈米科技碩博班
;
應用化學系
We have successfully fabricated SU-8 materials having oblique structures by a new electron beam technology.-We studied the contrast, sensitivity, etching, and thermal properties of SU-8, PMMA, and KrF resists to evaluate their suitability for the fabrication of oblique structures. Among these resists, SU-8 revealed the lowest contrast ratio, highest throughput, and best thermal stability, and so it became the candidate material for patterning the oblique structures. The technique we have developed involves five regional exposures of a thick SU-8 resist layer with various electron beam dosages. Furthermore, we discuss the surface morphology, reaction mechanism, and hydrophobicity after subjecting the SU-8 resist to a series of plasma treatments. The formation of surface nano-nodules during oxygen plasma treatment explains the surface hydrophobicity. We have carefully evaluated the effects of the electron beam writing dose and the design of the exposure area with respect to the inclined angle of the fabricated structure. (c) 2006 Elsevier B.V. All rights reserved.
Organic selective-area patterning method for microlens array fabrication
(2006-04-01)
Huang, WK
;
Ko, CJ
;
Chen, FC
;
光電工程學系
;
顯示科技研究所
Refractive microlens arrays (MLAs) are widely used in many electro-optical devices due to their high performance and low optical loss. To fabricate a microlens array effectively, we have proposed a novel fabrication method based on a selective-area patterning method. The surface properties of glass substrates were defined as either hydrophilic or hydrophobic regions by microcontact printing of self-assembled monolayers (SAMs). Consequently, the microlens arrays were self-organized on the hydrophilic regions after the lens materials were nozzle-spread followed by UV curing. As a result, we have demonstrated microlenses with 50, 75, and 100 Pm footprints, and f numbers as low as 5.4. The focused spot size of the 50 mu m lens was 9.82 mu m, which is near the diffraction limit. The optical measurement shows excellent light collecting efficiency of a microlens array, which is suitable for many electro-optical applications. Furthermore, all fabrication steps can be accomplished in ambient environment and at room temperature. It is anticipated that the present proposed method has great potential for mass production. (c) 2006 Elsevier B.V. All rights reserved.
Characterization of imprinting polymeric temperature variation with fluorescent Rhodamine B molecule
(2006-04-01)
Ko, FH
;
Weng, LY
;
Ko, CJ
;
Chu, TC
;
材料科學與工程學系奈米科技碩博班
The method to measure the imprint temperature variation of resist film with fluorescence probe technique was established. The maximal Rhodamine B concentration was 8 X 10(-4) M to achieve higher sensitivity and avoid precipitation problem. The temperature effect was a critical parameter on the temperature sensing, while imprinting pressure was not. The fluorescence intensity of Rhodamine B linearly decayed with time at various temperatures due to the formation of lactone-containing molecule during thermal stressing. The usual imprint time of less than 20 min was not affected by the signal decay effect due to limited percentage of signal variation during 100200 degrees C. The technique based on fluorescence probe method was successfully applied to measure the resist temperature variation of the imprint on the resist film of 6-in. wafer. (c) 2006 Elsevier B.V. All rights reserved.