Browsing by Issue Date, starting with "2011-07-19"

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Routing method and routing path recovery mechanism in wireless sensor network environment
(2011-07-19)
Lai Jun-Yu
;
Huang Kuei-Li
;
Wang Jui-Tang
;
Tseng Chien-Chao
;
Wu Chao-Nan
The present invention discloses an asymmetric routing method and routing path recovery mechanism. The wireless sensor network environment includes at least a management unit, at least a gateway, and mobile nodes. When joining, each mobile node obtains an unique ID code and, additionally, a depth as the gradient to the management unit. Accordingly, a mobile node sends an uplink packet via a nearby node with lower depth to the management unit; while the management unit transmits a downlink packet to a mobile node by utilizing the source route method. When the parent node of a mobile node is damaged or moves to another position or said mobile node with its sub-tree descendants changes their position together, the uplink routing path is recovered via selecting a nearby node of the sub-tree as relay node and the downlink routing path is recovered via sending a control message to the management unit.
Manufacture method of a multilayer structure having non-polar a-plane {11-20} III-nitride layer
(2011-07-19)
Lee Wei-I
;
Chen Jenn-Fang
;
Chiang Chen-Hao
A manufacture method of a multilayer structure having a non-polar a-plane {11-22} III-nitride layer includes forming a nucleation layer on a r-plane substrate, wherein the nucleation layer is composed of multiple nitride layers; and forming a non-polar a-plane {11-20} III-nitride layer on the nucleation layer. The nucleation layer features reduced stress, reduced phase difference of lattice, blocked elongation of dislocation, and reduced density of dislocation. Thus, the non-polar a-plane {11-20} III-nitride layer with flat surface can be formed.
Reply to Guedj et al.: Early transient increase of hepatitis C virus viral load in genotype 1 and 2 infections, and the use of mathematical modeling
(2011-07-19)
Hsu, Ching-Sheng
;
Chen, Hung-Chia
;
Jeng, Jenher
;
Kao, Jia-Horng
;
Chen, Ding-Shinn
交大e-News第098期
(2011-07-20)
Secretariat
;
國立交通大學秘書室
Signature of the Schwinger pair creation rate via radiation generated in graphene by a strong electric current
(2011-07-20)
Lewkowicz, M.
;
Kao, H. C.
;
Rosenstein, B.
;
電子物理學系
;
Department of Electrophysics
Electron-hole pairs are copiously created by an applied electric field near the Dirac point in graphene or similar two-dimensional electronic systems. It was shown recently that for sufficiently large electric fields E and ballistic times the I-V characteristics become strongly nonlinear due to Schwinger's pair creation rate, proportional to E(3/2). Since there is no energy gap the radiation from the pairs' annihilation is enhanced. The spectrum of radiation is calculated and exhibits a maximum at omega = root eEv(g)/h. The angular and polarization dependence of the emitted photons with respect to the graphene sheet is quite distinctive. For very large currents the recombination rate becomes so large that it leads to the second Ohmic regime due to radiation friction.
High-accuracy thickness measurement of a transparent plate with the heterodyne central fringe identification technique
(2011-07-20)
Wu, Wang-Tsung
;
Hsieh, Hung-Chih
;
Chang, Wei-Yao
;
Chen, Yen-Liang
;
Su, Der-Chin
In a modified Twyman-Green interferometer, the optical path variation is measured with the heterodyne central fringe identification technique, as the light beam is focused by a displaced microscopic objective on the front/rear surface of the test transparent plate. The optical path length variation is then measured similarly after the test plate is removed. The geometrical thickness of the test plate can be calculated under the consideration of dispersion effect. This method has a wide measurable range and a high accuracy in the measurable range. (c) 2011 Optical Society of America
DIGITAL-TO-ANALOG CONVERTER
(2011-07-21)
HSIEH WEN-HUNG
;
HUNG CHUNG-CHIH
The present invention relates to a digital-to-analog converter comprising a differentiation circuit, a conversion circuit, and an integration circuit. The differentiation circuit receives and differentiates a digital signal for producing a differentiation signal. The conversion circuit is coupled to the differentiation circuit. It receives the differentiation signal and produces a conversion signal according to a clock signal and the differentiation signal. The integration circuit is coupled to the conversion circuit. It receives and integrates the conversion signal for producing an analog signal. Thereby, the purpose of reducing distortion noises can be achieved.
UWB Gilbert downconverter with lumped-distributed phase-inverter rat-race coupler based on Chebyshev band-broadening technique
(2011-07-21)
Wei, H. -J.
;
Meng, C.
;
Chang, C. -H.
;
Huang, G. -W.
;
電子工程學系及電子研究所
A broadband Gilbert downconverter with a miniature phase-inverter rat-race coupler is demonstrated using 0.35 mu m SiGe BiCMOS technology. By lumped-distributed and band-broadening techniques, a large shrinkage ratio with wide bandwidth of Chebyshev response can be simultaneously attained in the spiral-shape coplanar-stripline phase-inverter rat-race coupler. The area of the demonstrated lumped-distributed phase-inverter rat-race coupler is 0.65 x 0.65 mm(2) and the experimental bandwidth ranging from 2.5 to 12.5 GHz is large enough to cover the UWB bandwidth. As a result, a broadband Gilbert downconverter with the proposed coupler achieves a conversion gain of 11-12 dB, IP(1dB) of -11 dBm, IIP(3) of -1 dBm and noise figure of 16 dB from 3 to 11 GHz.
Shock Tube Study on the Thermal Decomposition of Ethanol
(2011-07-21)
Wu, Chih-Wei
;
Matsui, Hiroyuki
;
Wang, Niann-Shiah
;
Lin, M. C.
;
應用化學系
The thermal decomposition of C(2)H(5)OH highly diluted in Ar (1 and 3 ppm) has been studied by monitoring H atoms using the atomic resonance absorption spectrometry (ARAS) technique behind reflected shock waves over the temperature range 1450-1760 K at fixed pressure: 1, 1.45, and 2 atm. The rate constant and the product branching fractions have been determined by analyzing temporal profiles of H atoms; the effect of the secondary reactions on the results has been examined by using a detailed reaction mechanism composed of 103 elementary reactions. The apparent rate constant of ethanol decomposition can be expressed as k(1)/s(-1) = (5.28 +/- 0.14) x 10(10) exp[-(23 530 +/- 980)/T] (T = 1450-1670 K, P = 1-2 atm) without a detectable pressure dependence within the tested pressure range of this study. Branching fractions for producing CH(3) + CH(2)OH (1a) and H(2)O + C(2)H(4) (1b) have been examined by a quantitative measurement of H atoms produced in the successive decompositions of the products CH(2)OH (1a): the pressure dependence of the branching fraction for channel 1a is obtained by a linear least-squares analysis of the experimental data and can be expressed as phi(1a) = (0.71 +/- 0.07) - (826 +/- 116)/T, (0.92 +/- 0.04) (1108 +/- 70)/T, and (1.02 +/- 0.10) (1229 +/- 168)/T for T = 1450-1760 K, at P = 0.99, 1.45, and 2.0 atm, respectively. The rate constant obtained in this study is found to be consistent with previous theoretical and experimental results; however, the pressure dependence of the branching fraction obtained in this study is smaller than those of previous theoretical works. Modification of the parameters for the decomposition rate in the falloff region is suggested to be important to improve the practical modeling of the pyrolysis and combustion of ethanol
Improved modulation speed of LED visible light communication system integrated to main electricity network
(2011-07-21)
Chow, C. W.
;
Yeh, C. H.
;
Liu, Y. F.
;
Liu, Y.
;
光電工程學系
In addition to the illumination purpose, using a light-emitting diode (LED) for indoor optical wireless communication has attracted much attention recently. Proposed and demonstrated is the use of a simple on-off keying (OOK) predistortion scheme together with a simple first-order resistance-capacitance equalisation circuit to increase the modulation speed of a white-light high-brightness LED (HB-LED). Optical filtering and complicated modulation formats are not required. Since only OOK modulation is used, the signal modulation and detection are very simple. Also are compared the different combinations of the system designs. By using first-order equalisation together with a predistortion, a bit-error rate of <10(-10) at 10 Mbit/s can be easily achieved when using the 1 MHz bandwidth phosphor-based white HB-LED.
PIEZOELECTRIC PANEL SPEAKER AND OPTIMAL METHOD OF DESIGNING THE SAME
(2011-07-21)
BAI MINGSIAN R.
;
TSAI YAO KUN
A piezoelectric panel speaker and an optimal method of designing the same is disclosed. In the structure of the speaker, at least one piezoelectric plate attached at a surrounding frame supports a diaphragm inside the surrounding frame. A spacer is inserted between the piezoelectric plate and the diaphragm. The structure of the piezoelectric plates fixed at the surrounding frame improves the speaker performance within the low frequency range. The finite element method is employed to build a mathematical model to simulate the sound pressure loading of the piezoelectric panel speaker. Also, the simulated annealing method is employed to approach the optimal design parameters of the speaker structure.
PHASE-LOCKED LOOP FREQUENCY SYNTHESIZER AND LOOP LOCKING METHOD THEREOF
(2011-07-21)
Chen Wei Zen
;
Lee Yen-Wei
A phase-locked loop frequency synthesizer and a loop locking method thereof are provided. The phase-locked loop frequency synthesizer includes a reference route sigma-delta modulator feedback circuit, a reference phase integration circuit coupled to the output end of the reference route sigma-delta modulator feedback circuit, a phase/frequency detector coupled to the output ends of the reference and feedback phase integration circuit, a loop filter coupled to the output end of the phase/frequency detector and the input end of the reference route sigma-delta modulator feedback circuit, an oscillator coupled to the output end of the loop filter, and a feedback phase integration circuit coupled to the output end of the oscillator and the input end of the phase/frequency detector. In the phase-locked loop frequency synthesizer, the oscillator generates corresponding frequency output signals which yield the advantages of resisting noise signals, enhancing resolution, and facilitating integration.
Novel Reversible Chemosensory Material Based on Conjugated Side-Chain Polymer Containing Fluorescent Pyridyl Receptor Pendants
(2011-07-21)
Chu, Hsuan-Chih
;
Lee, Yu-Hsien
;
Hsu, Shou-Jen
;
Yang, Po-Jen
;
Yabushita, Atsushi
A novel light-emitting monomer M1 and its side-chain polymer PI containing three conjugated aromatic pendants, including one pyridyl terminus, were successfully synthesized via Wittig and Pd-catalyzed Heck coupling reactions. The fluorescence of polymer P1 was efficiently quenched upon addition of different metal ions due to the facile energy transfers from the pendent groups of polymer PI to specific metal ions. Among these metal ions, PI exhibited extraordinary sensory selectivities for Ni(2+) and Cu(2+) ions over the other metal ions due to the stronger binding capabilities of Ni(2+) and Cu(2+) ions with polymer P1. From the time-resolved fluorescence (TRF) signals in photoluminescence spectra, the emergences of tau(1) decay components in polymer complexes (P1+Ni(2+)) and (P1-FCu(2+)) clearly indicated that their TRF traces consisted of two contributions, one from the complexes (tau(1)) and the other from free polymer P1 (tau(2)). Upon addition of Ni(2+) and Cu(2+) ions, polymer PI showed faster decay time constants (tau(1)) of metal ion quenching on TRF signals (i.e., better quenching efficiencies on photoluminescence) than its monomer M1. Furthermore, the on-off-on fluorescent switching behavior by adding a tridentate ligand 1,1,4,7,7-pentamethyl-diethylenetriamine (PMDTA) to the polymer complex (P1+Cu(2+)),for several successive cycles demonstrated a superior reusable chemosensor of P1 for further applications.
Induced Chain Alignment of Conjugated Polymers Within Nanoporous Template
(2011-07-22)
Lo, Kuan-Hsin
;
Ho, Rong-Ming
;
Liao, Yung-Ming
;
Hsu, Chain-Shu
;
Massuyeau, Florian
This work presents a simple method to generate ordered conjugated polymer nanoarrays through a pore-filling process for nanoporous polymer templates so as to enhance the efficiency of photoluminescence (PL). PL results combined with the morphological evolution examined by scanning probe microscopy revealed that the enhanced PL reaches maximum intensity as the template pores are completely filled by conjugated polymers. Polarized PL spectroscopy and grazing incidence Fourier transform infrared spectroscopy were used to determine the chain orientation of templated conjugated polymer; the spectroscopic results indicate a parallel chain orientation along the cylindrical direction of nanopores. The induced alignment of the polymer chains is attributed to a nanoscale spatial effect that increases the PL intensity and the lifetime of the conjugated polymer. The enhanced luminescence of nanostructured conjugated polymers is highly promising for use in designing luminescent nanodevices.
Synthesis of ethanol-soluble few-layer graphene nanosheets for flexible and transparent conducting composite films
(2011-07-22)
Nguyen, D. D.
;
Tai, N. H.
;
Chueh, Y. L.
;
Chen, S. Y.
;
Chen, Y. J.
We report a facile method of preparing few-layer graphene nanosheets (FLGs), which can be soluble in ethanol. Atomic force microscopy and high-resolution transmission electron microscopy studies reveal that FLGs have average thicknesses in the range of 2.6-2.8 nm, corresponding to 8-9 layers. A graphene/nafion composite film has a sheet resistance of 9.70 k Omega/sq at the transmittance of 74.5% (at 550 nm) while the nafion film on polyethylene terephthalate has a sheet resistance of 128 k Omega/sq at transmittance of 90.0%. For the cycling/bending test, almost no change in resistance was exhibited when the film was bent at an angle up to 140 degrees, and no obvious deviation in resistance could be found after 100 bending cycles was applied. In addition, an FLGs-poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) composite layer was demonstrated as the effective hole transporting layer to improve the hole transporting ability in an organic photovoltaic device, with which the power conversion efficiency was enhanced from 3.10% to 3.70%. The results demonstrated the promising applications of FLGs on graphene-based electronics, such as transparent electrode and flexible conducting film.
Designing heterostructures with higher-temperature superconductivity
(2011-07-22)
Le Hur, Karyn
;
Chung, Chung-Hou
;
Paul, I.
;
電子物理學系
;
Department of Electrophysics
We propose to increase the superconducting transition temperature T-c of strongly correlated materials by designing heterostructures which exhibit a high pairing energy as a result of magnetic fluctuations. More precisely, applying an effective theory of the doped Mott insulator, we envisage a bilayer Hubbard system where both layers exhibit intrinsic intralayer (intraband) d-wave superconducting correlations. Introducing a finite asymmetry between the hole densities of the two layers such that one layer becomes slightly more underdoped and the other more overdoped, we show a visible enhancement of T-c compared to the optimally doped isolated layer. Using the bonding and antibonding band basis, we show that the mechanism behind this enhancement of T-c is the interband pairing correlation mediated by the hole asymmetry which strives to decrease the paramagnetic nodal contribution to the superfluid stiffness. For two identical layers, T-c remains comparable to that of the isolated layer until moderate values of the interlayer single-particle tunneling term. These heterostructures shed new light on fundamental questions related to superconductivity.
Loycal atomic and electronic structures and ferroelectric properties of PbZr(0.52)Ti(0.48)O(3): An x-ray absorption study
(2011-07-25)
Ray, S. C.
;
Hsueh, H. C.
;
Wu, C. H.
;
Pao, C. W.
;
Asokan, K.
This work investigates local atomic and electronic structures of PbZr(0.52)Ti(0.48)O(3) (PZT) thin films with < 001 >, < 101 >, and < 111 > orientations using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy with theta = 0 degrees and 70 degrees incident angles. The EXAFS result indicates that the < 001 >-oriented PZT film has a polarization dominantly along the c-axis, while both < 101 >- and < 111 >-oriented PZT films have a dominant in-ab-plane polarization. The hysteresis-loop measurements show that the < 001 >-oriented PZT film has a much larger coercive field than those of other two PZT films, which indicates that the double-well potential along the c-axis is much deeper than that in the ab-plane. (C) 2011 American Institute of Physics. [doi:10.1063/1.3607475]
Loycal atomic and electronic structures and ferroelectric properties of PbZr0.52Ti0.48O3: An x-ray absorption study
(2011-07-25)
Ray, S. C.
;
Hsueh, H. C.
;
Wu, C. H.
;
Pao, C. W.
;
Asokan, K.
This work investigates local atomic and electronic structures of PbZr0.52Ti0.48O3 (PZT) thin films with < 001 >, < 101 >, and < 111 > orientations using extended x-ray absorption fine structure (EXAFS) and x-ray absorption near-edge structure (XANES) spectroscopy with theta = 0 degrees and 70 degrees incident angles. The EXAFS result indicates that the < 001 >-oriented PZT film has a polarization dominantly along the c-axis, while both < 101 >- and < 111 >-oriented PZT films have a dominant in-ab-plane polarization. The hysteresis-loop measurements show that the < 001 >-oriented PZT film has a much larger coercive field than those of other two PZT films, which indicates that the double-well potential along the c-axis is much deeper than that in the ab-plane. (C) 2011 American Institute of Physics. [doi:10.1063/1.3607475]
High Q microcavity light emitting diodes with buried AlN current apertures
(2011-07-25)
Cheng, Bo-Siao
;
Wu, Yun-Lin
;
Lu, Tien-Chang
;
Chiu, Ching-Hsueh
;
Chen, Cheng-Hung
We demonstrate a GaN-based high-Q microcavity light emitting diode (MCLED) with a buried AlN current aperture. A thin AlN layer is inserted on the InGaN/GaN multiple quantum wells as a current blocking layer and an optical confinement layer. The GaN-based MCLED is composed of a 29-pair GaN/AlN distributed Bragg reflector (DBR), an eight-pair of SiO(2)/Ta(2)O(5) dielectric DBR, and a three-lambda optical thickness InGaN/GaN active region. The current can be injected more effectively in the MCLED with a buried AlN current aperture. The output emission has a dominant emission peak wavelength at 440 nm with a very narrow linewidth of 0.52 nm, corresponding to a cavity Q-value of 846 at a driving current of 5 mA. (C) 2011 American Institute of Physics. [doi:10.1063/1.3617418]
Robust bi-stable memory operation in single-layer graphene ferroelectric memory
(2011-07-25)
Song, Emil B.
;
Lian, Bob
;
Kim, Sung Min
;
Lee, Sejoon
;
Chung, Tien-Kan
With the motivation of realizing an all graphene-based circuit for low power, we present a reliable nonvolatile graphene memory device, single-layer graphene (SLG) ferroelectric field-effect transistor (FFET). We demonstrate that exfoliated single-layer graphene can be optically visible on a ferroelectric lead-zirconate-titanate (PZT) substrate and observe a large memory window that is nearly equivalent to the hysteresis of the PZT at low operating voltages in a graphene FFET. In comparison to exfoliated graphene, FFETs fabricated with chemical vapor deposited (CVD) graphene exhibit enhanced stability through a bi-stable current state operation with long retention time. In addition, we suggest that the trapping/de-trapping of charge carriers in the interface states is responsible for the anti-hysteresis behavior in graphene FFET on PZT. (C) 2011 American Institute of Physics. [doi:10.1063/1.3619816]