Browsing by Issue Date, starting with "2010-08-22"

Now showing 1 - 20 of 45490

Solid-phase thermodynamic interpretation of ion desorption in matrix-assisted laser desorption/ionization
(2010-08-22)
Lai, Yin Hung
;
Wang, Chia Chen
;
Lin, Sheng Hsian
;
Wang, Yi Sheng
;
Lee, Yuan Tseh
交大e-News第077期
(2010-08-23)
Secretariat
;
國立交通大學秘書室
High-gain complementary inverter with InGaZnO/pentacene hybrid ambipolar thin film transistors
(2010-08-23)
Liu, Po-Tsun
;
Chou, Yi-Teh
;
Teng, Li-Feng
;
Fuh, Chur-Shyang
;
光電工程學系
Ambipolar thin film transistors (TFTs) with InGaZnO/pentacene heterostructure channels are demonstrated for a high-voltage-gain complementary metal oxide semiconductor (CMOS) inverter. The ambipolar TFT exhibits a electron mobility of 23.8 cm(2)/V s and hole mobility of 0.15 cm(2)/V s for the InGaZnO and pentacene, respectively. The thermal annealing process was also studied to adjust electron concentration reducing operating voltage of the CMOS inverter. The voltage gain achieves as high as 60 obtained in the first and third quadrants of the voltage transfer characteristic. The high performance and simple manufacture of the heterostructure CMOS inverter show promise as critical components in various electrical applications. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483616]
2-D modeling of dual-mode acoustic phonon excitation of a triangular nanoplate
(2010-08-23)
Tai, Po-Tse
;
Yu, Pyng
;
Tang, Jau
;
光電工程學系
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Department of Photonics
In this theoretical work, we investigated coherent phonon excitation of a triangular nanoplate based on 2-D Fermi-Pasta-Ulam lattice model. Based on the two-temperature model commonly used in description of laser heating of metals, we considered two kinds of forces related to electronic and lattice stresses. Based on extensive simulation and analysis, we identified two major planar phonon modes, namely, a standing wave mode related to the triangle bisector and another mode corresponding to half of the side length. This work elucidates the roles of laser-induced electronic stress and lattice stress in controlling the initial phase and the amplitude ratio between these two phonon modes. (C) 2010 Elsevier B.V. All rights reserved.
Formation, Binding, and Stability of O-Ag-CO(2)-Ag-O Compounds on Ag(100) Investigated by Low Temperature Scanning Tunneling Microscopy and Manipulation
(2010-08-26)
Hsieh, Ming-Feng
;
Li, Hong-Doa
;
Lin, Deng-Sung
;
Morgenstern, Karina
;
物理研究所
The understanding of reaction intermediates in heterogeneous catalysis has important implications for the design of novel catalysts. We investigate the adsorption of CO(2) on oxygen precovered Ag(100) at low temperature (17 K) by scanning tunneling microscopy and inelastic electron tunneling manipulation at 5 K. On the terraces, the adsorption leads to O-Ag-CO(2)-Ag-O compounds with reduced binding of the oxygen to the surface as compared to the separately adsorbed molecules. The compound can be either dissociated into a bistable O-Ag-CO(2) compound at 1.6 V, dissociated into its constituents at 2.2 V, or reacted at 6.5 V into a species, which we tentatively attribute to CO(3). The thus obtained carbon trioxide or carbonate is an intriguing reaction intermediate, because it is not stable in the gas phase. Our detailed study of coadsorbed species outlines a possibility to investigate precursors of reactions that involve the substrate atoms.
Tunable Fano-Kondo resonance in side-coupled double quantum dot systems
(2010-08-26)
Chung, Chung-Hou
;
Lee, Tsung-Han
;
電子物理學系
;
Department of Electrophysics
We study the interference between the Fano and Kondo effects in a side-coupled double quantum dot system where one of the quantum dots couples to conduction-electron bath while the other dot only side couples to the first dot via antiferromagnetic (AF) spin-exchange coupling. We apply both the perturbative renormalization-group (RG) and numerical renormalization-group (NRG) approaches to study the effect of AF coupling on the Fano line shape in the conduction leads. With particle-hole symmetry, the AF spin-exchange coupling competes with the Kondo effect and leads to a local spin-singlet ground state for arbitrary small coupling, so-called "two-stage Kondo effect." As a result, via NRG we find the spectral properties of the Fano line shape in the tunneling density of states rho(c)(omega) of conduction-electron leads shows double dip-peak features at the energy scale around the Kondo temperature and the one much below it, corresponding to the two-stage Kondo effect; it also shows an universal scaling behavior at very low energies. We find the qualitative agreement between the NRG and the perturbative RG approaches. Relevance of our work to the experiments is discussed.
Coherent multiple-stage optical rectification terahertz wave generator
(2010-08-26)
Pan, Ci-Ling
;
Huang, Jung Y.
;
Chang, Chen-Shiung
;
Chen, Ching-Wei
;
Lin, Yu-Shian
The present invention coherent multiple-stage optical rectification terahertz wave generator discloses the generation of single-cycle terahertz radiation with two-stage optical rectification in GaSe crystals. By adjusting the time delay between the pump pulses employed to excite the two stages, the terahertz radiation from the second GaSe crystal can constructively superpose with the seeding terahertz field from the first stage. The high mutual coherence between the two terahertz radiation fields is ensured with the coherent optical rectification process and can be further used to synthesize a desired spectral profile of output coherent THz radiation. The technique is also useful for generating high amplitude single-cycle terahertz pulses, not limited by the pulse walk-off effect from group velocity mismatch in the nonlinear optical crystal used.
Formation, Binding, and Stability of O-Ag-CO2-Ag-O Compounds on Ag(100) Investigated by Low Temperature Scanning Tunneling Microscopy and Manipulation
(2010-08-26)
Hsieh, Ming-Feng
;
Li, Hong-Doa
;
Lin, Deng-Sung
;
Morgenstern, Karina
;
物理研究所
The understanding of reaction intermediates in heterogeneous catalysis has important implications for the design of novel catalysts. We investigate the adsorption of CO2 on oxygen precovered Ag(100) at low temperature (17 K) by scanning tunneling microscopy and inelastic electron tunneling manipulation at 5 K. On the terraces, the adsorption leads to O-Ag-CO2-Ag-O compounds with reduced binding of the oxygen to the surface as compared to the separately adsorbed molecules. The compound can be either dissociated into a bistable O-Ag-CO2 compound at 1.6 V, dissociated into its constituents at 2.2 V, or reacted at 6.5 V into a species, which we tentatively attribute to CO3. The thus obtained carbon trioxide or carbonate is an intriguing reaction intermediate, because it is not stable in the gas phase. Our detailed study of coadsorbed species outlines a possibility to investigate precursors of reactions that involve the substrate atoms.
Wide spectral range confocal microscope based on endlessly single-mode fiber
(2010-08-30)
Hubbard, R.
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Ovchinnikov, Yu. B.
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Hayes, J.
;
Richardson, D. J.
;
Fu, Y. J.
We report an endlessly single mode, fiber-optic confocal microscope, based on a large mode area photonic crystal fiber. The microscope confines a very broad spectral range of excitation and emission wavelengths to a single spatial mode in the fiber. Single-mode operation over an optical octave is feasible. At a magnification of 10 and lambda = 900 nm, its resolution was measured to be 1.0 mu m (lateral) and 2.5 mu m (axial). The microscope's use is demonstrated by imaging single photons emitted by individual InAs quantum dots in a pillar microcavity. (C) 2010 Optical Society of America
A new low-voltage-driven GRIN liquid crystal lens with multiple ring electrodes in unequal widths
(2010-08-30)
Kao, Yung-Yuan
;
Chao, Paul C. -P.
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Hsueh, Chieh-Wen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This work is dedicated to design a novel liquid crystal (LC) lens device with multiple ring electrodes in unequal widths, in order to offer tunability on focusing quality and to lower the level of applied voltage. The number and widths of the multiple ring electrodes are pre-designed and optimized to offer the on-line tunability on individual electrode voltages to render a better refraction index distribution for focusing, as compared to the past hole-type LC lenses. The resulted refractive index distribution is expected to offer similar focusing effects based on the theory of the gradient refraction index (GRIN) lens. The transparent electrodes of this new LC lens are placed at the inner surface of the LC cell to minimize the driving voltages, in results, less than 10V, for the same level of focusing power and an easy practical operation. A new fabrication process in the wafer level to bury bus lines is developed for generating smooth electrical fields over the lens aperture. In addition, a dielectric layer is coated between electrodes and the LC layer. (C) 2010 Optical Society of America
Nonequilibrium occupation number and charge susceptibility of a resonance level close to a dissipative quantum phase transition
(2010-08-30)
Chung, Chung-Hou
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Latha, K. V. P.
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電子物理學系
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Department of Electrophysics
Based on the recent paper [Phys. Rev. Lett. 102, 216803 (2009)], we study the nonequilibrium occupation number n(d) and charge susceptibility chi of a resonance level close to dissipative quantum phase transition of the Kosterlitz-Thouless (KT) type between a delocalized phase for weak dissipation and a localized phase for strong dissipation. The resonance level is coupled to two spinless fermionic baths with a finite bias voltage and an Ohmic bosonic bath representing the dissipative environment. The system is equivalent to an effective anisotropic Kondo model out of equilibrium. Within the nonequilibrium renormalization-group approach, we calculate nonequilibrium magnetization M and spin susceptibility chi in the effective Kondo model, corresponding to 2n(d)-1 and chi of a resonance level, respectively. We demonstrate the smearing of the KT transition in the nonequilibrium magnetization M as a function of the effective anisotropic Kondo couplings, in contrast to a perfect jump in M at the transition in equilibrium. In the limit of large bias voltages, we find M and chi at the KT transition and in the localized phase show deviations from the equilibrium Curie-law behavior. As the system gets deeper in the localized phase, both n(d)-1/2 and chi decrease more rapidly to zero with increasing bias voltages.
Bimodel onset strain relaxation in InAs quantum dots with an InGaAs capping layer
(2010-08-30)
Chen, J. F.
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Chen, Ross C. C.
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Chiang, C. H.
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Chen, Y. F.
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Wu, Y. H.
Capping InAs quantum dots (QDs) with an InGaAs layer allows strain relaxation to induce a low-energy electron state below a set of fine dot family states, which is consistent with photoluminescence (PL) spectra. The evolution of InAs thickness suggests a bimodal onset relaxation, i.e., a fine dot family that is strain-relieved by indium outdiffusion from the QDs, as suggested by transmission electron microscopy, and a low-energy dot family that is strain relaxed by the generation of lattice misfits. The indium outdiffusion can explain an abnormal PL blueshift in 70 meV in the fine dot family at onset of strain relaxation. (C) 2010 American Institute of Physics. [doi:10.1063/1.3483757]
Selective acoustic phonon mode excitation of multi-mode silver nanoprisms
(2010-08-30)
Tai, Po-Tse
;
Yu, Pyng
;
Huang, Jane
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Tang, Jau
;
光電工程學系
Nanoprisms are known to exhibit two major planar phonon modes in ultrafast experiments, namely, a stronger mode related to the bisector height and a weaker mode related to half of the edge length. In this work we demonstrated photoacoustic excitation of a specific acoustic phonon mode in silver nanoprisms using two properly timed pump pulses. Using this technique, we could selectively excite only the weak totally symmetric mode while suppressing the dominant breathing mode. Via direct observation of such a mode, which is hardly detectable directly with the conventional single pump pulse technique, we could elucidate the roles of hot electrons in photoinduced ultrafast structural dynamics in laser-heated nanoparticles. (C) 2010 Elsevier B.V. All rights reserved.
Barrier-overpassing transporter
(2010-08-31)
Cheng
;
Pi-Ying
;
Guo
;
Fang-Fu
;
Wong
The present invention discloses a barrier-overpassing transporter, which comprises: a support frame carrying a rider or another load; a sensing/adjusting module detecting a tilting state of the support frame and maintaining the support frame in a horizontal state; a ground contact module arranged below the support frame supporting an effective load and lifting the support frame to overpass a surface of a barrier; and a wireless transceiver module collecting and transmitting information to enable adjustments and activities responding to interior states of the transporter. Thereby, the present invention can provide a safe, stable, reliable, comfortable, convenient and low-cost barrier-overpassing transporter.
Growth and photoresponse study of PdO nanoflakes reactive-sputter deposited on SiO2
(2010-09-01)
Huang, Chien-Jung
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Pan, Fu-Ming
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Chen, Hsiu-Ying
;
Li-Chang
;
材料科學與工程學系
This study prepares PdO nanostructures on a SiO2 substrate by reactive-sputter deposition and examines photoresponse characteristics of the thin films. PdO thin films deposited at 25 degrees C is composed of bowed nanoflakes standing on the SiO2 substrate, which have a single-crystalline structure after thermal anneal at 400 degrees C. The 400 degrees C-annealed nanoflake thin film has a band gap energy in the red-light range (similar to 2.06 eV), and exhibits a very sensitive photoresponse upon the UV (365 nm) illumination. The high photoresponse sensitivity of the 400 degrees C-annealed nanoflake thin film is ascribed to a lower density of recombination centers and traps due to an excellent crystallinity and a high carrier extraction efficiency due to a low electrical resistivity. A slight decrease in the photocurrent density during the initial stage of the UV illumination is attributed to adsorption of O-2(-) anions on the 400 degrees C-annealed nanoflakes. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3476567]
Magnetic Qubit in a Non-Magnetic Semiconductor Quantum Dot Molecule
(2010-09-01)
Voskoboynikov, O.
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Wijers, C. M. J.
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交大名義發表
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National Chiao Tung University
We consider a system of two vertical lens-shaped circular InAs/GaAs quantum dots when an external magnetic field is applied along the system's growth direction. The quantum dots have substantially different diameters in contrast to most of the known systems. We discuss a possibility to coherently drive coupled electronic ground states (to relocate electronic wave functions from one dot to another). This can be described as a manipulation of a magnetic iso-spin qubit. At the same time the relocation correlates with the anti-crossing behavior of the two lowest electronic states of the quantum dot molecule and generates unusual features of the magnetic susceptibility of the system. It follows from this theoretical study that in our non-magnetic system we can perform and monitor the magnetic qubit. The qubit can be dynamically driven by an external magnetic field and retraced from the magnetic susceptibility changes. A few single-qubit quantum gates can be performed.
Brain morphological changes associated with cyclic menstrual pain
(2010-09-01)
Tu, Cheng-Hao
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Niddam, David M.
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Chao, Hsiang-Tai
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Chen, Li-Fen
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Chen, Yong-Sheng
Primary dysmenorrhea (PDM) is the most prevalent gynecological disorder for women in the reproductive age. PDM patients suffer from lower abdominal pain that starts with the onset of the menstrual flow. Prolonged nociceptive input to the central nervous system can induce functional and structural alterations throughout the nervous system. In PDM, a chronic viscero-nociceptive drive of cyclic nature, indications of central sensitization and altered brain metabolism suggest a substantial central reorganization. Previously, we hypothesized that disinhibition of orbitofrontal networks could be responsible for increased pain and negative affect in PDM. Here, we further tested this hypothesis. We used an optimized voxel-based morphometry (VBM) approach to compare total and regional gray matter (GM) increases and decreases in 32 PDM patients with 32 healthy age and menstrual cycle matched (peri-ovulatory phase) controls. Abnormal decreases were found in regions involved in pain transmission, higher level sensory processing, and affect regulation while increases were found in regions involved in pain modulation and in regulation of endocrine function. Moreover. GM changes in regions involved in top-down pain modulation and in generation of negative affect were related to the severity of the experienced PDM pain. Our results demonstrate that abnormal GM volume changes are present in PDM patients even in the absence of pain. These changes may underpin a combination of impaired pain inhibition, increased pain facilitation and increased affect. Our findings highlight that longer lasting central changes may occur not only in sustained chronic pain conditions but also in cyclic occurring pain conditions. (C) 2010 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.
Parallel Newton-Krylov-Schwarz algorithms for the three-dimensional Poisson-Boltzmann equation in numerical simulation of colloidal particle interactions
(2010-09-01)
Hwang, Feng-Nan
;
Cai, Shang-Rong
;
Shao, Yun-Long
;
Wu, Jong-Shinn
;
機械工程學系
We investigate fully parallel Newton-Krylov-Schwarz (NKS) algorithms for solving the large sparse nonlinear systems of equations arising from the finite element discretization of the three-dimensional Poisson-Boltzmann equation (PBE), which is often used to describe the colloidal phenomena of an electric double layer around charged objects in colloidal and interfacial science. The NKS algorithm employs an inexact Newton method with backtracking (INB) as the nonlinear solver in conjunction with a Krylov subspace method as the linear solver for the corresponding Jacobian system. An overlapping Schwarz method as a preconditioner to accelerate the convergence of the linear solver. Two test cases including two isolated charged particles and two colloidal particles in a cylindrical pore are used as benchmark problems to validate the correctness of our parallel NKS-based PBE solver. In addition, a truly three-dimensional case, which models the interaction between two charged spherical particles within a rough charged micro-capillary, is simulated to demonstrate the applicability of our PBE solver to handle a problem with complex geometry. Finally, based on the result obtained from a PC cluster of parallel machines, we show numerically that NKS is quite suitable for the numerical simulation of interaction between colloidal particles, since NKS is robust in the sense that INB is able to converge within a small number of iterations regardless of the geometry, the mesh size, the number of processors. With help of an additive preconditioned Krylov subspace method NKS achieves parallel efficiency of 71% or better on up to a hundred processors for a 3D problem with 5 million unknowns. (C) 2010 Elsevier B.V. All rights reserved.
Persistent cognitive decline in older hospitalized patients in Taiwan
(2010-09-01)
Chen, Cheryl Chia-Hui
;
Chang, Yue-Cune
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Huang, Guan-Hua
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Peng, Jui-Hua
;
Tseng, Chien-Ning
P>Aim. This paper is a report of a study conducted to determine the prevalence and predictors of persistent and transient cognitive decline in older hospitalized patients over 6 months after hospital discharge. Background. Cognitive decline occurs in 16-35 center dot 5% of older hospitalized patients, but this decline may be persistent rather than transient. Distinguishing persistent from transient cognitive decline is clinically useful. Methods. For this prospective cohort study, 291 older patients were recruited from five medical and surgical units at a tertiary medical centre in Taiwan between 2004 and 2006. Participants were assessed for cognitive status by scores on the Mini-Mental State Examination at admission, discharge, 3 and 6 months postdischarge. Persistent cognitive decline was defined as continuing score reduction and >= 3-point reduction 6 months postdischarge. Transient decline was defined as >= 3-point reduction at some stage, with a total decline < 3 points 6 months postdischarge. Findings. The cognitive status of the majority of participants (57 center dot 4%, n = 167) decreased >= 3 points during follow-up. Of these decliners, 59 (35 center dot 3%) had persistent cognitive decline, with an average 5 center dot 32-point reduction 6 months postdischarge. Forty-six (27 center dot 5%) participants experienced transient cognitive decline. After multiple adjustments in logistic regression analysis, persistent decline was predicted by no in-hospital functional decline (OR = 0 center dot 16, P = 0 center dot 002), more re-admissions after discharge (OR = 2 center dot 42, P = 0 center dot 020), and older age (OR = 1 center dot 09, P = 0 center dot 048). Conclusion. A new perspective is needed on discharge planning on patients at risk for persistent cognitive decline. Nurses can oversee the delivery of care, identify cognitive decline, refer patients, and educate families on strategies to enhance cognitive functioning for their aging relatives.
Fuzzy decision maps: a generalization of the DEMATEL methods
(2010-09-01)
Tzeng, Gwo-Hshiung
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Chen, Wen-Hsien
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Yu, Rachung
;
Shih, Meng-Lin
;
科技管理研究所
The Decision making trial and evaluation laboratory (DEMATEL) method is used to build and analyze a structural model with causal relationships between different criteria. In this paper, it shows that DEMATEL is the specific case of fuzzy decision maps (FDM) when the threshold function is linear. Both FDM and DEMATEL have the same direct and indirect influence matrix. FDM incorporates the eigenvalue method, the fuzzy cognitive maps, and the weighting equation. In addition two numerical examples are illustrated to demonstrate the proposed results. On the basis of the mathematical proof and numerical results, we can conclude that FDM is a generalization of DEMATEL method.