Browsing by Issue Date, starting with "2003-04-11"

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Charge ordered ferromagnetic phase in manganites
(2003-04-11)
Minh-Tien, T
;
電子物理學系
;
Department of Electrophysics
A mechanism for charge ordered ferromagnetic phase in manganites is proposed. The mechanism is based on the double exchange in the presence of diagonal disorder. It is modeled by a combination of the Ising double-exchange and the Falicov-Kimball model. Within the dynamical mean-field theory the charge and spin correlation function are explicitly calculated. It is shown that the system exhibits two successive phase transitions. The first one is the ferromagnetic phase transition, and the second one is a charge ordering. As a result a charge ordered ferromagnetic phase is stabilized at low temperature.
半導體製程之對準標記
(2003-04-11)
李承士
;
張翼
本創作半導體製程之對準標記，該對準標記具備X、Y兩方向游標尺及半圓游標尺，且該對準標記係由主刻度與次刻度所組成；藉由本創作進行光罩對準校正，毋需多次的對準、曝光、顯影、檢驗誤差之繁瑣流程，僅需一次的對準操作即可以將前後道光罩偏差量控制在0.1μm，完成精確的光罩對準。
Field emission from aligned carbon nanofibers grown in situ by hot filament chemical vapor deposition
(2003-04-14)
Chen, CF
;
Lin, CL
;
Wang, CM
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Aligned high-aspect-ratio carbon nanofibers were grown in situ using modified hot filament chemical vapor deposition. The field-emission properties were then studied. An Fe-Cr wire filament acted as a catalytic source and a heat source. Carbon nanofibers were deposited on a Si substrate with CO2 as a carrier gas through ethanol. The experimental results indicate that the flow in the horizontal direction to the substrate produces carbon nanofibers with diameters of less than 10 nm. The field-emission current of 2 V/mum was 0.54 mA/cm2; the turn-on field of the sample was 1.1 V/mum. (C) 2003 American Institute of Physics.
On comparing the real and probed packet drop rates of a bottleneck router: the TCP traffic case
(2003-04-15)
Wang, SY
;
資訊工程學系
;
Department of Computer Science
In this paper, we address the question of whether the packet drop rate of a bottleneck router measured (experienced) by probe packets can accurately reflect the bottleneck router's real packet drop rate. To answer this question, we built a testbed network and conducted several real experiments on it. In these experiments, using various traffic types and loads, we compared the probed and the real packet drop rates of the bottleneck router. We also collected the internal queue length variation process of the bottleneck router and used it to do several post analyses to answer some 'what-if' questions. This paper presents some interesting findings derived from this study. (C) 2002 Elsevier Science B.V. All rights reserved.
Trace determination of nitrated polycyclic aromatic hydrocarbons using liquid chromatography with on-line electrochemical reduction and fluorescence detection
(2003-04-15)
Kuo, CT
;
Chen, HW
;
Lin, ST
;
環境工程研究所
;
Institute of Environmental Engineering
An efficient clean-up procedure coupled with a high performance liquid chromatography (HPLC) with on-line electrochemical (EC) reduction and fluorescence detection (FLD) was developed to quantify nitrated polycyclic aromatic hydrocarbons (NPAHs) in the airborne particulate. In this process, NPAHs were extracted ultrasonically followed by analysis by using a reversed phase column with an aqueous eluent containing 70% aqueous acetonitrile and sodium monocholoroacetate as a buffer solution. The extraction efficiencies were above 83% for 1-nitropyrene and 1,3-dinitropyrene (1,3-DNP) 1,6-DNP, and 1,8-DNP, and calibration graphs were linear with very good correlation coefficients (r > 0.999) and the detection limits were in the range of 1.0-2.2 pg for dinitropyrenes and nitropyrene. The proposed method provides a relatively simple and convenient procedure for determining the NPAHs samples in airborne particulate. (C) 2003 Elsevier Science B.V. All rights reserved.
Subcollinear acousto-optic tunable filter based on the medium with a strong acoustic anisotropy
(2003-04-15)
Zaitsev, AK
;
Kludzin, VV
;
光電工程學系
;
Department of Photonics
We design and investigate the properties of acousto-optical tunable filter (AOTF) based on tellurium dioxide (TeO2) single crystal. We use so-called "subcollinear" geometry of anisotropic acousto-optic interaction that occurs when the wavevector of incident light is collinear to acoustic energy vector. We have obtained the analytical formula of spectrum spread function of proposed AOTF and have found the condition determining the shape of that characteristic. Also we have designed and fabricated the experimental prototype of subcollinear AOTF. In our design we have used the reflection of acoustic wave that allowed to use crystal's media more effectively and reduce the AOTF size. The main advantage of filter based on proposed geometry is extremely low value of electrical driving power (20 mW) that makes it a strong candidate in many applications. (C) 2003 Elsevier Science B.V. All rights reserved.
Decoupling of degenerate positive-norm states in Witten's string field theory
(2003-04-15)
Kao, HC
;
Lee, JC
;
電子物理學系
;
Department of Electrophysics
We show that the degenerate positive-norm physical propagating fields of the open bosonic string can be gauged to the higher rank fields at the same mass level. As a result, their scattering amplitudes can be determined from those of the higher spin fields. This phenomenon arises from the existence of two types of zero-norm states with the same Young representations as those of the degenerate positive-norm states in the old covariant first quantized (OCFQ) spectrum. This is demonstrated by using the lowest order gauge transformation of Witten's string field theory (WSFT) up to the fourth massive level (spin-five), and is found to be consistent with conformal field theory calculation based on the first quantized generalized sigma-model approach. In particular, on-shell conditions of zero-norm states in the OCFQ stringy gauge transformation are found to correspond, in a one-to-one manner, to the background ghost fields in off-shell gauge transformation of WSFT. The implication of decoupling of scalar modes on Sen's conjectures is also briefly discussed.
Synthesis and properties of soluble aromatic polyamides derived from 2.2 '-bis(4-carboxyphenoxy)-9,9 '-spirobifluorene
(2003-04-15)
Wu, SC
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
The synthesis of a new bis(ether carboxylic acid), 2,2'-bis(4-carboxyphenoxy)-9,9'-spirobifluorene, in which two orthogonally arranged carboxyphenoxyfluorene entities are connected through an sp(3) carbon atom (the Spiro center), is reported. The direct phosphorylation polycondensation of this diacid monomer with various aromatic diamines yields aromatic polyamides containing 9,9'-spirobifluorene moieties in the main chain. The presence of the spiro segment restricts the close packing of the polymer chains and decreases interchain interactions, resulting in amorphous polyamides with enhanced solubility, and high glass-transition temperatures and good thermal stability are maintained through controlled segmental mobility. The glass-transition temperatures of these polyamides are in the range of 234-306degreesC, with 10% weight losses occurring at temperatures above 530 degreesC. (C) 2003 Wiley Periodicals, Inc.
DC to 8 GHz 11 dB gain Gilbert micromixer using GaInP/GaAs HBT technology
(2003-04-17)
Meng, CC
;
Lu, SS
;
Chiang, MH
;
Chen, HC
;
電信工程研究所
A wideband GaInP/GaAs heterojunction bipolar transistor (HBT) micromixer from DC to 8 GHz with I I dB single-ended conversion gain is demonstrated. The input return loss is better than 10 dB for frequencies up to 9 GHz. The single-to-differential input stage in a Gilbert micromixer renders good wideband frequency response and eliminates the need for common-mode rejection. IP1dB = -17 dBm and IIP3 = -7 dBm are achieved for a small local oscillator power of -2 dBm when LO = 5.35 GHz and PF = 5.7 GHz.
A survey on multi-loop networks
(2003-04-18)
Hwang, FK
;
應用數學系
;
Department of Applied Mathematics
Bermond, Comellas and Hsu gave an excellent survey on multi-loop networks, directed and undirected, in 1995, but only one and half page is on loop networks other than the directed double-loop. Hwang recently gave a substantial survey, but only on the directed double-loop. This survey is a companion of the latter survey by focusing on the other loop networks. (C) 2002 Published by Elsevier Science B.V.
A novel concept for finding proper orthogonal wavelets effectively to solve a large object scattering problem
(2003-04-18)
Chen, CM
;
Tarng, JH
;
Huang, JM
;
電信工程研究所
;
友訊交大聯合研發中心
[1] A novel concept of "visible energy" is proposed, and its magnitude is shown to be valuable information for determining whether the chosen orthogonal wavelet is proper in solving a large object scattering problem. With the properly chosen wavelets for the targeting problem the ( transformed) wavelet-domain impedance matrix can be sparsified effectively for solving electromagnetic integral problems. Visible energy is defined as the energy of all dilations of a single mother wavelet for an arbitrary translation in the spectral domain over the entire "visible region." It is found that for large matrix sizes, using wavelets with smaller visible energy will lead to a greater sparsification of the matrix. Numerical examples considering various scatterers with different shapes such as a circular cylinder, an L-shaped scatterer, and a duct show the validity of our findings.
古硯
(2003-04-20)
管管
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(2003-04-20)
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(2003-04-20)
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(2003-04-20)
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(2003-04-20)
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(2003-04-20)
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(2003-04-20)
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Current detection of superradiance and induced entanglement of double quantum dot excitons
(2003-04-25)
Chen, YN
;
Chuu, DS
;
Brandes, T
;
電子物理學系
;
Department of Electrophysics
We propose to measure the superradiance effect by observing the current through a semiconductor double-dot system. An electron and a hole are injected separately into one of the quantum dots to form an exciton and then recombine radiatively. We find that the stationary current shows oscillatory behavior as one varies the interdot distance. The amplitude of oscillation can be increased by incorporating the system into a microcavity. Furthermore, the current is suppressed if the dot distance is small compared to the wavelength of the emitted photon. This photon trapping phenomenon generates the entangled state and may be used to control the emission of single photons at predetermined times.
Theory of the vortex matter transformations in high-T-c superconductor YBCO
(2003-04-25)
Li, DP
;
Rosenstein, B
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
Flux line lattice in type II superconductors undergoes a transition into a "disordered" phase such as vortex liquid or vortex glass, due to thermal fluctuations and random quenched disorder. We quantitatively describe the competition between the thermal fluctuations and the disorder using the Ginzburg-Landau approach. The following T-H phase diagram of YBCO emerges. There are just two distinct thermodynamical phases, the homogeneous and the crystalline one, separated by a single first order transition line. The line, however, makes a wiggle near the experimentally claimed critical point at 12 T. The "critical point" is reinterpreted as a (noncritical) Kauzmann point in which the latent heat vanishes and the line is parallel to the T axis. The magnetization, the entropy, and the specific heat discontinuities at melting compare well with experiments.