Browsing by Issue Date, starting with "2001-12-15"

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Hybridization of electron, light-hole, and heavy-hole states in InAs/GaSb quantum wells
(2001-12-15)
Zakharova, A
;
Yen, ST
;
Chao, KA
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have investigated the hybridization of the electron states. the light-hole states and the heavy-hole states in InAs/GaSb broken-gap quantum wells. This effect is profound Mien the InAs layer and the GaSb layer are sufficiently thick such that the electron level lies below the heavy-hole level and the light-hole level at zone center. To calculate the dispersions and the wave functions in these structures we have applied the scattering matrix algorithm to the eight-band k.p model. We have found a hybridization gap as large as 20 meV resulting from the anticrossing of the electron and the light-hole dispersion curves. A multiple anticrossing of the electron states. the light-hole states and the heavy-hole states may occur when the heavy hole level lies in the hybridization gap produced by the electron states and the light-hole states. This unusual hybridization of the three subbands. which behaves differently for the "spin-up" and the "spin-down" states. has been investigated in details around the anticrossing point, While the electronlike and light holelike states mix strongly, the heavy holelike state may remain unperturbed.
Stability analysis of anisotropic inflationary cosmology
(2001-12-15)
Chen, CM
;
Kao, WF
;
物理研究所
;
Institute of Physics
The stability analysis of an anisotropic inflationary universe of the four-dimensional Neveu-Schwarz-Neveu-Schwarz string model with a nonvanishing cosmological constant is discussed in this paper. The accelerating expansion solution found earlier is shown to be stable against the perturbations with respect to the dilaton and axion fields once the dilaton field falls close to the local minimum of the symmetry-breaking potential. This indicates that the Bianchi type-I space tends to evolve to an isotropic flat Friedmann-Robertson-Walker space. This expanding solution is also shown to be stable against the perturbation with respect to anisotropic spatial directions.
Ground state of electron gases at negative compressibility
(2001-12-15)
Schakel, AMJ
;
電子物理學系
;
Department of Electrophysics
Two- and three-dimensional electron gases with a uniform neutralizing background are Studied at negative compressibility. Parametrized expressions for the dielectric function are used to access this strong-coupling regime, where the screened Coulomb potential becomes overall attractive for like charges. Closely examining these expressions reveals that the ground state with a periodic modulation of the charge density, albeit exponentially damped, replaces the homogeneous one at positive compressibility. The wave vector characterizing the new ground state depends on the density and is complex. having a positive imaginary part, as does the homogeneous ground state, and real part, as does the genuine charge density wave.
Quantum mechanical approach for photon-associated electron tunneling through a quantum dot
(2001-12-15)
Lin, KC
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
Photon-associated electron tunneling (PAT) in a quantum dot is studied by a fully quantum-mechanical approach. An experiment to determine the electron-photon coupling coefficient g and the photon number of the system is proposed to distinguish whether the system is in the quantum situation or the semiclassical situation. It is also found that the PAT current is assisted or suppressed depending on the shift of the environment photon-intensity-dependent photon sidebands.
管管作品十一首
(2001-12-15)
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管管作品十一首
(2001-12-15)
管管
Chlorine-induced Si surface segregation on the Ge-terminated Si/Ge(100) surface from core-level photoemission
(2001-12-15)
Lin, DS
;
Pan, SY
;
Wu, MW
;
物理研究所
;
Institute of Physics
This study investigated the thermal reactions on the Cl-terminated Si/Ge(100)-2x1 surface using synchrotron radiation photoemission spectroscopy. Populations of surface Cl-Ge and CI-Si bonds during annealing are monitored by measuring the intensities of their corresponding Ge 3d, Si 2p, and Cl 2p core-level components. Experimental results clearly demonstrate that no Si atoms are present on the surface after the deposition of 0.8 monolayer Si on the Ge(100) surface at 730 K and that CI termination pulls out the indiffused Si of about two atomic layers deep to form Cl-Si bonds upon annealing at 550-690 K. We attribute such chlorine induced Si segregation to a thermodynamic driving force that favors the CI-Si surface species. Above 680 K, chlorine is desorbed in the form of SiCl2, although the top surface layer of the starting Si/Ge(100) sample consists of Ge-Ge dimers only.
A new parallel adaptive finite volume method for the numerical simulation of semiconductor devices
(2001-12-15)
Li, YM
;
Liu, JL
;
Chao, TS
;
Sze, SM
;
應用數學系
Based on adaptive finite volume approximation, a posteriori error estimation, and monotone iteration, a novel system is proposed for parallel simulations of semiconductor devices. The system has two distinct parallel algorithms to perform a complete set of I-V simulations for any specific device model. The first algorithm is a domain decomposition on I-irregular unstructured meshes whereas the second is a parallelization of multiple I-V points. Implemented on a Linux cluster using message passing interface libraries, both algorithms are shown to have excellent balances on dynamic loading and hence result in efficient speedup. Compared with measurement data, computational results of sub-micron MOSFET devices are given to demonstrate the accuracy and efficiency of the system. (C) 2001 Elsevier Science B.V. All rights reserved.
管管作品十一首
(2001-12-15)
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Electron energy state dependence on the shape and size of semiconductor quantum dots
(2001-12-15)
Li, YM
;
Voskoboynikov, O
;
Lee, CP
;
Sze, SM
;
Tretyak, O
In this article we present a unified model for studying the effect of the sizes and shapes of small semiconductor quantum dots on the electron and hole energy states. We solved the three-dimensional effective one band Schrodinger equation for semiconductor quantum dots with disk, lenticular, and conical shapes. For small InAs/GaAs quantum dots we found a substantial difference in the ground state and first excited state electron energies for dots with the same volume but different shapes. Electron energy dependence on volume is found to be quite different from the commonly quoted V-2/3. The exponent can vary over a wide range and depends on the dot shapes. (C) 2001 American Institute of Physics.
管管作品十一首
(2001-12-15)
管管
High-tensile-property layered silicates/polyurethane nanocomposites by using reactive silicates as pseudo chain extenders
(2001-12-18)
Tien, YI
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Tethered layered silicates/polyurethane nanocomposites displaying high tensile strength and high elongation to break were synthesized by using reactive swelling-agent-modified silicates as pseudo chain extenders for a polyurethane prepolymer. The dispersion of layered silicates in polyurethane was found to be transformed from an intercalated to an exfoliated structure when the number of hydroxyl groups of the swelling agent increased as evidenced from the transmission electron microscopy and wide-angle X-ray diffraction analyses. The improved morphology of the nanocomposites resulted in an ultrahigh efficiency in enhancing the mechanical properties of polyurethane, despite variations in the molecular weight and in the extent of hydrogen bonding in the hard segment phase. In particular, a 34% increase in Young's modulus, a 1.7-fold increase in the tensile strength, and a 1.3-fold increase in the elongation to break occurred in the nanocomposite of polyurethane containing only 1 wt % trihydroxyl-group swelling-agent-modified silicates as compared to those of pristine polyurethane.
In situ compatibilized SAN/LCP blends through reactive copolymers
(2001-12-20)
Huang, JM
;
You, MF
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
Styrene-acrylonitrile-glycidyl methacrylate (SAG) copolymers with various contents of glycidyl methacrylate (GMA) were used to compatibilize the incompatible blends of styrene-acrylonitrile (SAN) and a liquid crystalline polymer (LCP). These SAG copolymers contain reactive glycidyl groups that are able to react with the carboxylic acid and/or hydroxyl end groups of the LCP to form the SAG-g-LCP copolymers during melt processing. The in situ-formed graft copolymers tend to reside along the interface to reduce the interfacial tension and to increase the interface adhesion. The morphologies of the SAN/LCP blends were examined by using scanning electron microscopy (SEM), where the compatibilized SAN/LCP blends were observed with greater numbers and finer fibrils than those of the corresponding uncompatibilized blends. The mechanical properties of the blends increased after compatibilization. The presence of a small amount (200 ppm) of ethyl triphenylphosphonium bromide (ETPB) catalyst further promotes the graft reaction and improves the compatibilization. (C) 2001 John Wiley & Sons, Inc.
The preventive effects of G115 on balloon injury-induced neointima formation in rats
(2001-12-28)
Wu, CH
;
Tsai, BR
;
Hsieh, WT
;
Chang, GY
;
Mao, SJT
After percutaneous transluminal coronary angioplasty (PTCA), 30-50% of the patients may present with restenosis within 6 months. The aim of this study was to search for a preventive remedy against the balloon injury-induced neointima formation. Ginseng, with its wide indications on immune and cardiovascular functions, has prompted us to explore its role in neointima formation. In the present study, we aimed to explore if a standardized Panax Ginseng extract G115 was able to inhibit neointimal formation. With BrdU luminencence assay, maximal proliferation of rat smooth muscle cells was reduced to 24% of control values by G115. Norepinephrine-induced vasocontraction was antagonized in 21% and 44% by 1.44mg/ml and 2.88mg/ml of G115, respectively. Neointima-to-lumen area ratio of balloon-injured rat carotid arteries was reduced 77.3% by G115 as compared to the sham control. These results demonstrate the preventive effects of ginsenosides on angioplasty-mediated neointima formation. (C) 2001 Elsevier Science Inc. All rights reserved.
智慧型電控馬達之研製與機電磁整合技術之研究---永磁同步馬達智慧型無感測位置控制技術之研究(I)
(2002)
鄒應嶼
;
TZOU YING-YU
;
交通大學電機與控制工程系
利用基因規劃預測核糖核酸二級結構
(2002)
胡毓志
;
HU YUH-JYH
;
交通大學資訊科學系
Reconstruction of the human brain from MRI-T1 using 3-d morphology and snake
(2002)
Lin, CY
;
Ching, YT
;
資訊工程學系
;
Department of Computer Science
Accurate reconstruction of the human brain in MRI-T1 images is valuable and important to clinical needs. In this paper, the morphology and snake techniques are proposed to reconstruct a human brain model. First step in our method is to preprocess the volumetric image to remove skull, muscle, fat, and other non-brain tissue. We use a method of 3-d region growing. It has the advantage over thresholding that the resulting objects will be spatially connected, since brain has the connected property. Second, we use clustering method, and than use them to produce an initial estimate of the cortical surface. Third, we propose a novel active contour algorithm to move the snake toward the cortex. Thus we can use the snake to segment the brain. We use a wavelet method to model the external force that significantly increases the capture range of a traditional snake. Afterwards, we render the volumetric image to display the brain from multiple views. Both simulated data and patient data have been use to test the proposed techniques. The proposed method combines various techniques of 3-D morphology, clustering, active contour, wavelet, and volume rendering to accurately, robustly, and automatically reconstruct brain from MRI-T1 images.
Editorial statement
(Routledge, 2002)
寬頻無線通訊系統的錯誤控制機制之設計(I)
(2002)
蘇育德
;
SU YU TED
;
交通大學電信工程系
異質介面電晶體之熱穩定性研究(II)
(2002)
李建平
;
LEE CHIEN-PING
;
交通大學電子工程系