Browsing by Author "Chang, Wei-Chen"

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Efficient methods of computing interior transmission eigenvalues for the elastic waves
(2020-04-15)
Chang, Wei-Chen
;
Lin, Wen-Wei
;
Wang, Jenn-Nan
;
應用數學系
;
Department of Applied Mathematics
We study the interior transmission eigenvalue problem for the elastic wave scattering in this paper. We aim to show the distribution of positive eigenvalues by efficient numerical algorithms. Here the elastic waves are scattered by the perturbations of medium parameters, which include the elasticity tensor C and the density rho. Let us denote (C-0, rho(0)) and (C-1, rho(1)) the background and the perturbed medium parameters, respectively. We consider two cases of perturbations, C-0 = C-1, rho 1 not equal rho(0) (case 1) and C-0 not equal C-1, rho(1) = rho(0) (case 2). After discretizing the associated PDEs by FEM, we are facing the computation of generalized eigenvalues problems (GEP) with matrices of large size. These GEPs contain huge number of nonphysical zeros (for case 1) or nonphysical infinities (for case 2). In order to locate several hundred positive eigenvalues effectively, we then convert GEPs to suitable quadratic eigenvalues problems (QEP). We then implement a quadratic JacobiDavidson method combining with partial locking or partial deflation techniques to compute 500 positive eigenvalues. (C) 2020 Elsevier Inc. All rights reserved.
Establishing an invar leveling calibration system
(2008-07-01)
Chen, Chun-Sung
;
Wu, Chien-Ting
;
Chang, Ming-Wei
;
Chang, Wei-Chen
;
土木工程學系
Precise height systems are widely utilized in civil engineering projects Such as high-speed railroads, and highways and bridge construction. However, highly precise height data is obtained using precise leveling. An extremely precise invar leveling rod is necessary for obtaining precise results. In this study, an automatic calibration system for invar leveling has been established by the National Measurement Laboratory (NML). The content belongs to the long scales calibration system of D17 of the NML. This system utilizes a steady frequency laser interferometer, a CCD microscopic monitor, and a precise moving mechanism. With this system, an invar rod and a mark invar leveling rod are applied to estimate uncertainty with a 95% confidence level. Uncertainty results are 22 mu m and 21 mu m for the invar leveling rods and mark invar leveling rods, respectively.
Transition of stable rectification to resistive-switching in Ti/TiO(2)/Pt oxide diode
(2010-06-28)
Huang, Jiun-Jia
;
Kuo, Chih-Wei
;
Chang, Wei-Chen
;
Hou, Tuo-Hung
;
電機工程學系
We have fabricated a Ti/TiO(2)/Pt oxide diode with excellent rectifying characteristics by the asymmetric Schottky barriers at the Ti/TiO(2) (0.13 eV) and the TiO(2)/Pt (0.73 eV) interfaces. Instead of homogeneous conduction, the current transport is governed by the localized oxygen-deficient TiO(2) filaments. In addition, the reproducible resistive-switching exists in the same structure, triggered by the forming process. The transition between two modes is ascribed to the destruction of the interface barriers at forming. The rectification stable up to 125 degrees C and 10(3) cycles under +/- 3 V sweep without interference with resistive-switching shows satisfactory reliability of TiO(2) diodes for one diode-one resistor memory devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3457866]
Transition of stable rectification to resistive-switching in Ti/TiO2/Pt oxide diode
(2010-06-28)
Huang, Jiun-Jia
;
Kuo, Chih-Wei
;
Chang, Wei-Chen
;
Hou, Tuo-Hung
;
電子工程學系及電子研究所
We have fabricated a Ti/TiO2/Pt oxide diode with excellent rectifying characteristics by the asymmetric Schottky barriers at the Ti/TiO2 (0.13 eV) and the TiO2/Pt (0.73 eV) interfaces. Instead of homogeneous conduction, the current transport is governed by the localized oxygen-deficient TiO2 filaments. In addition, the reproducible resistive-switching exists in the same structure, triggered by the forming process. The transition between two modes is ascribed to the destruction of the interface barriers at forming. The rectification stable up to 125 degrees C and 10(3) cycles under +/- 3 V sweep without interference with resistive-switching shows satisfactory reliability of TiO2 diodes for one diode-one resistor memory devices. (C) 2010 American Institute of Physics. [doi:10.1063/1.3457866]