Browsing by Author "Kuo, CH"

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Application of local mesh refinement in the DSMC method
(2001)
Wu, JS
;
Tseng, KC
;
Kuo, CH
;
機械工程學系
;
Department of Mechanical Engineering
The implementation of an adaptive mesh embedding (h-refinement) schemes using unstructured grid in two-dimensional Direct Simulation Monte Carlo (DSMC) method is reported. In this technique, local isotropic refinement is used to introduce new meshes where local cell Knudsen number is less than some preset value. This simple scheme, however, has several severe consequences affecting the performance of the DSMC method. Thus, we have applied a technique to remove the hanging mode, by introducing anisotropic refinement in the interfacial cells. This is completed by simply connect the hanging node(s) with the other non-hanging node(s) in the non-refined, interfacial cells. In contrast, this remedy increases negligible amount of work; however, it removes all the difficulties presented in the first scheme with hanging nodes. We have tested the proposed scheme for Argon gas using different types of mesh, such as triangular and quadrilateral or mixed, to high-speed driven cavity flow. The results show an improved flow resolution as compared with that of unadaptive mesh. Finally, we have triangular adaptive mesh to compute two near-continuum gas flows, including a supersonic flow over a cylinder and a supersonic flow over a 35 degrees compression ramp. The results show fairly good agreement with previous studies. In summary, the computational penalties by the proposed adaptive schemes are found to be small as compared with the DSMC computation itself. Nevertheless, we have concluded that the proposed scheme is superior to the original unadaptive scheme considering the accuracy of the solution.
Automatic mura detection system for liquid crystal display panels
(2006-01-01)
Fang, LT
;
Chen, HC
;
Yin, IC
;
Wang, SJ
;
Wen, CH
In this paper, we propose an automatic inspection system, which can automatically detect four types of muras on an LCD panel: cluster mura, v-band mura, rubbing mura, and light leakage mura. To detect cluster muras, the Laplacian of Gaussian (LOG) filter is used. A multi-resolution approach is proposed to detect cluster muras of different scales. To speed up the processing speed, this multi-resolution approach is actually implemented in the frequency domain. To detect v-band muras, we check the variation tendency of the projected I-D intensity profile. Then, v-band muras are detected by identifying these portions of the I-D profile where a large deviation occurs. To detect rubbing muras, we designed a frequency mask to detect distinct components in the frequency domain. To detect light leak muras, we apply image mirroring over the boundary parts and adopt the same LOG filter that has been used in detecting cluster muras. All four types of mura detection are integrated together in an efficient way and simulation results demonstrate that this system is indeed very helpful in detecting mura defects.
Automatic mura detection system for liquid crystal display panels - art. no. 60700G
(2006)
Fang, LT
;
Chen, HC
;
Yin, IC
;
Wang, SJ
;
Wen, CH
In this paper, we propose an automatic inspection system, which can automatically detect four types of muras on an LCD panel: cluster mura, v-band mura, rubbing mura, and light leakage mura. To detect cluster muras, the Laplacian of Gaussian (LOG) filter is used. A multi-resolution approach is proposed to detect cluster muras of different scales. To speed up the processing speed, this multi-resolution approach is actually implemented in the frequency domain. To detect v-band muras, we check the variation tendency of the projected I-D intensity profile. Then, v-band muras are detected by identifying these portions of the I-D profile where a large deviation occurs. To detect rubbing muras, we designed a frequency mask to detect distinct components in the frequency domain. To detect light leak muras, we apply image mirroring over the boundary parts and adopt the same LOG filter that has been used in detecting cluster muras. All four types of mura detection are integrated together in an efficient way and simulation results demonstrate that this system is indeed very helpful in detecting mura defects.
Comparison of oxide breakdown progression in ultra-thin oxide SOI and bulk pMOSFETs
(2004)
Chan, CT
;
Kuo, CH
;
Tang, CJ
;
Chen, MC
;
Wang, TH
Accelerated oxide breakdown progression in ultra-thin oxide (1.4nm) SOI pMOSFETs is observed, as compared to bulk devices. The accelerated progression is explained by the increase of hole stress current as a result of breakdown induced channel carrier heating in a floating-body configuration. Numerical simulation of hole tunneling current and hot carrier luminescence measurement are carried out to justify the proposed theory.
Design and investigation of calamitic liquid crystals with low aspect-ratios: rigid y-shaped 1,2,4-tris(4-alkoxyphenylethynyl)benzenes
(2005-12-07)
Hsu, HF
;
Chen, HC
;
Kuo, CH
;
Wang, BC
;
Chin, HT
The synthesis and characterization of triynylbenzenes, 1-iodo-2,4,5-tri(4-alkoxyphenyl-ethynyl)benzenes (1), are reported, and their structure-mesomorphism relationship is investigated. These compounds possess a y-shaped geometry with rigid linear spacers and a stable nematic phase that was achieved by lengthening the alkoxy chains or replacing the iodo group with a smaller atom. The low aspect ratios and identified calamitic nature of these rigid y-shaped liquid crystals, make them suitable as potential candidates to be used in the liquid crystal layer of liquid crystal display devices for improving viewing angles. In addition, the geometry of I was modified stepwise from a rigid y-geometry to a rigid rectangle for realization of the unstable nematic behaviors of the previously reported board-like 1,2,4,5-tetrakis(4-tridecyloxyphenyl-ethynyl)benzene that was expected to potentially show biaxial nematic phases. The sizes of the fourth side-arm and hence the aspect ratios of these tetra-substituted benzenes are ascribed to the less liquid crystallinity.
Frame-based subband Kalman filtering for speech enhancement
(1998)
Wu, WR
;
Chen, PC
;
Chang, HT
;
Kuo, CH
;
電信工程研究所
Kalman Filtering is an effective speech enhancement technique, in which speech and noise signals are usually modeled as autoregressive (AR) processes and represented in the state-space domain. Since AR coefficients identification and Kalman filtering require extensive computations, practical implementation of this approach is difficult. This paper proposes a simple and practical scheme that overcomes these problems. Speech signals are first decomposed into subbands. Subband speech signals are then modeled as low-order AR processes, such that low-order Kalman filters can be applied. Enhanced fullband speech signals are finally obtained by combining the enhanced subband speech signals. Using a frame-based algorithm, autocorrelation functions of subband speech are calculated and the Yuler-Walker equations are solved to obtain the AR parameters. Simulation results show that Kalman filtering in the subband domain not only greatly reduces the computational complexity but also achieves better performance compared to that in the fullband domain.
Single-electron emission of traps in HfSiON as high-k gate dielectric for MOSFETs
(2005)
Chan, CT
;
Tang, CJ
;
Kuo, CH
;
Ma, HC
;
Tsai, CW
A novel method for characterizing MOSFETs with HfSiON high-k gate dielectric is demonstrated for the first time by direct measurement of single-electron de-trapping. Individual high-k trapped electron emission is recorded, which is manifested by the step-like evolution of channel current. The physical path of electron de-trapping can be identified from the emission time of such single-electron de-trapping. The dependence of charge emission time on gate voltage and temperature is measured. An analytical model based on thermally assisted tunneling can predict the emission time behavior, trap activation energy, trap density, and total available traps in high-k gate dielectric.
The direct simulation Monte Carlo method using unstructured adaptive mesh and its application
(2002-02-10)
Wu, JS
;
Tseng, KC
;
Kuo, CH
;
機械工程學系
;
Department of Mechanical Engineering
The implementation of an adaptive mesh-embedding (h-refinement) scheme using unstructured grid in two-dimensional direct simulation Monte Carlo (DSMC) method is reported. In this technique, local isotropic refinement is used to introduce new mesh where the local cell Knudsen number is less than Some Preset Value. This simple scheme, however, has several severe consequences affecting the performance of the DSMC method. Thus, we have applied a technique to remove the hanging node, by introducing the an-isotropic refinement in the interfacial cells between refined and non-refined cells. Not only does this remedy increase a negligible amount of work, but it also removes all the difficulties presented in the originals scheme. We have tested the proposed scheme for argon gas in a high-speed driven cavity flow, The results show an improved flow resolution as compared with that of un-adaptive mesh. Finally, we have used triangular adaptive mesh to compute a near-continuum gas flow, a hypersonic flow over a cylinder, The results show fairly good agreement with previous studies. In summary, the proposed simple mesh adaptation is very useful in computing rarefied gas flows, which involve both complicated geometry and highly non-uniform density variations throughout the flow field. Copyright (C) 2002 John Wiley Sons, Ltd.
UV-LIGA interferometer biosensor based on the SU-8 optical waveguide
(2005-05-17)
Shew, BY
;
Kuo, CH
;
Huang, YC
;
Tsai, YH
;
機械工程學系
SU-8 resist was used as a core/cladding waveguide material to fabricate a Mach-Zehnder interferometer (MZI) for biochemical sensing. The refractive index of the SU-8 resist was fine-tuned with a Delta n of 0.004 for single-mode transmission. The UV lithography processes of the SU-8 resist were also optimized to pattern the high resolution (1 mu m) and high aspect ratio (A(R) = 6) Y-branch structure of the optical interferometer. Optical measurements reveal that the SU-8 MZI chip can efficiently transmit the NIR laser (lambda = 13 10 mu) with a total loss less than 6 dB. When one branch of the MZI is in contact with the analyte, the interfered intensity stabilizes after the soaking time exceeds 5 min. NaCl solution with a concentration of 10(-9) g/l can be detected using the SU-8 MZI chip. In the future, the polymer MZI chip can be mass-produced by molding process (or the LIGA process). The low-cost, label-free, real-time and high-sensitivity MZI chip will benefit many applications related to biological, environmental and industrial detection. (c) 2005 Elsevier B.V. All rights reserved.