Browsing by Author "Tsai, TL"

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0.13-mu m low-kappa-Cu CMOS logic-based technology for 2.1-Gb high data rate read-channel
(2004-05-01)
Guo, JC
;
Lien, WY
;
Tsai, TL
;
Chen, SM
;
Wu, CM
High-performance analog/digital elements have been successfully fabricated bya 0.13-mum low-kappa-Cu logic-based mixed-signal CMOS process in a single chip to enable a 2.1-Gb/s read-channel for hard disk drives that is a record-high data rate supported by fully CMOS solution. The high-performance analog devices demonstrate superior drivability, matching, noise immunity, and reliability by a unique dual-gate oxide module to support the aggressive oxide thickness scaling and maintain promisingly good reliability in all aspects.
An accurate integral-based scheme for advection-diffusion equation
(2001-10-01)
Tsai, TL
;
Yang, JC
;
Huang, LH
;
土木工程學系
;
Department of Civil Engineering
This paper proposes an accurate integral-based scheme for solving the advection-diffusion equation. In the proposed scheme the advection-diffusion equation is integrated over a computational element using the quadratic polynomial interpolation function. Then elements are connected by the continuity of first derivative at boundary points of adjacent elements. The proposed scheme is unconditionally stable and results in a tridiagonal system of equations which can be solved efficiently by the Thomas algorithm. Using the method of fractional steps, the proposed scheme can be extended straightforwardly from one-dimensional to multi-dimensional problems without much difficulty and complication. To investigate the computational performances of the proposed scheme five numerical examples are considered: (i) dispersion of Gaussian concentration distribution in one-dimensional uniform flow; (ii) one-dimensional viscous Burgers equation; (iii) pure advection of Gaussian concentration distribution in two-dimensional uniform flow; (iv) pure advection of Gaussian concentration distribution in two-dimensional rigid-body rotating flow; and (v) three-dimensional diffusion in a shear flow. In comparison not only with the QUICKEST scheme, the fully time-centred implicit QUICK scheme and the fully time-centred implicit TCSD scheme for one-dimensional problem but also with the ADI-QUICK scheme, the ADI-TCSD scheme and the MOSQUITO scheme for two-dimensional problems, the proposed scheme shows convincing computational performances. Copyright (C) 2001 John Wiley & Sons, Ltd.
An accurate integral-based scheme for dispersion equation
(2001)
Tsai, TL
;
Yang, JC
;
Huang, LH
;
土木工程學系
;
Department of Civil Engineering
This paper proposes an accurate integral-based scheme for solving dispersion equation. In the newly-proposed scheme the dispersion equation is integrated over a computational element using the quadratic polynomial interpolation function. Then elements are connected by the continuity of first derivative at boundary point of adjacent elements. The newly-proposed scheme is unconditionally stable and preserves a tridiagonal system of equations which can be solved efficiently by the Thomas algorithm. Using the method of fractional steps, the newly-proposed scheme, originally developed for one-dimensional problems, can be extended straightforward to multi-dimensional problems. To investigate the computational performances of the newly-proposed scheme five numerical examples are considered : (i) dispersion of Gaussian concentration distribution in one-dimensional uniform flow, (ii)one-dimensional viscous burger's equation, (iii) pure advection of Gaussian concentration distribution in two-dimensional uniform flow, (iv) pure advection of Gaussian concentration distribution in two-dimensional rigid-body rotating flow and (v) three-dimensional diffusion in a shear flow. In comparison not only with the QUICKEST scheme, fully time-centred implicit QUICK scheme and fully time-centred implicit TCSD scheme for one-dimensional problem but also with the ADI-QUICK scheme, ADI-TCSD scheme and MOSQUITO scheme for two-dimensional problems, the newly-proposed scheme shows convincing computational performances.
Body force effect on consolidation of porous elastic media due to pumping
(2006-01-01)
Tsai, TL
;
Chang, KC
;
Huang, LH
;
防災與水環境研究中心
;
Disaster Prevention and Water Environment Research Center
In this study, the linear poro-elasticity theory is applied to examine the body force effect on consolidation of porous media due to pumping. The steady-state solutions of displacement and incremental effective stress for a stratum of clay sandwiched between sandy strata are analytically given. The effect of body force could be represented by the body force number that depends on Lame's constants, porosity, and the thickness of porous media. The consolidation of clay is significantly related not only to the body force number but also to the ratio of water table depression in upper and lower sandy strata due to pumping. The neglect of body force will severely underestimate the displacement and incremental effective stress when porous media are soft or thick, or both. This might lead to potential flaws in engineering practice, such as the calculation of soil settlement.
Characteristics method using cubic-spline interpolation for advection-diffusion equation
(2004-06-01)
Tsai, TL
;
Yang, JC
;
Huang, LH
;
土木工程學系
;
防災與水環境研究中心
The characteristics method by using the cubic-spline interpolation is comparable to the Holly-Preissmann scheme in solving the advection portion of the advection-diffusion equation. In order to conduct a cubic-spline interpolation, an additional constraint must be specified at each endpoint. In general, four types of endpoint constraints are available, i.e., the first derivative, second derivative, quadratic, and not-a-knot constraints. The goal of this paper is to examine each type of endpoint constraints. Two hypothetical cases are used to conduct the investigation. Among the four types of constraints examined herein, the not-a-knot constraint and the first derivative constraint with high-order finite difference approximation yield the best results. However, as far as accuracy and simple implementation are concerned the not-a-knot constraint should be the best choice in solving the advection-diffusion equation.
Characteristics method with cubic-spline interpolation for open channel flow computation
(2004-10-30)
Tsai, TL
;
Chiang, SW
;
Yang, JC
;
防災與水環境研究中心
;
Disaster Prevention and Water Environment Research Center
In the framework of the specified-time-interval scheme, the accuracy of the characteristic method is Greatly related to the form of the interpolation. The linear interpolation was commonly used to couple the characteristics method (LI method) in open channel flow computation. The LI method is easy to implement, but it leads to an inevitable smoothing of the solution. The characteristics method with the Hermite cubic interpolation (HP method, originally developed by Holly and Preissmann, 1977) was then proposed to largely reduce the error induced by the LI method. In this paper, the cubic-spline interpolation on the space line or on the time line is employed to integrate with characteristics method (CS method) for unsteady flow computation in open channel. Two hypothetical examples, including gradually and rapidly varied flows, are used to examine the applicability of the CS method as compared with the LI method, the HP method, and the analytical solutions. The simulated results show that the CS method is comparable to the HP method and more accurate than the LI method. Without tackling the additional equations for spatial or temporal derivatives, the CS method is easier to implement and more efficient than the HP method. Copyright (C) 2004 John Wiley Sons, Ltd.
Development of dielectric composite with X7R characteristic
(2001)
Lee, WH
;
Ou, KH
;
Tsai, TL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A dielectric composite having K-value in excess of 10000 with Y5R characteristics (-55 similar to +125 degreesC, +/- 15%) has been successfully developed which in corporate two (Ba, Ca)(Ti,Zr)O-3-based ceramic with different Curie temperature as the principal components. A stacking alternately technique during screen printing and a usual cofiring with inner electrode technique are utilised to prepared this kind of multilayer product. In this study, it is determined that a proportion of high-T-c and low T-c materials and location of their Curie temperature could control and improve the change of the dielectric constant (K) over a temperature range from -55 to +125 degreesC.
Face selectivity in the 1,3-dipolar cycloaddition reactions of benzonitrile oxide with 5-substituted adamantane-2-thiones and 2-methyleneadamantanes
(1997-07-11)
Chung, WS
;
Tsai, TL
;
Ho, CC
;
Chiang, MYN
;
leNoble, WJ
The 1,3-dipolar cycloaddition reactions of benzonitrile oxide with 5-substituted adamantane-2-thiones (2-X) and 2-methyleneadamantanes (3-X) produced two geometrically isomeric Delta(2)-1,4,2-oxathiazolines (5-Xs) and two Delta(2)-isoxazolines (6-Xs), respectively. The substituent was varied from fluoro, chloro, bromo, to phenyl. X-ray single-crystal analysis confirmed the configuration of (Z)-5-F. The produce formation bias resulting from the favored attack of nitrile oxide on the zu-face is discussed in terms of transition-state hyperconjugation and frontier molecular orbital theory.
Fractional steps scheme of finite analytic method for advection-diffusion equation
(2005-01-01)
Tsai, TL
;
Tseng, CM
;
Yang, JC
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土木工程學系
;
防災與水環境研究中心
For simply finding local analytic solution, the time derivative in the traditional finite analytic (FA) method is generally replaced with a first-order finite difference approximation as a source term. However, this may induce excessive numerical diffusion, especially for advection-dominated transport problems. In this paper, a fractional steps scheme of the FA method without using the finite difference approximation to time derivative is proposed by applying the one-dimensional FA method whose local analytic solution is obtained from both spatial and time domains, together with the method of fractional steps. Four hypothetical examples, including two-dimensional and three-dimensional cases, are employed to investigate this newly proposed method as compared with the traditional FA method, the optimal unsteady FA method, and the alternating direction scheme of the hybrid FA method. The results show that the fractional steps scheme of the FA method can greatly diminish numerical diffusion and is superior to the other methods compared herein.
Groundwater modeling by layer based three-dimensional concept
(2000)
Tsai, TL
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Huang, LH
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Yang, JC
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土木工程學系
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Department of Civil Engineering
Due to its simplicity and efficiency, the conventional quasi three-dimensional concept has been widely applied in analyzing groundwater flow in multiaquifer system, especially for regional problem. But the conventional quasi three-dimensional concept is not able to deal with the discontinuous and interconnected strata and fully three-dimensional flow. Therefore, in order not only to overcome these shortcomings but also to maintain efficiency, we propose a new layer based three-dimensional concept to develop a groundwater simulation model. This new concept assumes that the pore pressure of every aquifer and aquitard in the vertical direction can be depicted by the quadratic polynomial interpolation function, then the vertical integration is performed on each layer to ensure the continuity of pore pressure and flux at the interfaces between any two layers. The finite analytical numerical method is adopted to develop the present groundwater simulation model. The results show that the present model is capable of simulating fully three-dimensional flow pattern.
Hybrid finite-difference scheme for solving the dispersion equation
(2002-01-01)
Tsai, TL
;
Yang, JC
;
Huang, LH
;
土木工程學系
;
Department of Civil Engineering
An efficient hybrid finite-difference scheme capable of solving the dispersion equation with general Peclet conditions is proposed. In other words, the scheme can simultaneously deal with pure advection, pure diffusion, and/or dispersion. The proposed scheme linearly combines the Crank-Nicholson second-order central difference scheme and the Crank-Nicholson Galerkin finite-element method with linear basis functions. Using the method of fractional steps, the proposed scheme can be extended straightforwardly from one-dimensional to multidimensional problems without much difficulty. It is found that the proposed scheme produces the best results, in terms of numerical damping and oscillation, among several non-split-operator schemes. In addition, the accuracy of the proposed scheme is comparable with a well-known and accurate split-operator approach in which the Holly-Preissmann scheme is used to solve the pure advection process while the Crank-Nicholson second-order central difference scheme is applied to the pure diffusion process. Since the proposed scheme is a non-split-operator approach, it does not compute the two processes separately. Therefore, it is simpler and more efficient than the split-operator approach.
Kinematic wave modeling of overland flow using characteristics method with cubic-spline interpolation
(2005-07-01)
Tsai, TL
;
Yang, JC
;
土木工程學系
;
防災與水環境研究中心
;
Department of Civil Engineering
Use of characteristics method integrated with cubic-spline interpolation technique (CSMOC scheme) for computation of one-dimensional and two-dimensional kinematic overland flow has been examined in this study. The characteristic trajectory is allowed to fall on space line and time line for interpolating the corresponding values at the foot of trajectory in terms of neighboring grid points. The effects of different endpoint constraints on use of cubic-spline interpolation are investigated. As far as accuracy and simplicity are concerned, the not-a-knot constraint could be a better choice. Three hypothetical examples are used to examine the capabilities of CSMOC scheme through the comparison with the analytical solution and the well-known Preissmann scheme. Some degrees of numerical diffusion and numerical oscillation, attenuating and overestimating the peak discharge, are induced by the Preissmann scheme. In contrast, the CSMOC scheme gives convincing results for the kinematic overland flow computations. (c) 2005 Elsevier Ltd. All rights reserved.
Modeling of rainfall-triggered shallow landslide
(2006-07-01)
Tsai, TL
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Yang, JC
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土木工程學系
;
防災與水環境研究中心
;
Department of Civil Engineering
By integrating hydrological modeling with the infinite slope stability analysis, a rainfall-triggered shallow landslide model was developed by Iverson (Water Resour Res 36:1897-1910, 2000). In Iverson's model, the infiltration capacity is assumed to be equivalent to the saturated hydraulic conductivity for finding pressure heads analytically. However, for general infiltration process, the infiltration capacity should vary with time during the period of rain, and the infiltration rate is significantly related to the variable infiltration capacity. To avoid the unrealistically high pressure heads, Iverson employed the beta-line correction by specifying that the simulated pressure heads cannot exceed those given by the beta line. In this study, the suitability of constant infiltration capacity together with the beta-line correction for hydrological modeling and landslide modeling of hillslope subjected to a rainfall is examined. By amending the boundary condition at ground surface of hillslope in Iverson's model, the modified Iverson's model with considering general infiltration process is developed to conduct this examination. The results show that the unrealistically high pressure heads from Iverson's model occur due to the overestimation of infiltration rate induced from the assumption that the infiltration capacity is identical to the saturated hydraulic conductivity. Considering with the general infiltration process, the modified Iverson's model gives acceptable results. In addition, even though the beta-line correction is applied, the Iverson's model still produces greater simulated pressure heads and overestimates soil failure potential as compared with the modified Iverson's model. Therefore, for assessing rainfall-triggered shallow landslide, the use of constant infiltration capacity together with the beta-line correction needs to be replaced by the consideration of general infiltration process.
Temperature and para-substituent effects on the face selectivity of 1,3-dipolar cycloaddition reactions of benzonitrile oxides with 5-substituted adamantane-2-thiones, N-benzyladamantyl-2-imines, and 2-methyleneadamantanes
(1999-02-19)
Tsai, TL
;
Chen, WC
;
Yu, CH
;
le Noble, WJ
;
Chung, WS
The 1,3-dipolar cycloaddition reactions of para-substituted benzonitrile oxides (5-Y) with 5-fluoroadamantane-2-thione (2-F) and -2-methyleneadamantane (3-F) as well as with variously 5-substituted-N-benzyladamantyl-2-imines (4-X) were examined. They produce two geometrically isomeric Delta(2)-1,4,2-oxathiazolines (7-F,Y), Delta(2)-isoxazolines (8-F,Y), and Delta(2)-1,2,4-oxadiazolines (11-X,Y), respectively. The face selectivity in the latter reaction was found to be similar to 1:1 regardless of the variations in Ei-substituent and the temperature. For the former two reactions, the para-substituent was varied from electron-withdrawing (Y = F, Cl, Br, CN, or NO2) to -releasing (Y = Me, or OMe). The face selectivity was measured in all cases. The differences ap for the reactions of 2- and 3-F with 5-Y were obtained from linear Hammett plots; they are +0.12 and 0.0, respectively. These low values and information from previous studies imply a concerted one-step mechanism with very little charge distribution differences in the transition states: These effects of temperature on the Z/E product ratios provide us, for the first time, with activation parameter differences between the syn- and anti transition states; their values are discussed. The product bias resulting from the favored attack of nitrile oxide on the zu face is discussed in terms of transition state hyperconjugation based on the experimental results and AM1 calculations.