Browsing by Author "Tsai, WC"

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A graded approach to shape representation
(1996-06-01)
Chen, PC
;
Tsai, WC
;
Hwang, SY
;
交大名義發表
;
資訊工程學系
Human beings perceived real-world objects in a graded manner, with macroviews providing global information about the objects and microviews providing more detailed information. Consequently, researchers in computer vision have directed their efforts toward building graded representations of objects, especially shapes of objects. Most previous approaches employed operations such as smoothing, blurring, or grouping to gradually obtain representations with different degrees of detail. Parameters of these operations are used to indicate the degree of detail, One objection to using operator parameters is that these parameters are difficult for viewers to interpret intuitively. To overcome this objection, we propose using a graded approach guided by a given similarity requirement to construct a more concise shape description. Our shape representation matches human intuition about detailing degree and suits machine requirement for concise description. (C) 1996 Academic Press, Inc.
A graded approach to shape representation
(1996-06-01)
Chen, PC
;
Tsai, WC
;
Hwang, SY
;
資訊工程學系
;
Department of Computer Science
Human beings perceived real-world objects in a graded manner, with macroviews providing global information about the objects and microviews providing more detailed information. Consequently, researchers in computer vision have directed their efforts toward building graded representations of objects, especially shapes of objects. Most previous approaches employed operations such as smoothing, blurring, or grouping to gradually obtain representations with different degrees of detail. Parameters of these operations are used to indicate the degree of detail, One objection to using operator parameters is that these parameters are difficult for viewers to interpret intuitively. To overcome this objection, we propose using a graded approach guided by a given similarity requirement to construct a more concise shape description. Our shape representation matches human intuition about detailing degree and suits machine requirement for concise description. (C) 1996 Academic Press, Inc.
A systolic architecture for elliptic curve cryptosystems
(2000)
Tsai, WC
;
Wang, SJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This article presents a new systolic architecture for the main operation in an elliptic curve cryptosystem over the finite field GF(2(m)). This proposed architecture is actually a finite field multiplier and is used to implement the addition operation in the elliptic curs-e cryptosystem. We apply partitioning scheme and parallelize the main operation in a straightforward systolic architecture to speed up the operation and then apply merging and re-timing schemes in the partitioned architecture to future improve the performance of this architecture. We compare this architecture with some previously proposed systolic architectures for the finite field arithmetics. The comparison shows that our architecture offers the lowest hardware complexity. This architectures can be easily adopted to build a low-complexity elliptic curve cryptosystem.
A-axis YBCO thin films deposited by DC magnetron sputtering
(1997-01-01)
Tsai, WC
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A-axis YBCO thin films deposited on SrTiO3 and MgO substrates were prepared using the template-layer method by off-axis magnetron sputtering. The thin films deposited on MgO with template layers displayed better electrical properties and crystallinity than those deposited on the substrates without template layers, whereas the crystallinity of films deposited on SrTiO3 by the template-layer method showed no improvement. The surface morphology of the films, observed by high-resolution scanning electron microscopy, indicates that the homoepitaxial growth of the a-axis films on template layers on MgO and SrTiO3 results in rougher surfaces than in the case of heteroepitaxial growth of template layers. The possible mechanisms contributing to these differences in surface roughness were carefully investigated. Atomic force microscopy was also used to characterize the initial growth of a-axis films on MgO and SrTiO3. According to the results, the initial growth of a-axis films on MgO and SrTiO3 resembles that of island growth.
Accurate logic-level power simulation using glitch filtering and estimation
(1996)
Tsai, WC
;
Shung, CB
;
Wang, DC
;
交大名義發表
;
電子工程學系及電子研究所
Power estimation tool is needed to be more fast and accurate when the power consumption is the chief concern during the chip design. Logic-level simulator is a good choice to estimate the power consumption of a chip design. In this paper we attempt to improve the accuracy of a logic-level simulator using glitch filtering and estimation techniques. We use logic-level simulator to filter some glitches and estimate the glitch power. We use slope of transition and time interval of two consecutive transitions to decide whether these transitions is partial glitches or full transitions. We estimate the transition power of each transition event and summed them up. The power simulation error is reduced from 35.8% to 7.9% referring to the Spice simulation.
Characterization of yttria-stabilized zirconia thin films grown by planar magnetron sputtering
(1997-08-28)
Tsai, WC
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Yttria-stabilized zirconia (YSZ) thin films were grown on Si by rf magnetron sputtering. Sputtering gun was positioned at various angles to the substrate normal to change the amount of plasma bombardment on the as-deposited films. YSZ films grown by off-axis sputtering (90 degrees) are readily (200)-preferred orientated but the preferred orientation of the film is deteriorated when the growth angle is decreased and, consequently, plasma bombardment is increased due to the decreasing growth angles. The off-axis grown YSZ films exhibit atomically smooth interfaces, which are not observed for those films grown by on-axis sputtering. The variation of oxide charge with the growth angle is studied with the Al/YSZ/Si structure. The plasma bombardment plays an important role on the crystallinity and, therefore, the defect type of the films and is also considered to be responsible for the Si outdiffusion occurring in an on-axis grown film. (C) 1997 Elsevier Science S.A.
Disordered Si/SiGe superlattices grown by ultrahigh vacuum chemical vapor deposition
(1996-02-01)
Chang, TC
;
Yeh, WK
;
Chang, CY
;
Jung, TG
;
Tsai, WC
A series of Si/Si1-xGex disordered superlattices with various degrees of disorder were grown in an ultrahigh vacuum chemical vapor deposition system (UHV/CVD). High-resolution double-crystal X-ray diffraction (HRXRD), and conventional cross-sectional transmission electron microscopy were used to evaluate the crystalline quality of these superlattices. A dynamical X-ray simulation program was employed to analyze the experimental rocking curves, Excellent matches between experimental rocking curves and simulated ones were obtained for all superlattices with various degrees of disorder.
Event-driven power estimation of CMOS circuits
(1997-10-01)
Tsai, WC
;
Shung, CB
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Fast and accurate power estimation has become an important topic with the increasing need for low power electronics. In this paper we address the problem of using event-driven simulation tools for power estimation. We identify and compare two approaches: input-driven and output-driven, and propose several ways of improvement. The estimation accuracy is degraded in event-driven power estimators due to superfluous and partial glitches. We described glitch filtering and estimation techniques pertaining to input-driven and output-driven power estimators. An output-driven power estimator, Peony, was developed which used the proposed path pouter idea to improve the estimation accuracy. It achieved significant power estimation accuracy improvement at a speed of two orders of magnitude faster than Spice.
Interfacial abruptness in Si/SiGe heteroepitaxy grown by ultrahigh vacuum chemical vapor deposition
(1997-09-01)
Tsai, WC
;
Chang, CY
;
Jung, TG
;
Chang, TC
;
Lin, HC
High-quality Si/Si1-xGex strained-layer superlattices have been grown in the temperature range 525 degrees C-550 degrees C by ultrahigh vacuum chemical vapor deposition. We employed X-ray reflection and high-resolution double-crystal X-ray diffraction measurements to study the dimensional and compositional variations in a Si/Si1-xGex superlattice. From the X-ray reflection results, the interfacial roughness of Si layers on SiGe, and SiGe layers on Si, is 0.1nm for growth at 525 degrees C and 0.2nm for growth at 550 degrees C. A simple model for estimating the interfacial abruptness of Si/Si1-xGex heterojunctions is proposed. In this model, a transition region with a linearly graded Ge composition is assumed to exist at both Si/Si1-xGex interfaces. The Ge composition x of a Si/Si1-xGex superlattice is found to increase with the growth time at a constant gas phase composition. This phenomenon can be explained by this model, and the thickness of the transition region and the transition time can be extracted from these fitting results. The transition thicknesses are found to be about 0.3-0.7nm for growth at 525 degrees C and 1-1.5nm for growth at 550 degrees C.
Interfacial abruptness in Si/SiGe heteroepitaxy grown by ultrahigh vacuum chemical vapor deposition
(1997-09-01)
Tsai, WC
;
Chang, CY
;
Jung, TG
;
Chang, TC
;
Lin, HC
High-quality Si/Si1-xGex strained-layer superlattices have been grown in the temperature range 525 degrees C-550 degrees C by ultrahigh vacuum chemical vapor deposition. We employed X-ray reflection and high-resolution double-crystal X-ray diffraction measurements to study the dimensional and compositional variations in a Si/Si1-xGex superlattice. From the X-ray reflection results, the interfacial roughness of Si layers on SiGe, and SiGe layers on Si, is 0.1nm for growth at 525 degrees C and 0.2nm for growth at 550 degrees C. A simple model for estimating the interfacial abruptness of Si/Si1-xGex heterojunctions is proposed. In this model, a transition region with a linearly graded Ge composition is assumed to exist at both Si/Si1-xGex interfaces. The Ge composition x of a Si/Si1-xGex superlattice is found to increase with the growth time at a constant gas phase composition. This phenomenon can be explained by this model, and the thickness of the transition region and the transition time can be extracted from these fitting results. The transition thicknesses are found to be about 0.3-0.7nm for growth at 525 degrees C and 1-1.5nm for growth at 550 degrees C.
Interfacial reactions of Ni on Si0.76Ge0.24 and Si by pulsed laser annealing
(1998-07-01)
Luo, JS
;
Lin, WT
;
Chang, CY
;
Tsai, WC
;
電子工程學系及電子研究所
Pulsed KrF laser annealing and vacuum annealing on the interfacial reactions of Ni/Si0.76Ge0.24 and Ni/Si were studied. For the Ni/ Si0.76Ge0.24 films annealed at temperatures above 300 degrees C, some Ge-rich Si1-xGex grains were formed between the Ge-deficient Ni germanosilicide grains, resulting in the island structure. For Ni/Si films homogeneous epitaxial NiSi2 films could be grown even at 600 degrees C. Ni silicide (germanosilicide) associated with the amorphous overlayer was generally formed at lower energy densities for Ni/Si, NiSi/Si, Ni/Si0.76Ge0.24 and Ni(Si1-xGex) /Si0.76Ge0.24 systems, respectively. At higher energy densities constitutional supercooling occurred. The energy densities at which constitutional supercooling appeared were higher for NiSi and Ni(Si1-xGex) than for Ni. For the continuous Ni(Si1-xGex) films grown at 200 degrees C in a vacuum furnace, subsequent laser annealing at an energy density of 0.6-1.0 J cm(-2) have shown to render homogeneous Ni(Si0.76Ge0.24)(2) and Si0.76Ge0.24 films without the island structure and Ge segregation. (C) 1998 Elsevier Science S.A. All rights reserved.
Interfacial reactions of the Co/Si1-xGex system
(1997-04-01)
Luo, JS
;
Lin, WT
;
Chang, CY
;
Tsai, WC
;
Wang, SJ
Thermal reactions of Co(200 Angstrom)/Si0.76Ge0.24(1500 Angstrom)/Si and Co(200 Angstrom)/Si0.54Ge0.46(1000 Angstrom)/Si systems in a vacuum of 1-2 X 10(-6) Ton. were studied. At temperatures above 200 degrees C Ge segregation appeared even though no silicides and/or germanosilicides were formed. At a temperature of 225-550 degrees C Co(Si1-yGey) was formed, in which the Ge concentration was deficient, The formation temperatures of CoSi2 in the Co/Si1-xGex systems, where x = 0.24 and 0.46, were above 575 degrees C, being relatively higher than that in the Co/Si system. At temperatures above 500 degrees C the island structure, Ge segregation to the surface of the exposed Si1-xGex films, and the penetration of reacted layer into the Si substrate occurred, At temperatures above 700 degrees C a SiC layer was grown on the film surface. For the Si0.54Ge0.46 films the penetration of the reacted layer into the Si substrate occurred even at 350 degrees C owing to the wave structure of the as-grown Si0.54Ge0.46 films. A Si layer interposed between Co and Si0.76Ge0.24 films is an effective scheme to grow a continuous CoSi, contact at 550-600 degrees C without inducing Ge segregation and hence the strain relaxation in the Si0.76Ge0.24 films.
Light emission from the porous boron delta-doped Si superlattice
(1996-02-01)
Chang, TC
;
Yeh, WK
;
Hsu, MY
;
Chang, CY
;
Lee, CP
We report the first study on the porous boron delta-doped Si superlattice. Visible photoluminescence (PL) was observed with multiple peaks from the porous boron delta-doped Si superlattice at room temperature. In the electroluminescence (EL) experiment, a bright yellow light emission was observed from the porous boron delta-doped Si superlattices. However, a weak red light emission was also observed from the conventional porous Si which is anodized at the same etching condition. As a result, the structure of the porous boron delta-doped Si superlattice has the ability of controlling the quantum size in porous Si and enhancing the light intensity from porous Si.
Local electric field effects in a SiGe quantum well investigated by photoluminescence
(1997-02-15)
Nilsson, S
;
Penner, U
;
Schmalz, K
;
Yassievich, IN
;
Chang, CY
We describe photoluminescence and admittance spectroscopy of p-type Si/Si0.25Ge0.25/Si quantum well structures with the SiGe quantum well surrounded by undoped Si spacer layers of various thickness. Holes confined in the SiGe quantum well create a local electric field, which induces potential barriers for holes in the surrounding Si: and a potential well for electrons in the vicinity of the Sice quantum-well region. Decreasing the thickness of one of the Si spacers from 30 nm to 5 nm increases the local electric field and shifts the SiGe-related near-band-edge photoluminescence spectrum to higher photon energies. This can be explained by a reduced exciton binding energy due to exciton polarization. The polarization is caused by the increasingly asymmetrical potential well for electrons and holes for the thinner Si spacer layers. In addition, admittance spectroscopy was carried out in order to measure the potential barriers for the confined holes for various thicknesses of the Si spacer layers. For thicker Si spacer layers, the results are in agreement with the photoluminescence data. For thinner Si spacer layers, thermally activated tunnelling of holes via the potential barrier was observed, Our interpretations are supported by theoretical calculations.
Mechanisms linking employee affective delivery and customer behavioral intentions
(2002-10-01)
Tsai, WC
;
Huang, YM
;
經營管理研究所
;
Institute of Business and Management
Past empirical evidence has indicated that employee affective delivery can influence customer reactions (e.g., customer satisfaction, service quality evaluation). This study extends previous research by empirically examining mediating processes underlying the relationship between employee affective delivery and customer behavioral intentions. Data were collected from 352 employee-customer pairs in 169 retail shoe stores in Taiwan. Results showed that the influence of employee affective delivery on customers' willingness to return to the store and pass positive comments to friends was indirect through the mediating processes of customer in-store positive moods and perceived friendliness. The study also indicated that employee affective delivery influences customers' time spent in store, which, in turn, influences customer behavioral intentions.
New VLSI architectures of RSA public-key cryptosystem
(1997)
Wang, PA
;
Tsai, WC
;
Shung, GB
;
交大名義發表
;
電子工程學系及電子研究所
In this paper, we propose several new VLSI architectures to reduce the hardware complexity and to increase the computation speed of the RSA Public-Key Cryptosystem. BY applying LSB-first algorithm in modular exponentiation, a different pipelining method is presented for area optimization. We modified the Montgomery algorithm in two way: (1) interleave each iteration to pipeline the critical path and (2) update the parallel input on every cycle for serial squaring. The first technique implies that the minimum cycle time can be reduced to approximately one half as before, and the second technique enables more efficient computations. We compare our architectures with the previously proposed architectures and found that our architectures offer a factor of two reduction in Area-Time product.
Off-axis unbalanced magnetron sputtering of YBa2Cu3O7 thin films
(1997-07-01)
Tsai, WC
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An unbalanced magnet assembly is used in DC off-axis sputtering to grow YBa2Cu3O7 superconducting thin films. The assembly with a stronger central magnet than the annular magnet directs plasma to bombard the off-axis substrate, resulting in deteriorated thin films. In contrast, the assembly with a weaker central magnet directs plasma away from the off-axis substrate and results in a film with a higher transition temperature and a smoother surface. Furthermore, the latter type of unbalanced DC magnetron sputtering gives a higher deposition rate and enables the grown film to be uniform in composition on static substrates over a range of 8 cm in length. These results reveal the feasibility of using the unbalanced magnetron for thin film growth.
On the off stoichiometry of cerium oxide thin films deposited by RF sputtering
(1996-04-01)
Chin, CC
;
Lin, RJ
;
Yu, YC
;
Wang, CW
;
Lin, EK
We have studied the stoichiometry of cerium oxide films deposited by RF sputtering as a function of deposition conditions using the resonant Rutherford backscattering method. We found that some films have an off-stoichiometry of CeOy with y greater than 2.0. Such an off-stoichiometry cannot be due to a mixture of the known phases of bulk cerium oxide samples. Those thin samples may have either cerium vacancies or interstitial oxygen atomic impurities. We have tried to determine the valence of the cerium ions by measuring the X-ray photoemission.
Perceived importance as a mediator of the relationship between training assignment and training motivation
(2003)
Tsai, WC
;
Tai, WT
;
經營管理研究所
;
Institute of Business and Management
In this study, we examined whether employees' perceived importance of the training program would be one variable that mediates the relationship between training assignment and training motivation. Data were collected from 184 employees belonging to 18 banks who attended government-sponsored training programs in Northern Taiwan. Participants were asked to complete two questionnaires: one at the beginning of the training program and the other at the middle. Results supported our hypothesis and showed that, compared to those who were volunteers, the employees who attended the training on a mandatory basis had a higher motivation for training. Moreover, organizations that force their employees to attend a given training program send out a clear message to employees that such training is important As employees perceive the training to be central to the achievement of organizational objectives, their training motivation increases.
Persistent photoconductivity in SiGe/Si quantum wells
(1998-07-15)
Tsai, LC
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Huang, CF
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Fan, JC
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Chang, YH
;
Chen, YF
Persistent photoconductivity (PPC) has been observed in boron-doped Si1-xGex/Si quantum wells. The decay kinetics of the PPC effect can be well described by a stretched-exponential function, I-ppc(t) = I-ppc(0)exp[-(t/tau)(beta)](0 < beta < 1), which is usually observed in many disorder materials. Through the studies of the PPC effect under various conditions, such as different temperature, different photon energy of photoexcitation, and different Ge content, we identify that the alloy potential fluctuations induced by compositional disorder are the origin of the PPC effect in Si1-xGex/Si quantum wells. (C) 1998 American Institute of Physics. [S0021-8979(98)00914-1].