Browsing by Issue Date, starting with "1997-12-18"

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Least-squares finite element methods for the elasticity problem
(1997-12-18)
Yang, SY
;
Liu, JL
;
應用數學系
;
Department of Applied Mathematics
A new first-order system formulation for the linear elasticity problem in displacement-stress form is proposed. The formulation is derived by introducing additional variables of derivatives of the displacements, whose combinations represent the usual stresses. Standard and weighted least-squares finite element methods are then applied to this extended system. These methods offer certain advantages such as that they need not satisfy the inf-sup condition which is required in the mixed finite element formulation, that a single continuous piecewise polynomial space can be used for the approximation of all the unknowns, that the resulting algebraic systems are symmetric and positive definite, and that accurate approximations of the displacements and the stresses can be obtained simultaneously. With displacement boundary conditions, it is shown that both methods achieve optimal rates of convergence in the H-1-norm and in the L-2-norm for all the unknowns. Numerical experiments with various Poisson ratios are given to demonstrate the theoretical error estimates.
Characterization of GaN epitaxial layers on SiC substrates with AlxGa1-xN buffer layers
(1997-12-18)
Lin, CF
;
Cheng, HC
;
Feng, MS
;
Chi, GC
;
材料科學與工程學系
High quality GaN epitaxial layers were obtained with AlxGa1-xN buffer layers on 6H-SiC substrates. The low-pressure metalorganic chemical vapor deposition (LP-MOCVD) method was used. The 500 Angstrom thick buffer layers of AlxGa1-xN (0 less than or equal to x less than or equal to 1) were deposited on SiC substrates at 1025 degrees C. The FWHM of GaN (0004) X-ray curves are 2-3 arcmin, which vary with the Al content in AlxGa1-xN buffer layers. An optimum Al content is found to be 0.18. The best GaN epitaxial film has the mobility and carrier concentration about 564 cm(2) V-1 s(-1) and 1.6 x 10(17) cm(-3) at 300 K. The splitting diffraction angle between GaN and AlxGa1-xN were also analyzed from X-ray diffraction curves. (C) 1997 Elsevier Science S.A.
Least-squares finite element methods for the elasticity problem
(1997-12-18)
Yang, SY
;
Liu, JL
;
應用數學系
;
Department of Applied Mathematics
A new first-order system formulation for the linear elasticity problem in displacement-stress form is proposed. The formulation is derived by introducing additional variables of derivatives of the displacements, whose combinations represent the usual stresses. Standard and weighted least-squares finite element methods are then applied to this extended system. These methods offer certain advantages such as that they need not satisfy the inf-sup condition which is required in the mixed finite element formulation, that a single continuous piecewise polynomial space can be used for the approximation of all the unknowns, that the resulting algebraic systems are symmetric and positive definite, and that accurate approximations of the displacements and the stresses can be obtained simultaneously. With displacement boundary conditions, it is shown that both methods achieve optimal rates of convergence in the H-1-norm and in the L-2-norm for all the unknowns. Numerical experiments with various Poisson ratios are given to demonstrate the theoretical error estimates.
Relation between fluxes for membrane reaction-diffusion transport studied by the matrix method
(1997-12-22)
Chen, JS
;
Chang, WY
;
應用化學系
;
Department of Applied Chemistry
The previous matrix-theoretical analysis of the time lags and mean first passage times for reaction-diffusion transport in the Laplace domain [J. Chem. Phys. 106, 8022 (1997)] has been extended to the problems of membrane permeation, absorption and desorption. A matrix transport equation has been derived to calculate the flux (in the Laplace domain) for specified initial and boundary conditions corresponding to membrane permeation, absorption or desorption. Seven equality relations between fluxes for reaction-free diffusion and one for diffusion accompanying reaction have been found. Among them are two new equality relations which have been discovered by this matrix analysis. (C) 1997 American Institute of Physics.
Relation between fluxes for membrane reaction-diffusion transport studied by the matrix method
(1997-12-22)
Chen, JS
;
Chang, WY
;
應用化學系
;
Department of Applied Chemistry
The previous matrix-theoretical analysis of the time lags and mean first passage times for reaction-diffusion transport in the Laplace domain [J. Chem. Phys. 106, 8022 (1997)] has been extended to the problems of membrane permeation, absorption and desorption. A matrix transport equation has been derived to calculate the flux (in the Laplace domain) for specified initial and boundary conditions corresponding to membrane permeation, absorption or desorption. Seven equality relations between fluxes for reaction-free diffusion and one for diffusion accompanying reaction have been found. Among them are two new equality relations which have been discovered by this matrix analysis. (C) 1997 American Institute of Physics.
The influence of magnesium on carbide characteristics and creep behavior of the Mar-M247 superalloy
(1997-12-22)
Bor, HY
;
Chao, CG
;
Ma, CY
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The study on microstructural and mechanical properties of weld heat affected zone of 7075-T651 aluminum alloy
(1997-12-22)
Hwang, RY
;
Chou, CP
;
機械工程學系
;
Department of Mechanical Engineering
Temperature dependence of Fermi level obtained by electroreflectance spectroscopy of undoped n(+)-type doped GaAs
(1997-12-29)
Huang, KM
;
Wang, KL
;
Wang, DP
;
Huang, KF
;
Huang, TC
The electroreflectance (ER) spectra of an undoped n(+)-type doped GaAs have been measured over a range of temperature from 25 to 400 K. Many Franz-Keldysh oscillations were observed above the band-gap energy, which enabled the electric field strength and, hence, also the Fermi level to be determined. The photovoltaic effect is shown to be negligible, even at the low temperature. The experiment shows that the Fermi level decreases with increasing temperature and has almost the same temperature dependence as the energy gap. It is pinned at about 0.63 of energy gap below the conduction band. (C) 1997 American Institute of Physics.
Synthesis of 4-oxo- and 4-anti-formyl-8,10,12,13-tetraoxapentacyclo[5.5.1.0(2,6).0(3,11).0(5,9)]tridecanes
(1997-12-29)
Wu, HJ
;
Chern, JH
;
應用化學系
;
Department of Applied Chemistry
The synthesis of 4-oxo- and 4-anti-formyl-8,10,12,13-tetraoxapentacyclo[5.5.1.0(2,6).0(3,11).0(5,9)]tridecanes has been accomplished. Ozonolysis of compounds 10a,b and 12a-c in dichloromethane at -78 degrees C followed by reduction with dimethyl sulfide gave the title compounds, 4-oxo-tetraoxa-cages 11a,b and 14a-c, in moderate yields. Ozonolysis of the endo-syn isomers 15a,b and 18a,b under the same reaction conditions gave 4-anti-formyl-tetraoxa-cages 17a,b and 20a,b, respectively. (C) 1997 Published by Elsevier Science Ltd.
Synthesis of 4-oxo- and 4-anti-formyl-8,10,12,13-tetraoxapentacyclo[5.5.1.0(2,6).0(3,11).0(5,9)]tridecanes
(1997-12-29)
Wu, HJ
;
Chern, JH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The synthesis of 4-oxo- and 4-anti-formyl-8,10,12,13-tetraoxapentacyclo[5.5.1.0(2,6).0(3,11).0(5,9)]tridecanes has been accomplished. Ozonolysis of compounds 10a,b and 12a-c in dichloromethane at -78 degrees C followed by reduction with dimethyl sulfide gave the title compounds, 4-oxo-tetraoxa-cages 11a,b and 14a-c, in moderate yields. Ozonolysis of the endo-syn isomers 15a,b and 18a,b under the same reaction conditions gave 4-anti-formyl-tetraoxa-cages 17a,b and 20a,b, respectively. (C) 1997 Published by Elsevier Science Ltd.
管管這一年十分熱鬧
(1997-12-31)
亮
Chimney-shaped and plateau-shaped gate electrode field emission arrays
(1998)
Tarntair, FG
;
Wang, CC
;
Hong, WK
;
Huang, HK
;
Cheng, HC
A triode structure of chimney-shaped field emitter arrays is proposed in this article. This triode structure includes the chimney-shaped emitter, thermal oxidation dioxide, and the plateau-shaped singlecrystalline silicon gate electrode. For the application of the matrix-addressable and large area flat panel display, the uniform structure of the emitters and the yield become critical manufacturing issues when attempting to control nano-meter size features. The uniformity and yield of the chimney-shaped emitters are very well controlled. The nano-sized gate-to-emitter separations can be created by the changing thickness of the insulator. The uniformity of the insulator and emitter material can be controlled within 3% which can be obtained by most large area thin film deposition tools, not by photolithography.
負型的古典距離正則圖之研究
(1998)
翁志文
;
WENG CHIH-WEN
;
交通大學應用數學系
The reliability of amorphous silicon thin film transistors for LCD under DC and AC stresses
(1998)
Cheng, HC
;
Huang, CY
;
Lin, JW
;
Kung, JJH
;
電子工程學系及電子研究所
In this paper, hydrogenated amorphous silicon and polycrystalline silicon thin film transistors have been stressed with various conditions including DC and AC. The charge trapping and defect state creation are the two mechanisms to degrade the transfer characteristics of the TFTs. For a-Si.H TFTs, the charge trapping occurs at high silicon content of silicon nitride (SiNx) gate dielectrics or performs at high gate electrical field. Defect stale creation dominates at low hydrogen concentration in a-Si:H. At the performance of AC signal, the degradation of transfer curves is associated with bias, frequency, and duty cycle. The characteristics of a-Si:PI TFTs shift more with increasing bias voltage and duty cycle. For the frequency effect, the transfer characteristics of a-Si:H TFTs decrease with increasing AC frequency under negative AC signal stress, however, they are independent of the frequency under positive AC signal stress.
Analysis of plane-wave scattering by bigratings
(1998)
Peng, ST
;
Hwang, RB
;
電信工程研究所
;
Institute of Communications Engineering
We present here a rigorous analysis of the plane-wave scattering by a class of bigratings, each of which consists of two separated gratings that may have different periods and different orientations. Inherently, this is a three-dimensional boundary value problem, regardless of the incidence condition. An exact formulation based on the method of mode matching is carried out, taking into account the effect of polarization couplings. Numerical results are shown for identifying physical phenomena associated with the class of bigrating structures. In particular, Wood's anomalies in the presence of a bigrating are carefully examined and the results are interpreted in terms of those well known for single gratings.
Mandarin telephone: Speech recognition for automatic telephone number directory service
(1998)
Wang, YR
;
Chen, SH
;
電信工程研究所
;
Institute of Communications Engineering
This paper discusses an HMM-based Mandarin telephone speech recognition method for implementing a prototype system of automatic telephone number directory service. It adopted the GPD/MCE training algorithm to train the HMM models for 100 final-dependent syllable initials and 40 syllable finals. The SBR method was used to compensate the speaker and channel effects. Besides, an RNN-based pre-classification scheme was employed to speed up the recognition search. A syllable recognition rate of 53.7% was achieved. This method was then used to implement an isolated-word recognizer for the prototype system to discriminate 1922 names of bank and insurance companies. Word recognition rates of 94.8% for top-1 and 97.9% for top-3 were achieved.
電腦視覺在虛擬實境中的應用---總計畫(II)
(1998)
陳稔
;
CHEN ZEN
;
交通大學資訊工程系
Dynamic spatial modeling approach for estimation of internal phosphorus load
(1998-01-01)
Kao, JJ
;
Lin, WL
;
Tsai, CH
;
環境工程研究所
;
Institute of Environmental Engineering
The effect of the pollution load generated internally from a reservoir on the effectiveness of an eutrophication control plan is significant and has gained increasing attention recently. Accurate estimation of the internal load is difficult because of its spatial and temporal variation. A procedure using a dynamic spatial modeling approach is proposed to improve the estimation. A case study of Posan off-stream reservoir is described to demonstrate the implementation of the procedure for data collection and model preparation, field sampling planning and investigation, laboratory analysis for phosphorus releasing rates, model integration of AGNPS and WASP, calibration and verification of the integrated model, and the internal load estimation. The procedure is expected to provide appropriate temporal and spatial phosphorus internal load estimation for an off-stream reservoir. (C) 1998 Elsevier Science Ltd. All rights reserved.
專家系統知識自動整合環境之研製
(1998)
曾憲雄
;
TSENG SHIAN-SHYONG
;
交通大學資訊科學系
發展一個成功的專家系統必須要有一個完整、一致且清晰的知識庫，所以，利用不同的知識擷取工具以獲取不同專家們的專業知識並加以整合，就成為建構專家系統的重要課題。然而，在知識的整合過程中，經常會產生知識庫內的規則不完整、不一致或重覆等問題。如何有效地整合不同的專家知識並降低彼此間的矛盾，就成為一個重要的研究方向。傳統的知識整合系統因為需要專家的介入而容易顯現出某些缺點，如：(1) 當知識之間有矛盾出現時，專家們必須介入解決，容易造成(但不一定會)不夠客觀的現象；(2) 整合過程所需時間很長；(3) 當專家愈多時，知識整合越困難、越複雜；這些缺點使得大型專家系統的發展變得非常費時。為了克服這些缺點，在本計畫中，我們提出一個知識自動整合方法。它運用了基因遺傳演算法的自我調整找尋技術，將不同專家所提供的知識或不同機器學習技術所推演得到的規則加以整合，並自動產生一個完整、一致且清晰的知識庫。我們的方法有以下之優點：(1) 只需要少許的整合時間；(2) 當專家所提供的知識愈豐富或機器學習技術所推演得到的規則愈多，知識整合愈有效率，知識庫愈準確；(3) 當知識之間有矛盾出現時，可不需要專家介入；(4) 整合過程中，可不需要專家介入，所以，它是客觀的；(5) 可以擴充至分散式知識整合環境。然而，本系統有一些限制，如:(1) 每一個欲整合之專家知識必須以規則集合形式表示；(2) 當欲整合之專家知識變少，系統必須產生一些仿冒知識(dummy knowledge)，而容易造成知識整合沒有效率；除了上述之優點及限制外，本系統具有很大的擴充性，一些常用的知識擷取工具及機器學習系統很容易整合於本系統中，來幫助系統獲取更多的領域知識。整個知識整合系統將與專家系統建構工具 CLIPS整合，為知識工程師提供完整的發展環境。有了環境的幫助，專家系統的發展將變得比較容易而有效率。本計畫中，我們預計完成一套專家系統的知識自動整合環境，包括 - 知識擷取模組、機器學習模組、知識整合模組以及知識修正模組。知識擷取模組收集了一些知識擷取工具，來幫助專家輸入領域知識。機器學習模組中儲存了一些著名的學習系統，可將過去發生過的案例歸納成一些規則。知識整合模組則負責整合由知識擷取模組所產生的領域知識及由機器學習模組所歸納產生的規則，並產生專家系統的知識庫。知識修正模組則運用於知識庫推理中，若有不適用之規則存在，則將自動找出並加以修正，隨時維持知識庫的一致性及準確性。在應用方面，我們將以醫學上腦瘤診斷及農業上�抻岳|種的實際應用領域進行實作。在應用領域中將邀請專門醫師及學者們作為專家，並依實際病歷及歷年紀錄的資料進行測試，以驗証計畫之成果。
On detection of bounded global predicates
(1998-01-01)
Wu, IC
;
Chen, LB
;
資訊工程學系
;
Department of Computer Science
Distributed programs often follow some bounded global predicates, for example, the total number of certain tokens is always the same or bounded in a range. In order to detect bounded global predicates, we can first derive the minimum and maximum global snapshots and then check if the minimum and maximum are out of the range, Recently, Chase and Garg proposed an efficient method to derive the minimum global snapshot by reducing this problem to a maximum network flow problem. A restriction of this method is that all message values (e.g,, the token number in messages) must be zero and all process state values (e.g,, the token number in processes) must be non-negative. In this paper, we propose an elegant technique, called normalization. By using this technique, we can remove the above restriction and also derive the minimum and maximum global snapshots at the same time.