Browsing by Issue Date, starting with "1996-03-04"

Now showing 1 - 20 of 85566

肥了秋陽瘦了乳房
(1996-03-04)
管管
Source of Ge centers in AlGaAs grown by organometallic vapor phase epitaxy and the effect of impurity getters
(1996-03-04)
Lee, WI
;
電子物理學系
;
友訊交大聯合研發中心
;
Department of Electrophysics
;
D Link NCTU Joint Res Ctr
A long term and comprehensive study has been performed to identify the origin of the Ge center in AlGaAs grown by organometallic vapor phase epitaxy. With a series of deductive investigations, AsH3 gas has been undoubtedly identified as the source of the Ge contamination. Depending on the AsH3 quality, one to two orders of magnitude of difference in Ge trap densities has been observed. Long-term observations indicate fairly constant Ge content throughout most of the AsH3 tank lifetime. Different impurity getters were attempted to remove the Ge contaminant. While most getters can eliminate the oxygen-related defects in AlGaAs, no getters were able to remove the Ge DX center. (C) 1996 American Institute of Physics.
Metalorganic chemical vapor deposition of tungsten nitride for advanced metallization
(1996-03-04)
Tsai, MH
;
Sun, SC
;
Chiu, HT
;
Chuang, SH
;
電子工程學系及電子研究所
In this study, the physical and electrical properties of tungsten nitride thin films deposited by thermal decomposition of bis(tertbutylimido)bis(tertbutylamido)tungsten have been investigated. The films have an excellent step coverage over high aspect-ratio contact holes as well as a low carbon concentration. Strong W-N double bonds in the precursor preserved the nitrogen atoms during the pyrolysis process. This method subsequently yielded low-resistivity films. A decrease in film resistivity from 4300 to 620 mu Ohm cm corresponded to an increase in the deposition temperature from 500 to 650 degrees C, X-ray diffraction (XRD) and wavelength dispersive spectroscopy (WDS) results indicated that the as-deposited films have face centered cubic (fcc) phase polycrystalline structures with excessive nitrogen atoms. (C) 1996 American Institute of Physics.
Phosphorus doping of Si and Si1-xGex grown by ultrahigh vacuum chemical vapor deposition using Si2H6 and GeH4
(1996-03-11)
Chen, LP
;
Huang, GW
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Chang, CY
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電控工程研究所
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Institute of Electrical and Control Engineering
100 ppm PH3 diluted in hydrogen is used as the n-type dopant gas in Si and Si1-xGex epilayers grown by ultrahigh vacuum chemical vapor deposition (UHVCVD) using Si2H6 and GeH4. The phosphorus concentration in Si increases linearly at a small PH3 flow rate and becomes nearly saturated at higher flow rates, while the phosphorus concentration in Si1-xGex only shows a nearly linear behavior with PH3 flow rate. The growth rates of Si and Si1-xGex epilayers decrease seriously (similar to 50%) and slightly (similar to 10%) with the increase of PH3 how rate, respectively. These results con be explained by a model based on the enhancement of hydrogen desorption rate at smaller PH3 flow rates and different levels of the effects of phosphorus blocking of surface-activated sites between Si and Si1-xGex epilayers at higher PH3 flow rates. (C) 1996 American Institute of Physics.
Hybrid method for modular exponentiation with precomputation
(1996-03-14)
Chen, CY
;
Chang, CC
;
Yang, WP
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資訊工程學系
;
Department of Computer Science
The authors present a new hybrid method for perfonming modular exponentiation using a hybrid ternary-quinary number system. A recent result concerning performing modular exponentiation with precomputation was presented by Dimitrov and Cooklev: their average number of modular multiplications is 0.3381n, where n is the length of the modulus, while the authors' proposed method only needs 0.3246n modular multiplications. Furthermore, compared to Dimitrov and Cooklev's approach, the authors' method reduces the amount of storage by 56.8% if the modulus is a 512 bit number.
A study of the Kuroshio's seasonal variabilities using an altimetric gravimetric geoid and TOPEX/POSEIDON altimeter data
(1996-03-15)
Hwang, CW
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交大名義發表
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土木工程學系
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National Chiao Tung University
;
Department of Civil Engineering
The first year of TOPEX/POSEIDON (T/P) altimeter data were used to study the seasonal variabilities of the Kuroshio Current. The intercomparison between the T/P and gauge sea levels at selected tide gauge stations around Taiwan shows that the two have a correlation of about 0.9 at the immediate vicinity of the deep ocean and both show an annual cycle with an amplitude of 15 cm. A 3' x 3' geoid for the Western Pacific was constructed by least squares collocation using gravity anomalies and sea surface gradients derived from Seasat, Geosat, ERS 1, and T/P altimetry. To account for the oceanographic signal in the altimeter data, we derived a covariance function for the gradients of the sea surface topography (SST) based on a global averaging concept and a spherical harmonic expansion of the Levitus SST to degree 50. The accuracy of the geoid ranges from 5 to 40 cm. The SST values derived from the geoid and the data along T/P's descending tracks were fitted to the hyperbolic functions in a two-step procedure to find the Kuroshio's seasonal axes and the parameters that describe its characteristics. The mean variabilities in the Kuroshio's path, maximum velocity, baroclinic transport, and width are 22 km, 19 cm, 8 Sv, and 27 km, respectively. The averaged percentage variability of all quantities is 25%. All the variabilities are relatively large near the northeast coast of Taiwan and the starting point of the Kuroshio Extension. The large-scale circulations over the Western Pacific were obtained by median filtering the SST. At the 1334-km spatial scale, the Pacific's subtropical gyre is clearly visible, and it shows different features over the four seasons and its kinetic energy shows possible correlations with the determined parameters. Over the South China Sea a warm ring with a radius of 300-400 km and a center at 15 degrees N, 113 degrees E was detected in the spring and summer.
作家連袂搭捷運,心花怒放
(1996-03-15)
馬溫妮
A new high-order non-uniform Timoshenko beam finite element on variable two-parameter foundations for vibration analysis
(1996-03-21)
Hou, YC
;
Tseng, CH
;
Ling, SF
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機械工程學系
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Department of Mechanical Engineering
A new finite element model of a Timoshenko beam is developed to analyze the small amplitude, free vibrations of non-uniform beams on variable two-parameter foundations. An important characteristic of the model is that the cross-sectional area, the second moment of area, the Winkler foundation modulus and the shear foundation modulus are all assumed to vary in polynomial forms, implying that the beam element can deal with commonly seen non-uniform beams having different cross-sections such as rectangular, circular, tubular and even complex thin-walled sections as well as the foundation of beams which vary in a general way. Thus this new beam element model enables users to handle vibration analysis of more general beam-like structures. In this paper, by using cubic polynomial expressions for the total deflection and the bending slope of the beam, the mass and stiffness matrices of the element are derived from energy expressions. The element model can accommodate various boundary conditions to represent a Timoshenko beam accurately. Excellent agreement with other investigators' results and a rapid rate of convergence with relatively few elements are demonstrated. This study also brings out the fact that the complicated form of this new beam model is necessary because of its advantage over linear or uniform approximations of the non-uniform foundation and/or geometrical properties of beams. The same accuracy being achieved with fewer elements is the main advantage. Finally, an optimum design problem is illustrated to emphasize the practical application of this element. (C) 1996 Academic Press Limited
翅膀
(1996-03-26)
管管
Chemistry of Ti(OiPr)Cl-3 with chloride and oxygen-containing ligands: The roles of alkoxide and solvents in the six-coordinate titanium complexes
(1996-03-27)
Gau, HM
;
Lee, CS
;
Lin, CC
;
Jiang, MK
;
Ho, YC
Ti((OPr)-Pr-i)Cl-3 reacts easily with various ligands to form a series of six-coordinate complexes, [Ti((OPr)-Pr-i)Cl-5](2-)(HAm+)(2) (Am = NEt(3) (7a) or NC5H5 (7b)), Ti((OPr)-Pr-i)Cl(3)L(2) (L = THF (8) or PhCHO (9)), Ti((OPr)-Pr-i)-Cl-3(PhCHO)(Et(2)O) (10), and [Ti((OPr)-Pr-i)Cl-2(mu-Cl)(PhC(O)OMe)](2) (11). Upon dissolution of 7a in THF, 8 was obtained. When 1 mol equiv of HNEt(3)Cl was added to 8, [Ti((OPr)-Pr-i)Cl-4(THF)](-)(HNEt(3))+ (12) was obtained. With the addition of another 1 mol equiv of HNEt(3)Cl, 12 was converted to 7a. One THF in 8 can be removed in vacuo to give the chloride-bridged dimer [Ti((OPr)-Pr-i)Cl-2(mu-Cl)(THF)](2) (13) which can be converted back to 8 by dissolving in THF. 13 was found to react with 2 mol equiv of HNEt(3)Cl or PhCHO to give 12 and Ti((OPr)-Pr-i)Cl-3(PhCHO)(THF) (14), respectively. The molecular structures of 7b, 8, and 10-13 show short Ti-(OPr)-Pr-i distances, and the relative bonding order of (OPr)-O---Pr-i > Cl-, THF > Et(2)O > PhCHO > mu-Cl- > RC(O)OMe is discussed based on the solid state structures. This bonding sequence is very useful for the prediction of the geometry for six-coordinate complexes of early transition metals with the following principle: The strongest ligand prefers a trans position to the weakest ligand, and the second strongest ligand favors a trans position to the second weakest ligand in the complex. Kinetically, the trans position to the isopropoxide is rather labile for substitution, and the lability of the trans ligand ensures the effectiveness of titanium alkoxides for subsequent reactions or as catalysts in many asymmetric organic syntheses.
Two-dimensional elastodynamic transient analysis by QL time-domain BEM formulation
(1996-03-30)
Wang, CC
;
Wang, HC
;
Liou, GS
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土木工程學系
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Department of Civil Engineering
A quadratic time-domain Boundary Element Method (BEM) for two-dimensional (2-D) elastodynamic transient wave analysis is presented. Emphasis is focused on developing time-domain fundamental convoluted kernels and methodology for quadratic temporal solution procedure which are never presented before. In the presented BEM method, the displacement temporal variation is assumed to be quadratic, the traction temporal variation is assumed to be linear (called QL method, a two-time-step piecewise continuity method), and the spatial variations are assumed to be quadratic variation. The QL method is compared with the LC method and the QC method by solving several example problems. Numerical study reveals that the QC and QL methods are more accurate and stable than the LC method, and the QL method is much better than the QC method for transient problems.
個性書店
(1996-03-30)
不詳
謁陵．感懷
(1996-03-31)
管管
謁陵．感懷
(1996-03-31)
管管
謁陵．感懷
(1996-03-31)
管管
謁陵．感懷
(1996-03-31)
管管
Derivation of the Glover-Doyle algorithms for general H-infinity control problems
(1996-04-01)
Hong, JL
;
Teng, CC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
We show that the Glover-Doyle algorithm can be formulated simply by using the (J,J')-lossless factorization method and chain scattering matrix description. This algorithm was first stated by Glover and Doyle in 1988. Because the corresponding diagonal block of the (J,J')lossless matrix in the general 4-block H-infinity control problem of the Glover-Doyle algorithm is not square, a new type of chain scattering matrix description is developed. With this description in hand, we obtain two types of state-space solution, which are similar to each other. Thus a similarity transformation between these solutions in the 4-block H-infinity control problem can also be obtained. The main idea of the solution is illustrated by means of block diagrams.
Synthesis of novel tetraacetal oxa-cage compounds from 2-methylthiofurans
(1996-04-01)
Lin, CC
;
Huang, FJ
;
Lin, JC
;
Wu, HJ
;
交大名義發表
Several novel tetraacetal oxa-cage compounds 9a-9f were synthesized from the corresponding 2-methylthiofurans 1a-1f by a short sequence. The structures of these tetraoxa-cage compounds were deduced from their spectral data and proven by X-ray analysis of 9a. Ozonolysis of the endo adducts 5a-5f in CH2Cl2 at -78 degrees C followed by reduction with dimethyl sulfide gave the tetraoxa-cages 9a-9f in 65-75% yields, respectively. Ozonolysis of the exo adduct 6a under the same reaction conditions gave the tetracarbonyl compound 10. The phenylthio group substituted tetraoxa-cage 13 and the tetraacetal oxa-cage 17, with one more carbon atom on the apex position, were also synthesized in a similar sequence.
New nonlinear algorithms for estimating and suppressing narrowband interference in DS spread spectrum systems
(1996-04-01)
Wu, WR
;
Yu, FF
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交大名義發表
;
電信工程研究所
;
National Chiao Tung University
It has been shown that the narrow-band (NB) interference suppression capability of a direct-sequence (DS) spread spectrum system can be enhanced considerably by processing the received signal via a prediction error filter, The conventional approach to this problem makes use of a linear filter. However, the binary DS signal, that acts as noise in the prediction process, is highly non-Gaussian, Thus, linear filtering is not optimal, Vijayan and Poor [11] first proposed using a nonlinear approximate conditional mean (ACM) filter of the Masreliez type and obtained significant results, This paper proposes a number of new nonlinear algorithms, Our work consists of three parts, 1) We develop a decision-directed Kalman (DDK) filter, that has the same performance as the ACM filter but a simpler structure, 2) Using the nonlinear function in the ACM and the DDK filters, we develop other nonlinear least mean square (LR IS) filters with improved performance, 3) We further use the nonlinear functions to develop nonlinear recursive least squares (RLS) filters that can be used independently as predictors or as interference identifiers so that the ACM or the DDK filter can be applied, Simulations show that our nonlinear algorithms outperform conventional ones.
An efficient construction of perfect secret sharing schemes for graph-based structures
(1996-04-01)
Sun, HM
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Shieh, SP
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資訊工程學系
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Department of Computer Science
In this paper, we propose an efficient construction of perfect secret sharing schemes for graph-based access structures where a vertex denotes a participant and an edge does a qualified pair of participants. The secret sharing scheme is based on the assumptions that the pairs of participants corresponding to edges in the graph can compute the master key but the pairs of participants corresponding to nonedges in the graph cannot. The information rate of our scheme is 1/(n-1), where n is the number of participants. We also present an application of our scheme to the reduction of storage and computation loads on the communication granting server in a secure network.