Browsing by Issue Date, starting with "1991-06-01"

Now showing 1 - 20 of 91258

NOVEL HETEROCYCLIC CAGE COMPOUNDS FROM 2-METHYLTHIOFURANS
(1991-06-01)
WU, HJ
;
HUANG, FJ
;
LIN, CC
;
交大名義發表
;
應用化學系
Some novel heterocyclic cage compounds 1a-1c were synthesized from the corresponding 2-methylthiofurans 2a-2c in a short sequence.
LOW-PRESSURE CHEMICAL VAPOR-DEPOSITION OF SILICON-CARBIDE THIN-FILMS FROM ORGANOPOLYSILANES
(1991-06-01)
CHIU, HT
;
WU, PF
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
(Me3Si)2SiMe2, (Me3Si)3SiMe and (Me3Si)4Si were used as precursors for the deposition of polycrystalline beta-SiC thin films on silicon substrates at 1000-1200-degrees-C in a low-pressure hot-wall chemical vapor deposition reactor. The thin films were analyzed by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy.
PREPARATION OF FINE-GRAINED BATIO3
(1991-06-01)
FAN, YC
;
CHENG, HC
;
TSENG, TY
;
交大名義發表
;
電控工程研究所
DYNAMIC-RANGE, STABILITY, AND FAULT-TOLERANT CAPABILITY OF FINITE-PRECISION RLS SYSTOLIC ARRAY BASED ON GIVENS ROTATIONS
(1991-06-01)
LIU, KR
;
HSIEH, SF
;
YAO, K
;
CHIU, CT
;
電信工程研究所
The QRD RLS algorithm is generally recognized as having good numerical properties under a finite-precision implementation. Furthermore, it is quite suited for VLSI implementation since it can be easily mapped onto a systolic array. However, it is still unclear how to obtain the dynamic range of the algorithm in order a wordlength can be chosen to ensure correct operations of the algorithm. In this paper, we first propose a quasi-steady state model by observing the rotation parameters generated by boundary cells will eventually reach quasi-steady-state regardless of the input data statistics if lambda is close to one. With this model, we can obtain upper bounds of the dynamic range of processing cells. Thus the wordlength can be obtained from upper bounds of the dynamic range to prevent overflow and to ensure correct operations of the QRD RLS algorithm. Then we reconsider the stability problem under quantization effects with a more general analysis and obtain tighter bounds than given in a previous work [13]. Finally, two fault-tolerant problems, the missing error detection and the false alarm effect, that arise under finite-precision implementation are considered. Detailed analysis on preventing missing error detection with a false alarm free condition is presented.
SYNTHESIS AND CHARACTERIZATION OF SIDE-CHAIN LIQUID-CRYSTALLINE POLYSILOXANES CONTAINING 4-ALKANYLOXYPHENYL TRANS-4-ALKYLCYCLOHEXANOATE SIDE GROUPS
(1991-06-01)
HSU, CS
;
LU, YH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The synthesis and characterization of nine polysiloxanes containing 4-alkanyloxyphenyl trans-4-n-alkylcyclohexane side groups are described. Six monomers which contain a pentenyloxy or a hexenyloxy flexible spacer display a nematic mesophase, while the other three monomers which contain an undecenyloxy flexible spacer display nematic, smectic A and smectic E mesophases. All synthesized polymers present two smectic mesophases except one containing 4-hexanyloxyphenyl trans-4-n-butylcyclohexanoate side groups presents one smectic mesophase and one containing 4-undecanyloxyphenyl trans-4-n-pentylcyclohexanoate side groups presents three smectic mesophases. Trans-cis isomerization of mesogens and side chain crystallization did not occur for any of the synthesized polymers.
A NEW PHASE IN AN FE-9.0AL-29.5MN-1.2SI ALLOY
(1991-06-01)
WU, CC
;
LIU, TF
;
機械工程學系
;
材料科學與工程學系
;
Department of Mechanical Engineering
A new type of precipitate (designated L phase) was observed within the ferrite matrix in an Fe-9.0Al-29.5Mn-1.2Si alloy after being aged at 550-degrees-C. Transmission electron microscopy examinations indicated that the L-phase precipitate has a monoclinic structure with lattice parameters a = 0.656 nm, b = 0.797 nm, c = 0.637 nm, and beta = 109.4 deg, and the orientation relationship between the L-phase precipitate and the ferrite matrix could be stated as follows: (1BAR01)alpha-parallel-to (001)L-phase (1BAR10)alpha-parallel-to (1BAR11)L-phase with a deviation of 0.3 deg (011)alpha-parallel-to (131)L-phase with a deviation of 1.5 deg The L phase has never been observed in various Fe-Al-Mn, Fe-Mn-Si, Fe-Al-Si, and Mn-Al-Si alloy systems before.
AMORPHOUS SI/SIC PHOTOTRANSISTORS AND AVALANCHE PHOTODIODES
(1991-06-01)
CHANG, CY
;
HONG, JW
;
FANG, YK
;
交大名義發表
;
National Chiao Tung University
The device structures, operation principles, optoelectronic characteristics, performance comparisons, and possible applications for various a-Si:H/a-SiC:H phototransistors and avalanche photodiodes are reviewed. Although these devices are made of amorphous semiconductors, its majority-carrier transport properties can tactfully avoid gap-state and defect related minority-carrier transport problems, and obtain good performances. Also, each of these devices has the distinct advantage of meeting the requirements of different practical applications. The unique and distinct advantages of these a-Si:H/a-SiC:H devices are first, a variety of peak response wavelengths are achievable by changing the composition or the well-to-barrier widths of the superlattice, secondly, a large-area-detector image sensor can be made on a glass substrate; and thirdly, the low-temperature of the amorphous films (approximately 250-degrees-C) possesses a very abrupt composition change and a doping profile, which are impossible in the single-crystalline semiconductors.
A NEW METHODOLOGY FOR DEVELOPING A FAST 2-DIMENSIONAL MOSFET DEVICE SIMULATOR
(1991-06-01)
PERNG, RK
;
LIN, PS
;
WU, CY
;
工學院
;
College of Engineering
A new efficient computation scheme using both analytical and numerical techniques has been developed and implemented in a SUbMicron MOS (SUMMOS) simulator. The main features of the proposed scheme are: (1) an efficient grid-partition method and an accurate initial guess technique for the Newton-like method are generated by the developed analytical model through solving the two-dimensional Possion's equation; (2) the accurate source and drain boundary potentials used in the analytical model for a MOSFET with the complicated device structure are provided by a simple model and further refined by a self-improved feedback technique. Comparisons between the initial guess using the analytical model and the final solution are analyzed. In addition, comparisons between the new scheme and the conventional algorithm using the continuation method is made via the number of Newton-iteration and the CPU time, and the superior performance of the new computation scheme is observed. Moreover, it is demonstrated that the SUMMOS simulator with the proposed computation scheme can provide efficient numerical simulation of MOSFET's in CMOS/VLSI.
TRACKING TECHNIQUE FOR MANEUVERING TARGET WITH CORRELATED MEASUREMENT NOISES AND UNKNOWN-PARAMETERS
(1991-06-01)
GUU, JA
;
WEI, CH
;
交大名義發表
;
電控工程研究所
;
National Chiao Tung University
The problem of tracking a manoeuvring target with sequentially correlated measurement noise is considered in the paper. Using Singer's method to model the manoeuvring target, the correlated measurement noise can be decorrelated by reformulating the measurement equation such that the conventional Kalman filter can be directly applied in this tracking problem. An analytical error analysis for this processing is derived. If some of the parameters are unknown, the conventional innovation correlation method can usually be employed to estimate these parameters adaptively. This method assumes that the measurement noise is white. If the measurement noise is sequentially correlated, this technique is not valid and the parameters can not be estimated with sufficient accuracy to obtain the desired tracking performance. By considering the effect of noise correlation, a modified computationally efficient method known as a multiple-level estimator is presented to improve the performance in estimating the unknown parameters in the presence of correlated measurement noise.
A PARTIAL VARIATIONAL ANALYSIS OF PLANAR DIELECTRIC ANTENNAS
(1991-06-01)
CHUNG, SJ
;
CHEN, CH
;
電信工程研究所
;
Institute of Communications Engineering
The reflection and radiation characteristics of a planar dielectric antenna with arbitrary geometrical configuration are analyzed numerically. A variational equation is first established based on the partial variational principle (PVP), and then solved by the finite element method coupled with the frontal solution technique. The radiation and boundary conditions are incorporated by combining the modal expansion method and the Green's function approach for exterior field representation. The reflection coefficients, the radiation patterns, and the directive and power gains of several antennas with linearized structures are studied and compared.
MEASUREMENT OF ULTRATHIN (LESS-THAN-100-A) OXIDE-FILMS BY MULTIPLE-ANGLE INCIDENT ELLIPSOMETRY
(1991-06-01)
CHAO, TS
;
LEE, CL
;
LEI, TF
;
交大名義發表
;
電控工程研究所
The application of the multiple-angle incident ellipsometry to measure the ultrathin (< 100 angstrom) oxide has been studied in this paper. First, four interfacial models are investigated by using a fitting scheme to fit ellipsometric data (DELTA, psi) at various incident angles, and the abrupt model is found to be the most appropriate model to model the transition region of the SiO2-Si interface. The sensitivities on the incident angle and the errors induced by the ellipsometric parameter variations are also analyzed. Ellipsometry is applied to measure the native oxides of Si wafers after they are treated with different cleaning processes, and it is also applied to measure refractive indexes and thicknesses of ultrathin thermally grown SiO2. It is believed that these are the most accurately measured results on the refractive indexes of ultrathin oxides. Also, an empirical formula for thermal oxide growth in dry O2 is obtained.
EFFECT OF RESIDUAL-STRESS ON COLD-FORMED STEEL COLUMN STRENGTH
(1991-06-01)
WENG, CC
;
交大名義發表
;
土木工程學系
;
National Chiao Tung University
;
Department of Civil Engineering
The effect of residual stress on the flexural buckling strength of cold-formed steel columns is studied. Based on the results of 93 column tests and the measured residual stresses, significant relation is observed between the reduction of column strength, the magnitude and distribution of residual stress, and the flat-width ratio of the plate element of the cold-formed section. In this study, a new concept called the "second reduction" is developed to account for the effect of the residual stresses on the local buckling behavior of cold-formed steel columns. Based on this concept, a possible design procedure is outlined for the prediction of the flexural buckling strength of cold-formed steel columns. The theoretical predictions are found to be in good agreement with the test results.
THE DELTA-DOPED IN0.25GA0.75AS/GAAS PSEUDOMORPHIC HIGH ELECTRON-MOBILITY TRANSISTOR STRUCTURES PREPARED BY LOW-PRESSURE METAL ORGANIC-CHEMICAL VAPOR-DEPOSITION
(1991-06-01)
CHANG, CY
;
LIN, W
;
HSU, WC
;
WU, TS
;
CHANG, SZ
The (800 angstrom)GaAs/In0.25Ga0.75As/(0.5-mu-m) GaAs strain layers with delta-doping in the GaAs cap layer were fabricated without using AlGaAs layers. Triethylgallium (TEG), trimethylindium (TMI), arsine (AsH3) and silane (SiH4) were used as the sources and dopants in these structures grown by the low-pressure metalorganic chemical vapor deposition (LP-MOCVD) technique for the first time to study these structures. The delta-doping was obtained by a stop-growth process by which a very thin and heavily doped layer (1.86 x 10(13) cm-2) can be realized. For the (delta-doped) GaAs/In0.25Ga0.75As/GaAs high electron mobility transistor (HEMT) structures, the concentration of two-dimensional electron gas (2-DEG) and the Hall mobilities were investigated. Experimental results show that a structure with (80 angstrom) In0.25Ga0.75As as the active channel and with a 70 angstroms spacer layer revealed the highest 2-DEG concentration and mobility product of 5.5 x 10(16) V-1.s-1 at a temperature of 77 K. These structures are easy to achieve by the LP-MOCVD mechod and are promising for high-performance field effect transistors (FETs).
PERFORMANCE ANALYSIS OF EFFICIENT CONCATENATED CODING SCHEME FOR ARQ PROTOCOLS
(1991-06-01)
LEE, TH
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
;
Center for Telecommunications Research
Benelli investigated the performance of two concatenated coding schemes for ARQ protocols. The two schemes differ in their strategies of retransmission. It was shown that the two schemes proposed by Benelli provide a significant improvement in throughput efficiency of ARQ protocols with respect to other similar schemes. The analysis presented by Benelli is complicated. An alternative analysis is provided. Some implementation problems of the Benelli's schemes are also discussed. An efficient retransmission strategy which avoids unnecessary retransmissions and maintains a fixed decoding complexity is proposed.
ANISOTROPIC SUPERCONDUCTING PROPERTIES OF ALIGNED (BI,PB)2CAN-1SR2CUNO2N+4+DELTA POWDERS (N = 1, 2, 3) WITH TC = 32, 94, AND 110 K
(1991-06-01)
SHI, JB
;
CHIOU, BS
;
KU, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The anisotropic superconducting properties of aligned powders embedded in epoxy for bismuth copper oxides with the compositions (Bi1.6Pb0.4)(Sr1.5La0.5)CuO6+delta (n = 1, T(c) = 32 K), Bi2Ca1.2Sr1.8Cu2O8+delta (n = 2, T(c) = 94 K), and (Bi1.85Pb0.15)Ca2.2Sr1.8Cu3O10+delta (n = 3, T(c) = 110 K) are reported. These c-axis-aligned samples were prepared in a 9.4-T applied magnetic field at room temperature The temperature dependence of the anisotropy ratio chi-c(T)/chi-ab(T) in the superconducting state is derived from both zero-field-cooled and field-cooled data using a small applied field H (less than or equal to the lower critical field H(c1)) parallel and perpendicular to the orthorhombic c axis. A highly anisotropic chi-c/chi-ab ratio was observed for all three systems, the maximum value of chi-c/chi-ab = 9.8 at 5 K and 10.8 at 85 K for the 2:2:2:3 compound (Bi1.85Pb0.15)Ca2.2Sr1.8Cu3O10+delta was observed. The field dependence of the anisotropy ratio chi-c(H)/chi-ab(H) for the 2:1:2:2 compound Bi2Ca1.2Sr1.8Cu2O8+delta up to 5 kG is discussed.
A MATHEMATICAL-MODEL FOR THE TOOTH GEOMETRY OF CIRCULAR-CUT SPIRAL BEVEL GEARS
(1991-06-01)
FONG, ZH
;
TSAY, CB
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A complete tooth geometry of the circular-cut spiral bevel gears has been mathematically modeled. The mathematical model has been divided into several independent modules, each representing an individual kinematic relation or tool-setting, with examples included. A comparison with the spiraloid model has also been made in this paper. The mathematical model can be applied to simulate and calculate the tooth profiles for the Duplex Method, Helical Duplex Method, Formate Method, and Modified Roll Method for circular-cut spiral bevel gears. It can also be applied to the computer numerical controlled (CNC) machining, computer-aided finite element stress analysis, and tooth contact analysis (TCA) for the spiral bevel gear.
PHASE-TRANSFORMATION IN AN FE-9.0AL-29.5MN-1.2SI ALLOY
(1991-06-01)
LIU, TF
;
UEN, GC
;
CHAO, CY
;
LIN, YL
;
WU, CC
The microstructure of an (alpha + gamma) duplex Fe-9.0Al-29.5Mn-1.2Si alloy has been investigated by means of transmission electron microscopy. In the as-quenched condition, extremely fine D0(3) particles were formed within the ferrite matrix by a continuous ordering transition during quenching. After being aged at 550-degrees-C, the extremely fine D0(3) particles existing in the as-quenched specimen grew preferentially along [100] directions. With increasing the aging time at 550-degrees-C, a (Si, Mn)-rich phase (designated as "L phase") began to appear at the regions contiguous to the D0(3) particles. The L phase has never been observed in various Fe-Al-Mn, Fe-Al-Si, Fe-Mn-Si, and Mn-Al-Si alloy systems before. When the as-quenched specimen was aged at temperatures ranging from 550-degrees-C to 950-degrees-C, the phase transformation sequence occurring within the (alpha + D0(3)) region as the aging temperature increases was found to be (alpha + D0(3) + L phase) --> (alpha + D0(3) + A13 beta-Mn) --> (B2 + D0(3) + A13 beta-Mn) --> (B2 + A13 beta-Mn) --> (alpha + A13 beta-Mn) --> (alpha + gamma) --> alpha.
A NEW SIMPLIFIED 2-DIMENSIONAL MODEL FOR THE THRESHOLD VOLTAGE OF MOSFETS WITH NONUNIFORMLY DOPED SUBSTRATE
(1991-06-01)
LIN, PS
;
WU, CY
;
工學院
;
College of Engineering
A new simplified two-dimensional model for the threshold voltage of MOSFET's is derived in terms of simple characteristic functions. These characteristic functions are transformed from the exact series solution of the two-dimensional Poisson's equation, in which the effects of a nonuniformly doped substrate and a finite graded source-drain junction depth have been included. The attractive features of the developed model are: 1) charge-screening effects are proposed to account for the weak dependence of the threshold voltage on the substrate bias for short-channel MOSFET's, and 2) exact source and drain boundary potentials can be approximated by their equivalent power functions. The accuracy of the simplified 2-D model has been verified by 2-D numerical analysis. Moreover, comparisons between the simplified 2-D model and the experimental results have been made, and good agreement has been obtained for wide ranges of channel lengths, applied substrate, and drain biases.
FRACTIONAL RATE MULTITREE SPEECH CODING
(1991-06-01)
GIBSON, JD
;
CHANG, WW
;
電信工程研究所
;
Institute of Communications Engineering
We present both forward and backward adaptive speech coders that operate at 9.6, 12, and 16 kb/s using integer and fractional rate trees, weighted squared error distortion measures, the (M,L) tree search algorithm, and incremental path map symbol release. We introduce the concept of multitree source codes and illustrate how the multitree structure allows scalar quantizer-based codes and scalar adaptation rules to be used for fractional rate tree coding. With a frequency weighted distortion measure, the forward and backward adaptive multitree coders produce near toll quality speech at 16 kb/s, while the backward adaptive 9.6 kb/s multitree coder substantially outperforms adaptive predictive coding and has an encoding delay less than 2 ms. Performance results are presented in terms of unweighted and weighted signal-to-noise ratio and segmental signal-to-noise ratio, sound spectrograms, and subjective listening tests.
MULTIPLEXED FIBEROPTIC SENSORS USING A DUAL-SLOPE FREQUENCY-MODULATED SOURCE
(1991-06-01)
CHIEN, PY
;
PAN, CL
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
We propose and demonstrate a multiplexed fiber-optic sensor system using a dual-slope (triangular) frequency-modulated laser source. The restrictions in the selection of beat frequencies of the multiplexed sensors in previous studies that employed ramp modulation wave forms are eliminated.