Browsing by Issue Date, starting with "1992-03-25"

Now showing 1 - 20 of 90751

COEXISTENCE OF DUCTILE, SEMI-DUCTILE, AND BRITTLE FRACTURES OF POLYCARBONATE
(1992-03-25)
CHANG, FC
;
CHU, LH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
The ductile-brittle transition behavior of polycarbonate and methylmethacrylate-butadiene-styrene (MBS) elastomer modified polycarbonate has been investigated in terms of notch radius and temperature. At -40-degrees-C and 21-mil notch radius, polycarbonate fractures in three possible modes, ductile (25%), semi-ductile (50%), and brittle (25%). This semi-ductile mode fracture has never been reported previously with brittle characterization, but to a greater extent in localized shear yielding on the fracture surface and intermediate toughness. A two-dimensional fracture mode diagram in terms of temperature and notch radius has been constructed to interpret the observed phenomena. This diagram can also predict the existence of other conditions under which the triplet fracture modes may also occur. Another unstable zone has also been identified where the fracture occurs in either ductile mode or brittle mode over a broad temperature range, instead of the narrow temperature range typically observed for polycarbonate. A model based on the excessive precrack strain just below yielding due to the greater notch radius is proposed to explain such observed semi-ductile mode fracture.
狀告月亮
(1992-03-28)
管管
NOVEL ANNEALING SCHEME FOR FABRICATING HIGH-QUALITY TI-SILICIDED SHALLOW N+P JUNCTION BY P+ IMPLANTATION INTO THIN TI FILMS ON SI SUBSTRATE
(1992-03-30)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A TiSi2 silicided shallow n + p junction with a leakage current density of about 3 nA/cm2, a forward ideality factor of 1.00, and a junction depth of about 0.11-mu-m has been fabricated by implanting P+ ions into thin amorphous-Si/Ti bilayer films on silicon substrate and subsequently processed by a rapid thermal annealing (RTA) at 800-degrees-C/60 s with a post-conventional furnace annealing (CFA) at 600-degrees-C/30 m. RTA not only minimizes the diffusion of knock-on Ti into the junction region, but also facilitates the silicidation and damage annihilation. The low-temperature CFA treatment following the high-temperature RTA process greatly increases the diffusion of dopants into the junction region and thus improves the junction characteristics significantly. The increased diffusion of dopants from the silicide layer into the junction region by the post-CFA process is attributed to the crystallization of the titanium silicide.
SYSTOLIC BLOCK HOUSEHOLDER TRANSFORMATION FOR RLS ALGORITHM WITH 2-LEVEL PIPELINED IMPLEMENTATION
(1992-04-01)
LIU, KR
;
HSIEH, SF
;
YAO, K
;
電信工程研究所
;
Institute of Communications Engineering
The QR decomposition, recursive least squares (QRD RLS) algorithm is one of the most promising RLS algorithms, due to its robust numerical stability and suitability for VLSI implementation based on a systolic array architecture. Up to now, among many techniques to implement the QR decomposition, only the Givens rotation and modified Gram-Schmidt methods have been successfully applied to the development of the QRD RLS systolic array. It is well known that Householder transformation (HT) outperforms the Givens rotation method under finite precision computations. Presently, there is no known technique to implement the HT on a systolic array architecture. In this paper, we propose a systolic block Householder transformation (SBHT) approach, to implement the HT on a systolic array as well as its application to the RLS algorithm. Since the data is fetched in a block manner, vector operations are in general required for the vectorized array. However, a modified HT algorithm permits a two-level pipelined implementation of the SBHT systolic array at both the vector and word levels. The throughput rate can be as fast as that of the Givens rotation method. Our approach makes the HT amenable for VLSI implementation as well as applicable to real-time high throughput applications of modern signal processing. The constrained RLS problem using the SBHT RLS systolic array is also considered in this paper.
INVESTIGATION ON THE STEADY-STATE RESPONSES OF ASYMMETRIC ROTORS
(1992-04-01)
KANG, Y
;
SHIH, YP
;
LEE, AC
;
交大名義發表
;
機械工程學系
This paper is to generalize the previous work by utilizing finite element formulation to accommodate the effects of both deviatoric inertia and stiffness due to asymmetry of flexible shaft and disk. A Timoshenko beam element is employed to simulate rotor-bearing systems by taking the gyroscopic moment, rotary inertia, shear deformation of shaft and, asymmetry of disk and shaft into account. Internal damping is not included but the extension is straightforward. Eulerian angles are used to describe the orientations of shaft element and disk, by which, in opposite to the vectorial approach, the mathematical formulation will be symmetric for angular displacements in two directions. The effects of the angle between the major axes of shaft and disk, deviatoric inertia of the asymmetric shaft, and characteristics of bearing on synchronous critical and subcritical speeds are estimated in conjunction with the harmonic balance method. Numerical examples show that the resonant speeds, at which peak responses occur, change due to various angles between major axes, asymmetry of shaft, stiffness, and damping of bearing.
MANY-SORTED 1ST-ORDER LOGIC DATABASE LANGUAGE
(1992-04-01)
YANG, JSH
;
CHIN, YH
;
CHUNG, CG
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
A database languages based on Many-Sorted First-Order Logic (MSFOL) have many, advantages over one based on One-Sorted First-Order Logic (OSFOL). The advantages includes ease-of-expressiveness, efficiency, and the abstraction mechanism. Many database researchers have used OSFOL to view the Relational Data Model (RDM); however, no RDM has been modelled by MSFOL. This paper first gives a formal definition for MSFOL and then its advantages of expressiveness and of abstraction are illustrated. Two reduction algorithms which can transform an MSFOL-based language into/from an OSFOL-based language are given. The semantic equivalence between languages based on MSFOL and Typed OSFOL is also proved. Recent extensions of RDMs require aggregation, classification, and generalisation/specialisation mechanisms which MSFOL-based languages can provide, but OSFOL-based languages cannot.
FORMATION AND CHARACTERIZATION OF A SUPERCONDUCTING POLYMER COMPOSITE
(1992-04-01)
CHEN, TM
;
HU, YH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
A series of ceramic superconductor/polymer composites showing good magnetic levitation and mechanical flexibility have been prepared by dispersing Bi2-xPbxSr2Ca2Cu3Oy powder in an acrylonitrile-butadiene-styrene (ABS) rubber matrix, followed by hot or cold pressing and curing. Typically, the resistivities of the as-prepared flexible superconducting (in a magnetic sense) tapes or discs of the composite do not reach zero; however, the magnetic flux exclusion is maintained in the temperature range T < T(c) (105 K). The composites showed a large diamagnetic susceptibility that increased with increasing volume fraction of superconductor filler as indicated by magnetization measurements. The electrical and magnetic properties and microstructure of these composites are presented and their implications for future work are discussed.
SUPPRESSION OF ANOMALOUS DIFFUSION OF ION-IMPLANTED BORON IN SILICON BY LASER PROCESSING
(1992-04-01)
JUANG, MH
;
WAN, FS
;
LIU, HW
;
CHENG, KL
;
CHENG, HC
Anomalous diffusion of ion-implanted boron in silicon has been suppressed by using the laser annealing (LA) technique. For the rapid thermal annealing process, the high-dosage boron implant significantly enhanced the anomalous diffusion of boron in Si largely due to increased density of interstitial clusters. The mechanism that electrically active dopants contribute to diffusion is confirmed. The dopant activation is primarily determined from the heating process rather than the holding time interval. Hence, the optimum annealing regime, attaining high-performance shallow p+-n junctions, is to increase the dopant activation efficiency during the temperature-ramping process as well as to shorten the holding interval. Having an ultrahigh heating rate, the LA technique serves as an excellent annealing scheme to significantly suppress the anomalous diffusion and considerably promote the dopant activation.
2-FREQUENCY FIBEROPTIC SENSOR SYSTEM USING HIGH-BIREFRINGENCE OPTICAL FIBER
(1992-04-01)
CHIEN, PY
;
PAN, CL
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A fiber sensor system based on high-birefringence optical fiber and a frequency-stabilized He-Ne Zeeman laser (lambda = 0.6328-mu-m) has been demonstrated. The small path-length changes of interest are extracted from the amplitude or phase of the laser beat frequency by using either the phase-sensitive detection or the phase-demodulation technique. A minimum detectable optical phase delay of 1.5 x 10(-6) rad/Hz1/2 or 17 x 10(-6) rad/Hz1/2 has been achieved.
A NEW TYPE OF POLARIZATION PHASE-SHIFTER FOR PHASE-SHIFTING INTERFEROMETRY
(1992-04-01)
SU, DC
;
SHYU, LH
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A new type of polarization phase shifter for phase shifting interferometry is presented. It is very simple and does not have any nonlinear errors as those in a conventional phase shifter PZT. It is suitable not only for a two-path interferometer, but also for a common-path interferometer. In addition to demonstrating its feasibility, it is introduced into a Twyman-Green interferometer to test a plane mirror and a good result is obtained.
THE GAIN AND OPTIMAL LENGTH IN THE ERBIUM-DOPED FIBER AMPLIFIERS WITH 1480 NM PUMPING
(1992-04-01)
LIN, MC
;
CHI, S
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光電工程學系
;
電信研究中心
;
Department of Photonics
The approximate analytic expressions for the gain and optimal length of the 1480 nm-pumped erbium-doped fiber amplifier with an arbitrary dopant distribution are obtained when the saturation by ASE is neglected. Numerical calculations show that the values predicted from the analytic expressions of the maximal gain and optimal fiber length as functions of input signal and pump powers are very accurate for narrow dopant distributions confined to the center of the fiber core.
RECONSTRUCTION OF THE SUM-RULE-CONSTRAINED CLASSICAL BINARY-COLLISION MODEL FOR INNER-SHELL IONIZATIONS
(1992-04-01)
KWEI, CM
;
CHEN, YF
;
TUNG, CJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Tung has constructed a sum-rule-constrained classical binary-collision model for the estimation of generalized oscillator strengths (GOS's) of the 1s and 2s subshells of atoms. He applied three sum rules to determine the momentum-dependent parameters introduced in the GOS function based on the classical binary-collision model. Several deficiencies have then been found regarding these sum rules that adopted the less accurate hydrogenic model and included the unwanted contribution from discrete excitations. In the present work, we have reconstructed this model by employing improved sum rules obtained from Hartree-Fock-Slater matrix element calculations. The refined model has been successfully applied to estimate ionization generalized oscillator strengths of atomic K and L shells.
AXIALLY PHASE-MATCHED PARAMETRIC 4-WAVE AND 6-WAVE MIXING IN POTASSIUM VAPOR
(1992-04-01)
LU, MH
;
LIU, YM
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
Systematic experimental observations of axially phase-matched parametric four- and six-wave mixing processes have been made in potassium vapor pumped on or near the 4S-6S two-photon resonance. An IR up-conversion with a beta barium borate crystal was used for the detection of IR emissions. All the predicted processes have been observed. It is found that the excitation spectra of the emissions for those processes observed in this work are quite different from the excitation spectra of similar processes in sodium vapor. A dye-dependence of some emissions generated by the axially phase-matched parametric six-wave mixing processes has been found by using different dyes in the dye laser. The reason for the dye-dependence is discussed.
THE REVERSE ANNEAL OF JUNCTION CHARACTERISTICS IN FORMING SHALLOW P+-N JUNCTION BY BF-2(+) IMPLANTATION INTO THIN CO FILMS ON SI SUBSTRATE
(1992-04-01)
JUANG, MH
;
CHENG, HC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Silicided shallow p+-n junctions, formed by BF2+ implantation into thin Co films on Si substrates and subsequently annealed, show a reverse anneal of junction characteristics in the temperature range between 550 and 600-degrees-C. The reverse anneal means a behavior showing the degradation of considered parameters with increasing anneal temperature. A higher implant dosage causes a more distinct reverse anneal. The reverse anneal of electrical characteristics was associated with the reverse anneal of substitutional boron. A shallow p+-n junction with a leakage current density lower than 3 nA/cm2, a forward ideality factor better than 1.01, and a junction depth of about 0.1-mu-m was therefore achieved by just a 550-degrees-C anneal.
SCANNING REGULAR LANGUAGES BY DUAL FINITE AUTOMATA
(1992-04-01)
WU, PC
;
WANG, FJ
;
YOUNG, KR
;
資訊科學與工程研究所
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Institute of Computer Science and Engineering
A regular language is generally accepted by a single finite automaton. An approach of dual finite automata is presented here. An input string is scanned by two deterministic finite automata (DFA's): reading from the string's head and tail respectively. One of them accepts the regular language itself; the other accepts the language's reversal. Whether a string is accepted depends on the states of both automata, when their reading heads meet. Dual finite automata can be applied in compiler generation and parallel computing.
SCALE-INVARIANT EFFECTIVE ACTION WITH TORSION
(1992-04-01)
KAO, WF
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交大名義發表
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電子物理學系
;
National Chiao Tung University
;
Department of Electrophysics
We considered a four-dimensional scale-invariant effective theory with a torsion field conformally coupled to a metric field. We find that the contribution from the torsion field is negligible in the evolution of the early universe. An exact solution is also obtained for k = 0 Friedmann-Robertson-Walker space in the vanishing cosmological constant limit. This solution is also a good approximation to k not-equal 0 spaces. Possible implications to the inflationary universe are also discussed.
A STUDY OF HARMONIC DISTORTIONS AND PERIOD DOUBLING IN DFB RIDGE WAVE-GUIDE LASER WITH STRONG CURRENT MODULATION
(1992-04-01)
KAO, YH
;
LIN, HT
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傳播研究所
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電信研究中心
;
Institute of Communication Studies
We report measurements of the harmonic distortions and period doubling (PD) in a 1.55-mu-m InGaAsP DFB laser under sinusoidal current modulation. It is found that most degradation of the modulated signal occurring with frequency near the submultiples of relaxation frequency is only for small-signal operation and is violated under large-signal operation. The dynamics can be satisfactorily predicted by employing the Tucker's large-signal model [Tucker and Kaminow, J. Lightwave Technol. LT-2 (1984) 385.].
IMAGE ESTIMATION USING FAST MODIFIED REDUCED UPDATE KALMAN FILTER
(1992-04-01)
WU, WR
;
KUNDU, A
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電信工程研究所
;
Institute of Communications Engineering
In this paper, we have proposed some modifications of the reduced update Kalman filter (RUKF) as applied to filtering of images corrupted by additive noise. First, we have reduced the computational complexity by reducing the state dimensionality. By doing so, it is shown in the paper that the computational requirement is reduced by an order of magnitude while the loss of performance is only marginal. Next, the RUKF is modified using the score function based approach to accommodate the non-Gaussian noise. The image is modeled as a nonstationary mean and stationary variance autoregressive Gaussian process. It is shown in the paper that the stationary variance assumption is reasonable if the nonstationary mean is computed by an edge and detail preserving efficient estimator of local nonstationary mean. Such an estimator called HMSMD filter is also described in the paper. Finally, detailed experimental results are provided which indicate the success of the new filtering scheme.
FORMATION OF BILAYER SHALLOW MOSI2/COSI2 SALICIDE CONTACT USING W/CO-MO ALLOY METALLIZATION
(1992-04-01)
YANG, FM
;
CHEN, MC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A very simple process to form a bilayer shallow MoSi2/CoSi2/Si silicided contact using W/Co54Mo46/Si bilayer alloy metallization has been developed. Two-step annealing in a conventional flowing-nitrogen furnace is employed. The first annealing is performed at a temperature of 500-600-degrees-C, with the W film passivating the underlying Co-Mo alloy layer from being oxidized and consuming some Co. A shallow contact is feasible by selectively etching away the remaining outer layer of the Mo-dominant Mo-Co alloy (or W-Co alloy) phase to deduct the metal source which would finally be transformed into silicides. Silicide lateral growth which is observed during the silicidation of Co on Si does not occur in the present system. This is presumably because the formation of CoSi2 is not preceded by Co2Si or CoSi due to the nonrich Co source in the Co-Mo alloy system. The second annealing performed at a higher temperature of 700-950-degrees-C is to further transform the CoSi2 and mixed-silicide layers obtained after the first annealing into separate layers of MoSi2 and CoSi2.
INCREMENTAL MANEUVER ESTIMATION MODEL FOR TARGET TRACKING
(1992-04-01)
CHANG, WT
;
LIN, SA
;
電信工程研究所
;
電信研究中心
;
Institute of Communications Engineering
Target maneuver has long been a problem of tracking small targets with the Kalman filter. We describe an incremental model for maneuver detection and estimation for use in target tracking with the Kalman filter. The approach is similar to the multiple Kalman filter bank, but with a memory for the maneuver status for the track under consideration. The advantage of this approach is that the target acceleration can be more accurately estimated.