Browsing by Issue Date, starting with "1992-03-10"

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GRAVITATIONAL STRESSES IN ANISOTROPIC RIDGES AND VALLEYS WITH SMALL SLOPES
(1992-03-10)
LIAO, JJ
;
SAVAGE, WZ
;
AMADEI, B
;
土木工程學系
;
Department of Civil Engineering
We present an approximate analytical solution for the effects of topography on near-surface gravity-induced stresses in symmetric anisotropic ridges and valleys. The solution can be used for laterally constrained ridges and valleys consisting of isotropic, transversely isotropic. or orthotropic rock with horizontal or vertical layers. A parametric study on the effect of anisotropy type and degree of rock anisotropy on gravity-induced stresses is presented. The magnitude of the predicted stresses is of the order of the characteristic stress rho-gH, where H is the height of the ridge or depth of the valley. The approximate solution is limited to ridges and valleys with small slopes not exceeding 10%.
SCALE-FACTOR-STABILIZED FIBEROPTIC GYROSCOPE BY DEEP PHASE MODULATION
(1992-03-15)
CHIEN, PY
;
PAN, CL
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A scale-factor-stabilized fiber-optic gyroscope by deep phase modulation is demonstrated. There are two servo loops included in this system. The first servo loop is used for stabilization of the light intensity output of the fiber-optic gyroscope. The second loop is used to stabilize the phase-modulation index. The third-harmonic frequency of the phase-modulation signal is used for detection of the Sagnac phase, shift by the lock-in technique.
OBSERVATION OF THE TRANSVERSE OPTICAL PHONON MODE IN CDS FILM AT 4880-A EXCITATION
(1992-03-15)
DAI, CM
;
CHUU, DS
;
電子物理學系
;
Department of Electrophysics
The transverse-optical (TO) phonon mode in a CdS film with a thickness less than 410 angstrom is observed at 4880 angstrom excitation wavelength which is above the band gap of CdS bulk (2.42 eV) at room temperature. This phenomenon is ascribed to the size quantization of the free carrier in the low-dimensional thin-film structure. The quantum size effect causes a blue shift of the band gap in the as-deposited CdS thin film. The Raman shift of the TO mode of CdS film is around 220 cm-1. The softening energy of the TO phonon mode is about 8 cm-1. It was found that this softening energy is independent of the film thickness.
EFFECT OF MELT TEMPERATURE ON THE FORMATION OF AIR POCKETS DURING SPLAT QUENCHING
(1992-03-15)
WANG, WK
;
KUO, CT
;
CHIN, TS
;
機械工程學系
;
Department of Mechanical Engineering
The effect of melt temperature on the formation of air pockets at the contact surface of the ribbons was studied. An alloy with a melting point slightly higher than room temperature (320 K) was used and was heated to 353, 573 and 773 K, respectively, to investigate the thermal effect of the melt temperature on the gas. Under high casting velocity (20 m s-1) and extremely low melting temperature (353 K), the air pockets were slender and parallel to the casting direction. The liquid melts with a higher casting temperature (773 K) induced coarse air pockets at various casting velocities, and the air pockets were coarser than those induced by the pressure of the gas boundary layer only. The heat flow analysis showed that the local pressure of the entrapped gas, built up by the thermal effect and assuming constant volume, is far greater than the pressure by the gas-boundary layer effect. Thus the thermal effect of the liquid melt should be taken into account in the formation of air pockets during splat quenching.
POTENTIAL DEPENDENCE OF THE BIFURCATION STRUCTURE IN GENERALIZED DUFFING OSCILLATORS
(1992-03-15)
WANG, CS
;
KAO, YH
;
HUANG, JC
;
GOU, YS
;
電子物理學系
The features of various bifurcations in forced Duffing oscillators are extensively investigated by means of numerical simulation. Some common features in four types of potential well are found. With reference to the transition boundaries in parameter space, the influences of local symmetry properties of the potential well on the bifurcation routes are indicated and definite functional forms of the border line in omega-k space separating the region with simple stable period-1 solutions from the region with complicated solutions are determined. A method combining Floquet theory with harmonic balance is presented to describe the mechanism of the transitions.
EFFECTS OF SB4/GA RATIOS ON THE ELECTRICAL-PROPERTIES OF GASB SCHOTTKY DIODES
(1992-03-15)
WANG, YH
;
HOUNG, MP
;
SZE, PW
;
CHEN, JF
;
CHO, AY
Au, Cu, Ag, and Al are deposited on Te-doped n-GaSb layers directly grown on lattice mismatched GaAs semi-insulating substrates. Sb4/Ga beam equivalent pressure ratios are found to profoundly influence the electrical properties of the Schottky diodes investigated here. The fact that both breakdown voltage and barrier height decrease with increasing Sb4/Ga ratios is attributed to the increase in surface state densities for samples grown at higher Sb4/Ga ratios. This suggestion is further confirmed by the model of surface state densities employing the relationship of barrier height to metal work function. The surface state densities are in the range of 2.3 x 10(14) to 1.2 x 10(15) states/cm2/eV corresponding to Sb4/Ga ratios of 2 to 9, respectively. X-ray rocking peaks of samples grown at various Sb4/Ga ratios, and subsequently subjected to annealing, indicate different interactions at the interfaces which might support the observations.
INFLUENCE OF IMPLANT CONDITION ON THE TRANSIENT-ENHANCED DIFFUSION OF ION-IMPLANTED BORON IN SILICON
(1992-03-15)
JUANG, MH
;
WAN, FS
;
LIU, HW
;
CHENG, KL
;
CHENG, HC
Under high-dosage boron implant, the implant condition was found to be important for reducing the transient-enhanced diffusion of boron in Si and forming shallow p + n junction with good rectifying characteristics as well as high dopant concentration in the diffused region. The BF2+-implantation resulted in not only an excellent dopant activation but also a reduced anomalous diffusion due to the formation of amorphous layer and the scarce defects underneath the amorphous/crystalline (a/c) interface. The B+-implanted crystalline samples manifested a poor activation efficiency, and a largely anomalous diffusion at the high temperature with prolonged-time annealing ascribed to much damage induced by the high-dose implant. The B+-implanted pre-Si+-amorphized samples also displayed severely transient-enhanced diffusion in spite of the good dopant activation.
SPATIAL DEPENDENCE OF INFLATON IN THE PRESENCE OF THE TORSION FIELD
(1992-03-16)
KAO, WF
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
;
Department of Electrophysics
We show that, in a class of induced gravity models with (or without) torsion, the associated scalar field (the inflaton) has to be spatial independent in order to admit a Robertson-Walker type solution. Details of the proof are presented. The proof requires a great deal of mathematics which also serves as a pedagogical exercise by itself.
BUCKLING ANALYSIS OF IMPERFECT FRAMES USING A STOCHASTIC FINITE-ELEMENT METHOD
(1992-03-17)
LIN, SC
;
KAM, TY
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A stochastic finite element method is developed for the buckling analysis of frames with random initial imperfections, uncertain sectional and material properties. The random geometrical imperfections of the frames are described by member initial crookednesses which are modeled as given initial displacement functions with amplitudes treated as random variables. The effects of the random initial geometric imperfections are formulated as a set of equivalent random nodal coordinates in the finite element discretization of the members. The mean-centered second-order perturbation technique is used to formulate the stochastic finite element method for the buckling analysis of the imperfect frames. Use of the present method is illustrated by several examples of buckling analysis of random frames. Results derived from the Monte Carlo method are also obtained for comparison.
一路梨花到承德
(1992-03-21)
管管
萬歲萬歲萬萬歲
(1992-03-24)
管管
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
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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.