Browsing by Issue Date, starting with "1991-11-15"

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COLLIMATION METHOD THAT USES SPIRAL GRATINGS AND TALBOT INTERFEROMETRY
(1991-11-15)
CHANG, CW
;
SU, DC
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
The tested light is projected onto an arrangement composed of two special spiral gratings, in which the second spiral grating is positioned at the Talbot image of the first one. From the shapes of the resultant moire fringes, the quality of collimation of the tested light can be easily checked.
AN ALL-FIBER FREQUENCY STABILIZER TO A SET OF LASER-DIODES BASED ON DOUBLE FIBER RESONATORS
(1991-11-15)
CHIEN, PY
;
PAN, CL
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A relative frequency statilization technique, using double fiber resonators as the frequency discriminator, has been demonstrated. By employing the frequency-division-multiplexing technique (FDM) to the laser diodes, the frequency offset between the tested laser diodes has been stabilized to DELTA-nu/nu less-than-or-equal-to 3.0 x 10(-9).
DISCONTINUOUS RADIAL TO AXIAL TRANSFORMATION OF DIRECTOR CONFIGURATION IN A CYLINDRICAL NEMATIC CAVITY
(1991-11-15)
LIANG, BJ
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CHEN, SH
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
The optical patterns of a nematic liquid crystal confined to a closed cylindrical cavity are observed through crossed polarizers. This optical pattern exhibits an annular phenomenon when the radius of the cylinder is varied. The minor dependence of the width of the bright annulus on the radius of the cavity is presented. The formation of the disclination ring is numerically studied and found to be the physical mechanism of the annular phenomenon. The characteristic length defined as the distance from the ring defect to the laterally cylindrical boundary is nearly invariant and is characterized to be the width of the bright annulus.
暮年初見中山陵有感
(1991-11-15)
管管
DEPOSITION OF SILICON-CARBIDE THIN-FILMS FROM DODECAMETHYLCYCLOHEXASILANE
(1991-11-15)
CHIU, HT
;
LEE, SF
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
CALCULATION OF LAG TIME FOR CONVECTIVE-REACTIVE DIFFUSION
(1991-11-28)
CHEN, JS
;
ROSENBERGER, F
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應用化學系
;
Department of Applied Chemistry
Closed form solutions for the steady-state permeability P and the lag time L of a linear diffusion system with concurrent convection and reaction were obtained by two methods. In the first method, we identify the singularity at s = 0 of the Laplace transform of the total amount of diffusant, Q(s), released into the receiver as representation of the asymptotic diffusion behavior. P and L are then obtained from the time-independent coefficients of an expansion of Q(s) about s = 0. In the second method, we transform the convective-reactive diffusion equation into a form that contains only first and second derivatives of the concentration distribution function. By comparison of the resulting equation with that for a heterogeneous diffusion system, relationships of the convection velocity and rate constant with the position-dependent partition coefficient in heterogeneous diffusion is found. Taking advantage of the known solutions for permeabiliy and lag time in heterogeneous diffusion, the corresponding expressions for P and L in convective-reactive diffusion are then obtained by transcription. These methods have the advantage over earlier approaches in that solutions in an infinite form are avoided.
MAGNETIC-RELAXATION IN A AG-SHEATHED HIGH-JC BI-PB-SR-CA-CU-O SUPERCONDUCTING TAPE
(1991-12-01)
CHEN, K
;
LEE, WH
;
HORNG, L
;
YANG, TJ
;
電子物理學系
The magnetic relaxation and magnetization curves were studied on the Ag-sheathed and highly c-axis oriented Bi-Pb-Sr-Ca-Cu-O tape with transport J(c) > 10(4) A/cm2 at 77 K. Zero-field-cooled (ZFC) in-field relaxation for applied field perpendicular to the sample a-b plane was investigated. It was found that the field-dependent relaxation rate had a maximum in the certain applied field at various temperatures. The applied field at this maximum was greater than H*, the first field for which currents flow through the entire volume of the sample in the Bean's critical state model. Pinning energies were estimated at the maximal relaxation rate in a series of temperatures.
GROWTH OF SINGLE-CRYSTALLINE COSI2 ON (111)SI AT LOW ANNEALING TEMPERATURES BY A NONULTRAHIGH VACUUM METHOD
(1991-12-01)
CHENG, HC
;
JUANG, MH
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
By reducing the thickness of the deposited cobalt film, high-quality single-crystalline CoSi2 phase with a sheet resistivity as low as 15-mu-OMEGA cm has been achieved. A deposition of 3 nm thick cobalt film on (111)Si substrate and a subsequent rapid thermal annealing (RTA) at 500-degrees-C were used. From the examinations of transmission electron microscopy (TEM), the single-crystalline CoSi2 structure was identified as type B orientation. As far as the authors are aware of, such an annealing temperature is the lowest for the solid phase growth of single-crystalline CoSi2 on the silicon substrate in the nonultrahigh vacuum (non-UHV) deposition and annealing systems. Hence, the deposition of thinner cobalt film on the silicon substrate would be favorable to the formation of polycrystalline CoSi2 grains and the growth of single-crystalline CoSi2 structure. It is attributed to the promoting ratio of interface energy and the smaller preliminarily-formed CoSi2 grains. No facet was observed for all samples annealed at 500-degrees-C. It indicates that a smooth single-crystalline CoSi2/Si interface is formed. Annealing at 450-degrees-C yielded coexisting polycrystalline and epitaxial CoSi2 phases. The samples annealed at 700-degrees-C would exhibit a highly strained single-ctystalline CoSi2/Si interface. Furthermore, annealing at 900-degrees-C would generate large pinholes in the CoSi2 crystal to relieve the interface free energy. Sheet resistance results and current-voltage characteristics of these specimens were measured and well correlated with the TEM observations.
COMPUTING LOCATION AND ORIENTATION OF POLYHEDRAL SURFACES USING A LASER-BASED VISION SYSTEM
(1991-12-01)
TSENG, DC
;
CHEN, Z
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資訊工程學系
;
Department of Computer Science
A laser-based vision system for computing the location and orientation of 3-D polyhedral surfaces is proposed. In this system, an expanded laser beam Passes through a code plate marked with equally spaced vertical and horizontal lines and impinges on a polyhedral object to create a spatial-encoded image for analysis. Then, based on the vanishing points or the directly available line directions of the perceived grid lines on the polyhedral surface, the polyhedral surface orientation can be inferred. In the meantime, the given dimensions of the grid pattern on the Plate are used to estimate the depth information of the polyhedral surfaces. More importantly, we shall solve the noise problem that occurs in the real image by a least squares estimation method and an iterative refinement method based on a geometric constraint criterion. Experiments are conducted to provide practical insight into the method. The experimental results indicate that the method is remarkably accurate and stable.
TRANSITION PHENOMENA OF YBA2CU3O7-X THIN-FILMS ON MGO AND SRTIO3 SUBSTRATES
(1991-12-01)
HAUNG, CJ
;
CHEN, YC
;
TSENG, TY
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The superconducting YBa2Cu3O7-x thin films were prepared by an in-situ DC sputtering system. The superconducting transition of the films in magnetic fields, applied parallel to the c-axis, was studied experimentally. Arrhenius plots of the resistivity data have shown that the dissipative flux motion of these samples could be explained by the thermally activated mechanism. In addition, we also found that the film on MgO substrate reveals a linear I-V curve, while the film on SrTiO3 substrate shows a nonlinear behavior. The relation between the activation energy and I-V behavior of the films on different substrates is also discussed.
THE CORRELATION BETWEEN SUPERCONDUCTIVITY AND CU-O BOND LENGTH FOR THE SINGLE CU-O LAYER COMPOUNDS WITH THE BI2SR2CUO6+DELTA-TYPE (2021) STRUCTURE
(1991-12-01)
KU, HC
;
SUN, SJ
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SHI, JB
;
電控工程研究所
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Institute of Electrical and Control Engineering
The structure and superconductivity in the single Cu-O layer bismuth (2021) system can be stabilized also by the doping of Na1+ ions. Contrary to the La-doped Bi2(Sr,La)2CuO6+delta system with T(c) enhancement up to 35 K. T(c) remains around 10 K for the Na-doped Bi2(Sr2-xNax)CuO6+delta system (0.0 less-than-or-equal-to x less-than-or-equal-to 0.4). The variation of T(c) with the Cu-O bond length r(Cu-0) in the Cu-O layer for the Bi family which consists of the systems (Bi,Pb)2Sr2CuO6+delta, Bi2(Sr,Na)2CuO6+delta, Bi2(Sr,La)2CuO6+delta and (Bi,Pb)2(Sr,La)2CuO6+delta indicates an optimum r(Cu-0) value of 1.906-1.913 angstrom with maximum T(c) of 35 K for these Bi(2021) compounds.
BISECTOR ANGLE ESTIMATION IN A NONSYMMETRIC MULTIPATH RADAR SCENARIO
(1991-12-01)
ZOLTOWSKI, MD
;
LEE, TS
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電信工程研究所
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Institute of Communications Engineering
In the classical problem of low-angle radar tracking, echoes return to the array via a specular path as well as by a direct path, with the angular separation between the two ray paths a fraction of a beamwidth. The performance of any bearing estimation scheme in this scenario is dependent on the phase difference between the direct and specular path signals at the centre of the array. The beamspace domain maximum likelihood (BDML) bearing estimator is a recently developed three-beam extension of the sum and difference beam technique employed in conventional radar. Nonsymmetric BDML breaks down when the phase difference is either 0-degrees or 180-degrees. In contrast, symmetric BDML, in which the point angle of the centre beam is the bisector angle between the two ray paths, can theoretically handle any phase difference, with the 0-degrees case giving rise to the best performance. A simple, closed-form bisector angle estimator is developed based on characteristic features of the 3 x 3 forward-backward averaged beamspace correlation matrix when the centre pointing angle is the true bisector angle. In this way, a 2-D parameter estimation problem is decomposed into two successive 1-D parameter estimation problems: estimation of the bisector angle, followed by estimation of the target bearing. Simulations are presented assessing the performance of the new bisector angle estimator and comparing the performance of symmetric BDML employing the new estimator with other ML based bearing estimation schemes in a simulated low-angle radar tracking environment.
A GLOBAL PINCHING THEOREM FOR COMPACT MINIMAL-SURFACES IN-S3
(1991-12-01)
HSU, YJ
;
交大名義發表
;
應用數學系
;
National Chiao Tung University
;
Department of Applied Mathematics
Let M be a compact minimally immersed surface in the unit sphere S3, and let S denote the square of the length of the second fundamental form of M. We prove that if parallel-to S parallel-to 2 less-than-or-equal-to 2 square-root 2-pi, then M is either the equatorial sphere or the Clifford torus.
A NUMERICAL STUDY OF TRANSIENT NATURAL-CONVECTION UNDER TIME-DEPENDENT GRAVITATIONAL ACCELERATION FIELD
(1991-12-01)
FU, WS
;
SHIEH, WJ
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A transient natural convection caused by abruptly heating of a vertical wall in a square enclosure which is under time-dependent gravitational acceleration field is studied numerically. During the computing process, a penalty finite element method is adopted to solve the governing equations. The factor of the time-dependent gravitational acceleration is included in Rayleigh number, therefore two variation of Rayleigh number are considered, one is from 10(5) via 10(6) to -10(5) and the other is from 10(4) via 10(5) to -10(4). Since the variations of flow field and temperature distribution of the fluid in the square enclosure are complicated and unpredictable, the isotherms, streamlines and time dependent heat transfer rate are examined for investigating the heat transfer mechanism during the transient process. The results show that the agreement of the heat transfer rate of this study with that of quasi-steady state is mainly dependent on the response of the variation rate of boundary layer along the vertical walls to that of time-dependent gravitational acceleration.
THE COUPLING NATURE OF PLASMON MODES AMONG DIFFERENT LAYERS IN A-SYSTEM COMPOSED OF CUO2 LAYERS AND CUO CHAINS
(1991-12-01)
YANG, TJW
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TSAY, SF
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WANG, SY
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電子物理學系
;
Department of Electrophysics
Using free electron gas model for sheets and chains, we obtain the dielectric function epsilon(q, omega) of a finite multilayer system composed of CuO2 sheets and CuO chains including the Coulomb interactions among layer-layer, chain-chain and chain-layer within the random-phase approximation (RPA). And then the dielectric function epsilon(q. omega) is diagonalized to find eigenvectors for different plasmon modes. Eigenvectors of the lowest (highest) frequency plasmon model for n = 4 and 5 systems are illustrated. We find that the range of Coulomb interactions strongly affects eigenvectors and plasmon dispersion.
A 30-MHZ TRELLIS CODEC CHIP FOR PARTIAL-RESPONSE CHANNELS
(1991-12-01)
SHUNG, CB
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SIEGEL, PH
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THAPAR, HK
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KARABED, R
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電子工程學系及電子研究所
We present a rate 8/10 matched-spectral-null (MSN) trellis codec chip which can increase noise tolerance in partial-response channels applicable to digital magnetic recording. The Viterbi detector in this codec features an area-efficient pipelined architecture and a modulo metric normalization technique. The chip was implemented in a 1.2-mu-m CMOS process with a die size of 22 mm2. It offers a 12-Mb/s data rate when operating at 30 MHz. Experimental results verified the predicted coding gain of 2.8 dB relative to the uncoded system at a bit-error rate of 10(-7).
THE INTERSECTIONS OF COMMUTATIVE LATIN SQUARES
(1991-12-01)
FU, CM
;
FU, HL
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GUO, SH
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應用數學系
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Department of Applied Mathematics
A latin square of order n is an nxn array such that each of the integers 1,2,...,n (or any set of n distinct symbols) occurs exactly once in each row and each column. A latin square L = [l(i),j] is said to be commutative provided that l(i),j = l(j),i for all i and j. Two latin squares, L = [l(i),j] and M = [m(i),j], are said to have intersection k if there are exactly k cells (i,j) such that l(i),j = m(i),j. Let I[n] = {0,1,2,...,n2-9,n2-8,n2-6,n2}, H[n] = I[n] union {n2-7,n2-4}, and J[n] be the set of all integers k such that there exists a pair of commutative latin squares of order n which have intersection k. In this paper, we prove that J[n] = I[n] for each odd n greater-than-or-equal-to 7, J[n] = H[n] for each even n greater-than-or-equal-to 6, and give a list of J[n] for n less-than-or-equal-to 5. This totally solves the intersection problem of two commutative latin squares.
ANISOTROPIC IRREVERSIBILITY LINES FOR C-AXIS ALIGNED POWDERS OF THE BI(2223) COMPOUND (BI,PB)2CA2SR2CU3O10+DELTA
(1991-12-01)
SHI, JB
;
KUO, PL
;
CHIOU, BS
;
KU, HC
;
電控工程研究所
Anisotropic irreversibility lines were observed for c-axis aligned powders of the Bi(2223) compound (Bi,Pb)2Ca2Sr2Cu3O10+delta (T(c) = 108 K). The aligned sample was prepared using powders embedded in epoxy and aligned in a 9.4 T applied magnetic field at room temperature. The anisotropic irreversibility lines H(r)(T) were measured with applied field H parallel and perpendicular to the c-axis. The simple power law H(r) = a.(1 - T/T(c))n with n = 2.19 (H perpendicular-to c) and n = 2.99 (H parallel-to c) were observed only in low applied field H less-than-or-equal-to 250 G. For applied field up to 4 kG, H(r)(T) lines were better fitted with the exponential law H(r) = b.exp(-T/t).
INTRAMOLECULAR DIELS-ALDER REACTIONS OF FURANS WITH ALLENYL ETHERS - FORMATION OF INDANONE AND TETRALONE
(1991-12-01)
LIN, CC
;
CHEN, LH
;
WU, HJ
;
交大名義發表
;
應用化學系
The intramolecular Diels-Alder reactions of the furans 3, 11a and 11b produced indanone 6 and tetralones 14a and 14b respectively, presumably via the corresponding allenyl ethers 4, 12a and 12b and the intramolecular cycloadducts 5, 13a and 13b.
PREPARATION AND CHARACTERIZATION OF SOME SUPERCONDUCTOR POLYMER COMPOSITES
(1991-12-01)
CHEN, TM
;
HU, YH
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交大名義發表
;
應用化學系
;
National Chiao Tung University
A technique for preparing flexible composites by dispersing high-T(c) bismuth-based superconductor filler in an ABS rubber matrix with transition temperature above 100K (based on magnetization measurements) has been developed. Superconducting tapes or discs of the Bi1.5Pb0.5Sr2Ca2Cu3Ox/ABS composites with flexibility was formed by wet or dry blending. Data obtained from dc resistivity and magnetization measurements on the composites and the features of microstructure are presented.