Browsing by Issue Date, starting with "1991-12-01"

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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
;
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
;
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
;
SHI, JB
;
電控工程研究所
;
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
;
電信工程研究所
;
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
;
TSAY, SF
;
WANG, SY
;
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
;
SIEGEL, PH
;
THAPAR, HK
;
KARABED, R
;
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
;
GUO, SH
;
應用數學系
;
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
;
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.
SINGLE-FAULT FAULT-COLLAPSING ANALYSIS IN SEQUENTIAL LOGIC-CIRCUITS
(1991-12-01)
CHEN, JE
;
LEE, CL
;
SHEN, WZ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This paper studies single-fault fault collapsing in sequential logic circuits. Two major phenomena, self-hiding (SH) and delayed reconvergence (DR), which arise from the existence of feedback paths and storage elements in sequential circuits, are analyzed and found to cause the dominance relationship which is valid in combinational circuits but no longer valid in sequential circuits. A fault-collapsing procedure is proposed to collapse faults in sequential circuits. It first collapses faults in the non-SAD (self-hiding and delayed-reconvergence) gates of the combinational part of the sequential circuit and then further collapses faults by identifying the prime fan-out branches. Finally, it collapses faults in feedback lines. The collapsed faults constitute a sufficient representative set of prime faults. This procedure has been applied to collapse faults for 31 benchmark sequential circuits [1] and the number of faults has collapsed to 43% of the original number.
ANISOTROPIC AC-SUSCEPTIBILITY RESPONSE OF A MELT-TEXTURED YBCO SUPERCONDUCTOR
(1991-12-01)
CHEN, YC
;
CHEN, K
;
HSU, SW
;
TSENG, TY
;
LU, SW
We report on low field measurements of the out-of-plane (c-axis parallel-to H) and in-plane (c-axis perpendicular-to H) ac susceptibilities of a melt-textured YBa2Cu3Ox superconductor with high transport J(c). With the field parallel to the ab-plane of the sample, an obvious second peak appears in the imaginary part of chi(ac) at T almost-equal-to 81 K with a width of 2-4 K depending on the ac field amplitude, which may be due to the interlayer weak-links in the melt-textured samples.
VIBRATION OF SURFACE FOUNDATIONS OF ARBITRARY SHAPES
(1991-12-01)
LIOU, GS
;
交大名義發表
;
土木工程學系
;
National Chiao Tung University
;
Department of Civil Engineering
Presented is a systematic procedure for generating impedance (or compliance) matrices for foundations with arbitrary shapes, resting on an elastic half-space medium. A technique to decompose prescribed harmonic tractions on the half-space medium is employed to solve analytically the differential wave equations in cylindrical coordinates. However, the interaction stresses due to the vibration of a foundation with arbitrary shape are described in rectangular coordinates, and assumed to be piecewise constant in the region of the arbitrary shape. A coordinate transformation matrix is introduced for the piecewise constant tractions in order to use the solution of the differential wave equations in cylindrical coordinates. Finite element modelling is assumed in rectangular coordinates for the foundation itself. The impedance matrix is then obtained for the finite element model, using a variational principle and the reciprocal theorem. A simple example of a rigid square plate resting on a half-space medium and subjected to vertical excitation is used to demonstrate the efficiency and effectiveness of the procedure. Some numerical aspects are investigated and some possible extensions of the procedure are also discussed.
RADIATIVE RECOMBINATION MECHANISMS OF GAAS1-XPX
(1991-12-01)
FENG, MS
;
HSIAO, HL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Dependence of excitation density and temperature of photoluminescence have been used to identify the radiative transitions of GaAs1-xPx in the indirect band-gap region (x = 0.85). At 16 K the spectra consisting of five recombination bands are observed from nitrogen-doped GaAsP. The transitions associated with nitrogen are found to dominate the recombination spectra. One of them is attributed to the recombination of excitons bound to isolated nitrogen atoms (Nx), another one is due to LO-phonon assisted transitions of Nx, and the other three are owing to donor-acceptor (D-A) and nitrogen pair transitions (NN). By combining the results of the excitation density and temperature dependence of the photoluminescence properties, the transition mechanisms for the luminescence are presented and discussed.
OPTIMAL-DESIGN OF A PILOT OTEC POWER-PLANT IN TAIWAN
(1991-12-01)
TSENG, CH
;
KAO, KY
;
YANG, JC
;
交大名義發表
;
機械工程學系
In this paper, an optimal design concept has been utilized to find the best designs for a complex and large-scale ocean thermal energy conversion (OTEC) plant. The OTEC power plant under this study is divided into three major subsystems consisting of power subsystem, seawater pipe subsystem, and containment subsystem. The design optimization model for the entire OTEC plant is integrated from these subsystems under the considerations of their own various design criteria and constraints. The mathematical formulations of this optimization model for the entire OTEC plant are described. The design variables, objective function, and constraints for a pilot plant under the constraints of the feasible technologies at this stage in Taiwan have been carefully examined and selected. The numerical optimization method called Sequential Quadratic Programming SQP) is selected to obtain the optimum results. The main purpose of this paper is to demonstrate the design procedure with the optimization techniques for engineering and economics in the OTEC plant so that anyone else can build upon their models according to their needs.
HIERARCHICAL SPANNING-TREES AND DISTRIBUTING ON INCOMPLETE HYPERCUBES
(1991-12-01)
TIEN, JY
;
YANG, WP
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
Incomplete hypercubes are gaining increasing attention as one of the possible solutions for the limitation on the number of nodes in the hypercubes. Distributing, in which one node sends distinct messages to distinct nodes, and its reverse operation are frequently used operations on data parallel computation. In this paper, we propose two types of spanning trees in incomplete hypercubes (composed of an n-cube and a k-cube): the binomial hierarchical spanning tree-binomial HST, and the balanced hierarchical spanning tree-balanced HST, for distributing (and its reverse operation). Distributing algorithms based on a balanced HST take better advantage of overlap between communication ports, or have speedup up to k/2 or n/2 over that based on the binomial HST when concurrently communication on all ports are possible, from the view point of communication complexity. An algorithm to construct hierarchical spanning trees in general incomplete hypercubes, which consist of an arbitrary number of nodes, is also devised.