Browsing by Issue Date, starting with "1993-04-14"

Now showing 1 - 20 of 89671

現代俳句
(1993-04-14)
管管
CONTRAST-REVERSIBLE PHOTOREFRACTIVE INCOHERENT-TO-COHERENT OPTICAL CONVERTER BY USING AN ANISOTROPIC STRONG VOLUME HOLOGRAM
(1993-04-15)
SUN, CC
;
CHANG, MW
;
HSU, KY
;
光電工程學系
;
Department of Photonics
An anisotropic strong volume hologram with a large coupling parameter is demonstrated in a normal-cut BaTiO3 crystal. We use this hologram to fabricate an incoherent-to-coherent optical converter that has a contrast-reversible output.
UNIQUE BEHAVIOR OF THICKNESS DEPENDENCE IN THE NONLINEAR WAVE-MIXING PROCESS WITH A NEMATIC THIN-FILM
(1993-04-15)
KUO, CL
;
WEI, JG
;
CHEN, SH
;
交大名義發表
;
光電工程學系
The dependence of the optimal electric biasing field and the diffraction efficiency on the thickness of the nematic thin film through the degenerate four-wave-mixing process is investigated. For relatively low optical pumps, the optimal bias monotonically increases with thickness, while the corresponding diffraction efficiency increases at first and then decays for a thickness even less than 150 mum, which is well within the phase-matching regime. For stronger pumps, the optimal bias can be doubly valued, and the curve of optimal bias versus thickness shows a closed loop. This behavior is unique to liquid crystals. The main mechanism is due to the twist effect of molecular orientation in addition to the scattering loss. Both the numerical and experimental results show these peculiar phenomena.
TORSION, COMPACTIFICATION, AND INFLATION
(1993-04-15)
KAO, WF
;
電子物理學系
;
Department of Electrophysics
We study possible implications of a ten-dimensional Einstein-Kalb-Ramond theory. It is speculated that the compactification process and inflationary process axe closely related. It is also found that the torsion field tends to vanish after the inflation era is completed. This is in fact a general feature for the torsion Lagrangian. Hence the contribution from the Kalb-Ramond action is negligible effectively after the inflationary era. Some solutions to the field equations are also presented.
HYDROGEN PLASMA-ENHANCED CHEMICAL VAPOR-DEPOSITION OF SILICON-CARBIDE THIN-FILMS FROM DODECAMETHYLCYCLOHEXASILANE
(1993-04-15)
CHIU, HT
;
HUANG, SC
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
HYDROGENATED AMORPHOUS SILICON-CARBIDE THIN-FILM LIGHT-EMITTING DIODE WITH QUANTUM-WELL-INJECTION STRUCTURE
(1993-04-15)
JEN, TS
;
CHEN, JY
;
SHIN, NF
;
HONG, JW
;
CHANG, CY
To improve the electroluminescence (EL) intensity of the hydrogenated amorphous silicon carbide (a-SiC:H) pin thin-film light-emitting diode (TFLED), a quantum-well-injection (QWI) structure has been incorporated into the i-layer of an a-SiC:H pin TFLED at the p-i interface. The obtained brightness of this QWI TFLED is 256 cd/m2 at an injection current density of 800 mA/cm2, which is about three orders of magnitude higher than the brightness of an a-SiC:H pin TFLED. Also, a comparatively lower EL threshold voltage of 6 V was observed for this a-SiC:H QWI TFLED.
(S, R, MU)-NETS AND ALTERNATING FORMS GRAPHS
(1993-04-28)
HUANG, TY
;
LAURENT, M
;
應用數學系
;
Department of Applied Mathematics
WDM/FDM STAR COUPLER WITH GAIN USING FIBER AMPLIFIERS
(1993-04-29)
CHEN, YK
;
CHI, S
;
光電工程學系
;
電信研究中心
;
Department of Photonics
An efficient amplified WDM/FDM star coupler is proposed. The size of the coupler can be increased by a factor of m using m fibre amplifiers. Furthermore, the complexity and cost of the proposed scheme are less than those of other configurations.
THE TOWERS OF HANOI PROBLEM WITH CYCLIC PARALLEL MOVES
(1993-04-29)
WU, JS
;
CHEN, RJ
;
交大名義發表
;
資訊工程學系
;
National Chiao Tung University
This paper discusses a variant of the towers of Hanoi problem with cyclic parallel moves. We propose an algorithm for this problem and show that the algorithm is optimal.
SAMPLE BUFFER - A PROGRESSIVE REFINEMENT RAY-CASTING ALGORITHM FOR VOLUME RENDERING
(1993-05-01)
KE, HR
;
CHANG, RC
;
資訊工程學系
;
Department of Computer Science
Ray-casting has been shown to be an excellent technique for rendering volume data. This paper describes a new ray-casting algorithm that employs the concept of progressive refinement for volume rendering. Volume data are embedded into a complete octree, and when the volume data are rendered, the octree is traversed according to a user-defined threshold. By reducing this threshold gradually, we can render increasingly refined images. Ray-casting is used to explore the octree, and a data structure called a sample buffer (SB) is introduced to reduce the time required to render a series of images. With this method, a satisfactory balance between image quality and computation time can be achieved.
DATA ENVELOPMENT ANALYSIS IN MEASURING THE EFFICIENCY OF FOREST MANAGEMENT
(1993-05-01)
KAO, C
;
CHANG, PL
;
HWANG, SN
;
管理科學系
;
Department of Management Science
管管簡介
(1993-05-01)
管管
OPTIMAL TILE PARTITION FOR SPACE REGION OF INTEGRATED-CIRCUITS GEOMETRY
(1993-05-01)
HSIAO, PY
;
LIN, CY
;
SHEW, PW
;
資訊工程學系
;
Department of Computer Science
An optimal tile partition (OTP) is presented for partitioning the space region of a VLSI layout plane into rectangular space tiles. It modifies the corner stitching data structure to optimise the space tile partition. There is a serious restriction in the original corner stitching data structure, i.e. the solid rectangles cannot overlap each other, whereas our OTP allows overlapping. This paper also shows three theorems with rigorous proofs and experimental results to obtain the minimal number of the space tiles through the OTP. Moreover, a dynamic plane-sweep algorithm based on region query for the OTP has been developed. Using the OTP, the memory efficiency and the local query operations of the original corner stitching data structure have been enhanced.
ANALYTIC-FUNCTIONS FOR ATOMIC MOMENTUM-DENSITY DISTRIBUTIONS AND COMPTON PROFILES OF K-SHELLS AND L-SHELLS
(1993-05-01)
CHEN, YF
;
KWEI, CM
;
TUNG, CJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
An analytical expression involving three parameters was proposed for atomic momentum-density distributions of K and L shells. This expression was based on the superposition of hydrogenic closed-shell momentum densities. Parameters in the expression were determined by requiring four of its moments to be equal to the corresponding Hartree-Fock results. An analytical function for the Compton profiles was then derived using the impulse approximation. Excellent agreement was found between the present results and detailed theoretical computations.
SUPERCONDUCTING PROPERTIES OF ORIENTED YBA2CU3O7-X FILMS ON MGO AND SRTIO3 SUBSTRATES
(1993-05-01)
HAUNG, CJ
;
TSENG, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Using single-target sputter deposition, the c-axis oriented YBa2Cu3O7-x films can be obtained on both MgO and SrTiO3 substrates by appropriately controlling the substrate temperature at 700-degrees-C. However, on examining a.c. susceptibility and electrical dissipation, we find that the films on a SrTiO3 substrate possess better superconducting properties, such as a stronger coupling between the superconducting grains; a higher potential energy for flux pinning; and a larger capacity for current conduction. Also, from the magnetization hysteresis measurement, the critical current density of 2.6 x 10(6) A cm-2 (77 K) and 4.5 x 10(7) A cm-2 (5 K) for the sample on the SrTiO3 substrate can be estimated.
DEVELOPMENT OF OSCILLATORY ASYMMETRIC RECIRCULATING FLOW IN TRANSIENT LAMINAR OPPOSING MIXED CONVECTION IN A SYMMETRICALLY HEATED VERTICAL CHANNEL
(1993-05-01)
LIN, TF
;
CHANG, TS
;
CHEN, YF
;
交大名義發表
;
機械工程學系
Detailed flow and thermal characteristics in transient laminar opposing mixed convection in a vertical plane channel subject to a symmetric heat input are numerically investigated. First, a linear stability analysis was employed to evidence the occurrence of flow bifurcation. Then, the unsteady Navier-Stokes equations along with the continuity and energy equations were respectively integrated by a third-order upwind and power-law finite-difference scheme with the resulting matrices inverted by the Fast Fourier Transform and conjugated gradient methods. Reverse flow in the form of symmetric, elongated recirculating cells is initiated earlier and is stronger in a lower Prandtl number fluid with higher opposing buoyancy and Reynolds number and longer heated section length. A t a high opposing buoyancy, sudden flow asymmetry and oscillation occur simultaneously in a nearly steady flow after the initial transient. Periodic flow and thermal evolution are noted in space and time. An empirical equation for the condition for inducing flow oscillation is proposed.
POLYHEDRAL FACE RECONSTRUCTION AND MODELING FROM A SINGLE IMAGE WITH STRUCTURED LIGHT
(1993-05-01)
CHEN, Z
;
HO, SY
;
TSENG, DC
;
資訊工程學系
;
Department of Computer Science
The determination of the 3-D geometric model of visible polyhedral faces from a single view is addressed. It applies a grid coding technique to derive the normal vector of each visible polyhedral face and the depth parameter of the race equation based on the given dimensions of the grid on the code plate. It is shown that the method is correspondenceless. Furthermore, it also determines the 3-D face model for all visible polyhedral faces including the occlusion relations between faces. Two edge reconstruction methods are given and their goodness are compared. For the determination of the final object model, three different integration methods are given. Some experiments are reported to illustrate the method.
ORIENTATION RELATIONSHIPS BETWEEN M2C CARBIDE AND THE AUSTENITE MATRIX IN AN FE-MN-AL-MO-C ALLOY
(1993-05-01)
PENG, SW
;
CHOU, CP
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
M2C carbides were observed to precipitate within the austenite matrix of an Fe-24-6Mn-6.6Al-3.1Mo-1.0C alloy after quenching from 1200-degrees-C and aging at 750-degrees-C. By means of transmission electron microscopy (TEM) and diffraction techniques, the orientation relationships between M2C (p) and the austenite (gamma) matrix were determined to be: (0001)p//(111)gamma, (1120BAR)p//(110BAR)gamma, (1100BAR)p//(112BAR)gamma. M2C carbide has been reported by many researchers to precipitate from the ferrite matrix or along austenite/ferrite boundaries in alloy steels containing Mo. However, little information concerning the formation of M2C in the austenite matrix has been provided. This investigation presents the first evidence for the existence of M2C carbide wholly within the austenite matrix and its relationship to the austenite. The energy-dispersive spectrometry (EDS) analyses were performed on M2C carbides, and the results indicate that the solubility of the M2C carbide for foreign atoms other than Mo is very limited.
AN EFFECTIVE SEARCH APPROACH TO CAMERA PARAMETER-ESTIMATION USING AN ARBITRARY PLANAR CALIBRATION OBJECT
(1993-05-01)
CHEN, Z
;
WANG, CM
;
HO, SY
;
交大名義發表
;
資訊科學與工程研究所
In this paper we shall present a new method for camera parameter estimation using an arbitrary planar calibration object. We begin with an approximate model for the perspective view and give a parameter-free normalized-line-segment-ratio relationship between the corresponding reference and sensed views. This representation makes parameter decoupling possible and reduces the library dimension from six to one. Then the estimation problem can be viewed as a library search problem. Various mechanisms are provided to reduce the library search time, including (a) library partition by clustering, (b) sensed cluster identification by binary search, and (c) sequential testing for view matching using sorted features. In addition, feature perturbation is also considered to achieve better robustness against feature noise. Both computer-generated and real data are included in experiments, illustrating how our method works.
OPTICAL-PATTERN SIMULATIONS FOR CLOSED CYLINDERS OF LIQUID-CRYSTALS
(1993-05-01)
LIANG, BJ
;
WEI, JG
;
CHEN, SH
;
光電工程學系
;
Department of Photonics
Optical patterns for the polarizing microscope textures of closed cylinders of liquid crystals (CCLCs) are studied by the Jones vector formulation. The simulated director configuration diagram of a CCLC with normal orientation at the walls contains four kinds of stable director configurations. The resulting texture under some approximations depends only on phase shifts. The patterns are characterized by dark brushes that coincide with the directions of the crossed polarizers. Additionally, there are concentric circle fringes. For the ring defect structure, the centre region of the cylinder exhibits a black extinction. However, this is not distinguishable as between the hyperbolic and radial structures for both the point and the ring defect patterns. Comparing the observed patterns with the simulated ones, we find that the dark cross brushes and the centre black extinction of simulated patterns are similar to those that are observed. However, the concentric circle fringes of the observed pattern are not in accordance with the simulated pattern.