Browsing by Author "Liu, CK"

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Dimensionality and Kosterlitz-Thouless transition in single grain Tl-2223 superconducting thin films
(1996-04-01)
Juang, JY
;
Lin, HC
;
Liu, CK
;
Wang, SJ
;
Yang, TH
Tl2Ba2Ca2Cu3O10+x (Tl-2223) superconducting films with microstructure consisted of submillimeter size grains combining with reactive ion etching technique, has enabled us to investigate the transport properties of this material in a more controllable manner. Both conductivity fluctuations based on the Aslamazov-Larkin theory and the Kosterlitz-Thouless transitions were studied to delineate the two dimensional nature of the material. It was found that, depending on the substrate used, the effective thickness of critical fluctuation and the detailed features of the K-T transition were very different. For films deposited on LaAlO3(100) substrates, the effective thickness of critical fluctuation is about 35 Angstrom compared to a value of 17.5 Angstrom obtained for films deposited on MgO(100) substrate, roughly equal to the c-axis lattice constant and the distance between the trilayer CuO2 planes, respectively. The effective vortex dielectric constant measuring the correlations between vortex pairs near K-T transition were estimated to be 3.0 and 1.6 for films on LaAlO3 and on MgO, repectively. Possible mechanisms based on the defect structures are proposed to account for the observed results.
Stiffness identification of laminated composite shafts
(1998-09-01)
Kam, TY
;
Liu, CK
;
機械工程學系
;
Department of Mechanical Engineering
Distributions of bending stiffness along the spans of laminated composite shafts are determined via a non-destructive evaluation approach. The finite element method formulated on the assumption of uniform bending stiffness within each element is used in the deflection analysis of the shafts. Differences between measured and theoretically predicted deflections at any two points on a shaft are used to construct an error function for deflection. The identification of bending stiffness is formulated as a minimization problem in which the elemental bending stiffnesses are determined to make the error function a global minimum. A global minimization technique and a bounding method for establishing side constraints are presented to solve the above minimization problem. Experiments are performed to study the feasibility and applications of the proposed method. (C) 1998 Elsevier Science Ltd. All rights reserved.