Browsing by Author "Tzeng, CS"

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Displacements and stresses due to a vertical point load in an inhomogeneous transversely isotropic half-space
(2003-07-01)
Wang, CD
;
Tzeng, CS
;
Pan, E
;
Liao, JJ
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土木工程學系
We present the solutions for displacements and stresses subjected to a vertical point load in a continuously inhomogeneous transversely isotropic half-space with Young's and shear moduli varying exponentially with depth. Planes of transverse isotropy are assumed to be parallel to the horizontal surface. The solutions for the half-space are obtained by superposing the solutions of two full spaces, one with a point load in its interior and the other with opposite traction of the first full space along the z = 0 plane. The Hankel transform in a cylindrical co-ordinate system is employed for deriving the solutions. However, the resulting integrals for displacements and stresses involve polynomial, exponential function, and Bessel function that cannot be given in closed form; hence, numerical techniques are adopted in this work. In order to check the accuracy of numerical procedures, the comparisons are carried out with the homogeneous solutions of Liao and Wang, and the calculated results agree with those to nine decimal places. Furthermore, two illustrative examples are presented to elucidate the effect of inhomogeneity, and the type and degree of rock anisotropy on the vertical surface displacement and vertical normal stress in the inhomogeneous isotropic/transversely isotropic rocks subjected to a vertical concentrated force acting on the surface. The calculated results show that the induced displacement and stress are decisively influenced by the inhomogeneity, and the degree and type of material anisotropy. The proposed solutions can more realistically simulate the actual stratum of loading problem in many areas of engineering practice. (C) 2003 Elsevier Ltd. All rights reserved.
Molecular techniques to identify freshwater eels: RFLP analyses of PCR-amplified DNA fragments and allele-specific PCR from mitochondrial DNA
(2002-10-01)
Lin, YS
;
Poh, YP
;
Lin, SM
;
Tzeng, CS
;
生物科技學系
Because of morphological ambiguity, traditional classification of freshwater eel elvers (of the genus Anguilla) has always been difficult and unreliable. This study analyzes 2 mitochondrial genes viz., cytochrome b and 12S ribosomal RNA (rRNA) genes from previous studies, to establish molecular standards for eel identification. Prediction of restriction fragment length polymorphism (RFLP) indicated that a combination of 3 enzyme results for cytochrome b revealed good resolution power. We also selected 39 specific nucleotide sites of the 2 genes at which the site is unique for individual species: thus these can potentially be used for identification by polymerase chain reaction (PCR). To verify the accuracy of our predictions, we examined 58 specimens from 4 species by DpnII and HaeIII digestions and by PCR amplification using species-specific primers. Consistent with the putative mutation rates, more than 95% and 99% of the specimens could be successfully identified by the RFLP and PCR methods, respectively. The molecular techniques developed here can be helpful in eel aquaculture and ecological studies.
Reassessment of morphological characteristics in freshwater eels (genus Anguilla, Anguillidae) shows congruence with molecular phylogeny estimates
(2005-05-01)
Lin, YS
;
Tzeng, CS
;
Hwang, JK
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生物科技學系
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Department of Biological Science and Technology
The morphology-based phylogeny of freshwater eels, proposed by V. Ege in 1939, has been accepted as the basis of eel classification since that time. However, this has been called into question by recent molecular studies. Most of the morphological characteristics recognized by Ege are morphometric. Since methods for the application of morphometric data to phylogeny construction have not been fully established, it is unclear whether the observed discrepancies between morphological and molecular data arise from intrinsic differences or from flawed analyses. Here, we have used two methods to assemble evolutionary trees from distance matrices constructed according to Ege's data, the neighbor-joining (NJ) method and the minimum network (MinNet) method; the latter is based on an evolutionary algorithm. After reanalysing Ege's morphological data, we found that both methods gave results consistent with those based on molecular data, although not with Ege's original classification. Therefore, we speculate that some morphological features Ege used to subdivide the eel groups may not be synapomorphic as he proposed, but symplesiomorphic or convergent . The method developed here may prove useful for constructing phylogeny for taxon groups where only continuous morphometric characteristics are recognized, such as the freshwater eels.