Papers by Author: S.Y. Wang

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Authors: Tian Bao Chang, H.D. Wang, Z.Q. Shen, S.Y. Wang
Authors: S.Y. Wang, Bo Lin Cheng, Can Wang, Wei Peng, S.Y. Dai, Zhao Hui Chen
Abstract: In this work, BST (x=0.7, 0.5, 0.3) films have been deposited onto Nb-SrTiO3 substrate with pulsed laser deposition. The crystal structure and surface morphology have been characterized by X-ray diffraction (XRD) and atomic force microscopy, respectively. XRD results revealed that in certain elaboration condition the films were aligned along (00l) direction, normal to the substrate surface. The dielectric loss, relative dielectric permitivity, and polarization of BST films strongly depended on Sr content at room temperature. The tunability of relative dielectric permitivity of BST films exhibited strongly dependence on Sr content, and BST-0.5 shows the maximun K (K = tunability/loss) value.
Authors: B.C. Cavenett, S.Y. Wang, K.A. Prior
Authors: Ming Li Huang, R.H.C. Wong, S.Y. Wang, Chun An Tang, R.M. Jaio
Abstract: This study is to evaluate the effect of the heterogeneity on the failure processes and strength characterization of brittle rock containing the single pre-existing crack (or flaw) under uniaxial compression loadings. The numerical simulation reproduces the evolution of the stress and strain fields in flaw propagation process, the mode of acoustic emission related to the heterogeneity of rock and the phenomenon related to discontinuous. It is shown that the lower the value of the homogeneous index, the more influence of local variation on the propagation process of the pre-existing flaw, and there occurs more randomly distributed microfractures throughout the specimen. Studying the details of macrofracture formation in relatively homogeneous specimens, it is interesting to find that there exists a 'constant jump' propagation pattern of the wing crack, which is responsible for the formation of the pre-existing flaw. The numerical results also demonstrate that the stress-strain relation and strength characterization depends strongly on the heterogeneity of the specimen. The heterogeneous rock has a gentler post-peak behavior and lower strength, while the more homogeneous specimen has a higher strength, accordingly, the curve becomes more linear and the strength loss is also rapidly.
Authors: Can Wang, Bo Lin Cheng, S.Y. Wang, S.Y. Dai, Zhao Hui Chen
Abstract: Compositional graded thin films of (Ba0.8Sr0.2)(Ti1-xZrx)O3 (BSTZ) are grown on MgO by pulsed laser deposition technique with four BSTZ ceramic targets. Gradients of composition are achieved by artificially tailoring composition in multilayered thin films to form compositional graded layers (CGL). In each CGL four individual layers of BSTZ with x = 0.36, 0.18, 0.08 and 0 are grown^in series with equal thickness. Three kinds of CGL samples comprising one, two or four CGLs have been elaborated with the same total thickness by varying the thickness of each CGL. Raman spectra show existence of tetragonal structure in all the multilayered BSTZ thin films. Raman peak at 535 cm-1 shifts to high frequency with increasing of compositional gradient, and the peak at 750 cm-1 also shows a small shift to high frequency. Moreover, other Raman peak is observed at about 830 cm-1, which is associated with phonon mode of cubic phase, and such peak shifts towards lower frequency with increasing of compositional gradient. The shift of Raman peak is related to variation of internal stress in BSTZ thin film due to increasing compositional gradient.
Authors: S.Y. Wang, B.G. Nong, Tian Bao Chang, H.D. Wang
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