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941.
Fringe element reconstruction technique for tracking the free surface in three‐dimensional incompressible flow analysis was developed. The flow field was calculated by the mixed formulation based on a four‐node tetrahedral element with a bubble function at the centroid (P1+/P1). Since an Eulerian approach was employed in this study, the flow front interface was advected by the flow through a fixed mesh. For accurate modelling of interfacial movement, a fringe element reconstruction method developed can provide not only an accurate treatment of material discontinuity but also surface tension across the interface. The effect of surface tension was modelled by imposing tensile stress directly on the constructed surface elements at the flow front interface. To verify the numerical approach developed, the developed algorithm was applied to two examples whose solutions are available in references. Good agreement was obtained between the simulation results and these solutions. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
942.
H.W. Choi C. Liu M.G. Cheong J. Zhang S.J. Chua 《Applied Physics A: Materials Science & Processing》2005,80(2):405-407
The effect of plasma exposure to n-type GaN surfaces has been examined. Etch pits are formed as a result of preferential sputtering at the sites of threading dislocations. Dark spots which are visible before plasma exposure can be attributed to screw dislocations, while those that emerge after plasma exposure are edge dislocations. The optimum condition for revealing defects clearly is derived, and has been adopted for the study of dislocations in a series of GaN epilayers grown under different conditions. A distinct trend in the dislocation density can be observed as the dopant concentration of the film varies. PACS 61.72.Ff; 68.37.Tj 相似文献
943.
The phenomena of the spin-Hall effect, initially proposed over three decades ago in the context of asymmetric Mott skew scattering, was revived recently by the proposal of a possible intrinsic spin-Hall effect originating from a strongly spin-orbit coupled band structures. This new proposal has generated an extensive debate and controversy over the past 2 years. On August 2006 the first workshop on the spin-Hall effect was held at the Asian Pacific Center for Theoretical Physics. Its purpose was to bring together many of the leading groups in this field to resolve such issues and identify future challenges. We offer this short summary to clarify formerly controversial issues now settled and help refocus the research efforts in new and important avenues. 相似文献
944.
S. H. Choh J. H. Kim I. -W. Park H. J. Kim D. Choi S. S. Kim 《Applied magnetic resonance》2003,24(3-4):313-319
Rare-earth ions of Nd3+ and Er3+ in nearly stoichiometric and MgO-doped LiNbO3 crystals, respectively, have been investigated by employing an X-band electron spin resonance (ESR) spectrometer. The grown crystal was heated in Li-rich powder at 1100°C in order to make it nearly stoichiometric by the vapor transport equilibrium technique. Due to the fact that the ESR linewidth is much narrower in the stoichiometric crystal than in the congruent LiNbO3, we were able to determine the hyperfine constants of143Nd and145Nd at 4 K. By codoping MgO into LiNbO3, a new Er3+ center has been observed with a differentg-tensor. We propose that the new Er3+ center in Mg-doped LiNbO3 occupies the niobium site due to the local excessive Mg2+ ion at the lithium site, whereas Nd3+ and Er3+ in congruent crystals reside at the lithium site. The proposal is consistent with theg-value anisotropy. 相似文献
945.
An efficient and general synthesis of benzopyrans is achieved by ethylenediamine diacetate-catalyzed reactions of resorcinols with α,β-unsaturated aldehydes in moderated yields. As an application of this methodology, biologically interesting confluentin, which was known to have an inhibitory effect on histamine release is synthesized in one step. Also, natural daurichromenic acid, which has highly potent anti-HIV activity, is successfully synthesized in one step. 相似文献
946.
Changsun Choi 《Journal of Mathematical Analysis and Applications》2006,323(1):78-87
We introduce the properties W∗D and BW∗D for the dual space of a Banach space. And then solve the dual problem for the compact approximation property (CAP): if X∗ has the CAP and the W∗D, then X has the CAP. Also, we solve the three space problem for the CAP: for example, if M is a closed subspace of a Banach space such that M⊥ is complemented in X∗ and X∗ has the W∗D, then X has the CAP whenever X/M has the CAP and M has the bounded CAP. Corresponding problems for the bounded compact approximation property are also addressed. 相似文献
947.
S.-M. Kwon H.-S. Choi K.-Y. Lee 《Archive of Applied Mechanics (Ingenieur Archiv)》2002,72(2-3):160-170
Summary The steady-state of a propagation eccentric crack in a piezoelectric ceramic strip bonded between two elastic materials under
combined anti-plane mechanical shear and in-plane electrical loadings is considered in this paper. The analysis based on the
integral transform approach is conducted on the permeable crack condition. Field intensity factors and energy release rate
are obtained in terms of a Fredholm integral equation of the second kind. It is shown for this geometry that the crack propagation
speed has influence on the dynamic energy release rate. The initial crack branching angle for a PZT-5H piezoceramic structure
is predicted by the maximum energy release rate criterion.
Received 23 January 2001; accepted for publication 18 October 2001 相似文献
948.
Hyun-Jun Choi Young-Ho Seo Ji-Sang Yoo Dong-Wook Kim 《Optics and Lasers in Engineering》2008,46(4):343-348
A digital holography interference pattern generated by a computer calculation (computer generated hologram, CGH) is one of the most expensive contents and its usage is being expanded. Thus, it is highly necessary to protect the ownership of a digital hologram. This paper introduces a watermarking scheme, a method to protect the ownership of digital holograms using the DCT domain data as the ones to be watermarked. This scheme shows very high imperceptibility and strong robustness against the anticipated attacks. We expect that the conclusions of this paper will be a very useful basis for further work in the area of electronic watermarking schemes for the digital holograms. 相似文献
949.
B. S. Choi 《Annals of the Institute of Statistical Mathematics》1985,37(1):535-539
Summary It is shown that a normal probability density can be characterized as a limit of conditional probability densities of i.i.d.
uniform random variables. 相似文献
950.