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71.
Wall boundary conditions in smoothed particle hydrodynamics (SPH) is a key issue to perform accurate simulations. We propose here a new approach based on a renormalising factor for writing all boundary terms. This factor depends on the local shape of a wall and on the position of a particle relative to the wall, which is described by segments (in two‐dimensions), instead of the cumbersome fictitious or ghost particles used in most existing SPH models. By solving a dynamic equation for the renormalising factor, we significantly improve traditional wall treatment in SPH, for pressure forces, wall friction and turbulent conditions. The new model is demonstrated for cases including hydrostatic conditions for still water in a tank of complex geometry and a dam break over triangular bed profile with sharp angle where significant improved behaviour is obtained in comparison with the conventional boundary techniques. The latter case is also compared with a finite volume and volume‐of‐fluid scheme. The performance of the model for a two‐dimensional laminar flow in a channel is demonstrated where the profiles of velocity are in agreement with the theoretical ones, demonstrating that the derived wall shear stress balances the pressure gradient. Finally, the performance of the model is demonstrated for flow in a schematic fish pass where both the velocity field and turbulent viscosity fields are satisfactorily reproduced compared with mesh‐based codes. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
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Karyne M. Rogers Kerry Somerton Pamela Rogers Julie Cox 《Rapid communications in mass spectrometry : RCM》2010,24(16):2370-2374
Carbon isotope analyses (δ13C) of some New Zealand Manuka honeys show that they often fail the internationally recognised Association of Official Analytical Chemists sugar test (AOAC method 998.12) which detects added C4 sugar, although these honeys are from unadulterated sources. Failure of these high value products is detrimental to the New Zealand honey industry, not only in lost export revenue, but also in brand and market reputation damage. The standard AOAC test compares the carbon isotope value of the whole honey and corresponding protein isolated from the same honey. Differences between whole honey and protein δ13C values should not be greater than +1.0‰, as it indicates the possibility of adulteration with syrups or sugars from C4 plants such as high fructose corn syrup or cane sugar. We have determined that during the standard AOAC method, pollen and other insoluble components are isolated with the flocculated protein. These non‐protein components have isotope values which are considerably different from those of the pure protein, and can shift the apparent δ13C value of protein further away from the δ13C value of the whole honey, giving a false positive result for added C4 sugar. To eliminate a false positive C4 sugar test for Manuka honey, prior removal of pollen and other insoluble material from the honey is necessary to ensure that only the pure protein is isolated. This will enable a true comparison between whole honey and protein δ13C isotopes. Furthermore, we strongly suggest this modification to the AOAC method be universally adopted for all honey C4 sugar tests. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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Keith M. Rogers 《Proceedings of the American Mathematical Society》2005,133(12):3543-3550
We find the sharp constant in a sublevel set estimate which arises in connection with van der Corput's lemma. In order to do this, we find the nodes that minimise divided differences. We go on to find the sharp constant in the first instance of the van der Corput lemma. With these bounds we improve the constant in the general van der Corput lemma, so that it is asymptotically sharp.
77.
E. Cohen J. W. Commelin Pfeffer van 't Hoff Ladenburg Adie Tammann Raoult Naccari Ponsot H. N. Morse D. W. Horn J. C. W. Frazer B. S. Hopkins E. J. Hoffmann W. L. Kennon L. F. Lovelace W. W. Holland F. M. Rogers P. B. Dunbar B. Mears B. F. Lovelace Berkeley Hartley Barlow und L. Kahlenberg 《Fresenius' Journal of Analytical Chemistry》1909,48(4-5):273-278
Ohne Zusammenfassung 相似文献
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S. Dymkou M. Dymkov E. Rogers K. Galkowski 《Integral Equations and Operator Theory》2008,60(2):201-216
Differential repetitive processes are a distinct class of continuous-discrete 2D linear systems of both systems theoretic
and applications interest. The feature which makes them distinct from other classes of such systems is the fact that information
propagation in one of the two independent directions only occurs over a finite interval. Applications areas include iterative
learning control and iterative solution algorithms for classes of dynamic nonlinear optimal control problems based on the
maximum principle, and the modelling of numerous industrial processes such as metal rolling, and long-wall cutting etc. The
new results in is paper solve a general optimal problem in the presence of non-stationary dynamics. 相似文献
80.
A.J. Belfield T.G. Rogers A.J.M. Spencer 《Journal of the mechanics and physics of solids》1983,31(1):25-54
We Consider fibre-reinforced elastic plates with the reinforcement continuously distributed in concentric circles ; such a material is locally transversely isotropic, with the circumferential direction as the preferred direction. For an annulus bounded by concentric circles, the exact solution of the traction boundary value problem is obtained. When the extension modulus in the fibre direction is large compared to other extension and shear moduli, the material is strongly anisotropic. For this case a simpler approximate solution is obtained by treating the material as inextensible in the fibre direction. It is shown that the exact solution reduces to the inextensible solution in the appropriate limit. The inextensible theory predicts the occurrence of stress concentration layers in which the direct stress is infinite ; for materials with small but finite extensibility these layers correspond to thin regions of high stress and high stress gradient. A boundary layer theory is developed for these regions. For a typical carbon fibre-resin composite, the combined boundary layer and inextensible solutions give an excellent approximation to the exact solution. The theory is applied to the problem of an isotropic plate, under uniform stress at infinity, containing a circular hole which is strengthened by the addition of an annulus of fibre-reinforced material. 相似文献