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1.
In this paper the second order characteristic (discontinuous bifurcation) condition is derived for the granular flow (fully plastic) equations. This second order bifurcation equation is shown to be formally identical to the first order localization requirement during steady elastoplastic deformation provided the elastic compliance tensor is substituted for the product of the plastic multiplier with the flow Hessian. For isotropic yield and flow functions the invariant form of the characteristic condition is given in detail, as well as an alternative expression in adapted co‐ordinates. The characteristic condition can be regarded as defining a hardening function which is maximized to identify the critical angles. When the method is applied to 3D Coulomb flow, Mohr's 3D fracture plane conditions are obtained uniquely. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
2.
Burkhard Fuchs 《Astrophysics and Space Science》2003,284(2):719-722
An update of the set of low surface brightness galaxies is presented which can be used to set constraints on the otherwise
ambiguous decompositions of their rotation curves into contributions due to the various components of the galaxies. The selected
galaxies show all clear spiral structure and arguments of density wave theory of galactic spiral arms are used to estimate
the masses of the galactic disks. Again these estimates seem to indicate that the disks of low surface brightness galaxies
might be much more massive than currently thought. This puzzling result contradicts stellar population synthesis models. This
would mean also that low surface brightness galaxies are not dominated by dark matter in their inner parts.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
3.
This paper is a continuation of previous research, which obtained a convenient solution for arbitrary surface fluxes before ponding. By means of Fourier Transformation this has been extended to derive analytical solutions of a linearized Richards' equation for arbitrary input fluxes after surface saturation. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
4.
In urban environments, one major concern with deep excavations in soft clay is the potentially large ground deformations in and around the excavation. Excessive movements can damage adjacent buildings and utilities. There are many uncertainties associated with the calculation of the ultimate or serviceability performance of a braced excavation system. These include the variabilities of the loadings, geotechnical soil properties, and engineering and geometrical properties of the wall. A risk‐based approach to serviceability performance failure is necessary to incorporate systematically the uncertainties associated with the various design parameters. This paper demonstrates the use of an integrated neural network–reliability method to assess the risk of serviceability failure through the calculation of the reliability index. By first performing a series of parametric studies using the finite element method and then approximating the non‐linear limit state surface (the boundary separating the safe and ‘failure’ domains) through a neural network model, the reliability index can be determined with the aid of a spreadsheet. Two illustrative examples are presented to show how the serviceability performance for braced excavation problems can be assessed using the reliability index. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
5.
沿海地区城市发展及地面沉降的系统控制 总被引:9,自引:0,他引:9
郑铣鑫 《海洋地质与第四纪地质》1992,12(1):57-65
本文运用系统工程原理,系统论述了地下水合理开发、管理和地面沉降系统控制,这对沿海地区地面沉降控制起到重要的作用。 相似文献
6.
东海陆架北部表层细粒级沉积物的级配及意义 总被引:3,自引:3,他引:3
本文依据东海陆架北部 2 3个表层沉积物样品的粒度分析资料 ,就东海陆架北部表层细粒级沉积物的级配及意义进行了研究。结果表明 ,研究区表层沉积物中细粒级部分以 <0 .0 16 mm为优势粒级 ,可占到总细粒级沉积物的 75 %以上。济州岛西南泥质区以细于 0 .0 0 8mm粒级的沉积物占据优势 ,长江口泥质区则以 <0 .0 16 mm粒级的沉积物为主 ,两泥质区细粒级沉积物的级配很不相同 相似文献
7.
8.
9.
Phytoplankton variability on the Faroe Shelf 总被引:2,自引:2,他引:2
10.