科研成果

The analytical stress-strain relation with heterogeneous parameters is derived for the heterogeneous brittle materials under a uniaxial extensional load, in which the distributions of the elastic modulus and the failure strength are assumed to be statistically independent. This theoretical solution gives an approximate estimate of the equivalent stress-strain relations for 3-D heterogeneous materials. In one-dimensional cases it may provide comparatively accurate results. The theoretical solution can help us to explain how the heterogeneity influences the mechanical behaviors. Further, a numerical approach is developed to model the non-linear behavior of three-dimensional heterogeneous brittle materials. The lattice approach and statistical techniques are applied to simulate the initial heterogeneity of heterogeneous materials. The load increment in each loading stage is adaptively determined so that the better approximation of the failure process can be realized. When the maximum tensile principal strain exceeds the failure strain, the elements are considered to be broken, which can be carried out by replacing its Young's modulus with a very small value. A 3-D heterogeneous brittle material specimen is simulated during a full failure process. The numerical results are in good agreement with the analytical solutions and experimental data.

数字对象唯一标识符作为数字图书馆的基础设施 ,具备网络环境下数字对象的标识、定位、管理等多种职能。本文分析了唯一标识符的类型、组成和构造原则 ,从逻辑标识、命名域相关、复杂性、完整性和互操作等角度论述唯一标识符的需求。在 W3C提供的 URI背景下 ,比较 URI、URL和 URN,并分析了相关命名语法和标识框架。最后介绍了 COOL URL的概念和命名需求。