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人群死亡规律研究

人群死亡规律研究

作者：李梧南京理工大学

学位级别：硕士

人口学者在研究生命表的基础上研究人口死亡规律时，把主要方法分成横向研究法和纵向研究法，本文就是把研究人口死亡的横向研究法上的一般函数与一些非常适合人口死亡力变化的函数相结合，得到全年龄区间的分段最佳拟合死亡率变化的函... 详细信息

人口学者在研究生命表的基础上研究人口死亡规律时，把主要方法分成横向研究法和纵向研究法，本文就是把研究人口死亡的横向研究法上的一般函数与一些非常适合人口死亡力变化的函数相结合，得到全年龄区间的分段最佳拟合死亡率变化的函数。并且从他们提出的一些函数出发，发现了一个非常适合模拟儿童少年时期与老年时期死亡率随年龄变化的分段函数的解析式，由于青壮年时期死亡率的变化非常没有规律，在青壮年时期我们还是采用前人的函数形式。于是就把全年龄区间的死亡率随年龄的变化用分段函数表示出来了，并且我们把这个分段函数修正出来的死亡率随年份的变化情况用线性回归来分析，得到未来几年的死亡率估计值。只是由于得到的是直线，便说明不能够进行长期预测。

关键词：死亡率韦伯(Weibull)模型冈柏兹(Gompertz)模型 Logit函数模型

Analytic solutions to a finite width strip with a single edge crack of two-dimensional quasicrystals

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Chinese Physics B 2011年第11期20卷 404-408页

作者：李梧 Institute of Applied Mathematics Xuchang University

In this paper, we investigate the well-known problem of a finite width strip with a single edge crack, which is useful in basic engineering and material science. By extending the configuration to a two-dimensional decagonal quasicrystal, we obtain the analytic solutions of modesⅠand Ⅱ using the transcendental function conformal mapping technique. Our calculation results provide an accurate estimate of the stress intensity factors K_Ⅰ and K_Ⅱ, which can be expressed in a quite simple form and are essential in the fracture theory of quasicrystals. Meanwhile, we suggest a generalized cohesive force model for the configuration to a two-dimensional decagonal quasicrystal. The results may provide theoretical guidance for the fracture theory of two-dimensional decagonal quasicrystals.

关键词： transcendental function conformal mapping quasicrystal stress intensity factor

A Dugdale-Barenblatt model for a strip with a semi-infinite crack embedded in decagonal quasicrystals

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Chinese Physics B 2013年第3期22卷 399-404页

作者：李梧解凌云 School of Science Taiyuan University of Technology Department of Physics Beijing Institute of Technology

The present study is to determine the solution of a strip with a semi-infinite crack embedded in decagonal quasicrystals,which transforms a physically and mathematically daunting problem.Then cohesive forces are incorporated into a plastic strip in the elastic body for nonlinear deformation.By superposing the two linear elastic fields,one is evaluated with internal loadings and the other with cohesive forces,the problem is treated in Dugdale-Barenblatt manner.A simple but yet rigorous version of the complex analysis theory is employed here,which involves a conformal mapping technique.The analytical approach leads to the establishment of a few equations,which allows the exact calculation of the size of cohesive force zone and the most important physical quantity in crack theory：stress intensity factor.The analytical results of the present study may be used as the basis of fracture theory of decagonal quasicrystals.

关键词： quasicrystals,conformal mapping,Dugdale-Barenblatt model,stress intensity factor

Plastic analysis of the crack problem in two-dimensional decagonal Al-Ni-Co quasicrystalline materials of point group 10,■

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Chinese Physics B 2011年第3期20卷 308-313页

作者：李梧范天佑 Department of Mathematics School of ScienceBeijing Institute of Technology Institute of Applied Mathematics Xuchang University

The fundamental plastic nature of the quasicrystalline materials remains an open problem due to its essential complicacy. By developing the proposed generalized cohesive force model, the plastic deformation of crack in point group 10, 10 decagonal quasicrystals is analysed strictly and systematically. The crack tip opening displacement （CTOD） and the size of the plastic zone around the crack tip are determined exactly. The quantity of the crack tip opening displacement can be used as a parameter of nonlinear fracture mechanics of quasicrystalline material. In addition, the present work may provide a way for the plastic analysis of quasicrystals.

关键词： quasicrystal crack plastic deformation

Anti-plane problem analysis for icosahedral quasicrystals under shear loadings

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Chinese Physics B 2014年第11期23卷 438-444页

作者：李梧柴玉珍 School of Science Taiyuan University of Technology

The present paper is concerned with the longitudinal shear elasticity of three-dimensional icosahedral quasicrystals. By virtue of the Dugdale hypothesis along with the method of complex potential theory, it involves two defect problems of the icosahedral quasicrystals. The first one is the calculation of stress intensity factors and the size of the cohesive force zone in a half-infinite crack. Meanwhile, the crack tip tearing displacements can be exactly derived. The other is the demonstration of the generalized stress intensity factors induced by a sharp V-notch as an extension of a crack. The generalized E-integral around the notch tip gives the energy release rate when the V-notch degenerates into a crack. Apart from their own usefulness in carrying out some simplified crack analyses, the results obtained in this work can particularly serve as a basis for fracture mechanics of anti-plane defect problems of icosahedral quasicrystals.

关键词： quasicrystal stress intensity factor crack tip tearing displacement energy release rate