基于多重子域代理模型的结构可靠性分析

基于合理子域概念，构建多重代理模型。多重代理模型在合理子域内采用经典响应面模型，在合理子域外采用经典Kriging模型，能够充分利用两种经典模型各自的优势。多重代理模型能够合理规避经典响应面模型中响应函数采取事先假定形式带来的可靠度评估风险，同时能够有效避免经典Kriging模型中试验点组合爆炸的问题。相比经典响应面模型，多重代理模型所需试验点数量并未增加，计算效率与经典响应面模型大体相同。算例表明，本文方法的计算结果与MCS的计算结果几乎一致，具有较好的计算精度。     

层合板三维-二维混合分区有限元法研究

本文提出了一种三维-二维混合分区有限元方法分析复合材料层合结构。构造了三维-二维过渡元素和三维的十七节点复合元素。本方法大大地减少了自由度,缩短了计算时间。算例表明,计算结果令人满意。本方法是可靠的并同样适用于其它结构。     

岩土工程勘察中土体取样合理子样数的探讨

合理子样数应随土的性质、指标特征、土样质量和工程要求而异。本文在分析了沿海平原各主要土层的物理力学性质指标变异性的基础上 ,运用概率统计方法 ,针对不同土层不同的物理力学性质指标提出了岩土工程勘察合理子样数确定原则。     

Generating ultrafilters in a reasonable way

We continue investigations of reasonable ultrafilters on uncountable cardinals defined in Shelah [8]. We introduce a general scheme of generating a filter on λ from filters on smaller sets and we investigate the combinatorics of objects obtained this way. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Convex decomposition of games and axiomatizations of the core and the D-core

This paper provides an axiomatic framework to compare the D-core (the set of undominated imputations) and the core of a cooperative game with transferable utility. Theorem 1 states that the D-core is the only solution satisfying projection consistency, reasonableness (from above), (*)-antimonotonicity, and modularity. Theorem 2 characterizes the core replacing (*)-antimonotonicity by antimonotonicity. Moreover, these axioms also characterize the core on the domain of convex games, totally balanced games, balanced games, and superadditive games.      

非线性弹性动力学率型广义变分原理及子域原理

本文基于拖带坐标描述和S-R分解定理,建立了包含速度梯度、动量、速度、应力和应变率等五类独立场变量的非线性弹性动力学率型广义变分原理和广义子域混合杂交变分原理.     

一种计算量小的构造合理最紧缩定域轨道的方法

提出一种计算量小的构造合理最紧缩定域化轨道的方法.非正交定域轨道(NOLMO)没有“正交化尾巴”,比正交定域轨道(OLMO)更局域化、更紧缩、更具可移植性,从而更适合用于化学问题的理论研究.但若在用变分法确定最大限度局域化NOLMO时单纯取消正交条件而不附加其它的限制,会得到趋于线性相关的不合理结果.提出用强制NOLMO与投影自然键轨道(PNBO)的重心重合代替正交化条件确定合理的最大限度局域化NOLMO(合理最紧缩定域轨道)的方法.对一系列不同类型分子的计算结果表明,用该方法可以得到空间分布合理及线性独立的NOLMO,延伸度与文献已有的最佳结果接近,而计算量大幅度降低.由于构造投影自然键轨道的计算量随分子中原子数目的增加只是线性增长,因此,该方法可以用来构造较大体系的合理最紧缩定域轨道     

COMPUTATION OF STRESS INTENSITY FACTORS BY THE SUB-REGION MIXED FINITE ELEMENT METHOD OF LINES

Based on the sub-region generalized variational principle,a sub-region mixed ver- sion of the newly-developed semi-analytical‘finite element method of lines’(FEMOL)is pro- posed in this paper for accurate and efficient computation of stress intensity factors(SIFs)of two-dimensional notches/cracks.The circular regions surrounding notch/crack tips are taken as the complementary energy region in which a number of leading terms of singular solutions for stresses are used,with the sought SIFs being among the unknown coefficients.The rest of the arbitrary domain is taken as the potential energy region in which FEMOL is applied to obtain approximate displacements.A mixed system of ordinary differential equations(ODEs) and al- gebraic equations is derived via the sub-region generalized variational principle.A singularity removal technique that eliminates the stress parameters from the mixed equation system even- tually yields a standard FEMOL ODE system,the solution of which is no longer singular and is simply and efficiently obtained using a standard general-purpose ODE solver.A number of numerical examples,including bi-material notches/cracks in anti-plane and plane elasticity,are given to show the generally excellent performance of the proposed method.     

The reassessment of the structural transition regions along the liquidus of Fe–Si alloys and a possible liquid–liquid structural transition in FeSi2 alloy

We reassessed the structural transition regions along the liquidus of Fe–Si alloys by using ab initio molecular dynamics simulation. Except for 50 at.% Si, structural transition compositions are found at both 30 at.% Si and 67 at.% Si (FeSi₂) which are eutectic alloys. We demonstrated that the liquid structure in the sub-region of 0～30 at.% Si is close-packed, and in the sub-region of 67～100 at.% Si liquid alloys have very open structure. From 30 at.% Si to 67 at.% Si, the close-packed structure gradually change into open one. These structure transition sub-regions are also supported by the formation enthalpy of liquid alloys. Furthermore, the predicted enthalpy change between 1585 K and 1873 K is so large that there is probably liquid–liquid transition with temperature at FeSi₂ alloy which is an important thermoelectric material. Discussions have been made on the materials phenomenon of several Fe–Si alloys based on the structural information.