扩展有限元方法计算多夹杂问题时圆形夹杂与四边形单元的几何关系

用扩展有限元法XFEM(Extended Finite Element Method)解决夹杂问题时,夹杂与基质的界面把单元分成若干部分.求单元刚度矩阵时,需要分别在这各个部分求积分.找到便于程序编制的描述各积分区域几何形状的方法是亟待解决的问题.本文把各积分区域的形成过程看成是圆对四边形的多次切割.考虑切剩区域与圆的关系时,把不完整的边仍看作完整的边,把切剩区域看成是四边形或是切去一两条边的四边形.采用排列组合的方法,把它们与圆的所有位置关系列了出来.     

Reactivity of the insecticide chlorpyrifos‐methyl toward hydroxyl and perhydroxyl ion. Effect of cyclodextrins

The reactivity of Chlorpyrifos‐Methyl ( 1 ) toward hydroxyl ion and the α‐nucleophile, perhydroxyl ion was investigated in aqueous basic media. The hydrolysis of 1 was studied at 25 °C in water containing 10% ACN or 7% 1,4‐dioxane at NaOH concentrations between 0.01 and 0.6 M ; the second‐order rate constant is 1.88 × 10^?2 M ^?1 s^?1 in 10% ACN and 1.70 × 10^?2 M ^?1 s^?1 in 7% 1,4‐dioxane. The reaction with H₂O₂ was studied in a pH range from 9.14 to 12.40 in 7% 1,4‐dioxane/H₂O; the second‐order rate constant for the reaction of HOO^? ion is 7.9 M ^?1 s^?1 whereas neutral H₂O₂ does not compete as nucleophile. In all cases quantitative formation of 3,5,6‐trichloro‐2‐pyridinol ( 3 ) was observed indicating an S_N2(P) pathway. The hydrolysis reaction is inhibited by α‐, β‐, and γ‐cyclodextrin showing saturation kinetics; the greater inhibition is produced by γ‐cyclodextrin. The reaction with hydrogen peroxide is weakly inhibited by α‐ and β‐cyclodextrin (β‐CD), whereas γ‐cyclodextrin produces a greater inhibition and saturation kinetics. The kinetic data obtained in the presence of β‐ or γ‐cyclodextrin for the reaction with hydroxyl or perhydroxyl ion indicate that the main reaction pathway for the cyclodextrin‐mediated reaction is the reaction of HO^? or HOO^? ion with the substrate complexed with the anion of the cyclodextrin. The inhibition is attributed to the inclusion of the substrate with the reaction center far from the ionized secondary OH groups of the cyclodextrin and protected from external attack of the nucleophile. Sucrose also inhibits the hydrolysis reaction but the effect is independent of its concentration. Copyright © 2008 John Wiley & Sons, Ltd.     

吡啶基咪唑[4,5-f]1,10-菲咯啉合成、表征及与瓜环作用的光谱学考察

设计合成了2个吡啶基菲咯啉衍生物2-(3-吡啶基)咪唑[4,5-f]1,10-菲咯啉(G1)和2-(4-吡啶基)咪唑[4,5-f]1,10-菲咯啉(G2),通过元素分析、质谱和核磁共振氢谱对其结构进行了表征。 利用紫外吸收光谱和荧光光谱法考察了所合成化合物与六元瓜环Q[6]、七元瓜环Q[7]的相互作用,以及体系pH值对主-客体相互作用的影响。 在酸性条件下,Q[6]、Q[7]与Gl以及Q[6]与G2均发生包合形成1∶1的包合物,并有荧光增敏作用;Q[7]与G2作用形成1∶2包合物,且对G2有荧光猝灭作用;Q[6]、Q[7]与G1的包合常数分别为3.00×104和1.86×104 L/mol;Q[6]、Q[7]与G2的包合常数分别为1.64×104和1.01×103 L/mol。 随着体系酸性减弱,瓜环与客体作用减弱,在中性条件下,瓜环未与客体发生包合作用。     

Micromechanics of semicrystalline polymers: Towards quantitative predictions

An initially qualitative two-phase elasto-viscoplastic micromechanical model for the mechanical performance of semicrystalline materials has previously been developed. In the last decade, a series of extensions to this model have been aimed towards quantitative predictions of the response of semi-crystalline polymers based on their microstructure. These developments included extensive experimental characterization and modelling of the yield kinetics, time-to-failure, creep and thermal shrinkage and expansion. This paper gives an overview of the route from the initially qualitative model to a model that quantitatively captures these complex aspects of the mechanical response of a semicrystalline polymer.     

多相材料有效性能预测的高精度方法

有效介质方法是常用的细观力学方法之一.其可用于计算多相材料的有效性能,并建立材料微细观结构和宏观性能的定量关系;有助于指导新材料设计,减少试验工作量等.然而,当夹杂含量升高时,传统有效介质方法的计算精度下降.本文以两相材料为研究对象,提出一种新的参考介质,即:为更合理考虑不同夹杂颗粒间的相互作用,假定参考介质的应变是基体相平均应变和某一修正张量的双点积.在此基础上,推导了新参考介质下两相材料的有效模量表达式,并给出该修正张量的近似计算方法;通过反复更新参考介质,采用多层次均匀化思路,将本文方法进一步用于多相材料性能的预测.为验证方法的有效性,将预测结果与已有模型结果和试验数据进行对比.结果表明本文方法较已有方法更为合理、有效.当夹杂含量升高时,本文方法较传统有效介质方法的计算精度有所提升.     

Debonded arc-shaped interface conducting rigid line inclusions in piezoelectric composites

We consider an arc-shaped conducting rigid line inclusion located at the interface between a circular piezoelectric inhomogeneity and an unbounded piezoelectric matrix subjected to remote uniform anti-plane shear stresses and in-plane electric fields. Moreover, one side of the rigid line inclusion has become fully debonded from the matrix or the inhomogeneity leading to the formation of an insulating crack. After the introduction of two sectionally holomorphic vector functions, the problem is reduced to a vector Riemann–Hilbert problem, which can be decoupled sequentially by repeated application of the orthogonality relations between the eigenvectors for two corresponding generalized eigenvalue problems.     

尖锐夹杂角端部局部应力场杂交有限元分析

本文首先利用作者曾提出的一维有限元特征分析方法计算所得到的尖锐夹杂角端部应力奇异指数和奇异应力场、位移场角分布函数,并依据Hellinger-Reissner原理,开发出了一个特殊的、能够反映夹杂角端部局部弹性现象的n结点多边形超级角端部单元,然后将该超级单元与标准的4结点杂交应力单元耦合在一起构建了一种分析异形夹杂角端部奇异弹性场的新型特殊杂交应力有限元方法.文中给出了两个应用算例,算例结果表明:本文方法不仅使用单元少、计算结果精度高,而且适用范围广,可拓展应用于分析复合材料微结构组织与力学行为关系.     

光谱法研究杀鼠剂溴鼠灵与环糊精超分子体系及分析应用

利用光谱法研究了β-环糊精与二代抗凝杀鼠剂溴鼠灵的超分子作用,根据Benesi-Hildebrand法确定二者的包络比为1∶1,室温下包络常数为1.048×104 L·mol-1。实验还考察了二者的包络机理,推测主要是溴鼠灵结构中的疏水基团联苯基进入了β-环糊精的疏水空腔。同时发现,超分子包络物的形成可以大大增强溴鼠灵的荧光发射,据此,建立了水溶液中测定溴鼠灵的荧光分析方法。在优化实验条件下,线性范围8.0×10-8～4.0×10-6 mol·L-1(r=0.999 4),检出限为8.8×10-9 mol·L-1,并成功地用于环境水中微量溴鼠灵的测定。     

Synthesis and crystal strcucture of two zinc inclusion complexes

X‐ray single crystals of these two inclusion complexes, [Zn(H₂O)₄L₂]·(4‐amino‐1‐naphthalene sulfonate)₂ (L = 1,3‐bis(4‐pyridyl) propane), 1 , and [Zn(H₂O)(bipy)₂]·(4‐amino‐1‐naphthalene sulfonate)(NO₃) (bipy = 4,4'‐bipyridine), 2 were achieved by the reaction of Zn(NO₃)₂ and 4‐amino‐1‐naphthalene sulfonate to 1,3‐bis(4‐pyridyl) propane and 4,4'‐bipyridine, respectively. As inclusion complexes, the cationic components of 1 and 2 were formed by two infinite zigzag chains, while, 4‐amino‐1‐naphthalene sulfonate made up the anionic parts of these two complexes. Thus, the whole molecules of these two complexes are neuter. Numous hydrogen bonds could be found in these two inclusion complexes, which help them to form three‐dimensional solid‐state packing structure architectures. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

吸收杂质热辐射诱导光学薄膜破坏的热力机制

光学元件的破坏是限制高功率激光系统发展的主要问题,理解光学元件的破坏机制对于高功率激光系统的设计、运行参量选择以及器件技术发展有重要影响.以热辐射模型为基础研究了杂质吸收诱导光学薄膜破坏的热力过程.研究发现薄膜发生初始破坏所需时间很短,脉冲的大部分时间是引起薄膜发生更大的破坏.在考虑吸收杂质发生相变的情况下,计算了吸收杂质汽化对薄膜产生的蒸汽压力,论证了薄膜发生宏观破坏的可能性.此模型能很好地解释光学薄膜的平底坑破坏形貌.