Elastic behaviour of a wedge sharp crack emanating from a disclination dipole near a semi-elliptical blunt crack

The interaction between a wedge disclination dipole and a crack emanating from a semi-elliptic hole is investigated. Utilising the complex variable method, the closed form solutions are derived for complex potentials and stress fields. The stress intensity factor at the tip of the crack and the image force acting on the disclination dipole center are also calculated. The influence of the morphology of the blunt crack and the position of the disclination dipole on the shielding effect to the crack and the image force is examined in detail. The results indicate that the shielding or anti-shielding effect to the stress intensity factor increases when the wedge disclination dipole approaches the tip of the crack. The effects of the morphology of the blunt crack on the stress intensity factor of the crack and the image force are very significant.     

Shielding Effect and Emission Criterion of a Screw Dislocation Near an Interfacial

Shielding effect and emission criterion of a screw dislocation near an interracial crisscross crack are dealt with in this paper. Utilizing the conformal mapping technique, the closed-form solutions are derived for complex potentials and stress fields due to a screw dislocation located near the interracial crisscross crack. The stress intensity factor on the crack tips and the critical stress intensity factor for dislocation emission are also calculated. The influence of the orientation of the dislocation and the morphology of the crisscross crack as well as the material elastic dissimilarity on the shielding effect and the emission criterion is discussed in detail. The results show that positive screw dislocations can reduce the stress intensity factor of the interracial crisscross crack tip （shielding effect）. The shielding effect increases with the increase of the shear modulus of the lower half-plane, but it decreases with the increase of the dislocation azimuth angle and the distance between the dislocation and the crack tip. The critical loads at infinity for dislocation emission increases with the increase of emission angle and the vertical length of the crisscross crack, and the most probable angle for screw dislocation emission is zero. The present solutions contain previous results as special cases.     

源于一道物理试题的数学发现

1．发现问题 （福建省福州市2009年高三最后一次模拟考试第21题）某人用如图1所示的方法传递物品．将一根长为L=8．0m的不可伸长的细绳，两端固定在相距为d=4．0m的A，B两等高点，运送物品的吊篮上方安装一只滑轮P，     

NUMERICAL ANALYSIS OF THE LARGE DEFLECTION OF AN ELASTIC-PLASTIC BEAM

ＩｎｔｒｏｄｕｃｔｉｏｎＷｉｔｈｔｈｅｄｅｖｅｌｏｐｍｅｎｔｏｆｎａｔｕｒａｌｓｃｉｅｎｃｅａｎｄｔｈｅｉｎｃｒｅａｓｉｎｇｒｅｑｕｉｒｅｍｅｎｔｉｎｔｅｃｈｎｏｌｏｇｙ,ｔｈｅｌａｒｇｅｄｅｆｌｅｃｔｉｏｎｎｏｎｌｉｎｅａｒｐｒｏｂｌｅｍｏｆｂａｒｓｉｓａｌｗａｙｓａｎｉｍｐｏｒｔａｎｔｒｅｓｅａｒｃｈｉｎｅｎｇｉｎｅｅｒｉｎｇａｐｐｌｉｃａｔｉｏｎｆｉｅｌｄ.Ｉｎｔｈｅ1960ｓ,ｔｈｅｒｅｓｅａｒｃｈｓｃｏｐｅｗａｓｏｎｌｙｌｉｍｉｔｅｄｔｏＥｕｌｅｒ’ｓＥｌａｓｔｉｃａｔｈｅｏｒｙ,ｗｈｉｃｈｗ…     

化学课堂笔记状况与学习成绩关系调查与思考

调查分析学生记课堂笔记的状况与化学成绩的相关性，提出了相应的教学对策，开发全体学生的智力和能力。     

Ti/AIN陶瓷界面反应的光电子能谱研究

用X射线光电子能谱(XPS)研究了在室温和超高真空条件下金属Ti淀积在AlN陶瓷表面上的化学反应过程.在金属Ti淀积之前,从AlN陶瓷的能谱中的Ols和Al2P的结合能可以看到因是样品的主要杂质,而且样品表面部分的Al被氧化.当样品淀积了金属Ti以后,发现刚淀积上去的Ti是氧化状态,还发现在Ti淀积的同时则Nls在高结合能处(402和406eV)出现新峰.随着Ti淀积厚度的增加,Ti低结合能的成份在增加而Al的氧化成份逐渐增加,Nls高结合能处的峰(402和406eV)也逐渐增高,更进一步成为主导地.N在 关键词：     

Crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth

The crystallographic tilt in GaN layers grown by epitaxial lateral overgrowth (ELO) on sapphire (0001) substrates was investigated by using double crystal X-ray diffraction (DC-XRD). It was found that ELO GaN stripes bent towards the SiN_x mask in the direction perpendicular to seeding lines. Each side of GaN (0002) peak in DC-XRD rocking curves was a broad peak related with the crystallographic tilt. This broad peak split into two peaks (denoted as A and B), and peak B disappeared gradually when the mask began to be removed by selective etching. Only narrow peak A remained when the SiN_x mask was removed completely. A model based on these results has been developed to show that there are two factors responsible for the crystallographic tilt: One is the non-uniformity elastic deformation caused by the interphase force between the ELO GaN layer and the SiN_x mask. The other is the plastic deformation, which is attributed to the change of the threading dislocations (TDs)—from vertical in the window regions to the lateral in the regions over the mask.     

英雄一世,学者一生--纪念吴杭生院士

2003年12月9日，伴随着贝多芬英雄交响曲的乐章，吴杭生先生的夫人、儿子、亲友、学生和同事将手中的鲜花放到他面前，向这位同命运抗争一生的英雄，这位视物理学为自己生命、求索一生的学者最后告别．     

第二类静电边值问题中对称性格林函数的一种制作方法

着重研究了Ｎｅｕｍａｎｎ静电边值问题中对称性格林函数的制作，并以同心球壳之间空间格林函数的制作为例加以说明，同时给出了Ｄｉｒｉｃｈｌｅｔ静电边值问题的相应结果。