LY12铝疲劳裂纹在冲击载荷下的演化研究

对LY12铝合金在低周疲劳条件下的裂纹情况和随后进行的动态拉伸条件下裂纹的发展给予了观察和统计分析，发现裂纹的累积数密度分布在损伤演化过程中保持指数形式，用NAG模型对实验结果进行分析，得出该材料裂纹演化发展方程的各种参数。     

保羅·郎之萬

一、生在劳动人民中间 1954年3月3日,在巴黎大學大禮堂中举行保罗·郎之万七十三壽辰慶祝大會。在大会上郎之万郑重地說明了他的思想。他说: “我之所以能够把我的全部力量用在科學工作和正義事业上,是由於我是在1870年战爭以後的環境中培养出來的。我的父母都是擁护共和制度的,甚至愿意犧牲他們的生命,同時我是生長在可爱的巴黎人民中间,對巴黎人我至今還是衷心熱爱的。我的父親虽然在十     

De Haas-van Alphen Effect of Free Electron Gas Revisited

The free electron gas in a uniform magnetic field at low temperature is restudied. The grand partition function previously obtained by Landau＇s quantitative calculation contains three parts, which are all approximate. An improved calculation is presented, in which two of the three parts are obtained in exact forms. A simple remedy for Landau and Lifshitz＇s qualitative calculation in the textbook is also given, which turns the qualitative result into the same one as obtained by the improved quantitative calculation. The chemical potential is solved approximately and the thermodynamic quantities are caiculated explicitly in both a weak field and a strong field. The thermodynamic quantities in a strong field obtained here contain both non-oscillating and oscillating corrections to the corresponding results derived from Landau＇s grand partition function. In particular, Landau＇s grand partition function is not sufficiently accurate to yield our nonzero results for the specific heat and the entropy. An error in the Laplace-transform method for the problem is corrected. The results previously obtained by this method are also improved.