DISSOLUTION OF IRON TO COPPER IN Fe60Cu40 ALLOY BY MECHANICAL ALLOYING AND SUBSEQUENT DECOMPOSITION

A metastable alloy with composition Fe₆₀Cu₄₀ can be prepared in single phase of a fcc structure by mechanical alloying, although Fe-Cu system is virtually immiscible in its equilibrium state at ambient temperature. The M?ssbauer spectra of this supersaturated solid solution could be fitted by two subspectra whose hyperfine magnetic fields are 200 kOe and 250kOe. In this metastable alloy, the iron atoms at the interface are easy to form clusters characterized as α-Fe at a temperature below 250℃, whereas the iron atoms in the body will cluster together at a higher temperature above 350℃ and behave as γ-Fe, and then transform to ferromagnetic bcc iron occurs.     

矩阵损失下带约束的回归系数非齐次线性估计的Minimax可容许性的特征

本文在矩阵损失下给出了带约束的回归系数线性估计在非齐次线性估计类中是Minimax可容许估计的充要条件。     

从“万用电表设计、制作和校准”实验浅谈对学生能力的培养

一、引言从对我院物理专业几届毕业生的调查来看,反映出的一个突出问题是,学生实验动手能力较差.适应中学物理实验教学有一定困难.我们从教学的角度进行了剖析,究其     

序约束下AR(p)-ARCH(q)模型参数的估计与检验

In this paper, we study a stationary AR(p)-ARCH(q) model with parameter vectors a and β. We propose a method for computing the maximum likelihood estimator (MLE) of parameters under the nonnegative restriction. A similar method is also proposed for the case that the parameters are restricted by a simple order: α1≥α2≥…≥αq, andβ1≥β2≥…βp. The strong consistency of the above two estimators is discussed. Furthermore, we consider the problem of testing homogeneity of parameters against the simple order restriction. We give the likelihood ratio (LR) test statistic for the testing problem and derive its asymptotic null distribution.     

双波段紫外光合成维生素D3实验研究

报道了双波段紫外光照射7脱氢胆甾醇合成维生素D₃的放大实验研究,发现它与激光两步照射合成法产物随时间变化曲线非常相似,维生素D₃的前身P₃的转化率约为61%,远高于传统的高压汞灯连续照射的产率.     

Tavis-Cummings模型中原子运动时光场的非经典特性

用全量子理论研究了原子运动时双原子Tavis-Cummings模型中光场的非经典特性. 分析了原子的运动、光场的初态和谐振腔的腔模结构对光场的压缩和反聚束效应的影响. 关键词： Tavis-Cummings模型 原子运动 压缩 反聚束效应     

Makarov势的Dirac方程的束缚态解

给出了Makarov型标量势与矢量势相等条件下的Dirac方程的束缚态解. Dirac方程的角向方程用因子分解方法求解，在得出角向波函数的过程中，自然地得到了属于同一本征值的不同角向波函数间的递推操作. 径向束缚态波函数用合流超几何函数表示，束缚态的能量方程可由径向波函数满足的边界条件得到. 关键词： Makarov势 Dirac方程 束缚态 因子分解方法     

这两个数列的通项公式能求出来吗?

对两道数列试题进行分析,给出其通项公式的求法.