Octave-spanning visible supercontinuum generation from an aluminum nitride single crystal pumped by a 355 nm nanosecond pulse

Supercontinuum generation(SC) of more than one octave spectrum spanning covering from 400 nm to 820 nm was achieved by pumping a piece of aluminum nitride(AIN) single crystal using a nanosecond 355 nm ultraviolet laser. The AlN with a thickness of ~0.8 mm was grown by an optimized physical vapor transport technique and polished with solidification technology. Compared to previously reported ones, the achieved visible SC exhibited the broadest spectrum spanning from bulk materials pumped by a nanosecond pulse laser. The visible supercontinuum in Al N presents new opportunities for bulk material-based white light SC and may find more potential applications beyond typical applications in integrated semiconductive photoelectronic devices.     

高能电子碰撞电离对高空核爆炸辐射电离的影响

利用数值模拟程序模拟了不同高度核爆炸下距离爆点不同位置处大气的X射线电离及演化过程,分析了高能电子碰撞电离过程对高空核爆炸电离效应的影响.结果表明:高能电子碰撞电离过程对高空核爆炸的电离结果产生了重要影响,在80 km爆高1 kt当量高空核爆炸条件下,在距离爆点1.5 km处高能电子的碰撞电离效应使得电子的峰值数密度提高了约2个数量级;随着时间的增加,高能电子能谱逐渐向低能方向发展,在5μs后高能电子数密度随电子能量近似呈负指数分布;电子峰值时间与爆高有关,随着爆高的增加而增大,电离的影响区域也随着爆高的增加而增大.在80 km爆高1 kt当量情况下电离效应对近百千米范围内的微波通信具有严重影响.     

分光光度法测定氨基羟基脲

建立了Fe(Ⅱ)-邻菲啰啉显色法测定HNO3体系中氨基羟基脲(HSC)的方法。在乙酸/乙酸钠缓冲体系中,HSC与Fe(Ⅲ)反应生成的Fe(Ⅱ)能与邻菲啰啉形成稳定的络合物,该络合物的最大吸收波长在510 nm。考察了缓冲溶液用量、反应时间等条件对吸光度(A)的影响。结果表明:HSC浓度在5~60μmol/L范围内遵循比尔定律,线性回归方程为:A=0.0292 cHSC(μmol/L),相关系数R2=0.9993。方法用于实际样品测定,加标回收率在100.1%~104.4%之间,检出限为3.8×10-2μmol/L,相对标准偏差0.04%~0.12%,满足HSC分析的需求。     

OSCILLATION CRITERIA FOR A CLASS OF HIGHER ORDER NEUTRAL DIFFERENTIAL EQUATIONS

We establish a new oscillation condition for even order neutral type differential equation of the following formwhere f is continuous and exists 1 ≤ k ≤ m(?)(t) ≡ Tk(t), a, (?)i ∈ C([0, ∞], R), i = 1, …,m. such that 0 ≤ a(t) ≤ L and     

偶数阶时滞微分方程的单调解

使用一种新技巧,研究了两类偶数阶时滞微分方程的单调正解的存在任,得到了方程存在单调正解的一些充要条件和充分条件。     

随机利率下增额寿险现值函数矩的一些结果

本文对随机利率采用 Wiener过程和 Orentein- Uhlenbeck过程建模 ,得到了增额寿险现值函数的矩的一些结果     

随机右删失下回归函数的正态逼近

在随机右删失下，我们考虑了模型Yi=g(xi) εi，1≤i≤n．当εi's不服从正态分布时。我们构造了g(x)的估计式gn^(x)，并且利用强逼近的结论，导出了gn^(x)-Eg^n(x)的正态逼近结果，得到了较快的收敛速度。     

有限空心圆柱体的三维非轴对称变形分析

本文应用Pickett双重级数展开法的思想研究了有限空心圆柱体的非轴对称三维变形问题。文中先将位移势函数展为Fourier级数和Fourier-Bessel级数之和,在一定边界条件下,两级数中的系数可以互相表示,这样,我们可获得一组联立代数方程组。求解此方程组,最后可求得问题的解。文中给出了一个计算实例,表明这样构造的解是收敛的。     

ON COMPUTATIONS OF STRESS INTENSITY FACTORS FOR STIFFENED HALF PLANES WITH IMPERFECTIONS AND CRACKS

In this paper we consider uniform extension problems for joined two half-planes withdifferent thickness and material behavior and one of which contains an elliptical hole,theother contains a crack.Along the boundary of these half-planes there is a stiffeningstringer.Computational formulas are given in power series form by complex variable—pertubation method.Results obtained here give extension to those of "Handbook of stressintensity factors".Numerical results of special cases in this paper coincide with those ofrefs.[1],[3].     

固体力学基础

《固体力学培础》(Foundation of Solid Mechanics 1965,Prentice-Hall)是论述现代固体力学理论基础的专门著作,它的著者是蒋铝美藉中国力学家冯元桢教授,该书系冯教授在加州理工学院给研究生讲授该课程时,撰写的力学教科书. 本忆侧重固体力学一般方法论的阐述,其突出特点是将深刻的物理、力学内容与正确