浅谈两类基本年金问题的解法和教法

什么是年金？顾名思义，年金就是一年中发生的金额．随着年金问题在经济活动中的广泛应用，年金已泛指业务期中每一期发生的金额．这里的期可以用任何时间为单位，金额可以相等可以不相等．年金问题不同于本金问题，本金问题直接应用单利基本公式［Ｓ＝Ｐ（１＋ｎｒ）］或...     

Dependence of Intrinsic Defects in ZnO Films on Oxygen Fraction Studied by Positron Annihilation

Defects in ZnO films grown by radio-frequency reactive magnetron sputtering under variable ratios between oxygen and argon gas have been investigated by using the monoenergetie positron beam technique. The dominate intrinsic defects in these ZnO samples are O vacancies （Vo） and Zn interstitials （Zni） when the oxygen fraction in the O2/Ar feed gas does not exceed 70% in the processing chamber. On the other hand, zinc vacancies are preponderant in the ZnO films fabricated in richer oxygen environment. The concentration of zinc vacancies increases with the increasing O2 fraction. For the oxygen fraction 85%, the number of zinc vacancies that could trap positrons will be smaller. It is speculated that some unknown defects could shield zinc vacancies. The concentration of zinc vacancies in the ZnO films varies with the oxygen fraction in the growth chamber, which is in agreement with the results of photolurninescence spectra.     

过敏性哮喘患者血清中钙镁钡铝锶含量的研究

３４例过敏性哮喘患者血清中钙、镁、钡、铝、锶的含量与对照组比较，结果显示（１）钙的含量明显下降，Ｐ＜０．０１；（２）钡和锶的含量升高，差异有显著性和高度显著性，Ｐ＜０．０５和Ｐ＜０．０１；（３）镁和铝的含量差异无显著性，Ｐ＞０．０５。     

反射波测井的菲涅尔带效应

基于反射波的单井远探测是声波测井发展的一个重要里程碑,可以有效探测距离井数米到数十米的异常反射体如裂缝,极大提升了声波测井的径向探测距离,在碳酸盐岩缝洞储层勘探开发有重要的作用。本文系统考察了有限尺寸裂缝的反射强度与声源频率和反射体距离的变化特征。模拟结果表明,无论是单极子还是偶极子,反射波的幅度都呈现出菲涅尔带效应。在一定距离内,反射波幅度随裂缝某一方向如宽度增大而增大,当宽带增加一定尺寸后,反射波幅度有一定的程度下降,然后小幅震荡。总之,反射波幅度与反射体尺寸不是简单的正相关,因此,基于反射波能量来评价反射体体积和储量是有条件的。     

高灵敏高稳定的碘化铯阴极密封式分幅变像管研制

为解决采用Au光电阴极、开放式结构的分幅变像管探测效率低、稳定性差的问题,研制了一种采用CsI光电阴极的密封式分幅变像管。为了对比不同光电阴极对X射线的响应强度,密封式分幅变像管制作有一条Au微带阴极和一条CsI微带阴极。完成了密封式分幅变像管的结构设计、工艺制作和实验测试。研究结果表明:当加载半高宽度200 ps、幅值?2.7 kV的选通脉冲时测得其时间分辨为65 ps;在非单色高能X射线源照射下,CsI阴极的静态响应强度是Au阴极的3.4倍;大气环境中存储1000 h后密封式分幅变像管的静态响应强度仅降低到完成制作时的83%。上述结果表明采用CsI阴极的密封式分幅变像管具有更高的探测效率和稳定性,可有效提升X射线分幅成像质量和可靠性。     

纳米复相陶瓷及其摩擦学研究进展

介绍了纳米复相陶瓷的结构和分类、制备方法和力学性能以及纳米复相陶瓷的强韧化机理,评述了纳米复相陶瓷的摩擦学研究进展,分析了影响纳米复相陶瓷摩擦磨损性能的主要因素,指出当前纳米复相陶瓷摩擦学研究领域存在的问题及有待于研究的课题.     

DYNAMIC BUCKLING OF ELASTIC-PLASTIC COLUMN IMPACTED BY RIGID BODY

The dynamic buckling of an elastic-plastic column subjected to an axial impact by a rigid body was discussed by using the energy law. The traveling process of elastic-plastic waves under impact action was analyzed by characteristics method. The equation of lateral disturbance used to analyze the problem was developed by taking into account the effect of elastic-plastic stress wave. The power series solution of this problem has been the power series approach. The buckling criterion of this problem was proposed by analyzing the characteristics of the solution. The relationship among critical velocity and impact mass, critical buckling length, hardening modulus was given by using theoretical analysis and numerical computation.     

域外奇点法分析折板结构

本文应用域外奇点法分析了棱柱形单跨折板结构，其中采用了作者推导的两边简支无限长薄板弯曲问题和平面应力问题的基本解。与折板结构的现有分析方法相比，这种方法具有计算量少，精度高等优点。     

平面加载下球壳飞片的运动

本文叙述了利用脉冲X射线摄影方法,观测半球壳飞片在平面爆轰波作用下的变形及运动规律,并将二维数值模拟结果同实验结果进行比较,两者的符合性较好。     

一种预测地基沉降的新模型

本文提出预测地基沉降的变速率指数迭代预测模型,并对该模型的原理进行了讨论。选用实例计算取得较好的拟合预测结果。