光速的测定

光速是最重要的物理常数之一,因此光速的测定历来为物理学者所普遍重视.光速测定的原理很简单(即利用公式c=s/t)但因为光速是个非常大的量,因此要精测它是不容易的.现在测量的方法很多,70年代外国许多大学已排有光速测量实验.我国至今排出的还不多.83年北京大学介绍了利用氦—氖激光测光速的示范实验.它是个很好的示范实验,但是它需要昂     

电阻环法模拟测量电子束流的大小和位置

本文介绍了通过测量束流在输运管壁上形成的感应电流，来确定直线感应加速器束流大小、位置的一种方法。实验证明，这种测量方法不会影响电子束在管道中的传输，且测量精度高，装置简单，并可装在真空系统的外面，便于维修。     

5,10,15,20—四(4-甲氧基-3-磺酸苯基)卟啉光度法测定痕量铜的研究

5,10,15,20-四(4-甲氧基-3-磺酸苯基)卟啉[T(4-MOP)PS_4]是一种新的水溶性卟啉显色剂.它与铜反应的最适pH=3.2,配合物的最大吸收波长为416.3um,配位比为1:1,摩尔吸光系数为 3.18×10~5 L·mol~(-1)·cm~(-1).显色后用0.10mol/LHC12.0ml酸化..该试剂具有灵剂度高选择性好的特点,无需加任何掩蔽剂可成功地用于头发和大米中痕量铜的测定,所得结果与原子吸收光度法很一致.方法的测定范围是0-3.5ugCu~(2+)/25m1.相关系数r=0.9991.     

Resonant Reaction in Rb-Cs Vapour Mixture Rb（5P1/2） ＋ Cs（6P3/2） → Cs（8S1/2）＋Rb（5S1/2）

We experimentally study energy-pooling collision in the Rb-Cs vapour mixture at low densities in a cell. Atoms are excited to Rb（5P1/2） and Cs（6P3/2） states using two single-mode diode lasers. To isolate the heteronuclear contribution in the fluorescence spectrum, a double-modulation technique is adopted. The excited-atom density and spatial distribution are mapped by monitoring the absorption of a counterpropagating single-mode diode laser beam, tuned to Rb（5P1/2 → 7S1/2） and Cs（6Pa/2 → 8S1/2） transitions, respectively, which could be translated parallel to the pump beams. The excited atom densities are combined with the measured fluorescence ratios to determine cross section for the energy-pooling process [i.e. Rb（5P1/2） ＋Cs （6P3/2） → Cs（8S1/2）＋Rb （5S1/2）]. The cross section is 3.79 × 10^-14 cm^2 ± 45%.     

抛物线内定长弦的一个性质

文[1]对一道高考题的解答作了比较详尽的剖析.原题如下(2004年浙江理第12题):若f(x)和g(x)都是定义在实数集R上的函数,且方程x-f[g(x)]=0有实数解,则g[f(x)]不可能是()(A)x2 x-15.(B)x2 x 15.(C)x2-15.(D)x2 15.文中赵老师在分析了相关资料中的三种错误解法之后,出示了一种“答     

Fe3O4 Segregation and Transport Properties of La0.67Ca0.33MnO3

Effect of Fe3O4 segregation at grain boundaries on the electrical transport and magnetic properties of La0.67Ca0.33MnO3 is investigated. The experimental results show that the Fe3O4 segregation not only shifts the paramagnetic-ferromagnetic transition temperature of La0.6TCa0.33MnO3 to a lower temperature region but also induces a new transition in a lower temperature region. Meanwhile, the transition processes observed in both the resistivity and magnetization curves are obviously widened. Compared to pure La0.67Ca0.33MnO3, we assume that the Fe3O4 segregation level at the grain boundaries can modify the electrical transport and magnetic properties of La0.67Ca0.33MnO3.     

Influence of Yb-Doped Nanoporous TiO2 Films on Photovoltaic Performance of Dye-Sensitized Solar Cells

Yb-doped TiO2 pastes with different Yb/TiO2 weight ratios are prepared in the sol-gel process to obtain dyesensitized solar cells （DSCs）. The nanocrystalline size of Yb-TiO2 becomes smaller and the lattice parameters change. Lattice distortion is observed and dark current is detected. It is found that a part of Yb existing as insulating oxide Yb2O3 state acts as barrier layers at the electrode-electrolyte interface to suppress charge recombination. A Yb-doped TiO2 electrode applied in DSCs leads to a higher open-circuit voltage and a higher fill factor. How the Yb-doped TiO2 films affect the photovoltaic response of DSCs is discussed.     

奇异协方差阵下有效前沿及有效组合的解析解

利用广义逆矩阵研究了协方差阵奇异时的投资组合问题,突破了传统方法中要求协方差阵可逆的限制,得到了证券市场存在有效组合的充要条件,并给出了有效前沿和有效组合的解析解,成功地推广了经典Markowitz模型,同时还将有助于证券组合有效子集的深入研究.     

A Mossbauer study of the magnetic coupling in iron phosphorous trisulfides

The polycrystalline sample of layered compound FePS_3 has been investigated by using M?ssbauer spectroscopy (12K to 300K), magnetic susceptibility measurements, x-ray diffraction and FTIR spectroscopy. The antiferromagnetic order exists below T_N=120.5±1K. The M?ssbauer spectra below T_N indicate that the magnetization axis is perpendicular to the layer of FePS_3, and the divalent iron cations are in their high spin configurations. By fitting the hyperfine field parameters near the Néel temperature, we obtain information on the nature of magnetic interactions in the material. The results show that the magnetic coupling can be treated by the two-dimensional Ising model, and it can be interpreted on the basis of a crystal-field effect.     

汉语句法的分段循环分析策略

定义了汉语的分段语法，并根据自然语言的分段循环结构，提出了汉语的分段循环分析策略．它的基本思想是确定语言的一组基本范畴，其相应的句法规则段及其之间的优先关系，对于每一个句法规则段，分别依次采用改进的Ｋｉｌｂｕｒｙ算法、它的优点在于分析过程中的项目集比较小，而且避免了无用分析树的产生，从而大大提高了分析效率．