一种直接用示波器观测单变量非线性系统状态的新方法

为解决用示波器观测单变量非线性系统难的问题, 本文提出了一种45°线法, 该方法能将随时间变化的连续信号以特殊的方式转换成直角坐标上45°线上的点图, 并可用通用双踪示波器 (模拟或数字均可)直接显示出来, 从而达到直接方便地观测和分析单变量被测系统运行时的各种状态, 如周期稳定态, 局部和全局不稳定态. 文中详细阐述了该方法的机理. 同时, 研究和解决了设计实现该方法物理电路的关键问题, 即从连续变化的信号中提取出能反映系统状态的有用信号. 由于蔡氏电路是典型的非线性系统, 且能随参数的变化产生各种丰富的状态, 本文选用该电路作为被测系统进行了大量的物理实验, 实验结果证实了该方法的有效性和实用性. 关键词： 45°线法 单变量系统 系统状态 双踪示波器     

Energy levels and spectral lines of Ne VIII

All experimental data on the valence-shell-excited and core-excited spectra of Li-like neon, including previously unpublished beam-foil spectroscopy data, have been compiled and critically evaluated. Seventeen spectral lines have been newly identified. Sets of recommended energy levels have been derived from the total list of observed lines and from selected results of theoretical and semi-empirical calculations. An accurate value of the ionization potential has been derived from existing theoretical calculations. Electronic supplementary material Online Material     

On collinear Griffiths points

J. Tabov has proved [1] that four Griffiths points are collinear if the vertices of a given quadrangle are on a circle. In this article we prove some generalization of this result in a very simple geometrical way (based on Desargues theorem). Received 9 July 1999; revised 13 December 1999.     

A rigid line in a confocal elliptic inhomogeneity embedded in an infinite medium under antiplane shear

An effective method is developed and used to investigate the antiplane problem of a rigid line in a confocal elliptic inhomogeneity embedded in an infinite medium. The analytical solution is obtained. The proposed method is based upon the use of conformal mapping and the theorem of analytic continuation. Special solutions which are verified by comparison with existing ones are provided. Finally, the characteristics of stress singularity at the tip of the rigid line inhomogeneity are analyzed and the extension forces for the crack and the rigid line inhomogeneity are derived. The project supported by the National Natural Science Foundation of China, the State Education Commission Foundation and the Failure Mechanics Lab of SEdC.     

凝视热成像系统MTF斜缝法测试技术研究

凝视热成像系统MTF测试不同于扫描系统，必须有解决其空间采样的混淆特性。在传统的线扩展函数法基础上发展起来的方法主要有：缝扫描法、最值法、斜斜法。实际使用中，前两种方法需要精确的定位技术，而斜缝法的数据处理较复杂。本文主要论述斜缝测试法，分析其工作原理，介绍其数据处理技术。     

交联网络和浓溶液中高分子链运动的NMR研究Ⅰ.NMR质子线型分析

用质子ＮＭＲ谱对交联凝胶高分子（聚丙烯酰胺－丙烯酸）网络与线型高分子（聚苯乙烯）浓溶液体系的ＮＭＲ线型进行了比较研究。结果表明，两种体系中高分子链段运动具有不同的特征：在充分溶胀的交联凝胶高分子网络中，交联点间的链段运动比较自由，交联点的运动则比较慢，使其质子谱呈现“超洛伦兹”线型；而在线型高分子浓溶液中，缠结点间的链段与缠结点一样，运动并不自由，使谱线呈现出类似固体的宽线宽的高斯线型     

塞曼效应与边缘离子温度的光谱测量

通过理论推导得到了谱线实际宽度和塞曼展宽之间的关系。在磁感应强度分别为1、2、2．5和3T的情况下，用数值方法进行了求解，用得到的结果拟合出了校正因子随离子温度变化的经验公式和拟合曲线，结果表明：离子温度较低时，塞曼效应对谱线宽度的影响很大，温度较高时，塞曼效应对谱线宽度的影响可以忽略。     

Special features of the EPR spectroscopy of a system of centers with different relaxation times

We found that the interaction of paramagnetic centers that have different relaxation times differs fundamentally from the interaction of centers having close relaxation times. Simulation showed that in this case there is an anomalous redistribution of the spectral-line intensity from the center to the wings with a virtually preserved distance between extremal points (super-Lorentzian shape of the line), which leads to underestimation of the total intensity recorded. The results obtained make it possible to explain a number of aspects of the radiospectroscopy of carbon materials of practical importance such as the nature of the generally accepted maximum on the curve for the dependence of the total intensity of an EPR signal on the temperature of the heat treatment of organic compounds and the degree of metamorphism of natural coals, the specific features of the effect of oxygen molecules and paramagnetic ions of metals on the EPR spectra of carbon materials, etc. Belarusian State University, 4, F. Skorina Ave., Minsk, 220080 Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 224–229, March–April, 1998.     

二维变系数对流扩散问题的特征配置法

1引言 在多种问题的数值模拟中均涉及抛物型对流扩散方程的数值求解问题.由于配置法 无需计算数值积分，计算简便，收敛阶高等优点，使之在工程技术和计算数学的许多领域 得到广泛的应用，但范围一般局限在一维常系数{1，21和二维常系数问题降，4]，90年代[s] 提出了二维变系数     

Absolute line intensities of CO2 in the 3090-3920 cm region

Absolute line intensities of ¹³C¹⁶O₂ were retrieved from high-resolution Fourier transform spectra recorded in the region 3090-3920 cm⁻¹. The uncertainty of the line intensity determination is estimated to be between 3 and 5% for the strong lines. The global fittings of the observed line intensities within the framework of the effective operators approach have been performed, reaching the experimental accuracy. A comparison of newly measured line intensities with those found in the HITRAN database is presented.