运动控制的数字随动系统

介绍了采用数字随动系统解决模拟伺服回路的设计技术，即选用智能化运动控制处理器用于无刷或有刷直流电动机控制。这种技术具有实时采集，操作简单，可靠性高，精度高等优点，在导航系统、雷达系统、火炮系统、汽车等领域具有广阔的发展前景。     

基于计数法测量激光多普勒测速仪的测速精度

为了测量所设计的激光多普勒测速仪(LDV)的测量精度,用均匀转动的斩波片代替高精度的转台作为标准的速度源,并基于单片机AT89S52,采用光计数的方法测量斩波片上某一固定位置的切向运动速度,LDV的测量结果与之相比较。实验结果表明,LDV测速的相对精度不超过8‰,稳定性较好。     

Flux vector splitting solutions for coupling hydraulic transient of gas-liquid-solid three-phase flow in pipelines

The gas-liquid-solid three-phase mixed flow is the most general in multiphase mixed transportation. It is significant to exactly solve the coupling hydraulic transient problems of this type of multiphase mixed flow in pipelines. Presently, the method of characteristics is widely used to solve classical hydraulic transient problems. However, when it is used to solve coupling hydraulic transient problems, excessive interpolation errors may be introduced into the results due to unavoidable multiwave interpolated calculations. To deal with the problem, a finite difference scheme based on the Steger-Warming flux vector splitting is proposed. A flux vector splitting scheme is established for the coupling hydraulic transient model of gas-liquid-solid three-phase mixed flow in the pipelines. The flux subvectors are then discretized by the Lax-Wendroff central difference scheme and the Warming-Beam upwind difference scheme with second-order precision in both time and space. Under the Rankine-Hugoniot conditions and the corresponding boundary conditions, an effective solution to those points located at the boundaries is developed, which can avoid the problem beyond the calculation region directly induced by the second-order discrete technique. Numerical and experimental verifications indicate that the proposed scheme has several desirable advantages including high calculation precision, excellent shock wave capture capability without false numerical oscillation, low sensitivity to the Courant number, and good stability.     

Arc rotation characteristics of a plasma centrifuge with a counter-rotating electrical discharge

Arc rotation velocities of a plasma centrifuge with a counter-rotating electrical discharge were measured by using double probes placed perpendicular to each other. The measurement results were compared with the results calculated from the analytic solutions suggested by Hong et al. The comparison revealed that the arc column near the electrodes can be rotated much faster by increasing the arc currents and magnetic fields. For example, the rotational velocity of the are column near the electrodes was increased from 75 to 150 m/s with the increase of magnetic flux density from 15 to 45 mT at the fixed arc current of 50 A. On the other hand, the rotational velocity of the arc column showed only negligible changes at the plane of symmetry, where the radial component of the arc current was designed to become zero due to the symmetry of the counter-rotating electrical discharge. From these measurement results and analytic solutions, gaseous mixtures of different masses can be separated effectively near the electrode regions of a plasma centrifuge with a counter-rotating electrical discharge.     

Relative angular precision in electron backscatter diffraction: A comparison between cross correlation and Hough transform based analysis

In the present study the relative angular resolution of an electron backscatter diffraction system based on Hough transform analysis has been determined with a silicon single crystal wafer. The resolution is found to be better than 0.1° and can be easily improved by repetition of measurements. A test measurement on a BaFe₂As₂ thin film, where disorientations of 0.1° and less are present, was performed using the cross correlation electron backscatter diffraction technique. The same measurement is evaluated with the Hough transform technique. Comparing both techniques give evidence of a relative resolution of better than 0.1°. However, in specimen areas with strain inhomogeneities a deviation along one rotation axis can be observed.     

矩形槽内水体大幅晃动分析中截断误差影响范围判断方法探讨

液体大幅晃动是目前CFD研究中一个热点。在CFD中,偏微分方程离散所产生的截断误差是主要的误差来源,且与网格尺度密切相关。本文首先从理论上介绍了截断误差的产生过程,由此过程可知截断误差与物理粘性的作用具有类似性。以此概念为基础,根据液体晃动动力响应的特点提出了在液体大幅晃动分析中,如何通过对物理粘性系数的参数敏感性分析,判断截断误差的作用范围从而判断计算精度是否满足要求的方法,最后与现有试验资料进行对比校核,验证了该方法的实用性。     

一种提高极值点处收敛精度的三阶WENO-Z格式

为了提高三阶WENO-Z格式在极值点处的计算精度,通过理论推导给出三阶WENO格式满足收敛精度的充分条件。采用泰勒级数展开的方式,推导给出所构造格式非线性权重的计算公式,并综合权衡计算精度和计算稳定性确定所构造格式的参数。通过两个典型的精度测试,验证了改进格式在光滑流场极值点区域逼近三阶精度。进一步选用激波与熵波相互作用和Richtmyer-Meshkov不稳定性等经典算例,证实了本文提出的改进格式WENO-PZ3相较其他格式（WENO-JS3和WENO-Z3）不仅具有较高的精度,而且降低了格式的耗散,提高了对流场结构的分辨率。     

基于NPP-VIIRS夜间灯光数据的山西省GDP空间化模拟

选取山西省为研究对象,以美国国家极轨合作仪件-可见红外成像辐射计套件（NPP-VIIRS）夜间灯光数据、GDP统计数据等为数据源,构建GDP空间化拟合模型,建立山西省GDP密度图,据此研究山西省经济的空间差异性。通过对NPP-VIIRS夜间灯光数据的空间化处理,提取灯光指数,并将其与GDP进行回归拟合,建立最佳回归模型,得到GDP密度拟合图;利用县级GDP数据进行线性纠正,从而提高GDP的模拟精度。结果表明：（1）NPP-VIIRS夜间灯光数据与GDP的相关性较高,可用于山西省GDP模拟;（2）与GDP分区建模相比,GDP整体建模的精度更高;（3）山西省GDP的空间分布整体呈由城市中心逐渐向周边辐射的特点,构成GDP过渡带。     

A quadrature method for a class of strongly oscillatory infinite integrals

A constructive process is presented which leads to a class of quadrature formulas with any preassigned compound precision for the numerical integration of rapidly oscillating functions on (0, ) of the forme ^–x F(x, x), where is a large parameter andF(·,y) is periodic of period unity iny.1980 Mathematics Subject Classification, Primary 41A55, Scondary 41A60