误差分析

Direct digital waveform synthesizer is a digital method that the radar signal is generally generated.The error resource of DDWS is presented.The principle that signal is reconstructed in digital-to-analog converters is analyzed in the DDWS structure.

介绍了直接数字波形合成(direct digital waveform synthesizer，DDWS)的误差来源，分析了DDWS结构中其数模转换器信号重构机理，比较研究了DAC信号重构误差对输出信号脉冲压缩结果的影响。

Then, 6 sets of error data under different temperature conditions are measured based on the proposed method, and the z-axis positoning errors are analyzed as examples.

基于这种方法，在不同的温度条件下测量了6组数控机床的空间定位误差，并以z轴定位误差为例进行了分析。

After that, the space feature of the spindle rotating error movement and the error movement of a straight moving measurement—frame are also analysed, by which, the axile multiple—lift separating method and the one step by another step separating method are set up.

其次，分析了主轴回转误差运动和测架直行误差运动的空间特征，并以此为依据，提出了轴向多层分离法和逐次两步分离法。

Aiming at the fracture in operation of damageable pump shaft used on locomotive, macroscopic and microscopic analysis of the pattern of fractured cross section in pump shaft is conducted and it is recognized that the fracture is typically caused by combined action of bending and torsion fatigue.

针对机车用水泵轴在使用中容易发生断裂的问题，对水泵轴断口的宏观和细观形貌进行了分析，认为断口为典型的弯扭复合疲劳断口。通过检测水泵轴上装配的齿轮，发现由于齿轮的加工误差过大，在轴的退刀槽根部造成了较大的附加拉应力，最终导致轴的断裂。因此及时消除齿轮的加工误差，同时提高安装精度，是防止此类断裂发生的关键

A general laser scanning altimetry equation is developed that describes an ideal system, followed by developing an error model for the laser scanner, and the INS and GPS units. The result is a modified laser equation that contains all errors introduced. The error model is evaluated by analyzing the difference between errorless equation and laser equation with errors.

本文从机载激光扫描测高对地定位的几何模型出发，详细推导了各项误差对机载激光扫描测高对地定位结果的影响关系式；详细分析了不同误差对激光脚点坐标的影响规律，并给出了相应的数值结果和量化指标。

In the intersatellite coherent optical communication, the vibration of a satellite will lead to a pointing error of transmitting and receiving antennas, which will decrease the signal-to-noise ratio and increase the bit error rate. In this paper, the Rayleigh distribution is taken as the pointing error model caused by satellite vibration, and PSK homodyne communication scheme is used as an example to analyze the influence of the satellite vibration on the system instantaneous BER and average BER. The simulation calculation result of BER is given.

针对星间相干激光通信中卫星平台的振动造成发射天线和接收天线的瞄准角误差，使系统信号信噪比下降，误码率增加，该文以瑞利分布作为振动造成的瞄准角误差模型，结合高斯本振光和艾里信号光外差检测模型，以PSK零差通信体制为例分析卫星振动对系统的瞬时误码率和平均误码率的影响，给出误码率仿真计算结果。

Data pre-processing technologies such as singular points elimination, registration and radius compensation are studied. Base on chord high difference algorithm, a new one called chord high difference-ratio algorithm is proposed to improve veracity and robusticity of singular points elimination. Then, a registration algorithm based on local surface reconstruction is proposed, which avoids infaust influence coming from single reference point error.

在弦高差法的基础上，提出了全新的弦高差—比法，提高了异常点剔除的准确性和柔韧性；提出了一种基于局部图形重构的重定位方法，该方法通过对特征球的最小二乘拟合，消除了单一参考点的精度对重定位的影响；在此基础上对重定位的误差进行了详细的分析，给出了精确的误差值，从数学的角度保证了重定位的精度；在三角网格法的基础上提出了基于Delaunay三角剖分的半径补偿新方法，有效改善了补偿矢量的计算效率和准确性。

Minimum Zone Evaluation of form error is needed for measurement uncertainty analysis and assessment of inspectability of Virtual Coordinate Inspecting System, it is also a basis of Minimum Zone Evaluation of form errors and attitude errors.

形状误差最小区域评定是虚拟坐标测量系统中测量不确定度分析和可测量性评估所必需的，也是一切形位误差最小区域评定的基础。

In this paper,a two dimension mathematical model of the interferential plane is brought out,and the function of the interferogram is established.

通过建立干涉面光强分布的二维数学模型，确立了干涉图函数的数学表达式，从调制度、相位误差和频率噪声的角度，对动镜倾斜误差进行了系统分析。

Chapter 8: We discuss the acceleration of multigrid by Krylov subspace approaches, and recognize the reason for slow convergence of algebraic multigrid methods is that error reduction is significantly less efficient for some very specific error components which may cause a few eigenvalues of the algebraic multigrid iteration matrix to be considerably closer to 1 than all the rest. However, the eigenvectors belonging to the few isolated eigenvalues can be expected to be typically captured after only a few conjugate gradient iterations, which accelerate algebraic multigrid algorithms. Theoretical analysis and numerical results of some practical problems show the iterant recombination accelerates algebraic multigrid convergence.

第八章：先介绍用Krylov子空间迭代法加速一般多重网格方法收敛的基本框架，然后紧紧抓住引起代数多重网格方法收敛减慢的根本原因往往是误差减小对几个特别的误差分量不明显，这导致代数多重网格方法的迭代矩阵的几个特征值接近于1，而共轭梯度方法则能比较典型地捕捉属于孤立特征值的特征向量，从而推导出有效的共轭梯度加速算法和程序实现，不仅从一些具体的实际应用例子的数值结果去验证迭代复合加速收敛的效果，而且还从理论上分析了预处理共轭梯度法加速代数多重网格法收敛的机理。

However, as the name（read－only memory）implies, CD disks cannot be written onorchanged in any way.

然而，正如其名字所指出的那样，CD盘不能写，也不能用任何方式改变其内容。

Galvanizes steel pallet is mainly export which suits standard packing of European Union, the North America. galvanizes steel pallet is suitable to heavy rack. Pallet surface can design plate type, corrugated and the gap form, satisfies the different requirements.

镀锌钢托盘多用于出口，替代木托盘，免薰蒸，符合欧盟、北美各国对出口货物包装材料的法令要求；喷涂钢托盘适用于重载上货架之用，托盘表面根据需要制作成平板状、波纹状及间隔形式，满足不同的使用要求。