一种计算热计量仪表误差的简便方法

热计量仪表中各组成部分的准确度对其热量计量准确度起着至关重要的作用。目前的有关标准与规程只给出了热计量仪表误差极限的计算方法 ,并由此确定其准确度等级。实际上 ,热计量仪表的误差并不是其各部分组件误差的代数和。文中根据热计量仪表误差计算的基本方法 ,提出了一种计算热计量仪表准确度的简化法 ,具有一定的准确性 ,便于在实际测量中使用     

液位定量式灌装机的灌装精度概率模型与可靠度计算模型

描述了控制液位定量式灌装机的灌装时间与灌装精度的关系，推导出实际灌装时间的理论计算公式。针对实际存在的各种随机变量对灌装时间的影响，建立了灌装时间的概率模型，提出基于灌装时间随机误差的灌状精度以及灌装精度可靠度概念，并相应建立出灌装精度概率模型与灌装精度可靠度计算模型。     

Boxcar滤波器和极化Refined Lee滤波器对极化SAR分类精度影响的评估

本文阐述了Boxcar滤波器和极化Refined Lee滤波器的滤波原理,比较了两种滤波器的滤波效果。通过滤波后的极化图像分类精度的比较发现,滤波能显著提高监督分类的精度,滤波是提高分类精度必不可少的技术环节,Boxcar滤波在提高分类精度方面要优于Refined Lee滤波,此外滤波窗口的大小对分类精度也有重要的影响。     

Boxcar滤波器和极化Refined Lee滤波器对极化SAR分类精度影响的评估

本文阐述了Boxcar滤波器和极化Refined Lee滤波器的滤波原理,比较了两种滤波器的滤波效果.通过滤波后的极化图像分类精度的比较发现,滤波能显著提高监督分类的精度,滤波是提高分类精度必不可少的技术环节,Boxcar滤波在提高分类精度方面要优于Refined Lee滤波,此外滤波窗口的大小对分类精度也有重要的影响.     

星敏感器曝光时间的优化

星敏感器曝光时间是影响星敏感器星点定位精度的因素之一.建立星敏感器星点像移模型和CCD噪声影响模型,分析了星点质心定位精度与曝光时间的关系,并以CCD47-20为例,对星敏感器的曝光时间进行了优化.结果表明:对于6.5等星,当星点光斑像移速度为4.67 pixels/s时,采用5×5窗口的亚像元质心算法,亚像元质心算法精度随曝光时间的延长而降低,CCD噪声对星点质心定位精度的影响随曝光时间的增加而减小;星敏感器的最佳曝光时间为200 ms,此时的星点质心定位精度优于1/50 pixel.     

光电脉搏波信号处理中呼吸干扰的抑制

动态光谱的检测精度与光电脉搏波的幅值检测精度直接相关．为了获取较高的幅值检测精度,抑制光电脉搏波中的呼吸干扰,采用基于相干平均的脉搏波特征参数重构滤波和小波变换相结合的方法对光电脉搏波原始测量信号进行处理．首先用相干平均法获取脉搏波特征参数并重构光电脉搏波信号;然后对原始信号减去光电脉搏波后的剩余部分进行小波频率分析,并提取呼吸干扰,处理结果表明,本文的方法可以提取到高精度的光电脉搏波幅值信息,抑制大部分的呼吸干扰,从而改善动态光谱的检测精度．     

Role of optics in the accuracy of depth-from-defocus systems

The depth-from-focus-defocus approach to 3D reconstruction is based on the fact that objects closer to or farther from the object in focus appear blurred, and the amount of blur increases with the distance from the object in focus. An important characteristic of any depth-from-defocus system is the depth reconstruction accuracy. Several 3D reconstruction algorithms have been proposed, and the influence of image noise and image spectrum on the system accuracy has been studied. However, so far the effect of optics on the accuracy has not been fully explored. Here, we derive an expression estimating the system accuracy as a function of its optical parameters. It turns out that optics plays a major role in the accuracy, and tenfold increase of the lens focal length, and the aperture can increase the overall accuracy by a factor of more than 1000. The derived expression allows one to review several results, revealing that the accuracy is defined primarily by the optics. We also provide guidelines for the design of new depth-from-defocus systems in compliance with predefined specifications by choosing the appropriate optics.     

Fractal study of the fluctuation characteristic in the calibration of the cryogenic thermocouples

The accuracy of the temperature measurement depends strongly on the accuracy of the temperature sensor. The commonly used cryogenic thermocouples are calibrated by using a specially designed calibration system. The calibration is performed in the temperature range of from liquid nitrogen temperature (about 77 K) to the room temperature (300 K). The calibration results show that the accuracy is around several tens of mK, which meets the requirement of the experiments. However, it is found that the temperature fluctuation of the thermocouple is quite larger even if the temperature is well controlled, which indicates that the non-linear aspect characteristic plays a certain role in the calibration. The temperature fluctuation of the calibration process is analyzed by using the non-linear analysis method.     

Automated sampling decision scheme for the AVM system

Reducing the sampling rate to as low as possible is a high priority for many factories to reduce production cost. Automatic virtual metrology based intelligent sampling decision (ISD) scheme had been previously developed for reducing the sampling rate and sustaining the virtual metrology (VM) accuracy. However, the desired sampling rate of the ISD scheme is fixed and set manually. Hence, whenever the VM accuracy gets worse, it cannot adaptively increase the default sampling rate in the ISD scheme. As a consequence, it would take more time to collect enough samples for improving the VM accuracy. Moreover, when the VM accuracy performs well all the time, it cannot automatically decrease the default sampling rate in ISD, which may result in unnecessary waste. Accordingly, this paper proposes an automated sampling decision (ASD) scheme to adaptively and automatically modify the sampling rate online and in real time for continuous improvement. The ASD scheme can monitor the VM accuracy online as well as update the VM models in real time for maintaining the VM accuracy when the VM accuracy becomes poor. Also, the ASD scheme can automatically reduce the sampling rate while the VM accuracy performs well.     

含损伤板的动载荷识别精度研究

为了深入研究动载荷识别问题,改善识别精度受测点信息和传感器布置数目限制的影响。首先采用逆问题正分析的方法,在时域正演法识别的理论基础上,研究结构损伤对载荷识别结果的影响,然后分析讨论测点位置、采样时间间隔对识别精度的影响。结果表明,在板结构有损伤的情况下,该方法能有效地识别出非损伤处的载荷且计算效率较高,但对于损伤处载荷的识别精度较低。另外,通过优化传感器的布置以及选择合适的采样时间间隔,可较大程度提高识别精度,为载荷识别的准确性提供参考。     

直流电动机在高精度光电跟踪系统中的应用

高精度光电跟踪系统用以完成对模拟动态目标的准确跟踪 ,要求跟踪元件响应快、动态性能好、精度高 ,因此跟踪元件的性能直接影响系统的跟踪特性和精度。直流力矩电机的优点是调速性能好 ,启动转矩大。正是这一特点 ,在高精度光电跟踪系统中尝试使用直流力矩电机控制反射镜跟踪目标。高精度光电跟踪系统要求在一个较大的视场内实现对静态目标和动态目标的高精度快速跟踪。     

力加载点对压电式多分量测力平台测量结果的影响

随着多分量测力技术的广泛应用,其准确度要求越来越高。本文通过实验的方式验证在压电式多分量测力平台的使用过程中,要确保加载力作用点在测力平台有效作用区域之内,从而保证测量准确度。本文对于多分量测力平台的规范使用具有指导作用,对提高多分量测力平台的测量准确度具有重要意义。     

Numerical evaluation of three-dimensional water impact by the displacement potential formulation

The numerical accuracy of the displacement potential approach for a three-dimensional water-impact problem is investigated. An examination of the elliptic paraboloid shows that the boundary-value problem for the displacement potential, as well as the velocity potential, can be solved accurately, even if the panel size of the numerical scheme is no small enough. The numerical accuracy of the position of the contact line is poor. However, the accuracy of the virtual mass is good because of the averaging effect along the contact line. A comparison with Scolan and Korobkin's designed body confirms the accuracy of the drop speed and the penetration displacement. The displacement potential approach is extended to the case of water impact with trapped air. The numerical accuracy of the calculated air pressure in the cavity is confirmed by comparison with an experimental result. With these results, the suitability of the displacement potential approach to the ship-slamming problem is demonstrated.     

线性模拟量数据采集系统准确度的一种评价方法

采用一种新的准确度表述方法来评价数据采集系统的准确度；同时讨论了该方法的数据采集系统各种误差与现有指标的兼容性问题。     

On the analysis of accuracy for two-equation transient problems

Fourier analysis of numerical accuracy has traditionally concentrated on the propagation behaviour of various methods. When systems of equations in more than one unknown are involved, analysis of propagation accuracy alone is shown to be incomplete. A distribution factor is introduced to complement the Fourier analysis in these cases, and application of the concept to two problems commonly encountered in the water resources field is demonstrated. The distribution factor is shown to provide important information which cannot be obtained from the customary analysis of propagation accuracy.     

微动操作手的误差分析

讨论了由两级并联机构串接而成的六自由度微动操作手的误差分析。为了评估其结构参数误差对末端操作器位姿的影响，利用矢量分析的方法建立了安装加工误差、驱动误差与末端位姿误差之间的关系式，并得出了若干对微动操作手的设计加工有指导意义的结论。这种分析的方法同样也可应用到其它并联或串联机构的误差分析研究中。     

Improving the accuracy of the integral equation in the hybrid FEM-DBCI method for open boundary electrostatic problems

In this paper, the accuracy of the integral equation of the hybrid finite-element-method-Dirichlet boundary condition iteration method is improved for the computation of open boundary electrostatic fields. This is achieved by selecting the integration curve (or surface) as lying in the middle of the triangular (or tetrahedral) elements. A notable improvement in accuracy is obtained compared with selecting the integration curve (or surface) as constituted by element sides.     

双目系统中图像随机噪声的分析

图像立体匹配的精度是保证双目系统测量准确性的重要因素，也是系统研制过程中需要解决的难点问题。对影响双目系统中图像立体匹配精度的随机噪声建立了一种局部统计量符合高斯分布的简化统计模型，基于这个噪声模型设计了滤波方案。实验表明，滤波后图像立体体匹配的精度优于1／4像素。     

On the accuracy of finite-difference and finite-element methods for the simulation of some incompressible flows

Four different finite-difference (FD) approximations and a finite-element (FE) scheme are compared with regard to their accuracy. The relative accuracy of the different schemes is problem dependent and it is not possible to estimate, a priori the accuracy of a given scheme. In the case of finite-differences first, second, fourth and sixth order approximations are used. In the case of finite-elements a non-upwinding artificial viscosity is used. The different numerical schemes have been applied to the simulation of the flow in a lid-driven cavity and in a bifurcating channel. In the former case, the absolute accuracy of each scheme could be determined. The FD scheme with upwinding turned out to be more accurate only for low Reynolds numbers (Re), whereas the artificial viscosity used with the FE is relatively more accurate with increasing Re. In the case of the bifurcating channel the FD and the FE schemes use different types of boundary conditions. Nevertheless the agreement between the results is, graphically, very good.     

机车轮对压装力准确性影响因素的研究

研究了在机车轮对压装过程中影响压装力检测准确性的因素。根据Navier-Stokes方程推导出流体动力作用对压装力检测准确性的影响;利用MATLAB的PDE工具对压装过程中液压油空间流速进行了动力学仿真,并以此分析了不同因素对压装力检测准确性的动力学影响;根据油缸变形公式及传统摩擦力公式,提出了影响压装力检测准确性的静力学因素,并通过实验验证了该方法的有效性与准确性。结果表明:通过选择合适的压装参数并采用二次曲线拟合压强与压装力关系,可以有效提高压装力检测的准确性。