Influence of X-ray Powder Diffraction Instrument Error on Crystalline Structure Analysis

Standard mica was used to correct the X-ray powder diffraction instrument error and mathematic methods were employed to find the correction equation. By analyzing mullite sample and comparing the corrected and uncorrected analysis results we found the former is obviously more reasonable. So the conclusion is that the X-ray powder diffraction instrument error greatly affects the crystalline structure analysis, and the above method is convenient and effective for the correction of instrument error.

Research on ballistic missile laser SIMU error propagation mechanism

It is necessary that the laser inertial system is used to further improve the fire accuracy and quick reaction capability in the ballistic missile strapdown inertial navigation system. According to the guidance controlling method and the output and error model of ballistic missile laser SIMU, the mathematical model of error propagation mechanism is set up and any transfer environmental function of error coefficient that affects the fire accuracy is deduced. Also, the missile longitudinal/lateral impact point is calculated using MATLAB. These establish the technical foundation for further researching the dispersion characteristics of impact point and reducing the laser guidance error.

Iterative identification of output error model for industrial processes with time delay subject to colored noise

To deal with colored noise and unexpected load disturbance in identification of industrial processes with time delay, a bias-eliminated iterative least-squares(ILS) identification method is proposed in this paper to estimate the output error model parameters and time delay simultaneously. An extended observation vector is constructed to establish an ILS identification algorithm. Moreover, a variable forgetting factor is introduced to enhance the convergence rate of parameter estimation. For consistent estimation, an instrumental variable method is given to deal with the colored noise. The convergence and upper bound error of parameter estimation are analyzed. Two illustrative examples are used to show the effectiveness and merits of the proposed method.

Dynamic Calibrating Technique for Super－Precision Gyrorotor Measuring Instrument

To ensure the accuracy of measurement in dynamic calibrating systems an important problem in the process of super-precision measuring gyrorotor.The conventional calibrating method which seriously affects the precision of measurement is analyzed systematically,and a statistical dynamic calibrating method is suggested in this paper.Test results indicate that the suggested method can significantly improve the calibrating process and system accuracy which is less than 0.05%.

Edgeworth Approximation of a Finite Sample Distribution for an AR(1) Model with Measurement Error

In this paper, we consider the finite sample property of the ordinary least squares (OLS) estimator for an AR(1) model with measurement error. We present the Edgeworth approximation for a finite distribution of OLS up to O(T1/2). We introduce an instrumental variable estimator that is consistent in the presence of measurement error. Finally, a simulation study is conducted to assess the theoretical results and to compare the finite sample performances of these estimators.

Estimating the Parameters Geographically Weighted Regression (GWR) with Measurement Error

Geographically weighted regression models with the measurement error are a modeling method that combines the global regression models with the measurement error and the weighted regression model. The assumptions used in this model are a normally distributed error with that the expectation value is zero and the variance is constant. The purpose of this study is to estimate the parameters of the model and find the properties of these estimators. Estimation is done by using the Weighted Least Squares (WLS) which gives different weighting to each location. The variance of the measurement error is known. Estimators obtained are . The properties of the estimator are unbiased and have a minimum variance.

A novel wide-range precision instrument for measuring three-dimensional surface topography

We developed a measuring instrument that had wide range, high precision, small measuring touch force. The instrument for three-dimensional (3D) surface topography measurement was composed of a high precision displacement sensor based on the Michelson interference principle, a 3D platform based on vertical scanning, a measuring and control circuit, and an industrial control computer. It was a closed loop control system, which changed the traditional moving stylus scanning style into a moving platform scanning style. When the workpiece was measured, the lever of the displacement sensor returned to the balanced position in every sample interval according to the zero offset of the displacement sensor. The non-linear error caused by the rotation of the lever was, therefore, very small even if the measuring range was wide. The instrument can measure the roughness and the profile size of a curved surface.

五轴数控机床旋转轴综合误差测量与辨识

针对五轴数控机床旋转轴的运动误差和几何误差的综合评估问题,在不考虑直线轴运动误差影响的情况下,提出了一种采用R-test测量仪的测量及其辨识方法。首先,测量过程按照参考球的两种不同高度设置进行,仅移动旋转轴,而不移动直线轴。其次,利用R-test测量仪对旋转轴的运动精度进行了测量。此外,假设旋转轴位置几何误差和工作台上参考球的设置误差是影响测量结果的因素,并通过最小二乘法对这些因素进行分离。采用IBS公司的R-test测量仪,对米克朗公司UCP800Duro立式五轴加工中心C轴的运动误差和几何误差进行了测量实验。研究结果表明,该方法能够正确识别旋转轴的运动误差和几何误差,可以有效地综合评估旋转轴的运动精度,并有助于进一步提高旋转工作台的精度。

大行程位移台干涉测距系统的误差补偿

双频激光干涉仪作为常用的精密光学非接触式测量设备,具有精度高、抗干扰能力强、灵活性好等优点。然而环境温度变化、机械振动等因素可能会影响其测量结果的准确性,并且影响程度会随着测量光程的增加而增大。针对基于双频激光干涉仪的大行程位移台测距系统,首先研究了位移台测距系统的测量原理,然后针对系统存在的各项误差进行了分析和补偿,最后,对系统进行综合误差补偿实验,短时间补偿量达到10-8 m量级,且时间越长补偿效果越好。该方法较现有的误差补偿方法更为完整,补偿量更大。

Data processing and error analysis for the CE-1 Lunar microwave radiometer

The microwave radiometer （MRM） onboard the Chang＇ E-1 （CE-I） lu- nar orbiter is a 4-frequency microwave radiometer, and it is mainly used to obtain the brightness temperature （TB） of the lunar surface, from which the thickness, temperature, dielectric constant and other related properties of the lunar regolith can be derived. The working mode of the CE-1 MRM, the ground calibration （including the official calibration coefficients）, as well as the acquisition and processing of the raw data are introduced. Our data analysis shows that TB increases with increasing frequency, decreases towards the lunar poles and is significantly affected by solar illumination. Our analysis also reveals that the main uncertainty in TB comes from ground calibration.

结合模糊测试和动态分析的内存安全漏洞检测

C语言因其在运行速度及内存控制方面的优势而被广泛应用于系统软件和嵌入式软件的开发。指针的强大功能使得它可以直接对内存进行操作,然而C语言并未提供对内存安全性的检测,这就使得指针的使用会导致内存泄露、缓冲区溢出、多次释放等内存错误,有时这些错误还会造成系统崩溃或内部数据破坏等的致命伤害。当前已存在多种能够对C程序进行内存安全漏洞检测的技术。其中动态分析技术通过插桩源代码来实现对C程序的运行时内存安全检测,但是只有当程序执行到错误所在路径时才能发现错误,因此它依赖于程序的输入;而模糊测试是一种通过向程序提供输入并监视程序运行结果来发现软件漏洞的方法,但是无法检测出没有导致程序崩溃的内存安全性错误,也无法提供错误所在位置等详细信息。除此之外,由于C语言的语法比较复杂,在对一些大型复杂项目进行分析时,动态分析工具经常无法正确处理一些不常见的特定结构,导致插桩失败或者插桩后的程序无法被正确编译。针对上述问题,通过将动态分析技术与模糊测试技术结合,并对已有方法进行改进后,提出了一种能够对包含特定结构的C程序进行内存安全检测的方法。文中进行了可靠性和性能的实验,结果表明,在增加对C语言中特定结构的处理方法之后,能对包含C语言中特定结构的程序进行内存安全检测,并且结合模糊测试技术后具有更强的漏洞检测能力。

临近空间火箭探空温度传感器设计与分析

太阳辐射误差是30~60 km高度的临近空间火箭探空仪观测误差的主要来源。为了降低太阳辐射误差,设计了一种圆环状的镀银铝板防辐射罩。首先,使用计算流体动力学(CFD)计算出无防辐射罩的探头和有防辐射罩的探头在不同的海拔高度、气流速度、太阳高度角下的太阳辐射误差,并且进行数据对比分析。之后,利用支持向量机(SVM)算法训练出仿真结果并且得到相应的预测模型,可以得出预测值与仿真值之间的均方根是0.036 K,预测值与仿真值之间差值的绝对值在0.08 K以内。最后,使用低气压风洞和太阳模拟器作为实验平台模拟出高空环境,将实验结果与算法预测结果进行对比。得出实验值与预测值平均测量误差为0.096 K,均方根误差为0.097 K。

噪声比对测试误差值探讨

通过使用不同仪器对不同类型声源开展多次现场测试,研究分析不同仪器在不同工况下的误差值范围,以期为噪声现场比对测试、新仪器验收等提供参考和借鉴。研究表明,在40~80dB声级区间内,对同一噪声源,使用不同仪器在相对接近的同一测点进行同步监测时,95%的比对差值可控制在±1.0dB之间;超过90%的比对差值在±0.8 dB之间;超过85%的比对差值在±0.7dB之间。声源强度越大、测试时间越长,比对差值相对越小。

储罐自动化仪表计量误差在线识别方法研究

针对站场油气储罐计量仪表的检测误差,以现场366座储罐正常计量数据为基础,设置0.5%~2.5%的误差率,构建数据驱动方法数据集,综合考虑误报率和窗口大小(25~125),针对7类算法(WIN-G、WIN-M、WIN-L、RuLSIF、KL-CPD、VAE和LSTM-VAE)进行综合性能评价,用现场检测的误差数据和正常数据进行算法验证,结果表明:在窗口大小100的条件下,LSTM-VAE算法性能最佳,正确报警率高于0.95。

基于圆心搜索算法评定圆度误差

圆度是评定形状误差的主要几何量之一,圆度误差是评定产品加工质量的重要参数。本文提出了一种基于圆心搜索算法评定圆度误差的方法,应用最小二乘原则,详细阐述圆心搜索算法的计算过程与算法思路,并通过真实数据验证该算法的效果。基于接触式影像仪软件开发平台,利用C++语言设计出圆度误差评定软件,能够快速求出圆度误差值,为现场检测提供方便。

T型轨道检查仪轨距测量固有误差及其补偿(下)

T型铁路轨道检查仪为T形小车结构,在测量曲线轨距时,由于测量原理存在缺陷,测得的轨距中会引入固有误差(D值误差),导致“假轨距”问题。在分析轨距测量原理和D值误差,以及D值误差对轨距测量准确度影响的基础上,讨论短纵梁、线形参数补偿、增加轨距辅助测头等处理“假轨距”问题的常见方法,提出惯性轨迹补偿方法,并在试验线路上验证轨距补偿效果。结果表明,采用惯性轨迹补偿方法补偿后,T型铁路轨道检查仪测得的轨距更接近实际轨距,且满足TB/T 3147—2020《铁路轨道检查仪》要求,重复性和一致性优于轨距辅助测头补偿方法。基于2种补偿方法效果的分析,提出优化铁路轨道检查仪标准的相关建议。

T型铁路轨道检查仪轨距测量固有误差及其补偿(上)

T型铁路轨道检查仪为T形小车结构,在测量曲线轨距时,由于测量原理存在缺陷,测得的轨距中会引入固有误差(D值误差),导致“假轨距”问题。在分析轨距测量原理和D值误差,以及D值误差对轨距测量准确度影响的基础上,讨论短纵梁、线形参数补偿、增加轨距辅助测头等处理“假轨距”问题的常见方法,提出惯性轨迹补偿方法,并在试验线路上验证轨距补偿效果。结果表明,采用惯性轨迹补偿方法补偿后,T型铁路轨道检查仪测得的轨距更接近实际轨距,且满足TB/T3147—2020《铁路轨道检查仪》要求,重复性和一致性优于轨距辅助测头补偿方法。基于2种补偿方法效果的分析,提出优化铁路轨道检查仪标准的相关建议。

水表检定的台位差和表位差现象分析

根据测量理论,由于真值不可得,测量误差是不可消除的,两组测量结果之间存在差异不可避免。水表检定过程中产生台位差和表位差是不可避免的,台位差和表位差主要是两组不同测量所对应的测量设备、测量方法以及各种显性的和隐性的测量条件存在一定的差异所致。分析台位差和表位差是否具有显著性,需要确定一个合理的用于判定测量结果一致性的准则,然后再根据实验过程来分析查找导致不合理偏差产生的原因。当测量结果比较表明存在显著的台位差或表位差时,应结合经验进行具体的成因分析,并采取措施加以消除。

长度计量仪器测量过程中的误差控制探讨

在技术发展过程中,许多行业都需要开展长度计量工作,长度计量需求增加,市场上陆续出现了多种类型的长度计量仪器,这些仪器在长度计量工作中具有至关重要的作用。长度计量仪器在测量时经常出现误差,影响结果的可用性。为得到相对准确的计量结果,除了选择恰当的计量仪器,还要规范操作步骤。基于此,本文重点分析了长度计量仪器测量过程中的误差原因,提出了控制误差的有效策略,以期对实际工作具有指导价值。

彩色多普勒超声仪血液流速测量值误差不确定度的评定研究

目的综合评定彩色多普勒超声仪血液流速测量误差的不确定度。方法选取医院在用的10台彩色多普勒超声仪依据标准JJF1438-2013、JJF(皖)130-2022、JJF(冀)3028-2023中血液流速校准的方法和要求,识别彩色多普勒超声仪血液流速测量误差的不确定度来源,并从标准不确定度、合成标准不确定度和扩展不确定度的评定等方面对血液流速测量值误差不确定度进行综合考量。结果重复性测量引入的不确定度为0.45 cm/s,标准器引入的不确定度分别为0.58 cm/s(仿血流模体本身)和0.03 cm/s(温度23℃),多普勒角度选择引入的不确定度为0.35 cm/s,流量计不准引入的不确定度为0.72 cm/s,流量修正系数引入的标准不确定度为0.29 cm/s,脉冲多普勒(PW)探头测量流速分辨力的不确定度为0.045 cm/s,合成标准不确定度为1.1 cm/s,扩展不确定度为2.2 cm/s。结论选取的10台彩色多普勒超声仪血液流速的不确定度评定结果真实可靠,能够为临床患者定量评估浅表血管的供血状态提供精准测量数据,保证患者各项指标的精确度。