砝码质量测量中的空气密度测量装置的研究

按照砝码质量测量时对空气密度测量的需求,分析了测量空气密度的公式法,研制了用于高准确度砝码质量测量的空气密度测量装置。根据CIPM-2007公式,该装置集成了温湿度、压力和CO2含量的测量,实现了对空气密度的自动实时测量。实验结果表明,当CO2含量达到937.4×10^-6时,与采用近似公式进行测量的数据的相对误差达到0.022%,验证了增加CO2含量测量对提高空气密度测量准确度的必要性。     

液体表面张力对静力称量法固体密度测量的影响

液体静力称量法是固体密度测量最常用也是测量准确度较高的一种方法。基于阿基米德原理,研究了表面张力对固体密度测量结果的影响。实验选取纯水和纯酒精2种液体作为工作介质,采用一套高准确度液体静力称量装置测量同一固体样品的密度值。实验结果表明,在表面张力小的液体（纯酒精）中固体样品密度测量结果的分散性明显优于在表面张力大的液体（纯水）中固体样品密度测量结果的分散性,为今后提高固体密度测量准确度提供参考方向。     

A new method of measurement of the different types of noisealtering the output signal of oscillators

Oscillator noise is generally modeled by a power law spectral density. Thus it is possible to characterize different noise sources, each of them corresponding to a particular power law. The measurement of the contribution of these sources is necessary to know their origin and to remedy these causes in order to improve oscillator performance. Usually, an estimation of the different types of noise present in a signal is obtained by using a variance. However, the sensitivity of these variances differs for each type of noise and then limits this method. On the other hand, the use of several variances, each of them more sensitive to one type of noise, permits one to notably improve the measurement accuracy. The method suggested here uses as many different variances as there are types of noise to measure. The improvement of measurement accuracy of the noise coefficient is discussed in this paper     

Routine Part-per-Million Mass Accuracy for High- Mass Ions: Space-Charge Effects in MALDI FT-ICR

The effect of ion space-charge on mass accuracy in Fourier transform ion cyclotron resonance mass spectrometry is examined. Matrix-assisted laser desorption/ionization is used to form a population of high-molecular-weight polymer ions with a wide mass distribution. The density of the ions in the analyzer cell is varied using ion remeasurement and suspended trapping techniques to allow the effect of ion space charge to be examined independently of other experimental influences. Observed cyclotron frequency exhibits a linear correlation with ion population. Mass errors of 100 ppm or more in externally calibrated mass spectra result when ion number is not taken into account. By matching the total ion intensities of calibrant and analyte mass spectra, the protonated ion of insulin B-chain, 3494.6513 Da, is measured with an accuracy of 0.07 ppm (average of 10 measurements, σ = 2.3 ppm, average absolute error 1.6 ppm) using a polymer sample as an external calibrant. Alternatively, the correction for space charge can be made by using a calibration equation that accounts for the total ion intensity of the mass spectrum. A calibration procedure is proposed and is tested with the measurement of the mass of insulin B-chain. A mass accuracy of 2.0 ppm (average of 20 measurements, σ = 4.2 ppm, average absolute error 3.5 ppm) is achieved. Space-charge-induced mass errors are more significant for samples with many components, such as a polymer, than for single-component samples such as purified peptides or proteins.     

A study on an online measurement method to determine the oil discharge ratio by utilizing Coriolis mass flow meter in a calorimeter

In this paper, an online measurement method of oil discharge ratio (ODR) is experimentally investigated based on a compressor calorimeter with the Coriolis mass flowmeter (CMF). In this method, the oil concentration is determined by a linear mixing law of the specific volume model using the density of the refrigerant, oil and refrigerant-oil mixture obtained by CMF. During the testing, the light absorption method is also conducted simultaneously for the comparison. The results indicate that the presented CMF based density method has an average relative deviation of 4.28%. The accuracy of the CMF based density method is superior to the light absorption method, which has the relative deviation of −8∼23% compared with the standard sampling method. The presented CMF-based method can be expected to be used for future ODR measurement due to its non-sampling, online, and accurate features.     

A method for correcting radial distortion based on verifying the planarity of specimens

Image distortion is inevitable when an image is captured through a lens. While the digital image measurement technique is getting popular, image distortion problem can result in significant error. A new distortion correction method is proposed in this study. The proposed method is based on the fact that a flat surface should keep flat when it is measured using three-dimensional (3D) digital image measurement technique. The 3D digital image measurement technique adopted in this research is the simplified 3D digital image correlation (DIC) method. Because radial distortion has a more noticeable influence than other types of distortions, this method deals only with radial distortion. A few experiments are carried out in this study to verify the correctness of this method and its accuracy. Both simulated data and actual image data are adopted in these experiments. The results show that this method can achieve a good accuracy. The standard deviations caused by random errors are about the same order as the random errors. It also shows that this method is suitable for both large and small distortion conditions.     

Photoreceptor counting and montaging of en-face retinal images from an adaptive optics fundus camera

A fast and efficient method for quantifying photoreceptor density in images obtained with an en-face flood-illuminated adaptive optics (AO) imaging system is described. To improve accuracy of cone counting, en-face images are analyzed over extended areas. This is achieved with two separate semiautomated algorithms: (1) a montaging algorithm that joins retinal images with overlapping common features without edge effects and (2) a cone density measurement algorithm that counts the individual cones in the montaged image. The accuracy of the cone density measurement algorithm is high, with >97% agreement for a simulated retinal image (of known density, with low contrast) and for AO images from normal eyes when compared with previously reported histological data. Our algorithms do not require spatial regularity in cone packing and are, therefore, useful for counting cones in diseased retinas, as demonstrated for eyes with Stargardt's macular dystrophy and retinitis pigmentosa.     

基于强震观测和ARMAV模型的混凝土坝模态识别

采用混凝土坝的实测振动响应识别结构模态参数是进行结构动力特性研究的一种可行的方式。基于混凝土坝的强震观测数据,提出采用矢量自回归滑动平均模型(Auto-Regressive Moving Average Vector,ARMAV)和稳态图法来进行混凝土坝结构模态参数识别。研究了结构实测振动响应时间序列的ARMAV模型表达形式,并通过引入辅助变量(Instrumental Variable,IV)技术,来求解模型中的未知系数;通过研究ARMAV模型系数矩阵与结构系统矩阵的关系,以便为结构模态识别提供理论依据;根据综合了各测点观测信息的平均标准化功率谱(Average Normalized Power Spectrum Density,ANPSD)来对传统的稳态图法进行改进,以实现强震激励下混凝土坝的系统定阶和虚假模态剔除。通过一个数值算例和一个工程实例,验证了提出的基于强震观测和ARMAV模型的结构模态参数识别方法的精度、有效性和工程适用性。     

冷轧带钢板形分段接触式检测过程的力学建模与仿真

建立了冷轧带钢板形应力分段接触式检测过程的ANSYS有限元模型,引入欧式距离方法表征检测误差,分析了在不同板形缺陷模式下,板形辊弯曲变形、板形辊分段区域宽度、板形辊直径、带钢包角、带钢厚度、卷取张力、带钢张力横向分布不对度等因素对板形检测精度的影响。仿真结果表明：随着板形辊弯曲变形程度的增大,板形应力检测精度大幅度降低。随着板形辊分段区域宽度的增大,板形检测精度大幅度降低;而随着板形辊分段区域宽度的减小,板形检测精度提高,但提高的幅度随着分段区域宽度的减小而越来越小。卷取工艺张力越低,板形检测精度越低;且当卷取张力增大到某一值时,再继续增大卷取张力对板形检测精度影响甚小。随着卷取张力横向分布不对称度的增大,板形检测精度降低。板形检测辊直径大小、带钢包角的变化以及带钢厚度的变化对板形检测精度没有影响。     

The efficiency of methods for measuring A/D converter linearity

In this paper, the efficiency of three methods commonly used to measure the linearity characteristics of precision Nyquist-rate analog-to-digital (A/D) converters is evaluated. The efficiency of each method, which is determined by the time required to obtain linearity estimates at a specified level of accuracy, is compared to the maximum efficiency that is theoretically achievable, as given by the Cramer-Rao bound. Simulation results are presented for two open-loop measurement methods, the tally and weight method and the code density method, demonstrating that the code density method obtains an efficiency close to the theoretical optimum over a wide range of measurement times and converter noise levels, whereas the tally and weight method falls short of the optimum for converters with noise levels exceeding ¼ LSB. The efficiency of the servo loop method, a common closed-loop method for measuring linearity, is similarly evaluated, and is found to fall short of the maximum efficiency that is theoretically achievable in the closed-loop configuration. A modified closed-loop measurement method is described that obtains an efficiency close to the theoretical optimum through the use of maximum-likelihood estimation     

基于相关函数矩阵及卷积神经网络的结构健康监测研究

环境激励下利用时域振动响应构建的内积矩阵是结构健康监测中一种较好的结构特征参数。为了提升结构健康监测方法的识别准确率,构建内积矩阵时往往需要较多的振动响应测点,这将直接影响方法的工程实用性。该文基于时域振动响应的相关性分析理论,将内积矩阵扩展到了相关函数矩阵,实现从少量的振动响应测点中获取更多的结构健康特征信息,以降低结构健康监测方法对测点数量的需求。进一步结合卷积神经网络优异的数据特征提取能力,以相关函数矩阵为输入、结构健康状态为输出,提出了基于相关函数矩阵及卷积神经网络的结构健康监测方法。典型航空加筋壁板螺栓松动监测的实验研究结果表明,仅采用结构上任意2个测点的时域振动响应,该文方法针对螺栓松动位置的识别准确率可达99%以上。     

Precision measurement and compensation of kinematic errors for industrial robots using artifact and machine learning

Industrial robots are widely used in various areas owing to their greater degrees of freedom (DOFs) and larger operation space compared with traditional frame movement systems involving sliding and rotational stages. However, the geometrical transfer of joint kinematic errors and the relatively weak rigidity of industrial robots compared with frame movement systems decrease their absolute kinematic accuracy, thereby limiting their further application in ultraprecision manufacturing. This imposes a stringent requirement for improving the absolute kinematic accuracy of industrial robots in terms of the position and orientation of the robot arm end. Current measurement and compensation methods for industrial robots either require expensive measuring systems, producing positioning or orientation errors, or offer low measurement accuracy. Herein, a kinematic calibration method for an industrial robot using an artifact with a hybrid spherical and ellipsoid surface is proposed. A system with submicrometric precision for measuring the position and orientation of the robot arm end is developed using laser displacement sensors. Subsequently, a novel kinematic error compensating method involving both a residual learning algorithm and a neural network is proposed to compensate for nonlinear errors. A six-layer recurrent neural network (RNN) is designed to compensate for the kinematic nonlinear errors of a six-DOF industrial robot. The results validate the feasibility of the proposed method for measuring the kinematic errors of industrial robots, and the compensation method based on the RNN improves the accuracy via parameter fitting. Experimental studies show that the measuring system and compensation method can reduce motion errors by more than 30%. The present study provides a feasible and economic approach for measuring and improving the motion accuracy of an industrial robot at the submicrometric measurement level.The full text can be downloaded at https://link.springer.com/article/10.1007/s40436-022-00400-6     

一种基于法布里-珀罗干涉仪的位移测量方法

介绍了一种基于法布里-珀罗干涉仪的位移测量方法,为了克服通常的法布里-珀罗干涉仪在位移测量范围方面的局限,采用两束可调激光分别对法布里-珀罗腔的两个相邻谐振峰的光频率进行追踪测量,能够得到任意时刻法布里-珀罗腔的长度,从而实现对测量镜位移的测量,测量范围可以达到毫米量级。对影响测量精度的主要因素进行了简要分析,结果表明采用本方法能够实现纳米级精度位移测量。     

Processing the Results of Measurements by Approximating the Distribution Density with Smoothing Cubic B-Splines

A method is developed for processing the results of measurements from a small sample utilizing the apparatus of normalized smoothing cubic B-splines. The choice of the spline mesh spacing providing a solution of the smoothing problem with a specified accuracy is justified. Analytical expressions are obtained for the probability distribution density and the numerical characteristics of the measurement results.     

部分编码结构光三维测量技术的研究

提出了一种部分编码结构光三维面形测量方法,将相位展开技术与条纹编码结合起来,既有效地减少了投影和拍摄的图像数量又提高了相位展开的可靠性.该方法利用部分编码技术对相邻的多根条纹进行整合,减小了条纹密度,然后再对整合后的条纹相位进行展开,最终得到整个图像的相位分布.实验证明,该方法可以较大程度地减少重建所需的画幅数,同时具有良好的精度和可靠性.     

Broad-band characterization of magnetic and dielectric thin filmsusing a microstrip line

A measurement method for the broad-band determination (100 MHz-10 GHz) of the permeability and permittivity of thin films with thicknesses of 1-10 μm has been developed. The technique is based on the measurement of the S parameters of a microstrip line loaded with the test sample. The S parameters are measured with a network analyzer. Besides its band width, the original feature of this method in comparison with existing techniques lies in the fact that the thin film does not entirely fill the cross section of the cell since it is directly laid on the substrate of the microstrip line. This leads to a simple and reproducible measurement process. It also permits the propagation of the electromagnetic wave along the film width of about a few millimeters, thus increasing the measurement accuracy. Moreover the method remains reliable for the characterization of bulk materials with the same cell and data processing program     

Displacement vector measurement using instantaneous ultrasound signal phase - multidimensional autocorrelation and doppler methods

Two new methods of measuring a multidimensional displacement vector using an instantaneous ultrasound signal phase are described, i.e., the multidimensional autocorrelation method (MAM) and multidimensional Doppler method (MDM). A high measurement accuracy is achieved by combining either method with the lateral Gaussian envelope cosine modulation method (LGECMM) or multidirectional synthetic aperture method (MDSAM). Measurement accuracy is evaluated using simulated noisy echo data. Both methods yield accurate measurements comparable to that of our previously developed cross-spectrum phase gradient method (MCSPGM); however, they require less computational time (the order, MDM < MAM approximate, equals MCSPGM) and would provide realtime measurements. Moreover, comparisons of LGECMM and MDSAM performed by geometrical evaluations clarifies that LGECMM has potentials to yield more accurate measurements with less computational time. Both MAM and MDM can be applied to the measurement of tissue strain, blood flow, sonar data, and other target motions.     

Dielectric Measurements of Sheet Materials

A simple method of determining the dielectric constant of sheet materials is described. For lossless and low-loss materials, the dielectric constant may be evaluated by a simple measurement of the guide wavelength in the presence of the dielectric. Since the latter measurement can be made accurately using simple standard equipment, the method gives good results. For medium or high-loss materials, it is necessary to measure the attenuation as well and solve a transcendental equation. However, the simplicity and the greater accuracy possible in the physical measurements make this method more accurate than previous methods.     

Z型多声道超声波流量计常见故障分析.docx

随着对流体的测量准确度、稳定性、适用性的要越来越高，如今多声道超声波流量计得到了广泛使用，因此在流量计运行过程中会遇到不同的异常故障，本文针对我厂近期出现长期负流量、声道信号消失、显示流量异常波动三次故障作出了专门的分析，通过这三次故障的分析，将流量计故障检查方向基本全部涵盖，希望能够有助于大家解决日常中遇到的相似问题。