Wear Measurement and Assessment of Explanted Cross-Linked PE Acetabular Cups Using a CMM

Wear has been considered the main limiting factor in the longevity of hip replacements. Wear analysis is thus essential for determining wear-related failure mechanisms and prediction of wear, which will consequently enable biomedical engineers to improve the design, material, and service life of the bearing components. This article presents wear measurement and assessment of the explanted conventional cross-linked polyethylene (XPE) and second-generation highly cross-linked polyethylene cups (X3) using a coordinate measuring machine (CMM). An expanded uncertainty analysis was performed to assess the performance of wear measurement. Wear measurement using the CMM method was validated with the gravimetric technique. The normalized error between volumetric wear measurement of the CMM method and that of the gravimetric technique was estimated to be always less than 1, suggesting that the CMM method applied to explanted hip wear measurements under the specific conditions was accurate and reliable. The approach to CMM measurement with uncertainty analysis was shown not only to locate 3D wear scar and wear direction but also to accurately quantify linear and volumetric wear with a maximum volumetric uncertainty of ±3.15 mm³ (95% confidence level). It is shown that identifying the key uncertainty components involved in the measurement process including validation, which contributes to an overall expanded uncertainty budget, is crucial to improve the confidence and the reliability of hip wear measurement results using a CMM.     

Traceability and uncertainty analysis in volume measurements

Laboratories must ensure that obtained results are reliable, for that it is necessary to calibrate glassware and proving tanks using the correct method and estimate of uncertainties. The aim of this work is to present the gravimetric method as a suitable and traceable method to calibrate glassware according to laboratory requirements. Moreover, the model for the calculation of the measurement uncertainty is described and it is proved to be completely suitable for the calibration by gravimetric method through a numerical example drawn from the INRIM uncertainty budget in the CCM.FF-K4 key comparison.     

The uncertainty of torque primary standards: a comprehensive analysis

The development of high-accuracy torque primary standards constitutes the first step towards the harmonisation of the unit of measurement and the realisation of a reliable traceability chain for torque transducers, torque wrenches and screwdrivers. In this paper, a detailed analysis of the uncertainty budget of torque primary standards is proposed. On the basis of the characteristics of the realisations set up by some of the European National Metrological Institutes, as they are available in the literature, the order of magnitude of the uncertainty such systems can achieve is derived. To this extent, attention has been focused on the main questions in the design and in carrying out the measurement of the quantities that determine the main contributions to the uncertainty. Particularly, from the latter point of view, an investigation on the measurement of the friction torque, which is responsible for the degradation of the metrological performances in the lower part of the working range, has been performed.     

Critical aspects of the uncertainty budget in the gravimetric PM measurements

The interest in particulate matter (PM) exposure studies leaded the regulatory authorities and the air quality management community in updating new air quality standards. In order to characterize the current exposure experienced by people, measurement should be carried out also taking into account periodic PM concentration fluctuations. For this purpose continuous or semi-continuous measurement techniques were developed even if the reference method used to measure the air quality standards is still based on the gravimetric analysis of particle collected through filtration technique over a period of 24 h.In this work the authors carried out a metrological characterization of the gravimetric method in measuring PM concentrations. The critical aspects of the technical standard in evaluating the uncertainty budget of PM measurement are stressed and the influence of single uncertainty contributions to the combined uncertainty is also shown. Finally, a comparison between European and US standards in PM measurement is made.     

三坐标机测量齿轮齿廓的不确定度评价

介绍了坐标测量中几种常用的不确定度评价方法.指出传统的三坐标测量机的测量不确定度评价方法大都不适用于评价坐标测量中面向对象的测量不确定度,并对使用蒙特卡洛方法评价测量不确定度进行了研究.首先,根据三坐标测量机详细标定文件及补偿策略说明建立测量模型.然后,将测量中的采样点通过测量模型生成大量测量结果,并以此评价测量不确定度.在齿廓评价实验中,评定齿廓误差的测量不确定度为0.96 μm时,多次评价结果之间的最大差值不超过0.03 μm,具有可靠的理论依据和较稳定的评定结果.文章指出,目前商用三坐标测量机大都不能为特定的测量对象提供测量不确定度报告,使用蒙特卡洛方法有希望改变此现状.     

Metrological evaluation of skin conductance measurements

Electrodermal activity is a frequently measured physiological response in various applications. It is also being increasingly used in clinical applications. Numerous published papers report results of skin conductance measurements in absolute values, but few are concerned with the quality of results. This paper describes a procedure for metrological evaluation of skin conductance measurement. Three commercial devices for measuring skin conductance were calibrated by comparison with a precision digital ohmmeter used as a reference. Combined measurement uncertainty of skin conductance meters was calculated by means of uncertainty of reference instrument and uncertainties due to measurement repeatability, reproducibility, resolution and environmental condition. Additionally, a procedure for evaluation of the effect of electrode displacement and electrode gel was shown. A model of finger skin conductance profile was build. Measurement uncertainty analysis showed that contributions due to resolution and sensitivity of the measuring device, usually obtained from specifications, are negligible when compared to uncertainty of measuring method. Our results indicate that measurement uncertainty does not meet target uncertainty requirements for certain applications.     

Integration of a laser interferometer and a CMM into a measurement system for measuring internal dimensions

In order to improve the existing comparative procedure for calibrating internal dimensions, we have developed a new measurement set-up for traceable absolute measurements. It consists of a co-ordinate measuring machine (CMM) and a laser interferometer (LI). The LI serves as a traceable measurement system, while the CMM is only used as a guiding system for the measuring probe. Extended research focused on defining probe parameters such as diameter, bending and indentation, as well as probing head repeatability and other error sources. The final goal of the research was to determine uncertainty of measurement under existing laboratory conditions. The main outcomes of the research and final uncertainty of measurement are presented in this article.     

Prediction of data variability in hand-arm vibration measurements

The long-term exposure to vibrations transmitted to the human upper limb by hand-held powered tools leads to a group of diseases commonly known as hand-arm vibration (HAV) syndrome. The risk deriving from the vibration exposure can be assessed with direct measurements, using data declared by the tool manufacturer or by retrieving measurements from specific databases. The discrepancies between data belonging to each of these three groups were evidenced in several studies. This paper analyzes the causes of the HAV measurements variability following the ISO GUM approach. The work process was modeled with a lumped parameter scheme of the tool-operator-measurement chain interactions. The measurement uncertainty has been identified propagating the uncertainties of the influencing parameters through the model. The soundness of the approach was verified by comparing the predicted and the observed variability in a specific case study. The major outcome of the proposed method is that the uncertainty budget allows understanding which parameters have to be controlled to limit data dispersion.     

Uncertainty evaluation associated with versatile automated gauging influenced by process variations through design of experiments approach

Recent advances in versatile automated gauging have enabled accurate geometric tolerance assessment on the shop floor. This paper is concerned with the uncertainty evaluation associated with comparative coordinate measurement using the design of experiments (DOE) approach. It employs the Renishaw Equator which is a software-driven comparative gauge based on the traditional comparison of production parts to a reference master part. The fixturing requirement of each production part to the master part is approximately ±1 mm for a comparison process with an uncertainty of ±2 μm. Therefore, a number of experimental designs are applied with the main focus on the influence of part misalignment from rotation between master and measure coordinate frames on the comparator measurement uncertainty. Other factors considered include measurement mode mainly in scanning and touch-trigger probing (TTP) and alignment procedure used to establish the coordinate reference frame (CRF) with respect to the number of contact points used for each geometric feature measured. The measurement uncertainty analysis of the comparator technique used by the Equator gauge commences with a simple measurement task using a gauge block to evaluate the three-dimensional (3D) uncertainty of length comparative coordinate measurement influenced by an offset by tilt in one direction (two-dimensional angular misalignment). Then, a specific manufactured measurement object is employed so that the comparator measurement uncertainty can be assessed for numerous measurement tasks within a satisfactory range of the working volume of the versatile gauge. Furthermore, in the second case study, different types of part misalignment including both 2D and 3D angular misalignments are applied. The time required for managing the re-mastering process is also examined. A task specific uncertainty evaluation is completed using DOE. Also, investigating the effects of process variations that might be experienced by such a device in workshop environments. It is shown that the comparator measurement uncertainties obtained by all the experiments agree with system features under specified conditions. It is also demonstrated that when the specified conditions are exceeded, the comparator measurement uncertainty is associated with the measurement task, the measurement strategy used, the feature size, and the magnitude and direction of offset angles in relation to the reference axes of the machine. In particular, departures from the specified part fixturing requirement of Equator have a more significant effect on the uncertainty of length measurement in comparator mode and a less significant effect on the diameter measurement uncertainty for the specific Equator and test conditions.     

平面度坐标测量的不确定度计算

目前的坐标测量只是给出平面度最小二乘检验的结果,并没有给出检验结果的不确定度.根据平面度最小二乘检验的基本原理和ISO/TS 14253-2给出的不确定度传递公式,提出了一种平面度坐标测量的不确定度的计算方法.该方法的特点是将平面方程的系数看作一个随机向量,通过计算该随机向量的均值和协方差矩阵来确定平面方程和平面度的检验结果及其不确定度.这不仅保证了平面度检验结果的完整性,而且符合新一代产品几何规范(GPS)标准的要求,从而可以提高工件检验的准确性.实验结果表明,根据平面度最小二乘检验的结果及其不确定度,可以根据ISO 14253-1给出的判定原则定量地判定平面是否合格.     

A computer simulation platform for the estimation of measurement uncertainties in dimensional X-ray computed tomography

The knowledge of measurement uncertainty is of great importance in conformance testing in production. The tolerance limit for production must be reduced by the amounts of measurement uncertainty to ensure that the parts are in fact within the tolerance. Over the last 5 years, industrial X-ray computed tomography (CT) has become an important technology for dimensional quality control. In this paper a computer simulation platform is presented which is able to investigate error sources in dimensional CT measurements. The typical workflow in industrial CT metrology is described and methods for estimating measurement uncertainties are briefly discussed. As we will show, the developed virtual CT (VCT) simulator can be adapted to various scanner systems, providing realistic CT data. Using the Monte Carlo method (MCM), measurement uncertainties for a given measuring task can be estimated, taking into account the main error sources for the measurement. This method has the potential to deal with all kinds of systematic and random errors that influence a dimensional CT measurement. A case study demonstrates the practical application of the VCT simulator using numerically generated CT data and statistical evaluation methods.     

LNG energy transfer uncertainty–sensitivity to composition and temperature changes

Determining and reducing the measurement uncertainty of LNG energy transfer in custody transfer operations is considered extremely important and challenging for industry. The European Metrology Research Programme (EMRP) for Liquefied Natural Gas (LNG) has been focused on reducing the uncertainty in the evaluation of LNG energy transfers by improving existing measurement methods, validating new measurement methods and development of new traceable calibration systems. Part of this project was to produce realistic measurement uncertainty budgets and to determine the sensitivity of the overall LNG energy transfer uncertainty to changes in the composition and temperature of different LNG cargoes.This paper provides details on the development of an uncertainty budget and the results from the sensitivity study. It was found that the uncertainty in the LNG energy transfer ranged from 0.56% to 0.77% when using the uncertainty budget for 461 LNG cargoes. The variation was mainly due to the difference in the LNG composition and its associated uncertainty.     

液相色谱-同位素稀释质谱法测定血清生长激素

复杂基质中低丰度蛋白质的准确定量分析一直是蛋白质研究的重点和难点。随着质谱技术的飞速发展,同位素稀释质谱法成为血清中低丰度蛋白质准确定量分析的重要方法。本研究以同位素标记的人生长激素为内标,通过C12和C4色谱柱两次分离收集目标馏分,建立了基于离线二维高效液相色谱分离血清样本的新方法。然后,结合高效液相色谱 同位素稀释质谱法,准确定量了人血清低丰度蛋白质生长激素的含量。通过对模拟样品（空白血清添加已知质量生长激素标准物质,理论含量为12.00 ng/g）和国际比对样品中生长激素（浓度未知）的测量及不确定度计算,定量结果分别为（11.45±2.33） ng/g和（12.84±1.46） ng/g。该方法准确性高、重复性好,为复杂基质低丰度蛋白质的准确定量分析提供了一种有效的测量方法和可溯源的分析结果。     

基于通用Dombi算子的测量不确定 度传递方法研究*

随机模糊变量RFVs法是近年来提出的一种基于可能性理论的测量不确定度评定和表示方法。RFVs法应用t-范数传递不确定度随机分量,是传统概率论方法的近似。针对Frank t-范数传递多个随机分量时近似误差累积变大的问题,提出使用二参数通用Dombi算子传递随机分量。首先简单介绍了RFVs的含义;然后说明了最优t-范数及其参数的选择方法,得到了GDO的最优参数,并用于获得联合可能性分布,结果表明GDO对于合成随机分量有很大改善;最后将GDO用于有功功率测量不确定度评定,并与Frank t-范数、传统GUM法和实验数据比较,使用GDO得到的置信区间能够很好地近似传统GUM法和实验数据分析结果。具有2个参数的GDO具有更大的灵活性,可以在传递多个不确定度随机分量的情况下获得满意的结果。     

Evaluating a task-specific measurement uncertainty for gear measuring instruments via Monte Carlo simulation

Evaluating the measurement uncertainty for gears with analytical or experimental methods is usually very time- and cost-consuming. In this paper we therefore present a Monte Carlo based method for evaluating the measurement uncertainty of gear measurements on gear measuring instruments, the VCMM-Gear, which is based on the method of the VCMM for coordinate measuring machines. Necessary extensions of the mathematical model of the measurement process in order to consider the significant uncertainty influences from rotary tables, workpiece clamping and scanning are described. Additionally the statistical reliability of the evaluated measurement uncertainty and the consideration of systematic error contributions to the measurement uncertainty are discussed. Finally the results of some first verification measurements are presented, giving a reliable impression of the capability and suitability of the VCMM-Gear.     

Possibilities for minimising uncertainty of dissimilar materials gauge blocks calibration by mechanical comparison

Mechanical comparison calibration of gauge blocks with dissimilar materials at the highest level is not wide spread because bigger national laboratories tend to calibrate non-steel gauge blocks with reference gauge block of like material. For smaller laboratories this is not viable economically due to the high costs of reference gauge block sets. Therefore, steel reference sets are used for calibrating gauge blocks from other materials. Lack of knowledge about material properties is causing a significant rise in calibration uncertainty. In order to improve best measurement capabilities, we have performed extensive research on gauge block material behaviour. For this purpose we have bought sample gauge blocks from all leading producers and evaluated their influences on the uncertainty budget, based on experimental measurements.The uncertainty budget of gauge blocks with dissimilar materials mechanical calibration, as well as the results of analytical and experimental research, is presented in this paper in detail. Significantly smaller uncertainty of gauge block calibration of dissimilar materials is achieved.     

A novel measurement method for transient detection based in wavelets entropy and the spectral kurtosis: An application to vibrations and acoustic emission signals from termite activity

This paper presents a novel non-destructive method for termite detection that uses the entropy of the continuous wavelet transform of the acoustic emission signals as an uncertainty measurement, to achieve selective frequency separation in complex impulsive-like noisy scenarios, with the aid of the spectral kurtosis as a validating tool. The goal consists of detecting relevant frequencies, by looking up the minima in the curve associated to the entropy of the difference between the raw data and the wavelet-based reconstructed version. By measuring the signal’s uncertainty, the scales corresponding to the entropy minima, or pseudo-frequencies, manage to target three main types of emissions generated by termites: the modulating components (enveloping curve), the carrier signals (activity, feeding and excavating), and the communicating impulses bursts (alarms). The spectral kurtosis corroborates the location of the entropy minima (optimum uncertainty) matching them to its maxima, associated to frequencies with the highest amplitude variability, and consequently minimizing the measurement uncertainty. The method is primarily conceived to cover the acoustic-range, in order to acquire signals via standard sound cards; a broaden high-frequency study is developed for the assessment, and with the added value of discovering new and higher frequency components of the species emissions. The potential of the method makes it useful for myriads of applications in the frame of nondestructive transient detection.     

基于QMC的齿轮测量中心测量不确定度评定方法

为评定齿轮测量中心测量不确定度,提出了一种基于拟蒙特卡罗法(quasi Monte-Carlo method,QMC)的齿轮测量不确定度评定方法。研究了齿轮测量中心的几何误差源,应用坐标变换法建立了齿轮测量中心精密测量模型,采用拟蒙特卡罗仿真法对齿轮测量中心测量不确定度进行了评定,并分析了评定的稳定性。评定实验表明,该方法可准确评定齿轮测量中心测量不确定度,评定结果最大偏差为2.35%,评定方法稳定。     

面向IP模式测控系统的PLSR-SBR双层压缩

针对以太网测控网络存在数据冲突导致系统实时性、可靠性降低问题,提出了基于偏最小二乘回归(PLSR)SBR的双层压缩方法。第一层建立主参量与所有辅助参量的确定模型,利用压缩有效性指标确定主成分,完成主参量的信息压缩。第二层基于改进的SBR,通过选取辅助参量中的基础序列,建立基础信号;在满足拟合误差条件下,逐步将每一个辅助参量序列映射到基础信号上,完成对辅助参量的数据压缩。该方法重点解决辅助参量和主参量中的解释潜变量和反映潜变量相关程度最大、基础信号由最少基础序列组成、辅助参量实现最小变长分解个数及基础信号独立更新原则等关键问题。最后将该方法应用于IP模式乙醇浓度测控系统。实验结果表明,在IP模式测控系统同时具有主参量和辅助参量,且不同参量间存在相关性时,该方法可在允许拟合相对误差为5%的情况下,使压缩率达到68%以上,从而有效地降低以太网测控网络数据冲突程度。