Propagation of Uncertainty Due to Non-linearity in Radiation Thermometers

The measurement of the non-linearity of radiation thermometers is important in the realization of ITS-90 above the silver point and in the calibration of primary or secondary radiation thermometers using multiple fixed points both above and below the silver point. A non-linearity function is usually derived, enabling correction of the measured signals. Uncertainties in this non-linearity function propagate to the uncertainty in the determination of an unknown temperature. Since the same non-linearity function is used both during calibration and in subsequent use of the thermometer, there is a high degree of correlation between the uncertainties in the corrected calibration signals and the corrected in-use signals. While these correlations obviously lead to zero uncertainty at the calibration points, it is difficult to determine the correlation coefficients for temperatures away from these points. This article sets out a mathematical framework, based on interpolation theory, for propagating the uncertainty due to non-linearity in which correlation is easily included. The method is illustrated for a thermometer realizing ITS-90 up to 3,000°C based on one fixed point (silver, gold, or copper), and also for alternative realization schemes based on two or more fixed points. The total non-linearity uncertainty for the multipoint schemes is considerably lower than for the ITS-90 method. The mathematical framework can also be applied to secondary calibrations below the silver point, where non-linearity is typically more problematic for the detectors used in this temperature range.     

滑动轴承油膜非线性动态特性的探讨

随着故障转子动力学理论研究的深入和故障诊断技术的发展,转子系统非线性振动的研究越来越重要,在给定输入的情况下,将滑动轴承特性视为“黑盒子”,以模式识别与参数估计的方法计算输出,基于系统识别和参数估计理论改进线性模型的刚度系数和阻尼系数,建立一种在线性模型基础上的改进模型,可以得到轴承特性较好的表征,对滑动轴承油膜非线性动态特性的深入研究作一探讨。     

压电陶瓷微位移器的非线性修正

针对压电陶瓷微位移器的非线性问题进行了深入的研究,提出了使用该方法可以将压电陶瓷微位器的非一性度从２５％降到４％,这是一种简单,方便,可靠,成本低的非线性补偿方法。文中对压电陶瓷位移器的非线性机理做了深入的研究,并给出一个基于ＩＢＭ４８６计算机与ＭＣＳ９８单片机以及测试试验台组成的一个完整的试验系统。