数字压力计标准装置的建立

按照弹簧管式精密压力表和真空表检定规程中给出的标准传递法,对压力表进行了测量,并根据不确定度评定方法,对压力表的测量结果进行了不确定度评定,完成了对数字压力计标准装置的建立.     

0.02级活塞式压力计示值误差测量结果的不确定度评定

本文主要介绍了0.02级活塞式压力计示值误差测量结果的不确定度评定方法。     

数字压力计测量不确定度评定的软件设计

用计算机VB语言来设计测量不确定度评定的程序,从具体评定数字压力计测量不确定度的例子着手,给出了计算机软件设计的思路和流程图。该软件可供使用人员进行测量不确定度的即时评定,从而提高工作效率。     

数字压力计示值误差测量值的不确定度评定

本文详细介绍了0.02级数字压力计示值误差测量结果的不确定度评定方法。     

活塞式压力计校准数字压力计的不确定度分析

以具体事例介绍了用活塞压力计校准数字压力计时,其校准结果的不确定度分析分析与评定过程,并给出其校准结果的扩展不确定度。     

0.05级数字压力计示值误差的测量值的不确定度评定

依据JJG875-2005《数字压力计》检定规程的要求,对0.05级数字压力计示值误差的测量值的不确定度进行评定。     

二等活塞压力计检定精密压力表测量结果的不确定度评定

本文分析了用二等活塞压力计检定精密压力表测量结果不确定度的来源,并对各项测量不确定度进行了评定,最后给出了10MPa点测量结果的扩展不确定度.     

数字压力计测量值的不确定度评定

介绍了应用活塞式压力计检定数字压力计的测量值的不确定度的评定方法。     

基于函数表达的数字压力计CMC表示方式的探讨

通过对3例不同测量范围的数字压力计校准结果的测量不确定度评定,计算出一系列扩展不确定度数值和测量压力数值,并利用Excel软件进行最小二乘法的直线拟合,得到一个关于压力测量值和数字压力计分辨力的线性函数表达式。经过分析评估,该线性函数可以较好地表示数字压力计整个测量范围的CMC,解决了数字压力计CMC无法恰当表示的难题。     

0.05级数字压力计标准装置不确定度评定

介绍了应用数字压力计检定精密压力表及普通压力表的测量值的不确定度的评定方法。     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Numerical study of methods of linearization of the output characteristics of radio-frequency sensors of the level of dielectric media

Different constructions of the sensing elements of radio-frequency level sensors based on sections of long lines are numerically investigated by means of the Matlab program for the purpose of minimizing the measurement error caused by the nonlinearity of the output characteristic. It is shown that the nonlinearity is lowest for U-shaped designs. The nonlinearity factor KN may be regulated by varying the capacitance of a correcting capacitor connected to the input of the sensing element and (or) the length of one of the sections of the long line. In selecting an optimal capacitance of the correcting capacitor KN ≤ 0.15% for control media with dielectric permittivity in the range 2.2–30.     

Possibilities of Decreasing the Errors of Determination of the Height of the Pole of a Sessile Drop of Melt

We analyze the possibilities of decreasing the errors of measuring the height of the pole of a sessile drop of melt above its equator by determining the position of the equator according to the midpoints of vertical chords of the image of the drop. The optimal distance between these chords and the edge of the image of the drop is chosen within 10–20% of the radius of the equator. The proposed method guarantees the same level of errors of evaluation of the height of the pole and the radius of the equator, which enables one to substantially increase the accuracy of evaluation of the capillary constant and the surface energy of the melt according to the geometric parameters of the sessile drop.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Estimation of potentialities of methods of summation of direct measurement errors

Conventional methods for summation of direct measurement errors are considered. Conditions under which these methods provide consistent results are stated. It is proposed to utilize for characteristic of the total error, its interval estimator or the half-sum of the value obtained by adding up its arithmetic and geometric random errors.Translated from Izmeritel'naya Tekhnika, No. 4, pp. 10–12, April, 1995.