Precision enhancement in 8 mm interferometry

A Q band interferometer for determining the complex permittivity of materials having dielectric loss factor within 10^–3 to 1, has been developed. The technique involves the use of a computer-assisted digital voltmeter for data acquisition and treatment. The method of computing the dielectric parameters from the deduced VSWR and minima displacement is outlined and precision increase with this type of measurement is discussed. Results for polar solutes in non polar and in polar solvants are presented. Measurements on solids within the temperature range 20–400°C are also discussed in conclusion.     

A set of procedures making real arithmetic of unlimited accuracy possible within ALGOL 60

The facilities to perform floating point arithmetic of unlimited accuracy and to continuously control the round-off error are often found desirable. The paper describes how the authors have implemented this feature using the ALGOL 60 procedure concept.     

Measurement uncertainty in water microbiology may not estimate the laboratory’s precision

It has been proposed that microbiology laboratories introduce a measurement uncertainty for organism counts. Suggested methods of achieving this involve studying replicate counts from subsamples. This will overwhelmingly estimate the natural variation in numbers of organisms present in different subsamples, and the different characteristics of strains of organisms within the species or group (e.g. the coliform bacteria) being counted. Thus any measure of the laboratorys competence, in terms of precision, will be masked. In chemistry there is likely to be much more complete homogeneity of an analyte in a test material and these replicate measures will illustrate whether the laboratory is competent in achieving accurate results.     

Evaluation of accuracy and precision in an inter-laboratory comparison of total mercury in hair

Three round robins, involving 22 laboratories from eight countries, were conducted at six month intervals. Each of the participating laboratories analysed four samples of NIES-13 in three subsequent round robins during July 2000–October 2001. The objective of the current study was to determine accuracy and precision among participants for the analysis of total mercury. Both accuracy and precision for total mercury determinations in powder hair samples were good. The median within-laboratory (within-run) CVs ranged from 3.1 to 3.9% for four CRM samples. Most laboratories showed a proportional bias relative to the consensus mean of up to 16%. Two laboratories reported results that, on average, were almost 30% higher than the consensus mean value. Significant among-laboratory imprecision was found in the present study. Improvements are needed to reduce the analytical imprecision in a few laboratories, and attention must be focused on calibration issues and methodology-related problems.

Error Estimation in Preconditioned Conjugate Gradients

In practical problems, iterative methods can hardly be used without some acceleration of convergence, commonly called preconditioning, which is typically achieved by incorporation of some (incomplete or modified) direct algorithm as a part of the iteration. Effectiveness of preconditioned iterative methods increases with possibility of stopping the iteration when the desired accuracy is reached. This requires, however, incorporating a proper measure of achieved accuracy as a part of computation. The goal of this paper is to describe a simple and numerically reliable estimation of the size of the error in the preconditioned conjugate gradient method. In this way this paper extends results from [Z. Strakoš and P. Tichy, ETNA, 13 (2002), pp. 56–80] and communicates them to practical users of the preconditioned conjugate gradient method. AMS subject classification (2000) 15A06, 65F10, 65F25, 65G50     

Uncertainty in aflatoxin B<Subscript>1</Subscript> analysis using information from proficiency tests

We describe how to calculate uncertainty in the determination of aflatoxin B₁ in nuts and maize using an HPLC method with prederivatisation with trifluoroacetic acid and fluorescence detection. The uncertainty is easily calculated using the information obtained from the participation in several proficiency tests. All the sources of uncertainty are grouped in two terms: (1) matrix variability, intermediate precision and sample heterogeneity, and (2) method concordance. This methodology has the advantage that no extra work needs to be done because all the information to calculate uncertainty comes from proficiency tests. The uncertainty values were calculated using samples whose concentration ranged between 2 and 20 g L^–1. The relative standard uncertainty computed for aflatoxin B₁ was 16.3%.     

System error removal and structure optimization based on Fizeau interferometer

In the process of interferometric testing, the measurement result is influenced by the system structure, which reduces the measurement accuracy. To obtain an accurate test result, it is necessary to analyze the test system, and build the relationship between the measurement error and the system parameters. In this paper, the influences of the system elements which include the collimated lens and the standard surface on the interferometric testing are analyzed, the expressions of phase distribution and wavefront error on the detector are obtained, the method to remove some element errors is introduced, and the optimization structure relationships are given.     

Measurement of spatial object''''s exterior attitude based on linear CCD

It is difficult to realize real-time measurement of exterior attitude by the traditional systems based on the area image sensor which have conflict between speed and accuracy.The subsystem for three-dimensional (3D) coordinate rcconstruction of point target (S3DCRPT) which is composed of three one-dimensional (1D) cameras based on linear charge-coupled device (CCD) can determine the distant light spots' spatial position. The attitude angle of the measured object is determined by the spatial solution while the coordinate reconstruction is separately carried on by the S3DCRPT with some point cooperation targets (PCTs) on the measured object. A new optical system is designed to solve the interference problem with one-to-one relationship between the PCTs and the S3DCRPT optical subsystems,which improves the measurement accuracy and saves space. The mathematical model of the attitude measurement is established,and partial and global calibrations are realized for the multi-camera attitude measurement system.The test results show the feasibility of the exterior attitude measurement based on linear CCD.     

问题导向式教学在基础化学实验课堂中的应用——以“探讨二草酸合铜酸钾中铜离子测定条件”为例

Due to the facts that textbook-obedience and termwise experimenting dominate in the general chemistry laboratory classrooms, we have designed and carried out the problem-oriented teaching in order to improve the motivation of learning among the students, where the student-centered exploratory studying and practicing mode is highly desired. Problem-oriented teaching does not lead to exclusive resolutions to specific problems or experiments. Instead, it is supposed to induce multiple choices among student groups to complete experiments or resolve problems, where in-group/between-group discussions and practices would greatly activate the experimenting processes. Therefore, the sense of personal acquisition and self-progression during learning in laboratory classrooms can be easily achieved, while the good laboratory teaching will be realized as well. In this paper, we set up a problem-oriented teaching in optimizing the titration condition during measuring the copper content of K₂[Cu(C₂O₄)₂] using PAN (1-(2-pyridylazo)-2-naphthol) as the indicator. Grouping practices and experiments finally produced complementary results, as well as the satisfactory teaching and learning impacts.     

分光光度法的精密度和准确度

在控制测定条件,使测定的结果服从正态分布时,分光光度法的精密度和准确度将分别等于０．６６Ｒ和０．６６Ｒ／ｎ。Ｒ是样本极差（Ｘｍａｘ－Ｘｍｉｎ）,ｎ是样本大小（容量）。