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1.
Generic issues and current approaches in the evaluation of bias studies with respect to estimation of measurement uncertainty are discussed, focusing on two main scenarios. In the first, for a within-laboratory assessment of a fully developed uncertainty budget, bias studies are carried out to verify the pre-established performance of a measurement procedure, and design corrective actions if necessary. In the second scenario, for an estimation of measurement uncertainty from within-laboratory validation data, bias studies are carried out to calibrate the whole measurement procedure and evaluate its performance, more specifically to estimate the uncertainty of measurement by combination of bias and precision estimates.
相似文献
Werner HaesselbarthEmail: Phone: +49-30-81041101Fax: +49-30-81045577 |
2.
The use of (certified) reference materials and quality control materials can form a suitable basis for evaluating measurement uncertainty of routine measurements. In particular when these materials are used for quality control purposes, it is not always evident how the quality control data can be used in the uncertainty budget of a routine measurement. Current guidance documents on the evaluation of measurement uncertainty and the use of reference materials treat this subject only in part, or in very generic terms. ISO/REMCO has established a new working group that will provide practical guidance and examples on how to use quality control data in the evaluation of measurement uncertainty. A short introduction to the subject is given.
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Adriaan M. H. van der VeenEmail: Phone: +31-15-2691733Fax: +31-15-2691670 |
3.
A procedure for estimation of measurement uncertainty of photometric analysis based on the ISO GUM method is presented. Two variations of the procedure—for the calibration graph and the standard addition method, respectively—are discussed. The variations are based on mathematical models involving 64 and 80 input quantities, respectively. The uncertainty of the result strongly depends on changes in experimental details. These dependencies are explored for a practical example of determination of the iron content of aluminum. The importance of taking uncertainty from sample preparation into account in uncertainty estimation is stressed. The number of effective degrees of freedom is calculated and discussed. The examples are available as GUM Workbench files in the Electronic Supplementary Material.Electronic Supplementary Material Supplementary material is available for this article at .
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Ivo LeitoEmail: Phone: +372-7-375259Fax: +372-7-375264 |
4.
Decision-making in the conformity assessment of exhaust gas analysers with due account of measurement uncertainty and limited sampling is considered. Risks of incorrect decisions where test results lie in the vicinity of a specification limit are assessed in terms of percentage probability and the costs of measurement and environmental consequences, with examples based on the metrological requirements on these analysers stipulated in the new EU Measurement Instrument Directive. An optimised uncertainty methodology is proposed for the first time in legal metrology based on quantitative testing of new instruments for type approval and initial verification, and gives valuable insight into traditional rules limiting uncertainty in conformity assessment in general. Further, an analysis of subsequent verification of exhaust gas analysers in use in society, leads to a new optimised uncertainty methodology based on attribute sampling.
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L. R. PendrillEmail: Phone: +46-33-165444Fax: +46-33-165620 |
5.
John Buckingham 《Accreditation and quality assurance》2005,10(3):121-122
The chemical and microbiological testing community is going through a rather difficult period of change. Publication of ISO/IEC 17025 (General requirements for the competence of Calibration and Testing Laboratories, 1999) [1] is placing additional demands on testing laboratories to ensure traceability and estimate uncertainty in their measurements. At the same time, laboratories must remain mindful of the need to provide relevant, timely and economic services to their clients. International Accreditation New Zealand (IANZ) and its accredited laboratories are currently focussing on establishing realistic methods for ensuring traceability to national and international standards and estimating measurement uncertainty. To this end, IANZ recognizes that it has an important role in providing as much advice and assistance as possible, not only to its accredited chemical laboratories but also to all those contemplating accreditation in New Zealand.
相似文献
John BuckinghamEmail: Phone: +64-9-4455900Fax: +64-9-4455890 |
6.
D. Brynn Hibbert 《Accreditation and quality assurance》2006,11(11):543-549
The paper reproduces a talk given at a 2-day symposium on quality assurance in chemistry held in Brisbane, Australia in 2005. Intended for an audience of analysts in the field, the theme of the symposium drew inspiration from the series of books by Douglas Adams “The Hitchhiker's Guide to the Galaxy”. An introduction to basic concepts of metrological traceability is followed by a discussion of practical steps to ensure metrological traceability of field measurement results. The relationship between metrological traceability and comparability of measurement results is discussed. To achieve metrological traceability in the field, the use of appropriate certified reference materials for calibration is recommended. Examples of atmospheric carbon dioxide and roadside breathalyzer measurements are given.
相似文献
D. Brynn HibbertEmail: Phone: +61-2-9385-4713Fax: +61-2-9385-6141 |
7.
John Barker 《Accreditation and quality assurance》2005,10(3):123-124
This article was presented to the CITAC workshop in Wellington, New Zealand on 3 May 2004. It explains the role of the Organisation Internationale de Métrologie Legalé (OIML) and work carried out to promote harmonisation in the field of legal metrology—the part of metrology relating to activities which result from statutory requirements and concern measurement, units of measurement, measuring instruments and methods of measurement and which are performed by competent bodies. It also discusses the publications issued to achieve harmonisation. The article also discusses New Zealands recent elevation to full membership of the OIML and the commitment to make the membership work to the benefit of the whole New Zealand measurement industry.
相似文献
John BarkerEmail: Phone: +64-4-4742823Fax: +64-4-4739400 |
8.
Vaporization enthalpies for the isomeric diazines were discussed within the context of recent measurements and estimation
techniques. It is suggested that pyridazine shows enigmatic behavior.
相似文献
Joel F. Liebman (Corresponding author)Email: |
9.
Cox Maurice G. Desenfant Michèle Harris Peter M. Siebert Bernd R. L. 《Accreditation and quality assurance》2003,8(12):548-554
Basic concepts and implementations of the model-based approach to uncertainty evaluation are discussed. One implementation is that of the law of propagation of uncertainty with the use of the central limit theorem as recommended in the Guide to the expression of uncertainty in measurement (GUM). Another is the propagation of distributions, the subject of a supplemental guide to the GUM, which is at an advanced stage of development. It falls in the category of other analytical and numerical methods indicated in the GUM. Two testing applications are used to illustrate the principles: tennis-ball rebound and tensile strength.
相似文献
Maurice G. CoxEmail: Phone: +44-20-8943-6096Fax: +44-20-8977-7091 |
10.
11.
Sampling is an integral part of nearly all chemical measurement and often makes a substantial or even a dominant contribution
to the uncertainty of the measurement result. In contrast with analysis, however, the uncertainty contribution from sampling
has usually been ignored. Indeed, far less is known about sampling uncertainty, although in some application sectors it is
known to exceed the analytical uncertainty, especially when raw materials (natural or industrial) are under test. In 1995
the authors of this paper proposed a framework of concepts and procedures for studying, quantifying, and controlling the uncertainty
arising from the sampling that normally precedes analysis. Many of the ideas were based on analogy with well-established procedures
and considerations relating to quality of analytical measurement, ideas such as validation of the sampling protocol, sampling
quality control and fitness for purpose. Since that time many of these ideas have been explored experimentally and found to
be effective. This paper is a summary of progress to date.
Presented at the AOAC Europe Workshop, November 2006, Limassol, Cyprus.
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Michael ThompsonEmail: |
12.
Stephen L. R. Ellison 《Accreditation and quality assurance》2006,11(3):146-152
The relationship between calibrated range, residual standard deviation and correlation coefficient r is discussed. It is shown that in typical chemical calibration applications with appropriately distributed calibration points (particularly, with range comparable to mean and with approximately even or with ‘successive dilution’ spacing), the linear correlation coefficient has valid application as a routine criterion for acceptable fit if used with due care.
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Stephen L. R. EllisonEmail: Phone: +44-20-8943-7325Fax: +44-20-8943-2767 |
13.
We compare the approach to measure uncertainties proposed in ISO 5725 and GUM from a statistician point of view. In particular
we give some warnings to the application of the expanded uncertainty introduced in GUM when the input variables are few and
we report some considerations on the relevant role of the interactions among the input variables in the measurement equation
as well as the role of statistical design of experiments to measure uncertainties.
相似文献
Laura DeldossiEmail: |
14.
Franco Pavese 《Accreditation and quality assurance》2007,12(10):525-534
In order to choose the right statistical tool, a basic issue for an accurate analysis of each specific problem is to understand
whether the set of replicated measurement results under examination is to be considered as pertaining to repeated measurements
or not. This issue is particularly important, since most of the traditional tools are valid only for repeated measurements,
but, in many cases, such as laboratory comparisons (in metrology and in testing), the measurements necessary to assess correctly
the measurand value and the associated uncertainty do not represent repeated measurements. The analysis performed in this
paper aims to shine some light on these issues, starting with a review of the basic concepts, such as repeatability, reproducibility,
accuracy, systematic error and bias, as defined in international documents and as used in the literature. The paper shows
that, currently, a full consensus on a common language and understanding has not yet been achieved, and then shows how this
fact reflects on the basic data models, especially those concerning inter-comparison data.
相似文献
Franco PaveseEmail: |
15.
Antonio Menditto Marina Patriarca Bertil Magnusson 《Accreditation and quality assurance》2007,12(1):45-47
Clear definitions of basic terms, used to describe the quality of measurements, is essential for communication among scientists
as well as when reporting measurement results to clients. Even if appropriate definitions are given in international standards
and guidelines, the understanding of some basic terms sometimes proves difficult. The reasons for this are various, e.g.,
the same words being defined rather differently in encyclopaedias and in international standards as well as concepts, well
established in some languages, that may be relatively new in other national communities and at large in the international
one. Here we present a matrix intended to clarify the relationships between the type of error affecting an analytical measurement,
the respective qualitative concepts (performance characteristics) and their quantitative expression.
相似文献
Antonio MendittoEmail: |
16.
This paper reviews matrix effects and interference in chemical analysis and the methods by which analytical chemists reduce their effects to either negligible or minimal magnitude. The aim is to provide a framework for estimating the contribution to uncertainty due to these effects in analysis, with or without the application of procedures for correcting them. The general characteristics of matrix effects and interference are discussed, and general principles for the estimation of uncertainty associated with matrix effects are introduced. The principal techniques available to minimise matrix effects are described, together with methods of uncertainty estimation where appropriate.The Analytical Methods Committee of the Royal Society of Chemistry has received and approved for publication the following report from its Matrix Effects Working Group. The constitution of the working group was Dr. S. Ellison (Chairman), Prof. M. Thompson, Dr. D. Bullock, Dr. J. Dean, Prof. T. Fearn, W. Hardcastle, Dr. T. Lynch, Dr. N. Reid, Dr. S. Scott, Dr. Thompson.
相似文献
Stephen L. R. EllisonEmail: |
17.
The influence of cryogenic mechanical milling on the structure and the thermal behavior of isotactic polypropylene was investigated by means of wide-angle X-ray scattering, differential scanning calorimetry and transmission electron microscopy. The results presented show that structural changes caused by mechanical milling at cryogenic temperatures are only partly reversible. The decrease in the degree of crystallinity as determined by differential scanning calorimetry with increasing milling time is attributed to a reversible transformation of the initial morphology into a nanostructured morphology, consisting of small fragments of the original isotactic polypropylene lamellae. During recrystallization from the molten state, there still exists an influence of the previous milling treatment, leading to significantly changed crystallization behavior. The reason for this behavior might be a decrease in the molecular weight or a change in the molecular weight distribution or the formation of long-chain branched polypropylene molecules induced by cryogenic mechanical milling.
相似文献
Michael StranzEmail: Phone: +49-231-7552579Fax: +49 231-7555978 |
18.
Sarah Gold Julian Eastoe Roberto Grilli David C. Steytler 《Colloid and polymer science》2006,284(11):1333-1337
A series of highly branched trichain sulfosuccinate surfactants have been synthesized and studied in condensed CO2 and aqueous environments. Aqueous critical micelle concentrations (CMCs) showed a general trend of increasing CMC with decreasing chain length, whereas increased branching appeared to increase solubility in CO2 and aid the dispersion of water. Near infrared spectra confirmed observed cloud with a large increase in solubility above the cloud pressures in this solvent.
相似文献
Julian EastoeEmail: Phone: +44-117-9289180Fax: +44-117-9251295 |
19.
Michael Noyong Buelent Ceyhan Christof M. Niemeyer Ulrich Simon 《Colloid and polymer science》2006,284(11):1265-1273
The formation and the optical features of two-dimensional aggregates formed by DNA-directed immobilization and cross-linking of bifunctional DNA–gold nanoparticles at flat gold substrates are analyzed. The samples are structurally characterized by atomic force microscopy to evaluate the particle size, the particle densities, and the degree of aggregation. The optical characteristics determined by UV/visible measurements are correlated with the structural features observed.
相似文献
Ulrich SimonEmail: |
20.
The molecular geometries, relative stabilities, binding energies, and dissociation energies of NaDyBr4 and its molecular ion are discussed. Both the bidentate and tridentate isomers are stable for the neutral species, while
only the bidentate form is stable for NaDyBr4
+.
相似文献
Magdolna Hargittai (Corresponding author)Email: |