Kouremeti, NataliaNevas, SauliusKazadzis, SteliosGroebner, Julian...
11页查看更多>>摘要：The overall aim of this study is to enable the traceable to International System of Units (SI) determination of column-integrated aerosol optical depth (AOD) retrieved from the passive remote sensing of the atmosphere using SI-traceable direct solar spectral irradiance measurements. A precision filter radiometer that measures direct solar spectral irradiance for the retrieval of AOD has been characterized and calibrated at the state-of-the-art calibration facilities of Physikalisch-Technische Bundesanstalt. The measured SI-traceable solar irradiances together with three state-of-the-art top-of-the-atmosphere (TOA) solar spectra have been used for retrieving AODs, which were validated against the reference AOD instruments of the World Aerosol Optical Depth Calibration Centre of the World Meteorological Organization (WMO). Calibration factors agreed within +/- 0.57% (3 sigma) using all three TOA spectra except for 368 nm (-1.1%) and 862 nm (1.8%) channels for one out of the three TOA spectra. Application of these results to the AOD retrieval showed AOD differences with the current reference methods/instruments well within the recommended WMO limits. The work provides a first step to opening a new era of AOD measurements traceability, providing a link to the SI through a laboratory-based approach, with the main advantages being the low uncertainty, the possibility of enhancing global AOD homogenization efforts and the chance to avoid calibration activities based on instrument relocations.
原文链接:
NSTL
Woods, S., INeira, J. E.Proctor, J. E.Rice, J. P....
11页查看更多>>摘要：We have developed generalized methods for electrical substitution optical measurements, as well as cryogenic detectors which can be used to implement them. The new methods detailed here enable measurement of arbitrary periodic waveforms by an electrical substitution radiometer (ESR), which means that spectral and dynamic optical power can be absolutely calibrated directly by a primary standard detector. Cryogenic ESRs are not often used directly by researchers for optical calibrations due to their slow response times and cumbersome operation. We describe two types of ESRs with fast response times, including newly developed cryogenic bolometers with carbon nanotube absorbers, which are manufacturable by standard microfabrication techniques. These detectors have response times near 10 ms, spectral coverage from the ultraviolet to far-infrared, and are ideal for use with generalized electrical substitution. In our first tests of the generalized electrical substitution method with FTS, we have achieved uncertainty in detector response of 0.13% (k = 1) and total measurement uncertainty of 1.1% (k = 1) in the mid-infrared for spectral detector responsivity calibrations. The generalized method and fast detectors greatly expand the range of optical power calibrations which can be made using a wideband primary standard detector, which can shorten calibration chains and improve uncertainties.
原文链接:- NSTL
Rossides, CharalambosTowsyfyan, HosseinBiguri, AnderDeyhle, Hans...
11页查看更多>>摘要：X-ray computed tomography (XCT) is increasingly used for dimensional metrology, where it can offer accurate measurements of internal features that are not accessible with other techniques. However, XCT scanning can be relatively slow, which often prevents routine uptake for many applications. This paper explores the feasibility of improving the speed of XCT measurements while maintaining the quality of the dimensional measurements derived from reconstructed volumes. In particular, we compare two approaches to fast XCT acquisition, the use of fewer XCT projections as well as the use of shortened x-ray exposure times for each projection. The study shows that the additional Poisson noise produced by reducing the exposure for each projection has significantly less impact on dimensional measurements compared to the artefacts associated with strategies that take fewer projection images, leading to about half the measurement error variability. Advanced reconstruction algorithms such as the conjugate gradient least squares method or total variation constrained approaches, are shown to allow further improvements in measurement speed, though this can come at the cost of increased measurement bias (e.g. 2.8% increase in relative error in one example) and variance (e.g. 25% in the same example).
原文链接:- NSTL
Yu YeHu XiangShi Wen-jingYe Zi-wei...
9页查看更多>>摘要：In an absolute gravimeter based on optical interferometry, the rotation of a falling body leads to inaccurate gravity measurement. By arranging the center of mass (COM) of the falling body together with its optical center (OC), the rotation error can be minimized rapidly. An optical measurement system with a two-stage pendulum structure is proposed to measure the distance between the COM and the OC of the falling body. The displacement of the OC is measured by an orthogonal interferometer while the falling body twists around the torsion wire, and the rotation angle of the falling body is measured synchronously by a photoelectric autocollimator. It is proved that a twist of the falling body by 2.4 degrees leads to a significant offset of about 0.2 nm along the direction of the laser beam. This results in a limit error of the measurement of the distance between the OC and the COM less than 1 mu m. Thus, the rotation error in absolute gravity measurement is reduced to 0.07 mu Gal.
原文链接:- NSTL
Cecelski, Christina E.Toman, BlazaLiu, Fong-HaMeija, Juris...
17页查看更多>>摘要：A model for errors-in-variables regression is described that can be used to overcome the challenge posed by mutually inconsistent calibration data. The model and its implementation are illustrated in applications to the measurement of the amount fraction of oxygen in nitrogen from key comparison CCQM-K53, and of carbon isotope delta values in steroids from human urine. These two examples clearly demonstrate that inconsistencies in measurement results can be addressed similarly to how laboratory effects are often invoked to deal with mutually inconsistent results from interlaboratory studies involving scalar measurands. Bayesian versions of errors-in-variables regression, fitted via Markov Chain Monte Carlo sampling, are employed, which yield estimates of the key comparison reference function in one example, and of the analysis function in the other. The fitting procedures also characterize the uncertainty associated with these functions, while quantifying and propagating the 'excess' dispersion that was unrecognized in the uncertainty budgets for the individual measurements, and that therefore is missing from the reported uncertainties. We regard this 'excess' dispersion as an expression of dark uncertainty, which we take into account in the context of calibrations that involve regression models. In one variant of the model the estimate of dark uncertainty is the same for all the participants in the comparison, while in another variant different amounts of dark uncertainty are assigned to different participants. We compare these models with the conventional errors-in-variables model underlying the procedure that ISO 6143 recommends for building analysis functions. Applications of this procedure are often preceded by the selection of a subset of the measurement results deemed to be mutually consistent, while the more discrepant ones are set aside. This new model is more inclusive than the conventional model, in that it easily accommodates measurement results that are mutually inconsistent. It produces results that take into account contributions from all apparent sources of uncertainty, regardless of whether these sources are already understood and their contributions have been included in the reported uncertainties, or still require investigation after they will have been detected and quantified.
原文链接:- NSTL
Doan Trang NguyenChoi, Yong MoonIm, SunghyukShin, Jinwoo...
20页查看更多>>摘要：Carbon dioxide emissions made up from fossil fuel is a weighted contribution to the total carbon dioxide emissions in Korea. To keep on track of the long-term mitigation pathway, the new solution for enhancing the emission flow measurements more accurately in industrial smokestacks is urgent. Thus, along with the popular instrument, an S-type pitot tube, three-dimensional (3D) pitot tubes have been introduced to determine the emission flow in smokestacks by international standards and Korean regulations. To comply with the regulations mandated in Korea, the Korea Research Institute of Standards and Science established the 3D pitot tube calibration system for stack flow measurements assembled to the airspeed standard system. This calibration system can produce accurate pitch and velocity calibration curves for 3D pitot tubes in the range of testing pitch angle within +/- 30 degrees, and have an expanded uncertainty attributed to the calibration curves (0.005-0.086) and (1.3-2.9)% for the prism pitot tube and (0.008-0.175) and (1.6-3.1)% for the spherical pitot tube.
原文链接:- NSTL
Shirono, KatsuhiroTanaka, HideyukiKoike, Masayoshi
13页查看更多>>摘要：In inspections for conformity assessment, an acceptance interval smaller than the tolerance interval is often determined in order to reduce the risk of consumers obtaining non-conforming items in the market. The presence of non-conforming items in the market impairs the evaluation of items by customers and may have an impact on revenue by decreasing prices. However, setting too small an acceptance interval reduces the revenue from the process by decreasing the number of the items available in the market. We thus propose a method to determine the optimum acceptance interval in conformity assessment by means of maximization of the revenue from processes. For this purpose, we give a mathematical model for the price of an item and its cost in the production process. Through theoretical analysis and simulations, it is shown that a parameter in the price model is the key in the optimization. In this paper we report a method for processes where no systematic effect component of measurement uncertainty exists, and in part 2 of this series we will report an extended method in which systematic effects are taken into consideration.
原文链接:- NSTL
Shirono, KatsuhiroTanaka, HideyukiKoike, Masayoshi
10页查看更多>>摘要：In this paper, optimization of acceptance interval in conformity assessment using the expression of the revenue that we showed in part 1 of this study is proposed under the condition of a systematic effect component being present in the measurement uncertainty. Systematic effect components are caused by unknown biases. Using the distribution based on the uncertainty information of the bias, we can develop the distribution of the revenue. Our idea is to set a percentile of the revenue distribution as the target of the maximization to reflect the systematic effect component in the optimization of the acceptance interval. We provide an equation for the optimum acceptance interval that can be numerically solved with little burden. We found that the choice of the probability for the percentile is an essential task in the optimization. Our proposed method incorporating the systematic effect seems to be sufficiently practical to be applied to actual processes.
原文链接:- NSTL
