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| 12. |
- Draxler, K., et al.
(författare)
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International comparison of current transformer calibration systems up to 10 kA at 50 Hz frequency
- 2016
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Ingår i: 2016 Conference on Precision Electromagnetic Measurements (CPEM 2016). - 9781467391344
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Konferensbidrag (refereegranskat)abstract
- Current transformers (CTs) are precision devices that scale high currents down to values that can be easily handled by measurement equipment. To support CT applications in revenue metering, a comparison on AC current transformer calibration systems was performed among 15 European national metrology institutes using a precision CT as the travelling device. The first comparison results for the transformation ratios (4, 5, 6, 8, 10) kA/5 A of the travelling CT at nominal burden of 5 VA and 15 VA indicate good agreement between the participating laboratories. The main differences are found for phase displacement, at least partly caused by the instability of the traveling standard.
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| 13. |
- Draxler, K., et al.
(författare)
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Results of an International Comparison of Instrument Current Transformers up to 10 kA at 50 Hz Frequency
- 2018
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Ingår i: CPEM 2018 - Conference on Precision Electromagnetic Measurements. - 9781538609736
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Konferensbidrag (refereegranskat)abstract
- Traceability of the current ratio is crucial for the measurement of electrical energy in revenue metering. A comparison of the AC current ratio was therefore performed within EURAMET in the time period 2012-2016, using a precision CT as the traveling device. The Czech Metrology Institute (CMI) as coordinator processed the measurement results of the 15 European participating laboratories. The comparison of the results for transformer ratios of (4, 5, 6, 8, 10) kA 5 A at 15 VA burden and (4 and 10) kA 5 A ratios at 5 VA burden indicates good agreement between the participating laboratories. The main differences are found for phase displacement, at least in part due to instability of the traveling standard. .
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| 18. |
- Bergman, Anders, et al.
(författare)
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Metrology for high voltage direct current
- 2010
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Ingår i: CPEM Digest (Conference on Precision Electromagnetic Measurements). - 9781424467952 ; , s. 669-670
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Konferensbidrag (refereegranskat)abstract
- HVDC energy transmission is crucial for a successful uptake of renewable energy sources in the grid. A research program is described, intended to provide metrology support for the needs of HVDC energy transmission. This program will provide improvements for the present HVDC metrology infrastructure: accurate measurement of HVDC, determination of losses in HVDC systems, on-site power quality measurements at HVDC substations, and DC metering. It is a combined effort of 7 European national metrology institutes, one university and one industrial partner. © 2010 IEEE.
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| 19. |
- Johannesson, Magnus, et al.
(författare)
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Genome-wide association meta-analysis of 78,308 individuals identifies new loci and genes influencing human intelligence
- 2017
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Ingår i: Nature Genetics. - : Nature Research (part of Springer Nature). - 1061-4036 .- 1546-1718.
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Tidskriftsartikel (refereegranskat)abstract
- Intelligence is associated with important economic and health-related life outcomes. Despite intelligence having substantial heritability (0.54) and a confirmed polygenic nature, initial genetic studies were mostly underpowered. Here we report a meta-analysis for intelligence of 78,308 individuals. We identify 336 associated SNPs (METAL P −8) in 18 genomic loci, of which 15 are new. Around half of the SNPs are located inside a gene, implicating 22 genes, of which 11 are new findings. Gene-based analyses identified an additional 30 genes (MAGMA P −6), of which all but one had not been implicated previously. We show that the identified genes are predominantly expressed in brain tissue, and pathway analysis indicates the involvement of genes regulating cell development (MAGMA competitive P = 3.5 × 10−6). Despite the well-known difference in twin-based heritability2 for intelligence in childhood (0.45) and adulthood (0.80), we show substantial genetic correlation (rg = 0.89, LD score regression P = 5.4 × 10−29). These findings provide new insight into the genetic architecture of intelligence.
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| 20. |
- Johannesson, Magnus, et al.
(författare)
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Meta-GWAS Accuracy and Power (MetaGAP) Calculator Shows that Hiding Heritability Is Partially Due to Imperfect Genetic Correlations across Studies
- 2017
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Ingår i: PLoS Genetics. - : Public Library of Science. - 1553-7404 .- 1553-7390. ; 13:1, s. 1-23
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Tidskriftsartikel (refereegranskat)abstract
- Large-scale genome-wide association results are typically obtained from a fixed-effects meta-analysis of GWAS summary statistics from multiple studies spanning different regions and/or time periods. This approach averages the estimated effects of genetic variants across studies. In case genetic effects are heterogeneous across studies, the statistical power of a GWAS and the predictive accuracy of polygenic scores are attenuated, contributing to the so-called ‘missing heritability’. Here, we describe the online Meta-GWAS Accuracy and Power (MetaGAP) calculator (available at www.devlaming.eu) which quantifies this attenuation based on a novel multi-study framework. By means of simulation studies, we show that under a wide range of genetic architectures, the statistical power and predictive accuracy provided by this calculator are accurate. We compare the predictions from the MetaGAP calculator with actual results obtained in the GWAS literature. Specifically, we use genomic-relatedness-matrix restricted maximum likelihood to estimate the SNP heritability and cross-study genetic correlation of height, BMI, years of education, and self-rated health in three large samples. These estimates are used as input parameters for the MetaGAP calculator. Results from the calculator suggest that cross-study heterogeneity has led to attenuation of statistical power and predictive accuracy in recent large-scale GWAS efforts on these traits (e.g., for years of education, we estimate a relative loss of 51–62% in the number of genome-wide significant loci and a relative loss in polygenic score R2of 36–38%). Hence, cross-study heterogeneity contributes to the missing heritability.
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