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Principal component analysis of colour measurements of patinas and coating systems for outdoor bronze monuments 总被引：1，自引：0，他引：1
Principal Component Analysis (PCA) was applied on colour measurements performed on outdoor bronze patinas and protective coating systems on bronze coupons in order to monitor natural weathering and cleaning effects. PCA chemometric technique is shown to be a powerful tool to analyse the large measurement data set which is needed to characterise these kinds of system. The results are compared with previous work where the CIELAB L*a*b space was used, in order to spot the advantages and disadvantages of both techniques and how they can complete each other in order to set up a workflow when dealing with large datasets of colour measurements. As previously stated, quicker colour variations in the early stage of natural weathering of bronze coupons are characterised, which is mainly due to lightness reduction. PCA analysis helps to visualise the different behaviour upon cleaning procedure of different monument patinas and colour difference reduction due to cleaning. It gives the advantage in a first screening phase to possibly highlight the presence of outliers, check the level of noise in the spectra, and select the variables which carry more information. Its integration in a workflow for colour measurement can help in speeding up the process of later analysing data with the well-established CIELAB system. 相似文献
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The Johns Hopkins University Center for Talented Youth (CTY) identifies students who reason well mathematically and/or verbally and offers summer and academic year programs of rigorous academic course work. Gender differences in test performance, even though not as large as previously reported, are noticeable, particularly among the highest test scores. The majority of students benefit from summer program participation, and have increased access to more advanced course work. No differences were found between 1982 and 1991 male and female populations in class ranking, liking of mathematics, or perception of support from peers, family members, and teachers. However, the lack of support from the peer group underscores the academic isolation of this group of students. 相似文献
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Maria Stella Valle Luciano Lombardo Matteo Cioni 《European Journal of Sport Science》2018,18(9):1217-1225
Learning precision ball throwing was mostly studied to explore the early rapid improvement of accuracy, with poor attention on possible adaptive processes occurring later when the rate of improvement is reduced. Here, we tried to demonstrate that the strategy to select angle, speed and height at ball release can be managed during the learning periods following the performance stabilization. To this aim, we used a multivariate linear model with angle, speed and height as predictors of changes in accuracy. Participants performed underarm throws of a tennis ball to hit a target on the floor, 3.42 m away. Two training sessions (S1, S2) and one retention test were executed. Performance accuracy increased over the S1 and stabilized during the S2, with a rate of changes along the throwing axis slower than along the orthogonal axis. However, both the axes contributed to the performance changes over the learning and consolidation time. A stable relationship between the accuracy and the release parameters was observed only during S2, with a good fraction of the performance variance explained by the combination of speed and height. All the variations were maintained during the retention test. Overall, accuracy improvements and reduction in throwing complexity at the ball release followed separate timing over the course of learning and consolidation. 相似文献