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Analysis of high-speed train flow structures under crosswind
Terence Avadiar,James Bell,David Burton,Heman Cormaty,Chao Li 대한기계학회 2016 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.30 No.9
The flow structures along the length of a High-Speed Train (HST) are experimentally investigated under simulated crosswind conditions. The experiment uses flow visualizations and velocity measurements in a wind tunnel on a HST model at various angles of yaw. Surface visualizations shows the development of a longitudinal vortex, originating at the nose which travels along the leeward side of the train. A hypothesis is presented and tested proposing flow structures may repeat when the Boundary layer (BL) on the roof of the HST reaches maximum development or is “pushed off”. A key motivation is to evaluate the validity of using shortened HST models in a wind tunnel to correctly represent full-length trains. Using this theory, a shortened train model appears unable to completely model full-scale HSTs at realistic yaw angles.
Efficacy of Dynamic Written Corrective Feedback on KFL Writing
오수빈,Teresa R. Bell,K. James Hartshorn,Norman W. Evans,Julie Damron 한국언어과학회 2022 언어과학 Vol.29 No.4
This study investigates the effectiveness of dynamic written corrective feedback(DWCF) on the writing of intermediate learners of Korean as a foreign language(KFL). Nineteen intermediate Korean learners at a large private university in the United States participated in this research and were divided into two groups. The treatment group(n=9) received DWCF, while the control group(n=10) did traditional types of take-home essay writing with direct feedback. Pre- and post-test results were analyzed to determine differences in linguistic accuracy, fluency, and complexity between the two groups. A mixed-model repeated measures ANOVA revealed that the treatment group's accuracy significantly increased compared to the control group, and there was no significant difference in fluency or complexity for either group. Based on the study results, DWCF is an effective teaching strategy to improve the linguistic accuracy of writings for intermediate Korean learners without negatively impacting fluency and complexity.
Mairs, Steve,Johnstone, Doug,Kirk, Helen,Lane, James,Bell, Graham S.,Graves, Sarah,Herczeg, Gregory J.,Scicluna, Peter,Bower, Geoffrey C.,Chen, Huei-Ru Vivien,Hatchell, Jennifer,Aikawa, Yuri,Chen, Wen American Astronomical Society 2017 The Astrophysical journal Vol.849 No.2
<P>Investigating variability at the earliest stages of low-mass star formation is fundamental in understanding how a protostar assembles mass. While many simulations of protostellar disks predict non-steady accretion onto protostars, deeper investigation requires robust observational constraints on the frequency and amplitude of variability events characterized across the observable SED. In this study, we develop methods to robustly analyze repeated observations of an area of the sky for submillimeter variability in order to determine constraints on the magnitude and frequency of deeply embedded protostars. We compare 850 mu m JCMT Transient Survey data with archival JCMT Gould Belt Survey data to investigate variability over 2-4 year timescales. Out of 175 bright, independent emission sources identified in the overlapping fields, we find seven variable candidates, five of which we classify as Strong, and the remaining two we classify as Extended to indicate that the latter are associated with larger-scale structure. For the Strong variable candidates, we find an average fractional peak brightness change per. year of |4.0|% yr(-1), with a standard deviation of 2.7% yr(-1). In total, 7% of the protostars associated with 850 mu m emission in our sample show signs of variability. Four of the five Strong sources are associated with a known protostar. The remaining source is a good follow-up target for an object that is anticipated to contain an enshrouded, deeply embedded protostar. In addition, we estimate the 850 mu m periodicity of the submillimeter variable source, EC 53, to be 567 +/- 32 days, based on the archival Gould Belt Survey data.</P>