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Turbulent Combustion Properties of Outwardly Propagating Flames
Kimitoshi TANOUE,Fumio SHIMADA,Takashi NASU,Takayuki KAWASHIMA,Toshiro HAMATAKE 한국자동차공학회 2001 한국자동차공학회 Symposium Vol.- No.-
In engine combustion. turbulence generated by flow field motion such as swirl and flimbic, in the cylinder affects the propagating flame initiated by spark plug. resulting in the enhancement or the mass consumption rate or reactants as compared with the corresponding laminar flames. This in turn increases the heat release rate and thus power available from an engine of a given size. In this context the modeling and prediction or turbulent flame properties are or importance from the application point or view. In the present work, turbulent burning velocities or outwardly propagating premixed flames for methane and propane, which are representative of lighter or heavier hydrocarbon respectively, are investigated under the framework or flamelet concept which is based on the assumption that a chemical reaction occurs in thin layers that arc convected and distorted by the turbulent now field. In flamelet concept, the flame-flow interaction can be described in terms of total flame front surface and local flame structure. The local flame properties defined by the displacement speed and reaction rate depend on local hydrodynamic strain rate and curvature effects. Furthermore, the name response to flow divergence and curvature depends strongly on the Lewis number, characterized by the ratio of molecular diffusivity to thermal diffusivity. For non-unity Lewis numbers, differential diffusion of heat and species results in a certain sensitivity of the local flame structure to strain rate and curvature. Although this thermo-diffusive mechanism is well known for laminar names or for low stretched flames, recent studies have showed that it influences the local and global name structure of turbulent premixed combustion with high stretch. The primary objective of the present paper is to study experimentally the turbulent burning velocity and derive the fundamental equations in consideration of interaction between averaged name stretch and Lewis numbers<br/> <br/>
Effect of the COVID-19 pandemic lockdown on the physique of school-age children in Japan
Takaya Junji,Higashino Hirohiko,Takaya Ryuzo,Sakaguchi Hiromi,Tanoue Jitsuo,Higashide Takashi,Moriguchi Hisako,Nakao Masatoshi,Takai Yasuyuki 대한소아내분비학회 2023 Annals of Pediatirc Endocrinology & Metabolism Vol.28 No.2
Purpose: Schools in Japan were closed nationwide from March to May 2020 because of the coronavirus disease 2019 (COVID-19) pandemic. Many suspect that this school closure affected children’s mental and physical health. We investigated changes in school-age children’s physiques to determine the effects of the COVID-19 lockdown and restrictions on their health. Methods: Data were extracted from a database of school physical examinations in Osaka elementary and junior high schools for 4 consecutive years from 2018 to 2021. The following characteristics were analyzed: short stature, tall stature, underweight, mild obesity, middle grade obesity, and severe obesity. The paired Student t-test was used to compare school examination data in the prepandemic period (2018–2019), pandemic lockdown (2019–2020), and post-lockdown period (2020–2021). Results: Obesity rates in elementary school students aged 6–12 years, particularly in boys, were significantly higher during the lockdown than they were in 2019. After the pandemic, the tall stature rate continued to rise, while rates of short stature and underweight decreased in both sexes in 2020. In junior high school students aged 12–15 years, rates of obesity and underweight tended to decrease in 2020. However, these rates rebounded and rose in 2021 when the lockdown was lifted. Conclusion: During the COVID-19 pandemic lockdown, elementary school students gained weight, while junior high school students lost weight. The lockdown that was implemented during the COVID-19 pandemic had an unfavorable effect on weight gain, particularly in young school-age children.