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In this paper, we use an analysis function for gas diffusion known as the Research Institute for Applied Mechanics, Kyushu University, Computational Prediction of Airflow over Complex Terrain (RIAM-COMPACT), which was developed for complex terrain, in Airflow Analyst software, and apply it to the spread and dissipation of a fluid layer (assuming the fluid layer contains COVID-19 particles). First, to verify the prediction accuracy of the gas diffusion using RIAM-COMPACT, comparisons with past wind tunnel test results conducted on simple and complex terrains are presented under neutral atmospheric stability. The results of the numerical simulations carried out in this study show good agreement with the wind tunnel experiments for both simple and complex terrains. Next, a model of the Japan National Stadium (Tokyo Olympic Stadium) was constructed using 3D detailed topographic Advanced World 3D Map (AW3D) data generated by combining high-resolution satellite images. We tried to reproduce the hypothetical spread and dissipation of the fluid layer (assuming the fluid layer contains COVID-19 particles) inside and outside of the Japan National Stadium using Airflow Analyst implemented with the RIAM-COMPACT analysis function for gas diffusion. We paid special attention to the effect of wind ventilation driven by natural wind. The numerical results under various scenarios show that ventilation driven by natural wind is very effective for the Japan National Stadium. [ABSTRACT FROM AUTHOR]

A linear inertial piezoelectric step drive intended for moving samples and probes weighting up to 120 g with a 3- to 5-Å step through distances of a few centimeters to tens of centimeters is described. The drive is low in cost and easy to assemble. [ABSTRACT FROM AUTHOR]

The article discusses the highlights of the IUTAM Symposium on Vortex Dynamics: Formation, Structure and Function which was held on March 10-14, 2013 in Fukoaka, Japan. Mentioned are the sessions that focused on the development of new mathematical methods and theoretical concepts in vortex dynamics, the theoretical, numerical and experimental issues associated with vortex dynamics and the members of the symposium's International Scientific Committee su8ch as professor D. G. Crowdy.