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Indoor air quality, especially in terms of particulate matter (PM), is a critical public health concern. Although various methods for removing indoor PM have been suggested, the effects of various influential factors on PM deposition have not been clearly understood. Here, the effect of the flow structure inside a test chamber on PM deposition was quantitatively investigated using flow visualization techniques. To elucidate the flow parameters that influence the PM deposition, the efficiency of PM removal and deposition constant were examined for different flow directions, flow velocities, and distances between the fan and the surface of the test chamber. The spatial distributions of the mean velocity and turbulence intensity inside the test chamber were obtained experimentally using a particle image velocimetry technique to understand the mechanism associated with PM deposition. The overall mean velocity, recirculating flow region, and turbulent intensity in the near-wall regions may partially explain the difference in the PM deposition under various flow conditions. [ABSTRACT FROM AUTHOR]

Pine cones fold their scales when it rains to prevent seeds from short-distance dispersal. Given that the scales of pine cones consist of nothing but dead cells, this folding motion is evidently related to structural changes. In this study, the structural characteristics of pine cones are studied on micro-/macro-scale using various imaging instruments. Raindrops fall along the outer scales to the three layers (bract scales, fibers and innermost lignified structure) of inner pine cones. However, not all the layers but only the bract scales get wet and then, most raindrops move to the inner scales. These systems reduce the amount of water used and minimize the time spent on structural changes. The result shows that the pine cones have structural advantages that could influence the efficient motion of pine cones. This study provides new insights to understand the motion of pine cones and would be used to design a novel water transport system. [ABSTRACT FROM AUTHOR]