“…The process is known as RSA and has been studied mostly using computer simulation. [18][19][20][21][22][23] In the latter, circles of the same radii were laid sequentially onto a plane, avoiding overlaps. One of the conclusions of the studies 19,21,23 is that there is an upper limit in ⌽, and the upper limit is about 0.547, much smaller compared with / ͑2 ϫ 3 1/2 ͒ = 0.9069, the area fraction for the hexagonal closest packing of circles.…”