FIG. 5.

(a) Effect of the airflow velocity on NP deposition, with the frequency kept at the rest-state 15 cycles per minute or 4 s per cycle. (b) Effect of the breathing frequency on NP deposition, with the airflow velocity kept at the rest-state $V_0=0.337$ mm/s. The number density of deposited particles ${\rho }_s$ is plotted against the number of breathing cycles. (c) Same as the above, with ${\rho }_s$ plotted against real time. (d) Effect of exercise on NP deposition, with the faster airflow ($V_0=1.91$ mm/s) and higher breathing frequency (20 cycles/min or 3 s per cycle). ${\rho }_s$ is plotted against the number of breathing cycles. (e) Same as the above, with ${\rho }_s$ plotted against real time.