الفهرس 
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Abstract
The flow of air in the human respiratory system was studied experimentally. Steady inspiratory and expiratory axial velocity profiles in a model of scale 2:1 of the human central airways were measured. The model was constructed out of transparent Prespex, and connected to a specially designed steady-flow system. The flow distribution among the five lobar bronchi was controlled. Fhe axial velocities were recorded along four diameters, each of ten measuring stations. The velocity profiles were mainly shaped by the geometry of the airway, the basic --haracteristics of these velocity profiles were independent 3f the branching asymmetry. The velocity profile in frontal 31ane had a peak velocity near the inner wall of the bifurcation, while in normal plane the velocity profiles generally had a double peak structure. During expiratory flow, the velocity profiles were asymmetric, with a peak or double peak depending on the relative +low in the two daughters.
The deposition of inhaled particles in the human respiratory tract was studied, both theoretically and experimentally. A finite-difference model +or aerosol impaction in the central airways had been presented. Deposition by impaction increased in branches with large branching angle. In the same site, deposition increased with increasing flow rate or particle diameter.