Condensation of zinc vapor in a supersonic carrier gas

A study of the condensation of a metal vapor in an inert carrier gas is made. Superheated zinc vapor is generated in a hot shot wind tunnel in a helium carrier gas and expanded in a converging-diverging nozzle. Static pressure measurements along the length of the nozzle are made to determine the location of the onset of condensation. A conical nominal Mach 5 (helium) nozzle is employed. The amount of supercooling before the onset of condensation is found to be approximately 430 K, measured along the isentrope over a range of initial zinc mass fractions of .35 to .70 for saturation partial pressures of zinc between 10 psia and 70 psia. The measurements are compared with results of an analysis based on the classical liquid drop model of nucleation. The computed results agree reasonably well with the measurements.     

Plane-wave expansions of the optical field

Plane-wave expansions of the type introduced by Whittaker are compared with plane-wave expansions of the type introduced by Weyl for wave fields radiated by sources confined to finite space-time domains. The domains of validity and the plane-wave amplitudes are determined for both types of expansions.     

Minimal blocking sets in finite planes

A result on enclosed (k,n)-arcs in PG(2,q) is used to characterise all minimal blocking sets of sizes =q +n in PG(2,q) with at least twon-secants. This also permits a slight extension of the bounds on blocking sets established by Blokhuis and Brouwer.