SynopsisTernary blends comprising bisphenol-A polycarbonate (PC), the polyhydroxyether of bisphenol-A (Phenoxy), and p l y ( c-caprolactone) (PCL) were found to be generally miscible at PCL levels greater than 60% by weight and to show multiple amorphous phases at lower PCL levels. The melting point depression of PCL in the miscible region of the ternary and in the miscible binary blends with PC and Phenoxy was examined to obtain the enthalpic interaction parameters, Bi,, for each of the three binary interactions. The parameters associated with the miscible binary blends were negative, as expected, and indicated that PCL interacts more exothermically with Phenoxy than with PC. The parameter associated with the Phenoxy/PC interaction was strongly positive as expected from the complete immiscibility shown by these materials. The interaction parameters were used to calculate the locus of compositions for which the heat of mixing is zero. The locus was found to agree well with the observed boundary between miscible and multiphase behavior in the ternary. This suggests that the phase behavior of ternary blends is largely determined by the same enthalpic considerations known to govern the phase behavior of binary blends.

Although there has been extensive research on the optical properties of shear layers, there have been no reported studies of the optical effects on large scale coherent structures existing in turbulent shear layers. The research reported here investigated the effects of such coherent structures and of external perturbation of the shear layer on the optical quality of a propagating laser beam. High-speed pictures suggest that the presence of large eddies influences the shape of the far-field intensity profiles. In addition, time-averaged pictures show that perturbing a shear layer can affect the Strehl ratio. These results demonstrate that the optical properties of shear layers may be controlled and improved. Nomenclature a = beam radius n = refractive index SR = Strehl ratio U = fluid velocity w x = view angle to the far field X = downstream distance from the splitter plate /3 = Gladstone-Dale constant 5 = visual shear-layer thickness X = wavelength of laser beam p r ef = reference fluid density () = time averaged

Two-dimensional Euler equations are solved directly using the second-order, explicit, MacCormack predictorcorrector and Godunov methods alternately for the investigation of free-shear-layer optical properties. The optical effects of coherent structures in the mixing layer are identified. As expected, far-field optical quality of a laser beam is degraded the most when a laser beam passes through the edge of the large eddies. The far-field optical performance can be improved significantly by controlling the coherent structures in the mixing layer. The growth of shear layer is retarded by fundamental frequency forcing, and it is found the Strehl ratio is the highest in the nongrowth region.

The separation of nitrogen isotopes by low temperature reaction of vibrationally excited nitrogen gas with oxygen has been studied, in which the formation of 15NO is theoretically favored. The potential yield and isotope separation coefficient β for this process were examined using a numerical simulation of the kinetic processes, which incorporated a steady-state isothermal model of the 14N2 and 14N15N vibrational distribution functions coupled with a non-steady-state kinetic model of the chemical system including N*2, O*2, N, O, and their reaction products. In the absence of O2, the vibrationally enhanced rate coefficient for the reaction N*2+O → NO+N was observed to be inversely proportional to the concentration of O atoms, due to VT loading of the N*2 distribution function. O2 was also found to greatly reduce the rate coefficient due to efficient depletion of the highly excited species via the reaction N2(v)+O2(0) → N2(v−1) +O2(1). Computed reaction yield increases dramatically if both the O*2 and N*2 vibrational temperatures are elevated, but only at the expense of greatly reduced β. The effective separative work for this process was estimated.

463Greek Symbols t = rate of dissipation of turbulent energy, m2/s3 p = viscosity, Pa s p = specific density, kg/m3 @ = (fuel-air ratio)/ (stoichiometric fuel-air ratio) = equiva-Subscripts 0 = initial (at flamefront) 1 = region ahead of flamefront 2 = zone of combustion 3 = region after flamefront i = index LFR = laminar-flow reactor PFR = plug-flow reactor r = radial component R = reactant TSB = thermally stabilized burner z = axial component Superscript -= mixed-mean value lence ratio