Wright-Patterson Air Force Base

About: Wright-Patterson Air Force Base is a other organization based out in Wright-Patterson AFB, Ohio, United States. It is known for research contribution in the topics: Laser & Microstructure. The organization has 5817 authors who have published 9157 publications receiving 292559 citations. The organization is also known as: Wright-Patterson AFB & FFO.

The physical basis of moisture transport in a cured epoxy resin system

Abstract: The moisture transport characteristics of a difunctional epoxy resin cured with different amounts of metaphenylene diamine, using two cure cycles, are reported. Besides studying the kinetics of moisture sorption at 20, 50, 75, and 100°C, the investigations also included measurement of thermal expansion coefficients and dynamic mechanical transition of the dry and wet samples. The moisture sorption of the sample is shown to be related to its specific volume and hence to its fractional free volume. In the glassy state, the free volume is apparently in the form of frozen voids, and moisture sorption/desorption at this temperature is of the Langmuir type with little or no bond formation. At higher temperatures the free volume is generated predominantly through segmental motion of the α transition. The Henry's Law mode becomes operative, and the moisture can now form bonds. The possible effect of nonuniform crosslink density on moisture sorption is also considered.

Effect of nonparabolicity on the energy levels of hydrogenic donors in G a A s − Ga 1 − x Al x As quantum-well structures

Abstract: Binding energies of the ground state and of a few low-lying excited states of a hydrogenic donor in a quantum-well structure consisting of a single layer of GaAs sandwiched between two-semi-infinite layers of ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Al}}_{x}\mathrm{As}$ are calculated, including the effect of nonparabolicity of the conduction band and following a variational approach. The effect of nonparabolicity of the conduction band is included by using an expression for the energy-dependent effective mass based on the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}$ approximation. The variations of the binding energies of these states as a function of the size of the GaAs quantum well for different values of the potential barrier (or equivalently for different values of Al concentration $x$) are calculated. These results are compared with those obtained with the use of a parabolic conduction band.

Kinetics of Crystallization of Stoichiometric SiO2 Glass in H2O Atmospheres

Abstract: Crystallization rates were measured in vacuum, dry nitrogen, and water-saturated nitrogen atmospheres from 1300° to 1540°C. In all cases the observed rates were linear. Three reactions appeared to contribute to crystallization: the intrinsic crystallization, the impurity effect of H2O vapor, and furnace contamination. Enhancement of crystallization by both water vapor and furnace contamination is attributed to the breaking of silicon—oxygen bonds of the glass structure. Competitive adsorption mechanisms were proposed to characterize the adsorption of water and impurity species. The activation energy for apparent intrinsic crystallization was 134 kcal/mole; the activation energy for crystallization in H2O vapor was 77 kcal/mole.