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.

An analysis of the isothermal hot compression test

Abstract: The nominally isothermal, uniaxial hot compression test has been analyzed with special reference to the effects of temperature nonuniformities and friction on sample deformation and flow stress estimates. A simple one-dimensional analysis was used to establish the influence of initial temperature nonuniformities, strain rate, and the temperature dependence of the flow stress on flow localization tendencies. Noticeable strain concentrations were predicted to occur only at high strain rates (∼10 s−1) in materials such as titanium alloys, but not in steels, for typical values of the initial temperature nonuniformity. More extensive numerical (finite element method) simulations of the compression test with various values of the friction shear factor corroborated the conclusions of the flow localization analysis. In addition, it was established that initial temperature nonuniformities, as well as friction, have an almost negligible effect on flow stress data deduced from measurements of average pressurevs true height strain, at least for reductions of the order of 50 pct. The analysis results were supported by observations of the deformation behavior of a near-gamma titanium aluminide and a low-alloy steel.

Biological versus electronic adaptive coloration: how can one inform the other?

Abstract: Adaptive reflective surfaces have been a challenge for both electronic paper (e-paper) and biological organisms. Multiple colours, contrast, polarization, reflectance, diffusivity and texture must all be controlled simultaneously without optical losses in order to fully replicate the appearance of natural surfaces and vividly communicate information. This review merges the frontiers of knowledge for both biological adaptive coloration, with a focus on cephalopods, and synthetic reflective e-paper within a consistent framework of scientific metrics. Currently, the highest performance approach for both nature and technology uses colourant transposition. Three outcomes are envisioned from this review: reflective display engineers may gain new insights from millions of years of natural selection and evolution; biologists will benefit from understanding the types of mechanisms, characterization and metrics used in synthetic reflective e-paper; all scientists will gain a clearer picture of the long-term prospects for capabilities such as adaptive concealment and signalling.

Wall pressure fluctuations in attached boundary-layer flow

Abstract: An examination has been made to derive a correlation for an aeroacoustic environment associated with attached compressible flow conditions. It was determined that fluctuating pressure characteristics described by incompressible theory as well as empirical correlations could be modified to a compressible state through a transformation function. In this manner, compressible data were transformed to the incompressible plane where direct use of more tractable prediction techniques are available for engineering design analyses. The investigation centered on algorithms associated with pressure magnitude and power spectral density. The method and subsequent prediction techniques are shown to be in excellent agreement with both incompressible and compressible flow data.

Prediction of the kinetics of static globularization of Ti-6Al-4V

Abstract: The time for the static globularization of alpha lamellae in Ti-6Al-4V was predicted using analytical and finite-difference models based on the diffusion-controlled migration of the edges of remnant pancake-shaped particles Similar to a previous two-dimensional analysis of the cylinderization of a semi-infinite, platelike second phase, the models quantified the influence of heat-treatment temperature, platelet thickness, and platelet diameter-to-thickness ratio on globularization kinetics The present approaches were validated by comparison to previous observations of static globularization of Ti-6Al-4V at 955 °C

Widely tunable, photoinvertible cholesteric liquid crystals.

Abstract: Researchers have examined the utility of this mesophase in a range of topical areas including optics (switchable or tunable fi lters), photonics (selective shutters), and lasing (mirrorless feedback cavity). [ 1 , 2 ] Like other liquid-crystal phases, CLCs are responsive to a range of stimuli including temperature, electric fi elds, and light. The color switching or tuning response to each of these stimuli has been recently reviewed. [ 3 ] In particular, photoresponsive CLCs offer the capability of dynamic selective refl ection cued by light itself. Photoresponsive CLCs have been examined for more than forty years. Early examinations looked at photodegradation of halide-containing cholestryl mixtures [ 4 , 5 ] as well as guest–host mixtures with photochromics such as azobenzene. [ 6 ] Vinogradov et al. were the fi rst to demonstrate comparably larger optical responses by employing photoresponsive chiral materials to formulate the CLC mixture. [ 7 ] In this case, a menthone chiral dopant yielded a approximately 400-nm tuning of the refl ection bandgap with exposure to a 442-nm helium–cadmium laser. Convergent to this effort, Feringa, [ 8 , 9 ] Schuster, [ 10–12 ] and others pursued the synthesis of novel photochiral materials, which at the time were focused towards the development of an optical switch. In these examinations, as well as others that have followed, a variety of photochromic chiral materials have been examined including menthone, [ 7 , 13 , 14 ] chiral olefi ns, fulgides, [ 15 , 16 ] azobenzene, [ 17–24 ] and overcrowded alkenes. [ 25–27 ]