Mesoscale modelling of optical turbulence in the atmosphere: The need for ultrahigh vertical grid resolution

The high-fidelity modelling of optical turbulence is critical to the design and operation of a new class of emerging highly sophisticated astronomical telescopes and adaptive optics instrumentation. In this study, we perform retrospective simulations of optical turbulence over the Hawaiian islands using a mesoscale model. The simulated...

Ionospheric calibration of low frequency radio interferometric observations using the peeling scheme

Calibration of radio interferometric observations becomes increasingly difficult towards lower frequencies. Below ?300 MHz, spatially variant refractions and propagation delays of radio waves traveling through the ionosphere cause phase rotations that can vary significantly with time, viewing direction and antenna location. In this article we...

Effects of cooling rate on corrosion properties of high strength aluminium alloys under atmospheric conditions

Long-term outdoor exposure tests were done to investigate the effect of cooling rate on corrosion and stress corrosion properties of extruded rods of the high strength aluminium alloys 2024-T4, 2023-T6, 7075-T6 and 7075-T73. The 2024 alloy exhibited a high susceptibility to SCC irrespective of best treatment and cooling rate, whereas 7075-T6 was...

Influence of environments on constant displacement stress corrosion crack growth in high strength aluminium alloys

An experimental investigation was carried out into the applicability of various corrosive environments for stress corrosion crack propagation testing of high strength aluminium alloys using double cantilever beam specimens. Testing under atmospheric conditions was used as a reference. It was found that stress corrosion crack growth under...

Testing of coatings and materials for jet engine components in simulated operational environments

Military aircraft flying low level missions in Western Europe encounter a very different environment from that in most of the United States. Industrial pullution causes atmospheric moisture to be highly acid, and the corrosion rate of jet engine components is greatly increased, with consequent high maintenance costs. To help combat this problem...

Environmental effects on crack grwoth in flight-simulation tests on 2024-T3 and 7075-T6 material Supplement: Compilation of test data from an investigation on the effect of environment on crack growth under flight-simulation loading

Flight-simulation tests based on a standardized gust load spectrum were carried out in normal air, very dry air and salt water. Specimen thicknesses were t = 2 mm and t = 10 mm, mean stress in flight was 70 or 55 MN/m². In all cases a significant effect of the environment was found. Fatigue lives for t = 10 ram were much shorter than for t = 2...