Development and application of a non-Gaussian atmospheric turbulence model for use in flight simulators

A method is described for generating time histories which model the frequency content and certain non-Gaussian probability characteristics of atmospheric turbulence including the large gusts and patchy nature of turbulence. Methods for time histories using either analog or digital computation are described. A STOL airplane was programmed into a 6-degree-of-freedom flight simulator, and turbulence time histories from several atmospheric turbulence models were introduced. The pilots' reactions are described

Finite element modeling of misalignment in interconnect vias

Electrical resistance and hence heat generation in semiconductor chips are becoming more significant issues particularily as generations of silicon devices continue to have smaller features. The resistance of interconnect vias is a significant source of heat generation because of the increasing number of these on chips and increases in via resistance due to reduced size. Finite element modeling of voltage drops and current flow through interconnect vias gives information to aid in designing geometry and materials used in forming vias. It can also be used for modeling the thermal distribution in a via and hence the contribution by vias to heating a chip. In this paper we examine the effect of misalignment of the via between the two metal layers M1 and M2 with regard to the interconnect via resistance. The effect of the interface specific contact resistance is examined in particular. Significant misalignment can be tolerated without increasing the via resistance. The heat generation due to electrical current flow in the via materials and interfaces is modelled using the samefinite element mesh and software. The output of the electrical analysis is used as the heat generation input for the therml analysis

Wheat rust epidemics

Stem rust of wheat is probably the most damaging plant disease in the world. The rust fungus attacks stems, leaves and heads, producing characteristic red-brown pustules which affect the plant\u27s ability to fill out the grain. Yield loss is directly related to the amount of rust in the crop and the length of time the crop is infected. In Western Australia it is not uncommon to find rust on crops in mid-October, but usually there is negligible loss of yield. In fact this pattern is quite normal throughout the world: In general, rust arrives too late to cause an epidemic. Why is this

Extreme X-ray variability in the luminous quasar PDS 456

We present evidence from Beppo-SAX and XMM-Newton of extreme X-ray variability in the high luminosity radio-quiet quasar PDS 456, the most luminous known AGN at z<0.3. Repeated X-ray flaring is found in PDS 456, over the duration of the 340 ksec long Beppo-SAX observation. The X-ray flux doubles in just 30 ksec, whilst the total energy output of the flaring events is as high as 10^51 erg. Under the assumption of isotropic emission at the Eddington limit, this implies that the size of the X-ray emitting region in PDS 456 is less than 3 Schwarzschild radii, for a 10^9 solar mass black hole. From the rates of change of luminosity observed during the X-ray flares, we calculate lower limits for the radiative efficiency between 0.06 and 0.41, implying that accretion onto a Kerr black hole is likely in PDS 456. We suggest that the rapid variability is from X-ray flares produced through magnetic reconnection above the disc and calculate that the energetics and timescale of the flares are plausible if the quasar is accreting near to the maximum Eddington rate. A similar mechanism may account for the extreme rapid X-ray variability observed in many Narrow Line Seyfert 1s. In the case of PDS 456, we show that the X-ray flaring could be reproduced through a self-induced cascade of about 1000 individual flares over a timescale of the order 1 day.Comment: 5 pages. Accepted for publication in MNRAS Letter

Comet and Meteorite Traditions of Aboriginal Australians

Of the hundreds of distinct Aboriginal cultures of Australia, many have oral traditions rich in descriptions and explanations of comets, meteors, meteorites, airbursts, impact events, and impact craters. These views generally attribute these phenomena to spirits, death, and bad omens. There are also many traditions that describe the formation of meteorite craters as well as impact events that are not known to Western science.Comment: Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures, 2014. Edited by Helaine Selin. Springer Netherland