Progress in coherent laser radar

Considerable progress with coherent laser radar has been made over the last few years, most notably perhaps in the available range of high performance devices and components and the confidence with which systems may now be taken into the field for prolonged periods of operation. Some of this increasing maturity was evident at the 3rd Topical Meeting on Coherent Laser Radar: Technology and Applications. Topics included in discussions were: mesoscale wind fields, nocturnal valley drainage and clear air down bursts; airborne Doppler lidar studies and comparison of ground and airborne wind measurement; wind measurement over the sea for comparison with satellite borne microwave sensors; transport of wake vortices at airfield; coherent DIAL methods; a newly assembled Nd-YAG coherent lidar system; backscatter profiles in the atmosphere and wavelength dependence over the 9 to 11 micrometer region; beam propagation; rock and soil classification with an airborne 4-laser system; technology of a global wind profiling system; target calibration; ranging and imaging with coherent pulsed and CW system; signal fluctuations and speckle. Some of these activities are briefly reviewed

Properties and Analysis of Thermally Aged Poly(ethylene oxide)

Recent studies have been performed into the use of polyethylene oxide (PEO) as a model system for observing the fundamental effects of adding micro and nano sized fillers to create polymeric composite systems. Many factors contribute to the successful creation of such a composite system, including dispersion of the filler and treatment of the material during creation. For example, while producing thin films of the materials for testing, high temperatures were used for short periods of time in open air to press the samples into small discs. It is well known that prolonged high temperature exposure can alter the chemistry and structure of polymeric materials and that small variations in the original chemistry, such as longer molecular weights or introduction of fillers, can reduce or possibly accelerate this 'ageing' effect. From these previous investigations many property changes were observed during addition of filler or variation of molecular weight, therefore to accurately attribute these changes to a cause the thermal ageing of the material should be observed. This investigation looks at the same 3 molecular weight PEO systems as those used in the previous investigations and analyses them for their vulnerability to thermal ageing. One thermally aged sample is then taken and tested alongside an unaged sample to observe the effects that the process has on the properties. This includes rheology in solution, differential scanning calorimetry (DSC), AC electrical breakdown, dielectric spectroscopy and Fourier transform infra-red (FTIR). By observing the property changes of aged samples it is possible to better understand the thermal ageing process occurring and possibly a way to reduce the effect, along with considering the effect with regard to the behaviour of the previously tested composite samples

The linear rms-flux relation in an Ultraluminous X-ray Source

We report the first detection of a linear correlation between rms variability amplitude and flux in the Ultraluminous X-ray source NGC 5408 X-1. The rms-flux relation has previously been observed in several Galactic black hole X-ray binaries (BHBs), several Active Galactic Nuclei (AGN) and at least one neutron star X-ray binary. This result supports the hypothesis that a linear rms-flux relation is common to all luminous black hole accretion and perhaps even a fundamental property of accretion flows about compact objects. We also show for the first time the cross-spectral properties of the variability of this ULX, comparing variations below and above 1 keV. The coherence and time delays are poorly constrained but consistent with high coherence between the two bands, over most of the observable frequency range, and a significant time delay (with hard leading soft variations). The magnitude and frequency dependence of the lags are broadly consistent with those commonly observed in BHBs, but the direction of the lag is reversed. These results indicate that ULX variability studies, using long X-ray observations, hold great promise for constraining the processes driving ULXs behaviour, and the position of ULXs in the scheme of black hole accretion from BHBs to AGN.Comment: 4 Pages, 3 figures, accepted for publication by MNRAS

Graded Lie algebras of maximal class IV

We describe the isomorphism classes of certain infinite-dimensional graded Lie algebras of maximal class, generated by an element of weight one and an element of weight two, over fields of odd characteristic.Comment: 38 pages. See also http://www-math.science.unitn.it/~caranti/ and http://users.ox.ac.uk/~vlee

Space and exclusion: does urban morphology play a part in social deprivation?

There is currently a growing interest in the spatial causes of poverty, particularly its persistence. This paper presents methodological innovations that have been developed for investigating the relationship between physical segregation and economic marginalization in the urban environment. Using GIS to layer historical poverty data, contemporary deprivation indexes and space syntax measures of spatial segregation, a multivariate system has been created to enable the understanding of the spatial process involved in the creation and stagnation of poverty areas as well as to analyse the street segment scale of configuration

Visualising London's Suburbs

2 - 4 April 200

Cavitation induced starvation for piston-ring/liner tribological conjunction

The study investigates the mechanism of ring-liner lubrication in the vicinity of the top and bottom dead centres of an internal combustion engine. Predicting lubricant transient behaviour is critical when the inlet reversal leads to thin films and inherent metal-to-metal interaction. It was found that the cavitation, which is located at the trailing edge of the contact before reversal, briefly survives after reversal as a confined bubble at the leading edge. This depletes the film promoting starvation. Several algorithms were compared. It is concluded that the lubricant film is thinner than initially thought