Spatial variability in correlation decay distance and influence on angular-distance weighting interpolation of daily precipitation over Europe

Angular-distance weighting (ADW) is a common approach for interpolation of an irregular network of meteorological observations to a regular grid. A widely used version of ADW employs the correlation decay distance (CDD) to (1) select stations that should contribute to each grid-point estimate and (2) define the distance component of the station weights. We show, for Europe, that the CDD of daily precipitation varies spatially, as well as by season and synoptic state, and is also anisotropic. However, ADW interpolation using CDDs that varies spatially by season or synoptic state yield only small improvements in interpolation skill, relative to the use of a fixed CDD across the entire domain. If CDDs are optimized through cross validation, a larger improvement in interpolation skill is achieved. Improvements are larger for the determination of the state of precipitation (wet/dry) than for the magnitude. These or other attempts to improve interpolation skill appear to be fundamentally limited by the available station networ

The influence of interpolation and station network density on the distributions and trends of climate variables in gridded daily data

We study the influence of station network density on the distributions and trends in indices of area-average daily precipitation and temperature in the E-OBS high resolution gridded dataset of daily climate over Europe, which was produced with the primary purpose of Regional Climate Model evaluation. Area averages can only be determined with reasonable accuracy from a sufficiently large number of stations within a grid-box. However, the station network on which E-OBS is based comprises only 2,316 stations, spread unevenly across approximately 18,000 0.22A degrees grid-boxes. Consequently, grid-box data in E-OBS are derived through interpolation of stations up to 500 km distant, with the distance of stations that contribute significantly to any grid-box value increasing in areas with lower station density. Since more dispersed stations have less shared variance, the resultant interpolated values are likely to be over-smoothed, and extreme daily values even more so. We perform an experiment over five E-OBS grid boxes for precipitation and temperature that have a sufficiently dense local station network to enable a reasonable estimate of the area-average. We then create a series of randomly selected station sub-networks ranging in size from four to all stations within the E-OBS interpolation search radii. For each sub-network realisation, we estimate the grid-box average applying the same interpolation methodology as used for E-OBS, and then evaluate the effect of network density on the distribution of daily values, as well as trends in extremes indices. The results show that when fewer stations have been used for the interpolation, both precipitation and temperature are over-smoothed, leading to a strong tendency for interpolated daily values to be reduced relative to the "true" area-average. The smoothing is greatest for higher percentiles, and therefore has a disproportionate effect on extremes and any derived extremes indices. For many regions of the E-OBS dataset, the station density is sufficiently low to expect this smoothing effect to be significant and this should be borne in mind by any users of the E-OBS dataset

Rotational Instabilities and Centrifugal Hangup

One interesting class of gravitational radiation sources includes rapidly rotating astrophysical objects that encounter dynamical instabilities. We have carried out a set of simulations of rotationally induced instabilities in differentially rotating polytropes. An $n$=1.5 polytrope with the Maclaurin rotation law will encounter the $m$=2 bar instability at $T/|W| \gtrsim 0.27$. Our results indicate that the remnant of this instability is a persistent bar-like structure that emits a long-lived gravitational radiation signal. Furthermore, dynamical instability is shown to occur in $n$=3.33 polytropes with the $j$-constant rotation law at $T/|W| \gtrsim 0.14$. In this case, the dominant mode of instability is $m$=1. Such instability may allow a centrifugally-hung core to begin collapsing to neutron star densities on a dynamical timescale. If it occurs in a supermassive star, it may produce gravitational radiation detectable by LISA.Comment: 13 pages (includes 11 figures) and 1 separate jpeg figure; to appear in Astrophysical Sources of Gravitational Radiation, AIP conference proceedings, edited by Joan M. Centrell

Effect of Leading Edge Protuberance on Thrust Production of a Dynamically Pitching Aerofoil

The paper presents a computational analysis of the characteristics of a NACA 634-021 aerofoil modified by incorporating sinusoidal leading-edge protuberances at Re = 14,000. The protuberances are from the tubercles of the humpback whale flipper with leading edge acting as passive-flow control devices that improve performance and manoeuvrability of the flipper. They are characterized by an amplitude and wavelength of 12% and 50% of the aerofoil chord length respectively. Three-dimensional CFD on the modified aerofoil oscillating about a point located on the centreline at quarter-chord has been performed with the frequency and amplitude of oscillation being 4Hz and 10 deg respectively. In addition to the lift and thrust coefficients, near wall flow visualisations and the shedding of vortices during oscillations are presented to illustrate the unsteady flow features on the performance of the oscillating flipper. The results show an improvement in the thrust production when compared to previous studies on similar symmetric aerofoil without the leading edge modifications

Advection Dominated Accretion Flows Around Kerr Black Holes

We derive all relevant equations needed for constructing a global general relativistic model of advectively cooled, very hot, optically thin accretion disks around black holes and present solutions which describe advection dominated flows in the gravitational field of a Kerr black hole.Comment: ApJ submitte

Intentional and unintentional non-adherence in community dwelling people with type 2 diabetes: the effect of varying numbers of medicines

People with type 2 diabetes are often prescribed multiple medicines which can be difficult to manage. Nonadherence to medicines can be intentional (e.g. active decision) or unintentional (e.g. forgetting). The objective of this study was to measure intentional and unintentional non-adherence to differing numbers of medicines prescribed in type 2 diabetes. A cross sectional survey using the Morisky medication adherence scale (with intentional and unintentional non-adherence subscales) was completed by 480 people prescribed oral antidiabetic drugs (OADs), antihypertensive agents and statins. A within-subject analysis of variance (ANOVA) showed that intentional non-adherence did not vary between OADs, anti-hypertensives and statins. Intentional non-adherence to statins significantly increased when the number of medicines prescribed was included as a between-subjects variable (p<0.05). Another within-subject ANOVA on unintentional non-adherence found a significant difference between OADs, anti-hypertensives and statins; unintentional non-adherence to OADs was significantly higher (p<0.05). When the number of medicines was added as a between-subject variable unintentional non-adherence was associated with higher numbers of medicines. This study shows the difference between intentional and unintentional non-adherence behaviours, and the effect that varying numbers of medicines can have on these behaviours

Ground vibration during the bentonite tunnelling process

The research was carried out during the bentonite shield tunnel drive for the Acton Grange trunk outfall sewer at Warrington, Cheshire. This tunnel is driven through cohesionless Drift deposits beneath a built-up urban environment, with a cover of less than 6m. The environmental effects of the ground vibration caused by the excavation process are investigated with particular regard to ground settlement by compaction. The geology of the area and the technical and commercial factors which led to the choice of the bentonite tunnelling system are described. Previous work on compaction by vibration is critically reviewed and methods to assess a soil's potential for compaction are given. The vibration instrumentation is described and relevant wave propagation theory is developed with emphasis on body waves from underground sources. Vibration data were recorded from transducers located in boreholes, on the pavement surface, on the tunnelling machine and on the concrete tunnel lining. These records were processed to characterise the vibrations in terms of peak particle velocities, frequency spectra and spatial attenuation.The maximum measured ground vibration (expressed in terms of resultant peak particle velocity) was 3.90 mm/s. The vibration was characterised by random high velocity particle motions resulting from impacts between the machine's disc cutters and glacial boulders in the tunnel face. Surface and subsurface settlement measurements were made along the tunnel line and structural damage to property above the tunnel was observed. Laboratory tests and other field data showed that the ground in this area was likely to settle at levels of vibration lower than those measured from the tunnelling machine. The vibration caused by the excavation process caused ground compaction which contributed to ground settlement and the ensuing damage to the overlying structures. The vibration was not likely to have damaged these properties directly but did cause considerable nuisance to the residents

An Investigation of the Appropriateness of Computer-Based Instruction to the Royal Australian Air Force CISCON Mustering

Currently, the Royal Australian Air Force (RAAF) uses traditional methods of training for all of its personnel, including the newly formed Communications and Information Systems Controllers (CISCON) mustering. The formation of this mustering and the concurrent formation on every RAAF base of a Base Information Systems Centre (BISC) brought to light training needs that were not being met. Using many different forms of stimulation to activate learning, computer-based instruction (CBI), in particular multimedia, represents an alternative method of presenting training.This research investigated the applicability of CBI to the RAAF by matching its features with the training needs of the CISCONs and demonstrated the application of multimedia design principles to a specific CISCON course. An analysis of BISC training needs suggested that CBI will operate as effectively as it has in similar studies thoroughly documented in the literature. This thesis has also demonstrated in a practical way the importance of considering the many multimedia design principles when designing CBI using an existing training course. This thesis directly supports the use of CBI to train CISCON working at the BISCs and further suggests that the RAAF should consider CBI for all of its future training