Design Lines

The two basic equations satisfied by the parameters of a block design define a three-dimensional affine variety $\mathcal{D}$ in $\mathbb{R}^{5}$. A point of $\mathcal{D}$ that is not in some sense trivial lies on four lines lying in $\mathcal{D}$. These lines provide a degree of organization for certain general classes of designs, and the paper is devoted to exploring properties of the lines. Several examples of families of designs that seem naturally to follow the lines are presented.Comment: 16 page

Viscoelastic deformation near active plate boundaries

Model deformations near the active plate boundaries of Western North America using space-based geodetic measurements as constraints are discussed. The first six months of this project were spent gaining familarity with space-based measurements, accessing the Crustal Dynamics Data Information Computer, and building time independent deformation models. The initial goal was to see how well the simplest elastic models can reproduce very long base interferometry (VLBI) baseline data. From the Crustal Dynamics Data Information Service, a total of 18 VLBI baselines are available which have been surveyed on four or more occasions. These data were fed into weighted and unweighted inversions to obtain baseline closure rates. Four of the better quality lines are illustrated. The deformation model assumes that the observed baseline rates result from a combination of rigid plate tectonic motions plus a component resulting from elastic strain build up due to a failure of the plate boundary to slip at the full plate tectonic rate. The elastic deformation resulting from the locked plate boundary is meant to portray interseismic strain accumulation. During and shortly after a large interplate earthquake, these strains are largely released, and points near the fault which were previously retarded suddenly catch up to the positions predicted by rigid plate models. Researchers judge the quality of fit by the sum squares of weighted residuals, termed total variance. The observed baseline closures have a total variance of 99 (cm/y)squared. When the RM2 velocities are assumed to model the data, the total variance increases to 154 (cm/y)squared

Viscoelastic deformation near active plate boundaries

Very Long Baseline Interferometry (VLBI) now has the capacity to monitor geodetic positions with precisions of a few 1 mm over continental baselines. For tectonic applications, one of the major products of the VLBI program is the determination of the rate of change of station locations. Vector site velocities are now routinely produced. One of the novel techniques, VLBI Euler poles, is discussed

A Far-Infrared Survey of Molecular Cloud Cores

We present a catalogue of molecular cloud cores drawn from high latitude, medium opacity clouds, using the all-sky IRAS Sky Survey Atlas (ISSA) images at 60 and 100~$\mu$m. The typical column densities of the cores are $N(H_2)\sim 3.8 \times 10^{21}$cm$^{-2}$ and the typical volume densities are $n(H_2) \sim 2 \times 10^3$cm$^{-3}$. They are therefore significantly less dense than many other samples obtained in other ways. Those cloud cores with IRAS point sources are seen to be already forming stars, but this is found to be only a small fraction of the total number of cores. The fraction of the cores in the protostellar stage is used to estimate the prestellar timescale - the time until the formation of a hydrostatically supported protostellar object. We argue, on the basis of a comparison with other samples, that a trend exists for the prestellar lifetime of a cloud core to decrease with the mean column density and number density of the core. We compare this with model predictions and show that the data are consistent with star formation regulated by the ionisation fraction.Comment: 13 pages, 7 figure

Children’s travel as pedestrians: an international survey of policy and practice

A survey of OECD member countries was carried out to provide high level data on a consistent basis to identify and account for current patterns of child road safety . This paper reports the findings relating to children, aged 0-14 years, as pedestrians. Key survey elements included analyses of fatality data, relationships between socio-economic, demographic factors and fatality rates, and a questionnaire based survey. League tables based on average child pedestrian fatality rates were constructed for each OECD member country participating in our questionnaire enabling identification of the top five countries with the lowest pedestrian fatality rate as Sweden, The Netherlands, Finland, Germany, and Denmark. Few countries had quantitative information about children’s travel and its absence means that assessments are difficult about children’s safety and the relative risks they face, especially as pedestrians. There are large variations in the amount of walking between countries and growing car use is becoming an issue in one third of OECD countries. The main findings from the questionnaire survey were that the majority of countries did not have information on high risk groups but of those that did, the cross cutting themes of socio-economic and ethnic minority groups, young children and urban areas were identified. Three characteristics distinguish top countries in the League table from those doing less well: a strong approach to the introduction of infrastructure measures for pedestrian safety, including low speed limits in residential areas; conducting road safety campaigns at least once a year; and having legislation which assumes driver responsibility in an accident involving a child pedestrian. Having compulsory road safety education for children aged 6-9 years was a characteristic shared by most countries, as was the promotion of child pedestrian education and training initiatives and the commissioning of research. However there is lower research activity in less well performing countries

Night-time accidents: a scoping study. Report to The AA Motoring Trust and Rees Jeffreys Road Fund

Context: Only a quarter of all travel by car drivers is undertaken between the hours of 19.00 and 08.00, but it is in this period that 40 percent of fatal and serious injuries are sustained by drivers. This indicates that car travel at night carries a greater risk of being killed or seriously injured than does travel during the day. The literature indicates that disproportionate numbers of young drivers, especially young men, are injured at night. But to be able to introduce measures targeted at this group more needs to be known about the purpose of their journeys, the types of roads they travel on, and how far they drive and at what times in the evening and at night. Older drivers tend to have fewer accidents at night, but little is currently known about how much can be accounted for by exposure related to their driving patterns. People over the age of 60 years form about 20 percent of the population, yet they make up over a quarter of traffic fatalities. These two groups of young and older drivers have been selected for study with the following aims: (a) to assess what information exists which relates to night-time exposure by activity and by group (young and older); (b) to assess what is known about exposure and risk to young and older drivers at night, in conjunction with an analysis of relevant accident data to provide a picture of the size of the potential problem areas, and gaps in current knowledge; (c) to identify people’s concerns, attitudes and beliefs with regard to the problems of night-time driving; and (d) to provide the basis for decision on what measures might be brought to bear on the problem, and what further research would be needed in order to point to focused action. This scoping study is in two parts and provides an assessment of the information available and hence the gaps in our knowledge on the nature and extent of night-time driving, and the risks involved at these times. The first part assesses the available data, and the second uses focus groups to gather the views of drivers themselves, together with their concerns, attitudes and beliefs with regard to the problems of night-time driving. The measurement of exposure, or amount of travel by car, of drivers of different age and gender is central to the assessment of the risk of being killed or injured in a road traffic accident. In this study, the measure of exposure used is distance travelled per person per year. This has been combined with casualty data to make preliminary assessments of risk to people of different ages and gender of driving at during the daytime and at night