37,274 research outputs found
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
Bigger Bursts From Merging Neutron Stars
GRB 990123 may have radiated more than one solar mass equivalent in just its
gamma emissions. Though this may be within the upper limit of the binding
energy available from neutron stars in the Schwarzschild metric, it is
difficult to imagine a process with the required efficiency of conversion to
gamma rays. Neutron stars of ~10 solar mass are permitted in the Yilmaz metric.
A merger of two neutron stars of maximum mass could release approximately 10
solar mass equivalent binding energy.Comment: 5 pages, 1 figure, submitted to ApJ Letter
Coherent and generalized intelligent states for infinite square well potential and nonlinear oscillators
This article is an illustration of the construction of coherent and
generalized intelligent states which has been recently proposed by us for an
arbitrary quantum system . We treat the quantum system submitted to the
infinite square well potential and the nonlinear oscillators. By means of the
analytical representation of the coherent states \`{a} la Gazeau-Klauder and
those \`{a} la Klauder-Perelomov, we derive the generalized intelligent states
in analytical ways
Rapid deconvolution of low-resolution time-of-flight data using Bayesian inference
The deconvolution of low-resolution time-of-flight data has numerous advantages, including the ability to extract additional information from the experimental data. We augment the well-known Lucy-Richardson deconvolution algorithm using various Bayesian prior distributions and show that a prior of second-differences of the signal outperforms the standard Lucy-Richardson algorithm, accelerating the rate of convergence by more than a factor of four, while preserving the peak amplitude ratios of a similar fraction of the total peaks. A novel stopping criterion and boosting mechanism are implemented to ensure that these methods converge to a similar final entropy and local minima are avoided. Improvement by a factor of two in mass resolution allows more accurate quantification of the spectra. The general method is demonstrated in this paper through the deconvolution of fragmentation peaks of the 2,5-dihydroxybenzoic acid matrix and the benzyltriphenylphosphonium thermometer ion, following femtosecond ultraviolet laser desorption
Generalized coherent and intelligent states for exact solvable quantum systems
The so-called Gazeau-Klauder and Perelomov coherent states are introduced for
an arbitrary quantum system. We give also the general framework to construct
the generalized intelligent states which minimize the Robertson-Schr\"odinger
uncertainty relation. As illustration, the P\"oschl-Teller potentials of
trigonometric type will be chosen. We show the advantage of the analytical
representations of Gazeau-Klauder and Perelomov coherent states in obtaining
the generalized intelligent states in analytical way
The quantum probability ranking principle for information retrieval
While the Probability Ranking Principle for Information Retrieval provides the basis for formal models, it makes a very strong assumption regarding the dependence between documents. However, it has been observed that in real situations this assumption does not always hold. In this paper we propose a reformulation of the Probability Ranking Principle based on quantum theory. Quantum probability theory naturally includes interference effects between events. We posit that this interference captures the dependency between the judgement of document relevance. The outcome is a more sophisticated principle, the Quantum Probability Ranking Principle, that provides a more sensitive ranking which caters for interference/dependence between documents’ relevanc
Are there any good digraph width measures?
Several different measures for digraph width have appeared in the last few
years. However, none of them shares all the "nice" properties of treewidth:
First, being \emph{algorithmically useful} i.e. admitting polynomial-time
algorithms for all \MS1-definable problems on digraphs of bounded width. And,
second, having nice \emph{structural properties} i.e. being monotone under
taking subdigraphs and some form of arc contractions. As for the former,
(undirected) \MS1 seems to be the least common denominator of all reasonably
expressive logical languages on digraphs that can speak about the edge/arc
relation on the vertex set.The latter property is a necessary condition for a
width measure to be characterizable by some version of the cops-and-robber game
characterizing the ordinary treewidth. Our main result is that \emph{any
reasonable} algorithmically useful and structurally nice digraph measure cannot
be substantially different from the treewidth of the underlying undirected
graph. Moreover, we introduce \emph{directed topological minors} and argue that
they are the weakest useful notion of minors for digraphs
Modification of the simple mass balance equation for calculation of critical loads of acidity.
Over the last few years, the simple mass balance equation for the calculation of critical loads of acidity has been gradually modified as the underlying critical load concepts have developed and as problems with particular forms of the equation have been identified, through application in particular countries. The first major update of the equation took place following a workshop held in Vienna, Austria (Hojesky et al. 1993). The workshop was held to discuss problems which had been identified when the then current form of the equation was applied in countries with high rainfall. The problems had largely arisen because of simplifications and assumptions incorporated into the early formulation of the equation. The equation was reformulated to overcome the problems identified at the workshop. However, further problems were identified when the reformulated equation was applied in the UK in situations with a combination of high rainfall, large marine inputs and widespread occurrence of organic soils. A small workshop was, therefore held in Grange-over-Sands, UK in late 1993 to dicuss the problems and to further re-evaluate the equation. The problems had arisen in the UK because of simplifications and assumptions made in the formulation concerning, in particular, cation leaching and uptake. As a result, a more rigorous treatment of these variables was incorporated into the equation. The reformulation of the equation, as derived at the September 1993 workshop is described below
Extremal extensions of entanglement witnesses: Unearthing new bound entangled states
In this paper, we discuss extremal extensions of entanglement witnesses based
on Choi's map. The constructions are based on a generalization of the Choi map
due to Osaka, from which we construct entanglement witnesses. These extremal
extensions are powerful in terms of their capacity to detect entanglement of
positive under partial transpose (PPT) entangled states and lead to unearthing
of entanglement of new PPT states. We also use the Cholesky-like decomposition
to construct entangled states which are revealed by these extremal entanglement
witnesses.Comment: 8 pages 6 figures revtex4-
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