34,770 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
A small angle neutron scattering and Mössbauer spectrometry study of magnetic structures in nanocrystalline Ni3Fe
Results are reported from small angle neutron scattering and Mössbauer spectrometry measurements on nanocrystalline Ni3Fe. The nanocrystalline materials were prepared by mechanical attrition and studied in the as-milled state, after annealing at 265 °C to relieve internal stress, and after annealing 600 °C to prepare a control sample comprising large crystals. The small angle neutron scattering (SANS) measurements were performed for a range of applied magnetic fields. Small differences were found in how the different samples reached magnetic saturation. From the SANS data obtained at magnetic saturation, we found little difference in the nuclear scattering of the as-milled material and the material annealed at 265 °C. Reductions in nuclear scattering and magnetic scattering were observed for the control sample, and this was interpreted as grain growth. The material annealed at 265 °C also showed a reduction in magnetic SANS compared to the as-milled material. This was interpreted as an increase in magnetic moments of atoms at the grain boundaries after a low temperature annealing. Both Mössbauer spectroscopy and small angle neutron scattering showed an increase in the grain boundary magnetic moments after the 265 °C annealing (0.2 and 0.4µB/atom, respectively), even though there was little change in the grain boundary atomic density
Applicability of 100kWe-class of space reactor power systems to NASA manned space station missions
An assessment is made of a manned space station operating with sufficiently high power demands to require a multihundred kilowatt range electrical power system. The nuclear reactor is a competitor for supplying this power level. Load levels were selected at 150kWe and 300kWe. Interactions among the reactor electrical power system, the manned space station, the space transportation system, and the mission were evaluated. The reactor shield and the conversion equipment were assumed to be in different positions with respect to the station; on board, tethered, and on a free flyer platform. Mission analyses showed that the free flyer concept resulted in unacceptable costs and technical problems. The tethered reactor providing power to an electrolyzer for regenerative fuel cells on the space station, results in a minimum weight shield and can be designed to release the reactor power section so that it moves to a high altitude orbit where the decay period is at least 300 years. Placing the reactor on the station, on a structural boom is an attractive design, but heavier than the long tethered reactor design because of the shield weight for manned activity near the reactor
THE WAIT-AND-SEE OPTION IN ASCENDING PRICE AUCTIONS
Cake-cutting protocols aim at dividing a ``cake'' (i.e., a divisible
resource) and assigning the resulting portions to several players in a way that
each of the players feels to have received a ``fair'' amount of the cake. An
important notion of fairness is envy-freeness: No player wishes to switch the
portion of the cake received with another player's portion. Despite intense
efforts in the past, it is still an open question whether there is a
\emph{finite bounded} envy-free cake-cutting protocol for an arbitrary number
of players, and even for four players. We introduce the notion of degree of
guaranteed envy-freeness (DGEF) as a measure of how good a cake-cutting
protocol can approximate the ideal of envy-freeness while keeping the protocol
finite bounded (trading being disregarded). We propose a new finite bounded
proportional protocol for any number n \geq 3 of players, and show that this
protocol has a DGEF of 1 + \lceil (n^2)/2 \rceil. This is the currently best
DGEF among known finite bounded cake-cutting protocols for an arbitrary number
of players. We will make the case that improving the DGEF even further is a
tough challenge, and determine, for comparison, the DGEF of selected known
finite bounded cake-cutting protocols.Comment: 37 pages, 4 figure
and Perelomov number coherent states: algebraic approach for general systems
We study some properties of the Perelomov number coherent states.
The Schr\"odinger's uncertainty relationship is evaluated for a position and
momentum-like operators (constructed from the Lie algebra generators) in these
number coherent states. It is shown that this relationship is minimized for the
standard coherent states. We obtain the time evolution of the number coherent
states by supposing that the Hamiltonian is proportional to the third generator
of the Lie algebra. Analogous results for the Perelomov
number coherent states are found. As examples, we compute the Perelomov
coherent states for the pseudoharmonic oscillator and the two-dimensional
isotropic harmonic oscillator
Energy Conversion Alternatives Study (ECAS), General Electric Phase 1. Volume 3: Energy Conversion subsystems and components. Part 2: Primary heat input systems and heat exchangers
Primary heat input systems and heat exchangers were evaluated for advanced energy conversion systems. Results are presented and discussed
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