2,792 research outputs found
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Does the threat of disqualification deter drivers from speeding?
Road Safety Research Report, number 96, is available from the National Archives: Department for Transport, and can be accessed from the link below.It has long been recognised that driving speeds that are excessive and inappropriate
to the conditions are a major contributory factor in road accidents, and a major issue
for road safety. Restraining driving speeds has proved to be a difficult task, given the
improvements over the years in both vehicle performance and road design.
Within the traditional āthree Esā countermeasures of engineering, education and
enforcement, recent years have seen the introduction of a wide range of engineering
measures designed to bring about speed reduction, but these tend to be restricted to
specific parts of the road network. New technologies such as Intelligent Speed
Adaptation (ISA) offer considerable promise, but mainly in the medium or longer term. Similarly, educative efforts to induce attitude and behaviour change in this context are bearing fruit, yet this is a long-term rather than short-term project. For the foreseeable future, enforcement will remain the principal means of influencing speed, by setting speed limits and imposing sanctions on drivers who are caught exceeding them.
The number of licence endorsements has increased enormously in recent years.
However, over the same period the number of disqualifications resulting from ātotting-upā points has decreased. This would seem to indicate that many drivers who accumulate up to 11 penalty points are either acting as if deterred by the threat of disqualification, or are avoiding disqualification in some other way. The extent to which penalty points act as a deterrent for the benefit of road safety in general is therefore an important issue, and this report describes work that has been carried out to study this issue by TRL and Brunel University, under contract to the Department for Transport
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Investigating the Intelligibility of a Computer Vision System for Blind Users
Computer vision systems to help blind usersare becoming increasingly common yet often these systems are not intelligible. Our work investigates the intelligibility of a wearable computer vision system to help blind users locate and identify people in their vicinity. Providing a continuous stream of information, this system allows us to explore intelligibility through interaction and instructions, going beyond studies of intelligibility that focus on explaining a decision a computer vision system might make. In a study with 13 blind users, we explored whether varying instructions (either basic or enhanced) about how the system worked would change blind usersā experience of the system. We found offering a more detailed set of instructions did not affect how successful users were using the system nor their perceived workload. We did, however, find evidence of significant differences in what they knew about the system, and they employed different, and potentially more effective, use strategies. Our findings have important implications for researchers and designers of computer vision systemsfor blind users, as well more general implications for understanding what it means to make interactive computer vision systems intelligible
Donor binding energy and thermally activated persistent photoconductivity in high mobility (001) AlAs quantum wells
A doping series of AlAs (001) quantum wells with Si delta-modulation doping
on both sides reveals different dark and post-illumination saturation
densities, as well as temperature dependent photoconductivity. The lower dark
two-dimensional electron density saturation is explained assuming deep binding
energy of Delta_DK = 65.2 meV for Si-donors in the dark. Persistent
photoconductivity (PPC) is observed upon illumination, with higher saturation
density indicating shallow post-illumination donor binding energy. The
photoconductivity is thermally activated, with 4 K illumination requiring
post-illumination annealing to T = 30 K to saturate the PPC. Dark and
post-illumination doping efficiencies are reported.Comment: The values of binding energy changed from previous versions because
of a better understanding for the dielectric permittivity. Also, the Gamma -
X donor states are better explaine
Biological Consequences of Tightly Bent DNA: The Other Life of a Macromolecular Celebrity
The mechanical properties of DNA play a critical role in many biological
functions. For example, DNA packing in viruses involves confining the viral
genome in a volume (the viral capsid) with dimensions that are comparable to
the DNA persistence length. Similarly, eukaryotic DNA is packed in DNA-protein
complexes (nucleosomes) in which DNA is tightly bent around protein spools. DNA
is also tightly bent by many proteins that regulate transcription, resulting in
a variation in gene expression that is amenable to quantitative analysis. In
these cases, DNA loops are formed with lengths that are comparable to or
smaller than the DNA persistence length. The aim of this review is to describe
the physical forces associated with tightly bent DNA in all of these settings
and to explore the biological consequences of such bending, as increasingly
accessible by single-molecule techniques.Comment: 24 pages, 9 figure
Social Security Reform: Risks, Returns, and Race
The debate over social security reform has far-reaching implications for the economic well-being of blacks and other minority groups. In this article, we examine how blacks have fared under the existing system, and then consider the likely consequences of moving toward a privatized system. Specifically, we consider the claim, recently advanced by some privatizers, that blacks receive an especially bad deal under the existing system and would be better off under a privatized system. We find that, for blacks as a group, this claim tends to overstate both the shortcomings of the existing system and the advantages of privatization. Furthermore, we urge that the racial impact of social security reform deserves serious and sustained consideration. While the path of reform will inevitably require difficult tradeoffs between competing policy goals and political constituencies, no serious reform proposal can ignore the issue of racial equality in the debate over social security
Reconstruction of Fractional Quantum Hall Edges
We study the interplay of interaction, confining potential and effects of
finite temperature at the edge of a quantum Hall liquid. Our exact
diagonalization calculation indicates that edge reconstruction occurs in the
fractional quantum Hall regime for a variety of confining potential, including
ones that correspond to a "sharp" edge. Our finite temperature Hartree-Fock
calculation for integer quantum Hall edges indicates that reconstruction is
suppressed above certain temperature. We discuss the implication of our results
on recent edge tunneling and microwave absorption experiments.Comment: Revised version. 5 papges RevTex with 5 eps figures embedded in the
tex
Experiments on the Fermi to Tomonaga-Luttinger liquid transition in quasi-1D systems
We present experimental results on the tunneling into the edge of a two
dimensional electron gas (2DEG) obtained with GaAs/AlGaAs cleaved edge
overgrown structures. The electronic properties of the edge of these systems
can be described by a one-dimensional chiral Tomonaga-Luttinger liquid when the
filling factor of the 2DEG is very small. Here we focus on the region where the
Tomonaga-Luttinger liquid breaks down to form a standard Fermi liquid close to
and show that we recover a universal curve, which describes all
existing data.Comment: 5 pages, localisation 2002, conference proceeding
Tunnelling Spectroscopy of Localized States near the Quantum Hall Edge
In the paper we dscuss experimental results of M. Grayson et al. on tunneling
- characteristics of the quantum Hall edge. We suggest a two step
tunneling mechanism involving localized electron states near the edge, which
might account for discrepancy between the experimental data and the predictions
of the chiral Luttinger liquid theory of the quantum Hall edge.Comment: 4 pages, revte
Fermi liquid to Luttinger liquid transition at the edge of a two-dimensional electron gas
We present experimental results on the tunneling into the edge of a two
dimensional electron gas (2DEG) obtained with a GaAs/AlGaAs cleaved edge
overgrown structure in a strong perpendicular magnetic field. While the 2DEG
exhibits typical fractional quantum Hall features of a very high mobility
sample, we observe the onset of a non-linear current-voltage characteristic in
the vicinity of nu=1. For filling factor nu<1 the system is consistent with a
non-Fermi liquid behavior, such as a Luttinger liquid, whereas for nu>1 we
observe an Ohmic tunneling resistance between the edge and a three dimensional
contact, typical for a Fermi liquid. Hence, at the edge, there is a transition
from a Luttinger liquid to a Fermi liquid. Finally, we show that the Luttinger
liquid exponent at a given filling factor is not universal but depends on
sample parameters.Comment: 4 pages, 4 figure
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