1,661 research outputs found
Road traffic pollution monitoring and modelling tools and the UK national air quality strategy.
This paper provides an assessment of the tools required to fulfil the air quality management role now expected of local authorities within the UK. The use of a range of pollution monitoring tools in assessing air quality is discussed and illustrated with evidence from a number of previous studies of urban background and roadside pollution monitoring in Leicester. A number of approaches to pollution modelling currently available for deployment are examined. Subsequently, the modelling and monitoring tools are assessed against the requirements of Local Authorities establishing Air Quality Management Areas. Whilst the paper examines UK based policy, the study is of wider international interest
Predicting real-time roadside CO and NO2 concentrations using neural networks
The main aim of this paper is to develop a model based on neural network (NN) theory to estimate real-time roadside CO and concentrations using traffic and meteorological condition data. The location of the study site is at a road intersection in Melton Mowbray, which is a town in Leicestershire, U.K. Several NNs, which can be classified into three types, namely, the multilayer perceptron, the radial basis function, and the modular network, were developed to model the nonlinear relationships that exist in the pollutant concentrations. Their performances are analyzed and compared. The transferability of the developed models is studied using data collected from a road intersection in another city. It was concluded that all NNs provide reliable estimates of pollutant concentrations using limited information and noisy data
Predicting real-time roadside CO and NO2 concentrations using neural networks
The main aim of this paper is to develop a model based on neural network (NN) theory to estimate real-time roadside CO and concentrations using traffic and meteorological condition data. The location of the study site is at a road intersection in Melton Mowbray, which is a town in Leicestershire, U.K. Several NNs, which can be classified into three types, namely, the multilayer perceptron, the radial basis function, and the modular network, were developed to model the nonlinear relationships that exist in the pollutant concentrations. Their performances are analyzed and compared. The transferability of the developed models is studied using data collected from a road intersection in another city. It was concluded that all NNs provide reliable estimates of pollutant concentrations using limited information and noisy data
Detecting and quantifying the contribution made by aircraft emissions to ambient concentrations of nitrogen oxides in the vicinity of a large international airport
Plans to build a third runway at London Heathrow Airport (LHR) have been held back because of concerns that the development would lead to annual mean concentrations of nitrogen dioxide (NO2) in excess of EU Directives, which must be met by 2010. The dominant effect of other sources of NOX close to the airport, primarily from road traffic, makes it difficult to detect and quantify the contribution made by the airport to local NOX and NO2 concentrations. This work presents approaches that aim to detect and quantify the airport contribution to NOX at a network of seven measurement sites close to the airport. Two principal approaches are used. First, a graphical technique using bivariate polar plots that develops the idea of a pollution rose is used to help discriminate between different source types. The sampling uncertainties associated with the technique have been calculated through a randomised re-sampling approach. Second, the unique pattern of aircraft activity at LHR enables data filtering techniques to be used to statistically verify the presence of aircraft sources. It is shown that aircraft NOX sources can be detected to at least 2.7 km from the airport, despite that the airport contribution is very small at that distance. Using these approaches, estimates have been made of the airport contribution to long-term mean concentrations of NOX and NO2. At the airport boundary we estimate that approximately 28 % (34 μg m-3) of the annual mean NOX is due to airport operations. At background locations 2-3 km downwind of the airport we estimate that the upper limit of the airport contribution to be less than 15 % (< 10 μg m-3). This work also provides approaches that would help validate and refine dispersion modelling studies used for airport assessments
Reducing Urban Pollution Exposure from Road Transport(RUPERT)
This paper presents the preliminary results of a two-year study on reducing urban pollution exposure from road transport (RUPERT). The main aim of this project
is to develop a new modelling framework for nitrogen dioxide, carbon monoxide and particulate matter to simulate exposures of different population groups
across a city, and to assess the impact of roadside concentrations on these exposures. This will be achieved by modelling the frequency distribution of
personal exposures (PEFDs) as a function of urban background and roadside concentrations, under different traffic conditions. The modelling approach combines new and existing models relating traffic and air pollution data, with particular emphasis of the impact of congestion, and the probabilistic modelling framework of personal exposure. Modelling of roadside concentrations consists of two main elements, namely the analysis of concentrations patterns at different roadside sites and of the relationship between traffic conditions and added
roadside pollution. Roadside concentrations are predicted using empirically derived relationships; statistical models, novel statistics and artificial neural
networks namely feed forward neural network and radial basis neural network. The exposure modelling is carried out by linking two models: the INDAIR model, which is designed to simulate probabilistically diurnal profiles of air pollutant concentrations in a range of microenvironments, and the EXPAIR model, which is designed to simulate population exposure patterns based on
population time-activity patterns and a library of micro-environmental concentrations derived from the INDAIR model
Quantitying the Effects of Traffic Calming on Emissions Using on-road Measurement
The objective of this work was to determine the effect of
one form of traffic calming on emissions. Traffic calming
is aimed at reducing average vehicle speeds, especially
in residential neighborhoods, often using physical road
obstructions such as speed bumps, but it also results in
a higher number of acceleration/deceleration events
which in turn yield higher emissions. Testing was
undertaken by driving a warmed-up Euro-1 spark ignition
passenger car over a set of speed bumps on a level
road, and then comparing the emissions output to a noncalmed
level road negotiated smoothly at a similar
average speed. For the emissions measurements, a
novel method was utilized, whereby the vehicle was
fitted with a portable Fourier Transform Infrared (FTIR)
spectrometer, capable of measuring up to 51 different
components in real-time on the road. The results
showed that increases in emissions were much greater
than was previously reported by other researchers using
different techniques. When traffic-calmed results were
compared to a smooth non-calmed road, there were
substantial increases in CO2 (90%), CO (117%), NOx
(195%) and THC (148%). These results form the basis
for a good argument against traffic calming using speed
bumps, especially for aggressive drivers. Slowing traffic
down with speed restrictions enforced by speed
cameras is a more environmentally friendly option
Evaluation of a FTIR Emission Measurement System for Legislated Emissions Using a SI Car
A series of chassis dynamometer test trials were
conducted to assess the performance of a Fourier
Transform Infra Red (FTIR) system developed for
on-road vehicle exhaust emissions measurements.
Trials used a EURO 1 emission compliant SI passenger
car which, alongside the FTIR, was instrumented to
allow the routine logging of engine speed, road speed,
throttle position, air-fuel ratio, air flow and fuel flow in
addition to engine, exhaust and catalyst temperatures.
The chassis dynamometer facility incorporated an
‘industry standard’ measurement system comprising
MEXA7400 gas analyzer and CVS bag sampling which
was the ‘benchmark’ for the evaluation of FTIR
legislated gas-phase emissions (CO, NOx, THC and
CO2) measurements.
Initial steady state measurements demonstrated strong
correlations for CO, NOx and THC (R2 of 0.99, 0.97
0.99, respectively) and a good correlation for CO2 (R2 =
0.92). Subsequent transient and total mass emissions
measurements from replicate samplings of four different
driving cycles (two standard cycles, FTP75 and NEDC,
and two novel cycles based on real-world data collected
in Leeds) also show good response of FTIR and
satisfied agreement between the FTIR and CVS bag
sampling measurements.
In general, the trial results demonstrate that the
on-board FTIR emission measurement system provides
reliable in-journey emissions data
Premature mortality in refractory partial epilepsy: does surgical treatment make a difference?
Background: Epilepsy carries an increased risk of premature death. For some people with intractable focal epilepsy, surgery offers hope for a seizure-free life. The authors aimed to see whether epilepsy surgery influenced mortality in people with intractable epilepsy. Methods: The authors audited survival status in two cohorts (those who had surgery and those who had presurgical assessment but did not have surgery). Results: There were 40 known deaths in the non-surgical group (3365 person years of follow-up) and 19 in the surgical group (3905 person-years of follow-up). Non-operated patients were 2.4 times (95% CI 1.4 to 4.2) as likely to die as those who had surgery. They were 4.5 times (95% CI 1.9 to 10.9) as likely to die a probable epilepsy-related death. In the surgical group, those with ongoing seizures 1 year after surgery were 4.0 (95% CI 1.2 to 13.7) times as likely to die as those who were seizure-free or who had only simple partial seizures. Time-dependent Cox analysis showed that the yearly outcome group did not significantly affect mortality (HR 1.3, 95% CI 0.9 to 1.8). Conclusion: Successful epilepsy surgery was associated with a reduced risk of premature mortality, compared with those with refractory focal epilepsy who did not have surgical treatment. To some extent, the reduced mortality is likely to be conferred by inducing freedom from seizures. It is not certain whether better survival is attributable only to surgery, as treatment decisions were not randomised, and there may be inherent differences between the groups.<br/
Analysing a complementarity experiment on the quantum-classical boundary
The complementarity experiment reported in Bertet [{\it{et al.}} (2001),
{\it{Nature}} {\bf{411}}, 166.] is discussed. The role played by entanglement
in reaching the classical limit is pointed out. Dissipative and thermal effects
of the cavity are calculated and a simple modification of the experiment is
proposed in order to observe the progressive loss of the capacity of ``quantum
erasing''as a manifestation of the classical limit of quantum mechanics.Comment: 7 pages, 4 figure
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