212 research outputs found
Network effects of intelligent speed adaptation systems
Intelligent Speed Adaptation (ISA) systems use in-vehicle electronic devices to enable the speed of vehicles to be regulated externally. They are increasingly appreciated as a flexible method for speed management and control, particularly in urban areas. On-road trials using a small numbers of ISA equipped vehicles have been carried out in Sweden, the Netherlands, Spain and the UK. This paper describes the developments made to enhance a traffic microsimulation model in order to represent ISA implemented across a network and their impact on the networks. The simulation modelling of the control system is carried out on a real-world urban network, and the impacts on traffic congestion, speed distribution and the environment assessed. The results show that ISA systems are more effective in less congested traffic conditions. Momentary high speeds in traffic are effectively suppressed, resulting in a reduction in speed variation which is likely to have a positive impact on safety. Whilst ISA reduces excessive traffic speeds in the network, it does not affect average journey times. In particular, the total vehicle-hours travelling at speeds below 10 km/hr have not changed, indicating that the speed control had not induced more slow-moving queues to the network. A significant, eight percent, reduction in fuel consumption was found with full ISA penetration. These results are in accordance with those from field trials and they provide the basis for cost-benefit analyses on introducing ISA into the vehicle fleet. Contrary to earlier findings from the Swedish ISA road trials, these network simulations showed that ISA had no significant effect on emission of gaseous pollutants CO, NOx and HC. Further research is planned to investigate the impact on emission with a more comprehensive and up to date modal emission factor database
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
Multispecies virial expansions
We study the virial expansion of mixtures of countably many different types of particles. The main tool is the Lagrange–Good inversion formula, which has other applications such as counting coloured trees or studying probability generating functions in multi-type branching processes. We prove that the virial expansion converges absolutely in a domain of small densities. In addition, we establish that the virial coefficients can be expressed in terms of two-connected graphs
Koszul binomial edge ideals
It is shown that if the binomial edge ideal of a graph defines a Koszul
algebra, then must be chordal and claw free. A converse of this statement
is proved for a class of chordal and claw free graphs
Patterns in rational base number systems
Number systems with a rational number as base have gained interest
in recent years. In particular, relations to Mahler's 3/2-problem as well as
the Josephus problem have been established. In the present paper we show that
the patterns of digits in the representations of positive integers in such a
number system are uniformly distributed. We study the sum-of-digits function of
number systems with rational base and use representations w.r.t. this
base to construct normal numbers in base in the spirit of Champernowne. The
main challenge in our proofs comes from the fact that the language of the
representations of integers in these number systems is not context-free. The
intricacy of this language makes it impossible to prove our results along
classical lines. In particular, we use self-affine tiles that are defined in
certain subrings of the ad\'ele ring and Fourier
analysis in . With help of these tools we are able to
reformulate our results as estimation problems for character sums
Hopf algebras and Markov chains: Two examples and a theory
The operation of squaring (coproduct followed by product) in a combinatorial
Hopf algebra is shown to induce a Markov chain in natural bases. Chains
constructed in this way include widely studied methods of card shuffling, a
natural "rock-breaking" process, and Markov chains on simplicial complexes.
Many of these chains can be explictly diagonalized using the primitive elements
of the algebra and the combinatorics of the free Lie algebra. For card
shuffling, this gives an explicit description of the eigenvectors. For
rock-breaking, an explicit description of the quasi-stationary distribution and
sharp rates to absorption follow.Comment: 51 pages, 17 figures. (Typographical errors corrected. Further fixes
will only appear on the version on Amy Pang's website, the arXiv version will
not be updated.
Brane Inflation, Solitons and Cosmological Solutions: I
In this paper we study various cosmological solutions for a D3/D7 system
directly from M-theory with fluxes and M2-branes. In M-theory, these solutions
exist only if we incorporate higher derivative corrections from the curvatures
as well as G-fluxes. We take these corrections into account and study a number
of toy cosmologies, including one with a novel background for the D3/D7 system
whose supergravity solution can be completely determined. This new background
preserves all the good properties of the original model and opens up avenues to
investigate cosmological effects from wrapped branes and brane-antibrane
annihilation, to name a few. We also discuss in some detail semilocal defects
with higher global symmetries, for example exceptional ones, that could occur
in a slightly different regime of our D3/D7 model. We show that the D3/D7
system does have the required ingredients to realise these configurations as
non-topological solitons of the theory. These constructions also allow us to
give a physical meaning to the existence of certain underlying homogeneous
quaternionic Kahler manifolds.Comment: Harvmac, 115 pages, 9 .eps figures; v2: typos corrected, references
added and the last section expanded; v3: Few minor typos corrected and
references added. Final version to appear in JHE
Bathymetry and geological setting of the Drake Passage (Antarctica)
IX Congreso Geológico de España, Huelva, Septiembre 2016The Drake Passage is an oceanic gateway of about 850 km width located between South America and the Antarctic Peninsula that connects the southeastern Pacific and the southwestern Atlantic oceans and is an important gateway for mantle flow, oceanographic water masses, and migrations of biota. This gateway developed within the framework of geological evolution of the Scotia Arc. As a consequence of this and subsequent submarine processes, this region shows a varied physiography. The new detailed map in the Drake Passage region is mainly founded on a compilation of precise multibeam bathymetric data obtained on cruises between 1992 and 2014, and covers the area between parallels 52ºS and 63ºS and meridians 70ºW and 50ºW. The new map that we present is based in a DTM with 200 m cell resolution of the seafloor in Drake Passage that permits identification of the main seafloor features and the map includes additional useful geological information. This work constitutes an international cooperative effort and is part of IBCSO project (International Bathymetric Chart of the Southern Ocean), under the SCAR umbrella.Instituto Geológico y Minero de España, EspañaBritish Antarctic Survey, Reino UnidoDepartamento de Geodinámica, Universidad de Granada, EspañaInstituto Andaluz de Ciencias de la Tierra, Consejo Superior de Investigaciones CientÃficas, EspañaInstituto Andaluz de Ciencias de la Tierra, Universidad de Granada, EspañaJet Propulsion Laboratory M/S 300-323, Estados UnidosAlfred Wegener Institute, AlemaniaKorea Polar Research Institute, CoreaDepartamento de GeologÃa y GeoquÃmica, Universidad Autónoma de Madrid, EspañaLamont-Doherty Earth Observatory, Columbia University, Estados Unido
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