35,483 research outputs found
Performance and prospects of smaller UK regional airports
This paper investigates the traffic and financial performance of smaller UK regional airports between 2001 and 2014. Fourteen airports that typically serve less than 5 million passengers per annum were selected for the analysis. A period of strong growth in passenger demand was experienced from 2001 to 2007, driven largely by low cost carriers. The period from 2007 to 2014 was characterised by declining demand, resulting in significant losses for many of the airports. Airline strategies, such as the use of an increased unit fleet size and average sector length, may further limit future prospects for smaller UK regional airports in favour of larger ones with greater local demand. The relationship between traffic throughput and the generation of aeronautical revenues seems to vary at airports. There is generally a strong and significant relationship between traffic throughput and the generation of commercial revenues and total operating costs at airports serving 3–5 million passengers, but the situation for airports serving fewer than 3 million
is less certain
Environmental Impact on the Southeast Limb of the Cygnus Loop
We analyze observations from the Chandra X-ray Observatory of the southeast
knot of the Cygnus Loop supernova remnant. In this region, the blast wave
propagates through an inhomogeneous environment. Extrinsic differences and
subsequent multiple projections along the line of sight rather than intrinsic
shock variations, such as fluid instabilities, account for the apparent
complexity of the images. Interactions between the supernova blast wave and
density enhancements of a large interstellar cloud can produce the
morphological and spectral characteristics. Most of the X-ray flux arises in
such interactions, not in the diffuse interior of the supernova remnant.
Additional observations at optical and radio wavelengths support this account
of the existing interstellar medium and its role in shaping the Cygnus Loop,
and they demonstrate that the southeast knot is not a small cloud that the
blast wave has engulfed. These data are consistent with rapid equilibration of
electron and ion temperatures behind the shock front, and the current blast
wave velocity v_{bw} approx 330 km/s. Most of this area does not show strong
evidence for non-equilibrium ionization conditions, which may be a consequence
of the high densities of the bright emission regions.Comment: To appear in ApJ, April 1, 200
Low cost carriers and the changing fortunes of airports in the UK
This paper investigates how low cost carrier (LCC) developments have affected the traffic and financial performance of UK airports from 2002 to 2014. Considerable growth in traffic was experienced from 2002 to 2007, especially at regional airports as a result of LCC expansion. This was replaced with a more volatile period from 2008 to 2014 where many of the regional airports that experienced the greatest increases in traffic during the early years, then experienced the largest reductions. This has clearly had an impact on their financial well-being, resulting in reduced profits for many airports. It has also meant that many regional airports that seemed like attractive investments as a result of LCC expansion are now less financially appealing, especially given that the LCC sector in the UK appears to be shifting capacity to larger regional airports, and in some cases, London airports
Casimir Effects in Renormalizable Quantum Field Theories
We review the framework we and our collaborators have developed for the study
of one-loop quantum corrections to extended field configurations in
renormalizable quantum field theories. We work in the continuum, transforming
the standard Casimir sum over modes into a sum over bound states and an
integral over scattering states weighted by the density of states. We express
the density of states in terms of phase shifts, allowing us to extract
divergences by identifying Born approximations to the phase shifts with low
order Feynman diagrams. Once isolated in Feynman diagrams, the divergences are
canceled against standard counterterms. Thus regulated, the Casimir sum is
highly convergent and amenable to numerical computation. Our methods have
numerous applications to the theory of solitons, membranes, and quantum field
theories in strong external fields or subject to boundary conditions.Comment: 27 pp., 11 EPS figures, LaTeX using ijmpa1.sty; email correspondence
to R.L. Jaffe ; based on talks presented by the authors at
the 5th workshop `QFTEX', Leipzig, September 200
Fermion Energies in the Background of a Cosmic String
We provide a thorough exposition, including technical and numerical details,
of previously published results on the quantum stabilization of cosmic strings.
Stabilization occurs through the coupling to a heavy fermion doublet in a
reduced version of the standard model. We combine the vacuum polarization
energy of fermion zero-point fluctuations and the binding energy of occupied
energy levels, which are of the same order in a semi-classical expansion.
Populating these bound states assigns a charge to the string. We show that
strings carrying fermion charge become stable if the electro-weak bosons are
coupled to a fermion that is less than twice as heavy as the top quark. The
vacuum remains stable in our model, because neutral strings are not
energetically favored. These findings suggests that extraordinarily large
fermion masses or unrealistic couplings are not required to bind a cosmic
string in the standard model.Comment: 38 pages, 6 figures, version accepted for publication in Phys Rev
UK Regional Connectivity on the North Atlantic: Hub-Bypassing or just changing hubs?
London Heathrow Airport (LHR) has maintained its position as the main gateway for UK passengers for international services, but has no services to many UK regional airports. This research examines whether UK regional airports have increased direct services to North Atlantic destinations or to other European hub airports in response to the lack of air services to the London area. The study analysed the changing dynamics of the UK aviation network from 1997 to 2017 as it pertains to hub connectivity and North Atlantic services. Both the number of connections from regional airports and the quality of those connections, measured in terms of the frequency of direct air services, have been examined. As most LCC passengers do not connect to other flights, only flights by full service carriers to both London and selected European hubs were considered.
The data indicate that regional airport connectivity development has been heterogeneous. Whilst the number of UK regional airports with service to LHR has remained stable, the frequency of service has decreased noticeably. The larger and more geographically distant regional airports of Edinburgh, Glasgow, and Manchester have been able to develop more connections to both European hub airports and to North American cities, and in many cases have seen an increase in frequencies as well. Birmingham Airport, although of similar size to the above-mentioned airports, has on the contrast experienced a reduction in its connections to North American airports and of frequency to the European hub airports examined. Smaller UK regional airports have also seen a reduction in frequencies to European airports
Mode Switching and Subpulse Drifting in PSR B0826-34
We present high-quality observations of PSR B0826-34 at 1374 MHz. The
emission from this pulsar exhibits strong bursts of pulses followed by long
periods of `null' pulses. When it is strong, the radiation extends through the
whole pulse period. We show for the first time that there is weak emission
during the `null' phases, which should therefore be considered to be a
different mode rather than a null. During this weak mode the profile is similar
to that observed in the strong mode at low radio frequency. Using a
phase-tracking method, the pattern of drifting subpulses during the strong mode
is seen to be coherent across the whole profile. The drift rate is variable and
includes positive and negative values. Thirteen subpulse bands have been
directly observed, covering the whole longitude range. The subpulses and their
spacings () are wider in one half of the profile than those in the other
half. This difference, and the variation of observed within the two
regions, can be accounted for if the magnetic pole is inclined to the rotation
axis by about 0.5 degrees. These two regions appear to represent radiation from
outer and inner cones. The intensity modulation of subpulses in all longitude
ranges is related to the magnitude of the drift rate.Comment: 8 pages, 10 figures. Accepted for publication in MNRA
Airline schedule and network competitiveness: A consumer-centric approach for business travel
The aim of this paper is to undertake a comparative analysis of the competitiveness of airline schedules and networks from a business traveller perspective with a particular focus on Europe and travel to and from this continent. A unique and innovative customer-centric model is developed using a passenger survey and airline schedule data to overcome the shortcomings of traditional models that lack the passenger viewpoint. The results show that Austrian Airlines/Vienna airport and Swiss/Zurich airport have the highest quality connections, whilst the top five competing European hubs are served by the Lufthansa group. The findings provide a significant opportunity to airlines to grow their knowledge and understanding of their competitive position and their ability to offer scheduling convenience to passenger
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