34,426 research outputs found
Multi-fuel rotary engine for general aviation aircraft
Design studies of advanced multifuel general aviation and commuter aircraft rotary stratified charge engines are summarized. Conceptual design studies were performed at two levels of technology, on advanced general aviation engines sized to provide 186/250 shaft kW/hp under cruise conditions at 7620 (25000 m/ft) altitude. A follow on study extended the results to larger (2500 hp max.) engine sizes suitable for applications such as commuter transports and helicopters. The study engine designs were derived from relevant engine development background including both prior and recent engine test results using direct injected unthrottled rotary engine technology. Aircraft studies, using these resultant growth engines, define anticipated system effects of the performance and power density improvements for both single engine and twin engine airplanes. The calculated results indicate superior system performance and 27 to 33 percent fuel economy improvement for the rotary engine airplanes as compared to equivalent airframe concept designs with current baseline engines. The research and technology activities required to attain the projected engine performance levels are also discussed
High angular resolution observation of the Sunyaev-Zel'dovich effect in the massive z=0.83 cluster ClJ0152-1357
X-ray observations of galaxy clusters at high redshift (z>0.5) indicate that
they are more morphologically complex and less virialized than those at
low-redshift. We present the first subarcmin resolution at 18 GHz observations
of the Sunyaev-Zel'dovich (SZ) effect for ClJ0152-1357 using the Australia
Telescope Compact Array. ClJ0152-1357 is a massive cluster at redshift z=0.83
and has a complex structure including several merging subclumps which have been
studied at optical, X-ray, and radio wavelengths. Our high-resolution
observations indicate a clear displacement of the maximum SZ effect from the
peak of X-ray emission for the most massive sub-clump. This result shows that
the cluster gas within the cluster substructures is not virialised in
ClJ0152-1357 and we suggest that it is still recovering from a recent merger
event. A similar offset of the SZ effect has been recently seen in the `bullet
cluster' by Malu et al. This non-equilibrium situation implies that high
resolution observations are necessary to investigate galaxy cluster evolution,
and to extract cosmological constraints from a comparison of the SZ effect and
X-ray signals.Comment: 5 pages, 4 figures, submitted to ApJ
Identifying success factors in urban surface BMP implementation: mission impossible?
The design and planning of structural and, to a lesser extent, non-structural controls for attenuating
urban surface runoff and associated pollutant loadings is now well established but their implementation varies according to scale of application and from country to country. The prime success factors driving the implementation of successful urban stormwater management controls are examined together with the problems and opportunities arising from the shift from single, centralised organisational implementation to multi-stakeholder engagement process and actions. Governance is
identified as a priority issue with varying hierarchical levels for stakeholder and governance processes contributing to the attainment of sustainable urban stormwater management. The relevance of achieving interaction between these levels to obtain the most appropriate drainage options is discussed through the application and integration of ‘individual’, ‘competitive’, ‘cooperative’,
‘collaborative’ and ‘coordination’ approaches
Diffractive jet production in a simple model with applications to HERA
In diffractive jet production, two high energy hadrons A and B collide and
produce high transverse momentum jets, while hadron A is diffractively
scattered. Ingelman and Schlein predicted this phenomenon. In their model, part
of the longitudinal momentum transferred from hadron A is delivered to the jet
system, part is lost. Lossless diffractive jet production, in which all of this
longitudinal momentum is delivered to the jet system, has been discussed by
Collins, Frankfurt, and Strikman. We study the structure of lossless
diffractive jet production in a simple model. The model suggests that the
phenomenon can be probed experimentally at HERA, with A being a proton and B
being a bremsstrahlung photon with virtuality . Lossless events should be
present for small , but not for larger than , where
is a characteristic size of the pomeron.Comment: 23 pages, REVTeX 3.0 with 8 postscript figures compressed with
uufiles, OITS 536 and AZPH-TH/94-0
Differential Cross Sections for Higgs Boson Production at Tevatron Collider Energies
The transverse momentum distribution is computed for inclusive Higgs
boson production at TeV. We include all-orders resummation of
large logarithms associated with emission of soft gluons at small . We
provide results for Higgs boson and masses from to 200 GeV. The
relatively hard transverse momentum distribution for Higgs boson production
suggests possibilities for improvement of the signal to background ratio.Comment: 12 pages, latex, 7 figure
Random Hamiltonian in thermal equilibrium
A framework for the investigation of disordered quantum systems in thermal
equilibrium is proposed. The approach is based on a dynamical model--which
consists of a combination of a double-bracket gradient flow and a uniform
Brownian fluctuation--that `equilibrates' the Hamiltonian into a canonical
distribution. The resulting equilibrium state is used to calculate quenched and
annealed averages of quantum observables.Comment: 8 pages, 4 figures. To appear in DICE 2008 conference proceeding
Lagrange-Poincare field equations
The Lagrange-Poincare equations of classical mechanics are cast into a field
theoretic context together with their associated constrained variational
principle. An integrability/reconstruction condition is established that
relates solutions of the original problem with those of the reduced problem.
The Kelvin-Noether theorem is formulated in this context. Applications to the
isoperimetric problem, the Skyrme model for meson interaction, metamorphosis
image dynamics, and molecular strands illustrate various aspects of the theory.Comment: Submitted to Journal of Geometry and Physics, 45 pages, 1 figur
The colour-magnitude relations of ClJ1226.9+3332, a massive cluster of galaxies at z=0.89
(Abridged) The colour-magnitude relations of one of the most massive, high
redshift clusters of galaxies known have been studied. Photometry has been
measured in the V, R, I, z, F606W, F814W, J and K bands to a depth of K*+2.5
and spectroscopy confirms 27 K band selected cluster members. The V-K colours
are equivalent to a rest-frame colour of ~2700A-J, and provide a very sensitive
measure of star-formation activity. HST ACS imaging has been used to
morphologically classify the galaxies.
The cluster has a low early-type fraction compared to nearby clusters, with
only 33% of the cluster members having types E or S0. The early-type member
galaxies form a clear red-sequence in all colours. The scatter and slope of the
relations show no evolution compared to the equivalent Coma cluster relations,
suggesting the stellar populations are already very old. The normalisation of
the relations has been compared to models based on synthetic stellar
populations, and are most consistent with stellar populations forming at z>3.
Some late-type galaxies were found to lie on the red-sequence, suggesting that
they have very similar stellar populations to the early-types.
These results present a picture of a cluster in which the early-type galaxies
are all old, but in which there must be future morphological transformation of
galaxies to match the early-type fraction of nearby clusters. In order to
preserve the tight colour-magnitude relation of early-types seen in nearby
clusters, the late-type galaxies must transform their colours, through the
cessation of star-formation, before the morphological transformation occurs.
Such evolution is observed in the late-types lying on the colour-magnitude
relation.Comment: Accepted for publication in MNRAS. 14 pages, 5 figure
Oxide-apertured microcavity single-photon emitting diode
We have developed a microcavity single-photon source based on a single
quantum dot within a planar cavity in which wet-oxidation of a high-aluminium
content layer provides lateral confinement of both the photonic mode and the
injection current. Lateral confinement of the optical mode in optically pumped
structures produces a strong enhancement of the radiative decay rate. Using
microcavity structures with doped contact layers, we demonstrate a
single-photon emitting diode where current may be injected into a single dot
A Solution to the Graceful Exit Problem in Pre-Big Bang Cosmology
We examine the string cosmology equations with a dilaton potential in the
context of the Pre-Big Bang Scenario with the desired scale factor duality, and
give a generic algorithm for obtaining solutions with appropriate evolutionary
properties. This enables us to find pre-big bang type solutions with suitable
dilaton behaviour that are regular at , thereby solving the graceful exit
problem. However to avoid fine tuning of initial data, an `exotic' equation of
state is needed that relates the fluid properties to the dilaton field. We
discuss why such an equation of state should be required for reliable dilaton
behaviour at late times.Comment: 16 pages LaTeX, 5 figures. To appear in Physical Review
- …