8,812 research outputs found
Energy Efficient Engine Program Advanced Turbofan Nacelle Definition Study
Advanced, low drag, nacelle configurations were defined for some of the more promising propulsion systems identified in the earlier Benefit/Cost Study, to assess the benefits associated with these advanced technology nacelles and formulate programs for developing these nacelles and low volume thrust reversers/spoilers to a state of technology readiness in the early 1990's. The study results established the design feasibility of advanced technology, slim line nacelles applicable to advanced technology, high bypass ratio turbofan engines. Design feasibility was also established for two low volume thrust reverse/spoiler concepts that meet or exceed the required effectiveness for these engines. These nacelle and thrust reverse/spoiler designs were shown to be applicable in engines with takeoff thrust sizes ranging from 24,000 to 60,000 pounds. The reduced weight, drag, and cost of the advanced technology nacelle installations relative to current technology nacelles offer a mission fuel burn savings ranging from 3.0 to 4.5 percent and direct operating cost plus interest improvements from 1.6 to 2.2 percent
Global analysis by hidden symmetry
Hidden symmetry of a G'-space X is defined by an extension of the G'-action
on X to that of a group G containing G' as a subgroup. In this setting, we
study the relationship between the three objects:
(A) global analysis on X by using representations of G (hidden symmetry);
(B) global analysis on X by using representations of G';
(C) branching laws of representations of G when restricted to the subgroup
G'.
We explain a trick which transfers results for finite-dimensional
representations in the compact setting to those for infinite-dimensional
representations in the noncompact setting when is -spherical.
Applications to branching problems of unitary representations, and to spectral
analysis on pseudo-Riemannian locally symmetric spaces are also discussed.Comment: Special volume in honor of Roger Howe on the occasion of his 70th
birthda
Deformation of Schild String
We attempt to construct new superstring actions with a -plet of Majorana
fermions , where is the dimensional space-time
index and is the two dimensional spinor index, by deforming the Schild
action. As a result, we propose three kinds of actions: the first is invariant
under N=1 (the world-sheet) supersymmetry transformation and the
area-preserving diffeomorphism. The second contains the Yukawa type
interaction. The last possesses some non-locality because of bilinear terms of
. The reasons why completing a Schild type superstring action
with is difficult are finally discussed.Comment: 12 pages, Latex, both title and abstract are changed, discussion of
some relations among our results, Nambu-Goto string and super Yang-Mills
theories, added. Results unchange
Ultrafast control of inelastic tunneling in a double semiconductor quantum
In a semiconductor-based double quantum well (QW) coupled to a degree of
freedom with an internal dynamics, we demonstrate that the electronic motion is
controllable within femtoseconds by applying appropriately shaped
electromagnetic pulses. In particular, we consider a pulse-driven AlxGa1-xAs
based symmetric double QW coupled to uniformly distributed or localized
vibrational modes and present analytical results for the lowest two levels.
These predictions are assessed and generalized by full-fledged numerical
simulations showing that localization and time-stabilization of the driven
electron dynamics is indeed possible under the conditions identified here, even
with a simultaneous excitations of vibrational modes.Comment: to be published in Appl.Phys.Let
Accumulation of Sellafield-derived radiocarbon (14C) in Irish Sea and West of Scotland intertidal shells and sediments
The nuclear energy industry produces radioactive waste at various stages of the fuel cycle. In
the United Kingdom, spent fuel is reprocessed at the Sellafield facility in Cumbria on the
north west coast of England. Waste generated at the site comprises a wide range of
radionuclides including radiocarbon (14C) which is disposed of in various forms including
highly soluble inorganic carbon within the low level liquid radioactive effluent, via pipelines
into the Irish Sea. This 14C is rapidly incorporated into the dissolved inorganic carbon (DIC)
reservoir and marine calcifying organisms, e.g. molluscs, readily utilise DIC for shell
formation. This study investigated a number of sites located in Irish Sea and West of Scotland
intertidal zones. Results indicate 14C enrichment above ambient background levels in shell
material at least as far as Port Appin, 265 km north of Sellafield. Of the commonly found
species (blue mussel (Mytilus edulis), common cockle (Cerastoderma edule) and common
periwinkle (Littorina littorea)), mussels were found to be the most highly enriched in 14C due
to the surface environment they inhabit and their feeding behaviour. Whole mussel shell
activities appear to have been decreasing in response to reduced discharge activities since the
early 2000s but in contrast, there is evidence of continuing enrichment of the carbonate
sediment component due to in-situ shell erosion, as well as indications of particle transport of
fine 14C-enriched material close to Sellafield
Transfer of K-types on local theta lifts of characters and unitary lowest weight modules
In this paper we study representations of the indefinite orthogonal group
O(n,m) which are local theta lifts of one dimensional characters or unitary
lowest weight modules of the double covers of the symplectic groups. We apply
the transfer of K-types on these representations of O(n,m), and we study their
effects on the dual pair correspondences. These results provide examples that
the theta lifting is compatible with the transfer of K-types. Finally we will
use these results to study subquotients of some cohomologically induced
modules
Neutral atomic carbon in the globules of the Helix
We report detection of the 609u line of neutral atomic carbon in globules of
the Helix nebula. The measurements were made towards the position of peak CO
emission. At the same position, we obtained high-quality CO(2-1) and 13CO(2-1)
spectra and a 135" x 135" map in CO(2-1). The velocity distribution of CI shows
six narrow (1 -> 2 km/sec) components which are associated with individual
globules traced in CO. The CI column densities are 0.5 -> 1.2 x 10^16/cm^2. CI
is found to be a factor of ~6 more abundant than CO. Our estimate for the mass
of the neutral envelope is an order of magnitude larger than previous
estimates. The large abundance of CI in the Helix can be understood as a result
of the gradual photoionisation of the molecular envelope by the central star's
radiation field.Comment: 5 pages, Latex, AAS macros, 3 EPS figures, to appear in Astrophysical
Journal Letter
On duality symmetries of supergravity invariants
The role of duality symmetries in the construction of counterterms for
maximal supergravity theories is discussed in a field-theoretic context from
different points of view. These are: dimensional reduction, the question of
whether appropriate superspace measures exist and information about non-linear
invariants that can be gleaned from linearised ones. The former allows us to
prove that F-term counterterms cannot be E7(7)-invariant in D=4, N=8
supergravity or E6(6)-invariant in D=5 maximal supergravity. This is confirmed
by the two other methods which can also be applied to D=4 theories with fewer
supersymmetries and allow us to prove that N=6 supergravity is finite at three
and four loops and that N=5 supergravity is three-loop finite.Comment: Clarification of arguments and their consistency with higher
dimensional divergences added, e.g. we prove the 5D 4L non-renormalisation
theorem. The 4L N=6 divergence is also ruled out. References adde
Two-Dimensional Helioseismic Power, Phase, and Coherence Spectra of {\it Solar Dynamics Observatory} Photospheric and Chromospheric Observables
While the {\it Helioseismic and Magnetic Imager} (HMI) onboard the {\it Solar
Dynamics Observatory} (SDO) provides Doppler velocity [], continuum
intensity [], and line-depth [] observations, each of which is
sensitive to the five-minute acoustic spectrum, the {\it Atmospheric Imaging
Array} (AIA) also observes at wavelengths -- specifically the 1600 and 1700
Angstrom bands -- that are partly formed in the upper photosphere and have good
sensitivity to acoustic modes. In this article we consider the characteristics
of the spatio--temporal Fourier spectra in AIA and HMI observables for a
15-degree region around NOAA Active Region 11072. We map the
spatio--temporal-power distribution for the different observables and the HMI
Line Core [], or Continuum minus Line Depth, and the phase and coherence
functions for selected observable pairs, as a function of position and
frequency. Five-minute oscillation power in all observables is suppressed in
the sunspot and also in plage areas. Above the acoustic cut-off frequency, the
behaviour is more complicated: power in HMI is still suppressed in the
presence of surface magnetic fields, while power in HMI and the AIA bands
is suppressed in areas of surface field but enhanced in an extended area around
the active region, and power in HMI is enhanced in a narrow zone around
strong-field concentrations and suppressed in a wider surrounding area. The
relative phase of the observables, and their cross-coherence functions, are
also altered around the active region. These effects may help us to understand
the interaction of waves and magnetic fields in the different layers of the
photosphere, and will need to be taken into account in multi-wavelength local
helioseismic analysis of active regions.Comment: 18 pages, 15 figures, to be published in Solar Physic
Astronomy in the Cloud: Using MapReduce for Image Coaddition
In the coming decade, astronomical surveys of the sky will generate tens of
terabytes of images and detect hundreds of millions of sources every night. The
study of these sources will involve computation challenges such as anomaly
detection and classification, and moving object tracking. Since such studies
benefit from the highest quality data, methods such as image coaddition
(stacking) will be a critical preprocessing step prior to scientific
investigation. With a requirement that these images be analyzed on a nightly
basis to identify moving sources or transient objects, these data streams
present many computational challenges. Given the quantity of data involved, the
computational load of these problems can only be addressed by distributing the
workload over a large number of nodes. However, the high data throughput
demanded by these applications may present scalability challenges for certain
storage architectures. One scalable data-processing method that has emerged in
recent years is MapReduce, and in this paper we focus on its popular
open-source implementation called Hadoop. In the Hadoop framework, the data is
partitioned among storage attached directly to worker nodes, and the processing
workload is scheduled in parallel on the nodes that contain the required input
data. A further motivation for using Hadoop is that it allows us to exploit
cloud computing resources, e.g., Amazon's EC2. We report on our experience
implementing a scalable image-processing pipeline for the SDSS imaging database
using Hadoop. This multi-terabyte imaging dataset provides a good testbed for
algorithm development since its scope and structure approximate future surveys.
First, we describe MapReduce and how we adapted image coaddition to the
MapReduce framework. Then we describe a number of optimizations to our basic
approach and report experimental results comparing their performance.Comment: 31 pages, 11 figures, 2 table
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