2,968 research outputs found
Preliminary estimates of environmental exposure for fuel and exhaust products, volume i. part i- methods and preliminary estimates for msfc. part 2- recommended experimental design for msfc
Environmental exposure for fuel and exhaust products with preliminary estimate
Experimental characterization of Gaussian quantum communication channels
We present a full experimental characterization of continuous variable
quantum communication channels established by shared entanglement together with
local operations and classical communication. The resulting teleportation
channel was fully characterized by measuring all elements of the covariance
matrix of the shared two-mode squeezed Gaussian state. From the experimental
data we determined the lower bound to the quantum channel capacity, the
teleportation fidelity of coherent states and the logarithmic negativity and
the purity of the shared state. Additionally, a positive secret key rate was
obtained for two of the established channels.Comment: 9 pages, 4 figures, submitted to Physical Review
Towards Einstein-Podolsky-Rosen quantum channel multiplexing
A single broadband squeezed field constitutes a quantum communication
resource that is sufficient for the realization of a large number N of quantum
channels based on distributed Einstein-Podolsky-Rosen (EPR) entangled states.
Each channel can serve as a resource for, e.g. independent quantum key
distribution or teleportation protocols. N-fold channel multiplexing can be
realized by accessing 2N squeezed modes at different Fourier frequencies. We
report on the experimental implementation of the N=1 case through the
interference of two squeezed states, extracted from a single broadband squeezed
field, and demonstrate all techniques required for multiplexing (N>1). Quantum
channel frequency multiplexing can be used to optimize the exploitation of a
broadband squeezed field in a quantum information task. For instance, it is
useful if the bandwidth of the squeezed field is larger than the bandwidth of
the homodyne detectors. This is currently a typical situation in many
experiments with squeezed and two-mode squeezed entangled light.Comment: 4 pages, 4 figures. In the new version we cite recent experimental
work bei Mehmet et al., arxiv0909.5386, in order to clarify the motivation of
our work and its possible applicatio
Balancing adaptivity and customisation : in search of sustainable personalisation in cultural heritage
Personalisation for cultural heritage aims at delivering to visitors the right stories at the right time. Our endeavour to determine which features to use for adaptation starts from acknowledging what forms of personalisation curators value as most meaningful. Working in collaboration with curators we have explored the different features that must be taken into account: some are related to the content (multiple interpretation layers), others to the context of delivery (where and when), but some are idiosyncratic (“match my mood”, “something that is relevant to my life”). The findings reveal that a sustainable personalization needs to accurately balance: (i) support to curators in customising stories to different visitors; (ii) algorithms for the system to dynamically model aspects of the visit and instantiate the correct behaviour; and (iii) an active role for visitors to choose the type of experience they would like to have today
Photometry of supernovae in an image series : methods and application to the Supernova Legacy Survey (SNLS)
We present a technique to measure lightcurves of time-variable point sources
on a spatially structured background from imaging data. The technique was
developed to measure light curves of SNLS supernovae in order to infer their
distances. This photometry technique performs simultaneous PSF photometry at
the same sky position on an image series. We describe two implementations of
the method: one that resamples images before measuring fluxes, and one which
does not. In both instances, we sketch the key algorithms involved and present
the validation using semi-artificial sources introduced in real images in order
to assess the accuracy of the supernova flux measurements relative to that of
surrounding stars. We describe the methods required to anchor these PSF fluxes
to calibrated aperture catalogs, in order to derive SN magnitudes. We find a
marginally significant bias of 2 mmag of the after-resampling method, and no
bias at the mmag accuracy for the non-resampling method. Given surrounding star
magnitudes, we determine the systematic uncertainty of SN magnitudes to be less
than 1.5 mmag, which represents about one third of the current photometric
calibration uncertainty affecting SN measurements. The SN photometry delivers
several by-products: bright star PSF flux mea- surements which have a
repeatability of about 0.6%, as for aperture measurements; we measure relative
astrometric positions with a noise floor of 2.4 mas for a single-image bright
star measurement; we show that in all bands of the MegaCam instrument, stars
exhibit a profile linearly broadening with flux by about 0.5% over the whole
brightness range.Comment: Accepted for publication in A&A. 20 page
Interactions In Space For Archaeological Models
In this article we examine a variety of quantitative models for describing
archaeological networks, with particular emphasis on the maritime networks of
the Aegean Middle Bronze Age. In particular, we discriminate between those
gravitational networks that are most likely (maximum entropy) and most
efficient (best cost/benefit outcomes).Comment: 21 pages, 6 figures, 2 tables. Contribution to special issue of
Advances in Complex Systems from the conference `Cultural Evolution in
Spatially Structured Populations', UCL, London, September 2010. To appear in
Advances in Complex System
Wigner's -matrix elements for - A Generating Function Approach
A generating function for the Wigner's -matrix elements of is
derived. From this an explicit expression for the individual matrix elements is
obtained in a closed form.Comment: RevTex 3.0, 22 pages, no figure
Photospheric and chromospheric magnetic activity of seismic solar analogs. Observational inputs on the solar/stellar connection from Kepler and Hermes
We identify a set of 18 solar analogs among the seismic sample of solar-like
stars observed by the Kepler satellite rotating between 10 and 40 days. This
set is constructed using the asteroseismic stellar properties derived using
either the global oscillation properties or the individual acoustic
frequencies. We measure the magnetic activity properties of these stars using
observations collected by the photometric Kepler satellite and by the
ground-based, high-resolution Hermes spectrograph mounted on the Mercator
telescope. The photospheric (Sph) and chromospheric (S index) magnetic activity
levels of these seismic solar analogs are estimated and compared in relation to
the solar activity. We show that the activity of the Sun is comparable to the
activity of the seismic solar analogs, within the maximum-to-minimum temporal
variations of the 11-year solar activity cycle 23. In agreement with previous
studies, the youngest stars and fastest rotators in our sample are actually the
most active. The activity of stars older than the Sun seems to not evolve much
with age. Furthermore, the comparison of the photospheric, Sph, with the
well-established chromospheric, S index, indicates that the Sph index can be
used to provide a suitable magnetic activity proxy which can be easily
estimated for a large number of stars from space photometric observations.Comment: Accepted for publication in A&
In memoriam two distinguished participants of the Bregenz Symmetries in Science Symposia: Marcos Moshinsky and Yurii Fedorovich Smirnov
Some particular facets of the numerous works by Marcos Moshinsky and Yurii
Fedorovich Smirnov are presented in these notes. The accent is put on some of
the common interests of Yurii and Marcos in physics, theoretical chemistry, and
mathematical physics. These notes also contain some more personal memories of
Yurii Smirnov.Comment: Submitted for publication in Journal of Physics: Conference Serie
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