2,857 research outputs found
Flexible format, computer accessed telemetry system
With this system, it is possible to sample and generate two or more simultaneous formats; one can be transmitted to ground station in real time, and other is stored for later transmission. Sensor output comparison data, plus information to control format, compression algorithm, and allowable degree of sensor activity, are stored in memory
Data multiplexer using a tree switch
Self-decoding FET-hybrid or integrated-circuit tree configuration uses minimum number of components and can be sequenced by clock or computer. Redundancy features can readily be incorporated into tree configuration; as tree grows in size and more sensors are included, percentage of parts that will affect given percentage of sensors steadily decreases
Energy deposition in microscopic volumes by high-energy protons
Microscopic energy deposition from passing protons in tissue spher
Bayesian weak lensing tomography: Reconstructing the 3D large-scale distribution of matter with a lognormal prior
We present a Bayesian reconstruction algorithm that infers the
three-dimensional large-scale matter distribution from the weak gravitational
lensing effects measured in the image shapes of galaxies. The algorithm is
designed to also work with non-Gaussian posterior distributions which arise,
for example, from a non-Gaussian prior distribution. In this work, we use a
lognormal prior and compare the reconstruction results to a Gaussian prior in a
suite of increasingly realistic tests on mock data. We find that in cases of
high noise levels (i.e. for low source galaxy densities and/or high shape
measurement uncertainties), both normal and lognormal priors lead to
reconstructions of comparable quality, but with the lognormal reconstruction
being prone to mass-sheet degeneracy. In the low-noise regime and on small
scales, the lognormal model produces better reconstructions than the normal
model: The lognormal model 1) enforces non-negative densities, while negative
densities are present when a normal prior is employed, 2) better traces the
extremal values and the skewness of the true underlying distribution, and 3)
yields a higher pixel-wise correlation between the reconstruction and the true
density.Comment: 23 pages, 12 figures; updated to match version accepted for
publication in PR
Changes in the frequency distribution of energy deposited in short pathlengths as a function of energy degradation of the primary beam
Frequency distributions of event size in deposition of energy over small pathlengths measured after penetration of 44.3 MeV protons through thicknesses of tissue-like materia
Contextual approach to quantum mechanics and the theory of the fundamental prespace
We constructed a Hilbert space representation of a contextual Kolmogorov
model. This representation is based on two fundamental observables -- in the
standard quantum model these are position and momentum observables. This
representation has all distinguishing features of the quantum model. Thus in
spite all ``No-Go'' theorems (e.g., von Neumann, Kochen and Specker,..., Bell)
we found the realist basis for quantum mechanics. Our representation is not
standard model with hidden variables. In particular, this is not a reduction of
quantum model to the classical one. Moreover, we see that such a reduction is
even in principle impossible. This impossibility is not a consequence of a
mathematical theorem but it follows from the physical structure of the model.
By our model quantum states are very rough images of domains in the space of
fundamental parameters - PRESPACE. Those domains represent complexes of
physical conditions. By our model both classical and quantum physics describe
REDUCTION of PRESPACE-INFORMATION. Quantum mechanics is not complete. In
particular, there are prespace contexts which can be represented only by a so
called hyperbolic quantum model. We predict violations of the Heisenberg's
uncertainty principle and existence of dispersion free states.Comment: Plenary talk at Conference "Quantum Theory: Reconsideration of
Foundations-2", Vaxjo, 1-6 June, 200
Cosmology with the lights off: Standard sirens in the Einstein Telescope era
We explore the prospects for constraining cosmology using gravitational-wave
(GW) observations of neutron-star binaries by the proposed Einstein Telescope
(ET), exploiting the narrowness of the neutron-star mass function. Double
neutron-star (DNS) binaries are expected to be one of the first sources
detected after "first-light" of Advanced LIGO and are expected to be detected
at a rate of a few tens per year in the advanced era. However the proposed ET
could catalog tens of thousands per year. Combining the measured source
redshift distributions with GW-network distance determinations will permit not
only the precision measurement of background cosmological parameters, but will
provide an insight into the astrophysical properties of these DNS systems. Of
particular interest will be to probe the distribution of delay times between
DNS-binary creation and subsequent merger, as well as the evolution of the
star-formation rate density within ET's detection horizon. Keeping H_0,
\Omega_{m,0} and \Omega_{\Lambda,0} fixed and investigating the precision with
which the dark-energy equation-of-state parameters could be recovered, we found
that with 10^5 detected DNS binaries we could constrain these parameters to an
accuracy similar to forecasted constraints from future CMB+BAO+SNIa
measurements. Furthermore, modeling the merger delay-time distribution as a
power-law, and the star-formation rate (SFR) density as a parametrized version
of the Porciani and Madau SF2 model, we find that the associated astrophysical
parameters are constrained to within ~ 10%. All parameter precisions scaled as
1/sqrt(N), where N is the number of cataloged detections. We also investigated
how precisions varied with the intrinsic underlying properties of the Universe
and with the distance reach of the network (which may be affected by the
low-frequency cutoff of the detector).Comment: 24 pages, 11 figures, 6 tables. Minor changes to reflect published
version. References updated and correcte
A comparison of the excess mass around CFHTLenS galaxy-pairs to predictions from a semi-analytic model using galaxy-galaxy-galaxy lensing
The matter environment of galaxies is connected to the physics of galaxy
formation and evolution. Utilising galaxy-galaxy-galaxy lensing as a direct
probe, we map out the distribution of correlated surface mass-density around
galaxy pairs for different lens separations in the Canada-France-Hawaii
Telescope Lensing Survey (CFHTLenS). We compare, for the first time, these
so-called excess mass maps to predictions provided by a recent semi-analytic
model, which is implanted within the dark-matter Millennium Simulation. We
analyse galaxies with stellar masses between in
two photometric redshift bins, for lens redshifts , focusing on
pairs inside groups and clusters. To allow us a better interpretation of the
maps, we discuss the impact of chance pairs, i.e., galaxy pairs that appear
close to each other in projection only. Our tests with synthetic data
demonstrate that the patterns observed in the maps are essentially produced by
correlated pairs that are close in redshift ().
We also verify the excellent accuracy of the map estimators. In an application
to the galaxy samples in the CFHTLenS, we obtain a
significant detection of the excess mass and an overall good agreement with the
galaxy model predictions. There are, however, a few localised spots in the maps
where the observational data disagrees with the model predictions on a
confidence level. Although we have no strong indications for
systematic errors in the maps, this disagreement may be related to the residual
B-mode pattern observed in the average of all maps. Alternatively, misaligned
galaxy pairs inside dark matter halos or lensing by a misaligned distribution
of the intra-cluster gas might also cause the unanticipated bulge in the
distribution of the excess mass between lens pairs.Comment: 21 pages, 12 figures; abridged abstract; revised version for A&A
after addressing all comments by the refere
Discriminants, symmetrized graph monomials, and sums of squares
Motivated by the necessities of the invariant theory of binary forms J. J.
Sylvester constructed in 1878 for each graph with possible multiple edges but
without loops its symmetrized graph monomial which is a polynomial in the
vertex labels of the original graph. In the 20-th century this construction was
studied by several authors. We pose the question for which graphs this
polynomial is a non-negative resp. a sum of squares. This problem is motivated
by a recent conjecture of F. Sottile and E. Mukhin on discriminant of the
derivative of a univariate polynomial, and an interesting example of P. and A.
Lax of a graph with 4 edges whose symmetrized graph monomial is non-negative
but not a sum of squares. We present detailed information about symmetrized
graph monomials for graphs with four and six edges, obtained by computer
calculations
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