8,072 research outputs found
Investigation of synchronous satellites for geodesy Quarterly progress report
Orbit calculations for synchronous geodetic satellites to observe continental drift and Chandler wobbl
Value distribution of the eigenfunctions and spectral determinants of quantum star graphs
We compute the value distributions of the eigenfunctions and spectral
determinant of the Schrodinger operator on families of star graphs. The values
of the spectral determinant are shown to have a Cauchy distribution with
respect both to averages over bond lengths in the limit as the wavenumber tends
to infinity and to averages over wavenumber when the bond lengths are fixed and
not rationally related. This is in contrast to the spectral determinants of
random matrices, for which the logarithm is known to satisfy a Gaussian limit
distribution. The value distribution of the eigenfunctions also differs from
the corresponding random matrix result. We argue that the value distributions
of the spectral determinant and of the eigenfunctions should coincide with
those of Seba-type billiards.Comment: 32 pages, 9 figures. Final version incorporating referee's comments.
Typos corrected, appendix adde
Intermediate wave-function statistics
We calculate statistical properties of the eigenfunctions of two quantum
systems that exhibit intermediate spectral statistics: star graphs and Seba
billiards. First, we show that these eigenfunctions are not quantum ergodic,
and calculate the corresponding limit distribution. Second, we find that they
can be strongly scarred by short periodic orbits, and construct sequences of
states which have such a limit. Our results are illustrated by numerical
computations.Comment: 4 pages, 3 figures. Final versio
Study of the global positioning system for maritime concepts/applications: Study of the feasibility of replacing maritime shipborne navigation systems with NAVSTAR
A geostationary reference satellite (REFSAT) that broadcasts every four seconds updated GPS satellite coordinates was developed. This procedure reduces the complexity of the GPS receiver. The economic and performance payoffs associated with replacing maritime stripborne navigation systems with NAVSTAR was quantified and the use of NAVSTAR for measurements of ocean currents in the broad ocean areas of the world was evaluated
No quantum ergodicity for star graphs
We investigate statistical properties of the eigenfunctions of the
Schrodinger operator on families of star graphs with incommensurate bond
lengths. We show that these eigenfunctions are not quantum ergodic in the limit
as the number of bonds tends to infinity by finding an observable for which the
quantum matrix elements do not converge to the classical average. We further
show that for a given fixed graph there are subsequences of eigenfunctions
which localise on pairs of bonds. We describe how to construct such
subsequences explicitly. These constructions are analogous to scars on short
unstable periodic orbits.Comment: 26 pages, 5 figure
Applications of remote sensing to stream discharge predictions
A feasibility study has been initiated on the use of remote earth observations for augmenting stream discharge prediction for the design and/or operation of major reservoir systems, pumping systems and irrigation systems. The near-term objectives are the interpolation of sparsely instrumented precipitation surveillance networks and the direct measurement of water loss by evaporation. The first steps of the study covered a survey of existing reservoir systems, stream discharge prediction methods, gage networks and the development of a self-adaptive variation of the Kentucky Watershed model, SNOPSET, that includes snowmelt. As a result of these studies, a special three channel scanner is being built for a small aircraft, which should provide snow, temperature and water vapor maps for the spatial and temporal interpolation of stream gages
Assessment of geophysical flows for zero-gravity simulation
The results of research relating to the feasibility of using a low gravity environment to model geophysical flows are presented. Atmospheric and solid earth flows are considered. Possible experiments and their required apparatus are suggested
Radiation Damage and Recovery Properties of Common Plastics PEN (Polyethylene Naphthalate) and PET (Polyethylene Terephthalate) Using a 137Cs Gamma Ray Source Up To 1 MRad and 10 MRad
Polyethylene naphthalate (PEN) and polyethylene teraphthalate (PET) are cheap
and common polyester plastics used throughout the world in the manufacturing of
bottled drinks, containers for foodstuffs, and fibers used in clothing. These
plastics are also known organic scintillators with very good scintillation
properties. As particle physics experiments increase in energy and particle
flux density, so does radiation exposure to detector materials. It is therefore
important that scintillators be tested for radiation tolerance at these
generally unheard of doses. We tested samples of PEN and PET using laser
stimulated emission on separate tiles exposed to 1 MRad and 10 MRad gamma rays
with a 137Cs source. PEN exposed to 1 MRad and 10 MRad emit 71.4% and 46.7% of
the light of an undamaged tile, respectively, and maximally recover to 85.9%
and 79.5% after 5 and 9 days, respectively. PET exposed to 1 MRad and 10 MRad
emit 35.0% and 12.2% light, respectively, and maximally recover to 93.5% and
80.0% after 22 and 60 days, respectively
HATS-1b: The First Transiting Planet Discovered by the HATSouth Survey
We report the discovery of HATS-1b, a transiting extrasolar planet orbiting
the moderately bright V=12.05 G dwarf star GSC 6652-00186, and the first planet
discovered by HATSouth, a global network of autonomous wide-field telescopes.
HATS-1b has a period P~3.4465 d, mass Mp~1.86MJ, and radius Rp~1.30RJ. The host
star has a mass of 0.99Msun, and radius of 1.04Rsun. The discovery light curve
of HATS-1b has near continuous coverage over several multi-day periods,
demonstrating the power of using a global network of telescopes to discover
transiting planets.Comment: Submitted to AJ 10 pages, 5 figures, 6 table
Modern control concepts in hydrology
Two approaches to an identification problem in hydrology are presented based upon concepts from modern control and estimation theory. The first approach treats the identification of unknown parameters in a hydrologic system subject to noisy inputs as an adaptive linear stochastic control problem; the second approach alters the model equation to account for the random part in the inputs, and then uses a nonlinear estimation scheme to estimate the unknown parameters. Both approaches use state-space concepts. The identification schemes are sequential and adaptive and can handle either time invariant or time dependent parameters. They are used to identify parameters in the Prasad model of rainfall-runoff. The results obtained are encouraging and conform with results from two previous studies; the first using numerical integration of the model equation along with a trial-and-error procedure, and the second, by using a quasi-linearization technique. The proposed approaches offer a systematic way of analyzing the rainfall-runoff process when the input data are imbedded in noise
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