24,485 research outputs found
Measurement of electric fields in the ionosphere, volume 2 Final report, Aug. 1966 - Sep. 1967
Electric field meter, using electron beam deflection techniques, for ionospheric measurement
Measurement of electric fields in the ionosphere. Volume 1 - Technical summary report Final report, Aug. 1966 - Sep. 1967
Design and performance of electron beam electric field meter for ionospheric measurements near spacecraf
The Monterey event in the Mediterranean: A record from shelf sediments of Malta
Oligo-Miocene carbonate platform and shelf sediments outcropping on the Maltese Islands provide an excellent archive of the paleoceanography of the central Mediterranean. A sequence of shallow water limestones, than shelf limestones, and marls, followed again by shallow water limestones, reflects drowning of a carbonate platform, the establishment of a shelf environment and, in the late Miocene, renewed progradation and aggradation of shallow water carbonates. The sequence recording the deepening of the Maltese platform contains several phosphorite hardgrounds and phosphorite pebble beds. These phosphorites were dated with strontium isotopes. Major episodes of phosphogenesis occurred between 25 and 16 Ma, and they are coeval with those phosphorite events reported from Florida and North Carolina. A Miocene carbon isotope and oxygen isotope stratigraphy was established on planktic and benthic foraminifera and on bulk samples. A major carbon isotope excursion with an amplitude of up to +l‰ between 18 and 12.5 Ma can be correlated with the globally recognized Monterey carbon isotope excursion. This is the first record of this event both in shallow water sediments and in the Mediterranean. The carbon isotope excursion precedes an oxygen isotope excursion which also was recognized in deep-sea records. Major episodes of phosphogenesis and platform drowning preceded the carbon isotope excursion by up to millions of years
Shock enhancement and control of hypersonic mixing and combustion
The possibility that shock enhanced mixing can
substantially increase the rate of mixing between
coflowing streams of hydrogen and air has been
studied in experimental and computational investigations.
Early numerical computations indicated that
the steady interaction between a weak shock in air
with a coflowing hydrogen jet can be well approximated
by the two-dimensional time-dependent interaction
between a weak shock and an initially circular
region filled with hydrogen imbedded in air. An experimental
investigation of the latter process has been
carned out in the Caltech 17 Inch Shock Tube in experiments
in which the laser induced fluorescence of
byacetyl dye is used as a tracer for the motion of the
helium gas after shock waves have passed across the
helium cylinder. The flow field has also been studied
using an Euler code computation of the flow field.
Both investigations show that the shock impinging
process causes the light gas cylinder to split into two
parts. One of these mixes rapidly with air and the
other forms a stably stratified vortex pair which mixes
more slowly; about 60% of the light gas mixes rapidly
with the ambient fluid. The geometry of the flow field
and the mixing process and scaling parameters are
discussed here. The success of this program encouraged
the exploration of a low drag injection system in
which the basic concept of shock generated streamwise
vorticity could be incorporated in an injector for
a Scramjet combustor at Mach numbers between 5
and 8. The results of a substantial computational
program and a description of the wind tunnel model and preliminary experimental results obtained in the
High Reynolds Number Mach 6 Tunnel at NASA Langley
Research Center are given here
Approximate theoretical performance evaluation for a diverging rocket
A simplified combustion model, which is motivated by available performance studies on the diverging rocket reactor, has been used as basis for an engine performance
evaluation. Comparison with conventional rocket configurations shows that an upper performance limit for the diverging reactor is comparable with performance
estimates for engines using an adiabatic work cycle. Development of the diverging reactor for engine applications may, however, offer some advantages for very hot, high-energy, propellant systems
Healthiness from Duality
Healthiness is a good old question in program logics that dates back to
Dijkstra. It asks for an intrinsic characterization of those predicate
transformers which arise as the (backward) interpretation of a certain class of
programs. There are several results known for healthiness conditions: for
deterministic programs, nondeterministic ones, probabilistic ones, etc.
Building upon our previous works on so-called state-and-effect triangles, we
contribute a unified categorical framework for investigating healthiness
conditions. We find the framework to be centered around a dual adjunction
induced by a dualizing object, together with our notion of relative
Eilenberg-Moore algebra playing fundamental roles too. The latter notion seems
interesting in its own right in the context of monads, Lawvere theories and
enriched categories.Comment: 13 pages, Extended version with appendices of a paper accepted to
LICS 201
Pulmonary Microvascular Injury Resulting from a Single Exposure to Low-Dose Thoracic Radiation
Phonon number quantum jumps in an optomechanical system
We describe an optomechanical system in which the mean phonon number of a
single mechanical mode conditionally displaces the amplitude of the optical
field. Using homodyne detection of the output field we establish the conditions
under which phonon number quantum jumps can be inferred from the measurement
record: both the cavity damping rate and the measurement rate of the phonon
number must be much greater than the thermalization rate of the mechanical
mode. We present simulations of the conditional dynamics of the measured system
using the stochastic master equation. In the good-measurement limit, the
conditional evolution of the mean phonon number shows quantum jumps as phonons
enter and exit the mechanical resonator via the bath.Comment: 13 pages, 4 figures. minor revisions since first versio
On the validity of the reduced Salpeter equation
We adapt a general method to solve both the full and reduced Salpeter
equations and systematically explore the conditions under which these two
equations give equivalent results in meson dynamics. The effects of constituent
mass, angular momentum state, type of interaction, and the nature of
confinement are all considered in an effort to clearly delineate the range of
validity of the reduced Salpeter approximations. We find that for
the solutions are strikingly similar for all
constituent masses. For zero angular momentum states the full and reduced
Salpeter equations give different results for small quark mass especially with
a large additive constant coordinate space potential. We also show that
corrections to heavy-light energy levels can be accurately
computed with the reduced equation.Comment: Latex (uses epsf macro), 24 pages of text, 12 postscript figures
included. Slightly revised version, to appear in Phys. Rev.
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