4,901 research outputs found
Statistical analysis of direct-strike lightning data (1980 to 1982)
Electromagnetic measurements are being made during direct lightning strikes by NASA Langley Center using a specially instrumented F-106B aircraft. The research is to aid refinement, characterization, and understanding of the lightning-aircraft interaction process and the lightning hazards to aircraft. Statistical methods are applied to characterize some aspects of the lightning data obtained from 176 strikes to the aircraft. Specific attention is given to the problem of estimating the upper extreme quantiles of the distributions of peak-to-peak values for currents and rates of change in the magnetic and flux densities. A formal treatment via a general location-scale family of models allows the estimation method to be adapted to the realized shapes the distributions. The shapes are examined by probability plotting methods
Storm hazards '79: F-106B operations summary
Preliminary flight tests with a F-106B aircraft were made on the periphery of isolated thunder cells using weather radar support. In addition to storm hazards correlation research, a direct-strike lightning measurement experiment and an atmospheric chemistry experiment were conducted. Two flights were made to close proximity to lightning generating cumulonimbus clouds; however, no direct lightning strikes were experienced. Although no discernible lightning transients were recorded, many operational techniques were identified and established
State Differentiation by Transient Truncation in Coupled Threshold Dynamics
Dynamics with a threshold input--output relation commonly exist in gene,
signal-transduction, and neural networks. Coupled dynamical systems of such
threshold elements are investigated, in an effort to find differentiation of
elements induced by the interaction. Through global diffusive coupling, novel
states are found to be generated that are not the original attractor of
single-element threshold dynamics, but are sustained through the interaction
with the elements located at the original attractor. This stabilization of the
novel state(s) is not related to symmetry breaking, but is explained as the
truncation of transient trajectories to the original attractor due to the
coupling. Single-element dynamics with winding transient trajectories located
at a low-dimensional manifold and having turning points are shown to be
essential to the generation of such novel state(s) in a coupled system.
Universality of this mechanism for the novel state generation and its relevance
to biological cell differentiation are briefly discussed.Comment: 8 pages. Phys. Rev. E. in pres
Universally Coupled Massive Gravity
We derive Einstein's equations from a linear theory in flat space-time using
free-field gauge invariance and universal coupling. The gravitational potential
can be either covariant or contravariant and of almost any density weight. We
adapt these results to yield universally coupled massive variants of Einstein's
equations, yielding two one-parameter families of distinct theories with spin 2
and spin 0. The Freund-Maheshwari-Schonberg theory is therefore not the unique
universally coupled massive generalization of Einstein's theory, although it is
privileged in some respects. The theories we derive are a subset of those found
by Ogievetsky and Polubarinov by other means. The question of positive energy,
which continues to be discussed, might be addressed numerically in spherical
symmetry. We briefly comment on the issue of causality with two observable
metrics and the need for gauge freedom and address some criticisms by
Padmanabhan of field derivations of Einstein-like equations along the way.Comment: Introduction notes resemblance between Einstein's discovery process
and later field/spin 2 project; matches journal versio
Magic number 7 2 in networks of threshold dynamics
Information processing by random feed-forward networks consisting of units
with sigmoidal input-output response is studied by focusing on the dependence
of its outputs on the number of parallel paths M. It is found that the system
leads to a combination of on/off outputs when , while for , chaotic dynamics arises, resulting in a continuous distribution of
outputs. This universality of the critical number is explained by
combinatorial explosion, i.e., dominance of factorial over exponential
increase. Relevance of the result to the psychological magic number
is briefly discussed.Comment: 6 pages, 5 figure
Radiation distributions in TCV
Total radiative powers measured by foil bolometer and AXUV camera systems are compared to SOLPS5 simulations in low and high density deuterium and helium diverted discharges on the TCV tokamak. For low density the match between simulation and measurements is satisfactory, but at high density strongly radiating regions outside the SOLPS5 simulation grid are seen in measurements and this may indicate the presence of enhanced convective particle transport in the low field side midplane region. The chord coverage of the foil bolometer system does not, however, allow detailed resolution in this region. The comparison of foil and AXUV data also demonstrates that ageing of the AXUV diodes under plasma irradiation combined with the unevenness of the diode spectral response, strongly limits their application for total radiative power measurements. (c) 2007 Elsevier B.V. All rights reserved
The caries experience of 5 year-old children in Scotland in 2013-2014, and in England and Wales in 2014-2015. Reports of cross-sectional dental surveys using BASCD criteria
Objective: We report the findings from and comment on the surveys of the oral health of 5-year-old children undertaken in Scotland
(2013-14), Wales (2014-15) and England (2014-15). This was the fourteenth survey in Scotland since 1988. In England and Wales it is the
third survey since 2007 when changes were required in consent arrangements. Method: Representative samples were drawn within Health
Boards across Scotland and local authorities across England and Wales. Consent was sought via opt-out parental consent in Scotland and
opt-in parental consent in England and Wales. Children examined were those aged five in England and those in Primary 1 (school year
aged 5 to 6) in Scotland and Wales. Examinations were conducted in schools by trained and calibrated examiners. Caries was visually
diagnosed at the dentinal threshold. Results: There is a continuing decline in d3mft in all three countries. d3mft was 1.27 (opt-out consent)
for Scotland, 0.84 for England (opt-in consent) and 1.29 for Wales (opt-in consent). Tooth decay levels remain higher in more deprived
areas across Great Britain, with clear inequalities gradients demonstrated across all geographies. Attempts to measure changes in dental
health inequalities across the three countries show no conclusive trends. Conclusion: Inter-country comparisons provide further oral health
intelligence despite differences in approach and timing. The third surveys in England and Wales using the new consent arrangements
have enabled trend analysis. Dental health inequalities gradients were shown across all geographies and all of the indicators of inequalit
The stellar populations of spiral disks.II Measuring and modeling the radial distribution of absorption spectral indices
The radial distributions of the Mg2 and Fe5270 Lick spectral indices have
been measured to large radial distances on the disks of NGC 4303 and NGC 4535
using an imaging technique based on interference filters. These data, added to
those of NGC 4321 previously published in Paper I of this series are used to
constraint chemical (multiphase) evolutionary models for these galaxies.
Because the integrated light of a stellar disk is a time average over the
history of the galaxy weighted by the star formation rate, these constraints
complement the information on chemical gradients provided by the study of HII
regions which, by themselves, can only provide the alpha-elements abundance
accumulate over the life of the galaxy. The agreement between the observations
and the model predictions shown here lends confidence to the models which are
then used to describe the time evolution of galaxy parameters such as star
formation rates, chemical gradients, and gradients in the mean age of the
stellar population.Comment: to be published in Astrophysical Journa
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