3,467 research outputs found
Calculated tissue current-to-dose conversion factors for nucleons below 400 mev
Monte Carlo computer program for calculation of energy deposition from high incident nucleons as function of tissue slab dept
The leaking mode problem in atmospheric acoustic-gravity wave propagation
The problem of predicting the transient acoustic pressure pulse at long horizontal distances from large explosions in the atmosphere is examined. Account is taken of poles off the real axis and of branch line integrals in the general integral governing the transient waveform. Perturbation techniques are described for the computation of the imaginary ordinate of the poles and numerical studies are described for a model atmosphere terminated by a halfspace with c = 478 m/sec above 125 km. For frequencies less than 0.0125 rad/sec, the GR sub 1 mode, for example, is found to have a frequency dependent amplitude decay of the order of 0.0001 nepers/km. Examples of numerically synthesized transient waveforms are exhibited with and without the inclusion of leaking modes. The inclusion of leaking modes results in waveforms with a more marked beginning rather than a low frequency oscillating precursor of gradually increasing amplitude. Also, the revised computations indicate that waveforms invariably begin with a pressure rise, a result supported by other theoretical considerations and by experimental data
Cosmic Microwave Background Observations as a Way to Discriminate Among Inflation Models
The upcoming satellite missions MAP and Planck will measure the spectrum of
fluctuations in the Cosmic Microwave Background with unprecedented accuracy. We
discuss the prospect of using these observations to distinguish among proposed
models of inflationary cosmology.Comment: To appear in the proceedings of the XXXIIIrd Rencontres de Moriond,
"Fundamental Parameters in Cosmology", 17-24 January, Les Arcs, France. 6
Pages, 2 figures, uses moriond.st
Experimental Research on 4-Duct Tandem VTOL Aircraft Configurations
This paper presents a brief summary of several wind-tunnel investigations conducted at the Langley Research Center of the NASA to study the aerodynamic and stability and control characteristics of several VTOL aircraft configurations powered by four tilting ducted propellers arranged in tandem pairs. Specifically the two rear ducts could be mounted close alongside the upper rear portion of the fuselage with small wing panels attached to the outboard side of the ducts or could be mounted outboard on the tips of a small wing located high on the rear portion of the fuselage. The two front ducts were always mounted close inboard on the forward part of the fuselage and could be mounted either in a high or low position on the fuselage. The results of the investigation indicated that aircraft of this type could have acceptable aerodynamic and static longitudinal and lateral stability and control characteristics in both transition and normal cruise flight except for the possible qualification that the lateral force due to sideslip is abnormally high and might cause the aircraft to be too sensitive to side gusts
Development of a KSC test and flight engineering oriented computer language, Phase 1
Ten, primarily test oriented, computer languages reviewed during the phase 1 study effort are described. Fifty characteristics of ATOLL, ATLAS, and CLASP are compared. Unique characteristics of the other languages, including deficiencies, problems, safeguards, and checking provisions are identified. Programming aids related to these languages are reported, and the conclusions resulting from this phase of the study are discussed. A glossary and bibliography are included. For the reports on phase 2 of the study, see N71-35027 and N71-35029
Latest inflation model constraints from cosmic microwave background measurements
In this addendum to Phys.Rev. D74 (2006) 023502, we present an update of
cosmological constraints on single-field inflation in light of the Wilkinson
Microwave Ansiotropy Probe satellite mission five-year results (WMAP5). We find
that the cosmic microwave background data are quite consistent with a
Harrison-Zel'dovich primordial spectrum with no running and zero tensor
amplitude. We find that the three main conclusions of our analysis of the WMAP
three-year data (WMAP3) are consistent with the WMAP5 data: (1) the
Harrison--Zel'dovich model is within the 95% confidence level contours; (2)
there is no evidence for running of the spectral index of scalar perturbations;
(3) From the WMAP 5 data alone, potentials of the form are
consistent with the data for , and are ruled out for .
Furthermore, consistent with our WMAP3 analysis, we find no evidence for
primordial tensor perturbations, this time with a 95% confidence upper limit of
for the WMAP5 data alone, and for the WMAP5 data taken in
combination with the Arcminute Cosmology Bolometer Array (ACBAR).Comment: 8 pages, 4 figures. V2: matches version accepted by PR
THE INVERSION LAYER: ESSAYS
This essay collection examines the ways in which places with rich histories exist through time. Five sites are examined, four of them in the Upper Peninsula and one of them in the Lower Peninsula of Michigan. The sites in âThe Best Souvenirâ and âThe Cloud Chamberâ are official museums, the site in âComfort in Buying Thingsâ is an active mall, the site in âThe Inversion Layerâ is a tourist destination, and the site in âA Beautiful Piece of Nowhereâ has no official memorial. All of these essays incorporate research but are grounded mostly in the authorâs experiences at his visits to these places. The essays explore how personal stories are interwoven with the places where they occur, and how these placesâ pasts are interwoven with the present day
Hagen site, 24DW1| A review of historical data and a reassessment of its ceramic assemblage and position in Northern Plains prehistory
WMAPping inflationary physics
We extract parameters relevant for distinguishing among single-field
inflation models from the Wilkinson Microwave Anisotropy Probe (WMAP) data set,
and from a combination of the WMAP data and seven other Cosmic Microwave
Background (CMB) experiments. We use only CMB data and perform a likelihood
analysis over a grid of models including the full error covariance matrix. We
find that a model with a scale-invariant scalar power spectrum (), no
tensor contribution, and no running of the spectral index, is within the
1- contours of both data sets. We then apply the Monte Carlo
reconstruction technique to both data sets to generate an ensemble of
inflationary potentials consistent with observations. None of the three basic
classes of inflation models (small-field, large-field, and hybrid) are
completely ruled out, although hybrid models are favored by the best-fit
region. The reconstruction process indicates that a wide variety of smooth
potentials for the inflaton are consistent with the data, implying that the
first-year WMAP result is still too crude to constrain significantly either the
height or the shape of the inflaton potential. In particular, the lack of
evidence for tensor fluctuations makes it impossible to constrain the energy
scale of inflation. Nonetheless, the data rule out a large portion of the
available parameter space for inflation. For instance, we find that potentials
of the form are ruled out to by the combined
data set, but not by the WMAP data taken alone.Comment: 22 pages, 13 figures. Higher resolution figures available at
http://home.fnal.gov/~rocky/Mapping
- âŠ