2,205 research outputs found
Heavy rain effects on airplane performance
The objective is to determine if the aerodynamic characteristics of an airplane are altered while flying in the rain. Wind-tunnel tests conducted at the NASA Langley Research Center (LaRC) have shown losses in maximum lift, reduction in stall angle, and increases in drag when a wing is placed in a simulated rain spray. For these tests the water spray concentration used represented a very heavy rainfall. A lack of definition of the scaling laws for aerodynamic testing in a two-phase, two-component flow makes interpolation of the wind-tunnel test uncertain. Tests of a large-scale wing are to be conducted at the LaRC. The large-scale wing is mounted on top of the Aircraft Landing Dynamics Facility (ALDF) carriage. This carriage (which is 70-foot long, 30-foot wide, and 30-foot high) is propelled with the wing model attached down a 3000-foot long test track by a water jet at speeds of up to 170 knots. A simulated rain spray system has been installed along 500 feet of the test track and can simulate rain falls from 2 to 40 inches/hour. Operational checks are underway and the initial tests should be completed by the Fall of 1989
Evidence For Ecological Character Displacement In Western American Catostomid Fishes
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/137612/1/evo04742.pd
The second US Naval Observatory CCD Astrograph Catalog (UCAC2)
The second USNO CCD Astrograph Catalog, UCAC2 was released in July 2003.
Positions and proper motions for 48,330,571 sources (mostly stars) are
available on 3 CDs, supplemented with 2MASS photometry for 99.5% of the
sources. The catalog covers the sky area from -90 to +40 degrees declination,
going up to +52 in some areas; this completely supersedes the UCAC1 released in
2001. Current epoch positions are obtained from observations with the USNO
8-inch Twin Astrograph equipped with a 4k CCD camera. The precision of the
positions are 15 to 70 mas, depending on magnitude, with estimated systematic
errors of 10 mas or below. Proper motions are derived by utilizing over 140
ground-and space-based catalogs, including Hipparcos/Tycho, the AC2000.2, as
well as yet unpublished re-measures of the AGK2 plates and scans from the NPM
and SPM plates. Proper motion errors are about 1 to 3 mas/yr for stars to 12th
magnitude, and about 4 to 7 mas/yr for fainter stars to 16th magnitude. The
observational data, astrometric reductions, results, and important information
for the users of this catalog are presented.Comment: accepted by AJ, AAS LaTeX, 14 figures, 10 table
Symbolic Manipulators Affect Mathematical Mindsets
Symbolic calculators like Mathematica are becoming more commonplace among
upper level physics students. The presence of such a powerful calculator can
couple strongly to the type of mathematical reasoning students employ. It does
not merely offer a convenient way to perform the computations students would
have otherwise wanted to do by hand. This paper presents examples from the work
of upper level physics majors where Mathematica plays an active role in
focusing and sustaining their thought around calculation. These students still
engage in powerful mathematical reasoning while they calculate but struggle
because of the narrowed breadth of their thinking. Their reasoning is drawn
into local attractors where they look to calculation schemes to resolve
questions instead of, for example, mapping the mathematics to the physical
system at hand. We model the influence of Mathematica as an integral part of
the constant feedback that occurs in how students frame, and hence focus, their
work
The enigmatic core L1451-mm: a first hydrostatic core? or a hidden VeLLO?
We present the detection of a dust continuum source at 3-mm (CARMA) and
1.3-mm (SMA), and 12CO(2-1) emission (SMA) towards the L1451-mm dense core.
These detections suggest a compact object and an outflow where no point source
at mid-infrared wavelengths is detected using Spitzer. An upper limit for the
dense core bolometric luminosity of 0.05 Lsun is obtained. By modeling the
broadband SED and the continuum interferometric visibilities simultaneously, we
confirm that a central source of heating is needed to explain the observations.
This modeling also shows that the data can be well fitted by a dense core with
a YSO and disk, or by a dense core with a central First Hydrostatic Core
(FHSC). Unfortunately, we are not able to decide between these two models,
which produce similar fits. We also detect 12CO(2-1) emission with red- and
blue-shifted emission suggesting the presence of a slow and poorly collimated
outflow, in opposition to what is usually found towards young stellar objects
but in agreement with prediction from simulations of a FHSC. This presents the
best candidate, so far, for a FHSC, an object that has been identified in
simulations of collapsing dense cores. Whatever the true nature of the central
object in L1451-mm, this core presents an excellent laboratory to study the
earliest phases of low-mass star formation.Comment: 15 pages, 9 figures, emulateapj. Accepted by Ap
Metal clad aramid fibers for aerospace wire and cable
High strength light weight metal clad aramid fibers can provide significant weight savings when used to replace conventional metal wire in aerospace cable. An overview of metal clad aramid fiber materials and information on performance and use in braided electrical shielding and signal conductors is provided
A New Spectroscopic and Photometric Analysis of the Transiting Planet Systems TrES-3 and TrES-4
We report new spectroscopic and photometric observations of the parent stars
of the recently discovered transiting planets TrES-3 and TrES-4. A detailed
abundance analysis based on high-resolution spectra yields [Fe/H] , K, and for TrES-3,
and [Fe/H] , K, and for TrES-4. The accuracy of the effective temperatures is supported
by a number of independent consistency checks. The spectroscopic orbital
solution for TrES-3 is improved with our new radial-velocity measurements of
that system, as are the light-curve parameters for both systems based on newly
acquired photometry for TrES-3 and a reanalysis of existing photometry for
TrES-4. We have redetermined the stellar parameters taking advantage of the
strong constraint provided by the light curves in the form of the normalized
separation (related to the stellar density) in conjunction with our
new temperatures and metallicities. The masses and radii we derive are
M_\star=0.928_{-0.048}^{+0.028} M_{\sun},R_\star = 0.829_{-0.022}^{+0.015}
R_{\sun}, and M_\star = 1.404_{-0.134}^{+0.066} M_{\sun},
R_\star=1.846_{-0.087}^{+0.096} R_{\sun} for TrES-3 and TrES-4, respectively.
With these revised stellar parameters we obtain improved values for the
planetary masses and radii. We find , for TrES-3, and
, for TrES-4. We confirm TrES-4 as the planet with the largest
radius among the currently known transiting hot Jupiters.Comment: 42 pages, 10 tables, 8 figures. Accepted for publication in the
Astrophysical Journa
The molecular clump towards the eastern border of SNR G18.8+0.3
The eastern border of the SNR G18.8+0.3, close to an HII regions complex, is
a very interesting region to study the molecular gas that it is probably in
contact with the SNR shock front. We observed the aforementioned region using
the Atacama Submillimeter Telescope Experiment (ASTE) in the 12CO J=3-2, 13CO
J=3-2, HCO+ J=4-3, and CS J=7-6 lines with an angular resolution of 22". To
complement these observations, we analyzed IR, submillimeter and radio
continuum archival data. In this work, we clearly show that the radio continuum
"protrusion" that was early thought to belong to the SNR is an HII regions
complex deeply embedded in a molecular clump. The new molecular observations
reveal that this dense clump, belonging to an extended molecular cloud that
surrounds the SNR southeast border, is not physically in contact with SNR
G18.8+0.3, suggesting that the SNR shock front have not yet reached it or maybe
they are located at different distances. We found some young stellar objects
embedded in the molecular clump, suggesting that their formation should be
approximately coeval with the SN explosion.Comment: Accepted for publication in A&A (Sept. 7, 2012
The Bolocam Galactic Plane Survey. XIV. Physical Properties of Massive Starless and Star Forming Clumps
We sort molecular clouds between from the
Bolocam Galactic Plane Survey based on observational diagnostics of star
formation activity: compact sources, mid-IR color-selected
YSOs, and masers, and UCHII regions. We also
present a combined -derived gas kinetic temperature and maser catalog for clumps from our own GBT 100m observations and
from the literature. We identify a subsample of () starless
clump candidates, the largest and most robust sample identified from a blind
survey to date. Distributions of flux density, flux concentration, solid angle,
kinetic temperature, column density, radius, and mass show strong ( dex)
progressions when sorted by star formation indicator. The median starless clump
candidate is marginally sub-virial () with of clumps
with known distance being gravitationally bound (). These samples
show a statistically significant increase in the median clump mass of M from the starless candidates to clumps associated with
protostars. This trend could be due to (i) mass growth of the clumps at
Msun Myr for an average free-fall Myr
time-scale, (ii) a systematic factor of two increase in dust opacity from
starless to protostellar phases, (iii) and/or a variation in the ratio of
starless to protostellar clump lifetime that scales as . By
comparing to the observed number of maser containing clumps we
estimate the phase-lifetime of massive ( M) starless clumps to
be ; the majority
( M) have phase-lifetimes longer than their average free-fall
time.Comment: Accepted for publication in ApJ; 33 pages; 22 figures; 7 table
Separated flow
A brief overview of flow separation phenomena is provided. Langley has many active research programs in flow separation related areas. Three cases are presented which describe specific examples of flow separation research. In each example, a description of the fundamental fluid physics and the complexity of the flow field is presented along with a method of either reducing or controlling the extent of separation. The following examples are discussed: flow over a smooth surface with an adverse pressure gradient; flow over a surface with a geometric discontinuity; and flow with shock-boundary layer interactions. These results will show that improvements are being made in the understanding of flow separation and its control
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