1,399 research outputs found
LaRC design analysis report for National Transonic Facility for 304 stainless steel tunnel shell. Volume 4S: Thermal analysis
For abstract, see N76-33552
LaRC design analysis report for National Transonic Facility for 304 stainless steel tunnel shell. Volume 7S: Special studies
For abstract, see N76-33552
Solar Ellerman Bombs in 1D Radiative Hydrodynamics
Recent observations from the Interface Region Imaging Spectrograph (IRIS)
appear to show impulsive brightenings in high temperature lines, which when
combined with simultaneous ground based observations in H, appear
co-spatial to Ellerman Bombs (EBs). We use the RADYN 1-dimensional radiative
transfer code in an attempt to try and reproduce the observed line profiles and
simulate the atmospheric conditions of these events. Combined with the MULTI/RH
line synthesis codes, we compute the H, Ca II 8542~\AA, and Mg II h \&
k lines for these simulated events and compare them to previous observations.
Our findings hint that the presence of superheated regions in the photosphere
(10,000 K) is not a plausible explanation for the production of EB
signatures. While we are able to recreate EB-like line profiles in H,
Ca II 8542~\AA, and Mg II h \& k, we cannot achieve agreement with all of these
simultaneously.Comment: Accepted into ApJL. 4 Figures, 1 Tabl
LaRC design analysis report for national transonic facility for 9% nickel tunnel shell. Volume 7: Special studies
For abstract, see N76-33543
LaRC design analysis report for National Transonic Facility for 9% nickel tunnel shell. Volume 3: Finite element analysis of plenum region including side access reinforcement, side access door and angle of attack penetration
For abstract, see N76-33543
Anonymous shell companies: A global audit study and field experiment in 176 countries
To test whether firms behave consistently with international law prohibiting anonymous incorporation, we conducted a global audit study and field experiment, using data from 1639 incorporation firms in 176 countries. We requested anonymous incorporation and randomly assigned references to international law, threat of penalties, norms of appropriate behavior, or a placebo. We find a substantial number of firms willing to flout international standards and show that those in OECD countries proved significantly less compliant with rules than in developing countries or tax havens. Firms in tax havens displayed significantly greater compliance and were sensitive to experimental interventions invoking international law
Bi2Te1.6S1.4 - a Topological Insulator in the Tetradymite Family
We describe the crystal growth, crystal structure, and basic electrical
properties of Bi2Te1.6S1.4, which incorporates both S and Te in its Tetradymite
quintuple layers in the motif -[Te0.8S0.2]-Bi-S-Bi-[Te0.8S0.2]-. This material
differs from other Tetradymites studied as topological insulators due to the
increased ionic character that arises from its significant S content.
Bi2Te1.6S1.4 forms high quality crystals from the melt and is the S-rich limit
of the ternary Bi-Te-S {\gamma}-Tetradymite phase at the melting point. The
native material is n-type with a low resistivity; Sb substitution, with
adjustment of the Te to S ratio, results in a crossover to p-type and resistive
behavior at low temperatures. Angle resolved photoemission study shows that
topological surface states are present, with the Dirac point more exposed than
it is in Bi2Te3 and similar to that seen in Bi2Te2Se. Single crystal structure
determination indicates that the S in the outer chalcogen layers is closer to
the Bi than the Te, and therefore that the layers supporting the surface states
are corrugated on the atomic scale.Comment: To be published in Physical Review B Rapid Communications 16 douuble
spaced pages. 4 figures 1 tabl
Simulations of the Mg II k and Ca II 8542 lines from an AlfvÉn Wave-heated Flare Chromosphere
We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating:
Alfven wave dissipation and electron beam collisional losses. Both mechanisms are capable of strong chro- ´
mospheric heating, and we show that the distinctive atmospheric evolution in the mid-to-upper chromosphere
results in Mg ii k-line emission that should be observably different between wave-heated and beam-heated simulations.
We also present Ca ii 8542Å profiles which are formed slightly deeper in the chromosphere. The
Mg ii k-line profiles from our wave-heated simulation are quite different from those from a beam-heated model
and are more consistent with IRIS observations. The predicted differences between the Ca ii 8542Å in the two
models are small. We conclude that careful observational and theoretical study of lines formed in the mid-toupper
chromosphere holds genuine promise for distinguishing between competing models for chromospheric
heating in flares
Extreme Sensitivity of Superconductivity to Stoichiometry in FeSe (Fe1+dSe)
The recently discovered iron arsenide superconductors, which display
superconducting transition temperatures as high as 55 K, appear to share a
number of general features with high-Tc cuprates, including proximity to a
magnetically ordered state and robustness of the superconductivity in the
presence of disorder. Here we show that superconductivity in Fe1+dSe, the
parent compound of the superconducting arsenide family, is destroyed by very
small changes in stoichiometry. Further, we show that non-superconducting
Fe1+dSe is not magnetically ordered down to low temperatures. These results
suggest that robust superconductivity and immediate instability against an
ordered magnetic state should not be considered as intrinsic characteristics of
iron-based superconducting systems, and that Fe1+dSe may present a unique
opportunity for determining which materials characteristics are critical to the
existence of superconductivity in high Tc iron arsenide superconductors and
which are not.Comment: Updated to reflect final version and include journal referenc
An inexpensive economical solar heating system for homes
A low-cost solar home heating system to supplement existing warm-air heating systems is described. The report is written in three parts: (1) a brief background on solar heating, (2) experience with a demonstration system, and (3) information for the homeowner who wishes to construct such a system. Instructions are given for a solar heating installation in which the homeowner supplies all labor necessary to install off-the-shelf components estimated to cost $2,000. These components, which include solar collector, heat exchanger, water pump, storage tank, piping, and controls to make the system completely automatic, are available at local lumber yards, hardware stores, and plumbing supply stores, and are relatively simple to install. Manufacturers and prices of each component used and a rough cost analysis based on these prices are included. This report also gives performance data obtained from a demonstration system which was built and tested at the Langley Research Center
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