15,285 research outputs found
Hypersonic research engine project. Phase 2: Aerothermodynamic Integration Model (AIM) test report
The Hypersonic Research Engine-Aerothermodynamic Integration Model (HRE-AIM) was designed, fabricated, and tested in the Hypersonic Tunnel Facility. The HRE-AIM is described along with its installation in the wind tunnel facility. Test conditions to which the HRE-AIM was subjected and observations made during the tests are discussed. The overall engine performance, component interaction, and ignition limits for the design are evaluated
Acoustical modeling study of the open test section of the NASA Langley V/STOL wind tunnel
An acoustic model study was carried out to identify effective sound absorbing treatment of strategically located surfaces in an open wind tunnel test section. Also an aerodynamic study done concurrently, sought to find measures to control low frequency jet pulsations which occur when the tunnel is operated in its open test section configuration. The acoustical modeling study indicated that lining of the raised ceiling and the test section floor immediately below it, results in a substantial improvement. The aerodynamic model study indicated that: (1) the low frequency jet pulsations are most likely caused or maintained by coupling of aerodynamic and aeroacoustic phenomena in the closed tunnel circuit, (2) replacing the hard collector cowl with a geometrically identical but porous fiber metal surface of 100 mks rayls flow resistance does not result in any noticable reduction of the test section noise caused by the impingement of the turbulent flow on the cowl
Use of ERTS data for a multidisciplinary analysis of Michigan resources
The author has identified the following significant results. The results of this investigation of ratioing simulated ERTS spectral bands and several non-ERTS bands (all collected by an airborne multispectral scanner) indicate that significant terrain information is available from band-ratio images. Ratio images, which are based on the relative spectral changes which occur from one band to another, are useful for enhancing differences and aiding the image interpreter in identifying and mapping the distribution of such terrain elements as seedling crops, all bare soil, organic soil, mineral soil, forest and woodlots, and marsh areas. In addition, the ratio technique may be useful for computer processing to obtain recognition images of large areas at lower costs than with statistical decision rules. The results of this study of ratio processing of aircraft MSS data will be useful for future processing and evaluation of ERTS-1 data for soil and landform studies. Additionally, the results of ratioing spectral bands other than those currently collected by ERTS-1 suggests that some other bands (particularly a thermal band) would be useful in future satellites
Linear response separation of a solid into atomic constituents: Li, Al, and their evolution under pressure
We present the first realization of the generalized pseudoatom concept
introduced by Ball, and adopt the name enatom to minimize confusion. This
enatom, which consists of a unique decomposition of the total charge density
(or potential) of any solid into a sum of overlapping atomiclike contributions
that move rigidly with the nuclei to first order, is calculated using
(numerical) linear response methods, and is analyzed for both fcc Li and Al at
pressures of 0, 35, and 50 GPa. These two simple fcc metals (Li is fcc and a
good superconductor in the 20-40 GPa range) show different physical behaviors
under pressure, which reflects the increasing covalency in Li and the lack of
it in Al. The nonrigid (deformation) parts of the enatom charge and potential
have opposite signs in Li and Al; they become larger under pressure only in Li.
These results establish a method of construction of the enatom, whose potential
can be used to obtain a real-space understanding of the vibrational properties
and electron-phonon interaction in solids.Comment: 13 pages, 9 figures, 1 table, V2: fixed problem with Fig. 7, V3:
minor correction
Squeezed state purification with linear optics and feed forward
A scheme for optimal and deterministic linear optical purification of mixed
squeezed Gaussian states is proposed and experimentally demonstrated. The
scheme requires only linear optical elements and homodyne detectors, and allows
the balance between purification efficacy and squeezing degradation to be
controlled. One particular choice of parameters gave a ten-fold reduction of
the thermal noise with a corresponding squeezing degradation of only 11%. We
prove optimality of the protocol, and show that it can be used to enhance the
performance of quantum informational protocols such as dense coding and
entanglement generation.Comment: 4 pages, 3 figure
Analysis and study of hospital communication via social media from the patient perspective
Currently, the online interaction between citizens and hospitals is poor, as
users believe that there are shortcomings that could be improved. This study
analyzes patients’ opinions of the online communication strategies of hospitals in
Spain. Therefore, a mixed-method is proposed. Firstly, a qualitative analysis through
a focus-group was carried out, so around twenty representatives of national,
regional and local patients’ associations were brought together. Secondly, the
research is supplemented with a content assessment of the Twitter activity of the
most influential hospitals in Spain. The results reveal that the general public
appreciate hospitals’ communication potential through social media, although they
are generally unaware of how it works. The group says that, apart from the lack of
interaction, they find it hard to understand certain messages, and some publications
give a biased picture. In order to improve communication, patients and
relatives are demanding that their perspective be taken into consideration in the
messages issued to enhance the quality of life and well-being of society
Self-contained Kondo effect in single molecules
Kondo coupling of f and conduction electrons is a common feature of
f-electron intermetallics. Similar effects should occur in carbon ring
systems(metallocenes). Evidence for Kondo coupling in Ce(C8H8)2 (cerocene) and
the ytterbocene Cp*2Yb(bipy) is reported from magnetic susceptibility and
L_III-edge x-ray absorption spectroscopy. These well-defined systems provide a
new way to study the Kondo effect on the nanoscale, should generate insight
into the Anderson Lattice problem, and indicate the importance of this
often-ignored contribution to bonding in organometallics.Comment: 4 pages, 5 figures (eps
ARPES and NMTO Wannier Orbital Theory of LiMoO - Implications for Unusually Robust Quasi-One Dimensional Behavior
We present the results of a combined study by band theory and angle resolved
photoemission spectroscopy (ARPES) of the purple bronze,
LiMoO. Structural and electronic origins of its unusually
robust quasi-one dimensional (quasi-1D) behavior are investigated in detail.
The band structure, in a large energy window around the Fermi energy, is
basically 2D and formed by three Mo -like extended Wannier orbitals,
each one giving rise to a 1D band running at a 120 angle to the two
others. A structural "dimerization" from to gaps
the and bands while leaving the bands metallic in the gap, but
resonantly coupled to the gap edges and, hence, to the other directions. The
resulting complex shape of the quasi-1D Fermi surface (FS), verified by our
ARPES, thus depends strongly on the Fermi energy position in the gap, implying
a great sensitivity to Li stoichiometry of properties dependent on the FS, such
as FS nesting or superconductivity. The strong resonances prevent either a
two-band tight-binding model or a related real-space ladder picture from giving
a valid description of the low-energy electronic structure. We use our extended
knowledge of the electronic structure to newly advocate for framing
LiMoO as a weak-coupling material and in that framework can
rationalize both the robustness of its quasi-1D behavior and the rather large
value of its Luttinger liquid (LL) exponent . Down to a temperature of
6K we find no evidence for a theoretically expected downward
renormalization of perpendicular single particle hopping due to LL fluctuations
in the quasi-1D chains.Comment: 53 pages, 17 Figures, 6 year
The Herschel exploitation of local galaxy Andromeda (HELGA) V: Strengthening the case for substantial interstellar grain growth
In this paper we consider the implications of the distributions of dust and
metals in the disc of M31. We derive mean radial dust distributions using a
dust map created from Herschel images of M31 sampling the entire far-infrared
(FIR) peak. Modified blackbodies are fit to approximately 4000 pixels with a
varying, as well as a fixed, dust emissivity index (beta). An overall metal
distribution is also derived using data collected from the literature. We use a
simple analytical model of the evolution of the dust in a galaxy with dust
contributed by stellar sources and interstellar grain growth, and fit this
model to the radial dust-to-metals distribution across the galaxy. Our analysis
shows that the dust-to-gas gradient in M31 is steeper than the metallicity
gradient, suggesting interstellar dust growth is (or has been) important in
M31. We argue that M31 helps build a case for cosmic dust in galaxies being the
result of substantial interstellar grain growth, while the net dust production
from stars may be limited. We note, however, that the efficiency of dust
production in stars, e.g., in supernovae (SNe) ejecta and/or stellar
atmospheres, and grain destruction in the interstellar medium (ISM) may be
degenerate in our simple model. We can conclude that interstellar grain growth
by accretion is likely at least as important as stellar dust production
channels in building the cosmic dust component in M31.Comment: 12 pages, 7 figures. Published in MNRAS 444, 797. This version is
updated to match the published versio
EC71-1506 Insect Control Guide for Household and Pets in Nebraska
Extension Curricular 71-1506 Insect control guide for household and pets
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