62,333 research outputs found
Development of nine-channel 10-micrometer (Hg, Cd)Te pushbroom IR/CCD system
The engineering development of the 9-channel detector array is documented. The development of the array demonstrates the feasibility of a self scanned multi-element infrared detector focal plane. Procedures for operating the array are outlined
Editorial: Controversies and solutions in environmental sciences: Addressing toxicity of sediments and soils
This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ 2007 Ecomed Publishers
High frequency, high power capacitor development
A program to develop a special high energy density, high power transfer capacitor to operate at frequency of 40 kHz, 600 V rms at 125 A rms plus 600 V dc bias for space operation. The program included material evaluation and selection, a capacitor design was prepared, a thermal analysis performed on the design. Fifty capacitors were manufactured for testing at 10 kHz and 40 kHz for 50 hours at Industrial Electric Heating Co. of Columbus, Ohio. The vacuum endurance test used on environmental chamber and temperature plate furnished by Maxwell. The capacitors were energized with a special power conditioning apparatus developed by Industrial Electric Heating Co. Temperature conditions of the capacitors were monitored by IEHCo test equipment. Successful completion of the vacuum endurance test series confirmed achievement of the main goal of producing a capacitor or reliable operation at high frequency in an environment normally not hospitable to electrical and electronic components. The capacitor developed compared to a typical commercial capacitor at the 40 kHz level represents a decrease in size and weight by a factor of seven
Flight research capabilities of the NASA/Army rotor systems research aircraft
A description is given of the capabilities and limitations of the Rotor Systems Research Aircraft (RSRA) that was demonstrated during the development contract, and assesses the expected research capabilities of the RSRA on delivery to the government
A Two-dimensional Infinte System Density Matrix Renormalization Group Algorithm
It has proved difficult to extend the density matrix renormalization group
technique to large two-dimensional systems. In this Communication I present a
novel approach where the calculation is done directly in two dimensions. This
makes it possible to use an infinite system method, and for the first time the
fixed point in two dimensions is studied. By analyzing several related blocking
schemes I find that there exists an algorithm for which the local energy
decreases monotonically as the system size increases, thereby showing the
potential feasibility of this method.Comment: 5 pages, 6 figure
Spin-tunnel investigation of a 1/13-scale model of the NASA AD-1 oblique-wing research aircraft
The spin and recovery characteristics of a 1/13-scale model of the NASA AD-1 oblique-wing research aircraft at wing-skew positions of 0, 25, 45, and 60 deg (right wing forward) were investigated. Spins were obtained for all wing-skew positions tested. For the unskewed wing position, two spin modes were possible. One spin mode was very steep and recoveries were obtained within 1 turn or less by rudder reversal. The second spin mode was flat and fast; the angle of attack was about 75 deg and the spin rate was about 145 deg/sec (2.5 seconds per turn). For the skewed wing positions, spins were obtained only in the direction of the forward-skewed wing (right wing forward). No spins were obtained to the left when the wing was skewed with the right wing forward. Recoveries should be attempted by deflecting the rudder to full against the spin, the ailerons to full with the spin, and movement of the wings to 0 deg skew. If the wing is skewed, the recovery may not be effected until the wing skew approaches 0 deg
Oxygen Absorption in Cooling Flows
The inhomogeneous cooling flow scenario predicts the existence of large
quantities of gas in massive elliptical galaxies, groups, and clusters that
have cooled and dropped out of the flow. Using spatially resolved, deprojected
X-ray spectra from the ROSAT PSPC we have detected strong absorption over
energies ~0.4-0.8 keV intrinsic to the central ~1 arcmin of the galaxy, NGC
1399, the group, NGC 5044, and the cluster, A1795. These systems have amongst
the largest nearby cooling flows in their respective classes and low Galactic
columns. Since no excess absorption is indicated for energies below ~0.4 keV
the most reasonable model for the absorber is warm, collisionally ionized gas
with T=10^{5-6} K where ionized states of oxygen provide most of the
absorption. Attributing the absorption only to ionized gas reconciles the large
columns of cold H and He inferred from Einstein and ASCA with the lack of such
columns inferred from ROSAT, and also is consistent with the negligible atomic
and molecular H inferred from HI, and CO observations of cooling flows. The
prediction of warm ionized gas as the product of mass drop-out in these and
other cooling flows can be verified by Chandra, XMM, and ASTRO-E.Comment: 4 pages (2 figures), Accepted for publication in ApJ Letters, no
significant changes from previous submitted versio
A New Approach to Large-Scale Nuclear Structure Calculations
A new approach to large-scale nuclear structure calculations, based on the
Density Matrix Renormalization Group (DMRG), is described. The method is tested
in the context of a problem involving many identical nucleons constrained to
move in a single large-j shell and interacting via a pairing plus quadrupole
interaction. In cases in which exact diagonalization of the hamiltonian is
possible, the method is able to reproduce the exact results for the ground
state energy and the energies of low-lying excited states with extreme
precision. Results are also presented for a model problem in which exact
solution is not feasible.Comment: 6 pages + 1 eps figur
Principles for increased resilience in critical networked infrastructures
We propose a framework for deploying stronger, intelligent resilience mechanisms in mission-critical ATM networks over and above that offered by physical n-fold redundancy. We
compare the challenges facing power and data network resilience and discuss disruptive threats to real-world operations. Using recorded live data from an ATM data network we argue our proposed architecture with deployable, distributed on-demand anomaly detection and monitoring modules provides enhanced fail-secure versus current fail-safe resilience
Newtonian Flow in Converging-Diverging Capillaries
The one-dimensional Navier-Stokes equations are used to derive analytical
expressions for the relation between pressure and volumetric flow rate in
capillaries of five different converging-diverging axisymmetric geometries for
Newtonian fluids. The results are compared to previously-derived expressions
for the same geometries using the lubrication approximation. The results of the
one-dimensional Navier-Stokes are identical to those obtained from the
lubrication approximation within a non-dimensional numerical factor. The
derived flow expressions have also been validated by comparison to numerical
solutions obtained from discretization with numerical integration. Moreover,
they have been certified by testing the convergence of solutions as the
converging-diverging geometries approach the limiting straight geometry.Comment: 23 pages, 5 figures, 1 table. This is an extended and improved
version. arXiv admin note: substantial text overlap with arXiv:1006.151
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