18,938 research outputs found
Quantitative flaw characterization with scanning laser acoustic microscopy
Surface roughness and diffraction are two factors that have been observed to affect the accuracy of flaw characterization with scanning laser acoustic microscopy. In accuracies can arise when the surface of the test sample is acoustically rough. It is shown that, in this case, Snell's law is no longer valid for determining the direction of sound propagation within the sample. The relationship between the direction of sound propagation within the sample, the apparent flaw depth, and the sample's surface roughness is investigated. Diffraction effects can mask the acoustic images of minute flaws and make it difficult to establish their size, depth, and other characteristics. It is shown that for Fraunhofer diffraction conditions the acoustic image of a subsurface defect corresponds to a two-dimensional Fourier transform. Transforms based on simulated flaws are used to infer the size and shape of the actual flaw
Microscopic two-nucleon overlaps and knockout reactions from C
The nuclear structure dependence of direct reactions that remove a pair of
like or unlike nucleons from a fast C projectile beam are considered.
Specifically, we study the differences in the two-nucleon correlations present
and the predicted removal cross sections when using -shell shell-model and
multi- no-core shell-model (NCSM) descriptions of the two-nucleon
overlaps for the transitions to the mass =10 projectile residues. The NCSM
calculations use modern chiral two-nucleon and three-nucleon (NN+3N)
interactions. The -removal cross sections to low-lying =0, B
final states are enhanced when using the NCSM two-nucleon amplitudes. The
calculated absolute and relative partial cross sections to the low energy
B final states show a significant sensitivity to the interactions used,
suggesting that assessments of the overlap functions for these transitions and
confirmations of their structure could be made using final-state-exclusive
measurements of the -removal cross sections and the associated momentum
distributions of the forward travelling projectile-like residues.Comment: 9 pages, 7 figure
Forebody and vertical stabilizer effects on directional stability of a reusable LOX/RP (061) booster AR 12161-2
Results are presented of a wind tunnel test on the directional stability of space shuttle booster configurations. The test was conducted at the 14-inch trisonic tunnel starting 6 December 1971 and continued through 11 December 1971 for a total of 66 occupancy hours. Configurations tested included a cylindrical body with two axisymmetrical noses, one with and without canopy, one delta wing, located in two positions, five vertical tails (including a V tail), two having split rudders, ventral fins, two sets of chines, three airbreathing engine pods, and rocket engine shrouds. The model scale was 0.003366
A formal theory of cubical complexes Formal report, 1 Sep. 1968 - 30 Apr. 1969
Algorithm for computation of test failures in cyclic circuit
Microscopic theory of solvent mediated long range forces: influence of wetting
We show that a general density functional approach for calculating the force
between two big particles immersed in a solvent of smaller ones can describe
systems that exhibit fluid-fluid phase separation: the theory captures effects
of strong adsorption (wetting) and of critical fluctuations in the solvent. We
illustrate the approach for the Gaussian core model, a simple model of a
polymer mixture in solution and find extremely attractive, long ranged solvent
mediated potentials between the big particles for state points lying close to
the binodal, on the side where the solvent is poor in the species which is
favoured by the big particles.Comment: 7 pages, 3 figures, submitted to Europhysics Letter
Earth-Moon trajectories, 1965-70
Analytical model for generation of earth-moon trajectory analysis dat
Statistical properties of online auctions
We characterize the statistical properties of a large number of online
auctions run on eBay. Both stationary and dynamic properties, like
distributions of prices, number of bids etc., as well as relations between
these quantities are studied. The analysis of the data reveals surprisingly
simple distributions and relations, typically of power-law form. Based on these
findings we introduce a simple method to identify suspicious auctions that
could be influenced by a form of fraud known as shill bidding. Furthermore the
influence of bidding strategies is discussed. The results indicate that the
observed behavior is related to a mixture of agents using a variety of
strategies.Comment: 9 pages, 4 figures, to be published in Int. J. Mod. Phys.
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