24,702 research outputs found
Numerical methods for the design and analysis of wings at supersonic speeds
Numerical methods for the design and analysis of arbitrary-planform wings at supersonic speeds are reviewed. Certain deficiencies are revealed, particularly in application to wings with slightly subsonic leading edges. Recently devised numerical techniques which overcome the major part of these deficiencies are presented. The original development as well as the more recent revisions are subjected to a thorough review
A linearized theory method of constrained optimization for supersonic cruise wing design
A linearized theory wing design and optimization procedure which allows physical realism and practical considerations to be imposed as constraints on the optimum (least drag due to lift) solution is discussed and examples of application are presented. In addition to the usual constraints on lift and pitching moment, constraints are imposed on wing surface ordinates and wing upper surface pressure levels and gradients. The design procedure also provides the capability of including directly in the optimization process the effects of other aircraft components such as a fuselage, canards, and nacelles
Constraints on proton structure from precision atomic physics measurements
Ground-state hyperfine splittings in hydrogen and muonium are very well
measured. Their difference, after correcting for magnetic moment and reduced
mass effects, is due solely to proton structure--the large QED contributions
for a pointlike nucleus essentially cancel. The rescaled hyperfine difference
depends on the Zemach radius, a fundamental measure of the proton, computed as
an integral over a product of electric and magnetic proton form factors. The
determination of the Zemach radius, (1.043 +/- 0.016) fm, from atomic physics
tightly constrains fits to accelerator measurements of proton form factors.
Conversely, we can use muonium data to extract an ``experimental'' value for
QED corrections to hydrogenic hyperfine data; we find that measurement and
theory are consistent.Comment: 4 pages, RevTeX 4; corrects errors, to be consistent with published
erratu
Spin Response and Neutrino Emissivity of Dense Neutron Matter
We study the spin response of cold dense neutron matter in the limit of zero
momentum transfer, and show that the frequency dependence of the
long-wavelength spin response is well constrained by sum-rules and the
asymptotic behavior of the two-particle response at high frequency. The
sum-rules are calculated using Auxiliary Field Diffusion Monte Carlo technique
and the high frequency two-particle response is calculated for several
nucleon-nucleon potentials. At nuclear saturation density, the sum-rules
suggest that the strength of the spin response peaks at 40--60
MeV, decays rapidly for 100 MeV, and has a sizable strength below
40 MeV. This strength at relatively low energy may lead to enhanced neutrino
production rates in dense neutron-rich matter at temperatures of relevance to
core-collapse supernova.Comment: 11 pages, 4 figures. Minor change. Published versio
Lithological maps of selected Apollo 14 Breccia samples
A booklet of mapped surfaces of some Apollo 14 samples was prepared as an intermediate step towards the preparation of a new Apollo 14 sample catalog. It contains recently obtained observations and pictures of some of the largest and less well documented Apollo breccia samples. Some of the samples (14303, 14305, 14306, and 14311) were chosen because they have large sawn surfaces. These were dusted and mapped using a binocular microscope through the window of the nitrogen cabinet
Peripheral volume measurements as indices of peripheral circulatory factors in the cardiovascular orthostatic response
Peripheral volume measurements as indices of circulatory factors in cardiovascular orthostatic respons
Incompatibility of modulated checkerboard patterns with the neutron scattering resonance peak in cuprate superconductors
Checkerboard patterns have been proposed in order to explain STM experiments
on the cuprates BSCCO and Na-CCOC. However the presence of these patterns has
not been confirmed by a bulk probe such as neutron scattering. In particular,
simple checkerboard patterns are inconsistent with neutron scattering data, in
that they have low energy incommsensurate (IC) spin peaks rotated 45 degrees
from the direction of the charge IC peaks. However, it is unclear whether other
checkerboard patterns can solve the problem. In this paper, we have studied
more complicated checkerboard patterns ("modulated checkerboards") by using
spin wave theory and analyzed noncollinear checkerboards as well. We find that
the high energy response of the modulated checkerboards is inconsistent with
neutron scattering results, since they fail to exhibit a resonance peak at
(pi,pi), which has recently been shown to be a universal feature of cuprate
superconductors. We further argue that the newly proposed noncollinear
checkerboard also lacks a resonance peak. We thus conclude that to date no
checkerboard pattern has been proposed which satisfies both the low energy
constraints and the high energy constraints imposed by the current body of
experimental data in cuprate superconductors.Comment: 5 pages, 5 figures, Fig.2 update
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