107,240 research outputs found
User's guide for CCT2WA (converting CCT's to work-addressable file)
The CCT2WA program, developed to convert the shuttle post-flight computer compatible tape data to a word addressable mass storage file, is described. The use of utility processors that can be used to copy word addressable files from mass storage to mass storage is also described
Accelerated Overlap Fermions
Numerical evaluation of the overlap Dirac operator is difficult since it
contains the sign function of the Hermitian Wilson-Dirac
operator with a negative mass term. The problems are due to having
very small eigenvalues on the equilibrium background configurations generated
in current day Monte Carlo simulations. Since these are a consequence of the
lattice discretisation and do not occur in the continuum version of the
operator, we investigate in this paper to what extent the numerical evaluation
of the overlap can be accelerated by making the Wilson-Dirac operator more
continuum-like. Specifically, we study the effect of including the clover term
in the Wilson-Dirac operator and smearing the link variables in the irrelevant
terms. In doing so, we have obtained a factor of two speedup by moving from the
Wilson action to a FLIC (Fat Link Irrelevant Clover) action as the overlap
kernel.Comment: 15 pages, 6 figures; V2 contains major revision of the introduction
and motivation sections. Conclusion and results unchanged v2.1: formatting
chang
FLIC Overlap Fermions
The action of the overlap-Dirac operator on a vector is typically implemented
indirectly through a multi-shift conjugate gradient solver. The compute-time
required depends upon the condition number, , of the matrix that is
used as the overlap kernel. While the Wilson action is typically used as the
overlap kernel, the FLIC (Fat Link Irrelevant Clover) action has an improved
condition number and provides up to a factor of two speedup in evaluating the
overlap action. We summarize recent progress on the use of FLIC overlap
fermions.Comment: Lattice2002(chiral
Antiferromagnetism in NiO Observed by Transmission Electron Diffraction
Neutron diffraction has been used to investigate antiferromagnetism since
1949. Here we show that antiferromagnetic reflections can also be seen in
transmission electron diffraction patterns from NiO. The diffraction patterns
taken here came from regions as small as 10.5 nm and such patterns could be
used to form an image of the antiferromagnetic structure with a nanometre
resolution.Comment: 10 pages, 7 figures. Typos corrected. To appear in Physical Review
Letter
Rotor redesign for a highly loaded 1800 ft/sec tip speed fan. 3: Laser Doppler velocimeter report
Laser Doppler velocimeter (LDV) techniques were employed for testing a highly loaded, 550 m/sec (1800 ft/sec) tip speed, test fan stage, the objective to provide detailed mapping of the upstream, intrablade, and downstream flowfields of the rotor. Intrablade LDV measurements of velocity and flow angle were obtained along four streamlines passing through the leading edge at 45%, 69%, 85%, and 95% span measured from hub to tip, at 100% of design speed, peak efficiency; 100% speed, near surge; and 95% speed, peak efficiency. At the design point, most passages appeared to have a strong leading edge shock, which moved forward with increasing strength near surge and at part speeds. The flow behind the shock was of a complex mixed subsonic and supersonic form. The intrablade flowfields were found to be significantly nonperiodic at 100% design speed, peak efficiency
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