206,350 research outputs found
Perfect colourings of isonemal fabrics by thin striping
Perfect colouring of isonemal fabrics by thin striping of warp and weft and
the closely related topic of isonemal prefabrics that fall apart are
reconsidered and their relation further explored. The catalogue of isonemal
prefabrics that fall apart is extended to order 20 for those of even genus.Comment: 25 pages, 20 figure
Special Lagrangians, stable bundles and mean curvature flow
We make a conjecture about mean curvature flow of Lagrangian submanifolds of
Calabi-Yau manifolds, expanding on \cite{Th}. We give new results about the
stability condition, and propose a Jordan-H\"older-type decomposition of
(special) Lagrangians. The main results are the uniqueness of special
Lagrangians in hamiltonian deformation classes of Lagrangians, under mild
conditions, and a proof of the conjecture in some cases with symmetry: mean
curvature flow converging to Shapere-Vafa's examples of SLags.Comment: 36 pages, 4 figures. Minor referee's correction
Expanded operational capabilities of the Langley Mach 7 Scramjet test facility
An experimental research program conducted to expand the operational capabilities of the NASA Langley Mach 7 Scramjet Test Facility is described. Previous scramjet testing in this facility was limited to a single simulated flight condition of Mach 6.9 at an altitude of 115,300 ft. The arc heater research demonstrates the potential of the facility for scramjet testing at simulated flight conditions from Mach 4 (at altitudes from 77,000 to 114,000 ft) to Mach 7 (at latitudes from 108,000 to 149,000 ft). Arc heater electrical characteristics, operational problems, measurements of nitrogen oxide contaminants, and total-temperature profiles are discussed
Evidence for In-Medium Changes of Four-Quark Condensates
Utilizing the QCD sum rule approach to the behavior of the omega meson in
nuclear matter we derive evidence for in-medium changes of particular
four-quark condensates from the recent CB-TAPS experiment for the reaction
gamma + A -> A' + omega (-> pi0 gamma) with A = Nb and LH2.Comment: Submitted to Phys. Rev. Lett., 4 page
Helical swimming in Stokes flow using a novel boundary-element method
We apply the boundary-element method to Stokes flows with helical symmetry,
such as the flow driven by an immersed rotating helical flagellum. We show that
the two-dimensional boundary integral method can be reduced to one dimension
using the helical symmetry. The computational cost is thus much reduced while
spatial resolution is maintained. We review the robustness of this method by
comparing the simulation results with the experimental measurement of the
motility of model helical flagella of various ratios of pitch to radius, along
with predictions from resistive-force theory and slender-body theory. We also
show that the modified boundary integral method provides reliable convergence
if the singularities in the kernel of the integral are treated appropriately.Comment: 30 pages, 10 figure
Methods of extending signatures and training without ground information
Methods of performing signature extension, using LANDSAT-1 data, are explored. The emphasis is on improving the performance and cost-effectiveness of large area wheat surveys. Two methods were developed: ASC, and MASC. Two methods, Ratio, and RADIFF, previously used with aircraft data were adapted to and tested on LANDSAT-1 data. An investigation into the sources and nature of between scene data variations was included. Initial investigations into the selection of training fields without in situ ground truth were undertaken
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