16,965 research outputs found
Kernel Approximation on Manifolds I: Bounding the Lebesgue Constant
The purpose of this paper is to establish that for any compact, connected
C^{\infty} Riemannian manifold there exists a robust family of kernels of
increasing smoothness that are well suited for interpolation. They generate
Lagrange functions that are uniformly bounded and decay away from their center
at an exponential rate. An immediate corollary is that the corresponding
Lebesgue constant will be uniformly bounded with a constant whose only
dependence on the set of data sites is reflected in the mesh ratio, which
measures the uniformity of the data.
The analysis needed for these results was inspired by some fundamental work
of Matveev where the Sobolev decay of Lagrange functions associated with
certain kernels on \Omega \subset R^d was obtained. With a bit more work, one
establishes the following: Lebesgue constants associated with surface splines
and Sobolev splines are uniformly bounded on R^d provided the data sites \Xi
are quasi-uniformly distributed. The non-Euclidean case is more involved as the
geometry of the underlying surface comes into play. In addition to establishing
bounded Lebesgue constants in this setting, a "zeros lemma" for compact
Riemannian manifolds is established.Comment: 33 pages, 2 figures, new title, accepted for publication in SIAM J.
on Math. Ana
Hypervelocity scramjet combustor-nozzle analysis and design
The progress report for the grant entitled 'Hypervelocity of Scramjet Combustor-Nozzle Analysis and Design' is presented. The three main tasks in the program are combustor modeling study, development of anaylsis capabilities for hypersonic scramjet nozzles, and development of optimum design methods for hypersonic scramjet nozzles. The research performed was documented in a series of technical publications and presentations at various conferences. A brief description of the research in each of the above three areas and a list of the resulting technical publications are included
Observations on North Dakota Sponges (Haplosclerina: Spongillidae) and Sisyrids (Neuroptera: Sisyridae)
Factors influencing occurrence, distribution, and ecology of sponges and sisyrids are discussed, with emphasis on northeastern North Dakota. New state records for North Dakota sponges, Eunapius Jraguis Leidy and Ephydatia fluviatilis L. and the sisyrids, Sisyra vicaria (Hagen) and Climacia areolaris (Hagen), and new county records for C. areolaris in northwestern Minnesota and Eunapius fragilis in northeastern North Dakota are reported. A rare association of the parasite, S. vicaria with the host, Ephydatia fluviatilis is also reported. Some physicochcmical relations of Eunapius fragilis found in the Forest River, North Dakota, are discussed
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Kinematic structure for robust mechanical architectures in robotic planetary exploration
This paper describes new research into the kinematic structure of autonomous robotic systems, and into the associated design processes. The approach aims to develop novel insights and applicable tools and techniques for designing advanced mechanical architectures for planetary exploration systems. These should provide enhanced functionality for tackling complex autonomous operations, and improved levels of robustness in the face of the inevitable system faults
Discreteness and the transmission of light from distant sources
We model the classical transmission of a massless scalar field from a source
to a detector on a background causal set. The predictions do not differ
significantly from those of the continuum. Thus, introducing an intrinsic
inexactitude to lengths and durations - or more specifically, replacing the
Lorentzian manifold with an underlying discrete structure - need not disrupt
the usual dynamics of propagation.Comment: 16 pages, 1 figure. Version 2: reference adde
The Hausdorff dimension of random walks and the correlation length critical exponent in Euclidean field theory
We study the random walk representation of the two-point function in
statistical mechanics models near the critical point. Using standard scaling
arguments we show that the critical exponent describing the vanishing of
the physical mass at the critical point is equal to . is
the Hausdorff dimension of the walk. is the exponent describing
the vanishing of the energy per unit length of the walk at the critical point.
For the case of O(N) models, we show that , where
is the crossover exponent known in the context of field theory. This implies
that the Hausdorff dimension of the walk is for O(N) models.Comment: 11 pages (plain TeX
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