NASA Scientific and Technical Aerospace Reports

incremental refinement of imagery without requiring all imagery to be re-rendered.
NTIS
Imagery; Laminates; Flow Visualization
20040068265 Lawrence Livermore National Lab., Livermore, CA
Radar Imaging of Spheres in 3D Using MUSIC
Chambers, D. H.; Berryman, J. G.; Jan. 21, 2003; In English
Report No.(s): DE2003-15004917; UCRL-ID-151577; No Copyright; Avail: National Technical Information Service (NTIS)
We have shown that multiple spheres can be imaged by linear and planar EM arrays using only one component of
polarization. The imaging approach involves calculating the SVD of the scattering response matrix, selecting a subset of
singular values that represents noise, and evaluating the MUSIC functional. The noise threshold applied to the spectrum of
singular values for optimal performance is typically around 1%. The resulting signal subspace includes more than one singular
value per sphere. The presence of reflections from the ground improves height localization, even for a linear array parallel to
the ground. However, the interference between direct and reflected energy modulates the field, creating periodic nulls that can
obscure targets in typical images. These nulls are largely eliminated by normalizing the MUSIC functional with the broadside
beam pattern of the array. The resulting images show excellent localization for 1 and 2 spheres. The performance for the 3
sphere configurations are complicated by shadowing effects and the greater range of the 3rd sphere in case 2. Two of the three
spheres are easily located by MUSIC but the third is difficult to distinguish from other local maxima of the complex imaging
functional. Improvement is seen when the linear array is replace with a planar array, which increases the effective aperture
height. Further analysis of the singular values and their relationship to modes of scattering from the spheres, as well as better
ways to exploit polarization, should improve performance. Work along these lines is currently being pursued by the authors.
NTIS
Radar Imagery; Spheres; Three Dimensional Models; Radiation Distribution
20040068304 NASA Ames Research Center, Moffett Field, CA, USA
Applications of Space-Filling-Curves to Cartesian Methods for CFD
Aftosmis, M. J.; Murman, S. M.; Berger, M. J.; December 28, 2003; 13 pp.; In English; 42nd AIAA Aerospace Sciences
Meeting and Exhibit, 6-11 Jan. 2004, Reno, NV, USA
Contract(s)/Grant(s): F19620-00-0099; DE-FG02-99ER-25053; DE-FC02-01ER-25472; 704-41-11
Report No.(s): AIAA Paper 2004-1232; No Copyright; Avail: CASI; A03, Hardcopy
This paper presents a variety of novel uses of space-filling-curves (SFCs) for Cartesian mesh methods in CFD. While
these techniques will be demonstrated using non-body-fitted Cartesian meshes, many are applicable on general body-fitted
meshes-both structured and unstructured. We demonstrate the use of single theta(N log N) SFC-based reordering to produce
single-pass (theta(N)) algorithms for mesh partitioning, multigrid coarsening, and inter-mesh interpolation. The intermesh
interpolation operator has many practical applications including warm starts on modified geometry, or as an inter-grid transfer
operator on remeshed regions in moving-body simulations Exploiting the compact construction of these operators, we further
show that these algorithms are highly amenable to parallelization. Examples using the SFC-based mesh partitioner show
nearly linear speedup to 640 CPUs even when using multigrid as a smoother. Partition statistics are presented showing that
the SFC partitions are, on-average, within 15% of ideal even with only around 50,000 cells in each sub-domain. The
inter-mesh interpolation operator also has linear asymptotic complexity and can be used to map a solution with N unknowns
to another mesh with M unknowns with theta(M + N) operations. This capability is demonstrated both on moving-body
simulations and in mapping solutions to perturbed meshes for control surface deflection or finite-difference-based gradient
design methods.
Author
Cartesian Coordinates; Computational Fluid Dynamics; Methodology; Hyperspaces; Curves (Geometry); Grid Generation
(Mathematics)
20040068307 Environmental Protection Agency, Washington, DC
Information Strategic Plan: Modernizing the Safe Drinking Water Information System for the Public Water System
Supervision Program
Jan. 2004; In English
Report No.(s): PB2004-104034; EPA/816-R-04-001; No Copyright; Avail: National Technical Information Service (NTIS)
This Information Strategic Plan describes OGWDW’s approach for the application of technology to manage the data
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