12,449 research outputs found
Recognition of 3-D Objects from Multiple 2-D Views by a Self-Organizing Neural Architecture
The recognition of 3-D objects from sequences of their 2-D views is modeled by a neural architecture, called VIEWNET that uses View Information Encoded With NETworks. VIEWNET illustrates how several types of noise and varialbility in image data can be progressively removed while incornplcte image features are restored and invariant features are discovered using an appropriately designed cascade of processing stages. VIEWNET first processes 2-D views of 3-D objects using the CORT-X 2 filter, which discounts the illuminant, regularizes and completes figural boundaries, and removes noise from the images. Boundary regularization and cornpletion are achieved by the same mechanisms that suppress image noise. A log-polar transform is taken with respect to the centroid of the resulting figure and then re-centered to achieve 2-D scale and rotation invariance. The invariant images are coarse coded to further reduce noise, reduce foreshortening effects, and increase generalization. These compressed codes are input into a supervised learning system based on the fuzzy ARTMAP algorithm. Recognition categories of 2-D views are learned before evidence from sequences of 2-D view categories is accumulated to improve object recognition. Recognition is studied with noisy and clean images using slow and fast learning. VIEWNET is demonstrated on an MIT Lincoln Laboratory database of 2-D views of jet aircraft with and without additive noise. A recognition rate of 90% is achieved with one 2-D view category and of 98.5% correct with three 2-D view categories.National Science Foundation (IRI 90-24877); Office of Naval Research (N00014-91-J-1309, N00014-91-J-4100, N00014-92-J-0499); Air Force Office of Scientific Research (F9620-92-J-0499, 90-0083
Simple bonding technique for high-temperature ceramic coatings
Coatings, consisting of zirconia powder bonded with orthophosphoric acid and a small amount of hydrofluoric acid, are hard, strong, and refractory, resist thermal shock, and provide good thermal protection. After the aqueous coating is applied to a metallic surface, only a 600 deg F cure is required before service
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Iron Oxide Grains in Stardust Track 121 Grains as Evidence of Comet Wild 2 Hydrothermal Alteration
Stardust Track 121 terminal grains contain Fe-oxide. These are consistent with the presence of hydrothermal alteration on the Comet Wild 2 parent body
Growth mechanisms of perturbations in boundary layers over a compliant wall
The temporal modal and nonmodal growth of three-dimensional perturbations in
the boundary-layer flow over an infinite compliant flat wall is considered.
Using a wall-normal velocity/wall-normal vorticity formalism, the dynamic
boundary condition at the compliant wall admits a linear dependence on the
eigenvalue parameter, as compared to a quadratic one in the canonical
formulation of the problem. This greatly simplifies the accurate calculation of
the continuous spectrum by means of a spectral method, thereby yielding a very
effective filtering of the pseudospectra as well as a clear identification of
instability regions. The regime of global instability is found to be matching
the regime of the favorable phase of the forcing by the flow on the compliant
wall so as to enhance the amplitude of the wall. An energy-budget analysis for
the least-decaying hydroelastic (static-divergence, traveling-wave-flutter and
near-stationary transitional) and Tollmien--Schlichting modes in the parameter
space reveals the primary routes of energy flow. Moreover, the flow exhibits a
slower transient growth for the maximum growth rate of a superposition of
streamwise-independent modes due to a complex dependence of the wall-boundary
condition with the Reynolds number. The initial and optimal perturbations are
compared with the boundary-layer flow over a solid wall; differences and
similarities are discussed. Unlike the solid-wall case, viscosity plays a
pivotal role in the transient growth. A slowdown of the maximum growth rate
with the Reynolds number is uncovered and found to originate in the transition
of the fluid-solid interaction from a two-way to a one-way coupling. Finally, a
term-by-term energy budget analysis is performed to identify the key
contributors to the transient growth mechanism
Do frailty and comorbidity indices improve risk prediction of 28-day ED reattendance? Reanalysis of an ED discharge nomogram for older people
Background: In older people, quantification of risk of reattendance after emergency department (ED) discharge is important to provide adequate post ED discharge care in the community to appropriately targeted patients at risk.
Methods: We reanalysed data from a prospective observational study, previously used for derivation of a nomogram for stratifying people aged 65 and older at risk for ED reattendance. We investigated the potential effect of comorbidity load and frailty by adding the Charlson or Elixhauser comorbidity index and a ten-item frailty measure from our data to develop four new nomograms. Model I and model F built on the original nomogram by including the frailty measure with and without the addition of the Charlson comorbidity score; model E adapted for efficiency in the time-constrained environment of ED was without the frailty measure; and model P manually constructed in a purposeful stepwise manner and including only statistically significant variables. Areas under the ROC curve of models were compared. The primary outcome was any ED reattendance within 28 days of discharge.
Results: Data from 1357 patients were used. The point estimate of the respective areas under ROC were 0.63 (O), 0.63 (I), 0.68 (E), 0.71 (P) and 0.63 (F).
Conclusion: Addition of a comorbidity index to our previous model improves stratifying elderly at risk of ED reattendance. Our frailty measure did not demonstrate any additional predictive benefit
Tungsten resonance integrals and Doppler coefficients First quarterly progress report, Jul. - Sep. 1965
Resonance integrals and Doppler coefficients of samples of natural tungsten, tungsten isotopes, and uranium oxide tungsten fue
Tungsten resonance integrals and Doppler coefficients Third quarterly report, Jan. - Mar. 1966
Reactivities, Doppler coefficients, and resonance integrals for tungsten isotope
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