21,951 research outputs found
Application of LANDSAT imagery in land use inventory and classification in Nebraska
There are no author-identified significant results in this report
Application of LANDSAT imagery in land use inventory and classification in Nebraska
There are no author-identified significant results in this report
Application of LANDSAT imagery in land use inventory and classification in Nebraska
The author has identified the following significant results. Center pivot irrigation systems can be inventoried from LANDSAT data in a timely and cost effective manner
Estimating vegetative biomass from LANDSAT-1 imagery for range management
Evaluation of LANDSAT-1, band 5 data for use in estimation of vegetative biomass for range management decisions was carried out for five selected range sites in the Sandhills region of Nebraska. Analysis of sets of optical density-vegetative biomass data indicated that comparisons of biomass estimation could be made within one frame but not between frames without correction factors. There was high correlation among sites within sets of radiance value-vegetative biomass data and also between sets, indicating comparisons of biomass could be made within and between frames. Landsat-1 data are shown to be a viable alternative to currently used methods of determining vegetative biomass production and stocking rate recommendations for Sandhills rangeland
Applications of remote sensing in resource management in Nebraska
There are no author-identified significant results in this report
Tracer Dispersion in a Self-Organized Critical System
We have studied experimentally transport properties in a slowly driven
granular system which recently was shown to display self-organized criticality
[Frette {\em et al., Nature} {\bf 379}, 49 (1996)]. Tracer particles were added
to a pile and their transit times measured. The distribution of transit times
is a constant with a crossover to a decaying power law. The average transport
velocity decreases with system size. This is due to an increase in the active
zone depth with system size. The relaxation processes generate coherently
moving regions of grains mixed with convection. This picture is supported by
considering transport in a cellular automaton modeling the experiment.Comment: 4 pages, RevTex, 1 Encapsulated PostScript and 4 PostScript available
upon request, Submitted to Phys. Rev. Let
Coevolutionary immune system dynamics driving pathogen speciation
We introduce and analyze a within-host dynamical model of the coevolution
between rapidly mutating pathogens and the adaptive immune response. Pathogen
mutation and a homeostatic constraint on lymphocytes both play a role in
allowing the development of chronic infection, rather than quick pathogen
clearance. The dynamics of these chronic infections display emergent structure,
including branching patterns corresponding to asexual pathogen speciation,
which is fundamentally driven by the coevolutionary interaction. Over time,
continued branching creates an increasingly fragile immune system, and leads to
the eventual catastrophic loss of immune control.Comment: main article: 16 pages, 5 figures; supporting information: 3 page
Effective Widths and Effective Number of Phonons of Multiphonon Giant Resonances
We discuss the origin of the difference between the harmonic value of the
width of the multiphonon giant resonances and the smaller observed value.
Analytical expressions are derived for both the effective width and the average
cross-section. The contribution of the Brink-Axel mechanism in resolving the
discrepancy is pointed out.Comment: 9 pages, 4 figure
Exponential Distributions in a Mechanical Model for Earthquakes
We study statistical distributions in a mechanical model for an earthquake
fault introduced by Burridge and Knopoff [R. Burridge and L. Knopoff, {\sl
Bull. Seismol. Soc. Am.} {\bf 57}, 341 (1967)]. Our investigations on the size
(moment), time duration and number of blocks involved in an event show that
exponential distributions are found in a given range of the paramenter space.
This occurs when the two kinds of springs present in the model have the same,
or approximately the same, value for the elastic constants. Exponential
distributions have also been seen recently in an experimental system to model
earthquake-like dynamics [M. A. Rubio and J. Galeano, {\sl Phys. Rev. E} {\bf
50}, 1000 (1994)].Comment: 11 pages, uuencoded (submitted to Phys. Rev. E
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