38,667 research outputs found
Extracting scene feature vectors through modeling, volume 3
The remote estimation of the leaf area index of winter wheat at Finney County, Kansas was studied. The procedure developed consists of three activities: (1) field measurements; (2) model simulations; and (3) response classifications. The first activity is designed to identify model input parameters and develop a model evaluation data set. A stochastic plant canopy reflectance model is employed to simulate reflectance in the LANDSAT bands as a function of leaf area index for two phenological stages. An atmospheric model is used to translate these surface reflectances into simulated satellite radiance. A divergence classifier determines the relative similarity between model derived spectral responses and those of areas with unknown leaf area index. The unknown areas are assigned the index associated with the closest model response. This research demonstrated that the SRVC canopy reflectance model is appropriate for wheat scenes and that broad categories of leaf area index can be inferred from the procedure developed
Signature extension for sun angle, volume 1
The author has identified the following significant results. Within a restricted zenith sun angle range of 35 - 50 degrees, it was empirically observed that canopy reflectance is mainly Lambertian. Reflectance changes with crop stage were simple shifts in scale in the sun angle range. It was noted that sun angle variations depend on canopy characteristics. Effects of the vegetative canopy were most pronounced at the larger solar zenith angles (20 %). The linear sun angle correction coefficients demonstrate a dependency on both crop stage (15-20 %) and crop type (10-20 %). The use of canopy reflectance modeling allowed for the generation of a simulated data set over an extremely broad envelope of sun angles
Some fundamental fracture mechanisms applicable to advanced filament reinforced composites
Stress analysis and fracture mechanisms of advanced fiber reinforced composite
Investigation of the reinforcement of ductule metals with strong, high modulus discontinuous, brittle fibers Quarterly report, 1 May - 1 Aug. 1968
Factors affecting tensile strength of ductile metals reinforced with short, brittle fiber
Signature extension for spectral variation in soils, volume 4
The reduced 1975-1976 field data at Garden City, Kansas are presented. These data are being used to evaluate the SRVC model predictions, to compare the ERIM-SUITS model with both the SRVC results and field data, and finally, to provide a data base for reviewing multitemporal trajectories. In particular, the applicability of the tasselled cap transformation is reviewed. The first detailed verification of this approach utilizing actual field measured data from the LACIE field measurement program, rather than LANDSAT data, is given
Berry phase in a non-isolated system
We investigate the effect of the environment on a Berry phase measurement
involving a spin-half. We model the spin+environment using a biased spin-boson
Hamiltonian with a time-dependent magnetic field. We find that, contrary to
naive expectations, the Berry phase acquired by the spin can be observed, but
only on timescales which are neither too short nor very long. However this
Berry phase is not the same as for the isolated spin-half. It does not have a
simple geometric interpretation in terms of the adiabatic evolution of either
bare spin-states or the dressed spin-resonances that remain once we have traced
out the environment. This result is crucial for proposed Berry phase
measurements in superconducting nanocircuits as dissipation there is known to
be significant.Comment: 4 pages (revTeX4) 2 fig. This version has MAJOR changes to equation
Three water sites in upper mantle olivine and the role of titanium in the water weakening mechanism
Infrared spectroscopy on synthetic olivines has established that there are at least
four different mechanisms by which hydrogen is incorporated into the crystal structure.
Two mechanisms occur in the system MgO-SiO2-H2O associated with silicon and
magnesium vacancies, respectively. A third mechanism is associated with trivalent cation
substitution, commonly Fe3+ in natural olivine, while the fourth mechanism, which is
the one most prevalent in natural olivines from the spinel-peridotite facies of the Earth’s
upper mantle, is associated with Ti4+ [Berry et al., 2005]. Here first principles calculations
based on density functional theory are used to derive the structure and relative energies
of the two defects in the pure MgO-SiO2-H2O system, and possible hydrogen-bearing
and hydrogen-free point defects in Ti4+-doped forsterite. Calculated structures are used to
compare the predicted orientation of the O-H bonds with the experimentally determined
polarization. The energies are used to discuss how different regimes of chemical
environment, temperature (T), pressure (P), and both water content and water fugacity
( fH2O), impact on which of the different hydroxyl substitution mechanisms are
thermodynamically stable. We find that given the presence of Ti impurities, the most
stable mechanism involves the formation of silicon vacancies containing two protons
charge balanced by a Ti4+ cation occupying an adjacent octahedral site. This mechanism
leads to the water-mediated formation of silicon vacancies. As silicon is known to be the
most slowly diffusing species in olivine, this provides a credible explanation of the
observed water weakening effect in olivine
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