4,860 research outputs found
A New Computer Approach to Mixed Feature Classification for Forestry Application
A new computer approach for mapping mixed forest features (i.e., classes, types) from computes classification maps is presented in both theory and application.
This approach is particularly useful and applicable to forestry stand mapping, where small areas are required to be absorbed into the surrounding to form homogeneous stands, and where mixed stands contain mixed proportions of different species of trees. Previous studies involving LANDSAT data show that mixed pine-hardwood stands are often erroneously classified as either pine or hardwood.
The present work utilizes a modification and an iterative application of a previously developed computer program called CLEAN . The program CLEAN was tested on binary (2 classes, labeled 0 or 1) classification images.
The modification called GETMIX operates on a multi-class image and works on one prespecified class in any one application. In any iteration, small sets of pixels with labels other than the prespecified class are eliminated, while small sets of pixels of the prespecified class are retained and have their labels temporarily changed to a new unique class.
This new iterative approach was tested on LANDSAT-1 data over Sam Houston National Forest, and proved to be successful in mapping those mixed softwood/hardwood stands which were unidentifiable previously. Also due to the cleaning effect of the program GETMIX, the spotty appearance on computer classification maps was smoothed, resulting in postprocessed maps that more closely resembled resource maps
Uses of zeta regularization in QFT with boundary conditions: a cosmo-topological Casimir effect
Zeta regularization has proven to be a powerful and reliable tool for the
regularization of the vacuum energy density in ideal situations. With the
Hadamard complement, it has been shown to provide finite (and meaningful)
answers too in more involved cases, as when imposing physical boundary
conditions (BCs) in two-- and higher--dimensional surfaces (being able to
mimic, in a very convenient way, other {\it ad hoc} cut-offs, as non-zero
depths). What we have considered is the {\it additional} contribution to the cc
coming from the non-trivial topology of space or from specific boundary
conditions imposed on braneworld models (kind of cosmological Casimir effects).
Assuming someone will be able to prove (some day) that the ground value of the
cc is zero, as many had suspected until very recently, we will then be left
with this incremental value coming from the topology or BCs. We show that this
value can have the correct order of magnitude in a number of quite reasonable
models involving small and large compactified scales and/or brane BCs, and
supergravitons.Comment: 9 pages, 1 figure, Talk given at the Seventh International Workshop
Quantum Field Theory under the Influence of External Conditions, QFEXT'05,
Barcelona, September 5-9, 200
Periodic chiral magnetic domains in single-crystal nickel nanowires
We report on experimental and computational investigations of the domain
structure of ~0.2 x 0.2 x 8 {\mu}m single-crystal Ni nanowires (NWs). The Ni
NWs were grown by a thermal chemical vapor deposition technique that results in
highly-oriented single-crystal structures on amorphous SiOx coated Si
substrates. Magnetoresistance measurements of the Ni NWs suggest the average
magnetization points largely off the NW long axis at zero field. X-ray
photoemission electron microscopy images show a well-defined periodic
magnetization pattern along the surface of the nanowires with a period of
{\lambda} = 250 nm. Finite element micromagnetic simulations reveal that an
oscillatory magnetization configuration with a period closely matching
experimental observation ({\lambda} = 240 nm) is obtainable at remanence. This
magnetization configuration involves a periodic array of alternating chirality
vortex domains distributed along the length of the NW. Vortex formation is
attributable to the cubic anisotropy of the single crystal Ni NW system and its
reduced structural dimensions. The periodic alternating chirality vortex state
is a topologically protected metastable state, analogous to an array of
360{\deg} domain walls in a thin strip. Simulations show that other remanent
states are also possible, depending on the field history. Effects of material
properties and strain on the vortex pattern are investigated. It is shown that
at reduced cubic anisotropy vortices are no longer stable, while negative
uniaxial anisotropy and magnetoelastic effects in the presence of compressive
biaxial strain contribute to vortex formation.Comment: 15 pages, 11 figure
The thermal equation of state of FeTiO_3 ilmenite based on in situ X-ray diffraction at high pressures and temperatures
We present in situ measurements of the unit-cell volume of a natural terrestrial ilmenite (Jagersfontein mine, South Africa) and a synthetic reduced ilmenite (FeTiO_3) at simultaneous high pressure and high temperature up to 16 GPa and 1273 K. Unit-cell volumes were determined using energy-dispersive synchrotron X-ray diffraction in a multi-anvil press. Mössbauer analyses show that the synthetic sample contained insignificant amounts of Fe^(3+) both before and after the experiment. Results were fit to Birch-Murnaghan thermal equations of state, which reproduce the experimental data to within 0.5 and 0.7 GPa for the synthetic and natural samples, respectively. At ambient conditions, the unit-cell volume of the natural sample [V_0 = 314.75 ± 0.23 (1 ) Ă
^3] is significantly smaller than that of the synthetic sample [V_0 = 319.12 ± 0.26 Ă
^3]. The difference can be attributed to the presence of impurities and Fe^(3+) in the natural sample. The 1 bar isothermal bulk moduli K_(T0) for the reduced ilmenite is slightly larger than for the natural ilmenite (181 ± 7 and 165 ± 6 GPa, respectively), with pressure derivatives K_0' = 3 ± 1. Our results, combined with literature data, suggest that the unit-cell volume of reduced ilmenite is significantly larger than that of oxidized ilmenite, whereas their thermoelastic parameters are similar. Our data provide more appropriate input parameters for thermo-chemical models of lunar interior evolution, in which reduced ilmenite plays a critical role
Scale Dependent Dimension of Luminous Matter in the Universe
We present a geometrical model of the distribution of luminous matter in the
universe, derived from a very simple reaction-diffusion model of turbulent
phenomena. The apparent dimension of luminous matter, , depends linearly
on the logarithm of the scale under which the universe is viewed: , where is a correlation length.
Comparison with data from the SARS red-shift catalogue, and the LEDA database
provides a good fit with a correlation length Mpc. The
geometrical interpretation is clear: At small distances, the universe is
zero-dimensional and point-like. At distances of the order of 1 Mpc the
dimension is unity, indicating a filamentary, string-like structure; when
viewed at larger scales it gradually becomes 2-dimensional wall-like, and
finally, at and beyond the correlation length, it becomes uniform.Comment: 6 pages, 2 figure
Involving users in OPAC interface design: Perspective from a UK study
This is the post-print versoin of the Article. The official published version can be accessed from the link below - Copyright @ 2007 SpringerThe purpose of this study was to determine user suggestions for a typical OPAC (Online Public Library Catalogue) applicationâs functionality and features. An experiment was undertaken to find out the type of interactions features that users prefer to have in an OPAC. The study revealed that regardless of usersâ Information Technology (IT) backgrounds, their functionality expectations of OPACs are the same. However, based on usersâ previous experiences with OPACs, their requirements with respect to specific features may change. Users should be involved early in the OPAC development cycle process in order to ensure usable and functional interface
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