23,956 research outputs found
An analysis of LANDSAT MSS scene-to-scene registration accuracy
Measurements were made for 12 registrations done by ERL for 8 registrations done by SRS. The results indicate that the ERL method is significantly more accurate in five of the eight comparison. The difference between the two methods are not significant in the other three cases. There are two possible reasons for the differences. First, the ERL model is a piecewise linear model and the EDITOR model is a cubic polynomial model. Second, the ERL program resamples using bilinear interpolation while the EDITOR software uses a nearest neighbor resampling. This study did not indicate how much of the difference is attributable to each factor. The average of all merged scene error values for ERL was 31.6 meters and the average for the eight common areas was 32.6 meters. The average of the eight merged scene error values for SRS was 40.1 meters
Feasibility study for locating archaeological village sites by satellite remote sensing techniques
There are no author-identified significant results in this report
An examination of knowledge prioritisation in secondary physical education teacher education courses
A number of terms have been used to describe knowledge needed for teaching, one of which is subject knowledge. How knowledge for teaching is conceptualised in teacher education prioritises some knowledge bases over other knowledge bases. Further, knowledge prioritised by student teachers is influenced by socialisation prior to and during an initial teacher education course and priorities for student teachers as they develop as teachers. Previous research in physical education teacher education points to the pre-eminence of content knowledge above other knowledge bases. The purpose of this study was to look at what knowledge is prioritised by student teachers, school-based mentors and university tutors working on three secondary physical education initial teacher education courses in England. Results showed that content knowledge was seen as having greater importance for student teachers and mentors, but university tutors generally conceptualised subject knowledge more broadly, suggesting that it should be seen as covering a number of knowledge bases needed for teaching. These results are discussed in relation to socialisation processes in education and phases of development. Although there is a clear physical education focus to this work, it is possible that student teachers learning to teach other subjects may also focus excessively on subject content knowledge above other knowledge bases
Evaluation of surface water resources from machine-processing of ERTS multispectral data
The surface water resources of a large metropolitan area, Marion County (Indianapolis), Indiana, are studied in order to assess the potential value of ERTS spectral analysis to water resources problems. The results of the research indicate that all surface water bodies over 0.5 ha were identified accurately from ERTS multispectral analysis. Five distinct classes of water were identified and correlated with parameters which included: degree of water siltiness; depth of water; presence of macro and micro biotic forms in the water; and presence of various chemical concentrations in the water. The machine processing of ERTS spectral data used alone or in conjunction with conventional sources of hydrological information can lead to the monitoring of area of surface water bodies; estimated volume of selected surface water bodies; differences in degree of silt and clay suspended in water and degree of water eutrophication related to chemical concentrations
Quasi-circular Orbits for Spinning Binary Black Holes
Using an effective potential method we examine binary black holes where the
individual holes carry spin. We trace out sequences of quasi-circular orbits
and locate the innermost stable circular orbit as a function of spin. At large
separations, the sequences of quasi-circular orbits match well with
post-Newtonian expansions, although a clear signature of the simplifying
assumption of conformal flatness is seen. The position of the ISCO is found to
be strongly dependent on the magnitude of the spin on each black hole. At close
separations of the holes, the effective potential method breaks down. In all
cases where an ISCO could be determined, we found that an apparent horizon
encompassing both holes forms for separations well inside the ISCO.
Nevertheless, we argue that the formation of a common horizon is still
associated with the breakdown of the effective potential method.Comment: 13 pages, 10 figures, submitted to PR
Electrodeposition from supercritical fluids
Recent studies have shown that it is possible to electrodeposit a range of materials, such as Cu, Ag and Ge, from various supercritical fluids, including hydrofluorocarbons and mixtures of CO2 with suitable co-solvents. In this perspective we discuss the relatively new field of electrodeposition from supercritical fluids. The perspective focuses on some of the underlying physical chemistry and covers both practical and scientific aspects of electrodeposition from supercritical fluids. We also discuss possible applications for supercritical fluid electrodeposition and suggest some key developments that are required to take the field to the next stage
Excision boundary conditions for black hole initial data
We define and extensively test a set of boundary conditions that can be
applied at black hole excision surfaces when the Hamiltonian and momentum
constraints of general relativity are solved within the conformal thin-sandwich
formalism. These boundary conditions have been designed to result in black
holes that are in quasiequilibrium and are completely general in the sense that
they can be applied with any conformal three-geometry and slicing condition.
Furthermore, we show that they retain precisely the freedom to specify an
arbitrary spin on each black hole. Interestingly, we have been unable to find a
boundary condition on the lapse that can be derived from a quasiequilibrium
condition. Rather, we find evidence that the lapse boundary condition is part
of the initial temporal gauge choice. To test these boundary conditions, we
have extensively explored the case of a single black hole and the case of a
binary system of equal-mass black holes, including the computation of
quasi-circular orbits and the determination of the inner-most stable circular
orbit. Our tests show that the boundary conditions work well.Comment: 23 pages, 23 figures, revtex4, corrected typos, added reference,
minor content changes including additional post-Newtonian comparison. Version
accepted by PR
Exponential complexity of an adiabatic algorithm for an NP-complete problem
We prove an analytical expression for the size of the gap between the ground
and the first excited state of quantum adiabatic algorithm for the
3-satisfiability, where the initial Hamiltonian is a projector on the subspace
complementary to the ground state. For large problem sizes the gap decreases
exponentially and as a consequence the required running time is also
exponential.Comment: 5 pages, 2 figures; v3. published versio
Solving the Initial Value Problem of two Black Holes
We solve the elliptic equations associated with the Hamiltonian and momentum
constraints, corresponding to a system composed of two black holes with
arbitrary linear and angular momentum. These new solutions are based on a
Kerr-Schild spacetime slicing which provides more physically realistic
solutions than the initial data based on conformally flat metric/maximal
slicing methods. The singularity/inner boundary problems are circumvented by a
new technique that allows the use of an elliptic solver on a Cartesian grid
where no points are excised, simplifying enormously the numerical problem.Comment: 4 pages, 3 figures. Minor corrections, some points clarified, and one
reference added. To appear in Phys. Rev. Let
A minimal no-radiation approximation to Einstein's field equations
An approximation to Einstein's field equations in Arnowitt-Deser-Misner (ADM)
canonical formalism is presented which corresponds to the magneto-hydrodynamics
(MHD) approximation in electrodynamics. It results in coupled elliptic
equations which represent the maximum of elliptic-type structure of Einstein's
theory and naturally generalizes previous conformal-flat truncations of the
theory. The Hamiltonian, in this approximation, is identical with the
non-dissipative part of the Einsteinian one through the third post-Newtonian
order. The proposed scheme, where stationary spacetimes are exactly reproduced,
should be useful to construct {\em realistic} initial data for general
relativistic simulations as well as to model astrophysical scenarios, where
gravitational radiation reaction can be neglected.Comment: 9 page
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