38,879 research outputs found
Blending single beam RoxAnn and multi-beam swathe QTC hydro-acoustic discrimination techniques for the Stonehaven area, Scotland, UK
Surface properties of the seabed in a 180 km2 area of coastal waters (14-57 m depth) off northeast Scotland were mapped by hydro-acoustic discrimination using single and multi-beam echosounders linked to signal processing systems (RoxAnn for the single beam, and Questor Tangent Corporation (QTC) Multiview for the multibeam). Subsequently, two ground truthing surveys were carried out, using grab and TV sampling. The RoxAnn and QTC-Multiview outputs showed strong similarity in their classifications of seabed types. Classifications generated by QTC-Multiview were used to supervise those based on seabed roughness and hardness indices produced by the RoxAnn system and thereby develop a ‘blended’ map based on both systems. The resulting hydro-acoustic classes agreed well with a cluster analysis of data on sediment grain sizes from the grab sampling, and indicated that the area could be described by distinct regions of surface texture and surficial sediments ranging from muddy sand to boulders and rock
Mathematical Tutorials in Introductory Physics
Students in introductory calculus-based physics not only have difficulty
understanding the fundamental physical concepts, they often have difficulty
relating those concepts to the mathematics they have learned in math courses.
This produces a barrier to their robust use of concepts in complex problem
solving. As a part of the Activity-Based Physics project, we are carrying out
research on these difficulties and are developing instructional materials in
the tutorial framework developed at the University of Washington by Lillian C.
McDermott and her collaborators. In this paper, we present a discussion of
student difficulties and the development of a mathematical tutorial on the
subject of pulses moving on strings.Comment: 8 pages, 2 figures, 1 table, 12 references and note
Recommended from our members
Persistent, symptomless, systemic, and seed-borne infection of lettuce by Botrytis cinerea
Experiments are presented which show that Botrytis cinerea, the cause of gray mould disease, is often present in symptomless lettuce plants as a systemic, endophytic, infection which may arise from seed. The fungus was isolated on selective media from surface sterilized sections of roots, stem pieces and leaf discs from symptomless plants grown in a conventional glasshouse and in a spore-free air-flow provided by an isolation propagator. The presence of B. cinerea was confirmed by immuno-labelling the tissues with the Botrytis-specific monoclonal antibody BC-12.CA4. As plants grew, infection spread from the roots to stems and leaves. Surface sterilization of seeds reduced the number of infected symptomless plants. Artificial infection of seedlings with dry conidia increased the rate of infection in some experiments. Selected isolates were genetically finger-printed using microsatellite loci. This confirmed systemic spread of the inoculating isolates but showed that other isolates were also present and that single plants hosted multiple isolates. This shows that B. cinerea commonly grows in lettuce plants as an endophyte, as has already been shown for Primula. If true for other hosts, the endophytic phase may be as important a component of the species population as the aggressive necrotrophic phase
The Green's function for the radial Schramm-Loewner evolution
We prove the existence of the Green's function for radial SLE(k) for k<8.
Unlike the chordal case where an explicit formula for the Green's function is
known for all values of k<8, we give an explicit formula only for k=4. For
other values of k, we give a formula in terms of an expectation with respect to
SLE conditioned to go through a point.Comment: v1: 16 pages, 0 figure
SU(4) Theory for Spin Systems with Orbital Degeneracy
The isotropic limit of spin systems with orbital degeneracy is shown to have
global SU(4) symmetry. On many 2D lattices, the ground state does not posses
long range order, which may explain the observed spin liquid properties of
. In the SU(4) Neel ordered state, spin-spin correlations can be
antiferromagneitc between two neighboring sites with parallel magnetic moments.Comment: 11 pages, 2 figures. submitted to PR
What if the Doha Round Fails? Implications for Canadian Agriculture
Many commentators assume that the WTO Doha Round negotiations have already failed and that this failure will not matter for Canadian agriculture. Neither view is correct. Most countries appear willing to make the effort needed to bring the negotiations to a make or break point in early 2008. If the Doha Round does eventually fail, an important opportunity to make the agricultural trading system significantly less distorted, more open and fair will have been lost. For Canadian agriculture, the failure to move the Doha Development Agenda (DDA) forward has more serious consequences than just missing the chance to improve the rules governing agricultural trade; it could signal a return to increased protectionism, more managed trade, a return to competitive subsidization, and an escalation in the number of trade disputes.International Relations/Trade,
What if the Doha Round Fails? Implications for Canadian Agriculture
Many commentators assume that the WTO Doha Round negotiations have already failed and that this failure will not matter for Canadian agriculture. Neither view is correct. Most countries appear willing to make the effort needed to bring the negotiations to a make or break point in early 2008. If the Doha Round does eventually fail, an important opportunity to make the agricultural trading system significantly less distorted, more open and fair will have been lost. For Canadian agriculture, the failure to move the Doha Development Agenda (DDA) forward has more serious consequences than just missing the chance to improve the rules governing agricultural trade; it could signal a return to increased protectionism, more managed trade, a return to competitive subsidization, and an escalation in the number of trade disputes.International Relations/Trade,
Three New Cool Brown Dwarfs Discovered with the Wide-field Infrared Survey Explorer (WISE) and an Improved Spectrum of the Y0 Dwarf WISE J041022.71+150248.4
As part of a larger search of Wide-field Infrared Survey Explorer (WISE) data
for cool brown dwarfs with effective temperatures less than 1000 K, we present
the discovery of three new cool brown dwarfs with spectral types later than T7.
Using low-resolution, near-infrared spectra obtained with the NASA Infrared
Telescope Facility and the Hubble Space Telescope we derive spectral types of
T9.5 for WISE J094305.98+360723.5, T8 for WISE J200050.19+362950.1, and Y0: for
WISE J220905.73+271143.9. The identification of WISE J220905.73+271143.9 as a Y
dwarf brings the total number of spectroscopically confirmed Y dwarfs to
seventeen. In addition, we present an improved spectrum (i.e. higher
signal-to-noise ratio) of the Y0 dwarf WISE J041022.71+150248.4 that confirms
the Cushing et al. classification of Y0. Spectrophotometric distance estimates
place all three new brown dwarfs at distances less than 12 pc, with WISE
J200050.19+362950.1 lying at a distance of only 3.9-8.0 pc. Finally, we note
that brown dwarfs like WISE J200050.19+362950.1 that lie in or near the
Galactic plane offer an exciting opportunity to measure their mass via
astrometric microlensing.Comment: Accepted for publication in the Astronomical Journa
Structures and materials technology for hypersonic aerospacecraft
Major considerations in structural design of a transatmospheric aerospacecraft are discussed. The general direction of progress in structures and materials technology is indicated, and technical areas in structures and materials where further research and development is necessary are indicated. Various structural concepts under study and materials which appear to be most applicable are discussed. Structural design criteria are discussed with particular attention to the factor-of-safety approach and the probabilistic approach. Structural certification requirements for the aerospacecraft are discussed. The kinds of analyses and tests which would be required to certify the structural integrity, safety, and durability of the aerospacecraft are discussed, and the type of test facility needed to perform structural certification tests is identified
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