71,588 research outputs found
Knots with distinct primitive/primitive and primitive/Seifert representatives
Berge introduced knots that are primitive/primitive with respect to the genus
2 Heegaard surface, , in ; surgery on such knots at the surface slope
yields a lens space. Later Dean described a similar class of knots that are
primitive/Seifert with respect to ; surgery on these knots at the surface
slope yields a Seifert fibered space. Here we construct a two-parameter family
of knots that have distinct primitive/Seifert embeddings in with the same
surface slope, as well as a family of torus knots that have a
primitive/primitive representative and a primitive/Seifert representative with
the same surface slope.Comment: 12 pages, 8 figures; 2 figures update
Towards a generalized theory of low-frequency sound source localization
Low-frequency sound source localization generates considerable amount of disagreement between audio/acoustics researchers, with some arguing that below a certain frequency humans cannot localize a source with others insisting that in certain cases localization is possible, even down to the lowest audible of frequencies. Nearly all previous work in this area depends on subjective evaluations to formulate theorems for low-frequency localization. This, of course, opens the argument of data reliability, a critical factor that may go some way to explain the reported ambiguities with regard to low-frequency localization. The resulting proposal stipulates that low-frequency source localization is highly dependent on room dimensions, source/listener location and absorptive properties. In some cases, a source can be accurately localized down to the lowest audible of frequencies, while in other situations it cannot. This is relevant as the standard procedure in live sound reinforcement, cinema sound and home-theater surround sound is to have a single mono channel for the low-frequency content, based on the assumption that human’s cannot determine direction in this band. This work takes the first steps towards showing that this may not be a universally valid simplification and that certain sound reproduction systems may actually benefit from directional low-frequency content
Instrumentation for Millimeter-wave Magnetoelectrodynamic Investigations of Low-Dimensional Conductors and Superconductors
We describe instrumentation for conducting high sensitivity millimeter-wave
cavity perturbation measurements over a broad frequency range (40-200 GHz) and
in the presence of strong magnetic fields (up to 33 tesla). A Millimeter-wave
Vector Network Analyzer (MVNA) acts as a continuously tunable microwave source
and phase sensitive detector (8-350 GHz), enabling simultaneous measurements of
the complex cavity parameters (resonance frequency and Q-value) at a rapid
repetition rate (approx. 10 kHz). We discuss the principal of operation of the
MVNA and the construction of a probe for coupling the MVNA to various
cylindrical resonator configurations which can easily be inserted into a high
field magnet cryostat. We also present several experimental results which
demonstrate the potential of the instrument for studies of low-dimensional
conducting systems.Comment: 20 pages including fig
Converting NAD83 GPS heights into NAVD88 elevations with LVGEOID, a hybrid geoid height model for the Long Valley volcanic region, California
A GPS survey of leveling benchmarks done in Long
Valley Caldera in 1999 showed that the application of the
National Geodetic Survey (NGS) geoid model GEOID99 to
tie GPS heights to historical leveling measurements would
significantly underestimate the caldera ground deformation (known from other geodetic measurements). The NGS
geoid model was able to correctly reproduce the shape of the
deformation, but required a local adjustment to give a realistic estimate of the magnitude of the uplift. In summer 2006,
the U.S. Geological Survey conducted a new leveling survey
along two major routes crossing the Long Valley region from
north to south (Hwy 395) and from east to west (Hwy 203 –
Benton Crossing). At the same time, 25 leveling bench marks
were occupied with dual frequency GPS receivers to provide a
measurement of the ellipsoid heights. Using the heights from
these two surveys, we were able to compute a precise geoid
height model (LVGEOID) for the Long Valley volcanic region.
Our results show that although the LVGEOID and the latest
NGS GEOID03 model practically coincide in areas outside
the caldera, there is a difference of up to 0.2 m between the
two models within the caldera. Accounting for this difference
is critical when using the geoid height model to estimate the
ground deformation due to magmatic or tectonic activity in the
calder
Three-body interactions in complex fluids: virial coefficients from simulation finite-size effects
A simulation technique is described for quantifying the contribution of
three-body interactions to the thermodynamical properties of coarse-grained
representations of complex fluids. The method is based on comparing the third
virial coefficient for a complex fluid with that of an approximate
coarse-grained model described by a pair potential. To obtain we
introduce a new technique which expresses its value in terms of the measured
volume-dependent asymptote of a certain structural function. The strategy is
applicable to both Molecular Dynamics and Monte Carlo simulation. Its utility
is illustrated via measurements of three-body effects in models of star polymer
and highly size-asymmetrical colloid-polymer mixtures.Comment: 13 pages, 8 figure
LANDSAT/coastal processes
The author has identified the following significant results. Correlations between the satellite radiance values water color, Secchi disk visibility, turbidity, and attenuation coefficients were generally good. The residual was due to several factors including systematic errors in the remotely sensed data, errors, small time and space variations in the water quality measurements, and errors caused by experimental design. Satellite radiance values were closely correlated with the optical properties of the water
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