12,517 research outputs found
A very low frequency radio astronomy observatory on the Moon
Because of terrestrial ionospheric absorption, very little is known of the radio sky beyond 10 m wavelength. An extremely simple, low cost very low frequency radio telescope is proposed, consisting of a large array of short wires laid on the lunar surface, each wire equipped with an amplifier and a digitizer, and connected to a common computer. The telescope could do simultaneous multifrequency observations of much of the visible sky with high resolution in the 10 to 100 m wavelength range, and with lower resolution in the 100 to 1000 m range. It would explore structure and spectra of galactic and extragalactic point sources, objects, and clouds, and would produce detailed quasi-three-dimensional mapping of interstellar matter within several thousand parsecs of the Sun
Competing Alignments of Nematic Liquid Crystals on Square Patterned Substrates
A theoretical analysis is presented of a nematic liquid crystal confined
between substrates pat- terned with squares that promote vertical and planar
alignment. Two approaches are used to eluci- date the behavior across a wide
range of length scales: Monte Carlo simulation of hard particles and
Frank-Oseen continuum theory. Both approaches predict bistable degenerate
azimuthal alignment in the bulk along the edges of the squares; the continuum
calculation additionally reveals the possi- bility of an anchoring transition
to diagonal alignment if the polar anchoring energy associated with the pattern
is sufficiently weak. Unlike the striped systems previously analyzed, the Monte
Carlo simulations suggest that there is no "bridging" transition for
sufficiently thin cells. The extent to which these geometrically patterned
systems resemble topographically patterned substrates, such as square wells, is
also discussed.Comment: 11 pages, 12 figure
Input output analysis for regional and land use evaluation with particular reference to forestry
ESTIMATING WILLINGNESS-TO-PAY USING A POLYCHOTOMOUS CHOICE FUNCTION: AN APPLICATION TO PORK PRODUCTS WITH ENVIRONMENTAL ATTRIBUTES
This paper utilizes a polychotomous choice function to investigate the relationship between socioeconomic characteristics and willingness-to-pay for embedded environmental attributes. Specifically, a two-stage estimation procedure with an ordered probit selection rule is used to predict the premium payers and the magnitude of the premium they are willing to pay.Research Methods/ Statistical Methods,
Estimating Willingness to Pay Using a Polychotomous Choice Function: An Application to Pork Products with Environmental Attributes
Bid data from a Vickrey auction for pork chops with embedded environmental attributes were analyzed. It was found that approximately 62% of the participants had a positive WTP for the most "environmentally friendly" package of pork. Thirty percent of the participants had no WTP, and 8% had a negative WTP. A polychotomous choice model was used to accommodate data having an anchoring point within the distribution of the data. Standard variables found in the WTP literature coupled with this model were used to predict participants who were premium payers and non-premium payers using an estimated ordered probit equation.anchoring points, environmental attributes, ordered probit, polychotomous choice functions, pork, Vickrey auction, willingness to pay, Consumer/Household Economics, Demand and Price Analysis,
Field tests of a portable MEMS gravimeter
Gravimeters are used to measure density anomalies under the ground. They are applied in
many different fields from volcanology to oil and gas exploration, but present commercial systems
are costly and massive. A new type of gravity sensor has been developed that utilises the same
fabrication methods as those used to make mobile phone accelerometers. In this study, we describe
the first results of a field-portable microelectromechanical system (MEMS) gravimeter. The stability
of the gravimeter is demonstrated through undertaking a multi-day measurement with a standard
deviation of 5.58 × 10−6 ms−2
. It is then demonstrated that a change in gravitational acceleration of
4.5 × 10−5 ms−2
can be measured as the device is moved between the top and the bottom of a 20.7 m
lift shaft with a signal-to-noise ratio (SNR) of 14.25. Finally, the device is demonstrated to be stable in
a more harsh environment: a 4.5 × 10−4 ms−2 gravity variation is measured between the top and
bottom of a 275-m hill with an SNR of 15.88. These initial field-tests are an important step towards
a chip-sized gravity senso
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