13,653 research outputs found
RURAL-TO-URBAN WATER TRANSFERS: MEASURING DIRECT FOREGONE BENEFITS OF IRRIGATION WATER UNDER UNCERTAIN WATER SUPPLIES
Irrigation water from a southeastern Colorado county has been sold to distant municipalities. The county's junior water right delivered limited and uncertain water supplies which were used on relatively poor soils. The ability of water markets to allocate water to the highest-valued use was addressed by assessing the direct foregone benefits of the transfer using deterministic and discrete stochastic sequential (DSSP) programming models. Crop mix predicted by the DSSP followed observed regional patterns. The DSSP was thus used to derive regional water demand from which foregone value was estimated. Direct regional foregone agricultural benefits were relatively low-due to uncertain water supplies and unproductive soils-indicating the market selected a low-valued supply for transfer.Resource /Energy Economics and Policy,
Far-infrared imaging of tokamak plasma
A 20-channel interferometer has been developed which utilizes a linear, one-dimensional microbolometer array to obtain single-shot density profiles from the UCLA Microtor tokamak plasma. The interferometer has been used to study time-dependent phenomena in the plasma density profile. Observations of the sawtooth instability clearly show the growth of the m=0 mode from a localized oscillation (r=1 cm) on axis to an oscillation of the entire plasma. Also, measurements during the initial startup phase of the discharge show evidence of hollow density profiles. In addition, a simultaneous measurement of the poloidal magnetic field has been developed which provides 20 channels of polarimetry. Interferometry and polarimetry both use the same imaging system and the spatial resolution of both measurements has been tested using plastic and crystal-quartz test objects. The signal-to-noise ratio for the polarimeter has also proved adequate for the expected Faraday rotation angle (alphamax=7°, Ip=70 kA, n=5×10^13 cm^−3)
The Radio Afterglow From GRB 980519: A Test of the Jet and Circumstellar Models
We present multi-frequency radio observations from the afterglow of GRB
980519 beginning 7.2 hours after the gamma-ray burst and ending 63 days later.
The fast decline in the optical and X-ray light curves for this burst has been
interpreted either as afterglow emission originating from a collimated outflow
-- a jet -- or the result of a blast wave propagating into a medium whose
density is shaped by the wind of an evolved massive star. These two models
predict divergent behavior for the radio afterglow, and therefore, radio
observations are capable, in principle, of discriminating between the two. We
show that a wind model describes the subsequent evolution of the radio
afterglow rather well. However, we see strong modulation of the light curve,
which we interpret as diffractive scintillation. These variations prevent us
from decisively rejecting the jet model.Comment: ApJ, submitte
The Cool ISM in Elliptical Galaxies. II. Gas Content in the Volume - Limited Sample and Results from the Combined Elliptical and Lenticular Surveys
We report new observations of atomic and molecular gas in a volume limited
sample of elliptical galaxies. Combining the elliptical sample with an earlier
and similar lenticular one, we show that cool gas detection rates are very
similar among low luminosity E and SO galaxies but are much higher among
luminous S0s. Using the combined sample we revisit the correlation between cool
gas mass and blue luminosity which emerged from our lenticular survey, finding
strong support for previous claims that the molecular gas in ellipticals and
lenticulars has different origins. Unexpectedly, however, and contrary to
earlier claims, the same is not true for atomic gas. We speculate that both the
AGN feedback and merger paradigms might offer explanations for differences in
detection rates, and might also point towards an understanding of why the two
gas phases could follow different evolutionary paths in Es and S0s. Finally we
present a new and puzzling discovery concerning the global mix of atomic and
molecular gas in early type galaxies. Atomic gas comprises a greater fraction
of the cool ISM in more gas rich galaxies, a trend which can be plausibly
explained. The puzzle is that galaxies tend to cluster around
molecular-to-atomic gas mass ratios near either 0.05 or 0.5.Comment: 37 pages, including 4 tables and 12 figures. Accepted for publication
in the Astrophysical Journa
Economic impacts of a rural-to-urban water transfer: a case study of Crowley County, Colorado
November, 1993.Includes bibliographical references (pages 49-51).Urban water supply agencies seeking to meet growing municipal water demands in the arid southwest are finding that the purchase of water from existing agricultural uses is, from their perspective, often more cost-effective than construction of additional storage. Colorado municipalities have been among the most active purchasers of irrigation water rights. Agriculture-to-urban water transfers have economic impacts at the local, regional and state levels. Although the transfers represent "willing buyer-willing seller" exchanges, and represent a gain for both parties to the transactions, concerns have been voiced over whether the economic values of the transacting entities fully take into account the values to the region and the state. Starting in the 1970s, water for urban use has been purchased in Crowley County, a small rural county in southeastern Colorado. Crowley County lands are irrigated from the Lower Arkansas River via the Colorado Canal. Some 85% of the water rights formerly serving 47,000 irrigated acres in Crowley County have been purchased by municipalities. This study had two main purposes. The first was to employ a nonmarket valuation technique to estimate the foregone direct economic benefits (opportunity costs) of irrigation water used in Crowley County. The second purpose was to estimate regional (direct plus secondary) employment impacts of the reduced irrigated agriculture.Grant no. 14-08-0001-GI551, Project no. 06; financed in part by the U.S. Dept. of the Interior, Geological Survey, through the Colorado Water Resources Research Institute
Economic impacts of agriculture-to-urban water transfers: a case study of Crowley County, Colorado
November 1993.Includes bibliographical references (pages 49-51).Grant no. 14-08-0001-G1551, project 06
Bloch oscillations of ultracold atoms: a tool for a metrological determination of
We use Bloch oscillations in a horizontal moving standing wave to transfer a
large number of photon recoils to atoms with a high efficiency (99.5% per
cycle). By measuring the photon recoil of , using velocity selective
Raman transitions to select a subrecoil velocity class and to measure the final
accelerated velocity class, we have determined with a relative
precision of 0.4 ppm. To exploit the high momentum transfer efficiency of our
method, we are developing a vertical standing wave set-up. This will allow us
to measure better than and hence the fine structure
constant with an uncertainty close to the most accurate value coming
from the () determination
Control Techniques for an Interior Permanent Magnet Synchronous Motor of an Electrified Vehicle
A system and method for controlling an interior permanent magnet sychronous motor (IPMSM) are presented. In an exemplary implementation, phase current ripple estimation techniques are utilized for variable frequency switching pulse-width modulation control of the IPMSM. In one implementation, the method includes controlling a three-phase inverter based on an initial switching frequency to generate a three-phase alternating current (AC) voltage for the IPMSM. Transformed voltages are determined in a rotating reference frame based on the three-phase AC voltage in the stationary reference frame. Current ripples are determined in the rotating reference frame based on the transformed voltages. Phase current ripples are determined in the stationary reference frame based on the current ripples in the rotating reference frame. A modified switching frequency for the three-phase inverter is determined based on the initial switching frequency and the phase current ripples. The three-phase inverter is then controlled based on the modified switching frequency
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