99,177 research outputs found
GIS Characterization of Beaver Watershed
Beaver Reservoir watershed is located in Northwest Arkansas including portions of Madison, Washington, Benton, Carroll, Franklin and Crawford counties. This watershed is important to the Northwest Arkansas region because it supplies most of the drinking water for the major towns and cities, and several rural water systems. The watershed consists of 308,971 ha with elevations ranging from approximately 341 m to 731 m above mean sea level. It includes the Springfield Plateau and the Boston Mountains provinces within the Ozark Plateau physiographic region. There are approximately 581 km of streams, 532 km of shore line, and 3712 km of roads in the watershed most of which are city streets and rural roads. The soils in the watershed vary extensively and are quite complex due to the differences in parent material, topography and time. Most parent material of the soils in the Springfield Plateau is limestone, whereas in the Boston Mountains the dominant parent material is sandstone and shale. The differences in soils have led to the differences in landuse and land cover. The near surface geology in the watershed is also divided by physiographic provinces. Most of the Springfield Plateau surface geology is limestone, whereas the Boston Mountains are primarily sandstone and shale. Spatial details of the streams, roads, soils and geology attributes in the watershed are presented in this report. The GIS database and characterization of the watershed offers an excellent beginning to future research and modeling of various water quality parameters in this and other watersheds
Private Rights versus Public Power: The Role of State Action in Alaska Constitutional Jurisprudence
Linear approximations of nonlinear systems can be obtained by fitting a linear model to data from a nonlinear system, for example, using the prediction-error method. In many situations, the type of linear model and the model orders are selected after estimating several models and evaluating them using various validation techniques. Two commonly used validation methods for linear models are spectral and residual analysis. Unfortunately, these methods will not always work if the true system is nonlinear. However, if the input can be viewed as if it has been generated by filtering white noise through a minimum phase filter, spectral and residual analysis can be used for validation of linear models of nonlinear systems. Furthermore, it can be shown that the input minimum phase property guarantees that a certain optimality result will hold. Here, the benefits of using minimum phase instead of non-minimum phase filters for input design will be shown both theoretically and in numerical experiments
Investigation of the Statistical and Spatial Distributions of Mercury Contaminated Fish, Surface Waters and Soils in Arkansas
Mercury (Hg) contamination of fish is a widespread problem throughout much of the United States and the world (Louisiana WWW page, 1997). Levels ofHg in fish suffic1ent to exceed the FDA action level of 1 mg kg-1 have been found in many water bodies, including some in Arkansas and Louisiana. As a result of the serious public health ramifications for developing fetuses and for people that subsist on native fish, fish consumption advisories due to Hg contamination have been issued in 29 states. Contamination of surface water bodies by Hg results from deforestation, forest fires, fossil fuels, mining, natural emissions and commercial emissions (Armstrong, 1994). In addition, Hg has a high affinity for organic matter in soil and sediments, and therefore, long-term storage of Hg is an environmental problem. An excellent review of the integration and synthesis of recent work on Hg pollution is given in several papers edited by Watras and Huckabee (1994). The general consensus of the reports in this document seems to be that increases in Hg levels can be attributed to one or more of several mechanisms including atmospheric deposition, acidification of soils and lakes by sulfur deposition followed by an increased sulfate reduction, and transport from other source areas
Space Charge Effects in Ferroelectric Thin Films
The effects of space charges on hysteresis loops and field distributions in
ferroelectrics have been investigated numerically using the phenomenological
Landau-Ginzburg-Devonshire theory. Cases with the ferroelectric fully and
partially depleted have been considered. In general, increasing the number of
charged impurities results in a lowering of the polarization and coercive field
values. Squarer loops were observed in the partially depleted cases and a
method was proposed to identify fully depleted samples experimentally from
dielectric and polarization measurements alone. Unusual field distributions
found for higher dopant concentrations have some interesting implications for
leakage mechanisms and limit the range of validity of usual semiconductor
equations for carrier transport.Comment: 23 pages, 11 figure
From isolated subgroups to generic permutation representations
Let be a countable group, the (compact, metric)
space of all subgroups of with the Chabauty topology and
the collection of isolated
points. We denote by the (Polish) group of all permutations of a countable
set . Then the following properties are equivalent: (i)
is dense in , (ii) admits a
"generic permutation representation". Namely there exists some such that the collection of permutation
representations is co-meager in
. We call groups satisfying these properties
solitary. Examples of solitary groups include finitely generated LERF groups
and groups with countably many subgroups.Comment: 21 page
Volcanism by melt-driven Rayleigh-Taylor instabilities and possible consequences of melting for admittance ratios on Venus
A large number of volcanic features exist on Venus, ranging from tens of thousands of small domes to large shields and coronae. It is difficult to reconcile all these with an explanation involving deep mantle plumes, since a number of separate arguments lead to the conclusion that deep mantle plumes reaching the base of the lithosphere must exceed a certain size. In addition, the fraction of basal heating in Venus' mantle may be significantly lower than in Earth's mantle reducing the number of strong plumes from the core-mantle boundary. In three-dimensional convection simulations with mainly internal heating, weak, distributed upwellings are usually observed. We present an alternative mechanism for such volcanism, originally proposed for the Earth and for Venus, involving Rayleigh-Taylor instabilities driven by melt buoyancy, occurring spontaneously in partially or incipiently molten regions
Single/Few Bunch Space Charge Effects at 8-GeV in the Fermilab Main Injector
For Project X, it is planned to inject a beam of 3x10**11 particles per bunch
into the Main Injector. Therefore, at 8-GeV, there will be increased space
charge tune shifts and an increased incoherent tune spread. In preparation for
these higher intensity bunches exploratory studies have commenced looking at
the transmission of different intensity bunches at different tunes. An
experiment is described with results for bunch intensities between 20 and 300
10**9 particles. To achieve the highest intensity bunches coalescing at 8-GeV
is required, resulting in a longer bunch length. Comparisons show that similar
transmission curves are obtained when the intensity and bunch length have
increased by factors of 3.2 and 3.4 respectively, indicating the incoherent
tune shifts are similar, as expected from theory. The results of these
experiments will be used in conjugation with simulations to further study high
intensity bunches in the Main Injector.Comment: 3 pp. 3rd International Particle Accelerator Conference (IPAC 2012)
20-25 May 2012, New Orleans, Louisian
6 Batch Injection and Slipped Beam Tune Measurements in Fermilab's Main Injector
During Nova operations it is planned to run the Fermilab Recycler in a 12
batch slip stacking mode. In preparation for this, measurements of the tune
during a six batch injection and then as the beam is slipped by changing the RF
frequency, but without a 7th injection, have been carried out in the Main
Injector. The coherent tune shifts due to the changing beam intensity were
measured and compared well with the theoretically expected tune shift. The tune
shifts due to changing RF frequency, required for slip stacking, also compare
well with the linear theory, although some nonlinear affects are apparent at
large frequency changes. These results give us confidence that the expected
tunes shifts during 12 batch slip stacking Recycler operations can be
accommodated.Comment: 3 pp. 3rd International Particle Accelerator Conference (IPAC 2012)
20-25 May 2012, New Orleans, Louisian
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