497 research outputs found
Development of a Land Use Mapping and Monitoring Protocol for the High Plains Region: A Multitemporal Remote Sensing Application
The purpose of this project was to develop a practical protocol that employs multitemporal remotely sensed imagery, integrated with environmental parameters to model and monitor agricultural and natural resources in the High Plains Region of the United States. The value of this project would be extended throughout the region via workshops targeted at carefully selected audiences and designed to transfer remote sensing technology and the methods and applications developed. Implementation of such a protocol using remotely sensed satellite imagery is critical for addressing many issues of regional importance, including: (1) Prediction of rural land use/land cover (LULC) categories within a region; (2) Use of rural LULC maps for successive years to monitor change; (3) Crop types derived from LULC maps as important inputs to water consumption models; (4) Early prediction of crop yields; (5) Multi-date maps of crop types to monitor patterns related to crop change; (6) Knowledge of crop types to monitor condition and improve prediction of crop yield; (7) More precise models of crop types and conditions to improve agricultural economic forecasts; (8;) Prediction of biomass for estimating vegetation production, soil protection from erosion forces, nonpoint source pollution, wildlife habitat quality and other related factors; (9) Crop type and condition information to more accurately predict production of biogeochemicals such as CO2, CH4, and other greenhouse gases that are inputs to global climate models; (10) Provide information regarding limiting factors (i.e., economic constraints of pumping, fertilizing, etc.) used in conjunction with other factors, such as changes in climate for predicting changes in rural LULC; (11) Accurate prediction of rural LULC used to assess the effectiveness of government programs such as the U.S. Soil Conservation Service (SCS) Conservation Reserve Program; and (12) Prediction of water demand based on rural LULC that can be related to rates of draw-down of underground water supplies
Metallization of Fluid Hydrogen
The electrical resistivity of liquid hydrogen has been measured at the high
dynamic pressures, densities and temperatures that can be achieved with a
reverberating shock wave. The resulting data are most naturally interpreted in
terms of a continuous transition from a semiconducting to a metallic, largely
diatomic fluid, the latter at 140 GPa, (ninefold compression) and 3000 K. While
the fluid at these conditions resembles common liquid metals by the scale of
its resistivity of 500 micro-ohm-cm, it differs by retaining a strong pairing
character, and the precise mechanism by which a metallic state might be
attained is still a matter of debate. Some evident possibilities include (i)
physics of a largely one-body character, such as a band-overlap transition,
(ii) physics of a strong-coupling or many-body character,such as a Mott-Hubbard
transition, and (iii) processes in which structural changes are paramount.Comment: 12 pages, RevTeX format. Figures available on request; send mail to:
[email protected] To appear: Philosophical Transaction of the Royal
Society
Entropy-Dominated Dissipation in Sapphire Shock-Compressed up to 400 GPa (4 Mbar)
Sapphire (single-crystal Al2O3) is a representative Earth material and is
used as a window and/or anvil in shock experiments. Pressure, for example, at
the core-mantle boundary is about 130 gigapascals (GPa). Defects induced by
100-GPa shock waves cause sapphire to become opaque, which precludes measuring
temperature with thermal radiance. We have measured wave profiles of sapphire
crystals with several crystallographic orientations at shock pressures of 16,
23, and 86 GPa. At 23 GPa plastic-shock rise times are generally quite long
(~100 ns) and their values depend sensitively on the direction of shock
propagation in the crystal lattice. The long rise times are probably caused by
the high strength of inter-atomic interactions in the ordered three-dimensional
sapphire lattice. Our wave profiles and recent theoretical and laser-driven
experimental results imply that sapphire disorders without significant shock
heating up to about 400 GPa, above which Al2O3 is amorphous and must heat. This
picture suggests that the characteristic shape of shock compression curves of
many Earth materials at 100 GPa pressures is caused by a combination of entropy
and temperature.Comment: 12 pages, 4 figure
Evolution of Ultracold, Neutral Plasmas
We present the first large-scale simulations of an ultracold, neutral plasma,
produced by photoionization of laser-cooled xenon atoms, from creation to
initial expansion, using classical molecular dynamics methods with open
boundary conditions. We reproduce many of the experimental findings such as the
trapping efficiency of electrons with increased ion number, a minimum electron
temperature achieved on approach to the photoionization threshold, and
recombination into Rydberg states of anomalously-low principal quantum number.
In addition, many of these effects establish themselves very early in the
plasma evolution ( ns) before present experimental observations begin.Comment: 4 pages, 3 figures, submitted to PR
Case management and Think First completion
“The final, definitive version of this article has been published in the Journal, Probation Journal, Vol 53 Issue 3, 2006, Copyright The Trade Union and Professional Association for Family Court and Probation Staff, by SAGE Publications Ltd at: http://prb.sagepub.com/ " DOI: 10.1177/0264550506066771This article considers the findings of a small-scale study of the practice of case managers supervising offenders required to attend the Think First Group. It explores the interface between one-to-one and group-based work within multi-modal programmes of supervision and seeks to identify those practices that support individuals in completing a group.Peer reviewe
The Structure of Jupiter, Saturn, and Exoplanets: Key Questions for High-Pressure Experiments
We give an overview of our current understanding of the structure of gas
giant planets, from Jupiter and Saturn to extrasolar giant planets. We focus on
addressing what high-pressure laboratory experiments on hydrogen and helium can
help to elucidate about the structure of these planets.Comment: Invited contribution to proceedings of High Energy Density Laboratory
Astrophysics, 6. Accepted to Astrophysics & Space Science. 12 page
Lattice Dynamics and the High Pressure Equation of State of Au
Elastic constants and zone-boundary phonon frequencies of gold are calculated
by total energy electronic structure methods to twofold compression. A
generalized force constant model is used to interpolate throughout the
Brillouin zone and evaluate moments of the phonon distribution. The moments are
used to calculate the volume dependence of the Gruneisen parameter in the fcc
solid. Using these results with ultrasonic and shock data, we formulate the
complete free energy for solid Au. This free energy is given as a set of closed
form expressions, which are valid to compressions of at least V/V_0 = 0.65 and
temperatures up to melting. Beyond this density, the Hugoniot enters the
solid-liquid mixed phase region. Effects of shock melting on the Hugoniot are
discussed within an approximate model. We compare with proposed standards for
the equation of state to pressures of ~200 GPa. Our result for the room
temperature isotherm is in very good agreement with an earlier standard of
Heinz and Jeanloz.Comment: 13 pages, 8 figures. Accepted by Phys. Rev.
'Reclaiming the criminal' : the role and training of prison officers in England, 1877-1914
This article examines the role and training of prison officers in England, between 1877 and 1914. It is concerned with the changing penal philosophies and practices of this period and how these were implemented in local prisons, and the duties of the prison officer. More broadly, this article argues that the role of the prison officer and their training (from 1896) reflect wider ambiguities in prison policy and practice during this period
The Coupled Electronic-Ionic Monte Carlo Simulation Method
Quantum Monte Carlo (QMC) methods such as Variational Monte Carlo, Diffusion
Monte Carlo or Path Integral Monte Carlo are the most accurate and general
methods for computing total electronic energies. We will review methods we have
developed to perform QMC for the electrons coupled to a classical Monte Carlo
simulation of the ions. In this method, one estimates the Born-Oppenheimer
energy E(Z) where Z represents the ionic degrees of freedom. That estimate of
the energy is used in a Metropolis simulation of the ionic degrees of freedom.
Important aspects of this method are how to deal with the noise, which QMC
method and which trial function to use, how to deal with generalized boundary
conditions on the wave function so as to reduce the finite size effects. We
discuss some advantages of the CEIMC method concerning how the quantum effects
of the ionic degrees of freedom can be included and how the boundary conditions
can be integrated over. Using these methods, we have performed simulations of
liquid H2 and metallic H on a parallel computer.Comment: 27 pages, 10 figure
Recommended from our members
Dynamic response of berea sandstone shock-loaded under dry, wet and water-pressurized conditions
A single-stage light-gas gun was used to perform shock-recovery experiments on Berea sandstone under dry, wet and hydrostatically water-pressurized conditions. The samples were impacted by flyer-plates to achieve stress levels in the range 1.3 to 9.8 GPa. The microstructure of the shocked samples was analyzed using scanning electron microscopy (SEM), laser particle analysis and X-ray computed microtomography (XCMT). The dry samples show strongly fragmented and irregularly fractured quartz grains with a considerably reduced porosity, whereas the wet and water-pressurized specimens show less grain damage and less porosity reduction. During shock compression the water in the pores distributes the stresses and therefore the contact force between the grains is reduced. The interaction between the grains during the shock process was modeled by explicitly treating the grain-pore structure using Smooth Particle Hydrodynamics (SPH) and the Discrete Element Method (DEM)
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