3,414 research outputs found
Identification Of Environmental Variables For Use In Monitoring For The Evaluation Of The Rural Environment Protection Scheme
Teagasc wishes to acknowledge the support of the Environmental RTDI Programme 2000–2006 in financing this research project.End of project reportThe aim of this study was to identify and select quantitative environmental attributes for a monitoring programme that may be integrated into an environmental evaluation of Ireland’s agri-environmental scheme. This was achieved primarily by reviewing a range of agri-environmental indicators and suggesting indicators that would be appropriate for monitoring the REPS. The study conducted a desk review to collate information on current best practice in monitoring for environmental quality. A Project Group (comprising representatives from the Environmental Protection Agency [EPA], Department of Agriculture and Food [DAF], Teagasc, and the project supervisors) advised on the ongoing development of the project. There was a consultation process with national experts, and with a selection of stakeholder organisations with an interest in monitoring the environmental impact of the REPS.Environmental Protection Agenc
Degenerate Variational Integrators for Magnetic Field Line Flow and Guiding Center Trajectories
Symplectic integrators offer many advantages for the numerical solution of
Hamiltonian differential equations, including bounded energy error and the
preservation of invariant sets. Two of the central Hamiltonian systems
encountered in plasma physics --- the flow of magnetic field lines and the
guiding center motion of magnetized charged particles --- resist symplectic
integration by conventional means because the dynamics are most naturally
formulated in non-canonical coordinates, i.e., coordinates lacking the familiar
partitioning. Recent efforts made progress toward non-canonical
symplectic integration of these systems by appealing to the variational
integration framework; however, those integrators were multistep methods and
later found to be numerically unstable due to parasitic mode instabilities.
This work eliminates the multistep character and, therefore, the parasitic mode
instabilities via an adaptation of the variational integration formalism that
we deem ``degenerate variational integration''. Both the magnetic field line
and guiding center Lagrangians are degenerate in the sense that their resultant
Euler-Lagrange equations are systems of first-order ODEs. We show that
retaining the same degree of degeneracy when constructing a discrete Lagrangian
yields one-step variational integrators preserving a non-canonical symplectic
structure on the original Hamiltonian phase space. The advantages of the new
algorithms are demonstrated via numerical examples, demonstrating superior
stability compared to existing variational integrators for these systems and
superior qualitative behavior compared to non-conservative algorithms
Effects of Humidity Swings on Adsorption Columns for Air Revitalization: Modeling and Experiments
The goal of this research was to develop a dynamic model which can predict the effect of humidity swings on activated carbon adsorption beds used to remove trace contaminants from the atmosphere in spacecraft. Specifically, the model was to be incorporated into a computer simulation to predict contaminant concentrations exiting the bed as a function of time after a humidity swing occurs. Predicted breakthrough curves were to be compared to experimentally measured results. In all respects the research was successful. The two major aspects of this research were the mathematical model and the experiments. Experiments were conducted by Mr. Appel using a fixed-bed apparatus at NASA-Ames Research Center during the summers of 1994 and 1995 and during the first 8 months of 1996. Mr. Appel conducted most of his mathematical modeling work at the University of Virginia. The simulation code was used to predict breakthrough curves using adsorption equilibrium correlations developed previously by M. D. LeVan's research group at the University of Virginia. These predictions were compared with the experimental measurements, and this led to improvements in both the simulation code and the apparatus
Carbon Dioxide Adsorption on a 5A Zeolite Designed for CO2 Removal in Spacecraft Cabins
Carbon dioxide adsorption data were obtained for a 5A zeolite manufactured by AlliedSignal Inc. (Des Plaines, Illinois). The material is planned for use in the Carbon Dioxide Removal Assembly (CDRA) for U.S. elements of the International Space Station. The family of adsorption isotherms covers a temperature range of O to 250 C, and a pressure range of 0.001 to 800 torr. Coefficients of the Toth equation are fit to the data. Isosteric heats of adsorption are derived from the equilibrium loading data
Methodological tests of the use of trace elements as tracers to assess root activity
peer-reviewedN.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).Background and aims
There is increasing interest in how resource utilisation in grassland ecosystems is affected by changes in plant diversity and abiotic conditions. Research to date has mainly focussed on aboveground responses and there is limited insight into belowground processes. The aim of this study was to test a number of assumptions for the valid use of the trace elements caesium, lithium, rubidium and strontium as tracers to assess the root activity of several grassland species.
Methods
We carried out a series of experiments addressing the reliability of soil labelling, injection density, incubation time, application rate and the comparability of different tracers in a multiple tracer method.
Results
The results indicate that it is possible to achieve a reliable labelling of soil depths. Tracer injection density affected the variability but not the mean level of plant tracer concentrations. Tracer application rates should be based on pilot studies, because of site- and species-specific responses. The trace elements did not meet prerequisites to be used in a multiple tracer method.
Conclusions
The use of trace elements as tracers is potentially a very useful tool to give insight into plant root activity at different soil depths. This work highlights some of the main benefits and pitfalls of the method and provides specific recommendations to assist the design of tracer experiments and interpretation of the results.N.J.H. was funded by the Irish Research Council, co-funded by Marie Curie Actions under FP7. The field experiments A, B and G were supported by the European Community's Seventh Framework Programme (FP7/2007-2013) under the grant agreements FP7-266018 (AnimalChange) and FP7- 244983 (MultiSward). Experiment F was supported by the German Science Foundation (FOR 456).European Unio
Modeling the Large Scale Structures of Astrophysical Jets in the Magnetically Dominated Limit
We suggest a new approach that could be used for modeling both the large
scale behavior of astrophysical jets and the magnetically dominated explosions
in astrophysics. We describe a method for modeling the injection of magnetic
fields and their subsequent evolution in a regime where the free energy is
magnetically dominated. The injected magnetic fields, along with their
associated currents, have both poloidal and toroidal components, and they are
not force free. The dynamic expansion driven by the Lorentz force of the
injected fields is studied using 3-dimensional ideal magnetohydrodynamic
simulations. The generic behavior of magnetic field expansion, the interactions
with the background medium, and the dependence on various parameters are
investigated.Comment: Accepted to ApJ, May 10, 2006 issue, 12 figures total (3 color
figures
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