1,758 research outputs found
Nitrate pollution from horticultural production systems : tools for policy and advice from field to catchment scales
The implementation of the Nitrates Directive has imposed a requirement to restrict N fertiliser and manuring practices on farms across the EU in order to reduce nitrate losses to water. These requirements have since been extended by the more demanding Water Framework Directive, which broadens the focus from the control of farm practices to a consideration of the impacts of pollutants from all sources on water quality at a catchment or larger scale. Together, these Directives set limits for water quality, and identify general strategies for how these might be achieved. However, it is the responsibility of policy makers in each Nation State to design the details of the management practices and environmental protection measures required to meet the objectives of the legislation, to ensure they are appropriate for their specific types of land use and climate. This paper describes various modelling tools for comparing different cropping and land use strategies, and illustrates with examples how they can inform policy makers about the environmental benefits of changing management practices and how to prioritise them. The results can help to provide the specific advice on N fertiliser and land use management required by farmers and growers at a field scale, and by environmental managers at a catchment or larger scale. A further example of how results from multiple catchments can be up-scaled and compared using Geographic Information Systems is also outlined
A Quarterly Model Of The Beef, Pork, Sheep, Broiler and Turkey Sectors
Livestock and meat, producers, processors -and consumers need to continually adjust plans as expected prices change and-affect - i-- expected relative profits and utility* from alternative uses\u27 or the resources they manage.- These decision makers demand information and analysis of anticipated-product-supplies- and price levels.
Positionally dependent ^(15)N fraction factors in the UV photolysis of N_2O determined by high resolution FTIR spectroscopy
Positionally dependent fractionation factors for the photolysis of isotopomers of N_2O in natural abundance have been determined by high resolution FTIR spectroscopy at three photolysis wavelengths. Fractionation factors show clear 15N position and photolysis wavelength dependence and are in qualitative agreement with theoretical models but are twice as large. The fractionation factors increase with photolysis wavelength from 193 to 211 nm, with the fractionation factors at 207.6 nm for ^(14)N^(15)N^916)O, ^(15)N^(14)N^(16)O and ^(14)N^(14)N^(18)O equal to −66.5±5‰,−27.1±6‰ and −49±10‰, respectively
Versatile module for experiments with focussing neutron guides
We report the development of a versatile module that permits fast and
reliable use of focussing neutron guides under varying scattering angles. A
simple procedure for setting up the module and neutron guides is illustrated by
typical intensity patterns to highlight operational aspects as well as typical
parasitic artefacts. Combining a high-precision alignment table with separate
housings for the neutron guides on kinematic mounts, the change-over between
neutron guides with different focussing characteristics requires no
readjustments of the experimental set-up. Exploiting substantial gain factors,
we demonstrate the performance of this versatile neutron scattering module in a
study of the effects of uniaxial stress on the domain populations in the
transverse spin density wave phase of single crystal Cr
Policy Optimization in a Noisy Neighborhood: On Return Landscapes in Continuous Control
Deep reinforcement learning agents for continuous control are known to
exhibit significant instability in their performance over time. In this work,
we provide a fresh perspective on these behaviors by studying the return
landscape: the mapping between a policy and a return. We find that popular
algorithms traverse noisy neighborhoods of this landscape, in which a single
update to the policy parameters leads to a wide range of returns. By taking a
distributional view of these returns, we map the landscape, characterizing
failure-prone regions of policy space and revealing a hidden dimension of
policy quality. We show that the landscape exhibits surprising structure by
finding simple paths in parameter space which improve the stability of a
policy. To conclude, we develop a distribution-aware procedure which finds such
paths, navigating away from noisy neighborhoods in order to improve the
robustness of a policy. Taken together, our results provide new insight into
the optimization, evaluation, and design of agents.Comment: NeurIPS 2023 Accepted Pape
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