73,311 research outputs found
A commentary on recent water safety initiatives in the context of water utility risk management.
Over the last decade, suppliers of drinking water have recognised the
limitations of relying solely on end-product monitoring to ensure safe water
quality and have sought to reinforce their approach by adopting preventative
strategies where risks are proactively identified, assessed and managed. This is
leading to the development of water safety plans; structured âroute mapsâ for
managing risks to water supply, from catchment to consumer taps. This paper
reviews the Hazard Analysis and Critical Control Point (HACCP) procedure on
which many water safety plans are based and considers its appropriateness in the
context of drinking water risk management. We examine water safety plans in a
broad context, looking at a variety of monitoring, optimisation and risk
management initiatives that can be taken to improve drinking water safety. These
are cross-compared using a simple framework that facilitates an integrated
approach to water safety. Finally, we look at how risk management practices are
being integrated across water companies and how this is likely to affect the
future development of water safety p
Performance Management in Portfolio School Districts
Explores the challenges of performance-based oversight of portfolio districts -- districts trying to provide diverse types of schools with common standards and accountability -- and the capacities needed. Includes profiles and best practices
Dundee Discussion Papers in Economics 189:Still hungry for success? Targeting the poor and the case of free school meals
Deconfinement transitions in a generalised XY model
We find the complete phase diagram of a generalised XY model that includes
half-vortices. The model possesses superfluid, pair-superfluid and disordered
phases, separated by Kosterlitz-Thouless (KT) transitions for both the
half-vortices and ordinary vortices, as well as an Ising-type transition. There
also occurs an unusual deconfining phase transition, where the disordered to
superfluid transition is of Ising rather than KT type. We show by analytical
arguments and extensive numerical simulations that there is a point in the
phase diagram where the KT transition line meets the deconfining Ising phase
transition. We find that the latter extends into the disordered phase not as a
phase transition, but rather solely as a deconfinement transition. It is best
understood in the dual height model, where on one side of the transition height
steps are bound into pairs while on the other they are unbound. We also extend
the phase diagram of the dual model, finding both O(2) loop model and
antiferromagnetic Ising transitions.Comment: 19 pages. v2: references added and minor changes. Appears in "John
Cardy's scale-invariant journey in low dimensions: a special issue for his
70th birthday
Coulomb blockade in silicon based structures at temperatures up to 50 K
Coulomb blockade has been observed in the current-voltage characteristics of structures fabricated in silicon germanium delta-doped material at temperatures up to 50 K. This is consistent with the estimated effective tunnel capacitance of 10 aF which is significantly smaller than the reported capacitances of tunnel junctions made from Al or GaAs/AlGaAs heterostructures
Use of synchrotron tomographic techniques in the assessment of diffusion parameters for solute transport in groundwater flow
This technical note describes the use of time-resolved synchrotron radiation tomographic energy dispersive diffraction imaging (TEDDI) and tomographic X-ray fluorescence (TXRF) for examining ion diffusion in porous media. The technique is capable of tracking the diffusion of several ion species simultaneously. This is illustrated by results which compare the movement of Cs+, Ba2+ and La3+ ions from solution into a typical sample of English chalk. The results exhibited somewhat anomalous (non-Fickian) behaviour and revealed heterogeneities (in 1D) on the scale of a few millimetres
Exact active subspace Metropolis-Hastings, with applications to the Lorenz-96 system
We consider the application of active subspaces to inform a
Metropolis-Hastings algorithm, thereby aggressively reducing the computational
dimension of the sampling problem. We show that the original formulation, as
proposed by Constantine, Kent, and Bui-Thanh (SIAM J. Sci. Comput.,
38(5):A2779-A2805, 2016), possesses asymptotic bias. Using pseudo-marginal
arguments, we develop an asymptotically unbiased variant. Our algorithm is
applied to a synthetic multimodal target distribution as well as a Bayesian
formulation of a parameter inference problem for a Lorenz-96 system
Towards a classification of vacuum near-horizons geometries
We prove uniqueness of the near-horizon geometries arising from degenerate
Kerr black holes within the collection of nearby vacuum near-horizon
geometries.Comment: 16 pages, 3 figures; minor changes to match published versio
Evaluating Pooled Evidence from the Reemployment Bonus Experiments
Social experiments conducted in Pennsylvania and Washington tested the effect of offering Unemployment Insurance (UI) claimants a cash bonus for rapid reemployment. This paper combines data from the two experiments and uses a consistent framework to evaluate the experiments and determine with greater certainty the extent to which a reemployment bonus can affect economic outcomes. Bonus offers in each of the experiments generated statistically significant but relatively modest reductions in UI receipt. Since the estimated impacts on UI receipt were modest, the reemployment bonuses did not generate the UI savings necessary to pay for administering and paying the bonuses. Hence, contrary to earlier findings from a bonus experiment conducted in Illinois, findings from the Pennsylvania and Washington experiments strongly suggest that a reemployment bonus is not a cost-effective method of speeding the reemployment of UI claimants.unemployment, insurance, bonus, experiments, O'Leary, Decker
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