4,593 research outputs found
Californians Need Beaches--Maybe Yours
Our nation faces a serious problem of congested recreational resources as a result of a rapid increase in population compounded by concomitant increases in urbanization and leisure time. These factors simultaneously increase the demand for more public recreational areas and reduce the amount of space available. Necessarily, this expending demand comes into conflict with the private property rights of those who hold title to lands particularly suited for public recreational purposes. A recently litigated aspect of this conflict involves the ownership of the beach areas of our nation\u27s sea coasts. Public interest demands public use, access, and enjoyment; traditional property concepts permit title to the vast majority of beaches to be privately held... It will be the purpose of this note to examine the effectiveness of some current judicial and legislative attempts to resolve this conflict. In addition, possible alternative approaches, in accordance with general public policy, will be suggested
Performance of Geant4 in simulating semiconductor particle detector response in the energy range below 1 MeV
Geant4 simulations play a crucial role in the analysis and interpretation of
experiments providing low energy precision tests of the Standard Model. This
paper focuses on the accuracy of the description of the electron processes in
the energy range between 100 and 1000 keV. The effect of the different
simulation parameters and multiple scattering models on the backscattering
coefficients is investigated. Simulations of the response of HPGe and
passivated implanted planar Si detectors to \beta{} particles are compared to
experimental results. An overall good agreement is found between Geant4
simulations and experimental data
Total Cross Sections for Neutron Scattering
Measurements of neutron total cross-sections are both extensive and extremely
accurate. Although they place a strong constraint on theoretically constructed
models, there are relatively few comparisons of predictions with experiment.
The total cross-sections for neutron scattering from O and Ca are
calculated as a function of energy from ~MeV laboratory energy with a
microscopic first order optical potential derived within the framework of the
Watson expansion. Although these results are already in qualitative agreement
with the data, the inclusion of medium corrections to the propagator is
essential to correctly predict the energy dependence given by the experiment.Comment: 10 pages (Revtex 3.0), 6 fig
Use of approximations of Hamilton-Jacobi-Bellman inequality for solving periodic optimization problems
We show that necessary and sufficient conditions of optimality in periodic
optimization problems can be stated in terms of a solution of the corresponding
HJB inequality, the latter being equivalent to a max-min type variational
problem considered on the space of continuously differentiable functions. We
approximate the latter with a maximin problem on a finite dimensional subspace
of the space of continuously differentiable functions and show that a solution
of this problem (existing under natural controllability conditions) can be used
for construction of near optimal controls. We illustrate the construction with
a numerical example.Comment: 29 pages, 2 figure
Measurement of the -asymmetry parameter of Cu in search for tensor type currents in the weak interaction
Precision measurements at low energy search for physics beyond the Standard
Model in a way complementary to searches for new particles at colliders. In the
weak sector the most general decay Hamiltonian contains, besides vector
and axial-vector terms, also scalar, tensor and pseudoscalar terms. Current
limits on the scalar and tensor coupling constants from neutron and nuclear
decay are on the level of several percent.
The goal of this paper is extracting new information on tensor coupling
constants by measuring the -asymmetry parameter in the pure Gamow-Teller
decay of Cu, thereby testing the V-A structure of the weak interaction.
An iron sample foil into which the radioactive nuclei were implanted was cooled
down to milliKelvin temperatures in a He-He dilution refrigerator. An
external magnetic field of 0.1 T, in combination with the internal hyperfine
magnetic field, oriented the nuclei. The anisotropic radiation was
observed with planar high purity germanium detectors operating at a temperature
of about 10\,K. An on-line measurement of the asymmetry of Cu
was performed as well for normalization purposes. Systematic effects were
investigated using Geant4 simulations.
The experimental value, = 0.587(14), is in agreement with the
Standard Model value of 0.5991(2) and is interpreted in terms of physics beyond
the Standard Model. The limits obtained on possible tensor type charged
currents in the weak interaction hamiltonian are -0.045
0.159 (90\% C.L.). The obtained limits are comparable to limits from other
correlation measurements in nuclear decay and contribute to further
constraining tensor coupling constants
Panel Discussion: Foreign Governmental Control of Multinational Corporations Marketing in the United States
This panel discussion focuses on debating the regulation of companies operating in more than one country. The primary emphasis is placed on oil companies
An Applied Framework for Incorporating Multiple Sources of Uncertainty in Fisheries Stock Assessments
Estimating fish stock status is very challenging given the many sources and high levels of
uncertainty surrounding the biological processes (e.g. natural variability in the demographic
rates), model selection (e.g. choosing growth or stock assessment models) and parameter
estimation. Incorporating multiple sources of uncertainty in a stock assessment allows
advice to better account for the risks associated with proposed management options, pro-
moting decisions that are more robust to such uncertainty. However, a typical assessment
only reports the model fit and variance of estimated parameters, thereby underreporting the
overall uncertainty. Additionally, although multiple candidate models may be considered,
only one is selected as the ‘best’ result, effectively rejecting the plausible assumptions
behind the other models. We present an applied framework to integrate multiple sources of
uncertainty in the stock assessment process. The first step is the generation and condition-
ing of a suite of stock assessment models that contain different assumptions about the
stock and the fishery. The second step is the estimation of parameters, including fitting of
the stock assessment models. The final step integrates across all of the results to reconcile
the multi-model outcome. The framework is flexible enough to be tailored to particular
stocks and fisheries and can draw on information from multiple sources to implement a
broad variety of assumptions, making it applicable to stocks with varying levels of data avail-
ability The Iberian hake stock in International Council for the Exploration of the Sea (ICES)
Divisions VIIIc and IXa is used to demonstrate the framework, starting from length-based
stock and indices data. Process and model uncertainty are considered through the growth,
natural mortality, fishing mortality, survey catchability and stock-recruitment relationship.
Estimation uncertainty is included as part of the fitting process. Simple model averaging is
used to integrate across the results and produce a single assessment that considers the
multiple sources of uncertainty.Versión del edito
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