23,653 research outputs found
FACTORS AFFECTING PARTICIPATION IN THE MILK DIVERSION PROGRAM IN THE U.S. AND NEW YORK
Participation in the 1984-85 Milk Diversion Program (MDP) is examined through the analysis of aggregate state level data for the U.S. and county level data from New York. Linear probability, logit and probit models of participation are estimated. The empirical results are highly similar across models and identify the important determinants of farmer participation in the MDP. Models explaining contracted diversion levels are also estimated but do not have the explanatory power of the participation models. The implications of the results for the analysis of U.S. dairy policy alternatives are discussed.Agricultural and Food Policy, Livestock Production/Industries,
ACHIEVING EFFICIENCY AND EQUITY IN IRRIGATION MANAGEMENT: AN OPTIMIZATION MODEL OF THE EL ANGEL WATERSHED, CARCHI, ECUADOR
The objective of this paper is to address the problems of inefficiency and inequity in water allocation in the El Angel watershed, located in Ecuador's Sierra region. Water is captured in a high-altitude region of the watershed and distributed downstream to producers in four elevation-defined zones via a system of canals. Upstream and downstream producers face radically different conditions with respect to climate and terrain. A mathematical programming model was created to study the consequences of addressing chronic water scarcity problems in the watershed by shifting water resources between the four zones. The model captures the nature of water use by humans, crops and dual purpose cattle. Its objective function maximizes producer welfare as measured by aggregate gross margin, subject to limited supplies of land, labor and water. Five water allocation scenarios are evaluated with respect to efficiency in land and water use and equity in income distribution. Results reveal that although water is the primary constrained resource downstream, in the upstream zones, land is far more scarce. The current distribution of water rights does not consider these differences and therefore is neither efficient nor equitable. Improvements in efficiency (resource use) and equity (income distribution) are associated with (1) a shift of water to the lower zone, and (2) the use of lower levels of irrigation intensity upstream. Furthermore, the scenarios that result in the most efficient use of resources also bring the greatest degree of equity in income distribution, indicating that these may be complementary, not conflicting, goals.Mathematical programming, water allocation, efficiency, equity, Resource /Energy Economics and Policy,
Lattice study of trapped fermions at unitarity
We present a lattice study of up to N=20 unitary fermions confined to a
harmonic trap. Our preliminary results show better than 1% agreement with high
precision solutions to the many-body Schrodinger equation for up to N=6. We are
able to make predictions for larger N which were inaccessible by the
Hamiltonian approach due to computational limitations. Harmonic traps are used
experimentally to study cold atoms tuned to a Feshbach resonance. We show that
they also provide certain benefits to numerical studies of many-body
correlators on the lattice. In particular, we anticipate that the methods
described here could be used for studying nuclear physics.Comment: 7 pages, 5 figures, presented at the XXVIII International Symposium
on Lattice Field Theory (Lattice 2010), Villasimius, Italy, June 14-19 201
The Grassmannian Sigma Model in SU(2) Yang-Mills Theory
Spin-charge separation in pure SU(2) Yang-Mills theory was recently found to
involve the dynamics of an O(3) non-linear sigma model and, seemingly, a
Grassmannian non-linear sigma model. In this article we explicitly construct
the Grassmannian sigma model of the form appearing in the the spin-charge
separated SU(2) theory through a quaternionic decomposition of the manifold,
thus verifying its relevance in this context. The coupling between this model
and the O(3) non-linear sigma model is further commented upon.Comment: 11 pages, undergraduate research project; version published in J.
Phys.
Lattice calculation for unitary fermions in a finite box
A fundamental constant in systems of unitary fermions is the so-called
Bertsch parameter, the ratio of the ground state energy for spin paired unitary
fermions to that for free fermions at the same density. I discuss how we
computed this parameter as well as the pairing gap using a recently developed
lattice construction for unitary fermions, by measuring correlation functions
for up to 38 fermions in a finite box. Our calculation illustrates interesting
issues facing the study of many-body states on the lattice, which may
eventually be confronted in QCD calculations as well.Comment: 7 pages, 6 figures, The XXVIII International Symposium on Lattice
Field Theory, Lattice2010, June 14-19, 2010, Villasimius, Ital
A smart environment for biometric capture
The development of large scale biometric systems require experiments to be performed on large amounts of data. Existing capture systems are designed for fixed experiments and are not easily scalable. In this scenario even the addition of extra data is difficult. We developed a prototype biometric tunnel for the capture of non-contact biometrics. It is self contained and autonomous. Such a configuration is ideal for building access or deployment in secure environments. The tunnel captures cropped images of the subject's face and performs a 3D reconstruction of the person's motion which is used to extract gait information. Interaction between the various parts of the system is performed via the use of an agent framework. The design of this system is a trade-off between parallel and serial processing due to various hardware bottlenecks. When tested on a small population the extracted features have been shown to be potent for recognition. We currently achieve a moderate throughput of approximate 15 subjects an hour and hope to improve this in the future as the prototype becomes more complete
Spin-Dependent Quantum Emission in Hexagonal Boron Nitride at Room Temperature
Optically addressable spins associated with defects in wide-bandgap
semiconductors are versatile platforms for quantum information processing and
nanoscale sensing, where spin-dependent inter-system crossing (ISC) transitions
facilitate optical spin initialization and readout. Recently, the van der Waals
material hexagonal boron nitride (h-BN) has emerged as a robust host for
quantum emitters (QEs), but spin-related effects have yet to be observed. Here,
we report room-temperature observations of strongly anisotropic
photoluminescence (PL) patterns as a function of applied magnetic field for
select QEs in h-BN. Field-dependent variations in the steady-state PL and
photon emission statistics are consistent with an electronic model featuring a
spin-dependent ISC between triplet and singlet manifolds, indicating that
optically-addressable spin defects are present in h-BN a versatile
two-dimensional material promising efficient photon extraction, atom-scale
engineering, and the realization of spin-based quantum technologies using van
der Waals heterostructures.Comment: 38 pages, 34 figure
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