17,611 research outputs found
REVERSE MIGRATION AND THE RURAL COMMUNITY DEVELOPMENT PROBLEM
Community/Rural/Urban Development,
A DEIM Induced CUR Factorization
We derive a CUR matrix factorization based on the Discrete Empirical
Interpolation Method (DEIM). For a given matrix , such a factorization
provides a low rank approximate decomposition of the form ,
where and are subsets of the columns and rows of , and is
constructed to make a good approximation. Given a low-rank singular value
decomposition , the DEIM procedure uses and to
select the columns and rows of that form and . Through an error
analysis applicable to a general class of CUR factorizations, we show that the
accuracy tracks the optimal approximation error within a factor that depends on
the conditioning of submatrices of and . For large-scale problems,
and can be approximated using an incremental QR algorithm that makes one
pass through . Numerical examples illustrate the favorable performance of
the DEIM-CUR method, compared to CUR approximations based on leverage scores
Documentation of animal health in organic pig herds
The health of weaned pigs should be described using several information sources to get an overall assessment of the health state in the herd. In this case study four organic pig herds each fattening between 800 and 3500 pigs per year provided data from clinical examination of a sample of animals, pathological findings at slaughter, post weaning mortality and medicine usage in the herd. Clinical symptoms were present in 8 – 18 % of the pigs, and 2 – 6 % of the pigs showed more serious symptoms of disease. At slaughter 10 – 17 % of the pigs got remarks for pathological lesions, primarily liver spots, abscesses and chronic pericarditis. The post weaning mortality varied between herds, while the usage of medicine was rather low in the herds. The herd health status can be aggregated in many ways. A suggestion is made for the four herds. According to this the good health state is achieved in herds combining a modest medicine usage with a low level of disease, measured by low prevalence of clinical symptoms, low number of remarks at slaughter and low mortality
Quantum emitters coupled to surface plasmons of a nano-wire: A Green function approach
We investigate a system consisting of a single, as well as two emitters
strongly coupled to surface plasmon modes of a nano-wire using a Green function
approach. Explicit expressions are derived for the spontaneous decay rate into
the plasmon modes and for the atom-plasmon coupling as well as a
plasmon-mediated atom-atom coupling. Phenomena due to the presence of losses in
the metal are discussed. In case of two atoms, we observe Dicke sub- and
superradiance resulting from their plasmon-mediated interaction. Based on this
phenomenon, we propose a scheme for a deterministic two-qubit quantum gate. We
also discuss a possible realization of interesting many-body Hamiltonians, such
as the spin-boson model, using strong emitter-plasmon coupling.Comment: 12 pages, 16 figure
Constituent quark scaling violation due to baryon number transport
In ultra-relativistic heavy ion collisions at \roots\approx200 GeV, the
azimuthal emission anisotropy of hadrons with low and intermediate transverse
momentum ( GeV/c) displays an intriguing scaling. In particular,
the baryon (meson) emission patterns are consistent with a scenario in which a
bulk medium of flowing quarks coalesces into three-quark (two-quark) "bags."
While a full understanding of this number of constituent quark (NCQ) scaling
remains elusive, it is suggestive of a thermalized bulk system characterized by
colored dynamical degrees of freedom-- a quark-gluon plasma (QGP). In this
scenario, one expects the scaling to break down as the central energy density
is reduced below the QGP formation threshold; for this reason, NCQ-scaling
violation searches are of interest in the energy scan program at the
Relativistic Heavy Ion Collider (RHIC). However, as \roots is reduced, it is
not only the initial energy density that changes; there is also an increase in
the net baryon number at midrapidity, as stopping transports entrance-channel
partons to midrapidity. This phenomenon can result in violations of simple NCQ
scaling. Still in the context of the quark coalescence model, we describe a
specific pattern for the break-down of the scaling that includes different flow
strengths for particles and their anti-partners. Related complications in the
search for recently suggested exotic phenomena are also discussed.Comment: 7 pages, 2 tables, 2 figures. Wording sharpened. Two tables added, to
quantify the estimate of stopped quark fraction
First Direct Detection Limits on sub-GeV Dark Matter from XENON10
The first direct detection limits on dark matter in the MeV to GeV mass range
are presented, using XENON10 data. Such light dark matter can scatter with
electrons, causing ionization of atoms in a detector target material and
leading to single- or few-electron events. We use 15 kg-days of data acquired
in 2006 to set limits on the dark-matter-electron scattering cross section. The
strongest bound is obtained at 100 MeV where sigma_e < 3 x 10^{-38} cm^2 at 90%
CL, while dark matter masses between 20 MeV and 1 GeV are bounded by sigma_e <
10^{-37} cm^2 at 90% CL. This analysis provides a first proof-of-principle that
direct detection experiments can be sensitive to dark matter candidates with
masses well below the GeV scale.Comment: Submitted to PR
Generation of optimum vertical profiles for an advanced flight management system
Algorithms for generating minimum fuel or minimum cost vertical profiles are derived and examined. The option for fixing the time of flight is included in the concepts developed. These algorithms form the basis for the design of an advanced on-board flight management system. The variations in the optimum vertical profiles (resulting from these concepts) due to variations in wind, takeoff mass, and range-to-destination are presented. Fuel savings due to optimum climb, free cruise altitude, and absorbing delays enroute are examined
Fault-tolerant Quantum Communication with Minimal Physical Requirements
We describe a novel protocol for a quantum repeater which enables long
distance quantum communication through realistic, lossy photonic channels.
Contrary to previous proposals, our protocol incorporates active purification
of arbitrary errors at each step of the protocol using only two qubits at each
repeater station. Because of these minimal physical requirements, the present
protocol can be realized in simple physical systems such as solid-state single
photon emitters. As an example, we show how nitrogen vacancy color centers in
diamond can be used to implement the protocol, using the nuclear and electronic
spin to form the two qubits.Comment: 4 pages, 3 figures. V2: Minor modifications. V3: Major changes in the
presentation and new titl
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