2,983 research outputs found
A Review of Regional Economic Models for Fisheries Management in the U.S.
In 1986, Andrews and Rossi reviewed input-output (IO)studies of U.S. fisheries. Since then, many more fisheries studies have appeared using IO and other types of regional economic models, such as Fishery Economic Assessment Models, Social Accounting Matrices, and Computable General Equilibrium models. However, to our knowledge no updated summary of these studies or models has appeared since 1986. This paper attempts to fill this gap by briefly reviewing the types of regional economic models that have been applied to fisheries, reviewing studies using these models that have been conducted for U.S. fisheries, and identifying data and modeling issues associated with regional economic analysis of fisheries in the U.S. The authors conclude that although economic impact analysis of fisheries policy is required under federal law, development of more representative regional economic models for this purpose is not likely to be forthcoming without increased information obtained through some type of comprehensive data collection program.Review, regional economic models, fisheries, IO, FEAM, SAM, CGE, IMPLAN, data., Community/Rural/Urban Development, Resource /Energy Economics and Policy, R1, R13, R15,
Twelve-spin "Schrodinger cat"
Pseudopure "cat" state, a superposition of quantum states with all spins up
and all spins down, is experimentally demonstrated for a system of twelve
dipolar-coupled nuclear spins of fully 13C-labeled benzene molecule oriented in
a liquid-crystalline matrix.Comment: Submitted to Applied Physics Letter
NMR and Relaxation in Superconductor
NMR and nuclear spin-lattice relaxation rate (NSLR) are reported at
7.2 Tesla and 1.4 Tesla in powder samples of the intermetallic compound
with superconducting transition temperature in zero field = 39.2 K. From
the first order quadrupole perturbed NMR specrum a quadrupole coupling
frequency of 835 5 kHz is obtained. The Knight shift is very small and it
decreases to zero in the superconducting phase. The NSLR follows a linear law
with = 165 10 (sec K) . The results in the normal phase indicate a
negligible -character of the wave function of the conduction electrons at
the Fermi level. Below the NSLR is strongly field dependent indicating
the presence of an important contribution related to the density and the
thermal motion of flux lines. No coherence peak is observed at the lower field
investigated (1.4 T)
Entanglement witnesses arising from Choi type positive linear maps
We construct optimal PPTES witnesses to detect PPT entangled
edge states of type constructed recently \cite{kye_osaka}. To do this,
we consider positive linear maps which are variants of the Choi type map
involving complex numbers, and examine several notions related to optimality
for those entanglement witnesses. Through the discussion, we suggest a method
to check the optimality of entanglement witnesses without the spanning
property.Comment: 18 pages, 4 figures, 1 tabl
Frame-like Geometry of Double Field Theory
We relate two formulations of the recently constructed double field theory to
a frame-like geometrical formalism developed by Siegel. A self-contained
presentation of this formalism is given, including a discussion of the
constraints and its solutions, and of the resulting Riemann tensor, Ricci
tensor and curvature scalar. This curvature scalar can be used to define an
action, and it is shown that this action is equivalent to that of double field
theory.Comment: 35 pages, v2: minor corrections, to appear in J. Phys.
Coupled-Trajectory Quantum-Classical Approach to Electronic Decoherence in Nonadiabatic Processes
We present a novel quantum-classical approach to nonadiabatic dynamics, deduced from the coupled electronic and nuclear equations in the framework of the exact factorization of the electron-nuclear wave function. The method is based on the quasiclassical interpretation of the nuclear wave function, whose phase is related to the classical momentum and whose density is represented in terms of classical trajectories. In this approximation, electronic decoherence is naturally induced as an effect of the coupling to the nuclei and correctly reproduces the expected quantum behavior. Moreover, the splitting of the nuclear wave packet is captured as a consequence of the correct approximation of the time-dependent potential of the theory. This new approach offers a clear improvement over Ehrenfest-like dynamics. The theoretical derivation presented in this Letter is supported by numerical results that are compared to quantum mechanical calculations.open2
Facial structures for various notions of positivity and applications to the theory of entanglement
In this expository note, we explain facial structures for the convex cones
consisting of positive linear maps, completely positive linear maps,
decomposable positive linear maps between matrix algebras, respectively. These
will be applied to study the notions of entangled edge states with positive
partial transposes and optimality of entanglement witnesses.Comment: An expository note. Section 7 and Section 8 have been enlarge
Reduction of gas bubbles and improved critical current density in Bi-2212 round wire by swaging
Bi-2212 round wire is made by the powder-in-tube technique. An unavoidable
property of powder-in-tube conductors is that there is about 30% void space in
the as-drawn wire. We have recently shown that the gas present in the as-drawn
Bi-2212 wire agglomerates into large bubbles and that they are presently the
most deleterious current limiting mechanism. By densifying short 2212 wires
before reaction through cold isostatic pressing (CIPping), the void space was
almost removed and the gas bubble density was reduced significantly, resulting
in a doubled engineering critical current density (JE) of 810 A/mm2 at 5 T, 4.2
K. Here we report on densifying Bi-2212 wire by swaging, which increased JE
(4.2 K, 5 T) from 486 A/mm2 for as-drawn wire to 808 A/mm2 for swaged wire.
This result further confirms that enhancing the filament packing density is of
great importance for making major JE improvement in this round-wire magnet
conductor.Comment: To be published in IEEE Transactions on Applied Superconductivity,
23, xxxxxx (2013
Lanczos exact diagonalization study of field-induced phase transition for Ising and Heisenberg antiferromagnets
Using an exact diagonalization treatment of Ising and Heisenberg model
Hamiltonians, we study field-induced phase transition for two-dimensional
antiferromagnets. For the system of Ising antiferromagnet the predicted
field-induced phase transition is of first order, while for the system of
Heisenberg antiferromagnet it is the second-order transition. We find from the
exact diagonalization calculations that the second-order phase transition
(metamagnetism) occurs through a spin-flop process as an intermediate step.Comment: 4 pages, 4 figure
Active cooling control of the CLEO detector using a hydrocarbon coolant farm
We describe a novel approach to particle-detector cooling in which a modular
farm of active coolant-control platforms provides independent and regulated
heat removal from four recently upgraded subsystems of the CLEO detector: the
ring-imaging Cherenkov detector, the drift chamber, the silicon vertex
detector, and the beryllium beam pipe. We report on several aspects of the
system: the suitability of using the aliphatic-hydrocarbon solvent PF(TM)-200IG
as a heat-transfer fluid, the sensor elements and the mechanical design of the
farm platforms, a control system that is founded upon a commercial programmable
logic controller employed in industrial process-control applications, and a
diagnostic system based on virtual instrumentation. We summarize the system's
performance and point out the potential application of the design to future
high-energy physics apparatus.Comment: 21 pages, LaTeX, 5 PostScript figures; version accepted for
publication in Nuclear Instruments and Methods in Physics Research
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