39,169 research outputs found
Dynamical Alignment in Three Species Tokamak Edge Turbulence
Three dimensional computations of self consistent three species gyrofluid
turbulence are carried out for tokamak edge conditions. Profiles as well as
disturbances in dependent variables are followed, running the dynamical system
to transport equilibrium. The third species density shows a significant
correlation with that of the electrons, regardless of initial conditions and
drive mechanisms. For decaying systems the densities evolve toward each other.
Companion tests with a simple two dimensional drift wave model show this
persists even if the third species is a passively advected test field.
Similarity in the transport character of electrons and the trace species does
not imply that the electrons themselves have a test particle transport
character.Comment: RevTeX 4, 21 pages, 15 figures, submitted to Physics of Plasma
Repair of honeycomb panels with welded breakaway studs
Damaged metallic honeycomb panels can be repaired by drilling holes and welding breakaway studs to both facing sheets. Minimal heat required for welding reduces distortion of highly stressed panels. Repairs can be made without the use of doublers and with greater strength when doublers are used
Zonal Flows and Electromagnetic Drift Wave Turbulence
Detailed computations of tokamak edge turbulence in three dimensional,
globally consistent flux tube geometry show an inhibition of the standard
scenario in which zonal ExB flows generated by the turbulence should lead to
transport barrier formation. It is found by comparison to slab geometry and by
analysis of the energetics that the zonal flow energy is depleted by toroidal
coupling to the pressure through the geodesic curvature. Edge transport
barriers would then depend on the physics of the neoclassical equilibrium.Comment: 14 pages including 5 figures, submitted to Physics Letters
Derivation via free energy conservation constraints of gyrofluid equations with finite-gyroradius electromagnetic nonlinearities
The derivation of electromagnetic gyrofluid equations is made systematic by
using the Hermite polynomial form of the underlying delta-f gyrokinetic
distribution function. The gyrokinetic free-energy functional is explicitly
used to set up the model. The gyrofluid free energy follows directly. The
interaction term in the gyrokinetic Lagrangian is used to obtain the gyrofluid
counterpart, from which the polarisation equation follows. One closure rule is
decided for taking moments over the kinetic gyroaveraging operator. These steps
fix the rest of the derivation of the conservative part of the gyrofluid
equations. Dissipation is then added in a form to obtain positive definite
dissipation and to obtain the collisional fluid equations in their appropriate
limit. Existing results are recovered, with the addition of a completely
consistent model for finite gyroradius effects in the nonlinearities
responsible for magnetic reconnection.Comment: RevTeX 4, 39 pages, no figures, submitted to Physics of Plasmas. From
version 1, corrected minor errors in equations, re-did some explanations,
added some references, From version 2, added a section on correspondence to
fluid/MHD models as asked by the referee. This version was accepted by
Physics of Plasma
The relationship between money and prices: some historical evidence reconsidered
This article describes a debate about the validity of the quantity theory of money and offers further evidence against it. The evidence is primarily from the North American colonies of Virginia, New York, and Pennsylvania and regards the issue of measuring the money supply. Studies have shown that changes in colonial money and inflation are inconsistent with the quantity theory. Some have argued that those studies measure money wrong: specie belongs in the measure because the colonies were on a fixed exchange rate system with Britain; changes in colonial paper money were offset by specie flows. When specie is counted, the quantity theory stands. This study responds with evidence that the critics are wrong: the colonies had no such fixed exchange rate regime, and movements in the stock of colonial paper currency cannot have been offset by specie flows. ; Reprinted in Quarterly Review, Fall 2002 (v. 26, no. 4)Money theory ; Economic history
James Madison's monetary economics
An analysis of Madison's essay, "Money," and a presentation of a model giving rise to equilibria that mimic general observations about the consequences of government policies like the one Madison describes for limiting inflation.Money ; Money theory ; Debts, Public
The US earned income tax credit, its effects, and possible reforms
In this paper, I first summarize how the US Earned Income Tax Credit (EITC) operates and describe the characteristics of recipients. I then discuss empirical work on the effects of the EITC on poverty and income distribution, and its effects on labor supply. Next, I discuss a few policy concerns about the EITC: possible negative effects on hours of work and marriage, and problems of compliance with the tax system. I then briefly discuss some possible reforms to the structure of the current EITC.Welfare reform; Earned income tax credit; EITC; Earnings subsidies; Tax credits; Poverty
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