136,140 research outputs found
Observation of explosive collisionless reconnection in 3D nonlinear gyrofluid simulations
The nonlinear dynamics of collisionless reconnecting modes is investigated,
in the framework of a three-dimensional gyrofluid model. This is the relevant
regime of high-temperature plasmas, where reconnection is made possible by
electron inertia and has higher growth rates than resistive reconnection. The
presence of a strong guide field is assumed, in a background slab model, with
Dirichlet boundary conditions in the direction of nonuniformity. Values of ion
sound gyro-radius and electron collisionless skin depth much smaller than the
current layer width are considered. Strong acceleration of growth is found at
the onset to nonlinearity, while at all times the energy functional is well
conserved. Nonlinear growth rates more than one order of magnitude higher than
linear growth rates are observed when entering into the small- regime
A notion of rectifiability modeled on Carnot groups
We introduce a notion of rectifiability modeled on Carnot groups. Precisely,
we say that a subset E of a Carnot group M and N is a subgroup of M, we say E
is N-rectifiable if it is the Lipschitz image of a positive measure subset of
N. First, we discuss the implications of N-rectifiability, where N is a Carnot
group (not merely a subgroup of a Carnot group), which include
N-approximability and the existence of approximate tangent cones isometric to N
almost everywhere in E. Second, we prove that, under a stronger condition
concerning the existence of approximate tangent cones isomorphic to N almost
everywhere in a set E, that E is N-rectifiable. Third, we investigate the
rectifiability properties of level sets of C^1_N functions, where N is a Carnot
group. We show that for almost every real number t and almost every
noncharacteristic point x in a level set of f, there exists a subgroup T_x of H
and r >0 so that f^{-1}(t) intersected with B_H(x,r) is T_x-approximable at x
and an approximate tangent cone isomorphic to T_x at x.Comment: 27 page
Engaging the Digitally Engaged Student: Comparing Technology-Mediated Communication Use and Effects on Student Learning
The role of communication technologies in the learning process is both a dynamic and complex issue. Yet, we know surprisingly little about how the use of specific communication technologies may influence classroom performance, key learning outcomes, and other measures of course satisfaction. The research reported here attempts to add to our knowledge about the role of communication in the technology enhanced classroom (TEC) education and in technology-enhanced online (TEO) education through a direct comparison of two courses. Our findings indicate additional support for “The No Significant Difference Phenomenon.” Furthermore, we found that prior experiences lead students to gravitate towards their preferred learning environments, and that basic website elements are required in any learning environment to enhance student outcomes. Finally, we found that when used appropriately, the benefits of communication technology use in education outweigh many of the drawbacks
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
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Who Is a “Veteran”?—Basic Eligibility for Veterans’ Benefits
The U.S. Department of Veterans Affairs (VA) offers a broad range of benefits to veterans of the U.S. Armed Forces and to certain members of their families. Among these benefits are various types of financial assistance, including monthly cash payments to disabled veterans, health care, education, and housing. Certain criteria must be met to be eligible to receive any of the benefits administered by the VA.
This report focuses on basic eligibility and entitlement requirements for former servicemembers for benefits administered by the VA. Certain VA benefits are available to current servicemembers, and the eligibility requirements for those benefits are not a component of this report.
The VA uses a two-step process to evaluate claims for benefits. First, the claimant must demonstrate eligibility for veterans’ benefits in general. That is, the claimant must prove that he or she is a bona fide veteran and verify certain related matters. Second, the veteran must prove entitlement to the particular benefit being sought
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
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