49,994 research outputs found
Thinking about the Future
Brian Gilbert, associate professor of chemistry, has been influential in the education of Kevin Romero, class of 2015
Optimisation of out-vessel magnetic diagnostics for plasma boundary reconstruction in tokamaks
To improve the low frequency spectrum of magnetic field measurements of
future tokamak reactors such as ITER, several steady state magnetic sensor
technologies have been considered. For all the studied technologies it is
always advantageous to place the sensors outside the vacuum vessel and as far
away from the reactor core to minimize radiation damage and temperature
effects, but not so far as to compromise the accuracy of the equilibrium
reconstruction. We have studied to what extent increasing the distance between
out-vessel sensors and plasma can be compensated for sensor accuracy and/or
density before the limit imposed by the degeneracy of the problem is reached.
The study is particularized for the Swiss TCV tokamak, due to the quality of
its magnetic data and its ability to operate with a wide range of plasma shapes
and divertor configurations. We have scanned the plasma boundary reconstruction
error as function of out-vessel sensor density, accuracy and distance to the
plasma. The study is performed for both the transient and steady state phases
of the tokamak discharge. We find that, in general, there is a broad region in
the parameter space where sensor accuracy, density and proximity to the plasma
can be traded for one another to obtain a desired level of accuracy in the
reconstructed boundary, up to some limit. Extrapolation of the results to a
tokamak reactor suggests that a hybrid configuration with sensors inside and
outside the vacuum vessel could be used to obtain a good boundary
reconstruction during both the transient and the flat-top of the discharges, if
out-vessel magnetic sensors of sufficient density and accuracy can be placed
sufficiently far outside the vessel to minimize radiation damage.Comment: 36 pages, 17 figures, Accepted for publication in Nuclear Fusio
NASA OAST and its role in space technology development
Several new programs, efforts in space research and technology, are introduced that the Office of Aeronautics and Space Technology has begun to support. The four key issues that currently are consuming NASA's energies and should be of great concern are listed. NASA is placing its emphasis in space on: (1) reconstituting the Shuttle capability; (2) maintaining the space station momentum; (3) resolving the current science mission backlog; and (4) rebuilding the technology base. Ways of implementing and funding these issues are discussed
Coping With Discrimination Among Mexican Descent Adolescents
The current research is designed to explore the relationship among discrimination stress, coping strategies, and self-esteem among Mexican descent youth (N = 73, age 11-15 years). Results suggest that primary control engagement and disengagement coping strategies are positively associated with discrimination stress. Furthermore, self-esteem is predicted by an interaction of primary control engagement coping and discrimination stress, such that at higher levels of discrimination stress, youth who engaged in more primary control engagement coping reported higher self-esteem. The authors’ findings indicate that Mexican descent youth are actively finding ways to cope with the common experience of negative stereotypes and prejudice, such that their self-esteem is protected from the stressful impact of discrimination and prejudice. Implications of these findings for Latino/a youth resilience are discussed
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