5,056 research outputs found
Strike point splitting induced by the application of magnetic perturbations on MAST
Divertor strike point splitting induced by resonant magnetic perturbations
(RMPs) has been observed on MAST for a variety of RMP configurations in a
plasma scenario with Ip=750kA where those configurations all have similar
resonant components. Complementary measurements have been obtained with
divertor Langmuir probes and an infrared camera. Clear splitting consistently
appears in this scenario only in the even configuration of the perturbation
coils, similarly to the density pump-out. These results present a challenge for
models of plasma response to RMPs.Comment: 9 pages, 4 figures, submitted to the proceedings of the 20th
Conference on Plasma Surface Interactions, to be published in the Journal of
Nuclear Material
Resolved CO(1-0) Nuclei in IRAS 14348-1447: Evidence for Massive Bulge Progenitors to Ultraluminous Infrared Galaxies
High-resolution, CO(1-0) interferometry of the ultraluminous infrared galaxy
IRAS 14348-1447 is presented. The merger system has a molecular gas mass of
\~3x10^10 solar masses and a projected nuclear separation of 4.8 kpc (3.5"),
making it one of the most molecular gas-rich galaxies known and an ideal
candidate for studying the intermediate stages of an ultraluminous merger
event. The CO morphology shows two molecular gas components associated with the
stellar nuclei of the progenitors, consistent with the idea that the molecular
disks are gravitationally bound by the dense bulges of the progenitor galaxies
as the interaction proceeds. In contrast, less luminous infrared galaxies
observed to date with projected nuclear separations of ~<5 kpc show a dominant
CO component between the stellar nuclei. This discrepancy may be an indication
that the progenitors of mergers with lower infrared luminosity do not possess
massive bulges, and that the gas is stripped during the initial encounter of
their progenitors. A comparison of the CO and radio luminosities of the NE and
SW component show them to have comparable radio and CO flux ratios of
f(NE)/f(SW) ~0.6, possibly indicating that the amount of star-forming molecular
gas in the progenitors is correlated with the supernovae rate. The estimate of
molecular gas masses of the nuclei and the extent of the radio emission are
used to infer that the nuclei of IR 14348-1447 have gas densities comparable to
the cores of elliptical galaxies.Comment: LaTex, 5 pages with 1 postscript and 1 jpg figure, ApJ Letters, in
pres
Particle, heat, and sheath power transmission factor profiles during ELM suppression experiments on DIII-D
Exact longitudinal plasmon dispersion relations for one and two dimensional Wigner crystals
We derive the exact longitudinal plasmon dispersion relations, of
classical one and two dimensional Wigner crystals at T=0 from the real space
equations of motion, of which properly accounts for the full unscreened Coulomb
interactions. We make use of the polylogarithm function in order to evaluate
the infinite lattice sums of the electrostatic force constants. From our exact
results we recover the correct long-wavelength behavior of previous approximate
methods. In 1D, , validating the known
RPA and bosonization form. In 2D , agreeing remarkably
with the celebrated Ewald summation result. Additionally, we extend this
analysis to calculate the band structure of tight-binding models of
non-interacting electrons with arbitrary power law hopping.Comment: 4 pages, 1 figure. Important typos and errors fixed, 2D dispersion
adde
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Reaction Bonded Silicon Carbide: SFF, Process Refinement and Applications
Reaction bonded silicon carbide (RBSiC) has a wide variety of industrial applications and
a manufacturing process based on Selective Laser Sintering (SLS) has been demonstrated in
previous research at the University of Texas. That study was directed toward semiconductor
manufacturing applications and was based on prior indirect SLS methods. Several key research
questions were addressed for three main manufacturing phases: preform SLS, binder burnout and
reactive infiltration. The current research is focused on development of material systems and
manufacturing capability and is directed toward a broader set of potential applications. Preform
formation utilizes SiC powder of an appropriate average particle size mixed with a multicomponent binder. The preform or green part is then placed in a vacuum furnace to carbonize
the binder. The details of the binder chemistry must support accurate SFF shapes and acceptable
surface roughness, a strong green part and maintenance of the part shape during the first furnace
operation. Finally, the physics and chemistry of the infiltration process, based on the
microstructure of the initial green preform, determine the viability of the manufacturing process
and the characteristics of the final composite material.
The functionality of metal, polymer and ceramic matrix composites can support the
growing SFF industry desire to move beyond functional prototyping and into manufacturing
arenas. This project is being explored for more general application to matrix composite
materials, especially highly functional systems tailored specifically for SLS. The goal is to
establish the governing principles of binder function, carbonization and infiltration as well as to
understand the interdependence of these phases in terms of manufacturing application. With this
understanding new applications and special SLS composites can support the development of new
products and a greater SFF manufacturing presence.
This paper provides an introduction to the material, a look at basic rapid manufacturing
trends, an overview of the previous work, a review of relevant RBSiC material science issues,
and an outline of the current study.Mechanical Engineerin
Industrial Sponsor Perspective On Leveraging Capstone Design Projects To Enhance Their Business
Capstone design projects have become commonplace among engineering and engineering technology programs. These projects are valuable tools when assessing students, as they require students to work in teams, communicate effectively, and demonstrate technical competency. The use of industrial sponsors enhances these projects by giving these projects more of a “real world” feel. Most of the research into capstone design projects focuses on student learning as well as the overall design process. However, very little research has been performed from the perspective of the industrial sponsor. In this paper, an industrial sponsor who has sponsored several large-scale capstone design projects presents their perspective on working with students on these projects. These projects serve as training systems for their existing employees and clients, and offer the sponsor the opportunity to evaluate the students as prospective future employees
NICMOS Imaging of the Nuclei of Arp 220
We report high resolution imaging of the ultraluminous infrared galaxy Arp
220 at 1.1, 1.6, and 2.22 microns with NICMOS on the HST. The
diffraction-limited images at 0.1--0.2 arcsecond resolution clearly resolve
both nuclei of the merging galaxy system and reveal for the first time a number
of luminous star clusters in the circumnuclear envelope. The morphologies of
both nuclei are strongly affected by dust obscuration, even at 2.2 microns :
the primary nucleus (west) presents a crescent shape, concave to the south and
the secondary (eastern) nucleus is bifurcated by a dust lane with the southern
component being very reddened. In the western nucleus, the morphology of the
2.2 micron emission is most likely the result of obscuration by an opaque disk
embedded within the nuclear star cluster. The morphology of the central
starburst-cluster in the western nucleus is consistent with either a
circumnuclear ring of star formation or a spherical cluster with the bottom
half obscured by the embedded dust disk. Comparison of cm-wave radio continuum
maps with the near-infrared images suggests that the radio nuclei lie in the
dust disk on the west and near the highly reddened southern component of the
eastern complex. The radio nuclei are separated by 0.98 arcseconds
(corresponding to 364 pc at 77 Mpc) and the half-widths of the infrared nuclei
are approximately 0.2-0.5 arcseconds. At least 8, unresolved infrared sources
-- probably globular clusters -- are also seen in the circumnuclear envelope at
radii 2-7 arcseconds . Their near-infrared colors do not significantly
constrain their ages.Comment: LaTex, 15 pages with 1 gif figure and 5 postscript figures. ApJL
accepte
A nuclear localization signal targets tail-anchored membrane proteins to the inner nuclear envelope in plants
Protein targeting to the inner nuclear membrane (INM) is one of the least understood protein targeting pathways. INM proteins are important for chromatin organization, nuclear morphology and movement, and meiosis, and have been implicated in human diseases. In opisthokonts, one mechanism for INM targeting is transport factor-mediated trafficking, in which nuclear localization signals (NLSs) function in nuclear import of transmembrane proteins. To explore whether this pathway exists in plants, we fused the SV40 NLS to a plant ER tail-anchored protein and showed that the GFP-tagged fusion protein was significantly enriched at the nuclear envelope (NE) of leaf epidermal cells. Airyscan subdiffraction limited confocal microscopy showed that this protein displays a localization consistent with an INM protein. Nine different monopartite and bipartite NLSs from plants and opisthokonts, fused to a chimeric tail-anchored membrane protein, were all sufficient for NE enrichment, and both monopartite and bipartite NLSs were sufficient for trafficking to the INM. Tolerance for different linker lengths and protein conformations suggests that INM trafficking rules might differ from those in opisthokonts. The INM proteins developed here can be used to target new functionalities to the plant nuclear periphery
Population adaptation for genetic algorithm-based cognitive radios
Abstract — Genetic algorithms are best suited for optimization problems involving large search spaces. The problem space encountered when optimizing the transmission parameters of an agile or cognitive radio for a given wireless environment and set of performance objectives can become prohibitively large due to the high number of parameters and their many possible values. Recent research has demonstrated that genetic algorithms are a viable implementation technique for cognitive radio engines. However, the time required for the genetic algorithms to come to a solution substantionally increases as the system complexity grows. In this paper, we present a population adaptation technique for genetic algorithms that takes advantage of the information from previous cognition cycles in order to reduce the time required to reach an optimal decision. Our simulation results demonstrate that the amount of information from the previous cognition cycle can be determined from the environmental variation factor (EVF), which represents the amount of change in the environment parameters since the previous cognition cycle. I
Field Guide to Exhumed Major Faults in Southern California
This field guide provides an overview of exposures and provides a field trip guide to localities of exhumed faults in southern California. We focus on exposures of faults that are documented or inferred to be exhumed from seismogenic depths. The goal of this guidebook is to provide geoscientists who are interested in fault zone mechanics and earthquake processes a summary of the results of the work on these sites
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