227 research outputs found
An assessment of the risk arising from electrical effects associated with carbon fibers released from commercial aircraft fires
The risks associated with electrical effects arising from carbon fibers released from commercial aviation aircraft fires were estimated for 1993. The expected annual losses were estimated to be about 100,000 (1977 dollars) in 1993 were established to be about one in ten thousand
A comparison of estimators for the two-point correlation function
Nine of the most important estimators known for the two-point correlation
function are compared using a predetermined, rigorous criterion. The indicators
were extracted from over 500 subsamples of the Virgo Hubble Volume simulation
cluster catalog. The ``real'' correlation function was determined from the full
survey in a 3000Mpc/h periodic cube. The estimators were ranked by the
cumulative probability of returning a value within a certain tolerance of the
real correlation function. This criterion takes into account bias and variance,
and it is independent of the possibly non-Gaussian nature of the error
statistics. As a result for astrophysical applications a clear recommendation
has emerged: the Landy & Szalay (1993) estimator, in its original or grid
version Szapudi & Szalay (1998), are preferred in comparison to the other
indicators examined, with a performance almost indistinguishable from the
Hamilton (1993) estimator.Comment: aastex, 10 pages, 1 table, 1 figure, revised version, accepted in
ApJ
High resolution charge-exchange spectroscopic measurements of aluminum impurity ions in a high temperature plasma
Charge-exchange recombination spectroscopy, which is generally used to measure low-Z impurities in fusion devices, has been used for measuring Al+11 and Al+13 impurities in the Madison Symmetric Torus reversed field pinch. To obtain the impurity ion temperature, the experimental emission spectrum is fitted with a model which includes fine structure in the atomic transition. Densities of these two ionization states, calculated from charge-exchange emission brightness, are used in combination with a collisional radiative model to estimate the abundance of all other charge states of aluminum in the plasma and the contribution of aluminum to the effective ionic charge of the plasma
Confinement of relativistic electrons in a magnetic mirror en route to a magnetized relativistic pair plasma
Publisher’s Note: “Dispersion calibration for the National Ignition Facility electron–positron–proton spectrometers for intense laser matter interactions” [Rev. Sci. Instrum. 92, 033516 (2021)] (Rev. Sci. Instrum. 92, 059902 (2021)
Electron-positron pairs, produced in intense laser-solid interactions, are
diagnosed using magnetic spectrometers with image plates, such as the National
Ignition Facility (NIF) Electron Positron Proton Spectrometers (EPPS). Although
modeling can help infer the quantitative value, the accuracy of the models
needs to be verified to ensure measurement quality. The dispersion of
low-energy electrons and positrons may be affected by fringe magnetic fields
near the entrance of the EPPS. We have calibrated the EPPS with six electron
beams from a Siemens Oncor linear accelerator (linac) ranging in energy from
-- as they enter the spectrometer. A Geant4 TOPAS
Monte-Carlo simulation was set up to match depth dose curves and lateral
profiles measured in water at source-surface distance. An
accurate relationship was established between the bending magnet current
setting and the energy of the electron beam at the exit window. The simulations
and measurements were used to determine the energy distributions of the six
electron beams at the EPPS slit. Analysis of the scanned image plates together
with the determined energy distribution arriving in the spectrometer provide
improved dispersion curves for the EPPS.Comment: Published in Review of Scientific Instruments, 5 pages, 3 figures,
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Sheared Poliodal Flows and Turbulence in the Edge Plasma Region of Stellarator and Tokamak Devices
Measurements of Extended Magnetic Fields in Laser-Solid Interaction
Magnetic fields generated from a laser-foil interaction are measured with
high fidelity using a proton radiography scheme with in situ x-ray fiducials.
In contrast to prior findings under similar experimental conditions, this
technique reveals the self-generated, Biermann-battery fields extend beyond the
edge of the expanding plasma plume to a radius of over 3.5 mm by t=+1.4 ns, a
result not captured in state-of-the-art magneto-hydrodynamics simulations. An
analysis of two mono-energetic proton populations confirms that proton
deflection is dominated by magnetic fields far from the interaction (>2 mm) and
electric fields are insignificant. Comparisons to prior work suggest a new
physics mechanism for the magnetic field generation and transport in
laser-solid interactions.Comment: 9 pages, 8 figure
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The perpendicular electron energy flux driven by magnetic fluctuations in the edge of TEXT-U
A fast bolometer was used for direct measurements of parallel electron energy flux in the edge of TEXT-U. The fluctuating component of the parallel electron energy flux, combined with a measurement of magnetic fluctuations, provides an upper limit to the perpendicular electron flux. This magnetically driven energy flux cannot account for the observed energy flux
Assessment of Resilience in Desalination Infrastructure Using Semi-Markov Models
As the supply of desalinated water becomes significant in many countries, the reliable long-term operation of desalination infrastructure becomes paramount. As it is not realistic to build desalination systems with components that never fail, instead the system should be designed with more resilience. To answer the question how resilient the system should be, we present in this paper a quantitative approach to measure system resilience using semi-Markov models. This approach allows to probabilistically represent the resilience of a desalination system, considering the functional or failed states of its components, as well as the probability of failure and repair rates. As the desalination plants are connected with the end-user through water transportation and distribution networks, this approach also enables an evaluation of various network configurations and resilience strategies. A case study addressing a segment of the water system in Saudi Arabia is given with the results, benefits, and limitations of the technique discussed.Center for Complex Engineering Systems at MIT and KACSTUnited States. National Aeronautics and Space Administration (Space Technology Research Fellowship, grant number NNX14AM42H
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