7,287 research outputs found
Introduction: A Fragmented Stew of Themes and Issues
The essays collected in this special issue of the journal grew out of the Rethinking the Past: Experimental Histories in the Arts conference that took place at the University of Technology, Sydney in July 2006.1 Drawing together scholars from a broad range of fields, the aim of the conference was to rethink the task of historiography via an exploration of experimental representations of, and/or engagements with, the past in fields as diverse as film, photography, literature, theatre, fictocritical writing, video, and new media. Scholars at UTS have, for many years, experimented with alternative, unconventional ways of both writingand engaging withthe past and, in 1996 (in this journals previous incarnation as The UTS Review), Stephen Muecke and Meaghan Morris devoted a special issue to the topic entitled `Is An Experimental History Possible
A method for developing design diagrams for ceramic and glass materials using fatigue data
The service lifetime of glass and ceramic materials can be expressed as a plot of time-to-failure versus applied stress whose plot is parametric in percent probability of failure. This type of plot is called a design diagram. Confidence interval estimates for such plots depend on the type of test that is used to generate the data, on assumptions made concerning the statistical distribution of the test results, and on the type of analysis used. This report outlines the development of design diagrams for glass and ceramic materials in engineering terms using static or dynamic fatigue tests, assuming either no particular statistical distribution of test results or a Weibull distribution and using either median value or homologous ratio analysis of the test results
Hard X‐ray polarimetry of solar flares with BATSE
We describe a technique for measuring the polarization of hard X‐rays from solar flares based on the angular distribution of that portion of the flux which is scattered off the top of the Earth’s atmosphere. The scattering cross section depends not only on the scatter angle itself, but on the orientation of the scatter angle with respect to the incident polarization vector. Consequently, the distribution of the observed albedo flux will depend on the direction and the polarization properties (i.e., the level of polarization and polarization angle) of the source. Since the albedo component can represent a relatively large fraction (up to 40%) of the direct source flux, there will generally be sufficient signal for making such a measurement. The sensitivity of this approach is therefore dictated by the effective area and the ability of a detector system to ‘image’ the albedo flux. The 4π coverage of the BATSE detectors on the Compton Gamma‐RayObservatory provides an opportunity to measure both the direct and the albedo flux from a given solar flare event. Although the BATSE design (with its large field‐of‐view for each detector) is not optimized for albedo polarimetry, we have nonetheless investigated the feasibility of this technique using BATSE data
The design of a gamma‐ray burst polarimeter
The study of the polarization properties of the gamma‐ray bursts is the one remaining unexplored avenue of research which may help to answer some of the fundamental problems regarding the nature of these mysterious objects. We have designed an instrument to measure linear polarization in cosmic gamma‐ray bursts at energies ≳50 keV. Here we describe the design of this instrument, which we call the Gamma‐ray Burst Polarimeter Experiment (GRAPE)
Specific heat of BaKFeAs, and a new method for identifying the electron contribution: two electron bands with different energy gaps in the superconducting state
We report measurements of the specific heat of
BaKFeAs, an Fe-pnictide superconductor with
= 36.9 K, for which there are suggestions of an unusual electron pairing
mechanism. We use a new method of analysis of the data to derive the parameters
characteristic of the electron contribution. It is based on comparisons of
-model expressions for the electron contribution with the total
measured specific heat, which give the electron contribution directly. It
obviates the need in the conventional analyses for an independent, necessarily
approximate, determination of the lattice contribution, which is subtracted
from the total specific heat to obtain the electron contribution. It eliminates
the uncertainties and errors in the electron contribution that follow from the
approximations in the determination of the lattice contribution. Our values of
the parameters characteristic of the electron contribution differ significantly
from those obtained in conventional analyses of specific-heat data for five
similar hole-doped BaFeAs superconductors, which also differ
significantly among themselves. They show that the electron density of states
is comprised of contributions from two electron bands with
superconducting-state energy gaps that differ by a factor 3.8, with 77
coming from the band with the larger gap. The variation of the specific heat
with magnetic field is consistent with extended -wave pairing, one of the
theoretical predictions. The relation between the densities of states and the
energy gaps in the two bands is not consistent with a theoretical model based
on interband interactions alone. Comparison of the normal-state density of
states with band-structure calculations shows an extraordinarily large
effective mass enhancement, for which there is no precedent in similar
materials and no theoretical explanation.Comment: 30 pages, 7 figures, submitte
Using BATSE to measure gamma-ray burst polarization
We describe a technique for measuring the polarization of hard x-rays from γ-ray bursts based on the angular distribution of that portion of the flux which is scattered off the top of the Earth’s atmosphere. The scattering cross section depends not only on the scatter angle itself, but on the orientation of the scatter angle with respect to the incident polarization vector. Consequently, the distribution of the observed albedo flux will depend on the direction and the polarization properties (i.e., the level of polarization and polarization angle) of the source. Although the BATSE design (with its large field-of-view for each detector) is not optimized for albedo polarimetry, we have nonetheless investigated the feasibility of this technique using BATSE data
Comment on ``Nonuniversal Exponents in Interface Growth''
Recently, Newman and Swift[T. J. Newman and M. R. Swift, Phys. Rev. Lett.
{\bf 79}, 2261 (1997)] made an interesting suggestion that the strong-coupling
exponents of the Kardar-Parisi-Zhang (KPZ) equation may not be universal, but
rather depend on the precise form of the noise distribution. We show here that
the decrease of surface roughness exponents they observed can be attributed to
a percolative effect
Simulation Based Evaluation of Integrated Adaptive Control and Flight Planning Technologies
The objective of this work is to leverage NASA resources to enable effective evaluation of resilient aircraft technologies through simulation. This includes examining strengths and weaknesses of adaptive controllers, emergency flight planning algorithms, and flight envelope determination algorithms both individually and as an integrated package
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