2,108 research outputs found
Regularization of the Roy Equations with a Smooth Cut-Off
The Roy equations for ÏÏ scattering are combined with unitarity to give a nonlinear system of equations for the determination of the lowâenergy amplitudes. A Hölder continuous interpolation between the input highâenergy absorptive parts and the output lowâenergy absorptive parts is implemented; and the resultant singular equations are regularized by means of an effective inelastic N/D method. If the scattering lengths, the CDD parameters, and the highâenergy absorptive parts satisfy certain constraints, then there exists a locally unique solution of the system
Multimodal Pilot Behavior in Multi-Axis Tracking Tasks with Time-Varying Motion Cueing Gains
In a large number of motion-base simulators, adaptive motion filters are utilized to maximize the use of the available motion envelope of the motion system. However, not much is known about how the time-varying characteristics of such adaptive filters affect pilots when performing manual aircraft control. This paper presents the results of a study investigating the effects of time-varying motion filter gains on pilot control behavior and performance. An experiment was performed in a motion-base simulator where participants performed a simultaneous roll and pitch tracking task, while the roll and/or pitch motion filter gains changed over time. Results indicate that performance increases over time with increasing motion gains. This increase is a result of a time-varying adaptation of pilots' equalization dynamics, characterized by increased visual and motion response gains and decreased visual lead time constants. Opposite trends are found for decreasing motion filter gains. Even though the trends in both controlled axes are found to be largely the same, effects are less significant in roll. In addition, results indicate minor cross-coupling effects between pitch and roll, where a cueing variation in one axis affects the behavior adopted in the other axis
Creating evidence towards making statements about classroom activity
In this paper I examine some of the issues underlying the creation of data in classroom based research. In particular, I focus on the status of evidence offered by a researcher describing childrenâs activity in order to demonstrate how the researcherâs interest necessarily conditions the various stages of any enquiry. I show how evidence is created through a process of selection and interpretation consequential to the researcher making assumptions about the situation he or she observes. I also show how the descriptions themselves, as offered by the researcher, become a material part of the situation being described. In the first section I consider the issues arising in the identifying and gaining access to lessons. This is followed by a discussion about the generation of data. Finally, I examine some of the difficulties to be faced in interpreting such data
VIS: the visible imager for Euclid
Euclid-VIS is a large format visible imager for the ESA Euclid space mission
in their Cosmic Vision program, scheduled for launch in 2019. Together with the
near infrared imaging within the NISP instrument it forms the basis of the weak
lensing measurements of Euclid. VIS will image in a single r+i+z band from
550-900 nm over a field of view of ~0.5 deg2. By combining 4 exposures with a
total of 2240 sec, VIS will reach to V=24.5 (10{\sigma}) for sources with
extent ~0.3 arcsec. The image sampling is 0.1 arcsec. VIS will provide deep
imaging with a tightly controlled and stable point spread function (PSF) over a
wide survey area of 15000 deg2 to measure the cosmic shear from nearly 1.5
billion galaxies to high levels of accuracy, from which the cosmological
parameters will be measured. In addition, VIS will also provide a legacy
imaging dataset with an unprecedented combination of spatial resolution, depth
and area covering most of the extra-Galactic sky. Here we will present the
results of the study carried out by the Euclid Consortium during the Euclid
Definition phase.Comment: 10 pages, 6 figure
Electron Multiplying CCDs
Electron multiplying CCD (EMCCD) technology has found important initial applications in low light surveillance and photon starved scientific instrumentation. This paper provides a description of the technology and discusses the attributes of the EMCCD which may make it useful for other detectors, particularly those which are photon starve
Net neutrality discourses: comparing advocacy and regulatory arguments in the United States and the United Kingdom
Telecommunications policy issues rarely make news, much less mobilize thousands of people. Yet this has been occurring in the United States around efforts to introduce "Net neutrality" regulation. A similar grassroots mobilization has not developed in the United Kingdom or elsewhere in Europe. We develop a comparative analysis of U.S. and UK Net neutrality debates with an eye toward identifying the arguments for and against regulation, how those arguments differ between the countries, and what the implications of those differences are for the Internet. Drawing on mass media, advocacy, and regulatory discourses, we find that local regulatory precedents as well as cultural factors contribute to both agenda setting and framing of Net neutrality. The differences between national discourses provide a way to understand both the structural differences between regulatory cultures and the substantive differences between policy interpretations, both of which must be reconciled for the Internet to continue to thrive as a global medium
Net neutrality discourses: comparing advocacy and regulatory arguments in the United States and the United Kingdom
Telecommunications policy issues rarely make news, much less mobilize thousands of people. Yet this has been occurring in the United States around efforts to introduce "Net neutrality" regulation. A similar grassroots mobilization has not developed in the United Kingdom or elsewhere in Europe. We develop a comparative analysis of U.S. and UK Net neutrality debates with an eye toward identifying the arguments for and against regulation, how those arguments differ between the countries, and what the implications of those differences are for the Internet. Drawing on mass media, advocacy, and regulatory discourses, we find that local regulatory precedents as well as cultural factors contribute to both agenda setting and framing of Net neutrality. The differences between national discourses provide a way to understand both the structural differences between regulatory cultures and the substantive differences between policy interpretations, both of which must be reconciled for the Internet to continue to thrive as a global medium
Mixed Weyl Symbol Calculus and Spectral Line Shape Theory
A new and computationally viable full quantum version of line shape theory is
obtained in terms of a mixed Weyl symbol calculus. The basic ingredient in the
collision--broadened line shape theory is the time dependent dipole
autocorrelation function of the radiator-perturber system. The observed
spectral intensity is the Fourier transform of this correlation function. A
modified form of the Wigner--Weyl isomorphism between quantum operators and
phase space functions (Weyl symbols) is introduced in order to describe the
quantum structure of this system. This modification uses a partial Wigner
transform in which the radiator-perturber relative motion degrees of freedom
are transformed into a phase space dependence, while operators associated with
the internal molecular degrees of freedom are kept in their original Hilbert
space form. The result of this partial Wigner transform is called a mixed Weyl
symbol. The star product, Moyal bracket and asymptotic expansions native to the
mixed Weyl symbol calculus are determined. The correlation function is
represented as the phase space integral of the product of two mixed symbols:
one corresponding to the initial configuration of the system, the other being
its time evolving dynamical value. There are, in this approach, two
semiclassical expansions -- one associated with the perturber scattering
process, the other with the mixed symbol star product. These approximations are
used in combination to obtain representations of the autocorrelation that are
sufficiently simple to allow numerical calculation. The leading O(\hbar^0)
approximation recovers the standard classical path approximation for line
shapes. The higher order O(\hbar^1) corrections arise from the noncommutative
nature of the star product.Comment: 26 pages, LaTeX 2.09, 1 eps figure, submitted to 'J. Phys. B.
Gut microbiota-derived propionate reduces cancer cell proliferation in the liver
Peer reviewedPublisher PD
The Interface Region Imaging Spectrograph (IRIS)
The Interface Region Imaging Spectrograph (IRIS) small explorer spacecraft
provides simultaneous spectra and images of the photosphere, chromosphere,
transition region, and corona with 0.33-0.4 arcsec spatial resolution, 2 s
temporal resolution and 1 km/s velocity resolution over a field-of-view of up
to 175 arcsec x 175 arcsec. IRIS was launched into a Sun-synchronous orbit on
27 June 2013 using a Pegasus-XL rocket and consists of a 19-cm UV telescope
that feeds a slit-based dual-bandpass imaging spectrograph. IRIS obtains
spectra in passbands from 1332-1358, 1389-1407 and 2783-2834 Angstrom including
bright spectral lines formed in the chromosphere (Mg II h 2803 Angstrom and Mg
II k 2796 Angstrom) and transition region (C II 1334/1335 Angstrom and Si IV
1394/1403 Angstrom). Slit-jaw images in four different passbands (C II 1330, Si
IV 1400, Mg II k 2796 and Mg II wing 2830 Angstrom) can be taken simultaneously
with spectral rasters that sample regions up to 130 arcsec x 175 arcsec at a
variety of spatial samplings (from 0.33 arcsec and up). IRIS is sensitive to
emission from plasma at temperatures between 5000 K and 10 MK and will advance
our understanding of the flow of mass and energy through an interface region,
formed by the chromosphere and transition region, between the photosphere and
corona. This highly structured and dynamic region not only acts as the conduit
of all mass and energy feeding into the corona and solar wind, it also requires
an order of magnitude more energy to heat than the corona and solar wind
combined. The IRIS investigation includes a strong numerical modeling component
based on advanced radiative-MHD codes to facilitate interpretation of
observations of this complex region. Approximately eight Gbytes of data (after
compression) are acquired by IRIS each day and made available for unrestricted
use within a few days of the observation.Comment: 53 pages, 15 figure
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