3,896 research outputs found
Feasibility of a 30-meter space based laser transmitter
A study was made of the application of large expandable mirror structures in future space missions to establish the feasibility and define the potential of high power laser systems for such applications as propulsion and power transmission. Application of these concepts requires a 30-meter diameter, diffraction limited mirror for transmission of the laser energy. Three concepts for the transmitter are presented. These concepts include consideration of continuous as well as segmented mirror surfaces and the major stow-deployment categories of inflatable, variable geometry and assembled-in-space structures. The mirror surface for each concept would be actively monitored and controlled to maintain diffraction limited performance at 10.6 microns during operation. The proposed mirror configurations are based on existing aerospace state-of-the-art technology. The assembled-in-space concept appears to be the most feasible, at this time
Subroutine allows easy computation in extended precision arithmetic
Subroutine called NPREC allows relatively simple computation of very large numbers or very small fractions with extreme accuracy. This subroutine handles numbers that consist of 35 binary bits /1 word/ for the exponent and 70 bits /2 words/ for the fraction
Study of color center formation in white powder compounds
White powder compounds of metal oxides for thermal protective coating of spacecraf
Learning Design: reflections on a snapshot of the current landscape
The mounting wealth of open and readily available information and the swift evolution of social, mobile and creative technologies warrant a re-conceptualisation of the role of educators: from providers of knowledge to designers of learning. This need is being addressed by a growing trend of research in Learning Design. Responding to this trend, the Art and Science of Learning Design workshop brought together leading voices in the field and provided a forum for discussing its key issues. It focused on three thematic axes: practices and methods, tools and resources, and theoretical frameworks. This paper reviews some definitions of Learning Design and then summarises the main contributions to the workshop. Drawing upon these, we identify three key challenges for Learning Design that suggest directions for future research
Quasiparticle Resonances in the BCS Approach
We present a simple method for calculating the energies and the widths of
quasiparticle resonant states. The method is based on BCS equations solved in
the Berggren representation. In this representation the quasiparticle
resonances are associated to the Gamow states of the mean field. The method is
illustrated for the case of neutron-rich nuclei O and Ni. It
is shown that the contribution of the continuum coupling to the pairing
correlations is small and largely dominated by a few resonant states close to
the continuum threshold.Comment: 14 pages, 2 figure
Drell-Yan Production at NNLL'+NNLO Matched to Parton Showers
We present results for Drell-Yan production from the GENEVA Monte-Carlo
framework. We combine the fully-differential NNLO calculation with higher-order
resummation in the 0-jettiness resolution variable. The resulting parton-level
events are further combined with parton showering and hadronization provided by
PYTHIA8. The 0-jettiness resummation is carried out to NNLL', which
consistently incorporates all singular virtual and real NNLO corrections. It
thus provides a natural perturbative connection between the NNLO calculation
and the parton shower regime, including a systematic assessment of perturbative
uncertainties. In this way, inclusive observables are correct to NNLO, up to
small power corrections in the resolution cutoff. Furthermore, the perturbative
accuracy of 0-jet-like resummation variables is significantly improved beyond
the parton shower approximation. We provide comparisons with LHC measurements
of Drell-Yan production at 7 TeV from ATLAS, CMS, and LHCb. As already observed
in collisions, for resummation-sensitive observables, the agreement
with data is noticeably improved by using a lower value of .Comment: 26 pages, 20 figure
Timing performance of 30-nm-wide superconducting nanowire avalanche photodetectors
We investigated the timing jitter of superconducting nanowire avalanche
photodetectors (SNAPs, also referred to as cascade switching superconducting
single photon detectors) based on 30-nm-wide nanowires. At bias currents (IB)
near the switching current, SNAPs showed sub 35 ps FWHM Gaussian jitter similar
to standard 100 nm wide superconducting nanowire single-photon detectors. At
lower values of IB, the instrument response function (IRF) of the detectors
became wider, more asymmetric, and shifted to longer time delays. We could
reproduce the experimentally observed IRF time-shift in simulations based on an
electrothermal model, and explain the effect with a simple physical picture
Electric circuit networks equivalent to chaotic quantum billiards
We formulate two types of electric RLC resonance network equivalent to
quantum billiards. In the network of inductors grounded by capacitors squared
resonant frequencies are eigenvalues of the quantum billiard. In the network of
capacitors grounded by inductors squared resonant frequencies are given by
inverse eigen values of the billiard. In both cases local voltages play role of
the wave function of the quantum billiard. However as different from quantum
billiards there is a heat power because of resistance of the inductors. In the
equivalent chaotic billiards we derive the distribution of the heat power which
well describes numerical statistics.Comment: 9 pages, 7 figure
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