18,888 research outputs found
The drag of magnetically suspended wind-tunnel models with nose-cones of various shapes
This article concerns the experimental determination of optimum nose-cones (minimum drag) of a body of revolution at supersonic and hypersonic speeds by means of ONERA magnetic suspension. The study concerns two groups of models, specifically: a group whose nose-cone has a profile in the shape of X(n); the AGARD B group whose nose-cone is plotted in accordance with a given law. The results obtained for the first group are comparable to those calculated with the approximations of Cole and Newton and the experiments carried out by Kubota
No-err typing aids
Device for aligning paper in typewriter to correct one letter or line of type is discussed. Two types of correcting devices are described and illustrations of the devices are provided
Photon Splitting and Pair Conversion in Strong Magnetic Fields
The magnetospheres of neutron stars provide a valuable testing ground for
as-yet unverified theoretical predictions of quantum electrodynamics (QED) in
strong electromagnetic fields. Exhibiting magnetic field strengths well in
excess of a TeraGauss, such compact astrophysical environments permit the
action of exotic mechanisms that are forbidden by symmetries in field-free
regions. Foremost among these processes are single-photon pair creation, where
a photon converts to an electron-positron pair, and magnetic photon splitting,
where a single photon divides into two of lesser energy via the coupling to the
external field. The pair conversion process is exponentially small in weak
fields, and provides the leading order contribution to vacuum polarization. In
contrast, photon splitting possesses no energy threshold and can operate in
kinematic regimes where the lower order pair conversion is energetically
forbidden. This paper outlines some of the key physical aspects of these
processes, and highlights their manifestation in neutron star magnetospheres.
Anticipated observational signatures include profound absorption turnovers in
pulsar spectra at gamma-ray wavelengths. The shapes of these turnovers provide
diagnostics on the possible action of pair creation and the geometrical locale
of the photon emission region. There is real potential for the first
confirmation of strong field QED with the new GLAST mission, to be launched by
NASA in 2008. Suppression of pair creation by photon splitting and its
implications for pulsars is also discussed.Comment: 18 pages, 3 embedded figures, invited review, to appear in Proc.
CASYS '07 Conference "Computing Anticipatory Systems," eds. D. Dubois, et al.
(AIP Conf. Proc., New York, 2008
Guide for a typewriter
The invention relates to accessories for typewriters, and more particularly to an improved guide for use in aligning a sheet of paper preparatory to an application of typed indicia to selected spaces. The device includes an aligning plate pivotally mounted on a line guide having formed therein a plurality of aligned apertures. The plate is so positioned that an aperture is positioned immediately above a target area for a type slug so that a slug will imprint a character in selected spaces
Global Fits of the CKM Matrix
We report upon the present status of global fits to Cabibbo-Kobayashi-Maskawa
matrix.Comment: 3 pages, 3 figures invited talk presented at EPS conference, Aachen
July 17-2
A Euclidean Geometric Invariant of Framed (Un)Knots in Manifolds
We present an invariant of a three-dimensional manifold with a framed knot in
it based on the Reidemeister torsion of an acyclic complex of Euclidean
geometric origin. To show its nontriviality, we calculate the invariant for
some framed (un)knots in lens spaces. Our invariant is related to a
finite-dimensional fermionic topological quantum field theory
Life cycle assessment of Swiss organic farming systems
The impacts of organic and integrated farming systems in Switzerland on the environment have been assessed in a comprehensive study by the life cycle assessment method. This paper reports a comparison of the treatments of the DOC experiment. Organic farming showed clear ecological advantages particularly for eco- and human toxicity, resource use and biodiversity. These ecological advantages only partly apply to nutrient losses and are not always found for single products. Per kg of organic product, higher impacts were often found for global warming potential, ozone formation, eutrophication and acidification compared to integrated production. In the same crop rotation with the same amount of organic fertilisers there were no systematic differences in soil quality of organic compared with integrated production. Further improvement of the environmental performance of organic farming should focus on achieving higher yields of good quality – especially in potatoes and cereals - by using inputs more efficiently and minimising nitrogen losses
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