14,091 research outputs found
Acoustic metafluids made from three acoustic fluids
Significant reduction in target strength and radiation signature can be
achieved by surrounding an object with multiple concentric layers comprised of
three acoustic fluids. The idea is to make a finely layered shell with the
thickness of each layer defined by a unique transformation rule. The shell has
the effect of steering incident acoustic energy around the structure, and
conversely, reducing the radiation strength. The overall effectiveness and the
precise form of the layering depends upon the densities and compressibilities
of the three fluids. Nearly optimal results are obtained if one fluid has
density equal to the background fluid, while the other two densities are much
greater and much less than the background values. Optimal choices for the
compressibilities are also found. Simulations in 2D and 3D illustrate
effectiveness of the three fluid shell. The limited range of acoustic
metafluids that are possible using only two fluid constituents is also
discussed.Comment: 12 pages, 11 figure
Francoprovençal: Documenting contact varieties in Europe and North America
This special issue of the International Journal of the Sociology of Language brings together articles from an international set of authors that situate the family of Francoprovençal (FP) dialects in terms of formal structures, contexts of contact, practice and policy. FP has been the subject of little scholarly attention. This dearth of research is largely the result of its ambiguous status. Ever since it was introduced by Ascoli (1878 [1874]), the notion of FP has been questioned. There has long been disagreement over its linguistic borders and the linguistic criteria used for demarcation. As late as 2007, scholars have asked: le francoprovençal existe-t-il ? [does FP exist?] (Tuaillon 2007: 9).
This is the first collection describing FP across its entire geographical distribution and assembling varied sociolinguistic approaches. Previous collections include a dialectology volume focusing on the status and structure of FP (Marzys (1971); a posthumous volume focusing on Lyonnais (Gardette 1983); and Fréchet (2009), consisting of descriptions of both FP and Occitan. These works – though important contributions to FP linguistics – provide little quantitative substance. Moreover, little work on FP has been produced in English, which limits access to researchers worldwide who might be interested in the sociolinguistic context of FP or comparison with other minority-language contexts. To begin to fill this void, we introduce FP, then outline the key themes of this issue and the range of sociolinguistic traditions covered
Spontaneous Breaking of Chiral Symmetry as a Consequence of Confinement
We show that at the leading order in the large- expansion a lattice QCD
motivated linear rising confinement potential at large distances leads to a
non-local four-quark interaction that realizes spontaneous breaking of chiral
symmetry (SBCS) in the same way the Nambu-Jona-Lasinio model does. The
dynamical quark mass , which represents the solution of the gap-equation, is
proportional to the square root of the string tension and takes the
form at the leading order in the large- expansion
with GeV. The Nambu-Jona-Lasinio phenomenological constant
, which is responsible for SBCS, is expressed in terms of the string
tension and the confinement radius.Comment: 10 pages, 0 figures, latex, IK-TUW-Preprint 930540
Investigation of the composition of the Luna 16 lunar sample
The concentrations of aluminum, manganese, sodium, chromium, iron, cobalt, and 12 rare earth elements were determined by neutron activation analysis using slow neutrons. Oxygen and silicon were determined using a fast neutron generator. Mossbauer spectroscopy was used to investigate iron compounds in Luna 16 regolith samples from the upper part of the core
Ordering variable for parton showers
The parton splittings in a parton shower are ordered according to an ordering
variable, for example the transverse momentum of the daughter partons relative
to the direction of the mother, the virtuality of the splitting, or the angle
between the daughter partons. We analyze the choice of the ordering variable
and conclude that one particular choice has the advantage of factoring softer
splittings from harder splittings graph by graph in a physical gauge.Comment: 28 pages, 5 figure
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