2,527 research outputs found
Structural Transparency – A New Wood Plastic Composite Girder
Transparency is one of the significant features of modern architecture. By utilisingtransparent materials the feeling of lightness can be conveyed. This paper shows thepossibility of employing transparent plastic as a load-bearing element. In order tobe able to use a new material as part of the building structure it is essential to knowits mechanical behaviour under various conditions like different temperatures,environmental impacts or the load duration. Proposals for the design of structuralelements that consist of these materials are still rare up to now since plastics arestill fairly new to the building industry. By combining transparent withconventional building materials it is possible to merge transparency and strength ina girder that comprises a combination of transparent thermoplastics and wood
On statistically stationary homogeneous shear turbulence
A statistically stationary turbulence with a mean shear gradient is realized
in a flow driven by suitable body forces. The flow domain is periodic in
downstream and spanwise directions and bounded by stress free surfaces in the
normal direction. Except for small layers near the surfaces the flow is
homogeneous. The fluctuations in turbulent energy are less violent than in the
simulations using remeshing, but the anisotropy on small scales as measured by
the skewness of derivatives is similar and decays weakly with increasing
Reynolds number.Comment: 4 pages, 5 figures (Figs. 3 and 4 as external JPG-Files
High-temperature liquid-mercury cathodes for ion thrusters Quarterly progress report, 1 Dec. 1966 - 28 Feb. 1967
High temperature liquid mercury cathodes for ion thrusters - thermal design analysi
Truncated-Unity Parquet Equations: Application to the Repulsive Hubbard Model
The parquet equations are a self-consistent set of equations for the
effective two-particle vertex of an interacting many-fermion system. The
application of these equations to bulk models is, however, demanding due to the
complex emergent momentum and frequency structure of the vertex. Here, we show
how a channel-decomposition by means of truncated unities, which was developed
in the context of the functional renormalization group to efficiently treat the
momentum dependence, can be transferred to the parquet equations. This leads to
a significantly reduced numerical effort scaling only linearly with the number
of discrete momenta. We apply this technique to the half-filled repulsive
Hubbard model on the square lattice and present approximate solutions for the
channel-projected vertices and the full reducible vertex.Comment: Consistent with published version in Phys. Rev.
Symmetry Decomposition of Chaotic Dynamics
Discrete symmetries of dynamical flows give rise to relations between
periodic orbits, reduce the dynamics to a fundamental domain, and lead to
factorizations of zeta functions. These factorizations in turn reduce the labor
and improve the convergence of cycle expansions for classical and quantum
spectra associated with the flow. In this paper the general formalism is
developed, with the -disk pinball model used as a concrete example and a
series of physically interesting cases worked out in detail.Comment: CYCLER Paper 93mar01
Anomalous power law of quantum reversibility for classically regular dynamics
The Loschmidt Echo M(t) (defined as the squared overlap of wave packets
evolving with two slightly different Hamiltonians) is a measure of quantum
reversibility. We investigate its behavior for classically quasi-integrable
systems. A dominant regime emerges where M(t) ~ t^{-alpha} with alpha=3d/2
depending solely on the dimension d of the system. This power law decay is
faster than the result ~ t^{-d} for the decay of classical phase space
densities
Liquid mercury cathode electron bombardment ion thrusters Summary report, 1 Aug. 1964 - 31 Oct. 1966
Life tests of liquid mercury cathodes for electron bombardment ion thruster
A Trace Formula for Products of Diagonal Matrix Elements in Chaotic Systems
We derive a trace formula for , where
is the diagonal matrix element of the operator in the energy basis
of a chaotic system. The result takes the form of a smooth term plus
periodic-orbit corrections; each orbit is weighted by the usual Gutzwiller
factor times , where is the average of the classical
observable along the periodic orbit . This structure for the orbit
corrections was previously proposed by Main and Wunner (chao-dyn/9904040) on
the basis of numerical evidence.Comment: 8 pages; analysis made more rigorous in the revised versio
Semiclassical Quantization by Pade Approximant to Periodic Orbit Sums
Periodic orbit quantization requires an analytic continuation of
non-convergent semiclassical trace formulae. We propose a method for
semiclassical quantization based upon the Pade approximant to the periodic
orbit sums. The Pade approximant allows the re-summation of the typically
exponentially divergent periodic orbit terms. The technique does not depend on
the existence of a symbolic dynamics and can be applied to both bound and open
systems. Numerical results are presented for two different systems with chaotic
and regular classical dynamics, viz. the three-disk scattering system and the
circle billiard.Comment: 7 pages, 3 figures, submitted to Europhys. Let
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