688 research outputs found
On the measurement of the proton-air cross section using cosmic ray data
Cosmic ray data may allow the determination of the proton-air cross section
at ultra-high energy. For example, the distribution of the first interaction
point in air showers reflects the particle production cross section. As it is
not possible to observe the point of the first interaction of a
cosmic ray primary particle directly, other air shower observables must be
linked to . This introduces an inherent dependence of the derived
cross section on the general understanding and modeling of air showers and,
therfore, on the hadronic interaction model used for the Monte Carlo
simulation. We quantify the uncertainties arising from the model dependence by
varying some characteristic features of high-energy hadron production.Comment: Conference proceedings for the Blois07/EDS07 (12th International
Conference on Elastic and Diffractive Scattering) Workshop DESY Hambur
Quantum Spin Tomography in Ferromagnet-Normal Conductors
We present a theory for a complete reconstruction of non-local spin
correlations in ferromagnet-normal conductors. This quantum spin tomography is
based on cross correlation measurements of electric currents into ferromagnetic
terminals with controllable magnetization directions. For normal injectors,
non-local spin correlations are universal and strong. The correlations are
suppressed by spin-flip scattering and, for ferromagnetic injectors, by
increasing injector polarization.Comment: 4+ page
From mirco-mechanical properties to tribological performance
Abrasive contacts are still too complex to allow reliable predictions of part performance. There is not a single material model with satisfying generality, yet. However, it should be a combination of the contact body’s relative elastic and plastic properties as well as the loading condition.1 In industry carbide- and boride-reinforced, metal matrix composites are often cladded on a base part with welding processes to counter abrasive wear. These composites generally pose structural features at a multitude of length scales. A millimeter thick coating is reinforced with carbides of 100 µm diameter. Precipitates of 1 to 10 µm decorate the matrix and during the major solidification, a metal-stable carbide-metal eutectic forms with domains widths of 1 µm and 100 – 200 nm lamella spacing.
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