7,774 research outputs found
Comment on "Correlation between Compact Radio Lout Quasars and Ultrahigh Energy Cosmic Rays"
In a recent paper, Farrar and Biermann argue that there is a strong
correlation between the direction of the five highest-energy cosmic-ray events
and compact, radio-loud quasars. This Comment shows that this analysis contains
several inconsistencies and errors so that the significance of any such
correlation is certainly greatly overestimated and perhaps nonexistent.Comment: 2 pages, REVTE
The Reuss Bound of the Strain Rate Potential of Viscoplastic FCC Polycrystals
The Reuss bound of the strain rate potential of face-centered cubic polycrystals without texture is numerically determined for all types of stress states. The numerical results indicate a strong dependence of the potential on the determinant of the stress deviator. This dependence implies that the viscoplastic f low is not proportional to the stress deviator. A simple analytical expression is found, which reproduces the numerical f indings over a wide range of strain rate sensitivities
Crystallographic Texture Induced Anisotropy in Copper: An Approach Based on a Tensorial Fourier Expansion of the CODF
We consider a tensorial Fourier expansion of the crystallite orientation distribution
function for aggregates of cubic crystals. The coefficient of rank four is determined explicitly.
It is shown that this coefficient governs the anisotropic bounds of the linear elastic behavior of
polycrystals. Recently, a phenomenological model has been proposed [4, 6], that describes the
evolving elastic anisotropy in copper. The model also reproduces the cyclic Swift effect, which is
due to a texture induced plastic anisotropy [7]. In the model the anisotropic part of the effective
elastic stiffness tensor is used to define a texture dependent quadratic yield function. The present
paper gives a new interpretation of the aforementioned model in terms of an approximation of the
crystallographic texture by means of a 4th-order coefficient of the tensorial Fourier expansion of
the crystallite orientation distribution function
The Discourse of Management and the Management of Discourse
Discourse is a pervasive tool of management; one might even say that discourse is what managers do. A widespread assumption among managers is that discourse is not only a pervasive tool, but an effective one for precise communication of information, for making decisions, and for enlisting action, essentially a transmission tool. This paper maintains that the transmission view is a limited conception of language use, one which leads to a faulty conception of what managers do. It ignores the need for an ethics of communication and misjudges the creative aspects of language use. Management discourse is a far more complex and fluid phenomenon, one requiring not just effective use, but management itself. In other words consideration of the discourse of management leads us to the need for the management of discourse.
Oxygen-related traps in pentacene thin films: Energetic position and implications for transistor performance
We studied the influence of oxygen on the electronic trap states in a
pentacene thin film. This was done by carrying out gated four-terminal
measurements on thin-film transistors as a function of temperature and without
ever exposing the samples to ambient air. Photooxidation of pentacene is shown
to lead to a peak of trap states centered at 0.28 eV from the mobility edge,
with trap densities of the order of 10(18) cm(-3). These trap states need to be
occupied at first and cause a reduction in the number of free carriers, i.e. a
consistent shift of the density of free holes as a function of gate voltage.
Moreover, the exposure to oxygen reduces the mobility of the charge carriers
above the mobility edge. We correlate the change of these transport parameters
with the change of the essential device parameters, i.e. subthreshold
performance and effective field-effect mobility. This study supports the
assumption of a mobility edge for charge transport, and contributes to a
detailed understanding of an important degradation mechanism of organic
field-effect transistors. Deep traps in an organic field-effect transistor
reduce the effective field-effect mobility by reducing the number of free
carriers and their mobility above the mobility edge.Comment: 13 pages, 14 figures, to be published in Phys. Rev.
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