8,593 research outputs found
Equivalent drawbead model in finite element simulations
In 3D simulations of the deep drawing process the drawbead geometries are seldom included. Therefore equivalent drawbeads are used. In order to investigate the drawbead behaviour a 2D plane strain finite element model was used. For verification of this model experiments were performed. The analyses showed that not only the restraining force should be applied but also the strain changes. The effects of the restraining force and the strain change were implemented in an equivalent drawbead. The effect of using the equivalent drawbead is demonstrated with a few example
Strategic Buyers, Horizontal Mergers and Synergies: An Experimental Investigation*
This paper reports an experiment designed to evaluate interrelationships between strategic buyers, market power and merger-induced synergies. The experiment consists of 40 posted-offer quadropolies. Treatments include the use of simulated or human buyers, seller consolidations and merger-induced fixed cost and unit cost synergies. In the simulated-buyer markets we observe behavior generally consistent with comparative static predictions: prices rise post-merger, and unit (but not fixed) cost synergies may exert some price-moderating effect. The addition of powerful buyers changes results markedly. Although prices are lower in the human buyer markets, outcomes are more variable and predicted comparative static effects are no longer observed.
The Effects of Spatio-temporal Resolution on Deduced Spicule Properties
Spicules have been observed on the sun for more than a century, typically in
chromospheric lines such as H-alpha and Ca II H. Recent work has shown that
so-called 'type II' spicules may have a role in providing mass to the corona
and the solar wind. In chromospheric filtergrams these spicules are not seen to
fall back down, and they are shorter-lived and more dynamic than the spicules
that have been classically reported in ground-based observations. Observations
of type II spicules with Hinode show fundamentally different properties from
what was previously measured. In earlier work we showed that these dynamic type
II spicules are the most common type, a view that was not properly identified
by early observations.The aim of this work is to investigate the effects of
spatio-temporal resolution in the classical spicule measurements. Making use of
Hinode data degraded to match the observing conditions of older ground-based
studies, we measure the properties of spicules with a semi-automated algorithm.
These results are then compared to measurements using the original Hinode data.
We find that degrading the data has a significant effect on the measured
properties of spicules. Most importantly, the results from the degraded data
agree well with older studies (e.g. mean spicule duration more than 5 minutes,
and upward apparent velocities of about 25 km/s). These results illustrate how
the combination of spicule superposition, low spatial resolution and cadence
affect the measured properties of spicules, and that previous measurements can
be misleading.Comment: Accepted for publication in ApJ. 5 pages, 3 figures. Movies of
figures 1 and 3 available via Data Conservanc
Spin current induced magnetization oscillations in a paramagnetic disc
When electron spins are injected uniformly into a paramagnetic disc, they can
precess along the demagnetizing field induced by the resulting magnetic moment.
Normally this precession damps out by virtue of the spin relaxation which is
present in paramagnetic materials. We propose a new mechanism to excite a
steady-state form of this dynamics by injecting a constant spin current into
this paramagnetic disc. We show that the rotating magnetic field generated by
the eddy currents provide a torque which makes this possible. Unlike the
ferromagnetic equivalent, the spin-torque-oscillator, the oscillation frequency
is fixed and determined by the dimensions and intrinsic parameters of the
paramagnet. The system possesses an intrinsic threshold for spin injection
which needs to be overcome before steady-state precession is possible. The
additional application of a magnetic field lowers this threshold. We discuss
the feasibility of this effect in modern materials. Transient analysis using
pump-probe techniques should give insight in the physical processes which
accompany this effect
The Generalised Liar Paradox: A Quantum Model and Interpretation
The formalism of abstracted quantum mechanics is applied in a model of the
generalized Liar Paradox. Here, the Liar Paradox, a consistently testable
configuration of logical truth properties, is considered a dynamic conceptual
entity in the cognitive sphere. Basically, the intrinsic contextuality of the
truth-value of the Liar Paradox is appropriately covered by the abstracted
quantum mechanical approach. The formal details of the model are explicited
here for the generalized case. We prove the possibility of constructing a
quantum model of the m-sentence generalizations of the Liar Paradox. This
includes (i) the truth-falsehood state of the m-Liar Paradox can be represented
by an embedded 2m-dimensional quantum vector in a (2m)^m dimensional complex
Hilbert space, with cognitive interactions corresponding to projections, (ii)
the construction of a continuous 'time' dynamics is possible: typical truth and
falsehood value oscillations are described by Schrodinger evolution, (iii)
Kirchoff and von Neumann axioms are satisfied by introduction of 'truth-value
by inference' projectors, (iv) time invariance of unmeasured state.Comment: 13 pages, to be published in Foundations of Scienc
The Formation of IRIS diagnostics. IV. The Mg II triplet lines as a new diagnostic for lower chromospheric heating
A triplet of subordinate lines of Mg II exists in the region around the h&k
lines. In solar spectra these lines are seen mostly in absorption, but in some
cases can become emission lines. The aim of this work is to study the formation
of this triplet, and investigate any diagnostic value they can bring. Using 3D
radiative magnetohydrodynamic simulations of quiet Sun and flaring flux
emergence, we synthesize spectra and investigate how spectral features respond
to the underlying atmosphere. We find that emission in the lines is rare and is
typically caused by a steep temperature increase in the lower chromosphere
(above 1500 K, with electron densities above 10 m). In both
simulations the lines are sensitive to temperature increases taking place at
column masses >= 5e-4 g cm. Additional information can also be inferred
from the peak-to-wing ratio and shape of the line profiles. Using observations
from NASA's Interface Region Imaging Spectrograph we find both absorption and
emission line profiles with similar shapes to the synthetic spectra, which
suggests that these lines represent a useful diagnostic that complements the
MgII h&k lines.Comment: 8 pages, 7 figures. Accepted for publication in Ap
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