123,852 research outputs found
Inclusion agglomeration in electrified molten metal: thermodynamic consideration
The effect of electric current on inclusion agglomeration in molten metal has been investigated. It is found that the agglomeration is dependent on the electric current density, distance between inclusions and orientation of electric field. Electric current retards the agglomeration unless two inclusions are aligned along or closely to the current flow streamlines and the distance between inclusions is less than a critical value. The mechanism is also validated in the computation of cluster agglomeration. The numerical results provide a comprehensive indication for the current-induced inclusion removal and current-induced inclusion elongation. When the inclusions are in long-thin shape, the calculation predicts the current-induced microstructure alignment and current-induced microstructure refinement phenomena
Cross-screening in observational studies that test many hypotheses
We discuss observational studies that test many causal hypotheses, either
hypotheses about many outcomes or many treatments. To be credible an
observational study that tests many causal hypotheses must demonstrate that its
conclusions are neither artifacts of multiple testing nor of small biases from
nonrandom treatment assignment. In a sense that needs to be defined carefully,
hidden within a sensitivity analysis for nonrandom assignment is an enormous
correction for multiple testing: in the absence of bias, it is extremely
improbable that multiple testing alone would create an association insensitive
to moderate biases. We propose a new strategy called "cross-screening",
different from but motivated by recent work of Bogomolov and Heller on
replicability. Cross-screening splits the data in half at random, uses the
first half to plan a study carried out on the second half, then uses the second
half to plan a study carried out on the first half, and reports the more
favorable conclusions of the two studies correcting using the Bonferroni
inequality for having done two studies. If the two studies happen to concur,
then they achieve Bogomolov-Heller replicability; however, importantly,
replicability is not required for strong control of the family-wise error rate,
and either study alone suffices for firm conclusions. In randomized studies
with a few hypotheses, cross-split screening is not an attractive method when
compared with conventional methods of multiplicity control, but it can become
attractive when hundreds or thousands of hypotheses are subjected to
sensitivity analyses in an observational study. We illustrate the technique by
comparing 46 biomarkers in individuals who consume large quantities of fish
versus little or no fish.Comment: 33 pages, 2 figures, 5 table
Lithium-ion battery thermal-electrochemical model-based state estimation using orthogonal collocation and a modified extended Kalman filter
This paper investigates the state estimation of a high-fidelity spatially
resolved thermal- electrochemical lithium-ion battery model commonly referred
to as the pseudo two-dimensional model. The partial-differential algebraic
equations (PDAEs) constituting the model are spatially discretised using
Chebyshev orthogonal collocation enabling fast and accurate simulations up to
high C-rates. This implementation of the pseudo-2D model is then used in
combination with an extended Kalman filter algorithm for differential-algebraic
equations to estimate the states of the model. The state estimation algorithm
is able to rapidly recover the model states from current, voltage and
temperature measurements. Results show that the error on the state estimate
falls below 1 % in less than 200 s despite a 30 % error on battery initial
state-of-charge and additive measurement noise with 10 mV and 0.5 K standard
deviations.Comment: Submitted to the Journal of Power Source
Refining MOND interpolating function and TeVeS Lagrangian
The phenomena customly called Dark Matter or Modified Newtonian Dynamics
(MOND) have been argued by Bekenstein (2004) to be the consequences of a
covariant scalar field, controlled by a free function (related to the MOND
interpolating function) in its Lagrangian density. In the context of this
relativistic MOND theory (TeVeS), we examine critically the interpolating
function in the transition zone between weak and strong gravity. Bekenstein's
toy model produces too gradually varying functions and fits rotation curves
less well than the standard MOND interpolating function. However, the latter
varies too sharply and implies an implausible external field effect (EFE).
These constraints on opposite sides have not yet excluded TeVeS, but made the
zone of acceptable interpolating functions narrower. An acceptable "toy"
Lagrangian density function with simple analytical properties is singled out
for future studies of TeVeS in galaxies. We also suggest how to extend the
model to solar system dynamics and cosmology, and compare with strong lensing
data (see also astro-ph/0509590).Comment: accepted for publication in ApJ Letter
Electric Field Effect in Diluted Magnetic Insulator Anatase Co:TiO2
An external electric field induced reversible modulation of room temperature
magnetic moment is achieved in an epitaxial and insulating thin film of
dilutely cobalt-doped anatase TiO2. This first demonstration of electric field
effect in any oxide based diluted ferromagnet is realized in a high quality
epitaxial heterostructure of PbZr0.2Ti0.8O3/Co:TiO2/SrRuO3 grown on (001)
LaAlO3. The observed effect, which is about 15% in strength in a given
heterostructure, can be modulated over several cycles. Possible mechanisms for
electric field induced modulation of insulating ferromagnetism are discussed.Comment: 14 pages, 4 figure
Short-coherence length superconductivity in the Attractive Hubbard Model in three dimensions
We study the normal state and the superconducting transition in the
Attractive Hubbard Model in three dimensions, using self-consistent
diagrammatics. Our results for the self-consistent -matrix approximation are
consistent with 3D-XY power-law critical scaling and finite-size scaling. This
is in contrast to the exponential 2D-XY scaling the method was able to capture
in our previous 2D calculation. We find the 3D transition temperature at
quarter-filling and to be . The 3D critical regime is much
narrower than in 2D and the ratio of the mean-field transition to is
about 5 times smaller than in 2D. We also find that, for the parameters we
consider, the pseudogap regime in 3D (as in 2D) coincides with the critical
scaling regime.Comment: 4 pages, 5 figure
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