526,685 research outputs found
Fletcher-Turek Model Averaged Profile Likelihood Confidence Intervals
We evaluate the model averaged profile likelihood confidence intervals
proposed by Fletcher and Turek (2011) in a simple situation in which there are
two linear regression models over which we average. We obtain exact expressions
for the coverage and the scaled expected length of the intervals and use these
to compute these quantities in particular situations. We show that the
Fletcher-Turek confidence intervals can have coverage well below the nominal
coverage and expected length greater than that of the standard confidence
interval with coverage equal to the same minimum coverage. In these situations,
the Fletcher-Turek confidence intervals are unfortunately not better than the
standard confidence interval used after model selection but ignoring the model
selection process
Long-timescale simulations of HO admolecule diffusion on Ice Ih(0001) surfaces
Long-timescale simulations of the diffusion of a HO admolecule on the
(0001) basal plane of ice Ih were carried out over a temperature range of 100
to 200 K using the adaptive kinetic Monte Carlo method and TIP4P/2005f
interaction potential function. The arrangement of dangling H atoms was varied
from the proton-disordered surface to the perfectly ordered Fletcher surface. A
large variety of sites was found leading to a broad distribution in adsorption
energy at both types of surfaces. Up to 4 % of the sites on the
proton-disordered surface have an adsorption energy exceeding the cohesive
energy of ice Ih. The mean squared displacement of a simulated trajectory at
175 K for the proton-disordered surface gave a diffusion constant of
610 cm/s, consistent with an upper bound previously reported
from experimental measurements. During the simulation, dangling H atoms were
found to rearrange so as to reduce clustering, thereby approaching a linear
Fletcher type arrangement. Diffusion on the perfectly ordered Fletcher surface
was estimated to be significantly faster, especially in the direction along the
rows of dangling hydrogen atoms. From simulations over the range in
temperature, an effective activation energy of diffusion was estimated to be
0.16 eV and 0.22 eV for diffusion parallel and perpendicular to the rows,
respectively. Even a slight disruption of the rows of the Fletcher surface made
the diffusion isotropic.Comment: 24 pages, 8 figures, 1 tabl
On Superluminal motions in photon and particle tunnelings
It is shown that the Hartman-Fletcher effect is valid for all the known
expressions of the mean tunnelling time, in various nonrelativistic approaches,
for the case of finite width barriers without absorption. Then, we show that
the same effect is not valid for the tunnelling time mean-square fluctuations.
On the basis of the Hartman-Fletcher effect and the known analogy between
photon and nonrelativistic-particle tunnelling, one can explain the
Superluminal group-velocities observed in various photon tunnelling experiments
(without violation of the so-called "Einstein causality").Comment: standard LaTeX file; accepted for publication in Phys. Lett.
The bactericidal effects of negative ions in air
The use of negative ions to improve indoor air quality has attracted increasing attention in recent years. Although the physical action of air ionisers is accepted, there is still debate over their apparent biocidal action. A recent clinical trial in an intensive care unit suggested that air ionisers may have a role in reducing the transmission of infection in healthcare environments1 and several authors have reported that ions inhibit the growth of a range of microorganisms. A further understanding of this process was gained through bench scale experiments exposing sessile cultures to positive and negative ions2. The aim of the work presented here was to follow on from the bench scale experiments to investigate the efficacy of negative ions with aerosolised microorganisms
The Davidon-Fletcher-Powell penalty function method: A generalized iterative technique for solving parameter optimization problems
The Fletcher-Powell version of the Davidon variable metric unconstrained minimization technique is described. Equations that have been used successfully with the Davidon-Fletcher-Powell penalty function technique for solving constrained minimization problems and the advantages and disadvantages of using them are discussed. The experience gained in the behavior of the method while iterating is also related
Critical analysis of the 'generalized coherent wave approximation'
The formalism developed by Fletcher (1967) to take account of the presence of short range order in the calculation of the electronic energy spectrum of amorphous covalent semiconductors is examined critically and found to have fundamental difficulties
Keepers Of The Light Conference 2000 Keynote Address
Donna Fletcher Crow is an author of historical fiction tracing the roots of Christianity in England, Scotland and Ireland.
She delivered this keynote address for the opening session of the A CL Conference, Point Loma Nazarene University, San Diego, California, June 14, 200
Frances Fletcher Family Papers
Miscellaneous papers found in the personal library of Dr. Frances Fletcher, long-time professor of English at Louisiana Tech University, including papers of or referring to Ward Fletcher, Joel Lafayette Fletcher, and Fletcher family genealogy.https://digitalcommons.latech.edu/manuscript-finding-aids/1144/thumbnail.jp
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