4,316 research outputs found
A pseudo empirical likelihood approach for stratified samples with nonresponse
Nonresponse is common in surveys. When the response probability of a survey
variable depends on through an observed auxiliary categorical variable
(i.e., the response probability of is conditionally independent of
given ), a simple method often used in practice is to use categories as
imputation cells and construct estimators by imputing nonrespondents or
reweighting respondents within each imputation cell. This simple method,
however, is inefficient when some categories have small sizes and ad hoc
methods are often applied to collapse small imputation cells. Assuming a
parametric model on the conditional probability of given and a
nonparametric model on the distribution of , we develop a pseudo empirical
likelihood method to provide more efficient survey estimators. Our method
avoids any ad hoc collapsing small categories, since reweighting or
imputation is done across categories. Asymptotic distributions for
estimators of population means based on the pseudo empirical likelihood method
are derived. For variance estimation, we consider a bootstrap procedure and its
consistency is established. Some simulation results are provided to assess the
finite sample performance of the proposed estimators.Comment: Published in at http://dx.doi.org/10.1214/07-AOS578 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org
Electron-nuclear entanglement in the cold lithium gas
We study the ground-state entanglement and thermal entanglement in the
hyperfine interaction of the lithium atom. We give the relationship between the
entanglement and both temperature and external magnetic fields.Comment: 7 pages, 3 figure
The Role of Chaos in One-Dimensional Heat Conductivity
We investigate the heat conduction in a quasi 1-D gas model with various
degree of chaos. Our calculations indicate that the heat conductivity
is independent of system size when the chaos of the channel is strong enough.
The different diffusion behaviors for the cases of chaotic and non-chaotic
channels are also studied. The numerical results of divergent exponent
of heat conduction and diffusion exponent are in consistent with the
formula . We explore the temperature profiles numerically and
analytically, which show that the temperature jump is primarily attributed to
superdiffusion for both non-chaotic and chaotic cases, and for the latter case
of superdiffusion the finite-size affects the value of remarkably.Comment: 6 pages, 7 figure
Heat conductivity in the presence of a quantized degree of freedom
We propose a model with a quantized degree of freedom to study the heat
transport in quasi-one dimensional system. Our simulations reveal three
distinct temperature regimes. In particular, the intermediate regime is
characterized by heat conductivity with a temperature exponent much
greater than 1/2 that was generally found in systems with point-like particles.
A dynamical investigation indicates the occurrence of non-equipartition
behavior in this regime. Moreover, the corresponding Poincar\'e section also
shows remarkably characteristic patterns, completely different from the cases
of point-like particles.Comment: 7 pages, 4 figure
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