130,161 research outputs found
Comparison of predictions from a ray tracing microcellular model with narrowband measurements
A new stochastic spatio-temporal propagation model (SSTPM) for mobile communications with antenna arrays
Bayesian Inference under Cluster Sampling with Probability Proportional to Size
Cluster sampling is common in survey practice, and the corresponding
inference has been predominantly design-based. We develop a Bayesian framework
for cluster sampling and account for the design effect in the outcome modeling.
We consider a two-stage cluster sampling design where the clusters are first
selected with probability proportional to cluster size, and then units are
randomly sampled inside selected clusters. Challenges arise when the sizes of
nonsampled cluster are unknown. We propose nonparametric and parametric
Bayesian approaches for predicting the unknown cluster sizes, with this
inference performed simultaneously with the model for survey outcome.
Simulation studies show that the integrated Bayesian approach outperforms
classical methods with efficiency gains. We use Stan for computing and apply
the proposal to the Fragile Families and Child Wellbeing study as an
illustration of complex survey inference in health surveys
State Complexity of Reversals of Deterministic Finite Automata with Output
We investigate the worst-case state complexity of reversals of deterministic
finite automata with output (DFAOs). In these automata, each state is assigned
some output value, rather than simply being labelled final or non-final. This
directly generalizes the well-studied problem of determining the worst-case
state complexity of reversals of ordinary deterministic finite automata. If a
DFAO has states and possible output values, there is a known upper
bound of for the state complexity of reversal. We show this bound can be
reached with a ternary input alphabet. We conjecture it cannot be reached with
a binary input alphabet except when , and give a lower bound for the
case . We prove that the state complexity of reversal depends
solely on the transition monoid of the DFAO and the mapping that assigns output
values to states.Comment: 18 pages, 3 tables. Added missing affiliation/funding informatio
Recommended from our members
Deploy diverse renewables to save tropical rivers.
A strategic mix of solar, wind and storage technologies around river basins would be safer and cheaper than building large dams, argue Rafael J. P. Schmitt, Noah Kittner and colleagues
Self-diffusion in a monatomic glassforming liquid embedded in the hyperbolic plane
We study by Molecular Dynamics simulation the slowing down of particle motion
in a two-dimensional monatomic model: a Lennard-Jones liquid on the hyperbolic
plane. The negative curvature of the embedding space frustrates the long-range
extension of the local hexagonal order. As a result, the liquid avoids
crystallization and forms a glass. We show that, as temperature decreases, the
single particle motion displays the canonical features seen in real
glassforming liquids: the emergence of a "plateau" at intermediate times in the
mean square displacement and a decoupling between the local relaxation time and
the (hyperbolic) diffusion constant.Comment: Article for the "11th International Workshop on Complex Systems
Topological Quantum Glassiness
Quantum tunneling often allows pathways to relaxation past energy barriers
which are otherwise hard to overcome classically at low temperatures. However,
this is not always the case. In this paper we provide simple exactly solvable
examples where the barriers each system encounters on its approach to lower and
lower energy states become increasingly large and eventually scale with the
system size. If the environment couples locally to the physical degrees of
freedom in the system, tunnelling under large barriers requires processes whose
order in perturbation theory is proportional to the width of the barrier. This
results in quantum relaxation rates that are exponentially suppressed in system
size: For these quantum systems, no physical bath can provide a mechanism for
relaxation that is not dynamically arrested at low temperatures. The examples
discussed here are drawn from three dimensional generalizations of Kitaev's
toric code, originally devised in the context of topological quantum computing.
They are devoid of any local order parameters or symmetry breaking and are thus
examples of topological quantum glasses. We construct systems that have slow
dynamics similar to either strong or fragile glasses. The example with
fragile-like relaxation is interesting in that the topological defects are
neither open strings or regular open membranes, but fractal objects with
dimension .Comment: (18 pages, 4 figures, v2: typos and updated figure); Philosophical
Magazine (2011
Conditional cash and in-kind transfers increase household total and food consumption in poor rural communities in Mexico
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