21,578 research outputs found
Plastic Deformation of 2D Crumpled Wires
When a single long piece of elastic wire is injected trough channels into a
confining two-dimensional cavity, a complex structure of hierarchical loops is
formed. In the limit of maximum packing density, these structures are described
by several scaling laws. In this paper it is investigated this packing process
but using plastic wires which give origin to completely irreversible structures
of different morphology. In particular, it is studied experimentally the
plastic deformation from circular to oblate configurations of crumpled wires,
obtained by the application of an axial strain. Among other things, it is shown
that in spite of plasticity, irreversibility, and very large deformations,
scaling is still observed.Comment: 5 pages, 6 figure
Structural properties of crumpled cream layers
The cream layer is a complex heterogeneous material of biological origin
which forms spontaneously at the air-milk interface. Here, it is studied the
crumpling of a single cream layer packing under its own weight at room
temperature in three-dimensional space. The structure obtained in these
circumstances has low volume fraction and anomalous fractal dimensions. Direct
means and noninvasive NMR imaging technique are used to investigate the
internal and external structure of these systems.Comment: 9 pages, 4 figures, accepted in J. Phys. D: Appl. Phy
Quantifying Equivocation for Finite Blocklength Wiretap Codes
This paper presents a new technique for providing the analysis and comparison
of wiretap codes in the small blocklength regime over the binary erasure
wiretap channel. A major result is the development of Monte Carlo strategies
for quantifying a code's equivocation, which mirrors techniques used to analyze
normal error correcting codes. For this paper, we limit our analysis to
coset-based wiretap codes, and make several comparisons of different code
families at small and medium blocklengths. Our results indicate that there are
security advantages to using specific codes when using small to medium
blocklengths.Comment: Submitted to ICC 201
Counting solutions from finite samplings
We formulate the solution counting problem within the framework of inverse
Ising problem and use fast belief propagation equations to estimate the entropy
whose value provides an estimate on the true one. We test this idea on both
diluted models (random 2-SAT and 3-SAT problems) and fully-connected model
(binary perceptron), and show that when the constraint density is small, this
estimate can be very close to the true value. The information stored by the
salamander retina under the natural movie stimuli can also be estimated and our
result is consistent with that obtained by Monte Carlo method. Of particular
significance is sizes of other metastable states for this real neuronal network
are predicted.Comment: 9 pages, 4 figures and 1 table, further discussions adde
Evaluation of the risk of death for very low-birthweight babies and comparation between neonatal intensive care units: application of ROC curves
In general, the neonatal rates of mortality are considered the most important measure for the evaluation of health services and the development of society. Babies with very low birthweight (<1500g at birth) contribute significantly to the increase of the mortality and morbidity rates.This study aims to compare, in the same set of babies, 4 different indexes of clinical seriousness; these indexes quantify the risk of death for babies with very low birthweight. The study was conducted on 169 new-borns with birthweight under 1500g, admitted to the Neonatology Unit of the Hospital Garcia de Orta in Portugal, between January 1992 and July 1995. The data were collected retrospectively on the same set of new-horns to permit the comparison of the different indexes. To compare Neonatal Intensive Care Units, we use another set of new-borns. These data (234 new-borns with very low birthweight) were collected in 4 different Portuguese hospitals (H-1, H-2, H-3 and H-4) during 1995.The 4 indexes studied were: CRIB (Clinical Risk Index for Babies), TISS (Neonatal Therapeutical Intervention Score System), SNAP (Score for Neonatal Acute Physiology) and SNAP-PE (Score for Neonatal Acute Physiology-Perinatal Extension). Also, included in the study was the variable WEIGHT (birthweight) because it is an important index to evaluate the initial risk of death.The selection of the best diagnostic test was based on the Receiver Operating Characteristic (RDC) curves. The results, based on the ROC curves, allow the conclusion that CRIB is the best index for evaluating the risk of neonatal death, and that hospital H-4 has better performance in terms of neonatal intensive care
Estudo das características fisiológicas de genótipos de milho contrastantes para tolerância a seca.
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