1,951 research outputs found
Jar Decoding: Non-Asymptotic Converse Coding Theorems, Taylor-Type Expansion, and Optimality
Recently, a new decoding rule called jar decoding was proposed; under jar
decoding, a non-asymptotic achievable tradeoff between the coding rate and word
error probability was also established for any discrete input memoryless
channel with discrete or continuous output (DIMC). Along the path of
non-asymptotic analysis, in this paper, it is further shown that jar decoding
is actually optimal up to the second order coding performance by establishing
new non-asymptotic converse coding theorems, and determining the Taylor
expansion of the (best) coding rate of finite block length for
any block length and word error probability up to the second
order. Finally, based on the Taylor-type expansion and the new converses, two
approximation formulas for (dubbed "SO" and "NEP") are
provided; they are further evaluated and compared against some of the best
bounds known so far, as well as the normal approximation of
revisited recently in the literature. It turns out that while the normal
approximation is all over the map, i.e. sometime below achievable bounds and
sometime above converse bounds, the SO approximation is much more reliable as
it is always below converses; in the meantime, the NEP approximation is the
best among the three and always provides an accurate estimation for . An important implication arising from the Taylor-type expansion of
is that in the practical non-asymptotic regime, the optimal
marginal codeword symbol distribution is not necessarily a capacity achieving
distribution.Comment: submitted to IEEE Transaction on Information Theory in April, 201
Capacity Analysis of Linear Operator Channels over Finite Fields
Motivated by communication through a network employing linear network coding,
capacities of linear operator channels (LOCs) with arbitrarily distributed
transfer matrices over finite fields are studied. Both the Shannon capacity
and the subspace coding capacity are analyzed. By establishing
and comparing lower bounds on and upper bounds on , various
necessary conditions and sufficient conditions such that are
obtained. A new class of LOCs such that is identified, which
includes LOCs with uniform-given-rank transfer matrices as special cases. It is
also demonstrated that is strictly less than for a broad
class of LOCs. In general, an optimal subspace coding scheme is difficult to
find because it requires to solve the maximization of a non-concave function.
However, for a LOC with a unique subspace degradation, can be
obtained by solving a convex optimization problem over rank distribution.
Classes of LOCs with a unique subspace degradation are characterized. Since
LOCs with uniform-given-rank transfer matrices have unique subspace
degradations, some existing results on LOCs with uniform-given-rank transfer
matrices are explained from a more general way.Comment: To appear in IEEE Transactions on Information Theor
Microscopic and self-consistent description for neutron halo in deformed nuclei
A deformed relativistic Hartree-Bogoliubov theory in continuum has been
developed for the study of neutron halos in deformed nuclei and the halo
phenomenon in deformed weakly bound nuclei is investigated. Magnesium and neon
isotopes are studied and some results are presented for the deformed
neutron-rich and weakly bound nuclei 44Mg and 36Ne. The core of the former
nucleus is prolate, but the halo has a slightly oblate shape. This indicates a
decoupling of the halo orbitals from the deformation of the core. The generic
conditions for the existence of halos in deformed nuclei and for the occurrence
of this decoupling effect are discussed.Comment: 7 pages, 2 figures; invited talk at the XXXV Brazilian Workshop on
Nuclear Physics, Sep 2-6, 2012, Maresias, Brazi
Halos in a deformed Relativistic Hartree-Bogoliubov theory in continuum
In this contribution we present some recent results about neutron halos in
deformed nuclei. A deformed relativistic Hartree-Bogoliubov theory in continuum
has been developed and the halo phenomenon in deformed weakly bound nuclei is
investigated. These weakly bound quantum systems present interesting examples
for the study of the interdependence between the deformation of the core and
the particles in the halo. Magnesium and neon isotopes are studied and detailed
results are presented for the deformed neutron-rich and weakly bound nuclei
42Mg. The core of this nucleus is prolate, but the halo has a slightly oblate
shape. This indicates a decoupling of the halo orbitals from the deformation of
the core. The generic conditions for the existence of halos in deformed nuclei
and for the occurrence of this decoupling effect are discussed.Comment: 6 pages, 2 figures; invited talk at the 2nd Int. Conf. on Nuclear
Structure & Dynamics (NSD12), Opatija, Croatia, 9-13 July 201
On Linear Operator Channels over Finite Fields
Motivated by linear network coding, communication channels perform linear
operation over finite fields, namely linear operator channels (LOCs), are
studied in this paper. For such a channel, its output vector is a linear
transform of its input vector, and the transformation matrix is randomly and
independently generated. The transformation matrix is assumed to remain
constant for every T input vectors and to be unknown to both the transmitter
and the receiver. There are NO constraints on the distribution of the
transformation matrix and the field size.
Specifically, the optimality of subspace coding over LOCs is investigated. A
lower bound on the maximum achievable rate of subspace coding is obtained and
it is shown to be tight for some cases. The maximum achievable rate of
constant-dimensional subspace coding is characterized and the loss of rate
incurred by using constant-dimensional subspace coding is insignificant.
The maximum achievable rate of channel training is close to the lower bound
on the maximum achievable rate of subspace coding. Two coding approaches based
on channel training are proposed and their performances are evaluated. Our
first approach makes use of rank-metric codes and its optimality depends on the
existence of maximum rank distance codes. Our second approach applies linear
coding and it can achieve the maximum achievable rate of channel training. Our
code designs require only the knowledge of the expectation of the rank of the
transformation matrix. The second scheme can also be realized ratelessly
without a priori knowledge of the channel statistics.Comment: 53 pages, 3 figures, submitted to IEEE Transaction on Information
Theor
Radioactive Decay of Specific Heavy Elements as an Energy Source for Late-Time Kilonovae and Potential JWST Observations
Revealing the temporal evolution of individual heavy elements synthesized in
the merger ejecta from binary neutron star mergers not only improves our
understanding of the origin of heavy elements beyond iron but also clarifies
the energy sources of kilonovae. In this work, we present a comprehensive
analysis of the temporal evolution of the energy fraction of each nuclide based
on the -process nucleosynthesis simulations. The heavy elements dominating
the kilonova emission within ~days are identified, including
Sb, Sb, Sb, Sb, Te, I,
Rn, Ra, Ra, and Ac. It is found that the
late-time kilonova light curve (~days) is highly sensitive to the
presence of the heavy element Ac (with a half-life of 10.0~days). Our
analysis shows that the James Webb Space Telescope (JWST), with its high
sensitivity in the near-infrared band, is a powerful instrument for the
identification of these specific heavy elements.Comment: 7 pages, 8 figures, accepted by MNRA
The effect of Etlingera elatior (Kantan) inflorescene aqueous extract on abberant crypy foci in Sprague dawley rats
This study investigated the effect of Kantan flowers (Etlingera elatior) aqueous extract on aberrant crypt foci (ACF) in Spraque dawley rats. They were divided into 8 groups; four groups each for cancer and normal. The rats were fed with respective concentrations of the flower extractions according to their groups. At the 17th week, the rats were sacrificed. The colons were removed and examined grossly and microscopically followed by scoring of aberrant crypt foci. Result showed no significant difference (p> 0.05) in the body weight increment,colon weight and colon pH among all groups also in the aberrant crypt foci (ACF) scores in proximal colon of cancer groups as well as in distal colon. Besides that, comparison between ACF score of proximal and distal colon using ANOVA and posthoc test revealed no significant differences (p> 0.05) in the ACF numbers between proximal and distal colon of rats. Histological result showed that no abnormal structures were seen in crypts of normal treatment groups Etlingera elatior inflorescence aqueous extract did not have significant effect in reducing aberrant crypt foci formation in Sprague dawley rats
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