850 research outputs found
Next Polar Science Computer System
The Tenth Symposium on Polar Science/Ordinary sessions: [OS] Space and upper atmospheric sciences, Wed. 4 Dec. /Entrance Hall (1st floor) at National Institute of Polar Research (NIPR
Statistical mechanical evaluation of spread spectrum watermarking model with image restoration
In cases in which an original image is blind, a decoding method where both
the image and the messages can be estimated simultaneously is desirable. We
propose a spread spectrum watermarking model with image restoration based on
Bayes estimation. We therefore need to assume some prior probabilities. The
probability for estimating the messages is given by the uniform distribution,
and the ones for the image are given by the infinite range model and 2D Ising
model. Any attacks from unauthorized users can be represented by channel
models. We can obtain the estimated messages and image by maximizing the
posterior probability.
We analyzed the performance of the proposed method by the replica method in
the case of the infinite range model. We first calculated the theoretical
values of the bit error rate from obtained saddle point equations and then
verified them by computer simulations. For this purpose, we assumed that the
image is binary and is generated from a given prior probability. We also assume
that attacks can be represented by the Gaussian channel. The computer
simulation retults agreed with the theoretical values.
In the case of prior probability given by the 2D Ising model, in which each
pixel is statically connected with four-neighbors, we evaluated the decoding
performance by computer simulations, since the replica theory could not be
applied. Results using the 2D Ising model showed that the proposed method with
image restoration is as effective as the infinite range model for decoding
messages.
We compared the performances in a case in which the image was blind and one
in which it was informed. The difference between these cases was small as long
as the embedding and attack rates were small. This demonstrates that the
proposed method with simultaneous estimation is effective as a watermarking
decoder
Bifurcation analysis in an associative memory model
We previously reported the chaos induced by the frustration of interaction in
a non-monotonic sequential associative memory model, and showed the chaotic
behaviors at absolute zero. We have now analyzed bifurcation in a stochastic
system, namely a finite-temperature model of the non-monotonic sequential
associative memory model. We derived order-parameter equations from the
stochastic microscopic equations. Two-parameter bifurcation diagrams obtained
from those equations show the coexistence of attractors, which do not appear at
absolute zero, and the disappearance of chaos due to the temperature effect.Comment: 19 page
A note on varieties of weak CM-type
CM-type projective varieties X of complex dimension n are characterized by
their CM-type rational Hodge structures on the cohomology groups. One may
impose such a condition in a weakest form when the canonical bundle of X is
trivial; the rational Hodge structure on the level-n subspace of is
required to be of CM-type. This brief note addresses the question whether this
weak condition implies that the Hodge structure on the entire is
of CM-type. We study in particular abelian varieties when the dimension of the
level-n subspace is two or four, and K3 . It turns out that the
answer is affirmative. Moreover, such an abelian variety is always isogenous to
a product of CM-type elliptic curves or abelian surfaces.Comment: 21 page
Towards Hodge Theoretic Characterizations of 2d Rational SCFTs: II
A characterization of rational superconformal field theories (SCFTs) on 1+1
dimensions with Ricci-flat Kahler targets was proposed by S. Gukov and C. Vafa
in terms of the Hodge structure of the target space. The article
[arXiv:2205.10299] refined this idea and extracted a set of necessary
conditions for a -target N=(1,1) SCFT to be rational; only a partial
effort was made, however, to study whether it also constitutes a sufficient
condition. It turns out that the set of conditions in [arXiv:2205.10299] is not
sufficient, and that it becomes a set of necessary and sufficient conditions by
adding one more condition in the case of . The Strominger--Yau--Zaslow
fibration in the mirror correspondence plays an essential role there. At the
end, we also propose a refined version of Gukov--Vafa's idea for general
Ricci-flat Kahler target spaces.Comment: 32 page
Rescue with an anti-inflammatory peptide of chickens infected H5N1 avian flu
Chickens suffering from avian flu caused by H5N1 influenza virus are destined to die within 2 days due to a systemic inflammatory response. Since HVJ infection (1,2) and influenza virus infection (3,4) cause infected cells to activate homologous serum complement, the systemic inflammatory response elicited could be attributed to the unlimited generation of C5a anaphylatoxin of the complement system, which is a causative peptide of serious inflammation. In monkeys inoculated with a lethal dose of LPS (4 mg/kg body weight), inhibition of C5a by an inhibitory peptide termed AcPepA (5) rescued these animals from serious septic shock which would have resulted in death within a day (6). Therefore, we tested whether AcPepA could also have a beneficial effect on chickens with bird flu. On another front, enhanced production of endothelin-1 (ET-1) and the activation of mast cells (MCs) have been implicated in granulocyte sequestration (7). An endothelin receptor derived antisense homology box peptide (8) designated ETR-P1/fl was shown to antagonize endothelin A receptor (ET-A receptor) (9) and reduce such inflammatory responses as endotoxin-shock (10) and hemorrhagic shock (11), thereby suppressing histamine release in the circulation (12). Thus, we also administered ETR-P1/fl to bird flu chickens expecting suppression of a systemic inflammatory response
Energetics and electronic structures of polymeric all-benzene hollow-cages and planar networks
We studied the energetics and electronic structure of polymerized benzene hollow-cages and sheet using the density functional theory with the generalized gradient approximation. The energetics and electronic structure of the polymeric benzene cages and sheet depend on their size and dimensionality. Because of the symmetric network topology as well as the constituent benzene units, the cages possess highly bunched states around the Fermi level. The energy gap between the highest occupied and the lowest unoccupied states of the cages is approximately proportional to their curvature, owing to the decrease of the strain. The polymerized benzene sheet is a direct gap semiconductor with the gap of 2.4 eV between the less dispersive states of the highest branch of the valence and the lowest branch of the conduction bands
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