503 research outputs found
Two-Dimensional Source Coding by Means of Subblock Enumeration
A technique of lossless compression via substring enumeration (CSE) attains
compression ratios as well as popular lossless compressors for one-dimensional
(1D) sources. The CSE utilizes a probabilistic model built from the circular
string of an input source for encoding the source.The CSE is applicable to
two-dimensional (2D) sources such as images by dealing with a line of pixels of
2D source as a symbol of an extended alphabet. At the initial step of the CSE
encoding process, we need to output the number of occurrences of all symbols of
the extended alphabet, so that the time complexity increase exponentially when
the size of source becomes large. To reduce the time complexity, we propose a
new CSE which can encode a 2D source in block-by-block instead of line-by-line.
The proposed CSE utilizes the flat torus of an input 2D source as a
probabilistic model for encoding the source instead of the circular string of
the source. Moreover, we analyze the limit of the average codeword length of
the proposed CSE for general sources.Comment: 5 pages, Submitted to ISIT201
Asymptotic Optimality of Antidictionary Codes
An antidictionary code is a lossless compression algorithm using an
antidictionary which is a set of minimal words that do not occur as substrings
in an input string. The code was proposed by Crochemore et al. in 2000, and its
asymptotic optimality has been proved with respect to only a specific
information source, called balanced binary source that is a binary Markov
source in which a state transition occurs with probability 1/2 or 1. In this
paper, we prove the optimality of both static and dynamic antidictionary codes
with respect to a stationary ergodic Markov source on finite alphabet such that
a state transition occurs with probability .Comment: 5 pages, to appear in the proceedings of 2010 IEEE International
Symposium on Information Theory (ISIT2010
A Universal Two-Dimensional Source Coding by Means of Subblock Enumeration
The technique of lossless compression via substring enumeration (CSE) is a kind of enumerative code and uses a probabilistic model built from the circular string of an input source for encoding a one-dimensional (1D) source. CSE is applicable to two-dimensional (2D) sources, such as images, by dealing with a line of pixels of a 2D source as a symbol of an extended alphabet. At the initial step of CSE encoding process, we need to output the number of occurrences of all symbols of the extended alphabet, so that the time complexity increases exponentially when the size of source becomes large. To reduce computational time, we can rearrange pixels of a 2D source into a 1D source string along a space-filling curve like a Hilbert curve. However, information on adjacent cells in a 2D source may be lost in the conversion. To reduce the time complexity and compress a 2D source without converting to a 1D source, we propose a new CSE which can encode a 2D source in a block-by-block fashion instead of in a line-by-line fashion. The proposed algorithm uses the flat torus of an input 2D source as a probabilistic model instead of the circular string of the source. Moreover, we prove the asymptotic optimality of the proposed algorithm for 2D general sources
In-situ observation and multi-physics simulation of reactive melt Infiltration of silicon melt into SiC-C Preform
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Quantum-number projection in the path-integral renormalization group method
We present a quantum-number projection technique which enables us to exactly
treat spin, momentum and other symmetries embedded in the Hubbard model. By
combining this projection technique, we extend the path-integral
renormalization group method to improve the efficiency of numerical
computations. By taking numerical calculations for the standard Hubbard model
and the Hubbard model with next nearest neighbor transfer, we show that the
present extended method can extremely enhance numerical accuracy and that it
can handle excited states, in addition to the ground state.Comment: 11 pages, 7 figures, submitted to Phys. Rev.
Homology cylinders of higher-order
We study algebraic structures of certain submonoids of the monoid of homology
cylinders over a surface and the homology cobordism groups, using Reidemeister
torsion with non-commutative coefficients. The submonoids consist of ones whose
natural inclusion maps from the boundary surfaces induce isomorphisms on higher
solvable quotients of the fundamental groups. We show that for a surface whose
first Betti number is positive, the homology cobordism groups are other
enlargements of the mapping class group of the surface than that of ordinary
homology cylinders. Furthermore we show that for a surface with boundary whose
first Betti number is positive, the submonoids consisting of irreducible ones
as 3-manifolds trivially acting on the solvable quotients of the surface group
are not finitely generated.Comment: 14 pages; 15 pages, to appear in Algebraic & Geometric Topolog
One Argonaute family member, Eif2c2 (Ago2), is essential for development and appears not to be involved in DNA methylation
AbstractTo elucidate the epigenetic role of RNAi in mammals, we disrupted the gene for Eif2c2 (Ago2), which works as the sole slicer of RNAi in the Argonaute family. In mice, disruption of Eif2c2 leads to embryonic lethality early in development after the implantation stage. This phenotype is completely different from that in a previous report, but somewhat similar to the disruption of Dicer1, another important component of RNAi. We also show that Eif2c2 is not required for the maintenance of DNA methylation in imprinted genes, centromeric repeats, and Xist. This suggests that developmental defects in the Eif2c2-deficient mouse are caused not at the transcriptional level, but rather at the posttranscriptional level through the miRNA–protein complex
Time-resolved measurements of two-color laser light emitted from GaAs/AlGaAs-coupled multilayer cavity
We measured the two-color laser oscillation from a GaAs/AlGaAs-coupled multilayer cavity at 18–42 °C using current injection. We confirmed simultaneous lasing by detecting the sum frequency generation signal generated by the two-color laser light, and performed time-resolved measurement using a streak camera with a spectrometer. From the observed time transient of the spectra at various temperatures, it it is clarified that the temperature change of the device, induced by current injection, modulates the effective cavity length. Therefore, the temperature control of the device is a key factor in stable two-color lasing and THz wave generation
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