Hokkaido University Collection of Scholarly and Academic Papers
(65.390 recursos)
HUSCAP (Hokkaido University Collection of Scholarly and Academic Papers) contains peer-reviewed journal articles, proceedings, educational resources and any kind of scholarly works of Hokkaido University.
6.
Analysis of a long-range random field quantum antiferromagnetic Ising model - Chakrabarti, Bikas K.; Das, Arnab; Inoue, Jun-ichi
We introduce a solvable quantum antiferromagnetic model. The model, with Ising spins in a transverse field, has infinite range antiferromagnetic interactions and random fields on each site following an arbitrary distribution. As is well-known, frustration in the random field Ising model gives rise to a many valley structure in the spin-configuration space. In addition, the antiferromagnetism also induces a regular frustration even for the ground state. In this paper, we investigate analytically the critical phenomena in the model, having both randomness and frustration and we report some analytical results for it.
7.
Specificity of hybridization between DNA sequences based on free energy - Tanaka, F; Kameda, A; Yamamoto, M; Ohuchi, A
We investigated the specificity of hybridization based on a minimum free energy (Delta G(min)) through gel electrophoresis analysis. The analysis, using 94 pairs of sequences with length 20, showed that sequences that hybridize each other can be separated using the constraint Delta G(min) < -14.0, but cannot be separated using the number of base pairs (BP) in the range from 9 to 18. This demonstrates that the Delta G(min) is superior to the BP in terms of the capability to separate specific from non-specific sequences. Furthermore, the comparison between sequence design based on Delta G(min) and that based on the...
12.
Spectrum Management of DSL Systems in Japan - Yoshii, Shinichiro
The Japanese broadband market is maturing due to expansion in the needs for richer IT lifestyles with higher bit rate access. DSL technologies have played an important role in such growth because of their lower cost and ease of deployment. In order to expand the coverage area and compete with faster services such as FTTH, the DSL family of technologies is diversifying, and there are various services on the market currently in Japan. It is very important to manage those different kinds of systems in order to minimize interference due to crosstalk. This paper describes the Japanese spectrum management standard...
15.
Modeling of autonomous problem solving process by dynamic construction of task models in multiple tasks environment - Ohigashi, Yu; Omori, Takashi
Traditional reinforcement learning (RL) supposes a complex but single task to be solved. When a RL agent faces a task similar to a learned one, the agent must relearn the task from the beginning because it doesn’t reuse the past learned results. This is the problem of quick action learning, which is the foundation of decision making in the real world. In this paper, we suppose agents that can solve a set of tasks similar to each other in a multiple tasks environment, where we encounter various problems one after another, and propose a technique of action learning that can...
16.
Application of the quantum spin glass theory to image restoration - Inoue, Jun-ichi
Quantum fluctuation is introduced into the Markov random-field model for image restoration in the context of a Bayesian approach. We investigate the dependence of the quantum fluctuation on the quality of a black and white image restoration by making use of statistical mechanics. We find that the maximum posterior marginal (MPM) estimate based on the quantum fluctuation gives a fine restoration in comparison with the maximum a posteriori estimate or the thermal fluctuation based MPM estimate.
17.
Dynamics of the maximum marginal likelihood hyperparameter estimation in image restoration: Gradient descent versus expectation and maximization algorithm - Inoue, Jun-ichi; Tanaka, Kazuyuki
Dynamical properties of image restoration and hyperparameter estimation are investigated by means of
statistical mechanics. We introduce an exactly solvable model for image restoration and derive differential
equations with respect to macroscopic quantities. From these equations, we evaluate relaxation processes of the
system to the equilibrium state. Our statistical mechanical approach also enables us to investigate the hyperparameter
estimation by means of maximization of the marginal likelihood by using gradient descent and the
expectation and maximization algorithm from the dynamical point of view.
18.
Image restoration using the Q-Ising spin glass - Inoue, Jun-ichi; Carlucci, Domenico M
We investigate static and dynamic properties of gray-scale image restoration by making use of the Q-Ising
spin glass model, whose ladder symmetry allows us to take in account the distance between two spins. We thus
give an explicit expression of the Hamming distance between the original and restored images as a function of
the hyperparameters in the mean field limit. Finally, numerical simulations for real-world pictures are carried
out to prove the efficiency of our model.
19.
Multistate image restoration by transmission of bit-decomposed data - Tadaki, Takashi; Inoue, Jun-ichi
We report on the restoration of gray-scale image when it is decomposed into a binary form before transmission. We assume that a gray-scale image expressed by a set of Q-Ising spins is first decomposed into an expression using Ising (binary) spins by means of the threshold division, namely, we produce (Q-1) binary Ising spins from a Q-Ising spin by the function F(σi-m)=1 if the input data σi∈{0,…,Q-1} is σi>~m and 0 otherwise, where m ∈{1,…,Q-1} is the threshold value. The effects of noise are different from the case where the raw Q-Ising values are sent. We investigate whether it is...
20.
Image restoration using the chiral Potts spin glass - Carlucci, Domenico M.; Inoue, Jun-ichi
We report on the image reconstruction (IR) problem by making use of the random chiral q-state Potts model, whose Hamiltonian possesses the same gauge invariance as the usual Ising spin glass model. We show that the pixel representation by means of the Potts variables is suitable for the gray-scale level image which cannot be represented by the Ising model. We find that the IR quality is highly improved by the presence of a glassy term, besides the usual ferromagnetic term under random external fields, as very recently pointed out by Nishimori and Wong. We give the exact solution of the...
1.
