Electronics and Communications in Japan (Part III: Fundamental Electronic Science)最新文献

The modeling of computation using logic circuits occupies an important position in the fundamentals of complexity theory including quantum complexity theory. Consequently, research into methods for computing logic functions on quantum circuits as well as for minimizing and simplifying such circuits has become extremely important. In this paper we explicitly formulate the depth minimization problem for quantum logic circuits and show that this problem is closely related to a geometric approach to deriving a lower bound on the size of a quantum logic circuit. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(10): 9–17, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20298

A variational Bayes method is proposed as an approximation method for implementing Bayesian posterior distribution with moderate computational complexity. Its effectiveness for real problems has been confirmed. The variational Bayes method is a method which generalizes the mean field approximation used in calculating partition functions in statistical physics. In recent years, the mathematical properties of the precision with which it is approximated have been investigated. In this paper, the authors consider the asymptotic stochastic complexity in the case of applying the mean field approximation to complete bipartite graph-type Boltzmann machines and theoretically derive that asymptotic form. Also, based on the results, the authors quantitatively consider the difference between Bayesian posterior distribution and the posterior distribution of the mean field approximation. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(9): 1– 9, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20307

Irradiation of ultrasonic waves induces cavitation in a solution, and a chemical action instigated by radicals occurs. This chemical action is reported to be most efficient in the region of several hundred kilohertz frequencies. Application of sonochemistry based on ultrasonic chemical action remains at the laboratory scale and has not yet reached the industrial practical scale. In order to realize practical applications of sonochemistry, there is a need to scale-up the sonochemical reactors. For this purpose, we used a 490-kHz cylindrical sonochemical reactor that is long in the irradiation direction, and used potassium iodide (KI) dosimetry, sonochemical luminescence, and calorimetry to evaluate the sonochemical reaction efficiency and reaction field of the reactor. We performed the evaluation with the ultrasonic irradiation direction in the horizontal and vertical directions. As a result, we observed sonochemical luminescence and a rise in temperature near the reflection surface, for both the horizontal and vertical irradiation. For the horizontal irradiation, the I₃⁻ concentration was evenly distributed in the irradiation direction. Moreover, we found that the sonochemical reaction efficiency was the same for both the horizontal irradiation and the vertical irradiation. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(8): 1– 8, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20315

In this paper, the author explains the recent evolution of algorithms for minimum partitioning problems in graphs. When the set of vertices of a graph having non-negative weights for edges is divided into k subsets, the set of edges for which both endpoints are contained in different subsets is called a k-way cut or k-cut. The problem of obtaining the k-way cut that minimizes the sum of the weights is an important research topic that appears in many practical applications such as VLSI design. In this paper, the author introduces recent results including cases in which sets of terminals or sets of terminal pairs that are to be separated are further specified in this problem and cases in which the objects to be partitioned are extended from graphs to hypergraphs or submodular set functions. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(10): 63– 78, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20341

A method to independently run two coexisting Linux systems on one computer is proposed. Up to the present time a virtual computer method has been used as a method to run multiple operating systems on one computer. This method has a problem, however, in which the guest operating system depends on the running state of the host operating system making it impossible to efficiently utilize the processing performance of each operating system. In contrast to this, because each operating system runs independently in the proposed method by time sharing the processes and exclusively dividing the other hardware resources, one of the operating systems and applications running on the operating systems are not influenced by the other operating system and the applications running on the operating system. This paper presents the proposed method and reports the results of performance evaluations when actually implemented in Linux. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(9): 56– 68, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20343

In H.264/MPEG-4 AVC a wide range of different prediction block forms and prediction signal generation methods are available. By selecting an optimal combination of coding modes from the multiple possible combinations of such modes, improvements in coding efficiency can be achieved. However, when using the rate-distortion optimized coding mode decision method based on the Lagrange multipliers, at the same time as seeing a significant improvement in coding efficiency, we are faced with the problem that the mode decision procedure becomes extremely demanding computationally. The H.264/MPEG-4 AVC high profile introduces adaptive block size transformations thereby making the number of combinations of coding mode that can be selected even larger than under the main profile. In this paper we investigate a method for hierarchically and adaptively reducing the number of mode combinations. Specifically we propose a method for quickly deciding the coding mode while limiting the reductions in coding efficiency by the correlation information between two mode decision cost functions in accordance with a quantization parameter. The results of experiments confirm that by using the proposed method, the encoding time excluding the motion search can be reduced by up to 4 times for the main profile and by up to 7 times for the high profile as compared to rate-distortion optimized coding mode decision. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(9): 41– 55, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20342

In the information and communications field, digital images have come to be widely used in mobile communications devices, and digital image processing is very important. Because of the different resolutions of the displays and output devices in each terminal, digital images undergo reduction and enlargement processing very frequently. Conventionally, reduction and enlargement processing is performed using an interpolation algorithm based on the sinc function. However, because the frequency band increases when digital images are enlarged, an enlarged image of sufficient quality cannot be attained through interpolation. In recent years, an enlargement method has been proposed which uses estimation of the frequency bands (high-frequency components) which increase with the enlargement of a digital image. The authors have also clarified interpolation algorithms using the preservation of step edge signals, coordinate point warping for generating peak signals, and signal amplitude biasing. They have implemented an interpolation algorithm which produces high-frequency components. In calculating the bias in this method, the smaller of the biases found to either side of the interpolation is selected. This choice is not necessarily optimal; the larger bias should be selected depending on certain conditions. For example, the selection of the larger bias makes it possible to preserve the precipitous changes in a step edge signal. This makes it possible to preserve step edge signals and generate peaks, without also using coordinate point warping, by selecting the optimal bias according to local information. The proposed interpolation algorithm using data-dependent biasing was compared to an interpolation algorithm using coordinate point warping and signal amplitude biasing. The proposed algorithm was found to have a similar performance and clearly shown to be a method with low computational complexity. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(8): 18–28, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20306

OFDM communication system has recently been attracting attention because of its features of high spectrum efficiency and robustness in a multipath environment. The OFDM signal often exhibits a high peak power. It is important to reduce the peak power, since communication quality is degraded and unnecessary outband power radiation is produced when such a signal is amplified by a nonlinear amplifier. This paper considers the peak power suppression problem in an oversampled OFDM signal and presents a solution using a mutually coupled neural network. The peak power suppression performance of the proposed method and the accompanying reduction of the outband radiation power and the bit error rate are evaluated by numerical experiments. Neuro-hardware which can handle the peak power suppression process in real time is experimentally constructed, and its performance is evaluated. © 2007 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 90(8): 54– 62, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.20285