Efficient probabilistic decision trees are required in various application areas such as character recognition. This paper presents a polynomial-time approximate algorithm for designing a probabilistic decision tree. The obtained tree is near-optimal for the cost, defined as the weighted sum of the expected test execution time and expected loss. The algorithm is advantageous over other reported heuristics from the viewpoint that the goodness of the solution is theoretically guaranteed. That is, the relative deviation of the obtained tree cost from the exact optimum is not more than a positive constant ε, which can be set arbitrarily small. When the given loss function is Hamming metric, the time efficiency is further improved by using the information theoretical lower bound on the tree cost. The time efficiency of the algorithm and the accuracy of the solutions were evaluated through computational experiments. The results show that the computing time increases very slowly with an increase in problem size and the relative error of the obtained solution is much less than the upper bound ε for most problems.

Principal Component Analysis (PCA) is a useful technique in feature extraction and data compression. It can be formulated as a statistical constrained maximization problem, whose solution is given by unit eigenvectors of the data covariance matrix. In a practical application like image compression, the problem can be solved numerically by a corresponding gradient ascent maximization algorithm. Such on-line algoritms can be good alternatives due to their parallelism and adaptivity to input data. The algorithms can be implemented in a local and homogeneous way in learning neural networks. One example is the Subspace Network. It is a regular layer of parallel artificial neurons with a learning rule that is completely homogeneous with respect to the neurons. However, due to the complete homogeneity, the learning rule does not converge to the unique basis given by the dominant eigenvectors, but any basis of this eigenvector subspace is possible. In many applications like data compression, the subspace is not sufficient but the actual eigenvectors or PCA coefficient vectors are needed. A new criterion, called the Weighted Subspace Criterion, is proposed, which makes a small symmetry-breaking change to the Subspace Criterion. Only the true eigenvectors are solutions. Making the corresponding change to the learning rule of the Subspace Network gives a modified learning rule, which can be still implemented on a homogeneous network architecture. In learning, the weight vectors will tend to the true eigenvectors.

A theoretical conjecture on fractal dimensions of a dendrite distribution in neural networks is presented on the basis of the dendrite tree model. It is shown that the fractal dimensions obtained by the model are consistent with the recent experimental data.

An application of wavelength conversion laser diodes (WCLDs) to a photonic cross-connect system using wavelength-division (WD) technology is presented. We propose a novel WD photonic cross-connect node architecture with multiwavelength selective filters. By using the filters, we can construct a nonblocking cross-connect switch by 2-stage connection. Next we describe the requirements to the optical devices in our switch, especially to the wavelength conversion devices in configuring a multistage connection of our switch. Finally, we have conducted the wavelength switching experiments using our wavelength conversion laser diode at a bit rate of 125Mb/s and shown its applicability to a WD photonic cross-connect system with over 3,000 channels.

Multiple-site diversity systems are foreseen for earth to satellite paths operating at frequencies above 10GHz in localities with high rain-induced attenuation. In some severe cases double-site protection can be proved to be inadequate and consequently triple-site diversity becomes indispensable. In the present paper, an approach for the prediction of the triple-site diversity performance based on an appropriate three-dimensional gamma distribution is proposed. The model is oriented for application to earth-space paths located in Japan and other locations with similar climatic conditions. Numerical results are compared with the only available set of experimental data taken from some parts of the United States. Some useful conclusions are deduced.

According to the development of optical communication technologies, it is getting easier to handle new devices, such as optical fibers, semiconductor light sources, guided wave devices, and optical integrated circuits. These devices have recently given considerable impact on the optical sensing field. The optical sensing shares the optical devices and the concepts of signal processing or system configuration with the optical communication. In this paper, the advanced lightwave sensing technology is discussed, considering the relation to the advanced optical communication technology. Distributed fiber sensors and the application of coherence characteristics of semiconductor light sources are the topics to be mainly discussed. In the distributed fiber sensors, the fiber plays both a role of low-loss transmission line and a role of lengthwise deployed sensing element. According to the change of characteristics of light propagating in the fiber, distribution of various physical parameters can be measured, such as the fiber loss, temperature, and strain. Optical Time Domain Reflectometry is employed to determine the location. Another tendency in the lightwave sensing field is the use of coherence characteristics of various semiconductor light sources. Low coherent source provide a highly sensitive inertial rotation sensor, that is, interferometric fiber optic gyroscope. Another type of optical gyroscope, optical passive ring-resonator gyro, has been studied as an application of a high coherence source. Frequency tunability of the semiconductor laser, especially that of tunable DFB or DBR lasers, can provide new ways in signal processing in the sensors. Optical coherence function can be synthesized also by utilizing the tunability. In conjunction with the progress in optical communication, lightwave sensing fields are steadily increasing.

This paper examines the key technologies and applications of optical frequency division multiplexing (OFDM) systems. It is clarified that a 100-channel OFDM system is feasible as a result of multichannel frequency stabilization, common optical amplification and channel selection utilizing a tunable optical filter. Transmission limitation due to fiber four-wave mixing is also described. Major functions and applications of the OFDM are summarized and the applicability of OFDM add/drop multiplexing is examined.

The subject of the paper is to analyze time complexity of the minimum modification problem in the Horn clause propositional logic. Given a set H of Horn clauses and a query Q in propositional logic, we say that Q is provable over H if and only if Q can be shown to be true by repeating Modus Ponens among clauses of H. Suppose that Q is not provable over H, and we are going to modify H and Q into H and Q , respectively, such that Q is provable over H . The problem of making such modification by minimum variable deletion (MVD), by minimum clause addition (MCA) or by their combination (MVDCA) is considered. Each problem is shown to be NP-complete, and some approximation algorithms with their experimental evaluation are given.

This paper deals with the problem of assigning tasks to the processors of a multiprocessor system such that the sum of execution and communication costs is minimized. If the number of processors is two, this problem can be solved efficiently using the network flow approach pioneered by Stone. This problem is, however, known to be NP-complete in the general case, and thus intractable for systems with a large number of processors. In this paper, we propose a network flow approach for the task assignment problem in homogeneous hypercube networks, i.e., hypercube networks with functionally identical processors. The task assignment problem for an n-dimensional homogeneous hypercube network of N (=2n) processors and M tasks is first transformed into n two-terminal network flow problems, and then solved in time no worse than O(M3 log N) by applying the Goldberg-Tarjan's maximum flow algorithm on each two-terminal network flow problem.

Optical couplers which are composed of three channel waveguides arranged two-dimensionally are investigated numerically. The mode-matching method that matches the boundary conditions in the sense of least squares is applied to this problem, using the hybrid-modal representation. The precise numerical results of the dispersion relations and field distributions are presented for the lowest three modes near the cutoff. The arrangement of three waveguides can be optimized so as to satisfy the condition for maximum power-transfer efficiency.

This paper presents a new fast fault simulation algorithm using a content addressable memory, which deals with zero-delay fault simulation of gate-level synchronous sequential circuits. The computation time of fault simulation for a single vector under the single stuck-at fault model is O(n2) for all the existing fault simulation algorithms on a sequential computers. The new algorithm attempts to reduce the computation time by processing many faults at a time by utilizing a property that a content addressable memory can be regarded as an SIMD type parallel computation machine. According to theoretical estimation, the speed performance of a simulator based on the proposed algorithm is equivalent to a fast fault simulator implemented on a vector supercomputer for a circuit of about 2400 gates.

This paper proposes a designing algorithm for quadrilateral recursive filters which consist of four quarter-plane filters in the four quadrants. This can realize a perfect zero-phase filtering which is essential for image processing. Furthermore, several parallel processing algorithms capable of performing under very high parallel efficiency are developed on line-connected and mesh-connected processor arrays. By these proposals, the advantage of two-dimensional non-causal zero-phase recursive digital filters is made clear.

For the efficient circuit simulation by the direct method, network tearing and latency techniques have been studied. This letter describes a circuit simulator SPLIT with hierarchical decomposition and latency. The block size of the latent subcircuit can be determined dynamically in SPLIT. We apply SPLIT to the MOS circuit simulation and verify its availability.

In general, dynamic channel assignment has a better performance than fixed channel assignment in a cellular mobile communication system. However, it is complex to control the system and a lot of equipments are required in each cell when dynamic channel assignment is applied to a large service area. Therefore, it is effective to limit the size of the service area in order to correct the defects of dynamic channel assignment. So, we propose an application of dynamic channel assignment to a part of a service area when fixed channel assignment is applied to the remaining part of the area. In the system, the efficiency of channel usage in some cells sometimes becomes terribly low. The system has such a problem to be improved. We show that the rearrangement of the channel allocation is effective on the problem.

The aim of this article is to show the effectiveness of exploiting separability in numerical analysis of nonlinear systems. Separability is a valuable property of nonlinear mappings which appears with surprising frequency in science and engineering. By exploiting this property, computational complexity of many numerical algorithms can be substantially improved. However, this idea has not been received much attention in the fields of electronics, information and communication engineerings. In recent years, efficient algorithms that exploit the separability have been proposed in the areas of circuit analysis, homotopy methods, integer labeling methods, nonlinear programming, information theory, numerical differentiation, and neural networks. In this article, these algorithms are surveyed, and it is shown that considerable improvement of computational efficiency can be achieved by exploiting the separability.

Dynamic behavior of a distributed parameter system described by the one-dimensional wave equation with a nonlinear boundary condition is examined in detail using a graphical method proposed by Witt on a digital computer. The bifurcation diagram, homoclinic orbit and one-dimensional map are obtained and examined. Results using an analog simulator are introduced and compared with that of the graphical method. The discrepancy between these results is considered, and from the comparison among the bifurcation diagrams obtained by the graphical method, it is denoted that the energy dissipation in the system considerably restrains the chaotic state in the bifurcation process.

A new model for a computer simulation of RF capacitive type hyperthermia has been developed by taking account of the following points. Blood flow is usually determined by many physiological parameters, but is regarded as a function of only blood temperature under some conditions. The temperature dependence of blood flow of tumors and normal tissues is assumed by referring the data obtained by Song et al. and Tanaka. The blood temperature which is elevated by externally applied power significantly affects temperatures of the body and the tumors. The transport of heat from the body surface is studied by considering air convection. These points are examined by experiments on a computer with simple phantom models and real patients. The results of simulation on the patient have shown a good agreement with clinical inspection based on CT images and a temperature of the stomach.

Mechanism for radiation phenomenon caused by a finite-length transmission line is discussed. Coupling of an external wave to a transmission line has been studied by using a circuit concept because of a TEM transmission. Since the relationship between coupling and radiation is reciprocal, radiation can be treated by using the circuit concept. It is shown that the equations obtained by using the field theory are quite coincident with those by the circuit theory. From the resultant, it can be concluded that the radiated fields are composed of those by the line current of TEM and the terminal currents. A method for an application of the circuit concept to radiation due to a trace on a printed circuit board is studied by comparing the experimental results.

We propose a new distributed signal (analog or digital) transmission system which has the immunity against the noisy channel. An information signal in transmitter is distributed by distributor and the distributed signal is transmitted. Received signal is reconstructed by the inverse distributor in receiver. In this system, an impulsive interference noise which disturbs the transmission signal in the channel passes decoder only, and this interference noise is distributed by the inverse distributor while the transmitted signal is reconstructed. Some appended signals make it possible to estimate the noise components which inversely distributed with the Fourier transformation as the distributor. Basing upon this principle, the transmission system will have an ability to suppress the impulsive interference, and the channel will have high noise immunity. The construction of receiver which can eliminate the impulsive noise is derived.

This paper presents an automatic creation method of 3D facial models which are needed for facial image generation by 3D computer graphics. A 3D facial model of a specific person is obtained from just the front and side view images without any human operation. The method has two parts; feature extraction and generic model modification. In the feature extraction part, the regions or edges which express the facial features such as eyes, nose, mouth or chin outline are extracted from the front and side view images. A generic head model is then modified based on the position and shape of the extracted facial features in the generic model modification part. As a result, a 3D model for persons is obtained. By using the specific model and the front and side view images, texture-mapped facial images can be generated easily.