Sadayuki Murashima

Lossless fractal image coding

Lossless fractal image coding (LFIC) is a new method to code images. The significant property of this method is that it is the first simple fractal image coding method that can regenerate images without data loss (lossless). The method, different from the other fractal image compression, needs no search for the matched domain-range. Therefore, the coding time of this method is also very fast compared with the other fractal image compression methods.

Correction Devisors for the Four-Point Probe Resistivity Measurement on Cylindrical Semiconductors (II)

Using the Neumann function, this paper gives the expressions of the correction devisors for the equally spaced and linearly arrayed four-point probes on the same generating line of a circular cylinder of infinite length. Also for the cylinder of semi-infinite and finite length, the effects of the non-conducting and conducting edges are considered. The correction devisors are given as the function of the ratio of the radius of the cylinder to the probe spacing with the parameter of the edge effect. Several special cases obtained using our idea coincide with other results already calculated by the method of images hitherto used.

A Code Whose Codeword Length is Shorter than log2* n in Almost All of Sufficiently Large Positive Integers

A recursive-type positive integer code is proposed. It prefixes the information about the length of the component of the codeword recursively. It is an asymptotically optimal code. The codeword length for a positive integer n is shorter than log2*n bits in almost all of sufficiently large positive integers, where log2*n is the log-star function.

One-dimensional resolution improvement of images in time series by genetic algorithm

Several frame images in a time series that can be taken by a TV camera system under specified conditions can be given improved one-dimensional resolution by solving a recurrence formula or by an inverse-filtering method. It appears that one-dimensional resolution improvement is the same as the problem of optimum search satisfying given conditions for the images in a time series. It is known that genetic algorithms are extremely effective in optimum search problems. In this paper, a genetic algorithm is investigated for one-dimensional improvement of the resolution of images in a time series. Some experimental results are presented. Also, it is shown that the proposed method is effective for improvement of the resolution of images in time series with noise.

New method for measuring the topology preservation of self-organizing feature maps

The topology preservation of self-organizing feature maps is an important property which is used in many applications. Various qualitative and quantitative approaches are known for measuring the degree of topology preservation. However, well-received measures for determining the topology preservation have not been presented yet. In this paper, we present a new method for measuring the degree of topology preservation based on the masked Delaunay triangulation. The topology preservation is completed when the masked Delaunay triangulation coincides with the output network shape. We demonstrate the usefulness of this measure for various examples of data manifolds. This method is also applied to measure the degree of topology preservation of the topology-representing network of T. Martinetz et al. (1994). In various simulations, this measure brought a reasonable degree of topology preservation.

Neumann Functions for Laplace's Equation for a Circular Cylinder of Finite Length

In this paper general solutions for the Neumann problem for a circular cylinder of finite length are presented in terms of re-defined Neumann functions. The Neumann function, which has a zero normal derivative on the boundary, does not exist in a finite region according to Gausss theorem. However, there exists a potential function due to a unit source which has a non-zero normal derivative. This function is defined as the Neumann function in the finite region. The Neumann functions for a circular cylinder of finite length are presented in three different forms. They correspond to three types of expressions of the potential function, called z-, r-, and -forms after Dougalls work. These Neumann functions play the same role in the Neumann type boundary value problem as Greens function in the Dirichlet type problem. The different forms are useful because they have their own regions of rapid convergence.

Analyses of Some Potential Problems in Cylindrical Coordinates in Connection with Four-Point Probe Technique

By the use of Greens function method, the expressions for the correction devisors are presented for the four point probe resistivity measurement of the semiconductor plate bounded vertically by a cylindrical surface under various boundary conditions. The cases of both linear and square probes are discussed. Some special cases are compared with the results already reported. In terms of numerical analysis, the two kinds of problems treated here are typical examples which are to be analyzed by use of the expressions of the r- and -forms, respectively.

Correction Devisors for the Four-Point Probe Resistivity Measurement on Parallelepiped Semiconductors

By use of the Greens function method, the expressions of the correction devisors for the equally spaced and linearly arrayed four-point probes on the centerline of a parallelepiped semiconductor are derived under the various boundary conditions. The numerical results of correction devisors are given in figures.

Information Capacity of Radiographic Images for the Random Signal and Continuous Objects

Some of the results in a previous paper, JJAP 7 (1968) 414, which deals with the random signal are considered again. The capacity is roughly proportional to the square bandwidth of the equipment. The reason is explained. To investigate the decrease of the capacity of actual continuous object from the random signal, capacities for three kinds of object spectrum, including that of bones in human bodies, are estimated using numerical examples. For wide object spectra, the wider bandwidth of a radio-graphic or inspecting equipment produces the greater capacity. For narrow object spectra or for low frequency objects, the capacity is proportional to the square spread of the object spectrum and the insertion of a low pass filter improves the capacity. The reasons are discussed in detail. Since eyes and an intensifying screen act as low pass filters, for low frequency objects, the capacity of the film directly exposed is increased by exposing with the screen or by inspecting by eyes.

The perfect recalling rate of morphological associative memory

Morphological associative memory is made up by replacing the sum of input signals by maximum or minimum operation. Ritter presented a procedure of associative memory, which utilizes associative memory matrix M and W sophisticatedly. This paper treats the recalling rate of associative memory. At first, conditions of perfect recalling are given. Then the perfect recalling rate of associative memory is derived based on these conditions. The formula of perfect recalling rate found out to be equal to the perfect recalling rate obtained by experiments.