Radioisotopes (RI) that may be formed by thermal neutron irradiation of natural geochemical materials are extracted from the table of radioactive isotopes (Browne and Firestone, 1986) . Their gamma-ray energies which are ordered with their gamma-ray intensities, their half-life, and in addition, thermal neutron capture cross sections and natural abundance ratios of target nuclides related to the production of these RI were tabulated into a radioisotope database.
Other RI that are categorized as natural RI, fission products, fast neutron reaction products and RI used for gamma-ray energy calibration were also comprehended. This database occupies a memory area of 144kbyte and is available as a floppy disk if requested.
This database is especially useful to identify nuclides when an instrumental neutron activation analysis (INAA) is performed on the natural materials. Two examples of gamma-ray assignment of natural zircons irradiated with thermal neutrons or not irradiated are presented. For this kind of work, the database was used as a library of RI table with reduced-memory formats.

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Binary relation is a mathematical concept useful to describe a relationship between two sets or an internal structure on one set. Several authors have used binary relations for formulation of geological relations and for algorithms of computer processing (Burns, 1975; Dienes, 1978; Dienes and Mann, 1977; Shiono and Wadatsumi, 1988, 1991) . Sakamoto and Shiono (1990) showed that stratigraphic sequence can be formulated in terms of partial ordering which is defined by a reflexive, antisymmetric and transitive relation on a set, and presented a Prolog program to infer the sequence by symbolic operations. However, from a view point of integration of the inference algorithm with other numerical processing, it is convenient to infer the sequence by numerical operations using relation matrices whose entry is 0 or 1.
In the present paper we review basic arithmetical operations of relation matrices (1) to find the properties of relations, (2) to operate the union, the intersection, and the composite of two relations, (3) to constitute a partition of a set under an equivalence relation, and (4) to arrange elements of a set into linear sequence according to a given partial ordering. Further, we present an algorithm and a Basic program to infer the stratigraphic sequence from the observations at field outcrops. The program includes many subroutines for elementary operations of relation matrices which can be applied to a wide variety of problems formulated in terms of binary relations.

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We explain a method to estimate the macroscopic electric conductivity and the permeability of the rock sample including network-like structure using the effective medium approximation. Geometry-originated conductivities of all channels in the network can be obtained by the network analysis for the image data (Nakano and Fujii, 1991a, b, c) . Using the distribution of the conductivities, the effective medium approximation estimates a network including the channels whose connectivities are equivalent to those of the original network, and all whose conductivities are the same value. In this paper, we explain theoretical basis of the effective medium approximation and introduce a computer program named“ema”to apply the approximation to the practical image data analysis.

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