Japan's Contribution Research Articles

Early Days of the Study of Electron Diffraction: In Memory of the Fifty Years of Electron Diffraction

A historical review is given of the discovery of electron diffraction as well as the succeeding development of electron diffraction studes. Efforts and struggles of early pioneers, both in abroad and in Japan, are described in some detail. It is pointed out that Japan's main contribution in the field of electron diffraction following Kikuchi's work of the cathoderay diffraction by mica crystals is characterized by efforts concentrated on“the electron diffraction physics”, in particular those related to the dynamical diffraction process and inelastic scattering. In this connection, discussions are given of a series of simple but typical examples of multi-wave problems that are related to some recent topics such as the critical-voltage effect. Also, reminiscence of Prof. Miyake's own works is presented, in which the main features of the phenomenon of surface-wave excitation are outlined.

Japan's contribution to the world's pollution vocabulary

Japan's contribution to the world's pollution vocabulary

地震のマグニチュードについて

This is the synopsis of one of the opening lectures at the symposium “Magnitudes of Earthquakes” which was held on April 15, 1957, at the Annual Meeting of the Seismological Society of Japan. First, history of the magnitude scale was briefly sketched and special attention was called to the assumption originally made by C. F. RICHTER that the ratio of maximum amplitude due to an earthquake to that due to the standard (M=0) earthquake depends only on the magnitude of the former and does not depend on the epicentral distance. Then followed the discussions of the relation between the maximum amplitude A and epicentral distance Δ, in particular reference to Japanese earthquakes. Various formulas by which to derive M from Δ and A were compared. The number N of earthquakes in terms of their magnitudes was the next subject of talk. It was pointed out that earthquakes in and near Japan are contributing well over 10% to the total number of earthquakes in the whole world. Then the amount of energy released by earthquakes was surveyed. Japan's contribution was estimated to be 0.5×1024erg/year in total or 1.5×103erg/cm2 year. This value 0.5×1024erg/year is again more than 10% of the total energy for the whole world which was estimated by the present writer to be 3.6×1024erg/year (one third of GUTENBERG's value.) Finally, the relations among M, E, V (earthquake volume), A (aftershock area), and x (ultimate strain of the crustal material) were discussed from the writer's own view point. The lecture closed with suggestions for future problems.