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Synopsis:In order to understand the mechanisms of internal cracks formation in the continuously cast slabs by a bow type machine in Hirohata works, influences of casting conditions have been surveyed. Metallographic structure near the internal cracks has been investigated, and by means of autoradiography, generation and growth of internal cracks have been estimated. The results obtained are as follows:1) As far as the investigated casting conditions are concerned, major cause for the internal cracks is the stress arising from correcting of bulging, which mainly depend on casting speed and specific rate of cooling water. Influences of solute elements are also recognized.2) Internal cracks are formed adjacent to the solid-liquid interface , where solute enriched liquid penetrates into the crack in solid phase. As a result of repeating the above phenomena taking place by the correcting of bulging, internal cracks are considered to grow gradually.

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The purpose of this study was to clarify the age-related effects of distances from the center of pressure (COP) to the center of mass (COM) (COP-COM distances) during one-leg standing (OLS) task. Healthy old and young adults (n = 11 each) participated in this study. The authors divided the task into 3 phases (accelerated, decelerated, and steady) based on the relationship between COM and COP. COP-COM distances in the older group were significantly reduced during the accelerated phase, then significantly increased during the decelerated and steady phases. Furthermore, distances during these phases correlated inversely with OLS time. The authors conclude that OLS time is shortened by the larger braking response to COM shifts just after leg-lifting, and the production of larger inertial forces to maintain COM position during the OLS in older individuals.