A new simple method was developed for growing ice single crystals from the melt. The the method is based on the tendency of dislocations or grain boundaries to run perpendicular to the growth-interface when they are continued from the seed crystal. Due to this tendency, dislocations or grain boundaries can be expelled out from a Czochralsky grown crystal when the growth-interface is kept convex, that is to say ideally conical. The new growth vessel was designed so as to keep the growth-interface convex. Special care was paid to keeping the narrow clearance unfrozen between the crystal and the vessel wall at the water-level. Even when a polycrystalline seed was used, all grain boundaries were expelled after the crystal of 5cm diameter had grow to 20cm length. Conditions of the growth were, 1) a pulling speed of 2cm·day^-1 with 0.33rpm rotation, 2) a temperature of circulating liquid around the growth vessel of 0.3-0.5°C, 3) an ambient air temperature of -17°C. The single crystal obtained at the tip of the 20cm grown crystal can be used as the seed for the next step of the growth to improve the crystal quality. After 3 cycles of such growth processes, a single crystal of 10³cm^-2 dislocation density was obtained.

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A new snow disposal system is studied to clear streets for traffic in cities in heavy snow districts. This system consists of a boiler and radiant water pipes under snow dumping grounds. The snow collected from many places is brought to the heated snow dumping grounds to be placed at roadsides and other open space where the accumulated snow is melted. The design concept of this ground heating system is described. Experiments were carried out at Kitakami, Iwate-Ken in 1980; the accumulated snow melted effectively from the bottom, which demonstrated the possibility to dispose a large amount of snow when heavy snowfall continues for a few days. This system also proves more economical than a conventional snow removal system.

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In the 1980-1981 winter, exceptionally heavy snows covered the southern Tohoku, Hokuriku, northern Chubu, and northern Kinki in Honshu island. This event was called “56-gosetsu” (heavy snow in the 56th year of Showa era, or 1981) which was heavier than the “38-gosetsu” in 1963. The total dead were 133 which was caused by avalanches, falling from roofs, falling into gutters, and sudden illness during snow removal, of these 65% were over 51 years of age. It is found that the increase in mortality in snowy cities is proportional to the deviation of the maximum snow depth from the average.

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[in Japanese]

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