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Kokubu, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu*; Kimura, Takaumi; Yamazaki, Hideo*; Yoshikawa, Shusaku*; Nagaoka, Shinji*
no journal, ,
Plutonium isotopes were released from Nagasaki atomic bomb which exploded on August 9, 1945. The isotopes are interesting in research on environmental radioactivity, because evident information of the plutonium release provide opportunities to simplify understanding of environmental behavior of Pu. The Nagasaki area is one of the oldest areas that were contaminated with the artificial Pu in the world. As the isotopic composition of Pu depends on its origin, Pu/Pu ratio is a useful tool for the identification of the source of Pu. This paper is intended to report the Pu/Pu ratios in sediments and surface soils and distribution of the Pu from the atomic bomb.
Sakai, Kazumi*; Ogata, Rui*; Kimura, Nobuharu*; Matsumoto, Yoshihiro*; Kurita, Keisuke
no journal, ,
Neutron imaging technique was applied to visualize grease fluidity in bearings which determines the bearing torque property. Two types of lithium (Li) greases with different thickeners were used in this study. The Li complex grease was superior in lowering bearing torque related to energy-saving performance. After bearing rotations, neutron radiography and computed tomography measurements of the greases distributed in the bearings were performed. Adhesion of the Li complex grease to bearing balls was quite limited, and most of the grease stayed on cage surfaces between the balls; adhesion of single Li soap grease to bearing balls was remarkable. The neutron radiography with bearing rotations was also conducted to capture the moment of the grease flow. The observation with bearing rotations revealed that single Li soap grease flows gradually not from the beginning of bearing rotations. Based on these results, the lubrication mechanisms will be proposed.
Sakai, Kazumi*; Ogata, Rui*; Yamada, Shuhei*; Kimura, Nobuharu*; Matsumoto, Yoshihiro*; Kurita, Keisuke
no journal, ,
Rolling element bearings with grease lubrication are widely used for axis rotations in motors. Unlike liquid lubricants, the fluidity of semisolid greases in bearings plays an important role in bearing performances. The fluidity is often described as channeling and churning states. The states are well known, however, cannot be seen from outside bearings. Therefore, visualizations of greases in bearings are beneficial to understand the grease fluidity, however, methods for non-destructive observations of the inside of bearings are limited. The neutron imaging technology was applied for non-destructive observation of the grease fluidity inside a ball bearing in this study. The technology is based on a characteristic that neutron passes through heavy elements and interacts to light elements. In other words, neutron can identify lubricants with light elements inside the bearing with heavy elements.