Yanosuke Otsuka

Yanosuke Otsuka (Japanese: 大塚弥之助) (11 July 1903 – 7 August 1950) was a Japanese geologist and professor.[1][2]

Yanosuke Otsuka
Yanosuke Otsuka in c. 1940
Born	(1903-07-11)11 July 1903 Tokyo, Japan
Died	7 August 1950(1950-08-07) (aged 47)
Nationality	Japanese
Spouse(s)	Chieko Otsuka (大塚千枝子)[1]
Children	Yoshiyuki Otsuka (大塚義之)[1] Natsuko Otsuka (大塚南津子)[1]
Scientific career
Fields	Geology

Yanosuke Otsuka was born in Nihonbashi, Tokyo on 11 July 1903.[1][2] He went to the Junior High School attached to Tokyo Higher Normal School, and after that to Shizuoka High School.[2] For his undergraduate studies, he entered the Department of Geology, Faculty of Science, Imperial University of Tokyo, where he graduated in 1929.[2] While he was student, he learned the methods of historical geology from Yoshiaki Ozawa, topography from Taro Tsujimura (辻村太郎), and Cenozoic biological stratigraphy from Shigeyasu Tokunaga (徳永重康).[2] After graduation, he entered the Earthquake Research Institute as an assistant in 1930, becoming an associate professor in 1939 and a professor in 1943.[1] He made significant contributions in characterizing the surface faults in the circum-Pacific area, effects of tsunamis, tectonics of crustal movements, taxonomy of molluscs, paleoclimatology, mapping of Cenozoic strata, and the Tertiary history of the Japanese islands.[1][2] He died prematurely from pulmonary tuberculosis on 7 August 1950, at the age of 47, because effective antimicrobial therapy was not yet available in Japan at the time.[1]

In biology, he is known for the Otsuka similarity coefficient[3][4] (also known as Otsuka-Ochiai[5] or Ochiai coefficient[6]), which can be represented as:

${\displaystyle K={\frac {|A\cap B|}{\sqrt {|A|\times |B|}}}}$

Here, ${\displaystyle A}$ and ${\displaystyle B}$ are sets, and ${\displaystyle |A|}$ is the number of elements in ${\displaystyle A}$. If sets are represented as bit vectors, the Otsuka similarity coefficient can be seen to be the same as the cosine similarity.