Cho Hun-hyun

Cho Hunhyun (born 10 March 1953) is a Korean 9-dan professional Go player. Considered one of the greatest players of all-time, Cho reached professional level in Korea in 1962. Since then, Cho has amassed 150 professional titles, more than any player in the world. He thrice held all of the open tournaments in Korea in 1980, 1982 and 1986. Cho has also won 11 international titles, third most in the world behind Lee Chang-ho (21) and Lee Sedol (15). He reached 1,000 career wins in 1995.

Early life (1962–1982)

Cho began learning Go at the age of four and passed the test for becoming a professional in 1962. In 1963, Cho was invited to Japan. Originally intended to study under Minoru Kitani, Kensaku Segoe took Cho under his tutelage. Segoe was responsible for bringing Go Seigen to Japan and also teaching Utaro Hashimoto, founder of the Kansai Ki-in. Cho was considered a 2 dan professional in Korea, but was demoted to 4 kyu upon arriving in Japan.

Cho passed the Nihon Ki-in professional exam three years later and became the first player to hold professional certificates from two Go associations. It was at this time when Cho was introduced to Hideyuki Fujisawa. Fujisawa began mentoring Cho, and the two kept a friendly relationship between each other until Fujisawa's death in 2009. Cho participated in some Japanese tournaments, finishing runner-up to Takaho Kojima in the 3rd Shin-Ei tournament. In 1972, Cho returned to Korea to begin mandatory military service. Cho won his first title in 1973, defeating Kim In in the 14th Chaegowi. That same year, Cho lost his first title to rival Seo Bongsoo in the 6th Myungin. Since 1973, Cho and Seo have met 65 times in the finals of tournaments, with Cho winning 53 of them. Their most recent title match-up came in the 1st Daejoo Cup in 2010.

Cho

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Aldehyde

An aldehyde /ˈældᵻhaɪd/ or alkanal is an organic compound containing a formyl group. The formyl group is a functional group, with the structure R-CHO, consisting of a carbonyl center (a carbon double bonded to oxygen) bonded to hydrogen and an R group, which is any generic alkyl or side chain. The group without R is called the aldehyde group or formyl group. Aldehydes differ from ketones in that the carbonyl is placed at the end of a carbon skeleton rather than between two carbon atoms. Aldehydes are common in organic chemistry. Many fragrances are aldehydes.

Structure and bonding

Aldehydes feature an sp²-hybridized, planar carbon center that is connected by a double bond to oxygen and a single bond to hydrogen. The C-H bond is not acidic. Because of resonance stabilization of the conjugate base, an α-hydrogen in an aldehyde (not shown in the picture above) is far more acidic, with a pKa near 17, than a C-H bond in a typical alkane (pKa about 50). This acidification is attributed to (i) the electron-withdrawing quality of the formyl center and (ii) the fact that the conjugate base, an enolate anion, delocalizes its negative charge. Related to (i), the aldehyde group is somewhat polar.

Cubohemioctahedron

In geometry, the cubohemioctahedron is a nonconvex uniform polyhedron, indexed as U₁₅. Its vertex figure is a crossed quadrilateral.

It is given Wythoff symbol 4/3 4 | 3, although that is a double-covering of this figure.

A nonconvex polyhedron has intersecting faces which do not represent new edges or faces. In the picture vertices are marked by golden spheres, and edges by silver cylinders.

It is a hemipolyhedron with 4 hexagonal faces passing through the model center. The hexagons intersect each other and so only triangle portions of each are visible.

Related polyhedra

It shares the vertex arrangement and edge arrangement with the cuboctahedron (having the square faces in common), and with the octahemioctahedron (having the hexagonal faces in common).

Tetrahexagonal tiling

The cubohemioctahedron can be seen as a net on the hyperbolic tetrahexagonal tiling with vertex figure 4.6.4.6.

Hexahemioctacron

The hexahemioctacron is the dual of the cubohemioctahedron, and is one of nine dual hemipolyhedra. It appears visually indistinct from the octahemioctacron.