• Journal for History of Mathematics
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• v.28 no.5
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• pp.233-248
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• 2015

Year 2014 was very special to Korean mathematical society. Year 2014 was the Mathematical Year of Korea, and the International Congress of Mathematicians "ICM 2014" was held in Seoul, Korea. The year 2014 was also the 330th anniversary year of the birth of Joseon mathematician Hong JeongHa. He is one of the best, in fact the best, of Joseon mathematicians. So it is worth celebrating his birth. Joseon dynasty adopted a caste system, according to which Hong JeongHa was not in the higher class, but in the lower class of the Joseon society. In fact, he was a mathematician, a middle class member, called Jungin, of the society. We think over how Hong JeongHa was able to write his mathematical book GuIlJib in Joseon dynasty.

• Journal for History of Mathematics
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• v.27 no.3
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• pp.155-164
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• 2014

Tianyuanshu and Zengcheng Kaifangfa introduced in the Song-Yuan dynasties and their contribution to the theory of equations are one of the most important achievements in the history of Chinese mathematics. Furthermore, they became the most fundamental subject in the history of East Asian mathematics as well. The operations, or the mathematical structure of polynomials have been overlooked by traditional mathematics books. Investigation of GuIlJib (九一集) of Joseon mathematician Hong JeongHa reveals that Hong's approach to polynomials is highly structural. For the expansion of $\prod_{k=11}^{n}(x+a_k)$, Hong invented a new method which we name Hong JeongHa's synthetic expansion. Using this, he reveals that the processes in Zhengcheng Kaifangfa is not synthetic division but synthetic expansion.

• Journal for History of Mathematics
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• v.27 no.1
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• pp.1-12
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• 2014

From the mid 17th century, Joseon mathematics had a new beginning and developed along two directions, namely the traditional mathematics and one influenced by western mathematics. A great Joseon mathematician if not the greatest, Hong JeongHa was able to complete the Song-Yuan mathematics in his book GuIlJib based on his studies of merely Suanxue Qimeng, YangHui Suanfa and Suanfa Tongzong. Although Hong JeongHa did not deal with the systems of equations of higher degrees and general systems of linear congruences, he had the more advanced theories of right triangles and equations together with the number theory. The purpose of this paper is to show that Hong was able to realize the completion through his perfect understanding of mathematical structures.

• KIPE Magazine
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• v.25 no.3
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• pp.30-37
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• 2020

• 한국생물공학회:학술대회논문집
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• 2000.04a
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• pp.185-188
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• 2000

Disinfection and molecular weight changes by electron beam irradiation has been examined. Before radiation, the viscosity of oven-dried HA decreased about 30% but the viscosity of vacuum-dried HA did not decrease. The number of viable cell depends on the relative humidity(RH). The cell number decreased about 30% in RH 0% and about 10% in RH 100%. After radiation, the decrease in the molecular weight of the hyaluronic acid was larger in the RH=0% than in the RH=100% and was larger in the vacuum-dried HA than in the oven-dried HA. The extent of disinfection were similar for all form.

• 한국도로학회지:도로
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• v.17 no.4
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• pp.56-61
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• 2015

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.207-207
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• 2008

• Proceedings of the Korean Vacuum Society Conference
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• 2008.02a
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• pp.222-222
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• 2008

• The Safety technology
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• no.200
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• pp.34-37
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• 2014

• Proceedings of the Korean Vacuum Society Conference
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• 2007.08a
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• pp.103-103
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• 2007