• Strategy21
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• 통권36호
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• pp.215-240
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• 2015

Jeong YagYong, who are the SilHak Scholar during 18^th to 19^th century, wrote the Sadaegore with his pupil Lee Cheong. This work is the guide of diplomacy, which are asked to write from King Jeongjo. Although this book was completed after King Jeongjo's death, it harbors the King's thoughts about diplomacy or the relationship with China. Haebanggo, one chapter of the book, is about marine policy and how to treat the castaways. In this chapter, Jeong YagYong provides various ways to deal with these problems in marine area and sea refugee I will examine the Jeong YagYong's thought about the problems and ways to address these problems. Futhermore, I will inquire Jeong's opinion on the boundary in marine area. He recognized that many border transgressions happened in marine area at that time and considered that as urgent political affairs. Haebanggo consists of two parts. First part of the book is about protect own island from other countries. The rest part is about cases of dealing with castaways and their transgression. I argue that Jeong YagYong intended to make distinct borderlines in marine area and empathized the necessity of protecting Joseon's islands from other countries.

• 한국수학사학회지
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• 제29권1호
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• pp.1-16
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• 2016

This study analyzes the contents and expression methods of Jeong Yag-yong's "Gugo Wonlyu". The 530-page long "Gugo Wonlyu" discusses 1541 formulas about Gu, Go, Hyun, Hwa, Gyo; however, it has only the results of formulas and no explanations about their inducement method. Therefore we do not know how he derives and verifies the formulas. In addition, it did not follow the basic form of oriental mathematics textbooks: problem-answer-solution, and presented all the formulas only with characters without using numbers. This is a very distinctive aspect compared to other mathematical textbooks. In addition, the formulas about 5-Hwa and 5-Gyo are addressed exactly in fixed order and covers a formula in various directions. This is a clear evidence that Jeong Yag-yong analyzed and studied the Gugosul thoroughly.

• 한국수학사학회지
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• 제32권3호
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• pp.97-108
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• 2019

This paper is an outgrowth of a study on recent papers and presentations of Hong Sung Sa, Hong Young Hee and/or Lee Seung On on Gugo Wonlyu which is believed to be written by the famous Joseon scholar Jeong Yag-yong. Most of what is discussed here is already explained in these papers and presentations but due to brevity of the papers it is not understood by most of us. Here we present them in more explicit and mathematical ways which, we hope, will make them more accessible to those who have little background in history of classical Joseon mathematics. We also explain them using elementary projective geometry which allow us to visualize Pythagorean polynomials geometrically.

• Journal of Advanced Marine Engineering and Technology
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• 제32권1호
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• pp.137-146
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• 2008

Nd:YAG pulse laser welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of butt welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

• 한국광학회:학술대회논문집
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• 한국광학회 2009년도 동계학술발표회 논문집
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• pp.279-280
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• 2009

• 한국수학사학회지
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• 제29권5호
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• pp.257-266
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• 2016

This paper is a sequel to our paper [3]. Although polynomials in the tianyuanshu induce perfectly the algebraic structure of polynomials, the tianyuan(天元) is always chosen by a specific unknown in a given problem, it can't carry out the role of the indeterminate in ordinary polynomials. Further, taking the indeterminate as a variable, one can study mathematical structures of polynomials via those of polynomial functions. Thus the theory of polynomials in East Asian mathematics could not be completely materialized. In the previous paper [3], we show that Jeong Yag-yong disclosed in his Gugo Wonlyu(勾股源流) the mathematical structures of Pythagorean polynomials, namely polynomials p(a, b, c) where a, b, c are the three sides gou(勾), gu(股), xian(弦) of a right triangle, respectively. In this paper, we show that Jeong obtained his results through his recognizing Pythagorean polynomials as polynomial functions of three variables a, b, c.

• 한국수학사학회지
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• 제28권6호
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• pp.301-310
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• 2015

Since Jiuzhang Suanshu, the main tools in the theory of right triangles, known as Gougushu in East Asia were algebraic identities about three sides of a right triangle derived from the Pythagorean theorem. Using tianyuanshu up to siyuanshu, Song-Yuan mathematicians could skip over those identities in the theory. Chinese Mathematics in the 17-18th centuries were mainly concerned with the identities along with the western geometrical proofs. Jeong Yag-yong (1762-1836), a well known Joseon scholar and writer of the school of Silhak, noticed that those identities can be derived through algebra and then wrote Gugo Wonlyu (勾股源流) in the early 19th century. We show that Jeong reveals the algebraic structure of polynomials with the three indeterminates in the book along with their order structure. Although the title refers to right triangles, it is the first pure algebra book in Joseon mathematics, if not in East Asia.

• 대한기계학회논문집A
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• 제30권4호
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• pp.428-434
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• 2006

Pulse laser welding of AISI 304 stainless steel plate was simulated to find optimal welding conditions by using commercial finite element code MARC. Due to geometric symmetry, a half model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. A moving heat source was designed on the basis of experimental data. As a result, Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년도 춘계 학술대회 개요집
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• pp.248-250
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• 2006

The study on a surface transformation hardening of a rod-shaped SM45C carbon steel is carried out by using CW Nd:YAG laser. Conventionally, $CO_2$ laser has been usually used as a laser source for a transformation hardening. however, it is needed to an additional absorbent coating like a colloidal graphite owing to a lower absorbtion rate. On the other hand, no cost and post-removal process of coating is required to Nd:YAG laser, due to a higher absorbtion rate relatively. Moreover, there is a merit which is capable of building up the more flexible processing system resulted from a beam delivery through a optical fiber. In this study, we were going to recognize characteristics of a transformation hardening using a optic head with a gaussian beam distribution.

• 대한기계학회논문집A
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• 제31권8호
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• pp.839-846
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• 2007

Nd:YAG pulse laser fillet welding of stainless steel plate was simulated to find welding condition by using commercial finite element code MARC. Full model of AISI 304 stainless steel plate was considered and user subroutines were applied to boundary condition for the heat transfer. Material properties such as conductivity, specific heat, mass density and latent heat were given as a function of temperature. As results, Three dimensional heat source model for pulse laser beam conditions of fillet welding has been designed by the comparison between the finite element analysis results and experimental data on AISI 304 stainless steel plate. Nd:YAG laser welding for AISI 304 stainless steel was successfully simulated and it should be useful to determine optimal welding condition.