Phase Transformation Modeling for Hypo Peritectic Steel in Continuous Cooling

Jun‑hyun Jo,Kyung‑woo Yi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.7

Phase change of steel during cooling affects the slab qualities in continuous casting. Especially, crack susceptibility of hypoperitectic steel is high because large volume shrinkage occurs by peritectic phase transformation during solidification andcooling. In continuous cooling, phase change is different from the behaviors under the equilibrium condition, such as undercoolingand extend of peritectic reaction, etc. Therefore, we develop a new phase change model considering thermodynamics,empirical equations, and carbon diffusion in each phase to predict phase change behavior during continuous cooling. Inthis model, phase change of hypo peritectic steel comprises 5 stages until all phases become the γ phase. The velocities ofthe δ/γ interface and phase fractions during cooling are calculated according to cooling rate, undercooling of the γ phase,and carbon contents. The results show that if solidification ends by the δ phase during dTp,the γ phase is formed by massivetransformation. On the contrary, if peritectic reaction starts with liquid, the γ phase is formed and grows by diffusionaltransformation. In latter case, massive transformation of remaining δ phase can occur with high undercooling or very fastcooling rates. This analysis shows that there are several different paths depending on carbon contents of hypo peritectic steels.

重峯 趙 憲의 歷史意識과 國難對策

李東俊 同德女子大學校 1976 同大論叢 Vol.6 No.1

Cho Hun(趙憲, 1544-1592) is commonly known as a general of the civilian army in the Seven Year War of Japanese Invasion, or as a commander of the “Righteous Army”(義兵) to repel the Japanese Invaders in 1592, who died in the battle of Kum San with 700 “Righteous Scholars”, after restoring Chung Ju. He was, however, not merely a courageous soldier but a person of vision and foresight as well as a great scholar. As he said, he was engaged in the Learning of the Way(道學) and belonged to the school of Korean New-Confucianism of the 16th century, succeeding the philosophical tradition formed by Cho Kwang Cho, Yi Hwang and Yi Yi. He was themodel man who did not separate practice from theory and revealed in his action the ideology as such. It was why he could perform the correct and all covering prognosis and diagnosis of the Japanese Invasion. Toyotomi Hideyoshi having almost unified Japan that had been in the age of war for a century, would try to conquer the Asian world including Korea, China and even India. He sent envoys oftentimes and also demanded Korean delegates. The then government of Korea was embarrased and not decisive. Ho Hun, with his correct historic sense, had already begun to warn the government, sine 5 years before the war, of the possibilities of Japanese invasion and urged to refuse the Japanese demands. He definitelydeclared that Japan would invade and suggested problems as these: A. Hideyoshi's reason for sending envoys to Korea was, on one hand, to gain the international approval of his new government, which would promote the Japanese domestic stability; on the other hand, to investigate the geographic situation of Korea and spy the political conditions, which was to lead his aggression successfully. Another thing was his plot to alienate Korea from china (ming) and make her isolated. B. To respond the national diffculies Cho Hun claimed to prepare immediate counter-measures as follows: a) To keep the national opinion from being split on account of the two parties, East and West, at that time, and to choose and perform only the proper suggestions by correct and able persons; b) To reform the national system anew by reducing the consumption of the royal family and higher class so that the people's burden would be cut down and to make them engaged in the productive works such as agriculture and industry or to commercial activities; c) To prepare the military defense in two ways of the land and the sea, he especiallyemphasized the naval defense around the south-eastern sea of Korea; d) To league the allied forces of the north-east Asian countries such as China, the Loochoo Islands, Siam, etc. to blockate Japan, by informing them of the coming Japanese invasion; e) And to arouse a revolutionary power in Japan to overthrow the Hideyoshi's government so that Hideyoshi could hardly move outwards. His views were, though not completely accepted by the statesmen then, proved to be advanced and correct ones. Now we are to remember that he was also a great thinker who influenced heavily both the school of “Righteousness”(義理學派) and that of “Pragmatic” thought(實學思想).

Numerical Analysis on Crack Generation Behavior of Hypo Peritectic Steel in Continuous Casting Process

Jun‑hyun Jo,Min‑seok Park,Kyung‑woo Yi 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.11

Hypo peritectic steels exhibit a high possibility of longitudinal crack during continuous casting. Therefore, many researchershave studied the mechanisms of crack generation in hypo peritectic steel. Stress in solidified shell, or volume contractionwith small liquid fractions were suggested as the mechanisms of crack generation. A new model was developed for predictingpossibility of crack generation by calculating strain rates in solid, volume contraction rate during solidification, and theprobability of liquid unfilling in continuous cooling processes. The results show that massive transformation from the δphase to the γ phase, and peritectic transformation during solidification can be the main crack generation mechanisms. Furthermore,a linear relationship exists between the amount of undercooling for peritectic transformation (dTp) and the carboncontent of the boundary for dividing the two crack generation mechanisms. Additionally, the longitudinal crack ratios ofthe field results are analyzed through strain rates in solid and liquid unfilling possibilities. Relative positions in the range ofhypo peritectic steel and effective carbon contents are suggested to analyze the crack ratio of steels with alloying elements. This analysis shows that the results obtained from the new models for crack generation possibility are usable, and dTpcangenerate the behavioral differences in crack generation according to the conditions.

버블 전과 버블 후의 인터넷기업 평가의 비교·분석

이준섭,김진백 한국정보사회진흥원 2004 정보화정책 Vol.11 No.1

본 연구에서는 2000년 발생하였던 인터넷 버블의 붕괴 전과 붕괴 후 국내 순수 인터넷기업을 평가하는데 중요한 요인들을 탐색하고자 한다. 인터넷기업 평가를 위해 다양한 형태의 재무 요인과 웹트래픽 요인이 사용되었고, 재무요인만을 고려한 재무 모형, 웹트래픽만을 고려한 웹트래픽 모형, 그리고 재무 요인과 웹트래픽 요인 모두를 포함한 결합 모형 형태의 분석이 행해졌으며, 특히 웹트래픽 요인에서 제공되는 추가적인 역할에 초점을 맞추었다. 웹트래픽은 인터넷기업을 평가함에 있어서 매우 중요한 변수로 가정되고 있다. 그 이유는 인터넷상에서의 방문자 없이는 미래의 매출로 이어지는 고객관계가 형성될 수 없기 때문이다. 본 연구에서 사용된 웹트래픽 측정치는 순방문자 수, 방문자 수, 도달률, 페이지뷰, 방문자당 페이지뷰, 방문자당 체제시간 등을 포함한다. 회귀분석결과 버블 붕괴 전과 붕괴 있어서 투자자들의 인터넷기업 평가내용이 변화되었다 버블 붕괴 전에는 웹트래픽 정보가 더 중요한 변수로 나타났으나, 버블 붕괴 후에는 웹트래픽과 재무정보 모두 중요한 역할을 하였다. 결과적으로 인터넷기업 평가에 있어서 재무정보도 중요하지만 웹트래픽 정보가 더 중요한 역할을 하는 것으로 나타났다.

경제적 상식이론의 탐색 : '은행'에 대한 아동들의 인식 조사를 중심으로 A Case Study on the Development of Elementary School Students' Ideas about "Bank"

이준혁 한국경제교육학회 2003 경제교육연구 Vol.10 No.2

舌音系 漢字音의 口蓋音化 : 諺簡 漢字音을 중심으로

이준환 한국어학회 2007 한국어학 Vol.34 No.-

The aim of this article is redebate the palatalization of Sheyin(舌音 : lingual sounds which are composed of Sheshangyin(舌上音) and Shetouyin(舌頭音)) in Sino-Korean. For this argument I mainly made use of Sino-Korean written in Eongan(諺簡). As a result, I came to a conclusion like below. Firstly, in palatalization of Sheyin, there is no distinction between Sheshangyin(舌上音) and Shetouyin. So, I could conclude that palatalization of Sheyin was happened in the same period and the palatalization of Shetouyin was not affected that of Sheshangyin. Secondly, palatalization of Sheyin was happened in /ㄷ, ㅌ/ which was followed by /i, j/. Namely palatalization in Sino-Korean was affected by palatalization of Modern-Korean and happened in the above phonological environment. Lastly, palatalization of Sheyin was not spreaded rapidly but step by step. This change is similar to palatalization in Modern-Korean. Judging from these, I came to a conclusion like this : the palatalization of Sheyin in Sino-Korean is unique change in itself, which rarely has nothing to do with palatalization in Modern-Chinese but internal factors.

효과적인 초등학교 경제교과서 개발을 위한 제언

이준혁 한국경제교육학회 2005 경제교육연구 Vol.12 No.2

데카르트와 라이프니츠의 신 이야기

이준호 동의대학교 인문과학연구소 1999 인간과 문화 연구 Vol.4 No.-

證券去來法의 爭點에 대한 입법론적 고찰

李俊燮 인천대학교 법학연구소 2000 仁川法學論叢 Vol.3 No.-

초등 사회과 경제 영역 교과서 내용 구성에 대한 학습자들의 평가

이준혁 이화여자대학교 교과교육연구소 2012 교과교육학연구 Vol.16 No.3

경제 관련 내용 요소들을 다루고 있는 초등 사회과 교과서는 그동안 ‘수요자 중심 교과서’라는 슬로건(Slogan) 하에 개발되어 왔다. 하지만 정작 교과서의 진정한 수요자라 할 수 있는 아동들이 교과서를 어떻게 평가하고 있는지, 그리고 무엇을 문제로 여기고 있는지를 검토해 보고자 하는 시도는 거의 이루어오지 못했다고 할 수 있다. 이러한 문제의식 하에, 본 연구에서는 초등 사회과 교과서 경제단원을 중심으로 아동들이 교과서에 대해 갖는 의견과 이들이 인식하는 문제점에 귀를 기울이고, 이에 기초하여 향후 경제단원의 개발 방향을 논의해 보고자 하였다. 이를 위해 초등학교 6학년 아동 118명을 대상으로, 이전 7차와 현행 사회과 교과서 경제단원에 대한 선호도와 선호 이유, 그리고 이들이 생각하는 현행 사회과 교과서 경제단원의 문제점을 면접을 통해 알아보고자 하였다. 조사 결과, 현행 사회과 교과서 경제단원은 그 매력적 특징에도 불구하고 내용이나 활동 문제들이 아동들의 눈높이에 맞게 표상되어 있지 못해 아동들로부터 높은 평가를 받지 못한 것으로 나타났다. 이러한 조사 결과에 비추어 볼 때, 학습자들의 눈높이에 맞는 사회과 교과서 경제단원의 편찬을 위해 다음과 같은 방향에서 해당 단원을 개발해야 할 것이다. ; i) 사례 중심과 설명 중심 내용 제시 방식의 조화, ii) 해설 지향적 내용 구성, iii) ‘안내된’ 경제 탐구 중심의 활동 문제 구성. 특히 후속 연구에서는 이 세 가지의 단원 개발 방향을 어떻게 구현할 것인가에 대한 구체적인 논의가 이루어질 필요가 있다고 하겠다. This study explored how economics-related units in elementary social studies textbooks were evaluated by school learners. For this purpose, 118 children from the sixth grade in B elementary school, Seoul, were interviewed with respect to the economics-related units in the current 2007 revised elementary social studies textbook and 7th elementary social studies textbook from which they learned some years ago. The following were indicated through these interviews. Most of the interviewees preferred the economics-related units of the past textbook to that of the current textbook, and they indicated that the content and questions in the economics-related units of the current textbook were so difficult that they had difficulty in understanding and solving them. Futhermore, they responded that the content in the conomics-related units of the current textbook was boring. These responses indicate that the economics-related units in the 2009 revised elementary social studies textbook need to be developed in the following directions: i) presentation of explanation-type content based on interesting stories and examples from the economic world, ii) presentation of explanations of economic concepts and terminology, iii) and presentation of fundamental activity-typed questions. These seem to be necessary for their understanding economic world. In the future, researchers need to discuss ways to put these directions into the economics-related units of the 2009 revised elementary social studies textbook.