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.

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).

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

평생학습도시 논의에 내재된 근대성 담론 비판과 미학적 학습도시의 가능성 검토

이병준 외 한국문화교육학회 2011 문화예술교육연구 Vol.6 No.2

도시에서의 공간은 정책 속에서 기능성, 효율성, 경제성을 기준으로 계획되어 왔다. 그러나 학습의 관점에서 볼 때 계획된 공간은 그곳에서 생활하고 체험하는 사람들의 인지구조에 강력한 영향력을 주기 때문에 기능성과 효율성이라는 경제적인 잣대로만 접근해서는 곤란하다. 도시공간이 주는 무형식학습의 영향은 지대하다고 볼 수 있으며 공간은 그 자체로 교육학적 성찰의 대상이라고 볼 수 있다. 또한 일상생활은 충동적이며, 계획에서 벗어난 것이고 그 복잡성과 개방성으로 인해 프로그램화할 수 없는 속성을 지니고 있다. 현재 평생학습의 문제를 도시와 연관하여 연구하는 학습도시이론과 정책은 계몽주의적, 통일적 시스템에 기반한 근대성에 머물러 획일적 방식의 톱다운식 운영, 단순 프로그램의 나열로 그 한계성을 보이고 있다. 이런 근대성에 기반한 한계들로 인해 현재의 학습도시 담론과 정책은 새로운 관점에서의 논의를 필요로 한다. 특히 최근 우리나라의 논의들은 창조도시 담론의 수용 속에서 문화적, 미학적 그리고 예술적 접근을 도시 속에 강조하고 있다. 이러한 논의가 학습도시 정책추진과 연결될 필요가 있다. 이에 본 연구는 학습도시에 내재한 근대성에 대해 비판적 분석, 그 한계성을 검토하고 그 대안으로 미학적 학습도시의 가능성을 검토해 보고자 한다. 이를 통해 평생교육실천가들에게 도시가 가진 문화, 예술, 공간 등의 문제가 도시 전체가 하나의 학습과 연관성 있는 텍스트로 인식되고, 평생학습도시담론에서 미학적 관점과의 조망 속에 여러 가지 제안점들을 도출해 낼 수 있을 것이다. The space in the city has been planned for functionality, efficiency and economic value in a policy. From an educational viewpoint, however, a planned spaceeffects to cognitive structure of the people living in there strongly. Therefore, the influence of formless learning from urban space and architecture can be huge. The space is an object for educational reflection in itself. Nevertheless, today’s Learning City Policy has stopped on modernity showing its limitation in top-down management with uniformed, standardized and enlightenment’s methods. But the daily life is spontaneous and the one out of plan and impossible to be programmed due to its complexity and openness. In this research, the alternative for these discussions of learning city will be found in postmodernism concept. After examining the characteristic of modernity to details and discussions of learning city based on it, the Aesthetic Learning City based on postmodernism is going to be discussed.

효과적인 초등학교 경제교과서 개발을 위한 제언

이준혁 한국경제교육학회 2005 경제교육연구 Vol.12 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.

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.

가정방문 물리치료서비스의 이용의사에 관한 연구

이충휘,원종혁,옥준영 한국전문물리치료학회 2000 한국전문물리치료학회지 Vol.7 No.1

As in house care is develops and becomes part of the health care delivery system in Korea, it is necessary to quantify the viewpoints of in-patients and outpatients. The purposes of this study are to analyze the utilization of house visits by physical therapist and to investigate the viewpoint of in- and out-patients who had rehabilitation treatment at 3 general hospitals in Wonju, Korea. Two hundred and fifty-eight questionnaires were analyzed and the major findings are as follows: 1. Sixty-five point seven percentage of respondents showed their willingness to utilize house visits by physical therapist if an in house physical therapy program were established. 2. The questionnaire used a Likert-type scale to ask the respondents their viewpoints on in house physical therapy services. Most respondents showed a positive attitude, answering 'I agree'. The findings show that house visits by physical therapists should be introduced as an integral system for the delivery of health care in Korea.

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.-