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22Cr-5.5Ni-3Mo 이상계 스테인리스강 용접부의 응력부식균열 전파 특성
김충언,강춘식 대한금속재료학회(대한금속학회) 1988 대한금속·재료학회지 Vol.26 No.2
The characteristics of SCC crack propagation in duplex stainless steel weldment made by SMAW GTAW and GMAW processes were investigated in 42% MgCl₂,142℃ boiling solution. From these experiments, it could be concluded that the strycture anisotrpy of y phase as well as the phase ratio played an important role in SCC resistance. GTA and GMA weld metal showed higher SCC resistance than base meta1 because of randomly distributed γ phase. The crack in weld metal had same opportunity of receiving keying effect as that in base metal, but it had less possibility of intersecting γ phase. The SCC resistance of the SMA weld metal and the HAZ was lower than that of the base metal because their phase ratio deviated from the proper phase ratio.
김충언,강춘식,김희진 대한용접접합학회 1987 대한용접·접합학회지 Vol.5 No.4
The impact toughness and SCC resistance of duplex stainless steel weldment made by GTAW, GMAW and SMAW processes was studied. The impact toughness of GTA weld metal was higher than that of GMA weld metal which contained more ferrite phase than GTA weld metal. The impact toughness of SMA weld metal was the lowest due to the harmful effect of inclusions inspite of richness of more ductile austenite phase. From these facts, it can be concluded that the important factors determining the weld metal toughness were the amount of ferrite phase and the cleaness of weld metal. While the SCC resistance of SMA weld metal was lower than that of base metal and nay other weld metal, the SCC resistance of GMA and GTA weld metal was higher than that of base metal but that of all the HAZ's were lower than that of base metal. Therefore, the impact toughness and SCC resistance of GTA and GMA weldment was pretty good as long as phase ratio was propertly controlled. Although the phase ratio was controlled, SMA weld metal could not get a good combination because the lack of shielding from the environment results in a high content of inclusions in weld metal.
중학교 생물과 학습방법 개선을 위한 현장연구 : 탐구활동을 통한 학습방법의 모색
김충언 韓國生物敎育學會 1976 생물교육 Vol.4 No.1
As a result of having excessively negative learning activities up to the present, most of the students have too much recourse to other's aid on their learning aspects. Their habits formed by negative activities may have effects on their nature and further on their capacities for solution to assigned problems by themselves when they grow to be citizens of community. In addition to that, when students want to be a man who is engaged in the science field, they are doubted even about being able to keep scientifically thinking of their subjects. Therefore the improvement of the traditional method has to be indeed intended for training up those who are able to keep thinking and solving the questions' getting rid of the dependent habits. Especially the improvement on the science study is a serious problem that requires immediate solution. We have to place emphases on science as progress studying how knowledges of science have been accumulated, not on science as product transmitted and memorized to us. It may be desirous work to improve the learning up attempting habits on the scionce field, in which fortunately students are concerned about and interested in their activities. 1. Students are immoderately passive on their learning aspects; because they have negatively studied merely to prepare the enterance examination in junior and senior high school. Therefore, if the negative method is continuously practised to students, they are uncertain whether they are able to get ability of solution to their questions as they grow to be citizens of community. If even in science education, the cramming education is positively enforced to students, the opportunities of upbringing of their scientific thought won't be offered to them. 2. If we train students to participate in positive learning activities, not only their interest to science but also their school records increase more than ever, in consequence of their assurance to the subject matters practised by positive activities, and of progress of active learning. 3. The advanced method has to be sought which aids the development of students nature, after completely seizing the essence of their interest and aptitude nearly denied now in school education. If the negative activities are practised to the students who have no thinking power, they will be fixed on the dependent habits. On the other hand, if they get trained on the procisely intended autonomic learning and on the scientific studying activities of solution to the assigned questions, they will form thinking capacity and broadminded nature. 4. The junior and senior high schools curricula have to be reconsidered, and the text compilation also nave to be precisely recomposed. As, every in each unit about the same contents, it has no connections and no direction far experiments, the effective learning to students was achieved, on the students' autonomic testing activities, with recomposing the text, fitted for experiments. 5. The method of experiment preceding theory-the conclusion. deduced from experiments is adapted to the theory-is mare effectual on the activities of the biology department. 6. As the method of deriving the conclusion from experiments before students infer what it will he is more stimulative to students than that of trying experiments after then know what it is, the activities of students get active arid interesting level also rises.
고등학교 생물과 교육과정에서 추구하는 목표와 (目標) 학력고사문제 (學力考査問題) 내객의 (內客) 비교
김충언 韓國生物敎育學會 1986 생물교육 Vol.14 No.2
Nowadays, everyone knows the importance of natural science education in the elementary school, junior and senior high school. It is true that many school-teachers of natural science exert all possible efforts to get a excellent result in science education. However one of the most important things is the preparation for the entrance examination to higher level education institutes. Therefore the contents of entrance examination must be in accordance with the objectives of natural science education which are regulated in the curriculum by the Ministry of Education. So in this article we have analysed the contents of items which have been see in university entrance examination after 1985, when the present curriculums were put into practice, and compared them with the objectives of biology education of present senor high schools curriculum. The results are as follows. The items of both subjects-$quot;BIO. I$quot; and $quot;BIO. II$quot;-in the entrance examination of 1987 educational year are successfully well suggested in respect of estimating the degree of achievement in the subject learning. So they are, as a whole, well accorded with the objective of the curriculum. On the other hand they seem to be somewhat unsatisfactory in respect of estimating the degree of systematic understanding of the $quot;basic concepts$quot;. However, we can find some defects in the items of entrance examination before 1986 educational year in following respect that the weights of subject contents were unevenly treated by the favour of suggesters. In addition, the problems of lowering and of simplication of the format still have rooms to be improved, Finally we can conclude that every suggester of entrance examination must have a good grasp of text contents of senior high school and of $quot;the curriculum$quot; before the setting of items.
고 코발트-니켈 이차 경화강에서의 M2C 석출물의 성장 거동에 관한 연구 : Part 1 . 시효처리의 영향 Part 1 . Effect of Tempering Treatments
김충언,이혁모,유충화 대한금속재료학회(대한금속학회) 1995 대한금속·재료학회지 Vol.33 No.10
The effect of tempering on the growth behavior of M₂C precipitates was examined. Applied tempering temperatures were 468, 482 and 510℃, and tempering time varied from 1 to 400 hours. The value of peak hardness was HRc 55 in all temperatures and the shift of peak hardness to earlier tempering time occurred with an increase in temperature. The peak hardness was obtained, when the average length and diameter of M₂C carbides were 4∼8 ㎚ and 1.5∼2.5 ㎚, respectively. The size of M₂C carbides increased with tempering time, and the size of carbides at 510℃ was larger than that at 482 or 468℃ in all tempering time. The aspect ratio of M₂C carbides was almost 3 in all tempering conditions. The amount of precipitated austenites increased with tempering time and temperatures. Experimental studies of grow th behavior of the carbides in this steel have been made by using TEM, SEM and X-ray diffraction.