http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
- 中文 을 입력하시려면 zhongwen을 입력하시고 space를누르시면됩니다.
- 北京 을 입력하시려면 beijing을 입력하시고 space를 누르시면 됩니다.
RISS 인기검색어
- 검색키워드
- 저자 : 이정흠 (검색결과 13 건)
-
-
-
북경의 겨울과 여름 대기 중 초미세먼지의 입자 특징 및 예방 대책
This paper is a review for characteristics of individual aerosol particles under haze days in summer and winter in Beijing, China and the results were compared to those of Korea. In order to better understand the impact of atmospheric particulate matter from different sources and to aid in the development of air pollution control plans, 108 aerosol samples were collected during the summer of 2014 and winter of 2015. The samples were analyzed with scanning electron microscopy-energy dispersive X-ray(SEM-EDX) technology. The results showed calcium-sulfate and carbonaceous particles significantly increased during hazy days. In the PM>2.5 fraction, amount of fugitive dust on clear days in summer was lower than that in winter. Organic carbon and S-rich particles rapidly increased during hazy days in summer. In winter time, average concentrations of organic carbon and special particles such as S-rich particles increased up to 145 times compared with the levels on clear days, resulted from coal burning. Total number of particles in the PM< 1 fraction were increased as much as 700%. During hazy days in the summer and winter, numbers of particles in the PM0.5-1 fraction increased 1.6 and 8 times, respectively. which were compared with the levels on clear days. The dominant particles in the atmospheric particulate matter varied with the different seasons. Most of the Beijing's smog came from automobile exhaust and carbon burning pollution. while sources of smog in Seoul are mainly automobile exhaust and factory pollution. Differences of main sources for smog between Beijing and Seoul suggest that eligible prevention measures are required to clear air conditions
-
초고강도강판 성형용 프레스금형의 CrN 코팅층 수명예측을 위한 마모시험법 연구
최근 자동차 산업 전반에서 강화된 환경규제에 대응하고자 초고강도강판 적용이 증가하고 있다. 일반적으로 초고강도강판은 열간 프레스가공으로 생산하지만 냉각장치 등 추가시설이 필요하며, 생산성이 낮은 단점이 있다. 이를 보완하고자 냉간 성형으로 초고강도강판을 성형하고자 하는 연구가 진행되고 있다. 냉간 성형으로 초고강도강판 차체 부품 성형 시 기존의 일반강보다 증가된 인장강도로 인해 소재 반력이 크게 증가하고 이로 인해 성형금형은 큰 접촉압력을 받게 된다. 성형금형이 큰 접촉압력을 받게 되면 긁힘, 소착 등 표면결함이 발생하며, 금형 파손 및 피로에 의한 피로파괴로 이어지게 된다. 이는 금형의 내구수명 저하와 직결되며 생산성 감소, 제품 품질 저하 등 산업 현장에서 큰 문제의 가능성을 의미한다. 따라서, 제품 양산 중에도 잦은 유지보수가 필요하며 이에 따른 비용 또한 증가하여 금형 제작비와 별도로 추가적인 비용이 발생하고 생산을 중단해야하는 심각한 문제까지 발생될 수 있다. 이와 같은 문제는 사전에 금형의 수명을 예측하여 적절한 시기에 효과적으로 대처하여 해결해야한다. 본 논문에서는 인장강도 1.5GPa급 초고강도강판을 소재로 성형되는 자동차 부품용 성형금형의 CrN 코팅층 수명예측을 위해 마모 특성을 정량화할 수 있는 마모시험법 및 기초 마모량 예측식을 제안하였다. 이를 위해 초고강도강 부품의 성형공정해석을 실시하고 성형중 소재와 금형간에 발생하는 접촉압력, 미끄럼거리, 상대속도 등 시험 인자의 범위를 도출하였다. 이 조건을 마모시험법에 적용하기 위해 마모시험과 동일한 조건의 접촉해석을 수행하고 수직하중에 따른 접촉압력을 도출하였다. 실제 금형 제작방법과 동일한 가공, 열처리 및 표면처리를 부과한 시험편을 제작하고, 시험편의 코팅층 특성을 분석하였다. CrN 코팅층 수명예측을 위한 마모시험과정에서 시험결과에 영향을 미치는 시편형상, 코팅 불량 등의 문제를 검토하였으며 이에 대한 해결방안을 제시하였다. 마모시험은 마모시험 장비 사양에 따라 시험조건을 선정하여 각 시험 인자와 CrN 코팅층 마모량의 관계를 파악할 수 있는 마모시험법을 제안하고 분석하였다. 실험계획법 및 분산분석을 실시하여 이들의 유의성을 판단하였다. 또한, 회귀분석을 실시하여 수직하중, 미끄럼거리, 상대속도로 구성된 세 가지 설계변수의 효과에 대해 추정하고 최적조합을 구성하여 기초마모예측식을 제안하고 수명예측을 실시하였으며, 속도 인자가 고려되지 않은 Archard모델과의 경향차이를 비교하였다. Currently, ultra-high strength steels(UHSS) are increasingly used to auto-body parts for the satisfaction of the environmental regulation. Many automotive parts with UHSS are manufactured by the non-conventional forming process such as hot press forming. However, the hot press forming process needs the complicated and expensive equipments for cooling and additional treatment, which results in the lower productivity in comparison to the conventional cold forming process. On the other hand, the cold forming process with UHSS has many problems during forming such as the low formability and the poor shape accuracy during forming. Also, it also suffers troubles such as the low durability of the tool surface due to the remarkably increased contact pressure and the friction between the tools and the blank. The excessive contact pressure causes the problem of surface defects such as chipping, scratch, crack, galling and so on. Therefore, it is necessary to predict the tool life during the forming process and to inform the change period of the stamping tools in the press shop. In this paper, a wear test method is proposed to predict the wear life of the CrN layer coated on the surface of the press tools for manufacturing the auto-parts with UHSS having the ultimate tensile strength of 1.5GPa. The finite element analysis is carried out for the stamping process of the center floor side member with UHSS to extract the range of the contact pressure, relative sliding velocity and the sliding distance between the tools and the blank. The contact analysis is also pursued to correlate the normal force range in the wear test with that in the stamping process. At first, the pin-on-disc type wear test is carried out in order to confirm the feasibility and the reproducibility of the wear amount according to the test conditions such as the normal force, the sliding velocity and the sliding speed. The problem of the inaccurate result is mainly originated from the inaccurate shape of the pin specimen and the surface defect on the coated surface. The wear tests are carried out to construct the prediction model of the CrN coating layer during the forming process. In order to construct, the prediction model, the study adopts the design of experiment(DOE) such as Taguchi method and response surface method (RSM). The orthogonal array is constructed in order to set up the experimental conditions with three design parameters such as the normal force, the sliding velocity and the sliding speed. From the measurement result according to the design variable, the wear depth is derived from the wear life equation from the regression analysis. The derived prediction model is then compared with the result of the Archard wear model, which fully describes that the proposed prediction model can effectively predict the wear life of the press tools for the auto-parts with UHSS.
-
-
한국어교육 프로그램 설계 연구 : ? 중국인 한국어 초급 학습자의 어학 성취도 분석을 중심으로 -
Korean, as the language of the Korean nation, has a total of 75 million users in the world, ranking 12th among the number of users in the world. In recent years, the world has been caught in the Hanryu hot blast. With the increasing economic and cultural exchanges between China and South Korea, the social demand for Korean-speaking talents is also increasing. This also makes many Chinese students who want to learn Korean become more and more. The most obvious thing is that there are not only more universities majoring in Korean, but also an increase in the number of students studying in South Korea every year. But South Korean companies in China, as well as Korean language teachers employed at universities, employ most of the foreign students who have returned from South Korea, while few graduate students majoring in Korean from domestic universities in China. Through the survey, it is found that foreign students who return from South Korea understand Korean and use Korean much better than those majoring in Korean who have not studied. Through the comparison of Korean education in five universities in China and Korean education in 5 universities in South Korea, it is concluded that the educational courses set up in Korean education are more professional and comprehensive than those in Chinese universities. More professional and more fully reflected in Korean education courses in South Korea, not only employ more Korean teachers, but also employ Korean teachers are very professional. Secondly, the Korean teaching materials used are not only many but also closer to the recent teaching trend. There is also a large and reasonable schedule of teaching courses at universities in South Korea. Korean education curriculum not only has advantages, but also has corresponding shortcomings, and in order to find out the shortcomings, we investigate and compare the results of 55 junior Korean students, and compare and analyze the results of the students in the middle of Korea University from the second semester to the end of the third semester of 2019. in order to find out the shortcomings of this aspect, we investigated and compared the results of 55 junior Korean students from 2019 to the end of the third semester. Get out the Korean language education curriculum, the corresponding shortcomings of the education curriculum. Through the comparison of the advantages and disadvantages of Korean education courses between Chinese and Korean universities, as well as the investigation and analysis of 55 junior Korean education students in Korean universities. This study designs a curriculum that is more suitable for students to complete the primary Korean language education. The design of this educational curriculum includes the following points. First, ask universities in China to reorganize the educational objectives and curricula of the Korean language. So that students can carry out comprehensive learning of Korean, teaching materials are not a single use of a textbook, but according to the current situation in South Korea, with compound trend of teaching materials to teach. So that students can learn more knowledge. Second, change the corresponding curriculum according to the conditions of all kinds of students, rather than let all students take the same curriculum, according to the advantages and disadvantages of each student, to change the educational curriculum accordingly. Third, in the Korean curriculum of Chinese universities, it is necessary to arrange more writing time, so that students can improve the level of Korean, or the use of the community in the future, is of great help. Fourth, in the Korean language curriculum of Chinese universities. According to the students' personal conditions to arrange the corresponding class time, because each person's ability to accept learning is different, all according to each person's own conditions, whether to arrange the corresponding supplementary classes, or other extracurricular activities. Through the use of the above educational courses, I hope that more students who learn Korean can learn Korean well, whether it is the study and understanding of Korean at that time, or the use of Korean in the future will provide great help.
-
본 논문에서는 전기적으로 큰 스트립 구조에 의한 전자파 산란문제를 파수영역(spectral domain)에서의 모먼트법(Moment method)을 이용하여 해석하였다. 공간-파수 영역(spatial-spectral domain)에서 그린함수(Green function)의 특성을 고찰한 후, 파수 영역에서 특정한 기저함수와 전개함수를 사용하여 전자파 수치해석에 널리 사용되고 있는 모먼트법과 기하광학(Geometrical Optics)/기하회절이론(Geometrical Theory of Diffractions)해 사이의 관계를 알아보았다. 그리고, 파수영역에서의 임피던스 행렬 분포를 관찰한 후, 기존의 모먼트법의 계산시간을 줄이면서 GO/GTD해보다 정확한 해를 구하는 방법을 제안하였다. 이 방법은 전기적으로 큰 전자파 산란 문제에 대해 보다 짧은 계산시간내에 GO/GTD보다 정확한 해를 구하는데 적용할 수 있을 것이다.
-
-
-
연관 검색어 추천
이 검색어로 많이 본 자료
활용도 높은 자료
