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Conceptual Design of a Table-top Terahertz Free-electron Laser
Y. U. Jeong,S. H. Park,K. Lee,J. Mun,K. H. Jang,J. Y. Lee,J. Sunwoo,김경남,Y.-H. Cha,B. H. Cha,D. H. Kim,G. M. Kazakevich 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.51
We have designed a table-top terahertz (THz) free electron laser (FEL). The main issue of the FEL design is to decrease radiation losses at the FEL resonator except outcoupling ratio. Also reducing the number of undulator periods and total undulator length is important to increase FEL conversion efficiency and to reduce its size. The FEL consists of a magnetron-based microtron having an energy of ∼5 MeV, a strong electromagnetic helical undulator having the period of ∼25 mm, and a cylindrical waveguide-mode optical resonator. The total diameter of the microtron is approximately 60 cm and the macropulse current is more than 50 mA. The condition for low-loss and high-gain oscillator of the table-top FEL has been studied by using a 2-D FEL code. Injection scheme of the electron beam to the undulator was optimized by calculating beam trajectories with a 3-D PIC code. The average THz power is calculated to be 1 W with the tunable wavelength range from 200 μm to 500 μm. The size of the system is expected to be 1 × 2 m<SUP>2</SUP>. The FEL is expected to be used for the real-time imaging of security inspection.
장유정 ( Chang¸ Yu-jeong ) 한국초등도덕교육학회 2021 초등도덕교육 Vol.- No.74
기후변화가 환경과 생태계, 인간의 삶에 미치는 영향이 커지면서 기후변화 교육의 중요성이 부각되고 있다. 이에 본 연구는 생활과 윤리 과목에서 내실 있는 기후변화 교육 방안을 마련하기 위해 교과서의 기후변화 관련 교육 내용을 분석하였다. 『생활과 윤리』 교과서는 기후변화의 의미와 특성, 영향, 대응 등 기후변화 교육의 내용요소를 모두 서술하고 있었다. 그리고 다양한 자료를 통해 토론, 의견 정당화를 촉진하며 기후변화의 특성, 대응 방안을 스스로 추론해볼 수 있도록 구성되어 있었다. 특히, 기후정의와 같은 내용요소는 타교과 교육과 차별되는 내용으로 기후변화 교육에서 도덕과 교육의 역할을 분명히 밝혀주고 있었다. 반면, 개인적·지역사회적 차원 등 다양한 차원에서 실천 방안을 모색하고 기후변화의 원인을 객관적으로 바라볼 수 있는 내용은 다소 부족하였다. 이에 본 연구는 텍스트의 서술뿐만 아니라 표, 다이어그램. 사진 등의 다양한 자료를 활용해 압축적으로 정보를 제공할 수 있는 방안을 제안하였다. As the impacts of climate change on the environment, ecosystem and human life grow, the importance of climate change education is being highlighted. Therefore, this study analyzed the contents of climate change-related education in textbooks to lay the foundation for substantial climate change education in ‘life and ethics’ subjects. ‘Life and ethics’ textbooks described every content of climate change education, such as the meaning, characteristics, impacts and responses of climate change. In addition, various datum were presented to infer the characteristics of climate change and countermeasures through activities such as discussion and justification of opinions. In particular, it dealt with the issue of climate justice. It provided an education that distinguished from other curriculum education. However, it was insufficient to find ways to act at the individual and local level and provide objective informations on the causes of climate change. Thus, this study is proposed a method to provide informations compressively using not only the descriptions of the text but also various datum such as tables, diagrams, and photos.
A Study on Factors Affecting Work Ability in Korean Workers
Yujeong Lee,Seong Rok Chang 대한인간공학회 2015 大韓人間工學會誌 Vol.34 No.4
Objective: The purpose of this study was to evaluate Korean workers" work ability and to identify its contributing factors. Background: In order for Korea to overcome the phenomena of becoming an aged society, older adults must participate in the workforce to balance out the population; workers" work ability must also be maintained. In addition, influential factors in employees" capabilities and degrees of importance thereof should be identified in advance to maintain work ability. Method: The Work Ability Index (WAI) questionnaire was completed by 5,708 Korean workers. Survey questionnaire consisted items of current work ability, physical and mental demands of the job, numbers of diseases, work impairment due to diseases, sick leaves, work ability in 2 years and mental resources. Results: Results indicated that work ability and length of service increased with age. It was also found that employees in administrative positions had greater work ability than site workers, workers directly managed by a supervisor had greater work ability than workers in cooperative firms, and workers who performed intellectual tasks had greater work ability than workers who performed physical labor. Job stress was additionally observed to contribute towards overall work ability. And musculoskeletal disorders (MSDs) were found to negatively affect work ability. Conclusion: The strongest determining factors in the work ability of Korean workers were stress level and mental state. Therefore, when the WAI is used to assess Korean workers, the weighting of WAI items pertaining to physical and mental abilities should be adjusted accordingly to account for these factors. Application: The result is expected to suggest that workers maintain work ability in an aged society.