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이재혁 경성대학교 한국한자연구소 2017 한자연구 Vol.0 No.19
Despite numerous errors already revealed in Shuo Wen Jie Zi by Xu Shen in Eastern Han dynasty, it is still considered to be an important literature in Chinese character studies. This study utilizes tools, such as mathematical functions, set and logic, to look into Shuo Wen Jie Zi from a new perspective. Through this approach, one can get a macro-scale tendency or trend. At the same time, one can pin-point numerous micro-scale errors. This study firstly defines functions that constitute the framework, and then processes the entire data set within Shuo Wen Jie Zi, addressing the topics associated with it.
A New Cytotoxic Prenylated Chalcone from Sophora flavescens
이재혁,백남인,김성훈,박희욱,Jae Heon Yang,Jeong Joo Lee,Seong Jin Kim,정승일,오찬호,Kyu-Hee Lee,김대근 대한약학회 2007 Archives of Pharmacal Research Vol.30 No.4
We have isolated a new prenylated chalcone from the roots of Sophora flavescens (Leguminosae). We determined that structure of this compound is 7,9,2’,4’-tetrahydroxy-8-isopentenyl-5- methoxychalcone (1) on the basis of spectroscopic analysis (1D and 2D NMR data). Compound 1 exhibited potent cytotoxicity against human acute promyelocytic (HL60), mouse lymphocytic (L1210) and human histiocytic (U937) leukemia cells.
이재혁 동북아시아문화학회 2019 동북아 문화연구 Vol.1 No.60
On the basis of Busan University of foreign studies, a methodical experiment was planned, during which a group of Korean students under the guidance of Professor Jae Hyuk Lee was offered the Russian by tandem method for a four-day trip to Sakhalin, as a supplement to the basic course of studying at the Busan University of foreign studies. For this experiment with the help of a survey were selected students of the second-third year undergraduate, studying Russian language and culture. Three groups were formed and their subjects of research projects were announced like these (“History and culture of the Sakhalin region”, “A. P. Chekhov on Sakhalin”, “the Fate of Sakhalin Koreans”). The level of knowledge of the Russian language in the three groups is about the same–about two years of learning a foreign language, and none of the participants of the experiment had previously had experience in tandem method. Before the trip to Russia (Sakhalin region, Yuzhno-sakhalinsk), it was decided to form 5 tandem pairs. The experiment was held in February 2018. The aim of this experiment was to test the hypothesis that the tandem method has an impact on the process of learning the Russian language and contributes to the most effective and complete formation of communicative competence. The results of the experiment confirmed the hypothesis about the effectiveness of the tandem method in the study of teaching Russian as a foreign language. The use of this method in the experiment included the following steps: 1) The teacher divided the students into groups of 3-4 people and gave each group one common task; 2) Each student performed a specific task facing him, then brought it to the discussion group; 3) The group formed a general plan for solving the research task, based on the results achieved by each individual; 4) The teacher determines the degree of correctness of the task and assesses the work done not individually, but by the whole group. The purpose of the project activity is the formation and development of intellectual skills related to creative and critical thinking. The learning process using this technology is characterized by the following features: 1) the new role of the teacher (in the collective form of tandem method): it defines the framework of the educational process and creates an appropriate learning environment, thus motivating further cognitive activity of a foreign language and culture; monitors the parity of both languages; activates communication; makes recommendations; monitors the process of communication; 2) Heterogeneity of groups: participants of the tandem proceed from the individual, real level of the partner; communication in tandem always occurs between two partners, but not between the teacher and the group. As an auxiliary method in the study of a foreign language at the University tandem method also has a huge impact on the learning process, because this method fills the gaps in the components of communicative competence. There is also a process of applying the acquired knowledge in practice. At any stage of the study of Russian as a foreign language tandem method is an effective way of forming socio-cultural competence -knowledge of cultural and historical characteristics of the native speaker, his habits and traditions, norms of behavior and etiquette and the ability to understand and use them in the communication process, as well as sociolinguistic competence -the ability to choose and use appropriate language tools depending on the situation and purpose of communication.
고속 공기 스핀들 설계를 위한 근사해석과 회전체동역학의 비교
이재혁,박상신 한국트라이볼로지학회 2019 한국윤활학회지(윤활학회지) Vol.35 No.5
This paper presents two methods for designing a high-speed air spindle operated over the rotational speed of 50,000 rpm. The first method is an approximate method, which assumes a symmetric spindle shape even though it is not symmetric in reality. The second is an analysis of rotordynamics using beam and solid models. The approximate method can be used to calculate the bearing load capacities, stiffness and damping coefficients, stability of the shaft system, and response of the forced excitation from the unbalanced mass. Designers can use this method to determine the dimensions of the desired spindle at the first stage of the design. The more detailed behavior of the spindle can be calculated using the rotordynamics theory using beam and solid models based on the Finite Element Method. In this paper, a spindle, with two air bearings, one motor at the end, and two air thrust bearings, is newly developed. The solutions from the two rotordynamics theories are compared with the solution obtained using the approximate method. The three calculations are in agreement, and the procedure for the design of a spindle system, supported on the externally pressurized air bearings, ispresented and discussed.
유한요소법을 이용한 구보용 2024-T3 재료의 동적 물성치 평가
이재혁,김형삼,이동식,박세만 명지대학교 대학원 1999 대학원논문집 Vol.3 No.-
There are two types of beam theories: the first one is the traditional Euler-Bernoulli theory while the second one is Timoshenko beam theory that considers additional effects of shear deformations and rotary inertia. In this investigation, the both theories are utilized to evaluate elastic constants. leading to direct comparisons of the two theories. Also, for a numerical analysis the commercial FEM program. ANSYS 5.3 is employed to conduct modelling of test specimens for a modal analysis, enhancing the understanding of the nature of the FEM analysis and allowing comparisons with experimental results.
이재혁 배재대학교 한국-시베리아센터 2020 한국시베리아연구 Vol.24 No.2
북극해 지역은 지구상에 마지막 남은 환경보전지역의 하나이다. 최근 들어 이 지역은 경제적 개발과 함께 보전이라는 중요한 문제를 내포하고 있다. 지구적 기후변화에 따른 북극해의 해빙으로 북극해를 통한 항로의 이용이 활발해질 것으로 기대되고, 새로운 지역에 대한 사람들의 호기심으로 북극권의 관광이 주목을 받고 있다. 러시아는 북극해 국립공원을 확장하거나 추가로 지정할 가능성이 높으며, 아시아에서 출발하는 북동항로 시작점인 베링 해 지역이 관광루트로 유력하다. 아직 관광객을 위한 인프라 구축이 미흡한 북극해지역에서는 해상 연계를 통한 크루즈관광 역시 효율적인 방법이 될 수 있다. 러시아의 레나강-삼각주 지역 등은 북극해의 개발 가능성과 함께 지리적으로 용이한 접근성과 생물학적 다양성을 갖는 지역으로 미래의 생태관광지로 주목할 필요가 있다. 그러나 북극권은 환경적인 영향에 민감한 지역으로 관광객들의 진입에 조심스런 접근이 필요한 지역이다. 환경 변화에 민감한 북극권의 관광에는 여행자와 조직기구의 책임 있는 관광 행위가 필요하다.