중첩격자를 이용한 제자리 및 전진 비행하는 헬리콥터 로터의 비정상 공력해석

임동균(Dong-Kyun Im),위성용(Seong-Yong Wie),김유진(Eugene Kim),권장혁(Jang-Hyuk Kwon),이덕주(Duck-Joo Lee) 한국전산유체공학회 2007 한국전산유체공학회 학술대회논문집 Vol.2007 No.-

In this paper, helicopter aerodynamics is simulated in hovering and forwarding flighst. The governing equation is the unsteady Euler equation. To consider the blade motion and moving effects, an overset grid technique is applied in this simulation. At the boundary, the Riemann invariants condition is used for inflow and outflow. To validate this method, the result is compared with Caradonna-Tung’s experimental data.

LCL 필터의 성능 검증을 위한 SPWM 제어기반의 3상 인버터 출력 파형 발생 장치 개발 및 적용 연구

임동균(Dong-Kyun Im),강창균(Chang-Kyun Kang),하원진(Won-Jin Ha),촐롱바타르(Chuluunbaatar Sandagdorj ),고윤석(Yun-Seok Ko) 한국전자통신학회 2022 한국전자통신학회 논문지 Vol.17 No.5

본 논문에서는 LCL 필터의 성능 검증을 위한 SPWM 제어기반의 3상 인버터 출력 파형 발생 장치를 개발하였다. 필터의 성능 검증을 위한 검사 신호를 얻기 위해 먼저, DSP 기반의 3상 SPWM 신호 생성 알고리즘을 개발하였으며, 동시에 3개의 하프 브리지 게이트 드라이버를 이용하여 SPWM 게이트 구동 신호들로부터 3상 SPWM 출력 파형을 발생시키기 위한 3상 전압형 인버터 회로를 설계하였다. 다음, 개발된 SPWM 기반 3상 인버터 출력 파형 장치의 검사 신호 발생 장치로서의 유효성을 검증하기 위해 하나의 LCL 필터가 실험, 제작되었으며, DSP 기반의 성능 검증 시스템이 실험적으로 구축되었다. 끝으로, 주어진 시비율을 가지는 출력 제어 실험에서 LCL 필터의 전 후의 3상 전압 파형을 비교함으로써 SPWM 기반 3상 인버터 출력파형 발생 장치의 유효성을 확인할 수 있었다. In this paper, a 3-phase inverter output waveform generator based on SPWM control was developed to verify the performance of the LCL filter. In order to obtain a test signal for verifying the performance of the filter, first, a DSP-based 3-phase SPWM signal generation algorithm was developed, and then a three-phase voltage source inverter circuit was designed using three half-bridge gate drivers. Next, one LCL filter was experimentally fabricated to verify the effectiveness of the developed SPWM-based 3-phase inverter output waveform generator as a test signal generator, and a DSP-based performance verification system was experimentally constructed. Finally, by comparing the three-phase voltage waveform before and after the LCL filter obtained in the output control experiment with the given time ratio, the effectiveness of the SPWM-based 3-phase inverter output waveform generator was verified.

숙의민주주의의 한계와 가능성 그리고 방법론적 개선 방향

임동균(Dong-Kyun Im),나윤영(Yoon Young Na) 충남대학교 사회과학연구소 2021 사회과학연구 Vol.32 No.2

This study reviews major criticisms against deliberative democracy, and discusses the possibility of whether deliberative democracy can overcome such criticisms. Furthermore, the problems of deliberative polling, one of the most actively used deliberative democracy techniques in Korean society, are critically examined, and directions for improvement are suggested. This paper shows that extant studies on the effects of deliberative democracy have collectively given positive answers to critical questions about deliberative democracy, such as the issue of the capacity of ordinary citizens to participate in deliberation, the possibility of changing opinions through deliberation, and the issue of accountability. As for deliberative polling, we suggest that the following issues need to be seriously considered in the future: the diversity of the participants, diversity in participation, flexibility concerning top-down and bottom-up approaches, consideration of the quality of participation, improvement in the role of a discussion moderator, consideration of emotion, and the need for a long-term perspective and design. In conclusion, this paper emphasizes that deliberative democracy is required to improve representative democracy and participatory democracy, and that deliberative democracy can be positively considered as a valid methodology to solve the dilemmas in policy decisions and political polarization in Korean society.

외기 유량에 따른 시스템 공기정화기의 유동 해석

임동균(Dong Kyun Im),김광원(Gwong Won Kim),장용재(Yoong Jae Jang) 대한기계학회 2020 大韓機械學會論文集B Vol.44 No.10

본 연구는 내기 및 외기가 적용된 시스템 공기정화기의 내부 유동 특성을 전산 유체기법으로 분석한 논문이다. 외기와 함께 실내 공기가 시스템 공기정화기의 필터를 통해 유입되는지를 관찰하기 위해 유선 분포와 중심 단면에서의 속도장을 분석하였으며 실제 시스템 공기정화기 운용 조건인 유입 속도(20 & 40CMH)와 팬의 회전 속도(480 & 1,210RPM)를 적용하였다. 또한, 외기 유입에 따른 필터 표면영향성을 분석하기 위해 속도장과 압력장 분포를 관찰하였다. 이를 통해 실제 모든 운용 조건에서 실내공기와 함께 모든 외기 유동이 필터를 통해 시스템 공기정화기로 유입되는 것을 확인하였고, 팬 회전속도 대비 외기 유입 속도가 빠를수록 필터에 발생하는 공력 분포의 변화량이 감소함을 확인하였다. In this study, the structures of the internal and external flows of an air purifier system were analyzed using the computational fluid dynamics technique. To observe the flows of outdoor and indoor air through the filter, they were analyzed using streamline and sectional velocity contours. The actual operating conditions of the air purifier system were applied to the inflow velocity (20 & 40 CMH) and rotational speed of the fan (480 & 1,210 RPM), and the velocity and pressure contour were analyzed at the filter cross-section. Consequently, it was found that when the air purifier system is operated at the fan rotation speed of 480 & 1,210 RPM, all the outside air is supplied to the room through the filter. Moreover, the change in the aerodynamic distribution in the filter is reduced at the inflow velocity of 40 CMH.

부분 내재적 조화 균형법을 이용한 주기적인 2차원 비정상 유동 해석

임동균(Dong-Kyun Im),박수형(Soo Hyung Park),권장혁(Jang Hyuk Kwon) 한국항공우주학회 2010 韓國航空宇宙學會誌 Vol.38 No.12

본 연구에서는 주기적 비정상 유동 해석을 위해 푸리에 변환을 이용하는 조화 균형법의 효율적인 해법을 제안한다. 내재적으로 유속항을 처리하고 외재적으로 조화 원천항을 처리하였다. 외재적 조화 균형법 보다 더 빠르게 수렴 시킬 수 있으며 내재적 조화 균형법을 적용할 때 추가되는 자코비안 행렬을 처리할 필요가 없다. 또한 완전 내재적 기법에 상응하는 수준의 수렴안정성을 확인할 수 있었다. 2차원 비정상 유동 문제로 피칭하는 NACA0012 익형에 적용하였으며 이중 시간 적분법 및 외재적 Runge-Kutta기법의 해와 매우 일치하는 결과를 얻었다. An efficient solution method for harmonic balance techniques with Fourier transform is presented for periodic unsteady flow problems. The present partially-implicit harmonic balance treats the flux terms implicitly and the harmonic source term is solved explicitly. The convergence of the partially Implicit method is much faster than the explicit Runge-Kutta harmonic balance method. The method does not need to compute the additional flux Jacobian matrix from the implicit harmonic source term. Compared with fully implicit harmonic balance method, this partial approach turns out to have good convergence property. Oscillating flows over NACA0012 airfoil are considered to verify the method and to compare with results of explicit R-K(Runge-Kutta) and dual time stepping methods.

중첩 격자를 이용한 제자리 및 전진 비행하는 헬리콥터 로터의 비정상 공력해석

임동균(Dong-Kyun Im),위성용(Seong-Yong Wie),김유진(Eugene Kim),권장혁(Jang Hyuk Kwon),이덕주(Duck-Joo Lee),박수형(Soo Hyung Park),정기훈(Ki-Hoon Chung),김승범(Seung-Bum Kim) 한국항공우주학회 2009 韓國航空宇宙學會誌 Vol.37 No.3

본 연구에서는 헬리콥터 로터 블레이드의 움직임을 모사하기 위해 중첩 격자 기법을 적용하여 헬리콥터 로터의 전진 및 제자리 비행을 모사하였다. 제자리 및 무양력 전진 비행은 Caradonna & Tung의 로터 블레이드를 적용하였으며 전진 비행은 AH-1G 로터 블레이드를 적용하여 수치해석 하였다. 전진 비행 시 cyclic pitch각에 대해서 Newton-Raphson 수렴 방법으로 수치 트림을 수행하였으며 수치 트림에 의한 결과를 실험 및 다른 수치해석결과와 비교하였을 때 실험값과 유사한 결과를 얻었다. 또한 수치 트림에 의한 결과는 로터 전진면에서 나타나는 BVI 현상을 잘 모사하였다. 지배 방정식은 3차원 비정상 오일러 방정식을 사용하였으며 원방 경계 조건으로 리만 불변치 경계조건을 적용하였다. In this paper, the helicopter aerodynamics is simulated in hovering and forward flight. Also, an overlapped grid technique is applied in this simulation to consider the blade motion and moving effects. The Caradonna & Tung's rotor blade was selected to analyze the unsteady aerodynamics in hovering and non-lift forward flight. Also, the AH-1G rotor blade was selected in forward flight. In forward flight case, the numerical trim was applied to determine the cyclic pitching angles using Newton-Raphson method, and the numerical results were in good agreement with experimental data, especially, the BVI effects were well simulated in advancing side in comparison other numerical results. The governing equation is a three dimensional unsteady Euler equation, and the Riemann invariants condition is used for inflow and outflow at the boundary.

디지털 시민성과 21세기 공적 영역

임동균 ( Im Dong-kyun ) 영미문학연구회 2022 안과 밖 Vol.- No.53

This essay investigates the characteristics of the contemporary public sphere and offers suggestions for enhancing digital citizenship in today’s platform society. It underscores the irony that, despite the vast expansion of the public domain, democracy has declined in most contemporary democracies. This paper suggests that the current public sphere is distinguished by four features, including democratic openness, fragmentation, homogenization, and mediatization, and provides explanations for each. It also explains how fragmentation, homogenization, and mediatization contribute to anti-democratic tendencies in the online public sphere. This paper then investigates the concept of digital citizenship and proposes methods for democratizing the online public sphere by utilizing individuals’ digital citizenship. In addition, strategies for promoting digital citizenship in education are discussed. It emphasizes the necessity to create and bolster the forces of de-automatization in order to combat the pernicious effects of computational capitalism and the pervasive influence of online platforms by fostering digital citizenship. The paper emphasizes the significance of exposing students to carefully designed democratic interactions using online platforms in alternative ways within the context of educational settings. The paper employs Bernard Stigeler's philosophy of technology and Luc Boltanski's pragmatic sociology for discussion.

누가 좋은 국민인가?: 시민적 의무에 대한 인식의 구조 연구

임동균 ( Dong-kyun Im ) 한국조사연구학회 2021 조사연구 Vol.22 No.2

이 논문은 시민성 개념의 중심요소 중 하나인 시민적 의무, 특히 좋은 시민으로서 수행해야 하는 책임에 대한 사람들의 인식을 분석하고, 사회적으로 존재하는 다양한 종류의 시민성 인식 체계들의 다양성과 특징을 분석하고자 하였다. 2014년 KGSS의 시민성 문항들을 활용하고, 태도에 있어서의 관계적 유사성을 드러낼 수 있는 상관관계 집단분석 기법을 활용하여, 좋은 시민이 행해야 하는 의무에 대한 한국인들의 인식을 체계적으로 분석하였다. 분석은 그러한 인식과 관련하여 서로 다른 4가지 집단이 있음을 보여주었는데, 법제도 시민성과 연대적 시민성을 별개로 인식하는 이원 구조 집단, 대부분의 시민적 의무들을 유사한 정도로 긍정하나 정치·사회 단체 참여는 별개로 생각하는 참여제외 집단, 다양한 시민적 의무들에 대해 비교적 긍정하지만 그것의 방향성이 국내에만 맞추어져 있는 국내중심 집단, 마지막으로 법을 잘 지키고 어려운 사람들을 도와야 하는 의무에는 긍정하지만, 그 이상의 적극적인 실천에는 덜 긍정하는 기본윤리 집단의 네 가지 집단이 추출되었다. 이와 같은 분석결과는 기존의 연구들이 보여주지 못한 시민적 의무 인식의 다양성과 인지적 구조의 특성들을 보여준다. This paper analyzes popular perceptions of civic obligations, particularly the ones recognized to be fulfilled by ‘good citizens.’ The paper attempts to reveal the various kinds of perceptions and understanding of citizenship and shows their structural characteristics. Employing the 2014 Korean General Social Survey data and using correlational class analysis as the methodological strategy, this paper systematically analyzes popular understanding of responsibilities that ‘good citizens’ bear. The results show that there are broadly four distinct, heterogeneous ways of perceptions of civic obligations, which are identified by correlational class analysis. The first group, titled ‘dual structure group’, possesses perceptions that are structured along the two distinct dimensions of citizenship, which are legal-institutional citizenship and solidarity citizenship. The second group, titled ‘all-but-participation’ group, regards most civic obligations as important and essential except for participation in civic and political organizations. The third group, titled ‘domestic-oriented’ group, focuses on civic obligations mostly within domestic contexts. The final group, titled ‘basic values’ group, thinks obligations related to basic duties as important but sees more active duties as less essential. These findings reveal the diversity of popular perceptions of civic duties, which are undetected by previous scholarship.

숙의민주적 공공갈등 해결과 ‘한국적 문화’의 문제에 대한 이론적 검토

임동균(Dong-Kyun Im),이상아(Sang A Lee) 충남대학교 사회과학연구소 2017 사회과학연구 Vol.28 No.3

There has been an increasing interest in using deliberative-democratic methods for public conflict resolution in Korea. At the same time, however, it has been also frequently argued that Korean culture is not compatible with deliberative-democratic conflict resolution. This paper criticizes such an argument and discusses why attributing the cause of conflict resolution failure to Korean culture is deeply problematic. To do so, the paper provides two main critiques. First, it discusses Geert Hofstedes cultural dimensions theory as a prime example of the ‘cultural approach, and points out the theorys fundamental inability and theoretical instability to offer coherent explanations regarding how culture affects the patterns and processes of conflict resolution. Second, it introduces various theories and insights from cultural sociology and sociological theory of action to discuss why it is problematic to simply assume that Korean culture hinders deliberative-democratic conflict resolution. Specifically, it focuses on three main possibilities to explain how deliberation can work in Korean contexts: 1) the depth of culture, 2) the creativity of problem-solving actors, and 3) the power of situations. The paper also emphasizes that past studies have often misunderstood the problems of institutions and political inequality as the problem of culture. It contends that the fundamental obstacle to the success of deliberative-democratic solutions is not Korean culture but the lack of consensus-building institutions and the large inequality of power between different actors involved in conflict situations. In conclusion, the paper proposes that it is possible to use deliberative-democratic methods in public conflict resolution situations in Korean-cultural contexts.

물 분사방식 초음파 검사 노즐의 와류방지형상에 따른 유동특성 분석

임동균(Dong-Kyun Im) 한국에너지학회 2022 에너지공학 Vol.31 No.2