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HITL 시뮬레이션 기반 돌풍 인식 알고리즘 설계 및 PX4 연동 시스템 연구
하종준(Jongjun Ha),이봉일(Bongil Lee),이예준(Yejun Lee),이진우(Jinwoo Lee),이현중(Hyeonjung Lee),고동현(Donghyeon Ko),이동진(Dongjin Lee) 항공우주시스템공학회 2025 항공우주시스템공학회 학술대회 발표집 Vol.2025 No.5
최근 무인항공기의 활용도가 증가함에 따라 다양한 기상 조건에서도 안정적으로 운용할 수 있는 기술 개발의 중요성이 커지고 있으며, 돌풍과 같은 급변 기류 상황에 자율적으로 대응할 수 있는 기술이 요구되고 있다. 본 논문에서는 수직이착륙 무인기(LC62-50B)의 동역학 모델을 기반으로 기체의 안정적인 자세 상태와 자세 제어 명령 데이터를 수집하고, 이를 통해 비지도 학습 기반 오토인코더를 학습하여 돌풍 인식 알고리즘을 설계하였다. 설계된 알고리즘은 ROS2 환경에서 구현되었으며, 돌풍을 인식할 경우 사전에 정의된 비상 착륙 지점으로 자동 복귀하도록 구현하였다. 또한, PX4와 ROS2를 연동한 HITL(Hardware-In-the-Loop) 시뮬레이션 환경을 구성하고, 돌풍 상황이 모사된 시뮬레이션을 통해 돌풍 인식 알고리즘의 성능을 검증하였다.
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Berry-phase phenomena in low-energy squeezed magnons
Jongjun Lee,Hyun-Woo Lee 한국자기학회 2025 한국자기학회 학술연구발표회 논문개요집 Vol.35 No.1
Berry-phase effects such as the magnon Hall effects have attracted strong theoretical interest in magnonic systems [1]. However, their experimental detection remains challenging due to the mismatch between regions of large Berry curvature and the population distribution dictated by Bose-Einstein statistics. In typical magnon bands, the Berry curvature is strongest at higher energies, where thermal occupation is exponentially suppressed, weakening the observable signal. In this work, we propose a method to enhance Berry-phase phenomena in magnon systems by introducing magnon squeezing. Squeezing terms, arising from nonlinear magnon interactions or external parametric driving, break the U(1) symmetry of the magnon pair creation and annihilation [2-4]. These interactions reshape the magnon band structure such that large Berry curvature emerges near the bottom of the lowest magnon band, where the Bose-Einstein distribution leads to significant occupation. As a result, the Berry-phase contribution to transport is amplified. We analyze a single-band magnon Hamiltonian incorporating squeezing and use the Bogoliubov-de-Gennes formalism to reveal an effective two-band structure [5]. The squeezing-induced avoided crossings between physical and fictitious magnon modes lead to sharply peaked Berry curvature in low-energy regions. Our results demonstrate that magnon squeezing provides a new framework for the experimental realization of Berry-phase phenomena in magnetic insulators and magnonic devices.
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Jongjun Lee,김경민,Shinyoung Im,Sang Ho Shin,Won Seok Chang,Mun Sei Oh 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.2
A combined heat and power (CHP) system generates electricity from thermal energy and generates heat by utilizing the remaining thermal energy. The system efficiency of the cogeneration system is 75~85 %, which is very high compared to existing only power generation facilities, so it is very useful for energy conservation and environmental protection. For this reason, interest in the cogeneration system is increasing worldwide. Generally, a cogeneration plant consists of a steam turbine alone or the combined power generation of a gas turbine and a steam turbine depending on the scale. The steam turbine is divided into a back-pressure type turbine and a condensing type turbine depending on the operational methodology of the steam turbine. In both cases, the shift in the return temperature of the district heating users influences the performance of the cogeneration plant, thus affecting the power generation costs of the power plant. It is possible to accurately estimate the change in the unit cost of the power generation caused by these changes, and to inflict it on the user, thereby changing the usage pattern of the user and reducing the energy consumption accordingly. In this study, the commercial combined cycle cogeneration system using back - pressure type turbine was simulated, and the change of performance of the combined heat and power plant was analyzed while changing the user facility's total return temperature. Based on the results of this analysis, a possible loss in the plant according to the change of return temperature was predicted. Also, the effect of each user’s return temperature on the plant loss was analyzed using an actual user's return temperature data. The economic-mechanical approach, such as this study, can alleviate dissatisfaction with the user's charge and to consume energy in a more rational way. It eventually can play a role in reducing carbon emissions.
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A histone deacetylase, MoHOS2 regulates asexual development and virulence in the rice blast fungus
Jongjune Lee,Jae-Joon Lee,Junhyun Jeon 한국미생물학회 2019 The journal of microbiology Vol.57 No.12
Histone acetylation/deacetylation represent a general and efficient epigenetic mechanism through which fungal cells control gene expression. Here we report developmental requirement of MoHOS2-mediated histone deacetylation (HDAC) for the rice blast fungus, Magnaporthe oryzae. Structural similarity and nuclear localization indicated that MoHOS2 is an ortholog of Saccharomyces cerevisiae Hos2, which is a member of class I histone deacetylases and subunit of Set3 complex. Deletion of MoHOS2 led to 25% reduction in HDAC activity, compared to the wild-type, confirming that it is a bona-fide HDAC. Lack of MoHOS2 caused decrease in radial growth and impinged dramatically on asexual sporulation. Such reduction in HDAC activity and phenotypic defects of ΔMohos2 were recapitulated by a single amino acid change in conserved motif that is known to be important for HDAC activity. Expression analysis revealed up-regulation of MoHOS2 and concomitant down-regulation of some of the key genes involved in asexual reproduction under sporulation-promoting condition. In addition, the deletion mutant exhibited defect in appressorium formation from both germ tube tip and hyphae. As a result, ΔMohos2 was not able to cause disease symptoms. Wound-inoculation showed that the mutant is compromised in its ability to grow inside host plants as well. We found that some of ROS detoxifying genes and known effector genes are de-regulated in the mutant. Taken together, our data suggest that MoHOS2-dependent histone deacetylation is pivotal for proper timing and induction of transcription of the genes that coordinate developmental changes and host infection in M. oryzae.
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