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동적하중을 받는 항공기 외부장착물의 피로수명 예측에 대한 연구
정회인(Hoein Jeong),박지환(Jihwan Park),손동훈(Donghun Son),장종윤(Jongyoun Jang) 한국소음진동공학회 2019 한국소음진동공학회 논문집 Vol.29 No.4
In this article, we evaluate the fatigue life of an aircraft external store under real dynamic loads of a helicopter. For estimation of fatigue life of an aircraft external store, we first measured the vibration after mounting an aircraft external store on the actual helicopter and analyzed the PSD. Then, the PSD for accelerated life test was calculated using VRS and time scaling. The natural frequency obtained from the ODS test was compared with the natural frequency of the FEM analysis. Moreover, the response PSD of the ODS test and the response PSD of the FEM analysis were compared. The stress cycle through the SN curve of the material was analyzed. The cumulative damage factor was analyzed via Miner’s rule. Finally, the fatigue life was predicted.
항공기 탑재 발사대의 발사관 장입 로켓의 로켓 장입 상태에 따른 동특성 변화 분석
정회인(Hoein Jeong),박지환(Jihwan Park),남규빈(Guebin Nam),이유경(Yukyoung Lee) 한국소음진동공학회 2020 한국소음진동공학회 논문집 Vol.30 No.5
This paper presents an analysis of a change in the dynamic characteristics with respect to the loading status of the rocket which is loaded in a launch tube of an airborne launcher. In addition, it determines the procedures for durability test. It was confirmed that the acceleration response of rockets depends on the distance of the airborne launcher from the mount, and the number of rockets loaded in the airborne launcher. The acceleration response increased with an increase in the distance of the airborne launcher from the mount, while it decreased with an increase in the number of rockets loaded in the airborne launcher. Consequently, it is proved that the most efficient test to verify the durability of the rocket is through loading one rocket at a suitable distance between the launcher and the mount. Moreover, frequency analysis showed that the natural frequency decreases and damping ratio increases as the number of rockets increases. This observation is expected to help in the design to avoid natural frequency.
항공기 외부 장착물 장착 경계조건의 중력 방향에 따른 동특성 영향 분석
박지환(Jihwan Park),정회인(Hoein Jeong),이유경(Yukyoung Lee),안선규 (Sungyu Ahn) 한국소음진동공학회 2020 한국소음진동공학회 논문집 Vol.30 No.5
In order to verify durability in the vibration environment of the Swaybrace-Lug mounting type aircraft external store, vibration testing was carried out in accordance with the MIL-STD-810. The vibration test fixture transmits vibrations that began at the bottom of the test fixture in contrast to direct vibrations in the Swaybrace-Lug mounting structure. Therefore, the inherent frequency of vibration may vary due to the influence of the test fixture and the vibration applied to the store may become excessive. Additionally, reverse mount vibration test fixture was designed for direct attachment to the Swaybrace-Lug mounting structure. To confirm this hypothesis, the resonant frequency and resonant response of the forward mounting and reverse mounting were compared at the frequency of interest. Additionally, confirmation was done by applying the Modal Assurance Criterion to objectively identify dynamic differences in mode frequencies.
Glomerulonephritis following COVID-19 infection or vaccination: a multicenter study in South Korea
( Hyung Woo Kim ),( Eun Hwa Kim ),( Yun Ho Roh ),( Young Su Joo ),( Minseob Eom ),( Han Seong Kim ),( Mi Seon Kang ),( Hoein Jeong ),( Beom Jin Lim ),( Seung Hyeok Han ),( Minsun Jung ) 대한신장학회 2024 Kidney Research and Clinical Practice Vol.43 No.2
Background: Despite the widespread impact of the severe acute respiratory syndrome coronavirus 2 (coronavirus disease 2019, COVID-19) and vaccination in South Korea, our understanding of kidney diseases following these events remains limited. We aimed to address this gap by investigating the characteristics of glomerular diseases following the COVID-19 infection and vaccination in South Korea. Methods: Data from multiple centers were used to identify de novo glomerulonephritis (GN) cases with suspected onset following COVID-19 infection or vaccination. Retrospective surveys were used to determine the COVID-19-related histories of patients who were initially not implicated. Bayesian structural time series and autoregressive integrated moving average models were used to determine causality. Results: Glomerular diseases occurred shortly after the infection or vaccination. The most prevalent postinfection GN was podocytopathy (42.9%), comprising primary focal segmental glomerulosclerosis and minimal change disease, whereas postvaccination GN mainly included immunoglobulin A nephropathy (IgAN; 57.9%) and Henoch-Schönlein purpura nephritis (HSP; 15.8%). No patient progressed to end-stage kidney disease. Among the patients who were initially not implicated, nine patients with IgAN/HSP were recently vaccinated against COVID-19. The proportion of glomerular diseases changed during the pandemic in South Korea, with an increase in acute interstitial nephritis and a decrease in pauci-immune crescentic GN. Conclusion: This study showed the characteristics of GNs following COVID-19 infection or vaccination in South Korea. Understanding these associations is crucial for developing effective patient management and vaccination strategies. Further investigation is required to fully comprehend COVID-19’s impact on GN.