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고체 연료 발사체의 상승 구간 위상 안정화 제어 알고리즘의 설계 기법
정기욱,이상돈,박종찬,이창훈,김찬호,안유영 한국항공우주학회 2024 韓國航空宇宙學會誌 Vol.52 No.9
본 연구에서는 고체 발사체의 공력 상승 구간을 위한 최적화 기반의 선형 제어 알고리즘 설계 방안을 제시한다. 제안된 자세 제어 구조에서는 고전적인 비례-미분 되먹임 제어를 통해 공력 안정화를 수행하며, 특히 동체 굽힘 현상의 위상 안정화를 위해 구조 필터를 도입하였다. 본 연구에서는 상승 구간에서 빠르게 변화하는 발사체 및 환경 변수들을 고려하여 시간에 대해 스케쥴링 된 제어 설계 변수를 사용하며, 각 시간 설계점에 대해 주어진 안정성 및 설계 규격을 만족하는 제어 변수를 찾기 위해 최적화 문제들을 정의한 후, 휴리스틱 최적화 기법을 통해 해결하였다. 이때, 구조 필터 설계와 되먹임 제어 알고리즘 사이의 상호보완 관계를 해결하기 위해 반복적 최적화 구조를 제안하여 최적의 제어 변수를 찾을 수 있도록 하였다. 제안된 설계 기법은 몬테-카를로 추출 기반의 선형 분석과 고충실도 6 자유도 시뮬레이션을 통해 검증되었으며, 제안된 기법이 발사체 제어 알고리즘 설계의 보조나, 제어 알고리즘의 자동 획득에 기여할 수 있음을 보였다. This study introduces a new optimization-based methodology in linear attitude controller design, specifically for solid launch vehicles during atmospheric ascent phase. A conventional proportional-derivative (PD) feedback structure with dedicated structural filter are employed to stabilize aerodynamic instability and phase-stabilize the structural bending effects. Considering rapidly time-varying nature of launch vehicle states and environments, we devise set of optimization problems to obtain time-scheduled design parameters that satisfies prescribed design criteria by heuristic optimization algorithm. Moreover, the iterative optimization scheme is proposed to resolve the trade-off relationship between the feedback algorithm and the filter. The effectiveness of the proposed methodology is verified by extensive Monte-Carlo sampling based linear analysis and high-fidelity 6-DOF simulations, thereby underlining the proposed method’s capabilities in assisting heuristic design process for engineers or automatically attaining optimal control parameters.
Aerodynamically Controlled Missile Flight Datasets and Its Applications
정기욱,김영원,이창훈 한국항공우주학회 2023 International Journal of Aeronautical and Space Sc Vol.24 No.1
This paper provides open flight datasets generated by extensive Monte Carlo simulations for an aerodynamically controlled missile under a fixed engagement scenario with the purpose of encouraging data analytics research in the missile application. With the fast advance in the field of data analytics, fueled by the recently developed machine learning and deep learning algorithms, the potential of applying the data analysis techniques to the domain of aerospace engineering is increasingly high, especially in the light of detecting anomalies and uncovering the hidden information in the flight data. A dataset is an essential ingredient in the research of data analytics and the development of new data analysis frameworks. However, since it is almost impossible or highly inefficient to construct a large dataset of guided missiles via physical experiments, a disclosed database is nearly non-existence. Even if this is possible, there is no open source dataset for academic research due to the security issue. Thus, by developing a high-fidelity 6-DOF (degree-of-freedom) simulation program, we generate realistic flight datasets of a guided missile, which can be used publicly. Furthermore, we provide illustrative examples of using the generated datasets for the purpose of demonstrating the potential of the application, that is, to detect abnormal data patterns to determine signs of the control loop instability during the flight.
정기욱,이지교,강지상,박재현,정유선,고대현,김형석,한규섭 대한수혈학회 2021 大韓輸血學會誌 Vol.32 No.3
Background: Pretransfusion testing is vital for safe transfusion. However, in situations without time to perform sufficient testing, all or part of the pretransfusion testing may be skipped to issue blood quickly. This study evaluated the safety of red blood cell (RBC) transfusion released by an emergency blood transfusion protocol through retrospective analysis at a tertiary hospital for eight years. Methods: All RBC transfusions following the emergency blood transfusion protocol from 2011 to 2018 at Seoul National University Hospital were included in the study. Crossmatching and unexpected antibody screening test results conducted after RBC release and the occurrence of hemolytic transfusion reactions were analyzed. Results: A total of 1,541 cases (5,299 RBCs issued) of emergency blood transfusion were identified. RBCs were issued after performing the immediate spin crossmatch without an unexpected antibody screening test in most cases (1,443; 93.64%), while RBCs were issued with no pretransfusion testing in 98 cases (6.36%). Antibody screening tests performed after the issue of RBCs showed that 17 (1.1%) cases were positive. Two units of RBCs from two different cases showed positive antiglobulin crossmatch test results. However, none of them were suspected to be associated with a hemolytic transfusion reaction. Conclusion: The incidence of incompatible RBC release was very low in patients receiving RBC transfusion through the emergency blood transfusion protocol suggesting it can be used safely with minimal risk of hemolytic transfusion reactions caused by incompatible blood transfusions. (Korean J Blood Transfus 2021;32:163-173)
정기욱,Myeognsook Seo,Young Hwan Cho,Young-Ok Park,So-Yoon Yoon,JungBok Lee,Dong-Hoon Yang,In Ja Yoon,So Young Seo,Hyo Jeong Lee,Sang Hyoung Park,Kyung Jo Kim,Byong Duk Ye,Jeong-Sik Byeon,Hwoon-Yong Jung 대한소화기 기능성질환∙운동학회 2018 Journal of Neurogastroenterology and Motility (JNM Vol.24 No.2
Background/Aims Fructose malabsorption (FM) mimics symptoms of irritable bowel syndrome (IBS), and its prevalence has increased. Diagnosing FM in IBS is challenging because of its overlap with small intestinal bacterial overgrowth (SIBO). We assessed the prevalence of FM by comparing patients with IBS with asymptomatic control individuals after excluding SIBO using the glucose hydrogen breath test (HBT). Methods Patients diagnosed with IBS and asymptomatic control individuals were enrolled prospectively. Dietary habits were assessed with the Food Frequency Questionnaire. After excluding SIBO, participants underwent HBTs with both 15 g and 25 g of fructose. Results Thirty-five patients with IBS and 35 age- and sex-matched asymptomatic control individuals were enrolled. The 15-g fructose HBT yielded positive results in 7 of the 35 (20.0%) patients with IBS and in 2 of 35 (5.7%) controls (P = 0.070). The 25-g fructose HBT was positive in 16 of the 35 (45.7%) patients with IBS and in 8 of the 35 (22.9%) controls (P = 0.040). Analysis of the Food Frequency Questionnaire responses showed no significant differences between the 2 groups in dietary intake, although patients with IBS showed a significantly higher mean fiber intake than controls (21.24 ± 11.35 g vs 15.87 ± 7.07 g, respectively, P = 0.040). Conclusions The 25-g fructose HBT identified FM in a significantly higher percentage of SIBO-negative patients with IBS than in asymptomatic control individuals, suggesting that FM may correlate with IBS. Education regarding dietary control of foods containing fructose may be useful for the management of patients with IBS.
광촉매 TiO<sub>2</sub> 함유 ZrO<sub>2</sub> 박막의 초친수성
정기욱,이태규,문종수,Jung, Ki-Uk,Lee, Tea-Gu,Mun, Chong-Soo 한국재료학회 2008 한국재료학회지 Vol.18 No.4
A $ZrO_2$ coating solution containing $ZrO_2$ photo-catalysis, which is transparent in visible light, was prepared by the hydrolysis of alkoxide, and thin films on the $SiO_2$ glass substrate were formed in a dipcoating method. These thin films were heat-treated at temperatures ranging from $250^{\circ}C-800^{\circ}C$ and their characteristics were subjected to thermal analysis, XRD, spectrometry, SEM, EDS, contact angle measurement, and AFM. Tetragonal $ZrO_2$ phase was found in the thin film heat treated at $450^{\circ}C$, and anatase $TiO_2$ phase was detected in the thin film heat-treated at $600^{\circ}C$ and above. The thickness of the films was approximately 300 nm, and the roughness was 0.66 nm. Thus, the film properties are excellent. The films are super hydrophilic with a contact angle of $4.0^{\circ}$; moreover, they have self-cleaning effect due to the photo catalytic property of anatase $TiO_2$.