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Park Yongun,Paing Yunn Me Me,Cho Namki,Kim Changyoun,Yoo Jiho,Choi Ji Woong,Lee Sung Hoon 한국응용약물학회 2024 Biomolecules & Therapeutics(구 응용약물학회지) Vol.32 No.3
Compared to other organs, the brain has limited antioxidant defenses. In particular, the hippocampus is the central region for learning and memory and is highly susceptible to oxidative stress. Glial cells are the most abundant cells in the brain, and sustained glial cell activation is critical to the neuroinflammation that aggravates neuropathology and neurotoxicity. Therefore, regulating glial cell activation is a promising neurotherapeutic treatment. Quinic acid (QA) and its derivatives possess anti-oxidant and anti-inflammatory properties. Although previous studies have evidenced QA’s benefit on the brain, in vivo and in vitro analyses of its anti-oxidant and anti-inflammatory properties in glial cells have yet to be established. This study investigated QA’s rescue effect in lipopolysaccharide (LPS)-induced behavior impairment. Orally administering QA restored social impairment and LPS-induced spatial and fear memory. In addition, QA inhibited proinflammatory mediator, oxidative stress marker, and mitogen-activated protein kinase (MAPK) activation in the LPS-injected hippocampus. QA inhibited nitrite release and extracellular signal-regulated kinase (ERK) phosphorylation in LPS-stimulated astrocytes. Collectively, QA restored impaired neuroinflammation-induced behavior by regulating proinflammatory mediator and ERK activation in astrocytes, demonstrating its potential as a therapeutic agent for neuroinflammation-induced brain disease treatments.
디젤 엔진 연소 해석을 위한 개선된 난류 분무 연소 모델의 연구
이용운(Yongun Lee),허강열(Kang Y. Huh),김현옥(Hyunok Kim),박경민(Kyungmin Park) 한국자동차공학회 2007 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
We present an improved model of turbulent spray combustion for a diesel engine in this study. The Conditional Moment Closure (CMC) routines are combined with KIVA to provide conditional flame structures to determine mean state variables, instead of mean reaction rates. An independent transport equation is solved for each flame group with equal mass of sequentially injected fuel group. Additional source terms due to evaporation are implemented in KIVA with scaled probability density function (PDF) and conditional scalar dissipation rates (CSDR). The expressions for vaporization source terms and scaling factors are based on recent direct numerical simulation (DNS) results. A heavy duty diesel engine is employed with early injection timings to test the improved CMC model. Soot modeling based on Lindstedt and Hiroyasu model is implemented in the KIVA code. Parametric investigation is performed with respect to EGR (Exhaust Gas Recirculation), injection timing and rpm. Measured pressure traces, NOx and soot emissions are reasonably reproduced in a wide range of engine operating conditions.
디젤 분무 연소에서 혼합 분율 스케일링의 영향에 대한 연구
이용운(Yongun LEE),허강열(Kangyoel Huh),박경민(Kyungmin Park),김현옥(Hyunok Kim) 한국자동차공학회 2006 한국자동차공학회 춘 추계 학술대회 논문집 Vol.- No.-
In this study we present an improved model of turbulent spray combustion to improve accuracy of diesel combustion simulations. Additional source terms due to vaporization are implemented in KIVA with Conditional Moment Closure (CMC) model. Probability density function(PDF) and conditional scalar dissipation rate are scaled to consider limited ranges of mixture fraction by the saturation condition. The expression for the vaporization source term and scaling factors are based on recent direct numerical simulation (DNS) results on turbulent spary combustion. A heavy duty diesel engine is used with early injection timings to test the CMC model with scaled PDF and conditional scalar dissipation. Two and three times the mean mixture fraction are employed as the limiting range for scaling, while another suggestion is based on local PDF lower than an arbitrary small value. Parametric investigation is performed with respect to EGR (Exhaust Gas Recirculation) rate and injection timing. Measured pressure traces and NOx emissions are reasonably well reproduced in wide engine operating conditions.
복합재 패널에서 유도 탄성파를 이용한 이미지 기반 손상탐지 기법 개발 : Part Ⅰ. 손상위치 탐지 알고리즘
김창식(Changsik Kim),전용운(Yongun Jeon),박정선(Jungsun Park),조진연(Jin Yeon Cho) 한국항공우주학회 2021 韓國航空宇宙學會誌 Vol.49 No.1
본 논문은 복합재 패널에서 압전 작동기를 사용하여 탄성파를 생성하고, 손상에서의 반사된 신호를 압전 감지기에서 탐지하여 손상위치를 추정할 수 있는 알고리즘을 개발하였다. 손상이 없는 신호와 손상이 있는 신호를 비교하여 손상신호를 추정하는 진단적 접근방법을 사용하였다. 신호 상관관계를 이용하여 탄성파의 군속도를 계산하고 압전기 위치정보를 이용하여 손상정보를 추출하였다. 하지만 탄성파의 비선형 특성으로 인해, 손상정보는 다양한 신호의 조합으로 구성되기 때문에, 손상위치를 명확히 구별하기 어렵다. 이에 본 논문에서는 손상에서 반사된 신호정보를 신호 도달거리의 면적으로 변환해서 손상의 중심위치를 찾는 누적함수 특성벡터 알고리즘(CSFV, cumulative summation feature vector)을 새롭게 제안하고, 특성벡터를 손상지수와의 곱으로 표현하는 가시화 기법을 적용하였다. 또한 복합재 패널에서 실험검증을 수행하고, 기존의 알고리즘과의 비교를 통해 제안된 알고리즘이 정확도 높게 손상위치를 검출할 수 있음을 보였다. In this paper, a new algorithm is proposed to estimate the damage location in the composite panel by extracting the elastic wave signal reflected from the damaged area. The guided elastic wave is generated by a piezoelectric actuator and sensed by a piezoelectric sensor. The proposed algorithm adopts a diagnostic approach. It compares the non-damaged signal with the damaged signal, and extract damage information along with sensor network and lamb wave group velocity estimated by signal correlation. However, it is difficult to clearly distinguish the damage location due to the nonlinear properties of lamb wave and complex information composed of various signals. To overcome this difficulty, the cumulative summation feature vector algorithm(CSFV) and a visualization technique are newly proposed in this paper. CSFV algorithm finds the center position of the damage by converting the signals reflected from the damage to the area of distance at which signals reach, and visualization technique is applied that expresses feature vectors by multiplying damage indexes. Experiments are performed for a composite panel and comparative study with the existing algorithms is carried out. From the results, it is confirmed that the damage location can be detected by the proposed algorithm with more reliable accuracy.
적층 파라미터를 활용한 복합재 팬 블레이드의 적층 패턴 최적설계
성윤주(Yoonju Sung),전용운(Yongun Jun),박정선(Jungsun Park) 한국항공우주학회 2020 韓國航空宇宙學會誌 Vol.48 No.6
본 논문에서는 복합재 팬 블레이드의 구조적 성능에 대한 근사 및 최적설계 기법을 제안하였다. 그리고 이들을 활용하여 복합재 팬 블레이드의 질량 및 형상의 변화 없이 강성을 최대화하기 위한 적층 패턴의 최적설계를 수행하였다. 이 때 설계 변수 및 설계 영역을 축소하기 위하여 적층 파라미터를 도입하였고, 적층 파라미터의 특성을 활용하여 높은 적합도를 갖는 반응표면 근사모델을 생성하였다. 또한 효율적인 최적해 탐색을 위해 도함수 기반 방법과 유전자 알고리즘을 결합한 2단계 최적화 방법을 적용하였으며, 다양한 요구조건들을 고려한 다목적 최적설계를 수행하였다. 마지막으로는 초기 모델과 최적설계 모델의 유한요소해석 결과를 비교하여 적층 파라미터 기반의 근사 및 최적설계 기법을 검증하였다. In this paper, approximation and optimization methods are proposed for the structural performance of the composite fan blade. Using these methods, we perform the optimal design of the stacking sequence to maximize stiffnesses without changing the mass and the geometric shape of the composite fan blade. In this study, the lamination parameters are introduced to reduce the design variables and space. From the characteristics of lamination parameters, we generate response surface model having a high fitness value. Considering the requirements of the optimal stacking sequence, the multi-objective optimization problem is formulated. We apply the two-step optimization method that combines gradient-based method and genetic algorithm for efficient search of an optimal solution. Finally, the finite element analysis results of the initial and the optimized model are compared to validate the approximation and optimization methods based on the lamination parameters.
복합재 패널에서 유도 탄성파를 이용한 이미지 기반 손상탐지 기법 개발 : Part Ⅱ. 손상크기 추정 알고리즘
김창식(Changsik Kim),전용운(Yongun Jeon),박정선(Jungsun Park),조진연(Jin Yeon Cho) 한국항공우주학회 2021 韓國航空宇宙學會誌 Vol.49 No.1
본 논문에서는 반사된 면적 결과와 반사된 위치 결과를 중첩하고, 가시화된 이미지에서 픽셀의 최대값에 대한 비율로 윤곽선을 추출하여 손상 크기를 추정하는 알고리즘을 제안하였다. 반사된 신호의 면적을 구하기 위해서 누적함수 특성벡터 알고리즘을 사용하였고, 반사된 신호의 위치를 구하기 위해서 신호 상관관계를 이용해서 측정신호로부터 손상 신호를 분리하였다. 그리고 제안한 손상크기 추정 알고리즘을 복합재 평판에서 실험 수행하여 검증하였다. 임의의 위치에서 반복 실험을 수행해서 제안된 알고리즘이 반복에 따른 재현성이 있음을 검증하였고, 손상크기 변화에 따라 손상 크기를 추정하고 분별할 수 있음을 검증하였다. In this paper, a new algorithm is proposed to estimate the damage size by combining the reflected area with the reflected position and extracting contours in proportion to the maximum value of pixels from the visible image. The cumulative summation feature vector algorithm is used to obtain the area of the reflected signal. To get the position of the reflected signal, the signal correlation algorithm is used to decompose the reflected signal from the damage. The proposed algorithm is tested and validated for composite panels. Repetitive experiments are performed and it is confirm that the proposed algorithm is reproducible. Further, it is verified that the damage size can be estimated appropriately by the proposed algorithm.