• 한국항공우주학회지
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• 제31권7호
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• pp.75-84
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• 2003

본 논문에서는 모델링 오차나 공력계수의 불확실성이 포함되어 있는 항공기 시스템에 대해서 신경회로망을 이용한 새로운 비선형 제어시스템 설계기법을 제안하였다. 비선형 적응제어법칙을 이용하여 신경회로망의 연결가중치를 변화시켰으며, 슬라이딩 제어법칙을 이용하여 신경회로망의 추정오차를 보상하였다. 제어시스템의 성능을 결정짓는 제어 매개변수들과 신경회로망 구조를 설계하기 위한 방법을 제안하였으며, 유전자 알고리듬을 이용하여 제어 매개변수들과 신경회로망 구조를 최적화하였따. 신경회로망의 구조탐색에 적합하도록 다수의 개체군을 형성하여 개체와 군이 동시에 전화하도록 하였다. 제안된 유전자 알고리듬에 의해 최적화된 구조를 갖는 신경회로망을 이용한 제어시스템을 항공기 종운동 모델에 적용하여 성능을 검증하였다.

• Toxicological Research
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• 제30권3호
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• pp.205-210
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• 2014

Didecyldimethylammonium chloride (DDAC) is used for various purposes, such as a fungicide for coolants, an antiseptic for wood, and disinfectant for cleaning. Despite the increasing likelihood of DDAC inhalation, available data on its toxicity from inhalation are scarce. Therefore, this study was aimed at confirming the toxicity of DDAC after inhalation exposure for 2 wk. Male Sprague-Dawley rats were exposed to approximately $0.15mg/m^3$, $0.6mg/m^3$, and $3.6mg/m^3$ DDAC aerosols in whole-body exposure chambers. After DDAC exposure for 2 wk, effects of DDAC on body weight, blood, bronchoalveolar lavage (BAL), and the lungs were verified. The mass median aerodynamic diameter of DDAC aerosols was $1.86{\mu}m$ and the geometric standard deviation was 2.75. The concentrations of DDAC aerosols for the low, medium, and high groups were $0.15{\pm}0.15mg/m^3$, $0.58{\pm}0.40mg/m^3$, and $3.63{\pm}1.56mg/m^3$, respectively. Body weight gain was significantly influenced by DDAC exposure. In the high group, a body weight decrease of 2.6 g was observed, whereas a 25.8 g increase was observed in the normal control group after the first 3 days. The low and medium groups showed 23.3 g and 20.4 g increases, respectively, after the first 3 days. Decreases in body weight were recovered during the next 4 days. In contrast, no changes were noted in hematological and blood biochemistry parameters after DDAC exposure. Furthermore, only mild effects were observed on bronchoalveolar cell differentiation counts and cell damage parameters in the BAL fluids of the medium and high groups. Although inflammatory cell infiltration and interstitial pneumonia were partially observed, fibrosis was not found in the lungs of the medium and high groups. In conclusion, body weight gain and the lungs were mainly affected by DDAC exposure. The no-observed-adverse-effect level (NOAEL) for DDAC was determined as $0.15mg/m^3$.

• 한국추진공학회지
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• 제18권5호
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• pp.95-100
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• 2014

극초음속 비행체에서는 공기와의 마찰열과 엔진열의 증가로 기체 내부의 열적 부하가 발생한다. 이는 비행체 내부 구조물의 변형을 일으키고 오작동을 발생시킬 수 있다. 흡열연료는 액체 탄화수소 연료로써 흡열반응을 통해 열을 흡수할 수 있는 연료이다. 본 연구에서는 exo-tetrahydrodicyclopentadiene을 모델연료로써 선정하고 제올라이트 촉매의 금속담지를 통하여 흡열특성의 변화를 측정하는 연구를 수행하였다. 이를 통하여 상용촉매보다 우수한 흡열성능을 가지는 촉매를 확보하였다. 본 연구의 목적은 흡열량 향상에 미치는 촉매의 특성을 연구하는 것이다. 이 촉매는 상용촉매를 대체하여 exo-THDCP를 흡열연료로 사용하는 시스템에 적용될 수 있을 것이다.

• Wind and Structures
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• 제19권4호
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• pp.443-465
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• 2014

Hyperbolic thin-shell cooling towers have complicated vibration modes, and are very sensitive to the effects of group towers and wind-induced vibrations. Traditional aero-elastic models of cooling towers are usually designed based on the method of stiffness simulation by continuous medium thin shell materials. However, the method has some shortages in actual engineering applications, so the so-called "equivalent beam-net design method" of aero-elastic models of cooling towers is proposed in the paper and an aero-elastic model with a proportion of 1: 200 based on the method above with integrated pressure measurements and vibration measurements has been designed and carried out in TJ-3 wind tunnel of Tongji university. According to the wind tunnel test, this paper discusses the impacts of self-excited force effect on the surface wind pressure of a large-scale cooling tower and the results show that the impact of self-excited force on the distribution characteristics of average surface wind pressure is very small, but the impact on the form of distribution and numerical value of fluctuating wind pressure is relatively large. Combing with the Complete Quadratic Combination method (hereafter referred to as CQC method), the paper further studies the numerical sizes and distribution characteristics of background components, resonant components, cross-term components and total fluctuating wind-induced vibration responses of some typical nodes which indicate that the resonance response is dominant in the fluctuating wind-induced vibration response and cross-term components are not negligible for wind-induced vibration responses of super-large cooling towers.

• Smart Structures and Systems
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• 제24권1호
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• pp.53-65
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• 2019

Misaligned wind-wave and seismic loading render offshore wind turbines suffering from excessive bi-directional vibration. However, most of existing research in this field focused on unidirectional vibration mitigation, which is insufficient for research and real application. Based on the authors' previous work (Sun and Jahangiri 2018), the present study uses a three dimensional pendulum tuned mass damper (3d-PTMD) to mitigate the nacelle structural response in the fore-aft and side-side directions under wind, wave and near-fault ground motions. An analytical model of the offshore wind turbine coupled with the 3d-PTMD is established wherein the interaction between the blades and the tower is modelled. Aerodynamic loading is computed using the Blade Element Momentum (BEM) method where the Prandtl's tip loss factor and the Glauert correction are considered. Wave loading is computed using Morison equation in collaboration with the strip theory. Performance of the 3d-PTMD is examined on a National Renewable Energy Lab (NREL) monopile 5 MW baseline wind turbine under misaligned wind-wave and near-fault ground motions. The robustness of the mitigation performance of the 3d-PTMD under system variations is studied. Dual linear TMDs are used for comparison. Research results show that the 3d-PTMD responds more rapidly and provides better mitigation of the bi-directional response caused by misaligned wind, wave and near-fault ground motions. Under system variations, the 3d-PTMD is found to be more robust than the dual linear TMDs to overcome the detuning effect. Moreover, the 3d-PTMD with a mass ratio of 2% can mitigate the short-term fatigue damage of the offshore wind turbine tower by up to 90%.

• 한국항공우주학회지
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• 제46권12호
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• pp.986-993
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• 2018

측 추력 제트는 유도무기의 자세제어 및 궤도 천이 기동을 하는 데 있어 기존의 핀과 같이 제어 면을 이용한 방식보다 우수한 기동성을 갖는다. 하지만 초음속 영역에서 비행 시 측 추력 제트로 인한 제트 간섭 유동이 발생하며 충격파와 경계층 유동, 와류 유동의 상호 작용으로 인해 매우 복잡한 유동 구조를 나타낸다. 특히 직격 파괴(hit-to-kill) 방식의 요격체의 경우 정밀한 제어 및 기동이 요구되기 때문에 제트 간섭 유동이 미치는 영향에 대한 분석이 필요하다. 기존의 제트 간섭 해석은 저고도 운용 조건에서 주로 수행되었으나 중고도 운용 조건의 경우 해석 사례가 많지 않으며 대기 조건으로 인해 분사 제트 유동이 상대적으로 크게 발달하는 특징을 갖는다. 본 연구에서는 중고도에서 비행하는 요격체 형상에 대해 받음각 조건에 따라 제트 간섭 유동 해석을 수행하였다. 해석 결과를 바탕으로 유동장의 구조적인 변화 특성을 분석하였으며, 공력 계수의 변화를 비교하였다.

• Journal of Preventive Medicine and Public Health
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• 제51권6호
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• pp.265-274
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• 2018

Objectives: A positive association between air pollution and both the incidence and prevalence of diabetes mellitus (DM) has been reported in some epidemiologic and animal studies, but little research has evaluated the relationship between air pollution and diabetic coma. Diabetic coma is an acute complication of DM caused by diabetic ketoacidosis or hyperosmolar hyperglycemic state, which is characterized by extreme hyperglycemia accompanied by coma. We conducted a time-series study with a generalized additive model using a distributed-lag non-linear model to assess the association between ambient air pollution (particulate matter less than $10{\mu}m$ in aerodynamic diameter, nitrogen dioxide [$NO_2$], sulfur dioxide, carbon monoxide, and ozone) and emergency department (ED) visits for DM with coma in Seoul, Korea from 2005 to 2009. Methods: The ED data and medical records from the 3 years previous to each diabetic coma event were obtained from the Health Insurance Review and Assessment Service to examine the relationship with air pollutants. Results: Overall, the adjusted relative risks (RRs) for an interquartile range (IQR) increment of $NO_2$ was statistically significant at lag 1 (RR, 1.125; 95% confidence interval [CI], 1.039 to 1.219) in a single-lag model and both lag 0-1 (RR, 1.120; 95% CI, 1.028 to 1.219) and lag 0-3 (RR, 1.092; 95% CI, 1.005 to 1.186) in a cumulative-lag model. In a subgroup analysis, significant positive RRs were found for females for per-IQR increments of $NO_2$ at cumulative lag 0-3 (RR, 1.149; 95% CI, 1.022 to 1.291). Conclusions: The results of our study suggest that ambient air pollution, specifically $NO_2$, is associated with ED visits for diabetic coma.

• 대한후두음성언어의학회지
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• 제29권2호
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• pp.83-86
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• 2018

Background and Objectives : This study aimed to evaluate efficacy and complication of injection laryngoplasty using calcium hydroxyapatite (CaHA) for unilateral vocal fold paralysis in Asian. Materials and Methods : A prospective study was conducted on the adult patients with unilateral vocal fold paralysis from May 2015 through January 2016. Injection laryngoplasty was performed by one laryngologist. All patients underwent prospective voice evaluation using the subjective and objective comprehensive battery of assessments, before the procedure and after the procedure at 3 months, and 6 months. Results : A total of 7 patients (5 males and 2 females) were included in this study. VHI-10 was significantly decreased after injection laryngoplasty, at postoperative 6 months (p=0.031), while VAS score and MDADI showed no difference. GRBAS scale gradually decreased in 3 months and 6 months follow-up without statistical significance. Acoustic analysis revealed that jitter, shimmer, and noise-to-harmonic ratio continuously decreased from the baseline at 3 months and 6 months, although statistical significance was not attained. In the aerodynamic analysis, maximal phonation time was gradually increased at 3months and 6 months with significant difference (p=0.016, 0.031, respectively). There was no side effect associated with the procedure. Conclusion : CaHA can be safely used in Asian patients and the onset of maximal efficacy seems to be slow than other studies with Caucasian patients.

• 한국전산구조공학회논문집
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• 제31권6호
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• pp.309-314
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• 2018

트윈 빌딩의 풍하중의 특성과 구조적 특성은 일반 고층건물보다 복잡하다. 이러한 특성을 조사하기 위해서 풍동실험을 통해서 트윈 빌딩의 풍압을 계측하였다. 계측된 데이터와 적합 직교 분해 기법을 이용하여 풍압의 패턴을 파악하였다. 1차 모드에서는 채널링 효과가 2차 모드에서는 와류 효과가 나타났다. 또한, 두 빌딩의 하중의 상관관계를 파악하였는데, 풍 방향 하중은 양의 상관관계를 가지며, 풍 직각 방향의 하중은 명확한 상관관계가 나타나지 않았다. 이러한 상관관계는 횡 방향 변위에도 영향을 미쳤다. 양의 상관관계를 가지면 트윈 빌딩을 연결하는 구조부재의 영향이 적게 작용한 반면에 음의 상관관계를 가지면 연결 구조부재의 영향이 횡 방향의 변위를 줄이는데 큰 영향을 미치게 되었다.

• 한국항공우주학회지
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• 제47권1호
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• pp.17-25
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• 2019

항공기의 Intake는 공간적 제약 또는 생존성 확보의 이유로 S형태의 곡률을 갖는 덕트를 가진다. 그러나 덕트의 곡률은 2차유동과 유동박리의 발생을 야기하며 불균일한 압력분포 생성의 원인이 된다. 본 연구에서는 RAE M 2129 S-Duct의 형상에 보조 Duct를 적용하여 경계층 흡입을 수행하였다. 경계층 흡입의 위치와 각도를 설계변수로 설정하였으며, 흡입면에서 동일 유량을 흡입하는 조건을 부여하였다. S-Duct의 전산해석 타당성을 검증하기 위하여 Port Side와 Starboard Side의 무차원 압력 분포를 ARA 실험값, 전산해석 값과 각각 비교하여 확인하였다. 본 연구에서는 유동 왜곡을 판단하는 공기역학적 성능인자로 유동 왜곡 계수를 사용 하였으며, 경계층 흡입에 의한 유동박리, 와류, 유량 분포 및 압력 분포를 비교 분석 하였다. 그 결과 경계층 흡입 적용 이전과 비교하여 최대 26.14%의 유동 왜곡 계수 저감 효과를 확인하였다.