• 전자공학회논문지CI
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• 제42권3호
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• pp.63-72
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• 2005

본 논문에서는 가상성형 시스템에 적합한 Radial Basis Function(RBF) 기반의 변형 기법과 변형된 얼굴 구성 요소를 얼굴 영상에 혼합하는 기법을 제시한다. 가상성형을 위한 변형 기법은 유동적인 얼굴 구성 요소들을 변형함에 있어 부드러움과 정확성을 가져야 하고 변형 부위 이외의 다른 얼굴 구성 요소에는 왜곡을 주지 않는 지역성도 가져야 한다. 이를 위해 제안된 가상성형 시스템은 자유형태 변형 모델을 기반으로 RBF에 의해 격자들의 변형 정도를 계산한다. 성형의 정확성을 위해 변형 오차는 기준곡선 정점들의 목표 위치와 실제 변형된 위치 사이의 오차제곱합을 이용하여 Singular Value Decomposition(SVD)에 의해 반복적으로 RBF 매핑 함수의 계수들을 계산하여 보정한다. 변형된 얼굴 구성 요소는 Euclidean Distance Transform(EDT)에 의해 계산된 혼합 비율을 사용하여 원본 얼굴 영상과 합성된다. 제안된 변형 기법과 합성 기법은 가상성형 결과의 정확도와 왜곡 측면에서 우수한 성능을 보인다는 것을 실험적으로 확인하였다.

• Imaging Science in Dentistry
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• 제45권3호
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• pp.159-168
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• 2015

Purpose: This study was performed to compare the metal artifacts from common metal orthodontic brackets in magnetic resonance imaging. Material and Methods: A dry mandible with 12 intact premolars was prepared, and was scanned ten times with various types of brackets: American, 3M, Dentaurum, and Masel orthodontic brackets were used, together with either stainless steel (SS) or nickel titanium (NiTi) wires. Subsequently, three different sequences of coronal and axial images were obtained: spin-echo $T_1$-weighted images, fast spin-echo $T_2$-weighted images, and fluid-attenuated inversion recovery images. In each sequence, the two sequential axial and coronal images with the largest signal-void area were selected. The largest diameters of the signal voids in the direction of the X-, Y-, and Z-axes were then measured twice. Finally, the mean linear values associated with different orthodontic brackets were analyzed using one-way analysis of variation, and the results were compared using the independent t-test to assess whether the use of SS or NiTi wires had a significant effect on the images. Results: Statistically significant differences were only observed along the Z-axis among the four different brands of orthodontic brackets with SS wires. A statistically significant difference was observed along all axes among the brackets with NiTi wires. A statistically significant difference was found only along the Z-axis between nickel-free and nickel-containing brackets. Conclusion: With respect to all axes, the 3M bracket was associated with smaller signal-void areas. Overall, the 3M and Dentaurum brackets with NiTi wires induced smaller artifacts along all axes than those with SS wires.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권3호
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• pp.529-561
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• 2014

The two-phase turbulent flow past an interface-piercing circular cylinder is studied using a high-fidelity orthogonal curvilinear grid solver with a Lagrangian dynamic subgrid-scale model for large-eddy simulation and a coupled level set and volume of fluid method for air-water interface tracking. The simulations cover the sub-critical and critical and post critical regimes of the Reynolds and sub and super-critical Froude numbers in order to investigate the effect of both dimensionless parameters on the flow. Significant changes in flow features near the air-water interface were observed as the Reynolds number was increased from the sub-critical to the critical regime. The interface makes the separation point near the interface much delayed for all Reynolds numbers. The separation region at intermediate depths is remarkably reduced for the critical Reynolds number regime. The deep flow resembles the single-phase turbulent flow past a circular cylinder, but includes the effect of the free-surface and the limited span length for sub-critical Reynolds numbers. At different Froude numbers, the air-water interface exhibits significantly changed structures, including breaking bow waves with splashes and bubbles at high Froude numbers. Instantaneous and mean flow features such as interface structures, vortex shedding, Reynolds stresses, and vorticity transport are also analyzed. The results are compared with reference experimental data available in the literature. The deep flow is also compared with the single-phase turbulent flow past a circular cylinder in the similar ranges of Reynolds numbers. Discussion is provided concerning the limitations of the current simulations and available experimental data along with future research.

• 한국항해항만학회:학술대회논문집
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• 한국항해항만학회 2006년도 추계학술대회 논문집(제1권)
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• pp.181-186
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• 2006

본 논문에서는 Freak Wave의 생성원인에 대하여 간략히 논의하였으며, 이 중 파랑-조류 비선형 상호작용에 대한 이론 및 수치적 해석기법의 역사와 장단점 등을 기술한다. 본 연구에서는 파랑-조류 상호작용에 대한 수치모델링 및 해석 기법을 개발하고 있다. 개발 중인 수치해석 기법은 공간적으로 불균일한 조류와 파랑의 비선형 상호작용을 해석하기 위하여 Navier-Stokes 방정식을 이용하여 유동현상을 모델링하였으며, 이산화를 위하여 스펙트랄요소법(Spectral Element Method; SEM)을 이용하였다. 또한 자유표면의 운동을 효과적으로 기술하기 위하여 ALE(Arbitrary Lagrangian-Eulerian)기법을 사용하였다. 본 연구의 유동 모델과 수치해석기법의 과정과 특성, 그리고 장점 등에 대하여 논의하였으며, 초기적인 수치해석 결과를 제시하였다. 이를 바탕으로 개발된 수치해석기법의 정확성 및 수렴성을 확인할 수 있다.

• 동의생리병리학회지
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• 제20권6호
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• pp.1593-1597
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• 2006

We hope to evaluate the effects of Gami-Choakwiyeum (GCKY) on the PPAR-${\gamma}$’ in the OVA induced asthma mouse model. Female BALB/c mice, 8 weeks of age and free of murine specific pathogens were used. Mice were sensitized by intraperitoneal injection of OVA emulsified in aluminum hydroxide in a total volume of 200 ${\mu}{\ell}$ on one day and 14 days. On 21, 22, and 23 days after the initial intraperitoneal injection of OVA, the mice were challenged using an ultrasonic nebulizer. GCKY was administered 7 times by oral gavage at 24 hour intervals fromdays 19 after intraperitoneal injection of OVA. Bronchoalveolar lavage was perfromed 72 hours after the last challenge, and total cell numbers in the BAL fluid were counted. Also, the level of PPAR-${\gamma}$ of normal and OVA-induced asthma moused with/without administration of GCKY were measured by Western blot analysis. For the histologic examination, the specimens were stained with hematoxylin 2 and eosin-Y.(H & E). Numbers of total cells were increased significantly at 72 h after OVA inhalation compared with numbers of total cells in the normal and the administration of GCKY. Especially, the increased numbers of eosinophils in BAL fluids after OVA inhalation were significantly increased. However, the numbers of eosinophils reduced by the administration of GCKY. Western blot analysis revealed that PPAR-${\gamma}$ levels in nuclear level were increased slightly after OVA inhalation compared with the levels in the normal group. After the administration of GCKY, PPAR-${\gamma}$ levels in cytosolic and nuclear levels at 72 h after OVA inhalation were markedly increased. On pathologic examination, there were many acute inflammatory cells around the alveoli, bronchioles, and airway lumen of mice with OVA-induced asthma compared with inflammatory cells in the normal group. However, acute inflammatory cells around alveoli, bronchioles, and airway lumen markedly decreased after administration of GCKY, GCKY can increase a PPAR-${\gamma}$ level and could be an effective treatment in asthma patients through the PPAR-${\gamma}$ mechanism for bronchial asthma.

• 대한기계학회논문집
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• 제11권2호
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• pp.345-353
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• 1987

본 연구에서는 구 주위의 혼합대류에 대하여 전 영역에 걸쳐 유효한 매개변수 를 차원해석에 의해 유도하고 이를 적용하여 지배방정식을 비상사 경계층 방정식의 형 태로 변환하고 이를 유한차분법에 의해 수치적으로 해석하였다. 단순 강제대류에서 부터 단순 자연대류 까지의 전 영역에 걸쳐 구 주위의 속도 및 온도분포,국소열전달계 수 및 마찰계수를 Gr/Re$^{2}$의 함수로 구하였으며 Prandtl수가 0.7과 7인 유체에 대 하여 계산을 수행함으로써 Prandtl수의 변화에 따른 강제대류 및 자연대류의 비교강도 의 영향에 대하여 고찰하였다. 자연대류의 영향에 의한 벽면에서의 운동에너지증가 에 따른 유동의 박리점 이동에 대하여도 고찰하였다.

• 대한핵의학회지
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• 제16권1호
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• pp.31-39
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• 1982

The purpose of the present study is to evaluate the clinical and diagnostic significance of incidental findings of renal and urinary tract abnormalities, and extraosseous uptake of bone scans. The authors analyzed bone scans using $^{99m}Tc-MDP$(methylene diphosphonate) in 1238 cases of bone disease from April, 1979 to March, 1981. The results obtained were as follows. 1. Total extraosseous abnormalities were 112 cases (9%), which include 64 cases (5%) of renal and urinary tract abnormalities and 48 case(4%) of other extraosseous uptakes. 2. Renal and urinary tract abnormalities were 32 cases(50%) of obstruction, 14 cases(22%) of nonvisualization, 6 cases of space occupying lesion in kidney, 8 cases of kidney displacement and 4 cases of urinary bladder deformities. 3. Other extraosseous uptakes were 16 cases (33%) of body fluid collection, 15 cases of tumor uptake, 9 cases of free pertechnetate uptake and 8 others.

• 한국수자원학회논문집
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• 제52권spc2호
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• pp.855-863
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• 2019

어류의 어도 이용효율평가를 위해서는 유인효율과 통과효율로 분리하여 분석할 때, 각각의 효율을 증대시킬 수 있는 방향으로 어도 설치 및 관리 계획이 수립될 수 있다. 기 설치된 어도는 어류 모니터링을 통해 보다 직접적으로 각각의 효율을 평가할 수 있다. 반면 어도를 계획할 때, 또는 여건상 어류 모니터링이 어려운 경우, 수리해석을 통해 간접적으로 어도 효율을 평가할 수 있다. 본 연구에서는 어도의 효율평가가 가능한 수리해석 기법을 제시하였다. 유인효율 분석에는 어류 물리서식처 모듈이 장착된 River-2D모형을 사용하였고, 효율의 지표로 가중가용면적을 제안하였다. 통과효율 분석에는 자유 수면을 가지고 수리구조물상의 유체거동을 해석할 수 있는 3차원 모형(Flow-3D)을 해석 도구로 이용하였다. 그리고 덕천강 백곡보에 설치된 아이스하버 어도를 선택하여 어도 효율을 가늠해 보았고, 실제 어류 모니터링자료와 비교해 보았다. 그 결과 수리해석 자료를 정량적으로 어도 효율로 치환하기는 어렵지만, 대체적인 경향성 파악에는 도움을 줄 수 있었다.

• 한국추진공학회지
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• 제22권2호
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• pp.96-107
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• 2018

고체추진기관 내에 점화기와 추진제 그레인 간격에 따라 화염에 의해 발현되는 내부 유동 형태에 대해 전산유체해석(CFD)를 이용하여 살펴보았다. 실린더형과 슬롯형 추진제 그레인에 대해 실린더형은 간격 1 mm, 3 mm, 5 mm, 슬롯형은 점화기의 화염 분출구가 넓은 간격에 위치한 경우와 좁은 간격에 위치한 경우에 대해 수치 해석을 수행하였다. 실린더형은 간격이 좁을수록 점화기와 추진제 사이에 고압력이 형성되며, 점화기 말단 부근에서 압력 강하 또한 상대적으로 크게 나타났다. 실린더형은 간격에 영향을 받았으나, 슬롯형은 화염 분출구 위치에 관계없이 압력 형태가 유사하게 나타났으며, 실린더형 간격 5 mm와 유사한 결과를 보였다.

• 대한조선학회지
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• 제11권1호
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• pp.9-16
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• 1974

To contribute towards more accurate estimation of the virtual inertia coefficient for the horizontal vibration of ships, three dimensional correction factor $J_H$ for the added mass of finitely long elliptic prismatic bars in horizontal vibration in a free surface of an ideal fluid are calculated. In the problem formulation Dr. T. Kumai's quasi-finite length concept[1,11,12] is employed. Now that, in Dr. Kumai's work[1] for the horizontal vibration the mathematical model was a circular cylinder, the principal aim of the authors' work is to investigate the influence of the beam-draft ratio B/T on $J_H$. The numerical results of this work are shown in Fig.3 graphically, from which we may recognize that the influence of B/T on $J_H$ is remarkable as much as that of the length-draft ratio L/T(refer to Fig.1 also). In Fig.3 the curves for B/T=2.00 are of those based on Dr. Kumai's result[1]. On the other hand, the experimental data obtained by Burril et al.[9] for the horizontal vibration of finitely long prismatic bars of various cross-section shapes are compared with the theoretical added mass coefficients defined by combination of the authors' $J_H$ from Fig.3 and two dimensional coefficients $C_H$ obtained by Lewis form approximation for the corresponding sections. They are in reasonable correspondence with each other as shown in Fig.2. Finally, considering that the longitudinal profile of full-form ship's hull is well resembled to that of an elliptic cylinder and that the influences of other factors such as the sectional area coefficient and the shape of section contour itself can be well merged in the two dimensional added mass coefficient, the authors recommend that the data given in Fig.3 may be successfully adopted for the three dimensional correction factor the added mass in the horizontal vibration of hull-form ships.