• International Journal of Naval Architecture and Ocean Engineering
• /
• 제4권2호
• /
• pp.151-161
• /
• 2012

The present study numerically investigates the aerodynamic characteristics of two-dimensional wings in the vicinity of the ground by solving two-dimensional steady incompressible Navier-Stokes equations with the turbulence closure model of the realizable k-${\varepsilon}$ model. Numerical simulations are performed at a wide range of the normalized ground clearance by the chord length ($0.1{\leq}h/C{\leq}1.25$) for the angles of attack ($0^{\circ}{\leq}{\alpha}{\leq}10^{\circ}$) in the prestall regime at a Reynolds number (Re) of $2{\times}10^6$ based on free stream velocity $U_{\infty}$ and the chord length. As the physical model of this study, a cambered airfoil of NACA 4406 has been selected by a performance test for various airfoils. The maximum lift-to-drag ratio is achieved at ${\alpha}=4^{\circ}$ and h / C = 0.1. Under the conditions of ${\alpha}=4^{\circ}$ and h / C = 0.1, the effect of the Reynolds number on the aerodynamic characteristics of NACA 4406 is investigated in the range of $2{\times}10^5{\leq}Re{\leq}2{\times}10^9$. As Re increases, $C_l$ and $C_d$ augments and decreases, respectively, and the lift-to-drag ratio increases linearly.

• Journal of Chest Surgery
• /
• 제17권4호
• /
• pp.780-785
• /
• 1984

We had studied 20 cases of VSD patients whose murmur was sustained after open heart surgery from 1977 to 1984. The postoperative cardiac catheterization was performed on post-op. 20th day. Their ages ranged from 5 to 25 years old. Among them, 4 patients had significant residual shunt which required reoperation. [1 patient; re-op, 3 patient; refused]. Sex ratio was 13:7 in male and female. Associated anomalies were PDA, ASD, Pulmonary stenosis, Mitral insufficiency. Except 1 case, all of them was Kirklin type II VSD. Postoperative complications were I RBBB, residual shunt, cardiac tamponade due to bleeding, wound infection. Preoperative pulmonary artery systolic pressure was highly related to residual shunt in our study. Postoperative LVEDV returned to normal range on the 3rd week.

• Journal of Chest Surgery
• /
• 제23권5호
• /
• pp.987-993
• /
• 1990

An unusual but often lethal complication of mitral valve replacement is rupture of the left ventricle. From March 1977 through June 1990, 424 mitral valve replacements were performed as isolated or combined procedures. Rupture of the posterior wall of the left ventricle was observed in 3 patients. Their was one type I and two type II rupture. Once the diagnosis was made, all of the patient were connected to the heart-lung machine again and total cardiopulmonary bypass is re-established. Repair was attempted in all of them from the outside of the heart. One of them was successively repaired but two were failed due to myocardial ischemia by circumflex coronary artery injury and failure of adequate closure of the ruptured site. From this results, we concluded that prevention is the best solution. But if we encountered this condition, early diagnosis and rapid treatment may improve the patient`s chances for survival.

• 한국전산유체공학회지
• /
• 제17권1호
• /
• pp.1-7
• /
• 2012

This paper deals with a parametric study on inclined elliptical dimples to enhance heat transfer in a channel. Three-dimensional Reynolds-averaged Naiver-Stokes equations are solved to estimate flow and heat transfer in dimpled channel. As turbulence closure, the low-Re shear stress transport model is employed. Two non-dimensional geometric variables, dimple ellipse diameter ratio and angle of main diameter to flow direction are selected for the parametric study. The inclined elliptical dimples show higher heat-transfer performance but with higher pressure drop compared to the circular dimples. And there is an optimum inclination angle that gives the maximum heat transfer.

• 대한기계학회논문집
• /
• 제18권10호
• /
• pp.2664-2674
• /
• 1994

Drag, lift, and pitching moment measurements have been made on a range of slanted-base ogive cylinders, using the KANOMAX wind tunnel and balance system. Test Reynolds numbers(based on model maximum diameter) varied from $0.54{\times}10^{5}{\;}to{\;}1.56{\times}10^{5}$. Crossflow velocity maesurement was conducted by 5-hole pitot tube at $Re_{D}=1.46{\times}10^{5}$. For two base angle $({\theta}=30$ and 45 deg.), aerodynamic forces and moment were measured with increasing angle of attack(0~30 deg.). Two types of wake flow were observed, a quasisymetric turbulent closure or a longitudinal vortex flow. Aerodynamic characteristics differ dramatically between the two wake types. It was found that the drag, lift and pitching moment coefficients increased with increasing angle of attack.

• Journal of Korean Neurosurgical Society
• /
• 제44권5호
• /
• pp.341-344
• /
• 2008

The authors present a case of 68-year-old woman who underwent resection of a metastatic adenocarcinoma in the left parietooccipital area. The intraoperative course was uneventful; however, after closure of the scalp incision, increased bleeding from the suture line was noted. A computerized tomography scan that was performed immediately after operation revealed acute epidural hemorrhage with mass effect under the bone flap. The patient developed disseminated intravascular coagulation and immediate re-exploration was performed. This patient was successfully treated owing to early recognition of the condition and immediate treatment with transfusion. Neurosurgeons should be alert that hypercoagulabe state is common in cancer patients and consumptive coagulopathy can occur after resection of metastatic brain tumor.

• 대한수학회보
• /
• 제43권1호
• /
• pp.179-188
• /
• 2006

For a given p-valent analytic function g with positive coefficients in the open unit disk $\Delta$, we study a class of functions $f(z) = z^p - \sum\limits{_{n=m}}{^\infty} a_nz^n(a_n{\geq}0)$ satisfying $$\frac 1 {p}{\Re}\;(\frac {z(f*g)'(z)} {(f*g)(z)})\;>\;\alpha\;(0{\leq}\;\alpha\;<\;1;z{\in}{\Delta})$$ Coefficient inequalities, distortion and covering theorems, as well as closure theorems are determined. The results obtained extend several known results as special cases.

• Journal of Chest Surgery
• /
• 제48권2호
• /
• pp.99-104
• /
• 2015

Background: We report our initial experiences of robot-assisted cardiac surgery using the da Vinci Surgical System. Methods: Between February 2010 and March 2014, 50 consecutive patients underwent minimally invasive robot-assisted cardiac surgery. Results: Robot-assisted cardiac surgery was employed in two cases of minimally invasive direct coronary artery bypass, 17 cases of mitral valve repair, 10 cases of cardiac myxoma removal, 20 cases of atrial septal defect repair, and one isolated CryoMaze procedure. Average cardiopulmonary bypass time and average aorta cross-clamping time were $194.8{\pm}48.6$ minutes and $126.1{\pm}22.6$ minutes in mitral valve repair operations and $132.0{\pm}32.0$ minutes and $76.1{\pm}23.1$ minutes in myxoma removal operations, respectively. During atrial septal defect closure operations, the average cardiopulmonary bypass time was $128.3{\pm}43.1$ minutes. The median length of stay was between five and seven days. The only complication was that one patient needed reoperation to address bleeding. There were no hospital mortalities. Conclusion: Robot-assisted cardiac surgery is safe and effective for mitral valve repair, atrial septal defect closure, and cardiac myxoma removal surgery. Reducing operative time depends heavily on the experience of the entire robotic surgical team.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• 제16권2호
• /
• pp.113-121
• /
• 1994

Large oral defects following tumor resection pose formidable challenge for the reconstructive surgeon. Ideally, wound closure should utilize like tissue in providing expedient, single-stage closure, returning maximum function while minimizing deformity. Recent methods have reported and utilize variable mucocutaneous flaps. However, the ideal reconstruction has yet to defined. The small bowel serves as a readily available donor site for satisfying reconstructive needs in oropharyngeoesophageal defects. Segments of jejunum may be opened along the antimesenteric border and transferred to oral defect as free tissue transfers. Some of the benefits of this technique have included a one-stage procedure, abundant donor tissue with characteristics similar to oral mucosa, near normal facial appearance, preservation of maximum tongue function and relief of annoying xerostomia by jejunal mucous secretion. Three cases re presented in which two cases show successful use of this flap. The other one patient developed total necrosis of this flap. We report cases of reconstruction using free jejunal flap transfer in oral reconstruction.

• 한국전산구조공학회논문집
• /
• 제25권4호
• /
• pp.293-300
• /
• 2012

본 논문에서는 직교이방성 적층평판에서의 균열생성 및 전파로 이루어진 층간분리해석을 다룬다. 기존의 p-유한요소가 가지고 있는 요소의 강건성을 균열진전해석에 적용하여, 균열진전시 모델링을 재구성하지 않고, 균열 선단부에 해당되는 꼭지점 모드의 위치만을 이동하도록 하여, 요소망을 단순화시켰다. 이와 같은 층간분리해석에 대해서 이 논문에서의 주요 목적은 다음 두 가지이다. 첫째, 적층복합 재료의 층간분리해석 시, 일반적인 유한요소 모델과 비교하여 매우 간단한 요소망을 가지는 모델을 제안하는 것이다. 모델의 타당성을 평가하기 위해 적층 복합재료로 구성된 이중 외팔보 해석을 통하여, 기존 참고문헌 값과의 비교를 수행하였다. 둘째, 제안된 모델을 내부균열을 갖는 적층평판의 층간분리해석에 적용하여 여러 가지 거동 양상에 대한 평가이다. 이와 같은 목적을 수행하기 위하여 로바토 형상함수를 이용한 완전층별요소가 고려되었으며, 선형탄성파괴역학에 기초한 3차원 가상균열닫힘법을 이용하여 에너지 방출률을 산정하였다.