• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.414-419
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• 2011

Missile am fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 60 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure distribution, etc. are analyzed according to the angle of attack. The results at a low angle of attack are compared with other results before a stall condition. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution on the airfoil surface, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.

• 대한기계학회논문집A
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• 제31권3호
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• pp.322-330
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• 2007

This paper quantifies the effect of a bend angle of a pipe bend on plastic loads, via small strain and large strain FE limit analyses using elastic-perfectly plastic materials. To consider the effect of the attached straight pipe, two limiting cases are considered. One case corresponds to the pipe bend without the attached straight pipe, and the other to that with a sufficiently long attached straight pipe. For the former case, the FE results suggest that the limit load is not affected by the bend angle for both in-plane bending and internal pressure. For the latter case, however, the bend angle affects plastic loads. An interesting finding is that the plastic load smoothly changes from the limit load of the straight pipe when the bend angle approaches zero to the plastic load of the $90^{\circ}$ pipe bend when the bend angle approaches 90 degree. Based on such observations, closed-form plastic load solutions are proposed for the pipe bend with an arbitrary bend angle under in-plane bending and internal pressure.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제26권2호
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• pp.204-210
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• 2000

The mandibular contour determines the shape of the lower part of the face and thus influences the appearance of the face. A patient with a large, squarish, or broad face who desires a small, round, or slender face can undergo mandibular contouring surgery to reduce the width of the lower face. The successful correction of a prominent mandibular angle by conventional angle ostectomy has been reported. But, in the majority of patients with a widened facial appearance, both the mandibular angle and part of the mandibular body anterior to it are protuberant laterally, so both must be resected. The purpose of this study is to introduce a new method of performing mandibular contouring surgery, more effectively and easily, and to reduce postoperative complication and evaluate its results. We treated 6 patients who has prominent mandibular angle using multiple step osteotomy with angle-splitting ostectomy. The advantages of this new method are as following. (1) easily performable (2) effective mandibular contouring surgery by reducing the width of lower face (3) producing a natural relief of the mandibular angle (4) low risk of soft tissue damage and complications (5) shortening of the operation time. etc.

• 한국전산유체공학회지
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• 제18권1호
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• pp.1-6
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• 2013

Missile and fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 50 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure, entropy distribution, etc. are analyzed according to the angle of attack. The results of average lift coefficients are compared with other results according to the angle of attack. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. The primary and secondary oscillating frequencies are analyzed by the effects of these unsteady aerodynamic characteristics.

• 전력전자학회논문지
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• 제3권4호
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• pp.418-425
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• 1998

본 논문에서는 위상각 제어에서 주어진 턴온 각에서 최대의 토크를 유지하기 위한 적절한 턴오프 각을 자기동조방식(self-tuning method)에 의해 결정하는 방식을 제안하였다. 엔코더에 의해 샘플링 시간(sampling time)동안 구해진 펄스 수는 바로 이전의 샘플링시간 동안 구해진 펄스 수와 비교하여 턴오프 각을 앞으로 또는 뒤로 이동한다. 이러한 과정을 되풀이함으로서 최대 토크를 발생하는 턴오프 각을 결정하게 된다. 실제 회로에서는 원 칩 마이크로프로세서에 의해 처리되었으며 실험을 통해 턴온 각이 변하더라도 자기동조방식에 의해 턴오프 각을 조정하면 빠른 속도가 유지됨을 보여 주었다.

• 척추신경추나의학회지
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• 제1권2호
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• pp.93-100
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• 2006

Objectives: To invesgate correlation between the scoliotic curve and BMI, cervical lordosis, lumbar lordosis and Ferguson angle in spinal scoliotic patient. Methods: The study was composed of 14 scoliosis patients beyond cobb'a angle $10^{\circ}$ (sample I group) and 15 scoliosis patients over cobb'a angle $10^{\circ}$ (sample II group). The patients were evaluated with X-ray findings of full spine AP and lateral views and statistically analyzed. Results: 1. Sample II group showed a significant decrease in BMI as compared with Sample I group(P<0.05). 2. Scoliotic curve had s negative relationship with $BMI({\gamma}=0.406)$ 3. Scolotic patients had a lower cervical angle than normal man. Conclusion: 1. The larger the scoliotic angle, the lower BMI 2. There are no concemed scoliotic curve and cervical lordosis, lumbar lordosis and Ferguson angle.

• 한국자동차공학회논문집
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• 제21권1호
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• pp.121-127
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• 2013

In this study, suspension geometry is controlled to improve vehicle handling performance. The toe and camber of the rear suspension is controlled independently by using a double knuckle structure designed to enhance the vehicle cornering stability. Camber and toe changes in the rear wheel during high speed turning maneuver are important factors that influence the vehicle stability. Toe in the rear outer wheel plays a dominant role in cornering. A control algorithm for the camber and the toe angle input is developed to carry out the control simulation of the vehicle such as single lane change, the steady state cornering, the double lane change and the step steering simulation. Effects of the camber and toe angle control are analyzed from the computer simulations. A double lane change simulation revealed that the suspension mechanism with variable camber angle and variable toe angle decreases the peak body slip angle and peak yaw rate, 50% and 10%, respectively.

• 한국의류학회지
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• 제18권2호
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• pp.211-220
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• 1994

The purpose of this study was to analyze the foot type by cluster analysis for footwear. The sample size for the study was 200 college womens between age 19 and 23 in Pusan urban area. There were measured 17 items of the foot for factor analysis and cluster analysis. The result was as follows : 1. 1'here were 9 items selected by factor analysis. 2.'rho cluster analysis of the foot must be analyzed by direct and indirect measurement indivisually. 3. The cluster analysis of the direct measurement ; Cluster 1 : 1'he foot length is all much the same to mean value of this age group and the items of width and circumference are relatively small to other clusters. Cluster 2 ; The foot length is relatively small to other clusters and the items of width and circumference are all much the same to mean value of this age group. Cluster 3 ; The foot sine Is relatively large to other clusters. 4. The cluster analysis of indirect measurement ; Cluster 1 ; The (cot print angle is high find Metatarso-Phalanx angle is transformed Cluster 2 ; The foot print angle is low and Melatarso-Phalanx angle is normal. Cluster 3 : Tho foot print angle Is middle and Metatarso-Phalanx angle is all the mush same to mean value of this age group. Cluster 4 . The foot print angle Is the most value and Metatarso-Phalanx angle is normal.

• 한국자동차공학회논문집
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• 제16권6호
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• pp.148-156
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• 2008

This paper is the first of 2 companion papers which investigate in-cylinder swirl generation characteristics according to inlet valve angle. Two DOHC 4 valve engines, one has wide intake valve angle and the other has narrow valve angle, were used to compare the characteristics of swirl motion generation in the cylinder. One intake port was deactivated to induce swirl flow. A PIV (Particle Image Velocimetry) was applied to measure in-cylinder velocity field according to inlet valve angle during intake stroke. The results show that the stronger swirl motion is observed in wide valve angle engine at the early intake stage; however, the swirl motion is gradually distorted by the intake flow component passing through valve area near the cylinder wall as the stroke proceeds. The tumble motion also does so in wide angle. On the contrary, the swirl and tumble motions, which are not clear at the initial stage, become better and better arranged as the piston goes down and up again after bottom dead center.

• 한국운동역학회지
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• 제14권1호
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• pp.1-12
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• 2004

The purpose of this study is to provide training materials for practical use by investigating the kinematical variables of the successful landing by the type of the salto backward such as Tuck, Pike. For this study, the subjects are 4 male national gymnasts using 3-dimensional cinematographic method. Based on the results of this study, the conclusions are drawn as follows. 1. In flight phase, Tuck and Pike show fast extension after completing minimum angle of hip joint passing through the peak. It is very important factor to control body with gaining time before landing while decreasing the velocity of flight rotaion. 2. In Landing phase, the angles of each joint for successful landing are shown as $92deg{\sim}100deg$ for knee angle, $52deg{\sim}57deg$ for hip angle, and $56deg{\sim}70deg$ for shoulder angle. 3. Tuck and Pike dramatically decrease the height of COG, and horizontal/vertical velocity of COG from TD to LD. Also, it is shown that the knee angle, the hip angle and the shoulder angle decrease drastically. On the other hand, the angular velocity of trunk rotation shows negative direction and due to this, the angle of trunk rotation is shown as re-flexion.