• Structural Engineering and Mechanics
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• 제61권4호
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• pp.497-510
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• 2017

A framed structure may be composed of two sub-structures, which are linked by a hinged joint. One sub-structure is the primary system and the other is the secondary system. The primary system, which is subjected to the periodic external load, can give rise to an auto-parametric resonance of the second system. Considering the geometric-stiffness effect produced by the axially internal force, the element equation of motion is derived by the extended Hamilton's principle. The element equations are then assembled into the global non-homogeneous Mathieu-Hill equations. The Newmark's method is introduced to solve the time-history responses of the non-homogeneous Mathieu-Hill equations. The energy-growth exponent/coefficient (EGE/EGC) and a finite-time Lyapunov exponent (FLE) are proposed for determining the auto-parametric instability boundaries of the structural system. The auto-parametric instabilities are numerically analyzed for the two frames. The influence of relative stiffness between the primary and secondary systems on the auto-parametric instability boundaries is investigated. A phenomenon of the "auto-parametric internal resonance" (the auto-parametric resonance of the second system induced by a normal resonance of the primary system) is predicted through the two numerical examples. The risk of auto-parametric internal resonance is emphasized. An auto-parametric resonance experiment of a ${\Gamma}$-shaped frame is conducted for verifying the theoretical predictions and present calculation method.

• 한국가구학회지
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• 제14권2호
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• pp.87-96
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• 2003

This study explores aesthetics and materials used in domestic and international hanger designs from 1850 to 2003. At the second half of the nineteenth century, most hangers were handmade and made of wood and metal. At the first half of the twentieth century, such diverse materials as paper, plastics, and leather began to use other than such typical materials as wood and metal at the previous decades. However, from the second half of the twentieth century the use of different types of plastics led to artistic abnormal shapes within typical triangular types. Moreover, this study also examines hangers by its functions: primary, portable, and multi-functional types.

• Korean Journal of Mathematics
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• 제26권4호
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• pp.675-681
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• 2018

In the paper, by virtue of techniques in combinatorial analysis, the authors simplify three families of nonlinear ordinary differential equations in terms of the Stirling numbers of the first kind and establish a new family of nonlinear ordinary differential equations in terms of the Stirling numbers of the second kind.

• 대한소아치과학회지
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• 제35권1호
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• pp.167-174
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• 2008

하악 유구치와 제1대구치는 보통 근심과 원심에 하나씩 2개의 치근을 가지나 원심설측에 독립적으로 존재하는 부가치근을 갖는 경우가 발견된다. 발생 빈도는 하악 제1대구치의 경우 백인에서는 3% 정도로 드물게 나타나지만 중국이나 일본, 에스키모, 북미 인디언 등 황인종에서는 20% 내외로 비교적 높다. 유구치의 경우는 제1대구치보다는 적게 발생되고 제1유구치보다는 제2유구치에서 더 많이 발생한다. 하악 유구치에 부가치근이 관찰되면 후방에 있는 유구치와 제1대구치에서도 부가치근이 발생할 가능성이 높으며 부가 치근을 가지는 하악 제1유구치의 치관의 형태는 원심설측에 존재하는 부가치근의 영향으로 삼각형 모양을 나타낼 수 있다. 본 증례는 연세대학교 치과대학병원 소아치과에 내원한 5명의 환아에게서 발생된 하악 유구치와 제1대구치의 부가 치근에 관한 보고로서 부가치근을 가진 유구치는 치근의 수와 치관의 형태 등에 문제가 있으므로 치수치료나 기성금관 수복, 발치 시에 정확한 진단과 치료가 필요할 것으로 사료된다.

• 대한토목학회논문집
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• 제26권5B호
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• pp.469-479
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• 2006

본 연구에서는 사행수로에서 주 흐름과 이차류의 특성을 정량적으로 분석하고자 중심각이 $150^{\circ}$이고 사행도 1.52인 S자형 사행수로에서 실험을 수행하였다. 평균수심과 유량을 달리하여 다양한 실험 조건 하에서 수행한 실험을 통해 다중 만곡부를 갖는 사행수로에서 이차류의 공간적 변화양상을 관찰하였다. 실험결과, 주 흐름은 실험조건에 관계없이 직선구간에서 좌우 대칭적인 유속분포를 보였고, 만곡부에서는 내안쪽에 최대유속이 발생하고 외안쪽에 최소유속이 발생하는 현상을 발견 할 수 있었다. 이렇게 주 흐름이 최단노선을 따라 발생하는 현상은 기존 연구자들의 결과와 일치하는 것이다. 이차류의 거동은 첫번째 만곡부보다 두 번째 만곡부에서 더욱 활발하게 발달하고 외안 회전류가 뚜렷히 나타남을 발견하였다. 이차류의 강도는 직선구간에서는 낮게 나타나고 만곡부에서는 증가하는 주기적인 현상을 보였으며, 만곡부의 이차류 강도가 직선구간보다 2~3배 크게 나타났다. 또한, 두 번째 만곡부에서 이차류 강도의 최대값이 발생했다. 주 흐름방향의 난류 강도와 Reynolds 전단응력을 분석한 결과, 주 흐름 난류 강도는 주 흐름의 유속편차가 클수록 증가하는 것으로 나타났고 Reynolds 전단응력은 주 흐름방향 유속의 편차가 크게 벌어지는 동시에 이차류가 활발히 생성되는 지점에서 크게 나타나는 경향을 보였다.

• Journal of Yeungnam Medical Science
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• 제27권2호
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• pp.98-104
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• 2010

원발성 전 종격동 종양은 종격동 종양의 반이상을 차지하고 그 종류도 다양하다. 흉선 상피 종양이 가장 흔하고 악성 흉선종은 드물다. 생식세포종은 두 번째로 흔한 전 종격동 종양으로 보다 어린나이에 발생하며 대부분 양성이다. 임파종은 대부분 전신성 질환의 흉부 침습 형태로 나타나나 원발성 흉부 임파종은 Hodgkin씨 병이 많다. 저자는 대표적인 전종격동 종양의 임상증상과 영상의학적 소견을 소개한다.

• Advances in pediatric surgery
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• 제11권1호
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• pp.34-39
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• 2005

Two cases of primary torsion of the greater omentum were described. The first patient was a 5-year-old boy who was admitted to the hospital because of severe abdominal pain for 1 day. The The clinical features were similar to perforated acute appendicitis. Laparotomy revealed a normal appendix and the greater omentum twisted around its pedicle. The second patient was a 7-year-old girl admitted to the hospital because of abdominal pain in right lower quadrant for 2 days. The clinical features? were that of acute appendicitis. Laparotomy revealed a normal appendix and primary torsion of greater omentum around its pedicle. In both cases, resection of twisted omentum and incidental appendectomy were done. The microscopic findings in two cases consisted of congestion and vascular hemorrhage. Both patients recovered uneventfully. Torsion of the greater omentum, therefore, may be added to the entities to consider in the differential diagnosis of acute appendicitis.

• 한국의류산업학회지
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• 제4권2호
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• pp.163-168
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• 2002

For the purpose of investigating the factor of foot and calf growth of primary-school children who are fast-growing during this period a group of the 1st graders of primary-school had been the subject of this measurement in 1995 and there after they became the subject again in 1997, 1999 when they were the 3th, 5th graders measurement was carried out in 30 items including status and weight and marthin-type measure and foot-print were used for this measurement as the result, stature is correlated with height items and length items of foot and calf weight is correlated with width and circumference items of foot and calf angle of the first toe showed the highest growth like 3rd graders, heel circumference had rapidly grown rather than in the part of foot circumference in the factor analysis df foot measurement of 10-year, the first, second factors, appeared the size of shoes, in case of 12-year the first factor with status appeared the size of shoes.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 하계종합학술대회 논문집 Ⅳ
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• pp.2407-2410
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• 2003

In this paper, we propose a new stereoscopic video conversion methodology that converts two-dimensional (2-D) MPEG-4 video to stereoscopic video. In MPEG-4, each Image is composed of background object and primary object. In the first step of the conversion methodology, the camera motion type is determined for stereo Image generation. In the second step, the object-based stereo image generation is carried out. The background object makes use of a current image and a delayed image for its stereo image generation. On the other hand, the primary object uses a current image and its horizontally-shifted version to avoid the possible vertical parallax that could happen. Furthermore, URFA(Uncovered Region Filling Algorithm) is applied in the uncovered region which might be created after the stereo image generation of a primary object. In our experiment, show MPEG-4 test video and its stereoscopic video based upon out proposed methodology and analyze Its results.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.43-46
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• 2012

The oxygen concentration of primary oxidizer is decided under 10% due to flammable risk. It can be a spontaneous combustion inside burner or tube if the excess oxygen is added to primary oxidizer in Oxy-PC burner. In this case, the rest oxygen which can not be injected to primary oxidizer should be injected to another port. If added it to a second oxidizer, the ignition is unstable at outlet of burner. Accordingly an extra lancing port is needed to insert into the burner unlike other common air mode. And the flame formation and combustion characteristic differ from lancing port position. Therefore we observed flame formation which has stable combustion characteristic according to the shape and position of lancing port.