• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 춘계학술대회논문집
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• pp.254-257
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• 1998

The twisting and the bending of extruded product are caused by the shapes of products and by the shapes of die surfaces and by the shapes of die land. Because the elliptical shape and the circular shape of the extruded product have the symmetry line of cross-section area, the twisting and the bending of product has not occurred. But the analysis by the DEFORM-3DTM show that the twisting and the bending of extruded product can be occurred by the twisting of the twisting of the die land and by the curving of the die land. The results by the analysis show that the twisting angle of the extruded procduct increases by the twisting angle of the die land and the curvature of the extruded products increases by the radius of bending of the die land.

• 한국광학회지
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• 제1권2호
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• pp.204-209
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• 1990

Nd:YAG 레이저봉을 이용한 간단한 간섭장치를 구성하여 단일펄스 및 고반복률 펌핑 후 레이저봉의 간섭효과에 의한 간섭무늬의 이동갯수를 이용하여 레이저봉의 온도를 측정하였으며, 간섭무늬의 시간적인 변화와 열확산 방정식을 풀어서 얻은 레이저봉의 온도와 비교하였다. 아울러 레이저봉에 누적된 열에너지의 공간분포와 정도를 측정하여 본 연구에서 사용된 금도금된 섬광관 펌핑 반사체에 의한 레이저봉의 펌핑 균일도 및 열전달률을 평가하였다.

• 한국추진공학회지
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• 제23권5호
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• pp.107-114
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• 2019

다양한 군용기에서, S자 형상의 디퓨저(흡입구)는 터보팬 엔진의 블레이드가 외부에 노출되는 것을 방지하기 위해 사용된다. 군용 항공기의 흡입구 형상은 F-22와 같은 직사각형, F-16과 같은 초승달모양, MG-25와 같은 타원형 등으로 다양하다. 본 연구에서는 수치해석을 통해 다양한 입구 형상을 갖는 S자 디퓨저의 공력 성능을 평가하였다. 또한, S형 덕트 중단부 단면 형상을 초승달 모양으로 변경하여 공력 성능에 미치는 영향을 분석하였다. 결과적으로, 공력 성능은 다양한 입구 모양에 따라 압력회복률에 약간의 차이를 보였다. 또한 압력왜곡은 직사각형 입구 형태에서 가장 낮았다. 중간단면의 형상이 타원형에서 초승달 모양으로 변경되었을 때, 전체 압력 회복은 높은 수준을 유지했다. 압력왜곡의 경우 초승달 형의 중간 단면을 갖는 덕트가 타원형 중간 단면 덕트보다 균일한 압력 분포를 나타내었다.

• 한국의류학회지
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• 제14권4호
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• pp.292-304
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• 1990

The surface change of upperarm and shoulder blade area are caused by the extensive upper limb movement, thus it is necessary to measure the amount of change for constructing the clothing. Moire photography was taken after plastic casters of upperarm and shoulder blade area was prepared. 1. For the shoulder blade area, subjects showed the same change of surface area for the various limb positions, wherease, for the upperarm only at the $0^{\circ}\;and\;180^{\circ}$ limb position, same change was observed. 2. As the movement of the upperarm was increased, surface area of axillary part was increased and that of shoulder part was decreased. 3. To make a bodice pattern, the minimum size of the back with the ease were $\frac{B}{4}$+3.13 cm R for normal wear and $\frac{B}{4}$+5.75 cm for active wear. 4. As the movement of the arm was increased, the cross section for the upperarm were changed to elliptical shape. 5. For each horizontal basic line, there was a positive correlation between the amount of change of shoulder blad area and that of upperarm area.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.239-242
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• 2009

Friction stir spot welding (FSSW), developed based on principle of friction stir welding, has been paid attention as a new solid-state spot welding process. Since FSSW can produce high-quality weld in Al alloys more easily than resistance spot welding, this process has been already used for construction of Al components in the automotive industries. Despite the large industrial interests in FSSW, fundamental knowledge on welding phenomena of this process has not been fully understood. In this study, FSSW phenomena, such as the consolidation mechanism, the microstructural evolution and the material flow, were examined in Al alloy 6061. This study clarified that the elliptical zone found in the vicinity of the pin hole on the cross section was characterized by the initially lapped surface of two sheets. Moreover, the following material flow was proposed; capture of the upper material with the threads on the pin surface, spiral flow along the tool rotation, and then release at the tip of the pin.

• 한국물환경학회지
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• 제25권4호
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• pp.547-552
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• 2009

Because of refractory property of light, the travel path of UV light becomes longer than the straight line and shorter solely in water as UV light passes sequentially through air, quartz and water. Note that water significantly absorbs UV light. Hence, UV intensity shall be estimated to be lower when refraction is neglected than it is considered. Reflection is also critical for the design of UV radiation system. While the reflection at the interface of air and quartz is low enough to ignore, it is too high to be ignored at the interface of quartz and water. Assuming constant power, smaller length to width ratio of UV reactor is beneficial and single-lamp system is preferred to multi-lamps. Under the given cross section, optimal lamp positions could be decided. For example of an elliptical reactor with dual lamps, the optimal lamp locations shall be the 1/3 and 2/3 position of the longer axis.

• 대한수의학회지
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• 제26권2호
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• pp.195-199
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• 1986

The papillary tubercles (PTs) developed on the splenic capsule of normal Landrace pigs were collected and their histological structures were observed with light microscope. The results were summarized as follows : 1. The external features of the PTs were smooth spherical or oval form protruded on the splenic capsules. On cross section of PTs, the shapes were predominantly round or elliptical single follicular form, and were often multifollicular and irregular form in some PTs. 2. The PTs were interposed into the splenic capsule. Therefore the peripheral boundary of PT was consisted of splenic capsular tissue and this tissue was covered with mesothelium, The basal tissues of PT were consisted of thick connective tissue and smooth muscle of splenic capsule, and capsular foramen for transport tract between splenic parenchyma and the PT was found at the center of the basal boundary of PT. 3. The basal region of PT was composed of parenchyma and this tissue was the splenic red pulp but the central and peripheral regions of PT contained much more erythrocytes than in the splenic parenchymae. 4. The splenic parenchymae adjoining to PT contained more erythrocytes than in other splenic parenchymal regions and parallel fixed cells directed to the capsular foramen.

• Wind and Structures
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• 제22권6호
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• pp.663-684
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• 2016

Conical vortices generated at the corner regions of large-span flat roofs have been investigated by using the Particle Image Velocimetry (PIV) technique. Mean and instantaneous vector fields for velocity, vorticity, and streamlines were measured at three visual planes and for two different flow angles of $15^{\circ}$. The results indicated that conical vortices occur when the wind is not perpendicular to the front edge. The location of the leading edge corresponding to the negative peak vorticity and maximum turbulent kinetic energy was found at the center of the conical vortex. The wind pressure reaches the maximum near the leading edge roof corner, and a triangle of severe suctions zone appears downstream. The mean pressure in uniform flow is greater than that under turbulent flow condition, while a significant increase in the fluctuating wind pressure occurs in turbulent streams. From its emergence to stability, the shape of the vortex cross-section is nearly elliptical, with increasing area. The angle that forms between the vortex axis and the leading edge is much smaller in turbulent streams. The detailed flow structures and characteristics obtained through FLUENT simulation are in agreement with the experimental results. The three dimensional (3-D) structure of the conical vortices is clearly observed from the comprehensive arrangement of several visual planes, and the inner link was established between the vortex evolution process, vortex core position and pressure distribution.

• 한국전산구조공학회논문집
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• 제25권2호
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• pp.175-182
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• 2012

본 연구에서는 뒤틀림을 받고 있는 정사각형 단면의 중공단면 보를 최소자승법과 경계요소법을 이용하여 수치 해석하고 구조물을 해석하였다. 임계하중은 하중을 점차적으로 증가하여 구조물이 파괴가 발생하여 안정성을 상실하는 상태에서 가장 작은 하중을 의미한다. 뒤틀림을 받고 있는 beam은 일반 구조물에서 많이 발생하는 현상이며, 구조물의 안정성에 크게 영향을 미치고 있다. 최소자승법과 경계요소법은 복잡한 구조물에서도 물론, 다양한 경계조건을 포함하는 문제에 이르기까지 구조물의 안정성을 검사하는데 효과적인 수치해석 방법이다. 특히 뒤틀림의 문제에서는 단순성 및 일반성에 기인하여 매우 적합한 해석방법이다. 본 연구에서는 뒤틀림을 받고 있는 중공단면 보의 해석해를 유도하여 최소자승법으로 수치 해석하고 또한 경계요소법을 적용하여 빔의 안정성을 비교 검토하였다. 개발한 컴퓨터 프로그램의 타당성을 증명하기 위하여 삼각형, 사각형 그리고 타원형 단면에 대하여 각각 해석하여 해석해와 비교 검토하였다.

• 한국어류학회지
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• 제21권4호
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• pp.283-286
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• 2009

고려홍어의 모식산지인 한반도 남서해안에서 포획한 암컷개체의 자궁에서 직접 적출한 난각 2개를 새롭게 기재하였다. 본종의 난각은 다른 종과 비교하여 보통 크기이고, 뿔(horn)을 포함한 전장은 124.5~133.7 mm, 뿔을 제외한 주부(main portion)의 체장은 102.8~109.4 mm, 최대폭은 41.0~42.2 mm이다. 측면에서 볼 때 배쪽으로 불룩한 비대칭이고, 표면은 비교적 부드러운 편이지만 세로로 미세한 고랑(longitudinal striations)은 뚜렷하고, 매우 발달한 섬유다발(견상사(絹狀絲) silky fibers)로 덥혀 있다. 앞뒤의 apron은 뚜렷하며, 네 뿔은 짧고 튜브모양이고 그 횡단면은 타원형이고, 앞쪽 뿔은 안쪽으로 심하게 구부러져 있으며, 호흡공(respiratory fissure)은 네 뿔의 끝부분에 위치한다. 신선한 상태에서 밝은 갈색이다.