• 한국전산유체공학회지
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• 제3권2호
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• pp.27-38
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• 1998

Rotating flow of a stratified fluid contained in a circular cylinder with unstable temperature gradient imposed on the side wall of it has been numerically studied. The temperatures at the endwall disks are constant. The top disk of the container is coider than that of the bottob disk, as much as the temperature difference n${\Delta}$T, (0${\leq}$n${\leq}$3). Flows in the vessel are driven by an impulsive rotation of the hot bottom disk with respect to the central axis of the cylinder. Flow details have been acquired. For this flow, the principal balance in the interior core is characterized by a relationship between the radial temperature gradient and the vertical shear in the azimuthal velocity. As the buoyancy effect becomes appreciable, larger portions of the meridional fluid transport are long-circuit from the bottom disk to the interior region via the side wall.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2009년도 하계학술발표대회 논문집
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• pp.847-852
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• 2009

Feedwater heaters of many nuclear power plants have recently experienced severe wall thinning damange, which will increase as operating time progresses. Several nuclear power plants in Korea have experienced wall thinning damage in the area around the impingement baffle inside feed-water heater installed downstream of the turbine extraction stream line. At that point, the extract steam from the turbine is two phase fluid at high temperature, high pressure, and high speed. Since it flows to reverse direction after impinging the impingement baffle, the shell wall of feedwater heaters may be affected by flow-accelerated corrosion. In this paper, to compare wall thinning range according to change entrance nozzle diameter and position with reference numerical analysis model's wall thinning range, various numerical analysis models applied. In case of changing diameter, four different diameter is applied. And a side of nozzle position, two different position-vertical type and parallel type-is applied. And then this paper describes operation of numerical analysis which is composed similar condition with real feed water heater. In conclusion, this study shows effective design for shall wall thinning by changing nozzle diameter and position.

• 한국인터넷방송통신학회논문지
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• 제19권5호
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• pp.211-217
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• 2019

제주의 3대 발명은 1234년 김구 판관의 밭담, 제주 사람들의 방목문화 관습에서 나온 정낭, 1406년 문방귀의 묘의 신문인 올레 등을 들 수 있다. 돌과 돌의 수 눌음에서 나온 외담인 밭담은 친족사회인 괸당을 만들었다. 30m/s 이상 불어오는 태풍에도 약 1.5m 높이인 밭담은 무너지지 않는다. 마찬가지로 제주 사회의 괸당도 어떤 어려움이 닥쳐도 서로 도와 무너지지 않는다. 밭담을 쌓을 때는 밑돌인 괸돌 둘을 나란히 평면으로 붙이고 그 위에 왼쪽 윗돌로 괴고 옆에 오른쪽 윗돌을 상보적으로 붙인다. 밭담이 밑에서 위쪽으로 한 돌, 두 돌 붙여나가는데 가운데 돌은 조금 작거나 큰 비정형 돌들로 쌓으면 하나의 공간에선 평면 밭담이 된다. 괸당은 할아버지, 할머니-아버지, 어머니-나를 중심으로 가깝고, 먼 혈족이 수직관계를 나타낸다. 밭담은 밑에서 위로 쌓아가는 수직관계인 데 반하여, 괸당은 윗대 할아버지 친족에서 아랫대의 손자까지 피를 나누어가는 수평 관계다. 본 논문은 밭담 가운데 돌이 큰 돌(작은 돌)을 놓는가에 대해서 비직교 대칭 하중 Hadamard 행렬로 접근한다.

• 한국수자원학회논문집
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• 제46권9호
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• pp.947-956
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• 2013

급경사 산지하천 수충부의 호안은 대부분 콘크리트 옹벽으로 되어있다. 표면이 매끄러운 콘크리트 옹벽호안은 유속을 더 강화시키기 때문에 수충부 홍수피해의 원인이 되기도 한다. 본 연구에서는 개수로의 한 측벽에 설치한 정사각형 단면의 세로돌출줄눈이 흐름저항에 미치는 영향을 파악하기 위해 수리실험을 수행하였다. 돌출줄눈의 설치간격은 무차원 돌출줄눈 간격 ${\lambda}_{nv}$를 기준으로 조도유형 d형과 k형을 포함하도록 설계하였다. 흐름의 Froude 수는0.81~1.12의 범위였다. 흐름저항은 돌출줄눈의 설치간격과 유량에 좌우되었다. ${\lambda}_{nv}$가 9일 때 흐름저항이 가장 큰 것으로 나타났다. 세로돌출줄눈은 유량이 증가하면 d형 조도에서는 흐름저항을 감소시켰으나 k형 조도에서는 흐름저항을 증가시켰다. 흐름저항의 증가폭은 ${\lambda}_{nv}$이 9~12의 범위에서 상대적으로 더 크게 나타났다. 세로돌출줄눈에 의한 흐름저항은 대부분 형상저항에 의한 것이며 그 등가조도높이는 수심규모로 발생할 수 있고 흐름저항에 미치는 영향이 매우 크다. 측벽의 세로돌출줄눈은 흐름저항을 증가시키고 최대유속의 발생위치를 수로의 횡단면 중앙방향으로 이동시키는 수단으로 사용될 수 있을 것이다.

• 콘크리트학회논문집
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• 제17권2호
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• pp.293-302
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• 2005

This study describes data from determination of the optimum mix proportion and site application of the mass concrete placed in bottom slab and side wall having a large depth and section as main structures of LNG in-ground tank. This concrete requires low heat hydration, excellent balance between workability and consistency because concreting work of LNG in-ground tank is usually classified by under-pumping, adaptation of longer vertical and horizontal pumping line than ordinary pumping condition. For this purpose, low heat Portland cement and lime stone powder as cementitious materials are selected and design factors including unit cement and water content, water-binder ratio, fine aggregate ratio and adiabatic temperature rising are tested in the laboratory and batch plant. As experimental results, the optimum unit cement and water content are selected under $270kg/m^3$ and $l55{\~}l60 kg/m^3$ separately to control adiabatic temperature rising below $30^{\circ}C$ and to improve properties of the fresh and hardened concrete. Also, considering test results of the confined water ratio($\beta$p) and deformable coefficient(Ep), $30\%$ of lime stone powder by cement weight is selected as the optimum replacement ratio. After mix proportions of 5cases are tested and compared the adiabatic temperature rising($Q^{\infty}$, r), tensile and compressive strength, modulus of elasticity, teases satisfied with the required performances are chosen as the optimum mix design proportions of the side wall and bottom slab concrete. $Q^{\infty}$ and r are proved smaller than those of another project. Before application in the site, properties of the fresh concrete and actual mixing time by its ampere load are checked in the batch plant. Based on the results of this study, the optimum mix proportions of the massive concrete are applied successfully to the bottom slab and side wall in LNG in-ground tank.

• 한국지반공학회논문집
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• 제23권8호
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• pp.87-95
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• 2007

본 연구에서는 대심도 풍화대에 시공되는 2차로 도로터널을 기준으로 터널의 굴착방법과 지반보강그라우팅에 의한 지반변위 및 지반응력의 분석을 통하여 최적의 시공방안을 찾고자 하였다. 터널 직경은 약 12m를 적용하였으며, 상부 강관다단그라우팅 및 측벽 보강그라우팅을 적용하였다. 검토된 굴착방법은 링컷 굴착방법과 중벽분할 굴착방법이다. 터널 천단의 소성율과 연직응력비를 분석한 결과, 풍화대지반에 굴착되는 터널에서 토피고(H)가 터널직경(D)의 4배 이상일 경우(H>4D) 대심도 터널로 판단할 수 있었다. 해석결과 중벽분할 굴착방법이 링컷 굴착방법에 비하여 대심도 풍화대 NATM터널에서 안정성이 높은 굴착방법으로 판단할 수 있었다. 또한, 측벽 보강그라우팅 실시로 터널 내공변위 및 침하 발생을 억제할 수 있었다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2003년도 하계학술대회 논문집 Vol.4 No.2
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• pp.892-895
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• 2003

This paper describes on RIE(Reactive Ion Etching) characteristics of 3C-SiC(Silicon Carbide) grown on Si(100) wafers. During RIE of 3C-SiC films in this work, $CHF_3$ gas is used to form of polymer as a side wall for excellent anisotropy etching. From this process, etch rates are obtained a $60{\sim}980{\AA}/min$ by various conditions such as $CHF_3$ gas flux, $O_2$ addition ratio, RF power and electrode distance. Also, approximately $40^{\circ}$ mesa structures are successfully formed at 100 mTorr $CHF_3$ gas flow ratio, 200 W RF power and 30 mm electrode distance. Moreover, vertical side wall is fabricated by anisotropy etching with 50% $O_2$ addition ratio and 25 mm electrode distance. Therefore, RIE of 3C-SiC films using $CHF_3$ could be applicable as fabrication process technology for high-temperature 3C-SiC MEMS applications.

• 한국가스학회지
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• 제10권1호
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• pp.56-60
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• 2006

지하식 LNG 저장탱크의 Bottom Slab와 Side Wall의 연결부(코벨)는 응력집중을 완화하기 위하여 앵커바를 사용하여 부분적으로 고정되는 힌지 조건을 갖는다. 그러므로 LNG저장탱크 하중 조건인 LNG온도, 지하수압 등에 의해 방사 방향과 수직 방향으로 변형된다. 멤브레인 설계 관점에도 이러한 변형값이 직접 전달되어 중첩되므로 중요한 부분이다. 본 논문에서는 코벨부의 실제 거동을 조사하기 위하여 센서를 설치하여 온도, 하중 그리고 변위를 측정하였다. 또한 FEM 해석으로 예측한 하중조건에 대한 설계 값과 비교하여 합리적인 설계를 제시하고자 하였다.

• Archives of Plastic Surgery
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• 제36권4호
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• pp.503-506
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• 2009

Purpose: Unilateral breast reconstruction after mastectomy confront the challenges of recreating a natural appearing breast mound and achieving symmetricalness of the breasts. If the patient's remaining breast is large compared to reconstructed breast, the most common procedure is reduction mammoplasty of the large breast side. The authors experienced a new method of breast reconstruction using the excess breast tissue from the contralateral breast after breast reduction. Methods: The excess tissue from the contralateral breast after vertical reduction mammoplasty with superior pedicle and remaining lower breast tissue were transferred to the mastectomy site breast through the subcutaneous tunnel on the chest wall. The main blood supplies of the flap are perforator branches of the 4th, 5th and 6th anterior intercostal artery. After elevating and detaching the flap on the lower lateral area of the breast, the turn overed flap is fixed on the upper portion of the chest wall of the mastectomy site. Results: On two cases of the breast reconstructions, remaining excess breast tissue from reduction mammoplasty was transferred to the contralateral breast side as pedicles. Both patient and operator were satisfied with the outcome of the reconstruction as the breasts were symmetrical and natural shape. Conclusion: We have performed unilateral breast reconstruction using the excess breast tissue after reduction mammoplasty of the contralateral breast. As Oriental women's breasts are relatively smaller than that of Caucasian women, delayed breast reconstruction cases of Oriental women with large breasts(macromastia) seem to be ideal for this procedure.

• Corrosion Science and Technology
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• 제12권5호
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• pp.227-232
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• 2013

A number of components installed in the secondary system of nuclear power plants are exposed to aging mechanisms such as FAC (Flow-Accelerated Corrosion), Cavitation, Flashing, and LDIE (Liquid Droplet Impingement Erosion). Those aging mechanisms can lead to thinning of the components. In April 2013, one (1) inch small bore piping branched from the main steam line experienced leakage resulting from wall thinning in a 1,000 MWe Korean PWR nuclear power plant. During the normal operation, extracted steam from the main steam line goes to condenser through the small bore piping. The leak occurred in the downstream of an orifice. A control valve with vertical flow path was placed on in front of the orifice. This paper deals with UT (Ultrasonic Test) thickness data, SEM images, and numerical simulation results in order to analyze the extent of damage and the cause of leakage in the small bore piping. As a result, it is concluded that the main cause of the small bore pipe wall thinning is liquid droplet impingement erosion. Moreover, it is observed that the leak occurred at the reattachment point of the vortex flow in the downstream side of the orifice.