• 한국강구조학회 논문집
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• 제12권1호통권44호
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• pp.65-73
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• 2000

상용 유한요소해석 프로그램인 ABAQUS(ver5.8)를 이용하여 전단력을 받는 더블앵글 접합부의 3D 해석을 수행하여 접합부의 모멘트-회전 관계곡선을 구하고 앵글과 볼트의 응력분포를 관찰한다. 해석시 주요 매개변수로는 볼트수, 게이지거리, 앵글의 두께로 하였으며 유한요소해석 결과로 구한 모멘트-회전곡선을 Richard가 제시한 예측식에 적용한 후 회귀분석을 통하여 접합부 거동을 예측하는 데 필요한 매개변수인 초기강성, 소성강성, 참조모멘트, 곡선형태변수를 구한다. 또한 매개변수들이 게이지거리, 앵글의 두께 및 볼트 수 변화에 따른 그래프를 작성하고 또한 이 그래프를 이용하여 접합부의 모멘트 및 LRFD의 접합부 분류에 따른 소성모멘트에 대한 접합부 모멘트의 비를 계산한다.

• 한국환경농학회지
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• 제33권1호
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• pp.17-23
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• 2014

시설재배 참외 주산지에서는 농가별로 가용 경지면적이 제한되어 있어 동일 포장을 이용한 장기간 연작이 불가피하므로 토양의 염류집적 문제와 함께 선충 피해가 매우 심각하다. 참외 휴경기에 하우스의 비닐을 제거하고 김장배추를 재배하는 이모작 체계는 다음 작기 참외 재배 시 토양 선충 밀도를 줄이는데 아무런 영향을 미치지 못하였다. 일반 참외 연작 하우스와 비교하여 참외-미나리 이모작 하우스에서는 다음 작기 참외 재배기간 동안 6월까지는 토양의 선충 밀도가 상대적으로 낮았는데, 이는 토양을 3개월 정도의 담수 상태로 유지함으로써 얻을 수 있는 효과로 판단된다. 참외-미나리 이모작 하우스에서 다음 작기 참외 정식 전에 살선충제를 처리한 경우에는 참외 재배 후반기까지 선충 밀도가 피해유발수준 이하로 유지되었다. 농가에서 휴경기에 배추와 미나리를 윤작물로 재배하는데, 이러한 단기윤작은 참외 연작 비닐하우스 토양의 선충을 효과적으로 방제하는 방법이 되지 못한다. 따라서 객토, 토양소독, 윤작물 재배 등의 친환경적인 선충방제 수단을 적극적으로 활용하고 그 효과를 극대화할 수 있는 방안들이 강구되어야 할 것이며, 필요에 따라서 적절한 살선충 약제를 사용함으로써 작물생산에 미치는 선충의 피해를 최소화시킬 수 있을 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제53권7호
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• pp.2207-2220
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• 2021

Lead alloy is used as coolant in Lead-based cooled Fast Reactor (LFR). The natural characteristics of lead alloy are combined with the simple structural design of LFR. This constitutes the inherent safety characteristics of LFR. The main work of this paper is to take the main coolant pump (MCP) in the lead-cooled fast reactor (LFR) as the research object, and to study the flow pattern distribution of the internal flow field under the reverse rotation pump condition, the reverse rotation positive-flow braking condition and the reverse rotation negative-flow braking condition. In this paper, the double-outlet volute type and the space guide vane are selected as the potential designs of the CLEAR-I MCP. In this paper, the CFD method is used to study the potential reverse accident of the MCP. It is found that the highest flow velocity in the impeller appears at the impeller outlet, and the Q-H curves of the two design programs basically coincide. The space guide vane type MCP has better hydraulic performance under the reverse rotation positive-flow condition, the Q-H curves of the two designs gradually separate with increasing flow rate, and the maximum flow velocity inside the space guide vane type MCP is obviously lower than that of the double-outlet volute type. For the reverse rotation test of MCP, only the condition of the forward rotating pump of the main coolant pump is tested and verified. For the simulation of the MCP in LBE medium, it proved that the turbulence model and basic settings selected in the simulation are reliable.

• 한국농림기상학회지
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• 제9권2호
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• pp.100-108
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• 2007

험준한 산지에 위치한 광릉 KoFlux 슈퍼사이트는 기복이 진 지형과 산골 순환으로 인해 풍속이 약한 것이 특징이다. 따라서 에디 공분산 방법을 이용한 플럭스 관측에 좌표회전이 미치는 효과를 이해하는 것이 필수적이다. 본 논문에서는 세 가지의 직교 좌표 체제 (이중, 삼중 및 planar fit 회전)의 특징을 살펴 보고, 이들을 광릉 슈퍼사이트에서 관측된 플럭스 자료에 적용하였다. 'Planar Fit(PF)' 좌표회전으로부터 유추해 낸 초음파 풍속계의 연직 풍속의 평균 차감은 대략 $\pm0.05ms^{-1}$이었다. 바람이 부는 경우, 이중 회전 $(\bar{v}=\bar{w}=0)$에서 산출된 열, 수증기 및 $CO_2$의 난류 플럭스는 PF 회전에서 나온 결과와 거의 같았다. 그러나 바람이 잔잔한 경우에는 이중 회전이 큰 값의 편의를 나타내었다. 대기 지표층의 중요한 스케일링 모수인 마찰 속도는 좌표 회전 방법의 선택에 따라 더 민감하게 반응하였다.

• 한국의료질향상학회지
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• 제23권2호
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• pp.11-20
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• 2017

Purpose: The purpose of this study was to determine the effects of rotation direction during curved walking on gait parameters in stroke patients. Methods: A group of thirty subjects with stroke (Berg Balance Scale score${\geq}41$ were fifteen, Berg Balance Scale score${\leq}40$ were fifteen) were enrolled in this study. Testing indications included two directions for rotation in each subject. These indications were for rotation toward the affected and unaffected side in stroke patients. The gait speed, affected side single support duration, affected side double support duration were recorded. The obtained data were analyzed by using paired t-test and Wilcoxon signed rank test in the group that are below and above 40 points of Berg Balance Scale score. Results: There was significant increase affected side single support duration was turned the affected side in stroke patients that presented a Berg Balance Scale score${\geq}41$ (p<.05). There were significant increase gait speed, affected side single support duration, and significant decrease affected side double support duration while subjects were turned the affected side in stroke patients that presented a Berg Balance Scale score${\leq}40$ (p<.05). Conclusion: This result may be effective to rotate in the paralyzed direction to improve the ability of the paralyzed lower limb to gain weight during gait training for stroke patients with a Berg Balance Scale score<40. Therefore, walking training program for hemiplegic patient needs to be suggested in the direction of turning for suitable balance ability.

• 대한기계학회논문집
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• 제19권7호
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• pp.1709-1719
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• 1995

The primary objective of the paper is to obtain the basic information of the natural convection of a stratified with various parametric conditions related to rotating speed, temperature and concentration gradient. For the purpose of it, experiments are performed in a stably stratified salt-water solution with lateral heating in a stationary or rotating annulus. The experiment covers the ranges of Ar=2, Le=100, R $a_{\ta}$=2 10$^{5}$ and Ta=0, 10$^{5}$ - 2.5*10$^{8}$ . Many interesting flow phenomena are observed and rotation effects are examined. Particularly as Taylor number increases (rotation increases) at a given R $a_{\ta}$, the generation of rolls at hot wall is inhibited and the formation and merging process of layers are delayed.

• Journal of Ship and Ocean Technology
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• 제6권1호
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• pp.1-15
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• 2002

A new concept for launching free-fall lifeboats, proposed by Yokohama National University is described in this paper. It has been pointed out that, using the conventional single-skid free-fall system, the potential for dangerous lifeboat motions (in which the lifeboat moves backward or jerks on the surface after entering the water) increases with the fall height of the lifeboat. One of the principal causes of this undesirable motion is vertical rotation of the lifeboat during its restricted fall at the edge of the launching skid. Thus a new "double-skid"launching concept is proposed to effectively eliminate the rotation of the lifeboat at the skid end and to enable the lifeboat to move smoothly after entering the water. In order to evaluate the performance of the proposed method, a series of model experiments and numerical simulations is carried out in which two lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle and skid height are investigated, and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.

• 호남수학학술지
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• 제45권4호
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• pp.585-597
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• 2023

We introduce the rotational hypersurface x = x(u, v, s, t) constructed by double rotation in five dimensional Euclidean space 𝔼⁵. We reveal the first and the second fundamental form matrices, Gauss map, shape operator matrix of x. Additionally, defining the i-th curvatures of any hypersurface via Cayley-Hamilton theorem, we compute the curvatures of the rotational hypersurface x. We give some relations of the mean and Gauss-Kronecker curvatures of x. In addition, we reveal Δx=𝓐x, where 𝓐 is the 5 × 5 matrix in 𝔼⁵.

• Journal of Yeungnam Medical Science
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• 제3권1호
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• pp.237-241
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• 1986

본 교실에서 백서의 대퇴동맥을 이용하여 혈관감자의 회전없이 continuous suture로 미세혈관 문합을 시행해본 결과 다음과 같은 결론을 얻었다. end-to-end anastomosis시 double c1app의 회전이 어려울 정도로 작업공간이 제한된 경우나 end-to-side anastomosis시 secondary Vessel의 길이가 짧아서 후벽을 잘 볼 수 없는 경우에 continuous suture을 이용하면 Back wall을 완전히 노출시킨 상태에서 쉽게 혈관 문합을 시행할 수 있으며 문합시간도 단축시킬 수 있을 것으로 사료된다.

• 대한기계학회논문집
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• 제19권7호
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• pp.1731-1740
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• 1995

Experimental investigations have been made to study the double-diffusive nature of convection of an initially stratified salt-water solution due to heating from below in a rotating cylindrical cavity. The objective is to examine the flow phenomena and the heat transfer characteristics according to the changes in temperature gradient, concentration gradient and rotating velocity of cavity. Thermal and solutal boundary conditions at side wall are adiabatic and impermeable, respectively. The top and bottom plate are maintained each at constant temperature and concentration. The cavity is put into a state of solid body rotation. Like the stationary case, the types of initially-formed flow pattern are classified into three regimes depending on the effective Rayleigh number and Taylor number; stagnant flow regime, single mixed-layer flow regime and successively formed multi-mixed layer flow regime. At the same effective Rayleigh number, the number of initially-formed mixed layer and its growth rate decrease as the effect of rotation increases. The temperature and concentration profiles are both uniform in each layer due to convective mixing in the layered-flow regime, but look both liner in stagnant flow regime and single mixed-layer flow regime. At the interface between adjacent layers, the temperature changes smoothly but the concentration changes rapidly.