• Nuclear Engineering and Technology
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• 제49권6호
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• pp.1287-1300
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• 2017

Based on the observation that ignoring the angle dependency of multigroup resonance cross sections within a fuel pellet would result in nontrivial underestimation of the spatial self-shielding of flux, a parametrized spectral superhomogenization (SPH) factor library (PSSL) method is developed as a practical means of resolving the problem. Region-wise spectral SPH factors are calculated by the normal and transport corrected SPH iterations after ultrafine group slowing down calculations over various light water reactor pin-cell configurations. The parametrization is done with fuel temperature, U-238 number density, fuel radius, moderator source represented by ${\Sigma}_{mod}V_{mod}$, and the number density ratio of resonance nuclides to that of U-238 in a form of resonance interference correction factors. The parametrization is successful in that the root mean square errors of the interpolated SPH factors over the fuel regions of various pin-cells are within 0.1%. The improvement in reactivity error of the PSSL method is shown to be superior to that by the original SPH method in that the reactivity bias of -200 pcm to -300 pcm vanishes almost completely. It is demonstrated that the environment effect takes only about 4% in the reactivity improvement so that the pin-cell based PSSL method is effective in the assembly problems.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1999년도 춘계학술발표회요약집
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• pp.155-155
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• 1999

Pool boiling critical heat flux (CHF) have been investigated using plate type test sections with different widths (3 cm & 4 cm) and lengths (10 cm, IS cm & 20 cm) under various incli- nation angles. As the inclination angle increases from $0^{\circ}$ (horizontally facing downward plate) to $30^{\circ}$, CHF sharply increases. After that angle, CHF gradually increases with the increase of the inclination angle. There must be a transition angle between $0^{\circ}$ and $30^{\circ}$, at which the CHF increase rate remarkably changes. According to the comparison of present and previous ex- periments, the transition angle may be affected by heater size and increase with the increase of heater size. The size effect of heated surface on CHF is noticeable in the L15 & L20 series and W4 series; however, it seems to be difficult to find the size effect in L10 series and W3 series.

• 대한족부족관절학회지
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• 제6권1호
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• pp.60-65
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• 2002

Purpose: The purposes of the present study were to find the ideal insertion position syndesmosis screw and relation to the surrounding anatomical structures when indirectly inserting the screw anteriorly at a 30 angle at 3 cm proximal portion of the ankle join t. Materials and Methods: We performed computed tomography from the axial view in 20 normal individuals at 3 cm proximal portion of the ankle joint and divided the lateral side of the fibula into 4 sections. We drew a line from the middle of each of these 4 sections to the posterolateral tibia at a 30 angle and determined the relationship between each of these lines and the surrounding anatomical structures and confirmed the site at which each of these 4 lines passed through the posterolateral tibia which divided into 3 sections and the site of the fibula at which each of these lines passed through the middle 1/3 portion of the tibia. Results: The posterior 3/4 portion of the fibula that passed through the middle 1/3 portion of the posterolateral tibia in 18 cases. The portion did not approach the surrounding anatomical structures(Peroneal vessels and the muscular portion of FHL). Conclusion: The ideal insertion position of syndesmosis screw at 3 cm proximal portion of the ankle joint at a 30 angle is the posterior 3/4 portion of the lateral side of the fibula, and injury to the surrounding anatomical structures could be avoided when the screw passes through the middle 1/3 portion of the posterolateral tibia.

• Journal of Advanced Marine Engineering and Technology
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• 제27권5호
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• pp.666-674
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• 2003

An experimental investigation was performed to study the characteristics of turbulent swirling flow in an axisymmetric annuli. The swirl angle measurements were performed by flow visualization technique using smoke and dye liquid along the test tube. Using the Particle Image Velocimetry method, this study found the time-mean velocity distribution and turbulent intensity with swirl for Re = 20.000. 30.000, 50.000. and 70.000 along longitudinal sections and the results appear to be physically reasonable.

• 대한기계학회논문집A
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• 제27권3호
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• pp.372-380
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• 2003

Impact tests were conducted to study the effect of angle ply and metal laminate on impact damage characteristics of Fiber Metal laminates (FML). Impact tests were conducted using drop weight impact machine and damage behavior were analyzed by comparing with load-displacement curve and surface observation and microscopic observation of cross sections. The effect of angle ply on impact characteristics of FML are influenced by property of metal laminate. i.e., when the metal laminate is not enough to strong to prevent fiber debonding, Angle ply FML is superior to singly oriented ply (SOP) FML because angle ply enhance the stiffness by fiber supports and prevent (rack propagation. However, when the metal laminate is enough to strong to prevent fiber debonding, SOP FML is superior to Angle ply FML because the fiber of lower ply in Angle ply FML are more stressed than that of SOP FML.

• 지질공학
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• 제18권1호
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• pp.45-54
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• 2008

본 연구에서는 기 조사된 편마암 지역에서의 급경사지재해 발생지역 및 미발생지역에 대한 현장조사자료 및 토질시험자료를 토대로 통계적인 분석방법인 의사결정나무모형을 이용하여 급경사지재해 예측기법을 개발하였다. 편마암 지역에서의 조사된 급경사지재해 자료는 서울 및 경기지역에서 1998년 집중호우로 발생된 104개소구간이다. 이 가운데 예측모델 개발에 활용된 자료수는 결측치를 제외한 61개소로서, 급경사지재해 발생구간 34개소와 미발생구간 27개소이다. 의사결정나무모형을 이용한 통계적인 분석은 카이제곱 통계량, 지니 지수 및 엔트로피 지수를 적용하여 실시하였다. 분석결과 사면경사, 포화도 및 사면고도가 분리기준으로 선택되었으며, 엔트로피 지수를 이용한 의사결정나무모형 예측모델이 정확도가 가장 높은 것으로 나타났다. 선정된 급경사지재해 예측모델의 분리기준은 최상위부터 사면경사, 포화도 및 사면고도의 순서로 선택되었으며, 각각의 분리기준치는 사면경사의 경우 $17.9^{\circ}$, 포화도의 경우 52.1%, 사면고도의 경우 320m로 결정되었다.

• 한국기계가공학회지
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• 제6권4호
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• pp.76-80
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• 2007

Two roll straightener showed the remarkable improvement in straightness betterment of the bar compared with other types of straightener. So, in this study we designed a two-cross straightener curvature for the straightness improvement of a bar and contact sections with respect to the variation of the gap between two-cross roll using nonlinear contact analysis. The Displacement in terms of a intersection angle between roll and bar was predicted on with the effect of a straightness and plastic deformation behaviors of the bar according to the roll drive of a two cross-roll straightener.

• 한국원자력학회:학술대회논문집
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• 한국원자력학회 1996년도 춘계학술발표회논문집(2)
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• pp.337-342
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• 1996

The pool-boiling critical heat flux (CHF) of water on small flat plates has been experimentally investigated focusing on the effects of the inclination angle and size of the heated surface under near atmospheric pressure. The second-phase experiment was accomplished to find out the general CHF behavior for over-all inclination angles from -90$^{\circ}$ to 90$^{\circ}$using two plate-type test sections (30$\times$150 mm and 40$\times$150 mm) submerged in a slightly subcooled water pool. Test results generally confirm the first-phase findings and show little effect of inclination angle for inclined upward-facing cases. CHF position moves to lower position with the increase of the heater characteristic size and inclination angle(from -30$^{\circ}$to 60$^{\circ}$).

• 한국생산제조학회지
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• 제20권2호
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• pp.202-206
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• 2011

Works on the strength and stiffness in the structural members are carried out widely with various material and cross-sections with ever increasing safety concerns, they are presently applied in various fields including railroad trains, air crafts and automobiles. In addition to this, problem of lighting structural members became important subject by control of exhaust gas emission, fuel economy and energy efficiency. So, Light weight of member structures is necessary for the high performance and various functions. In this study, the CFRP flat and circular member was manufactured by CFRP prepreg sheet in autoclave. Carbon FRP is an anisotropy material whose mechanical properties change with its fiber orientation angle, so this study apply to the effects of the fiber orientation angle on the bending characteristics of the member. Each CFRP flat and circle are compared by strength and stiffness.

• 오토저널
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• 제10권3호
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• pp.51-59
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• 1988

The wake structure behind a van type vehicle was studied experimentally with a 5-hole yawhead probe. Through an effective calibration method of the 5-hole yawhead probe, the flow properties such as velocity vector, total pressure and static pressure were obtained on two cross sections within the wake. These results combined with the surface flow visualization performed in the previous study, yielded some information about the wake structure. When the model was placed in a stream with zero yaw angle, two counter rotating vortices were observed behind the model which pull down the surface flow on each side of the model. With increasing the yaw angle, the surface flow on the windward side changed to divide the flow in two directions, one flows upward on the upper part and the other flows downward on the lower part of the windward side. Hence a new weak vortex was created on the upper windward side, which resulted 3 vortices within the wake. The size and the strength of the vortices increased with yaw angle.