• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.340-340
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• 2011

자연하천의 안정은 하상경사, 유사이동, 원지반의 상태, 저수로의 깊이, 하도 및 하안의 구조와 하안식생 등에 달려있다. 이 중 하상경사는 가장 중요한 요소로써 하도의 안정을 위해서는 무엇보다도 이를 적절하게 유지하는 방안을 모색하여야 한다(김혜주 등, 2003). 이러한 자연하천의 안정을 위하여 주로 하상유지시설을 설치하는 것이 보편적이다. 이러한 낙차공의 설치는 하천설계기준을 근거로 하상의 안정성 확보라는 설치 목적에 맞게 설계 및 시공이 이루어져 하도의 안정에는 나름대로 효과적이지만 하천환경의 연속성 차단 등 다양한 생태·환경적 폐해가 나타나고 있는 것으로 알려져 있다(김혜주 등, 2003). 이러한 단점을 보완하기 위해 낙차공과 같은 횡단구조물의 본체에 어도를 설치하거나 계단형 또는 경사형 본체를 갖는 구조물이 제안되고 있으나 현재까지 제안된 보완적인 방법들로는 근본적인 생태단절을 해소하기에는 무리가 있다. 따라서 낙차공 등 하천 수공구조물 설치로 인해 야기되는 생태 환경적 문제를 해결하기 위해서는 대상하천에 서식하는 생물에 대한 이해가 우선 이루어져야 하며 이를 바탕으로 설계 및 시공하는 것이 가장 효과적이다. 이를 위해서는 구조물 설치에 따라 변화되는 수리현상에 대한 정확한 분석이 필요하다. 이에 본 연구에서는 국내외에서 제안되고 있는 낙차공 중 통나무를 이용한 낙차공의 평면형태에 따른 하류부 세굴현상을 수리실험을 통해 분석하였다. 본 연구에서는 평면형태(horizontal)에 따른 세굴영향을 파악하고자 평면각을 $70^{\circ}$에서 최대 $180^{\circ}$로 변화시켜 세굴 실험을 수행하였다. 상향 V형만을 고려한 이유는 하향 V형의 경우($\theta$>$180^{\circ}$)에는 낙차공을 월류하는 흐름으로 인해 구조물 하류부 좌 우안측에 세굴이 발생하기 쉽기 때문에 자연하천의 경우 호안측 침식이 발생한 수 있고 또한 실험수로 벽면영향으로 인해 세굴형태가 왜곡될 우려가 있어 하향 형태의 낙차공은 실험대상에서 제외하였다. 낙차공의 평면 형태가 세굴심에 미치는 영향을 검토한 결과, 유입 Froude 수( )에 대해 높은 상관이 있으며 또한 평면각도에 따라 변하는 낙차공의 횡단길이가 낙차공 하류부의 세굴심에 큰 영향을 미치고 있음을 확인할 수 있었고, 세굴길이의 경우, 평면형태에 따른 세굴길이와 세굴심의 비는 낙차공의 평면각도의 증가에 따라 세굴 길이가 짧아짐을 확인할 수 있었다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.10
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• pp.3964-3973
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• 2010

The main purpose of this study is the vertical circulation elements(stairs, elevator, ramp) in a Museum. The first is numerically analyzed in the study. And museum of Korea was limited to the case. The result of the study can be summarized as follows. 1. 50% of cases have 3~4 vertical circulation elements.; (1) ~8 elements: 1(3%), (2) 7 elements: 2(5%), (3) 6 elements: 5(13%), (4) 5 elements: 6(16%), (5) 4 elements: 8(21%), (6) 3 elements: 11(29%), (7) 2 elements: 4(11%), (8) 1 element: 1(3%). 2. There was "stairs alone", "elevator + stairs", "elevator + stairs + ramp", "stairs + ramp" in museum of Korea. Cases of "elevator alone", "ramp alone", elevator + ramp", "stairs + elevator + ramp" was not.; (1) stairs alone: 8(21%), (2) elevator + stairs: 21(55%), (3) elevator + stairs + ramp: 8(21%), (4) stairs + ramp: 1(3%).

• Journal of the Korean Geotechnical Society
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• v.21 no.2
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• pp.105-111
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• 2005

Shaking table tests are performed to investigate the seismic behavior of the batter pile and to bring up the countermeasures to improve the seismic performance of the batter pile. First of all, this study demonstrates how batter piles and vertical piles behave under static lateral loadings. Secondly, the vulnerability of batter plies under dynamic lateral loadings is demonstrated showing the axial forces and bending moments mobilized at the pile heads during shaking table tests. Thirdly, countermeasures to overcome the vulnerability of behavior piles during earthquakes are pursued. The countermeasures investigated in this study include introduction of a rubber element at the pile head and the deck plate connection, and introduction of hinge connection. Finally, the slope of batter piles which induces the minimum pile forces during the dynamic loadings are investigated and found to be 8:3 (Vertical to Horizontal).

• Proceedings of the KAIS Fall Conference
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• 2007.05a
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• pp.104-107
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• 2007

현재까지 수리학 분야에서 가장 많이 회자되고 인용된 공식이 있다면 아마도 1800년에 발표한 Manning의 유속 공식이라고 해도 과언은 아닐 것이다. 그만큼 그 쓰임새가 많았을 뿐만 아니라 사용의 편리생과 정확도에서도 매우 우수하였기 때문일 것이다. 그러나, 아무리 우수한 공식이라도 약점이 있듯이, Manning의 유속공식 역시 조도계수n을 추정하는데 많은 어려움이 있는 것도 주지의 사실이다. 이러한 어려움을 극복하기 위하여, 본 연구에서는 확률통계에서 사용되는 엔트로피 개념을 이용한 3차원 유속분포식인 Chiu의 유속공식을 사용하였다. 그러나 지금까지 실증적으로 Chiu의 유속공식과 Manning땅의 유속공식을 비교분석하였던 논문은 Chiu와 Choo의 논문에서 일부 언급된 것 외 논문에서는 찾아볼 수 없는 것이 현실이다. 따라서 본 연구에서는 하상경사를 임의로 변경 가능한 실험수로를 선택하여 정밀법에 의한 유속측정을 우선 실시하였다. 같은 지점의 같은 단면에서 하상경사(${\Theta}$)가 0.000935부터 0.025794까지 28번의 경사변화를 주고 각 경사마다 유량을 측정하여 28개의 유량측정 데이터를, Chiu의 유속공식과 Manning의 유속공식에 각각 적용하여, Chiu의 M과 Manning의 n사이의 관계뿐만 아니라, 하상경사변화에 따른 관련인자들을 함께 분석하였으며, 실측된 평균유속과도 함께 분석하였다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.4 no.1
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• pp.1-6
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• 2003

A novel Solid Freeform Fabrication System, which makes prototype by cutting tapes at the boundary of object and accumulating the tapes, has been developed. In order to overcome the staircase shape at the surface of prototype, the laser beam is irradiated tangent to the surface. Five axis cutting system and the tangent cutting trajectory generation algorithm have been developed.

• Journal of the Korean Wood Science and Technology
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• v.28 no.2
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• pp.19-24
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• 2000

Effects of the cross-sectional dimension and moisture profile of wood specimens on the ultrasonic sound velocities of radiata pine heartwood and sapwood. Each moisture profile model specimen was made by composing five wood pieces with various moisture contents. As the cross-sectional dimensions decreased the ultrasonic velocities of both heartwood and sapwood decreased by 4~8%. In the ultrasonic signals transmitted through the specimens low frequency components more dominated than high frequency components as the dimension of cross section increased. The specimens with the same average MCs and different moisture profiles showed different ultrasonic velocities. By plotting the ultrasonic velocities against the average moisture contents of the inner three pieces of the moisture profile model specimens it was revealed that three distinct plot patterns existed.

• Journal of the Korean Society of Radiology
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• v.5 no.5
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• pp.223-229
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• 2011

When negative electron in x-ray tube is accelerated in to a high speed and then the currency of the electron is blocked by the target, x-ray happens by the conversion of the energy. The real area where the fast accelerated electron collides to a target area is called actual focal spot. When the string focused size is observed at the central ray side, where the direction x-ray comes out, the size seems to be reduced. This focus is called effective focal spot. According to radiation angle of x-rays tube, the degree of the negative pole side presents higher value than inclination, the amount of exposed radiation that patient receives differs by the angle of positive pole, which means effective focal spot is the variable. This paper presents the correlation between size of effective focal spot and amount of exposed radiation to the patient by it, and effective research for homogenized dose dispersion by the size of effective focal spot. In conclusion, following the focal size, effective range which was -8cm ~ 0 cm on average, was found and average dose rate was 0.019 R/min. Through this range, for patients with small radiation exposure, image with good density and resolution in aspect of diagnosing will be able to be obtained.

• Journal of radiological science and technology
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• v.35 no.2
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• pp.83-92
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• 2012

In anteroposterior projection for cervical vertebra, it is general that the incidence angle of X-ray is $15^{\circ}$ to $20^{\circ}$ degrees to head in order to prevent overlap of mandible and occipital bone and to observe array of cervical interbody and shapes of joints. However, the angle is appropriate for foreigners that was determined by foreign literature review long ago, and there have been few researches of incidence angle for Koreans' body type. The purpose of in this study are to identify the incidence angle appropriate for Koreans and to present methodology. In order to measure the incidence angle, 1,044 patients who visited S Hospital located in Seosan were selected and measured of average length of cervical vertebra, OID, axis angle, and FID. The incidence angle was calculated from the applied formula by measuring average values per age groups and sex (see Formula 1 and 2). The average length of cervical vertebra was 6cm: the length was increased from teenagers to twenties but was decreased since thirties. The difference between males and females was around 1cm (p<.01). The OID was almost the same regardless of age groups and sex. As for axis angle, the slope was increased in teenagers and twenties, but was decreased since thirties. The difference between males and females was around 2 degrees (p<.01). The FID measurements were almost the same regardless of age groups and sex, and when the incidence angle was measured from these values, the teenagers were $15.9^{\circ}$, the twenties were $16.9^{\circ}$, the thirties were $16.6^{\circ}$, the forties were $16.2^{\circ}$, the fifties were $15.9^{\circ}$, and the sixties were $14.5^{\circ}$, indicating that the angle was increased from teenagers to the twenties but decreased since the thirties. While the angles of males and females were measured to be the same in the teenagers, the angle was different between males and females by $2^{\circ}$. When the incidence angle statistically analyzed with measurement of average length of cervical vertebra, OID, axis angle, and FID, all of them were shown to have correlations with the incidence angle (p<.01). Conclusively, it was shown that the incidence angle was measured differently from average length of cervical vertebra, OID, FID, and axis slope, as well as from age and sex. Therefore, it can be suggested that the anteroposterior radiation test for cervical vertebra should be conducted by different incidence angles based on age and sex. The data of this study may be used as reference in determining the incidence angle of cervical vertebra tests for the future.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 1998.10a
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• pp.28-28
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• 1998

단일 충돌제트의 경우 충돌면에서의 열전달 효과는 제트 출구와 충돌면 사이의 간격, 노즐 형상에 따른 제트출구의 초기조건, Re$_{D}$수 변화와 충돌면의 형상이나 표면거칠기 등에 따라 변화하게 된다. 그러나 수직 충돌제트의 경우 정체영역에서의 국소적인 열전달 향상은 용이하나 반경 방향으로 열전달이 점차 감소하게 된다. 따라서 충돌면의 전반적인 열전달 향상을 위해서는 열전달이 정체점보다 상대적으로 낮은 영역에서 열전달 향상이 필요하다. 또한, 실제 적용시 충돌면의 형상이나 협소한 공간에서 노즐위치의 제약으로 인하여 충돌제트가 수직으로 분사되는 경우보다 경사진 제트가 더욱 많이 응용된다. 더욱이, 수직충돌제트가 사용되는 많은 상황에서도 주위의 다른 공기 흐름의 영향으로 인하여 실제 제트가 경사각을 갖고 분사되어진다 이러한 경사충돌제트의 중요성에도 불구하고 경사충돌제트에 대한 연구는 수직충돌제트에 대한 연구보다 상대적으로 적게 이루어져 왔다.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.779-786
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• 2002

A boundary element method with a Lagrangian approach and B-spline technique is employed to investigate characteristics of solitary waves attacking on beach slopes. By comparing numerical solutions with available laboratory measurements, it is shown that the maximum run-up heights of the present model are more agreeable than those of the existing numerical model. Variations of run-up heights and velocity vectors for different slopes are also described. Characteristics of hydrodynamic pressure acting beach slopes are investigated in detail.