• 한국해안·해양공학회논문집
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• 제24권6호
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• pp.400-403
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• 2012

본 연구에서 건물이 밀집되어 있는 해안도시에서의 지진해일 범람에 대한 평면수리모형실험을 수행하였다. 해안도시는 미국 서해안에 위치한 도시인 Seaside를 1/50으로 축소하여 평면수조에 설치하였다. 본 실험에서 범람지역에서의 지진해일의 파고 및 수평속도 측정하였는데, 31개 지점에서 계측하였으며 입사된 지진해일의 파고는 원형 스케일 10 m로 설정하였다. 범람양상과 속도는 건물의 위치 및 배열상태에 따라 크게 다르게 계측되었다. 또한, 도시의 주요 도로를 따라 계측된 지진해일 범람 파고 및 수평속도를 이용하여 모멘텀 플럭스(Momentum flux)를 계산하였다. 모멘텀 플럭스는 해안선에서부터 육지방향으로 파가 진행하면서 감소하는 일반적인 경향을 나타내었다. 범람파고와 모멘텀 플럭스는 도로가 형성된 구역에서 감쇄가 적게 나타났다. 본 연구를 통해 수평 유속이 구조물에 미치는 외력에 중요한 영향을 준다는 것을 알게 되었다.

• 대한조선학회논문집
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• 제51권6호
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• pp.503-509
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• 2014

This paper describes the time-domain numerical method for prediction of slamming loads on a ship in waves using the strip theory. The slamming loads was calculated considering the relative vertical velocity between the instantaneous ship motion and wave elevation. For applying the slamming force on a ship section, the momentum slamming theory and the empirical formula-based bottom slamming force were used corresponding to the vertical location of wetted body surface. Using the developed method, the vertical bending moments, relative vertical velocities, and impact forces of S175 containership were compared in the time series for various section locations and wave conditions.

• Journal of Astronomy and Space Sciences
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• 제32권4호
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• pp.419-425
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• 2015

In this study, a new idea for developing a space scale for measuring mass in a microgravity environment was proposed by using the inertial force properties of an object to measure its mass. The space scale detected the momentum change of the specimen and reference masses by using a load-cell sensor as the force transducer based on Newton's laws of motion. In addition, the space scale calculated the specimen mass by comparing the inertial forces of the specimen and reference masses in the same acceleration field. By using this concept, a space scale with a capacity of 3 kg based on the law of momentum conservation was implemented and demonstrated under microgravity conditions onboard International Space Station (ISS) with an accuracy of ${\pm}1g$. By the performance analysis on the space scale, it was verified that an instrument with a compact size could be implemented and be quickly measured with a reasonable accuracy under microgravity conditions.

• 한국운동역학회지
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• 제16권4호
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• pp.135-145
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• 2006

The aim of this study was to find out the differences of biomechanical factors from touching down the vaulting board to landing when techniques of 1/1Turn, stretched, and Tucked were performed on the old vaulting horse and on the new vaulting table. Three national representative men gymnasts were sampled for this study. Three dimension motion analyses by means of six Sony PD-150 video cameras with the velocity of 60 fps were used. As a result of analyzing the kinetic data from two kind of vaulting table, the following conclusions were made. 1. There was not significant differences of angular momentum between the old and the new vaulting table in all three techniques except the phase of stepping on the vaulting board and contacting the vaulting horse in the Tucked technique. IN the two phases above, the angular momentum in the new vaulting table was greater than that of the old vaulting horse. 2. There were few significant differences between the old and the new vaulting horses in the horizontal and vertical reaction force according to techniques when stepping was performed. However, it appeared tendency that the horizontal and vertical reaction force in the new vaulting table was a little greater than that of the old vaulting horse when the 1/1Turn, the Stretched and the Tucked were performed.

• 한국안전학회지
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• 제30권6호
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• pp.63-69
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• 2015

In this study, a 2D hydrodynamic model equipped with critical dry depth scheme was developed to reproduce the flow over staircase. The channel geometry of hydraulic experiment conducted by Ishigaki et al. was generated in the computational space, and the developed model was validated against flow properties such as discharge, velocity and momentum. In addition, the water surface profile and the velocity distribution evolved in flow over two layers staircases were analyzed. When the initial water depth at the upper floor was 0.3 m, the maximum velocity at lower floor was 4.2 m/s, and the maximum momentum was $1.2m^3/s^2$, and its conversion to force per unit width was 1.2 kN/m. This value was equivalent to the hydrostatic force with 50 cm water depth, and evacuation became difficult, as proposed by Ishigaki et al. For the flow over staircases connecting two layers, the maximum run-up height in flat part connecting two layers was approximately two times higher than the initial water depth in upper floor, and the rapid shock wave with sharp front and long tail was propagated.

• 한국운동역학회지
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• 제26권2호
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• pp.191-195
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• 2016

Purpose: The purpose of this study was to analyze the immediate effects of ankle restriction with an elastic band on ground reaction force during a golf swing. Method: There were five subjects who were teaching pros with an average golf score of 75. A force platform (9281B, Switzerland) was used. The independent variable was the presence of an elastic band. The dependent variables were three-dimensional ground reaction forces to analyze the transfer of momentum with the timing, control and coordination of the three forces. A paired t-test within subject repeated measure design was used via an SPSS 20.0. Results: Wearing an elastic band around one's ankles significantly makes shorter time differences between the moment of cross anterior / posterior forces and vertical force and median value of anterior / posterior forces during the backswing, between medial and lateral maximum and anterior / posterior force from the top of the back swing to the mid down swing, and creates an anterior / posterior maximum force. Conclusion: Wearing an elastic band around one's ankles affects control and coordination between three dimensional forces, and anterior force power according to each phase of the golf swing.

• 대한기계학회논문집B
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• 제37권7호
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• pp.675-682
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• 2013

전단 동축 분사기의 Inner-stage와 Outer-stage의 기체 분사 비율 변화에 따른 축방향 유동 분포 특성과 분무 분열 특성을 실험적으로 연구였다. 무차원 측정 거리를 Z/d=100까지 변화시킴에 따라 운동량 교환, 공기역학적 항력, 점성 혼합의 영향으로 완전 발달된 유동의 형태를 나타내었다. Inner-stage의 기체분사와 Outer-stage의 기체 분사의 영향은 Z/d=5 이내의 영역에서 간섭받지 않고 분무 초기에 Inner-stage에서 분사된 기체 전단력에 의해 분열됨을 파악할 수 있었으며, Z/d=10 이상의 영역에서 완전 발달된 유동으로 변화하며, 유동의 혼합이 진행됨을 관찰 할 수 있었다. Inner-stage의 운동량 플럭스 비 0.84 이내에서 Outer-stage의 운동량 플럭스 비가 증가함에 따라 SMD가 감소하는 경향을 나타내었으며, Inner-stage의 운동량 플럭스 비가 1.38 이상의 조건에서 SMD의 분포가 유사하게 나타나는 경향을 관찰할 수 있었다.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 1996년도 제7회 학술강연회논문집
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• pp.27-41
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• 1996

In this study the heat transfer and fluid flow of the molten pool in stationary gas tungsten arc welding using argon shielding gas were investigated. Transporting phenomena from the welding arc to the base material surface, such as current density, heat flux, arc pressure and shear stress acting on the weld pool surface, were taken from the simulation results of the corresponding welding arc. Various driving forces for the weld pool convection were considered, self-induced electromagnetic, surface tension, buoyancy, and impinging plasma arc forces. Furthermore, the effect of surface depression due to the arc pressure acting on the molten pool surface was considered. Because fusion boundary has a curved and unknown shape during welding, a boundary-fitted coordinate system was adopted to precisely describe the boundary for the momentum equation. The numerical model was applied to AISI 304 stainless steel and compared with the experimental results.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2001년도 춘계학술대회 논문집
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• pp.839-843
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• 2001

For robotic endoscope, some researchers suggest pneumatic actuators based on inchworm motion. But, the existing endoscopes are not seemed to be replaced completely because human intestine is very sensitive and susceptible to damage. We design and test a new locomotion of robotic endoscope able to maneuver safely in the human intestine. The actuating mechanism is composed of two solenoids at each side and a single permanent magnet. When the current direction is reversed, repulsive force and attractive at the opposition side propels permanent magnet. Impact force against robotic endoscope transfer momentum from moving magnet to endoscope capsule. The direction and moving speed of the actuator can be controlled by adjusting impact force. Modeling and simulation experiments are carried out to predict the performance of the actuator. Simulation experiments show that force profile of permanent magnet is the dominant factor for the characteristic of the actuator. The results of simulations are verified by comparing with the experimental results.

• 한국레이저가공학회지
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• 제6권3호
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• pp.11-17
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• 2003

Recoil force exerted on the substrate during a nanosecond laser ablation of silicon is measured. The ablation sample is placed at the end of a 400 $\mu\textrm{m}$ thick and 13 mm long silicon cantilever. The vibration amplitude of the cantilever induced by the recoil force is measured in real time with a probe beam. By comparing the deflection amplitude of the cantilever with a theoretical model, the recoil momentum is estimated. For laser irradiance in the order of 10$\^$11/ W/$\textrm{cm}^2$, the recoil pressure reached a value over 40${\times}$10$\^$9/ Pa.