• 한국운동역학회지
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• 제20권4호
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• pp.429-436
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• 2010

The purpose of this study was to analyze the kinematic factors and throwing variables for the 3-turn and 4-turn techniques and for release as well as to provide technical advice for improving athletic performance in hammer throwing. Data analysis led to the following conclusions: To increase the rotation speed for the 3-turn and 4-turn techniques, the time elapsed during the 1-foot support period should be decreased the distance between the rotating foot and the rotation axis should be small and the height of the hip joint should be increased at the times of release The throwing angle at the moment of release should be more than 40 degrees, and the throwing position should be taken vertically high at the shoulder joints. To accelerate the motion of the hammer, the speed should not be reduced during the 1-foot support period but should be increased during the 2-foot support period for much greater acceleration. In the 3-turn technique, the angles of the shoulder axis and hummer string should be dragged angle at the maximum point and lead angle at the minimum point, and dragged angle at the maximum and minimum points in the 4-turn at the time of relase The upper body should be quickly bent backward, the knee angle should be extended, and the angles of the shoulder axis and hammer string should be dragged angle close to 90 degrees.

• 한국항해항만학회지
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• 제33권8호
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• pp.505-511
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• 2009

선박의 대형화에 따른 풍압면적의 증가 및 갑작스런 돌풍 등 자연환경의 급격한 변화 등으로 묘박 중인 선박이 주묘 되는 현상이 자주 발생되고 있다. 특히, 선박운항자의 관점에서는 풍속 및 파랑 등의 외력 변화에 따른 주묘 발생 시점 및 주묘 형태, 주묘시의 속력과 주변 선박 또는 장애물과의 충돌 가능성 등을 고려한 적절한 대응 방안이 모색되어야 한다. 본 논문은 실습선 한바다호가 단묘박으로 묘박 중 기상이 점점 악화되면서 실제로 주묘가 발생한 현상을 검토한 것으로, 묘박 당시의 풍압력, 유압력, 표류력, 선체운동 그리고 파주력 등을 분석하여 주묘의 발생 가능성 및 한계 외력을 고찰하였다. 또한, 당시의 외력 조건하에서 발생한 주묘패턴을 분석하여 선수방위 변화량, 스윙폭, 주묘 속도 등을 확인하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2967-2970
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• 2007

In a usual painting process, a liquid drop spreads on canvas by being dragged along a paintbrush. To obtain the fundamental understanding of the painting process from the mechanical point of view, we experimentally investigate various dynamic behavior of a liquid drop that spreads between moving solid plates. It is shown that three distinct types of drop spreading take place, i.e. shearing, spreading, and intact dragging, depending on the liquid viscosity and surface tension, the plate speed, and the wettability. We suggest a regime map based on the capillary number and the receding contact angle, which indicates the boundaries between different types of spreading behavior in a dimensionless space.

• 한국분무공학회지
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• 제11권3호
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• pp.168-175
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• 2006

The static pressure distribution and flow characteristics inside the high-pressure swirl spray were investigated by measuring the static pressure inside the spray and applying the computational fluid dynamics (CFD). The static pressure difference between inner and outer part of spray was measured at different axial locations and operating conditions using a piezo-resislive pressure transducer. To obtain the qualitative value of swirl motion at different operating conditions, the spray impact-pressure at the nozzle exit was measured using a piezo-electric pressure transducer, and the flow angle was measured using a microscopic imaging system. The flow characteristics inside the high pressure swirl spray was simulated by the 1-phase 3-dimensional CFD model. The effect of pressure alternations on spray development was discussed with macroscopic spray images and a mathematical liquid film model. The results showed that the static pressure drop is observed inside the swirl spray as a result of the dragged air motion and the centrifugal force of the air. The recirculation vortex inside the spray was also observed inside the swirl spray as a result of the adverse pressure gradient along the axial locations. The results of analytical liquid film model and macroscopic spray images showed that the static pressure structure is one of the main parameters affecting the swirl spray development.