• Proceedings of the Korean Society For Composite Materials Conference
• /
• 2005.04a
• /
• pp.184-186
• /
• 2005

모든 건설재료에서 치수의 한계가 있다. 현수선교나 사장교인 경우 강재를 사용하면 최대지간 거리 $5000m{\sim}7000m$ 가 가능하나, 유리섬유 복합재료를 시용하면 이의 2 배, 탄소섬유 복합재료를 사용하면 이의 3 배가 가능하다. 지간 거리가 20,000m 가 되면 가장 중요한 하중은 바람하중이다. 복합재료의 여러 장점 때문에 거대한 규모의 건물, 교량등 구조물이 건설될 때 구조 기술자는 풍(바람)하중을 구하고 다룰 수 있어야 한다. 이 논문에서는 구조 기술자가 풍 하중을 구할 수 있게 기초 이론과 기본기술을 제공하고 있다.

• Proceedings of the KIEE Conference
• /
• 2001.04a
• /
• pp.90-92
• /
• 2001

The lift and drag forces on various magnet moving with a velocity is developed above a closed loop coil. These forces are affect by resistance and inductance of circuit, velocity of magnet. To obtain strong magnetic flux density, the magnet is replaced by Halbach array. This paper presents analysis of force between linear motion Halbach array and a closed loop having the constant resistance and inductance as a various speed.

• Journal of Biomedical Engineering Research
• /
• v.13 no.3
• /
• pp.235-244
• /
• 1992

In this paper, fluttering behavior of mechanical monoleaflet tilting disc heart valve prostheses during the opening phase was analyzed taking into consideration the impact between the occluder and the guiding strut at the fully open position. The motion of the valve occluder was modeled as a rotating system, and equations were derived by employing the moment equilibrium principle. Forces due to lift, drag, gravity and buoyancy were considered as external forces acting on the occluder. The 4th order Runge-Kutta method was used to solve the governing equations. The results iimonstrated that the occludes reaches steady equilibrium position only after damped vibration. Fluttering frequency varies as a function of time after opening and is in the range of 8-84 Hz. Valve opening appears to be affected by the orientation of the valve relative to gravitational force. The opening velocities are in the range of 0.65-1.42m/sec and the dynamic loads by impact of the occludes and the strut are in the range of 90-190 N.

• Journal of Biomedical Engineering Research
• /
• v.12 no.3
• /
• pp.149-156
• /
• 1991

In this paper, fluttering behavior of mechanical bileaflet heart valve prosthesis was analyzed taking into consideration of the impact between valve plate and stopper Vibration system of the valve was modeled as a rotating system, and equations are induced by moment equilibrium equations. Lift force, drag force, gravity and buoyancy were considered as external forces acting on the valve plate/ The 4th order Runge-Kutta method was used to solve the equations. Valve plate does not come to the static equilibrium position at a stretch, but come to that position after under damping vibration. Damping ratio increases as the cardiac optput increases, and the mean damping ratio is in the range of 0.16~40.25. Fluttering frequency does not have any specific value, but varies as a function of time. It is in the range of 10~40Hz. Valve opening appears to be affected by the orientation of the of the valve relative to gravitational forces.

• Journal of Advanced Marine Engineering and Technology
• /
• v.25 no.4
• /
• pp.857-868
• /
• 2001

The aerodynamic forces and wake structures of the non-rotating downstream cylinder which is located behind the spinning upstream cylinder in tandem and staggered arrangement have been investigated by experimental method at Re= $1.32{\times}10^4$. The measurements of wake flow and pressure distributions of downstream cylinder are carried out in various spin parameters by combination of both longitudinal spacing rations L/d=1.5, 3.0, 4.5 and transverse spacing ratios T/d =0.0, -0.5, 0.5. For the present experiment, it has been found that the spin parameter of spinning upstream cylinder affect more easily the downstream cylinder in tandem arrangement than that in staggered arrangement.

• Journal of Ocean Engineering and Technology
• /
• v.10 no.3
• /
• pp.125-137
• /
• 1996

Experimental wind tunnel tests have been attempted to investigate the aerodynamic characteristics of floating offshore structure using some types of scaled mldels. The static behaviors of lift, drag forces and pitching moment of its models are measured to exammine the relationship between wind loads and incidence angle, wind velocity, shape of models. The effect of solid ground has been obtained also.

• Journal of the Korean Society for Aviation and Aeronautics
• /
• v.21 no.2
• /
• pp.26-32
• /
• 2013

The rotorcraft makes lift and control forces by the rotor thrust. At the development phase of the rotorcraft, the operational limitations have to be established. And it shall be demonstrated to operate the rotorcraft safely within the limitations. This paper introduces establishment and evaluation results of operational rotor speed limitations for the medium class utility rotorcraft. And it shows the follow-up activities after design changes of rotor speed indicators and aural warning systems for implementing the rotor speed limitations.

• Proceedings of the KSME Conference
• /
• 2008.11b
• /
• pp.2754-2758
• /
• 2008

Numerical investigation has been carried out for laminar flow ($Re{\leq}150$) past a square cylinder in cross freestream with an angle of attack. This study would be the first step towards understanding flow-induced forces on cylindrical structures under a strong gust of wind from the viewpoint of wind hazards. Collecting all the numerical results obtained, we propose contour diagrams of drag/lift coefficients and Strouhal number (St) on an Re-Angle plane.

• Structural Engineering and Mechanics
• /
• v.5 no.2
• /
• pp.149-165
• /
• 1997

A dynamic time-history analysis of the coupled internals and core in the vertical direction is performed as a part of the fuel assembly qualification program. To reflect the interaction between the fuel rods and grid cage, friction element is developed and is implemented. Also derived here is a method to calculate a hydraulic force on the reactor internals due to pipe break. Peak responses are obtained for the excitations induced from earthquake and pipe break. The dynamic responses such as fuel assembly axial forces and lift-off characteristics are investigated.

• Wind and Structures
• /
• v.23 no.2
• /
• pp.143-155
• /
• 2016

The interaction between two different shaped structures is very important to be understood. Fluid-structure interactions and aerodynamics of a circular cylinder in the wake of a V-shaped cylinder are examined experimentally, including forces, shedding frequencies, lock-in process, etc., with the V-shaped cylinder width d varying from d/D = 0.6 to 2, where D is the circular cylinder diameter. While the streamwise separation between the circular cylinder and V-shaped cylinder was 10D fixed, the transverse distance T between them was varied from T/D = 0 to 1.5. While fluid force and shedding frequency of the circular cylinder were measured using a load cell installed in the circular cylinder, measurement of shedding frequency of the V-shaped cylinder was done by a hotwire. The major findings are: (i) a larger d begets a larger velocity deficit in the wake; (ii) with increase in d/D, the lock-in between the shedding from the two cylinders is centered at d/D = 1.1, occurring at $d/D{\approx}0.95-1.35$ depending on T/D; (iii) at a given T/D, when d/D is increased, the fluctuating lift grows and reaches a maximum before decaying; the d/D corresponding to the maximum fluctuating lift is dependent on T/D, and the relationship between them is linear, expressed as $d/D=1.2+{\frac{1}{e}}T/D$; that is, a larger d/D corresponds to a greater T/D for the maximum fluctuating lift.