• 한국전산유체공학회:학술대회논문집
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• 2005.10a
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• pp.293-298
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• 2005

We calculate the coordinates of an axisymmetric nozzle with a central body. This nozzle ensures a transonic flow with a plane sound surface, which is orthogonal to the symmetry axis and has a wall kink at the sonic point, The Chaplygin transformation in the subsonic part of the flow leads the Dirichlet problem for a system of nonlinear equations. The definition domain of the solution in the velocity-hodograph plane is taken as a rectangle. This enables one to obtain the nozzle with a monotonic distribution of velocity along its subsonic part. In the nonlinear differential equation, the linear Chaplygin operator for plane flows is separated, which allows the iterative calculation of the solution. The supersonic part of the nozzle is calculated under the assumption that the flow at the nozzle exit is uniform and parallel to the symmetry axis; i.e., the supersonic jet outflows to the submerged space with the same pressure. The calculation is performed by the characteristic method. The exact solution of Tricomi equation for near-sonic flows with the straight sonic line is used to 'move away' the sound plane. The velocity distribution alone the supersonic part of the nozzle is also monotonic, which ensures the absence of the boundary-layer separation and, therefore, the adequacy of the ideal-gas model. calculations show that the flow in the supersonic part of the nozzle is continuous (compression shocks are absent)

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.2
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• pp.31-37
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• 2008

In this paper, we analyzed the dynamic behavior of magnetic fluid in a circular pipe with multiple permanent magnets. Magnetic fluid react on magnetic field against the normal fluid. In other words, magnetic fluid flow has the electromagnetism and fluid mechanics. So magnetic fluids has studied about the fluids properties and experiment. In this paper we studied the magnetic fluids velocity and pressure distribution for the novel type actuator. Because the velocity and pressure distribution is the important element of the magnetic fluids flow. First, we analyzed the Maxwell equation for the multiple permanent magnet and then concluded the governing equations for the magnetic fluid flow using the equation of Navier-Stokes. And, we simulated the dynamic behavior of magnetic fluid flow using the FEM(Finite Element Method). And we illustrated the relation between magnetic field and dynamic behavior of magnetic fluid flow.

• Journal of Ocean Engineering and Technology
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• v.13 no.2 s.32
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• pp.138-146
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• 1999

The viscous flow around a ship hull is calculated by the use of RANS(Reynolds-averaged Navier-Stokes) solver. Reynolds stresses are midelled by using the k-${epsilon}$ turbulence model and the law is applied near the body. Body fitted corrdinates are introduced for the treatment of the complex boundary of the ship hull form and the governing equations in the physical domain transformed into ones in the computational domain. The transformed equations are numerically solved by an employment of FVM(Finite Volume Method). SIMPLE(Semi-Implicit Pressure Linked Equation) method is adopted in the calculation of pressure and the solution of the sidcretized equation is obtained by the line-by-line method with the use of TDMA(Tri-Diagonal Matrix Algorithme). To assure the proprietty of this computing method, HSVA tanker and Dyne hull are calculated ar both model and ship scale Reynolds number. Their reaults of pressure distributions on fore and aft body, axial velocity contours and transverse velocity velocity vectors and viscous resistance coefficients are compared with other's experiments and calculations.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1997.11a
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• pp.167-172
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• 1997

The electron swarm parameters and Energy distribution function have been calculated for electrons motion through CH$_4$ pure gas under the action of uniform electric field for 0.1$\leq$E/N(Td)$\leq$300, at the 300( $^{\circ}$K), using MCS method and Boltzmann transport equation. And then the resulting values of electron drift velocity were compared to experimental data and adjustment made in assumed cross sections until good agreement was obtained. The electron drift velocity is very useful in the fields of study relating to the conductive and dielectric phenomena of gas medium. The electron energy distribution in gas discharge are generally nonmaxwellian , and must be calculated by a numerical solution of the Boltzmann equation which takes in the elastic and inelastic collisions. To analyze the physical phenomena and properties (or electron swarm motion in a gas under the influence of an electric field, the energy distribution function of electrons and the theoretical deriveration of the electron drift velocity are calculated by the Backward Prolongation with respect to the Boltzmann transport equation as a parameter of E/N(Td).

• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.115-118
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• 1991

The temperature distribution on the superconducting thin-film is analyzed as moving constant field is applied above upper critical field. The distribution of magnetic field is derived in the normal spot. Governing equation is obtained with the help of the equation of conservation of energy. The temperature distribution and the heat dissipation are obtained through computer simulation by the method of numerical analysis. Maximum temperature is occured in the most right side inside normal spot. The temperature is increased abruptly inside the normal spot, and decreased more gradually outside normal spot in the direction of moving field as velocity is increased. Increasing the velocity rather than increasing magnitude of the normal spot and the applied field makes maximum temperature larger. Heat dissipation is affected by the velocity rather than the magnitude of normal spot and the applied field.

• Journal of the Korean Society for Railway
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• v.8 no.4
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• pp.337-341
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• 2005

Algorithm for passenger flow analysis based on DEM(Discrete Element Method) is newly developed. In the new algorithm, there are many similarity between multi phase flow and passenger flow. The velocity component of 1st phase corresponds to the direction vector of cell, each particle to each passenger, volume fraction to population density and the momentum equation of particle to the walking velocity equation of passenger, etc. And, the walking velocity of passenger is also represented by the function of population density. Key algorithms are developed to determine the position of passenger, population density and numbering to each passenger, To verify the effectiveness of new algorithm, passenger flow analysis for simple railway station model is conducted. The results for passenger flow in the model station are satisfying qualitatively and quantitatively.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.559-562
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• 1995

In the crane control system, it is reguired that the travelling time of the crane must be reduced as much as possible and the swing must be stoped at the end point. In paper, we present a hybrid control method which include the optimal regulator and velocity pattern controller in order to make high performance of the anti-sway. To implement the control algorithm, the dynamic equation is linearlized at an equilibrium point, so that the liner time invariant state equation can be obtained. In order to experiment the crane control, we consider 1 over 10 of the gantry crane which is used in a port. As a result, the hybrid control method improve efficient anti-sway control more than conventional velocity pattern control. It is expected that the proposed system will make an important contribution to the industrial fields.

• Journal of the Korea Institute of Military Science and Technology
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• v.20 no.2
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• pp.238-245
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• 2017

This paper deals with the scale effects of warhead on concrete penetration. We investigated the scale effects using finite element analysis and Young's penetration equation. As the scale of penetration test decreases, the strain rate effects of target increases, and then strength of concrete target increases. This means the residual velocity and penetration depth of warhead decreases as the test model size decreases. Young's penetration equations are transformed with various penetrator mass and scale cases as a function of scale ratio. Penetration distance and residual velocity are not simply changed by the geometric scaling law.

• Proceedings of the KSME Conference
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• 2003.11a
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• pp.1625-1630
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• 2003

An iterative modal analysis approach is developed to determine the effect of the transverse open cracks and the moving mass on the dynamic behavior of simply supported pipe conveying fluid. The equation of motion is derived by using Lagrange's equation. The influences of the velocity of moving mass, the velocity of fluid flow and a crack have been studied on the dynamic behavior of a simply supported pipe system by numerical method. The crack section is represented by a local flexibility matrix connecting two undamaged beam segments. that is, the crack is modelled as a rotational spring. Totally, as the velocity of fluid flow is increased, the mid-span deflection of simply supported pipe conveying fluid is increased. The position of the crack is middle point of the pipe, the mid-span deflection of simply supported pipe presents maximum deflection.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.307-307
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• 2000

The swing motion of the spreader during and after movement causes an efficiency problem of position control in unmaned gantry crane. The objective of this research is to design implementable stabilizing controllers that minimize the swing motion of spreader in precise position control. The dynamic equations related to trolley, rope, and spreader are derived. For constitute a similar actual system, we introduced a conception of spring and damper in the connector. It is located between the trolley and link that is used in stead of rope. We derived dynamic equation by appliance that friction and external disturbance are occurred to the connector. We constituted of position servo system and velocity servo system for the control of position and velocity of the trolley and constituted of lag compensator system for the control of sway of the spreader. And we will show an effect of the proposed system in this research finally.