• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.405-408
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• 2005

This paper presents the characteristics of antenna factors for sleeve dipole antennas with a broad bandwidth. The coupled integral equations for the unknown current distributions on each elements are derived and solved by applying Galerkin's method of moments. The flatness of antenna factor is considered by variation of the length and number of sleeve elements.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 1999.11a
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• pp.116-119
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• 1999

This paper presents a feeder waveguide array of slot array antennas for Direct Broadcasting from Satellite(DBS). The feed structure consists of a single waveguide placed on the same layer as radiating waveguide and is characterized by the unit divider, called a $\pi$-Junction. This K-function with an inductive wall splits part of the power into two branch waveguide through one coupling window, and can excite densely arrayed waveguide at equal phase and amplitude. The power dividing characteristics of a cascade of $\pi$ -functions are analyzed by Galerkin's method of moments. From the optimum simulation results based on the feeder waveguide using $\pi$ -Junction at 3.95GHz, we obtained the scattering matrices of the feeder divided power at 11.85CHz.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05a
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• pp.68-73
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• 2000

An arc model based on the N-S equations modified by adding an energy source term to take account of the arc is developed and solved using Taylor-Galerkin FEM. The numerical method is applied to the simulation of the interruption process of a puffer type GCB. Moving boundary conditions of the arc chamber during operation is taken into account. The thermal interruption capability of an actual puffer type GCB will be predicted and compared with that of the measured result.

• Proceedings of the KIEE Conference
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• 2000.11b
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• pp.277-279
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• 2000

This paper proposes two kinds of the eddy current brake which uses permanent magnet. The one, like multipolar excitation consists of hexahedron shape of a segmented permanent magnetic and iron situated in the air-gap. The other, like multipolar excitation consists of only a segmented permanent magnetic. We use a finite element method to compute the flux distribution in the model. Also, we use the Galerkin-FEM with linear interpolation function may oscillate between the adjacent nodes to calculate the braking and attraction force. The advantages of the Halbach array are discussed.

• 연구논문집
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• s.24
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• pp.81-96
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• 1994

To investigate failure mechanisms observed in carbon-phenolic thermal insulators, differential equations which govern the decomposition process in a deformable anisotropic porous solid are derived for three-dimensional axisymmetric constructions. The governing equations not only couple the material deformation with pore pressure, but also couple pressure and temperature, which means that heat convected by the pyrolysis gases is properly accounted for. Then the Bubnov-Galerkin finite element method is applied to these equations to transform them into a semidescrete finite element system. A thermal insulation liner in the cowl region under typical operating conditions is analyzed to find a mechanism for plylift. The results from the structural analysis show across-ply failure in the cowl zone. The mechanism for plylift is hypothesized as a sequential procedure : 1) the across-ply failure which is the precursor to plylift and 2) the local fiber buckling caused by generation of excessive in-plane compressive stress. To prevent plylift, the across-ply stress can be reduced by using appropriate material ply angles in cowl zone design.

• Journal of the Korean Society for Precision Engineering
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• v.3 no.2
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• pp.28-38
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• 1986

An analytical and experimental investigation is made to the dynamic responese of a cantilever with a tip mass that models some of the basic phenomena involved in the response of a flexible manipulator with a tip mass on its free end under the given rotating motion. The system equation is derived from the Hamilton's principle on the basis of the Euler-Bernoulli hypothesis and an approximate solution is obtained from model analysis using Galerkin's method for the vibation response of the system subjected to a sudden stop after an impulsive rotation. Experiment was performed to verify the validity of the theoretical analysis. Results are given for the vibration amplitude of the free end with respect to tip mass ratio, non-dimensionalized rotating velocity, rotating angle and non- dimensionalized hub length. The rotating condition to minimize the vibration amplitude of the free end can be determined for the given basic paramenters.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.6
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• pp.208-215
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• 2001

The paper presents both theoretical and experimental study fur dynamic instabilities of a vortical cantilevered pipe with two attached lumped masses conveying fluid. The two attached lumped masses can be considered as valves or some mechanical paras in real pipe systems. Eigenvalue behaviors depending on the flow velocity are investigated for the change of Positions and magnitudes of an attached lumped mass and a tip mass. In order to verify appropriate of numerical solutions, experiments were accomplished. Theoretical predictions have a good agreement with experimental ones.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.12
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• pp.979-985
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• 2002

The paper presents the dynamic stability of a vertical cantilevered pipe conveying fluid and haying translational linear spring supports. Real pipe systems may have some elastic hanger supports or other mechanical attached parts. which can be regarded as attached spring supports. Governing equations are derived by energy expressions, and numerical technique using Galerkin's method is applied to the equations of small motion of the pipe. Effects of spring supports on the dynamic stability of a vortical cantilevered pipe conveying fluid are fully investigated for various locations and spring constants of elastic supports.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.792-795
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• 2005

The vibration of a curved pipe conveying fluid is studied when the pipe is clamped at both ends. To consider the nonlinearity, this study adopts the Lagrange strain theory for large deformation and the extensible dynamics based on the Euler-Bemoulli beam theory for slenderness assumption. By using the Hamilton principle, the non-linear partial differential equations are derived. To investigate the dynamic characteristics of the system the discretized equations of motion are derived from the Galerkin method. The natural frequencies varying with the flow velocity are computed. From these results, we should consider the nonlinearity to analyze dynamics of a curved pipe conveying fluid more precisely.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11a
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• pp.337-340
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• 2005

Rotating annular disks are widely used in data storage devices such as CDs, DVDs(digital versatile disks), and HDs(hard disks). Higher data transfer rate in data storage disks could not be achieved by polycarbonate disks in the present market. The problem can be solved by applying the fiber-reinforce composite materials to the disks. In this paper, an application of composite materials to rotating disks is proposed to increase the critical speed. Dynamic equation is formulated in order to calculate the natural frequency and critical speed for rotating composite by the Galerkin method. The results show that the radially reinforced disk is more effective in increasing critical speed than the circumferentially reinforced disk.