• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1119-1124
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• 2001

Nonlinear Vibration of a flexible circular ring is studied in this paper. Based upon the von Karman strain theory, the nonlinear governing equations are derived, in which the in-plane bending and extension displacements as well as the out-of-plane bending displacement are fully coupled. After discretizing the governing equations by the Galerkin approximation method, we obtain the linearlized equation by using the pertubation method. The results from the linearlized equations show that the in-plane displacement has effects on the natural frequencies of the out-of-plane displacement.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.5
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• pp.119-124
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• 2000

A finite element method is applied to investigate the characteristics of the fluid flow and heat transfer performance in a channel in terms of the various effects of baffle cuts, baffle angles, and leakages. The results show that the decrease of a baffle cut gives a good heat transfer enhancement. However, it also increases pressure drop. In the case of an inclined baffle, the result shows that the pressure drop decreases with a reasonable heat transfer performance. But a steeply inclined baffle gives adverse effects on the performance of the channel. The clearances between baffle-to-shell and tube-to-baffle affect the overall performance. The effects of these parameters are discussed in details.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.36 no.4
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• pp.252-258
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• 1987

Time periodic finite element solutions for sinusoidally excited electromagnetic field problems in moving media are presented. Solutions by the Galerkin method contain spurious oscillations when grid Peclet number is more than one. To suppress these oscillations an upwind finite element method using two different time periodic test functions is introduced. One is multiplied to second and first-order space derivative terma and the other to the time derivative term. Test functions are obtained from trial functions by adding or subtracting quadratic bias functions with appropriate scaling factors. Phase differences are considered between trial functions and bias functions. For simple interpretations of the phase differences, complex scaling factors are used. The proposed method is developed to give nodally exact solutions for uniform grid spacing in one dimensional problems. Based on the one dimensional results, a two dimensional upwinding scheme is also derived.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.198-206
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• 2006

The dynamic responses of both the in-plane and out-of-plane vibrations are investigated for an axially moving membrane. The equations of motion are derived for the moving membrane with no-slip boundary conditions by using the extended Hamilton principle. Based on the Galerkin method, the discretized equations of motion are derived. The generalized-time integration method is applied to compute the dynamic responses for the in-plane and out-of-plane motions. From the computed results, the responses are compared between the in-plane and out-of-plane vibrations. Furthermore. the effects of velocity and acceleration on the dynamic behaviours for displacements and stresses are presented.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.16 no.2 s.107
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• pp.169-175
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• 2006

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 disks by the Galerkin method. The orthogonal functions are used in series solution. A companion paper(Part II) presents and discusses the numerical results of vibration analysis and critical speed for rotating polar orthotropic disk using the formulation and solution method given in this paper (Part I).

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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• 2001.11a
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• pp.204-211
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• 2001

For the treatment of high compressibility number in the Reynolds equation, a new class of exponential high-order shape functions has been recently introduced in the literatures. In this paper a FE lubrication analysis method of high speed gas mechanical face seals is developed, implementing these shape functions. Their validity and usefulness are presented using 1-D gas bearing models. And a validation of developed 2-D analysis code is shown with a gas flat and spiral groove face seal models.

• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.335-338
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• 1988

A numerical method is presented for the scattering by the perfectly conducting cylinder with arbitrary cross sections. The relevant integral equation considered by the E-field formulation is solved by method of moments, and thereby the surface current induced as well as the radar cross section of the scatterer are numerically computed to specify the scattering nature of the scatterer. Two separate methods, one with point matching and the other Galerkin's method, are considered to make cross checks to the results obtained. Taking two half pulses suggested to expand the surface current shows savings in computation time and accurate solutions for the corners on the scatterer.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.9
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• pp.1579-1588
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• 2003

In this paper, the finite element equations for the transient linear viscoelastic stress analysis are presented in time domain, whose variational formulation is derived by using the Galerkin's method based on the equations of motion in time integral. Since the inertia terms are not included in the variational formulation, the time integration schemes such as the Newmark's method widely used in the classical dynamic analysis based on the equations of motion in time differential are not required in the development of that formulation, resulting in a computationally simple and stable numerical algorithm. The viscoelastic material is assumed to behave as a standard linear solid in shear and an elastic solid in dilatation. To show the validity of the presented method, two numerical examples are solved nuder plane strain and plane stress conditions and good results are obtained.

• Structural Engineering and Mechanics
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• v.14 no.1
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• pp.71-84
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• 2002

A finite element formulation for the time-domain analysis of linear transient elastodynamic problems is presented based on the weak form obtained by applying the Galerkin's method to the integro-differential equations which contain the initial conditions implicitly and does not include the inertia terms. The weak form is extended temporally under the assumptions of the constant and linear time variations of field variables, since the time-stepping algorithms such as the Newmark method and the Wilson ${\theta}$-method are not necessary, obtaining two kinds of implicit finite element equations which are tested for numerical accuracy and convergency. Three classical examples having finite and infinite domains are solved and numerical results are compared with the other analytical and numerical solutions to show the versatility and accuracy of the presented formulation.

• Structural Engineering and Mechanics
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• v.41 no.5
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• pp.617-632
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• 2012

An isogeometric approach is presented for static analysis of thin plate problems of various geometries. Non-Uniform Rational B-Splines (NURBS) basis function is applied for approximation of the thin plate deflection, as for description of the geometry. The governing equation based on Kirchhoff plate theory, is discretized using the standard Galerkin method. The essential boundary conditions are enforced by the Lagrange multiplier method. Several typical examples of thin plate and thin plate on elastic foundation are solved and compared with the theoretical solutions and other numerical methods. The numerical results show the robustness and efficiency of the proposed approach.