• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.94-102
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• 2007

Applications of bonded dissimilar materials such as large scale integration (LSI) packages, ceramics/metal and resin/metal bonded joints, are very increasing in various industry fields. It is very important to analyze the thermal stress and stress singularity at interface edge in LSI. In order to investigate stress singularities on the bonded interface edges and delamination of die pad and resin in the IC package. In this paper, stress singularity factors(${\Gamma}_i$) and stress intensity factors($K_i$) considering thermal stress in the IC package were analyzed by using the 2-dimensional elastic boundary element method(BEM).

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.458-463
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• 2000

The mechanical structures generally have discontinuous parts such as the cracks, notches and holes owing to various reasons. In this paper, in order to analyze effectively these singularity problems using the finite element method, a mixed analysis method which an analytical solution and finite element solutions are simultaneously used is newly proposed. As the analytical solution is used in the singularity region and the finite element solutions are used in the remaining regions except this singular zone, this analysis method reasonably provides for the numerical solution of a singularity problem. Through various numerical examples, it is shown that the proposed analysis method is very convenient and gives comparatively accurate solution.

• Current Optics and Photonics
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• v.1 no.6
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• pp.631-636
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• 2017

We firstly develop a straightforward method to generate full $Poincar{\acute{e}}$ beams with any polarization geometry over an arbitrary order $Poincar{\acute{e}}$ sphere. We implement this by coaxial superposition of two orthogonal circular polarized beams with alternative topological charges with the help of a Mach-Zehnder interferometer. Secondly we find the existence of singularity points. And the inner relationship between their characteristics and the order of $Poincar{\acute{e}}$ spheres is also studied. In summary, this work provides a convenient and effective way to generate vector beams and to control their polarization states.

• Proceedings of the KIEE Conference
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• 1999.07a
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• pp.217-219
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• 1999

This paper presents a study of 2-dimensional(2-D) eddy current problem using boundary element method(BEM). When compared with finite element method(FEM), there are only a few unknown variables in BEM because it implements numerical analysis only for the surface or boundary of a model. As a result, a lot of computational memory and time can be saved. In order to analyze 2-D eddy current problem, potentials and its derivatives(flux) in a boundary are used as variables. The Mantel function of the second kind of the zero order is used here as a fundamental solution. In order to remove singularity and to solve the integral equations in a boundary, Subtracting Singularity Method and Gauss Quadrature Formula are adopted in this paper.

• Journal of the Korean Society for Precision Engineering
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• v.32 no.3
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• pp.253-261
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• 2015

A parallel mechanism with redundancy can be regarded as a means for not only maximizing the benefits of parallel mechanisms but also overcoming their drawbacks. We proposed a novel parallel mechanism by eliminating an unnecessary degree of freedom of the configuration space. Because of redundancy, however, the solution for the inverse kinematics of the developed parallel mechanism is infinite. Therefore, we defined a cost function that can minimize the movement time to the target orientation and found the solution for the inverse kinematics by using a numerical method. In addition, we proposed a method for determining the boundary of the geometric singularity in order to avoid singularities.

• Computational Structural Engineering
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• v.10 no.3
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• pp.185-193
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• 1997

The order of the stress singularity that occurs at the termination of an interface between materials exhibiting bilinear stress-strain response under plane strain conditions has been calculated, The governing equation of elasticity together with traction-free boundary condition and interface continuity condition defines a two-point boundary value problem. The stress components near the free edge are assumed to be proportional to r/sup s-1/, with solutions existing only for certain values of s. Finding these values entails the solution of an eigenvalue problem. Because it has been impossible to integrate the differential equations analytically, the integration has been performed numerically with a shooting method coupled with a Newton improvement scheme.

• Computational Structural Engineering
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• v.9 no.1
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• pp.93-99
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• 1996

In the particular situations where the crack is terminated at an interface of two materials, the order of stress singularity depends on the elastic constants which specify the properties of two materials. A multidomain boundary element technique is used to solve a crack normal to bimaterial interface. A correct order of shape function is used for displacement by using the isoparametric elements by shifting adequately the side nodes adjacent to this crack tip. A shape function containing the same order of singularity as that in the interface crack is also used for the interpolation of traction. Numerical testing of a binaterial with a crack normal to the interface is carried out with three-node elements. The results obtained are compared with the previous solutions.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.10
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• pp.7189-7195
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• 2015

The method of moments (MoM) is implemented to simulate scattering from a PEC (perfectly electric conductor) cylinder in the TE(transversw electric) EFIE (Electric Field Integral Equation) approach. The procedure expresses the singularity integral and the hypersingularity integral in terms of an analytic function and employs a singularity isolation process coupled with numerical technique along the discretized segment to evaluate the self terms. It is known that, in the MoM technique, the choice of base functions and test functions is very important for the accuracy and convergence of the numerical analysis. Thus, in this paper, three conditions, obtained from the combination of basis functions and test functions, are adopted to get the induced currents on the PEC surface. These currents are compared to the analytical one in the relative rms current error to get the condition that shows fast convergence rate. The fast order of convergence of the current error, 2.528, is obtained under the combination of pulse basis function/delta test function.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.1
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• pp.73-79
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• 2001

In this study, a submerged plate-type breakwater is considered, which is supported by elastic foundation. This breakwater makes use of wave phase interaction among the incident, diffracted and radiated waves. We apply a three-dimensional singularity distribution method within the linear potential theory in order to describe the wave field. The submerged plate is assumed to be rigid and the elastic support be a linear spring with constant stiffness. A typical rectangle plate is exemplified for numerical calculation. The thickness of the plate is carefully selected in order to guarantee the solution to be stable by checking the condition number of the system matrix. A parametric study is carried out for examining the effect of the stiffness of the elastic support on performance of the breakwater. We also examine the effect of the submerged depth.

• The Transactions of the Korean Institute of Electrical Engineers D
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• v.50 no.2
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• pp.59-64
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• 2001

In this paper, we propose an alternate method for determining the uniqueness of the reconstruction of a complex sequence from its phase. Uniqueness constraints could be derived in terms of the zeros of a complex polynomial defined by the DFT of the sequence. However, rooting of complex polynomials of high order is a very difficult problem. Instead of finding zeros of a complex polynomial, the proposed uniqueness criteria show that non-singularity of a matrix can guarantee the uniqueness of the reconstruction of a complex sequence from its phase-only data. It has clear advantage over the rooting method in numerical stability and computational time.