• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.12
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• pp.2040-2047
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• 2001

In this paper, a singularity problem of the state transition matrix is investigated in the spatial propagation when the spatial matrix differential equation is constructed via time finite element analysis. A parametric study shows that the degree of singularity of the state transition matrix depends on the degree of flexibility of the structures. As an alternative to avoid the numerical problems due to the singularity, an analytic solution fur spatial propagation of the flexible structures is proposed. In the proposed method, the spatial properties of the structure are analytically expressed by a combination of transcendental functions. The analytic solution serves fast and accurate results by eliminating the possibility of the error accumulation caused by the boundary condition. Several numerical examples are shown to validate the effectiveness of the proposed methods.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1993.10a
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• pp.593-597
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• 1993

This paper introduces robust trajectory planner for obstacle and singularity avoidance in a nonresonant robot manipulator. In this work, we propose new trajectory generator in cartesian space by use of Bezier function. Also, SR-inverse is used for obstacle and singularity avoidance of nonredundant robot. This result is verified with 3-D simulator which has been developed to examine the effectiveness of the suggested method.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.8 no.1
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• pp.35-44
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• 1999

In a view point of earth environmental protection and social requirement, adhesively bonded structures of aluminum alloys have become to be employed for the purpose of decreasing fuel ratio by weight reduction and to improve performance in various engineering fields such as aircrafts, automobiles, rolling stocks and so on. In spite of such wide applications in adhesively bonded structures of aluminum alloys, the quantitative fracture criterion and evolution method of its bonded strength have not been established yet. The objective of this paper is to establish fracture criterion considering stress singularity at interface edges in adhesively bonded structures of aluminum alloys. Through the analyses of boundary element method and static fracture experiments with three different types of specimens in the adhesively bonded joints of aluminum alloys, its fracture criterion was proposed and discussed about strength evolution of adhesively bonded structures.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.1
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• pp.100-108
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• 2004

In this paper, the new casing oscillator, which is a construction machine and which structure is similar to that of a parallel manipulator with redundancy, is proposed. The singularity analysis of this machine is performed by two different methods. First, the singularities are found by the numerical method at configurations where the rank of the Jacobian matrix becomes deficient. The singularities are outside the workspace. To investigate the physical information on these configurations, the singularities are examined by the geometric method at configurations where the casing oscillator cannot resist the external forces and moments applied to the upper platform due to losing static equilibrium. The results of the geometric method are the same as those of the numerical method. It proves that the new casing oscillator is free from the singularity, which causes serious problems to a parallel manipulator.

• Selected Papers of The Society of Naval Architects of Korea
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• v.2 no.1
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• pp.1-17
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• 1994

For a planar curve-sided panel with constant or linear density distributions of source or doublet in the singularity methods, Cantaloube and Rehbach show that the surface integral can be transformed into contour integral by using Stokes'formulas. As an extension of their formulations, this paper deals with a planar polygonal panel for which we derive the closed-forms of the potentials and the velocities induced by the singularity distributions. Test calculations show that the analytical evaluation of the closed-forms is superior to numerical integration (suggested by Cantaloube and Rehbach) of the contour integral. The compact and explicit expressions may produce accurate values of matrix elements of simultaneous linear equations in the singularity methods with much reduced computer time.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.3
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• pp.243-248
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• 2010

This study addresses spacecraft moment of inertial estimation approach using Modified Rodrigues Parameters(MRP). The MRP offer advantage by avoiding singularity in Kalman Filter design for attitude determination caused by the norm constraint of quaternion parameters. Meanwhile, MRP may suffer singularity for large angular displacement, so that we designed appropriate reference attitude motion for accurate estimation. The proposed approach is expected to provide stable error covariance update with accurate spacecraft mass property estimation results.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.9
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• pp.159-165
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• 2003

Most engineers interested in stress singularities have focused mainly on the research of power stress singularities for v-notched cracks in dissimilar materials. The logarithmic stress singularity was discussed a little in Bogy's paper. The power-logarithmic stress singularity was reported by Dempsey and Sinclair. It was indicated that the logarithmic singularity is only a special case of power-logarithmic stress singularities. Then, Dempsey reported specific cases which have power-logarithmic singularities even fur homogeneous boundary conditions. It was known that logarithmic stress singularities for v-notched cracks in dissimilar materials occurs when the surfaces of a v-notched crack have constant tractions. In this paper, using the complex potential method, the stresses and displacements having logarithmic stress singularities were obtained and the coefficients vectors were calculated by a numerical program code: Mathematica. It was shown that our analysis models don't have logarithmic stress singularities under the constant tractions, although the coefficient vectors are existing.

• Proceedings of the KSME Conference
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• 2000.04a
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• pp.170-175
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• 2000

Bimaterial containing an in-plane or an out-of-plane singularity embedded in the inclusion or in the unbounded matrix is first analyzed by using analytic continuation. Next, the series forms of solutions for the trimaterial with two concentric circular inclusions having an identical singularity are found based on an alternating technique using the solution for the bimaterial case. The sum of the first three or four terms of solutions derived provides an excellent approximation for most of material combinations. By applying continuous distributions of dislocations, the trimaterial solution obtained in this study may be used to solve crack problems in the same material.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.12
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• pp.1020-1027
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• 2014

Singularity indices for steering law design of CMGs have been analyzed. Several qualitative criteria to evaluate the suitability of indices have been suggested. Fast calculation and consistency with the condition number of the input matrix are the most important ones. Based on these criteria, modified indices have been proposed. Properties of infinite value and finite value indices have been compared and an ad hoc method to combine those properties has been presented. Computer simulation results are given to verify the proposed method.

• Current Optics and Photonics
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• v.1 no.4
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• pp.396-401
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• 2017

In this article, we proposed hybrid polarization singularity configurations, based on the superposition of two orthogonal circularly polarized components, one of which is a light beam with two optical vortices. The topological configurations are the hybridization of lowest-order polarization singularities, but are different from high-order polarization singularities. Our numerical simulation may provide a theoretical basis for expanding the variety of polarization singularity configuration.