• Journal of Ocean Engineering and Technology
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• v.11 no.4
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• pp.7-22
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• 1997

A finite element analysis is performed for lateral buckling problems on the basis of a geometrically nonlinear formulation for a beam with small elastic strain but with possibly large rotations. The total Lagrangian formulation for a general large deformation, which involves finite rotations, is chosen and the exponential map is used to treat finite rotations from the Eulerian point of view. For lateral buckling, the point of vanishing determinant of the resulting unsymmetric tangent stiffness is traced to examine its relationship to bifurcation points. It is found that the points of vanishing determinant is not corresponding to bifurcation points for large deformations in general, which suggests that the present unsymmetric tangent stiffness is not an exact first derivative of internal forces with respect to displacement. This is illustrated through several numerical examples and followed by appropriate discussion.

• Proceedings of the KIEE Conference
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• 2008.10c
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• pp.38-40
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• 2008

Distribution of Permanent magnet used in the spindle motor on the ODD is arranged by magnetizer. In general, permanent magnet is putted between yoke and back yoke of magnetizer so that symmetric magnetization distribution. But the magnet has unsymmetric magnetization distribution because of eccentricity of the yoke in mass production. So, in this paper we discuss the effect of asymmetric magnetization distribution on back EMF and cogging torque of the spindle motor.

• Magazine of the Korean Society of Agricultural Engineers
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• v.28 no.1
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• pp.68-74
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• 1986

The governing differential equations and the boundary conditions for the free vibra- tion of the unsymmetric parabolic arch with fixed ends are derived on the basis of the equilibrium equations and the D'Alembert principle. The effect of the rotary inertia as well as the extensional and the flexural deformations is considered in the governing differential equations. A trial eigenvalue method is used for determining the natural frequencies. The Ru- uge-Kutta method is used in this method to perform the integration of the differential equations. The detailed studies are made of the lowest three vibration frequencies for the par- abolic chord length equal to 10m. The effect of the rotary inertia is analyzed and it's numerical data are presented in table. And as the numerical results the frequency versus the rise of arch and the radius of gyration are presented in figures.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.11-16
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• 2002

The differential equations governing free vibrations of the elastic, horizontally curved beams with unsymmetric axis are derived in Cartesian coordinates rather than in polar coordinates, in which the effect of torsional inertia is included. Frequencies are computed numerically for the sinusoidal curved beams with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Cartesian coordinates. The lowest four natural frequency parameters are reported, with and without torsional inertia, as functions of three non-dimensional system parameters: the horizontal rise to chord length ratio, the span length to chord length ratio, and the slenderness ratio.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1997.10a
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• pp.239-246
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• 1997

The general formulation of free vibration and stability analysis of unsymmetric thin-walled space frames and beam-columns is presented. The kinetic and total potential energy is derived by applying the extended virtual work principle, introducing displacement parameters defined at the arbitrarily chosen axis and including second order terms of finite semitangential rotations. In formulating the finite element procedure, cubic Hermitian polynomials are utilized as shape functions of the two node space frame element. Mass, elastic stiffness, and geometric stiffness matrices for the unsymmetric thin-walled section are evaluated. In order to illustrate the accuracy and practical usefulness of this formulation, finite element solutions for the free vibration and stability problems of thin-walled beam-columns and space frames are presented and compared with available solutions.

• Computational Structural Engineering
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• v.11 no.4
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• pp.197-207
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• 1998

전단변형 효과를 무시하는 경우에 비대칭 선형 변단면을 갖는 박벽 공간 보의 안정성 해석을 위한 일반이론을 유도한다. 비대칭 선형 변단면의 임의점을 통과하는 부재축과 단면의 주축의 방향과 무관하고 부재축과 직각을 이루는 두 개의 좌표축을 도입하여 직각좌표계를 정의한다. 정의된 좌표축을 기준으로 유한한 회전각의 2차항을 고려하는 변위장을 도입하여 연속체에 대한 가상일의 원리로부터 탄성변형에너지, 그리고 초기응력에 의한 포텐셜에너지를 유도한다. 이를 이용하여 비대칭 선형 변단면을 갖는 박벽 공간 보의 안정성해석을 위한 평형방정식을 제시한다. 3차 Hermitian 다항식을 변위파라미터의 형상함수로 사용하여 박벽 공간 보의 탄성강도 및 기하강도행렬을 상정할 뿐만 아니라, 단면의 좌표축에 상관없이 임의의 위치에 작용하는 하중에 대한 하중보정강도행렬(load-correction stiffness matrix)을 제시한다. 본 이론 및 방법의 타당성을 검증하기 위하여 수치해석을 수행하고 문헌의 결과 및 쉘요소를 사용한 해석결과와 비교하여 본 이론의 정당성을 입증한다.

• Bulletin of the Korean Chemical Society
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• v.10 no.1
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• pp.113-114
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• 1989

• Bulletin of the Korean Chemical Society
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• v.15 no.7
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• pp.602-604
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• 1994

• Bulletin of the Korean Chemical Society
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• v.15 no.3
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• pp.179-181
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• 1994

• Applied Chemistry for Engineering
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• v.26 no.3
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• pp.280-286
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• 2015

Two series of unsymmetric dimesogenic compounds containing a butylene or pentamethylene group as the flexible spacer were synthesized and their thermal and mesomorphic properties were studied. Mesogenic groups of the synthesized compounds consisted of a cholesteryl and an azobenzene group with lateral substituent. Chemical structures and mesomorphic properties of the synthesized compounds were investigated by FT-IR, $^1H$-NMR, differential scanning calorimeter (DSC), and polarizing optical microscope (POM). All synthesized compounds, apart from $D5-OCH_3$, showed enantiotropic liquid crystal phases. Compounds having an even number of carbon atoms in the flexible spacer exhibited wide mesophase temperature ranges and high isotropic transition temperatures. Regarding the effect of lateral substituents, compounds with bulky substituents exhibited decreased mesophase temperature ranges and isotropic transition temperatures, while those with polar substituents showed the increased thermal stability of the smectic phase.