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윤성호,엄기상,Yun Seong-Ho,Eom Ki-Sang 한국전산구조공학회 2005 한국전산구조공학회논문집 Vol.18 No.4
본 논문에서는 기하학적으로 비선형인 유연한 Timoshenko 보의 대변위 운동방정식에 유한요소를 사용하여 정식화하였다. 비선형 구속방정식은 라그랑지 상수를 이용하여 운동방정식에 통합되었다. 정식화하는 과정과 수치해석에서 선형과 비선형 영향을 파악하였고, 코리올리스(Coriolis)힘과 회전자(Gyroscopic)힘의 효과는 관성력과 감쇠력과는 달리 일반적인 외력으로 간주하여 해석할 수 있었다. Newmark의 시간적분과 Newton-Raphson 반복법을 사용한 수치예제를 통해 정식화의 효용성을 보여주었다. This paper established the dynamic model of a flexible Timoshenko beam capable of geometrical nonlinearities subject to large overall motions by using the finite element method. Equations of motion are derived by using Hamilton principle and are formulated in terms of finite elements in which the nonlinear constraint equations are adjoined to the system using Lagrange multipliers. The Newmark direct integration method and the Newton-Raphson iteration are employed here for the numerical study which is to demonstrate the efficiency of the proposed formulation.
김혜현,이석호,호원경,엄기상 한국뇌신경과학회 2022 Experimental Neurobiology Vol.31 No.6
Dopaminergic projection to the hippocampus from the ventral tegmental area or locus ceruleus has been considered to play an essential role in the acquisition of novel information. Hence, the dopaminergic modulation of synaptic plasticity in the hippocampus has been widely studied. We examined how the D1 and D2 receptors influenced the mGluR5-mediated synaptic plasticity of the temporoammonic-CA1 synapses and showed that the dopaminergic modulation of the temporoammonic-CA1 synapses was expressed in various ways. Our findings suggest that the dopaminergic system in the hippocampal CA1 region regulates the long-term synaptic plasticity and processing of the novel information.
윤성호(Seungho Yun),엄기상(Kisang Eom) 한국자동차공학회 2004 한국자동차공학회 지부 학술대회 논문집 Vol.- No.-
for the linearlized differential algebraic equation of the nonlinear constrained system, exact initial values of the accelerations are needed to solve itself. It may be very troublesome to perform the inverse operation for obtaining the incremental quantities since the mass matrix contains zero element in the diagonal. This fact makes the mass matrix impossible to be positive definite. To overcome this singularity phenomenon the mass matrix needs to be modified to allow the feasible application of predictor and corrector in the iterative computation. In this paper the proposed numerical algorithm based on the modified mass matrix combines the conventional implicit algorithm, Newton-Raphson method and Newmark method. The numerical example presents reliabilities for the proposed algorithm via comparisions of the 4th order Runge-Kutta method. The proposed algorithm seems to be satisfactory even though the acceleration, Lagrange multiplier, and energy show unstable behavior. Correpondingly, it provides one important clue to another algorithm for the enhancement of the numerical results.