• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.441-448
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• 2000

An investigation into the nonlinear free vibrations of a cantilever beam which can have not only planar motion but also nonplanar motion is made. Using Galerkin's method based on the first mode in each motion, we transform the boundary and initial value problem into an initial value problem of two-degree-of-freedom system. The system turns out to have two normal modes. By Synge's stability concept we examine the stability of each mode. In order to check validity of the stability we obtain the numerical Poincare map of the motions neighboring on each mode.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.7
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• pp.1589-1596
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• 2010

In this paper, we propose the method that reduce computational complexity for intermode decision using CBP(coded block pattern) and coded information of colocated-MB(macro block). Proposed method classifies MB into best-CBP and normal-CBP according to the characteristics of CBP. On best-CBP, it eliminates the computation for $8{\times}8$ mode on intermode decision process because the probability for SKIP mode and M-Type mode is 96.3% statistically. On normal-CBP, it selectively eliminates the amount of computation for bit-rate distortion cost, because it uses coded information of colocated-MB and motion vector cost in deciding SKIP mode and M-Type mode. The simulation results show that the proposed method reduces total coding time to 58.44% in average, and is effective in reducing computational burden in videos with little motion.

• Journal of KSNVE
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• v.3 no.1
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• pp.77-82
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• 1993

In general, the dynamic analysis with FEM(Finite Element Method) of large structures requires large computer memory space and long computational time. For the purpose of economical dynamic analysis of large structures, most of engineers want to use an efficient solution algorithm. This paper reports the modified CMS(Component Mode Synthesis) method which uses more efficient algorithm than the classical CMS method. In this paper, it is shown that Ritz vector sets can play the role of normal mode vector sets of substurctures in the CMS algorithm. The modified CMS method has good convergence performance compared with that of the classical CMS method.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.435-440
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• 2000

It is shown, in nonlinear two-degree-of freedom system, that the bifurcating modes are created by the stability changes of normal modes. There are four types of stability criterion, each of which gives rise to a distinct functional form of bifurcating modes; the bifurcating mode is born in the form of eigenfunction through which the stability is changed. Then a procedure is formulated to compute the bifurcating mode by the method of harmonic balance. Application of bifurcating mode to forced vibrations is introduced.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 1986.04a
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• pp.194-197
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• 1986

The normal mode parameters of microstrip coupled lines are datermined from the self and mutual capacitance and inductance of microstrip lines. In this paper, these capacitance are computed by using the relaxation method based on Quas1-TEM model for shoelded structure. Using these results, the normal mode parameters of two and three microstrip coupled lines are obtained.

• Journal of KSNVE
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• v.9 no.5
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• pp.975-983
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• 1999

This paper describes the dynamic characteristics of the joint structures in case of using the simplified beam model in the F. E. analysis. The modeling errors, when replace the shell with the beam, are investigated through F. E. normal modes analysis. Normal mode analysis were performed to obtain the natural frequencies of the L and T shaped joints with various type of channels. The results were analyzed to access the effects of the models on the accuracy of F.E. analysis by identifying the geometric factors which cause the error. The geometric factors considered are joint angle, channel length, thickness and area ratio of the hollow section to the filled one. The joint stiffness evaluation technique is developed in this study using normal modes analysis with Lumped Mass. With this method, the progressively improved results of F. E. analysis are obtained using the simplified beam model. The static and normal modes analysis are performed with the joint stiffness values obtained by the Kazunori Shimonkakis' virtual stiffness method and the proposed method and these simplified modeling errors are compared.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1998.04a
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• pp.392-398
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• 1998

In order to check the validity of nonlinear normal modes of continuous, systems by means of the energy-based formulation, we consider a beam with a nonlinear boundary condition. The initial and boundary e c6nsl of a linear partial differential equation and a nonlinear boundary condition is reduced to a linear boundary value problem consisting of an 8th order ordinary differential equations and linear boundary conditions. After obtaining the asymptotic solution corresponding to each normal mode, we compare this with numerical results by the finite element method.

• International Journal of Control, Automation, and Systems
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• v.5 no.4
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• pp.410-418
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• 2007

For the purpose of fault detection of the primary control surface, real-time estimation of the longitudinal stability and control derivatives of the DURUMI-II using the flight data is considered in this paper. The DURUM-II, a research UAV developed by KARI, is designed to have split control surfaces for the redundancy and to guarantee safety during the fault mode flight test. For fault mode analysis, the right elevator was deliberately fixed to the specified deflection condition. This study also mentions how to implement the multi-step control input efficiently, and how to switch between the normal mode and the fault mode during the flight test. As a realtime parameter estimation technique, Fourier transform regression method was used and the estimated data was compared with the results of the analytical method and the other available method. The aerodynamic derivatives estimated from the normal mode flight data and the fault mode data are compared and the possibility to detect the elevator fault by monitoring the control derivative estimated in real time by the computer onboard was discussed.

• The Journal of the Acoustical Society of Korea
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• v.35 no.4
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• pp.243-252
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• 2016

In this paper, the incoherent reverberation model based on coupled normal mode method is presented. In the range dependent environment, one way coupled normal mode method is used to calculate the pressure from a source to a scatterer patch and the pressure from a scatterer patch to a receiver. For the computational efficiency, the sound propagation from a source/receiver to the scatterer patch is assumed to occur only in the 2D plane where a source/receiver and scatterer patch are located. For the model verification, problems of the reverberation modeling workshop I and II sponsored by the US office of Naval Research are calculated and the results are compared with the incoherent reverberation model results based on the ray method.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.422-427
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• 2001

The component mode synthesis method allows the elastic deformation of each component in the flexible multibody system by a sum of modes and modal coordinates. This paper focuses on the selection of boundary conditions and deformation modes for redundantly constrained flexible components in mechanical system dynamics. The result of a flexible body dynamic analysis with only normal modes is used to identify proper boundary conditions of a static modes and a desired set of static modes which will be used in the final model. A simple four bar mechanism is used to explain the procedure and a space satellite with solar panels is analyzed using the proposed method.