• Journal of the Korean Mathematical Society
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• v.43 no.3
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• pp.659-676
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• 2006

In this paper, we consider three-component reaction-diffusion system. With an integral condition and a global coupling, this system gives us an interesting free boundary problem. We shall examine the occurrence of a Hopf bifurcation and the stability of solutions as the global coupling constant varies. The main result is that a Hopf bifurcation occurs for global coupling and this motion is transferred to the stable motion for strong global coupling.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.47 no.11
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• pp.795-802
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• 2019

This paper deals with position-attitude coupling motion during spacecraft relative operation, and suggests dual quaternion-based kinematics for the problem. The position-attitude coupling motion can occur when the target point is located at an arbitrary point on the satellite body, not the center of mass. This is especially apparent in close proximity operation case. The dual quaternion-based kinematics directly reflects the angular velocity state, so that the coupling motion in which the change of attitude affects the position can be concisely defined. In this study, a new dual quaternion-based kinematics is presented along with a conventional approach to solve the coupling problem. Numerical simulations show that the position error for the target point is generated by the coupling motion, and verify that the dual quaternion-based kinematics can solve this problem.

• Journal of Navigation and Port Research
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• v.27 no.5
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• pp.451-458
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• 2003

A ship with small metacentric height or high speed vessel performs relatively large roll angles in her manoeuvring motion. Roll coupling effect should be taken into consideration for accurate prediction of manoeuvring motion of such a ship. This paper proposes a new mathematical model of ship manoeuvring motion taking coupling effect of roll into consideration. Some kinds of manoeuvring motion are simulated by computer, based upon the proposed model. The simualted results by proposed model here are compared with those by existing model. The proposed model is found to be practical and useful for prediction of manoeuvring motion with roll effect.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.1300-1303
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• 1996

In this paper a typical problem is examined that a light, general aviation airplane, such as Cessna or Navion, in gliding turn flight shows helical-dive phenomenon when pilots try to stop the descent by using elevator only. It is known from pilot's experience that in a certain flight trim it is impossible to recover from helical-dive by using elevator only. From this study it is shown that helical-dive phenomenon is involved with longitudinal/lateral dynamics coupling to airplane's aerodynamics. Also this phenomenon consists of three parts of flight dynamics; first of all, fast longitudinal motion occurs, then is followed by a little slow lateral motion, and finally logitudinal/lateral coupled motion is fully developed.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1227-1234
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• 2017

The two-degree-of-freedom direct drive induction motor, which is capable of linear, rotary and helical motion, has a wide application in special industry such as industrial robot arms. It is inevitable that the linear motion and rotary motion generate coupling effect on each other on account of the high integration. The analysis of this effect has great significance in the research of two-degree-of-freedom motors, which is also crucial to realize precision control of them. The coupling factor considering the coupling effect is proposed and addressed by 3D finite element method. Then the corrected mathematical model is presented by importing the coupling factor. The results from it are verified by 3D finite element model and prototype test, which validates the corrected mathematical model.

• Journal of the Korean Society for Precision Engineering
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• v.14 no.3
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• pp.137-146
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• 1997

External linkage type spine motion analysis was developed for relative trunk motion respect to the pelvis. A special programs for calculation of the relative angular motion and for graphical display were also developed. The developed device assured its accuracy and conveniency after application to 15 normal vol- unteers. Compare to the normal subjects, 18 patients treated with fixations and decompression surgery showed relatively large coupling motion. Optimal trajectory of the trunk motion derived from mathematical model in flexion and extension matched well with measurement for normal subjects.

• Journal of Ocean Engineering and Technology
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• v.8 no.2
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• pp.151-156
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• 1994

The equations of motion of a submarine pipeline with the internal flowing fluid and subject to hydrodynamic loadings are derived by using Hamilton's principle. Coupling between the bending and the longitudinal extension due to axial load and thermal expansion are considered. Coupling between the twisting and extension are not considered. The equations of motion are well agreed with the results which are derived by the vector method.

• International Journal of Naval Architecture and Ocean Engineering
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• v.6 no.3
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• pp.652-669
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• 2014

This paper concerns the kinematic characteristics of a coupling device in a deep-seabed mining system. This coupling device connects the buffer system and the flexible pipe. The motion of the buffer system, flexible pipe and mining robot are affected by the coupling device. So the coupling device should be considered as a major factor when this device is designed. Therefore, we find a stable kinematic device, and apply it to the design coupling device through this study. The kinematic characteristics of the coupling device are analyzed by multi-body dynamics simulation method, and finite element method. The dynamic analysis model was built in the commercial software DAFUL. The Fluid Structure Interaction (FSI) method is applied to build the deep-seabed environment. Hydrodynamic force and moment are applied in the dynamic model for the FSI method. The loads and deformation of flexible pipe are estimated for analysis results of the kinematic characteristics.

• Journal of Navigation and Port Research
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• v.41 no.1
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• pp.1-8
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• 2017

The estimation of non-linear ship motion is one of the most important issues in recent studies of ship stability. In this paper, bispectral analysis and bicoherence analysis were introduced in order to analyze the non-linear ship motion. In addition to the previously observed non-linear pitching motion in following seas, this study observed the non-linear phase coupling of pitching motion in following & quartering seas, and starboard beam seas. By comparing phase coupling between each frequency quantitatively via the bicoherence analysis, it was confirmed that non-linear phase coupling was much stronger in frequency regions other than the peak frequencies of a power spectrum. Furthermore, it was found out that the results of bicoherence calculation were analagous to each other, although the different normalization methods were applied.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.393-399
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• 2008

A modeling method for the modal analysis of a pre-twisted multi-packet blade system undergoing rotational motion is presented in this paper. Blades are idealized as pre-twisted cantilever beams that are fixed to a rotating disc. The stiffness coupling effects between blades due to the flexibilities of the disc and the shroud are modeled with discrete springs. The coupling effect between chordwise and flapwise bending deflection is also considered. Hybrid deformation variables are employed to derive the equations of motion. To obtain more general information, the equations of motion are transformed into dimensionless forms in which dimensionless parameters are identified. The effects of the dimensionless parameters and the number of packets as well as blades on the modal characteristics of the rotating multi-packet pre-twisted blade system are investigated with some numerical examples.