• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.611-613
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• 1998

A structure of musculotendon model with a fatigue profile is investigated. The Hill-type musculotendon model can predicts the decline in muscle force for a given fatigue profile. It consists of nonlinear activation and contraction dynamics based on the physiological concepts. It is normalized for generalization to deal with the various muscles. Muscle force generated by continuous tetanic electrical monophasic pulsewidth modulation stimulation is decreased in time. A fatigue profile is expressed by a function of intramuscular acidification and applied to the relationship between muscle force and shortening velocity in contraction dynamics. The results of computer simulation are well matched with data in a literature which are isometrically performed for knee extension muscles. Also change in optimal fiber length has an effect only on muscle time, constant not on the steady-state tetanic force.

• Journal of Magnetics
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• v.18 no.4
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• pp.432-442
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• 2013

For magnetically suspended flywheel (MSFW) with gimballing capability, demerits of Lorentz force-type magnetic bearings and common reluctance force-type magnetic bearings are analyzed, a novel reluctance forcetype magnetic bearing (RFMB) including radial and axial magnetic bearing units with 4 separate biased permanent magnets and two conical stators is presented. By equivalent magnetic circuits' method, its magnetic properties are analyzed. To reduce the eddy loss, it was designed as radial poles with shoes and its rotor made of Iron-based amorphousness. Although the uniformity of magnetic flux density in the conical air gap determines mainly the additional tilting torque, the maximum additional tilting torques is 0.05Nm and the rotor tilting has no influence on its forces when the rotor tilts or the maximum changes does not exceed 14% when the rotor drifts and tilts simultaneously. The MSFW with this RFMB can meet the maneuvering requirement of spacecraft theoretically.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1999.10a
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• pp.325-332
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• 1999

As part of the conceptual disign of cable and membrane structures, the adequate shape is decisive with respect to load bearing behaviour and aesthetic expression of the structure. The force densities which are the force-length ratio are very useful parameters for the description of equilibrium state of any general cable-net structures. Because equilibrium states are obtained by solving linear equations the force desity method has a advantage compared with other solution strategies. But if there are futher restrainted conditions in force density the linear method will be extended to nonlinear one. The numeriacl methods are based upon least square and general inverse method for sieving nonlinear eqations. In this paper, the results from two methods is compared through several examples.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.9
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• pp.786-795
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• 2000

In this paper, a new impedance force control method for deburring and polishing process is proposed. The proposed method is robust to deal with unknown environment stiffness as unknown well as environment location. An adaptive technique is used to minimize the force error occurred due to unknown environment surface profile. A robust position control algorithm based on time-delayed information is used to cancel out uncertainties in robot dynamics. A three link robot manipulator is used to demonstrate performances of the proposed control on deburring and polishing tasks. Stability analysis for the adaptive control is presented and its results are confirmed by simulations.

• Journal of Institute of Control, Robotics and Systems
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• v.17 no.10
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• pp.1014-1020
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• 2011

This presents a motion and force estimation system of human fingers by using an Electromyography (EMG) sensor module and a data glove system to be proposed in this paper. Both EMG sensor module and data glove system are developed in such a way to minimize the number of hardware filters in acquiring the signals as well as to reduce their sizes for the wearable. Since the onset of EMG precedes the onset of actual finger movement by dozens to hundreds milliseconds, we show that it is possible to predict the pattern of finger movement before actual movement by using the suggested system. Also, we are to suggest how to estimate the grasping force of hand based on the relationship between RMS taken EMG signal and the applied load. Finally we show the effectiveness of the suggested estimation system through several experiments.

• Journal of Welding and Joining
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• v.34 no.6
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• pp.20-27
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• 2016

This study deals with the proper conditions of the trail rolling method (TRM) for the prevention of the buckling welding distortion at the AA5083 GMA butt weldment. For it, the effect of the working conditions of TRM including the rolling depth and the rolling distance between the welding torch and the roller on the longitudinal welding shrinkage force of the weldment was evaluated by using 3 dimensional thermo-mechanical FE analyses. The longitudinal welding shrinkage force inducing the buckling welding distortion at the GMA butt weldment was mitigated with an increase in the rolling depth and the rolling distance between the welding torch and the roller. Based on the results, the proper conditions of trail rolling method were established to reduce the longitudinal welding shrinkage force of the GMA butt weldment to below the critical value corresponding to the bucking distortion.

• The Bulletin of The Korean Astronomical Society
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• v.41 no.1
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• pp.46.3-47
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• 2016

We construct a solar eruption model with a background solar wind by performing three-dimensional zero-beta magnetohydrodynamic (MHD) simulation. The initial configuration of a magnetic field is given by nonlinear force-free field (NLFFF) reconstruction applied to a flux emergence simulation. The background solar wind is driven by upflows imposed at the top boundary. We analyzed the temporal development of the Lorentz force at the flux tube axis. Based on the results, we demonstrate that a solar eruption is caused by the imbalance between magnetic pressure gradient force and magnetic tension force. We conclude that this imbalance is produced by a weak but continuously existing solar wind above an active region.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2000.10a
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• pp.377-386
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• 2000

Hybrid mass dampers consist of passive tuned mass dampers and active mass dampers. They have the advantage that passive tuned mass dampers are still operated even when active mass dampers are stopped by excessive disturbances or power failure. This paper begins first with the comparative analysis of tuned mass dampers, hybrid mass dampers, and active mass dampers. Next more detailed study is carried out on the hybrid mass dampers: cascade hybrid mass dampers (CHMD) and active tuned mass dampers (ATMD). CHMD is regarded as more reasonable device because of its lighter active mass than ATMD's. However CHMD can not neglect stroke saturation problem caused by the length limitation of active damper mass. We compensate the saturation problem with nonlinear restoring force. The restoring force is calculated based on the states and phases of active mass dampers and added to the control force. It is shown that the presented compensation method prevents CHMD from saturation behavior without apparent changes of control force and responses compared to those in case of not considering the saturation problem.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2005.05a
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• pp.413-418
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• 2005

This paper proposes a measurement method for the surface of micro-parts by using AFM(Atomic Force Microscope). To this end, two techniques are presented to extend the capacity of AFM. First, the measurement range is extended by using an image matching method based on correlation coefficients. To account for the inaccuracy of the coarse stage implemented in AFM's, the image matching technique is applied to two neighboring images intentionally overlapped with each other. Second, a method to measure the shape of relatively large specimen is presented by using the inherent trigger mechanism due to the atomic force. The proposed method is proved effective through a series of experiments.

• Proceedings of the KSR Conference
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• 2005.11a
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• pp.1203-1208
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• 2005

This study is the evaluation of rating of railway prestressed concrete beam bridges by prediction of residual effective prestress force. Therefore, developed prediction method is based on the center camber of prestressed concrete beam, structural design report of various PSC beams, construction reference materials of PSC beams. Both rating evaluation and residual effective prestress force by developed method is compared with evaluation by structural design. This comparison results shows that this developed method is very effective method. Therefore evaluation of rating by prediction of residual effective prestress force will be used for evaluation of the rating of railway PSC beam bridges.