• Journal of the Korean Society for Precision Engineering
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• v.18 no.10
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• pp.101-108
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• 2001

In this study, the static and dynamic characteristics of endmilling process were modelled and the analytic realization of chatter mechanism was discussed. In this reward, We have discussed on the comparative assessment of recursive time series modeling algorithms that cal represent time machining process and detect the abnormal machining behaviors in precision endmilling operation. In this study, simulation and experimental works were performed to show the malfunctional behaviors. For this purpose, new recursive algorithm(RLSM) was adopted for the oil-line system identification and monitoring of a machining process, we can apply these new algorithms in real process for detection of abnormal chatter. Also, The stability lobe of chatter was analysed by varying parameter of cutting dynamics in regenerative chatter mechanics.

• International Journal of Fluid Machinery and Systems
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• v.8 no.1
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• pp.23-35
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• 2015

This paper presents the rotordynamic performance measurement of oil-free turbocharger (TC) supported on gas foil bearings (GFBs) for 2 liter class diesel vehicles and comparison to floating ring bearings (FRBs). Oil-free TC was designed and developed via the rotordynamic analyses using dynamic force coefficients from GFB analyses. The rotordynamics and performance of the oil-free TC was measured up to 85 krpm while being driven by a diesel vehicle engine, and compared to a commercial oil-lubricated TC supported on FRBs. The test results showed that the GFBs increased the rotor speed by ~ 20% at engine speeds of 1,500 rpm and 1,750 rpm, yielding the reduction of turbine input energy by more than 400 W. Incidentally, an external shock test on the oil-free TC casing was conducted at the rotor speed of 60 krpm, and showed a good capability of vibration damping due to the well-known dry friction mechanism of the GFBs.

• Journal of the Semiconductor & Display Technology
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• v.16 no.1
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• pp.34-39
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• 2017

Semiconductor is one of the most internationally competitive areas among domestic industries, the major concern of which is the stability of the wafer manufacturing processes. The first process for the manufacturing of the semiconductor wafers is the ingot growing. The vibrations are supposed to be the most important factors for the ingot quality. In order to maintain the ingot quality, the growers have the automatic shut-down equipments which are activated by vibrations, and are sensitive enough to react to the earthquakes generated in Japan. In this study, the structure of an ingot grower was analyzed through experiments and computer simulations, and further the effects of design alterations to suppress the vibrations have been investigated. The final result shows that the vibrations can be reduced substantially to improve the stability of the structure.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.9 no.1
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• pp.49-54
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• 2010

An integrated machining center is developed for high precision and productivity manufacturing. The developed machine is composed of the high precision spindle using ball bearings, the high stiffness bed and the three axis CNC controller with the high resolution AC servo motor. In this paper, structural and modal analysis for the developed machine are carried out to check the design criteria of machine. The analysis is carried out by FEM simulation with using the commercial software, CATIA V5, ANSYS and ARMD. The simulation model of machine is made by shell and solid finite elements. This study also presents the measurement system on the modal analysis of an integrated machining center. The weak part of the machine is found by the analytical evaluation. The results provide with the structural modification data for good dynamic behaviors. And the safety of machine is confirmed by the modal analysis of modified machine design. As this study results can be trustworthy with the analysis of ANSYS and CATIA, integrated machining center can be successfully developed.

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.465-469
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• 2013

Proton transfer reaction is one of the most fundamental processes in chemistry and life science. Excited state intramolecular proton transfer (ESIPT) has been studied as a model system of the proton transfer, since it can be conveniently initiated by light. We report ESIPT reaction dynamic of 1-hydroxy-anthraquione (1-HAQ) in solution by highly time-resolved fluorescence. ESIPT time of 1-HAQ is determined to be $45{\pm}10$ fs directly from decay of the reactant fluorescence and rise of the product fluorescence. High time resolution allows observation of the coherent vibrational wave packet motion in the excited state of the reaction product tautomer. The coherently excited vibrational mode involves large displacement of the atoms, which shortens the distance between the proton donor and the acceptor. With the theoretical analysis, we propose that the ESIPT of 1-HAQ proceeds barrierlessly with assistance of the skeletal vibration, which in turn becomes excited coherently by the ESIPT reaction.

• Journal of the Semiconductor & Display Technology
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• v.15 no.1
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• pp.56-64
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• 2016

It is generally accepted that the surface quality of wafer edge is mostly damaged by the vibrations of the edge grinding machine. The surface quality of wafer edge is supposed to be the most dominant factor of the cracks, scratches, burrs and chips on the edge surfaces, which are the main defects of the wafers. In this study, the structure of a wafer edge grinder has been investigated through the frequency response experiment and the computer simulation to find ways to suppress the vibrations from the structure. The main reasons of the structural vibrations were analyzed. And further the design alterations were deduced from the results of the experiment and the simulation, and applied to the machine to check the effects of those alterations and to eventually improve the structural stability. The result shows that the machine can have much improved stability with relatively simple design changes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.715-720
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• 2005

The rotating transmission is made up of belts, mass disks and gears. This precise piece of equipment is controlled electro-mechanically by the mote. and operation program. The control strategy and the transmission can be changed by belts' stiffness and change of the mass and gear. This transmission can be modeled as a rigid body, and also finds broad application in such diverse fields as machine tools, the cruise control system in automobiles, and control in the attitude and gimbals of spacecraft. The study of the rotating transmission excited by its base motion is not only able to predict the rotational performance, but obtain the fundamental data for vibration isolation. In this thesis, we studied the response abilities such as steady overshoot, undershoot and ect. and the response velocities such as rising time, settling time, and ect. in the rotating transmission through PD control experiment.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2009.05a
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• pp.180-185
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• 2009

Actuator-induced disturbance is one of the crucial factors of spacecraft attitude pointing and stability in fine attitude control problems. The control moment gyros (CMGs) are known as very attractive actuators from the point of high power and low weight. In order to develop a CMG as an actuator for fine controls, CMG-induced disturbances should be analyzed. Therefore, this paper aims to develop an analytic model and predict the effect of disturbances of CMGs by assuming static and dynamic imbalances. The proposed model is induced by the Lagrangian method on the basis of the small signal assumption. In this research, mechanical system of the CMG is designed and the main components of CMG are producted.

• Structural Engineering and Mechanics
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• v.10 no.6
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• pp.517-532
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• 2000

A direct output feedback control scheme was recently proposed by the authors for single-story building structures resting on flexible soil body. In this paper, the control scheme is extended to mitigate the seismic responses of multi-story buildings. Soil-structure interaction is taken into account in two parts: input at the soil-structure interface/foundation and control algorithm. The former reflects the effect on ground motions and is monitored in real time with accelerometers at foundation. The latter includes the effect on the dynamic characteristics of structures, which is formulated by modifying the classical linear quadratic regulator based on the fundamental mode shape of the soil-structure system. Numerical result on the study of a $\frac{1}{4}$-scale three-story structure, supported by a viscoelastic half-space of soil mass, have demonstrated that the proposed algorithm is robust and very effective in suppressing the earthquake-induced vibration in building structures even supported on a flexible soil mass. Parametric studies are performed to understand how soil damping and flexibility affect the effectiveness of active tendon control. The selection of weighting matrix and effect of soil property uncertainty are investigated in detail for practical applications.

• Journal of the Semiconductor & Display Technology
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• v.17 no.3
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• pp.59-64
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• 2018

In recent years, the solar cell market has steadily grown with the demand for new energies. And wire sawing is one of the most critical processes in manufacturing solar cell wafer which is supposed to affect the breakage of wafers most during the process and afterwards. Generally, the defects of the wafers are generated from the structural vibrations of the machine. In the sawing process, the vibrations cause unnecessary normal stress on the cut surface of wafers, and eventually create the surface damage or leave the residual stress. In this study, the dynamic properties of a wire saw have been analyzed through the frequency response test and the computer simulation. And the effects of the design alterations have been investigated to stabilize the machine structure and further to reduce the vibrations. The result shows that relatively simple design alterations of supporting structure without any change of major parts of the machine can suppress the vibrations of the machine effectively.