• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.9-11
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• 1999

This paper presents the problems of design and theoretical model of electrostatically driven axial-gap type wobble motor. The motor design benefits from large axial rotor-to-stator overlap and large gear ratios, and motor designs with rotor radii of 50 and $100{\mu}m$ are capable of generating torques in the [nNm] range at high electrostatic fields. Because of the large gear ratio, smaller angular steps and lower rotational speed are obtained, compared to radial-gap motor design. Aspects like gear ratio, torque generation, excitation schemes and torque coverage, normal forces, friction are addressed.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.11
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• pp.73-82
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• 2008

A dynamic model of reducer for generating facility of electric pourer having bevel gear pair and planetary gear train is developed by lumped method. The model accounts for the shaft and bearing flexibilities, gyroscopic effects and the force couplings among the transverse and torsion motions due to gearing. Vibration/noise analysis as well as strength of bevel gear pair and planetary gear train are considered. Exciting forces of high reducer for generating facility of electric power areconsidered as the mass unbalance of the rotors, misalignment and a function of gear transmission error. A Campbell diagram, in which the excitation sources caused by the mass unbalance of the rotors, misalignment and the transmitted errors of the gearing are considered, shows that, at the operating speed, there are not critical speed.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.20 no.11
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• pp.1071-1077
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• 2010

The reduction of the vehicle interior noise has been the main interest of noise and vibration harshness(NVH) engineers. A passenger vehicle has various and complicated transmission paths of sound and vibration. In order to identify the mechanism of transfer path, estimation of excitation force and exact modeling of transfer path are required. This paper presents method for estimating the noise source contribution on the road noise of the vehicle in a multiple input system where the input sources may be coherent with each other. And vector synthesis technique is employed to identify the characteristics of road noise and its transmission to vehicle compartment through noise and vibration analysis. Vibration reduction efficiency of each transfer path is evaluated by comparing individual vector components obtained virtual simulation.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.245-249
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• 2015

Vertically coupled low density InGaAs quantum dots (QDs) buried in GaAs matrix were grown with migration enhanced molecular beam epitaxy method as a candidate for quantum information processing devices. We performed excitation power-dependent photoluminescence measurements at cryogenic temperature to analyze the effects of vertical coupling according to the variation in thickness of spacer layer. The more intense coupling effects were observed with the thinner spacer layer, which modified emission properties of QDs significantly. The low surface density of QDs was observed by atomic force microscopy, and scanning transmission electron microscopy verified the successful vertical coupling between low density QDs.

• New & Renewable Energy
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• v.6 no.4
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• pp.41-49
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• 2010

Over the last decade, wind turbine industry has rapidly increased around world. These days many parts of the wind generators are induction generator. But it has some problems such as gearbox failure, rotor excitation and maintenance. Thus many manufacturers are considered permanent magnet synchronous generator named PMSG and direct drive. PMSG uses NdFeB magnet has many the advantage compare with induction generator. In this study, 3MW class outer rotor type PMSG for wind turbine is proposed. The generator features 2.6m stator outer radius, 1200mm stator length, 81 pole pairs, 14 rated rpm, 42kN/$m^2$ shear force density and 94.2% efficiency. Design and analysis generator using FEM program. Then calculate and derivate no load voltage, losses, conductor temperature. To reduce total harmonic distortion and cogging torque, the stator is applied the stator skewing. And to evaluate the designed generator, compare with other generators by active mass per rating torque and torque density.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.841-844
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• 2003

In the semiconductor and the optical industry a new transport system which can replace the conventional sliding system is required. These systems are driven by magnetic field and conveyer belt. The magnetic field damages semiconductor and contact force scratches the optical lens. The ultrasonic wave driven system can solve these problem. In this paper, the vibration behavior of flexural beam in the ultrasonic transport system is verified using Laser Scanning Vibrometer. The experiments for verifying vibration are performed in three conditions such as in the maximum transport speed, in the zero speed, and in the change of transport direction.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.5
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• pp.601-610
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• 1986

The acoustic intensity in the very near field of a vibrating surface reveals information about the location of sound sources and sinks. A system model of tennis racket was developed from simultaneous measurement of excitation force, surface vibration and the near field sound pressure. The characteristics of structural dynamics were obtained by standard experimental modal analysis techniques while the sound radiation characteristics were determined by estimating the acoustic intensity. In this paper, the information about vibration behviour was obtained by acoustic intensity method and some, experiments for verification were carried out. Close correlation was found between experimentally determined acoustic intensity and vibration mode patterns of the tennis racket.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.3
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• pp.360-372
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• 1998

This study deals with the interaction between buoyancy-induced convection and externally imposed excitation in the form of harmonic rocking and the effect of the interaction upon heat transfer in low-Pr liquids. A wide array of system responses are discussed using the spectral collocation numerical technique. The superposition of buoyancy and Coriolis forces leads to complex fluid flow and heat transfer. The transition to chaotic convection is accelerated, and heat transfer rates are reduced as the enclosure is excited at the fundamental frequency of oscillation associated with the pure buoyancy-driven case. Average heat transfer rates are correlated for Pr=0.02 and 0.03. The heat transfer is affected more in the Pr=0.03 liquid than the case of Pr=0.02.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.11 no.9
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• pp.398-405
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• 2001

The maximum and mean indicated pressure of two stroke low speed diesel engine has been continuously increased with a view of increasing engine power and also reducing fuel consumption. As a result, axial excitation has been increased comparing to that of the previous one. So the axial vibration damper in standard one is applied to all two stroke low speed diesel engine at the free end of crankshaft. Though many studies were carried out for marine use, few has been made for diesel power plant because there was little demand for power plant. Nowadays, diesel engine is much to be used for many benefits. In this paper, the optimum design of axial vibration on the 65 kW diesel power plant with tow 9K80MC-S engines of 9 cylinders was carried out. And the axial-torsional coupled vibration of this shafting system is identified by theoretical analysis and vibration measurement.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1218-1222
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• 2006

The bolts fixing the valve cover to the engine were often reported to be failed in a wheel loader model. Recently this failures were continually repeated in the specified equipment. In order to identify the fatigue fractures of the bolts, various vibration tests were carried out. From these tests, it was found out that the failure was due to the resonance between the excitation force of engine and the transverse mode of engine valve cover. So, the several modifications for the bolts were considered to avoid the resonance. Finally, the bolt failure problem was clearly resolved.