• Wind and Structures
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• v.2 no.1
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• pp.69-83
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• 1999

The most common used control device on tall buildings and high-rise structures is active and passive tuned mass damper (ATMD and TMD). The major advantages of ATMD and TMD are discussed. The existing installations of various passive/active control devices on real structures are listed. A set of parameter optimization methods is proposed to determine optimal parameters of passive tuned mass dampers under wind excitation. Simplified formulas for determining the optimal parameters are proposed so that the design of a TMD can be carried out easily. Optimal design of wind-induced vibration control of frame structures is investigated. A thirty-story tall building is used as an example to demonstrate the procedure and to verify the efficiency of ATMD and TMD with the optimal parameters.

• Proceedings of the KIEE Conference
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• 2002.07b
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• pp.613-615
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• 2002

This paper deals with power factor of doubly fed induction generator for wind power generation in range of sub- and super-synchronous speed. To supply active and reactive power to grid. stator is connected to grid directly and rotor is connected to back-to-back PWM inverter for excitation. According to excitation level. DFIG could operate at the different mode. i.e., unity, leading, and lagging power factor.

• ETRI Journal
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• v.27 no.1
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• pp.95-101
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• 2005

Waveguide structures of the stand-alone electroabsorption (EA) modulator and the electroabsorption modulated laser (EML) are investigated using the 3D beam propagation method. The EA waveguide structures with InP-based passivation layers show saturation in the extinction ratio (ER) due to the stray light traveling through the passivation layers. This paper demonstrates that narrower passivation layers suppress stray-light excitation in the EA waveguide, increasing the ER. A taper structure in the isolation section of the EML waveguide can reduce the mode mismatch and suppress the excitation of the stray light, increasing the ER further. Low-index-polymer passivation layers can confine the mode more tightly in the active waveguide, yielding an even higher ER.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.05a
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• pp.1011-1015
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• 2000

In this paper, the case studies of reducing rotational errors is theoretically done for a grinding spindle with an active magnetic bearing system. The rotational errors acting on the magnetic bearing spindle are due to mass unbalance of rotor, runout, grinding excitation and unmodeled nonlinear dynamics of electromagnets. The adaptive feedforward method based on LMS algorithm is discussed to compensate output and input disturbances, and investigated its effectiveness by numerical simulation. The feedforward control reduced external excitation and rotational error for specified frequency. The interpolation method using impulse function for cancelling the electrical 'uncut is studied. These methods show their effectiveness for the rotational accuracy of the improving magnetic bearing spindle through some simulation results of the rotational error decreased by them.

• Journal of Advanced Marine Engineering and Technology
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• v.30 no.8
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• pp.843-852
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• 2006

Vibration/noise analysis as well as strength of planetary gear train are considered in order to develop a transmission for a high-speed ship. The vibration model of a gear pair is developed with considering the elastic deformation of the active teeth and the body to be a rigid. Excitation forces of the transmission system are considered as the mass unbalance of the rotors. misalignment and a function of gear transmission error which comes from the modified tooth surface. 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 the critical speed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.142-147
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• 2003

This paper is concerned with the experiment of vibration isolation device whit can cope with heave, pitch and roll type vibrations. This new device consists of S-shaped piezoceramic actuators supporting each corner of the plate. Small piezoceramic sensors are located at the middle of each side. This paper also presents the development and the movement of the system. The active control technique was also developed to cope with base excitation. Experimental results show that vibrations can be reduced by the new device in the case of base excitation of harmonic type.

• Journal of the Korean Society for Railway
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• v.4 no.1
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• pp.16-22
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• 2001

This paper describes two different systems which can compensate harmonic currents generated in the power system. As non-linear loads increase gradually in industry fields, harmonic current generated in the electric power network system also increases. Harmonic current makes a power network current distorted and generates heat, vibration, noise in the power machinery. Many approaches have been applied to compensate harmonic currents generated in the power network system. Among various approaches, in this paper, two kinds of approaches are compared and evaluated. They are flywheel compensator based on secondary excitation of wounded rotor induction motor(WRIM) and primary excitation of squirrel cage induction motor(SCIM). Both systems have a common structure. They use a flywheel as a energy storage device and use PWM inverters.

• Journal of Surface Science and Engineering
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• v.23 no.4
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• pp.197-207
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• 1990

Atomic layer epitaxy is a relatively new epitaxial pprocess chracterized by the alternate and separate exposure of a susbstrate surface to the reactants contaning the constituent element of a compound semicoductror. The ideal ALE is expected to provide sevral advantageous as petcts for growing complicated heterostrutures such as relativly easy controls of the layer thinkness down to a monolayer and in forming abrupt heterointerfaces though monolayer self-saturatio of the growth. In addition, since ALE is stongly dependent on the surface reaction, the growth can also be controlled by photo-excitation which provides activation can be energies for each step of the reaction paths. The local growth acceleration by photo-excitation can be exploited for growing several device strures on the same wafer, which provides another important practical advantage. The ALE growth of GaAs has advanced to the point the laser opertion has been achieved from AlGs/GaAs quantun well structures where thee active layers were grown by thermal and Ar-laser assisted ALE. The status of the ALE growth of GaAs and other III-V compounds will be reviewed with respect to the growth saturation behavior and the electrical properties of the grown crystals.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.3
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• pp.407-416
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• 2021

An active phased array antennas can not only electrically steer the beam by controlling the weighting of the excitation signal, but can also form a pattern null in the direction of the interference source. The weight of the excitation signal to steer the main beam can be easily calculated based on the position of the radiating element. In addition, the weight of the excited signal for pattern null formation can also be calculated by setting the required radiation pattern and using WLSM(Weighted Least Squares Method). However, in a general wireless communication network environment, the location of the interference source is unknown. Therefore, an adaptive pattern null synthesis is needed. In this paper, it was confirmed that pattern null synthesis according to the required radiation characteristic was possible. And based on this, adaptive pattern null synthesis into the direction of an interference source was studied using a binary search algorithm based on observation area. As a result of conducting a simulation based on the presented technique, it was confirmed that adaptive pattern null forming into the direction of an interference is possible in efficient way.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.457-462
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• 2006

This paper is concerned with the active vibration control experiment on cylindrical shell equipped with Macro Fiber Composite(MFC) actuators. The MFC actuators were glued to the cylindrical shell in circumferential directions. To verify the theoretical result, vibration test using impact hammer and accelerometer was carried out. It was found from experiments that theoretical result predicts experimental result to some extent. The positive position feedback controllers were designed and applied to the test article. It was observed that the resonant amplitude of the fundamental mode was reduced by 20dB thus achieving active vibration control. The active vibration control of the response subject to non resonant excitation has been of interest. We developed the combination of the positive position feedback controller which can cope with the fundamental mode and the positive position feedback controller which can counteract the external disturbance with non resonant frequency. It was found from experiments that the hybrid controller can suppress the vibration amplitude successfully.