• The Journal of the Acoustical Society of Korea
• /
• v.21 no.7
• /
• pp.600-605
• /
• 2002

In this paper, a Negative Impedance Converter (NIC) circuit was employed for the electro-mechanical characteristic control of a thickness mode piezoelectric vibrator. Two circular plane piezoelectric vibrators were bonded together and the NIC circuit was connected to one of the vibrators. The theoretical and experimental analysis of the characteristics shown that the quality factor and the electro-acoustic efficiency of the vibrator with the NIC circuit could be improved by 20 times and 2.5 times, respectively.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.2213-2215
• /
• 2000

In this paper we implemented a novel re-entrant mode microstrip directional coupler for realizing the high directivity characteristic using finite element (FE) analysis. In microstrip configuration, the high directivity can be reached by matching the even- and odd-mode effective phase velocities. Through the values of capacitance obtained from 2-dimensional finite element(FE) analysis, the phase velocities for each mode and the design parameter were extracted for the proposed coupled-line configuration. Based on the extracted design parameter with phase matching condition we designed and fabricated 30dB directional coupler at 850MHz. Experimental results show good performance with excellent isolation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.20 no.12
• /
• pp.1077-1081
• /
• 2007

Thermal expanded core (TEC) fiber can reduce, being advantaged from thermal diffusion technology, connection loss by expanding the tolerance in relation to axial offset and gap when making optical connection having mode field diameter (MFD) of optical fiber expanded locally. In this paper, TEC fiber fabrication system based on the frame brushing techniques using twin-torch tip was designed and developed in order to maintain a stable thermal diffusion and single-mode when manufacturing TEC fiber. We were able to obtain that varied kinds of TEC fibers of which MFD could have been extended between $20\;{\mu}m$ and $40\;{\mu}m$ by TEC fiber fabrication system. In addition, the characteristic of connection loss was measured by alignment two TEC fibers of which MFD was $30\;{\mu}m$.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.25 no.1
• /
• pp.29-36
• /
• 2020

In this study, a variable step algorithm is proposed on the basis of the perturb and observe method. The proposed algorithm can follow the maximum power point (MPP) quickly when solar irradiance changes rapidly. The proposed technique uses the voltage change characteristic at the MPP when the environment changes because of insolation or temperature. The MPP is tracked through the voltage control using a variable step method. This method determines the sudden change of solar irradiance by setting the threshold value and operates in fast tracking mode to track the MPP rapidly. When the operation point reaches the MPP, the mode switches to the variable step mode to minimize the steady state error. In addition, the output disturbance is decreased through the optimization of the control method design. The performance of the proposed MPPT algorithm is verified through simulation and experiment.

• Proceedings of the KIPE Conference
• /
• 2001.07a
• /
• pp.34-37
• /
• 2001

In this paper the comparison of conventional PI control and nonlinear sliding mode control is presented for Switched Reluctance Motor(SRM). SRM drives require a nonlinear controller for high dynamic Performance but the high nonlinearity makes a poor performance in conventional PI control. However SRMs with sliding mode control achieve a robust performance for speed control. In this paper nonlinear sliding mode controller is suggested for high performance speed. State equation and modeling are proposed. And we present the speed comparison of PI control and SLMC.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2003.11a
• /
• pp.103-105
• /
• 2003

The principle of the ultra-high frequency (UHF) method to detect partial discharge(PD) in GIS is to measure the UHF electromagnetic waves excited by PD pulses. Such electromagnetic waves propagate along the GIS busbar in the TEM-mode, TE-mode, TM-mode. And the coaxial busbar of the GIS acts as a waveguide in which the UHF electromagnetic waves travel. This paper was studied the analysis on damping characteristic of electromagnetic waves excited by PD in GIS and presented the method to yield the cutoff frequency for determine the minimum band of sensor that detect the PD pulse.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2001.11b
• /
• pp.775-779
• /
• 2001

In optical disk drive (ODD), disk rotation speed has been increasing rapidly to achieve high data transfer rate. High servo bandwidths for focusing and tracking actuator are required to follow dynamic disturbance by high rotation speed in ODD. However, the servo bandwidth is significantly limited by some vibration modes which are induced by the flexibility of moving part. In this work, the vibration modes affecting bandwidth of actuators are suppressed by modifying actuating force by VCM. For this, the relation between the horizontal component of the actuating force and vibration mode is analyzed and force characteristic affecting to vibration mode is obtained through electromagnetic and structural analysis using simulation program.

• Bulletin of the Korean Chemical Society
• /
• v.6 no.2
• /
• pp.57-60
• /
• 1985

Normal mode calculations about the extended double six ring (D6R) subunit cluster model of Faujasite-type zeolites have been done by using the valence force field with reasonably adjusted force constants. We have studied for four X, Y zeolites species varying in M$_{f}$(Al/Si + Al) values. The calculated characteristic frequencies of D6R mode (${\nu}_{D_{6}R}$) and the rate of change of ${\nu}_{D_{6}R}$ with the mole fractions of aluminum, M$_{f}$ (Al/Si + Al) values agree well with Flanigen's experimental data; the experimental slope is -79 cm$^{-1}$, while the calculated slope is -82 cm$^{-1}$. Those are the improved results as compared to Blackwell's theoretical study; his predicted slope is -94 cm$^{-1}$.

• Transactions of the Korean Society for Noise and Vibration Engineering
• /
• v.20 no.10
• /
• pp.946-952
• /
• 2010

A method for the identification of structural characteristic parameters of a steel bar in the matrices form such as stiffness matrices and mass matrices from frequency response function(FRF) by genetic algorithm is proposed. As the method is based on the finite element method(FEM), the obtained matrices have perfect physical meanings if the FRFs got from the analysis and the FRFs from the experiments were well coincident each other. The identified characteristic matrices from the FRFs with maximun 40 % of random errors by the genetic algorithm are coincident with the characteristic matrices from exact FEM FRFs well each other. The fitted element diameters by using only 2 points experimental FRFs are similar to the actual diameters of the bar. The fitted FRFs are good accordance with the experimental FRFs on the graphs. FRFs of the rest 9 points not used for calculating could be fitted even well.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2013.05a
• /
• pp.1377-1378
• /
• 2013