• Journal of the Korean Geotechnical Society
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• v.16 no.1
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• pp.203-210
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• 2000

Recently, environmental vibration by train operation has been getting such an attention that the ISO puts it into the environmental vibration regulation. However, the reasonable and efficient countermeasures against such a kind of vibration is not well established, especially in residential areas near the railroad. Therefore, it is very important to estimate the ground vibration induced by the train operation for the design and construction of track supporting structures as well as structures near the track. In this study a model estimating dynamic load on track due to train operation and analysis technique of propagation of ground vibration were developed. Futhermore, the estimated vibration from this model was compared with the actual measurement data in the field and found to be reasonably acceptable.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.11C
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• pp.1052-1057
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• 2006

The implement the adaptive partial response maximum likelihood (PRML) detector with tilt analyzer for asymmetric high-density optical storage system. For the estimation of disc tilt, we exploit spc patterns in each data frame. Because of using the ROM table to renew the coefficients of equalizer and reference values of branches, the complexity of the hardware is reduced. The proposed PRML has been designed and verified by VerilogHDL and synthesized by the Synopsys Design Compiler with Hynix $0.35{\mu}m$ STD cell library. In the result, the total gate count is 35K, and the maximum operating frequency is 140MHz.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.50 no.7
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• pp.324-332
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• 2001

In this paper, it is suggested that the selection method of parameter of Power System Stabilizer(PSS) with robustness in low frequency oscillation for Static VAR Compensator(SVC) using a Real Variable Elitism Genetic Algorithm(RVEGA). A SVC, one of the Flexible AC Transmission System(FACTS), constructed by a fixed capacitor(FC) and a thyristor controlled reactor(TCR), is designed and implemented to improve the damping of a synchronous generator, as well as controlling the system voltage. The proposed PSS parameters are optimized using RVEGA in order to maintain optimal operation of generator under the various operating conditions. To decrease the computational time, real variable string is adopted. To verify the robustness of the proposed method, we considered the dynamic response of generator speed deviation and generator terminal voltage by applying a power fluctuation and three-phase fault at heavy load, normal load and light load. Thus, we prove the usefulness of proposed method to improve the stability of single machine-infinite bus with SVC system.

• Proceedings of the KIEE Conference
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• 2001.07c
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• pp.1340-1342
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• 2001

ZnO thin films are Prepared on Si(111) substrate by RF magnetron sputtering. Two-step deposition method is proposed to obtain ZnO thin films with high c-axis (002) TC value and electrical resistivity. This method consists of the following two-step deposition procedures: 1st-deposition for 10$\sim$30 min without oxygen at 100W and 2nd-deposition with oxygen added in the range of $O_2/(Ar+O_2)$ = 10 $\sim$ 50%. SAW filters with IDT/ZnO/Si(111) configuration are also fabricated. From the frequency response characteristics, the insertion loss and the side-lobe rejection are estimated.

• Proceedings of the KIEE Conference
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• 2000.11a
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• pp.180-183
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• 2000

The Battery Energy Storage System(BESS) has lots of advantages such as load levelling, quick response emergency power(spinning reserve), frequency and voltage control, improvement of reliability, and deferred generation and transmission construction. The economic feasibility requires justification from the customer side of meter to promoting the dissemination of BESS nationally. In this paper, we proposed the economic assessment model of customer owned Battery Energy Storage System(BESS) which is complemented and improved the existing model. The proposed model is applied to the typical customer type(light-industrial commercial, and residential) which are taken from the statistical analysis on the load profile survey of Korea Electric Power COmpany (KEPCO). The economic assessment performed for each customer type to justifying their economic feasibility of BESS installation from the economic measures such as payback period, overall benefits, ROI, and ROR. The results of this paper are useful to the customer investment decision making and the national energy policy & strategy.

• Journal of the Korean Ceramic Society
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• v.53 no.2
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• pp.178-183
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• 2016

Ferroelectric relaxor ceramics with $BaTiO_3-NaNbO_3-Bi(Mg_{1/2}Ti_{1/2})O_3$ ternary compositions (BT-NN-BMT) have been prepared by sol-gel powder synthesis and consequent bulk ceramic processing. Through the modified chemical approach, fine and single-phase complex perovskite compositions were successfully obtained. Temperature and frequency dependent dielectric properties indicated typical relaxor characteristics of the BT-NN-BMT compositions. The ferroelectric-paraelectric phase transition became diffusive when NN and BMT were added to form BT based solid solutions. BMT additions to the BT-NN solid solutions affected the high temperature dielectric properties, which might be attributable to the compositional inhomogeneity of the complex perovskite and resulting weak dielectric coupling of the Bi-containing polar nanoregions (PNRs). The temperature stability of the dielectric properties was good enough to satisfy the X9R specification. The quasi-linear P-E response and the temperature- stable dielectric properties imply the high potential of this ceramic compound for use in high temperature capacitors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.25-28
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• 2000

A capacitance-type humidity sensors in which porous silicon layer is used as humidity-sensing material was developed. This sensors was fabricated monolithically to be compatible with the typical IC process technology except for the formation of porous silicon layer. As the sensors is made as a mesa structure, the correct measurement of capacitance is expected because it can remove the effect of the parasitic capacitance from the bottom layer and another junctions. To do this, the sensor was fabricated using process steps such as localized formation of porous silicon, oxidation of porous silicon layer and etching of oxidized porous silicon layer. From completed sensors, capacitance response was measured on the relative humidity of 25 to 95% at room temperature. As the result the measured capacitance showed the increase over 300% at the low frequency of 120Hz, and showed little dependence on the temperature between 10 to $40^{\circ}C$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.05b
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• pp.47-50
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• 2000

The optical characteristics of merocyanine dyes have been investigated widely due to their possible application to the high efficiency photo-electric devices. The optical systems are mostly fabricated using vacuum evaporation, casting and Langmuir-Blodgett method and the arrangement and orientation of dye molecules is one of the most important factors in the study on the optical characteristics. In this study, we fabricated the molecular systems through the LB techniques and investigated the optical characteristics of merocyanine dye LB film using the oscillation characteristics of quartz crystal. It was quite interesting behavior that the resistance and frequency shift at the parallel resonance under the UV irradiation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.20 no.10
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• pp.895-900
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• 2007

Partial discharge(PD) test can be performed either when the rotating machine is not operating(off-line) or during normal machine operation(on-line). This paper presents an on-line and off-line PD test on a large hydro-generator and induction motor using the same PD acquisition system(PDAS) and ceramic coupler(CC) sensor. PD signal characteristics of CC sensor proved similar with that of epoxy mica coupler(EMC) sensor as a results of PD test for simulated defect winding and frequency response test. A comparison of on-line and off-line PD test for PD characteristic parameters-phase resolved PD(PRPD), maximum PD value(Qmax) and PD occurrence energy(POE)-indicated that on-line PD test could reliably and effectively diagnose insulation conditions which were verified by off-line PD test.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.320-320
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• 2010

In the case of existing ultrasonic motors, they have characteristics such as outstanding response speed, speed and high efficiency. However, it's very hard to use practically them as small motors due to complicated structure and expensive cost. This paper proposed v-type ultrasonic linear motor. Stator of the motor is composed of thin elastic body and four ceramics attached to upper and bottom areas of the body. The ceramics have each direction of polarization. When two harmonic voltages which had $90^{\circ}$ phase difference were applied to the ceramics, the symmetric and anti-symmetric displacements were generated at the tip to make the elliptical motion. To find out a model that generates maximum displacement at contact tip, FEM program was used with change of leg-angle. In addition, optimal model was chosen by considering magnitude and shape of displacement according to change of frequency.