• The Transactions of the Korean Institute of Power Electronics
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• v.27 no.3
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• pp.214-220
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• 2022

This paper proposes a test device designed for developing a high-voltage multilayer ceramic capacitor (MLCC). The proposed topology consists of an energy recovery circuit for charging/discharging capacitor, a flyback converter, and a boost converter for supplying power and a bias voltage application to the energy recovery circuit. The energy recovery circuit designed with a half-bridge converter has auxiliary switches operating before the main switches to prevent excessive current from flowing to the main switches. A prototype has been designed to verify the reliability of target capacitors following the voltage fluctuation with a frequency range below 65 kHz. To conduct high root mean square (RMS) current to the capacitor as a load, the MLCC test was conducted after the topology verification was completed through the film capacitor as a load. Through the agreement between the RMS current formula proposed in this paper and the MLCC test results, the possibility of its use was demonstrated for high-voltage MLCC development in the future.

• Journal of Ocean Engineering and Technology
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• v.38 no.2
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• pp.43-52
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• 2024

Investigating ship motion under real conditions is vital for evaluating the seakeeping performance, particularly in the design process stage. This study examined the influence of the principal particulars of a trawler on its seakeeping performance. The wave conditions in the Bering Sea are investigated using available data. The length-to-beam (L/B) and beam-to-draft (B/T) ratios of the ship are changed by 10% for the numerical simulation. The response amplitude operator (RAO) motion, root mean square (RMS) value and sensitivity analysis are calculated to evaluate the influence of the trawler dimensions on ship motions. The peak RAO motion affected the ship motions noticeably because of the resonance at the natural frequency. The L/B and B/T ratios are important geometric parameters of a ship that significantly influence its RMS motion, particularly in the case of roll and pitch. The change in the B/T ratio has a good seakeeping performance based on a comparison of the roll and pitch with the seakeeping criteria. The present results provide insights into the seakeeping performance of ships due to the influence of the principal dimensions in the design stage.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.28 no.6
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• pp.573-578
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• 2010

Precise determination of satellite positions is necessary to improve positioning accuracy in GNSS. In this study, GLONASS orbits were predicted from broadcast ephemeris using the 4th-order Runge-Kutta numerical integration method and their accuracy dependence on the integration step and the integration time was analyzed. The 3D RMS (Root Mean Square) differences between the results from I-second integration step and 300-second integration step was about 3 cm, but the processing time was one hundred times less for the I-second integration time case. For trials of different integration times, the 3D RMS errors were 8.3 m, 187.3 m, and 661.5 m for 30-, 150-, and 300-minutes of integration time, respectively. Though this integration-time analysis, we concluded that the accuracy gets higher with a shorter integration time. Thus we suggest forward and backward integration methods to improve GLONASS positioning accuracy, and with this method we can achieve a 5-meter level of 3-D orbit accuracy.

• Korean Journal of Optics and Photonics
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• v.17 no.3
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• pp.256-261
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• 2006

Wavefront aberrations of a laser beam that was reflected from an off-axis parabolic (OAP) mirror were measured to evaluate the optical performance of the OAP mirror. For a diamond turned OAP mirror, the root-mean-square (rms) value of higher-order aberrations was only $0.03{\mu}m$ for the laser beam size of about 34 mm. The other OAP mirror which was polished at a domestic company had the rms value of higher-order aberrations of $2.07{\mu}m$ for the same beam size. Although the diamond turned OAP mirror was well fabricated to have a small amount of aberrations, the aberrations were induced by the misalignment of the OAP mirror. Especially, 0 degree astigmatism increased with the sensitivity of $0.372{\mu}m/mrad$ when the OAP mirror was tilted in the tangential plane, which agreed well with the calculated results using a commercial ray tracing software.

• Journal of Korean Medicine Rehabilitation
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• v.25 no.4
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• pp.93-103
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• 2015

Objectives The purpose of this study is to compare the effects of ultra sound (U/S) and chuna on lumbago by meridian muscle electrography (MMEG). we performed U/S and chuna on erector spinae muscle. Methods This study was carried out on 20 lumbago patients. 20 patients were divided into U/S group and chuna group. U/S group take treatment 5 minutes. Chuna group take treatment 10 minutes. After performing U/S and chuna treatment 6 times, we compared both in terms of VAS, ODI, ROM, root mean square (RMS) and special edge frequency (SEF) on erector spinae muscle. The effect of each treatments are compared by Wilcoxon's signed rank test. The difference of effect between both groups are compared by Wilcoxon's rank-sum test. Results 1. Both U/S group and chuna group showed significant improvement in VAS and ODI after treatment. 2. U/S group showed insignificant improvement in both RMS and SEF. 3. Chuna group showed significant improvement in SEF at left lower point and RMS at left upper point. 4. Both U/S group and chuna group showed insignificant improvement in ROM. 5. There are no significant differences between both groups except SEF at left upper point. Conclusions According to above results, we found out that performing U/S or chuna on erector spinae muscle has effect in terms of VAS and ODI. But, in terms of SEF, we found out different result for both side. And we can't found out effect in terms of RMS and ROM of L-spine.

• Wind and Structures
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• v.23 no.3
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• pp.231-251
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• 2016

This paper presents the experimental results of the wind tunnel tests for three symmetric, rectangular, tall building models on a typical open terrain considering the torsional motion-induced vibrations. The time histories of the wind pressure on these models under different reduced wind speeds and torsional amplitudes are obtained through the multiple point synchronous scanning pressure technique. Thereafter, the characteristics of both the Root Mean Square (RMS) coefficients and the spectra of the base shear/torque in the along-wind, across-wind, and torsional directions, respectively, are discussed. The results show that the RMS coefficients of the base shear/torque vary in the three directions with both the reduced wind speeds and the torsional vibration amplitudes. The variation of the RMS coefficients in the along-wind direction results mainly from the change of the aerodynamic forces, but sometimes from aeroelastic effects induced by torsional vibration. However, the variations of the RMS coefficients in the across-wind and torsional directions are caused by more equal weights of both the aerodynamic forces and the aeroelastic effects. As such, for the typical tall buildings, the modification of the aerodynamic forces in the along-wind, across-wind, and torsional directions, respectively, and the aeroelastic effects in the across-wind and torsional directions should be considered. It is identified that the torsional vibration amplitudes and the reduced wind speeds are two significant parameters for the aerodynamic forces on the structures in the three directions.

• Aerospace Engineering and Technology
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• v.11 no.2
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• pp.149-157
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• 2012

In this paper, the performance of the sequential filter for a space debris collision management system is analyzed by using the flight data of KOMPSAT-2. To analyze the performance of the sequential filter, the results of batch filter used in the orbit determination system of the KOMPSAT-2 ground station is used as reference data. The overlap method is also used to evaluate the orbit accuracy. This paper shows that the orbit determination accuracy of the sequential filter is similar to that of the KOMPSAT-2 ground station, but dissimilar characteristics exist due to the filter difference. In addition, it is also shown that the orbit determination accuracy is order of 1m root mean square by using 30 hour GPS navigation solutions and 6 hour comparison period for the overlap method.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.10 no.3
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• pp.221-228
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• 2016

In this paper, we introduce our simulation software for EEG signal accuracy improvement. Users can check and train own EEG signal accuracy using our simulation software. Subjects were shown emotional imagination condition with landscape photography and logical imagination condition with a mathematical problem to subject. We use that EEG signal data, and apply Independent Component Analysis algorithm for noise removal. So we can have beta waves(${\beta}$, 14-30Hz) data through Band Pass Filter. We extract feature using Root Mean Square algorithm and That features are classified through Support Vector Machine. The classification result is 78.21% before EEG signal accuracy improvement training. but after successive training, the result is 91.67%. So user can improve own EEG signal accuracy using our simulation software. And we are expecting efficient use of BCI system based EEG signal.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.1
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• pp.7-13
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• 2011

Accurate response analysis of long span bridges subjected to seismic excitation is important for earthquake hazard mitigation. In this paper, the performance of a typical four span continuous reinforced concrete bridge model subjected to asynchronous multiple seismic excitations at the supports is investigated in both the time and frequency domains and the results are compared with that from a relevant uniform support excitations. In the time domain analysis, a linear modal superposition approach is used to compute the peak response values. In the frequency domain analysis, linear random vibration theory is used to determine the root mean square response values where the cross correlation effects between the modal and the support excitations on the seismic response of the bridge model are included. From the two sets of results, a practical range of peak factors which are defined to be the ratio of peak and the root mean square responses are suggested for displacements and forces in members. With reliable practical values of peak factors, the frequency domain analysis is preferred for the performance based design of bridges because of the computational advantage and the generality of the results as the time domain analysis only yields results for the specific excitation input.

• KIEE International Transactions on Power Engineering
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• v.3A no.3
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• pp.130-138
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• 2003

This paper presents a discrete wavelet transform approach for determining the beginning and end times of voltage sags. Firstly, investigations in the use of some typical mother wavelets, namely Daubechies, Symlets, Coiflets and Biorthogonal are carried out and the most appropriate mother wavelet is selected. The proposed technique is based on utilizing the maximum value of Dl (at scale 1) coefficients in multiresolution analysis (MRA) based on the discrete wavelet transform. The results are compared with other methods for determining voltage sag duration, such as the Root Mean Square (RMS) voltage and Short Time Fourier Transform (STFT) methods. It is shown that the voltage sag detection technique based on the wavelet transform is a satisfactory and reliable method for detecting voltage sags in power quality disturbance analysis.