• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.3
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• pp.185-192
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• 2017

This paper proposes a single-stage interleaved soft-switching electrolytic capacitor-less EV charger with reduced component count and simple circuit structure. The proposed charger achieves ZVS turn-on of all switches and ZCS turn-off of all diodes without regard to voltage and load variation. It achieves high power density even without an input filter due to CCM operation and bulky electrolytic capacitors and without a low-frequency component in the transformer. A 2 kW prototype of the proposed charger with sinusoidal charging is built and tested to verify the validity of the proposed operation.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.2
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• pp.76-82
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• 1997

The discrimination of flaw shape and sizing is very important subject in the material evaluation for semiconductor and new materials. The aim of this paper is to investigate the spectrum analysis of artificial defect signal captured from steel ball embedded in the resin. The results show that it can be evaluated quantitatively the size of artificial defect, from the amplitude variation of same frequency if the probe with same diameter and focal length is used. Comparing with the amplitude variation of the high frequency component and low frequency component obtained from the distance of defect center position, it can be estimated steel ball and flat bottm defect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.1098-1101
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• 2003

Complex impedances with frequency and voltage variation were analyzed in ITO/$Alq_3$/Al device structure at thickness 100 nm and 200 nm of $Alq_3$, respectively. At low frequency, complex impedance is mostly expressed by resistive component, and at the high frequency by capacitive component. Also, we have evaluated resistance, capacitance and permittivity.

• Journal of Institute of Control, Robotics and Systems
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• v.18 no.3
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• pp.161-167
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• 2012

It is known that big brown bats can distinguish echo of a prey at various angles. In this paper, we suggest a new object localization strategy using ultrasonic echolocation. We calculate the relative energy ratio between a high frequency component of ultrasound signal and a low frequency component of ultrasound signal for a target object. We found the measure depends on bearing angle of the object in space. We also tested energy ratio of echoed FM ultrasound signals depending on frequency, based on cross-correlation. It can determine the relative angular position of objects even though the reflected signals are congested form each object.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.22 no.8
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• pp.641-644
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• 2009

We have studied on the microwave characteristics for the meander type inductors on the MgO substrates and $Al_2O_3$ substrates by employing 3-D high frequency simulation, respectively. Proper designs of meander type inductors were proposed and confirmed through the high frequency simulations, 5, 7, 9, 11, and 13 turns meander type inductors have been choose to analyze the electrical properties for the microwave passive component applications. The Al top electrodes have 282 nm length, 45 nm width, 100 nm thickness and 15 nm gap. The simulations were carried out from 50 MHz to 30 GHz, Frequency dependent inductances and quality factor were calculated by employing the equivalent circuit model of meander type inductors. The self resonances frequency of meander type inductor were shifted from high frequency to low frequency range as the number of the turn of inductors was increased. From the microwave simulations, the inductances and quality factors of meander type inductors were extracted through the scattering parameter.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.453-456
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• 2005

Significance verification of electric fabric compared with existing electrode is very useful for the wearable and ubiquitous healthcare. In this paper, we verified the significance between Ag/AgCl electrode and electric fabric in dry-normal condition through heart rate variability analysis. We can find 98 % or more similarity about low frequency and high frequency which is important parameter for the heart rate variability analysis between two different electrodes in experiment. From this result, we confirmed that the power spectral density of low frequency, high frequency component from the electric fabric has high similarity compared with the result of heart rate variability from Ag/AgCl electrode in dry-normal condition.

• Journal of the Korean Society for Railway
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• v.7 no.3
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• pp.232-238
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• 2004

The dynamic characteristics of the current collection process of the high-speed railway are investigated through signals acquired during a test run. The signals are obtained from accelerometers, load cells, and strain gauges attached to various positions of the pantograph, and they are processed in time-and frequency-domains to obtain the dynamic characteristics. The main natural frequency of the pantograph is found to be 8.5Hz. There also are components at low frequencies varying linearly with the train speed. The contact frequency components above 20Hz is attenuated as they pass through the secondary suspension. The main frequency component of the load cell signal is found to be related with the rolling motion of the panhead generated by the stagger in the catenary.

• Journal of the Korean Geophysical Society
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• v.6 no.1
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• pp.25-29
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• 2003

We suggest a method that vectorially composes 3-component earthquake records in the frequency domain, to reduce the uncertainties in the analysis of the Fourier amplitude spectrum. The use of the Fourier amplitude spectrum composed from 3 components has two advantages. First, it provides a more accurate estimate of seismic moment by eliminating the vector-partition term that appears in individual component. Second, it provides more accurate estimates of seismic moment, corner frequency, high-frequency decay constant($χ$) .etc., by enhancing the shape of the Fourier amplitude spectrum. The latter is especially useful in the analysis of small earthquakes with low signal-to-noise ratios.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.1
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• pp.56-67
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• 2012

In this thesis, to compensate the sweep nonlinearity occurring in the high resolution radar system using FMICW or FMCW, the method of the estimation of the nonlinearity is proposed. The nonlinear phase component caused by the nonlinear characteristic of the radar system is modelled as a linear combination of the sinusoidal functions consisting of various magnitudes and phases(systematic nonlinear phase error) and a random component(stochastic nonlinear phase error). From two IF signals that are measured respectively independently for two reference point targets lying in different distances which are known, a sparse linear equation is made and solved by least squares method to estimate the nonlinear phase component. The estimated component can be used for predistortion method to compensate the sweep nonlinearity.

• Journal of the Korean Society for Nondestructive Testing
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• v.20 no.6
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• pp.490-500
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• 2000

A new technique for the source location of acoustic emission (AE) in plates whose thichness are close to or thinner than the wavelength has been studied by introducing wavelet transform de-noising technique. The detected AE signals were pre-processed using wavelet transform to be decomposed into the low-frequency, high-amplitude flexural components and the high-frequency, low-amplitude extensional components. If the wavelet transform de-noising was employed, we could successfully filter out the extensional wave component, one of the critical errors of source location in plates by arrival time difference method. The accuracy of source location appeared to be significantly improved and independent of the setting of gain and threshold, plate thickness, sensor-to-sensor distance, and the relative position of source to sensors. Since the method utilizes the flexural component of relatively high amplitude, it could be applied to very large, thin-walled structures in practice.