• Journal of the korean academy of Pediatric Dentistry
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• v.4 no.1
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• pp.45-52
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• 1977

The purpose of this study was to provide information concerning the dental caries incidence in cerebral palsy children, and to aid improvement of their oral health. The author examined 106 cerebral palsy children and 185 normal children as control group, between 3 and 15 years of age. The obtained results were as follows: 1) In the DMF person rate, DMFT rate and DMFT index, cerebral palsy children (74.68%, 16.24% and 2.76 respectively) showed remarkable increment compare to normal children. (14.28%, 6.95% and 1.20 respectively.) 2) In the df person rate, dft rate and dft index, cerebral palsy children(93.33%, 37.41% and 6.22 respectively) showed remarkable increment compare to normal children. (78.64%, 20.68% and 3.29 respectively.) 3) There showed no significant in sexual differences. 4) In the dental caries incidence of the permanent teeth, athetosis and paraplegia type was found higher than other types. 5) Cerebral palsy children was found higher than normal children in the oral hygiene index. 6) There was found out necessity of the continuous dental enlightenment and treatment through this study.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.2
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• pp.67-73
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• 2015

Distance relay is widely used for the protection of long transmission line. Most of distance relay used to calculate line impedance by measuring voltage and current using DFT. So if there is a computation error due to the influence of phasor by DC offset component, due to excessive vibration by measuring line impedance, overreach or underreach can be occurs, and then abnormal and non-operation of distance relay can be issue. It is very important to implement the robust distance relaying that is not affected by DC offset component. This paper describes an enhanced distance relaying based on the DC offset elimination filter to minimize the effects of DC offset on a long transmission line. The proposed DC offset elimination filter has not need any prior information. The phase angle delay of the proposed DC offset filter did not occurred and the gain error was not found. The enhanced distance relay uses fault current as well as residual current. The behavior of the proposed distance relaying using off-line simulation has been verified using data about several fault conditions generated by the ATP simulation software.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.457-467
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• 2018

This paper presents performance comparison of several high-resolution frequency estimation algorithms for pure real tone signal. Algorithms are DFT (Discrete Fourier Transform - for reference purpose), Jacobsen, Candan, reassignment and Cedron. Each algorithm is evaluated under various experimental conditions, e.g., different SNR (Signal to Noise Ratio), window function and window length and performance is compared in the perspective of bias, MSE (Mean Square-Error) and variance. Experimental results indicate that Cedron algorithms works well in the most cases. For actual usage in the engineering problem, each algorithm needs additional analysis and modification.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.11a
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• pp.27-28
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• 2021

The search for new corrosion inhibitors for different corrosive mediums is a never-ending task. In the present work, the corrosion inhibition behavior and adsorption mechanism of two novel synthetic thiazolidinedione derivatives noted MTZD and ATZD in 3.5 wt.% NaCl solution on copper were investigated. Electrochemical, scanning electron microscope (SEM), atomic force microscopy (AFM) techniques were used along with first-principles DFT calculations. At maximum inhibitor concentration i.e., 300 ppm corrosion inhibition efficiency reached maximum up to 90% and 96% for MTZD and ATZD, respectively, and thereby followed the order of ATZD > MTZD. The inhibition efficiency increased up to 24 h of immersion, and then decreased after 48h immersion. The potentiodynamic curves suggested that the inhibition action of tested compounds is a mixed type of inhibitor. The first-principles DFT calculations suggested that compounds under investigation formed covalent bonds with Cu(111) surface via reactive sites. SEM and AFM results confirmed the formation of protective barrier that prevent corrosion attack.

• The Journal of the Acoustical Society of Korea
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• v.43 no.4
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• pp.406-413
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• 2024

The proposed method uses Generalized Cross Correlation - Phase Transform (GCC-PHAT) method with nonlinear preprocessing and a frequency domain low-pass filter. In this paper, by reinterpreting the calculation process of GCC-PHAT as DFT, we derive that there is an effective frequency band used for time delay estimation in GCC-PHAT, and by using only the effective band using a low-pass filter, the noise component is reduced and it improvesthe time delay performance in impulsive noise environments. By comparing the proposed method with the traditional GCC-PHAT in an impulsive noise environment, we show that the GCC-PHAT becomes more robust to the impulsive noise.

• Proceeding of EDISON Challenge
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• 2017.03a
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• pp.365-371
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• 2017

본 연구에서는 $Ni_2P$에서의 물의 산화를 Density Functional Theory(DFT) 계산을 이용하여 그 메커니즘을 확인하였다. 기존의 $Ni_2P$ 각 면의 표면 에너지에 관한 연구를 바탕으로 하여 P termination 된 (0001)면을 선택하였고 흡착 에너지를 계산하여 표면에 hydroxide와 oxygen coverage를 결정하였다. 산소 생성반응의 각 단계는 두 개의 site에서 계산되었고 두 site 모두 반응 결정 단계는 $^*OOH$가 형성되는 단계였다. 과전압 값을 비교한 결과 center site가 더 선호됨을 확인하였고 Center site에서 pH=14 일 때의 과전압 값은 0.64 eV으로 계산되었다.

• Proceeding of EDISON Challenge
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• 2015.03a
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• pp.400-404
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• 2015

2차원 물질인 metal mono chalcogenides(MMC) 중 GaS와 GaSe를 대상으로 하여 층과 층 사이의 van der Waals(vdW) 상호작용을 density functional theory(DFT) 계산을 이용해 연구하였다. Local density approximation(LDA)와 generalized gradient approximation (GGA)의 두 가지 다른 exchange correlation functional을 이용하고, 또한 두 개의 층 사이에 작용하는 van der Waals 상호작용을 고려한 LDA-D2, GGA-D2 계산을 수행하였다. 이와 같은 네 가지 방법으로 층간거리를 바꾸어 binding energy curve를 계산하였다. 그 결과 GGA-D2계산이 MMC의 층간 상호 작용을 가장 잘 기술하였다.

• The Journal of the Acoustical Society of Korea
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• v.5 no.2
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• pp.19-28
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• 1986

DSP LSE을 이용하여 디지털 DTMF 수신기를 구현하는 방법으로는 IIR 디지털 필터, Counter 방법, DFT 방법, FFT 방법 및 PARCOR 방법등이 제안되어 왔다. 그 중에서도 IIR 디지털 필터를 이용 한 방법은 기존의 아나로그 DTME 수신기를 그대로 디지털화 한 것이기 때문에 성능이 제일 우수한 것 으로 알려져 있다. 그러나 IIR 디지털 필터를 이용하여 그것을 구현할 때 필터의 계수, roundoff 잡음, overflow 등 고려해야 할 사항이 많다. 본 논문에서는 이러한 문제점들을 해결하면서 CCITT 사양들을 만족하는 디지털 DTMF 수신기 구현에 관한 연구결과를 제시하였다. DSP LSI을 이용해서 수신기를 hardware 제작할 때 이 결과들을 수정없이 이용할 수 있다고 기대된다.

• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.270-272
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• 2016

제일원리 전자구조 계산을 통하여 현재 활발하게 연구가 진행되고 있는 MoS2 layer에 다양한 전이금속 물질을 치환하여 수소 흡착에너지를 구해보고, 수소 발생 촉매로서 적합한 구조를 구해 보았다. 또한 계산된 density of state의 형태를 분석하여 수소발생반응의 가능성을 알아보았다. 계산 결과, MoS2 layer의 경우 ground states에서 약 2.53eV의 흡착에너지를 가졌고, Ge과 Ir을 치환한 구조에 경우에 대해서는 각각 0.02eV와 -0.12eV로 계산되었다.

• Proceedings of the Korean Information Science Society Conference
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• 1999.10a
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• pp.337-339
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• 1999

최근 시계열 데이터에서 유사한 패턴을 탐색하는 기법이 다양한 응용분야에서 중요한 연구 주제로 자리잡고 있다. 본 논문에서는 시계열의 트랜드를 정의하고 유사한 트랜드를 가지 시계열을 찾음으로써 유사성의 개념을 좀 더 확장, 발전시켰다. 즉, 시계열에서의 트렌드를 두 개의 이동 평균 선의 관계를 통해 정의함으로써 두 시계열 간의 거리만으로 유사도를 측정했던 기존 연구와는 달리 좀 더 패턴을 가진 수열들을 찾고 이것을 기존의 DFT방법을 이용하여 대용량의 시계열 데이터베이스에서 사용자가 정의한 임계치 이하로 차이가 나는 시계열에 대해 유사 시계열로서 최종적으로 검색하게 된다.