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임형규,이창기 한국컴퓨터산업학회 2004 컴퓨터産業敎育學會論文誌 Vol.5 No.2
기존 음성 인식의 실세계 적용에서 큰 문제점은 잡음이다. 본 논문에서는 잡음이 섞인 음성 신호로부터 잡음 성분을 분리해 내는 방법을 제안한다. 이 방법은 잡음이 섞인 음성 신호에 독립성분분석(ICA:Independent Component Analysis)을 사용한 암묵신호 분리(blind source separation)를 적용하여 잡음 성분을 제거하게 된다. 잡음이 혼합된 음성 신호에 독립성분분석을 전처리(preprocessing) 과정에 이용함으로써 인식성능을 향상시킬 수 있다. 깨끗한 음성 신호에 음악과 거리잡음을 섞었을 경우 인식률이 잡음 없는 음성의 인식률보다 각각 최대 14.98%, 13.78%까지 저하되었다. 그러나 독립성분분석으로 복원된 음성의 경우 잡음 없는 음성의 인식률 수준(각각 97.39%, 96.49%)으로 나타났으며, 독립성분분석을 이용한 음성의 잡음 제거가 인식률 향상에 좋은 결과를 가져옴을 확인 할 수 있다. Noisy speech recognition is one of most important problems in speech recognition. In this paper, a method which efficiently removes the mixed noise with speech, is proposed. The proposed method is based on the ICA to separate the mixed noise. ICA(Independent component analysis) is a signal processing technique, whose goal is to express a set of random variables as linear combinations of components that are statistically as independent from each other as possible.
임형규,김형준 한국공업화학회 2017 한국공업화학회 연구논문 초록집 Vol.2017 No.1
Recently, many experimental and theoretical efforts are intensified to develop high-performance catalysts for electrochemical CO<sub>2</sub> conversion. Many experiments show that the inclusion of room temperature ionic liquid (RTIL) in the electrolyte promotes the CO<sub>2</sub> conversion; however, there is no unified picture of the role of RTIL, which prohibits further optimization of the reaction medium. Using a state-of-the-art multiscale simulation, we unveil the atomic origin of the catalytic promotion effect of RTIL during CO<sub>2</sub> conversion. Unlike the conventional belief, which assumes a specific intermolecular coordination by the RTIL component, we find that the promotion effect is collectively manifested by tuning the reaction microenvironment. This mechanism suggests the critical importance of the bulk properties over the detailed chemical variations of the RTIL components in designing the optimal electrolyte components, which is further supported by our experimental validations.
Atomistic Hybrid QM/MM Method for Interface Multiscale Simulations
임형규 한국공업화학회 2019 한국공업화학회 연구논문 초록집 Vol.2019 No.0
The solid-liquid interface system is a core physicochemical component existed in many types of electrochemical heterogeneous reaction systems related to various energy and environmental applications. Despite its widespread use in a variety of commercial applications, the detailed physicochemical understanding is still at an early stage due to the difficulty of analysis. From the recent advances in computer technology, the first-principle quantum mechanics method and the molecular mechanics method are actively used in various chemical research fields. Notably, the multi-scale simulation framework which utilizes both methods is a promising tool to analyze the complex electrified solid-liquid interface system in atomic-scales. In this presentation, I would present a new advanced multi-scale simulation framework, so-called DFT-CES, and its future development roadmap to unveil the detailed property of electrified solid-liquid interface systems.
주파수 추적 방식에 의한 이식형 의료기기용 무선전력전달 장치 구현
임형규,이장우,김동욱,이정현,성기웅,김명남,조진호,Lim, H.G.,Lee, J.W.,Kim, D.W.,Lee, J.H.,Seong, K.W.,Kim, M.N.,Cho, J.H. 대한의용생체공학회 2010 의공학회지 Vol.31 No.5
Recently, many implantable medical devices have been developed and manufactured in many countries. In these devices, generally, energy is supplied by a transcutaneous method to avoid the skin penetration due to the power wires. As the most transcutaneous power transmission methods, the electromagnetic coupling between two coils and resonance at a specific frequency has been used widely. However, in case of a transcutaneous power transmitter with a fixed switching frequency to drive an electromagnetic coil, inefficient power transmission and thermal damage by the undesirable current variation may occur, because the electromagnetic coupling state between a primary coil and a secondary coil is very sensitive to skin thickness of each applied position and by person. In order to overcome these defects, a transcutaneous power transmitter of which operating frequency can be automatically tracked into the resonance frequency at each environment has been designed and implemented. Through the results of experiments for different coil surroundings, we have been demonstrated that the implemented transcutaneous power transmitter can track automatically into a varied resonance frequency according to arbitrary skin thickness change.
터널굴착이 지반환경에 미치는 영향에 관한 연구 - 계룡산 터널의 시뮬레이션 결과를 중심으로 -
임형규,장윤영,Lim, Hyung-Gyu,Chang, Yoon-Young 한국지하수토양환경학회 2008 지하수토양환경 Vol.13 No.5
본 연구에서는 터널 굴착으로 인한 지하수 영향 등 지반 환경 문제 해결을 위한 합리적인 평가 방법을 정립하고 이를 국민적 초미의 관심사 중 하나인 호남고속철도 계룡산 터널 구간에 적용하므로써, 계룡산 구간을 통과하는 터널 구간에 대한 환경문제(지하수/토양)를 사전에 연구하여 최적의 대안을 도출코자 한다. 지하수 유동모델링 결과 터널 굴착에 따른 지하수의 유출 및 지하수위 강하가 발생하며 터널굴착 완료 후에 지하수위가 회복되는 양상을 보인다. 따라서 구간에 분포하는 연약구간에 대해서는 특수 그라우팅이 필요할 것으로 사료된다. In this study, impact of tunnel construction on groundwater level and flow was investigated by simulation modeling, and tried to find optimal assessment method for minimization of geo-environmental problems due to tunnel construction. As a study area, Gyerong mountain area scheduled for tunnel construction was selected and the impact of tunnel construction on geo-environment compared to situation before construction was simulated. Simulation result showed that groundwater level down was observed during tunnel construction and recovered after completion of tunnel construction.
임형규,김철수,Im Hyung-kyu,Kim Cheol-su 한국컴퓨터산업학회 2005 컴퓨터産業敎育學會論文誌 Vol.6 No.2
본 논문은 잡음 환경의 음성 인식을 위하여 음성에 부가된 잡음을 제거하는 방법으로 프레임 단위로 웨이브렛 변환을 하여 웨이브렛 계수의 표준편차를 이용하여 시간 적응 임계값을 정하는 새로운 방법을 제안한다. 음성의 특성을 고려하기 위하여 고주파 성분을 많이 가지는 무성음의 경우는 첫 번째 스케일의 detail 신호에서, 저주파 성분을 많이 가지는 유성음의 경우는 세 번째 스케일의 approximation 신호의 표준편차를 이용하여 시간 적응 임계값을 설정하였다. 또한 제안한 방법으로 잡음을 제거한 후에도 묵음구간에 잔여 잡음이 존재하게 되므로 묵음구간을 검출하여 묵음구간의 잔여 잡음을 제거하였다. 실험을 통해 제안한 방법이 일반적인 웨이브렛 변환과 웨이브렛 패킷 변환을 이용한 방법보다 SNR과 MSE측면에서 향상됨을 확인 할 수 있었다. This paper proposed a new time adapted threshold using the standard deviations of Wavelet coefficients after Wavelet transform by frame scale. The time adapted threshold is set up using the sum of standard deviations of Wavelet coefficient in level 3 approximation and weighted level 1 detail. Level 3 approximation coefficients represent the voiced sound with low frequency and level 1 detail coefficients represent the unvoiced sound with high frequency. After reducing noise by soft thresholding with the proposed time adapted threshold, there are still residual noises in silent interval. To reduce residual noises in silent interval, a detection algorithm of silent interval is proposed. From simulation results, it is demonstrated that the proposed algorithm improves SNR and MSE performance more than Wavelet transform and Wavelet packet transform does.