신년 / 신년을 당하는 마음

한형섭 기독교대한성결교회 활천사 1941 활천 Vol.220 No.-

SSVEP 기반 졸음 퇴치 도로시설물 개발

한형섭,류장협,정의필,Han, Hyungseob,Ryu, Janghyub,Chong, Uipil 한국융합신호처리학회 2016 융합신호처리학회 논문지 (JISPS) Vol.17 No.2

운전자에게 각성뇌파를 생성할 수 있는 SSVEP기반의 졸음퇴치 도로시설물 시제품 개발을 위하여 실험을 통한 표준 인터페이스 모델의 개발 및 실험 검증 자료를 구축하는데 있다. 먼저 프로그램 시뮬레이션으로 SSVEP 자극 프로그램을 만들어서 체커 보드의 자극패턴을 만들었고 SSVEP의 주파수를 베타파 영역(13~30Hz) 내에 설정하였다. 고속도로 졸음취약지점에서 설치하여 운전중에 SSVEP 광자극에 대한 효과검증에 관한 실험 결과 주간과 야간 모두 고속도로 운전 중 SSVEP 광자극을 받으면 순간 베타파가 증가하는 것을 확인하였고, 5분 유지기 동안 보다 높은 각성상태를 유지하는 것으로 확인되었다. The purpose of this paper is to develop the algorithm of human arousal inducing interface using steady-state visual evoked potential(SSVEP) and its verification through experiments. In order to develop the model, computer-based SSVEP program simulation is preliminary performed. From the results of the simulation, stimulus pattern is decided to checkerboard and SSVEP frequency range is set into beta wave (13~30Hz). After the experiment on proving the effect of SSVEP flashing stimulation while driving by installing it at the location of people mostly falling asleep in the highway, the result confirms that both during the night and the day, after SSVEP flashing stimulation, a wave Beta immediately increases and the subjects keep high stimulation for the 5 minute maintaining stage.

Bone Formation Within the Vicinity of Biodegradable Magnesium Alloy Implant in a Rat Femur Model

한형섭,김영율,김유찬,조성윤,차필령,석현광,양석조 대한금속·재료학회 2012 METALS AND MATERIALS International Vol.18 No.2

The purposes of this preliminary study were to investigate the effect of increased Ca contents (5-10 wt%Ca) in Mg-Ca alloy on the mechanical properties and osseous healing rate in a standard rat defect model. Mechanical tests were performed using a compression system followed by qualitative histological analysis using the hemotoxylin and eosin (H&E) staining method and quantitative reverse transcriptase polymerase chain reaction (reverse transcriptase PCR). Mg-Ca alloy degraded fast in vivo while displaying a high level of the bone formation markersOC and ALP. Favorablemechanical strength properties were displayed as Ca content increased from 5 wt% to 10 wt% to show its potential to be considered as a load bearing implant material. The resultfrom this study suggests that the developed Mg-Ca alloy has the potential to serve as a biocompatible load bearing implant material that is degradable and possibly osteoconductive.

Reduction of Initial Corrosion Rate and Improvement of Cell Adhesion Through Surface Modification of Biodegradable Mg Alloy

한형섭,이선희,김원주,전호정,석현광,안재평,김유찬 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.1

In this study, the surface modification of biodegradable pure Magnesium and Mg-5wt%Ca-1wt%Zn alloywas performed through immersion in HBSS, inorganic salt solution and cell media to reduce initial hydrogenevolution and improve cell adhesion. The formation of different CaP-like coatings from immersion ofpure Mg and Mg alloy were observed using Cryo FIB analysis and their performances were measuredthrough cell adhesion, quantification of released Mg ions, and cell cytotoxicity assays. The coating layersdisplayed significant reduction of initial corrosion rate, and cell adhesion for both pure Mg and Mg alloyappeared to be influenced by the amino acids and proteins in the cell media. In general, Mg alloy showeda denser coating layer with higher Ca contents, resulting in greater reduction of initial corrosion rate andimproved cell adhesion, when compared to pure Mg. This is due to saturation of Ca around the corrosionsite that provided much favorable environmental condition to produce denser calcium phosphate coatingmixture. The result from this study suggests that the surface modification of biodegradable Mg alloy byimmersion in alkaline solutions can be utilized to obtain ideal biodegradable orthopedic implant materialwith reduced initial hydrogen evolution rate and improved cell adhesion.

개선된 스펙트럼 분석법을 이용한 징소리 분석

한형섭,조상진 한국공학안전보건예술학회 2012 한국공학예술학회 논문지 Vol.4 No.-

사운드 모델링 방식은 크게 물리적 모델링과 스펙트럼 모델링으로 나눌 수 있다. 물리적 모델링이 악기의 소스 영역에서 사운드를 파라미터화 시키는 것이라면 스펙트럼 모델링은 사람이 기저막에서 인지할 수 있는 입력신호 를 주파수영역에서 파라미터화 하는 기술로 사람의 청각의 인지메커니즘을 모델링하는 것이다. 본 논문에서는 기 존의 스펙트럼 모델링 분석방법은 전통 타악기 징의 분석에 적합하지 못함을 밝히고, 이를 해결하기 위해 피크 검출 및 피치 추적 알고리듬을 수정한 개선된 스펙트럼 분석법을 제안한다. 스펙트럼 모델링의 잔여신호와 피치 추적의 결과를 비교하여 제안한 알고리듬의 우수성을 보였고, 기존의 방법으로는 밝힐 수 없었던 징의 소프닝 현 상과 맥놀이 현상을 해석할 수 있었다. The modeling methods for generating musical sounds are largely categorized into two major sections: physical modeling and spectrum modeling. Spectrum modeling is to parameterize a sound recognizing at the human auditory cognitive mechanism in frequency domain. This paper proposes a modified spectral modeling synthesis (SMS) technique for Korean traditional percussion instrument, Jing, showing that the Pitch tracking technique in conventional SMS can not represent characteristics of percussion instruments. Comparing residuals and pitch tracking results for the previous and the proposed algorithm, the proposed algorithm shows that softening effects and beat phenomena can be interpreted and parameterized.

Conventional and Improved Cytotoxicity Test Methods of Newly Developed Biodegradable Magnesium Alloys

한형섭,김희경,김유찬,석현광,김영율 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.6

Unique biodegradable property of magnesium has spawned countless studies to develop ideal biodegradable orthopedic implant materials in the last decade. However, due to the rapid pH change and extensive amount of hydrogen gas generated during biocorrosion, it is extremely difficult to determine the accurate cytotoxicity of newly developed magnesium alloys using the existing methods. Herein, we report a new method to accurately determine the cytotoxicity of magnesium alloys with varying corrosion rate while taking in-vivo condition into the consideration. For conventional method, extract quantities of each metal ion were determined using ICP-MS and the result showed that the cytotoxicity due to pH change caused by corrosion affected the cell viability rather than the intrinsic cytotoxicity of magnesium alloy. In physiological environment, pH is regulated and adjusted within normal pH (~7.4) range by homeostasis. Two new methods using pH buffered extracts were proposed and performed to show that environmental buffering effect of pH, dilution of the extract, and the regulation of eluate surface area must be taken into consideration for accurate cytotoxicity measurement of biodegradable magnesium alloys.

졸음 예방 운전자를 위한 각성뇌파유도 인터페이스 개발

한형섭,정의필 한국공학안전보건예술학회 2016 한국공학예술학회 논문지 Vol.8 No.1

운전자에게 각성뇌파를 생성할 수 있는 SSVEP기반의 졸음퇴치 도로시설물 시제품 개발을 위 하여 실험을 통한 표준 인터페이스 모델의 개발 및 실험 검증 자료를 구축하는데 있다. 먼저 프 로그램 시뮬레이션으로 SSVEP 자극 프로그램을 만들어서 체커 보드의 자극패턴을 만들었고 SSVEP의 주파수를 베타파 영역(13~30Hz)내에 설정하였다. 이러한 모델을 기반으로 실제 LED 전광판을 만들었고 검증된 8채널 뇌파 측정기를 이용하여 실험 프로토콜대로 피험자를 대상으로 뇌파를 취득하여 분석하였다. 분석결과 14명 중 11명의 피험자에서 평상시 뇌파와 비교하여 SSVEP 자극 후 평소보다 높은 각성상태를 5분 동안 유지하여 의미있는 결과를 보였다. The purpose of this paper is to develop the algorithm of human arousal inducing interface using steady-state visual evoked potential(SSVEP) and its verification through experiments. In order to develop the model, computer-based SSVEP program simulation is preliminary performed. From the results of the simulation, stimulus pattern is decided to checkerboard and SSVEP frequency range is set into beta wave (13~30Hz). Based on this model the LED check boards were made and tested by Poly G-1, 8 channel developed by the LATHA.. We had meaningful results so that the proposed system has an effect on inducing driver’s alertness for 11 persons of 14 persons.

강섬유의 혼입율에 따른 콘크리트의 압축·할열인장·휨강도 및 연성능력의 변화

金潤一,李政勳,韓炯燮 관동대학교 1999 關大論文集 Vol.27 No.2

The effects of hooked steel fibre with different volume of steel fibre(0.5. 1.0. 1.5. 2.0%) on compressive. split tensile. flexural strength and toughness of concrete were investigated experimentally. The test results have shown that compressive. split tensile and flexural strength has been improved due to increase of the volume of steel fibre. especially flexural toughness has been on the increse comsiderably. The test gives lower improvement of compressive strength than that of split tensile and flexural strength. Steel Fibre Reinforced Concrete(SFRC) has considerable improvement in the toughness behaviour since steel fibres preserve the integrity of the material and the improve load-carrying capacity beyond matrix cracking.

신경회로망 기반 고장 진단 시스템을 위한 고장 신호별 특징 벡터 결정 방법

한형섭(Han, Hyung-Seob),조상진(Cho, Sang-Jin),정의필(Chong, Ui-Pil) 한국소음진동공학회 2010 한국소음진동공학회 논문집 Vol.20 No.11

As rotating machines play an important role in industrial applications such as aeronautical, naval and automotive industries, many researchers have developed various condition monitoring system and fault diagnosis system by applying various techniques such as signal processing and pattern recognition. Recently, fault diagnosis systems using artificial neural network have been proposed. For effective fault diagnosis, this paper used MLP(multi-layer perceptron) network which is widely used in pattern classification. Since using obtained signals without preprocessing as inputs of neural network can decrease performance of fault classification, it is very important to extract significant features of captured signals and to apply suitable features into diagnosis system according to the kinds of obtained signals. Therefore, this paper proposes the decision method of the proper feature vectors about each fault signal for neural-network-based fault diagnosis system. We applied LPC coefficients, maximum magnitudes of each spectral section in FFT and RMS(root mean square) and variance of wavelet coefficients as feature vectors and selected appropriate feature vectors as comparing error ratios of fault diagnosis for sound, vibration and current fault signals. From experiment results, LPC coefficients and maximum magnitudes of each spectral section showed 100 % diagnosis ratios for each fault and the method using wavelet coefficients had noise-robust characteristic.

AR계수와 SVM을 이용한 뇌파 기반 운전자의 졸음 감지 시스템

한형섭(Hyungseob Han),정의필(Uipil Chong) 한국지능시스템학회 2012 한국지능시스템학회논문지 Vol.22 No.6

운전 중 운전자의 졸음은 교통 사망사고를 일으키는 중요한 요인이며 음주운전보다도 더 위험할 수 도 있다. 이러한 이유로 운전자의 졸음을 판별하고 경고하는 시스템 개발이 최근에 매우 중요한 이슈로 떠올랐다. 그중에서도 졸음과 가장 밀접한 관련이 있는 생체 신호 분석이 많이 적용되는데 그중에서도 뇌파(Electroencephalogram, EEG)와 안구전도(Electrooculogram, EOG)를 분석하는 연구가 주류를 이루고 있다. 본 논문에서는 실험 프로토콜를 바탕으로 측정된 뇌파를 주파수별로 분석하여 운전자의 상태별 뇌파 데이터베이스를 구축하였고 선형예측(Linear Predictive Coding, LPC) 계수와 Support Vector Machine(SVM)을 이용한 운전자 졸음감지 시스템을 제안한다. 실험결과로 졸음의 뇌파분석에서 알파파가 감소하며 세타파가 증가하는 추세를 보였으며, LPC 계수가 각성, 졸음 및 수면상태의 특징을 잘 반영하였다. 특히 제안한 시스템은 적은 샘플(250ms)에서도 96.5%의 높은 분류 결과를 얻어 짧은 순간에 일어날 운전시 돌발 상황을 실시간으로 예측할 수 있는 가능성을 보였다. One of the main reasons for serious road accidents is driving while drowsy. For this reason, drowsiness detection and warning system for drivers has recently become a very important issue. Monitoring physiological signals provides the possibility of detecting features of drowsiness and fatigue of drivers. One of the effective signals is to measure electroencephalogram (EEG) signals and electrooculogram (EOG) signals. The aim of this study is to extract drowsiness-related features from a set of EEG signals and to classify the features into three states: alertness, drowsiness, sleepiness. This paper proposes a drowsiness detection system using Linear Predictive Coding (LPC) coefficients and Support Vector Machine (SVM). Samples of EEG data from each predefined state were used to train the SVM program by using the proposed feature extraction algorithms. The trained SVM program was tested on unclassified EEG data and subsequently reviewed according to manual classification. The classification rate of the proposed system is over 96.5% for only very small number of samples (250ms, 64 samples). Therefore, it can be applied to real driving incident situation that can occur for a split second.