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Creep-Groan 소음과 온/습도에 따른 마찰계수와의 상관관계 고찰
이충근(Chungkeun Lee),김제균(Jekyun Kim),김성수(Seongsoo Kim) 한국트라이볼로지학회 2005 한국트라이볼로지학회 학술대회 Vol.2005 No.11
Recently, as state-of-the-art parts like ABS, TCS, ESP are developed, vehicle's dynamic characters have been improved remarkably. And the customer's expectation for driver's convenience and stillness of vehicle grows day by day. So, the noise and VIbration generated by vehicle when the vehicle starts or stops is one of constant discontent of the customer. Now it is the problem which must be solved quickly. Widely, we can divide the Noise of vehicle into two parts. The one is low frequency noise, GROAN(Creep-Groan) and the other is high frequency noise, SQUEAL. We have already studied a lot about high frequency noise, SQUEAL but don't know much about low frequency noise, GROAN(Creep-Groan). We thought Creep-Groan Noise is due to stick-slip phenomena and proved that Creep-Groan is reliable to stick-slip by our preceding experiments. In this paper, we'll study the relations of temperature-humidity conditions and friction characteristic of friction materials (especially the difference between static friction coefficient and dynamic friction coefficient). So we fabricated 9 sample friction materials, and gained the difference between static friction coefficient and dynamic friction coefficient(Δμ) by experiment under 9 temperature-humidity conditions to determine the relationship of GROAN(Creep-Groan) Noise and temperature-humidity conditions.
측정부 온도 부하에 따른 광용적맥파 파형 요동 특성 분석
이충근(Chungkeun Lee),신항식(Hangsik Shin) 대한전기학회 2015 전기학회논문지 Vol.64 No.2
Applicable range of Photoplethysmography (PPG) becomes wider as a non-invasive physiological measurement technique. However, PPG waveform is easy to be distorted by ambient light or vascular variation from temperature changes. Especially, irregular variation of PPG waveform caused by ambient temperature not only severely distorts the PPG, but also leads miss interpretation in clinical applications. Therefore, the investigation of between temperature and PPG waveform is quite important in using PPG. The purpose of this research is to quantify the PPG waveform characteristic and to investigate the waveform variation following the temperature change on measuring site. To quantify the fluctuation of PPG waveform, we use two techniques; detrended fluctuation analysis (DFA) and AC/DC analysis of PPG. We record PPG under temperature stress, which applied by medical use heat pack (40℃) and ice pack (0℃). Ten participants were applied to the experiment, and the result was evaluated to approve the temperature effect with statistical method, Wilcoxon signed rank test. The result shows that the AC component (p<0.05) and perfusion index DFS scale exponent (p<0.01) of PPG have the significance to temperature stress except for a DC component of PPG.
측정자세에 따른 광용적맥파의 성분과 혈관 경직도에 관한 연구
이충근(Chungkeun Lee),신항식(Hang Sik Shin),김진권(Jinkwon Kim),이병우(Byoungwoo Lee),이명호(Myounggho Lee) 대한전기학회 2010 정보 및 제어 심포지엄 논문집 Vol.2010 No.10
Photoplethysmography is composed by non-pulsatile(DC) and pulsatile(ac) component. Photoplethysmographic ac is represent blood volume changes in peripheral artery by cardiac output, and DC means a based blood volume before pulsation. Increased based blood volume increases an arterial diameter, blood pressure and stiffness. This paper is aim to assess the arterial stiffness by photoplethysmographic DC in supine and sitting positions. We considered that blood volume could be parameter as assessment of arterial stiffness.
이충근(Chungkeun Lee),박성하(Sungha Park),하종원(Jong-Won Ha) 한국컴퓨터정보학회 2012 한국컴퓨터정보학회 학술발표논문집 Vol.20 No.2
맥압증폭은 대동맥과 말초기관과의 혈압기능 평가 및 심혈관 질환을 예측하는 주요 매개변수로 나이와 관련이 높다. 그러나, 기존의 맥압증폭을 구하기 위해서는 관혈적인 방법으로 대동맥압을 측정하거나 혹은 전달함수와 같은 복잡한 대동맥압 추정 알고리즘을 구현하여 측정하여야 한다. 그러나, 유헬스를 활용한 스마트케어 환경에서 복잡한 알고리즘은 오히려, 계산량을 높이고, 시스템가격을 높일 수 있으므로, 최대한 단순화된 알고리즘이 필요하다. 본 논문에서는 맥압증폭을 주파수영역의 에너지 관점으로 맥압증폭을 접근하였고, 대동맥압 추정없이 추정할 수 있는 새로운 지수를 제안한다.
슬관절 운동 평가를 위한 생체 임피던스 측정용 전도성 섬유 센서의 여기 주파수별 특성 평가
이병우(Byung Woo Lee),이충근(Chungkeun Lee),김진권(Jin Kwon Kim),정완진(Wanjin Jeong),이명호(Myoungho Lee) 대한전기학회 2011 전기학회논문지 Vol.60 No.7
This study describes a conductive fabric sensor and determines an optimum excitation frequency of the sensor to evaluate knee joint movements. Subjects were composed of 15 males (age: 30.7±5.3) with no known problems with their knee joints. The upper side of subjects’ lower limbs was divided into two areas and the lower side of subjects’ lower limbs was divided into three areas. The sensors were attached to 1 for 3 spot from a hip joint and to 3 for 4 spot from a knee joint which are the optimum conductive fabric sensor configuration to evaluate knee joint movements. As a result, the optimum excitation frequency for evaluating knee joint movements using conductive fabric sensors was 25 ㎑. Average and standard deviation of bio-impedance changes from 15 subjects were 92.1±137.2 Ω at 25 ㎑. The difference of bio-impedance changes between 25 ㎑ and 50 ㎑ was statistically significant (p<0.05) and the difference of bio-impedance changes between 25 ㎑ and 100 ㎑ was also statistically significant (p<0.001). These results showed that conductive fabric sensors are more sensitive to measure bio-impedance for evaluating knee joint movements as an excitation frequency decreases.
김용호(Yong-Ho Kim),이충근(Chungkeun Lee),안강민(Kang-Min Ahn),김용준(Yong-Jun Kim),이명호(Myoungho Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
This paper reports an implantable microelectrode for monitoring compound nerve action potential of a peripheral nerve that is regenerated form a dissection. The microelectrode is realized using a biocompatible polymer substrate (PI2611, HDMicrosystems) and the gold electrode. It may provide a new method for inspecting functions of a regenerated peripheral nerve while a current method is gait analysis that is a footprint study. The proposed device had implanted into a sciatic nerve of a rat for 3 months, and compound action potential from the regenerated nerve was recorded through the microelectrodes.