• 대한의용생체공학회:의공학회지
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• 제37권1호
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• pp.1-6
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• 2016

The biomedical information (heart rate, HRV, $SpO_2$ etc) from the Photoplethysmography (PPG) signal section can be estimated without the motion artifacts if the PPG signal section in the motion artifacts is detected accurately. But the PPG signal is easily exposed to the motion artifacts by the decrease of the medical instrument size and applying as portable or wearable. Besides, it is difficult to completely eliminate the motion artifacts from the PPG signal without distortion and ensure reliability as well. In this paper, the method was suggested to determine the motion artifacts or not on the PPG signal of the section divided into intervals of constant length. By comparing the spectrum of each section, it can be determined whether the motion artifacts are or not after obtaining the spectrum of each section by the Goertzel algorithm. Moreover, an amount of computation while maintaining a high detection rate can be reduced by using the Goertzel algorithm.

• 대한의용생체공학회:의공학회지
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• 제38권3호
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• pp.137-141
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• 2017

The indirect-contact bio-electric measurements using capacitive electrodes show large motion artifacts in comparison with conventional direct-contact measurements. It is necessary to measure the motion artifacts quantitatively, for the researches of reducing the motion artifacts. In this study, a device for quantitative measurement of motion artifacts was built. Using the device, an electrode was rubbed against some cloth(cotton) and the voltage variation of the electrode was measured as motion artifact in several environmental conditions(temperature and relative humidity). The measured waveforms agreed with that expected by the triboelectricity and the prior observations of the motion artifacts. Therefore, the results demonstrated the usability of the measurement system built in this study. The measurement system will be a great contribution to future research for reducing motion artifact.

• International Journal of Control, Automation, and Systems
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• 제5권6호
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• pp.701-706
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• 2007

The measurement accuracy for heart rate or $SpO_2$ using photoplethysmography (PPG) is influenced by how well the noise from motion artifacts and other sources can be removed. Eliminating the motion artifacts is particularly difficult since its frequency band overlaps that of the basic PPG signal. Therefore, we propose the Periodic Moving Average Filter (PMAF) to remove motion artifacts. The PMAF is based on the quasi-periodicity of the PPG signals. After segmenting the PPG signal on periodic boundaries, we average the $m^{th}$ samples of each period. As a result, we remove the motion artifacts well without the deterioration of the characteristic point.

• Journal of information and communication convergence engineering
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• 제10권1호
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• pp.91-95
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• 2012

The photoplethysmography (PPG) signal measured from a mobile healthcare device contains various motion artifacts occurring from a patient’s movements. Recently, to reject the motion artifacts, the method of using an acceleration sensor was suggested, but such sensors are very expensive. Therefore, this study deals with a novel sensor device to replace the acceleration sensor, and evaluated the performance of the proposed sensor experimentally. In the results of the experiments, it is shown that the proposed sensor device can reconstruct the PPG signal despite the occurrence of motion artifacts, and also that the variation rate in heart rate analysis was 1.22%. According to the experimental results, the proposed method can be applied to design a low-cost device.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
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• pp.987-990
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• 2009

Motion-induced artifacts on LCDs appear as blurred boundaries and/or color aberration between the moving objects and background. Perceived degree of the motion-induced artifacts depends on the blur width as well as color difference. This paper presents a quantitative measure for the motion-induced artifacts on LCDs. Performance of the proposed measure is verified by calculating correlation coefficients between the proposed measures and the results of human visual tests performed on the 240 Hz and 120 Hz scanning LCD TVs.

• 대한자기공명의과학회:학술대회논문집
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• 대한자기공명의과학회 1999년도 춘계학술대회 제3차 심포지움
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• pp.34-42
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• 1999

의료영상에서 인공물(Artifacts) 이라 함은 영상이 얻어지는 신체부위와 아무런 관련이 없으나 얻어진 영상에는 마치 영상의 일부분으로 나타나는 모든 것을 가리킨다. 따라서 영상에서 이들 인공물들은 실제 조직의 해부학적인 구조를 나타내지 않으므로 영상 판독에 영향을 주어 잘못된 진단을 초래할 수도 있다. 그러나 MR 영상이 가능한 이래로 새로운 여러 종류의 MR 인공물들이 많이 발견 되었으나 다행스럽게도 거의 모든 MR 인공물들은 쉽게 설명이 가능하며, 따라서 이들 인공물들에 의한 진단 오류의 가능성은 매우 희박한 실정이다. 그러나 새로운 영상방법이나 혹은 새로운 펄스대열이 계속 고안됨에 따라 새로운 종류의 인 공물들이 생겨날 가능성은 항상 존재하고 있다. 지금까지 알려진 여러 MR 인공물들은 그 생겨난 원인에 따라 다음과 같이 크게 세 가지로 분류가 가능하다. I. Motion Artifacts 1. Voluntary motion 2. Involuntary motion 1) Bowel Peristalsis 2) Respiration 3) Cardiac and vessel pulsation 4) Swallowing 3. Fluid motion 1) Blood flow 2) Cerebrospinal fluid flow II. Reconstruction Artifacts 1. Aliasing 2. Partial volume averaging 3. Truncation (Ringing) 4. Central point III. Magnetic and RF Field Related Artifacts 1. Chemical shift 1) First kind 2) Second kind 2. Susceptibility 1) Dental 2) Metal 3. Magic angle 4. Zipper 5. Bad data point 6. RF field inhomogeneity 7. Magnetic field inhomogeneity 8. Eddy current 9. slice overlapping 10. Zebra 11. RF overflow

• 방송공학회논문지
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• 제21권4호
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• pp.472-483
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• 2016

본 논문에서는 MC-FRUC(Motion Compensated Frame Rate Up-Conversion) 에서 사용될 수 있는 주파수 영역에서의 블로킹 현상(blocking artifacts) 검출 알고리즘을 제안한다. MC-FRUC 알고리즘은 블록 단위로 움직임 벡터를 계산하여 움직임 보상을 수행함으로써 블록 경계선 주변에서 블로킹 현상이 발생할 수 있다. 본 논문에서는 효율적인 블로킹 현상 검출을 위해 보간된 영상(interpolated frame)의 주파수 성분을 분석하여 블록경계에서 블록킹 현상을 감소시킨다. 실험결과에서 제안된 알고리즘이 기존의 FRUC 방법보다 더 나은 주관적 화질을 보인다. 제안한 방법은 또한 기존의 BDMC(Bi-Directional Motion Compensation) 대비 평균 약 0.45 dB PSNR(Peak Signal to Noise Ratio)이 향상되었다.

• 한국컴퓨터정보학회논문지
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• 제19권2호
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• pp.101-107
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• 2014

본 연구에서는 PPG 신호에 포함되어 있는 동잡음을 제거하기위해 사용되는 가속도 센서를 대체하기 위한 새로운 PPG 센서와 그 신호처리 기법을 제안하며, 제안된 방법은 청색광으로부터 추정된 동잡음을 기반으로 하여 광용적 맥파의 동잡음을 제거하는 것이다. 제안된 방법의 성능을 평가하기위해 청색광 LED와 적색광 LED, 포토센서를 이용하여 센서 프로브 설계하고 제작하였고, 제작된 센서 프로브와 적응필터를 이용하여 동잡음 제거 처리를 하였다. 실험의 결과에서는 제안된 센서와 신호처리 방법이 동잡음이 발생하더라도 신호 복원이 잘되었으며, 신호 대잡음비도 기존의 이동평균필터 보다 4.5배 이상 향상되었다. 이 실험의 결과로부터 제안된 방법이 저가의 헬스케어 단말기 설계에 적용될 수 있을 것이다.

• 센서학회지
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• 제27권3호
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• pp.192-198
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• 2018

Pulse oximetry is a non-invasive method for monitoring how much oxygenated hemoglobin is present in the blood. The principle of pulse oximetry is based on the red infrared light adsorption characteristics of oxygenated and deoxygenated hemoglobin. Even through the convenience of a pulse oximeter, its weak signal-to-noise ratio against motion artifacts and low perfusion makes it difficult to be accepted by execs devices. Several researchers have suggested the use of an adaptive noise cancellation (ANC) algorithm. They have demonstrated that ANC is feasible for reducing the effects of motion artifacts. Masimo Corporation developed a discrete saturation transformation (DST) algorithm that uses a reference signal and ANC. In commercial devices, it is very hard to escape it because Masimo's patents are very powerful and a better method is yet to be developed. This study proposes a new method that can measure noise saturation as well as accurate oxygen saturation from signals with high motion artifacts without using ANC and DST. The proposed algorithm can extract a normal signal without noise from a signal with motion artifacts. The reference signal from a pulse oximeter simulator was used for the evaluation of our proposed algorithm and achieved good results.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
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• pp.902-905
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• 2006

Plasma Display Panels(PDPs) suffer from motion artifacts because of subfield driving method. In this paper, a modified motion compensation method is proposed. We apply the optimized mapping table to the higher subfield group and the fill-up method to the lower subfield group to generate optimum mapping patterns. This method does not concentrate 'on' mappings on higher subfields. Therefore it can possibly become a more robust motion compensation.