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Optical property measurement of turbid media using continuous-wave light sources
Beop-Min Kim 한국물리학회 2004 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.44 No.2
Both the integrating sphere (IS) method and the diuse video re ectometry (VR) method are used to measure the optical properties of turbid media, and the results are compared. Target samples are made using absorbers and scatterers of known optical properties mixed with pure water. The VR method measures the absorption coecient with high accuracy even when the absorption coecient is as low as that of water. On the other hand, the IS method signicantly overestimates the absorption coecient depending on the optical penetration depth. The IS method seems to estimate the scattering coecient with better accuracy than the VR method does. The results show that the IS method has to be used with much care, especially when the absorption coecient is low and the penetration depth is high.
Kim, Hyoungjun,Yoon, Jangyeol,Lee, Geumbee,Paik, Seung-ho,Choi, Gukgwon,Kim, Daeil,Kim, Beop-Min,Zi, Goangseup,Ha, Jeong Sook American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.25
<P>We report the fabrication of an encapsulated, high-performance, stretchable array of stacked planar micro-supercapacitors (MSCs) as a wearable energy storage device for waterproof applications. A pair of planar all-solid-state MSCs with spray-coated multiwalled carbon nanotube electrodes and a drop-cast UV-patternable ion-gel electrolyte was fabricated on a polyethylene terephthalate film using serial connection to increase the operation voltage of the MSC. Additionally, multiple MSCs could be vertically stacked with parallel connections to increase both the total capacitance and the areal capacitance owing to the use of a solid-state patterned electrolyte. The overall device of five parallel-connected stacked MSCs, a microlight-emitting diode (mu-LED), and a switch was encapsulated in thin Ecoflex film so that the capacitance remained at 82% of its initial value even after 4 din water; the mu-LED was lit without noticeable decrease in brightness under deformation including bending and stretching. Furthermore, an Ecoflex encapsulated oximeter wound around a finger was operated using the stored energy of the MSC array attached to the hand (even in water) to give information on arterial pulse rate and oxygen saturation in the blood. This study suggests potential applications of our encapsulated MSC array in wearable energy storage devices especially in water.</P>
Kim, Hyung-Jin,Kim, Pil Un,Hyeon, Min Gyu,Choi, Youngwoon,Kim, Jeehyun,Kim, Beop-Min The Optical Society 2016 Applied Optics Vol.55 No.26
<P>Dual-depth spectral-domain optical coherence tomography (SD-OCT) enables high-resolution in vivo whole-eye imaging. Two orthogonally polarized beams from a source are focused simultaneously on two axial positions of the anterior segment and the retina. For the detector arm, a 1 x 2 ultrafast optical switch sequentially delivers two spectral interference signals to a single spectrometer, which extends the in-air axial depth range up to 9.44 mm. An off-pivot complex conjugate removal technique doubles the depth range for all anterior segment imaging. The graphics-processing-unit-based parallel signal processing algorithm supports fast two-and three-dimensional image displays. The obtained high-resolution anterior and retinal images are measured biometrically. The dual-depth SD-OCT system has an axial resolution of similar to 6.4 mu m in air, and the sensitivity is 91.79 dB at 150 mu m from the zero-delay line. (C) 2016 Optical Society of America</P>
Image Analysis Algorithm for the Corneal Endothelium
Kim Young-Yoon,Kim Beop-Min,Park Hwa-Joon,Im Kang-Bin,Lee Jin-Su,Kim Dong-Youn The Korean Society of Medical and Biological Engin 2006 의공학회지 Vol.27 No.3
The number of the living endothelial cells and the shape of those are very import clinical parameters for the evaluation of the quality of cornea. In this paper, we developed the automated endothelial cell counting and shape analysis algorithm for a confocal microscope. Since, the endothelial images from the confocal microscope has a non-uniform illumination and low contrast between cell boundaries and cell bodies, it is very difficult to segment the cells from the endothelial images. To cope with these difficulties, we proposed the new two stage image processing algorithm. At first stage algorithm, we used a high-pass filter and histogram equalization to compensate the non-uniform brightness pattern and a morphological filter and a watershed method are applied to detect the boundary of cells. From this stage, we could count the number of cells in an endothelial image. At second stage algorithm, we used a Voronoi diagram method to classify the shape of cells. This cell shape analysis and the percent of hexagonal cells are very sensitive in detecting the early endothelium damage. To evaluate the performance of the proposed system, we p개cessed seven endothelial images obtained using a confocal microscope. The proposed system correctly counted 95.5% cells and classified 92.0% of hexagonal cell shapes. This result is better than any others in this research area.
Development of Wireless NIRS System with Dynamic Removal of Motion Artifacts
Beop-Min Kim,Choong-Ki Kim,Dalkwon Koh,Seungduk Lee 대한의용생체공학회 2011 Biomedical Engineering Letters (BMEL) Vol.1 No.4
Purpose Along with recent advances in neuroscience, nearinfrared spectroscopy (NIRS) has been widely used to measure changes in cerebral oxygenation non-invasively. An NIRS system can be constructed to be portable unlike other imaging modalities, but its signals are often distorted by artifacts generated by arterial pulsation, vasomotion and head motion. To overcome these problems, we have developed a wireless NIRS system with a real time accelerometer that allows noise reduction. Methods Our wireless NIRS system includes a microcontroller,a Bluetooth communication, a fPCB (flexible printed circuit board), an accelerometer, batteries, LEDs (light emitting diode) and PDs (photodiode). Distorted signal caused by head motion was removed by active noise cancellation (ANC)algorithm. Results Two different tasks, arterial occlusion and brain hypoxia, were tested to validate the performance of our system. During arterial occlusion and breath holding, the NIRS signal showed corresponding hemodynamic changes such as increase in deoxy-hemoglobin (Hbr) and decrease in oxy-hemoglobin (HbO2) concentrations. Signal distortions generated by head motion were effectively removed. Conclusions Wireless NIRS system combined with real time noise cancellation algorithm has great potential to be utilized in brain-computer interface (BCI) for physically challenged people, dynamic exercise tasks and cognitive studies for children. Furthermore we expect the system will be highly applicable in neuroscience.
자율주행 차량의 스티어링 휠 디자인에 따른 사용자 경험 측정 도구 개발
우민선(Min Sun Woo),이인규(In Gyu Lee),김법민(Beop Min Kim),연규필(Kyupil Yeon),김용민(Yong Min Kim) 한국자료분석학회 2023 Journal of the Korean Data Analysis Society Vol.25 No.6
본 연구의 목적은 자율주행 5단계 차량 내에서 스티어링 휠 디자인에 따른 탑승자의 사용자 경험을 측정하는 표준화된 도구를 개발하는 것이다. 문헌 고찰을 통해 구성된 사용자 경험 예비문항에 대해 전문가 집단을 대상으로 내용타당도를 증명한 후 문항 분석을 시행하였으며 문항 20개를 초기 문항으로 선정하였다. 이후 18개의 스티어링 휠 디자인에 대해 21명의 실험 참가자를 대상으로 사용자 경험 설문을 진행하였다. 각각의 디자인은 독립적인 상황으로 간주되어 21명의 실험 참가자에게 수집된 378부의 설문 데이터를 기반으로 도구의 타당도와 신뢰도를 검증하였다. 타당도 분석 결과, 총 19개의 문항을 통해 인자 4개가 추출되었으며 각 인자의 이름을 ‘신뢰감’, ‘사용 의도’, ‘공간 활용성’, ‘정보 접근성’으로 명명하였다. 신뢰도 분석 결과, 인자 4개와 전체 도구의 신뢰도는 모두 Cronbach’s α 계수가 0.7 이상인 것을 확인하였다. 본 연구에서는 자율주행 차량의 다양한 스티어링 휠 디자인을 대상으로 활용될 수 있는 사용자 경험 측정 도구를 개발하였으며, 추후 개발될 스티어링 휠 디자인에 대해 사용자 경험을 평가하는 표준화된 측정 도구로서 활용될 수 있을 것으로 기대한다. The purpose of this study is to develop a standardized scale for measuring the user experience of passengers regarding the steering wheel design in Level 5 autonomous vehicles. Preliminary items for user experience were constructed through literature review, and content validity was proved for the expert group. After a pilot test of 20 items, a user experience survey was conducted with 21 participants, evaluating 18 steering wheel designs. Each design was considered an independent case, and reliability and validity were confirmed based on 378 survey data collected from 21 participants. As a result of the validity analysis, four factors were extracted through a total of 19 items. Each factor was named ‘Trust', ’Intention to use', ‘Space utilization', and ’Information accessibility'. The reliability of four factors and the total scale confirmed that Cronbach's α coefficient was higher than 0.7. In this study, a user experience measurement scale that can be applied to various steering wheel designs of autonomous vehicles was developed. It is expected that it can be used as a standardized measurement scale to evaluate user experience for the steering wheel design to be developed in the future.
Hyeon, Min Gyu,Kim, Hyung-Jin,Kim, Beop-Min,Eom, Tae Joong Optical Society of America 2015 Optics express Vol.23 No.18
<P>We propose a spectral domain optical coherence tomography (SD-OCT) system that uses a single line-scan detection scheme for balanced detection. Two phase-opposed spectra, generated by two optical fiber couplers, were detected by using a spectrometer with fast optical switching. A 2.69 km optical fiber was introduced to provide a proper time delay to prevent phase errors caused by the difference in measurement time between the two opposing spectra and unstable output voltages for controlling the galvano-scanner. Hence, a phase difference of ?? was obtained between the spectra over the sample depth without a phase error, which improved sensitivity by approximately 6 dB compared to that of conventional SD-OCT. We directly showed and compared the OCT images before and after applying the proposed balanced detection method in a phantom and in vivo sample.</P>