• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2007.05a
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• pp.42-44
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• 2007

본 연구에서는 체성분 측정용 스마트 의류의 프로토타입을 개발하고 평가함으로써 헬스케어 의류로써의 개발 가능성을 탐색하고자 하였다. 직물 전극을 사용하여 두 가지 타입으로 개발된 실험의복을 피험자에게 착용하도록 한 후 자세의 변화 및 1차 착용, 탈의 후 2차 착용에 따른 체성분을 측정한 결과, 동일 자세 내에서는 의복 타입 및 1, 2차 반복 착용에 관계없이 비교적 일관성 있는 임피던스 측정치를 얻을 수 있었으며, 착용자의 신체 부위별 측정도 가능한 것으로 분석되었다.

• The Journal of the Acoustical Society of Korea
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• v.33 no.5
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• pp.291-299
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• 2014

To probe the temperature elevation effect caused by ultrasound, a tissue mimicking phantom was newly suggested. A carrageenan gel was adopted to realize not only the required transparency for visualization but also acoustic characteristics similar to human tissue. To visualize the temperature elevation inside phantom, thermochromic film with a critical temperature of discoloration was introduced. Acoustic characteristics of the tissue mimicking phantom were examined when the concentrations of carrageenan and sucrose changed. As the results, the attenuation coefficient of the phantom could be controlled in the range of 0.44~0.49 dB/cm/MHz, and the acoustic impedance in the range of 1.52~1.77 Mrayls. We could control the acoustic characteristics of the phantom by different concentration of carrageenan and sucrose, and it was possible to examine the temperature elevation caused by ultrasound in the phantom. The suggested method was verified by noninvasively visualizing the temperature elevation due to planar and focused ultrasound using the fabricated phantom.

• Journal of Biomedical Engineering Research
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• v.21 no.3 s.61
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• pp.261-271
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• 2000

The present study investigated flow dynamics of a two-dimensional abdominal aortic bifurcation model under sinusoidal flow conditions considering wall motion. impedance phase angle(time delay between pressure and flow waveforms), and non-Newtonian fluid using computational fluid dynamics. The wall shear stress showed large variations in the bifurcated region and the wall motion reduced amplitude of wall shear stress significantly. As the impedance phase angle was changed to more negative values, the mean wall shear stress (time-averaged) decreased while the amplitude (oscillatory) of wall shear stress increased. At the curvature site on the outer wall where the mean wall shear stress approached zero. influence of the phase angle was relatively large. The mean wall shear stress decreased by $50\%$ in the $-90^{\circ}$ phase angle (flow wave advanced pressure wave by a quarter period) compared to the $0^{\circ}$ phase angle while the amplitude of wall shear stress increased by $15\%$. Therefore, hypertensive patients who tend to have large negative phase angles become more vulnerable to atherosclerosis according to the low and oscillatory shear stress theory because of the reduced mean and the increased oscillatory wall shear stresses. Non-Newtonian characteristics of fluid substantially increased the mean wall shear stress resulting in a less vulnerable state to atherosclerosis.

• Proceedings of the Acoustical Society of Korea Conference
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• 1998.06c
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• pp.445-448
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• 1998

고유음향 임피던스가 다른 물질이 층상구조를 이루고 있는 매질내에서 임의의 한 층에 형성된 이차원 초음파 음장이 다른 매질로 전파될 때에의 특성을 각스펙트럼법에 의해 해석하였다. 음원으로서는 baffle된 원형 트랜스듀서를, 층상구조를 매질로서는 물과 생체조직(지방)의 경계를 각각 고려하였다. 해석에 있어서는 먼저 각스펙트럼 분해요소, 즉, 음원의 크기 및 거리에 의존하는 기준음장의 최적 크기와 샘플링 간격을 균질매질을 이용하여 결정한 다음, 그 요소를 층상매질에 적용하였다. 그 결과, 경계면에서의 입사각(공간주파수)의 의존하는 투과계수에 입사음장의 곱으로 나타내어지는 투과음장은 각스펙트럼법에 의해 짧은 시간내에 정도 높게 산출될 수 있음을 보인다.

• Proceedings of the KOSOMBE Conference
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• v.1991 no.05
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• pp.71-73
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• 1991

In this study electrical impedance plethysmograph was developed and each ten digital blood flow was measured for eight normal males and a patint with digital arterial reconstruction surgery. Blood flow of the digit with surgery was approximately fourty percent compared to that of the other normal digit. For the normal subjects, right-handed subjects generally have larger blood flow in right fingers than that in left fingers while it was reverse for the left-handed subjects. The relative average magnitude of the digital blood flow is the third, first, second, fourth, and fifth digit in descending order for the left and right hand, respectively. Blood flow of the fifth digit for all subjects except one was the smallest among the five digits.

• Proceedings of the KOSOMBE Conference
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• v.1991 no.05
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• pp.5-7
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• 1991

We have developed an efficient and robust image reconstruction algorithm for static impedance imaging. This improved Newton-Raphson method produced more accurate images by reducing the undesirable effects of the ill-conditioned Hessian matrix. We found that our electrical impedance tomography (EIT) system could produce two-dimensional static images from a physical phantom with 7% spatial resolution at the center and 5% at the periphery. Static EIT image reconstruction requires a large amount of computation. In order to overcome the limitations on reducing the computation time by algorithmic approaches, we implemented the improved Newton-Raphson algorithm on a parallel computer system and showed that the parallel computation could reduce the computation time from hours to minutes.

• Journal of Biomedical Engineering Research
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• v.12 no.1
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• pp.23-28
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• 1991

In this study electrical impedance plethysmograph was developed and each ten digital blood flow was measured for eight nomal males and a patient tvith digital arterial reconstruction surgery. Blood flow of the digit with surgery was approximately fourty percent compared to that of the other normal digit. For the normal subjects, right - handed subjects generally have larger blood flow in right fingers than that in left fingers while it was reverse for the left - handed subjects. The relative average magnitude of the digltal blood flow Is the third, first, second, fourth, and fifth digit in descending order for the left and rich hand, respectively. Blood flow of the fifth digit for all subjec!s except one was the smallest among the five digits.

• Journal of Biomedical Engineering Research
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• v.10 no.3
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• pp.279-284
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• 1989

Measurement of cardiac output during exercise by noninvasive technique is very needed in the area of sports medicine. However there are only two noninvasive techniques, one of which is $CO_2$ subscript rebreathing technique and the other one is impedance cardiography. While $CO_2$ rebreathing technique needs special breathing and metablic steady state, impedance cardiography has motion Uiiau problem. In this study maior sources of the mothion artifact during treadmill exercise was found experimentally to. be the impact caused by each step on the treadmill. Thus special shoes to reduce the impact were developed. These are the shoes with silicon rubber and hard sponge attached to the soles. It was possible to measure cardiac output with the newly developed shoes for Burke protocol whose speed of the treadmill was constant 3.5 miles/hour while it was impossibel with the conventional exercise shoes.

• Proceedings of the KIEE Conference
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• 2005.11b
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• pp.78-79
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• 2005

60 [Hz] 전자기장의 생체 영향은 오랜 연구가 있었지만 아직도 논란이 많은 분야이다. 본 연구에서는 인체 팬텀 모델을 사용하여 1-3[G]자계인가 시 유도 전류를 측정하였다. 또한 2차윈 다매질장의 실험모델을 제작하여 유도전류 측정하고 이를 해석해와 비교를 통해 정확도를 검토 하였다. 또한 인체 단면을 2차원 임피던스법을 이용하여 계산한 결과와 이의 팬텀 모델 제자 후 전류를 측정한 간과 비하였다. 마지막으로 인체를 실물에 가깝게 하기위해 3차원 다매질장의 모델로 모의하여 장기, 폐, 간, 실장, 뇌 등의 구성 요소에 각각의 전도도를 부여한 인체 팬텀 모델을 제작해 유도 전류를 측정하였다.

• Journal of Biomedical Engineering Research
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• v.15 no.4
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• pp.413-418
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• 1994

In electrical impedance tomography (EIT), we use boundary current and voltage measurements to provide the information about the cross-sectional distribution of electrical impedance or resistivity One of the major problems in EIT has been the inaccessibility of internal voltage or current data in finding the internal impedance values. We propose a new image reconstruction method using internal current density data measured by NMR. We obtained a two-dimensional current density distribution within a phantom by processing the real and imaginary MR images from a 4.7T NMR machine. We implemented a resistivity image reconstruction algorithm using the finite element method and sensitivity matrix. We presented computer simulation results of the image reconstruction algorithm and furture direction of the research.