• 대한수학회논문집
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• 제16권3호
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• pp.459-485
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• 2001

The aim of EIT (electrical impedance tomography) system is to image cross-section conductivity distribution of a human body by means of both generating and sensing electrodes attached on to the surface of the body, where currents are injected and voltages are measured. EIT has been suffered from the severe ill-posedness which is caused by the inherent low sensitivity of boundary measurements to any changes of internal tissue conductivity values. With a limited set of current-to-voltage data, figuring out full structure of the conductivity distribution could be extremely difficult at present time, so it could be worthwhile to extract some necessary partial information of the internal conductivity. We try to extract some key patterns of current-to-voltage data that furnish some core information on the conductivity distribution such s location and size. This overview provides our recent observation on the location search and the size estimation.

• 대한의용생체공학회:의공학회지
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• 제33권1호
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• pp.39-46
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• 2012

Electrical impedance tomography(EIT) can produce functional images with conductivity distributions associated with physiological events such as cardiac and respiratory cycles. EIT has been proposed as a clinical imaging tool for the detection of stroke and breast cancer, pulmonary function monitoring, cardiac imaging and other clinical applications. However EIT still suffers from technical challenges such as the electrode interface, hardware limitations, lack of animal or human trials, and interpretation of conductivity variations in reconstructed images. We improved the KHU Mark2 EIT system by introducing an EIT electrode interface consisting of nano-web fabric electrodes and by adding a synchronized biosignal measurement system for gated conductivity imaging. ECG and respiration signals are collected to analyze the relationship between the changes in conductivity images and cardiac activity or respiration. The biosignal measurement system provides a trigger to the EIT system to commence imaging and the EIT system produces an output trigger. This EIT acquisition time trigger signal will also allow us to operate the EIT system synchronously with other clinical devices. This type of biosignal gated conductivity imaging enables capture of fast cardiac events and may also improve images and the signal-to-noise ratio (SNR) by using signal averaging methods at the same point in cardiac or respiration cycles. As an example we monitored the beat by beat cardiac-related change of conductivity in the EIT images obtained at a common state over multiple respiration cycles. We showed that the gated conductivity imaging method reveals cardiac perfusion changes in the heart region of the EIT images on a canine animal model. These changes appear to have the expected timing relationship to the ECG and ventilator settings that were used to control respiration. As EIT is radiation free and displays high timing resolution its ability to reveal perfusion changes may be of use in intensive care units for continuous monitoring of cardiopulmonary function.

• 대한기계학회논문집A
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• 제31권3호
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• pp.285-294
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• 2007

Previously, ASCI(Automation System for Curtain-wall Installation) which combined with a multi-DOF manipulator to a mini-excavator was developed and applied on construction site. As result, the operation by one operator and more intuitive operation method are proposed to improve ASCI's operation method which need one person with a remote joystick and another operating an excavator. The human-robot cooperative system can cope with various and untypical constructing environment through the real-time interacting with a human, robot and constructing environment simultaneously. The physical power of a robot system helps a human to handle heavy construction materials with relatively scaled-down load. Also, a human can feel and response the force reflected from robot end effecter acting with working environment. This paper presents the feasibility study regarding the application of the proposed human-robot cooperation control for construction robot through experiments on a 2DOF manipulator.

• 한국전기전자재료학회논문지
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• 제30권6호
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• pp.366-371
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• 2017

In this paper, we introduce an electrocardiogram (ECG) system designed to solve problems caused by wetgels and motion artifacts in measuring active movement. The system is called a dry-contact ECG and was designed by considering impedance matching between skin and electrode as well as the frictional electricity between electrode and clothes. In order to create the system, we measured impedance on the skin-electrode interface, and the result was applied to the electronic circuit scheme. Moreover, we added an electrode on the back of the measurement electrode to make a flow path to ground the electrical noise. The final ECG circuit and novel electrode were used to detect real human cardiac signals from a subject who was tested while standing still and walking. The signals obtained from the two activities were nicely shaped, without any motion artifact noise. We took electrode size into account in this study because the impedance depended on the area of the electrode. An electrode of 50 mm diameter showed the best curve for the ECG signal without any electrical noise.

• 대한의용생체공학회:의공학회지
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• 제29권6호
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• pp.436-442
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• 2008

Magnetic resonance electrical impedance tomography(MREIT) has been suggested to produce cross-sectional conductivity images of an electrically conducting object such as the human body. In most previous studies, recessed electrodes have been used to inject imaging currents into the object. An MRI scanner was used to capture induced magnetic flux density data inside the object and a conductivity image reconstruction algorithm was applied to the data. This paper reports the performance of a thin and flexible carbon-hydrogel electrode that replaces the bulky and rigid recessed electrode in previous studies. The new carbon-hydrogel electrode produces a negligible amount of artifacts in MR and conductivity images and significantly simplifies the experimental procedure. We can fabricate the electrode in different shapes and sizes. Adding a layer of conductive adhesive, we can easily attach the electrode on an irregular surface with an excellent contact. Using a pair of carbon-hydrogel electrodes with a large contact area, we may inject an imaging current with increased amplitude primarily due to a reduced average current density underneath the electrodes. Before we apply the new electrode to a human subject, we evaluated its performance by conducting MREIT imaging experiments of five swine legs. Reconstructed conductivity images of the swine legs show a good contrast among different muscles and bones. We suggest a future study of human experiments using the carbon-hydrogel electrode following the guideline proposed in this paper.

• Clinical and Experimental Pediatrics
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• 제48권7호
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• pp.696-700
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• 2005

목 적 : 소아 체지방 평가에 있어 여러 가지 방법 중 BIA를 이용한 체성분 분석은 비침습적이고, 경제적이며, 방사선 노출의 위험이 없이 검사가 용이해 반복 시행할 수 있다는 장점이 있는 반면 검사 결과의 정확성에 대해 확인해 볼 필요가 있다. 이에 BIA 및 이중 DEXA에 의한 측정치들을 비교하여 BIA의 타당성을 알아보고자 하였다. 방 법 : 2003년 7월에서 10월까지 4개월 동안 부산대학교병원 소아과 방문하였던 소아 100명(남아 58명, 여아 42명)을 연구대상으로 하여 연구 대상자들에 대하여 각각 신장, 체중, 피부두께를 측정하였으며, BIA 및 DEXA법을 이용하여 체성분(체지방량, 제지방량, 제지방률, 체수분량)을 분석하였다. 결 과 : BIA와 DEXA법을 통한 검사상 FBM, LBM, %BF의 상관관계는 남녀 모두에서 통계학적으로 의미있는 양의 상관관계를 보였으며, 통계학적으로 의미가 있었다(P<0.001). 특히 FBM에서 남녀 모두 상관 계수가 높았다. 결 론 : 소아 비만의 평가에 있어 BIA를 통한 체성분 분석은 장치가 간단하고 특별한 기술을 필요로 하지 않으며, 비침습적이면서 경제적일 뿐 아니라 측정치가 객관적이고 정확한 것으로 분석되었다.

• 한국전자통신학회논문지
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• 제12권4호
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• pp.539-544
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• 2017

본 논문에서는 휴먼 카운팅 시스템을 위한 광대역 패치 안테나가 공기 유전체 층을 이용하여 설계, 제작 및 측정되었다. 제안된 안테나는 5 mm의 공기 유전체 위에 정사각형 구조의 패치 구조를 가지며, CPW 전송선로 구조의 입력부와 패치면의 수직 연결은 계단형 임피던스 구조로 구현하였다. 3차원 EM 설계를 통해 최적화된 광대역 패치 안테나는 16.6 * 16.6 * 5.0 mm3의 크기로 3D 프린터를 이용하여 안테나 지그를 제작하여 지그 위에 제작되었다. 제작된 안테나는 7.2 ~ 9.8 GHz 주파수에서 2:1 이하의 VSWR과 5.71 dBi의 최대 이득을 가지며, $70^{\circ}$의 반전력 빔폭 특성을 나타내었다.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2014년도 추계학술대회
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• pp.484-487
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• 2014

본 논문에서는 근거리에서 심박동, 호흡, 맥박 등 인체 신호를 효율적으로 검출할 수 있는 소출력 안테나 특성에 대하여 분석하였다. 이러한 환경에서 안테나는 펄스 신호를 사용하므로 광대역에서 임피던스가 주파수에 안정적인 특성이 요구된다. 이러한 요구 특성은 이득과 trade-off 관계가 있으나 본 논문에서는 근거리에서 사용하므로 방향성 및 이득을 높이기 위한 어레이 형태는 고려하지 않았다. 일반적으로 이러한 요구 사항을 만족하는 안테나는 주파수 독립(Frequency Independent) 안테나로 분류된다. 스파이럴(spiral), 시뉴어스(sinuous), 대수 주기(log-periodic) 안테나 등이 해당되며 소형으로 구현될 수 있다. 본 논문에서는 중심 주파수가 5 GHz인 UWB 펄스 트랜시버에 원형 패치 안테나와 시뉴어스 안테나를 접속하고 시험한 결과를 분석해서 기술하였다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.106-109
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• 2000

The virtual reality - haptic device is developed for the purpose used in the work that human cannot approach and that need elaborate exercises. To render haptic, the total system is constituted master, haptic device, and slave, remote manipulator. Human operates the remote manipulator. Human operates the remote manipulator relying on the hapti devices and stereo graphic. And then the force and scene of the remote manipulator is fed-back from each haptic devices and virtual devices. The feedback information gets system gain exactly. The system gain provides the most exact haptic and virtual devices. The feedback information gets system gain exactly. The system gain provides the most exact haptic and scene to human by the location, the graphic rendering and the haptic rendering algorithm on real-time. In this research, 3D haptic device is developed for common usage and make human feel the haptic when human contacts virtual object rendered by computer graphic. The haptic device is good for tracing location and producing devices because of the row structure. Also, openGL and Visual Basic is utilized to the algorithms for haptic rendering. The haptic device of this research makes the interface possible not only with virtual reality but also with the real remote manipulator.

• 한국안전학회지
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• 제32권1호
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• pp.33-40
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• 2017

This paper addresses the assessment methods used to evaluate the magnetic exposure of a human to ELF EMF (Extremely Low Frequency Electromagnetic Field) which is caused by the process of power delivery from 60 Hz commercial power. These days the main concern is primarily focused on the magnetic field. For the exposure assessment, both numerical studies and laboratory experiments were studied and the results of the two compared for methodological suitability. The numerical analyses employ the Impedance Method (IM), Boundary Element Method (BEM), and Finite Element Method (FEM) and the laboratory experiments used various human phantom models made with conductivities congruent to human organs and then exposed to uniform/non-uniform magnetic fields to produce eddy currents. Under these conditions a number of examples have been evaluated and the reliability assessed to present the pros and cons of each methodology.