• Journal of Microbiology and Biotechnology
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• 제18권1호
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• pp.145-152
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• 2008

A cell-based in vitro exposure system was developed to determine whether oxidative stress plays a role in the cytotoxic effects of volatile organic compounds (VOCs) such as benzene, toluene, xylene, and chlorobenzene, using human epithelial HeLa cells. Thin films based on cysteine-terminated synthetic oligopeptides were fabricated for immobilization of the HeLa cells on a gold (Au) substrate. In addition, an immobilized cell-based sensor was applied to the electrochemical detection of the VOCs. Layer formation and immobilization of the cells were investigated with surface plasmon resonance (SPR), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS). The adhered living cells were exposed to VOCs; this caused a change in the SPR angle and the VOC-specific electrochemical signal. In addition, VOC toxicity was found to correlate with the degree of nitric oxide (NO) generation and EIS. The primary reason for the marked increase in impedance was the change of aqueous electrolyte composition as a result of cell responses. The p53 and NF-${\kappa}B $ downregulation were closely related to the magnitude of growth inhibition associated with increasing concentrations of each VOC. Therefore, the proposed cell immobilization method, using a self-assembly technique and VOC-specific electrochemical signals, can be applied to construct a cell microarray for onsite VOC monitoring.

• 전기전자학회논문지
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• 제19권2호
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• pp.219-224
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• 2015

전기 임피던스 단층촬영 기법은 전극들을 통해 전류를 주입하고 이에 유기되는 전압을 측정한 후, 이들 데이터를 기반으로 내부의 도전율 분포를 영상으로 복원하는 방법이다. 이 논문에서는 기존의 Gauss-Newton 방법의 역행렬 항목의 차원을 도메인의 원소의 개수가 아닌 데이터의 개수의 차원으로 바꿔줌으로써, 관심 도메인 내부의 도전율 분포를 보다 빠르게 추정할 수 있는 방법을 제안하였다. 그리고 자코비안 행렬의 대각성분의 최소-최대를 이용하여 조정인자를 계산하는 방법을 함께 제안하였다. 몇 가지 시나리오를 설정하고 모의실험을 통해 제안한 방법의 복원 성능을 비교분석하였다.

• 한국통신학회논문지
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• 제38C권9호
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• pp.813-821
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• 2013

본 논문에서는 공진기의 임피던스 변화에 근거한 생체 신호 센서를 제안한다. 제안된 생체 신호 센서는 호흡과 심장 박동 같은 생체 신호를 감지할 수 있고, 시스템은 공진기, 발진기, SAW 필터, 그리고 파워 감지기로 구성되어있다. 인체와 같은 유전체의 주기적인 움직임은 근거리 장 영역 안에서 공진기의 임피던스 변화를 야기하며, 따라서 공진기의 공진 주파수의 변화는 발진기의 발진 주파수 변화에 영향을 끼친다. 여기서 SAW 필터 저지대역의 가파른 주파수 응답특성은 작은 양의 주파수 편차를 큰 변화로 바꿀 수 있다. 기존의 센서의 감지 거리를 확장시키는 것을 목적으로 ISM 대역 870 MHz 대역에서 동작 시켰으며, 최대 거리 120 mm에서 호흡과 심장 박동신호의 검출을 확인하였다.

• ETRI Journal
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• 제37권2호
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• pp.204-211
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• 2015

For this study, we designed an implantable rectangular spiral antenna for medical biotelemetry in the Medical Implant Communications Service band (402 MHz to 405 MHz). The designed antenna has a U-shaped loop for impedance matching. The antenna impedance is easily adjusted by controlling the shape and length of the U-shaped loop. Significant design parameters were studied to understand their effects on the antenna performance. To verify the potential of the antenna for the desired applications, we fabricated a prototype and measured its performance in terms of the resonant characteristics and gain radiation patterns of the antenna. In the testing phase, the prototype antenna was embedded in human skin tissue-emulating gel, which was developed to simulate a real operation environment. The measured resonant characteristics show good agreement with the simulations, and the -10 dB frequency band is within the range of 398 MHz to 420 MHz. The antenna exhibits a maximum gain of -22.26 dBi and an antenna efficiency of 0.215%.

• 대한전기학회논문지:전력기술부문A
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• 제52권7호
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• pp.421-428
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• 2003

After the cable is installed, many geometric factors, such as bowing types of the cable and the length difference of the cable between each minor section will cause the impedance unbalance between cables. The impedance unbalance will increase or decrease the sheath circulating currents, which are critical to human safety and sustaining the capabilities of electric power. Accordingly, in this paper, a new method is also proposed to reduce the sheath circulating currents and an reduction equipment according to the theory of the new method is developed. The reduction equipment is tested when the cable is on service. The test results show that it can reduce the sheath circulating currents by up to 97.8［%］. This confirms the validation of the new method and the reduction equipment, and assures the safe operation of the transmission cables. In order to illustrate the safe operation of the cable with new current reduction equipment at transient state due to lightning and single line-to-ground fault, extensive simulations have been made. Then the protection scheme of sheath circulating currents reduction equipment is proposed by adopting the new device of RDP(Reduction Device Protector).

• 대한의용생체공학회:의공학회지
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• 제28권2호
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• pp.280-286
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• 2007

The wearable sensor glove was developed using EDA sensors and conducting fabric. EDA(Electro-dermal Activity) signal is an electric response of human skin. There are SIL(Skin Impedance Level) and SIR(Skin Impedance Response) in EDA. SIL consists mostly of a DC component while SIR consists of an AC component. The relationship between drowsiness and the EDA signal is utilized. EDA sensors were made using a conducting fabric instead of AgCl electrodes, for a more suitable, more wearable device. The EDA signal acquisition module was made by connecting the EDA sensor gloves through conductive fabric lines. Also, the EDA signal acquisition module can be connected to a PC that shows the results of the EDA signal processing analysis and gives proper feedback to the user. This system can be used in various applications to detect drowsiness and prevent accidents from drowsiness for automobile drivers.

• International Journal of Fuzzy Logic and Intelligent Systems
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• 제3권2호
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• pp.244-250
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• 2003

In this paper, the relationship between a slave robot and the uncertain remote environment is modeled as the impedance to generate the virtual force to feed back to the operator. For the control of a tele-operated mobile robot equipped with camera, the tele-operated mobile robot take pictures of remote environment and sends the visual information back to the operator over the Internet. Because of the limitation of communication bandwidth and narrow view-angles of camera, it is not possible to watch the environment clearly, especially shadow and curved areas. To overcome this problem, the virtual force is generated according to both the distance between the obstacle and robot and the approaching velocity of the obstacle. This virtual force is transferred back to the master over the Internet and the master(two degrees of freedom joystick), which can generate force, enables a human operator to estimate the position of obstacle in the remote environment. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. This force reflection improves the performance of a tele-operated mobile robot significantly.

• 제어로봇시스템학회논문지
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• 제9권8호
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• pp.585-591
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• 2003

A virtual force is generated and fed back to the operator to make the teleoperation more reliable, which reflects the relationship between a slave robot and an uncertain remote environment as a form of an impedance. In general, for the teleoperation, the teleoperated mobile robot takes pictures of the remote environment and sends the visual information back to the operator over the Internet. Because of the limitations of communication bandwidth and narrow view-angles of camera, it is not possible to watch certain regions, for examples, the shadow and curved areas. To overcome this problem, a virtual force is generated according to both the distance between the obstacle and the robot and the approaching velocity of the obstacle w.r.t the collision vector based on the ultrasonic sensor data. This virtual force is transferred back to the master (two degrees of freedom joystick) over the Internet to enable a human operator to estimate the position of obstacle at the remote site. By holding this master, in spite of limited visual information, the operator can feel the spatial sense against the remote environment. It is demonstrated by experiments that this collision vector based haptic reflection improves the performance of teleoperated mobile robot significantly.

• 대한산업공학회지
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• 제39권4호
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• pp.253-259
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• 2013

Investment scenarios in the transportation network design problem usually contain installation or expansion of multi-mode transportation links. When one applies the mode choice analysis and traffic assignment sequentially for each investment scenario, it is possible that the travel impedance used in the mode choice analysis is different from the user equilibrium cost of the traffic assignment step. Therefore, to estimate the travel impedance and mode choice accurately, one needs to develop a combined model for the mode choice and traffic assignment. In this paper, we derive the inverse demand and the excess demand functions for the multi-mode multinomial logit mode choice function and develop a combined model for the multi-mode variable demand traffic assignment problem. Using data from the regional O/D and network data provided by the KTDB, we compared the performance of the partial linearization algorithm with the Frank-Wolfe algorithm applied to the excess demand model and with the sequential heuristic procedures.

• 인터넷정보학회논문지
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• 제17권2호
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• pp.59-65
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• 2016

색채 환경에 따라 인지반응의 상관관계를 분석한 결과가 다양한 산업분야에 적용되고 있다. 특히, 의학 분야에서 색채 환경기반 생체신호를 수집하여 환자 상태의 파악과 치료 그리고 뇌활동의 규명에 관련된 연구가 활발하게 진행되고 있다. 그러나 기존 연구들은 색채조명 또는 LED를 이용한 색채 환경을 구축하여 다양한 실험을 진행하고 있으나 다른 광원에 노출 되어 심리적인 영향을 주는 문제점을 갖고 있다. 따라서, 본 논문에서 제안하는 시스템은 HMD(Head-Mounted-Display)를 이용하여 피험자에게 완벽한 색채 환경조건을 제공하고자 한다. 그리고 인체반응정도 측정을 위해 기억력-주의력 테스트하는 동안 BMS(Bio-Medical-System)으로 생체정보를 수집하여 색채별 인체반응정도 측정뿐만 아니라 심리적인 변화에 대한 상관관계를 확인할 수 있는 시스템을 제안한다. 제안한 시스템을 통하여 수집하는 생체정보는 심전도(ECG), 호흡(Respiration), 산소포화도(SpO2), 임피던스(Bio-Impedance), 혈압(Blood-Pressure) 이며 데이터베이스에 저장한다. 이와함께, 인체의 인지반응을 측정하기위해 기억력-주의력 테스트는 앱으로 구현하여 색채 조건별 인지반응 정보를 측정하고 결과를 확인 할 수 있다. 제안한 시스템을 통하여 수집된 인체반응정보를 활용하여 생리학적 정보의 정량화하는 연구를 진행할 수 있으며, 색채 환경과 생리학적 정보의 상관관계를 분석하여 의학적 진단 및 치료에 응용이 될 것으로 기대한다. 향후 연구로 구축한 시스템을 통해 수집된 데이터를 분석 및 시각화 기능을 추가하고, 치매 질환의 예측 및 치료를 위한 시스템으로 확장하여 재활프로그램으로서의 유효성을 평가하고자 한다.