• Computers and Concrete
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• v.8 no.2
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• pp.229-241
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• 2011

In this work, cement paste samples with 1% (by cement mass) of a conductive carbon fiber admixture have been studied under uniaxial compression. Three different arrangements were used to measure the resistivity of the samples. According to the results obtained, the resistance should be measured using the four wire method in order to obtain good sensitivity and repeatability. The effect of the load value and the load rate on the fractional change of the volume resistivity has been determined. It has been observed that the gage factor (fractional change in resistance respect to strain) increases when the maximum load is increased, and the loading rate does not affect significantly this parameter. The effect of the sample ambient humidity on the material piezoresistivity has also been studied, showing that the response of the composite is highly affected by this parameter.

• Proceedings of the Optical Society of Korea Conference
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• 2009.02a
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• pp.303-303
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• 2009

• Proceedings of the Optical Society of Korea Conference
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• 2002.07a
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• pp.58-59
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• 2002

광섬유 격자(Fiber Bragg Grating)는 광통신 및 센서 분야에 매우 유용하다. 이를 이용한 센서는 온도, 스트레인 등을 측정 할 수 있어, 토목, 건설 및 항공분야에 지능형 구조물에 응용하고 있다. 본 논문에서는 이러한 광섬유 격자의 스트레인에 의한 응답특성을 이용한 동적 시스템을 구성하였으며, 광섬유격자에 하중을 인가하여 따른 응답 특성을 측정 분석하였다. (중략)

• Proceedings of the Korean Fiber Society Conference
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• 2003.10a
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• pp.23-24
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• 2003

We synthesized a poly[2-(2'-hydroxyphenyl) benzoxazole] under the two step procedures of Suzuki coupling polymerization with corresponding monomers followed by the deprotection of benzyl group. The polymer in DMF solution is applicable to colorimetric sensing fluoride anion, which shows a color change from colorless to yellow. High sensitivity to fluoride anion compared to other anions such as phosphate, chloride, and sulfate is ascribed to the high coordination ability of the 2-(2'-hydroxy phenyl)benzoxazole moiety in the polymer chain. Emission shift by metal cations, which can be applied to fluorescent sensing w as also observed in the polymer solution.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.3
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• pp.130-138
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• 2002

수압실험 동안 광섬유 브래그 격자(FBG) 센서를 이용하여 필라멘트 와인딩된 복합재료 탱크의 변형률을 모니터링하였다. 20개의 FBG 센서와 20개의 스트레인 게이지를 복합재료 탱크의 돔과 실린더 부분에 부착하였다. 광섬유 센서를 위한 고출력 광원으로는 파장 이동 광섬유 레이저(WSFL)을 이용하였다. 실험결과로부터, 많은 수의 센서를 필요로 하는 대형 구조물의 건전성 모니터링에 FBG 센서 시스템이 유용함을 확인할 수 있었다.

• 한국신재생에너지학회:학술대회논문집
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• 2007.06a
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• pp.635-638
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• 2007

In this paper, we described the fundamental concepts of proposed structural health monitoring system for Uldolmok Tidal Current Power Plant focusing on the use of smart sensors including fiber bragg grating sensors and macro fiber composite sensors. The structural health monitoring system can play an important role to maintain the structural safety for offshore structures like as bridges and high-rise buildings. In the case of tidal current power plant, the monitoring system is much more important since the structures are usually constructed at the site with severer environmental loadings such as high current speed.

• Structural Monitoring and Maintenance
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• v.5 no.1
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• pp.129-150
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• 2018

This paper presents the structural performance monitoring of an urban footbridge located in Hangzhou, China. The structural health monitoring (SHM) system is designed and implemented for the footbridge to monitor the structural responses of the footbridge and to ensure the structural safety during the period of operation. The monitoring data of stress and displacement measured by the fiber Bragg grating (FBG)-based sensors installed at the critical locations are used to analyze and assess the operation performance of the footbridge. A linear regression method is applied to separate the temperature effect from the stress monitoring data measured by the FBG-based strain sensors. In addition, the static vertical displacement of the footbridge measured by the FBG-based hydrostatic level gauges are presented and compared with the dynamic displacement remotely measured by a machine vision-based measurement system. Based on the examination of the monitored stress and displacement data, the structural safety evaluation is executed in combination with the defined condition index.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.1081-1085
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• 2008

To measure the curvature, in this paper, we investigate an optical curvature sensor based on the fiber Bragg gratings. We observed the variation of the Bragg resonant wavelength shift to measure the curvature change. From the experimental results, we knew that the Brags resonant wavelength shift was lineally increased with the increase of the curvature from $0\;m^{-1}$ to $10\;m^{-1}$. It's slope is about $8.8\;pm/m^{-1}$. On the other hand, the spectral reflection decreased with the increase of the curvature.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.105.4-105
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• 2001

This paper describes a newly designed multipoint process monitoring system based on a NIR acousto-optic tunable filter. The NIR multipoint process monitoring system consists of a NIR AOTF device for wavelength selection, an InGaAs array sensor, and a specially designed iin-line type of optical fiber probe. Unlike a FTS(Fourier Transform Spectrometry) or grating based monitoring system, an AOTF has no moving parts, and it can be rapidly tuned to any wavelength in its operating range within microseconds. Thus, the AOTF is advantageous in terms of faster spectral imaging capability and rigidity required for industrial monitoring environment. In the current feasibility evaluation, an enhanced optical fiber probe with 3 monitoring points was used. However, ...

• Journal of Institute of Control, Robotics and Systems
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• v.13 no.3
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• pp.210-217
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• 2007

The theoretical formulations are derived for calculating optical power change for intensity modulated fiber optical microphone. The optical power change is due to optical paths, misalignment and geometry of optical coupler. Based on the theoretical equations, three different optical couplers are simulated with respect to several angles of optical couplers. In order to evaluate the formulation, a multi-mode to multi-mode coupler which is one of abovementioned optical couplers is designed and characterized by carving out both static experiments and dynamic experiments. Considering experimental results, this paper conclude that the theoretical formulations is very useful for design optical coupler and this kind of fiber optic sensor is adequate to microphone.