• 한국해안·해양공학회논문집
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• 제23권1호
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• pp.26-33
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• 2011

본 연구에서는 항만구조물의 구조건전성 모니터링을 위한 Imote2 센서 플랫폼 기반의 고민감도 스마트 무선센서를 개발하였다. 이를 위해 첫째, 고성능 Imote2 센서 플랫폼을 기반으로 하고, 고민감도 MEMS 가속도계를 탑재한 스마트 무선센서를 설계하였다. 둘째, 스마트 무선센서가 독자적으로 모니터링을 수행할 수 있도록 하는 내장 소프트웨어를 설계하였다. 마지막으로, 개발된 스마트 무선센서의 성능을 모형 케이슨 구조물에서의 실험을 통해 검증하였다.

• 한국정밀공학회지
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• 제16권1호통권94호
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• pp.108-115
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• 1999

Since grinding is a more complicated process than any other machining process, it is hard for operators to setup a grinding machine properly and to find out correctly abnormal grinding states resulting in damages to products. Abnormalities would be caused by improper setup, improper dressing/grinding conditions which are likely to be occurred without skilled operators' attention. In this study, an AE monitoring unit is developed to help operators conduct with ease setup, and set properly dressing/grinding conditions. AErms(root-mean-square) signal being monitored, on-going process states during grinding and dressing is visualized for machine operators to judge whether the processes are in good condition. Evaluation tests are carried out on centerless grinding machines-both cylindrical and internal. The developed AE monitoring system is verified to be useful to check grinding/dressing states in process even in the centerless grinding of which process is most unknown among various grinding methods because of the complex structure.

• 한국정보통신학회논문지
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• 제20권1호
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• pp.200-206
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• 2016

수배전반 전기사고 사전 예방을 위해 전기 관리자가 시간과 장소에 구애받지 않고 전력설비의 상태를 실시간으로 감시할 수 있는 시스템 개발이 필요하다. 본 논문에서는 사물인터넷 기반 수배전반 상태 모니터링 시스템을 제안한다. 제안된 시스템은 기존 수배전반 및 제어반 등에 설치하여 수배전반 및 제어반의 상태정보와 제어정보를 인터넷망과 연결된 클라우드 서버와 근거리 무선통신망으로 실시간 전송된다. 관리자는 관리자 단말기를 통해 언제, 어디서나 상태정보 모니터링을 신속하고 용이하게 관리할 수 있으며, 수배전반 상태정보의 성능평가 결과 판정기준 ${\pm}5%$ 이내 오차범위 내의 측정결과를 얻었다.

• Earthquakes and Structures
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• 제12권6호
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• pp.673-687
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• 2017

A three-dimensional; structural health monitoring; vertical; planar; cross-sample entropy; multiscaleA three-dimensional structural health monitoring (SHM) system based on multiscale entropy (MSE) and multiscale cross-sample entropy (MSCE) is proposed in this paper. The damage condition of a structure is rapidly screened through MSE analysis by measuring the ambient vibration signal on the roof of the structure. Subsequently, the vertical damage location is evaluated by analyzing individual signals on different floors through vertical MSCE analysis. The results are quantified using the vertical damage index (DI). Planar MSCE analysis is applied to detect the damage orientation of damaged floors by analyzing the biaxial signals in four directions on each damaged floor. The results are physically quantified using the planar DI. With progressive vertical and planar analysis methods, the damaged floors and damage locations can be accurately and efficiently diagnosed. To demonstrate the performance of the proposed system, performance evaluation was conducted on a three-dimensional seven-story steel structure. According to the results, the damage condition and elevation were reliably detected. Moreover, the damage location was efficiently quantified by the DI. Average accuracy rates of 93% (vertical) and 91% (planar) were achieved through the proposed DI method. A reference measurement of the current stage can initially launch the SHM system; therefore, structural damage can be reliably detected after major earthquakes.

• Smart Structures and Systems
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• 제13권6호
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• pp.943-957
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• 2014

When subjected to fatigue loading, the main failure mode of partially prestressed concrete (PPC) structure is the fatigue fracture of tensile reinforcement. Therefore, monitoring and evaluation of the steel stresses/strains in the structure are essential issues for structural design and healthy assessment. The current study experimentally investigates the possibility of using fiber Bragg grating (FBG) sensors to measure the steel strains in PPC beams in the process of fatigue loading. Six full-scale post-tensioned PPC beams were exposed to fatigue loading. Within the beams, the FBG and resistance strain gauge (RSG) sensors were independently bonded onto the surface of tensile reinforcements. A good agreement was found between the recorded results from the two different sensors. Moreover, FBG sensors show relatively good resistance to fatigue loading compared with RSG sensors, indicating that FBG sensors possess the capability for long-term health monitoring of the tensile reinforcement in PPC structures. Apart from the above findings, it can also be found that during the fatigue loading, there is stress redistribution between prestressed and non-prestressed reinforcements, and the residual strain emerges in the non-prestressed reinforcement. This phenomenon can bring about an increase of the steel stress in the non-prestressed reinforcement.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2015년도 춘계학술대회
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• pp.116-119
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• 2015

다수의 이동센서노드를 이용한 환경감시 알고리즘을 제안한다. 제안하는 알고리즘은 사전 정보가 없는 개활 지역에서 이동센서노드들을 배치하여 센싱 커버리지를 최대화 하는 것을 목적으로 한다. 이동센서노드는 보다 높은 센싱 커버리지를 획득하기 위하여 최대의 센싱 커버리지를 획득할 때 까지 반복적으로 재배치된다. 커버리지 최대화를 위하여 ILP(Integer Linear Programming) 기반의 최적화 문제를 구성한다. 시뮬레이션 결과에 의하면 제안된 알고리즘은 이동센서노드들을 보다 높은 관심지역으로 이동시킬 수 있으며 최대의 센싱 커버리지 획득이 가능함을 시뮬레이션을 통하여 검증한다.

• 한국소음진동공학회논문집
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• 제14권2호
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• pp.119-127
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• 2004

Butterfly valves are popularly used in service in the industrial and water works pipeline systems with large diameter because of its lightweight, simple structure and the rapidity of its manipulation. Sometimes cavitation can occur. resulting in noise, vibration and rapid deterioration of the valve trim, and do not allow further operation. Thus, the monitoring of cavitation is of economic interest and is very importance in industry. This paper proposes a condition monitoring scheme using statistical feature evaluation and support vector machine (SVM) to detect the cavitation conditions of butterfly valve which used as a flow control valve at the pumping stations. The stationary features of vibration signals are extracted from statistical moments. The SVMs are trained, and then classify normal and cavitation conditions of control valves. The SVMs with the reorganized feature vectors can distinguish the class of the untrained and untested data. The classification validity of this method is examined by various signals that are acquired from butterfly valves in the pumping stations and compared the classification success rate with those of self-organizing feature map neural network.

• 환경영향평가
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• 제19권6호
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• pp.617-623
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• 2010

It is the most important subject to figure out characteristics of the wastewater inflows of sewerage treatment plant(STP) when situation models are applied to operation of the biological processes and in the automatic control based on ICA(Instrument, Control and Automation). For the purposes, real-time influent monitoring method has been applied by using on-line monitoring equipments for the process optimization in conventional STP. Since, the influent of STP is consist of complex components such as, COD, BOD, TN, $NH_4$-N, $NO_3$-N, TP and $PO_4$-P. MRA2(Microbial Respiration Analyzer 2), which is capable of real-time analyzing of wastewater characteristics is used to overcome the limitations and defects of conventional online monitoring equipments in this study. Rapidity, accuracy and stability of developed MRA2 are evaluated and compared with the results from on-line monitoring equipments for seven months after installation in Full-scale STP.

• 한국임상수의학회지
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• 제27권4호
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• pp.392-396
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• 2010

Blood glucose curves in the management for diabetic patients have several limitations including intermittent assessment of blood glucose concentration, hospitalization, patient restraint, and repeated phlebotomy. The aim of this study was to apply and evaluate a wireless continuous glucose monitoring system (CGMS) in healthy dogs. Subcutaneous interstitial glucose concentrations in 7 dogs were continuously monitored and recorded by wireless CGMS. During induced hyperglycemia, the interstitial glucose concentrations were compared with whole blood glucose concentrations measured by glucometer and serum glucose concentrations measured by automated chemistry analyzer, respectively. There were no significant differences among interstitial, whole blood and serum glucose concentrations. The interstitial glucose concentrations had a good correlation to serum glucose concentrations. The real-time wireless CGMS is a valuable tool for monitoring system of glucose concentrations in dogs. Use of the CGMS for diabetic patients will provide accurate information over traditional blood glucose curves.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2009년도 춘계 학술발표회
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• pp.38-47
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• 2009

Scour means the erosion of bed material by flow change when a bridge is constructed in a stream. Scour is one of the critical factors of a bridge failure. There are several methods for the monitoring of scour near bridge foundations; Sounding rods, Magnetic sliding collar System, Sonar system, underwater camera system and so on. In general, Sonar system is preferred due to its convenience and good accuracy. In this study, the new scour monitoring system was developed using profiling sonar sensor. The new system can measure a line profile of a seabed and has small size due to the effectively designed data logger. The performance of the new scour monitoring system was evaluated at a bridge pier in tidal environment. The measured local scour depths were discussed with the result of the empirical formulas; CSU, Froehlich, Laursen and Neill.