• KIEE International Transactions on Electrophysics and Applications
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• 제5C권6호
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• pp.257-263
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• 2005

WDM optical communication system requires wavelength division multiplexing, reverse multiplexing and optical filter. OADM is a device that can separate or combine specific wavelength of channel from the transmission line. This paper suggests OADM that uses 2 steps FBG based on MZI structure. The OADM that uses 2 steps FBG can minimize the system size and reduce the value of side lobe remarkably. The results obtained in this paper can be used for design and application of OADM that uses 2 steps FBG.

• 한국구조물진단유지관리공학회 논문집
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• 제18권1호
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• pp.138-149
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• 2014

본 연구에서는 불특정 분포하중에 대한 다경간 연속 보 구조물의 변형률 분포를 추정하는 기법을 제시하였다. 본 추정 기법은 해석적 방법이 아닌 계측한 변형률 데이터로부터 최소제곱법을 이용한 커브 피팅을 통해 변형률 분포를 추정하였다. 제시한 다경간 보 연속 구조물의 변형률 추정 기법은 멀티플렉싱이 가능한 FBG센서를 이용하여 다경간 연속 강재 보 정적 가력 실험을 통해 검증하였다. 실험을 통해서 분포 하중과 집중하중에 의한 변형률 분포의 추정 정확성 및 변형률 추정에 사용되는 계측점 수에 따른 추정 오차에 대한 검토를 수행하였다. 5.89 (하중 step1), 6.26% (하중 step2) 오차로 최대 변형률 지점에서의 변형률을 추정할 수 있었다. 추정을 위한 변형률 계측 센서 수를 감소시킨 경우 오차가 증가 (0.26~0.37%)하는 것 또한, 확인할 수 있었다. 회귀분석적 기법을 통해 다경간 보의 변형률 분포를 추정함으로써 특정 형상의 분포 하중에 대해서만 적용이 가능한 해석적 변형률 추정 기법의 한계를 넘어 불특정 분포 하중에 대한 변형률 분포 추정이 가능해졌고 추정 변형률 분포를 통해 최대변형률 발생 위치까지 확인할 수 있게 되었다.

• 한국한의학연구원논문집
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• 제13권3호
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• pp.105-110
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• 2007

This work reports the pulse diagnosis system using FBG sensors which can display pulse signals detected while oriental medical doctors are conducting pulse diagnoses and simultaneously pressing the sensors by three fingers. Each optical fiber has five FBG sensing units fabricated in 2 mm width and 2 mm inter-sensor spacing. Three optical fibers with the FBG units in the parallel line configuration are then placed on each finger-pressing region and thus overall 9 fibers are used for the pulse measurements on the so-called "chon", "gwan", and "ch대k". A fixture holding the optical fiber arrays is able to adjust the height of the FBG sensing units while placing the fibers on the wrist. The pulse signals detected by the FBG sensors from chon, kwan, and chuk have been analyzed using 4 channel spectrum analyzer connected to the optical fibers. The measured pulse signals exhibit variations due to the nonuniform pressure distributions applied. resulting in the differences in the detected pulse signals between fiber lines. However. this work is the first step towards objective and quantitative analyses of the pulse diagnosis in oriental medicine which has traditionally been performed on subjective basis. Future works will be devoted to improving sensor stability, developing the way applying pressure and algorithms reporting the objective classification of the pulse status from systemic measurements using the sensors instead of relying on the clinicians' diagnoses subjectively performed. A successful pulse diagnosis system emerging in the future is expected to contribute to education as well as promoting pulse diagnosis in oriental medicine to the scientific research area.

• 한국지반공학회논문집
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• 제27권6호
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• pp.17-26
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• 2011

그라운드 앵커공법은 현재 우리나라에서 가장 일반적으로 사용되는 사면보강공법들 중 하나이다. 그러므로 앵커로 보강된 사면의 안정성을 장기간 확인하기 위해서는 그라운드 앵커의 긴장력을 측정하는 것이 매우 중요하다. 그러나 전통적인 로드 셀 방식의 측정기술을 제외하고는 특별한 기술이 개발된 것이 없다. 본 논문에서는 지반구조물의 보강을 위해 널리 사용되는 그라운드 앵커의 단기 및 장기 장력을 측정하기 위해 기존에 현장에서 주로 사용되는 스트레인게이지 또는 V/W 타입 로드 셀을 대체할 수 있는 새로운 방법에 대하여 기술하였다. 사용된 센서는 스트레인게이지 또는 V/W타입의 센서에 비해 크기가 작고 내구성이 우수하며 전자기파에 의한 노이즈 발생이 없는 광섬유 브래그격자(Fiber Bragg Grating ; FBG)센서이다. FBG 센서를 내장한 7연 강연선을 이용하여 원하는 위치에서 변형률 감지가 가능한 인장형 앵커를 제작하고 앵커 정착장을 연암과 화강풍화토 지반조건에 각각 2세트(set)씩 시공하여 현장인발실험을 수행하였다. 재하-제하단계를 포함하는 전 하중단계에서 FBG센서로 측정된 변형률로부터 장력 모니터링을 수행하였고 기존 로드 셀로 측정된 결과와 비교하였다. 현장 인발실험 결과, 제안된 광섬유 센서를 이용한 그라운드 앵커의 시공 중 긴장력 측정결과 실내 UTM 결과와 달리 약간의 차이가 있으나 실용적인 차원에서는 충분히 활용 가능한 것으로 확인되었다.

• Smart Structures and Systems
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• 제21권5호
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• pp.687-694
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• 2018

The problem of wheel tread defects has become a major challenge for the health management of high-speed rail as a wheel defect with small radius deviation may suffice to give rise to severe damage on both the train bogie components and the track structure when a train runs at high speeds. It is thus highly desirable to detect the defects soon after their occurrences and then conduct wheel turning for the defective wheelsets. Online wheel condition monitoring using wheel impact load detector (WILD) can be an effective solution, since it can assess the wheel condition and detect potential defects during train passage. This study aims to develop an FBG-based track-side wheel condition monitoring method for the detection of wheel tread defects. The track-side sensing system uses two FBG strain gauge arrays mounted on the rail foot, measuring the dynamic strains of the paired rails excited by passing wheelsets. Each FBG array has a length of about 3 m, slightly longer than the wheel circumference to ensure a full coverage for the detection of any potential defect on the tread. A defect detection algorithm is developed for using the online-monitored rail responses to identify the potential wheel tread defects. This algorithm consists of three steps: 1) strain data pre-processing by using a data smoothing technique to remove the trends; 2) diagnosis of novel responses by outlier analysis for the normalized data; and 3) local defect identification by a refined analysis on the novel responses extracted in Step 2. To verify the proposed method, a field test was conducted using a test train incorporating defective wheels. The train ran at different speeds on an instrumented track with the purpose of wheel condition monitoring. By using the proposed method to process the monitoring data, all the defects were identified and the results agreed well with those from the static inspection of the wheelsets in the depot. A comparison is also drawn for the detection accuracy under different running speeds of the test train, and the results show that the proposed method can achieve a satisfactory accuracy in wheel defect detection when the train runs at a speed higher than 30 kph. Some minor defects with a depth of 0.05 mm~0.06 mm are also successfully detected.

• 보건교육건강증진학회지
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• 제32권5호
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• pp.73-81
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• 2015

Objectives: We tried to confirm physical activity of 1,000 Kcal per week was a meaningful point in controlling coronary artery disease risks in female older adults. Methods: Participants were 66 female older adults recruited from senior welfare center. Participants were provided with accelerometer (e-step, Kenz, Japan) for measuring daily energy expenditure. Graded exercise test was done for measuring aerobic fitness. Blood glucose and lipid were analyzed. Framingham risk score was calculated based on blood glucose, blood lipid, and smoking. These variables were compared between the group expended more than 1,000 Kcal/week and the group with energy expenditure below 1,000 Kcal/week. Results: The group expended over 1,000kcal/week showed to be superior to the counterpart group in following variables; AC(Abdominal Circumference), %BF, $HR_{rest}$(resting heart rate), $VO_{2peak}$, FBG, LDL-C, TG, BDI-II, QOL, AR(Absolute Risk), RR(Relative Risk). Conclusions: The group expended over 1,000 Kcal/week was likely to have less probability in CAD than group expended less than 1,000 Kcal/week. The result of this study suggests the important role of active daily life that can be replaced with that of regular exercise especially for those who are not available to do structured exercise.