• KSCE Journal of Civil and Environmental Engineering Research
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• v.42 no.3
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• pp.311-322
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• 2022

This study performed 4-point flexural tests of reinforced concrete to which was attached a distributed optical fiber sheet and carbon fiber reinforced polymer (CFRP) sheets in order to assess the effect of the CFRP sheets and the applicability of a BOTDR sensor simultaneously. To evaluate the reinforcing effect, various degrees of CFRP sheet attachment were manufactured, and to evaluate the sensing ability, strains obtained from a BOTDR sensor were compared with strains measured from electric resistance strain gauges that were attached to the concrete surface. From the results, the reinforcing effects were evidently different according to the attachment type of the CFRP sheets, and it was confirmed that the main influencing factor on the reinforcing effect was the type of attachment rather than the attachment area. The reinforced concrete structural behavior was visualized with strains measured from the BOTDR sensor as load increased, and it was identified that load was concentrated in the CFRP reinforced area. Strains from the BOTDR sensor were similar to those from the electric resistance strain gauge; thereby a BOTDR sensor can be effective in the analysis of structural behaviorsof massive infrastructure. Finally, the strain from a BOTDR sensor was high where CFRP sheet fall-off occurs, and it would therefore be efficient to track local damage locations of CFRP sheets by utilizing a BOTDR sensor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.04a
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• pp.215-215
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• 2014

현재 가장 많이 사용되고 있는 스프링식 안전밸브는 스프링과 설정치 드리프트, 누설 취약성, 채터링에 의한 시트 파손등의 문제점을 지니고 있다. 안전밸브 디스크에서 발생하는 유체 누설은 안전밸브 설정압력 개방에 영향을 주며, 시트(Seat)면의 이물질 삽입, 균열 및 유체에 의한 침식(Erosion) 등에 의해 밸브 핵심 부품이 쉽게 손상되어 기기 성능 저하를 초래하게 된다. 따라서 유체 누설을 조기에 탐지하고 정량화하여 해당 기기의 상태정보 제공을 통한 누설 감지 기법 연구가 요구된다. 원자력 발전소의 경우 밸브에서 유체가 누설되면 밸브의 오작동 및 운전 안정성 저해 요인이 된다. 따라서 본 연구에서는 음향방출법을 이용하여 안전밸브의 유체 누설을 평가하고, 안전밸브의 음향신호 측정 위치 선정 및 누설량에 따른 음향신호를 분석하고자 한다.

• Journal of the Korean Magnetics Society
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• v.23 no.3
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• pp.83-88
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• 2013

The soft magnetic Fe-Si-Cr flakes with the thickness of about 1 ${\mu}m$ were annealed at 500 and $700^{\circ}C$ for 1 h, and the composite sheets for electromagnetic wave noise absorber available for quasi-microwave band were fabricated by using these annealed flakes and polymer. Further the power loss characteristics of the composite sheets was investigated to clarify the annealing effect on electromagnetic wave absorption properties. The power loss decreased in the frequency range of several GHz when the annealed flakes were used as compared to the sheet using the as-milled FeSiCr alloy flakes. Moreover the sheets using annealed flakes exhibited lower value of real and imaginary part of complex permeability. These inferior electromagnetic wave absorption properties of the composite sheets using annealed alloy flakes were considered to be obtained by the enhanced eddy current effect upon annealing-induced recovery of microstructure and resulted low complex permeability.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.1
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• pp.130-140
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• 2007

Fiber-sheet and steel-plate strengthening methods have been mainly used for strengthening the RC structures. However, recently the application of these two methods have dramatically decreased due to premature debonding failure between concrete surface and fiber-sheet and heavy self-weight of steel-plate. This article presents experimental results of shear behavior in RC beams strengthened with GSP(Glass fiber-Steel composite Plate). The thin steel plate in GSP makes usage of the anchoring system possible, which could delay or prevent the premature debonding failure. Three reference beams and 60 strengthened beams with GSP were tested. The experimental results showed that strengthened beams with GSP considerably increased in shear capacity compared with the reference beams.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.125-126
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• 2012

• Journal of the Korean Society for Nondestructive Testing
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• v.23 no.2
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• pp.133-139
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• 2003

In order to extend the life time of building and civil infra-structure, nowadays, patch type fibrous composite materials are widely used. Repaired concrete columns and beams gain the stiffness and strength, but they lose toughness and show brittle failure. Usually, the cracks of concrete structures are visible with naked eyes and the status of the structure in the life cycle is estimated with visible inspection. After repairing of the structure, crack visibility is blocked by repaired carbon sheets. Therefore, structural monitoring after repairing is indispensible and self diagnosis method with optical fiber sensor is very useful. In this paper, peel-out effects is detected with optical fiber sensors and the strain difference between main structure and repaired carbon sheets when they separate each other.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2021.10a
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• pp.208-210
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• 2021

As the number of objects connected to the Internet increases rapidly, intelligent device development projects are gradually expanding that provide direct value to humans, away from simple monitoring functions, including sensors and communication functions, or delivery to servers.It is expected that the device will develop a technology that analyzes surrounding sensing information and changes the surrounding environment in consideration of users' preferences or safety. By establishing a biosignal measurement system in a developed product that can bring various effects using air, it will be possible to grasp the user's condition through a pattern of change in pressure distribution when seated. This paper proposes a construction system that enhances the comfort of using an air car seat through contact between a temperature measurement sensor and a user, and enables effective management of measured biosignals by linking them with an air pump control system.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.75-80
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• 2014

In previous study, make an attempt to estimate exhaust valve seat and seat-ring wear acceleration factor for engine durability test with measuring and consideration of wear mechanism. But found abnormal initial wear rate in exhaust valve seat-ring. And have to improve exhaust valve seat-ring wear rate for reliability reason, because next GDI/Turbo engine is based on this engine and GDI/Turbo engine have higher combustion pressure and higher thermal load. In this study, Trying to find the cause of abnormal wear factor, improve valve-train durability by change specification & design of parts and verify variant parts for improving durability of valve-train. And then I would like to propose a design guide line of valve-train system in a reliability point of view, besides make a complement of previous study.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.13 no.6
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• pp.37-45
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• 2014

Ball valves are used as a key element in the process industries. The industrial development of valves has increased steadily, but continued improvement requires high design reliability and long service life. Currently, the development of high performance valves is not easy because of the lack of relevant technology in Korea. Valves are being imported at a level of up to 58 percent of the domestic market, which represents a value of almost 7 million US dollars. Therefore, in this work, the improvement of the design and performance of industrial valves has been studied in an attempt to achieve valves that will have longer service life and better output during operation. The structural stability was evaluated using the ANSYS FSI (Fluid-Structural Interaction) module. Moreover, to obtain maximum product reliability, torque analysis simulation was performed to compare and experimental results. The simulation results were used to predict the change in torque by changes in shape, thereby reducing the time and cost of manufacturing a number of prototypes for experimental validation.

• Journal of the Korean Institute of Telematics and Electronics
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• v.22 no.2
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• pp.90-96
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• 1985

The properties of plasma-enhanced CVD phosphorous silicate glass (PECVD PSG) for passivation layer are studied . Phosphorous contentration was analyzed with X-ray fluores-cence. As a result, PECVD PSG has a limiting phosphors concentration of about 8 mole%. Curves relating to etcll rate, infrared absorption ratio, and sheet resistivity were adapted to monitor phosphorous concentration indirectly Dielectric properties, step coverage, crack resistance, and gettering effect are discussed in both of atmospheric pressure CVD (APCVO) and PECVD oxide. PECVD SiO2 film have density of about 2.4 g/㎤ at deposition rate of 450$\AA$/min, refractive index of about 1.53, and breakdown at fields of II-13 MV/cm. Crack resistance of PECVD oxide is greater than APCVD oxide. PECVD PSG films contained with 2 mole % phosphorous show good step coverage and gettering ability. The obtained results show more advantages in PECVD PSG than in APCVD PSG for device passivation.