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Kim, Sun Hong,Seo, Hyunseon,Kang, Jiheong,Hong, Jaeyoung,Seong, Duhwan,Kim, Han-Jin,Kim, Jaemin,Mun, Jaewan,Youn, Inchan,Kim, Jinseok,Kim, Yu-Chan,Seok, Hyun-Kwang,Lee, Changhee,Tok, Jeffrey B.-H.,Bao American Chemical Society 2019 ACS NANO Vol.13 No.6
<P>Both self-healable conductors and stretchable conductors have been previously reported. However, it is still difficult to simultaneously achieve high stretchability, high conductivity, and self-healability. Here, we observed an intriguing phenomenon, termed ?electrical self-boosting?, which enables reconstructing of electrically percolative pathways in an ultrastretchable and self-healable nanocomposite conductor (over 1700% strain). The autonomously reconstructed percolative pathways were directly verified by using microcomputed tomography and <I>in situ</I> scanning electron microscopy. The encapsulated nanocomposite conductor shows exceptional conductivity (average value: 2578 S cm<SUP>?1</SUP>; highest value: 3086 S cm<SUP>?1</SUP>) at 3500% tensile strain by virtue of efficient strain energy dissipation of the self-healing polymer and self-alignment and rearrangement of silver flakes surrounded by spontaneously formed silver nanoparticles and their self-assembly in the strained self-healing polymer matrix. In addition, the conductor maintains high conductivity and stretchability even after recovered from a complete cut. Besides, a design of double-layered conductor enabled by the self-bonding assembly allowed a conducting interface to be located on the neutral mechanical plane, showing extremely durable operations in a cyclic stretching test. Finally, we successfully demonstrated that electromyogram signals can be monitored by our self-healable interconnects. Such information was transmitted to a prosthetic robot to control various hand motions for robust interactive human-robot interfaces.</P> [FIG OMISSION]</BR>
홍성철(Sungchul Hong),최현상(Hyunsang Choi),홍창희(Changhee Hong) 한국산학기술학회 2015 한국산학기술학회 학술대회 Vol.2015 No.1
실내 GIS는 그동안 전통적인 측량기법과 CAD 도면을 이용하여 구축되었으며, 2차원 공간모델을 이용하여 공간정보서비스를 제공하였다. 하지만, 2차원 모델은 복잡한 공간을 표현하고 정보를 공유하는데 한계가 있으므로, 다양한 공간정보 서비스를 구현하기 위해 3차원 실내모델의 필요성은 점점 커지고 있다. 이에 본 논문에서는 건축도면과 지상라이다를 이용한 ‘3차원 실내 모델 구축 절차’를 제안하고, 복잡한 실내공간을 가지는 테스트베드에 적용하여 효용성을 검증하였다.
Failure Mode of Piezoelectric Sensor for Accelerated Life Test
Changhee Park,Hyun-Joong Hwang,Gyechun Cho,Chang-Ho Hong 한국방사성폐기물학회 2022 한국방사성폐기물학회 학술논문요약집 Vol.20 No.2
The high-level nuclear waste (HLW) repository is a 500-1,000 m deep geological disposal system with a very long life expectancy for disposing of high-level waste, which is known to have a half-life of several thousand years. This repository is subject to harsh environmental conditions, such as high temperature and radiation from high-level waste, that can cause deterioration and crack. When radiation escapes through cracks, it can injure persons on the ground. Therefore, it is essential to install a sensor that can detect problems such as cracks. But, since the high-level nuclear waste (HLW) repository is sealed with bentonite and backfill, the sensor cannot be removed or replaced once it has been installed. Therefore, it is necessary to develop a highly durable monitoring sensor that can withstand harsh environmental conditions. Before attempting to improve durability, it is first required to assess durability quantitatively. And an accelerated life test is a widely used method for assessing durability. However, it is important to obtain the same failure mode when conducting a reliability test, such as an accelerated life test. If the accelerated life test is conducted using different failure modes, the dependability of the results is inevitably diminished. Therefore, in this study, a representative failure mode for the piezoelectric sensor used in the accelerated life test was derived through experiments and literature research.
위상 교정 디지털 필터를 이용한 최적화된 수평축 영상 축소기의 하드웨어 설계 및 구현
홍두일,이봉근,강봉순,홍창희 동아대학교 정보기술연구소 2002 情報技術硏究所論文誌 Vol.9 No.2
In this paper, we propose a hardware implementation of optimized image downscaler. This image downscaler uses phase correction digital filters for horizontal scalings. It improves scaling precisions and decreases the loss of data, compared with pixel drop. In order to achieve the optimized hardware, digital filters are implemented by the multiplexer -adder architecture instead of adder - multiplexer. This image downscaler is designed by using the Verilog-HDL and verified by Xilinx Virtex XCV 2000E-6BG560 FPGA and ITU-R BT.601.
Life Prediction of Monitoring Piezoelectric Sensor Under Temperature Condition of HLW Repository
Changhee Park,Hyun-Joong Hwang,Chang-Ho Hong,Sokpheanika Chea,Gye-Chun Cho 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.1
The high-level nuclear waste (HLW) repository is a 500-1,000 m deep underground structure to dispose high-level nuclear waste. The waste has a very long half-time and is exposed to a number of stresses, including high temperatures, high humidity, high pressure These stresses cause the structure to deteriorate and create cracks. Therefore, structural health monitoring with monitoring sensors is required for safety. However, sensors could also fail due to the stresses, especially high temperature. Given that the sensors are installed in the bentonite buffer and the backfill tunnel, it is impossible to replace them if they fail. That’s why it is necessary to assess the sensors’ durability under the repository’s environmental conditions before installing them. Accelerated life test (ALT) can be used to assess durability or life of the sensors, and it is important to obtain the same failure mode for reliability tests including ALT. Before conducting the test, the proper stress level must be designed first to get reliable data in a short time. After that, acceleration of life reduction with increasing temperature and temperature-life model should be determined with some statistical methods. In this study, a methodology for designing stress levels and predicting the life of the sensor were described.
Investigation of Radiation Effect on the HLW Repository Monitoring Sensors
Changhee Park,Sokpheanika Chea,Chang-Ho Hong,Jeonguk Bang,Gye-Chun Cho 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
The high-level nuclear waste (HLW) repository disposes of high-level nuclear waste at a depth of 500 m to 1,000 m underground. Structural health monitoring must be accompanied by the complex environmental conditions of high temperature, high humidity, radiation, and mechanical stress. A thermocouple for measuring temperature, total stress meter and pore pressure meter for measuring stress and water pressure, relative hygrometer and electrical resistivity sensor (TDR or SUS) for measuring humidity, accelerometer for measuring crack signals, and strain gauge for measuring displacement are used. For safety, after disposing of HLW in the HLW repository, access to the disposal tunnel gets blocked, making it impossible to replace or remove the monitoring sensors. So, it is necessary to evaluate the effect of the HLW repository’s environmental conditions on the monitoring sensors and enhance their durability through quantitative life evaluation and shielding. Before evaluating the life of accelerometers and strain gauges used in the HLW repository, an experimental study is conducted to determine failure modes and failure mechanisms under radiation conditions, which are unique environmental conditions of the HLW repository.