http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
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.
Park, Honghwi,Lim, Changhee,Lee, Chang-Ju,Kang, Jaewoon,Kim, Jaeeuk,Choi, Muhan,Park, Hongsik IOP 2018 Nanotechnology Vol.29 No.41
<P>Graphene grown on a copper (Cu) substrate by chemical vapor deposition (CVD) is typically required to be transferred to another substrate for the fabrication of various electrical devices. PMMA-mediated wet process is the most widely used method for CVD-graphene-transfer. However, PMMA residue and wrinkles that inevitably remain on the graphene surface during the transfer process are critical issues degrading the electrical properties of graphene. In this paper, we report on a PMMA-mediated graphene-transfer method that can effectively reduce the density and size of the PMMA residue and the height of wrinkles on the transferred graphene layer. We found out that acetic acid is the most effective PMMA stripper among the typically used solutions to remove the PMMA residue. In addition, we observed that an optimized annealing process can reduce the height of the wrinkles on the transferred graphene layer without degrading the graphene quality. The effects of the suggested wet transfer process were also investigated by evaluating the electrical properties of field-effect transistors fabricated on the transferred graphene layer. The results of this work will contribute to the development of fabrication processes for high-quality graphene devices, given that the transfer of graphene from the Cu substrate is essential process to the application of CVD-graphene.</P>
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.
Doping effects of multiferroic manganitesYMn0.9X0.1O3(X=Al, Ru, and Zn)
Park, Junghwan,Kang, Misun,Kim, Jiyeon,Lee, Seongsu,Jang, Kwang-Hyun,Pirogov, A.,Park, J.-G.,Lee, Changhee,Park, S.-H.,Kim, Hyoung Chan American Physical Society 2009 Physical review. B, Condensed matter and materials Vol.79 No.6
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.
Park Changhee,Lee Sunggi 대한화학회 2022 Bulletin of the Korean Chemical Society Vol.43 No.7
We report a one-pot sulfa-Michael addition reaction using a disulfide and a pyridine-borane complex under blue light irradiation. This novel synthetic approach has a broad substrate scope and a high functional group tolerance. Mechanistic studies suggest that sequential radical and ionic processes provide a practical solution for constructing carbon–sulfur bonds.