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Seung-gu Kang,Hyun-chul Lee 한국방사성폐기물학회 2018 방사성폐기물학회지 Vol.16 No.2
As a rule, geological disposal is considered a safe method for final disposal of high-level radioactive waste. However, some long-lived fission products like 99Tc and 129I contained in spent nuclear fuel are highly mobile as less sorbing anionic species in the subsurface environment and can mainly cause exposure dose to the ecosystem by emission of beta rays in the hundreds of keV range. Therefore, if these two nuclides can be separated and converted with high efficiency into radioactively unharmful nuclides, this would have a positive effect on disposal safety. One candidate method is to transmute these two nuclides in nuclear reactors into short-lived nuclides or into stable nuclides. For this purpose, it is necessary to evaluate which reactor type is more efficient in burning these two nuclides. In this study, the simulation results of nuclear transmutation of 99Tc and 129I in light water reactor (PWR), heavy water reactor (CANDU) and fast neutron reactor (SFR, MET-1000) are compared and discussed.
Experimental investigation on the CO2 laser cutting of soda-lime glass
SeungGu Kang,Joonghan Shin 대한기계학회 2020 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.34 No.8
This study reports on complete glass cutting using a single CO 2 laser beam with a low power of several tens of watts. In this study, the morphological characteristics of a cut surface and the process window for complete cutting were investigated at various process conditions. The damage threshold (in laser energy per unit length) for the glass surface was found to be ~0.0203 J/mm. Increasing the laser energy above this level induced surface melting and crack generation, and the complete cutting of the glass eventually occurred due to huge crack propagation along the scan direction when the laser energy was above 0.67 J/mm. The line edge roughness (LER) measured along the cut surface was in the range of 106-500 μm and tended to increase with the laser energy. According to the result of the process window test, it was found that the process conditions using low laser power (8 and 16 W) and scan speed (12 and 15 mm/s) have a relatively wide process margin for cutting.
Records of Peale's Peregrine Falcon Falco peregrinus pealei in Korea
Seung-Gu Kang 한국조류학회II 2013 한국조류학회지 Vol.20 No.2
Two Two Peale"s Peregrine falcons (Falco peregrinus pealei), a subspecies of the Peregrine Falcon, were recorded; One was collected on 19 January 2011 from a local wildlife medical center and the other one was observed on 12 March 2012 at Taejong-dae (N 35°03"08.57", E 129°05"31.90"), respectively in Busan, South Korea. The subspecies F. p. pealei is larger and darker than the other subspecies F. p. japonensis, and the wing and tail feathers of F. p. pealei are darker and less barred. Since only a few records exist, my findings may provide useful information toward understanding the morphological characteristics and distribution of this subspecies.
Home-range of the Common Kestrel (Falco tinnunculus) in the Suburban Area of Busan
( Seung Gu Kang ),( Wee Haeng Hur ),( In Sup Lee ) 한국환경생태학회 2015 한국환경생태학회지 Vol.29 No.2
The current study analyzed the home range size of the Common Kestrel (Falco tinnunculus) by observation using the natural markings in the suburban area of Busan from December 2009 to May 2010. In all, 26 individual kestrels were observed in the study area, of which 14 individual kestrels were frequently observed (more than five times) and 12 were observed less frequently (less than five times). Mean home range sizes of the 14 frequently observed kestrels were estimated using two different methods (minimum convex polygon (MCP) method and fixed kernel (FK) method): 34.49 ㏊(2.74.163.96 ㏊) by 100% MCP, 41.35 ㏊(3.54. 99.02 ㏊) by the 95% FK, 14.33 ㏊(0.20-31.57 ㏊) by the 75% FK and 5.75 ㏊(0.52.14.74 ㏊) by the 50% FK. The mean home range size was larger for males than for females estimated at 51.50 ㏊(15.04.163.96 ㏊) and 11.80㏊(2.74.24.48 ㏊), respectively, by the 100 % MCP method and 8.02 ㏊(2.38.14.74 ㏊) and 2.72 ㏊ (0.52.4.28 ㏊), respectively, by the 50 % Fixed Kernel method. The home range sizes by sexes in breeding pairs differed during the wintering and breeding seasons; the sizes decreased among females but increased among males during the breeding season. Such differences of home range sizes between sexes could be attributed to parental role division during the breeding season. Females stay in the nest or next to it during laying, incubating, and feeding activities, and males go far away from their nest sites to forage areas for their fledglings for most of the breeding period.
Characterization of metakaolin-based lightweight geopolymers with various foaming agents
Yoorim Rho,SeungguKang 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.S1
In this study, lightweight foamed geopolymers based on metakaolin were synthesized and characterized. By considering thecompressive strength, density, and crystal phase of the specimens according to the type and amount of forming agent, thepossibility of replacing Al powder, a foaming agent, with Si sludge in lightweight foamed geopolymers was analyzed. Thespecimens foamed with Al powder had lower density than those with Si sludge. However, the compressive strength of theformer was higher than that of the specimens foamed with Si sludge, owing to a more uniform pore distribution andmicrostructure. Through this study, lightweight foamed geopolymers having density of 0.36~1.05 g/cm3 and compressivestrength of 0.7~4.7 MPa can be prepared by controlling the process conditions such as the amount of Si sludge added, alkaliactivator concentration, L/S ratio, etc. The possibility of Si sludge replacing Al powder as a foaming agent thus has beendemonstrated. The lightweight foamed geopolymer fabricated in this study can be applied to various fields as it can meet therequired physical properties according to the application.
Nano-crystallized glass-ceramic of BaO-TiO2-SiO2 system containing ZrO2
Byeong-Guk Kang,SeungguKang 한양대학교 세라믹연구소 2020 Journal of Ceramic Processing Research Vol.21 No.S1
Fresnoite (Ba2TiSi2O8) materials, which exhibit piezoelectricity, ferroelectricity, and nonlinear optical properties, can be usedas core materials for optical communication and optical information processing devices. In this study, glass-ceramics withnanometer size fresnoite crystal phase were prepared from BaO-TiO2-SiO2 (BTS) glass containing ZrO2 as a nucleating agentand their microstructure, crystallization behavior, and photoluminescence properties were analyzed. The heat treatmentprocess for glass-ceramics was designed based on data obtained by non-isothermal analysis using differential thermal analysis(DTA). The crystal morphology and microstructure of the prepared specimens were analyzed by X-ray diffraction analysis(XRD), optical microscopy (OM), and field emission scanning electron microscopy (FE-SEM), respectively. The luminescenceproperties of the specimens were analyzed by photoluminescence (PL) measurements. When the BTS glass with 15 wt% ZrO2(15Z)was heat treated at 1,015 oC, a dendritic structure by gathering very small spherical crystalline phases of 10-30 nm wasformed. In addition, when the 15Z was excited by light of 309 nm wavelength, strong light of 469 nm wavelength was emitted,and this light appeared to be blue light close to white in the Commission International de l'Eclairage (CIE) diagram.