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Sea Water Interation into Coastal Aquifer in Cheju Island by Isotope Analysis
AHN, JONGSUNG,TAKAMURA, HIROKI,CHOI, MOOWOONG 한국지하수학회 1995 지하수 Vol.4-5 No.-
The environmental isotopes (oxygen-18, deuterium, tritium) study and chemistry on water samples from Cheju Island, a volcanic island, were carried out to interpret the general hydrologic relations, sea water intrusion and to estimate the residence time. The result of tritium analysis indicated fast infiltration of meteoric water into underground and rapid mixing process between rain water and groundwater. The results of oxygen-18 and deuterium analysis demonstrated that most of the wells in the eastern part of the island were influenced by sea water intrusion. Based on chemical analysis of water samples, most of groundwater in study area were classified into Na-Cl type and showed high chloride/bicarbonate ratios. Considering the salt contents of groundwater, it is considered that the catchment basin may be small, that the mixing process might rapidly occur, and that the groundwater is diluted by precipitation in July through August. Sea water intrusion in the northeastern part of the island has proceeded to inward island at least 3㎞ from the coastal line and in the south eastern part about 700m.
Occurrence and Biotransformation of Ochratoxin A during Pepper Sauce Fermentation
Jongsung Ahn,Han-sub Jang,Young-Jin Song,양태호,장광엽 한국응용생명화학회 2011 Applied Biological Chemistry (Appl Biol Chem) Vol.54 No.6
Gochujang, a savory and pungent fermented sauce, is a Korean ethnic food composed primarily of fermented soybean cake, red pepper powder, glutinous rice, and salt. Industrial gochujang is fermented following inoculation with Aspergillus oryzae and Bacillus subtilis as starter microorganisms. In contrast, a wide variety of natural fungi and bacteria are used in fermentation and aging of artisanal gochujang, the aging period of which is longer than 6 months. We monitored ochratoxin A (OTA) contamination of red pepper and gochujang available in the Korean retail market and explored the possibility that microorganisms in gochujang might degrade OTA present in contaminated red pepper during soybean fermentation and aging. We report here that OTA can be easily biotransformed serially to several products by B. subtilis (KTCT 1021) under the conditions of our experiments. The dynamic microbial activity in gochujang might contribute to the low occurrence of ochratoxin A in this product despite the use of highly contaminated pepper powder, one of the main ingredients of gochujang. At the same time, however, an inappropriate fermentation process and the long aging period are assumed to be sources of contamination. Studies to identify critical control points and to prevent fungal spoilage by the development of high quality starters should be followed up to enable the artisan to produce OTAfree gochujang.
구동축의 등속조인트 방식에 따른 진동특성의 실험적 연구
사종성(Jongsung Sa),안태길(Taekil Ahn),강태원(Taewon Kang) 한국생산제조학회 2019 한국생산제조학회지 Vol.28 No.1
The vibrational characteristics of automotive idling and driving were investigated experimentally using various types of constant velocity joint. Plunging force (PF) and generating axial force (GAF) are the most influential quantities related to vibration characteristics of constant velocity joint. The results of the MTS test set and vibration test show that PF has higher values and GAF aggravates the automotive idling and shudder vibration characteristics. Furthermore, the variation amplitude and the harmonic periods of the vibrational characteristics in the axial direction of the shaft affect the significantly idle vibration of the drive shaft. The measured apparent mass and acceleration data are useful in calculating the PF of the drive shaft, which has no dynamic absorber.