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김동호 ( Kim Dong Ho ),홍창우 ( Hong Chang Woo ),이주형 ( Lee Ju Hyong ),이봉학 ( Lee Bong Hak ) 한국농공학회 2002 韓國農工學會誌 : 전원과 자원 Vol.44 No.2
Concrete containing discontinuous discrete steel fiber in a normal concrete is called steel fiber reinforced concrete(SFRC). Tensile as well as flexural strengths of concrete could be substantially increased by introducing closely spaced fibers which delay the onset of tension cracks and increase the tension strength of cracks. However, many properties of SFRC have not been investigated, especially properties on repeated loadings. Thus, the purposes of this dissertation is to study the flexural fatigue characteristics of SFRC considering cumulative damage. A series of experimental tests such as compressive strength, splitting tensile strength, flexural strength, flexural fatigue, and two steps stress level fatigue were conducted to clarify the basic properties and fatigue-related properties of SFRC. The main experimental variables were steel fiber fraction (0, 0.4, 0.7, 1, 1.5%), aspect ratio (60, 83). The principal results obtained through this study are as follows: The results of flexural fatigue tests showed that the flexural fatigue life of SFRC is approxmately 65% of ultimate strength, while that of plain is less than 58%. Especially, the behavior of flexural fatigue life shows excellent performance at 1.0% of steel-fiber volume fraction. The cumulative damage test of high-low two stress levels is within the value of 0.6 ∼ 1.1, while that of low-high stress steps is within the value of 2.4 ∼ 4.0.
서울지역 교육시설 및 공원 내 토양 중 분원성대장균군 오염실태
김혜라 ( Hye Ra Kim ),김능희 ( Neung Hee Kim ),박형숙 ( Hyong Suk Park ),김두환 ( Doo Hwan Kim ),이주형 ( Ju Hyung Lee ) 한국동물위생학회 2014 한국동물위생학회지 (KOJVS) Vol.37 No.4
Fecal coliform bacteria are indicators of fecal contamination and of the potential presence of pathogens associated with animal excreta, wastewater, sludge. This study examined the distribution of fecal coliform in sand of the playground at educational facilities and parks in Seoul. Fecal coliform were detected from 61 (22.1%) places out of 276 playgrounds. Escherichia (E) coli (75.4%) was found most frequently, followed by Cronobacter (Cro) sakazakii (8.7%), Klebsiella (K) pneumoniae (7.2%) and Actinobacter baumannii (4.3%). We also tested the bacteria for their susceptibility to 16 antibiotics using disk diffusion method. All the isolates were highly susceptible to cefepime, gentamicin, tetracycline, ciprofloxacin, enrofloxacin, nalidixic acid and sulfamethoxazole/ trimethoprim, but resistant to apramycin and cephalothin. E. coli and Cro. sakazakii were highly resistant to apramycin (100% and 83.3%), followed by cephalothin (51.9% and 50%) and ampicillin (19.2% and 16.7%). K. pneumoniae was highly resistant to ampicillin and apramycin (100%, respectively) but the remaining antibiotics were susceptible.