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미세기포와 용존공기부상 반응조를 이용한 산업폐수 내 미세플라스틱 제거
김도균 ( Dokyun Kim ),김민경 ( Minkyung Kim ),모경 ( Kyung Mo ),김문일 ( Moonil Kim ),김용범 ( Yong-beom Kim ),김현진 ( Hyunjin Kim ) 한국폐기물자원순환학회(구 한국폐기물학회) 2021 한국폐기물자원순환학회 춘계학술발표논문집 Vol.2021 No.-
최근 환경적 문제가 대두되면서 활발하게 진행 되고 있는 대부분의 미세플라스틱에 대한 연구는 해양에서의 미세플라스틱과 관련된 연구가 대부분이며 하·폐수 처리장에서 처리되지 않고 방류된 미세플라스틱에 대한 연구는 미비한 실정이다. 최근 연구에 따르면 하·폐수 처리장에서 미세플라스틱을 제대로 처리하지 못하고 있으며 처리수가 방류된 하천에서 더 다량의 미세플라스틱이 검출되었다는 연구 결과가 있다. 하천에 방류된 미세플라스틱은 해양으로 유입될 수 있으며 이는 근본적인 미세플라스틱 문제 해결을 위해서는 하·폐수 처리장에서의 미세플라스틱 제거가 이루어져야 한다는 것을 의미한다. 본 연구에서는 산업폐수 내 미세플라스틱 제거에 대하여 연구하였으며 미세플라스틱 제거를 위해 미세기포와 용존공기부상(DAF) 기술을 적용하였다. 실험에 사용된 폐수로는 세탁공장에서 발생한 세탁폐수를 사용하였다. DAF 1ton/h 반응조에 주입할 응집제의 종류와 주입량을 산정하기 위하여 폴리염화알루미늄, 황산알루미늄, 염화제1철, 고분자응집제를 사용하여 세탁폐수에 대해 Jar-test 실험을 진행하여 탁도와 TSS를 측정하였으며 폴리염화알루미늄과 고분자 응집제를 병합 주입하는 것이 최적으로 도출되었다. DAF 반응조에 응집제를 주입하여 생성된 Floc은 미세기포를 이용하여 부상 처리하였다. 원폐수와 처리수 내 미세플라스틱의 분석은 탁도 및 TSS측정, FT-IR과 Raman분광기를 통하여 정성·정량 분석을 진행하였다. 탁도와 TSS값을 분석한 결과 원폐수 대비 처리수의 제거율은 각각 80.9%, 80.4%를 나타내었으며 FT-IR을 통해 미세플라스틱 제거율을 판단한 결과 67.9%를 나타내었다. TSS값으로 측정한 미세플라스틱 제거율과 FT-IR을 이용하여 측정한 미세플라스틱의 제거율이 상이한 이유는 TSS 측정에 사용되는 GF/C 필터로 측정할 수 있는 0.45㎛의 공극 이하의 미세플라스틱들이 폐수 내 존재하여 TSS값에 측정되지 않았다고 판단할 수 있다.
Lee, Hyukmin,Yoon, Eun-Jeong,Kim, Dokyun,Kim, Jung Wook,Lee, Kwang-Jun,Kim, Hyun Soo,Kim, Young Ree,Shin, Jong Hee,Shin, Jeong Hwan,Shin, Kyeong Seob,Kim, Young Ah,Uh, Young,Jeong, Seok Hoon American Society for Microbiology 2018 Antimicrobial Agents and Chemotherapy Vol.62 No.9
<P>A total of 281 nonduplicated Staphylococcus aureus blood isolates were collected from January to May 2017 from eight hospitals in South Korea to investigate the epidemiological traits of ceftaroline resistance in methicillin-resistant S. aureus (MRSA). Cefoxitin-disk diffusion tests and the mecA gene PCR revealed that 56.6% (159/281) of the S. aureus isolates were MRSA, and most belonged to ST5 (50.3%, 80/281) and ST72 (41.5%, 66/281). Of the MRSA isolates, 44.0% (70/159) were nonsusceptible to ceftaroline (MIC >= 2 mg/liter), whereas all of the methicillin-susceptible S. aureus isolates were susceptible to the drug. Eight amino acid substitutions in penicillin-binding protein 2a (PBP2a), including four (L357I, E447K, I563T, and S649A) in the penicillin-binding domain (PBD) and four (N104K, V117I, N146K, and A228V) in the non-PBD (nPBD) of PBP2a, were associated with ceftaroline resistance. The accumulation of substitutions in PBP2a resulted in the elevation of ceftaroline MICs: one substitution at 1 to 2 mg/liter, two or three substitutions at 2 to 4 mg/liter, and five substitutions at 4 or 16 mg/liter. Ceftaroline resistance in MRSA might be the result of clone-specific PBP2a polymorphism, along with substitutions both in PBD and nPBD, and the elevated ceftaroline MICs were associated with the substitution sites and accumulation of substitutions.</P>
Kim, Dokyun,Hong, Seongjin,Choi, Hyuntae,Choi, Bohyung,Kim, Jaeseong,Khim, Jong Seong,Park, Hodong,Shin, Kyung-Hoon Elsevier 2019 Environment international Vol.133 No.2
<P><B>Abstract</B></P> <P>To determine distributions, bioaccumulation, and trophic transfer of freshwater cyanobacterial toxins such as microcystins (MCs), surface water, suspended solids, sediments, and coastal organisms were collected from seven stations in inner and outer regions of the estuary dam in the Geum River Estuary in June and July 2017. Concentrations of MC variants (MC-LR, -RR, and -YR) in the multimedia samples were analyzed using a HPLC-MS/MS. Trophic position (TP) of organisms (fish, bivalve, gastropod, decapod, and polychaete) was determined by nitrogen stable isotope analyses of both bulk tissues and amino acids. From July to August 2017, great concentrations of MCs were detected in discharged freshwater ranging from 0.4 to 75 μg L<SUP>−1</SUP>. Considerable amounts of MCs are delivered to the Geum River Estuary in summer season. MCs spread far away as dissolved phases (18.7–49.5 ng L<SUP>−1</SUP>) in July when large amount of freshwater was discharged during the rainy season. Concentrations of MCs in marine organisms varied among species, ranging from 40 to 870 ng g<SUP>−1</SUP> dw. Bioaccumulated MCs tend to decrease with increasing TP of organisms, suggesting that MCs are biodiluted through the marine food web. Compound-specific isotope analysis (nitrogen of amino acids) provides more reliable TPs compared with those by bulk isotope analysis in a closed estuary (such as the Geum River Estuary) with large fluctuations in the isotope ratio of primary producers.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Great concentrations of MCs are detected in discharged freshwater via the estuary dam. </LI> <LI> The MCs well dissolve in water when they entered the coastal ecosystem. </LI> <LI> MC-LR is the most abundant among three MCs variants in coastal organisms. </LI> <LI> Bioaccumulated MCs decrease with increasing trophic positions of organisms. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Dokyun Kim 한국사회학회 2015 韓國社會學 Vol.49 No.3
This paper aims at explaining the dynamics of welfare capitalism in Japan. As opposed to previous studies, it emphasizes the role of fiscal system by raising the question of how savings encouragement combined with low taxation affected the welfare dynamics. During the industrialization period, the Japanese government mobilized private savings as if it were public money. This capital mobilization strategy made the features of the Japanese welfare system exceedingly different from those of western countries, both by making it possible for the government to maintain the small tax state and by enabling households to actively utilize savings assets as a welfare measure. This distinctive institutional setting had an enormous effect on welfare dynamics after the oil shocks of the 1970s by making it difficult for the government to introduce the new consumption tax and by increasing the importance of assetbased welfare. With the emphasis on fiscal system, this paper contributes to the development of comparative welfare capitalism studies which have explored the possible linkage of welfare and capitalism.
Two-Dimensional Mechanism of Hovering Flight by Single Flapping Wing
Dokyun Kim,Haecheon Choi 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.1
Numerical simulations are conducted to investigate the mechanism of hovering flight with an inclined stroke. The Reynolds numbers considered are 150 and 1000 based on the maximum translational velocity and wing chord length. Three mechanisms responsible for high vertical force generation, suggested by Dickinson et al.(1999), are confirmed and more elaborated in the present study. First, we show that the vertical force during downstroke is larger than that from the quasi-steady analysis due to the delayed stall mechanism. Second, the wing-wake interaction of reducing the negative vertical force during the stroke reversal is explained in terms of the reattachment of the vortex, shed previously during downstroke, on the wing, by which the wing is submerged in a low pressure region during upstroke and has a smaller negative vertical force. Finally, the rotational circulation is explained by advancing the rotation timing of the wing at supination using both the numerical simulation and inviscid potential theory.