낙동강에서 분리된 Aphanizomenon flos-aquae (Cyanophyceae) 균주의 목 표 유 전자를 이용한 잠재적 독 소 생성능 및 계통학적 분 석

류희성,안성민,임창건,신라영,박종근,이정호 한국수생태학회(구 한국하천호수학회) 2017 생태와 환경 Vol.50 No.1

The identity of toxin producers remains only hypothesis unless there were identified by strain isolation and analytical confirmation of both the cyanotoxin production and the genetic identity of the monoculture. The purposes of this study were to identify a morphologic and phylogenetic classification in Aphanizomenon flos-aquae strains isolated from the Nakdong River and to investigate the potential ability of the strains to produce toxins such as saxitoxin and cylindrospermopsin using target genes. The 16S rRNA and sxtA, sxtI, cyrA, cyrJ genes were analyzed on two strains (DGUC001, DGUC003) isolated from the Nakdong River. Morphological features of the strains were observed a shape of aggregated trichomes in parallel fascicles which can reach up to macroscopic size and a hyaline terminal cell without aerotope. In addition, the 16S rRNA phylogenetic analyses showed that the strains were identified as the same species with high genetic similarity of 98.4% and grouped within a monospecific andsupported cluster I of Aphanizomenon flosaquae selected from GenBank of the NCBI. The cyrA and cyrJ genes encoding for the cylindrospermopsinbiosynthesis were not detected in the present study. The sxtA gene was in detected both the two strains, whereas the sxtI gene which had been suggested as a suitable molecular marker to detect saxitoxin-producing cyanobacteria was not found both the strains. Thus, the two strains isolated from Nakdong River were identified as the same species of Aphanizomenon flos-aquae Ralfs ex Bornet et Flahault 1888, the two strains were confirmed as potential non-producing strains of the saxitoxin and cylindrospermopsin.

Fisheries resources management of crucian carp based on assessment of fish stock and potential yield in the mid-upper system of Seomjin River

류희성,이정준,장성현,이정호 한국생태학회 2014 Journal of Ecology and Environment Vol.37 No.4

This study was undertaken to suggest an effective fisheries resources management system by using stock assessment and potential yield analyses of crucian carp population in the mid-upper system of the Seomjin River. Fieldwork was conducted seasonally from 2008 to 2009 in the mid-upper system of the Seomjin River. The stock assessment was carried out by the swept area method and the potential yield was estimated by improved fisheries resource potential estimation system based on the Allowable Biological Catch. Also, the yield-per-recruit analysis was used to review the efficient management implication of the resource, Carassius auratus. As a result, the age at first capture (tc) was estimated as 1.468 year, converted body length (BL) was 10.8 cm. Meaning the current fishing intensities, the instantaneous coefficient of fishing mortality (F) was 0.067 year-1, and the yield-per-recruit analysis showed that the current yield per recruit was estimated to be 15.999 g with F and tc. The instantaneous rate of fishing mortality that provides for Allowable Biological Catch (FABC) based on the current tc and F was estimated as 0.618 year-1. Therefore, the optimum fishing intensities could be achieved at the higher fishing intensity for Carassius auratus. The calculated annual stock of C. auratus was estimated as 7,608 kg, and the potential yield was estimated as 343 kg with tc and F at the fixed current level. Using yield-per-recruit analysis, if F and tc were set at 0.618 year-1 and 2 year, the yield per recruit and total allowable catch would be predicted to increase to 62 g and 2,531 kg by about 3.9 times and 7.3 times, respectively.

낙동강 상류 수역에서 남조류 발생과 천이패턴 - Aphanizomenon 속을 중심으로 -

류희성,박혜경,이혜진,신라영,천세억 한국물환경학회 2016 한국물환경학회지 Vol.33 No.2

This study investigated the occurrences and succession patterns of harmful cyanobacteria, as well as environmental factors, during a 3-year period (September 2012 to August 2015) in the upper region of the Nakdong River around Sangju weir. A total of 27 cyanobacterial taxa were observed in this study, and classified into 26 species and 1 variety belonging to 11 genera, 5 families, and 3 orders. Cell density ranged from 24 to 42,001 cells/ml, with a geometric mean of 33 cells/ml, during the survey period. The dominant orders differed depending on the survey year; order Oscillatoriales in 2013, Chroococcales in 2014 and Nostocales in 2015. An Aphanizomenon bloom occurred in June 2015 at which time the highest cell density of 36,873 cells/ml was detected in the upper region of the Nakdong River, whereas the Aphanizomenon spp. Cell density had been low prior to that time (190–1,704 cells/ml). An Aphanizomenon bloom also occurred at around the same time downstream in the Young River, a major inflow branch of the Nakdong River. The Aphanizomenon cell density along the Nakdong River increased markedly after joining of the Young River, indicating that the Aphanizomenon bloom in the Young River caused a bloom in the Nakdong River. Meteorological and environmental parameters, such as very low precipitation, higher water temperature, pH, and TP concentration, and lower TN/TP ratio, in May and June of 2015 than in 2013 and 2014 exerted marked effects on the Aphanizomenon bloom in June 2015 in the Young River.

시멘트 시료에 대한 삼축압축 환경에서의 수압파쇄시험 연구

류희성,장현식,장보안,Riu, Hee-Sung,Jang, Hyun-Sic,Jang, Bo-An 대한지질공학회 2017 지질공학 Vol.27 No.3

주입액의 점성도와 응력상태에 따른 균열전파 특성을 분석하기 위해 실험실 규모의 수압파쇄시험을 실시하였다. 시험에 사용된 시료는 시멘트 몰탈을 사용하여 제작되었으며, 각 변의 길이가 20 cm인 정육면체 형태이다. 제작된 시료는 최대강도를 갖기 위해 수중에서 약 1달간 양생과정을 거쳤다. 독립적인 가압시스템을 가지고 있는 진삼축압축장치로 시료에 압력을 가하여, 실제의 지반에서 작용하는 원위치응력 상태를 재현하였다. 시추 환경 재현을 위해 시료에 소형 시추공을 천공한 후, 일정한 주입속도로 수압파쇄시험을 실시하였다. 수압파쇄시험 과정에서 시추공에 주입된 유체의 압력을 실시간으로 측정하였으며, 동시에 미소파괴음(AE) 신호를 측정하였다. 수압파쇄시험의 모든 과정이 끝난 후 생성된 균열의 형태를 육안으로 관찰하였다. 일차파쇄압력은 주입액의 점성도 증가에 따라 지수형태를 보이며 증가하였다. 수압파쇄시험으로 인해 생성된 균열의 형태는 최대주응력과 최소주응력의 차이인 편차응력의 크기에 따라 서로 다른 양상을 보였다. 낮은 편차응력의 조건에서는 단일의 균열이 아닌 다중 균열이 생성되거나, 균열 성장과정에서 방향이 휘어지는 경향을 보였고, 이에 반해 높은 편차응력의 조건에서 생성된 균열은 단일 면상의 균열이 발생하였다. AE 분석에서도 편차응력이 클수록 미세균열이 단일 면상으로 집중되어 발생되는 경향을 보였다. 이러한 연구결과는 수압파쇄 방법을 이용한 암반파쇄에서 편차응력이 클 때보다 작을 때 더 복잡한 균열이 발생된다는 것을 보여준다. 따라서 셰일가스를 개발할 때 생산량을 높이기 위해서는 복잡한 균열을 발생시킬 수 있는 편차응력이 작은 조건에서 수압파쇄가 적용되는 것이 효과적일 것으로 판단된다. We conducted hydraulic fracturing experiments on cement samples to investigate the dependency of fracture propagation on the viscosity of injection fluid and the in situ stress state. Ten cubic samples (20 cm side length) were produced using cement that was cured in water for more than one month. Samples were placed in a tri-axial compression apparatus with three independent principal stresses. An injection hole was drilled and the sample was hydraulically fractured under a constant injection rate. We measured injection pressures and acoustic emissions (AE) during the experiments, and investigated the fracture patterns produced by hydraulic fracturing. Breakdown pressures increased exponentially with increasing viscosity of the injection fluid. Fracture patterns were dependent on differential stress (i.e., the difference between the major and minor principal stresses). At low differential stress, multiple fractures oriented sub-parallel to the major principal stress axis propagated from the injection hole, and in some samples the fracture orientation changed during propagation. However, at high differential stress, a single fracture propagated parallel to the major principal stress axis. AE results show similar patterns. At low differential stress, AE source locations were more widespread than at high differential stress, consistent with the fracture pattern results. Our study suggests that hydraulic fracturing during shale gas extraction should be performed parallel to the orientation of minimum differential stress.

진삼축 하에서 수압파쇄 및 플라즈마파쇄법에 의한 균열발달 특성 분석

류희성,장현식,장보안 대한지질공학회 2015 대한지질공학회 학술발표회논문집 Vol.2015 No.2

특별함, 그 이상의 꿈과 변화를 위해

류희성 대한사립학교장회(구 대한사립중고등학교장회) 2015 私學 Vol.141 No.-

고전압방전을 이용한 지중 암반의 파쇄 효과 연구

류희성,장현식,장보안 대한지질공학회 2018 대한지질공학회 학술발표회논문집 Vol.2018 No.1

고전압방전에 의한 파쇄기술 및 균열형태 분석

류희성,장현식,장보안 대한지질공학회 2017 대한지질공학회 학술발표회논문집 Vol.2017 No.2

고전압방전에 의한 암반파쇄의 실험적 연구

류희성,장현식,장보안 대한지질공학회 2017 대한지질공학회 학술발표회논문집 Vol.2017 No.1

진삼축 압축장치를 활용한 원위치응력 조건에서의 수압파쇄시험 연구

류희성,장현식,장보안 대한지질공학회 2016 대한지질공학회 학술발표회논문집 Vol.2016 No.2