• Korean Journal of Environmental Biology
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• v.23 no.3 s.59
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• pp.304-314
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• 2005

The occurrence of cyanobacterial bloom in Korean lakes of the summer is generalized. The characteristic of cyanobacterial community was explored. And the developmental stage of cyanobacterial bloom was divided into three phases, 'preparatory phase', 'bloom phase' and 'extinction phase' Cyanobacterial bloom started during the end of June at site 1, transition Bone of Lake Daecheong. The period of water bloom in normal year was about 60~70 days at site 4, lacustrine Bone, but it was unusually 11 days from July 19 in 1999. M. aerugilnosa first occurred in June, had a peak of standing crop curve from the end of August to the beginning of September in 1998 and 2002 and the end of July in 1999 and 2001. The standing crop of M. aeruginosa occupied $68.1\%$ of phytoplankton, $74.2\%$ of cyanobacteria and $88.8\%$ of genus Microcystis, Anabaena spp. first occurred in April, was above 10,000 cells $mL^{-1}$ from the end of August to about the middle of September in 1998. The effect of rainfalls on cyanobacterial bloom was different according to the phases. The rainfalls of preparatory phase assist the growth of cyanobacteria, but accelerate the decrease of cyanobacteria in extinction phase. In bloom phase, the heavy rainfalls reduce the development of the bloom, while the slight ones display only a little effects.

• Korean Journal of Ecology and Environment
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• v.36 no.3 s.104
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• pp.269-276
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• 2003

The study was performed to understand the relationships of cyanobacterial bloom and environmental factors in Lake Daechung. The samples were collected weekly from June to October in 2001. The cyanobacterial bloom was divided into the three phases of the early phase, the middle phase and the late phase by phytoplankton standing crops. For the early phase, the correlation coefficients between chl- a and TP, and chl- a and $PO_4$-P were 0.986 and 0.894 respectively. Therefore, phosphorus was a main environmental factor in the development of cyanobacterial bloom. Zeu/Zm ratio and chl-a showed negative correlation of r = -0.995. At the late phase, $PO_4$-P showed the highest relationship (r = 0.958), and TP and temperature showed relatively high relationships (r = 0.857 and r = 0.813). At the late phase, $NH_3$-N showed highly positive relationship (r = 0.921). It was confirmed that $PO_4$-P was the most important contribution factor for the bloom through the regression analysis on the environmental factors. As the result, the decrease of Zeu/Zm ratio and the increase of P concentration influenced cyanobacterial bloom developed rapidly in the early phase. Also the cyanobacterial bloom was decreased in proportion to decreasing of $NH_3$-N concentration in the late phase. It was expected that observation of $NH_3$-N may be a very useful factor on monitoring of the decreasing situation of the bloom.

• Convergence Security Journal
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• v.13 no.4
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• pp.47-52
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• 2013

VANET(Vehicular Ad-hoc Network) is a kind of ad hoc networks which is consist of intelligence vehicular ad nodes, and has become a hot emerging research project in many fields. It provides traffic safety, cooperative driving and etc. but has also some security problems that can be occurred in general ad hoc networks. In VANET, it has been studies that group signature method for user privacy. However, among a group of group key generation phase and group key update phase, RSU(Road-Side Unit) and the computational overhead of the vehicle occur. In this paper, we propose an efficient group key management techniques with CBF(Counting Bloom Filter). Our group key management method is reduced to the computational overhead of RSU and vehicles at the group key generation and renewal stage. In addition, our method is a technique to update group key itself.

• Journal of environmental and Sanitary engineering
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• v.15 no.1
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• pp.1-6
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• 2000

A milky gray scum was observed at some water area of the lake Daecheong in the summer of 1997 and 1998. To identify a causing organism of scum and affecting factors, we observed the scum material by a phase contrast microscope and surveyed the phsico-chemical water quality during the outbreak of scum. The scum was found out to be clogging cysts of amoeboid protozoan, Asterocaelum sp.(Protozoea Sarcodina Aconchulinida), grazer of filamentous cyanobacteria, Anabaena genus. The protozoan scum appeared during Anabaena bloom period, which continued for a while. This protozoan was presumed acting as a regulator of Anabaena bloom in the lake Daecheong during the summer season. Moreover this is the first report on Asterocaelum sp. a grazing filamentous cyanobacteria occurred in Korean freshwater.

• Korean Journal of Microbiology
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• v.34 no.4
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• pp.188-193
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• 1998

The authors examined the variations of environmental factors, the distributions of cyanobacteria, heterotrophic bacteria, and microorganisms that inhibit the growth of Anabaena cylindrica according to development and extinction of cyanobacterial bloom at a site in Daechung Dam reservoir. And certified the relationship between each other. Water temperature variated in a typical pattern. pH and concentrations of dissolved oxygen and chlorophylla was high in bloom period, and lowered with the decline of bloom. Phosphorus played as a growth-limiting factor at this study site. Total nitrogen concentration increased during blooming period, which indicated that nitrogen has been fixed by aquatic organisms such as cyanobacteria. Cyanobacteria distributed from June 17, and such cyanobacterial species as Anabaena spp., Aphanizomenon spp., Microcystis spp., Oscillatoria spp. and Phormidium spp. was detected during study period. Anabaena spp. distributed relatively highly distributed from July 23 to September 22, and disappeared completely at September 29. Heterotrophic bacterial and cyanobacterial populations varied inverse-proportionally. There was a relevancy between the variations of Anabaena spp., heterotrophic bacteria, and microorganisms that inhibit the growth of Anabaena cylindrica. Microorganisms that inhibit the growth of Anabaena cylindrica distributed from early growth phase of Anabaena spp. population to immediately after the extinction of Anabaena spp. With the population of Anabaena cylindrica growth-inhibiting microorganisms decreasing, increases of heterotrophic bacterial population followed it. Thease results indicate that microorganisms have a part in the extinction of cyanobacterial bloom, especially at its destroying period.

• Korean Journal of Environmental Agriculture
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• v.34 no.2
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• pp.139-148
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• 2015

BACKGROUND: The aim of this study was to isolate and identify algicidal bacterium that tends to kill the toxic dinoflagellate Alexandrium catenella, and to determine the algicidal activity and algicidal range of algicide. METHODS AND RESULTS: Among of algicidal bacteria isolated in this study, NH-3 isolate was the strongest algicidal activity against A. catenella. NH-3 isolate was identified on the basis of biochemical characteristics and analysis of 16S rRNA gene sequences. The NH-3 isolate showed over 99% homology with Arthrobacter oxydans, and was designated as Arthrobacter sp. NH-3. The optimal culture conditions were $25^{\circ}C$, initial pH 7.0, and 2.0% (w/v) NaCl concentration. The algicidal activity of Arthrobacter sp. NH-3 was significantly increased to maximum value in the late of logarithmic phase. Arthrobacter sp. NH-3 showed algicidal activity through indirect attack, which excreted active substance into the culture filtrate. When 10% culture filtrate of NH-3 was applied to A. catenella, 100% of algal cells were destroyed within 30 h. In addition, the algicidal activities were increased in dose and time dependent manners. The pure algicide was isolated from the ethyl acetate extract of the culture filtrate of NH-3 by using silica gel column chromatography and high performance liquid chromatography (HPLC). We investigated the algicidal activity of this algicide on the growth of harmful algal bloom (HAB) species, including A. catenella. As a result, it showed algicidal activity against several HAB species at a concentration of $100{\mu}g/mL$ and had a relatively wide host range. CONCLUSION: Taken together, our results suggest that Arthrobacter sp. NH-3 and its algicide could be a candidate for controlling of toxic and harmful algal blooms.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.7 no.8
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• pp.1890-1910
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• 2013

Routing overlay offers an ideal methodology to improve the end-to-end communication performance by deriving a backup path for any node pair. This paper focuses on a challenging issue of selecting a proper backup path to bypass the failures on the default path with high probability for any node pair. For existing backup path selection approaches, our trace-driven evaluation results demonstrate that the backup and default paths for any node pair overlap with high probability and hence usually fail simultaneously. Consequently, such approaches fail to derive a robust backup path that can take over in the presence of failure on the default path. In this paper, we propose a three-phase RBPS approach to identify a proper and robust backup path. It utilizes the traceroute probing approach to obtain the fine-grained topology information, and systematically employs the grid quorum system and the Bloom filter to reduce the resulting communication overhead. Two criteria, delay and fault-tolerant ability on average, of the backup path are proposed to evaluate the performance of our RBPS approach. Extensive trace-driven evaluations show that the fault-tolerant ability of the backup path can be improved by about 60%, while the delay gain ratio concentrated at 14% after replacing existing approaches with ours. Consequently, our approach can derive a more robust and available backup path for any node pair than existing approaches. This is more important than finding a backup path with the lowest delay compared to the default path for any node pair.

• Journal of Korean Society on Water Environment
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• v.26 no.5
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• pp.834-840
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• 2010

To find out the toxin production characteristics of Korean harmful cyanobacteria, we isolated 14 cyanobacterial strains from Korean lakes and rivers and analyzed the kinds and cellular content of microcystins (MCYSTs) of cyanobacterial isolates using cultured biomass. And we measured the MCYSTs production by growth phase of two representative toxic strains, Microcystis aeruginosa (HG-015) and Anabaena planktonica (HG-012). Among seven cyanobacteral species, Microcystis wesenbergii showed the highest cellular MCYSTs content. MCYST-RR was the most dominant toxin reaching more than 85% of MCYSTs produced by isolated cyanbacterial strains. During the mass culture, Microcystis aeruginosa (HG-015) showed the highest yield and accumulation of MCYSTs in the exponential growth phase. However the cellular content of chlorophyll a and MCYSTs of Anabaena planktonica (HG-012) showed higher value in the stationary and early death phase than in the exponential growth phase. Our results suggest that control and removal of harmful cyanobacterial bloom before exponential growth phase may be effective to prevent health risk of cyanobacterial toxins in the drinking water sources.

• Journal of architectural history
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• v.23 no.1
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• pp.51-62
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• 2014

Architecture is a product of numerous influences, as shown in the apprenticeships of Kim, Jung-Up and Kim, Swoo-Geun with Le Corbusier's influences. Therefore, its identity is need to be re-defined based on such complex relationships. The rhetorical images of 'the Map of Misreading', as the core of the poetic identification proposed by Harold Bloom's 'the Theory of Influence', provide an efficient way of explaining the relations between architectural apprenticeships and identities. This research is to re-build a new methodology of architectural criticism based on it. The diachronic transformations of the architecture of Seung, Hyo-Sang also had very characteristic 'revisionary ratios' about his precursor Kim, Swoo-Geun. As an antithetic stance of his precursor's final phase, his early days works pursued continuously geometric abstraction and objective images of the architecture of Adolf Loos. However, his recent works are showing the obvious symptoms of regression to his origins. Finally, the architectural identity should be re-conceptualized as a complexity, based on inter-textuality from complex influences. This new architectural identity can be reflected into the modern obsessive identity.

• Korean Journal of Ecology and Environment
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• v.38 no.3 s.113
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• pp.304-312
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• 2005

Effects of two endocrine disrupters (EDs) , nonylphenol (NP) and diethylhexyl phthalate (DEHP), on the population growth and morphology of two freshwater HABs (harmful algal blooms) , Microcystis aeruginosa and Stephanodiscus hantzschii, which frequently evoked the hazard bloom in an eutrophic lakes and reservoirs worldwide, were examined with seven different concentrations of EDs (0.01, 0.05, 0.1, 1,2, 2.5 and 3 ppm). Even at concentration below 0.01 ppm, NP strongly inhibited the algal growth of both M. aeruginosa and S. hantzschii, regardless of the algal growth phase. Morphologically, the algal cell treated with NP gradually lost green color in cytoplasm, became smaller in cell size, and then, was hardly seen in microscopic field. On the other hand, DEHP employed did not affect two algae at all concentrations, and rather stimulated the growth by about 10% with a treatment at 3.00 ppm compared to control. These results indicate that the continuous input of EDs, DEHP into the natural water system plays a crucial role to enhance or help an outbreak of algal bloom in eutrophic waters.