• Ocean and Polar Research
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• v.25 no.4
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• pp.625-631
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• 2003

While phytoplankton diversity and productivity in the Southern Ocean has been widely studied in recent years, most attention has been given to elucidating environmental factors that affect the dynamics of micro-plankton (mainly diatoms) and nano-plankton (mainly Phaeocystis antarctica). Only limited effects have been given to studying the occurrence and the potential risks associated with the blooming of dinoflagellates in the relevant waters. This study focused on the appearance and toxicological characteristics of a toxic dinoflagellate, Alexandrium tamarense, identified and isolated from the Drake Passage in a research cruise from November to December 2001 The appearance of A. tamarense in the Southern Ocean indicates the risk of a paralytic shellfish poisoning (PSP) outbreak there and is therefore of scientific concern. Results showed that while the overall quantity of A. tamarense in water samples from 30meters below the sea surface often comprised less than 0.1% of the total population of phytoplankton, the highest concentration of A. tamarense (20 cells $L^{-1}$) was recorded in the portion of the Southern Ocean between the southern end of South America and the Falkland Islands. Waters near the Polar Front contained the second highest concentrations of 10-15 cells $L^{-1}$. A. tamarense was however rarely found in waters near the southern side of the Polar Front, indicating that cold sea temperatures near the Antarctic ice does not favor the growth of this dinoflagellate. One strain of A. tamarense from this cruise was isolated and cultured for further study in the laboratory. Experiments showed that this strain of A. tamarense has a high tolerance to temperature variations and could survive at temperatures ranging from $5-26^{\circ}C$. This shows the cosmopolitan nature off. tamarense. With regard to the algal toxins produced, this strain of A. tamarense produced mainly C-2 toxins but very little saxitoxin and gonyailtoxin. The toxicological property of this A. tamarense strain coincided with a massive death of penguins in the Falkland Islands in December 2002 to January 2003.

• Ocean Science Journal
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• v.40 no.2
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• pp.67-78
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• 2005

Complex physical, chemical and biological interactions off the Korean coast created several striking patterns in the phytoplankton blooms, which became conspicuous during the measurements of ocean color from space. This study concentrated on analyzing the spatial and temporal aspects of phytoplankton chlorophyll variability in these areas using an integrated dataset from a Sea-viewing Wide Field-of-view Sensor (SeaWiFS), Advanced Very High Resolution (AVHRR) sensor, and Conductivity Temperature Depth (CTD) sensor. The results showed that chlorophyll concentrations were elevated in coastal and open ocean regions, with strong summer and fall blooms, which appeared to spread out in most of the enclosed bays and neighboring waters due to certain oceanographic processes. The chlorophyll concentration was observed to range between 3 and $54\;mg\;m^{-3}$ inside Jin-hae Bay and adjacent coastal bays and 0.5 and $8\;mg\;m^{-3}$ in the southeast sea offshore waters, this gradual decrease towards oceanic waters suggested physical transports of phytoplankton blooms from the shallow shelves to slope waters through the influence of the Tsushima Warm Current (TWC) along the Tsushima Strait. Horizontal distribution of potential temperature $(\theta)$ and salinity (S) of water off the southeastern coast exhibited cold and low saline surface water $(\theta and warm and high saline subsurface water $({\theta}>12^{\circ}C; S>34.4)$ at 75dBar, corroborating TWC intrusion along the Tsushima Strait. An eastward branch of this current was called the East Korean Warm Current (EKWC), tracked with the help of CTD data and satellite-derived sea surface temperature, which often influenced the dynamics of mesoscale anticyclonic eddy fields off the Korean east coast during the summer season. The process of such mesoscale anticyclonic eddy features might have produced interior upwelling that could have shoaled and steepened the nutricline, enhancing phytoplankton population by advection or diffusion of nutrients in the vicinity of Ulleungdo in the East Sea.

• Journal of the Korean Society of Visualization
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• v.17 no.3
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• pp.24-31
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• 2019

Recently, an air-lift bio-reactor operated by micro bubbles has been utilized to product hydrogen fuel. To enhance the performance, characteristics of hydrodynamics inside the bio-reactor were analyzed using a numerical simulation for two-phase flow. An Eulerian model was employed for both of liquid and gas phases. The standard k-ε model was used for turbulence induced by micro bubbles. A Population Balance Model was employed to consider size distribution of bubbles. A hollow cylinder was introduced at the center of the reactor to reduce a dead area which disturbs circulation of CO bubbles. An appropriate diameter of the draft tube and hollow cylinder were optimized for better performance of the bio-reactor. The optimum model could be obtained when the cross-sectional area ratio of the hollow cylinder to the reactor, and the width ratio of the riser to the downcomer approached 0.4 and 3.5, respectively. Consequently, it is expected that the optimum model could enhance the performance of the bio-reactor with the homogeneous distribution and higher density of CO, and more effective mixing.

• The Plant Pathology Journal
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• v.17 no.3
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• pp.149-153
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• 2001

A total of 2109 isolates of Botrytis cinerea were collected from infected plants fo strawberry, tomato, and cucumber in Korea from 1994 to 1996. Based on in virtotests for mycelial growth on potato-dextrose agar containing fungicides, the esolates were classified into six phenotypic groups : SSR, SRR, RSS, RRS, RSR, and RRR, representing sensitivity (S) or resistance (R) to carbendazim, procymidone, and diethofencarb. In that order the isolation frequencies of the SSR, SRR, RSS, RRS, RSR, and RRR phenotypes were 28.7, 1.1, 28.8, 39.4, 1.0, and 0.9%, respectively. Three isolates from each SSR, SRR, RSS, RRS, and RSR and an isolate of RRR phenotype were selected and evaluated for their fitness-related characteristics such as pathogenic aggressiveness, mycelial growth rate, sporulation, and sclerotial formation. Competitive abilities of the SSR, SRR, RSS, RRS, and RSR phenotypes were also compared by inculating mixtures of conidial suspensions of two phenotypes to cucumber plant, and then determining re-isolation frequencies from lesions. In general, significant differences in fitness-related characteristics, except pathogenic aggressiveness, were found not only between but also within phenotype groups. In the competitiveness tests, carbendazim-sinsitive phenotypes (SSR and SRR) were found to be more competitive than the resistant ones (RSS and RSR), whereas, the procymidone-resistant phenotypes (SRR and RRS) appeared to be more competitive than the sensitive ones (SSR, RSS, and RSR). There was no consistent dominance in competitiveness between the diethofencarb-resistant and sensitive phenotypes. The RSR phenotype was the least competitive among the five phenotypes.

• Korean Journal of Environmental Agriculture
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• v.20 no.1
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• pp.63-66
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• 2001

To investgate growth effect of tomato by Bacillus sp. WRD-1 isolated from soil, the Bacillus sp. WRD-1 cultures were treated into tomato cultivated soil with different dilutions (1:100, 1:300, and 1:500) and autoclaved Bacillus cultures as control. Growth and yeild of tomato enhanced in treatments of the Bacillus cultures compared to control. The populations of native bacteria and actinomyces were increased twice in field treated with Bacillus sp. WRD-1 cultures, but the number of mold was decreased. Since the Bacillus sp. WRD-1 promoted growth of tomato and affected population dynamics of microorganism in field, this strain is prominent candidate as a microbial biocide to improve soil potential.

• ALGAE
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• v.23 no.4
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• pp.277-288
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• 2008

The relationship between nutrients and phytoplankton dynamics was investigated daily from 12 April to 22 July 2003 in Sagami Bay, Japan. According to multidimensional scaling (MDS) and cluster analysis, phytoplankton community was divided into four distinct groups. The first group was consisted of centric diatom species, such as Guinardia spp., Detonula spp., Letocylindrus danicus, Skeletonema costatum, Eucampia zodiacus and Chaetoceros spp.. The second and third clusters comprised mainly diatoms and dinoflagellates, respectively. The other cluster was restricted to the samples collected during the last sampling period when the rainfall and river discharge was frequently recorded. Canonical correspondence analysis (CCA) was applied to analyze four groups respectively, which focused on the effects of nutrients concentration and ratio on phytoplankton variations. Based on CCA analysis, most species of centric diatom were negatively correlated with DSi concentrations and Si/N ratio. Nutrients were strongly limited phytoplankton growth during the summer when the rainfall was not observed, whereas river discharge by rainfall and counterclockwise coastal currents (although the surface circulation pattern is often altered by Kuroshio Current, the counterclockwise coastal currents are generally dominant) has brought phytoplankton population accumulation and triggered the micoalgae growth in western part of the bay. Phosphorous (P) was strongly limited after significantly increases in the phytoplankton abundances. However, silicate (Si) was not a major limiting factor for phytoplankton production, since Si/DIN and Si/P ratio did not create any potential stoichiometric limitation. This indicates that high Si availability contributes favorably to the maintenance of diatom ecosystems in Sagami Bay.

• Animal cells and systems
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• v.4 no.2
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• pp.131-140
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• 2000

The pattern of variations in cone sex ratio and pollen traits such as pollen number and size was examined for two years in populations of red pines In Korea. We evaluated; (1) the relationship between tree size and cone sex ratio, (2) the relationship between year and cone sex ratio, and (3) the relationship between cone sex ratio and pollen traits. Larger trees in height and circumference at breast height produced more male as well as female cones. However, cone sex ratio was independent of these plant sizes. Across the two populations, both female cone numbers per tree and male cone numbers per new shoot increased 2.2 and 1.2 times, respectively, in 1999 compared to 1998, while the yearly pattern of male cone-bearing shoots per tree differed significantly between populations. Thus, cone sex ratio varied significantly between years in one of the two populations. Pollen traits such as the number of pollen grains and diameter did not vary significantly among populations. Pollen diameter and grain numbers per male cone were significantly negatively correlated with the cone sex ratio in two populations and one population, respectively. Trees which stopped female cone production in the first year and those which produced female cones in both years differed in the cone sex ratio and pollen size in the second year. The long duration of one reproductive episode and the potential of masting in red pines emphasize the need to conduct long-term studies on the dynamics of cone production, cone sex ratio, and simultaneous changes in pollen traits in red pines.

• Korean journal of applied entomology
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• v.29 no.2
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• pp.104-112
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• 1990

Studies were conducted to investigate hosts, life cycle, population dynamics and natural enemies of mulberry scale, Pseudaulacaspis pentagona Ta. & Tozz., from 1987 to 1988 in southern region of Korea. The host plants were 22 families and 74 species. Host plants belonged to genus Prunus in general were severely damaged due to mulberry scale. Mulberry scale was most likely to have three generations a year with first occurrence of larval stage from mid-May to late June, second occurrence from mid-July to mid-August and third occurrence from early September to late October including 3 peaks in early and mid-June, late July and mid-September. In case of each stage occurrence, eggs were peaked on 10th day, larvae on 25th day and adults on 7th day from beginning of occurrence, respectively. Natural enemies were observed as parasitoids of 3 species such as Aphytis diaspidis, Archenomus orientalis and Apterencyrtus mocrophagus and as predators of 3 species such as Chilocorus Kuwanae, Chilocorus rubidus and Hormonia axyridis. Shoot growth was affected by mulberry scale and Lepra to dwindle as much as half of normal growth.

• International Journal of Control, Automation, and Systems
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• v.2 no.4
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• pp.463-474
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• 2004

Game theory is a method of mathematical analysis developed to study the decision making process. In 1928, Von Neumann mathematically proved that every two-person, zero-sum game with many pure finite strategies for each player is deterministic. In the early 50's, Nash presented another concept as the basis for a generalization of Von Neumann's theorem. Another central achievement of game theory is the introduction of evolutionary game theory, by which agents can play optimal strategies in the absence of rationality. Through the process of Darwinian selection, a population of agents can evolve to an Evolutionary Stable Strategy (ESS) as introduced by Maynard Smith in 1982. Keeping pace with these game theoretical studies, the first computer simulation of coevolution was tried out by Hillis. Moreover, Kauffman proposed the NK model to analyze coevolutionary dynamics between different species. He showed how coevolutionary phenomenon reaches static states and that these states are either Nash equilibrium or ESS in game theory. Since studies concerning coevolutionary phenomenon were initiated, there have been numerous other researchers who have developed coevolutionary algorithms. In this paper we propose a new coevolutionary algorithm named Game theory based Coevolutionary Algorithm (GCEA) and we confirm that this algorithm can be a solution of evolutionary problems by searching the ESS. To evaluate this newly designed approach, we solve several test Multiobjective Optimization Problems (MOPs). From the results of these evaluations, we confirm that evolutionary game can be embodied by the coevolutionary algorithm and analyze the optimization performance of our algorithm by comparing the performance of our algorithm with that of other evolutionary optimization algorithms.

• Korean journal of applied entomology
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• v.39 no.1
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• pp.13-19
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• 2000

This studies was carried out to investigate the natural enemies of citrus red mite, pononychus citri and seasonal occurrence of its major beneficial insects in Yuzu groves (Chonnam province) from 1996 to 1998. Natural enemies against citrus red mite were 9 species including Oligota kashmirica benifica, 0. yasumatsui, Stethorus punctillum, Chrysopa pallens, Propylea japonica, Orius sauteri, Scolothrips takahashii, Amblyseius womersleyi and one unidentified species of thrips (Family: Phlaeothripidae). Among them, Oligota kashmirica benzficu and Stethorus punctillum were found to be dominant species. 0 . kushmirica henifica had 4-5 generations from middle May to middle November with peak in early September. S. punctillum had 3 generations from late May to late October with peak of late June to middle July. Population dynamics between predator ( 0 . kushmiricu benifica and S. punctillum) and prey (Panonychus citri) were quite well synchronized until September but predator density was decreased abruptly after October.