• Journal of Internet Computing and Services
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• v.14 no.5
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• pp.101-117
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• 2013

As the number of online game user has been rapidly increased thanks to the recent vitalization of online contents market, not only new business opportunity but also the opportunity to create high profits have been provided as well. However, the increase of the number of online game user and the rapid expansion of the market evoke a cutthroat completion among online game service providers, and also high barriers to entry to online game market have been erected. Thus, what kinds of efforts need for the business success and sales increase in online game market? In lots of researches regarding online contents business, the deepening of loyalty was considered as a critical factor for the business success. According to the study on user's behavior in online environment, users would experience the Flow while using online service, and then, if they were in state of the Flow, they would use the service constantly. High customer loyalty to online game means high will to use the online game too. The purpose of this research was i) to examine what factors enable users to be naturally immersed in online game while playing it, ii) to examine what properties of online game can make game more interesting and exciting, iii) to verify that such factors are critical in deepening customer loyalty, and iv) to suggest some essential factors to be fun and exciting games, on where the focus should be put, and the directionality for the development for sales expansion of online game developer or online game service provider. The research results are as below: First, the involvement and the perceived quality which were characteristics of brand appeared to be factors most affecting Flow. This shows that once game user get interested in online game that user has played frequently, even though new games are released, user will continuously flow the game not moving to new games, and also shows that users not only get more interested but also put more trust in games in the site to where users are frequently going than games in other sites, and consequently user can increasingly flow the game. Second, the compensation and graphics which are the characteristics of contents appeared to be factors affecting Flow. Proper compensation which is given to game users triggers fun and interests in game and makes them flow more and more. And graphics make users to feel game space as if real space and let them flow in game with more reality. Third, challenges, support, and the stability which are technical characteristics appeared to be factors affecting Flow. Challenges enable users to not only experience new virtual world but also solve various difficulties and obstacles. Once users feel fun and interests through this challenge, they can naturally flow games. In addition, the stability of network provides reliability in security and hacking. By doing so, it can induce users to flow more and more. Lastly, when aforementioned characteristics including contents characteristics, technical characteristics, and brand characteristics are organically combined each other, game users feel fun and total minutes are naturally increased, so that game users experience Flow, and consequently the customer loyalty will be deepened as well.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.77-85
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• 2008

Grazing rates (GR) and pseudofaeces production (PFP) of native snail, Chinese mystery snail (Cipangopaludina chinensis malleata Reeve) on natural colonial morphs of Microcystis aeruginosa was measured. C. chinensis was collected from the upstream of the Geum River (Boryeong, Korea), where they co-habituated with Unio douglasiae and Lanceolaria acrorhyncha. The experiments were performed to evaluate the GR and PFP at different conditions such as; incubation time (1, 3, 5, 7, 9 and 11 hr), body size (3 to 6.1 cm, n=28), snail density (0.5, 1, 1.5 and 2.0 ind. $L^{-1}$) and prey concentration (168.3, 336.7, 505.0 and $673.0{\mu}g\;Chl-{\alpha}L^{-1}$). All experiments were triplicated, and conducted in transparent acrylic vessel (3L in volume). Regarding feeding time, a highest GR (0.538L $gAFDW^{-1}h^{-1}$) and PFP $(7.18mgAFDW^{-1})$ appeared at 1hr and 7hr after snail stocking, respectively. Interestingly, the snail, smaller than 4.5cm in body size, showed a wide range of GR ($-4.173{\sim}1.087L\;gAFDW^{-1}h^{-1}$) for the initial period (1 and 4hrs of stocking), compared to those greater than 4.5cm, which showed a stable FR, higher than 0.5L $gAFDW^{-1}h^{-1}$. Upon density effect, the density of 1.5 ind. $L^{-1}$ induced the most effective inhibition on Microcystis biomass with highest PFP. On the prey concentration, highest GR (0.897L $gAFDW^{-1}h^{-1}$) and PFP (3.67 mg $gAFDW^{-1}h^{-1}$) were induced at the level of $168.3{\mu}g\;Chl-{\alpha}L^{-1}$ and $673{\mu}g\;Chl-{\alpha}L^{-1}$, respectively. GR and PFP of this freshwater snail on the cyanobacterial bloom (M. aeruginosa) varied with the feeding conditions, and they were comparatively high for a short period of time less than 7hrs regardless of the stocking condition. Our results suggest that this freshwater snail has a potential to control cyanobacterial bloom when provided with suitable condition.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.35-41
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• 2008

Nutrient Enrichment Bioassays (NEBs) were conducted in the laboratory during June $22{\sim}28$, 2006 in order to determine primary limiting factor on the phytoplankton growth. For the NEBs, the water was sampled using a 10L polyethylene-lined container and dispensed into 2.5L container in the laboratory. The algal growths response in the control (C) and three treatments of phosphorus (P), 2-fold phosphorus (2P), and nitrate nitrogen $(NO_3-N)$ were monitored during 7 days. In the cubitainers which were spiked as P (T1) and 2P (T2) Chl-${\alpha}$ concentrations were decreased during the test period and the final concentrations was low than initial values. However, Chl-${\alpha}$ in the cubitainers which were spiked as $NO_3$(T3) and $P+NO_3$(T4) showed significant increases compared to the initial values, indicating that in the short-term experiments, nitrogen seemed to be a primary limiting nutrient during the periods of NEBs experiment. Long-term ambient nutrient data of TP and TN, and TN:TP mass ratios, however, showed a potential phosphorus limitation on phytoplankton growth and previous other researchers showed a variations of limiting nutrients by nitrogen or phosphorus depending on the seasons sampled and locations. In this study nitrogen as primary limiting nutrient in the NEBs seem to be an seasonal effect rather than the consistent nitrogen limitation.

• Korean Journal of Ecology and Environment
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• v.41 no.spc
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• pp.50-60
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• 2008

We performed the experiment to evaluate the effect of different DO concentrations (0.5, 4.5 and 9.0 $mgO_2L^{-1}$) and water depths (20, 50 and 80 cm) on the filtering rate, mortality, and pseudifeces production of Unio douglasiae against the cyanobacterial bloom (mainly Microcystis aeruginosa). A solitary-living bivalve U. douglasiae was collected in the upstream region of the North Han River (Korea). The harvested mussels were carefully transferred to the laboratory artificial management system, which was controlled temperature $(18{\pm}2^{\circ}C)$, flow rate (10L $h^{-1}$), food $(Chlorella^{TM})$, sediment (pebble and clay), light intensity (ca. $20{\mu}mol$ photons), and photocycle (12 L : 12 D). In the field observation, the mussel mortality was significantly correlated with water temperature, pH and DO concentration (P<0.05). The mortality was decreased with water depth; 65, 90, 80% of mortality at 20, 50, 80 cm water-depth, respectively. Filtering rate (FR) showed the highest value at 50 cm water depth, and thereby the concentration of chlorophyll-${\alpha}$ decreased continuously by 94% of the control at the end of the experiment. In contrast, FR decreased by 34% of the initial concentration at 20 cm water depth. Over the given water-depth range, the mussel FR ranged from $0.15{\sim}0.20L\;gAFDW^{-1}hr^{-1}$ during the 18hrs of experiment, and thereafter, they appeared to be approximately 0.11, 0.26 and 0.30 L $gAFDW^{-1}hr^{-1}$ at 20, 50 and 80cm water depth, respectively. FR was highest with the value of 0.46L $gAFDW^{-1}hr^{-1}\;at\;0.5mgO_2 L^{-1}$ at the early stage of the experiment, while it increased with DO concentration. Maximum pseudofaeces production was 11.2 mg $gAFDW^{-1}hr^{-1}\;at\;9.0mgO_2L^{-1}$. Our results conclude that U. douglasiae has a potential to enhance water quality in eutrophic lake by removing dominant cyanobacteria, but their effects vary with environmental parameters and the water depth at which they are located.

• Korean Journal of Environmental Agriculture
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• v.31 no.1
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• pp.37-44
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• 2012

BACKGROUND: Many edible mushrooms are known to accumulate high levels of heavy metals. This research was focused on health risk assessment to investigate the mushrooms in Korea, arsenic (As), cadmium (Cd), lead (Pb) and mercury (Hg) contaminations in edible mushrooms in cultivated areas were investigated, and health risk was assessed through dietary intake of mushrooms. METHODS AND RESULTS: The heavy metals in mushrooms were analyzed by ICP/MS after acid digestion. Probabilistic health risk were estimated by Monte-Carlo simulation techniques. The average contents of As, Cd, Pb, and Hg were $0.035{\pm}0.042$ mg/kg, $0.017{\pm}0.020$ mg/kg, $0.043{\pm}0.013$ mg/kg, and $0.004{\pm}0.004$ mg/kg, respectively. The results showed that contents of Cd and Pb did not exceed maximum residual levels established by European Uion regulation (Cd 0.20 mg/kg and Pb 0.30 mg/kg). For health risk assessment, estimated intakes in all age populations did not exceed the provisional tolerable daily intake of As and Hg, provisional tolerable monthly intake of Cd, provisional tolerable weekly intake of Pb. The Hazard Index (HI) were ranged from $0.03{\times}10^{-4}{\sim}0.01{\times}10^{-3}$ for As, $0.02{\times}10^{-3}{\sim}0.81{\times}10^{-3}$ for Cd, $0.06{\times}10^{-3}{\sim}0.38{\times}10^{-3}$ for Pb, and $0.08{\times}10^{-4}{\sim}0.14{\times}10^{-3}$ for Hg at general population. CONCLUSION: The HI from the ratio analysis between daily exposure and safety level values was less than 1.0. This results demonstrated that human exposure to heavy metals through dietary intake of mushrooms might not cause adverse effect.

• Journal of Environmental Impact Assessment
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• v.23 no.4
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• pp.251-270
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• 2014

The purpose of this study is to offer the basic data and method for assessing the naturaliness of temple environment by applying the ecological index of plant to quantitatively and objectively assess the flora and to understand the flora distributed in major temple forest. The ecological index of plant was based in the surveyed flora. The whole flora were summarized as 535 taxa including 103 families, 310 genera, 426 species, 5 subspecies, 82 varieties and 22 forms. And, the numbers of taxa in the Beopheungsa were 267 taxa, 314 taxa of the Daeseungsa and 296 taxa of the Seongjusa. The rare plants were 9 taxa including Aristolochia contorta, Viola albida, Arisaema heterophyllumand so forth, and the Korean endemic plants were 11 taxa including Clematis trichotoma, Stewartia pseudocamellia, Vicia chosenensis and so forth. The specific plants by floristic region were 51 taxa including Wistaria floribunda, Celtis aurantiaca, Angelica gigas and so forth, and the pteridophyta were 26 taxa including Osmunda japonica, Polystichum braunii, Onoclea orientalis and so forth. The naturalized plants were 35 taxa including Fallopia dumetorum, Conyza canadensis, Xanthium strumarium and so forth, the invasive alien plants were 3 taxa including Ambrosia artemisiifolia, Aster pilosus and Eupatorium rugosum. In the results of analysing the ecological index of plant in whole temple forests, RI(Rare Index) was 1.7%, 2.1% of EI(Endemic Index), 9.5% of SI(Specific Index), 1.2 of PI(Pteridophyta Index) and 6.5% of NI(Naturalized Index) in narrow sense. In broad sense, FI(Flora Index) was 11.0%, 1.5% of RI, 3.4% of EI, 4.8% of SI, 10.1% of PI, 10.9% of UI(Urbanized Index) and 25.0% of DI(Disturbed Index). The FI of the Daeseungsa was the highest among the three temple forests. In narrow sense, the RI, SI, NI and DI of the Beopheungsa was high, the seongjusa was higher the EI and SI. In broad sense, the RI and SI of the Beopheungsa, the EI, SI and PI of the Seongjusa, the UI is high in the Daeseungsa. In future, if we will analyze ecological index of plant in other temple forests, we will offer the help to establishing the plan of conservation and restoration on ecosystem in whole temple forests.Environmental Specimen Banks (ESBs) are playing pivotal role in monitoring the effect of environmental pollution on the ecosystem based on the retrospective analysis of the representative samples collected regularly and stored in cryogenic condition.

• Journal of The Korean Society of Grassland and Forage Science
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• v.25 no.3
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• pp.159-168
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• 2005

This experiment was carried out during the period from May to October 1998 to determine the effect of fermented sawdust swine manure application (SSM) on the herbage production of Japanese millet and soil properties in the Cheju brown volcanic ash soil. The randomized block design (T1 : basic chemical fertilizer, N 200 kg/ha + $P_2O_5\;300 kg/ha+K_2O$ 200kg/ha ; T2 : 1/2 basic chemical fertilizer, N $100+P_2O_5\;150+K_2O$ 100kg/ha; T3 : 1/2 basic SSM, N 100kg/ha, T4:basic SSM, N 200kg/ha; T5:2 times basic SSM, N 400 kg/ha ; T6:4 times basic SSM, N 800 kg/ha) was used. At the same application level of nitrogen 200kg/ha, the application of $100\%$ chemical fertilizer (T1) had significantly lower dry matter yield than that of $50\%$ chemical fertilizer and $50\%$ SSM (T2) or $100\%$ SSM (T4)(p<0.01). Dry matter yield increased with an increase of SSM application to N 400kg/ha level but decreased at N 800 kg/ha level. P, K and Ca contents of Japanese millet tended towards to decrease with an increase of SSM level. The application of chemical fertilizer lowered P and K content of Japanese millet in comparison with that of SSM (p<0.05). pH, available phosphorus. exchangeable potassium, Ca and Mg content of soil studied showed a significant increase with an increase of SSM application level (p<0.05). However, at the same application level of N 200kg/ha, there was statistically no significant difference between chemical fertilizer and SSM in those contents of soil after experiment. The bacterial number of soil among microbial population increased with an increase of SSM level, in June, 1998 (p<0.05), but there was no regular tendency, in October. The rate of bacteria to fungus in soil had a tendency to decrease with an increase of SSM level. In conclusion, it is recommended to use N 400kg/ha of SSM or N 100 kg/ha of chemical fertilizer+N 100 kg/ha of SSM for Japanese millet.

• Journal of The Korean Society of Grassland and Forage Science
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• v.19 no.3
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• pp.203-210
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• 1999

Of all the nutrients in liquid manure, N has the greatest potential both for the environment and for increasing forage yields. This experiment was carried out to determine the effect of different types and N rates of liquid manure on mineral content and nitrate-N of oats(Avena sativa L.), soil chemical characteristics in Suweon. Seven treatments consisting of chemical fertilizer $120kg\;N\;ha^{-1}$, liquid cattle manure 120, 240 and $360kg\;N\;ha^{-1}$, liquid swine manure 120, 240 and $360kg\;N\;ha^{-1}$ were arranged in a randomized complete block design with three replications. Compared with the plot of chemical fertilizer, increasing liquid manure N rates increased mineral contents of oats. Nitrate-N contents of oats were ranged from 1,881 to $2,605mg\;kg^{-1}$ in all treatments, which was orderly ranked as chemical fertilizer>liquid cattle manure $360kg\;N\;ha^{-1}$> liquid swine manure $240kg\;N\;ha^{-1}$. Contents of exchangeable cation of the soil were appeared to be higher with increasing liquid manure N rates. Amount of total-N and inorganic-N in soil affected by increasing liquid manure N rates, and there was the highest at liquid swine manure $360kg\;N\;ha^{-1}$ among the treatments. Nitrate-N concentration in infiltration water was not remarkably variable during the experimental period. Based on the results of this experiment, it is suggested that the amount of nitrogen in soil was orderly ranked as liquid swine manure $360kg\;N\;ha^{-1}$, followed by liquid swine manure $240kg\;N\;ha^{-1}$.

• Korean Journal of Ecology and Environment
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• v.47 no.3
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• pp.186-193
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• 2014

This study aimed to analyze spatio-temporal trends of phenological characteristics in South Korea by using MODIS EVI. For the phenology analysis, we had applied double logistic function to MODIS time-series data. Our results showed that starting date of phenology seems to have a tendency along with latitudinal trends. Starting date of phenology of Jeju Island and Mt. Sobeak went back for 0.38, 0.174 days per year, respectively whereas, Mt. Jiri and Mt. Seolak went forward for 0.32 days, 0.239 days and 0.119 days, respectively. Our results exhibited the fluctuation of plant phonological season rather than the change of phonological timing and season. Starting date of plant phenology by spatial distribution revealed tendency that starting date of mountain area was late, and basin and south foot of mountain was fast. In urban ares such as Seoul metropolitan, Masan, Changwon, Milyang, Daegu and Jeju, the phonological starting date went forward quickly. Pheonoligcal attributes such as starting date and leaf fall in urban areas likely being affected from heat island effect and related warming. Our study expressed that local and regional monitoring on phonological events and changes in Korea would be possible through MODIS data.

• Journal of Life Science
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• v.16 no.6
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• pp.942-948
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• 2006

This study was performed to determine whether the length of the feeding of the controlled experimental diet to the dam resulted in changes to the dam milk or pup brain fatty acid composition. As a first method, females have been obtained at 3 weeks of age and fed the experimental diet throughout their growth to adulthood including mating, pregnancy, and lactational periods. As a second method, in order to shorten this long and expensive process, time-pregnant dams were obtained as early as possible from a commercial supplier, on day 3 of gestation, and immediately switched to the experimental diet. At birth, the milk of dams prepared by these two different methods was compared by collecting the stomach contents of the pups. This showed a slight increase in docosahexaenoic acid (DHA) and arachidonic acid (AA) in the pup stomach contents from the time-pregnant dams. There were no significant changes in the brain fatty acid composition of pups between the two different lengths of the experimental diet intake. By the 10 days of age, there were only minor differences in the milk fatty acid composition of pup stomach contents from the two sets of dams. However, the pup brains of the time-pregnant groups at 10 days showed increased AA and DHA due to intake of the chow diet including AA, DHA and eicosapentaenoic acid (EPA). Thus, the history of the maternal feeding could affect the results under these particular circumstances, but the differences were minimal.