• Information Systems Review
• /
• v.11 no.1
• /
• pp.161-179
• /
• 2009

Nowadays an increasing number of Internet users are running individual websites as Blog or Cyworld. As this type of personal media has a great influence on communication among people, business comes to care about Network Effect, Network Software, and Social Network. For instance, Cyworld created the web service called 'Minihompy' for individual web-logs, and acquired 2.4milion users in 2007. Although many people assumed that the popularity of Minihompy, or Blog would be a passing fad, Cyworld has improved its service, and expanded its Network with various contents. This kind of expansion reflects survival efforts from infinite competitions among ISPs (Internet Service Provider) with focus on enhancing usability to users. However, Cyworld's Network Effect is gradually diminished in these days. Both of low production cost of service vendors and the low searching/conversing costs of users combine to make ISPs hard to keep their market share sustainable. To overcome this lackluster trend, Cyworld has adopted new strategies and try to lock their users in their service. Various efforts to improve the continuance and expansion of Network effect remain unclear and uncertain. If we understand beforehand how a service would improve Network effect, and which service could bring more effect, ISPs can get substantial help in launching their new business strategy. Regardless many diverse ideas to increase their user's duration online ISPs cannot guarantee 'how the new service strategies will end up in profitability. Therefore, this research studies about Network effect of Cyworld's 'Minihompy' using System-Dynamics method which could analyze dynamic relation between users and ISPs. Furthermore, the research aims to predict changes of Network Effect based on the strategy of new service. 'Page View' and 'Duration Time' can be enhanced for the short tenn because they enhance the service functionality. However, these services cannot increase the Network in the long-run. Limitations of this research include that we predict the future merely based on the limited data. We also limit the independent variables over Network Effect only to the following two issues: Increasing the number of users and increasing the Service Functionality. Despite of some limitations, this study perhaps gives some insights to the policy makers or others facing the stiff competition in the network business.

• Journal of Korean Society of Forest Science
• /
• v.87 no.3
• /
• pp.358-365
• /
• 1998

To offer the basic information for sustainable production of forest resources and conservation of the global environment, change in potential natural vegetation (PNV) associated with climate change due to doubling atmospheric carbon dioxide ($2{\times}CO_2$) was estimated with the global natural vegetation mapping system based an K${\ddot{o}}$ppen scheme. The system interpolates climate data spherically to each grid cell, determines the vegetation types onto the grid cell, and produces potential vegetation map and area on the globe and continents. The climate data consist of the current, ($1{\times}CO_2$) climate prior to AD 1958 observed at some 2,000 stations and the doubling ($2{\times}CO_2$) climate estimated from Meteorological Research Institute of Japan. The vegetation zone under the $2{\times}CO_2$ climate scenario expanded mainly toward the poles due to the rise in temperature. The changed PNV area on the globe amounts to 1/3 (4.91 billion (G) ha) of the total land area (15.04 Gha). Kappa statistic for judging agreement between the patterns of vegetation distribution under $1{\times}CO_2$ climate and $2{\times}CO_2$ climates shows good agreement (0.63) for the globe as a whole. The most stable areas are desert and ice. The potential forest area (PFA) was estimated at 6.82 Gha of the land area in $2{\times}CO_2$ climate scenario. In terms of continental changes in PFA, North America and Asis are increased under the $2{\times}CO_2$ climate. However, the potential forest arms of the other continents are decreased by the climate. Europe has no change in the PFA. Especially, the expansion of desert area in Oceania would be accelerated by the $2{\times}CO_2$ climate.

• Journal of Animal Science and Technology
• /
• v.48 no.3
• /
• pp.453-466
• /
• 2006

To comply with stricter regulations provoked by increasing odor nuisance, it is imperative to practice effective odor control for sustainable livestock production. This study was conducted to assess odor and odorous compounds emitted from liquid animal manure with different treatment methods such as Fresh Manure(without treatment, FM), Anaerobic Digestion(AD) and Thermophilic Aerobic Digestion(TAD) and their application to soil. Air samples were collected at the headspace of liquid manure, upland and paddy soil, and analyzed for odor intensity and offensiveness using an olfactometry; odor concentration index using odor analyser; nitrogen-containing compound such as ammonia(NH3) using fluorescence method; and sulfur containing compounds such as hydrogen sulfide(H2S), methyl mercaptan(MeSH), dimethyl sulfide(DMS) and dimethyl disulfide(DMDS) using gas chromatography-pulsed flame photometric detector, respectively. Odor intensity, offensiveness and concentration index from TAD liquid manure was statistically lower than those from FM and AD(p<0.01). Mean concentrations of H2S, MeSH, DMS, DMDS and NH3 were 65.93ppb, 18.55ppb, 5.26ppb, 0.33ppb and 10.57ppm for liquid manure with AD; and 5.15ppb, 0.97ppb, 0.80ppb, 0.56ppb and 1.34ppm for liquid manure with TAD, respectively. More than 60% of malodorous compounds related to nitrogen and sulfur were removed by heterotrophic microorganisms during TAD treatment. When liquid manure was applied onto upland and paddy soil, NH3 removal efficiencies ranged from 51 to 94% and 22 to 91% for AD and TAD liquid manure, respectively. The above results show that liquid manure with TAD is superior to AD and FM with respect to the odor reduction and odor problem caused by land applied liquid manure is directly related to the degree of odor generated by the manure treatment method.

• Korean Journal of Agricultural and Forest Meteorology
• /
• v.6 no.2
• /
• pp.107-117
• /
• 2004

If doubtlessly contributes much to agriculture and rural development. The roles can be summarized as; 1. to activate rural areas and to provide more comfortable and safe rural life with equivalent services to those in urban areas, facilitating distance education, tole-medicine, remote public services, remote entertainment etc. 2. To initiate new agricultural and rural business such as e-commerce, real estate business for satellite officies, rural tourism and virtual corporation of small-scale farms. 3. To support policy-making and evaluation on optimal farm production, disaster management, effective agro-environmental resource management etc., providing tools such as GIS. 4. To improve farm management and farming technologies by efficient farm management, risk management, effective information or knowledge transfer etc., realizing competitive and sustainable farming with safe products. 5. To provide systems and tools to secure food traceability and reliability that has been an emerging issue concerning farm products since serious contamination such as BSE and chicken flu was detected. 6. To take an important and key role for industrialization of farming or lam business enterprise, combining the above roles.

• Horticultural Science & Technology
• /
• v.34 no.6
• /
• pp.818-829
• /
• 2016

This study evaluated the responses of 18 potato cultivars to three levels of salinity stress (electrical conductivity, EC: 1.0, 4.0, and $8.0dS{\cdot}m^{-1}$). Stem, leaf, root, chlorophyll, tuber yield, and proline content were investigated and statistically analyzed using analysis of variance (ANOVA) and correlations. Stem number and stem diameter were not affected by salinity, but stem length and aerial weight showed highly significant responses to salinity. Aerial weight decreased with increasing salinity levels in most cultivars, while it increased in some the cultivars 'Daejima', 'Goun', 'Haryeong', and 'LT-8'. Leaf number, leaf area index, and leaf weight were most significantly affected by salinity and the cultivar ${\times}$ salinity interaction. Root length, root weight, total chlorophyll and chlorophyll a were affected by salinity, but not by the cultivar ${\times}$ salinity interaction. The opposite trend was shown in chlorophyll b. Although there was great variability among cultivars, tuber yield decreased in all cultivars, and was most significantly influenced by salinity and the cultivar ${\times}$ salinity interaction. 'Superior', 'Kroda', 'Romana', and 'Duback' gave better tuber yields under salinity at EC 4.0 and $8.0dS{\cdot}m^{-1}$ than the cultivars with better aerial weights. Proline content was increased by salinity in all cultivars, and was more remarkable in the cultivars with better aerial weights than in cultivars such as 'Superior' and 'Kroda' with better tuber yields. Leaf number, leaf area index, leaf weight, and root length parameters were considered to be useful criteria in the evaluation of salt tolerance because of their high positive correlation with tuber yield; however, given its negative correlation with tuber yield under high salinity, proline content was not. Salinity tolerances varied greatly among potato cultivars. The low correlation between growth and yields of aerial parts under high salinity suggests that, in commercial agriculture, it might be more practical to compare relative yields to controls. Additionally, 'Superior', 'Kroda', 'Romana', and 'Duback' might be very useful cultivars to use in breeding programs to develop salinity-tolerant potatoes, as well as for sustainable potato production in saline areas.

• Journal of Life Science
• /
• v.26 no.8
• /
• pp.955-962
• /
• 2016

Fish-meat gel is an intermediate product used in a variety of surimi-based seafood. One of the most-used raw materials of fish-meat gel is Alaska Pollock due to its high-quality meat in terms of gel strength and texture. However, increasing demand for fish-meat gel, along with overexploitation of the wild catch Alaska Pollock, has put the industry in need of low-cost sustainable alternative sources for fish-meat gel. Pagrus major (PM) is a widely aquacultured fish known for having white meat that is low in fat. The current study compares the quality of fish-meat gel prepared from aquacultured PM to that of high and mid-grade Alaska Pollock fish-meat gel. Gels were compared in terms of gel strength, texture, color, and protein pattern. Results indicated that fish-meat gels prepared from PM were superior to Alaska Pollock fish-meat gels with regard to gel strength, hardness, springiness, chewiness, cutting strength, and breaking force. In addition, although not matching in quality, PM exhibited a cohesiveness, whiteness, and expressible moisture content comparable to Alaska Pollock of both grades. Protein pattern analysis also showed that PM and Alaska Pollock fish-meat gels had similar protein profiles before and after gel preparation. Therefore, P. major is suggested as a potential substitute for Alaska Pollock in fish-meat gel production.

• Journal of Animal Science and Technology
• /
• v.50 no.3
• /
• pp.391-400
• /
• 2008

Odor management is significantly concerned with sustainable livestock production because odor nuisance is a primary cause for complaint to neighbors. This study was conducted to measure the concentration of odorous compounds, odor intensity, and odor offensiveness at unit process in animal waste treatment facility combined composting and methane fermentation process by an instrumental analysis and direct olfactory method. Ammonia, sulfur-containing compounds, and volatile fatty acid were analyzed at each process units and boundary area in summer and winter, respectively. Higher concentration of odorants occurred in the summer than in the winter due to high ambient temperature. The maximum concentration of odorants was detected in composting pile when mixed manure was being turned followed by inlet, curing, outlet, and screen & packing process. Highest concentration of detected odorous compounds was ammonia ranging from 3.4 to 224.7 ppm. Among the sulfur-containing compounds measured, hydrogen sulfide was a maximum level of 2.3 ppm and most of them exceeded reported odor detection thresholds. Acetic acid was the largest proportion of VFA generated, reaching a maximum of 51 to 89%, followed by propionic and butyric acid at 1.9 to 35% and 1.8 to 15%, respectively. Malodor assessment by a human panel appeared a similar tendency in instrumental analysis data. Odor quotient for predicting major odor-causing compounds was calculated by dividing concentrations measured in process units by odor detection thresholds. In the composting process, hydrogen sulfide, ammonia, dimethyl sulfide, and methyl mercaptan were deeply associated with odor-causing compounds, while the major malodor compounds in the inlet process were methyl mercaptan, hydrogen sulfide, and butyric acid.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.19 no.4
• /
• pp.302-307
• /
• 2014

To examine the trophic ecology of the ascidian Styela clava in an aquaculture system of Korea, stable carbon and nitrogen isotopes were analyzed monthly in S. clava, coarse ($>20{\mu}m$, CPOM) and fine particulate organic matters ($0.7<<20{\mu}m$, FPOM). CPOM (means: $-18.5{\pm}1.2$‰, $9.3{\pm}0.7$‰) were significantly higher ${\delta}^{13}C$ and ${\delta}^{15}N$ values than those ($-20.5{\pm}1.5$‰, $8.4{\pm}0.5$‰) of FPOM. S. clava had mean ${\delta}^{13}C$ and ${\delta}^{15}N$ values of $-18.9({\pm}1.7)$‰ and $11.6({\pm}0.7)$‰, respectively. S. clava were more similar to seasonal variations in ${\delta}^{13}C$ and ${\delta}^{15}N$ values of FPOM than those of CPOM, suggesting that they rely largely on the FPOM as a dietary source. In addition, our results displayed that the relative importance between CPOM and FPOM as dietary source for the ascidians can be changed according to the availability of each component in ambient environment, probably reflecting their feeding plasticity due to non-selective feeding irrespective of particle size. Finally, our results suggest that dynamics of pico- and nano-size plankton (i.e., FPOM) as an available nutritional source to S. clava should be effectively assessed to maintain and manage their sustainable aquaculture production.

• Korean Journal of Soil Science and Fertilizer
• /
• v.43 no.6
• /
• pp.930-936
• /
• 2010

There is very important to investigate long-term trend of soil chemical properties and quality index for sustainable agriculture and production of agricultural safety products. Monitoring on soil chemical properties in paddy soils was conducted as one cycle with 4 years from 1999 to 2007. Paddy soil samples were taken from 4,007, 1,970, 2,070 sites in 1999, 2003 and 2007, respectively. With these data, soil quality index (SQI) was evaluated by method that Yoon et al suggested in 2004. Chemical properties of paddy soils were 5.8 for pH, 24 g $kg^{-1}$ for organic matter, 132 mg $kg^{-1}$ for available phosphate, 0.29 cmol_c\; kg-1 for exchangeable potassium, 4.7 $cmol_c\;kg^{-1}$ for exchangeable calcium, 1.3 $cmol_c\;kg^{-1}$ for exchangeable magnesium and 126 mg $kg^{-1}$ for available silicate in 2007. Long-term change was shown that pH has increased gradually whereas exchangeable potassium has decreased. However, reasonably large changes were found. Exchangeable calcium and available silicate level in 1999 was 4.0 $cmol_c\;kg^{-1}$, 86 mg $kg^{-1}$, but had risen to 4.7 $cmol_c\;kg^{-1}$, 126 mg $kg^{-1}$ in 2007, respectively. The change of paddy soils quality index was increased gradually and increasement of silicate quality index was higher than other quality indicators.

• Journal of Korean Society of Forest Science
• /
• v.100 no.4
• /
• pp.591-597
• /
• 2011

Forest carbon stock changes in a national forest were assessed by CBM-CFS3 model with different management scenarios to support decision making for a long term forest planning. Management scenarios were composed with 4 different levels of timber harvesting - current harvesting level (scenario1), 30% increment in each period (scenario2), 3 times increment (scenario3), and 5 times increment (scenario4). For each scenarios, changes in total carbon stocks, carbon stocks of each carbon pools, carbon stocks of harvested wood products (HWP) and age class structure were estimated over 100-year planning horizon. The estimated total carbon stock including HWP at the end of final period (100 years) was 433.1 tC/ha under scenario 1, but the age class structure has skewed right to the upper classes, which is not desirable for sustainable forest management. Under the scenario 4, however, the total carbon stock decrease to 385.5 tC/ha and the area of old growth forest show a significant decline. The estimated total carbon stock under scenario 2 and 3 were 411.7 tC/ha and 410.5 tC/ha respectively, and it was able to maintain the initial level of the forest carbon stocks during the planning horizon. Also the age class structures under the scenario 2 and 3 were evenly distributed from class 1 to class 8. Overall, scenario 2 and 3 were the most acceptable forest management options, in terms of carbon stock changes and age class structure.