• The Korean Journal of Ecology
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• v.20 no.4
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• pp.275-283
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• 1997

Vertical and temporal characteristics of desalinized reclaimed soil were analyzed from reclaimed coastal land on the western coast of Korea. Of the vertical changes during desalting, pH valuse were the lowest at the topsoil without regard to reclaimation time. The content of C1 were designated as the early period (the first 2-4 years) which decreased exponentially and the later period(the last 5-7 years) which was almost constant, from top to down. In temporal changes of the soil attributes, pH values increased for 5 years and decreased at 6 year after reclamation. Chlorine leaches more rapidly than Na does, K and Ca are constant but Mg increases as time elapsed after reclamation. Sometimes the content of Ca and K in the reclaimed soil are of higher concentration than that of the seawater after reclamation. During desallinization as exemplified by decreasing EC of the soil, Cl and Na are rapidly leached, but K, Ca and Mg are somewhat enhanced. The ration of Na/Cl in the soil equals 1 when the EC registers 5 mmho and then increases dramatically as the EC decreases. Rapid leaching of $Cl^{-}$ elicits an increasing pH valus. The electrostatic balance of the soil is achived by replacement of $Cl^{-}$ with $OH^{-}$ until stationary or until a decreasing pH value is reached again.

• Journal of Energy Engineering
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• v.7 no.1
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• pp.89-95
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• 1998

Maintenance scheduling of generators plays an important role in evaluating supply reliability of power systems. Since generators must be maintained and inspected, the generation planner must schedule planned outages during the year. Several factors entering into this scheduling analysis include: seasonal load-demand profile, amount of maintenance, size of the units, elapsed time from last maintenance, and availability of maintenance crew. This paper proposes a new maintenance scheduling algorithm for the alternatives of long-term generation expansion planning by using LOLP levelization method which is known as an effective method for the generator's maintenance scheduling. To get the best supply reliability of power systems, we change the maintenance period to levelize the reliability over all period. The proposed algorithm is applied to a real size power system and the better reliability results are obtained.

• Ocean and Polar Research
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• v.31 no.3
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• pp.257-264
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• 2009

Seventeen females of the mud crab Scylla serrata, from the State of Kosrae, Micronesia, were transported to the Fisheries Resources Research Institute, Gyeongsangnam-do, in oxygen-filled plastic bags. After acclimatization to a $30^{\circ}C$ holding temperature, nine females were selected for seed production trials. Spawning was hastened using eyestalk ablations; however, this may not be required in commercialscale mud crab seed production. Primary spawning produced an average of 2.4 million hatched larvae, whereas secondary spawning produced 0.4 million. About 10 days elapsed between spawning and hatching and 30 days between hatching and crablet. Mass mortalities up to 90% were observed between stages zoea 1 and zoea 2 in every trial. The highest survival rate from zoea 1 to crablet was estimated at 0.25%. Most commercial shrimp hatcheries in Korea are equipped with almost all necessary facilities and could be converted easily to mud crab hatcheries, able to run three to four times per year using hatchery technologies developed for blue crabs and Chinese mitten crabs.

• Korea Journal of Hospital Management
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• v.6 no.2
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• pp.22-36
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• 2001

The hospital bankruptcy rate is increasing, therefore it is very important to predict the bankruptcy using the existing hospital management information. The hospital bankruptcy is often measured in year intervals, called grouped duration data, not by the continuous time elapsed to the bankruptcy. This study introduces a hierarchical generalized linear model(HGLM) for analysis of hospital bankruptcy data. The hazard function for each hospital may be influenced by unobservable latent variables, and these unknown variables are usually termed as random effects or frailties which explain correlations among repeated measures of the same hospital and describe individual heterogeneities of hospitals. Practically, the data of twenty bankrupt and sixty profitable hospitals were collected for five years, and were fitted to HGLM. The results were compared with those of the logit model. While the logit model resulted only in the effects of explanatory variables on the bankruptcy status at specific period, the HGLM showed variables with significant effects over all observed years. It is concluded that the HGLM with a fixed ratio and a period of total asset turnrounds was justified, and could find significant within and between hospital variations.

• East Asian Economic Review
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• v.27 no.3
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• pp.179-211
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• 2023

This paper investigates the relationship between the spread of COVID-19 and time preference. In contrast to previous studies that compared time preferences before and during the pandemic, this study estimates time preferences during the COVID-19 period using eight surveys conducted over two years. Additionally, a regression analysis was conducted on the number of new COVID-19 cases and the time elapsed since the outbreak, with estimated time preference as the dependent variable. Despite a small sample size, statistically significant results were obtained, showing that as the number of new cases increased, time preference also increased. However, this effect diminished over time and disappeared by the end of 2021 in Japan. This may be due to the public's growing familiarity with the risks of COVID-19 and the availability of vaccines and treatments. Despite a significant increase in new cases in 2022, time preference was lower than immediately after the outbreak, and this was reflected in private investments. Immediately after the outbreak of COVID-19, private investments decreased by 12% compared to the previous year, but the investments are returning in 2022 despite the surge in the number of cases. The trend of time preference explains the trend of Japanese private investments very well.

• The Korean Journal of Ecology
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• v.17 no.3
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• pp.345-353
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• 1994

Litter production and decomposition were investigated for 2 years in the oak, Quercus acutissima, and the pitch pine, Pinus rigida, stands in the vicinity of Kongju, Chungnam Province. Litter production was measured with litter trap at monthly basis. Litterbag method was used for the measurement of litter decomposition. Litter producion continued throughout the year, but showed a peak in autumn. Second peak in May or June was caused by falling of bud scales and reproductive organs. Average litter production in the oak and the pitch pine stands were $567.1g{\cdot}m^{-2}{\cdot}yr^{-1}\;and\;653.2g{\cdot}m^{-2}{\cdot}yr^{-1}$, respectively. Litter production in this study area were higher than those in other reports. Nutrient concentrations in litter were the highest in summer when the least litter production occurred, and the lowest in autumn when the greatest litter production occurred, except for calcium in the oak stand. Nutrient concentrations of the oak litter were higher than those in the pitch pine litter. After 1 year, % remaining mass of oak and pitch pine litter was 43.6% and 58%, respectively. After 21 months elapsed, % remaining mass of oak and pitch pine litter was 22.2% and 33.2%, respectively.

• Journal of Intelligence and Information Systems
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• v.24 no.1
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• pp.141-166
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• 2018

Information technology improves the efficiency of humanities research. In humanities research, information technology can be used to analyze a given topic or document automatically, facilitate connections to other ideas, and increase our understanding of intellectual history. We suggest a method to identify and automatically analyze the relationships between arguments contained in unstructured data collected from humanities writings such as books, papers, and articles. Our method, which is called history mining, reveals influential relationships between arguments and the philosophers who present them. We utilize several classification algorithms, including a deep learning method. To verify the performance of the methodology proposed in this paper, empiricists and rationalism - related philosophers were collected from among the philosophical specimens and collected related writings or articles accessible on the internet. The performance of the classification algorithm was measured by Recall, Precision, F-Score and Elapsed Time. DNN, Random Forest, and Ensemble showed better performance than other algorithms. Using the selected classification algorithm, we classified rationalism or empiricism into the writings of specific philosophers, and generated the history map considering the philosopher's year of activity.

• Journal of Korean Society of Forest Science
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• v.82 no.4
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• pp.381-395
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• 1993

To investigate the procedure of natural plant succession on cutting slope in the forest roads, considered elapsed years and regional distribution, data were collected from natural and artificial treatment slope. And to elucidate the effective methods of revegetation on forest road slope, each seeding experiments carried out with 4 species(Themeda triandra, Lysimachia clethroides, Artemisia princeps and Lespedeza cyrtobotrya). The pioneer species on cutting slope in the forest road were Pinus densiflora, Lespedeza bicolor, Rhubus crataegiflora etc. in wood species, and Arundinella spp., Lysimachia barystachys, Artemisia spp. etc. in herb species. In process of year, plant coverage was increased and average of plant coverage was 30% in road slope which elapsed 5 years after construction. On short slope less than 3m, broadcast seeding method with straw mulch was more effective way than the other methods. Slope revegation work should be adapted with forest road construction work and revegetation work with native species will be effective.

• Journal of the Korean GEO-environmental Society
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• v.19 no.11
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• pp.23-30
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• 2018

According to recent ground collapse occurrence, ground subsidence is increasing every year in downtown area, which is a social problem. The purpose of this study is to investigate the relationship between ground water level lowering and ground collapse through laboratory model experiments. After mixing 1:1 granite weathered soil with sand, sandy soil was formed as a relative density of 30%, 50%, and 80%. And then the changes of soil discharge with change of groundwater level were compared. The physical property of material of which particle distribution were well graded with maximu dry unit weight of $1.94kg/cm^3$ and internal friction angle of 37degrees. Ground water levels were measured at 10 cm, 20 cm, and 30 cm from the bottom. As a result, the experiment shows that the higher the groundwater level works the higher the discharge velocity and the magnitude of underground cavity also increases with elapsed time. Finally, the cumulative quantity of soil discharge occurred up to 30 kg at the elapsed time, 35 minutes. It was also confirmed that the range of ground collapse increased due to soil discharge with ground water level lowering.

• Korean Journal of Medicinal Crop Science
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• v.27 no.4
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• pp.284-291
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• 2019

Background: Ginseng root rot disease, caused by Cylindrocarpon destructans and Fusarium solani is a major cause of replant failure in continuous cropping ginseng. Methods and Results: To control replant injury in soil infected with C. destructans and F. solani, biosolarization was performed by covering the plot with transparent polyethylene film after adding green manure of maize and sunflower for the summer season. Per 10 a, fresh and dry weight of maize was 10.1 and 2.5 tons, respectively, and that of sunflower was 8.1 tons and 1.2 tons, respectively. Mean maximum temperature at 20 cm depth was $33.2^{\circ}C$, $41.5^{\circ}C$ and $41.8^{\circ}C$ in the control, maize-incorporated and sunflower-incorporated plots, respectively. The elapsed time over $40^{\circ}C$ was 36.4 h in the maize-incorporated plot and 77.3 h in the sunflower-incorporated plot. Biosolarization increased $NO_3$ content in soil, while content of organic matter, Ca, and Mg was decreased. Electrical conductivity, $NO_3$ and $P_2O_5$ in soil significantly increased after two years of biosolarization. The number of spores of C. destructans in soil was significantly decreased by biosolarization, and sunflower treatment was more effective than maize treatment in decreasing the number of spores. Root yield of 3-year-old ginseng was significantly increased by biosolarization, however, there was no significant difference between maize and sunflower treatments. Rate of root rot in 3-year-old ginseng decreased to 16.5% with the incorporation maize and 5.0% with the incorporation of sunflower, while that in control 25.6%. Conclusions: Biosolarization was effective in inhibiting ginseng root rot by decreasing the density of root rot disease and improving soil chemical properties.