• KIPS Transactions on Software and Data Engineering
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• v.12 no.3
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• pp.125-132
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• 2023

In this study, we compared the performance of machine learning models for predicting Vapor Pressure Deficits (VPD) in greenhouses that affect pore function and photosynthesis as well as plant growth due to nutrient absorption of plants. For VPD prediction, the correlation between the environmental elements in and outside the greenhouse and the temporal elements of the time series data was confirmed, and how the highly correlated elements affect VPD was confirmed. Before analyzing the performance of the prediction model, the amount and interval of analysis time series data (1 day, 3 days, 7 days) and interval (20 minutes, 1 hour) were checked to adjust the amount and interval of data. Finally, four machine learning prediction models (XGB Regressor, LGBM Regressor, Random Forest Regressor, etc.) were applied to compare the prediction performance by model. As a result of the prediction of the model, when data of 1 day at 20 minute intervals were used, the highest prediction performance was 0.008 for MAE and 0.011 for RMSE in LGBM. In addition, it was confirmed that the factor that most influences VPD prediction after 20 minutes was VPD (VPD_y__71) from the past 20 minutes rather than environmental factors. Using the results of this study, it is possible to increase crop productivity through VPD prediction, condensation of greenhouses, and prevention of disease occurrence. In the future, it can be used not only in predicting environmental data of greenhouses, but also in various fields such as production prediction and smart farm control models.

• Journal of Korean Society for Atmospheric Environment
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• v.26 no.6
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• pp.666-682
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• 2010

The forecasting system for Today's and Tomorrow's PM10 was developed based on the statistical model and the forecasting was performed at 9 AM to predict Today's 24 hour average PM10 concentration and at 5 PM to predict Tomorrow's 24 hour average PM10. The Today's forecasting model was operated based on measured air quality and meteorological data while Tomorrow's model was run by monitored data as well as the meteorological data calculated from the weather forecasting model such as MM5 (Mesoscale Meteorological Model version 5). The observed air quality data at ambient air quality monitoring stations as well as measured and forecasted meteorological data were reviewed to find the relationship with target PM10 concentrations by the regression analysis. The PM concentration, wind speed, precipitation rate, mixing height and dew-point deficit temperature were major variables to determine the level of PM10 and the wind direction at 500 hpa height was also a good indicator to identify the influence of long-range transport from other countries. The neural network, regression model, and decision tree method were used as the forecasting models to predict the class of a comprehensive air quality index and the final forecasting index was determined by the most frequent index among the three model's predicted indexes. The accuracy, false alarm rate, and probability of detection in Tomorrow's model were 72.4%, 0.0%, and 42.9% while those in Today's model were 80.8%, 12.5%, and 77.8%, respectively. The statistical model had the limitation to predict the rapid changing PM10 concentration by long-range transport from the outside of Korea and in this case the chemical transport model would be an alternative method.

• The Journal of Asian Finance, Economics and Business
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• v.6 no.3
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• pp.41-53
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• 2019

Building a target capital structure is one of the most important decisions in corporate financial management. The purpose of this article is to identify the determinants of capital structure and adjustment mechanism toward the target leverage. The partial adjustment model was applied on a sample of 306 non-financial companies listed on Vietnam stock exchange market during the period of 2008-2017. By the fixed effect model estimation method, the research results have discovered the factors of growth opportunities, firm size, tangible fixed assets and firm's unique characteristics have a positive effect on the target capital structure of enterprises. Besides, profitability and dividend payment have a negative effect on the target capital structure of enterprises. Accordingly, the research results show that the average adjustment speed toward target leverage of the firms is 90.03%. Research results also demonstrate firms have higher or lower debt ratio than the target debt ratio, capital surplus or capital deficit also have an impact on the adjustment rate toward the target capital structure. The research results are consistent with the Dynamic Trade-off Theory. From this result, this article has provided policy implications for non-financial companies listed on Vietnam's stock market in building a reasonable target capital structure according to operating timeline to maximize enterprise value.

• The Korean Journal of Financial Management
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• v.23 no.2
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• pp.109-141
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• 2006

The central factor in the pecking order theory of financial structure is the asymmetric distribution of information between managers and less-informed outside investors. Myers and Majluf (1984) show that this asymmetry leads managers to prefer internal funds to external funds. Funds are raised through equity issues only after the capacity to issue debt has been exhausted. In contrast, according to static tradeoff theory, an optimum financial structure exists by the tradeoff between tax saving by debt and bankruptcy costs. This study examines the recent changes of Korean firms' financial structure and financing behavior and the determinants of financial structure. The sample of firms comes from the period of $1996{\sim}2004$, and the number of firms is 32,003. The major findings are as follows. First, in contrast with previous studies using US firms as sample, Korean firms have been using debt financing as their major financing instrument. Especially, the firms in the fund deficit situation relies much more on $long{\sim}term$ and $short{\sim}term$ debts rather than on equity issues. Second, as is the case with previous studies using US firms sample indicates, the financing deficit variable can not explain perfectly the net debt issue. However, compared with net equity issue variable, net debt issue variable is more closely related to the financing deficit variable. Third, when financing deficit variable is added to the current list of explanatory variables of financial structure determinants model, it has a significant and positive explanatory power. In addition, the coefficients of determinants are much improved. Thus, it is concluded that although pecking order theory is not perfect, it appears to be more useful compared to static tradeoff theory, at least in explaining the recent financing behavior of Korean manufacturing firms.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.1937-1945
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• 2015

This study was conducted to investigate the relationship between depression and adult attention deficit hyperactivity disorder(ADHD) of college students. Collage students up to 350 people self-report survey was conducted using the Conners ADHD Rating Scale Korean version and Beck Depression Inventory. Adult ADHD symptoms prevalence was 5.1 % and the highest form of carelessness. Depression grade was $8.38{\pm}6.86$ points of college students and female students was higher than male students is depression grade, severe depression and modurate depressive symptoms were 2.1 %. Model of explanatory were slightly higher in 33.5%, adult ADHD affects depression and coexistence rate of adult ADHD symptoms and depressive symptoms was found to be 3.1%. Therefore, adult ADHD symptoms prevalence and depression of collage students seems to be relationship. Given the wide range of social and emotional problems due to adult ADHD seems necessary measures to establish a social dimension to adult ADHD.

• Journal of Korean Neurosurgical Society
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• v.57 no.5
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• pp.335-341
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• 2015

Objective : The main causes of spinal cord ischemia are a variety of vascular pathologies causing acute arterial occlusions. We investigated neuro-protective effects of kefir on spinal cord ischemia injury in rats. Methods : Rats were divided into three groups : 1) sham operated control rats; 2) spinal cord ischemia group fed on a standard diet without kefir pretreatment; and 3) spinal cord ischemia group fed on a standard diet plus kefir. Spinal cord ischemia was performed by the infrarenal aorta cross-clamping model. The spinal cord was removed after the procedure. The biochemical and histopathological changes were observed within the samples. Functional assessment was performed for neurological deficit scores. Results : The kefir group was compared with the ischemia group, a significant decrease in malondialdehyde levels was observed (p<0.05). Catalase and superoxide dismutase levels of the kefir group were significantly higher than ischemia group (p<0.05). In histopathological samples, the kefir group is compared with ischemia group, there was a significant decrease in numbers of dead and degenerated neurons (p<0.05). In immunohistochemical staining, hipoxia-inducible factor-$1{\alpha}$ and caspase 3 immunopositive neurons were significantly decreased in kefir group compared with ischemia group (p<0.05). The neurological deficit scores of kefir group were significantly higher than ischemia group at 24 h (p<0.05). Conclusion : Our study revealed that kefir pretreatment in spinal cord ischemia/reperfusion reduced oxidative stress and neuronal degeneration as a neuroprotective agent. Ultrastructural studies are required in order for kefir to be developed as a promising therapeutic agent to be utilized for human spinal cord ischemia in the future.

• The Korean Journal of Ecology
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• v.23 no.2
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• pp.117-123
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• 2000

Changing patterns and the possibility of climate change in the area of Cheiudo island, the southernmost Island in Korea, were analyzed using daily temperature and Precipitation data observed at the Cheiu Regional Meteorological Office from May 1923 to December 1998. A hydrologic simulation model "BROOK" was used to simulate and analyze the dynamics of daily soil moisture content and soil moisture deficit by applying the daily weather data. During the period, significantly increasing pattern was observed in temperature data of both annual and monthly basis, while no significantly changing pattern was observed in precipitation data. During the last 76 years. mean annual temperature was observed to have risen about 1.4$^{\circ}C$, which may show the Possibility of the initiation of climate change on the island whose validity should be tested in future studies after long-term studies on temperature. Based on the simulation, due to increased temperature, significant increase was predicted in evapotranspiration. while no significant decrease was detected in simulated soil moisture content during the period. Changing pattern of annual soil moisture content was markedly different from those of precipitation. In some dominant trees, negative effects of the drought of the late season for the previous year were shown to be statistically significant to radial growth of the tree for the current year. As annual variation of radial growth of trees is mainly affected by the soil moisture content. the information on the dynamics of soil moisture deficit possibly provides us with useful information for the interpretation of tree growth decline on the mountain. mountain.

• Child Health Nursing Research
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• v.4 no.2
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• pp.255-264
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• 1998

Disease prevention and health promotions are basically needed to be healthy, health education is the most useful mean to accomplish them. Preschool children are being developped, their health problem can effect their health status through their lives. This study was attempted to survey for status of health education of kindergarten for preshoolers and to provide the basic precious data for nursing intervention. The subjects were 51 kidergarten teachers. The data were collected by the questionaires, which consiste of 25 items concerning daily life habits of children and 1 item concerning the problems of health education for preschoolers. The data were analyzed by SAS program. The results of this study are as folleowed ; 1. The most frequently educated subjects were 'adequate and safe play' and 'hand washing', 'walking and running straightly', 'oral hygiene or tooth brushing', 'walking staires'. 2. The most frequently used teaching method was the explaining. 3. The most frequently used instructional method was the pictures. The slide films and OHP was seldomly used media. 4. The most effective teaching method which perceived by the kindergarten teachers was role play . Discuss ion and compensation/reinforcement were comparatively effective method also. 5. The most effective instructional media which perceived by the kindergarten teachers was a real object/model. 6. The problems of health education for preschoolers were 'deficiency of developped health educational programs' and 'inconsistency between parents' education and kindergarten teachers' education', 'deficiency of instructional media'. The other problems were' the knowledge deficit of teachers themselves' and 'the difficulty of measure the effect of education', 'time deficit'. Conclusionally, we have to realize the health of children is the future of our health, and reinforce the health education for preschoolers to accomplish the disease prevention and health promotion.

• Radiation Oncology Journal
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• v.7 no.1
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• pp.123-132
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• 1989

A radiation beam incident on an irregular or sloping surface produces the non-uniformity of absorded dose. The use of a tissue compensator can partially correct this dose inhomogeneity. The tissue compensator is designed based on the patient's three dimensional contour. After required compensator thickness was determined according to tissue deficit at $25cm\pm25cm$ field size, 10cm depth for 6MV x-rays, tissue deficit was mapped by isoheight technique using laser beam system. Compensator was constructed along the designed model using 0.8mm lead sheet or 5mm acryl plate. Dosimetric verification were peformed by film dosimetry using humanoid phantom. Dosimetric measurements were normalized to central axis full phantom readings for both compensated and non-compensated field. Without compensation, the percent differences in absorbed dose ranged as high as $12.1\%$ along transverse axis, $10.8\%$ along vertical axis. With the tissue compensators in place, the difference was reduced to $0\~43\%$ Therefore, it can be concluded that the compensator system constructed by isoheihnt technique can produce good dose distribution with acceptible inhomogeneity, and such compensator system can be effectively applied to clinical radiotherapy.

• Journal of Oriental Neuropsychiatry
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• v.21 no.1
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• pp.71-88
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• 2010

Objectives: This research investigates the effect of the DHJHT extract on Alzheimer's disease. Specifically, the effects of the DHJHT extract on (1) the behavior (2) the infarction area of the hippocampus, and brain tissue injury in AD mice induced with ${\beta}A$ were investigated. Methods: The effects of the DHJHT extract on the proinflammation cytokines mRNA expression and production of BACE, APP and ${\beta}A$ in in BV2 microglial cell line treated by lipopolysacchaide(LPS) plus ${\beta}A$ were investigated. The effects of the DHJHT extract on the behavior of the memory deficit mice induced by scopolamine were investigated. Results: 1. The DHJHT extract suppressed the expression of IL-$1{\beta}$, IL-6, TNF-$\alpha$, COX-2, and NOS-II, BACE and APP mRNA in BV2 microglial cell line treated by LPS plus ${\beta}A$. 2. The DHJHT extract suppressed the expression of ${\beta}A$ production in BV2 microglial cell line treated with LPS plus ${\beta}A$. 3. The DHJHT extract showed significantly inhibitory effect on the scopolamine-induced impairment of memory in the experiment of Morris water maze. 4. The DHJHT group suppressed the expression of IL-$1{\beta}$, TNF-$\alpha$, MDA, and CD68+/CD11b+ in the brain tissue of the mice with AD induced by ${\beta}A$. 5. The DHJHT group reduced the infarction area of hippocampus, and controlled the injury of the brain tissue in the mice with AD induced by ${\beta}A$. 6. The DHJHT group reduced tau protein, and GFAP in the brain tissue of the mice with AD induced by ${\beta}A$. Conclusions: These results suggest that the DHJHT group may be effective for the treatment of AD. Thus, DHJHT could be considered among the future therapeutic drugs indicated for the treatment of AD.