• Journal of Biosystems Engineering
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• v.43 no.4
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• pp.285-295
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• 2018

Purpose: The aim of this study is to develop a three-wheel riding cultivator for improving the performance of the current four-wheel riding cultivators in the market. Methods: A prototype three-wheel riding cultivator with the rated power of 15.5-kW, a primary hydrostatic and a two-speed selective gear transmission shifts, front/rear three-wheel drive, a hydraulic wheel tread adjustment, and the mid-section attachment of the major implements was designed and constructed. Its specifications and basic performance are investigated. Results: The maximum speeds of the prototype at the low and high stages were measured to be approximately 7.31, and 11.29 km/h in forward travel, respectively, and approximately 3.60, and 6.37 km/h in rearward travel, respectively. The minimum ground clearance is shown to be 670 mm. The rotating speeds of the power takeoff (PTO) shaft at the low and high stages are shown to be approximately 795 and 1,140 rpm, respectively. The tread of the rear wheels, the minimum radius of turning, and the maximum lifting height of the parallel link device are measured to be within 1,320-1,720 mm, 2.80 m, and 390 mm, respectively. Approximately 25.3% and 74.7% of the total weight of the prototype are distributed in the front and rear wheels on flat ground, respectively. When the tread of rear wheels increased from 1,320 to 1,720 mm, the left and right static lateral overturning angles increased from $33.4^{\circ}$ to $39.1^{\circ}$ and from $29.0^{\circ}$ to $36.1^{\circ}$, respectively. Conclusions: The prototype three-wheel riding cultivator showed a wide range of travel and PTO speeds, high minimum ground clearance, small minimum radius of turning, and easy control of the rear wheel tread. Further, the easy observation of cultivating operations by mid-mounting the implements can improve quality of work. Therefore, the prototype is expected to contribute to the riding mechanization of cultivating operations for various upland crops in Korea.

• Journal of The Korean Association For Science Education
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• v.39 no.2
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• pp.173-186
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• 2019

The purpose of this study is to design and apply a pilot inquiry experiment focusing on the epistemological issues of scientific activities, and derive educational implications by analyzing experimental activities and reflective discussions. Three graduate students who major in science education participated in the study voluntarily. Participants showed the characteristics of stable enquiry in Experiment 1. However, the small but continuous changes in Experiment 2 led the experiment to a phase of fluid enquiry seeking new theories. Participants mobilized various resources, proposed new hypotheses, and models and requested additional experiments to verify them. In the process of reflective discussions, the participants led to the following three epistemological issues. First, at the beginning of the experiment, their observations were theoretically dependent. Second, when the observations were no longer coherent with theory, they face a crisis, and the adjustment of observation and theory proceeds. Third, stable enquiry and fluid enquiry are performed according to the relationship between observation and theory. The educational implications of school science inquiry based on the above process and results are as follows: First, this study shows that fluid enquiry can follow stable enquiry naturally, and examples of the activities are presented together. Second, in this study, it was confirmed that participants could draw up epistemological issues based on their experiences through reflective discussions following inquiry.

• Environmental and Resource Economics Review
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• v.30 no.4
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• pp.557-579
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• 2021

Collective energy is an intermediate stage in energy conversion and has a great influence on the power structure as a distributed power source. However, the problem of the collective energy business has recently emerged due to the worsening profitability of some collective energy operators. This study measured the technical efficiency of major operators through the estimation of the production efficiency of Korean collective energy operators, and based on this, we looked at ways to improve the profit structure of operators. After collecting detailed data from 16 collective energy operators between 2016 and 2019, the production efficiency of operators was estimated using the panel stochastic frontier model. As a result of the estimation, combined steam power operators showed the highest production efficiency and reverse CHP operators showed the lowest efficiency. Furthermore, as a result of examining the factors influencing profitability, it was confirmed that production efficiency has a positive effect on overall profitability. However, businesses with a high proportion of heat production, such as small district electricity operators, profitability was lower. This phenomenon is due to the structural limitations of the current heat sales market. Hence, the adjustment of the heat sales unit price is necessary to improve profitability of collective energy operators.

• Journal of Life Science
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• v.31 no.12
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• pp.1072-1078
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• 2021

The oral pathogen Streptococcus mutans is considered a major causative agent of dental caries in humans. The use of dental hygiene products, including toothpaste and mouthwash, is used for caries control. However, food intake can lead to the recurrence of oral microorganisms. This study aimed to explore why this bacterium dies so quickly during prolonged incubation and to assess whether this growth characteristic is closely associated with the secretion of metabolic products. Notably, the number of live S. mutans cells rapidly declined after 24 hr during the entire period tested, whereas the number of Escherichia coli cells, an indicator strain, remained steady over the same period. To test whether the S. mutans supernatants contained possible signals that accelerated the death of neighbor cells, we obtained the individual supernatants at the above time points. Following pH neutralization, the cells in which the supernatant was supplemented with glucose grew well. However, pH adjustment alone could not fully recover cell growth in conditions in which the supernatant was supplemented, with or without glucose. These phenotypes of S. mutans may be associated with signaling, not only resulting from nutrient depletion. The findings on the survival phenotype of S. mutans provide new insights into cell-cell communication in the biology of this bacterium.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.5
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• pp.449-463
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• 1990

To obtain the basic informations on quality improvement, seed protein and amino acid composition were analyzed in 460 strains of perilla germplasm. Among the tested strains, total protein content ranged from 17.9% to 28.1 % with the 23.6% of varietal means. Form the experiment, Namji, Sandong, and Eunjin were selected as high protein strains of which content was as high as 28.1%. In protein content, collected strains from Jeonnam province showed highest, and was not significantly different by maturity, but this characteristics showed differences by seed coat color and 1,000 seed weight. The significantly negative correlation was observed between protein content and seed setting ratio. However it was observed that significant and high positive correlation between protein and oil content. A calibration for an Infra-Alyzer 450 using log reflectance readings at 2208, 1982, 1940 and 1722nm could be used without adjustment for the measurment of the protein content in perilla with a standard deviation of differences against micro-kjeldahl of 0.27%. The amino acid composition of perilla was similar to the other oilseed crops, and showed a relatively high lysine and methionine content. Further, amino acid composition of perilla seed was exellently characterized with bal ance and higher than FAO recommendation. Major amino acids were indentified as a glutamic acid and arginine in perilla seed protein.

• Korean Journal of Culture and Social Issue
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• v.21 no.2
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• pp.131-158
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• 2015

This study examined the relationship between physical education and externalizing(aggression) and internalizing(depression, social withdrawal) problem behaviors among adolescents. The moderating role of gender and time in the association between physical education and problem behavior was also identified. This study used data from the second, third, and fourth waves of the middle school student cohort (N=2,133, N=2,151, N=1,979) of the Korean Children-Youth Panel Survey(KCYPS). Main analyses involved multilevel growth model with interaction terms. The dependent variables were aggression, depression, and social withdrawal. The independent variables were gender and physical education (exercise hours) at school. The control variables were abuse, school-adjustment, annual household income and parents' highest level of education. The major longitudinal findings of this study are as follows: First, there was significant change according to the passage of time only in aggression among externalizing and internalizing problems. Second, gender differences exist in aggression and depression. Third, exercise hours of physical education had a negative relationship with internalizing problems. Fourth, there were no gender differences over time in both externalizing and internalizing problems. Fifth, the interaction between exercise hours of physical education and time was statistically significant for social withdrawal. Sixth, the interaction between exercise hours of physical education and gender was statistically significant for depression. The results of this study may become an academic basis for suggesting policy directions that promote increased exercise hours in physical education classes at school.

• The Journal of the Korea Contents Association
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• v.20 no.8
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• pp.448-465
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• 2020

This study analyzed the effect of self-determination of the intellectually disabled on the quality of life, focusing on the effect of controlling family functions, with the intellectually disabled as the subject of the study. In order to achieve this goal, it was designated as an intellectual disabled person at the early age of 18 to 25 who were diagnosed with intellectual disabilities, and it was selected as a disabled person living in the community, and it selected major welfare institutions that were most frequently used by people with intellectual disabilities in the early age of 20 years, considering the difficulties of conducting the survey. The research results are as follows. First, "self-determination, psychological capacity, and self-realization" of the intellectually disabled were found to affect the quality of life (physical well-being, physical well-being, social well-being, productive activities and development, psychological and emotional well-being). Second, differences in "self-determination (self-reliance, psychological capacity, self-realization)" did not occur in accordance with the "population statistical. Third, differences occurred in the "quality of life (physical well-being, physical well-being, social well-being, productive activities and development, psychological and emotional well-being" of the intellectually disabled. Fourth, the relationship between "self-determination" and "quality of life" of the intellectually disabled resulted in the adjustment effect of family functions. This study is meaningful in that it demonstrated the service practice that should be provided to people with early adult intellectual disabilities in the field of practice by verifying the relationship between self-determination, family function and quality of life viewed from the perspective of the parties.

• Korean Journal of Remote Sensing
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• v.40 no.4
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• pp.397-418
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• 2024

The Land Surface Temperature (LST) is a crucial parameter in identifying drought. It is essential to identify how LST can increase its accuracy, particularly in mountainous and hill areas. Increasing the LST accuracy can be achieved by applying early data processing in the correction phase, specifically in the context of topographic correction on the Lambertian model. Empirical evidence has demonstrated that this particular stage effectively enhances the process of identifying objects, especially within areas that lack direct illumination. Therefore, this research aims to examine the application of the Lambertian model in estimating LST using the Multi-Channel Method (MCM) across various physiographic regions. Lambertian model is a method that utilizes Lambertian reflectance and specifically addresses the radiance value obtained from Sun-Canopy-Sensor(SCS) and Cosine Correction measurements. Applying topographical adjustment to the LST outcome results in a notable augmentation in the dispersion of LST values. Nevertheless, the area physiography is also significant as the plains terrain tends to have an extreme LST value of ≥ 350 K. In mountainous and hilly terrains, the LST value often falls within the range of 310-325 K. The absence of topographic correction in LST results in varying values: 22 K for the plains area, 12-21 K for hilly and mountainous terrain, and 7-9 K for both plains and mountainous terrains. Furthermore, validation results indicate that employing the Lambertian model with SCS and Cosine Correction methods yields superior outcomes compared to processing without the Lambertian model, particularly in hilly and mountainous terrain. Conversely, in plain areas, the Lambertian model's application proves suboptimal. Additionally, the relationship between physiography and LST derived using the Lambertian model shows a high average R² value of 0.99. The lowest errors(K) and root mean square error values, approximately ±2 K and 0.54, respectively, were achieved using the Lambertian model with the SCS method. Based on the findings, this research concluded that the Lambertian model could increase LST values. These corrected values are often higher than the LST values obtained without the Lambertian model.

• Information Systems Review
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• v.26 no.1
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• pp.151-172
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• 2024

Metaverse, which supports social and economic activities in the virtual world, is being cited as the core of future Web 3.0 businesses. However, most of the major metaverse platforms currently adhere to the Web 2.0 system and are operated in a centralized manner. Accordingly, this study investigated the form of metaverse operation by examining the case of Decentraland, a metaverse platform operated as DAO, a decentralized autonomous organization in the form of Web 3.0. From the case analysis, we found that Decentraland had positive characteristics such as a horizontal operating structure, fair profit distribution, and transparency, but there were challenges including the possibility of returning to centralization in the operating process, the possibility of abuse of an autonomous system, and inefficiency in decision-making. Therefore, in this study, the timing of transition to DAO governance was discussed, and DAO's efforts for business continuity and the need for adjustment for autonomous operation were suggested as implications. The implications presented in this study are expected to contribute to materializing not only practical but also theoretical aspects of platform operation aimed at web 3.0 as well as the metaverse.

• Neonatal Medicine
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• v.17 no.1
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• pp.34-43
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• 2010

Purpose : The aim of this study was to examine whether hypercapnia during the first seven days of life was associated with severe intraventricular hemorrhage (IVH) in preterm infants requiring mechanical ventilation. Methods : A matched pair analysis was performed for 19 preterm infants with severe IVH(grade$\geq$3) and 38 infants with no severe IVH (normal or grade 1), who required mechanical ventilation for more than seven days. The univariate and multivariate analysis of severe IVH with maximal and minimal $PaCO_2$, averag $PaCO_2$, SD of $PaCO_2$, and difference in the $PaCO_2$ were assessed. The major perinatal factors and maximal ventilator index (VI) were also compared. Results : Infants with severe IVH had a higher maximal $PaCO_2$ (86.1$\pm$18.4 mmHg vs. 60.1$\pm$ 11.6 mmHg, P <0.001) and mean $PaCO_2$ (47.5$\pm$5.6 mmHg vs. 41.2$\pm$6.3 mmHg, P=0.004) and a larger SD or difference in $PaCO_2$ (14.0$\pm$4.4 mmHg vs. 9.0$\pm$2.4 mmHg; 60.3$\pm$20.9 mmHg vs. 35.5$\pm$11.8 mmHg, P <0.001). However the minimal $PaCO_2$ values did not differ between the groups. Disseminated intravascular coagulation, pulmonary hemorrhage, and the air leak syndrome were more frequent in the IVH group than in the controls. The maximal VI on each day was higher in the IVH group. The multivariate logistic regression analysis after controlling for bleeding tendency showed that the air leak syndrome, maximal VI, and maximal $PaCO_2$ were independently associated with severe IVH [OR, 1.324 (95% CI, 1.011-1.733; P=0.041)]. Conclusion : Extreme hypercapnia was significantly associated with severe IVH in preterm infants, after adjustment for major perinatal risk factors. Frequent monitoring of the $PaCO_2$ may be important for early detection of inadvertent hypercapnia and prompt correction of high PaCOS levels.