• The Journal of Bigdata
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• v.9 no.1
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• pp.101-113
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• 2024

Federated learning has garnered attention as an efficient method for training machine learning models in a distributed environment while maintaining data privacy and security. This study proposes a novel FedRFBagging algorithm to optimize the performance of random forest models in such federated learning environments. By dynamically adjusting the trees of local random forest models based on client-specific data characteristics, the proposed approach reduces communication costs and achieves high prediction accuracy even in environments with numerous clients. This method adapts to various data conditions, significantly enhancing model stability and training speed. While random forest models consist of multiple decision trees, transmitting all trees to the server in a federated learning environment results in exponentially increasing communication overhead, making their use impractical. Additionally, differences in data distribution among clients can lead to quality imbalances in the trees. To address this, the FedRFBagging algorithm selects only the highest-performing trees from each client for transmission to the server, which then reselects trees based on impurity values to construct the optimal global model. This reduces communication overhead and maintains high prediction performance across diverse data distributions. Although the global model reflects data from various clients, the data characteristics of each client may differ. To compensate for this, clients further train additional trees on the global model to perform local optimizations tailored to their data. This improves the overall model's prediction accuracy and adapts to changing data distributions. Our study demonstrates that the FedRFBagging algorithm effectively addresses the communication cost and performance issues associated with random forest models in federated learning environments, suggesting its applicability in such settings.

• Journal of Bio-Environment Control
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• v.32 no.4
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• pp.466-474
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• 2023

In recent years, the government has strongly promoted multi-purpose utilization of paddy field. However, poor drainage causes waterlogging stress in upland crops, requiring subsurface drainage technology, resulting in high installation and management costs. To address this issue, a low-cost and high-efficiency technique was developed that utilizes wasted coir substrates which have characteristics of high porosity and good drainage, for upland crop cultivation in paddy fields. Soybeans were grown in both paddy soil and wasted coir slab with two planting densities (80×20 cm and 60×20 cm). The results showed that the coir substrates had better performance than the paddy soil in terms of soil physical and chemical properties and the growth and yield of upland crops are improved. The treatments using wasted coir substrate showed a 41.4% increase in yield and a 21.3% increase in protein content compared to PS treatment. Our findings demonstrate that recycling waste coir substrates to grow upland crops is a positive cultivation strategy to solve some drainage problems in paddy fields. This approach offers a sustainable solution for upland crop production while also addressing the issue of waste management in agriculture.

• Journal of Practical Engineering Education
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• v.16 no.4
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• pp.529-540
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• 2024

In industrial sites, experiential virtual training contents are partially used to replace high-risk and high-cost training, and virtual training contents development is also becoming active along with the increasing demand for non-face-to-face industries. Existing studies mainly focused on quantitative research through surveys, and only measured the change in users' learning commitment. This study attempted to investigate the effect of the combination of theoretical education and virtual training on the improvement of actual job performance in a dual vocational training environment by conducting an experimental study. This study studied whether the combination of theoretical education and virtual training can improve the performance of vocational training in dual vocational training (comparative work and learning) in which companies and schools participate. The results of pre- and post-evaluation of vocational training using traditional vocational training and virtual training contents were compared with 24 vocational training trainees. As a result of the study, it was demonstrated that the outcome of virtual training education was higher than that of traditional vocational training, and the combination of virtual reality-based education was more effective in theoretical education. This study suggests that the virtual training content presents a new paradigm for industrial safety education, and through the interview results of trainees, it was confirmed that virtual training can lead to a change in attitude toward safety beyond just knowledge transfer. This contributes to the prevention of safety accidents in industrial sites and provides important implications for improving the quality of vocational training.

• Journal of the Korean Regional Science Association
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• v.40 no.3
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• pp.3-21
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• 2024

A safe residential environment enhances the quality of human life and promotes community development through self-actualization. It significantly affects regional stability by influencing the physical and psychological environment necessary to satisfy basic needs, providing a sense of security and alleviating anxiety. Safety is a major housing need; however, current housing policies tend to focus predominantly on housing supply. This emphasis limits the fulfillment of higher-level needs due to poor housing conditions and housing cost burdens faced by young households. Therefore, this study aims to identify areas affected by the stigma effect by analyzing the discrepancy between perceived crime risk and actual crime occurrence among single-person young households. The study compares these stigmatized areas with regions where the perceived crime risk is lower than the actual crime occurrence to identify differences in housing needs satisfaction and to prioritize policy interventions. Additionally, the study examines differences in housing needs satisfaction and importance based on gender to inform policy priorities. By considering the stigma effect on regional housing needs and gender-specific deficiencies, this study provides significant policy implications.

• Convergence Security Journal
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• v.21 no.4
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• pp.109-115
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• 2021

Currently, with the development of 5G and IoT technology, it is being used in connection with the things used in real life through a network. However, attempts to use networked computers for malicious purposes are increasing, and attacks using malicious codes that infringe the confidentiality and integrity of user information are becoming more intelligent. As a countermeasure to this, research is being conducted on a method of detecting malicious packets using a security control system and AI technology, supervised learning. The cyber security control system is being operated inefficiently in terms of manpower and cost. In addition, in the era of the COVID-19 pandemic, remote work has increased, making it difficult to respond immediately. In addition, malicious code detection using the existing AI technology, supervised learning, does not detect variant malicious code, and has an inaccurate malicious code detection rate depending on the quantity and quality of data. Therefore, in this study, by converging malicious packet detection technologies through various machine learning and deep learning models, the accuracy of malicious packet detection is increased, the false positive rate and the false positive rate are reduced, and a new type of malicious packet can be efficiently detected when intrusion. We propose a malicious packet detection technology.

• Korean journal of applied entomology
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• v.52 no.2
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• pp.115-123
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• 2013

A microbial insecticide "Bt-Plus" has been developed to enhance an insecticidal efficacy of an entomopathogenic bacterium, Bacillus thuringiensis (Bt). However, its wettable powder formulation is not preferred by farmers and industry producers due to relatively high cost. This study aimed to develop a soluble concentrate formulation of Bt-Plus. To this end, an optimal mixture ratio of two bacterial culture broths was determined to be 5:4 (v/v) of Bt and Xenorhabdus nematophila (Xn) along with 10% ethanol preservative. In addition, Bt broth was concentrated by 10 times to apply the mixture at 1,000 times fold dilution. The resulting liquid formulation was sprayed on cabbage crop field infested by late instar larvae of the diamondback moth, Plutella xylostella. The field assay showed about 77% control efficacy at 7 days after treatment, which was comparable to those of current commercial biopesticides targeting P. xylostella. For storage test in both low and room temperatures, the liquid formation showed a relatively stable control efficacy at least for a month. To develop a quality control technique to exhibit a stable control efficacy of Bt-Plus, Bt spore density ($5{\times}10^{11}$ spores/mL) and eight active component concentrations of Xn bacterial metabolites in the formulation products have been proposed in this study.

• Progress in Medical Physics
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• v.25 no.3
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• pp.143-150
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• 2014

In general radiotherapy, mega-voltage (MV) x-ray images are widely used as the unique method to verify radio-therapeutic fields. But, the image quality of MV images is much lower than that of kilo-voltage x-ray images due to scatter interactions. Since 1990s, studies for the scatter correction have performed with digital-based MV imaging systems. In this study, a novel method for the scatter correction is suggested using scatter to primary ratio (SPR), instead of conventional methods such as digital image processing or scatter kernel calculations. We measured two MV images with and without a solid water phantom describing a patient body with given imaging conditions, and calculated un-attenuated ratios. Then, we obtained SPR distributions for the scatter correction. For experimental validation, a line-pair (LP) phantom using several Al bars and a clinical pelvis MV image was used. As the result, scatter signals of the LP phantom image were successfully reduced so that original density distribution of the phantom was restored. Moreover, image contrast values increased after SPR correction at all ROIs of the clinical image. The mean value of increases was 48%. The SPR correction method suggested in this study has high reliability because it is based on actually measured data. Also, this method can be easily adopted in clinics without additional cost. We expected that the SPR correction can be an effective method to improve the quality of MV image guided radiotherapy.

• Journal of The Korean Society of Grassland and Forage Science
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• v.19 no.1
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• pp.41-48
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• 1999

This experiment was carried out to determine the effect of the silage additives on improvement of quality of fresh rice straw silage using round bale at the forage experimental field, grassland and forage crops division, National Livestock Research Institute, RDA, Suwon from 1997 to 1998. The experiment was arranged in a randomized block design with three replication. The treatments used in this study were consisted of different additives(control, formic acid, molasses, molasses+urea and inoculant). The rice straw silage with molasses+urea treatment resulted in high crude protein content and in vitro dry matter digestibility were increased with molasses of inoculant treatments compare with the control. The mean dry matter of formic acid treatment material was higher than with control but there was no significant difference in dry matter content among the additives treatments. The pH of molasses treatments significantly increased the proportion of lactic acid(P<0.05) and decreased the proportion of butyric acid. The total organic acid content of all treatments had low around 2%. Ammonia-N of molasses+urea treatment was significantly(P<0.05) higher than that of others, but formic acid or inoculant treatments was lower below 10% per total nitrogen. Over a 7d feeding period, the dry matter intake per cattle on the inoculant treatment was higher that on both the untreated round bale silage of fresh rice straw and rice straw hay. Producing cost per kilogram of round bale silage of fresh rice straw was decreased according to the increasement of harvesting area. It is suggested that application of round bale silage system to fresh rice straw with molasses or inoculant was the best treatment for improving preservation as silage, and that animal intake was enhanced by addition of inoculant to fresh rice straw.

• Journal of Aquaculture
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• v.8 no.4
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• pp.261-269
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• 1995

A practical control diet was prepared and compared with raw fish ($80\%$ frozen horse mackerel + $20\%$ commercial binder meal) and moist pellet ($50\%$ frozen horse mackerel + $50\%$commercial binder meal) diets to develop a practical diet formulation for Korean rockfish (Sebastes schlegeli). Korean rockfish averaging 68.5g were fed with the three experimental diets for 11 months. Final average body weight was approximately 330g and showed no significant difference between fish groups (P>0.05). Feed efficiency of fish from control diet was significantly lower than those of fish from raw fish and moist pellet diets (P<0.05). Protein and lipid retention efficiency of fish ranged $26.9-28.8\%$ and $86.5-110.2\%$, respectively, without any significant difference between the different diets. At the end of the experiment, chemical composition for the various parts of fish body and flesh quality of the raw fish were examined. The data showed that there was no significant difference between fish from the different diet groups for moisture, protein and lipid contents of whole body, liver, and dorsal muscle. Also, thirty three panelists did not find any difference in color, smell, texture, and taste of the raw fish flesh. These results suggest that Korean rockfish can be cultured with a laboratory practical feed without any negative effects on growth, nutrient utilization, chemical composition of fish, and quality of raw fish. Therefore, the next step in developing practical feed is to modify the control diet for improving fish performance and reducing feed cost.

• Journal of the Korean Society of School Health
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• v.14 no.1
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• pp.131-143
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• 2001

The primary aim of this dissertation is to contribute to the improvement of methods in physical examination by providing quality information for the current school system and advice for improving status. Present status, controversial points and possible remedies in physical examination were analyzed on a frequency and percentage basis. An $x^2$-test was used to verify the statistics between the results from the examination and each variable. In case of multiple categories of variables, an $x^2$ cs was adopted. Chronological data as well as both total and sampling physical examination data verified the statistics using an $x^2$-test. This thesis is based both on the data from middle school health care specialists in Gyunggi Province and on the analysis of physical examinations reported from local schools to the municipal education agency from 1997 to 1999. The results of the study are as follows: First, according to the survey, only 29.0% of the total schools had their school doctors examine all the students while most of the educational institutions failed to implement the whole process of physical examination on the list. It also turned out that the more students the schools have, the lower the rate of implementation of physical examination by school doctors(p=0.014). Second, the average time a school doctor spends for checkup turned out to be approximately 1.7 minutes per student This means that the quality of the physical examination is not guaranteed in the process. Third, 47.7% of those surveryed say that a dental examination was performed, each taking 21.24 seconds on average. In addition, it shows that some 31.5% wanted to have a task force team for dental checkups at the local health center. Given the fact that dental caries among students is progressively on the rise, the dental health centers that are now set up in some elementary schools should be expanded to cover the whole educational institution in order to raise awareness of the importance of dental care. Fourth, 48.5% of those surveyed say that a comprehensive physical examination should be adopted to promote the health of high schoolers. Since it takes a lot of public funds to implement a comprehensive method, it is essential to make sure that in-depth studies should be based on the frequency and methods of physical examination. Fifth, regarding such diseases among 3rd year middle school students in 1999, statistics shows that there was a slight difference in the prevalence rate of color blindness, and allergic diseases for male students ; and color blindness, hearing disturbance and allergic disease for female students. For those items, however, it is too little to say that there is a significant difference and accordingly it is assumed to be a problem of the measuring process. Sixth, the result of analysis on the sample physical examination and the total physical examination of the year 1999 shows as follows: For male students in the 3rd year of middle school, a slight difference appeared to those students in 11 items including eye problems and eye disease, otitis media, tonsillar hypertrophy, spinal shape, respiratory urinary allergic disease and other abnormal diseases(p<0.05). Particularly, the prevalence rate between students with and without disease was shown to be two times more in the following: eye problems, otitis media, tonsill hypertrophy, allergic diseases, etc. For female students in the 3rd year, prevalence rate showed little difference in 14 items(p<0.05). For items including eye problem, otitis media, tonsill hypertrophy, allergic disease, etc. it was shown that the rate was two times more between students with and without diseases. Physical examinations under the current school system are not producing any fundamental results for the health of the students. Methods and results are not trustworthy. Accordingly, a drastic overhaul of the current practices is needed in frequency, methods and items on the list in order to promote the health of the students. Cost-benefit studies as well as political considerations to ensure the development of efficient methods for physical examination are urgently needed at this moment.