• The Journal of Bigdata
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• v.8 no.1
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• pp.157-165
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• 2023

Seafood is a major source of protein in many countries and its consumption is increasing. In Korea, consumption of seafood is increasing, but self-sufficiency rate is decreasing, and the importance of safety management is increasing as the amount of imported seafood increases. There are hundreds of species of aquatic products imported into Korea from over 110 countries, and there is a limit to relying only on the experience of inspectors for safety management of imported aquatic products. Based on the data, a model that can predict the customs inspection results of imported aquatic products is developed, and a machine learning classification model that determines the non-conformity of aquatic products when an import declaration is submitted is created. As a result of customs inspection of imported marine products, the nonconformity rate is less than 1%, which is very low imbalanced data. Therefore, a sampling method that can complement these characteristics was comparatively studied, and a preprocessing method that can interpret the classification result was applied. Among various machine learning-based classification models, Random Forest and XGBoost showed good performance. The model that predicts both compliance and non-conformance well as a result of the clearance inspection is the basic random forest model to which ADASYN and one-hot encoding are applied, and has an accuracy of 99.88%, precision of 99.87%, recall of 99.89%, and AUC of 99.88%. XGBoost is the most stable model with all indicators exceeding 90% regardless of oversampling and encoding type.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.4
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• pp.307-315
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• 2023

Korea controls the departure of vessels based on the Maritime Safety Act such that only ships with seaworthiness can navigate in bad weather, but scientific evaluation results and quantitative basis for the designation of ships subject to control are insufficient. Opinions for improvement are being raised for a reasonable departure control operation. The purpose of this study is to evaluate the adequacy of the current departure control standards through actual measurement of tugboats, which are the type of vessels subject to control when a wind and wave advisory is effective, and to present quantitative grounds for improvement of controls. A sensor was installed on the tugboat to measure the ship's three-axis motion and hull acceleration, and the hull motion performance was measured by operating in the sea area with a significant wave height of 3 m. The measured values were compared and analyzed based on seaworthiness evaluation factors and limit value standards. The actual ship was excluded from the current control standard according to tonnage, but as a result of the analysis, the pitch value exceeded the operation standard, and a risk to navigation safety existed. The results of this study suggest the need for additional actual measurement studies that can represent various ship types and specifications and review ship departure control targets.

• Journal of Korea Entertainment Industry Association
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• v.13 no.8
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• pp.469-478
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• 2019

This study is an empirical survey of the job status and job satisfaction of early childhood teachers. The subjects of this study were teachers of early childhood education in (the province of) Chungcheongnam-do. The Early Childhood Education Institution was conducted with 255 teachers for teachers working in public day care centers, private day care centers, public kindergartens and private kindergartens. o carry out this study, we analyzed the collected questionnaires by using the SPSS statistical package program. T-test, χ²-validation and ANOVA analysis were used for this study, and Scheffé analysis was applied as a post hoc analysis. As a result of this study, job status was examined by type, age, educational attainment, and educational experience. The satisfaction level of educational institutions was highest in the national public day care centers, and the age was 50 years or older, and the education level was high in graduate school. In addition, the job satisfaction of early childhood teachers was significantly analyzed in relation to fellow teacher, relationship with the director, self-identity and teaching environment. Through this study, understanding the current job status and satisfaction of early childhood education teachers can be used as an important data in preparing a plan to raise their job performance and work efficiency.

• Journal of The Geomorphological Association of Korea
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• v.18 no.4
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• pp.59-78
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• 2011

In this study, the tidal flat research history of South Korea was organized by type and period. South Korea's tidal flat research history was largely divided into four fields: sediment research of tidal flat, research using satellite imagery, research on the Quaternary environment change and tidal flats, and ecological research on tidal flats. The comprehensive review of the South Korean tidal flat research history showed that tidal flats had been researched on since the period of Japanese colonial period, but most of the past studies were related to fisheries. Then, in the 1960s, the studies started to focus on the reclaimed land created through reclamation projects. The research on tidal flats from a geomorphological perspective fundamentally started in the 1970s, and the importance of tidal flats became more widely known in the 1980s. Most of the studies then were about the sedimentary environment and the form of landform, the ecosystem, and morphological changes. Since the 2000s, research has been carried out on satellite imagery data together with field survey, to continuously monitor the changes in the sedimentary facies of tidal flats, and in the sedimentary environment. There have been many academic studies on the geographic field of tidal flats, but the research performance on tidal flats in terms of geomorphology is still a blue ocean that has been touched by only a few. Therefore, it is hoped that various studies on Korean tidal flats will be conducted by geomorphologists in the future, and that such area will be established as an important field of study in geomorphology.

• Health Policy and Management
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• v.33 no.3
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• pp.355-362
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• 2023

Background: Financial efficiency in monetary units and operational efficiency in non-monetary units are separately classified and evaluated. This is done to prevent the duplication of monetary units and non-monetary units in inputs and outputs. In addition, analyses are conducted to determine the factors that affect each aspect of efficiency. To prevent duplication of monetary and non-monetary units in inputs and outputs, financial efficiency, consisting of monetary units, and operational efficiency, comprising non-monetary units, are separately classified and evaluated. Furthermore, an analysis is conducted to identify the factors that affect each aspect of efficiency. Methods: This study conducted a panel analysis of 34 regional public hospitals and influencing factors on efficiency for 5 years from 2015 to 2019. Financial efficiency and operational efficiency were calculated through data envelopment analysis. Moreover, multiple regression analysis was conducted to identify the factors that influence both financial efficiency and operational efficiency. Results: The factors that affect financial efficiency include the number of medical institutions within the treatment area and the ratio of patients receiving medical care. Additionally, operational efficiency is influenced by the type of medical institution, the number of medical institutions within the treatment area, and the number of nursing positions per 100 beds. Conclusion: In order for regional public hospitals to faithfully fulfill their functions and roles as regional base public hospitals, several measures are necessary. Firstly, continuous monitoring and reasonable support are required to ensure efficient operation and performance. Secondly, a financial support plan tailored to the characteristics of local medical centers is needed. Additionally, local medical centers should strive to enhance their own efficiency.

• Journal of Internet of Things and Convergence
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• v.10 no.1
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• pp.1-6
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• 2024

In order to increase the use of electric vehicles (EVs) and minimize grid strain, microgrid using renewable energy must take an important role. Microgrid may use fossil fuels such as small diesel power, but in many cases, they can be supplied with energy from renewable energy, which is an eco-friendly energy source. However, renewable energy such as solar and wind power have variable output characteristics. Therefore, in order to meet the charging and discharging energy demands of electric vehicles and at the same time supply load power stably, it is necessary to review the configuration of electric vehicle charging infrastructure that utilizes diesel power or electric vehicle-to-grid (V2G) as a parallel energy source in the microgrid. Against this background, this study modelized a microgrid that can stably supply power to loads using solar power, wind power, diesel power, and V2G. The proposed microgrid uses solar power and wind power generation as the primary supply energy source to respond to power demand, and determines the operation type of the load's electric vehicles and the rotation speed of the load synchronous machine to provide stable power from diesel power for insufficient generations. In order to verify the system performance of the proposed model, we studied the stable operation plan of the microgrid by simulating it with MATLAB /Simulink.

• Membrane Journal
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• v.33 no.6
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• pp.439-446
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• 2023

Ceramic membranes are generally used for various industrial processes operating under extreme conditions because of its high thermal and chemical stability. However, due to the trade-off phenomenon of permeability and mechanical strength, preparation of high permeability-high strength membrane is necessary. In this study, the change in characteristics and performances of ceramic membranes was analyzed depending on the type of polymer binder and its mixing ratio. Because the solubility between solvent and polymer binder was higher in PSf (polysulfone) than in PES (polyethersulfone), the viscosity and discharge pressure of the PSf-based dope solution were higher than those of PES-based dope solution. When PSf was used as a polymer binder, ceramic membrane showed high mechanical strength and low water permeability due to the dense structure. On the other hand, in case of PES, the mechanical strength was slightly reduced and the water permeability was increased. It was confirmed that the optimum mixing ratio of the PSf and PES with high water permeability and mechanical strength was 9:1.

• Journal of the Korea Society of Computer and Information
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• v.28 no.10
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• pp.1-8
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• 2023

If there is a defect in the wheel bearing, which is a major part of the car, it can cause problems such as traffic accidents. In order to solve this problem, big data is collected and monitoring is conducted to provide early information on the presence or absence of wheel bearing failure and type of failure through predictive diagnosis and management technology. System development is needed. In this paper, to implement such an intelligent wheel hub bearing maintenance system, we develop an embedded system equipped with sensors for monitoring reliability and soundness and algorithms for predictive diagnosis. The algorithm used acquires vibration signals from acceleration sensors installed in wheel bearings and can predict and diagnose failures through big data technology through signal processing techniques, fault frequency analysis, and health characteristic parameter definition. The implemented algorithm applies a stable signal extraction algorithm that can minimize vibration frequency components and maximize vibration components occurring in wheel bearings. In noise removal using a filter, an artificial intelligence-based soundness extraction algorithm is applied, and FFT is applied. The fault frequency was analyzed and the fault was diagnosed by extracting fault characteristic factors. The performance target of this system was over 12,800 ODR, and the target was met through test results.

• Journal of the Korean Society of Marine Environment & Safety
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• v.29 no.7
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• pp.992-1001
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• 2023

OWEC (Overtopping Wave Energy Converter) is a wave power generation system using the wave overtopping. The performance and safety of the OWEC are affected by wave characteristics, such as wave height, period. To mitigate this issue, optimal OWEC designs based on wave characteristics must be investigated. In this study, the environmental conditions along the Ulleungdo coast were used. The hydraulic efficiency of the OWEC was calculated using SPH (Smoothed Particle Hydrodynamics) by comparing 4 models that changed the substructure. As a result, it was possible to change the substructure. Through design optimization, a new truss-type structure, which is a substructure capable of carrying the design load, was proposed. Through a case study using member diameter and thickness as design variables, structural safety was secured under allowable stress conditions. Considering wave load, the natural frequency of the proposed structure was compared with the wave period of the relevant sea area. Harmonic response analysis was performed using wave with a 1-year return period as the load. The proposed substructure had a reduced response magnitude at the same exciting force, and achieved weight reduction of more than 32%.

• Clean Technology
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• v.29 no.4
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• pp.327-332
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• 2023

This study investigated synthesis gas production via steam reforming of biogas. Ni-Al₂O₃ and Ni-CeO₂ catalysts were synthesized using the co-precipitation method, with controlled precipitation agent injection rates. Catalytic performances were tested at various temperatures, with a gas composition ratio of CH₄:CO₂:H₂O = 1:0.67:3 and a gas hourly space velocity (GHSV) of 647,000 mL h^-1 gcat^-1. The rate of precipitation agent injection influenced the characteristics of the catalysts depending on the type of support used. As the temperature increased, both the CO₂ reforming of methane and the reverse water gas shift reactions occurred. The Ni-Al₂O₃ catalyst, synthesized with a single injection of the precipitation agent, exhibited the best catalytic activity under conditions with sufficient steam supply among the prepared catalysts, due to its high Ni dispersion.