• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.2
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• pp.175-181
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• 2024

In electrical power substations, bulky iron-core potential transformers (PTs) are installed in a tank of gas-insulated switchgear (GIS) to measure system voltages. This paper proposed a low-power voltage transformer (LPVT) that can replace the conventional iron-core PTs in response to the demand for the digitalization of substations. The prototype LPVT consists of a capacitive voltage divider (CVD) which is embedded in a spacer and an impedance matching circuit using passive components. The CVD was fabricated with a flexible PCB to acquire enough insulation performance and withstand vibration and shock during operation. The performance of the LPVT was evaluated at 80%, 100%, and 120% of the rated voltage (38.1 kV) according to IEC 61869-11. An accuracy correction algorithm based on LabVIEW was applied to correct the voltage ratio and phase error. The corrected voltage ratio and phase error were +0.134% and +0.079 min., respectively, which satisfies the accuracy CL 0.2. In addition, the voltage ratio of LPVT was analyzed in ranges of -40~+40℃, and a temperature correction coefficient was applied to maintain the accuracy CL 0.2. By applying the LPVT proposed in this paper to the same rating GIS, it can be reduced the length per GIS bay by 11%, and the amount of SF6 by 5~7%.

• Clean Technology
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• v.28 no.1
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• pp.79-93
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• 2022

In this study, an electronics industrial wastewater activated sludge model (e-ASM) to be used as a Water Digital Twin was calibrated based on real high-tech electronics industrial wastewater treatment measurements from lab-scale and pilot-scale reactors, and examined for its treatment performance, effluent quality prediction, and optimal process selection. For specialized modeling of a high-tech electronics industrial wastewater treatment system, the kinetic parameters of the e-ASM were identified by a sensitivity analysis and calibrated by the multiple response surface method (MRS). The calibrated e-ASM showed a high compatibility of more than 90% with the experimental data from the lab-scale and pilot-scale processes. Four electronics industrial wastewater treatment processes-MLE, A2/O, 4-stage MLE-MBR, and Bardenpo-MBR-were implemented with the proposed Water Digital Twin to compare their removal efficiencies according to various electronics industrial wastewater characteristics. Bardenpo-MBR stably removed more than 90% of the chemical oxygen demand (COD) and showed the highest nitrogen removal efficiency. Furthermore, a high concentration of 1,800 mg L^-1 T MAH influent could be 98% removed when the HRT of the Bardenpho-MBR process was more than 3 days. Hence, it is expected that the e-ASM in this study can be used as a Water Digital Twin platform with high compatibility in a variety of situations, including plant optimization, Water AI, and the selection of best available technology (BAT) for a sustainable high-tech electronics industry.

• Korean Journal of Remote Sensing
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• v.39 no.5_1
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• pp.655-667
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• 2023

Algal bloom outbreaks are frequently reported around the world, and serious water pollution problems arise every year in Korea. It is necessary to protect the aquatic ecosystem through continuous management and rapid response. Many studies using satellite images are being conducted to estimate the concentration of chlorophyll-a (Chl-a), an indicator of algal bloom occurrence. However, machine learning models have recently been used because it is difficult to accurately calculate Chl-a due to the spectral characteristics and atmospheric correction errors that change depending on the water system. It is necessary to consider the factors affecting algal bloom as well as the satellite spectral index. Therefore, this study constructed a dataset by considering water quality, hydrological and meteorological factors, and sentinel-2 images in combination. Representative ensemble models random forest and extreme gradient boosting (XGBoost) were used to predict the concentration of Chl-a in eight weirs located on the Nakdong river over the past five years. R-squared score (R²), root mean square errors (RMSE), and mean absolute errors (MAE) were used as model evaluation indicators, and it was confirmed that R² of XGBoost was 0.80, RMSE was 6.612, and MAE was 4.457. Shapley additive expansion analysis showed that water quality factors, suspended solids, biochemical oxygen demand, dissolved oxygen, and the band ratio using red edge bands were of high importance in both models. Various input data were confirmed to help improve model performance, and it seems that it can be applied to domestic and international algal bloom detection.

• Journal of Navigation and Port Research
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• v.46 no.1
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• pp.1-10
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• 2022

This study aims to investigate changes in the demand for ship officers in response to changes in the shipping industry environment in which Maritime Autonomous Surface Ships (MASS) emerge according to the application of the fourth industrial revolution technology to ships, and it looks into changes in the skill of ship officer. It also analyzes and proposes a plan for nurturing ship officers accordingly. As a result of the degree of recognition and AHP analysis, this study suggests that a new training system is required because the current training and education system may cover the job competencies of emergency response, caution and danger navigation, general sailing, cargo handling, seaworthiness maintenance, emergency response, and ship maintenance and management, but tasks such as remote control, monitoring diagnosis, device management capability, and big data analysis require competency for unmanned and shore-based control. By evaluating the importance of change factors in the duties of ship officers in Maritime Autonomous Surface Ships, this study provides information on ship officer educational institutions' response strategies for nurturing ship officers and prioritization of resource allocation, etc. The importance of these factors was compared and evaluated to suggest changes in the duties of ship officers and methods of nurturing ship officers according to the introduction of Maritime Autonomous Surface Ships. It is expected that the findings of this study will be meaningful as it systematically derives the duties and competency factors of ship officers of Maritime Autonomous Surface Ships from a practical point of view and analyzed the perception level of each relevant expert to diagnose expert-level responses to the introduction of Maritime Autonomous Surface Ships.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.48 no.6
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• pp.452-459
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• 2003

A new demand for vegetable peanut (Arachis hypogaea L.) in Korea has increased farmers interest in growing vegetable peanut. Compared to grain peanut production, vegetable peanut production enables the growth period to be shortened by 20 or 30 days and farmers to adopt various cropping systems and to return crop residues in the soil. With the purpose of establishing desirable cropping systems for sustainable vegetable peanut production, three field experiments were conducted from 2000 to 2001 at Milyang, the southeastern part of Korea. Main focuses were given into the effect of cropping systems for vegetable peanut production on each crop's yield and soil sustainability. The cropping systems investigated were single vegetable peanut, peanut-radish-green barley, peanut-barley, and peanut-garlic cropping system, with or without crop residue incorporation in the soil. Among the cropping systems investigated for sustainable vegetable peanut production, peanut-only and peanut-radish-green barley cropping systems showed vulnerable to diseases and lodging while peanut-barley and peanut-garlic cropping systems showed higher stability in response to diseases and lodging, consequently leading to higher yield potential of vegetable peanut production. In the peanut-barley cropping system, both barley and peanut residues returned to the soil played an important role in soil improvement as well as in significantly increased grain yield of peanut and barley. A particular notice was taken to the pronounced increase in Trichoderma population and the amount of nitrogen mineralization induced by the returned barley residue. Soil structure, compactness, pH, and fertility were positively influenced by the returned crop residues, which apparently increased sustainability in vegetable peanut production systems.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.4
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• pp.1-7
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• 2018

The gases emitted from internal combustion engines using fossil fuels are causing many social problems, such as environmental pollution, global warming, and adverse health effects on the human body. In recent years, the demand for renewable energy has increased, and government policy support and research and development are also active. In the collecting part of a solar energy system, which is widely used at home, propylene glycol (PG) (anti-freeze), as a heating medium, is mixed with water at a fixed value of 50%, and the heat is transferred to the collecting part at subzero temperatures. On the other hand, when leakage occurs in the heat medium in the heat collecting part, supplemental water is supplied to the solar heat collecting part due to the characteristics of the solar heat system, so that the concentration of antifreeze in the replenishing water becomes low. As a result, the temperature of the solar heat collecting part is lowered resulting in a frost wave, which causes economic damage. The purpose of this study was to develop a device capable of controlling the antifreeze concentration automatically in response to a temperature drop to prevent freezing of the heat collecting part generated in the solar energy system. The electrical conductivity of the H2O component was larger than that of PG, and the resistance increased with decreasing temperature. The PG concentration control values of 40, 50, and 60% should be controlled through calibration with a PG concentration of 39.6, 50.7, and 60.1%.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.5
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• pp.551-561
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• 2024

Underground utility tunnels are spaces densely packed with various infrastructure facilities, such as power, telecommunications, and water supply and drainage systems, making internal environment management crucial. An investigation into accident cases and on-site demands in these tunnels revealed that while fires and floods are the most common types of incidents, the demand for real-time condensation prevention and response is frequent according to on-site managers. Condensation occurs due to the difference in humidity and temperature between the inside and outside of the tunnel. Frequent or prolonged condensation can lead to metal pipe corrosion, electrical failures, and reduced equipment lifespan. Therefore, this study developed a control algorithm and monitoring system to prevent condensation in underground utility tunnels. The proposed control algorithm estimates the likelihood of condensation in real-time based on the measured temperature and humidity and suggests appropriate responses for each stage to the managers. Finally, a practical condensation prevention monitoring system was built based on the developed algorithm, verifying the feasibility and applicability of this technology in the field.

• Korean Security Journal
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• no.62
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• pp.255-276
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• 2020

The mandatory police system, which plays a pivotal role in securing security and securing social safety as a security assistant, is expected to face difficulties in supplying the mandatory police manpower and securing absolute police manpower in the future according to the Ministry of Defense's abolition of the conversion service system. In this situation, this study intends to provide a concrete plan to replace the mandatory police officers as security assistants, recruiting contractors from civilians who are not military service resources or regular police officers, and using them for security assistance. More ultimately, this study goes beyond securing obligatory police to reduce or abolish mandatory police, which has been dealt with in previous studies. It aims to present the rescue and operation directions so that the police can provide quality public security services. In order to achieve the purpose of this study, this study 1) analyzes the current situation of police personnel, derives the necessity and justification of securing the police personnel or increasing the number of police personnel due to changes in security demand and security environment, and 2) After discussing the necessity and direction of reorganization, 3) deriving policy implications through analysis of foreign cases operating similar systems to derive specific plans for the introduction of security contractors for private contract workers in Korea. This study reviewed the specific operation plan and legal and institutional maintenance plan of private contract workers. In order to achieve these research objectives, this study 1) analyzes the current status of the police manpower and derives the necessity and justification of securing an absolute police manpower or increasing the manpower of the police in response to changes in security demand and security environment, and the current security aid system. 2) After discussing the necessity and orientation of reorganization of exinsting system of assistant police officer, 3) derive policy implications through analysis of foreign cases utilizing security aids similar to Korea, and 4) The specific operation plan and legal and institutional maintenance plan were presented. including security aids for private contract workers in Korea, from recruitment procedures to activities.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.1
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• pp.46-52
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• 2017

Social attention to information security field is inspired, and manpower demand forecast of this area is getting high. This study surveyed information security knowledge of practitioners who work in a field of information security such as computer and network system. We analyzed a connection between survey data, information protection job system that was suggested by NICE, IT skills that NCS and KISA classified and security field classification system. Base on data that analyzed, this study suggests a curriculum that trains professional manpower who perform duties in the field of information security. Suggested curriculum can be applied to 2 year college, 3 year college and 4 year college. Suggested curriculum provides courses that students who want to work in a field of information security must learn during the college. Suggested courses are closely connected to a related field and detailed guideline is indicated to each course to educate. Suggested curriculum is required, and it combines a theoretical education that become basis and a practical education so that it is not weighted to learn theory and is not only focusing on learning simple commands. This curriculum is established to educate students countermeasures of hacking and security defend that based on scenario that connected to executive ability. This curriculum helps to achieve certificates related to a field more than paper qualification. Also, we expect this curriculum helps to train convergent information security manpower for next generation.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.2
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• pp.81-89
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• 2002

The Battery Energy Storage System (BESS) has lots of advantages such as load leveling, quick response emergency power (spinning reserve), frequency and voltage control, improvement of reliability, and deferred generation and transmission construction. However, it is very critical that economic feasibility requires justification from the customer side of meter to promoting the dissemination of BESS in nation widely. In this paper, we proposed the economic assessment model of customer owned BESS which is complemented and improved the existing model. The proposed model is applied to the typical customer types, i.e. light industrial, commercial, and residential, which are taken from the statistical analysis on the load profile survey of Korea Electric Power COmpany (KEPCO). The economic viability performed for each customer load type to justifying their economic feasibility of BESS installation from the economic measures such as payback period, Net Present Worth (NPW), Rate Of Return (ROR). The results show that the BESS has economic benefits to the specific customer type, i.e. residential customer. Therefore, the government and the energy agency should be committing the support program, such as tax incentive, financial support, to disseminate the BESS nation widely. The results of this paper are useful to the customer investment decision-making and the national energy policy & strategy in Korea.