• Korean Journal of Environmental Agriculture
• /
• 제40권3호
• /
• pp.231-238
• /
• 2021

BACKGROUND: Metal contamination of farmlands nearby abandoned mines is a serious environmental problem. This study was conducted to evaluate the efficiency of stabilizers on different type of the soils contaminated with metals. METHODS AND RESULTS: The texture of silt loam soil initially contaminated with heavy metal was artificially adjusted to loam and sandy loam by adding sand, and the soil organic matter content (1.5%) was also altered by adding peat to the soils at 3.5 and 8.0%. The soils were mixed with 3% (w/w) of each limestone, dolomite, and steel slag. For the soils with different textures, the bioavailability of As was found to be the lowest in sandy loam compared to others metals such as Cu, Pb, and Zn. The efficacy of limestone and dolomite was not significantly different compared to the soils having different organic matter contents, but the stabilization efficiency of steel slag increased as the soil organic matter content increased. Moreover, stabilizers showed inhibition effect on the uptake of metals to plant. CONCLUSION: The stabilizers were found as effective materials to immobilize metals in soil and to decrease plant uptake of metals. Studies are needed to deeply elucidate the interaction between influencing factors and various stabilizers.

• The Journal of the Korea institute of electronic communication sciences
• /
• 제16권2호
• /
• pp.279-286
• /
• 2021

Recently, the effort of enterprises are visualized to correspond for 4th industrial revolution and climate change. Reaching the operation of industrial facilities are one of these efforts and is actively progressing under identical condition between real and virtual world through introduction of cyber-physical system (CPS). However, the problem on no unified definition for CPS still exists. Thus, in this paper, we review the previous concept of CPS. We propose new concept of CPS with four sections such as real world section, communication section, virtual world section and management section. We also propose definite concept by classifying the layer of each section. In order to confirm the possibility of application for proposed concept of CPS, we applied simple motor. We compare the result for torque between real motor and virtual motor. Finally we confirm that the applicability of proposed concept of CPS is very high.

• The Journal of the Korea institute of electronic communication sciences
• /
• 제17권5호
• /
• pp.815-824
• /
• 2022

The growing integration of intermittent renewable sources like offshore wind energy increases the need for transferring electric energy over long distances, which may include sea crossings. One of the solutions available for bulk electric power transmission across large distances encompassing wide and deep sea is using HVDC submarine power cables. However, there are no standards or research related to the calculation of the continuous allowable current with various ocean conditions of a DC power cable that does not have an alternating magnetic field. In this study, assuming the typical two types of subsea cable models and two areas of the south coast and the west coast marine conditions, a continuous allowable current simulation of DC cables was performed. As a simulation result, the DC cable continuous allowable current find out the gradient reduction characteristics based on subsea base depth.

• Journal of Software Assessment and Valuation
• /
• 제16권2호
• /
• pp.127-133
• /
• 2020

As the usages of artificial intelligence is increased, the demand to algorithms for small portable devices increases. Also as the embedded system becomes high-performance, it is possible to implement algorithms for high-speed computation and machine learning as well as operating systems. As the machine learning algorithms process repetitive calculations, it depend on the cloud environment by network connection. For an stand alone system, low power consumption and fast execution by optimized algorithm are required. In this study, for the purpose of smart control, an energy measurement sensor is connected to an embedded system, and a real-time monitoring system is implemented to store measurement information as a database. Continuously measured and stored data is applied to a learning algorithm, which can be utilized for optimal power control, and a system interfacing various sensors required for energy measurement was constructed.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
• /
• 제18권4호
• /
• pp.1-11
• /
• 2022

In this study, the thermal runaway of NCM and LFP batteries were compared and analyzed through numerical analysis under various conditions. Comparing the thermal runaway of the NCM622 (18650) battery cell and the LFP (18650) battery cell through oven test simulation, the LFP battery did not show thermal runaway, whereas the NCM622 battery temperature increased to 710℃ in 12 minutes. To observe the thermal runaway and propagation of the prismatic LFP battery cell, the internal temperature was set at 200℃ and the oven test simulation was conducted. It was found that thermal runaway occurred at 391℃ after 47 minutes. As a result of observing thermal runaway propagation by placing five NCM622 and LFP battery cells, the thermal runaway propagation was clearly observed in the case of the NCM622 battery, but in the case of the LFP battery, thermal runaway was not observed after the first cell. From the third battery cell, it was confirmed that the temperature change was very insignificant, and through this, it is considered that the LFP battery is relatively safe compared to the NCM battery in terms of the thermal runaway propagation of the battery.

• Transactions of the Korean hydrogen and new energy society
• /
• 제34권2호
• /
• pp.226-233
• /
• 2023

In this study, we compared the performance of several refrigeration cycles using different refrigerants and utilizing the cold heat of liquefied natural gas (LNG) for the liquefaction of carbon dioxide. The final conditions for the liquefied CO₂ were set to -20℃ and 20 bar. The refrigerants used included R404a, ammonia, propane, and propylene using a vapor recompression refrigeration cycle. For the refrigeration cycle, the CO₂ at room temperature and pressure was compressed in a two-stage compression process with an intermediate cooling stage using a refrigeration unit. To compare with the liquefaction process using refrigeration, we compressed the CO₂ to 8 bar in a single compression stage and cooled it to around -50℃ using the cold heat of the LNG before liquefying it. Results showed that using ammonia as the refrigerant required the least amount of compressor power for the liquefaction process, and the heat transfer area of the evaporator was the smallest when using propylene as the refrigerant. Using the cold heat of LNG instead of refrigeration using R404a resulted in approximately 69% less energy consumption.

• The Journal of the Korea institute of electronic communication sciences
• /
• 제17권2호
• /
• pp.299-308
• /
• 2022

Recent, energy transition policies are driving to increase in the number of small photovoltaic(PV) generators. It is difficult for system operators to accurately anticipate the amount of power generated from such small scale PV generation, and this may disrupt dispatch schedules and result in an increase in cost. The need for a Virtual Power Plant(VPP) is emerging as a way of resolving these problems, as it would integrate small-scale PV plants and eliminate uncertainty about the amount of power generated, control voltage, and provide power reserves. In this paper, the cost evaluation methods are described for determination of VPP cloud charges both Net Present Value(NPV) method and Profitability Index(PI) method, the calculated outcomes of the two types of cost evaluation methods are presented in detail. It seems we secure profitability as we get 1.22 of profitability index from calculation results, it may be attractive for the aggregator as NPV is enough for satisfying profitability.

• Korean Journal of Hazardous Materials
• /
• 제2권1호
• /
• pp.12-17
• /
• 2014

With a rapid growth of domestic industry in korea, now about 25,000 kinds of chemicals are being distributed, and it has been known that just about 15% of them has toxic substances. Recently, South Koreans have an anxiety about the stability and accidents of chemicals because chemical accidents like Gumi hydrofluoric acid accident have occurred. The U.S. has adopted the systems like EPCRA (Emergency Planning and Community Right-to-Know Act), TRI (Toxic Release Inventory) and TSCA (Toxic Substances Control Act), and is also managing the hazardous chemicals by providing the information about them to its people and site workers. Japan's Ministry of Health, Labor and Welfare also has adopted J-CHECK system and is implementing it to let Japanese people know the information of safety of chemicals about REACH. However, the Korean government has a difficult situation to mediate the different idea with the Korean industry to make lower statute of Pre-legislation registration & evaluation of chemicals that will be implemented and Chemical Material Control Association that is being implemented. Especially city and country areas located in the industrial areas need political improvement focusing on vulnerable area through the check about current situation of hazardous chemicals of jurisdiction and management method, but the information about the management situation of small scale work places is insufficient. Therefore this study set up the urgent management area in Ansan Smart Hub through NFPA code according to the types of accident and dander characteristics of each chemical being used in the companies that have less than 50 workers and deal with chemicals located in Ansan Smart Hub in Gyeonggi-do.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• 제24권2호
• /
• pp.127-132
• /
• 2024

Recently, secondary batteries, commonly known as rechargeable batteries, find widespread applications across various industries. Particularly valued for their compact and lightweight characteristics, they play a crucial role in diverse portable electronic devices such as smartphones, laptops, and tablets, offering high energy density and efficient charge-discharge capabilities. Moreover, they serve as vital components in electric vehicles and contribute significantly to the field of renewable energy as part of Energy Storage Systems(ESS). However, despite advancements in this technology, issues such as reduced lifespan, cracking, damage, and even the risk of fire can arise due to excessive charging and discharging of secondary batteries. To address these challenges, Battery Management System(BMS) are employed to protect against overcharging and improve overall performance. Nevertheless, understanding the protective range settings of BMS using lithium-ion batteries, the most commonly used secondary batteries, and lead-acid batteries can be challenging. Therefore, this paper aims to utilize a battery charge-discharge tester and simulator to investigate the charging and discharging characteristics of lithium-ion batteries and lead-acid batteries, addressing the associated challenges of reduced lifespan, cracking, damage, and fire hazards in secondary batteries.

• Journal of Bio-Environment Control
• /
• 제30권4호
• /
• pp.419-428
• /
• 2021

In order to develope a mobile-based greenhouse energy calculation program, firstly, the overall thermal transmittance of 10 types of major covers and 16 types of insulation materials were measured. In addition, to estimate the overall thermal transmittance when the cover and insulation materials were installed in double or triple layers, 24 combinations of double installations and 59 combinations of triple installations were measured using the hotbox. Also, the overall thermal transmittance value for a single material and the thermal resistance value were used to calculate the overall thermal transmittance value at the time of multi-layer installation of covering and insulating materials, and the linear regression equation was derived to correct the error with the measured values. As a result of developing the model for estimating thermal transmittance when installing multiple layers of coverings and insulating materials based on the value of overall thermal transmittance of a single-material, the model evaluation index was 0.90 (good when it is 0.5 or more), indicating that the estimated value was very close to the actual value. In addition, as a result of the on-site test, it was evaluated that the estimated heat saving rate was smaller than the actual value with a relative error of 2%. Based on these results, a mobile-based greenhouse energy calculation program was developed that was implemented as an HTML5 standard web-based mobile web application and was designed to work with various mobile device and PC browsers with N-Screen support. It had functions to provides the overall thermal transmittance(heating load coefficient) for each combination of greenhouse coverings and thermal insulation materials and to evaluate the energy consumption during a specific period of the target greenhouse. It was estimated that an energy-saving greenhouse design would be possible with the optimal selection of coverings and insulation materials according to the region and shape of the greenhouse.