• The Journal of the Korea institute of electronic communication sciences
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• v.17 no.6
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• pp.1013-1024
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• 2022

In addition to the assessment measure of electric quality levels, load loss are also a factor in hindering the financial profits of electrical sales companies. Therefore, accurate analysis of load losses generated from distributed power networks is very important. The accurate calculation of load losses in the distribution line has been carried out for a long time in many research institutes as well as power utilities around the world. But it is increasingly difficult to calculate the exact amount of loss due to the increase in the congestion of distribution power network due to the linkage of distributed energy resources(DER). In this paper, we develop smart grid big data infrastructure in order to accurately analyze the load loss of the distribution power network due to the connection of DERs. Through the preprocess of data selected from the smart grid big data, we develop a load loss analysis model that eliminated 'veracity' which is one of the characteristics of smart grid big data. Our analysis results can be used for facility investment plans or network operation plans to maintain stable supply reliability and power quality.

• Journal of Digital Convergence
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• v.19 no.11
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• pp.255-266
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• 2021

Investment demand for factory facilities has increased due to the balloon effect caused by housing price regulation. This study investigated the impact of the real estate market and macroeconomic factors on the bid price ratio of apartment auctions and factory auctions, focusing on the metropolitan area. To this end, we reviewed theories and previous studies on real estate auctions, and examined how macroeconomic variables affect bid price ratio of apartments and factories using the panel vector autoregressive model. It was found that the increase in the apartment bid price ratio increases as the participation in apartment auctions increases. However, as the factory bid price ratio increases, the factory bid price ratio does not increase, it was confirmed that the positive (+) relationship between the successful bid price ratio and the bid price ratioe does not exist, unlike previous studies. Based on the analysis results, it is suggested that the real estate market and macroeconomic factors should be considered for the stable operation of the related relevant auction system. This study has limitations in that it is limited to the metropolitan area. In the future, research that expands the scope of research to the whole country and provinces should be conducted.

• Journal of the Korean Society of Marine Environment & Safety
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• v.28 no.5
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• pp.809-818
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• 2022

The number of ships using liquefied natural gas (LNG) as fuel is increasing to respond to the International Maritime Organization's (IMO) air pollutant emission regulations. At the same time, the need to expand LNG bunkering infrastructure for stable fuel supply and demand for ships is emerging. LNG bunkering is carried out in three ways: truck to ship (TTS), pipe to ship (PTS), and ship to ship (STS). In foreign countries, all three methods are being carried out, but in Korea, LNG bunkering is carried out only with the TTS method owing to the lack of infrastructure. LNG bunkering is a high-risk operation. For safe bunkering operations, the competence of the workers is extremely important, and a professional training course is required to strengthen the competence. This study was conducted to design training contents for LNG bunkering workers for fostering LNG bunkering experts and performing safe and systematic bunkering work. To this end, the current status of LNG-fueled ships and bunkering was identified, and related domestic and abroad educational contents were analyzed. In addition, opinions on the importance of educational contents were collected through expert questionnaires. Consequently, we designed training contents suitable for various training targets and divided them into basic and advanced training courses, with a duration of 4 days, and proposed. Based on the designed training contents, if additional research is conducted by sufficiently reflecting Korea's bunkering environment, it will be of great help to improve the competence of LNG bunkering workers and to foster human resources.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.32 no.5
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• pp.1019-1034
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• 2022

Malware attacks become more prevalent in the hyper-connected society of the 4th industrial revolution. To respond to such malware, automation of malware detection using artificial intelligence technology is attracting attention as a new alternative. However, using artificial intelligence without collateral for its reliability poses greater risks and side effects. The EU and the United States are seeking ways to secure the reliability of artificial intelligence, and the government announced a reliable strategy for realizing artificial intelligence in 2021. The government's AI reliability has five attributes: Safety, Explainability, Transparency, Robustness and Fairness. We develop four elements of safety, explainable, transparent, and fairness, excluding robustness in the malware detection model. In particular, we demonstrated stable generalization performance, which is model accuracy, through the verification of external agencies, and developed focusing on explainability including transparency. The artificial intelligence model, of which learning is determined by changing data, requires life cycle management. As a result, demand for the MLops framework is increasing, which integrates data, model development, and service operations. EXE-executable malware and documented malware response services become data collector as well as service operation at the same time, and connect with data pipelines which obtain information for labeling and purification through external APIs. We have facilitated other security service associations or infrastructure scaling using cloud SaaS and standard APIs.

• Membrane Journal
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• v.32 no.6
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• pp.442-455
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• 2022

High-temperature polymer electrolyte membrane fuel cell (HT-PEMFC) has been studied as an alternative to low-temperature PEMFC due to its fast activation of electrodes and high resistance to electrode poisoning by carbon monoxide. It is highly required to develop stable PEMs operating at high temperatures even doped by ion-conducting materials for the development of high-performance and durable HT-PEMFC systems. A number of studies have been conducted to develop polybenzimidazole (PBI)-based PEMs for applications in HT-PEMFC due to their high interaction with doped ion-conducting materials and outstanding thermomechanical stability under high-temperature operation. This review focused on the development of PBI-based PEMs showing high performance and durability. Firstly, the characteristic behavior of PBI-based PEMs doped with various ion-conducting materials including phosphoric acid was systematically investigated. And then, a comparison of the physicochemical properties of the PEMs according to the different membrane manufacturing processes was conducted. Secondly, the incorporation of porous polytetrafluoroethylene substrate and/or inorganic composites to PBI matrix to improve the membrane performances was studied. Finally, the construction of cross-linked structures into PBI-based PEM systems by polymer blending method was introduced to improve the PEM properties.

• Membrane and Water Treatment
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• v.14 no.3
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• pp.129-140
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• 2023

The appropriate injection of H₂O₂ is essential to produce hydroxyl radicals (OH·) by mixing H₂O₂ quickly and exposing the resulting H₂O₂ solution to UV irradiation. This study focused on evaluating mixing device of H₂O₂ as a design factor of UV/H₂O₂ AOP pilot plant using a surface water. The experimental investigation involved both experimental and model-based analyses to evaluate the mixing effect of different devices available for the H₂O₂ injection of a tubular hollow pipe, elliptical type of inline mixer, and nozzle-type injection mixer. Computational fluid dynamics analysis was employed to model and simulate the mixing devices. The results showed that the elliptical type of inline mixer showed the highest uniformity of 95%, followed by the nozzle mixer with 83%, and the hollow pipe with only 18%, after passing through each mixing device. These results indicated that the elliptical type of inline mixer was the most effective in mixing H₂O₂ in a bulk. Regarding the pressure drops between the inlet and outlet of pipe, the elliptical-type inline mixer exhibited the highest pressure drop of 15.8 kPa, which was unfavorable for operation. On the other hand, the nozzle mixer and hollow pipe showed similar pressure drops of 0.4 kPa and 0.3 kPa, respectively. Experimental study showed that the elliptical type of inline and nozzle-type injection mixers worked well for low concentration (less than 5mg/L) of H₂O₂ injection within 10% of the input value, indicating that both mixers were appropriate for required H₂O₂ concentration and mixing intensity of UV/ H₂O₂ AOP process. Additionally, the elliptical-type inline mixer proved to be more stable than the nozzle-type injection mixer when dealing with highly concentrated pollutants entering the UV/H₂O₂ AOP process. It is recommended to use a suitable mixing device to meet the desired range of H₂O₂ concentration in AOP process.

• Journal of the Korean Geotechnical Society
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• v.26 no.5
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• pp.37-48
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• 2010

In this study, the seepage flow monitoring method by the hydraulic head loss rate was developed for the purpose of application to offshore construction site enclosed by cofferdams in which seepage force varies periodically. The amount of the hydraulic head loss rate newly defined in this graph was in a range between 0 and 1. The zero of the rate means the existence of flow with no seepage resistance. The 1 of the rate means no seepage flow through the ground. The closer to 1 the coefficient of determinant in the hydraulic head loss graph is, the more the ground through which seepage water flows is stable. The closer to 0 the coefficient of determinant in the hydraulic head loss graph is, the more the ground through which seepage water flows was unstable and the higher the possibilities of existence of empty space or of occurrence of piping on the seepage flow pass in the ground is. The hydraulic head loss graph makes it possible to monitor sensitively the situation of seepage flow state, and the graph helps to understand easily the seepage flow state at the specific section on the whole cofferdam.

• Journal of Cadastre & Land InformatiX
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• v.53 no.1
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• pp.47-63
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• 2023

The Seoul Metropolitan Government is building and operating digital twin-based urban spatial information to solve various problems in the city and provide public services. Two essential factors to ensure the stable utilization of spatial information for the implementation of such a digital twin city are the latest and quality of the data. However, it is time-consuming and costly to maintain continuous updating of high-quality urban spatial information. To overcome this problem, we studied efficient urban spatial information construction technology and the operation, management, and update procedures of construction data. First, we demonstrated and applied automatic 3D building construction technology centered on point clouds using the latest hybrid sensors, confirmed that it is possible to automatically construct high-quality building models using high-density airborne lidar results, and established an efficient data management plan. By applying differentiated production methods by region, supporting detection of urban change areas through Seoul spatial feature identifiers, and producing international standard data by level, we strengthened the utilization of urban spatial information. We believe that this study can serve as a good precedent for local governments and related organizations that are considering activating urban spatial information based on digital twins, and we expect that discussions on the construction and management of spatial information as infrastructure information for city-level digital twin implementation will continue.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.535-542
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• 2010

Precise estimation of a structure's dynamic characteristics is indispensable for ensuring stable dynamic responses during lifetime especially for the structures which can experience resonance such as railway bridges. In this paper, the results of forced vibration tests of different excitation methods (vibration exciter and impact hammer) are compared to examine the differences and the cause of differences of extracted natural frequencies. Consequently a natural frequency modification method is suggested to eliminate effects of non-structural disturbance factors. Also, sequential forced vibration tests are performed before and after track construction according to the construction stage of a railway bridge, and the variation of natural frequencies are examined. Effect of added mass of vibration exciter and variation of support condition due to the level of excitation force are concluded as the major cause of natural frequency differences. Thus eliminating these effects can enhance the reliability of the extracted natural frequencies. Construction of track affects not only the mass of structure but also the stiffness of the structure. Also, the amount of increase in stiffness varies according to the level of structural deflection. Therefore, reasonable estimation of the level of structural response during operation is important for precise natural frequency calculation at design phase.

• Journal of Appropriate Technology
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• v.5 no.2
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• pp.62-69
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• 2019

Supplying stable electric power is one of the important objectives of the Official Development Assistance (ODA) because it is strongly related with improving living standards and income levels in the region. However, rural areas in many developing countries are not properly connected to national power grids, and even areas connected to national power grids are frequently blacked out due to limitations in power capacity. These lack of electric power is a major obstacle to improving income levels and improving living standards in those areas. The Korea-Tanzania Innovative and Energy Center (iTEC), which was established by Seoul National University in cooperation with the Nelson-Mandela Africa Institute of Science and Technology and Technology (NM-AIST) try to build a small solar power plant using a smart-off grid in rural area of Tanzania, where there is no electricity. 10 kW and 7 kW solar power plants are built in Mkalama Village in Kilimanajaro Region and Ngurdoto Village in Arusha Region to provide power to about 50 households each. In addition, smart monitoring systems were installed to collect data about status of power system and power consumption of each house. iTEC seeks for sustainable improvement the income level and quality of life of rural residents in developing countries through the construction of small solar power plants using smart-off grid, and the implementation of various connected projects.