• Smart Structures and Systems
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• v.22 no.6
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• pp.727-741
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• 2018

To mitigate vibrations, tuned mass dampers(TMD) are widely used for long span bridges or high-rise buildings. Due to some durability concerns, such as fluid degradation, oil leakage, etc., the alternative solutions, such as the non-contacted eddy current damping (ECD), are proposed for mechanical devices in small scales. In the present study, a new eddy current damping TMD (ECD-TMD) is proposed and developed for large scale civil infrastructure applications. Starting from parametric study on finite element analysis of the ECD-TMD, the new design is enhanced via using the permanent magnets to eliminate the power need and a combination of a copper plate and a steel plate to improve the energy dissipation efficiency. Additional special design includes installation of two permanent magnets at the same side above the copper plate to easily adjust the gap as well as the damping. In a case study, the proposed ECD-TMD is demonstrated in the application of a steel arch bridge to mitigate the wind-induced vibrations of the flexible hangers. After a brief introduction of the configuration and the installation process for the damper, the mitigation effects are measured for the ambient vibration and forced vibration scenarios. The results show that the damping ratios increase to 3% for the weak axis after the installation of the ECD-TMDs and the maximum vibration amplitudes can be reduced by 60%.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.6
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• pp.129-134
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• 2021

Recently, the demand for electricity is gradually increasing due to the rapid industrial development and the improvement of living standards. In the case of Korea, which is highly dependent on fossil fuels due to such a surge in electricity demand, reduction and freezing of greenhouse gas emissions due to international environmental regulations will immediately lead to a contraction in industrial activities. Accordingly, there are many difficulties in competition with advanced countries that want to link the environment with the country's industrial production activities, and the development of alternative energy as a countermeasure is of great interest around the world. Among these new power generation methods, small-scale power generation facilities with relatively small capacity include photovoltaic generation, wind power generation, and fuel cell generation. Among them, the fuel cell attracts the most attention in consideration of continuous operation, high power generation efficiency, and long-term durability, which are important factors for practical use. Therefore, in this paper, the fuel cell power generation system was researched and constructed by designing the power conversion circuit necessary to finally obtain the AC power used in our daily life by using the DC power generated from the fuel cell as an input.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.6
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• pp.508-519
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• 2006

In solar power system, the height and azimuth of the sun are important parameters which control generated power magnitude. The tracking method that controls the daily generation magnitude according to latitude and longitude using the two axles is often used in the existing sunlight tracking system today. In this two-axle PV track control system, the self-load is concentrated on one FRAME. It is influenced of the regular load, snow load and the wind load, etc. It is difficult to set up the system in the conventional building. This research is a development about the small-scale economy track device of independent load-dispersing solar generation system. The position tracking algorithm is through the new coordinates transformation calculating the height and azimuth of the sun.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.10-15
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• 2003

This paper presents the digital computer performance evaluations of the three-phase self-excited induction generator (SEIG) driven by the variable speed prime mover such as the wind turbine using the nodal admittance approach steady-state frequency domain analysis with the experimental results. The three-phase SEIG setup is implemented for small-scale rural renewable energy utilizations. The experimental performance results give a good agreement with those ones obtained from the digital computer simulation. Furthermore, a feedback closed-loop voltage regulation of the three-phase SEIG as a power conditioner which is driven by a variable speed prime mover employing the static VAR compensator (SVC) circuit composed of the thyristor phase controlled reactor (TCR) and the thyristor switched capacitor(TSC) is designed and considered herein for the wind-turbine driven the power conditioner. To validate the effectiveness of the SVC-based voltage regulator of the terminal voltage of the three-phase SEIG, an inductive load parameter disturbances in stand-alone are applied and characterized in this paper. In the stand-alone power utilization system, the terminal voltage response and thyristor triggering angle response of the TCR are plotted graphically. The simulation and the experimental results prove the effectiveness and validity of the proposed SVC which is controlled by the Pl controller in terms of fast response and high performances of the three-phase SEIG driven directly by the rural renewable energy utilization like a variable-speed prime mover.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.23 no.2
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• pp.51-56
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• 2015

This paper presents the procedure of drag prediction for EAV-1, based on a numerical analysis correlated to an in-flight test. EAV-1, developed by Korea Aerospace Research Institute, is a small-sized UAV to test a hydrogen-fuel cell power system. The long-endurance test flight of 4.5 hours provides numerous in-flight data. The thrust and drag of EAV-1 during the flight test are estimated based on the wind-tunnel test results for EAV-1's propeller performance. In addition, the CFD analysis using a commercial Navier-Stokes code is carried out for the full-scale EAV-1. The computational result suggests that the initial CFD analysis substantially under-predicts the in-flight drag in that the discrepancy is up to 27.6%. Therefore, additional investigation for more accurate drag prediction is performed; the effect of propeller slipstream is included in the CFD analysis through "fan disk" modelling. Also, the additional drag from airplane trim and load factor that actually exists during the flight test in a circular path is considered. These supplemental analyses for drag prediction turn out to be effective since the drag discrepancy reduces to 2.3%.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1702-1704
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• 2005

In solar power system, the height and azimuth of the sun are important parameters which control generated power magnitude. The way that controls the daily generation magnitude according to latitude and longitude and uses two axles is often used in the existing sunlight racing system now. In this two-axle sunlight track control system the self-load is concentrated on one FRAME. It is influenced of the regular load, snow load and the wind load, etc. It is difficult to set up the system in the building already built up. This research is a development about the small-scale economy track device of independent load-dispersing type solar generation system. The position track algorithm is through calculating the trail of height and azimuthal of the sun calculation to follow the sun.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.590-596
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• 2020

In the island areas where system connection with the commercial power grid is difficult, it is quite important to find a method to efficiently manage energy produced with independent microgrids. In this paper, a prosumer management system for P2P power transaction was realized through the testing the power meter and the response rate of the collected data for the power produced in the small-scale microgrids in which hybrid models of solar power and wind power were implemented. The power network of the microgrid prosumer was composed of mesh structure and the P2P power transaction was tested through the power meter and DC power transmitter in the off-grid sites which were independently constructed in three places. The measurement values of the power meter showed significant results of voltage (average): 380V + 0.9V, current (average): + 0.01A, power: 1000W (-1W) with an error range within ±1%. Stabilization of the server was also confirmed with the response rate of 0.32 sec. for the main screen, 2.61 sec. for the cumulative power generation, and 0.11 sec for the power transaction through the transmission of 50 data in real time. Therefore, the proposed system was validated as a P2P power transaction system that can be used as an independent network without transmitted by Korea Electric Power Corporation (KEPCO).

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.15 no.2
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• pp.95-102
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• 2022

It is a study for the evaluation of the stability of the distribution automation system for the expansion of renewable energy. Through the Renewable Energy 3020 Implementation Plan, the government plans to expand new renewable energy and convert it to participatory energy that improves the quality of life of the people by 2030. The government has set a target of 20% of domestic supply energy for renewable energy generation by 2030. It is planning to establish more than 95 percent of its new facilities with clean energy such as solar power and wind power. By expanding the supply of renewable energy, new energy businesses and distributed power industry were fostered, and short-distance, low-voltage, and small-scale power generation were rapidly expanded rather than large-scale power development in the past. Due to this demand, the importance of power distribution facility operation has emerged and the need for distribution automation system is increasing. This paper discusses the development of a power distribution simulator for the performance and function evaluation of power distribution automation systems and presents the results of an interlocking test with the power distribution automation system. In order to introduce an advanced system into the power distribution system, it is necessary to take advantage of the transmission and distribution system. The DNP3.0 protocol is used in the distribution system and the IEC61850 protocol is used in the transmission and distribution system. It was concluded that the functions and performance of operations were satisfied when these two protocols are mixed and used in the distribution automation system.

• Journal of the Korean Association of Geographic Information Studies
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• v.23 no.4
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• pp.101-119
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• 2020

Recently, as a plan to improve the particulate matter and thermal environment in the city, urban forests acting as wind ventilation corridor(wind ventilation forest) are promoted nationwide. This study analyzed the conditions for the creation of wind ventilation forest(vulnerable areas of the particulate matter and thermal environment, distribution of wind ventilation forest, characteristics of ventilation corridor) of in Pyeongtae-si, one of the target cities of wind ventilation forest project. Based on the results, the direction of developing on the wind ventilation forest in Pyeongtaek-si was suggested. As a result of deriving areas vulnerable to particulate matter and thermal environment, it was most vulnerable in urban areas in the eastern area of Pyeongtaek-si. Especially, emissions were high from industrial complexes and roads such as the Pyeongtaek-si thermal power plant, ports, and the national road no. 1. The wind ventilation forest in Pyeongtaek-si was distributed with small-scale windgenerating forests, wind-spreading forests, and wind-connection forests fragmented and disconnected. The characteristic of the overall wind ventilation corridor in Pyeongtaek-si is that the cold air generated from Mt.Mubong, etc., strongly flowed into Pyeongtaek-si and flowed in the northwest direction. Therefore, it is necessary to preserve and expand the wind-generating forests in Pyeongtaek-si in the long term, and it was important to create wind-spreading forests and wind-connection forests so that cold air could flow into the vulnerable area. In addition, in industrial complexes and roads where particulate matter is generated, planting techniques should be applied to prevent the spread of particulate matte to surrounding areas by creating wind-spreading forests considering the particulate matter blocking. This study can be used not only as the basis data for wind ventilation forest project in Pyeongtaek-si, but also as the basis data for urban forest creation and management.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.423-433
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• 2019

In order to predict the seabed topography change due to the construction of offshore wind power structures in the west-southern sea of Korea, field observations for tides, tidal currents, suspended sediment concentrations and seabed sediments were carried out at the same time. These data could be used for numerical simulation. In numerical experiments, the empirical constants for the suspended sediment flux were determined by the trial and error method. When a concentration distribution factor was 0.1 and a proportional constant was 0.05 in the suspended sediment equilibrium concentration formulae, the calculated suspended sediment concentrations were reasonably similar with the observed ones. Also, it was appropriate for the open boundary conditions of the suspended sediment when the south-east boundary corner was 11.0 times, the south-west was 0.5 times, the westnorth 1.0 times, the north-west was 1.0 times and the north-east was 1.0 times, respectively, using the time series of the observed suspended sediment concentrations. In this case, the depth change was smooth and not intermittent around the open boundaries. From these calibrations, the annual water depth change before and after construction of the offshore wind power structures was shown under 1 cm. The reason was that the used numerical model for the large scale grid could not reproduce a local scour phenomenon and they showed almost no significant velocity change over ± 2 cm/s because the jacket structures with small size diameter, about 1 m, were a water-permeable. Therefore, it was natural that there was a slight change on seabed topography in the study area.