• Journal of Korean Society of Disaster and Security
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• v.13 no.4
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• pp.65-74
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• 2020

Continuous and accurate instrument of river water usage is needed for sustainable river water management. Although the instrument methods applicable to each point of use of river water are different, more precise direct instrument methods are required at the point of major open channel. Users of river water should select appropriate direct instrument methods to measure usage, but there is a lack of standards and verification research. In this study, the H-Q rating curve method, ultrasonic method, and microwave method were applied directly to the test basin in the upper basin of Mangyeong river, and the accuracy of measurement data was evaluated by comparing absolute error between discharge data calculated by instrument method. When comparing the calculated discharge of point units, the ultrasonic method showed the best results of the actual measurement. Through continuous instrument, the sum of the daily and monthly units was compared, and the ultrasonic and microwave methods were shown to be highly accurate. Based on the results of this study, it is hoped that the appropriate direct measurement method can be selected according to the importance of the river water use facility, considering that the ultrasonic method and the microwave method are relatively costly compared to the water level-flow relationship method.

• The Journal of the Korea institute of electronic communication sciences
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• v.16 no.1
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• pp.61-68
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• 2021

The application of renewable energies such as wind and solar has become an inevitable choice for many countries in order to achieve the reduction of greenhouse gases and healthy economic development. However, due to the intermittent characteristics of renewable energy, the issue with integrating a larger proportion of renewable energy into the grid becomes more prominent. A complex energy system, usually consists of two or more renewable energy sources used together to provide increased system efficiency as well as greater balance in energy supply. Compared with the power system, control and optimization of the complex energy system become more difficult in terms of modeling, operation, and planning. The main purpose of the complex energy system retrofit for samado island with microgrid system is to coordinate the operation with various distributed energy resources, energy storage systems, and power grids to ensure its reliability, while reducing the operating costs and achieving the optimal economic benefits. This paper suggests the improved complex energy system of samado island with optimal microgrid system. The results of test operation show about 12% lower SOC variation band of ESS, elimination of operation limit in PV and reduction of operation time in diesel generator.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.523-529
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• 2020

Power distribution management system is essential for the efficient management and operation of power distribution networks. The power distribution system is a system that manages the distribution network based on IT, and has been evolving along with the development of the power industry. The current power distribution system is designed to operate at a relatively low network transmission speed based on the independent operation of the main equipment. However, due to distributed resources such as photovoltaic or energy storage devices, which are rapidly increasing in popularity in recent years, the operation of future distribution environments is becoming more complex, and various information needs to be collected in real time. In this study, the requirements of the next-generation power distribution system were derived to overcome the limitations of the existing power distribution system, and based on this, the communication network system and performance requirements for the distribution system were defined. In order to verify the performance of the designed system, a software-based terminal device simulator was developed because it takes excessive time and cost to introduce a large-scale system such as a power distribution system. Using the simulator, a test environment similar to the actual operation was established, and the number of terminal devices was increased up to 1,000. The proposed system was shown to satisfy the requirements to support the functions of the next-generation power distribution system, recording less than 10 % of the communication network bandwidth.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.3
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• pp.85-91
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• 2021

Type 1 and type 2 buildings must regularly conduct precise safety inspections and precise safety diagnosis for the safety and maintenance of facilities, and the safety grade of the building is determined according to the results of the implementation. In addition, the cycle of inspection and diagnosis is determined according to the safety grade of the building. In order to determine the safety grade of the building, a precise safety inspection conducts condition evaluation, and a precise safety diagnosis conducts condition evaluation and safety evaluation. Therefore, since the inspection and diagnosis cycle is determined according to the safety grade of the building, the condition evaluation and safety evaluation must be precise. However, in the case of member unit evaluation, which is the first step in evaluating the current condition, the evaluation grade is determined by using the representative value of the measurement result, and this may result in an error in the evaluation grade. To solve this problem, this study analyzed evaluation criteria for each evaluation item and presented evaluation criteria using inequalities to respond to measurement results and evaluation scores. In addition, we present a functional formula that can reflect performance scores for each evaluation item.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.434-439
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• 2020

Selective laser melting (SLM) manufactures an alloy using laser as a heat source, and has recently been introduced in the dental industry. However, there is a lack of analytical research on metal-ceramic restorations achieved by SLM. This study evaluates and compares the metal-ceramic bond strength of Co-Cr alloys produced by selective laser melting and casting methods. Co-Cr samples required for this study were produced through the sintering process of ceramics, by applying the SLM and CAST methods. The metal-ceramic bond strength was measured by applying the shear bond strength test. In order to determine the area fraction of adherent ceramic, Si content of the specimen was measured using scanning electron microscopy SEM/ EDS. Results of the metal-ceramic bond strength and AFAC were analyzed by t-test (α = 0.05). No significant difference was observed comparing the bond strength of SLM and CAST Co-Cr alloys (P> 0.05). However, the SLM group had much better ceramic adherence than the CAST group (P < 0.001). Moreover, oxidation characteristics were similar for both SLM and CAST Co-Cr alloys, but metal structures were different. These results imply that although the bond of ceramic and Co-Cr alloy is not related to the manufacturing method, SLM alloys impart better ceramic adherence. This indicates that alloys made with SLM can be used to fabricate upper implant prostheses in the future. In particular, it is expected to overcome the shortcomings of the CAST method, and save time and cost.

• The Journal of the Korea Contents Association
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• v.22 no.7
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• pp.55-62
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• 2022

The perovskite solar cell is an active part of research in renewable energy fields such as solar energy, wind, hydroelectric power, marine energy, bioenergy, and hydrogen energy to replace fossil fuels such as oil, coal, and natural gas, which will gradually disappear as power demand increases due to the increase in use of the Internet of Things and Virtual environments due to the 4th industrial revolution. The perovskite solar cell is a solar cell device using an organic-inorganic hybrid material having a perovskite structure, and has advantages of replacing existing silicon solar cells with high efficiency, low cost solutions, and low temperature processes. In order to optimize the light absorption layer thin film predicted by the existing empirical method, reliability must be verified through device characteristics evaluation. However, since it costs a lot to evaluate the characteristics of the light-absorbing layer thin film device, the number of tests is limited. In order to solve this problem, the development and applicability of a clear and valid model using machine learning or artificial intelligence model as an auxiliary means for optimizing the light absorption layer thin film are considered infinite. In this study, to estimate the light absorption layer thin-film optimization of perovskite solar cells, the regression models of the support vector machine's linear kernel, R.B.F kernel, polynomial kernel, and sigmoid kernel were compared to verify the accuracy difference for each kernel function.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.5
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• pp.15-21
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• 2021

Electrically powered airplanes can reduce CO₂ emissions from fossil fuel use and reduce airplane costs in the long run through efficient energy use. For this reason, advanced aviation countries such as the United States and the European Union are leading the development of innovative technologies to implement the full-electric airplane in the future. Currently, the research and development to convert existing two-seater engine airplanes to electric-powered airplanes are underway domestically. The airplane converted to electric propulsion is the KLA-100, which aims to carry out a 30-minute flight test with a battery pack installed using the engine mounting space and copilot space. The lithium-ion battery installed on the airplane converted to electric propulsion was designed with a specific power of 150Wh/kg, weight of 200kg, and a C-rate 3~4. This study confirmed the possibility of a 30-minute flight with a designed battery pack before conducting a flight test of a modified electrically propelled airplane. The battery performance was verified by dividing the 30-minute flight profile into start/run stage, take-off stage, climbing stage, cruise stage, descending stage, and landing/run stage. The final target of the 30-minute flight was evaluated by calculating the battery capacity required for each stage. Furthermore, the flight performance of the electrically propelled airplane was determined by calculating the flight availability time and navigation distance according to the flight speed.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.36 no.3
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• pp.266-270
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• 1991

Storage in the form of brown or milled rice saves space and cut cost rather than storage of rough rice, the common way of grain storage in Korea. But, brown or milled rice may be more susceptable to grain aging and sensory change than rough rice. Rice stored in government warehouse for 20 months after harvest was hulled into brown or milled rice and packaged with kraft paper bag (paper package), polyprophylen (PP package), and polyethylene (PE package). Then, after those rice packages were stored under room condition for one year, we investigated germinability, fat acidity, and sensory change to determine milling and packaging effects. Germinability of rough and brown rice was decreased significantly after long-term storge. In germination rate, Chucheong cultivar was lower than Milyang #23, brown rice was lower than rough rice, but there was no differences within packaging materials. TTC test which had a significant correlation with germinability can be used as a handy procedure for predicting grain germination. Fat acidity was increased as the order of rough < milled < brown rice in terms of milling, and PP < paper < PE package in terms of packaging materials. Especially, storage of brown rice increased fat acidity above 30 mg KOH, indicating one of characteristics of grain aging. To prevent from high fat acidity it was necessary to store in forms of rough grain with paper or PP packaging and milled rice with paper, or PP, or PE packaging. In sensory test of stored grain, eating quality in brown rice was the worst because of acidification of fatty acid. Also, eating quality of stored grain became worse as fat acidity increased.

• Journal of Platform Technology
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• v.10 no.4
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• pp.25-38
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• 2022

Recently, it is reported that the Korean Unmanned Aerial Vehicle (UAV) interface protocol (K-4586) based on STANAG-4586 is being developed to secure interoperability between UAVs. The core elements of the K-4586-based Unmanned Aircraft System (UAS) are the Core UAV Control System (CUCS), Vehicle Specific Module (VSM), Data Link Interface (DLI), and C4I systems. In UAS based on K-4586, the DLI function for transmitting and receiving messages to link UAVs is included in VSM and CUCS respectively. The Generator/Analyzer (G/A) tool is an apparatus that is developed for protocol conformance verification for VSM and CUCS, and G/A tools with DLI message transmitting and receiving should be developed separately. Core applications (VSM, CUCS, DLI) and G/A tools based on K-4586 may be developed independently depending on the developers. If the DLI message modules are different for each developer, the scope and results of protocol conformance verification will be dissimilar, and some problems may happen during system integration. In this study, common DLI message module based on the API was designed to provide the DLI message transmitting and receiving function necessary to the development of core applications and the protocol conformance verification tool of based on K-4586. When applying the proposed common DLI message module, it can be expected to shorten the UAS system development period and reduce costs, and ensure conformance of protocol. In this paper, the design and implementation method for the common DLI message module based on API was proposed and the results of functional test was described.

• Journal of the Korea Society for Simulation
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• v.19 no.4
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• pp.11-19
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• 2010

ZigBee is a standard for wireless personal area networks(WPANs) based on the IEEE 802.15.4 standard. It has been developed for low cost and low power consumption. There are two alternative routing schemes that have been proposed for the ZigBee standard: Ad-hoc On-Demand Distance Vector(AODV) and tree routing. The tree routing forwards packets from sensors to a sink node based on the parent-child relationships established by the IEEE 802.15.4 MAC topology formation procedure. In order to join the network, a sensor node chooses an existing node with the strongest RSSI(Received signal strength indicator) signal as a parent node. Therefore, some nodes carry a large amount of traffic load and exhaust their energy rapidly. To overcome this problem, we introduce a new metric based on link quality and traffic load for load balancing. Instead of the strength of RSSI, the proposed scheme uses the new metric to choose a parent node during the topology formation procedure. Extensive simulation results using TOSSIM(TinyOS mote SIMulator) show that the CFR scheme outperforms well in comparison to the conventional tree routing scheme.