• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.353-356
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• 2015

Due to high oil prices, environmental pollution, the study of electric vehicles have been actively promoted. Charger for the electric vehicle is being developed using wireless rather than cable options. In this paper, we got more efficiency from using a superconducting transmission coil compared to using a normal coil. We implemented a wireless power transmission system using a magnetic induction at a frequency of 63.1 kHz. For comparison, a transmitter was designed using a superconducting coil and a normal coil. In addition, a receiver used a normal coil to apply for electric vehicles. The applied voltage and current were12 V and 5 A. Efficiency at a distance of 40 ~ 80 mm was measured. As a result, the superconducting transmission coil had a higher efficiency than the normal transmission coil. However, the receiving coil should be normal conductor for stable operation considering that it was put in moving electric vehicle. The efficiency was increased to 44 % at a distance of 40 mm when the diameter of normal receiving coil was 120 mm.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.12a
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• pp.62-62
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• 2020

Ginseng is a shade-plant cultivated using shading facilities. However, at too low light levels, root growth is poor, and at high light levels, the destruction of chlorophyll reduces the photosynthesis efficiency due to leaf burn and early fall leaves. The ginseng has a lightsaturation point of 12,000~15,000 lux when grown at 15 to 20℃ and 9,500 lux at 25℃. This study was conducted to select the optimal light intensity of 3-year-old ginseng grown in blue-white film plastic house. The seeds were planted in the blue-white film plastic house with different light receiving rate (March 17, 2020). Between April and September, the average air temperature in the house was 20.4-20.7℃. Average soil temperature was 18.3℃-18.5℃. The chemical properties of the test soil was as follows. The pH level was 7.0-7.4, EC was 0.5-0.6 dS/m, OM was at the levels of 33.6-37.7 g/kg, P₂O₅ was 513.0-590.8 mg/kg, slightly higher than the allowable 400 mg/kg. The amount of light intensity, illuminance, and solar radiation in the blue-white film house was increased as the light-receiving rate increased and the amount of light intensity was found to be 9-14% compared to the open field, 8-13% illuminance and 9-14% solar irradiation respectively. The photosynthesis rate was the lowest at 3.1 µmolCO²/m²/s in the 9% light blue-white plastic house and 4.2 and 4.0 µmolCO²/m²/s in the 12% and 14% light blue-white plastic house, respectively. These results generally indicate that the photosynthesis of plants increases with the amount of light, but the ginseng has a lower light saturation point at high temperatures, and the higher the amount of light, the lower the photosynthetic efficiency. The SPAD (chlorophyll content) value decreased as the increase of light-receiving rate, and was the highest at 32.7 in 9% light blue-white plastic house. Ginseng germination started on April 11 and took 13-15 days to germinate. The overall germination rate was 82.9-85.8%. The plant height and length of stem were long in the 9% light-receiving plastic house. The diameter of stem was thick in the 12-14% light-receiving plastic house. In the 12% and 14% light-receiving plastic house, the length and diameter of taproot was long and thick, so the fresh weight of root per plant was 20 g or more, which was heavier than 16.9 g of the 9% light-receiving plastic house. The disease incidence (Alternaria blight, Gray mold and Damping-off etc.) rate were 0.9-2.7%. The incidence of Sclerotinia rot disease was 7.5-8.4%, and root rot was 0-20.0%. The incidence ratio of rusty root ginseng was 34.4-38.7% level, which was an increase from the previous year's 15% level.

• Journal of Advanced Navigation Technology
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• v.23 no.2
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• pp.166-171
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• 2019

This paper has designed a current mode class D power amplifier to increase the transmission efficiency of a 6.78 MHz wireless power transfer (WPT) transmitter and to ensure stable characteristics even when the transmitting and receiving coil intervals change. By reducing the loss due to the parasitic capacitor component of the transistor, which limits the theoretical efficiency of the linear amplifier, this research has improved the efficiency of the power amplifier. The circuit design simulator was used to design the high efficiency amplifier, and the power output and efficiency characteristics according to the load impedance change have been simulated and verified. In the simulation, 42.1 dBm output and 95% efficiency was designed at DC bias 30 V. The power amplifier was fabricated and showed 91% efficiency at the output of 42.1 dBm (16 W). The transmitting and receiving coils were fabricated for wireless power transfer of the drone, and the maximum power added efficiency was 88% and the output power was $42.1dBm{\pm}1.7dB$ according to the load change causing from the coil intervals.

• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.237-243
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• 2015

This paper presented the design of wireless power transfer (WPT) system using electromagnetic induction techniques and analysed WPT efficiency. Also, we presented the optimum coil condition by measuring the efficiency variation according to some receiving coil parameter changes. Voltage change is measured by receiving coil position for the designed transmitting and receiving circuit. Voltage change according to inductance variation at the same position and charging time are compared at the same environment by using a developed application program to realize an optimum WPT system. Developed wireless power transfer system using electromagnetic induction techniques uses 125 kHz. It takes 16 minutes by using wired charger, and 23 minutes by using wireless charger for charging from 50% to 60% charging status.

• Proceedings of the KSRS Conference
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• 2002.10a
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• pp.810-814
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• 2002

According to the image level definition for KOMPSAT-2 in KOMPSAT-2 Ground Station Specification, the level 0 is frame formatted, unprocessed data at full resolution; any and all communications artifacts (e.g., synchronization frames, communications headers) removed. The level 0 is used for two purposes: 1) exchange of imagery between image receiving & processing element (IRPE), and 2) image transfer from the Receiving & Archiving Subsystem to Search & Processing Subsystem. On-board processing of imagery data of KOMPSAT-2 includes JPEG-like compression and encryption besides conventional CCSDS packetization. The encryption is used to secure imagery data from any intervention during downlink and compression allows real-time downlink of image data reducing data rate produced from the camera. While developing ground receiving system for KOMPSAT-2, it was necessarily to define level 0 products. In this paper, we will suggest level 0 product definition for KOMPSAT-2 and explain reasons of the decisions made. The key factor used while defining the level 0 products is the efficiency of whole ground receiving system. The latter half of the paper will explain the implementation of software that generates level 0 products. The necessary steps to produce level 0 products will be explained, and the performance achieved will be presented.

• Journal of the Institute of Electronics and Information Engineers
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• v.51 no.1
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• pp.47-51
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• 2014

In this paper, unit cell and arrayed cover for improving the transfer efficiency of resonant wireless power transfer system is proposed. We used the characteristic of zero refractive index for focusing a magnetic field between the transmitting resonator and receiving resonator. For zero refractive index, we designed the unit cell structure that have a negative value of effective permeability. The size of proposed unit cell based on metamaterial structure is $70mm{\times}70mm{\times}3.2mm$, operating frequency is 13.56 MHz. And, the size of arrayed cover is $400mm{\times}400mm{\times}3.2mm$, is consists of 2-layers. The transfer efficiency of the proposed wireless power transfer system are 94.8 %, 93.2 %, 91.4 %, 90.8 % at 100 mm, 200 mm, 300 mm and 400 mm (distance between transmitting and receiving resonator), respectively. And proposed WPT system has a transfer efficiency high than 90 % over the overall distances.

• Journal of the Korean Operations Research and Management Science Society
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• v.37 no.4
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• pp.125-138
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• 2012

Health care that is considered to be one of the major factors for the quality of life is nowadays receiving a great deal of attention, and thus there is a growing need in Korea to identify the efficiency of national medical service and enhance the competitiveness. Although there exist studies on the medical service efficiency about general hospitals and local hospitals, they mostly deal with the efficiency problems from a domestic and regional perspective. In response, this paper analyzes the competitive efficiency of national medical service with respect to 16 OECD countries, by exploiting Data Envelopment Analysis (DEA) and Malmquist Productivity Index (MPI). Building on the DEA and MPI analysis results, this paper identifies the competitive position of Korean national medical service and suggests implications for the medical service improvement.

• Journal of Aquaculture
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• v.13 no.3
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• pp.259-265
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• 2000

Four experimental diets were formulated to contain white fish meal (WFM) andvor BAIFA-M as the main animal protein source to determine the optimum BAIFA-M level to replace WFM protein. The diets contained 100% WFM + 0% BAIFA-M in the diet M$_0$ (control) . 70%, WFM+30%, BAIFA-M in the diet M$_{30}$, 55 % WFM+45 % BAIFA-M in the diet M$_{45}$, ; 40 % WFM+60 % BAIFA-M in the diet M$_{60}$. The four groups of rockfish (232 g), receiving the four different diets, were fed for 8 weeks. Groups receiving M$_0$, M$_{30}$ and M$_{45}$/ diets did not show significant (P>0.05) difference in growth and feed efficiency; however, the group fed on M$_{60}$/ showed significantly slower growth and lower feed efficiency than the others. Body composition showed no significant difference among the four dietary groups. WFM protein can be replaced by BAIFA-M up to 45 % in the diet of the rockfish.

• Journal of Power Electronics
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• v.19 no.1
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• pp.211-219
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• 2019

In magnetically coupled resonant (MCR) wireless power transfer (WPT) systems, the introduction of additional intermediate coils is an effective means of improving transmission characteristics, including output power and transmission efficiency, when the transmission distance is increased. However, the position of intermediate coils in practice influences system performance significantly. In this research, a three-coil MCR WPT system is adopted as an exemplification for determining how the spatial position of coils affects transmission characteristics. With use of the fundamental harmonic analysis method, an equivalent circuit model of the system is built to reveal the relationship between the output power, the transmission efficiency, and the spatial scales, including the axial, lateral, and angular misalignments of the intermediate and receiving coils. Three cases of transmission characteristics versus different spatial scales are evaluated. Results indicate that the system can achieve relatively stable transmission characteristics with deliberate adjustments in the position of the intermediate and receiving coils. A prototype of the three-coil MCR WPT system is built and analyzed, and the experimental results are consistent with those of the theoretical analysis.

• Current Photovoltaic Research
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• v.10 no.4
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• pp.111-115
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• 2022

For the high efficiency of the photovoltaic module, a high-output solar cell, which is the basis of photovoltaic power generation, is required. As the light receiving area of the solar cell increases, the light receiving area of the photovoltaic module also increases. Accordingly, recent trend is to use large-area solar cells such as M6 and M8 instead of M2-based solar cells for manufacturing the photovoltaic module and a study on the mechanical stiffness of the module with increased size is required. In this study, a mechanical load test corresponding to IEC-61215 was performed among the reliability tests of large-area photovoltaic modules. In order to confirm the degree to which the mechanical load test affects the photovoltaic module, the output and EL images were checked by sequentially increasing the pressure by 600 Pa at a pressure of 2400 Pa. Also, factors such as output and efficiency of large-area photovoltaic modules were verified through mechanical load testing of actual large-area photovoltaic modules and the rate of change was very small at 1%.