• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.30 no.3
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• pp.202-208
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• 2019

In this study, an active element pattern (AEP) of a printed dipole was analyzed in 1D and 2D arrays. First, an AEP of the printed dipole was obtained using the simulation in the 2D infinite array. The scan blindness in the 2D array occurred in the E-plane direction at around ${\pm}36^{\circ}$; however, it was barely observed in the 1D array. To analyze the cause of the scan blindness in the 2D array, the dispersion properties of a unit cell was obtained and compared with the scan blindness by frequency change. The difference between the scan blindness of the 1D and 2D arrays was clarified using the comparison of the Q value in the unit cell in the 1D and 2D arrays. Then, the coupling of the electric field in the E-plane direction was observed when nine elements were separated between the two ports in a linearly arranged dipole structure. Finally, the printed dipole array was fabricated, and an AEP was measured for the $11{\times}1$ and $11{\times}3$ sub arrays. The proposed theory was verified using these observations and by comparison with the simulation results.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.50 no.9
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• pp.599-608
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• 2022

Urban air mobility (UAM) equipped with rotor system is subject to ground effect at vertiport during takeoff and landing. The aerodynamic performance of the aircraft in ground effect should be analyzed for the safe operation. In this study, The ground effects on the aerodynamic performance and wake structure of the quadcopter electric vertical takeoff and landing (eVTOL) configuration equipped with coaxial counter-rotating propellers were investigated by using the lattice Boltzmann method (LBM). The influence of the ground effect was observed differently in the upper and lower propellers of the coaxial counter-rotating propeller system. There was no significant change in the aerodynamic performance of the upper propeller even if the propeller height above the ground was changed, whereas the averaged thrust and torque of the lower propeller increased significantly as propeller height decreased. In addition, the amplitude of the thrust fluctuation tended to increase as the propeller height decreased. The propeller wake was not sufficiently propagated downstream and was diffused along the ground due to the outwash flow developed by the ground effect. The impingement of the rotor wakes on the ground and a fountain vortex structure were observed.

• Journal of Satellite, Information and Communications
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• v.1 no.2
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• pp.63-70
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• 2006

This paper presents the results of Ka band qualification model multiplexers for COMS Payload to be launched in 2008. These are the input and output multiplexers of the satellite transponder to use available frequency resources effectively and the diplexer of the satellite antenna to use the same reflector for both transmitting and receiving frequency bands, respectively. The input multiplexer with four frequency channels has four(4) independent channel filters which consist of an 8-pole elliptic band-pass filter for high frequency selectivity and a 2-pole equalizer for group delay equalization. For low insertion loss, mass and volume reduction, manifold type os employed for output multiplexer. E-plane T-junction is used for either splitting or combining a frequency band into two sub-bands. Asymmetric inductive irises are used to tune the receiving filter easily. The electrical performance and environmental test such as vibration test, mechanical shock test, thermal vacuum test and EMC test are performed and the results of all qualification model multiplexers are compliant to the requirement of each multiplexer. Followed by this qualification, the flight model equipment will be developed.

• Journal of Advanced Navigation Technology
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• v.19 no.3
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• pp.224-229
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• 2015

In this paper, we derived the design equation and implemented the unequal Gysel power divider that is one external resistors using the ABCD parameters analysis. Conventional unequal Gysel divider is difficult to obtain the characteristics of isolation and return loss at between output ports because it can't select a theoretical value of external resistor. To solve those problems, we design the new unequal Gysel power divider with transmission lines and one external resistor that has the characteristics of conventional unequal Gysel divider. To validate this design method, we simulated and measured an 4: 1 unequal Gysel power divider at the center frequency 1 GHz. The measured performances agreed well with the simulation results.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2018.10a
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• pp.57-57
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• 2018

관상용, 식용 및 약용으로도 이용되는 석죽목 석죽과의 여러해살이풀인 오랑캐장구채는 국내에서는 중부 이북지방의 유용 자생식물로 조경산업에의 이용가치가 크나, 이용성 증대 등을 위한 재배기술은 미흡하다. 지피식물용 재배조건의 구축을 위하여 2017년 7월 31일부터 10월 9일까지 약 10주간 본 연구를 수행하였다. 실험재료로 종자에서 육묘한 유묘를 사용하였으며, 유묘의 소질, 이식조건 및 재배관리에 대한 생육의 영향을 조사하였다. 유묘의 소질로는 162구 트레이에서 cell당 4립씩 파종하여 육묘된 유묘가 초장 및 건물중이 높았고, 특히 4립 파종구는 마디수를 제외한 생육량이 다른 처리구에 비해 유의적으로 큰 차이가 있었다. 경제성을 고려할 때, 상토는 혼합비료(N-P-K) $300-200-200mg{\cdot}L^{-1}$가 첨가된 마사토:피트모스(3:1) 혼용토를 충진한 처리구가 효과적이었다. 또한, 코트비료의 기비처리는 포트당 20알 처리구에서 지하부 생체중이 무거웠으나, 엽면적 등 다른 생육량을 고려할 때 기비하지 않은 처리가 효과적이다. 재배관리에 있어서 차광처리는 습기 등의 환경에 약한 유묘의 특성상 차광하지 않고 배치하는 것이 모든 생육량이 높았다. 이식 후에는 추비처리를 하는 것이 효과적이며, 추비농도는 엽수 등을 고려할 때 $500mg{\cdot}L^{-1}$ hyponex이 적합하였다.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2012.10a
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• pp.941-944
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• 2012

Microprocessor is widely used in various industries. So it is very important to learn about it. But it is very difficult because students must know about both hardware and software of it. Student usually learn about it with a complete educational product in many technical high school. It make them to have no chance to mixed various electronic parts such as sensors, motors and so on. It cause them to low the creative product making ability. So we adjust new course with the arduino instead of the complete educational product to microprocessor education. It help student to high the electronic part mixing ability and the creative electronic product making ability.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.152.2-152.2
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• 2011

본 연구는 2012년 시행할 예정인 신재생에너지 공급의무화제도(RPS) 하에서 신재생에너지 전력에 대한 추가비용 발생 시 국민들이 RPS 제도의 목표 및 형태에 대하여 어떤 선호를 가지고 있으며, RPS 제도에 대한 소비자들의 만족도를 높이기 위한 개선점이 있는지 알아보고자 수행되었다. 이에 소비자 선호를 조사하는 대표적인 연구방법론인 조건부가치평가법(CVM)을 활용하여, RPS 제도 하에서 발생 가능한 소비자 선호, 구성요소 합산효과 및 지역별 선호의 차이의 3개 주제에 대한 연구를 3차례 설문을 통해 수행하였다. 해당 연구의 주요 내용을 요약하면 다음과 같다. 첫째, 우리나라 국민들의 신재생에너지 전력에 대한 WTP는 가구당 1,456~1,560원/월 수준으로 이는 우리나라 가구당 월 평균 전기요금의 약 3.7~3.5% 수준에 해당한다. 이를 토대로 추산한 신재생에너지 전력 이용에 대한 국민들의 편익은 2011년 신재생에너지 보급 관련 예산의 42.4% 정도인 것으로 나타났다. 둘째, 국민들은 에너지원의 선택에 대한 비용 차이가 있을 시에는 개별 신재생에너지원을 대체재(substitutes)로 인식하였다. 그러나 에너지원의 선택에 대한 비용 차이가 없는 경우에는 특정 신재생에너지원에 대한 선호를 보이며, 특히 태양광에 대한 선호도가 가장 높게 도출되었다. 셋째, 소비자들의 선호도에 따른 재생에너지 포트폴리오를 적용한 결과, 우리나라 국민들은 연 2,618~2,806 GWh 규모의 신재생에너지 전력을 생산하는데 소요되는 추가비용을 지불할 의사가 있는 것으로 분석되었다. 이는 2010년도 우리나라 전체 전력 수요의 0.62~0.66% 정도로 RPS에서 목표로 하는 의무비율을 이행하기에는 부족한 것으로 보인다. 넷째, 신재생에너지 전력에 대한 선호는 지역별로 다르게 나타났다. 이는 지역 간 저항응답의 비율, 재생에너지 시설 인근 경험 및 재생에너지 시설 입지에 대한 찬반의사 등의 지역별 차이에서 기인하는 것으로 분석되었다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.23 no.7
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• pp.768-773
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• 2012

A branch-line hybrid using microstrip artificial transmission lines(ATLs) with slotted-triangular patches is proposed. The proposed artificial transmission line is compact in structure as well as easy to adjust the characteristic impedance and electrical length of equivalent transmission line by changing the slot's parameters; hence, it is useful for miniaturizing conventional transmission lines. The designed branch-line hybrid, because of the use of the right angled isosceles triangular shaped artificial transmission lines as building blocks, has no useless empty space, and hence optimally miniaturized. A fabricated 3 dB branch-line hybrid shows the coupling variation of ${\pm}0.5$ dB and the phase difference between two output ports of $91^{\circ}{\pm}4^{\circ}$ within 15 % bandwidth at 2.45 GHz center frequency. The size of proposed branch-line hybrid is only 38% of the conventional branch-line hybrid.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.21 no.5
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• pp.19-26
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• 2021

This report proposes a waveguide spatial combiner with high power low loss. The proposed spatial combiner implements high power by combining from the center of each port through a waveguide. In particular, we implement low loss using TE01 mode, which has the lowest transmission track loss among modes of circular waveguide, and miniaturization is achieved by applying a new mode conversion method. IIn addition, it was confirmed that it was suitable for high output by calculating the insulation breakdown voltage of the new mode conversion structure through E-field analysis. The final 8-way waveguide spatial combiner was designed and manufactured, and the insertion loss was less than 0.4dB and the combining efficiency was 97% or more, confirming that the electrical performance was very good compared to the planar combining method.

• International Area Studies Review
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• v.20 no.4
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• pp.37-56
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• 2016

The purpose of this research is to present the implication for Korean firms' entry into the power market in Myanmar. This study investigated the characteristics of the Myanmar power market and analyzed SWOT, focusing on energy policy, power supply and demand, energy relations with neighboring countries and climate change issue. Opportunity factors are changes in energy strategies, the launch of an energy integration organization, changes in the power energy portfolio, rapid economic and power demand growth, and a clean development mechanism. The threats are high nonfulfillment of a contract, high power loss rates and low electricity distribution rates, increased energy exports to neighboring countries, and vulnerability to climate change. We suggest the use of CHP (Combined Heat and Power), Clean Development Mechanism (CDM), and Multilateral Development Bank (MDB).