• The Journal of Korean Institute of Communications and Information Sciences
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• v.38A no.7
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• pp.571-579
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• 2013

This paper proposes an energy-efficient mode selection and power allocation scheme in device-to-device (D2D) communication system as an underlay coexistence with cellular networks. We analyze the energy efficiency which is defined as the summation of the energy efficiencies for all devices. The proposed scheme consists of two steps. First, we calculate the transmission power maximizing the energy efficiency for all possible modes of each device. Although the proposed power cannot maximize the system capacity, we prove that the proposed transmission power is the optimal power which maximizes the energy efficiency. In the second step, we select a mode which has the maximal energy efficiency among all possible mode combinations of the devices. Then we can jointly obtain the transmission power and the mode which can maximize the energy efficiency. The proposed scheme has the optimal performance with respect to the energy efficiency and outperforms the conventional schemes.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.42 no.3
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• pp.639-648
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• 2017

Electronic warfare systems for extracting information of the threat signals can be employed under the circumstance where the power of the received signal is weak. To precisely and rapidly detect the threat signals, it is required to use methods exploiting whole energy of the received signals instead of conventional methods using a single received signal input. To utilize the whole energy, numerous sizes of windows need to be implemented in a detector for dealing with all possible unknown length of the received signal because it is assumed that there is no preliminary information of the uncooperative signals. However, this grid search method requires too large computational complexity to be practically implemented. In order to resolve this complexity problem, an approach that reduces the number of windows by selecting the smaller number of representative windows can be considered. However, each representative window in this approach needs to cover a certain amount of interval divided from the considering range. Consequently, the discordance between the length of the received signal and the window sizes results in degradation of the detection performance. Therefore, we propose the weighted energy detector which results in improved detection performance comparing with the conventional energy detector under circumstance where the window size is smaller than the length of the received signal. In addition, it is shown that the proposed method exhibits the same performance under other circumstances.

• Journal of Energy Engineering
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• v.27 no.3
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• pp.28-35
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• 2018

Guidelines and institutional support for buildings are being promoted around the world as measures for environmental pollution and energy conservation. In Korea, standards are prepared according to the energy saving design standards of new buildings as amended in 2013.09.01 and the zero energy building for new buildings mandatory process is being prepared from the recommendations. Nevertheless, the government's binding power on smaller buildings is insufficient. Energy savings were analyzed for the recently constructed office buildings (application of external insulation technique) and propose a dual envelope techniques were proposed for energy reduction.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.2
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• pp.3-8
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• 2017

This paper considers an application of distributed antenna system (DAS) to a system of intra-vehicle wireless energy transfer (WET). The intra-vehicle WET system has features such as limited mobility of energy receiver, static channel environment and short distance between transmitter and human body. Under these conditions, location of transmitter highly affects the amount of energy received by human body and the energy received by energy receiving devices. We compare centralized antenna system (CAS) and the DAS in intra-vehicle WET system by simulation. The results show the DAS has superior performance to the CAS.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.127.2-127.2
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• 2010

우리나라는 기후변화 대응을 준비하기위해 2008년도에 수립한'국가에너지기본계획(2008-2030)'에 따라 2030년까지 신재생에너지 비중을 2.4%에서 11%까지 달성을 목표로 정하고 신재생에너지 분야를 성장시키기 위해 국가기술개발 및 산업화 전략을 수립해 추진하고 있다. 이에 발맞추어 건물용 연료전지시스템의 경우, 2006년도부터 1kW급 가정용 연료전지시스템 모니터링 사업의 일환으로 3년간 210대가 도시가스사 및 지자체 등을 중심으로 설치되어 운전되어지고 있다. 특히, 2010년부터 시범보급사업이 추진되어 올해 200대를 시작으로 2011년에 300대, 2012년에 500대가 일반가정에 보급되어질 예정이다. 하지만 현재 6천만원인 연료전지시스템 가격을 실제 보급가능한 가격인 5백만원 이하로 저감시키는 것이 현 시점에서 가장 시급한 문제로 대두되어지고 있는 실정이다. 본 연구에서는 그린홈 보급확대를 위한 건물용 연료전지의 보조기기인 블로워의 가격저감을 위한 연구의 일환으로 블로워의 안전성능 평가방법을 개발하여 보조기기의 가격저감 및 안전성을 확보하고자 한다. 1kW급 건물용 연료전지시스템의 여러 블로워 중 도시가스용 연료승압 블로워, 선택산화 공기 블로워, 버너 공기 블로워 및 캐소드 공기 블로워의 안전성능 평가방법을 제시함으로서, 국내 블로워 제조사의 설계방향을 제시하고 연료전지시스템의 안전성을 확인하고자 한다. 특히, 내구성, 기밀, 가혹조건시험 및 소음, 진동, 습도, 온도와 같은 내주위환경시험 등의 평가결과를 제조사에 feedback하여 안전성능 개선에 이바지하고자 한다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.9
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• pp.743-749
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• 2015

The purpose of this study is to predict the performance of an indirect evaporative cooling system, and to evaluate its energy saving effect when applied to the exhaust heat recovery system of an air-handling unit. We derive the performance correlation of the indirect evaporative cooling system using a plastic heat exchanger based on experimental data obtained in various conditions. We predict the variations in the performance of the system for various return and outdoor air conditioning systems using the obtained correlation. We also analyze the energy saving of the system realized by the exhaust heat recovery using the typical meteorological data for several cities in Korea. The average utilization rate of the sensible cooling system for the exhaust heat recovery is 44.3% during summer, while that of the evaporative cooling system is 96.7%. The energy saving of the evaporative cooling system is much higher compared to the sensible cooling system, and was about 3.89 times the value obtained in Seoul.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.47-56
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• 2001

In order to assure the safety of NPP structures, margin of safety or conservatism is incorporated in each design step. Seismic risk evaluation of NPP structures is performed based on the realistic capacity and response of structure eliminated the safety margin and conservatism. In this study, the comparative study on the various evaluation methods of the inelastic energy absorption capacity was performed. The inelastic energy absorption capacity due to the nonlinear behavior of structures has significant effect on the results of seismic probabilistic risk assessment. And the comparison study of the HCLPF(high confidence of low probability of failure) values according to the inelastic energy absorption factors was performed. As a conclusion, the inelastic energy absorption factor of NPP containment structure is estimated about 1.5~1.75. It is essential to estimate the nonlinear behavior of structure and its ductility factor correctly for the seismic risk assessment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.6
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• pp.744-750
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• 2020

In this paper, we propose a deep learning based transmit power control (TPC) scheme to improve the spectral and energy efficiency of wireless communication systems. In the wireless communication system, the positions of multiple transceivers follow a uniform distribution, and the performances of spectral and energy efficiency for the proposed TPC scheme are analyzed assuming the Nakagami fading channels. The proposed TPC scheme uses batch normalization to improve spectral and energy efficiency in deep learning based training. Through simulation, we compare the results of the spectral and energy efficiency of the proposed TPC scheme and the conventional one for various area sizes that limit the position range of the transceivers and Nakagami fading factors. Comparing the performance results, we verify that the proposed scheme provides better performance than the conventional one.

• Transactions of the Korean hydrogen and new energy society
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• v.25 no.3
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• pp.311-318
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• 2014

Performance degradation of a battery in 20 kWh energy storage system (ESS) under various operating conditions was studied. And energy saving of the ESS was also monitored by connecting with 20 kW photovoltaic (PV). PV-connected ESS saved 5~7% of energy consumption in 2013 compared to that without such system in 2012. As charge-discharge cycle increased, capacity decreased and the performance degradation was glaringly obvious after 40 cycles. And as charge and discharge rate increased, the performance degradation was more serious. After 50 charge-discharge cycles, a lot of degraded product was deposited on the surface of anode and cathode electrodes, and the cathode side was more contaminated. Therefore, in order to maintain the cell performance, it was more important to protect the degradation of the cathode side.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.208.1-208.1
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• 2011

우리나라 전국의 사찰수는 약 22,000개로 추정되며, e-나라지표에 의하면 사찰 역사가 오래되거나 전통 양식의 건축물과 문화재 등을 간직한 사찰로 문화체육관광부가 지정하는 전통사찰은 2010년 3월말 현재 전체의 4.2%인 935개로 알려져 있다. 대도시에 위치한 사찰을 제외하면 일반적으로 사찰은 계곡에 위치하여 인근에 하천이 있으며, 유역이 작아 유량은 적으나 경사가 심해 낙차를 크게 얻을 수 있다. 또한 설계제원이 비슷한 전통사찰들을 그룹핑하고 소수력발전시스템을 Kit형태로 표준화하여 개발한다면 초기투자비를 저감할 수 있는 장점도 있다. 따라서 본 연구에서는 전통사찰에 소수력발전의 적용가능성을 타진하기 위하여 유역면적이 $49.71km^2$인 사찰 1지점을 선정하여 인근의 하천을 이용한 소수력발전 성능특성을 분석하였다. 분석결과 단위 유효낙차당 설비용량은 약 9.3kW, 연간전기생산량은 약 28,602kWh로 산정되었으며, 낙차가 커질수록 설비규모와 연간전기생산량은 비례하여 증가될 것으로 추정된다. 부존자원이 부족하여 에너지해외의존도가 97%가 넘는 현실을 감안할때 전통사찰에 대한 타당성 조사를 통해 소수력발전을 적용함으로서 사찰에서 사용되는 전기에너지의 절약과 친환경 재생에너지의 활용을 확대해 나가는 것이 바람직 할 것으로 사료된다.