• 한국정보통신학회논문지
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• 제24권5호
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• pp.662-665
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• 2020

Energy Efficiency in any WSN (Wireless Sensor Network) is a critical issue to elongate the life of the batteries equipped in sensors. LEACH(Low Energy Adaptive Clustering Hierarchy) is one of the mostly used routing algorithms which reduce the amount of transmitted data and save the energy in the network. In this paper, a new technique to select channels in routing algorithms is suggested and compared with the LEACH, ALEACH and PEGASIS. This technique forms clusters depending upon the node density as the deployement of the nodes is random. As a result, the proposed algorithm presents the better performance of the energy efficiency than those of the current algorithms.

• 한국멀티미디어학회논문지
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• 제24권8호
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• pp.1068-1075
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• 2021

Wireless sensor network (WSN) can be usefully used in battlefields requiring rapid installation and operation by enabling surveillance and reconnaissance using small sensors in areas where any existing network infrastructure is not formed. As WSN uses battery, energy efficiency acts as a very important issue in network survivability. Layer-based routing protocols have been studied a lot in the aspect of energy efficiency. Many research selected LEACH and PEGASIS protocols as their comparison targets. This study examines the two protocols and LECEEP, a protocol designed by combining their advantages, and proposes a new protocol, A-LECEEP, which is more energy efficient than the others. The proposed protocol can increase energy efficiency compared to the existing ones by eliminating unnecessary transmissions with multiple chains configuration.

• 지역연구
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• 제33권1호
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• pp.3-16
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• 2017

본 논문은 에너지 효율성 지표로써 투입물로 에너지뿐만 아니라 노동과 자본 등을 동시에 고려한 총요소 에너지 효율성을 DEA에 기초하여 2005-2013년 기간 동안 우리나라 16개 시 도의 제조업 부문에 대하여 추정하였다. 추정결과에 의하면, 단일요소 에너지 효율성과 총요소 에너지 효율성 간에 차이가 존재하여 두 지표를서로 보완적으로 사용할 필요성이 있는 것으로 나타났다. 한편, 총요소 에너지 효율성 지표는 대부분의 시 도들에서 높게 나타났는데 서울, 광주, 울산, 경북 등은 프런티어에 위치하지만, 강원, 부산, 대구, 인천 등은 상대적으로 매우 비효율적인 것으로 나타났다. 또한 패널 토빗 모형을 통해 총요소 에너지 효율성의 결정 요인을 추정한 결과에 의하면, 대기업의 생산액 비중이 클수록, 에너지 다소비업종의 생산액 비중이 작을수록, 그리고 전력 사용 비중이 클수록, 총요소 에너지 효율성에 긍정적인 영향을 주는 것으로 추정되었다.

• 한국수소및신에너지학회논문집
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• 제30권4호
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• pp.303-311
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• 2019

Reversible solid oxide fuel cell (RSOFC) has become a prospective device for energy storage and hydrogen production. Many studies have been conducted around the world focusing on system efficiency improvement and realization. The system should have not only high efficiency but also a certain level of simplicity for stable operation. External waste steam utilization was proved to remarkably increase the efficiency at solid oxide electrolysis system. In this study, RSOFC system coupled with waste steam was proposed and optimized in term of simplicity and efficiency. Ejector for fuel recirculation is selected due to its simple design and high stability. Three system configurations using ejector for fuel recirculation were investigated for performance of design condition. In parametric study, the system efficiencies at different current density were analyzed. The system configurations were simulated using validated lumped model in EBSILON(R) program. The system components, balance of plants, were designed to work in both electrolysis and fuel cell modes, and their off-design characteristics were taken into account. The base case calculation shows that, the system with suction pump results in slightly lower efficiency but stack can be operated more stable with same inlet pressure of fuel and air electrode.

• Journal of Electrochemical Science and Technology
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• 제10권2호
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• pp.115-122
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• 2019

In order to improve the current efficiency and reduce the energy consumption in the electrosynthesis of ammonium persulfate, electrolytic properties of a perfluorosulfonic cation exchange membrane named PGN membrane and the $Al_2O_3$ ceramic membrane in the electrosynthesis of ammonium persulfate were studied and compared in a pilot electrolytic cell using a welded platinum titanium as the anode and a Pb-Sb alloy as the cathode. The effect of cell voltage, electrolyte flow rate and electrolysis time of the electrolytes on the current efficiency and the energy consumption were studied. The results indicated that the PGN membrane could improve current efficiency to 95.12% and reduce energy consumption to $1110kWh\;t^{-1}$ (energy consumption per ton of the ammonium persulfate generated) under the optimal operating conditions and the highest current efficiency of the $Al_2O_3$ ceramic membrane was 72.61% with its lowest energy consumption of $1779kWh\;t^{-1}$. Among 5 times of the electrolysis of the electrolytes, the lowest current efficiency of the PGN membrane was 85.25% with the highest energy consumption of $1244kWh\;t^{-1}$ while the lowest current efficiency of the $Al_2O_3$ ceramic membrane was 67.44% with the highest energy consumption of $1915kWh\;t^{-1}$, which suggested the PGN membrane could be used in the 5-stage electrolytic cell for the industrially continuous electrosynthesis of ammonium persulfate. Therefore the PGN membrane can be efficient to improve the current efficiency and reduce the energy consumption and can be applied in the industrial electrosynthesis of ammonium persulfate.

• 한국태양에너지학회 논문집
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• 제34권6호
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• pp.1-10
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• 2014

The efficiency of the maximum power point tracking(MPPT) of inverter which is used in grid-connected photovoltaic systems is changed according to dynamic environment conditions. Hence, this paper evaluates the performance of the proposed method and other MPPT algorithm on the basis of European Efficiency Test(EN50530). The modeling of MPPT algorithm is made by the Matlab & Simulink. In the result of simulation, the more control period is shorter, the more MPPT efficiency is higher. Also, the Proposed MPPT algorithm has higher performance than other MPPT algorithm with no regard to control period.

• 한국산림과학회지
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• 제95권5호
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• pp.562-568
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• 2006

This study was conducted to examine the energy content and photosynthetic efficiency of Quercus mongolica stands in Korea. Study sites were located in Mt. Joongwang, Gangwon-do (1,000 m and 800 m above sea level), Mt. Baekwoon, Jeollanam-do (800 m a.s.l.), Mt. Halla, Jeju-do (1,000 m a.s.l.), Mt. Taehwa, Gyeonggi-do (350 m a.s.l.), and Mt. Wolak, Chungcheongbuk-do (300 m a.s.l.). Total energy content and annual energy accumulation in Q. mongolica stands were 2,916-6,435 GJ/ha and 284-441 GJ/ha, respectively. Lower latitude (N.L.) stands of Q. mongolica showed higher energy contents than higher latitude stands, but Quercus stands in Mt. Baekwoon had higher annual energy accumulation than those in Mt. Halla located at a lower latitude. During the growing season, the photosynthetic efficiency of 60 to 70-year-old Q. mongolica stands ranged from 1.19 to 1.34% while that of 35-year-old stands did from 1.87 to 1.95%. There were no significant differences in photosynthetic efficiency among the latitudes because solar radiation was higher in low latitudes.

• 한국수소및신에너지학회논문집
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• 제34권5호
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• pp.389-397
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• 2023

This study compares domestic and foreign research on renewable energy-based water electrolysis clean hydrogen. Domestic studies from 2010 to 2023 focused on technological efficiency, energy efficiency, and system efficiency, with few analyzing infrastructure and technology trends. Overseas research initially focused on technological efficiency and stability, but has since shifted to economic and environmental impact, policy effectiveness, industry-university-research cooperation, and sustainability. To improve water electrolysis technology production, this study suggests prioritizing technology stability over efficiency, resolving government regulations and resident acceptance issues, promoting industry-university-institute cooperation for rapid commercialization of research results, and developing a strategy for sustainable development of renewable energy-based water electrolysis technology.

• 한국태양에너지학회 논문집
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• 제26권4호
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• pp.39-45
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• 2006

The decrease in the summer peak electric load in our country is very important. The government has arranged and implemented a lot of support policies and statutes to decrease the peak electric load. And the ice thermal energy storage system is known as one of the alternatives. The purpose of this paper is to evaluate the efficiency and thermal characteristics of the closed ice thermal energy storage system using screw capsules. The measured thermal energy storage density is about 18.4 USRT-h/m3 (=232.9 MJ/m3), which is higher than 13.0 USRT-h/m3 (=164.6 MJ/m3), a low criterion of normal performance. And The efficiency of the discharging process and the total energy utilization is 96.2% and 2028.4 kcal/kWh respectively.

• 한국수소및신에너지학회논문집
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• 제26권4호
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• pp.331-338
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• 2015

Solar air heaters (SAHs) are simple in design and widely used for solar energy collection devices, and a packed bed is one of typical solar energy storage systems of thermal energy captured by SAHs. This paper presents mathematical modeling and simulation on the thermal performance of various packed bed energy storage systems. A MATLAB program is used to estimate the thermal efficiency of packed bed SAH. Among the various packed bed energy storage systems considered, the wire mesh screen packed bed SAH shows the best thermal efficiency over the entire range of design conditions. The maximum of thermal efficiency of packed bed SAH with wire mesh screen matrices has been found to be 0.794 for Re=2000 - 20000 and ${\Delta}T/I=0.002-0.02$.