• 자원ㆍ환경경제연구
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• 제30권3호
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• pp.471-501
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• 2021

본 연구는 투입물 거리함수에 의한 메타확률 프런티어 방법을 사용하여 1998년부터 2018년까지 4개 소득그룹의 이산화탄소 기준의 환경효율성(EE)을 측정하였다. 에너지 소비가 이산화탄소 배출을 증가시키고, 노동과 자본투입을 증가하면 이산화탄소 배출을 감소시킬 것임을 보여주고 있다. 또한 그룹환경효율성(GEE: Group Environmental Efficiency), 메타환경효율성(MEE: Meta Environmental Efficiency) 및 환경격차(EGR: Environmental Gap Ratio)를 비교하였다. 결과는 GEE가 과대평가되고 MEE는 이 기간 동안 하향세를 보여주고 있다. 중하위 소득그룹의 EGR은 가장 높았다. 그리고 고소득 및 중상위 소득그룹의 MEE 및 EGR이 상대적으로 낮았다. 환경효율성을 높이려면 화석에너지를 저감하고 기준 환경 문제를 해결하는 방법이 보다 과학적이고 기술적인 방법을 찾아 필요가 있음을 시사한다.

• Journal of Radiation Protection and Research
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• 제41권2호
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• pp.179-183
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• 2016

Background: As an important detecting device, TLD is a widely used in the radiation monitoring. It is essential for us to study the property of detecting element. The aim of this study is to calculate the thermo-luminescence efficiency of TL elements. Materials and Methods: A batch of thermo-luminescence elements were irradiated by the filtered X-ray beams of average energies in the range 40-200 kVp, 662 keV $^{137}Cs$ gamma rays and then the amounts of lights were measured by the TL reader. The deposition energies in elements were calculated by theory formula and Monte Carlo simulation. The unit absorbed dose in elements by photons with different energies corresponding to the amounts of lights was calculated, which is called the thermo luminescent efficiency (${\eta}^{(E)}$). Because of the amounts of lights can be calculated by the absorbed dose in elements multiply ${\eta}^{(E)}$, the ${\eta}^{(E)}$ can be calculated by the experimental data (the amounts of lights) divided by absorbed dose. Results and Discussion: The deviation of simulation results compared with theoretical calculation results were less than 5%, so the absorbed dose in elements was calculated by simulation results in here. The change range of ${\eta}^{(E)}$ value, relative to 662 keV $^{137}Cs$ gamma rays, is about 30% in the energy range of 33 keV to 662 keV, is in accordance by the comparison with relevant foreign literatures. Conclusion: The ${\eta}^{(E)}$ values can be used for updating the amounts of lights that are got by the direct ratio assumed relations with deposition energy in TL elements, which can largely reduce the error of calculation results of the amounts of lights. These data can be used for the design of individual dosimeter which used TLD-2000 thermo-luminescence elements, also have a certain reference value for manufacturer to improve the energy-response performance of TL elements by formulation adjustment.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 추계학술대회 논문집 전력기술부문
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• pp.192-194
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• 2006

In this paper, the situation of energy efficiency standards for motors and diffusion states are analyzed and a new methodology is proposed using diffusion models and learning curves. The existing diffusion models could not explain affects from new appliances' penetration during the diffusion. But a mixed diffusion model with learning curves or learning ratio is studied to explain this penetration.

• 신재생에너지
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• 제4권4호
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• pp.17-22
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• 2008

A low concentrating (< 5X) photovoltaic module with aluminum reflectors is fabricated and evaluated which is designed to reduce the affection of the high temperature to the solar cell modules preventing the efficiency lowering. As results, the output power is increased of 1.97X from the concentrating photovoltaic module which is designed with the concentrating ratio of 2.25X and to control the module temperature cooling the module by air circulation. Also, the effect of the concentrating module with aluminum reflectors on the conventional PV module is investigated at the field. The result shows the increase of the output power more than about 20% and the improvement of the module efficiency of 1.4X in spite of the increase of average module temperature.

• 설비공학논문집
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• 제12권7호
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• pp.649-658
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• 2000

Thermodynamic modeling of low-pressure scroll compressor was developed by combining continuity and energy conservation equation. Suction gas heating was considered using energy balance inside the low pressure shell. Pressure, temperature and mass of refrigerant-22 as a function of orbiting angle were calculated by solving the governing equations using fourth order Rung-Kutta scheme. Motor efficiency was taken by experiments with a variation of frequency. The developed model was applied to the analysis of an inverter driven scroll compressor with a variation of frequency, pressure ratio and operating conditions. The model was verified with the experimental results at the same operating conditions. The developed model was adequate to predict performance of the inverter driven scroll compressor as a function of operating conditions. Calculated parameters from the model were discharge temperature, mass flow rate, power input, COP, and thermodynamic properties with respect to orbiting angle. To enhance the performance of a scroll compressor, it is essential to diminish leakage at low frequency level and improve the mechanical efficiency at high frequency level.

• 한국수소및신에너지학회논문집
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• 제22권4호
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• pp.481-487
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• 2011

A fuel cell vehicle using a polymer electrolyte membrane fuel cell (PEM FC) as power source produces electric power by consuming the fuel, hydrogen. The unconsumed hydrogen is recirculated and reused to gain higer stack efficiency and to maintain the humidity in the anode side of the stack. So it is needed considering fuel efficiency to recirculated hydrogen. In this study, the indirect hydrogen recirculation flow rate measurement method for fuel cell vehicle is presented. By modeling of a convergent nozzle ejector and a hydrogen recirculation blower for the hydrogen recirculation of a PEM FC, the hydrogen recirculation flow rate was calculated by means of the mass balance and heat balance at Anode In/Outlet.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2012년도 제44회 KOSCO SYMPOSIUM 초록집
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• pp.189-192
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• 2012

The flameless combustion has been considered as one of the promising combustion technology for high energy efficiency and reducing NOx and CO emissions. To investigate the effects of fluid conditions on the formation of flameless combustion, a numerical approach was performed. The flameless combustion possesses lower temperature region and more uniform temperature distribution than conventional flame. The results show that the flow rate of the system which mainly influence on recirculation ratio is the most important parameter for flameless combustion.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
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• pp.61-61
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• 2011

Polymer solar cells have become one of the rising next generation solar cells due to their potential for lightweight and bendable plastic solar modules. Recently, the power conversion efficiency of polymer solar cells has reached ~8 %, which can make ~6 % plastic solar modules when it comes to the modular aperture ratio of ~80 %. Although this efficiency is far behind that of conventional inorganic solar cells, the plastic solar modules are expected to create new energy market into which the inorganic solar modules could not make inroads. In the near future, the plastic solar modules can be integrated with consumer electronics that should overcome the regulation of energy consumption. For this application, the polymer solar cells should be fabricated in a variety of module shapes, which can be resolved by employing conventional and/or advanced coating and molding technologies of plastics products. In this tutorial, the fundamental aspect of polymer solar cells will be briefly introduced and then recent trends in terms of materials and devices will be reviewed together with showing recent results in organic nanoelectronics laboratory.

• 태양에너지
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• 제11권2호
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• pp.34-40
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• 1991

Thermal stratification enhancement for the higher extraction efficiency of hot water storage tank was experimentally studied with transparent fiber glass cylindical tank($350{\ell}$, D=516mm, H=1680mm). Height to diameter ratio (H/D =1,2,3), flow rate(Q= 8,10,12LPM), inlet-outlet temperature differences(${\Delta}T=20,25,30^{\circ}C$), and geometry of inlet-outlet port were the parameters. In particular, three kind of distributors were used for geometry of inlet-outlet port. As a result, it was possible to get extraction efficiency of 95% by using the distributor having variable diameter but keeping a constant diameter of perforation. So it is recommendable to design the distributor so that the main pipe decrease in diameter toward the dead end.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권4호
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• pp.161-169
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• 2003

The applications of SRM(Switched Reluctance motor) are dramatically increasing due to a simple mechanical structure, a high efficiency and a high speed drive characteristics. Energy recovery in the regenerative region is very important when SRM is used in traction drive. This is to reduce energy loss during mechanical braking and/or to have a high efficiency drive. To control excitation voltage during motoring and regenerating voltage in the generator operation in the SRM, multi-level voltage control is effective. This paper suggests multi-level inverter which is useful for motoring and regenerative operation. The proposed method is verified through simulations and experiments.