• 한국태양에너지학회:학술대회논문집
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• 2012.03a
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• pp.370-375
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• 2012

국가개발연구원(KDI)에서는 새만금에 40MW 용량의 국산 풍력발전단지 조성을 위한 예비타당성 조사를 실시하였다. 본 사업에 대한 KDI의 비용편익 분석 결과 순 현재가치가 0보다 작고, B/C 비율은 0.73으로 경제적 타당성이 나타나지 않았다. 하지만 모든 비용과 편익을 화폐가치로 환산해 내는 비용편익분석은 여러 가지 외부효과로 인해 사업의 타당성 연구자들에 의해 주관적인 결과물이 나오기도 한다. 이에 따라 본 논문에서는 새만금 풍력발전 시범단지의 경제성 평가 재검토 연구를 실시하였다. 본 논문에서는 기존 경제성 평가 항목에 대하여 여러 가지 쟁점을 제시하고, 그 중에서 대기오염물질 저감 비용과 학습효과(learning effect)로 인한 비용 절감 편익을 추가적으로 산정하였다. 여기서 학습효과의 학습속도(learning rate) 를 세 가지 시나리오로 나누어 분석하였다. 두 가지의 추가 편익을 KDI의 기존 예비타당성 조사 분석에 추가한 순 현재가치는 상당한 양의 값이 나왔고, B/C 비율은 8.8 로 편익이 비용에 비해 크게 증가했다. 이러한 항목들의 포함 여부에 따라 타당성 결과가 현저하게 달라짐을 알 수 있다. 향 후 비용편익 분석이 정책 결정에 적절히 반영되기 위해서는 외부효과를 고려한 환경 비용, 그리고 학습효과와 같은 추가적인 사항들이 면밀히 검토되어야 한다. 시장에 기반하지 않은 이러한 외부효과로 인한 항목들은 대상과 시기에 따라 매우 다른 결과를 보여주기에 이에 대한 세부적인 연구가 필요한 시점이다.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.21 no.8
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• pp.439-447
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• 2009

Cogeneration system produces power as well as heat recovered from waste heat during power generation process. This system has higher energy efficiency than that of the power plant. In this study the optimal design for the cogeneration system with the increase of the capacity considering life cycle cost(LCC) analysis has been performed in the general facilities such as hotels and hospitals under the assumption of electricity cost of 95 won/kWh, the initial cost of cogeneration system of 1,500,000 won!kW and the value of 0.5${\sim}$1.0 in the ratio of heat to power. The optimal ratio of cogeneration capacity divided by average electricity load of facility was found out more than 0.5 in case of electricity cost with the increase of>30%, and the percentage of $CO_2$ reduction was about 9%. The most important factors in the economic analysis of cogeneration system was found out the electrity cost and the initial cost of cogeneration system. Also the ratio of heat to power at the value of>0.5 was not affected in the economy of cogeneration system, but was very important in the $CO_2$ reduction.

• Nuclear Engineering and Technology
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• v.20 no.1
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• pp.47-53
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• 1988

The objective of this study is to evaluate the reliability of the High Head Safety Injection System (HHIS) of KNU 5, 6, 7 and 8 following the removal of safety injection signal (s-signal) from the mini-flow bypass line valves of charging/safety injection pumps. The unavailability of HHSIS and the rupture probability of a charging/safety injection pump have been computed for two different cases; with s-signal on and removed. The results show that when the s-signal is removed from the mini-flow bypass line valves, the unavailability of HHSIS slightly increases while the rupture probability of a charging/safety injection pump is significantly reduced. Hence, based upon the results of this study we conclude that it is more reasonable to remove the s-signal from the mini-flow bypass line valves of KNU 5, 6, 7 and 8 in the normal plant operation. And to improve the availability of HHSIS, the modification of operational procedures and the emphasis on operator training are recommended.

• Nuclear Engineering and Technology
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• v.9 no.4
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• pp.211-222
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• 1977

The decomposition of all the individual chemicals used in the Harwell inactive vitrification pilot plant has been studied by means of a thermal balance. Weight loss curves to 110$0^{\circ}C$ have been obtained. The four materials (sodium nitrate, cesium nitrate, lithium nitrate and ruthenium nitroso-nitrate solution) showed a greater weight loss than that based on an oxide yield, and hence these compounds of their products of decomposition are volatile below 110$0^{\circ}C$. The remaining materials suffered a weight loss no more than that corresponding to a full yield of the oxide, and hence they were not volatile below 110$0^{\circ}C$. Most of chemicals begin to decompose at less than 75$^{\circ}C$ but the nitrates of cesium, strontium, barium and sodium not until 295$^{\circ}C$ to 59$0^{\circ}C$. The results obtained can be used in the analysis of process conditions in the vitrification and calcination of highly radioactive wastes and also of the thermal decomposition behaviour of mixtures containing those materials.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.208-208
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• 2017

No-tillage practices are expected to provide several benefits such as increasing soil organic matter, reducing labor time and saving energy cost compared with conventional tillage practices. This study was conducted to investigate the effects of no-tillage dry-seeding on rice growth and soil properties in comparison with other rice cultivation methods, machine transplanting and wet-hill-seeding on puddled paddy. Rice seedling establishment was slightly higher in no-tillage dry-seeding treatment ($145seedling\;m^{-2}$) than wet-hill-seeding on puddled paddy treatment ($111seedling\;m^{-2}$), but the seedling establishment in both treatments fell within the optimum range for direct seeding rice cultivation. Plant height, number of tillers and chlorophyll content (SPAD value) of rice in no-tillage dry-seeding treatment were higher than those of the other treatments. However, no significant differences in grain yield was observed among three cultivation methods, and the yield ranged 5.8 to $5.9ton\;ha^{-1}$. The heading date from seeding under no-tillage dry-seeding treatment was on average 109 days, which was similar to that under machine transplanting treatment (112 days), but 10 days later than that under wet-hill-seeding on puddled paddy treatment (99 days). Grain quality characteristics grown in no-tillage dry-seeding were similar to those grown in the other cultivation methods. These results indicate that no-tillage dry-seeding practice is comparable to conventional tillage system in terms of seedling establishment, growth, yields and grain quality.

• Applied Chemistry for Engineering
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• v.30 no.6
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• pp.652-658
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• 2019

Direct hydrazine fuel cells (DHFCs) have been considered to be one of the promising fuel cells because hydrazine as a liquid fuel possesses several advantages such as no emission of CO₂, relatively high energy density and catalytic activity over platinum group metal (PGM)-free anode catalysts. Judging from plenty of research works, however, regarding key components such as electrocatalysts as well as their physicochemical properties, it becomes quite necessary to understand better the underlying processes in DHFCs for the long term stability. Herein, we highlight recent studies of DHFCs in terms of a systematic approach for developing cost-effective and stable anode catalysts and electrode structures that incorporate mass transport characteristics of hydrazine, water and gas bubbles.

• 한국신재생에너지학회:학술대회논문집
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• 2007.11a
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• pp.156-160
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• 2007

Ejector system is a device to transport a low-pressure secondary flow by using a high-pressure primary flow. Ejector system is, in general, composed of a primary nozzle, a mixing section, a casing part for suction of secondary flow and a diffuser. It can induce the secondary flow or affect the secondary chamber pressure by both shear stress and pressure drop which are generated in the primary jet boundary. Ejector system is simple in construction and has no moving parts, so it can not only compress and transport a massive capacity of fluid without trouble, but also has little need for maintenance. Ejectors are widely used in a range of applications such as a turbine-based combined-cycle propulsion system and a high altitude test facility for rocket engine, pressure recovery system, desalination plant and ejector ramjet etc. The primary interest of this study is to set up an applicable model and operating conditions for an ejector in the condition of sonic and subsonic, which can be extended to the hydrogen fuel cell vehicle. Experimental and theoretical investigation on the sonic and subsonic ejectors with a converging-diverging diffuser was carried out. Optimization technique and numerical simulation was adopted for an optimal geometry design and satisfying the required performance at design point of ejector for hydrogen recirculation. Also, some sonic and subsonic ejectors with the function of changing nozzle position were manufactured precisely and tested for the comparison with the calculation results.

• Journal of Korean Society of Water and Wastewater
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• v.31 no.2
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• pp.177-186
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• 2017

This study concerned the analysis on the efficiency of the conversion of water tank type supply system to direct water supply system to examine the feasibility of the conversion, as well as the calculation of optimal conversion range that enables the supply of safe, high-quality water at stable pressure in accordance with the standards of water supply facility. The results of this research showed that when converting water supply system from water tank type supply system to direct water supply system, more nodal points could be properly converted and more reduction of electricity usage was expected in case water pressure rather than residence time was fixed. This means that higher efficacy can be obtained by fixing water pressure when converting water supply system. However, since the number of the locations that received on-spot inspection was small and the electricity usage measured was not exclusively by water supply facility, it is difficult to judge that such reduction of electricity usage accurately represents reduced electricity usage by water supply facility alone. therefore, after having secured on-spot information about a larger number of locations in apartment complexes that have converted water supply system, and utilizing information about electricity usage exclusively by water supply facility, the proposed method of this research could be applied to accurately deducing expected reduction of electricity usage by water supply facilities of various other apartment complexes. It is also considered possible to deduce an effective operation method of water supply system by finding out an area that shows low pressure or low residual chlorine concentration in the optimal conversion range of water supply, followed by estimating the proper location of pumping station or the proper chlorine dosage at the power purification plant that supply water to the target area.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.5
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• pp.399-409
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• 2018

Prussian blue is known as a superior material for selective adsorption of radioactive cesium ions; however, the separation of Prussian blue from aqueous suspension, due to particle size of around several tens of nanometers, is a hurdle that must be overcome. Therefore, this study aims to develop granule type adsorbent material containing Prussian blue in order to selectively adsorb and remove radioactive cesium in water. The surface of granular activated carbon was grafted using a covalent organic polymer (COP-19) in order to enhance Prussian blue immobilization. To maximize the degree of immobilization and minimize subsequent detachment of Prussian blue, several immobilization pathways were evaluated. As a result, the highest cesium adsorption performance was achieved when Prussian blue was synthesized in-situ without solid-liquid separation step during synthesis. The sample obtained under optimal conditions was further analyzed by scanning electron microscope-energy dispersive spectrometry, and it was confirmed that Prussian blue, which is about 9.7% of the total weight, was fixed on the surface of the activated carbon; this level of fixing represented a two-fold improvement compared to before COP-19 modification. In addition, an elution test was carried out to evaluate the stability of Prussian blue. Leaching of Prussian blue and cesium decreased by 1/2 and 1/3, respectively, compared to those levels before modification, showing increased stability due to COP-19 grafting. The Prussian blue based adsorbent material developed in this study is expected to be useful as a decontamination material to mitigate the release of radioactive materials.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.27 no.1
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• pp.28-33
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• 2017

SiC fiber can be used up to $1800^{\circ}C$ in both inert and air atmosphere without any problems such as melting and oxidation. SiC fibers can be applied to dust filtering processes as a bag filter at a high temperature above $700^{\circ}C$, which is far beyond the temperature range of currently available industrial bag filter. However the studies for the degradation of SiC fibers were still lacked in the harsh environment of steel industries and thermoelectric power plants. In this study, SiC fibers were reacted with steel dust and thermal power plant dust at a high temperature of $500^{\circ}C$ or higher, and the degraded shape of the fiber surface was observed by SEM. Also the degree of oxygen diffusion on the surface and inside of SiC fiber was analyzed by EDS.