• Journal of The Korean Society of Grassland and Forage Science
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• v.14 no.1
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• pp.13-17
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• 1994

To find out the effects of phosphatic fertilizer application level on the dry matter yield and nutrient contents of grasses, this experiment was arranged as a randomized complete block design with six treatments(0, 50, 100, 150, 200 and 250kg $P_2O_5$/ ha) and conducted at hill land in Gwangju, Gyeonggi Province from September, 1989 to October, 1992. The results obtained are summarized as follows : 1. As the phosphatic fertilization level increase, the early growth and cover degree of grasses wintered were more favorable and plant length was higher. 2. With 150kg $P_2O_5$/ ha application for three years, the average dry matter yield of grasses, 10,112kgl ha was sirnilared to that of 200kg $P_2O_5$/ ha and the yield was composed of 77.2% grasses(7,808kg/ ha), 19.2% legumes(l,937kg 1 ha) and 3.6% weeds(367kg / ha). 3. The crude protein and energy productivity of grasses increase as phosphatic fertilization level was increased, but those were not different between 150 and 250kg $P_2O_5$ 1 ha. Therefore, phosphatic fertilization level must be applied with 150kg / ha for a reasonable management in hilly grassland.

• The KSFM Journal of Fluid Machinery
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• v.18 no.1
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• pp.20-28
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• 2015

The pump-turbine impeller is the key component of pumped storage power plant. Current design methods of pump-turbine impeller are private and protected from public viewing. Generally, the design proceeds in two steps: the initial hydraulic design and optimization design to achieve a balanced performance between pump mode and turbine mode. In this study, the 3D inverse design method is used for the initial hydraulic impeller design. However, due to the special demand of high performance in both pump and reverse mode, the design method is insufficient. This study is carried out by modifying the geometrical parameters of the blade which have great influence and need special consideration in obtaining the high performance on the both modes, such as blade shape type at low pressure side (inlet of pump mode, outlet of turbine mode) and the blade lean at blade high pressure side (outlet of pump mode, inlet of turbine mode). The influence of the geometrical parameters on the performance characteristic is evaluated by CFD analysis which presents the efficiency and internal flow results. After these investigations of the geometrical parameters, the criteria of designing pump-turbine impeller blade low and high sides shape is achieved.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.05a
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• pp.274-278
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• 2003

In recent, an application of high energy density beam we/ding is increasing to obtain the high quality in weldments. Laser welding, especially, has been recognized as an useful method and its beam power has also increased according to the development of relevant technology. However, welding method in the fields of power plant is conservative because their structures have required to endure high temperature and pressure. So, authors conduct the numerical simulation in order to consider the possibility of laser welding on the material of the pressure vessels ($2\frac{1}{4}Cr-1Mo$ steel). As a result of this study, we can confirm the advantages of laser welding and obtain useful information for the experiments of weldability.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.121-125
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• 2015

Distribution of rare earth metals (REMs) and rare valuable metals (RVMs) contents in coal ashes (fly ash, bottom ash, and pond ash) and leachate from 11 coal-fired power plants in Korea were investigated. Coal ashes and leachates were found to contain important REMs and RVMs such as Yttrium (Y) and Neodymium (Nd), which was in the range of 23~75 mg/kg. However, it still requires developing effective recovery and separation methods in order to utilize REMs and RVMs in ash and leachate. Recovery of valuable elements (Y and Nd) from various and extensive ash sources (8.21 million tons/year in 2013) can provide the existing power plants with additional profit; therefore, it can significantly improve economics of the power plants.

• KEPCO Journal on Electric Power and Energy
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• v.1 no.1
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• pp.109-113
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• 2015

초임계 이산화탄소 발전 시스템 구축을 위해서는 고온, 고압의 열악한 환경에 노출되는 터빈, 열 교환기, 압축기와 같은 핵심 부품들의 내식성 평가는 반드시 수행되어야 한다. 이를 위해 후보소재 3종 Ferritic-Martensitic Steel (T92), Austenitic Steel (SS316L), Ni-based Alloy (IN738LC)를 선정하여 고온의 유사 초임계 $CO_2$ 발전 환경에서의 내식성 평가를 진행하였다. $600^{\circ}C$, $700^{\circ}C$의 2개의 온도 구간에서 $CO_2$ 분위기를 조성하여 800 시간 동안 노출시킨 뒤, Weight Change, Surface Morphology, Cross Section, Composition을 분석하였다. Cr-rich Protective Layer를 형성하는 Ni-based Alloy와 Fe/Cr-rich oxide를 형성하는 Austenitic Steel은 우수한 부식 저항성을 보인 반면에 Ferritic-Martensitic Steel은 높은 Weight Change와 Fe-rich Non-Protective Oxide가 관찰되어 상대적으로 낮은 부식 저항성을 보였다.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.61 no.9
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• pp.1260-1268
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• 2012

Recently, lack of power reserve margin was observed quite often. In this paper, we studied the method to secure power source for a short time, to cut the utility power peak load, and to reduce the users electricity bills. Emergency diesel generator of an office building is to be converted into a dual-fuel engine generator which is responsible for a portion of the peak load. Compared to the conventional diesel fuel generator, the proposed dual-fuel engine is able to reduce the generation power cost by dual-fuel combustion, and it also mitigates the building's utility power peak load by charging the building's peak load. If the dead resources (a group of emergency dual-fuel engine generators), as a Virtual Power Plant, are operating in peak time, we can significantly reduce future large power development costs. We investigated the current general purpose electricity bills as well as the records of the building electric power usage, and calculated diesel engine generator renovation costs, generation fuel costs, driving conditions, and savings in electricity bills. The proposed dual-fuel engine generation method reduces 18.1% of utility power peak load, and turned out to be highly attractive investment alternative which shows more than 27% of IRR, 76 million won of NPV, and 20~53 months of payback periods. The results of this study are expected to be useful to developing the policy & strategy of the energy department.

• Environmental Engineering Research
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• v.19 no.3
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• pp.185-195
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• 2014

Despite the enormous technical and economic efforts to improve environmental conditions, currently about 40% of the global population (or 2 billion people) are still lack access to safe water supply and adequate sanitation facilities. Pollution problems and transmission of water- related diseases will continue to proliferate. The rapid population growth and industrialization will lead to a reduction of arable land, thus exacerbating the food shortage problems and threatening environmental sustainability. Natural systems in this context are a transdisciplinary approach which employs the activities of microbes, soil and/or plants in waste stabilisation and resource recovery without the aid of mechanical or energy-intensive equipments. Examples of these natural systems are: waste stabilisation ponds, aquatic weed ponds, constructed wetlands and land treatment processes. Although they require relatively large land areas, the natural systems could achieve a high degree of waste stabilisation and at the same time, yield potentials for waste recycling through the production of algal protein, fish, crops, and plant biomass. Because of the complex interactions occurring in the natural systems, the existing design procedures are based mainly on empirical or field experience approaches. An integrated kinetic model encompassing the activities of both suspended and biofilm bacteria and some important engineering parameters has been developed which could predict the organic matter degradation in the natural systems satisfactorily.

• Analytical Science and Technology
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• v.15 no.6
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• pp.567-573
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• 2002

The most important and largest commercial outlet of fly ash in Korea is a replacement material of Portland cement in concrete industry. The high level of unburned carbon in ash brings about some malfunctions in concrete. Therefore, fly ash is refined to improve the quality as a concrete additive. In this process, a lot of the residual carbon is produced, and discarded now. In the present study, to find out a valuable outlet of the enriched carbon samples, the basic morphology of residual carbon in fly ash from Boryung power plant was investigated. The unburned carbon characterization included shape, size measurement, and chemical analysis was examined using scanning electron microscope (SEM) and energy dispersive X-ray spectrometer (EDX).

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.146-150
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• 2001

전기집진기는 여타의 집진 설비에 대한 집진 효율과 유지 보수성이 우수한 설비이며 소결공장의 배출분진과 같은 고온($120{\~}160^{\circ}C$)의 미세분자($5{\~}12{\mu}m$) 및 고비저항($10^{12}{\~}10^{13} {\Omega}cm$)을 포집할 때 DC 하전에 비해 Pulse 하전이 효과적이며 Energy 절감이($60{\~}90\%$) 된다. 본 논문은 소결공장의 DC 하전에서 Pulse 하전으로 전환 시 EP 특성 및 부하변화에 따른 제어방안을 제시한다. 현재 제철소의 소결 전기집진기 경우 정수 직후에는 전압이 정상적으로 공급하다가 시간이 지남에 따라서 DC 전압이 낮아지고 Back Corona 현상이 발생하여 서서히 분진농도는 급격히 상승하는 문제점을 가지고 있다. 이에 비해 Pulse 하전으로 운전할 경우에는 Back Corona 현상 발생억제로 출구농도 상승 기울기를 조장방법 및 Ramping 장치와 관련장치 등을 최적으로 운용할 수 있는 방법을 소결공장 실험하였다.

• Journal of the Korean Institute of Landscape Architecture
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• v.17 no.3
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• pp.35-47
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• 1990

This study was executed to analyze the vegetational landscape structure and administration planning of Heonin Royal Tomb forest by three kinds of ordination techniques (PCA, RA and DCA) and comparison of the couple photographs between 1920s and 1980s. Seventeen sites in the recreation area and fifteen sites in the protective area were sampled with clumped sampling method in June 1988 and five quadrats were examined in each site. Environmental impact grade 3, 4 and 5 area covered 56.4% of the surveyed area and these area should be restored by the input of human energy. Pinus densifora community of actual vegetation covered 8.4%, Alnus japonica 24.2% and Quercus community 40.9% of the total area. And the afforested vegetation of Pinus koraiensis and Pinus rigida covered 23.1 % The recreation area was divided by P. densiflora, P. densiflora-Quercus aliena, A. japonica-Q.aliena, A. japonica and the protective area by Q. acutissima, Q. aliena, A. japonica-Q. aliena.. DCA ordination showed that successional trends of tree species seem to be from P. densiflora, Sorbus alnifolia, Styrax obassia to Q. variabilis Q. serrata in P. densiflora community and from A. japonica through A. ginnala to Q. aliena in A. japonica community of the upper layer. By the comparison of the couple photographs between 1920s and 1980s, we can recognize the change of historical landscape composed of P. densiflora community and those community is succeeded to Q. aliena.