• Fisheries and Aquatic Sciences
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• 제10권1호
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• pp.30-36
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• 2007

We present age and growth data for Ilisha elongata, based on 363 specimens caught in 1999 and 2000 around Jeju Island and the southwest coast of Korea. Scale and ring radii of each ring group showed a direct one-to-one relationship, with ring radius increasing as scale radius increased. The relationship between fork length and scale radius was FL=39.553SR+60.935 for females, FL=39.474SR+54.026 for males, and FL=39.608SR+57.547 for both sexes. Monthly changes in the marginal index indicated that a new ring appears once each year (in July). Maximum age, mean age and mean fork length of fish were 10 years, 5.0 years, and 349mm, respectively. Von Bertalanffy's growth equations were $FL_t=495.4{\times}[1-\exp(-0.2586(t+0.6487))]$ for fork length (mm) and $W_t=1,112.5{\times}[1-\exp(-0.2586(t+0.6487))]^{2.874}$ for body weight (g) for both sexes. Monthly changes in the gonadosomatic index (GSI) indicated that the spawning period was in June and July, which corresponded closely with ring formation time. Differences in monthly GSI changes in 1999 and 2000 may be related to water temperature variation. Fecundity ranged from 5,664 to 176,290 eggs per individual (n=43, fork length 264-470mm). The relationship between fecundity(F) and fork length was $F=7.7{\times}10^{-7}{\times}FL^{4.9269}$.

• 상하수도학회지
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• 제35권4호
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• pp.277-284
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• 2021

The ballasted flocculation effects of the mill scale and magnetite on activated sludge were investigated. Both ballasted flocculants (BF) could remarkably improve the sludge settleability in terms of zone settling velocity (ZSV) and sludge volume index (SVI). With the BF dosage of 0.2 to 2.0 g-BF/g-SS, the magnetite particles showed better efficiency on improving settling behavior of activated sludge than the mill scale due to higher surface area and hydrophobic property. The efficiency of SVI₃₀ with magnetite injection was 2.5 to 11.3% higher than mill scale injection and that of the ZSV appreciated from 23.7% to 44.4% for magnetite injection. Averaged floc size of the BF sludge with magnetite dosage (0.5 g-BF/g-SS) was 2.3 times higher than that of the control sludge. Dewaterability of the sludge was also greatly improved by addition of the BF. The specific resistance to filtration (SRF) was reduced exponentially with increasing the dosage of BF. However, the BF's particle size effect on the SRF looks to be marginal. Consequently, for improving the dewaterability, the BF played a physical role to remove the pore water of the biological flocs by intrusive attachment and a chemical role to induce aggregation of the flocs by charge neutralization.

• Environmental Engineering Research
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• 제23권1호
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• pp.70-75
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• 2018

A pilot scale anaerobic fixed-bed with a reactor volume of $2.8m^3$ was built to treat slaughterhouse wastewater. Bamboo rings were chosen as support media mainly because of their cheaper price in underdeveloped countries. Even with their lower porosity and specific surface, the reactor performance showed a maximum 95% COD removal efficiency at an organic loading rate (OLR) of $1kg\;COD/m^3-d$ with its corresponding hydraulic retention time (HRT) of 7.5 d. At a higher OLR of $4.0kg\;COD/m^3-d$, the COD removal efficiency of 75% was achieved with an HRT of 2 d. No big difference in COD removal efficiencies was found between the reactors operated in both upflow and downflow modes. Their operational behavior and effluent characteristics were similar. The effluent COD/TKN ratio of 6.67 at an OLR of $4.0kg\;COD/m^3-d$ was only marginal acceptable range for a subsequent biological denitrification process. Otherwise carbon supplementation is required at a lower OLR.

• 한국주거학회:학술대회논문집
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• 한국주거학회 2008년 추계학술발표대회 논문집
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• pp.102-107
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• 2008

The National Rental Houring has been built for solving the lack of house for the low-income group. However the national rental housing that the low-income group didn't feel aliention' we should improve the quality of National Rental housing. The purpose of this study aims to identify the facts for improving the social integra as the preference of Rental lived in Gwangju. The findings are as follows. The residents had marginal characteristics such as low income, the aged and were satisfied with the residential environment so they want to stay there as long as they can. However, they were dissatisfied with the scale of housing, housing facilities. Therefore, It is important to improve housing condition witch they enhance their self existence.

• 신재생에너지
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• 제10권1호
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• pp.41-49
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• 2014

For a proper valuation of wind power project, it is necessary to consider volatilities of key parameters such as annual energy production, electricity sales price, and long term interest rate. Real option methodology allows to calculate option values of these parameters. Volatilities to be considered in wind project valuation are 1) annual energy production (AEP) estimation due to meteorological variation and estimation errors in wind speed distribution, 2) changes in system marginal price (SMP), and 3) interest rate fluctuation of project financing which provides refinancing option to be exercised during a loan tenor for commercial scale projects. Real option valuation turns out to be more than half of the sales value based on a case study for a FIT scheme wind project that was sold to a financial investor.

• 자원ㆍ환경경제연구
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• 제11권1호
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• pp.1-29
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• 2002

Faced with large scale of outdoor recreation resources and variety of demanders' desire, it would be necessary for the managers to estimate the values of individual attributes rather than a bundle of characteristics of outdoor recreation sites. By extending the Brown and Mendelsohn's (1984) approach we are able to estimate the beneficial effects of the improvement of individual attributes. Sampling 208 fishermen who visited 11 free fishing sites located in Daegu and Gyeongbuk, the functions of marginal willingness to pay for scenery and non-crowdedness were estimated. If 1 unit of scenery could be improved from its average value a fisherman, on average, would receive benefit of as much as 3,840 won. The average beneficial effect of the non-crowdedness improvement would amount to 2,220 won.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1997년도 하계학술대회 논문집 D
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• pp.797-799
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• 1997

This paper presents an operation and planning model of integrated energy systems which consist of small scale cogeneration systems, thermal accumulator, ice storage and electrical energy storage systems. In the proposed planning model, an optimization of total cost which contains investment, operation, thermal shortage and salvage costs has carried out with the maximum principle based on the lifetime of each system component and unit price per capacity. From this model, optimal investment capacity per annum can be determined during the studied periods using the marginal costs according to the operation characteristics of each system component.

• 에너지공학
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• 제5권1호
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• pp.87-92
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• 1996

본 연구는 전력계통이 3개의 발전기로 구성되었고, 요금적용 시간대가 3개인 경우 동태적 최적화를 이용한 최적 가격 및 투자 정책을 도출하기 위한 것이다. 이를 위하여 최대원리법(Maximum Principle)을 이용하였으며, 종전에는 수요함수에서 고려되지 않았던 교차가격 탄력성을 수요함수에 포함시켰다. 분석 결과 다음과 같은 결론을 얻을 수 있다. 첫째, 설비가 충분한 경우 각 시간대의 최적 가격은 단기한계비용과 일치한다. 그러나 시간이 경과함에 따라 수요증가에 의하여 설비제약이 활성화되면 각 시간대의 가격은 설비비를 포함하는 장기한계비용 형태를 띄게 된다 둘째, 각 시간대에 있어서 발전기의 설비비의 분담은 요금적용 시간대의 길이에 의하여 영향을 받는다. 즉, 해당 시간대의 요금적용 시간대가 길어지면 길어질수록 해당시간대에 대응되는 설비의 설비비 분담은 감소하고, 짧아지면 질수록 설비분담은 높아지게 된다. 셋째, 동태적 분석에서의 설비투자는 기본적으로 각 시간대의 수요증가율과 같은 비율로 증가하며, 또한 신규설비 투자규모는 각 시간대의 투자설비를 서로 분담하게 된다.

• Journal of Forest and Environmental Science
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• 제29권4호
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• pp.249-256
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• 2013

The aim of the study was to reveal the scope and benefits derives from establishing carbon forests in a country like Bangladesh. Carbon forestry is the modernized forestry practice that evolves no cutting of trees or vegetation rather conserves them in the wood. Trees might be the source of carbon sink at large scale by establishing carbon forests. To find out how and in what extent forests of Bangladesh could contribute to global emission reduction, tree species of economic importance were taken into account about their carbon sequestration potential. Data source was a secondary one. Bangladesh has subtropical evergreen and deciduous forest tree species. Here trees can sequester almost 45-55 percent organic carbon in their biomass. On an average, trees in different types of stands can sequester 150-300 tC/ha. Carbon value of these forests might be 7,500-15,000 USD per hactre (assuming 50 USD per equivalent $tCO_2$). Thus, accounting tree carbon credits of total forested lands of Bangladesh, there might be a lump sum value of $1.89{\times}10^{10}-3.79{\times}10^{10}$ USD. If soil carbon is added, this amount would jump. Alternatively, there are two times higher spaces as marginal lands than this for starting carbon forestry. However, carbon forestry concept is still a theoretical conception unless otherwise their challenges are addressed and solved. Despite of this, forests of Bangladesh might be the key showcase for conserving biodiversity in association with carbon capture. Protected areas in Bangladesh are of government wealth, however, degraded and denuded waste and marginal lands might be the best fit for establishing carbon forests.

• 한국산업정보학회논문지
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• 제19권6호
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• pp.87-96
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• 2014

마크업은 Hall(1988)에 의해 한계비용에 대한 가격의 비율로 정의된 이후, 신케인지언들은 시장구조와 경기변동 사이의 관계를 설명하는 데에 마크업의 개념을 이용하여 왔다. 여러 문헌에서 마크업이 경기역행적임을 나타내는 이론모형이 제시되었으며, 실증증적으로 대부분의 연구는 마크업이 경제전체적으로 또는 산업별로 경기역행적임을 밝히고 있다. 또한 한국의 경우 마크업에 관한 대부분의 연구에서 분석대상은 주로 제조산업에 집중된 반면, 특히 서비스산업에서 산업구조의 특성을 밝히는 실증적 분석은 연구가 매우 저조하다고 할 수 있다. 따라서 본 논문은 한국의 5개 서비스산업을 대상으로 마크업의 실증모형을 작성하고 직접적으로 5개의 서비스 산업의 마크업을 측정하고 마크업의 결정요인들을 자기회귀시차모형(ADL(1,1))을 이용하여 분석하였다.