• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.337-337
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• 2017

가뭄은 일반적으로 강수량의 부족에 기인하며, 수자원의 이용 및 관리에 큰 영향을 미치는 자연재해이다. 2013년부터 2015년까지 우리나라의 연 평균 강수량은 각각 1,162mm, 1,173mm, 948mm로 평년대비 89.0%, 89.8%, 72.1%의 적은 강수를 보였다. 이는 마른장마, 평년보다 적게 발생한 태풍 등의 영향 인 것으로 판단되며 이러한 강수의 부족으로 인해 전국적으로 가뭄이 빈번하게 발생하였다. 이에 가뭄의 대처방안에 대한 관심이 증대되었고, 가뭄을 정량적으로 표현하고자 하는 연구들이 진행되었다. 가뭄은 크게 수문학적, 기상학적, 농업적 가뭄으로 구분되며 각각의 기준에 따라 다양한 변수들을 이용한 지표들이 개발되었다. 개발된 가뭄 지표는 가뭄을 평가하고 대비하기 위한 의사결정에 유용한 자료로 사용되고 있다. 농업적 가뭄은 강우부족, 실제와 잠재증발산량의 차이, 토양수분 부족, 저수지 또는 지하수위의 저하 등 농작물의 생육과 수확량에 직접적인 영향을 미치는 특성들을 고려하여 평가해야 하며, 이러한 특성들을 고려한 가뭄 지수로는 저수지 가뭄지수(RDI), 토양수분지수(SMI), 통합농업가뭄지수(IADI) 등이 개발되었다. 저수지 가뭄지수는 가뭄발생의 위험과 크기를 순별 가용저수량의 빈도를 이용하여 나타낸 가뭄 지표이다. 따라서 가뭄 지표를 산정하는데 사용된 자료의 기간에 따라 그 값의 차이가 존재한다. 본 연구에서는 각각 10개년, 20개년, 30개년 기간의 백산저수지 농업지구 저수량 자료를 사용하여 2011년부터 2015년까지의 저수지 가뭄지수를 산정하였으며 이를 각각 비교하였다. 2006년부터 2015년까지 10개년 기간의 자료를 사용하여 산정한 가뭄지수는 2012년 ~ 2015년에 가뭄을 나타내고 있었고 특히, 2015년 6월 상순과 중순의 가뭄지수가 -4.1으로 가장 심한 가뭄을 나타내었다. 1996년부터 2015년까지 20개년 기간의 자료를 사용하여 산정한 가뭄지수는 2012 ~ 2015년에 가뭄을 나타내며 2015년 6월 상순과 중순의 가뭄지수는 각각 -0.9, -1.0으로 10개년의 기간을 사용하였을 때보다 완화된 모습을 보였다. 1986년부터 2015년까지 30개년 기간의 자료를 사용하여 산정한 가뭄지수는 2011년부터 2015년까지 가뭄을 나타내고 있었으며, 2015년 6월 상순과 중순의 경우 각각 -1.7, -1.0으로 20개년 자료를 사용하였을 때보다 심한 가뭄을 나타내지만, 10개년 자료를 사용하였을 때보다 완화된 가뭄을 나타내었다. 백산저수지의 경우 2011년부터 2015년까지 가뭄이 발생하였으나, 용수공급이 불가능 할 정도의 가뭄이 발생하지는 않은 것으로 조사되었으며, 30개년 자료를 사용한 가뭄지수가 이와 가장 근사한 가뭄정도를 나타내고 있다. 이는 저수량자료의 기간이 크면 빈도값의 신뢰성이 높아지기 때문인 것으로 판단되며 저수지 가뭄지수의 경우 저수량 자료가 누적될수록 좀 더 정확한 가뭄상황을 표현할 수 있을 것으로 판단된다.

• Korean Journal of Environmental Agriculture
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• v.27 no.2
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• pp.171-177
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• 2008

The application in agricultural fields of pig slurry composting biofiltraton amending smell and nutrient unevenness, it is important for the appropriate nitrogen nutrient management to promote the availability of the crops and to minimize the risk of adversely environmental effects. The objective of this study was to determine the application rates of the preplant pig slurry composting biofiltration for red pepper(Capsicum annuum L.) by considering the yield response and the fruit quality such as sugar, capsaicinoid content. Red peppers were grown on plastic film ground under five different pig slurry(PS) application rates and mineral fertilizer(MF 100%) as a control. The effects of a single application of five different doses of PS: PS 0%(no kg N $ha^{-1}$), PS 50%(51.5 kg N $ha^{-1}$), PS 75%(77.3 kg N $ha^{-1}$), PS 100%(103 kg N $ha^{-1}$) and PS 125%(129 kg N $ha^{-1}$) were compared with the recommended mineral treatment(103 kg N $ha^{-1}$) in the pre-planting. The sidedressing N application(87 kg N $ha^{-1}$) was applied to the mineral fertilizer in all treatments. Red peppers were harvested at the mature red stage through five times from 72 days after transplanting(DAT) to 133 DAT. The results indicated that the yield of red pepper was increased with the increase of the N application rates from PS 0% to PS 100%. The highest yield was obtained in PS 100% by 20,843 kg $ha^{-1}$, although there were no significant differences in yield among PS 100, PS 125% and MF 100%. In addition, The contents of soluble sugar and capsaicinoids were not significantly different in all treatments. Accordingly, fertilization recommendations of red pepper to substitute PS for the mineral fertilizer were considered to PS 100%.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.3
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• pp.662-669
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• 1994

In the combustion system, the optimum spray conditions reduce the pollutant emission of exhaust gas and enhance the fuel efficiency. The spray characteristics-the drop size, the drop velocity, the number density and the mass flux, become increasingly important in the design of combustor and in testifying numerical simulation of spray flow in the combustor. The purposes of this study are to clarify the spray characteristics of twin-fluid nozzle and to offer the data for combustor design and the numerical simulation of a spray flow. Spatial drop diameter was measured by immersion sampling method. The mean diameter, size distribution and uniformity of drop were analyzed with variations of air/liquid mass flow ratio. The results show that the SMD increases with the liquid supply flow rate and decreases with the air supply velocity. The radial distribution of SMD shows the larger drops can diffuse farther to the boundary of spray. And the drop size range is found to be wider close to the spray boundary where the maximum SMD locates.

• Journal of agriculture & life science
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• v.52 no.6
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• pp.37-47
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• 2018

The objective of this study was to analyze the influences of forest management activity on the diameter distribution of Larix kaempferi Carriere stands in South Korea. We used 232 managed stands data, 47 unmanaged stands data of National Forest Inventory for this study. We employed the Weibull distribution function for estimating diameter based on percentiles and parameter recovery method. The results revealed that the average diameter breast height movements and growth of tree in the managed stands higher than the unmanaged stands according to the scenario: age, site index, and tree density change. The finding shows the percentage of the total amount of large class diameter was also high in the managed stands. The results of this study could be apply for the estimation of multi-products of timbers per diameter classes and stand structure development for Larix kaempferi Carriere stands in South Korea.

• Korean Journal of Environmental Agriculture
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• v.38 no.3
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• pp.166-172
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• 2019

BACKGROUND: Increase in the ratio of small berries in blueberry production decreases the farmers' profits due to weakening market competitiveness and lowering harvest efficiency. One of the reasons for increased small berries is over fruit-load. For improving productivity and competitiveness of blueberry in Korea, hand-thinning can be applied to increase fruit quality before the developing adequate chemical thinning methods. This study was conducted to investigate the proper timing and methods for floral buds thinning in rabbiteye blueberry. METHODS AND RESULTS: Eight years old bushes of rabbiteye bluberries 'Brightwell' as a primary cultivar and 'Powderblue' as a pollinizer were used for this study. Fruit size distribution by leaf-to-fruit ratio was investigated by counting the number of leaves and fruits in canes of 127 'Brightwell' plants whose fruit set varied. Fifty percent of flowers/floral buds were removed in four different floral buds stages such as bud swell, late pink bud, full bloom, and petal fall, and the consumed time for thinning and fruit characteristics were recorded to investigate the effect and proper timing of floral buds thinning. Fruit weight and soluble solids content tended to increase in proportion to leaf-to-fruit ratio and the production of the number of fruits less than 13 mm in diameter decreased when leaf-to-fruit ratio was more than 2.5. Manual floral buds thinning by hands was fastest in full bloom stage and slowest in bud swelling stage. In all cultivars, fruit size was significantly smaller in non-thinning treatment than thinning, and there was, however, no significant difference in total fruit yield. The number of fruits less than 13 mm in diameter increased in both cultivars as floral buds thinning was delayed. Consumed time for picking 90% berries out of total berries per bush was shortest in full bloom stage thinning in 'Brightwell' and bud swelling, full bloom thinning in 'Powderblue'. These were 25 and 20 days faster than no thinning, respectively. CONCLUSION: Although the effect of floral buds thinning varied depending on the cultivars, our results confirmed that floral buds thinning was effective for the early intensive harvesting and the increase of the large fruit ratio and the harvesting productivity. Also, in order to increase thinning efficiency, it is recommended to remove the flower buds before the full bloom stage.

• Journal of the Korean Institute of Landscape Architecture
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• v.45 no.5
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• pp.97-104
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• 2017

Greenspace enlargement through proper landscape planting is essential to creating a low carbon society. This study analyzed changes in stem diameter growth rates(DGR), ratios of below ground/above ground biomass(B/A), and carbon sequestration by age of major landscape tree species. Landscape trees for study were 11 species and 112 individuals planted in middle region of Korea. The DGR and B/A were analyzed based on data measured through a direct harvesting method including root digging. The carbon sequestration by tree age was estimated applying the derived regression models. The annual DGR at breast height of trees over 30 years averaged 0.72 cm/yr for deciduous species and 0.83 cm/yr for evergreen species. The B/A of the trees over 30 years averaged 0.23 for evergreen species and 0.40 for deciduous species, about 1.7 times higher than evergreen species. The B/A by age in this study did not correspond to the existing result that it decreased as tree ages became older. Of the study tree species, cumulative carbon sequestration over 25 years was greatest with Zelkova serrata(198.3 kg), followed by Prunus yedoensis(121.7 kg), Pinus koraiensis(117.5 kg), and Pinus densiflora (77.4 kg) in that order. The cumulative carbon sequestration by Z. serrata offset about 5% of carbon emissions per capita from household electricity use for the same period. The growth rates and carbon sequestration for landscape trees were much greater than those for forest trees even for the same species. Based on these results, landscape planting and management strategies were explored to improve carbon sequestration, including tree species selection, planting density, and growth ground improvement. This study breaks new ground in discovering changes in growth and carbon sequestration by age of landscape trees and is expected to be useful in establishing urban greenspaces towards a low carbon society.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.3
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• pp.189-194
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• 2001

It is possible to use hairy vetch as green manure for corn not only in corn single cropping but also in double cropping system of corn and fall oats. Fall oats and hairy vetch were mixed-sown after corn harvest and harvested as forage in the early of November, and then hairy vetch stubble was over-wintered and incorporated into soil at corn planting as green manure without N fertilizer (FO+HV-GM). Other treatments were fall oats without N fertilizer on corn (FO-0N) and with N fertilizer 200kg/ha on corn (FO-200N), hairy vetch green manure without N fertilizer on corn (HV-GM), and fell winter follow without N fertilizer on corn (WF-0N). Soil nitrate content, corn growth and nitrogen uptakes, and yield of corn were measured and compared during 2-year experimental seasons. Dry matter and N amount of hairy vetch at the plot of FO+HV-GM were 60% less than those at the plot of HV-GM. The N effect of hairy vetch green manure on corn at the plot of HV-GM was similar to that at FO-200N plot for two years. Soil nitrate at the plot of FO+HV-GM was below the half of those at plots of HV-GM and FO-200N at 6-leaf stage of corn. N uptake of corn at the plot of FO+HV-GM at silking stage was 30% less than those at plot of HV-GM and FO-200N. However, soil nitrate at 6-leaf stage of corn and the amount of nitrogen uptake of corn at silking stage increased two times and 30-40 kg/ha, respectively, compared with those at the plot of FO-0N. Corn yield at FO+HV-GM decreased about 2 ton/ha due to the decrease of corn grain weight in the first year compared with plot of HV-GM and FO-200N, but its difference was not shown in succeeding second year. Corn N uptake at FO+HV-GM decreased 60 kg/ha and 20 kg/ha in 1999 and 2000, compared with plot of HV-GM and FO-200N, respectively, but increased 30kg/ha and 45kg/ha compared with the plot of FO-0N in 1999, 2000, respectively. Therefore, it is estimated that hairy vetch green manure in fall oats-corn double cropping system can reduce nitrogen chemical fertilizer on corn as much as 50-100 kg/ha although its N effect is much lower than the N effect of hairy vetch green manure in corn single cropping of which N effect is over 200 kg/ha.

• Korean Journal of Environmental Agriculture
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• v.14 no.1
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• pp.1-6
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• 1995

This experiment was carried out to clarify the evapotranspiration and water use efficiency in rice plant canopy. Two rice cultivars, Daechungbyo(japonica type) and Samgangbyo(Tongil) were planted on the field of Suwon Weather Forecast Station in 1989. Evapotranspiration, dry matter production and leaf area of rice plant were measured to investigate the water use efficiency. There was significant correlation between cumulative evapotranspiration and dry matter production of aboveground. The parameter of linear regression was 4.13. The ratio of cumulative top dry matter production per cumulative evapotranspiration was increased until $5.5{\sim}5.9$ leaf area index. The de Wit's "m" value revealed maximum record at heading-flowering stage. At the harvest, the values were ranged from 175.5 to 191.7. The parameter of cumulative solar radiation to dry matter production was $1.011{\sim}1.248$. The evapotranspiration ratio(g.water/g.DW) of Samgangbyo(278) was higher than that of Daechungbyo (299.9). The efficiency of evapotranspiration(g.DW/g. water) was 1.58 in Daechungbyo and 1.98 in Samgangbyo.

• Journal of Korea Port Economic Association
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• v.22 no.3
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• pp.59-78
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• 2006

The purpose of this paper is to analyze the trend on scale efficiency of the Port of Gwangyang from 1994 to 2004 using CCR, BCC, and Malmquist index approaches. The main results are as follows. first, scale efficiency shows a 50% similar [5(94/95, 95/96, 97/98, 2001/2002, 2003/2004) out of 10] pattern to technical efficiency change. Second, total factor productivity increased at 48.57% rate of growth on average in 6 out of 10 periods except 96/97, 97/98, 99/2000, and 2000/2001. 2003/2004 period is the one period experiencing rapid total factor productivity changes, mainly due to technical progress. Third, the ranking order of accumulative indices is scale efficiency change, TFP change, efficiency change, technical change, and pure efficiency change. The main policy implication of this paper is that according to the CCR, BCC, and Malmquist results, the Port of Gwangyang should develop the plan for enhancing the 5 Malmquist indices with following the management way of benchmarking ports.

• Korean Journal of Plant Resources
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• v.27 no.2
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• pp.194-201
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• 2014

This study was carried out to investigate the characteristics and infection effects of AMF with soil samples collected at some sites in Gyeonggi province, Korea. AMF spore and characteristics of infection structure in upland plant root were observed as wet sieving and staining method, growth of Capsicicum annum was compared between treatment and non treatment. AMF spores isolated from each soil sample were ellipse or circle type and the colors were soft yellow and white. The colonization rate of AMF with soil infection of Zea mays roots was 13.3~83.3%, the rate of infected soil collected from Z. mays was higher on average. When compared to the growth of C. Annum with control after infection on C. annum, it wasn't showing many differences in fresh weight, dry weight and height, but the yield of fruit of C. annuum showed double than the control group.