• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.180.1-180.1
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• 2010

Wind turbine noise is generally lower than that from other environmental noise sources such as road and railway noise. Nevertheless, some residents living more than 1km away from wind turbines have claimed that they suffer sleep disturbance due to wind turbine noise. Several researchers have maintained that residents near a wind farm may perceive large amplitude modulation of wind turbine noise at night, and this amplitude modulation is the main cause of the noise annoyance. However, to date only few studies exist on the prediction of the amplitude modulation of wind turbine noise. Thus, this study predicts amplitude modulated noise generated from a generic 2.5MW wind turbine. Semi-empirical noise models are employed to predict the modulation depth and the overall sound pressure level of the wind turbine noise. The result shows that the amplitude modulation is observed regardless of atmospheric stability, but the modulation depth in a stable atmosphere is 1~3dB higher than that in an unstable atmosphere near the plane of rotation where the blades move downward. Moreover, using the result of the noise prediction, this study estimates the maximum perceptible distance of the wind turbine noise cause by amplitude modulation. The result indicates that the wind turbine noise can be perceived at a distance of up to 1600m in the range of about 30~60 degree from the on axis in a extremely low background noise environment.

• Korean Journal of Materials Research
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• v.19 no.9
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• pp.457-461
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• 2009

Recently, metal molding has become essential not only for automobile parts, but also mass production, and has greatly influenced production costs as well as the quality of products. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and, when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate this, microstructural changes and hardness characteristics of three parts (the surface treatment part, heat affect zone, and parental material) are observed with the change of laser beam speed and surface temperature. Moreover, the depth of the hardened area is observed with the change of the laser beam speed and temperature.

• Journal of The Korean Society of Grassland and Forage Science
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• v.4 no.3
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• pp.220-225
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• 1984

In the grassland ecosystem dominated by Phragmites longivalvis in the delta of Nak Dong River, the production, decomposition, and accumulation of organic were estimated by the theoretical analysis. The amounts of organic carbon and organic matter of litter are $1020.43g/m^2\;and\;591.90g/m^2$, respectively. The amounts of organic matter and organic carbon on the grassland floor is $1154.96g/m^2\;and\;669.93g/m^2$, the ratio of annual litter production 'L' to the amount of accumulation on the top mineral soil (F, H and $A_2$ horizons) provided estimates of decay constant k. Constant k is 0.884 in the Phragmites longivalvis community. The vertical levels of organic matter and organic carbon is the highest in 120-140 cm of photosythetic system and in 0-20 cm of non-photosyntic system.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.1
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• pp.107-116
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• 2006

The main purpose of this study is to develop the greenhouse gas emission factor for power plant using bituminous coal. The power plant is a major source of greenhouse gases among the sectors of fossil fuel combustion, thus information of its emission factors is very essential to the establishment of control strategies for the greenhouse gas emissions. These emission factors derived in this study were compared with those of U. S. EPA, AGO and CCL. The $CO_{2}$ concentrations in the flue gas were measured using NDIR analyser and the GC-FID with a methanizer. The amount of carbon (C) and hydrogen (H) in fuel was measured using an elemental analyzer. Calorific values of fuel were also measured using a calorimeter. Caloric value of bituminous coal used in the power plants were 5,957 (as received basis), 6,591 (air-dried basis) and 6,960 kcal/kg (dry basis). Our estimates of carbon emission factors were lower than those of IPCC. The CO2 emission factors for the power plants using bituminous coal were estimated to be 0.791 Mg/MWh (by carbon contents and caloric value of the fuel) and 0.771 Mg/MWh (by $CO_{2}$ concentration of the flue gas). The $CO_{2}$ emission factors estimated in this study were $3.4\sim 5.4\%$ and $4.4\sim 6.7\%$ lower than those of CCL (2003) and U. S. EPA (2002).

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.4
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• pp.67-75
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• 1990

Performances of a total of 6 selected sediment transport formulas including Engelund & Hansen(EH)'s, Ackers & White(AW)'s, Yang(YN)'s, Brownlie(BR)'s, Karim & Kennedy (KK)'s, and Rijn(RJ)'s ones, which have been known to be relatively reliable, were tested using the 1,399 measured sediment discharge data points of the 20 rivers selected from Brownlie's compendium of sediment discharge. The calculated results were plotted with the input parameters such as the unit discharge, mean velocity, flow depth, energy slope, and median diameter respectively, and trend of each formula's performance was analyzed. These analyses revealed that, in general, EH's and RJ's formulas are more reliable, BR's, AW's, and KK's ones are moderately reliable, and YN's one is less reliable. AW's formula drastically overestimates sediment discharge for fine sediment(D<0.15mm), and YN's one under-estimates sediment discharge for streams with large water discharge(q>5 cms/m).

• Journal of Advanced Marine Engineering and Technology
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• v.35 no.5
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• pp.600-607
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• 2011

Recently, high carbon steel has become essential not only for shipbuilding parts, but also mass production. Its surface has been treated by carburizing, nitriding and induction hardening, but these existing treatments cause considerable deformation and increase the expense of postprocessing after treatment; furthermore, these treatments cannot be easily applied to parts that requiring the hardening of only a certain section. This is because the treatment cannot heat the material homogeneously, nor can it heat all of it. Laser surface treatment was developed to overcome these disadvantages, and when the laser beam is irradiated on the surface and laser speed is appropriate, the laser focal position is rapidly heated and the thermal energy of surface penetrates the material after irradiation, finally imbuing it with a new mechanical characteristic by the process of self-quenching. This research estimates the material characteristic after efficient and functional surface treatment using HPDL, which is more efficient than the existing CW Nd:YAG laser heat source. To estimate, microstructural changes and hardness characteristics of two parts (the surface treatment part, and parental material) are observed with the change of laser beam speed and surface temperature.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.3
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• pp.251-260
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• 2014

Biomass burning is one of the significant emission source of PM and CO, but a few studies are reported in Korea. Air pollutants emission from biomass burning such as wood stove and boiler, and wood-pellet stove and boiler were estimated in this study. Activity levels related to biomass burning such as fuel types, amount of fuel loading, and location and temporal variation were investigated by field survey over Korea. Fuel loadings were 14.9 kg/day for wood stove, 31.3 kg/day for wood boiler, 12.8 kg/day for wood-pellet stove, 32.5 kg/day for wood-pellet boiler during the season of active use. These were mostly burned in winter season from october to april of next year. Estimated annual emissions from wood stove & boiler were CO 76,677, $NO_x$ 710, $SO_x$ 70, VOC 20,941, TSP 6,605, PM10 2,921, PM2.5 1,851, and NH3 7 ton/yr, respectively. Emissions from wood-pellet stove and boiler were CO 32,798, $NO_x$ 1,830, $SO_x$ 25, VOCs 5,673, TSP 629, PM10 457, PM2.5 344, and $NH_3$ 2 ton/yr, respectively. When the emission estimates are compared with total emissions of the national emission inventory (CAPSS: Clean Air Policy Support System), Those occupy 12.5%, 2.8% of total national emission for CO and PM10, respectively. These results show wood and wood-pellet burning appliances were one of the major source of air pollution in Korea. In future, these types of heaters need to be regulated to reduce air pollution, especially in suburb area.

• Asian-Australasian Journal of Animal Sciences
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• v.11 no.1
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• pp.89-96
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• 1998

The experiment was conducted with 120 barrows weaned at 21 days of age to estimate their lysine requirement weaned at 21 days of age when other important amino acids were fortified to get optimal ratio to lysine. The treatments were 1.15% (control), 1.25%, 1.35%, 1.45%, 1.55%, 1.65% total lysine in the diet. Based on the growth performance total lysine requirement of 21-day old pigs appears to be 1.45%. The lowest digestibilities of dry matter and crude fat were found in pigs fed 1.15% total lysine diet and the highest were found in pigs fed 1.65% total lysine diet with no significant differences among treatments. Nitrogen digestibility increased as the total lysine level increased up to 1.35% (p < 0.05) and remained relatively constant beyond 1.35%. However, the best nitrogen digestibility was observed in pigs fed 1.45% total dietary lysine. Gross energy, crude ash and phosphorus digestibilities did not differ due to the increase in total lysine level. The amounts of excreted dry matter and nitrogen differed significantly by the increase in lysine level up to 1.35% (p < 0.05), while phosphorus excretion was not influenced by the lysine level. Dry matter and nitrogen excretion were reduced by 13.6% and 18.4%, respectively, when 1.45% lysine was offered to the pigs compared to the those fed on 1.15% lysine diet. The amino acid digestibilities increased as the total lysine level increased up to 1.45% (p < 0.05), and remained constant beyond 1.45%. The lysine requirement for the pigs weighing 6 to 14 kg seems to be higher than the previous estimates and in order to reduce pollutant excretion the accurate nutrient requirement should be set and applied to the animal.

• Asian Journal of Turfgrass Science
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• v.10 no.2
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• pp.105-115
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• 1996

To find out the mineral cycles of calcium, magnesium and sodium in dynamic grassland cosystems in a steady state condition, this investigation was conducted along the northwest side on Mt. Kwanak. The experimental results may he suromarized on the communities of a Zoysia japonica and a Miscanthus sinesis as follows. As compared with some properties of the surface soils among two semi-natural grasslands, cal- cium (Ca) was greater quantity in a Zoysia japonica, whereas, in a Miscanthus sicensis, sodium (Na)and magnesium (Mg) were greater in Mt. Kwanak. For the case of steady production and release, the ratio of annual mineral production to the amount accumulated on the top of mineral soil in a steady state provides the estimates of release constant k. The release constants of Ca, Mg and Na of the litter were 0.42, 0.25 and 0.29 in the Zoysia japonica grassland, and were 0.41, 0.54 arid 0.62 in the Miscanthus sinensis grassland, respect- ively. The half times of Ca, Mg and Na required for the release or accumulation of the litter on the grassland were 1.65, 2.77 and 2.39 in the Zoysia japonica, and were 1.69, 1.28 and 1.12 in the Miscauthus sinensis, respectively. The increasing order of the turnover parameters of the elements was Ca, Na and Mg in the Zoysia japonica grassland, and was Na, Mg and Ca in the Miscanthus Si nens is grassland. The amounts of annual cycles for Ca, Mg, Na in the grassland ecosystem under the steady-state conditions were 1.29, 0.20 and 0.12 g /m$^2$ in the Zoysia japonica grassland and 3.91, 1.04 and 0.61 g /m$^2$ in the Miscanthus sinensis grassland.

• Asian-Australasian Journal of Animal Sciences
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• v.18 no.9
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• pp.1209-1216
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• 2005

This study aimed to use field data collected by the Hokkaido Dairy Cattle Milk Recording and Testing programs to estimate genetic parameters for concentration of milk urea nitrogen (MUN) and predicted Digestive Crude Protein Percentage of requirement (DCPun). Edited data consisted of 5,797,500 test-day records of MUN and yields of milk, fat, and protein obtained from 783,271cows in Holstein herds in Hokkaido, Japan. Data were divided into four datasets; for the first, second, third and fourth lactations. Two analyses were performed on data from each lactation. First, ANOVA was used to estimate the significance of the effects of several environmental factors on MUN and DCPun, after absorbing the Herd-Test-Day (HTD) effects. The effects of DIM and age.season effects had significant impact on MUN and DCPun. The second used a multi-traits repeatability model (MTRM) to estimate heritabilities and genetic correlations of milk with MUN and DCPun. Heritability estimates for MUN and DCPun in the first, second, and third lactations were 0.21:0.16, 0.20:0.16, and 0.20:0.18, respectively. Genetic correlations for milk with MUN and DCPun in the first, second, and third lactations were 0.02 - 0.17, and -0.25 - -0.39, respectively. The results indicate that MUN and DCPun are possibly effective tools for improving the energy balance, but that the relationships between MUN and other economically important traits such as feed efficiency, metabolic disease and fertility are still necessary.