• Journal of Korean Society of Environmental Engineers
• /
• v.34 no.10
• /
• pp.671-677
• /
• 2012

In this study, the characteristics of emulsified fuel and engine emissions were studied with an engine dynamometer. In the results of physical property analysis, the margin of error of net calorific value and gross calorific value was ${\pm}0.5%$, were almost same theoretical calculation and results of physical property analysis test. In emulsified fuel, density and viscosity increased with increasing water contents. Emulsified fuel which is composed of water and Bunker-A was manufactured by using homogenizer and ultrasonic generator in $80^{\circ}C$. Phase separation did not take place in $20^{\circ}C$ and $50^{\circ}C$. In the results of engine dynamometer test, NOx concentration and smoke density were reduced with increasing water contents in using emulsified fuel. Total NOx could be reduced by about 41%, 10%, 32% and 28% at 1,000 rpm, 1,200 rpm, 1,500 rpm and 2,500 rpm respectively. Total smoke density was reduced to 42%, 65%, 70%, 62%, and 82% at 1,000 rpm, 1,200 rpm, 1,500 rpm, 2,000 rpm, and 2,500 rpm respectively.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.36 no.4
• /
• pp.405-412
• /
• 2012

In the MCFC power generation system, the combustor supplies a high temperature mixture of gases to the cathode and heat to the reformer by using the off-gas from the anode; the off-gas includes high concentrations of $H_2O$ and $CO_2$. Since a combustor needs to be operated in a very lean condition and avoid local heating, a catalytic combustor is usually adopted. Catalytic combustion is also generally accepted as one of the environmentally preferred alternatives for generation of heat and power from fossil fuels because of its complete combustion and low emissions of pollutants such as CO, UHC, and $NO_x$. In this study, experiments were conducted on catalytic combustion behavior in the presence of Pd-based catalysts for the BOP (Balance Of Plant) of 5 kW MCFC (Molten Carbonate Fuel Cell) power generation systems. Extensive investigations were carried out on the catalyst performance with the gaseous $CH_4$ fuel by changing such various parameters as $H_2$ addition, inlet temperature, excess air ratio, space velocity, catalyst type, and start-up schedule of the pilot system adopted in the BOP.

• Journal of the Korean Society for Railway
• /
• v.20 no.1
• /
• pp.1-10
• /
• 2017

Brake squeal noise has been a challenging problems for a long time. It is very annoying to passengers and residents near tracks. Two methods have been applied to reduce or eliminate brake squeal noise. One is to improve frictional materials; the other is to optimize the topology and structures of brake pads. In this study, we developed two kinds of brake pads; one is a pad whose frictional material is different from the KTX brake pad friction material; the other is a flexible pad that has the same frictional material as that of the KTX brake pad, but a different structure. Squeal noise and friction coefficients were measured and analyzed using a full-scale brake dynamometer. It was found that the dynamometer test can simulate the squeal noise of KTX trains at stations. The squeal frequency of the KTX at 4500Hz was exactly reproduced; this value of 4500Hz was one of the natural frequencies of the KTX brake disc. It was also found that the squeal noise depended on the caliper pressure, initial disc temperature and braking speed. The average friction coefficient was 0.35~0.45. The new pad lowered the squeal noise by 17.3~21.6dB(A).

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.21 no.5
• /
• pp.134-140
• /
• 2017

In this study, the flexural behavior of high strength concrete members with different curing condition of 90 MPa of compressive strength was investigated. Experimental parameters included normal and low temperature curing conditions, tensile steel amount and concrete compressive strength. 8 beam members were fabricated and flexural tests were carried out. Crack spacing, load-deflection relation, load-strain relation and ductility index were determined. Experimental results show that as the amount of rebar increases, the number of cracks increases and the crack spacing decreases. The higher the concrete strength, the smaller the number of cracks, but the effect is significantly smaller than the amount of rebar. As a result of comparison with the proposed average crack spacing in the design criteria, the experimental results are slightly larger than the results of the proposed formula, but the proposed formula does not reflect the concrete strength and curing conditions. The ductility index of normal temperature cured members was 3.36~6.74 and the ductility index of low temperature cured members was 1.51~2.82. The behavior of low temperature cured members was found to be lower than that of normal temperature cured members. As a result of comparing the ductility index with the existing studies similar to the experimental members, the ductility index of the high strength concrete member was larger than the ductility index of the ordinary strength concrete of the previous study. Further research is needed to understand more specific results.

• Journal of Wetlands Research
• /
• v.17 no.1
• /
• pp.38-44
• /
• 2015

In Korea, most rainfall events occur during summer which then leads to an increasing concern regarding high influx of non-point source pollutants since the pollutant loadings from these non-point sources are very significant. In particular, the first flush of roof-harvested rainfall is said to contain the most highest concentration of nutrients and heavy metals. Accordingly, it is important to develope the possible water quality management options in treating the contaminants and considering reclaimed water reuse. The rain garden could be one of suitable alternatives in addressing this issue. In this study, the development of an effective adsorption media and its application to a lab-scale rain garden was tested to evaluate the removal rate of various nutrient and organic matter (TN, TP, CODcr), and heavy metals (Cu, Cd, Pb). Results showed that carbonized peatmoss produced at higher temperature have better adsorption capacity as compared to the one produced at a lower temperature. When the carbonized peatmoss was applied as rain garden media, the highest removal of TN, TP, and CODcr was observed compared to no carbonized peatmoss applied rain garden. Therefore, this study showed that the carbonized peatmoss would be effectively applied to the rain garden for removing nutrients and heavy metals from roof-harvested rainwater.

• Journal of the Korean Institute of Gas
• /
• v.22 no.3
• /
• pp.7-12
• /
• 2018

Thermal NOx is generated in a high temperature environment in a combustion facilities. Exhaust gas recirculation method is widely used among various methods for reducing nitrogen oxides in combustion devices. In the present study, the computational fluid dynamic analysis was accomplished to elucidate the cold flow characteristics in the flue gas recirculation burner with both outlets opening. Because the reciculation pipes is installed toward the tangential direction, the swirling flow is formulated in the burner and the phenomenon of the reverse flow creation is detected at the center area of circular burner. We are confirmed that this is the similar trend with the burner with one side outlet closed. From the present study, it was seen that the recirculated inflow from both recirculated burner outlets increased by about 5% compared to the burner with one side outlet opening. At the outlet located at the exhaust gas recirculation pipe inlet(gas exit 1), the inlet flow was formed in the entire region. At the opposite outlet(gas exit 2), the total flow was discharged, but the center part of the burner was observed to have a reverse flow. The flow rate at the gas exit 2 was 3 ~ 5 times larger than the flow rate at the gas exit 1.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.12
• /
• pp.8408-8415
• /
• 2015

The purpose of this study is to propose and analyse new technology of structural elements design for Korean-style house(Hanok). Design of modern apartment building adopts many aesthetic elements from Hanok, however, these are only for the decorations of interior. In this study, projected Hanok eaves were studied in terms of the length of solar insolation. Inclined front slab system has been proposed utilizing sloping roof to an apartment building section. This system can provide the same sunshine radiation length and outside view to all levels of building to overcome the limitation of traditional hanok. It also can be applied to all residences the vertical garden concept of hanok. Inclined slab system showed 20% more efficient than flat slab system in terms of solar insolation length. This study also suggested a double deck slab system for not only reducing apartment floor impact noise but also connecting concept of traditional maru system in hanok. Double deck system reduces 66% of floor impact noise comparing with single deck slab of modern apartment buildings.

• Journal of the Korean Institute of Landscape Architecture
• /
• v.30 no.4
• /
• pp.28-36
• /
• 2002

The main purpose of this study was to estimate a new regression model to explain the relationship between urban forest and air temperature in summer, 2001. This study consists of two parts: correlation coefficient analysis and regression analysis. According to correlation coefficient analysis, thermal infra-red radiations of the major land use categories found significant difference in each category. However there were no significant relationship between the data (thermal infra-red radiation and NDVI) derived from Landsat-7 ETM+ image and air temperature at Automatic Weather Stations(AWSs). After estimating various regression models for summer air temperature, the final models were chosen. The final regression models consisted of two variables such as forest m and traffic facilities area. The regression models explained over 78% of the variability in air temperatures. The regression models with variables of forest area and traffic facilities area showed that the coefficient of the first variable was even more significant than the second one. However, the negative impact of the traffic facilities area was slightly greater than the positive impact of the forest area. Consequently, the effects of forest area and traffic facilities area were apparent to explain summer air temperature in Seoul. Therefore two policies have the most important implications to mitigate the summer air temperature in Seoul: to expand and to conserve the urban forest; and to change the Oafnc facilities'characteristics. The results from this study are expected to be useful not merely in informing the public that urban forest mitigates summer air temperahne, but in urging the necessity of budgets for trees and managing urban forests. It is recommended that field swey of summer air temperature be Performed for the vadidation of the models. The main purpose of this study was to estimate a new regression model to explain the relationship between urban forest and air temperature in summer, 2001. This study consists of two parts: correlation coefficient analysis and regression analysis. According to correlation coefficient analysis, thermal infra-red radiations of the major land use categories found significant difference in each category. However there were no significant relationship between the data (thermal infra-red radiation and NDVI) derived from Landsat-7 ETM+ image and air temperature at Automatic Weather Stations(AWSs). After estimating various regression models for summer air temperature, the final models were chosen. The final regression models consisted of two variables such as forest m and traffic facilities area. The regression models explained over 78% of the variability in air temperatures. The regression models with variables of forest area and traffic facilities area showed that the coefficient of the first variable was even more significant than the second one. However, the negative impact of the traffic facilities area was slightly greater than the positive impact of the forest area. Consequently, the effects of forest area and traffic facilities area were apparent to explain summer air temperature in Seoul. Therefore two policies have the most important implications to mitigate the summer air temperature in Seoul: to expand and to conserve the urban forest; and to change the traffic facilities'characteristics. The results from this study are expected to be useful not merely in informing the public that urban forest mitigates summer air temperature, but in urging the necessity of budgets for trees and managing urban forests. It is recommended that field survey of summer air temperature be Performed for the vadidation of the models.

• International Journal of Highway Engineering
• /
• v.11 no.2
• /
• pp.99-109
• /
• 2009

Fine-size exposed aggregate portland cement concrete pavements (FEACP) have surface texture of exposed aggregate by removing upper 2$\sim$3mm mortar of surface of which curing is delayed by using delay-setting agent. FEACPs have advantages of maintaining low-noise and adequate skid-resistance level during the performance period than general portland cement concrete pavements. It is necessary to ensure the durability environmental loading to prevent unexpected distress during the service life of FEACP. In the process of curing, volume change accompanied change in by moisture and temperature could be an important cause of crack in concrete to construct for successful FEACP, The use of chloride containing deicer may accelerate defects of concrete pavement, such as crack and scaling. This study aim to evaluate environmental loading resistance of FEACP, based on the estimation of shrinkage-crack-control-capability by moisture evaporation and scaling by deicer in freeze-thaw reaction.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.34 no.1
• /
• pp.135-143
• /
• 2014

This study classified abnormal sea surface temperature changes of the central pacific region according to three evolution patterns. Focusing on typhoons that affect the Korean Peninsula, the research analyzed typhoon's occurrence spot and track, change in the central pressure characteristics, and the characteristics of change in typhoon precipitation and the number of occurrences of heavy rainfall in the Nakdong River Basin. As a result of analysis, in case of prolonged-decaying years and symmetric-decaying years, typhoon-related summer rainfall and heavy rainy days appeared to be higher than long-term average. But in case of abrupt-decaying years, the pattern of general decrease appeared. This is because typhoon's occurrence spot is located comparatively near the Korean peninsula, typhoon's central pressure is high, and typhoon's route generally moves to Japan. As the outcome, this study is expected to reduce flood damage through analyzing the characteristics of typhoon's activity according to CP El Ni$\tilde{n}$o evolution patterns and the characteristics of local typhoon rainfall. In addition, it is expected to provide useful information for establishing adaptation and mitigation to climate change.