• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.275-278
• /
• 2005

In this study, the dynamic properties of a floor impact sound isolation pad expressed in terms of the natural frequency, the dynamic stiffness per unit area and the loss factor are measured by the resonant method. By using the measured dynamic properties, the vibration transmissibility diagram is obtained for each isolation pad, which is compared with the values tested by the impact sound sources at the room in an apartment. From the comparative results, it is found that the noise reduction Performances. of isolation pads are closely connected with the natural frequency and the dynamic stiffness per unit area.

• Korean Journal of Environmental Agriculture
• /
• v.34 no.1
• /
• pp.64-68
• /
• 2015

BACKGROUND: Heavy metals (Al, As, Cd, Cr, Cu, Li, Hg, Ni, Pb, and Zn) were analyzed to elucidate the impact of weir construction on their concentrations in sediments of Geum River, Korea. We also attempted to investigate the source of the heavy metals in sediments. METHODS AND RESULTS: For this study, sediments were collected from May through June in 2012. The concentrations of heavy metals except Hg were determined by inductively coupled plasma mass spectrometer, and Hg was measured by automatic mercury analyzer. More clay were accumulated in the furthest stations in the upstream direction starting from the weirs. Most of the heavy metals showed higher concentrations in the most upstream located station of Geumnam Weir. However, high concentrations were not observed in the most upstream stations of the other weirs. The concentrations of Hg and As were much higher in sediments of Gap Stream. CONCLUSION: Gap Stream may be a potential source for high deposits of As and Hg. Presence of the dams may not play an important role in controlling heavy metal concentrations in sediments. It is necessary to monitor heavy metal concentrations for a longer time period to study the effect of environmental changes on heavy metal distribution in Geum River.

• Journal of Welding and Joining
• /
• v.32 no.1
• /
• pp.47-52
• /
• 2014

Due to of high intensity, lower noise and easy controllability of the heat, induction heating system became well known. Induction heating method has been suggested as substitute for the gas heat source and adopted in the automation of curved hull forming system. In this study, an investigation was accomplished to find the effects on the change of material properties when the induction heating was applied on the mild steel plate. Plates were heated using weaving method to get sufficiently heat affected zone and then cooled with water or in the air. The mechanical properties of the heated plate were evaluated. As results, the tensile test, impact test and microstructures satisfied the class rule.

• KIEAE Journal
• /
• v.9 no.6
• /
• pp.81-87
• /
• 2009

The purpose of the present study is to establish structural noise analyzing method for apartments building floor with structural-acoustic coupling analysis modeling. Noise through floor in the room is recognized as a significant problem with the consequence that noise isolation technique has been studied in the various fields of industry. From among noise factors, resonance sound is the main reason for solid noise of the floor, which is occurred by mechanical vibrations of the acoustic boundary line and the change of velocity. To analyse this phenomenon, numerical computation methods are provided in many fields, In this study, evaluation method for slab is established using finite element method, and a case study for analyzing acoustic phenomenon was suggested. The results show that numerical method, especially F.E.M, has a good approximation to predict noise at floors.

• Journal of Korean Society on Water Environment
• /
• v.28 no.5
• /
• pp.676-685
• /
• 2012

As impermeable layer continues to increase with the urbanization process, direct input of nonpoint source pollutants into water bodies via stormwater has caused serious effects on the aquatic ecosystem. Potential applications of rain gardens are increasing not only as best management practices (BMP) for reducing the level of nonpoint source pollutants but also as an ecological engineering alternative for low impact development (LID). In this study, remediation performance of various planting types, such as a mixed planting system with shrubs and herbaceous plants, was assessed quantitatively to effectively manage stormwater and increase landscape applicability. The mixed planting system with Rhododendron lateritium and Zoysia japonica showed the highest removal performance of $76.9{\pm}7.6%$ and $58.4{\pm}5.0%$ for total nitrogen and $89.9{\pm}7.9%$ and $82.4{\pm}5.2%$ for total phosphorus at rainfall intensities of 2.5 mm/h and 5.0 mm/h, respectively. The mixed planting system also showed the highest removal performance for heavy metals. The results suggest that a rain garden with the mixed planting system has high potential applicability as a natural reduction system for nonpoint source pollutants in order to manage stormwater with low concentrations of pollutants and will increase water recycling in urban areas.

• Journal of the Korean Wood Science and Technology
• /
• v.30 no.3
• /
• pp.75-84
• /
• 2002

In order to find out impact insulation properties, various types of current radiant floor heating systems and light-framed floors that are used in light-framed residential buildings were evaluated for two types of impact sources at the same time. Sound Pressure Level (SPL) was different from each impact sources for those spectrum patterns and peaks. In case of light-framed floor framework, the excitation position and the assumed effective vibrating area have effects on sound pressure level but it is not considerable, and Normalized SPL was reduced for each frequency by increasing the bending rigidity of joist. The mortar layer in the radiant heating system had relatively high density and high impedance, therefore, it distributed much of the impact power when it was excited, and reduced the Normalized SPL considerably. Nevertheless, Increasing a thickness of mortar layer had little influence on SPL. Ceiling components reduced the sound pressure level about 5~25 dB for each frequency. Namely, it had excellent sound insulation properties in a range from 200 to 4,000 Hz frequency for both heavy and lightweight impact sources. Also, there was a somewhat regular sound insulation pattern for each center frequency. The resilient channel reduced the SPL about 2~11 dB, irrelevant to impact source. Consequently, current radiant floor heating systems which were established in light-framed residential buildings have quite good impact sound insulation properties for both impact sources.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2006.05a
• /
• pp.1425-1431
• /
• 2006

In this study, An analysis of correlation between the vibration transmissions and the dynamic characteristics for floor impact sound insulation materials through model test was carried out. As the results, the correlation coefficients between the vibration transmissions and the dynamic characteristics for floor impact sound insulation materials were over 0.8 at the heavy and light floor impact source and less dynamic stiffness was more effective in reducing the vibration transmission.

• Journal of Environmental Impact Assessment
• /
• v.16 no.2
• /
• pp.169-176
• /
• 2007

The paved areas in nonpoint source are highly polluted landuses because of high imperviousness and pollutant mass emissions, such as sand, cereals, and dust from vehicle activities. Most of them in highways are collected by cleaning trucks or discharged to the adjacent soil and water system through the drain ditch in stormwater. Therefore, it is necessary to investigate the relationship between water concentration and total pollutant loadings from the paved areas. From the experiment, CODcr concentration of the cleaning wastewater was 17 times greater than that of the stormwater runoff. Also, concentrations of heavy metals (Cu, Fe, Zn) were 1.3 to 1.5 times higher when compared to the stormwater runoff. While total discharged loadings was insignificant in the cleaning wastewater. In conclusion, these results provide some evidence that the stormwater runoff may be managed carefully to the aspect of total pollutant loadings and the cleaning wastewater may be handled cautiously with the pollutant concentrations in highways.

• Proceedings of the Korean Environmental Health Society Conference
• /
• 2004.06a
• /
• pp.92-106
• /
• 2004

Elemental dry deposition fluxes were measured using dry deposition plates from March to June 1998 in Seoul, Korea. During this spring sampling period several yellow sand events characterized by long-range transport from China and Mongolia impacted the area. Understanding the impact of yellow-sand events on atmospheric dry deposition is critical to managing the heavy metal levels in the environment in Korea. In this study, the measured flux of a primarily crustal metal, Al and an anthropogenic metal, Pb was used with two hybrid receptor models, potential source contribution function (PSCF) and residence time weighted concentration (RTWC) for locating sources of heavy metals associated with atmospheric dry deposition fluxes during the yellow-sand events in Seoul, Korea. The PSCF using a criterion value of the 75th percentile of the measured dry deposition fluxes and RTWC results using the measured elemental dry deposition fluxes agreed well and consistently showed that there were large potential source areas in the Gobi Desert in China and Mongolia and industrial areas near Tianjin, Tangshan, and Shenyang in China. Major industrial areas of Shenyang, Fushun, and Anshan, the Central China loess plateau, the Gobi Desert, and the Alaskan semi-desert in China were identified to be major source areas for the measured Pb flux in Seoul, Korea. For Al, the main industrial areas of Tangshan, Tianjin and Beijing, the Gobi Desert, the Alashan semi-desert, and the Central China loess plateau were found to be the major source areas. These results indicate that both anthropogenic sources such as industrial areas and natural sources such as deserts contribute to the high dry deposition fluxes of both Pb and Al in Seoul, Korea during yellow-sand events. RTWC resolved several high potential source areas. Modeling results indicated that the long-range transport of Al and Pb from China during yellow-sand events as well as non yellow-sand spring daytimes increased atmospheric dry deposition of heavy metals in Korea.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
• /
• 2005.05a
• /
• pp.387-390
• /
• 2005

Finite element method was applied to the vibration analysis of concrete slab system in apartment building. To save the time and cost the 2 dimensional finite element model was proposed. At first, experimental results show that sound peak components to influence the overall level and the rating of floor impact sound insulation were coincident with natural frequencies of the reinforced concrete slab. Second, there is linear relationship between the impact sound pressure level and vibration acceleration level. Third, 2 dimensional finite element model was enough to analyze the vibration analysis of floor structure system.