• Explosives and Blasting
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• v.19 no.3
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• pp.91-104
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• 2001

As in Korean environments with mountainous and hilly areas, the rock generally has to be removed in construction or civil engineering work in tunnelling or excavation for development in urban area. Explosives should be used for blasting, which may cause serious problems on local people for their claim for compensation due to ground vibration, noise. For safe and economic blasting, geology and engineering characteristics of rocks such as discontinuities of rock or weathering are very important factors, together with site characteristics for prediction of ground vibration. In this study, conducted were the detailed study for major rocks most widely distributed in the South-east area, in-situ geological survey, geological and geochemical analysis, and further laboratory uniaxial rock stress, seismic velocity of core samples together with in-situ seismic velocity measurements. Regulations on ground vibration and noise were reviewed for assessing their adaptabilities, and a total of 4,856 measured blasting vibration data were examined for enhancing the confidence level in estimating the predictive formulation using scaled distance statistically.

• Architectural research
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• v.11 no.2
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• pp.27-34
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• 2009

The purpose of this study is to investigate the problem of crack repair materials and methods in existing concrete structure and to propose the effective injection method on crack repair by packer type. The result of this study is as follows. It is investigated that the crack width in the inner matrix of concrete structure is decreased about 30-40% than that in the surface of the concrete structure. Also it is showed that the possibility which could be monolithic with injection part became higher if the injection part is installed near to surface of concrete on the punching method to vertical direction against crack area. The injection of repair material can be poured smoothly under about $10N/mm^2$ pressure on the condition that cracks are monolithic with injection part without dust by drill. The method which is effective injection for a repair material is the punching method in compliance with coredrill. But, the research continuously is necessary about minimum injection pressure.

• Journal of Korean Society for Atmospheric Environment
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• v.33 no.4
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• pp.306-318
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• 2017

Heavy diesel vehicles are one of major sources of urban fine dust in Korea and other developing countries. In this study, an auxiliary device assisting fuel atomization, which is called FAD (Fuel Activation Device), was closely reviewed through numerical simulation. As calculated, the diesel flow velocity passing across FAD increased up to 1.68 times, and it enhanced the cavitation effect which could improve the injected fuel atomization. Super cavitation phenomenon, which is the most important effect on nozzle injection, has occurred until the cavitation number (${\sigma}$) decreased from 1.15 to 1.09, and atomized droplets via a nozzle of which opening was $500{\mu}m$ distributed less than $200{\mu}m$ in sauter mean diameter (SMD).

• Proceedings of the KSRS Conference
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• v.1
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• pp.305-307
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• 2006

A multi-spectral photometer was set up as an NASA/AERONET site at Kinki University campus in Higashi-Osaka in 2002 for measuring urban aerosols. In addition, the SPM-613D (Kimoto Electric) commenced measurement of suspended particles matter (SPM) as $PM_{10}$ and $PM_{2.5}$ on March 15, 2004 at the same AERONET site. The obtained results revealed that the poor air quality of the Higashi-Osaka site is due not only to anthropogenic particles from local emissions, such as diesel vehicles and chemical industries, but also to dust particles brought from continental desert areas by large scale climatic conditions. To understand the characteristics of background atmosphere over Higashi-Osaka, we examined the relationship between $PM_{2.5}$ concentration and aerosol optical thickness (AOT) at a wavelength of 0.87 μm based on AERONET data for background atmosphere (AOT<0.2). We obtained a linear regression line between AOT and $PM_{2.5}$ concentration. Using the linear relationships between AOT and $PM_{2.5}$, we show ground-level concentrations of $PM_{2.5}$ of background atmosphere from Terra/MODIS satellite measurements.

• Journal of environmental and Sanitary engineering
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• v.1 no.1 s.1
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• pp.47-58
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• 1986

The underground living spaces have become one of the major environment of this decade in urban area. This study was carried out to examine contamination level for purpose of preservation of the pleasant underground environment. Three subway stations and three underground shopping centers in Seoul and two underground shopping centers in Busan were selected and surveyed by measuring gaseous pollutants $(SO_2,\; NO_2,\;CO,\;HC,\; HCHO,\;CO_2)$, dust, airborne microbes, and the other air condtions (temperature, humidity, air pressure, air flow, kata cooling power). These examined data were compared with four kinds of standard (building sanitation management, room air quality standards, occupational safety and health standards, ventilation equipment) as environmental hygiene.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.E1
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• pp.32-43
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• 2008

Source samples were collected to construct source profiles for 9 different source types, including soil, road dust, gasoline/diesel-powered vehicles, a municipal incinerator, industrial sources, agricultural/biomass burning, marine aerosol, and a coal-fired power plant. Seasonal profiles for 'Chinese aerosol', aerosols derived from the urban area of China, were reconstructed from seasonal $PM_{2.5}$ compositions reported in Beijing, China. Ambient $PM_{2.5}$ at a receptor site was also measured during each of the four seasons, from April 2001 to February 2002, in Seoul. The Chemical Mass Balance receptor model was applied to quantify source contributions during the study period using the estimated source profiles. Consequently, motor vehicle exhaust (33.0%), in particular 23.9% for diesel-powered vehicles, was the largest contributor affecting the $PM_{2.5}$ levels in Seoul, followed by agricultural/biomass burning (21.5%) and 'Chinese aerosol' (13.1%), indicating contributions from long-range transport. The largest contributors by season were: for spring, 'Chinese aerosol' (31.7%); for summer, motor vehicle exhaust (66.9%); and for fall and winter, agricultural/biomass burning (31.1% and 40.1%, respectively). These results show different seasonal patterns and sources affecting the $PM_{2.5}$ level in Seoul, than those previously reported for other cities in the world.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.761-772
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• 2020

This research investigated the meteorologically relevant characteristics of high PM_2.5 episodes in Busan. The number of days when daily mean PM₁₀ concentration exceeded 100 ㎍/㎥ and the PM_2.5 concentration exceeded 50 ㎍/㎥ over the last four years in Busan were 24 and 58, respectively. Haze occurrence frequency was 37.6% in winter, 27.4% in spring, 18.6% in fall, and 16.4% in summer. Asian dust occurrence frequency was 81.8% in spring, 9.1% in fall and winter, and 0% in summer. During summer in Busan, high PM_2.5 episode occurred under the following meteorological conditions. 1) Daytime sea breeze. 2) Mist and haze present throuout the day. 3) Anti-cyclone located around the Korean peninsula. 4) Stable layer formed in the lower atmosphere. 5) Air parcel reached Busan by local transport rather than by long-range transport. These results indicate that understanding the meteorological relevance of high PM_2.5 episodes could provide insight for establishing a strategy to control urban air quality.

• Journal of Environmental Science International
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• v.29 no.7
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• pp.749-760
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• 2020

This study investigates the characteristics of diurnal, seasonal, and weekly roadside and residential concentrations of PM₁₀ and PM_2.5 in Busan, as well as relationship with meteorological phenomenon. Annual mean PM₁₀ and PM_2.5 concentrations in Busan were 44.2 ㎍/㎥ and 25.3 ㎍/㎥, respectively. The PM_2.5/PM₁₀ concentration ratio was 0.58. Diurnal variations of PM₁₀ and PM_2.5 concentrations in Busan were categorized into three types, depending on the number of peaks and times at which the peaks occurred. Roadside PM₁₀ concentration was highest on Saturday and lowest on Friday. Residential PM₁₀ concentration was highest on Monday and lowest on Friday. Residential PM_2.5 concentration was highest on Monday and Tuesday and lowest on Friday. PM₁₀ and PM_2.5 concentrations were highest on Asian dust and haze, respectively. The results indicate that understanding the spaciotemporal variation of fine particles could provide insights into establishing a strategy to control urban air quality.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.E1
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• pp.45-48
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• 2006

Mass size distributions of atmospheric particles in Cheonan were determined using a high volume air sampler equipped with a 5-stage cascade impactor. Bimodal distributions that are typical for urban atmospheric particles were obtained. A MMD of the fine particle mode was $0.47{\pm}0.05{\mu}m$ with a GSD of $2.72{\pm}0.21$, and those of the coarse particles were $5.15{\pm}0.18{\mu}m\;and\;2.09{\pm}0.09$, respectively. The annual average concentrations of TSP, PM10, PM2.5, and PM1 were 74.1, 67.5, 54.2, and $42.3{\mu}g/m^3$, respectively. Although the daily PM10 concentrations were under the current National Standard, the daily PM2.5 concentrations frequently exceeded the US Standard even in non asian dust periods. The fractions of PM 10, PM2.5, and PM1 in TSP were $0.905{\pm}0.013,\;0.723{\pm}0.022,\;and\;0.572{\pm}0.029$, respectively, and fine mode particles occupied $57{\sim}72%$ of the total particle mass. The results indicate that fine particles were at the concerning level, and should be the target pollutant for the regional air quality strategy in Cheonan.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.1489-1497
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• 2009

The rectifier for Electric railway is one of the most important facilities in DC urban railway which converts power from KEPCO(AC 22.9kV) to the electric mil car(DC 1.5kV), therefore it should be managed as the best condition for the drive. There are several things to cause performance degradation and deterioration of parts such as pollutants occurred by it established under the ground such as dust or foreign substances, rapid changes of driving current, and pyrogen which put the rectifier for Electric railway in malfunction. On the flow of time, the rectifier for Electric railway is causing a malfunction or failure which drive electric rail car in operations as well as loss of life. In this research we try to find the way of removing the various components of mal-functions in the performance of the rectifier for Electric railway by Over-Haul and reform itself, which gives us to get the chance investment of the reduction, the reliability of power supply to the electric rail car.