• Environmental Analysis Health and Toxicology
• /
• v.20 no.2 s.49
• /
• pp.167-178
• /
• 2005

This study was carried out to evaluate the temporal, spatial, and seasonal variations of VOC, and to characterize the VOC concentrations in two large industrial complexes located in Pohang and Gumi cities. Twenty -four hours continuous sampling of selected VOC was made with STS 25 sequential tube samplers and double-bed adsorbent tubes. Air samples were collected every three hour interval for 7 consecutive days in each site during summer and winter. VOC were determined by thermal desorption coupled with GC/MS. A total of 27 VOCs of environmental concern were determined, including aliphatic, aromatic and halides. Generally. concentrations of toxic VOC were higher in Gumi than Pohang, and VOC levels in industrial areas were typically several-fold higher than those in residential areas. The most abundant VOC appeared to be toluene for both cities. However, chlorinated VOC were higher in Gumi than Pohang, while aromatic VOC were more abundant in Pohang than in Gumi. Two cities showed relatively different variations of VOC concentrations within a day. It is likely that traffic related sources are major factors affecting the VOC in Pohang, and industrial solvents usages are important sources in Gumi. These results imply that the occurrence and levels of atmospheric VOC are strongly dependent on the type of industries in each city. Therefore, in order to develop any control strategies or to establish the priority rankings for VOC in large industrial complexes, the type of industries and the occurrence of VOC in the atmosphere should be taken into consideration.

• Asian Journal of Atmospheric Environment
• /
• v.12 no.2
• /
• pp.153-164
• /
• 2018

We measured $^1H$ and $^{13}C$ nuclear magnetic resonance (NMR) spectra of Humic-like substances (HULIS) in urban atmospheric aerosols isolated by diethylaminoethyl (DEAE) and hydrophilic-lipophilic balance (HLB) resin to characterize their chemical structure. HULIS isolated by DEAE resin were characterized by relatively high contents of aromatic protons and relatively low contents of aliphatic protons in comparison with HULIS isolated by HLB resin, while the contents of protons bound to oxygenated aliphatic carbon atoms were similar. These results were consistent with the results of the $^{13}C$ NMR analysis and indicate that hydrophobic components were more selectively adsorbed onto HLB, while DEAE resins selectively retained aromatic carboxylic acids. Furthermore, we demonstrated that the chemical structural features of HULIS were significantly different between spring and summer samples and that these disparities were reflective of their different sources. The estimated concentrations of HULIS in spring were found to be regulated by vehicle emissions and pollen dispersion, while the behavior of HULIS in summer was similar to photochemical oxidant and nitrogen dioxide concentrations. The proportion of aliphatic protons for summer samples was higher than that for spring samples, while the proportion of aromatic protons for summer samples was lower than that for spring samples. These seasonal changes of the chemical structure may also involve in their functional expression in the atmosphere.

• KIEAE Journal
• /
• v.12 no.2
• /
• pp.65-75
• /
• 2012

The rapid urbanization caused drastic temperature changes in Korea. Excessive urbanization and development result in unpredictable and abnormal climate change all over the world. These changes are reflected in Korean government policy and research about cities, such that various research endeavors have been undergone recently. There are lots of ways to improve the urban environment; the easiest way to solve the urban heat effect problem is to make green spaces within the city. Even though we can't enlarge green spaces over the city limitlessly, it is desperately need for a methodology to efficiently create green space in limited area. Based on awareness of issues as mentioned earlier, we would like to propose landscaping method that can increase thermal comfort in the same area. For this study, simulating the change of temperature, mean radiant temperature, PMV were done due to number of species planted in apartment complex. To increase the reliability of the simulation, first above all, field measurement for temperature change was performed in apartment complex, where residential building are arranged in the form of ㄷ. And based on this data, Envi-met simulation was performed varying 1-7 kinds of species divided by grass, shrubs, arbor (deciduous, conifers) planted in apartment complex. As a result, there was a change less than $1^{\circ}C$ with the increasing number of species in daytime, but the average radiation temperature about $6-7^{\circ}C$ was reduced. In addition, PMV index was improved by more than 0.5 point. Thermal comfort indicator improved significantly depending on the number of species during the day, on the other hand, there were no significant changes at night. As a consequence, this study has shown that not single-species planting but mixed planting varied the number of species would improve the thermal comfort in the same area of landscaping space at daytime.

• The Journal of the Institute of Internet, Broadcasting and Communication
• /
• v.12 no.6
• /
• pp.189-197
• /
• 2012

In this paper, we propose an optimal path search algorithm that applies the received signal strength between a mobile device and a satellite. Because the common path search algorithm is only based on the shortest path search, it is difficult to provide stable multimedia services for the satellite mobile devices. The proposed algorithm provides the stable communication environment for the satellite mobile devices based on received signal strength. In Satellite communications, changes in the radio quality are severe depending on the receiving environment. Therefore, an accurate analysis of the receiving environment characteristics is very important for providing stable multimedia services of satellite communications. The causes of radio attenuation are atmosphere attenuation, vegetation attenuation and buildings attenuation. These factors were applied to analyze the received signal strength. The proposed algorithm can search the optimal path in urban for stable satellite multimedia services.

• Atmosphere
• /
• v.21 no.3
• /
• pp.229-241
• /
• 2011

The continuous urbanizations by a rapid economic growth and a steady increase in population are expected to have a possible impact on meteorology in the downwind region. Long-term (1972~2007) trends of precipitation have been examined in the mid-Korean peninsula for the westerly condition only, along with the sensitivity simulations for a golden day (11 February 2009). During the long-term period, both precipitation amount (PA) and frequency (PF) in the downwind region (Chuncheon, Wonju, Hongcheon) of urban area significantly increased for the westerly and light precipitation ($PA{\leq}1mm\;d^{-1}$) cases, whereas PA and PF in the mountainous region (Daegwallyeong) decreased. The enhancement ratio of PA and PF for the downwind region vs. urban region remarkably increased, which implies a possible urbanization effect on downwind precipitation. In addition, the WRF simulation applied for one golden day demonstrates enhanced updraft and its associated convergence in the downwind area (about 60 km), leading to an increase in the cloud mixing ratio. The sensitivity experiments with the change in surface roughness demonstrates a slight increase in cloud water mixing ratio but a negligible effect on precipitation in the upwind region, whereas those with the change in heat source represents the distinctive convergence and its associated updraft in the downwind region but a decrease in liquid water, which may be attributable to the evaporation of cloud droplet by atmospheric heating induced by an increase in an anthropogenic heat. In spite of limitations in the observation-based analysis and one-day simulation, the current result could provide an evidence of the effect of urbanization on the light precipitation in the downwind region.

• Atmosphere
• /
• v.27 no.1
• /
• pp.67-77
• /
• 2017

In this study, we analyzed the characteristics of flow around the Daeyeon automatic weather station (AWS 942) and established formulas estimating inflow wind speeds at a computational fluid dynamics (CFD) model domain for the area around Pukyong national university using a computational fluid dynamics (CFD) model. Simulated wind directions at the AWS 942 were quite similar to those of inflows, but, simulated wind speeds at the AWS 942 decreased compared to inflow wind speeds except for the northerly case. The decrease in simulated wind speed at the AWS 942 resulted from the buildings around the AWS 942. In most cases, the AWS 942 was included within the wake region behind the buildings. Wind speeds at the inflow boundaries of the CFD model domain were estimated by comparing simulated wind speeds at the AWS 942 and inflow boundaries and systematically increasing inflow wind speeds from $1m\;s^{-1}$ to $17m\;s^{-1}$ with an increment of $2m\;s^{-1}$ at the reference height for 16 inflow directions. For each inflow direction, calculated wind speeds at the AWS 942 were fitted as the third order functions of the inflow wind speed by using the Marquardt-Levenberg least square method. Estimated inflow wind speeds by the established formulas were compared to wind speeds observed at 12 coastal AWSs near the AWS 942. The results showed that the estimated wind speeds fell within the inter quartile range of wind speeds observed at 12 coastal AWSs during the nighttime and were in close proximity to the upper whiskers during the daytime (12~15 h).

• Atmosphere
• /
• v.25 no.4
• /
• pp.685-692
• /
• 2015

In this study, the effects of trees on flow and scalar dispersion in an urban street canyon were investigated using a computational fluid dynamics (CFD) model. For this, we implemented the drag terms of trees to the CFD model, and compared the CFD-simulated results to the wind-tunnel results. For comparison, we considered the same building configuration as the wind-tunnel experiment. The trees were located at the center of street canyon with the aspect ratio (defined as the ratio of the street width to the building height) of 1. First, the flow characteristics were analyzed in the tree-free and high-density tree cases and the results showed that the CFD model reproduced well the flow pattern of the wind-tunnel experiment and reflected the drag effect of trees in the street canyon. Then, the dispersion characteristics of scalar pollutants were investigated for the tree-free, low-density tree and medium-density tree cases. In the tree-free case, the nondimensionalized concentration distribution simulated by the CFD model was quite similar to that in the wind-tunnel experiment in magnitude and pattern. The correlation coefficients between the measured and simulated concentrations are more than 0.9 in all the cases. As the tree density increased, nondimensionalized concentration increased (decreased) near the wall of the upwind (downwind) building, which resulted from the decrease in wind speed case by the drag effect of trees. However, the CFD model underestimated (overestimated) the concentration near the wall of upwind (downwind) building.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.14 no.4
• /
• pp.126-132
• /
• 2010

Carbonation is the results of the interaction of carbon dioxide gas in the atmosphere with the alkaline hydroxides in the concrete. Reinforced steel corrosion due to concrete carbonation is one of main factors on the decrease in durability of RC structure. This study investigates the influence of carbonation on the bridges under various environment condition and quantifies the effect of carbonation various domestic field data. The failure probability of durability is evaluated on the basis of reliability concept. In addition, service life of the structures is predicted based on the intended probability of durable failure in domestic concrete specification. According to experimental results of the carbonation depth, the carbonation depth increased with structural age. It is analyzed that carbonation velocity of the structures under urban area and sea condition is 1.6-1.9 times faster than the river condition. Service life of the bridges under urban area and sea condition is decreased about 2.4-3.3 times than river condition.

• Fire Science and Engineering
• /
• v.30 no.5
• /
• pp.26-35
• /
• 2016

Sprinkler installations shall be operated at normal operating temperature of the atmosphere as a fire sprinkler head in any facility to control and extinguish the fire when the fire initially. Recently, however, some flush type quick response automatic sprinkler heads in slow fire place is a problem that can not be normal operation are raised. In this paper, by using the experimental model of the Apartment house of Commons and Cabinet burner size bedrooms fire conditions to form a slow growth rate and can supply more than 0.2 MPa pressure is the minimum pressure that can be applied inside the pipe in the field experiment was conducted. In the majority of experiments lush type quick response automatic sprinkler heads which is used in the country it was confirmed to be incompletely opened as the Cold Soldering occur. This phenomenon is likely to fail early fire suppression and control because they can cause the spread of fire and casualties needed to complement domestic product testing and type approval standards through additional research.

• Atmosphere
• /
• v.24 no.2
• /
• pp.225-234
• /
• 2014

Analysis of the cause of death (Statistics Korea) showed that heat wave caused 442 deaths (21 per a year) from 1991 to 2011 in Korea. The number of summer heat-related deaths (heat disorders) increased exponentially as heat wave prolonged. In 1994 when the extreme heat wave prevailed, there were 92 heat-related deaths. Seasonally, heat-related deaths occurred most frequently in early August when air temperature is highest for a year, but it is frequent as well in late July when air temperature increases rapidly after withdrawal of Changma. The frequency of deaths by age has begun to increase from 40s and more than half of total deaths were occurred in the elderly (${\geq}60$). Except retired elderly, the most vulnerable group (job and age) was the elderly agricultural workers and the next was the jobless people in 40 s~50 s, assumed as homeless people. The most vulnerable regions were Hapcheon-gun, Uiryong-gun, and Sanchen-gun, which are inland rural area in Gyeongsang-do where the heat wave occurs most frequently in Korea. The heat-related death rate increased rapidly when air temperature exceeded $33^{\circ}C$ in both of the urban and rural area. Interestingly, the heat-related death were observed in the relatively lower temperature in the cities ($29^{\circ}C$), as compare to the rural area ($31^{\circ}C$).