• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.1
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• pp.149-155
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• 2013

In this study, factors that affect the air entrainment within a closed conduit by air drawn in through an air vent are investigated using a hydraulic scale model, which represents a gated circular conduit system connected to the intake tower of an irrigation reservoir. In addition, using data obtained during the hydraulic experiments, experimental equations are developed to estimate the amount of air drawn in through the air vent. In case of pressurized flow conditions downstream of hydraulic jumps, the relationships between $\frac{Q_a}{Q_w}$ and $Fr_g-1$ of the data form a experimental equation, $\frac{Q_a}{Q_w}=0.0304(Fr_g-1)^{1.0622}$; in case of free surface flow conditions, $\frac{Q_a}{Q_w}=0.0271(Fr_g-1)^{1.8205}$. Comparing two data sets observed under the two flow regimes with the results of previous researchers, patterns of the data sets are similar to the results estimated using the equations presented previously, and this indicates that the quality of the data obtained during the hydraulic experiments is ensured. In addition, it is revealed that air entrainment phenomena in the regions close to air vents are affected by the characteristics of supercritical flows downstream of gates. Finally, it is concluded that the equation developed for pressurized flow conditions can be applied to design of air vents.

• Journal of Environmental Health Sciences
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• v.49 no.1
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• pp.30-36
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• 2023

Background: Among various pollutants, fine particle (PM_2.5, defined as particle less than 2.5 nm in aerodynamic diameter) shows the most consistent association with adverse health effects. There is scientific evidence documenting a variety of adverse health outcomes due to exposure to PM_2.5. Objectives: This study aims to assess the health benefits of that would be achieved by meeting the World Health Organization's air quality guidelines for PM_2.5 using AirQ+ and BenMAP. Methods: We estimated PM_2.5 related health benefits in Korea from implementing the World Health Organization's air quality guidelines (annual average 5 ㎍/m³ and 10 ㎍/m³) and Korea's National Ambient Air Quality Standard (annual average 15 ㎍/m³). We used World Health Organization's AirQ+ and U.S. Environmental Protection Agency's Environmental Benefits Mapping and Analysis Program. Results: The annual number of avoided PM_2.5 related premature deaths exceeding WHO guideline levels was assessed using both AirQ+ and BenMAP. We estimated that the health benefits of attaining the World Health Organization's air quality guidelines for PM_2.5 (annual average 5 ㎍/m³) would suggest an annual reduction of 26,128 (95% confidence interval [CI]: 17,363~34,024) and 26,853 (95% CI: 18,527~34,944) premature deaths. Conclusions: Our study provided useful information to policy makers and confirms that the reduction of PM_2.5 concentration would result in significant health benefits in Korea.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.11a
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• pp.387-388
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• 2008

This paper presents the design approach and test results of the Q-band precision subminiature coaxial adaptor based on transmission line theory using multi-step impedance and air-holes to increase its cutoff frequency. In order to increase the frequency performance, the adaptor is designed with hooked structure, fixing step, multi-air-holes, and outer conductor. The return loss increments due to the hooked structure and multi air-holes are minimized to 2 dB and 1.5 dB, respectively. A VSWR(Voltage Standing Wave Ratio) of <1.2 is obtained from DC to 40 GHz, while guaranteeing the durability of the adaptor from room-temperature$(25^{\circ}C)$ to $120^{\circ}C$.

• Animal cells and systems
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• v.6 no.1
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• pp.59-64
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• 2002

To restore the forest ecosystem severely damaged by air pollution around industrial complexes, plants tolerant to the polluted environment were selected by transplant and pot culture experiments. A restoration plan by arranging those tolerant species was prepared based on the ecological diagnostic results on an area that requires restoration. Transplant experiment in Ulsan and Yeocheon areas, the representative industrial complexes in Korea, selected eight tolerant species of Quercus aliena, Q. acutissima, Q. dentata, Q. mongolica, Q. serrata, Ligustrum japonicum, Styrax japonica, and Poncirus trifoliata. Cultivation in the polluted soil transported from the Ulsan and Yeocheon industrial complexes chose five tolerant plants of Q. aliena, Q. acutissima, Q. serrata, Styrax japonica, and Alnus firma. A plan to restore the forest ecosystem of Mt. Dotjil, which experienced the severest ecosystem degradation in the Ulsan industrial complex, was prepared by applying those tolerant species along with treatment for soil amelioration. Arrangement of the tolerant species was designed by considering their ecological characteristics including distribution range on topography and shade tolerance. Soil amelioration was focused on the improvement of fertility and moisture conditions.

• Journal of Korean Society on Water Environment
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• v.25 no.6
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• pp.896-901
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• 2009

In this study, in order to apply the air and pure oxygen in the Jet Loop Reactor (JLB) in which the oxygen transfer rate is high, differentiate the operation mode according to each air flowrate and liquid flowrate and investigate the oxygen transfer characteristic, an experiment was carried out. The oxygen concentration with the air flowrate ($Q_g$) and liquid flowrate ($Q_L$) was identical but the oxygen transfer coefficient ($K_L{\cdot}a$) is linear depending on degree of two factors. The width of an increase is small in $0.1min^{-1}$ when the air flowrate is 0.2 L/min with increasing the liquid flowrate. Whereas, the increment was exposed to be very high for $1.5min^{-1}$ when the air flowrate was 5 L/min. In the experiments using the pure oxygen, it was 30 mg/L of oxygen concentration finally and it was 3.5 times than using the air. But the time reached the saturated concentration was similar to using the air, and $K_L{\cdot}a$ was similar to using the air too. Analysis between two independent variable and oxygen transfer of the correlation is the same model like $K_L{\cdot}a={0.0161Q_L}^{1.5371}{Q_g}^{0.5433}$ using with coefficient non linear regression analysis. It was resulted that the liquid flowrate were approximately three times than air flowrate on effect to oxygen transfer rate.

• Journal of the Korean Society of Clothing and Textiles
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• v.15 no.4 s.40
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• pp.367-372
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• 1991

In this study, we discussed about the factors effected upon the initial maximum value of heat flux ($q_{max}$). Thermal conductivity, thermal transmittance and surface air cavity of wool fabrics were examind and their correlation to the $q_{max}$ was studied. The factors were examined which had an effect upon the $q_{max}$ of an objective measure of warm/cool feeling. It was simulated by Thermo-Labo apparatures. We selected twenty sorts of pure wool woven fabrics for men's fall -winter cloth (all Wool). The conclusions are as follows; 1. There was not a certain correlation between the $q_{max}$ and the thermal conductivity of wool fabric. 2. When the fabrics touched on the copper plates, the thickness of wool fabric had a negative correlation to the $q_{max}$. The thermal transmittance had a positive correlation. Both of them had a good correlation to the $q_{max}$. 3. As a major factor, the thickness of fabric effected on the $q_{max}$.

• Korean Journal of Environment and Ecology
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• v.24 no.6
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• pp.648-656
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• 2010

Global warming brings changes of natural ecosystems and affects on the plant growth response. Quercus acutissima and Q. variabilis are taxonomically similar and dominant native species in deciduous forests in South Korea. In order to understand the growth response of Q. acutissima and Q. variabilis to global warming condition, we cultivated the seedling of the two oak species in ambient condition(control) and treatment with elevated $CO_2$(700~800ppm) and increased air temperature(approximately $3^{\circ}C$ above than control). Then we measured the growth characteristic among them and analyzed the relationship between two species using PCA ordination. Stem length and total plant weight of Q. acutissima were significantly affected by elevated $CO_2$ concentration and increased air temperature. Stem diameter and weight of Q. variabilis were significantly affected by elevated $CO_2$ concentration and increased air temperature(p<0.05). The variation characteristics of Q. acutissima were changed more than Q. variabilis by elevated $CO_2$ concentration and increased air temperature. These result suggested that Q. acutissima was more sensitive to global warming situation than Q. variabilis in central region of Korea. PCA ordination showed that two species were arranged by two distinct groups based on 10 characters by elevated $CO_2$ and increased air temperature.

• Asian Journal of Atmospheric Environment
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• v.7 no.4
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• pp.227-233
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• 2013

Scientific evidence shows that ambient air quality is one of the major environmental issues related to human health. The aim of this paper was to provide quantitative data on the short-term impact of air pollution on the mortality and morbidity of people living in Suwon city. There are some studies that have conducted health impacts of the air pollution in Seoul, Korea. However, there are few studies of the health effects on air pollution conducted in satellite cities of the Seoul Metropolitan area. For this reason, we investigated the health effects of air pollution in Suwon city, one of the highly populated satellite cities of Seoul. In order to estimate the short-term mortality impact of air pollution, this study applied the approach suggested by the World Health Organization (WHO), using AirQ2.2.3 software. Daily concentrations of $PM_{10}$, $O_3$, $NO_2$, and $SO_2$ were used to assess human exposure and health effects, in terms of attributable proportion of the health outcome, annual number of excess cases of mortality for all causes, and cardiovascular and respiratory diseases. Among the four considered air pollutants, $PM_{10}$ had the highest health impact on the 1,118,000 inhabitants of Suwon city, causing an excess of total mortality of 105 out of 4,254 in a year. Sulfur dioxide had the least health impact. Ozone and nitrogen dioxide each caused 42.7 and 81.3 excess cases of total mortality in a year. The results are also in line with those of other international studies that apply AirQ software.

• Clean Technology
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• v.23 no.2
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• pp.205-212
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• 2017

We investigated the performance of a jet loop reactor (JLR) with the two-fluid venturi-type swirl nozzle (TVSN) during experiment for ammonia removal by air stripping from a synthetic wastewater, and compared it with that of a JLR with the two-fluid venturi-type conventional nozzle (TVCN), with the variation of pH, liquid circulation rate ($Q_L$), and air flow rate ($Q_G$). Their performance levels were compared based on the ammonia removal efficiency and overall mass transfer coefficient ($K_La$). Investigated parameters in a JLR were pH (10-12), air flow rate ($Q_G=5-20L\;min^{-1}$), and liquid circulation rate ($Q_L=25-35L\;min^{-1}$). Throughout the experiment, the ammonia removal efficiency and $K_La$ in a JLR with TVSN was higher than in a JLR with TVCN. This may be due to the enhanced turbulent intensity by swirling flow formed in the JLR with TVSN compared to that with TVCN. Further, we obtained higher $K_La$ when pH, $Q_L$ and $Q_G$ were increased. In particular, $K_La$ was increased more efficiently by increasing $Q_G$ than by increasing pH and $Q_L$.

• Journal of the Korean Magnetics Society
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• v.6 no.3
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• pp.179-188
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• 1996

This paper discussed on the impedance analysis of the planar air core inductors having spiral pattern and meander pattern. The width and distance of conductor, and number of turns were varied. As the width of conductor increased, both resistance and inductance decreased and there existed an maximum value in Q for spiral pattern. But Q increased with increasing width of conductor in meander pattern. In spiral pattern, there existed a distance between conductors where inductance became constant and Q became maximum, while the distance between conductors must be as large as possible to obtain large Q because the mutual inductance of meander pattern inductor has negative sign due to opposite current direction at adjacent conductor. Resistance and inductance increased with increasing the number of turns. There existed maximum Q at certain number of turns in spiral pattern. But Q became small in the meander pattern because increase of resistance was larger than increase of inductance with increasing number of turns.