• Journal of Environmental Health Sciences
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• v.32 no.3
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• pp.207-214
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• 2006

This study was designed to assess the level of nitrogen dioxide from several microenvironments including inside the home, outdoors near the home, inside the school, outdoors near the school, and on the road for 42 primary schoolchildren during the month of December 2002 in Seoul, Korea. The average personal, indoor, outdoor $NO_2$ levels, and indoor/outdoor ratio were 45.08 ppb, 27.89 ppb, 30.96 ppb, and 0.89, respectively. The indoor $NO_2$ concentrations were significantly associated with the presence of a smoker with a gas stove. The estimated personal $NO_2$ exposure using time-weighted average equation of $34.64{\pm}5.29$ ppb was significantly lower than the measured personal exposure of $45.08{\pm}5.50$ ppb. Our results indicate that indoor $NO_2$ levels were associated with the presence of a smoker and a gas stove. Moreover, personal $NO_2$ exposure with a gas stove in the house was significantly higher than those without a gas stove.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.481-487
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• 2010

The equivalent circuits intended to analyze the characteristics of IPT systems can be shown in structures similar to those of existing transformers. IPT systems are composed of combinations of the primary and secondary coils based on magnetic coupling, and the performances are determined by the lengths or the degrees of magnetic coupling of current collecting conductors(secondary) and feeding rails (primary) and system performances become the maximum when they are coupled under the optimum condition. To maximize the output currents of the secondary side, the shapes of iron cores and the structures of coils etc should be considered. To this end, three types of IPT system simulation models were selected and they were analyzed using an electromagnetic field analyzing program. To compare the types with each other, the sizes of the IPT systems and the primary side voltages etc were made to be the same. The electromagnetic fields were analyzed while changing the thicknesses of the cores and the lengths of the air gap etc and the results were analyzed in order to derive the optimum specifications.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.1008-1013
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• 2009

The theoretical simulation to predict the variation of supplying heat according to control methods of DHS(District Heating System) have been done by TRNSYS(A Transient System Simulation Program) 16. The physical system for DHS consists of primary and secondary supplying heating loop which is divided by based on heat exchanger for heating demand of building. The simulation results showed that control of secondary supplying heat had influenced more than primary supplying heat control to total energy consumption of DHS. And the outside temperature reset control of primary supplying heating loop could be reduced until about 4% overheating of each zone.

• Journal of the Korean Society of Visualization
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• v.10 no.2
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• pp.20-24
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• 2012

Increasing the active catalyst surface area is important in improving a converter's efficiency. In addition, uniform flow is advantageous in that it produces more efficient catalytic conversion. This results in the ability to use a smaller catalytic converter with uniform flow as opposed to a larger converter requirement for non-uniform flow. Therefore, it is important to characterize the internal flow of the catalytic converter. To characterize the system's flow patterns, velocity measurements were taken at the mid and exit planes of a ceramic honeycomb catalytic converter at flow rates of 37.8 l/s and 94.4 l/s. Measurements were conducted using LDV. The profiles were measured along both the major and minor axis of the planes. Primary flow direction velocities measured along the minor axis, at both flow rates, varied greatly at the mid plane and somewhat at the exit plane. The areas of greatest air flow were seen near the edges of the walls and on the side of the converter opposite the flow's entrance region. It also appears that the high velocities opposite the intake are due to the design of the entrance region. The entrance region is possibly too small to properly redirect the vertically entering fluid into an evenly distributed flow in the primary flow direction.

• The Bulletin of The Korean Astronomical Society
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• v.35 no.2
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• pp.58.1-58.1
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• 2010

Telescope Array (TA) experiment in Utah, USA, observes ultrahigh-energy cosmic rays (UHECRs); UHECRs refer cosmic rays with energy above $10^{18}eV$. Using COSMOS and CORSIKA, we have produced a library of over 1000 thinned extensive air shower (EAS) simulations with the primary energies ranging from $10^{18.5}eV$ to $10^{20.25}eV$ and the zenith angle of primary cosmic ray particle from $0^{\circ}$ to $45^{\circ}$. Here, we present the energy spectrum of particles arriving at the ground. We have also calculated the detector response evaluated using GEANT4 simulations. Here, we discuss S(800), i.e. the signal at a distance of 800 m from the shower core, as the primary energy estimator.

• The Plant Pathology Journal
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• v.28 no.2
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• pp.172-184
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• 2012

An infection risk model for Phytophthora blight on chili pepper was developed to estimate the first date of disease occurrence in the field. The model consisted of three parts including estimation of zoosporangium formation, soil water content, and amount of active inoculum in soil. Daily weather data on air temperature, relative humidity and rainfall, and the soil texture data of local areas were used to estimate infection risk level that was quantified as the accumulated amount of active inoculum during the prior three days. Based on the analysis on 190 sets of weather and disease data, it was found that the threshold infection risk of 224 could be an appropriate criterion for determining the primary infection date. The 95% confidence interval for the difference between the estimated date of primary infection and the observed date of first disease occurrence was $8{\pm}3$ days. In the model validation tests, the observed dates of first disease occurrence were within the 95% confidence intervals of the estimated dates in the five out of six cases. The sensitivity analyses suggested that the model was more responsive to temperature and soil texture than relative humidity, rainfall, and transplanting date. The infection risk model could be implemented in practice to control Phytophthora blight in chili pepper fields.

• Korean Journal of Materials Research
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• v.26 no.3
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• pp.123-129
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• 2016

The morphology, crystal structure and size of aerosol nanoparticles generated by erosion of electrodes made of different materials (titanium, copper and aluminum) in a multi-spark discharge generator were investigated. The aerosol nanoparticle synthesis was carried out in air atmosphere at a capacitor stored energy of 6 J, a repetition rate of discharge of 0.5 Hz and a gas flow velocity of 5.4 m/s. The aerosol nanoparticles were generated in the form of oxides and had various morphologies: agglomerates of primary particles of $TiO_2$ and $Al_2O_3$ or aggregates of primary particles of $Cu_2O$. The average size of the primary nanoparticles ranged between 6.3 and 7.4 nm for the three substances studied. The average size of the agglomerates and aggregates varied in a wide interval from 24.6 nm for $Cu_2O$ to 46.1 nm for $Al_2O_3$.

• Korean Journal of Materials Research
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• v.30 no.5
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• pp.223-230
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• 2020

As a case study on aspect ratio behavior, Kaolin, zeolite, TiO₂, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 mm media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D₅₀, ~6 ㎛ are shifted to submicron size, D₅₀ ~0.6 ㎛ after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

• Journal of the Korean Society of Propulsion Engineers
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• v.4 no.4
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• pp.1-8
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• 2000

For the purpose of a cost effective design of practical subsoni $c^ersonic ejector systems, an experiment was carried out using a superheated steam as a primary driving flow. The superheated steam jet was produced by several different kinds of subsonic and supersonic nozzles. The secondary flow of atmospheric air inside a plenum chamber was drawn into the primary steam jet. The vacuum performance of the plenum chamber was investigated for a wide range of the ejector operation pressure ratio. The result showed that the static pressure of the mixed flow at the ejector throat is only a function of the ejector operation pressure ratio, regardless of the primary nozzle type employed.ed.

• Particle and aerosol research
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• v.20 no.1
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• pp.13-24
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• 2024

The concentrations of polycyclic aromatic hydrocarbons (PAHs) and elemental carbon (EC) in particulate matter, typical primary aerosols have decreased in Seoul between 2003 and 2018 (80% for PAHs and 85% for EC). The yearly mean benzo[a]pyrene (BaP) concentration has been lower than 1 ng/m3 since 2010-2011, the target value set by the European Union (EU) and China. A series of policies related to solid fuel and vehicle in South Korea and China should be effective in the reduction of the ambient PAHs and EC concentrations. But the emission data of PAHs and EC at both countries did not support that hypothesis. Possible causes are uncertainties in the emission inventories of primary carbonaceous aerosols in South Korea and China, although there may be a minor effect of the emissions from North Korea on the concentrations in Seoul. Thus the further policy directions against PAHs and EC such as improvements of emissions inventories and measurements, intensive regulation of non-road mobile sources and control of PAHs derivatives are discussed.