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Choi N.R.,Ewha Womans University | Lee S.P.,Chosun University | Lee J.Y.,Chosun University | Jung C.H.,Kyungin Womens College | Kim Y.P.,Ewha Womans University
Chemosphere | Year: 2016

Seventy three individual organic compounds in the atmospheric particulate matter with an aerodynamic diameter of less than or equal to a nominal 10 μm (PM10) over Seoul were identified and quantified from April 2010 to April 2011 using gas chromatography/mass spectrometry (GC/MS). These organic compounds were classified into five groups, n-alkanes, polycyclic aromatic hydrocarbons (PAHs), mono-carboxylic acids, di-carboxylic acids (DCAs), and sugars based on their chemical structures and properties. The organic compounds showed higher seasonal average concentrations from fall to winter than from spring to summer due to source strength, except some organic compounds among mono-carboxylic acids, DCAs, sugars such as undecanoic acid, methylmalonic acid, and fructose. Through qualitative data analysis using seasonal concentration variations and relevant diagnostic parameters, it was found that (1) anthropogenic sources such as combustion of fossil fuel and biomass burning attributed more to the formation of the organic aerosols than biogenic sources, and (2) the ambient level of n-alkanes, PAHs, and some compounds of DCAs and sugars was elevated in winter due to the increased primary emissions and larger transport from outside of the organic compounds in winter. © 2015 Elsevier Ltd. Source


Jung C.H.,Kyungin Womens College | Kim Y.P.,Ewha Womans University
Separation and Purification Technology | Year: 2013

The ideal cut of an aerosol separator should remove all particles larger than the cut diameter and allow particles less than the cut diameter to penetrate. However, it is impossible to obtain a true cut because generally, the aerosol separator shows a fractional efficiency curve with a slope, and these differences in efficiency lead to structural errors in aerosol separation [15,11,14]. This study adapts the generalized Lapple equation to describe the fractional efficiency of a cyclone and calculated the penetration efficiency through a PM2.5 collector. Sensitivity analysis for penetration error has been conducted between a real separation collector and an ideal collector. This study also derives an analytical approximated solution and shows that the approximated calculations agree very well with numerical results, especially for low geometric standard deviation and large slope parameter. Based on this measurement error calculation, the mass difference ratio of PM2.5 separator between different collectors with different slope parameter (β) and geometric mean diameter was compared. Subsequently, this study shows that conventional separators have different separation (penetration) efficiency even if their cut diameter is the same depending on the slope parameter and particle size distribution, calculates the bias with polydispersed aerosol size distributions with different slope parameter and shows an easy way to estimate the penetration error using analytical approximated solutions. © 2012 Elsevier B.V. All rights reserved. Source


Park Y.,OIC Language Visual Ltd. | Lee R.,Kyungin Womens College
Educational Technology and Society | Year: 2011

This study defines a blog as a contemporary web-based environment that can make a difference in adult informal learning practice. An online survey with 70 adult bloggers in Korea was undertaken to understand the nature of adults' blogging and its meanings in terms of learning. This study investigates (a) adults' blogging experiences related to learning, (b) bloggers' perceptions of the usefulness of blogging in terms of four perspectives on learning processes (i.e., learning as an acquisition process, a reflection process, a practice-based community process, and an embodied co-emergent process), and (c) the link between adult informal learning and blogging. The findings show that the majority of participants became aware of positive changes, including learning experiences, in everyday life after blogging. Among the four perspectives on learning processes, bloggers perceived blogging mainly as acquisition and/or reflection oriented learning process. Also, adult bloggers identified the characteristics of learning through blogging as 'self-directed,' 'practical,' 'situative,' 'unlimited and accessible,' and 'self-regulated,' which are distinguished from those of formal education in schools. This study therefore implies that the blog can be a meaningful learning environment and the blogging can be a significant factor in having the informal learning for adults more enriched and fulfilled. © International Forum of Educational Technology & Society (IFETS). Source


Bae S.Y.,Ewha Womans University | Jung C.H.,Kyungin Womens College | Kim Y.P.,Ewha Womans University
Journal of Aerosol Science | Year: 2010

An aerosol dynamics equation for the below-cloud scavenging process considering phoretic and electric charging effects in addition to the conventional mechanisms (the Brownian diffusion, interception, and impaction) is developed by using the moment method. Then, the dynamics of particle size distribution by the below-cloud scavenging process is calculated by using the developed equation and verified with the measurement data. The calculated particle size distribution changes are quite small compared to the measured changes. The calculated removal rate is smaller by 10-2-10-3 than the measured data when only the conventional mechanisms are considered. With the extended mechanisms, the scavenging coefficient increases upto 20 times, mainly for the particle size range of 0.1 μm Source


Jung C.H.,Kyungin Womens College | Lee S.S.,National Oceanic and Atmospheric Administration | Bae S.Y.,Prediction Institute | Kim Y.P.,Ewha Womans University
Aerosol and Air Quality Research | Year: 2013

This study found that the minimum collection efficiency particle diameter during precipitation is a function of rain intensity. The raindrop size distribution was parameterized with a log normal size distribution as a function of rain intensity, and the minimum collection efficiency and minimum collection efficiency diameter were obtained analytically. The results show that, during precipitation, both the minimum scavenging coefficient diameter and the minimum scavenging coefficient increase along with rain intensity. A comparison of the minimum collection efficiency diameters for various falling velocities reveals that there is not much of a difference in the diameters. Both the numerical and analytical results of this study agree well, without much loss of accuracy. © Taiwan Association for Aerosol Research. Source

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