• Journal of Korean Society for Atmospheric Environment
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• v.16 no.5
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• pp.487-497
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• 2000

Spring time is a favorable season to be easily observed the Yellow Sand phenomenon in East Asia. In particular most of the phenomenon tend to occur in April. However, Yellow Sand phenomenon was observed from almost the whole country of Korea in winter of 1966, 1977 and 1999. The features of the synoptic weather pattern in the source regions, air stream flow between the source region and Korea, the measurement of TSP concentration, aerosol size distribution, and chemical composition of snow samples associated with Yellow Sand phenomenon were investigated. The result showed the characteristic evolutionary feature of the synoptic system associated with Yellow Sand phenomena, that is, a strong low level wind mobilized the dust within 2 or 3 days before Yellow Sand phenomenon being observed in Seoul. The wind was remarkably intensified in the source region on January 24, 1999 under the strong pressure gradient, A trajectory analysis showed that the Yellow Sand particle could be reached to Korea within 2 days from the source region, Gobi desert, through Loess plateau and Loess deposition region. The TSP concentration at the top of Kwanak mountain during the Yellow Sand phenomenon is abruptly increasing than the monthly mean concentration. The size resolved number concentration of aerosols ranging from 0.3 to 25${\mu}{\textrm}{m}$ was analyzed during Yellow Sand episode. It was evident that aerosols were distinguished by particles in the range of 2-3 ${\mu}{\textrm}{m}$ to result in the abrupt increase in January 1999, After Yellow Sand phenomenon, there was heavy snow in Seoul. By the analysis of snow collected during that time, it was observed that both the Ca(sup)2+ concentration and pH were increased abnormally compared to those in the other winter season.

• 한국연소학회:학술대회논문집
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• 2014.11a
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• pp.95-96
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• 2014

In this study, the nano-particle emitted from Gasoline Direct Injection(GDI) vehicles was measured using the Engine Exhaust Particle Sizer(EEPS) on a chassis dynamometer. In addition, driving mode were divided into cold start mode(CVS-75, NEDC) and hot start mode(NIER-6, NIER-9) to evaluated the characteristics in the various operating conditions. The Particle Number(PN) concentration was analyzed for various driving patterns, i.e., acceleration, deceleration, idling, cruising and the phases of mode. In a result, Total concentration of PN for size was concentrated from 50 to 100 nm and acceleration represents the highest concentration among the driving pattern. It is believed that the increases quantity of fuel, and mixture will be richer than other patterns.

• Particle and aerosol research
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• v.12 no.1
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• pp.21-26
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• 2016

In order to realize In-line and convenient measurement for solid-gas two phase flows, Light Transmission Fluctuation (LTF) based on the random variation of transmitted light intensity, light scattering theory and cross-correlation method was presented for online measurement of particle size, concentration and velocity. The statistical relationship among transmitted light intensity, particle size and particle number in measurement zone was described by Beer-Lambert Law. Accordingly, the particle size and concentration were determined from the fluctuation signal of transmitted light intensity. Simultaneously, the particle velocity was calculated by cross-correlation analysis of two neighboring light beams. By considering the influence of concentration variation in industrial applications, the improved algorithm based on spectral analysis of transmitted light intensity was proposed to improve measurement accuracy and stability. Therefore, the online measurement system based on LTF was developed and applied to measure pulverized coal in power station and raw material in cement plant. The particle size, concentration and velocity of powder were monitored in real-time. It can provide important references for optimal control, energy saving and emission reduction of energy-intensive industries.

• Asian Journal of Atmospheric Environment
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• v.4 no.3
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• pp.141-149
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• 2010

Aerosol size and number concentration were observed in the atmospheric boundary layer over Beijing (from near the ground to 1,200 m) on March 15 (a clear day) and 16 (a dusty day), 2005. The results were further compared with lidar measurements in order to understand the dependency of extinction on the particle size distribution and their vertical changes. The boundary layer atmosphere was composed of several sub-layers, and a dry air layer appeared between 400 and 1,000 m under the influence of dust event. In this dry air layer, the concentration of the fine-mode particles (diameter smaller than $1.0\;{\mu}m$) was slightly lower than the value on the clear day, while the concentration of coarse-mode particles (diameter larger than $1.0\;{\mu}m$) was remarkably higher than that on the clear day. This situation was attributed to the inflow of an air mass containing large amounts of Asian dust particles and a smaller amount of fine-mode particles. The results strongly suggest that the fine-mode particles affect light extinction even in the dusty atmosphere. However, quantitatively the relation between extinction and particle concentration is not satisfied under the dusty atmospheric conditions since laser beam attenuates in the atmosphere with high concentration of particles. Laser beam attenuation effect becomes larger in the relation between extinction and coarse particle content comparing the relation between extinction and fine particle content. To clarify this problem technically, future in situ measurements such as balloon-borne lidar are suggested. Here extinction was measured at 532 nm wavelength. Measurements of extinction at other wavelengths are desired in the future.

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.549-558
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• 1995

Mn-Zn ferrite granules were prepared by spray drying of the slurry containing different kinds and concentration of binders at various spray drying temperatures and atomizing pressures. The characteristics of the spraydried granules were analyzed according to the processing variables of spray drying and the slurries containing different solid loading and kinds and concentration of binders. Typical shape of the spray dried granules was spherical. The granules spray dried at 15$0^{\circ}C$ were more spherical and containing lower hollow percentage than any other granules prepared at higher temperature. The granules prepared at higher atomizing pressures were more spherical and become smaller in size. The granules prepared using slurry containing higher solid loading were larger in size and less defective in shape. As increasing the concentration of binder the number of donut-shaped granules was increased and the size distribution become broader. The granules prepared using the slurry containing PVA 205 were more spherical than those containing PVA 217 and PVA 117. As the amount of granules which were donut-shaped or dimpled increased the compaction response were less effective. The hollows were not fractured completely even at hight pressures and remained after sintering.

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.3
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• pp.153-159
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• 2007

Nano-Particles are influenced on the environmental protection and human health. The relationships between transient vehicle operation and nano-particle emissions are not well-known, especially for diesel passenger vehicles with DPF. In this study, a diesel passenger vehicle was measured on condition of DPF regeneration and no regeneration on a chassis dynamometer test bench. The particulate matter (PM) emission from this vehicle was measured by its number, size and mass measurement. The mass of the total PM was evaluated with the standard gravimetric measurement method while the total number and size concentrations were measured on a NEDC driving cycle using Condensation Particle Counter (CPC) and EEPS. Total number concentration by CPC was $1.5{\times}10^{1l}N/km$, which was 20% of result by EEPS. This means about 80% of total particle emission is consist of volatile and small-sized particles(<22nm). During regeneration, particle emission was $6.2{\times}10^{12}N/km$, was emitted 400 times compared with the emission before regeneration. As for the particle size of $22{\sim}100nm$ was emitted mainly, showing peak value of near 40nm in size. This means regeneration decreased the mean size of particles. Regarding regeneration, PM showed no change while the particle number showed about 6 times difference between before and after regeneration. It seems that the regeneration influences on particle number emissions are related to DPF-fill state and filtration efficiency.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.365-370
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• 2014

For real-time monitoring of colloidal nanoparticles (NPs) in aqueous media, a light sheet type dark-field microscopy system combined with a microfluidic concentration gradient generator (${\mu}FCGG$-LSDFM) was developed. Various concentrations of colloidal Au NPs were simultaneously generated with the iFCGG and characterized with the LSDFM setup. The number concentrations and hydrodynamic size distributions were measured via particle counting and tracking analysis (PCA and PTA, respectively) approaches. For the 30 nm Au NPs used in this study, the lower detection limit of the LSDFM setup was 3.6 ng/mL, which is about 400 times better than that of optical density measurements under the same ${\mu}FCGG$ system. Additionally, the hydrodynamic diameter distribution of Au NPs was estimated as $39.7{\pm}12.2nm$ with the PTA approach, which agrees well with DLS measurement as well as the manufacturer's specification. We propose this ${\mu}FCGG$-LSDFM setup with features of automatic generation of NP concentration gradient and real-time monitoring of their physicochemical characteristics (e.g., number concentration, and hydrodynamic size distribution) as an important component of future high-throughput screening or high-content analysis platforms of nanotoxicity.

• Journal of Forest and Environmental Science
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• v.30 no.2
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• pp.218-225
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• 2014

Studies were carried out to standardize and develop a suitable macro-propagation technology for large scale production of superior clonal stock through stem cuttings in Commiphora wightii Arnott (Bhandari), a data deficient medicinal plant of arid region. For the purpose, three experiments were conducted. The first experiment was tried to elucidate the impact of various cutting diameters (0.50-0.75 cm, 0.75-1.00 cm, 1.00-1.50 cm, and >1.50 cm) in combination with varying growing conditions (sunlight, shade house and mist chamber) on shoot sprouting and rooting without using exogenous plant growth regulators. Cutting diameter (size 0.75-1.00 cm) in mist chamber has shown maximum sprouting (90.00%) and rooting (73.33%), primary root (6.67) and secondary root (16.67) followed by 1.00-1.51 cm in mist chamber. Minimum sprouting (40.00%), rooting (33.33%), number of shoot (1.33), primary root (1.00) and number of secondary root (1.00) was recorded in cutting diameter (size >1.50 cm) in sunlight. Second experiment was performed to find out optimum growth regulator concentration of rooting hormone (100, 200, 500 and 1000 ppm) of Indole-3-acetic acid (IAA) and Indole-3-butyric Acid (IBA) on adventitious root formation on cuttings diameter (size 0.25-0.50 cm) in comparison to control. Maximum rooting percentage (93.33%) was recorded in 200 ppm followed by 500 ppm (86.66%) of IBA as compared to control, which showed only 60 per cent sprouting. Third experiment was performed with newly formed juvenile micro-cuttings treated with varying concentrations of IAA and IBA. The juvenile cuttings (size 6-10 cm, basal dia <0.25 cm) were selected as micro-cuttings. The cuttings treated with IBA (500 ppm) showed 64.30% rooting as compared to other treatments. Results of above experiments indicate that cuttings (size 0.75-1.00 cm dia) may be developed in mist chamber for better performance. While using heavier cuttings, no growth promoting hormones is required however; growth regulator 200 ppm concentration of IBA rooting hormone was observed optimum for promoting macro-propagation in stem cuttings of lower diameter class (0.25-0.50 cm).

• Asian Journal of Atmospheric Environment
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• v.6 no.4
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• pp.288-303
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• 2012

In this study, real time measurements of particle number size distribution in urban Gwangju, coastal Taean, and industrial Yeosu in Korea were conducted in 2008 to understand the occurrence of ultrafine particle (UFP) (<100 nm) events, the variation of its concentration among different sampling sites, and UFP formation pathways. Also, to investigate seasonal and long-term variation of the UFP number concentration, data were collected for the period of 5 years (2007, 2008, 2010, 2011, and 2012) in urban Gwangju. Photochemical and combustion events were found to be responsible for the formation of UFP in the urban Gwangju site, whereas only photochemical event led to the formation of UFP in the coastal Taean site. The highest UFP concentration was found in industrial Yeosu (the average UFP number fractions were 79, 59 and 58% in Yeosu, Gwangju, and Taean, respectively), suggesting that high amount of gas pollutants (e.g., $NO_2$, $SO_2$, and volatile organic carbon (VOC)) emitted from industries and their photochemical reaction contributed for the elevated UFP concentration in the industrial Yeosu site. The UFP fraction also showed a seasonal variation with the peak value in spring (61.5, 54.5, 50.5, and 40.7% in spring, fall, summer, and winter, respectively) at urban Gwangju. Annual average UFP number concentrations in urban Gwangju were $5.53{\times}10^3\;cm^{-3}$, $4.68{\times}10^3\;cm^{-3}$, $5.32{\times}10^3\;cm^{-3}$, $3.99{\times}10^3\;cm^{-3}$, and $2.16{\times}10^3\;cm^{-3}$ in the year 2007, 2008, 2010, 2011, and 2012, respectively. Comparison of the annual average UFP number concentration with urban sites in other countries showed that the UFP concentrations of the Korean sites were lower than those in other urban cities, probably due to lower source strength in the current site. TEM/EDS analysis for the size-selected UFPs showed that the UFPs were classified into various types having different chemical species. Carbonaceous particles were observed in both combustion (soot and organics) and photochemical events (sulfate and organics). In the photochemical event, an internal mixture of organic species and ammonium sulfate/bisulfate was identified. Also, internal mixtures of aged Na-rich and organic species, aged Ca-rich particles, and doughnut shaped K-containing particles with elemental composition of a strong C with minor O, S, and K-likely to be originated from biomass burning nearby agricultural area, were observed. In addition, fly ash particles were also observed in the combustion event, not in the photochemical event.

• Macromolecular Research
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• v.12 no.2
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• pp.233-239
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• 2004

We prepared thermally robust fully crosslinked poly(methyl methacrylate-co-divinyl benzene) ［poly(MMA-co-DVB)］microspheres successfully by precipitation polymerization in the absence of a stabilizing agent. The DVB concentration plays a pivotal role not only in the formation of the individually stable microspheres but also in the polymerization characteristics, including the particle size, the uniformity of size, the polymerization yield, and the thermal properties. The number-average diameter of the microspheres increased linearly, from 0.72 to 2.15 $\mu\textrm{m}$, and the particle size distribution became narrower, by elevating the uniformity from 1.35 to 1.12, as the DVB concentration increased from 20 to 75 mol%. In addition, the yield of the polymerization increased, from 73.4 to 98.6%, as the DVB concentration increased. Since the prepared particles possess fully crosslinked microstructures, no glass transition temperatures were observed, but all the samples prepared with DVB concentrations ranging from 20 to 75 mol% possess enhanced thermal properties. Based on the DSC and TGA data, the thermal stability of the mesospheres prepared by the precipitation polymerization is significantly improved as a result of crosslinking with DVB.