• Journal of The Geomorphological Association of Korea
• /
• v.24 no.1
• /
• pp.63-76
• /
• 2017

This research was classified mountain areas with high ecological, environmental and resource value among the macro scaled terrain that can be checked at the space scale of less than 1:1,000,000 and analyzed the topographical characteristics. It has been confirmed that the mountains of the Korean peninsula belong to the groups IV, V, VI(classification by Kapos et al.(2000)) as a result of applying the quantitative standards for designation of mountain areas to the global mountain system. The area of mountains calculated using high resolution DEM is equivalent to 48% of the area of the Korean peninsula, and the result is quite different from the general idea of which 70% is the mountain area of the Korean peninsula. The mountain areas show the distribution of geomorphons, that is different from the plains and the hills and also, it shows the differences between the mountains of the groups IV~ VI classified according to the altitude. As a result of analyzing the relations among type pattern, slope, and relief, specific geomorphons are concentrated at $10^{\circ}$ and $20^{\circ}$ and it shows the possibility to classify the mountainous areas into two groups based on the result that the distribution of landform patterns are bimodal in the relation to the amount of relief.

• Nuclear Engineering and Technology
• /
• v.53 no.1
• /
• pp.79-92
• /
• 2021

Venturi tube is based on turbulent flow, whereby the microbubbles can be generated by the turbulent fragmentation. This phenomenon is common in several venturi bubblers used by the nuclear, aerospace and chemical industries. The first objective of this paper is to study the liquid-phase velocity field experimentally and develop correlations for the turbulent quantities. The second objective is to research velocity field characteristics theoretically. Stereoscopic PIV measurements for the velocity field have been analyzed and utilized to develop the turbulent kinetic energy in the venturi tube. The tracking properties of the tracer particles have been verified enough for us to analyze the turbulence field. The turbulence kinetic energy has a bimodal distribution trend. Also, the results of turbulence intensity along the horizontal direction is gradually uniform along the downstream. Both the mean velocity and the fluctuation velocity are proportional to the Reynolds number. Besides, the distribution trend of the mean velocity and the velocity fluctuation can be determined by the geometric parameters of the venturi tube. An analytical function model for the flow field has been developed to obtain the approximate analytical solutions. Good agreement is observed between the model predictions and experimental data.

• Korean Journal of Veterinary Research
• /
• v.6 no.1
• /
• pp.82-91
• /
• 1966

Studies On the myelinated fibers of the recurrent laryneal nerves were made in five, species of domestic animals namely dog, pig, goat, horse and Korean ox. Throughout the studies, the following characteristics of the myelinated fibers were obtained. 1. The number, size and cross sectional area of the myelinated fibers seemed to be proportionally related to the animal body weights. 2. The highest peak of diameter size frequency distribution of the myelinated fibers, observed at the right cranial level, in dog, goat and horse were 4-6 micron group, while in the case of Korean ox, 10-12 micron group was the highest. 3. The highest peak of diameter size frequency distribution of the myelinated fibers, observed at the right caudal level of Korean ox was 6-8 micron group, and 4-6 micron group was the highest in the other animals. 4. The highest peak of diameter size frequency distribution of the myelinated fibers obsered at the left cranial level was same to that of right cranial level. 5. The highest peak of diameter size frequency distribution of the myelinated fibers, observed at the left caudal levels in dog, goat, horse and Korean ox was 4-6 micron group, while in case of pig, $14-16{\mu}$ group was the highest. 6. The largest cross sectional areas were found in the group of 10-16 micron in all species of animals. 7. The fiber diameter size frequency distribution of recurrent laryngeal nerves of dog, goat, pig and horse were bimodal and Korean ox seemed to be a unimodal.

• Journal of Environmental Health Sciences
• /
• v.32 no.6
• /
• pp.543-555
• /
• 2006

During a twenty-day period in 2005, a nine-stage Andersen cascade impactor was used to determine the seasonal size distribution of atmospheric particles and its inorganic ion species sampled for 24hr in Iksan city, located southwest of the Korean peninsula. Samples were analyzed for major water-soluble ion species using Dionex-100 ion chromatograph. Average fine and coarse mass concentrations of atmospheric particles were, respectively, 31.4 and $82.6{\mu}g\;m^{-3}$ in spring and 35.8 and $73.4{\mu}g\;m^{-3}$ in fall-winter during the sampling period of 2005, while measurements of 69.8 and 9.9 were obtained in the sampling period of summer, The size distribution of particulate mass concentration during the non-Asian dust period was generally bimodal, whereas the size distribution of particulate mass concentration during the Asian dust period was unimodal due to the significant increase of coarse particles, which originated from long-range transport of soil dust particles from loess regions of the Asian continent. Among ionic species, $SO{_4}^{2-},\;NH{_4}^+,\;K^+$ were mainly distributed in fine particles due to their characteristics of emission sources and gas-to-particle conversion, while $Na^+,\;Mg^{2+}\;and\;Ca^{2+}$ were dominantly in coarse particles. However, $NO_3{^-}\;and\;Cl^-$ were distributed in both coarse particles and fine particles. Although $SO{_4}^{2-}$ was mainly distributed in fine particles, the size distributions of $SO{_4}^{2-}$ in coarse mode were significantly increased during the Asian dust events compared to those during the non-Asian dust period. $Ca^{2+}$ showed the most abundant species in the atmospheric particles during the Asian dust period. $NH{_4}^+$ was found to mainly exist as $(NH_4)_2SO_4$ in fine particles.

• Advances in nano research
• /
• v.7 no.2
• /
• pp.125-134
• /
• 2019

The Origanum vulgare L.-mediated synthesis of Ag nanoparticles was successfully realized within the present study. Various concentrations of the $AgNO_3$ used as a silver precursor (1, 2.5, 5, 10 and 100 mM) were used. Very rapid formation of Ag nanoparticles was observed, as only minutes were necessary for the completion of the reaction. With the increasing concentration, red shift of the surface plasmon resonance peak was observed in the Vis spectra. According to photon cross-correlation spectroscopy results, the finest grain size distribution was obtained for the 2.5 mM sample. The transmission electron microscopy analysis of this sample has shown bimodal size distribution with larger crystallites with 100 nm size and smaller around 10 nm. The antibacterial activity was also the best for this sample so the positive correlation between good grain size distribution and antibacterial activity was found. The in-depth discussion of antibacterial activity with related works from the materials science point of view is provided, namely emphasizing the role of effective nanoparticles distribution within the plant extract or matrix. The antibacterial activity seems to be governed by both content of Ag nanoparticles and their effective distribution. This work contributes to still expanding environmentally acceptable field of green synthesis of silver nanoparticles.

• Korean Journal of Materials Research
• /
• v.34 no.1
• /
• pp.27-33
• /
• 2024

Al₂O₃ has excellent sintering properties and is important in semiconductor manufacturing processes that require high-temperature resistance and chemical inertness in a plasma environment. In this study, a comprehensive analysis of the chemical characteristics, physical properties, crystal structure, and dispersion stability of three commercially available Al₂O₃ powders was conducted. The aim was to provide a technological foundation for selecting and utilizing appropriate Al₂O₃ powders in practical applications. All powders exhibited α-Al₂O₃ as the main phase, with the presence of beta-phase Na₂O-11Al₂O₃ as the secondary phase. The highest Na⁺ ion leaching was observed in the aqueous slurry state due to the presence of the secondary phase. Although the average particle size difference among the three powders was not significant, distinct differences in particle size distribution were observed. ALG-1SH showed a broad particle size distribution, P162 exhibited a bimodal distribution, and AES-11 displayed a uniform unimodal distribution. High-concentration Al₂O₃ slurries showed differences in viscosity due to ion release when no dispersant was added, affecting the electrical double-layer thickness. Polycarboxylate was found to effectively enhance the dispersion stability of all three powders. In the dispersion stability analysis, ALG-1SH exhibited the slowest sedimentation tendency, as evidenced by the low TSI value, while P162 showed faster precipitation, influenced by the particle size distribution.

• Journal of the Korean Vacuum Society
• /
• v.10 no.2
• /
• pp.275-281
• /
• 2001

We used the discrete-sectional model to analyze the particle growth by coagulation of particles in silane plasma reactor, considering the Gaussian distribution function for particle charges. The effects of process conditions such as monomer size and mass generation rate of monomers on particle growth in plasma reactor were analyzed theoretically/ Based on the Gaussian distribution function of particle charges, the large particles of more than 40 nm in size are almost found to be charged negatively, but some fractions of small, tiny particles are in neutral state or even charged positively. As the particle size and surface area increase with time by particle coagulation, the number of charges per particle increases with time. As the large particles are generated by particle coagulation, the particle size distribution become bimodal. The results of discrete-sectional model for the particle growth in silane plasma reactor were in close agreement with the experimental results by Shiratani et al. [3] for the same plasma conditions. We believe the model equations for the particle charge distribution and coagulation between particles can be applied to understand the nano-sized particle growth in plasma reactor.

• Journal of Korean Society for Atmospheric Environment
• /
• v.17 no.E1
• /
• pp.1-7
• /
• 2001

The elemental characteristics of atmospheric aerosols were investigated as a function of particle size and water solubility. The aerosol particles were samples at 12 individual size ranges between 0.01 and 30㎛. Collected aerosol particles were separated into both soluble and insoluble components. The concentrations of 15 elements in both components were determined by a PIXE analysis using a 2.0 MeV-proton beam. In general, the mass size distribution of particulate matter was represented as a bimodal distribution. The maximum rations of S in July and December were 5.5 and 3.8 %, and they appeared in the size range of 0.47∼1.17㎛(stage No. 6 or 7) . The ratios of a S at non-separated size were 3.1 and 2.2 % in July and December, respectively, On the other hand, the maximum rations of Si in July and December were 7.0 and 5.4% and they appeared in the size range of 5.1∼30㎛(stage No. 0∼2). The ratios of Si at the non-separated size were 2.1 and 1.8% in July and December, respectively, The mass diameter of 12 elements ranged between 0.59㎛ of S and 3.20 of Fe. More than 90% of atmospheric aerosols consisted of the light elements such as C, N, O, H and Al. The soluble component was dominant in the smaller size range and the insoluble component in the larger size range. Large portions of Si. Ti and Fe existed in insoluble state. By contrast, S, Cl, Ca, Zn and Br were dissolved in water.

• Journal of Environmental Science International
• /
• v.13 no.4
• /
• pp.377-387
• /
• 2004

This study has been performed to clarify the characteristics of temporal and spatial distribution of surface ozone concentration over Jeju Island, one of the cleanest areas in Korea with low emissions of air pollutants. Ozone data are monitored at four sites in Jeju Island. These monitoring sites are located at two urban area(referred to Ido and Donghong), coastal area(Gosan site) and forest site(Chuna site). Ozone data has been routinely collected at these sites for the late four years. The patterns of seasonal cycle of ozone concentrations at all stations show the bimodal with the peaks on spring and autumn and a significant summer minimum. However, the patterns of diurnal variations at rural station, i.e., Gosan and Chuna sites are considerably different to those at urban stations such as Ido and Donghong sites. The patterns of $\DeltaO_3$ variations are very similar with those of monthly mean ozone concentrations and $\DeltaO_3$ values are exceeded 30 ppb, at urban stations. This may be that urban stations are more influenced by local photochemical reactions rather than rural stations. In order to assess the potential roles of meteorological parameters on ozone formation, the meteorological parameters, such as radiation, temperature, and wind are monitored together with ozone concentrations at all stations. The relationships of meteorological parameters to the corresponding ozone concentration are found to be insignificant in Jeju Island. However, at Gosan and Donghong stations, when the sea breeze blew toward the station, the ozone concentration is considerably increased.

• Journal of Korean Society of Occupational and Environmental Hygiene
• /
• v.26 no.1
• /
• pp.30-37
• /
• 2016

Objectives: This study was performed to measure and evaluate the concentration, size distribution and fugitive emission of particulate matter from process operations at foundries. Methods: Particle matter was collected from three foundries, and samples were also collected from a background site for calculating the fugitive emission concentration of the foundries. For the collection of the samples, a Nanosampler cascade impactor was used. Results: The concentration of TSP in the samples collected from the three foundries was $0.675{\sim}1.222mg/m^3$, $PM_{10}$ was $0.525{\sim}1.018mg/m^3$ and $PM_{2.5}$ was $0.192{\sim}0.615mg/m^3$. The mass size distribution was bimodal or monomodal with maximum peak at two stage(size $2.5{\sim}10{\mu}m$). The mass median aerodynamic diameter(MMAD) was $1.80{\sim}3.98{\mu}m$. The fugitive emission concentration of TSP varies in the range of 0.65 to $1.21mg/m^3$, which exceeds the emission standard of fugitive dust($0.5mg/m^3$). Conclusions: Particle concentration and size is an important industrial hygiene factor to protect foundry workers. Furthermore, the presence of high emission of particulate pollutants has a significant negative impact on the ambient air of the study area. Therefore, it is important to improve both the process and prevention facility in oder to reduce particulate pollutants in foundries.