• Progress in Superconductivity and Cryogenics
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• v.24 no.3
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• pp.19-23
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• 2022

We have been developing a magnetic separation device that can be used in low magnetic fields for paramagnetic materials. Magnetic separation of paramagnetic particles with a small particle size is desired for volume reduction of contaminated soil in Fukushima or separation of iron scale from water supply system in power plants. However, the implementation of the system has been difficult due to the needed magnetic fields is high for paramagnetic materials. This is because there was a problem in installing such a magnet in the site. Therefore, we have developed a magnetic separation system that combines a selection tube and magnetic separation that can separate small sized paramagnetic particles in a low magnetic field. The selection tube is a technique for classifying the suspended particles by utilizing the phenomenon that the suspended particles come to rest when the gravity acting on the particles and the drag force are balanced when the suspension is flowed upward. In the balanced condition, they can be captured with even small magnetic forces. In this study, we calculated the particle size of paramagnetic particles trapped in a selection tube in a high gradient magnetic field. As a result, the combination of the selection tube and HGMS (High Gradient Magnetic Separation-system) can separate small sized paramagnetic particles under low magnetic field with high efficiency, and this paper shows its potential application.

• YAKHAK HOEJI
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• v.32 no.5
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• pp.362-369
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• 1988

Monthly variation of mutagenicity by airborne particulate were studied according to particle size of the particulate. Airborne particulates were collected in Shinchon of Seoul which is commocial and traffic area in 1986. And those were separately collected into two parts such as fine particle (less than $2.5{\mu}m$ aerodynamic diameter) and coarse particle (greater than $2.5{\mu}m$). Extractable organic matters(EOM) were extracted and mutagenicity of the EOM was tested in Salmonella thyphimurium TA 98 by Ames method. While the concentration of coarse particle did not show the seasonal variation, that of fine particle showed great seasonal variation. The contents and mutagenicity of EOM in fine particles were higher than those of coarse particles. So fine particles were expected to contribute to the 90% of mutagenicity in atmosphere by suspended particulates. The content of EOM and mutagenicity by suspended particulates in atmosphere were highest in January all the year around and also higher as much as 6 and 30 times than in July, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.37 no.4
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• pp.323-329
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• 2004

In situ particle size and volume concentration of suspended sediment was measured at the mouth of Seomjin River Estuary In February 2001, using an optical instrument, 'LISST-100'. Time variation of in situ particle size and concentration shows: (1) during ebb tide, Seomjin River supplies relatively fine-grained particles with less-fluctuated, compared to during flood tide, and well-behaved concentrations following the tidal cycle; and (2) during flood tide, relatively coarse-grained particles with highly variable in size distribution and concentration flow upstream from Kwangyang Bay. This explains a poor correlation $(r^{2}=0.10)$ between sediment concentration and beam attenuation coefficient during flood and a high degree of correlation $(r^{2}=0.80)$ during ebb tide. Relatively fine grained and well defined, monotonous size distribution may promote the correlation between concentration and beam attenuation coefficient due to optical homogeneity of particles during ebb tide. Abundance of large aggregates with time-varying size and shape distributions may be mainly responsible for variations in optical properties of the sediment during flood tide, and thus may confound the relationship between the two variables. The difference in particle sizes and shapes between flood and ebb tides can also be observed on SEM images.

• Journal of Navigation and Port Research
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• v.35 no.4
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• pp.323-334
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• 2011

Suspended and sinking particles were collected in austral summer during ODP Leg 119 to the Indian Ocean sector of the Antarctic Ocean. Field work was carried out at four sampling sites in Prydz Bay. Two of these sites were located in the Outer Bay, and two in the Inner Bay. At the four locations, a total of ten deployments of a sediment trap array were made. The concentrations of chlorophylls and their degradation products both in suspended and sinking particulate matter in Prydz Bay were analyzed using HPLC. Chlorophylls a and c were the dominant algal pigments both in suspended and sinking particles. Because of the abundance of fecal pellets at Site 740, the mean fluxes at 200 m averaged 6 fold greater than that at 50 m. This implies that a dense swarm of zooplankters, presumably large copepods and/or salps, may "feed and excrete" mainly in between 100-200 m depths at this site, closest to land in Prydz Bay. Interestingly, The flux of phaeophorbide a was generally similar in magnitude to that of chlorophyll a throughout the study areas. This is an evidence that materials escaping from near-surface regions in austral summer derive mainly from the gazing of zooplankters. "New production" from sediment-trapped CHL pigment fluxes in Prydz Bay was estimated using f-ratio of 0.15, ranging from 520 to $1,605\;{\mu}gC\;m^{-2}\;day^{-1}$.

• Journal of Environmental Science International
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• v.20 no.11
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• pp.1357-1371
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• 2011

Suspended and sinking particles were collected during ODP Leg 119 to the Indian Ocean sector of the Antarctic Ocean. Field work was carried out at four sampling sites in Prydz Bay. Two of these sites were located in the Outer Bay, and two in the Inner Bay. At the four locations, a total of ten deployments of a sediment trap array were made. The concentrations of carotenoids both in suspended and sinking particulate matter in Prydz Bay were analyzed using HPLC. Fucoxanthin was the dominant carotenoid pigments both in suspended and sinking particles. The present study also indicates that 19'-hexanoyoxyfucoxanthin-containing prymesiophytes (Phaeocystis spp.) was abundant in the study area. The flux rates of carotenoids were generally highest at 50 m, and approximately double the flux rates at deeper horizons, however, at Inner Bay sites, the mean flux rates of carotenoids were greatest at 200 m, and 3 times greater than that of 50 m. Such anomalous high fluxes at 200 m imply that grazers were locally abundant between 100 m and 200 m at these sites close to land, and this hypothesis is supported by visual evidence of lots of fecal pellets in the 200 m trap. Integrates standing stocks versus sinking pigments data support that particulate material in Prydz Bay was not recycled rapidly.

• Journal of the Korean Institute of Gas
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• v.19 no.3
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• pp.25-31
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• 2015

Effects of residence time on the MIT(Minimum Ignition Temperature) in suspended Mg particles are examined by using MIT experimental data and calculation results of terminal velocity. With increasing of the average particle diameter, we were able to identify that MIT of Mg dusts increased and the calculated residence time of particle decreased exponentially. Also, the influence on terminal velocity due to temperature increase increased slightly with increasing of average particle diameter.

• Journal of environmental and Sanitary engineering
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• v.20 no.4 s.58
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• pp.51-58
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• 2005

Photocatalytic degradation using $TiO_2$ Particles suspended in a reactor was experimentally performed to degrade the formaldehyde of indoor pollutants. Exponential increase of degradation appears to prove light availability due to the scattering of W light by particles themselves. Comparative removal studies of formaldehyde were done in both cases of dipping and spraying immobilized techniques of $TiO_2$ Particles suspended in solution. Experiments were performed under several different experimental conditions such as initial concentration of formaldehyde, UV intensity and concentration of photocatalysts. Optimal conditions to degrade formaldehyde were obtained under the conditions of $30\;mg/cm^2$ concentration of catalyst and UV intensity of 30 Watt at the distance of 30 cm using immobilized technique by dipping coating.

• Water for future
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• v.27 no.3
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• pp.115-121
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• 1994

Cohesie sediment movement in estuarine systems is strongly affected by the phenomena of aggregation and flocculation. Aggregation is the process where primary particles are clustered together in tightly-packed formations; flocculation is the process where aggregates and single particles are bonded together to form large particle groups of very low specific density. The size, shape and strength of the flocculants control the rate of deposition and the processes of pollutant exchange between suspended sediments and ambient water. In estuarine waters, suspended sediments above the lutocline form the mobile suspension zone while below the lutocline they form the stationary suspension zone. Suspended particles in the mobile zone are generally in a dispersed state and the controlling forces are the Brownian motion and the turbulent flow fluctuations. In the stationary suspension zone, the driving force is the gravity. This paper discusses the settling and particle flocculation characteristics under quiescient flow conditions. Particles are entering the study domain randomly. Particles in the mobile suspension zone are simulated by using the Smoluchowski's model. Flocs created in the mobil suspension zone are moving into the stationary suspension zone where viscosity and drag effects are important. Utilizing the concepts of the maximum Feret's diameter and the Minkowski's sausage logic, the fractal dimension of the flocs within the stationary suspension is estimated and then compared with results obtained by other studies.

• Journal of Korean Society for Atmospheric Environment
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• v.2 no.2
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• pp.60-65
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• 1986

Atmospheric particulates were collected at a site near the front gate of the Yonsei University using nine stages Andersen air sampler and the distribution of seasonal particle size was investigated. Rubber, Pb and Zn contents of the collected particulates in each stage were determined. Particle size distribution of atmospheric particulate, which was made by concentration distribution curve method, was usually divided into two groups, course (particles larger than 1 - 2 $\mu m in diameter$) and fine (particles smaller than 1 - 2 \mu m in diameter$) groups, regardless of sampling period. More than 80 percent of the total rubber contents in atmospheric particulates were larger than $5 \mu m$ in diameter, meaning that most of rubber particles were originated from tire tread. After benzene extraction for 4 hrs, the extracts were analyzed by Curie-point pyrolysis gas chromatography for rubber content. Pb and Zn contents were determined by atomic absorption spectroscopy. The annual average concentration of rubber particles was $4.2 \mu g/m^3$, which corresponded to 2.2% of the annual average total suspended particulates. Average concentration of styrene brtadiene rubber was about five times that of natural rubber. Annual average concentrations of Pb and Zn were $1.2 \mu g/m^3 and 0.4 \mu g/m^3$ respectively, which corresponded to about 0.7% and 0.2% of the annual average total suspended particulates.

• Journal of Korean Society for Atmospheric Environment
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• v.2 no.3
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• pp.34-44
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• 1986

Particle size distribution of airborne suspended particulate concentrations according to particle size in the events of yellow sand phenomena, have been measured and analyzed by using Andersen air sampler for four years, January 1982 through December 1985. The conclusions are as follows: 1. Yellow sand phenomena, generally, occur between March and May. 2. The frequent occurrences of yellow sand were observed during March and April and airborne suspended particulate concentrations in the cases of yellow sand appeared to be 2 $\sim$ 3.4 times higher than those of normal conditions. 3. Geometric mean particle diameter and its geometric mean standard deviation by logarithmic normal distribution sheet, were quite close to each other and log-distribution curves showed similar shapes. 4. Analysis by particle size distribution curve showed bi-modal distribution. 5. Concentrations of coarse particles in normal conditions were 1.2 $\sim$ 2 times higher than those of fine particles and, similarly, coarse particle concentrations in yellow sand cases were 1.3 $\sim$ 2.5 times higher than those of fine particles. 6. Concentrations of coarse particles in yellow sand cases were 2 $\sim$ 3.6 times higher than those in normal conditions and those of fine particles were 1.7 $\sim$ 3.5 times higher.