• 한국대기환경학회지
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• 제10권1호
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• pp.57-63
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• 1994

In order to comprehension of the behaviour of PAHs in air which is known as carcinogens and/or mutagens suspended Particulates in ambient air were collected by Anderson air sampler from 1992. 6 to 1993. 5 in Seoul. Ten species of PAHs( Phen, An, Fl, R, Py, BaAn, BaP, Chry, BeP, DiB(a, h)An, I123p) were analyzed to understand monthly variations of PAHs distribution of PAHs concentration according to particle size, and correlation between PAHs and independent charactierstics of PAHs The highest concentration of TSP was 155.58$\mu\textrm{g}$/㎥ in May and the lowest was 60$\mu\textrm{g}$/㎥ in August. Concentration of TSP was more affected by coarse particles in spring, otherwise which was more affected by fine particles in winter. According to results of anaylsis of samples that were collected by Anderson air sampler, concentration of PAHs was more high in winter than that in summer. In almost samples collected by Anderson air sampler, concentration of PAHs was more high in coarse particles than in fine particles, but BaP well known as carcinogenic matter had more high concentration in fine particles(56-97.5%) than that in coarse particles(2.5-46%). Correlation between concentrations of TSP and PAHs was more high in fine Particles than in coarse Particles. Both fine particles and coarse particles have negative correaltion with radiation.

• 한국대기환경학회지
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• 제1권1호
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• pp.71-82
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• 1985

The effect on the particulate matters in the atmosphere was investigated in Seoul area from March, 1984 to Aprill, 1985. Aerosols were collected by filters on nine stages Andrsen Air Sampler, and size distribution and total concentration of the aerosols, Fe and Pb were measured. In spring with Yellow Sand the concentration of particles in aerosols was 185.55$\mug/m^3$ and CP/TA was 65.9%. But in spring without Yellow Sand those of particles was 135.45$\mug/m^3$ and CP/TA was 58.6%. Accordingly the concentration of coarse particles with Yellow Sand was higher than without them in Spring. Above results indicate that in Seoul Area the main source of air pollution originated from natural burdens, especially from soil. The concentration of Pb was similarly valued through both seasons in Seoul area but fine particles valued above coarse particles. On the other hand, in urban area, the natural and anthropogenic sources have influenced on the concentration of Pb. With referred to particle size distribution for Fe, the concentration of coarse particles was 0.168$\etag/m^3$ (CP/TA: 74.3%) in Spring with Yellow Sand, 0.096$\mug/m^3$ (CP/TA: 71.6%) without Yellow Sand and 0.083$\mug/m^3$ (CP/TA: 67.4%) in winter, respectively. Compared with fine particles, all of them were higher. It indicated that the origin of coarse particles in urban air was not related to anthropogenic source. The concentration of Fe was influenced by Yellow Sand and contributed to air pollution.

• 한국환경보건학회지
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• 제32권6호
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• pp.543-555
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• 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.

• Journal of the Korean Wood Science and Technology
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• 제33권2호통권130호
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• pp.40-55
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• 2005

This study was carried out to discuss the feasibility of wood and plastic wastes as the raw materials for wood particle-plastic composites. For this purpose, composites were manufactured from coarse and fine wood particles and polypropylene fibers by nonwoven web process. And the effect of wood particle size on the performance of the composites were analyzed according to ASTM D 1037-93. In the physical properties of composites, water absorption decreased with the increase of target density and polypropylene fiber content. And the composites with fine wood particles appeared to have slightly lower water absorption than those with coarse wood particles. Thickness swelling did not vary significantly with the increase of target density but increased with the increase of wood particle content. And the composites with fine wood particles were significantly lower in thickness swelling than those with coarse wood particles. In the mechanical properties of composites, dry and wet MOR showed the increasing tendency with the increase of polypropylene fiber content and target density. Dry and wet MOE showed the increasing tendency with the increase of target density but only wet MOE exhibited the increasing tendency with the increase of polypropylene fiber content. Composites with fine wood particles appeared to be generally higher in wet MOR and MOE than those with coarse wood particles. In conclusion, composites with fine wood particles showed generally higher performance than those with coarse ones. Also, composites were significantly superior to control particleboards in the performance, especially in water absorption and thickness swelling.

• 한국농공학회논문집
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• 제46권2호
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• pp.49-57
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• 2004

Generally, the properties of aggregate greatly affect the physical and mechanical properties of concrete. Flat and elongated particles in coarse aggregates, for some construction uses, may interfere with consolidation and be difficult to place. In this study, an experiment to evaluate properties of flat and elongated particles as coarse aggregate in concrete was conducted. The experiments include slump test, air content test and compressive strength test. The test result of slump and change of slump was rapidly decreased by percentage of flat and elongated particles. But it had not a trend by increasing percentage of flat and elongated particles. Compressive strength of hardened concrete does not make any differences in comparison.

• Advances in materials Research
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• 제12권4호
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• pp.331-349
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• 2023

Foam concrete can be considered as environmental friendly material due to its low weight, its minimal cost and a possibility to add waste materials in its production. This paper investigates the possibility of producing foam concrete with waste glass as powder and aggregate. Then, the effect of using waste glass on strength and drying shrinkage of foam concrete was examined. Also, the effect of incorporating polypropylene fibers (12 mm length and proportion of 0.5% of a mix volume) on distribution of waste glass as coarse particles within 1200 kg/m³ foam concrete mixes was evaluated. Waste glass was used as powder (20% of cement weight), as coarse particles (25%, 50% and 100% instead of sand volume) and as fine particles (25% instead of sand volume). From the results, the problem of non-uniform distribution of coarse glass particles was successfully solved by adding polypropylene fibers. It was found that using of waste glass as coarse aggregate led to reduce the strength of foam concrete mixes. However, using it with polypropylene fibers in combination helped in increasing the strength by about 29- 50% for compressive and 55- 71% for splitting tensile and reducing the drying shrinkage by about (31- 40%). In general, not only the fibers role but also the uniformly distributed coarse glass particles helped in improving and enhancing the strength and shrinkage of the investigated foam concrete mixes.

• Geomechanics and Engineering
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• 제17권1호
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• pp.19-30
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• 2019

Recent research on the behavior of silty sand tends to advocate the use of equivalent skeleton void ratio to characterize the density state of this type of soil. This paper presents an investigation to explore the physical meaning of the equivalent skeleton void ratio by means of DEM simulations for assemblies of coarse and fine particles under biaxial shear. The simulations reveal that the distribution pattern of fine particles in the soil skeleton plays a crucial role in the overall macroscopic response: The contractive response observed at the macro scale is mainly caused by the movement of fine particles out of the force chains whereas the dilative response is mainly associated with the migration of fine particles into the force chains. In an assembly of coarse and fine particles, neither all of the fine particles nor all of the coarse ones participate in the force chains to carry the external loads, and therefore a more reasonable definition for equivalent skeleton void ratio is put forward in which a new parameter d is introduced to take into account the fraction of coarse particles absent from the force chains.

• 한국산학기술학회논문지
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• 제12권2호
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• pp.1020-1026
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• 2011

천안시 대기 입자 중 수용성 이온성분의 특성을 분석한 결과, 양이온은 $Na^+$과 $NH_4^+$이, 음이온은 $NO_3^-$와 $SO_4^{2-}$이 조대입자와 미세입자에서 모두 주요한 이온성분으로 조사되었다. 분석된 수용성 이온성분의 농도는 미세입자가 조대입자보다 높은 농도로 나타났으며, 겨울과 봄철에 높은 농도를, 여름철에 가장 낮은 농도를 나타냈다. 총 수용성 이온 성분은 전체 입자의 질량 중 조대입자에서는 계절별로 봄 24.4%, 여름 33.2%, 가을 40.7%, 겨울 39.6%를, 미세입자에서는 각각 43.0%, 59.7%, 55.4%, 53.2%를 차지하는 것으로 분석되어, 조대입자 보다는 미세입자에서 차지하는 비율이 컸으며, 다른 계절보다는 봄철에 낮은 비율을 나타냈다. 이들 수용성 이온성분의 요인분석을 수행한 결과 조대입자는 2개의 요인이, 미세입자는 4개의 요인이 추출되었다. 이로부터 조대입자의 경우 자연적 배출원으로 부터의 기여가 70.03%로, 미세입자의 경우 인위적 배출원으로 부터의 기여가 66.01%로 추정되었다.

• 에너지공학
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• 제5권2호
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• pp.131-137
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• 1996

Typical size distribution of emission particulates is bi-modal in shape with particles in the fine mode (< 2.0 $\mu\textrm{m}$) and the coarse mode. An experimental study of pressure drop across the industrial gas cleaning filters has been conducted using particle mixture of fine alumina and coarse Arizona dusts with a rotating aerosol disperser to generate the bi-modal test aerosol. Pressure drop increased linearly with increasing mass loading. The pressure drop was found to be strongly dependent upon the mass ratio of fine to coarse particles. The smaller the mass ratio of fine to coarse particles and the higher face velocity are, the faster pressure drop rises. The fine particles and the greater inertia of the particle moving fast would cause a denser cake formation on the filter surface, resulting in a greater specific resistance to the gas flow.

• Asian Journal of Atmospheric Environment
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• 제12권1호
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• pp.78-86
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• 2018

Filter-based sampling techniques are the conventional way to collect particulate matter, but particles collected and entangled in the filter fibers are difficult to be removed and thus not suited for the following cell- and animal-based exposure experiments. Collecting aerosol particles in powder form using a cyclone instead of a filter would be a possible way to solve this problem. We developed a hybrid virtual-impactor/cyclone high-volume fine and coarse particle sampler and assessed its performance. The developed system achieved 50% collection efficiency with components having the following aerodynamic cut-off diameters: virtual impactor, $2.4{\mu}m$; fine-particle cyclone, $0.18-0.30{\mu}m$; and coarse-particle cyclone, $0.7{\mu}m$. The virtual impactor used in our set-up had good $PM_{2.5}$ separation performance, comparable to that reported for a conventional real impactor. The newly developed sampler can collect fine and coarse particles simultaneously, in combination with exposure testing with collected fine- and coarse-particulate matter samples, should help researchers to elucidate the mechanism by which airborne particles result in adverse health effect in detail.