• Journal of Korean Society for Atmospheric Environment
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• v.22 no.1
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• pp.35-41
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• 2006

The steel foundries with electric arc furnaces handling metal scraps have recently gained an attention as a potential source of dusts. The present study focuses on the analysis of dust emissions and removals during furnace charging and melting processes by commercial CFD software named FLUENT. A body fitted grid system consisting of 880,000 meshes was first generated by Gambit for the electric arc furnace with the capacity of 60 ton/cycle and then FLUENT was invoked to solve the corresponding NavierStokers equation for the momentum, temperature and dust concentration. The entire processes from metal charging to metal melting were simulated to investigate the unsteady behaviors of fluid flows and dust concentrations. The model simulation results showed that as the top of the electric arc furnace opened for metal charging, hot plumes bursted out from the furnace rose strongly by buoyance and escaped mostly through the main hood. Therefore, the capacity of main hoods determined the vent efficiency in the metal charging process. As the furnace was closed after the metal charging and the metal melting processes was followed, the hot flow stream stretching from the furnace to the main hood was dissipated fast and the flow from the inlet of the bottom of the left hand side to the main and monitoring hoods constituted the main stream. And there was only a slow flow in the right hand side of the furnace. Therefore, the dust concentrations were calculated higher in the left hand side of the furnace, which was consistent with observations.

• Korean Chemical Engineering Research
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• v.54 no.3
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• pp.367-373
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• 2016

Many of plastic powders handled in industry are combustible and have the hazard of dust fire and explosion accidents. However poor information about the safe handling has been presented in the production works. The aim of this research is investigated experimentally on explosive characteristics of various plastic powders used in industry and to provide additional data with safety informations. The explosibility parameters investigated using standard dust explosibility test equipment of Siwek 20-L explosion chamber. As the results, the dust explosion index ($K_{st}$) of ABS ($209.8{\mu}m$), PE ($81.8{\mu}m$), PBT ($21.3{\mu}m$), MBS ($26.7{\mu}m$) and PMMA ($14.3{\mu}m$) are 62.4, 59.4, 70.3, 303 and 203.6[$bar{\cdot}m/s$], respectively. And flame propagation velocity during plastic dust explosions for prediction of explosive damage was estimated using a flame propagation model based on the time to peak pressure and flame arrival time in dust explosion pressure assuming the constant burning velocity.

• Proceedings of the KIEE Conference
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• 1998.07e
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• pp.1681-1683
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• 1998

Unlike AC, DC dielectric characteristics of the spacer are very influenced by the quantity and the distribution of surface charges. A general impression of the distribution of surface charges is obtained if electrostatic powders are sprinkled over the surface. The distribution of surface charge was investigated with dust figures. Mechanism of charge accumulation on the spacer of $SF_6$ GIS has been studied using various types of model spacers which have different depths. As a result, it was found that charge accumulation was dominantly influenced by the normal component of the electric field and the usage of embedded electrodes was an adequate method to lessen field concentration around the triple junction. The guide of the optimum depth of the spacer was proposed.

• Journal of Astronomy and Space Sciences
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• v.17 no.1
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• pp.11-18
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• 2000

We have modeled the observed spectral energy distributions(SEDs) of young stellar objects (YSOs) in giant molecular clouds (GMCs). We propose the theoretical modles for the dust envelopes around YSOs. The YSOs in a GMC may share the same initial chemical composition. In this paper, we compare the model SEDs with the observations of the YSOs. Dust shells of the YSOs are composed of a mixture of astronomical silicate and graphite grains. We propose the models for the evolution of the GMCs comparing the shape of the SEDs on the IRAS 2-color diagram with the age.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.216-225
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• 2003

Fine particles with aerodynamic diameter less than 2.5 ${\mu}m$ (PM2.5) were collected from three sites in Beijing during April, August, and November 2000 and January 2001. After chemical components in samples are analyzed, a chemical mass balance (CMB) receptor model using PARs as tracers is applied to quantify the source contributions to PM2.5 in Beijing. The results show that the major sources are coal combustion, fugitive dust, vehicle exhaust, secondary sulfate and nitrate, and organic matter while biomass burning and construction dust contribute only a small fraction. In addition, source inventory in Beijing is used to determine the primary source contributions. The two methods result in comparable results. Source apportionment at three sampling sites presents similar contributions to PM2.5 although the sites are far away from each other. However, distinct seasonal pattern is presented for the source contributions from coal combustion, fugitive dust, biomass burning, secondary sulfate and nitrate.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.110-115
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• 1998

An axisymmetric Navier-Stokes procedure has been developed to analyze the pulse jet flow in a ceramic filter unit for the dust dislodging process. Using Baldwin-Lomax turbulence model as a closure relationship, the SIAF(Scalar Implicit Approximate Factorization) algorithm together with the ${\delta}^k-Correction$ iterative time marching scheme is adopted to solve the unsteady compressible Navier-Stokes equations. After some validation tests, the code has been applied to solve the pulse jet flow and examine the effects of geometry and reservoir pressure condition on the pressure level inside the filter unit. To avoid dealing with the uncertainty of such factors as the cohesion of the collected dust and the adhesion of the dust to the medium and also to simplify the analysis, the filter wall is assumed to be impermeable. The results for various test cases are presented.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2003.04a
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• pp.145-148
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• 2003

The batch experiments showed that 0.515mM 4-chlorophenol and its oxidation intermediates could be totally decomposed within 60 minutes by 1g/L steelers' dust and 0.485mM hydrogen peroxide at pH 2.7. The rate constants in the simplified kinetic model proposed in this study were estimated by fitting to the experimental data obtained in $H_2O$$_2$/steelers' dust system. Using the estimated kinetic rate constants, the simulation of 4-chlorophenol, ferrous iron, hydrogen peroxide, and hydroxyl radical concentration was performed. The predicted concentrations of 4-chlorophenol and hydrogen peroxide corresponded to the actual concentrations.

• Journal of Korean Society for Atmospheric Environment
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• v.16 no.6
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• pp.633-640
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• 2000

The effects of structure modification of the vortex finder on the collection efficiency and pressure drop have been investigated. The pressure drop in a cyclone having the two stage vortex finder is higher than that in a conventional cyclone and increases proportionally with the increase of square of gas inlet velocity in both cases. The pressure drop of both conventional cyclone of friction resistance at the boundary layer. The collection efficiency of fine dust has been enhanced by addition of vortex finder in a conventional cyclone and gas inlet velocity showing maximum dust removal efficiency increase to 17 m/s(1.7 times of saltation velocity). Optimum size of two stage vortex finder has been induced to 13 cm I.D$\times$2.6cm Length from the results of overall dust collection efficiency. Previous models were tested for the simulation of collection efficiency of cyclone having two stage vortex finder and the Dietz model predict the similar value with experimental results of the present study.

• The Bulletin of The Korean Astronomical Society
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• v.44 no.1
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• pp.64.1-64.1
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• 2019

Thermal fracture and cracking near the perihelion are found to be a possible mechanism to produce the dust trail of the near-Earth asteroid, (3200) Phaethon (Jewitt and Li, 2013, ApJ 771, L36). It is, however, not well understood how the debris particles were escalated from the regolith against the asteroid's gravity. Thus, the scenario that these debris particles are responsible for the detected activities (Li and Jewitt, 2013, ApJ, 145, 154), is not complete yet. Here, we hypothesize that the thermal radiation pressure around the perihelion passage would exert substantial force outwards from the regolith on dust grains, and they can be lifted up and contributes the dust tail formation with further help of solar radiation pressure. Our modeling indicates that particles with sizes of roughly ~1-10 micron can be ejected from Phaethon by the mechanism, while a detailed model of gravitational field is required for accurate estimation of the particle size range. Our idea is not necessarily limited to Phaethon case, but is applicable to any atmosphereless bodies.

• International Journal of Contents
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• v.17 no.4
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• pp.35-45
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• 2021

In this study, we analyzed the factors that affect public awareness campaigns on social media platforms and developed an integrated model for measuring the persuasiveness of environmental social media campaigns. A survey questionnaire was created and distributed on Facebook with the goal of reaching individuals in their 20s and 40s in Vietnam, and 395 valid replies were gathered. The findings showed that the STOPS was reconfirmed as a suitable theoretical framework for analyzing the public's behaviour intention to conduct information related to the issue of fine dust, especially on social media. Furthermore, it also showed that social media efficacy has a moderating effect on the relationship between public's situational recognition and informational behaviour intention. This suggested that through social media platforms, personal characteristics play a vital part in developing effective environmental campaigns. Implications for both theory and practice were discussed.