• Journal of the Korean Institute of Gas
• /
• v.27 no.4
• /
• pp.62-69
• /
• 2023

The use of low-grade coal is continuously increasing with the development of combustion technology and cost reduction for coal used in thermal power plants . During combustion, the latent heat of evaporation due to moisture is large, and there is a risk of spontaneous combustion and dust explosion during the process of storing and pulverizing coal. This study compared and evaluated the minimum explosive concentration and explosive strength of four types of coal dust-fine, coal dust-coarse, wood pallet+organic dust, and wood chip with coal powder collected from domestic power plant D. The minimum explosive concentration of coal dust was measured according to JIS Z 8818:2002, and the explosion strength was tested according to ASTM E1226 using a Siwek 20 L Chamber Apparatus. As a result of the minimum explosive concentration test, it was found that coal dust-fine has a risk of dust explosion, and since an explosion occurs at a dust concentration of 130 g/m³ of wood chips, it was found that there is a risk of explosion at the lowest dust concentration. According to the dust explosion class standard, Kst is less than 200 bar m/s, and all samples fall under the explosion class St 1, and the dust has a low risk of explosion.

• Proceedings of the Korea Air Pollution Research Association Conference
• /
• 2010.04a
• /
• pp.173-174
• /
• 2010

• Asian Journal of Atmospheric Environment
• /
• v.3 no.1
• /
• pp.9-18
• /
• 2009

This study aimed at assessing the association between exposure to severe air pollution in the past and the subsequent transition in lung cancer mortality among persons who lived in an industrial city. Vital statistics from 1983 to 2006 and the data on air pollution measurements from 1960 to 1990 in Amagasaki City, Japan, were used. Pearson correlation coefficients were calculated between the standardized mortality ratios (SMRs) for lung cancer and the air pollution levels in 6 wards of Amagasaki City. The associations between changes in air pollution levels and the annual SMRs were also evaluated in the light of a potential latency period. The levels of air pollution were extremely high in the 1960s, and they decreased since 1970. The SMRs for lung cancer in 1989-1993 among females for 6 wards were significantly associated with the amounts of both sulfur oxides and dust fall in the past for each ward. The positive associations were observed between the annual SMRs among females and the amounts of both pollutants when the lag time of 20-30 years was taken into account. These results suggest that severe air pollution in the 1960s in an industrial city affected the subsequent increase in lung cancer mortality.

• 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.

• The Research Journal of the Costume Culture
• /
• v.25 no.2
• /
• pp.117-129
• /
• 2017

The purpose of this study was to investigate meteorological factors' effects on clothing sales based on empirical data from a leading apparel company. The daily sales data were aggregated from "A" company's store records for the Fall/Winter season from 2012 to 2015. Daily weather data corresponding to sales volume data were collected from the Korea Meteorological Administration. The weekend effect and meteorological factors including temperature, wind, humidity, rainfall, fine dust, sea level pressure, and sunshine hours were selected as independent variables to calculate their effects on A company's apparel sales volume. The analysis used a SAS program including correlation analysis, t-test, and multiple-regression analysis. The study results were: First, the weekend effect was the most influential factor affecting sales volume, followed by fine dust and temperature. Second, there were significant differences in the independent variables'effects on sales volume according to the garments' classification. Third, temperature significantly affected outer garments'sales volume, while top garments' sales volume was not influenced significantly. Fourth, humidity, sea level pressure and sunshine affected sales volume partly according to the garments' item. This study can provide proof of significant relationships between meteorological factors and the sales volume of garments, which will serve well to establish better inventory strategies.

• Fashion & Textile Research Journal
• /
• v.19 no.4
• /
• pp.434-447
• /
• 2017

This study investigated the effects of influencing factors on the sales volume of apparel products. Based on previous studies, weekend effect, discount rate, and meteorological factors including daily average temperature, rainfall, sea level pressure, and fine dust were selected as independent variables to calculate their effects on sales quantity of apparel products. The daily sales data during 2015 - 2016 were collected from casual brands and outdoor brands which "A" apparel manufacturing company had operated. The actual data of "A" company were analyzed using SAS(R) 9.4 and SAS(R) Enterprise Miner 14.1. The results of this study were as follows: First, the influencing factors on total sales volume of apparel products were proved to be the weekend effect, discount rate, and fine dust. Second, the analysis of influencing factors on sales volume of apparel products according to season showed: 1) In casual brands, the average temperature had a significant influence on the sales volume of spring/summer products, and the sea level pressure affected the sales volume of summer/fall/winter products significantly. 2) In outdoor brands, the average temperature and the fine dust had a significant influence on the sales volume of all season's products. The sea level pressure affected the sales volume of summer/fall/ winter products significantly. The weekend effect and the discount effect affected the sales volume of apparel products partly. Third, the effect of rainfall was not proven significant, which was different from the results of past studies.

• Analytical Science and Technology
• /
• v.13 no.2
• /
• pp.179-188
• /
• 2000

Trace elements in air samples artificially loaded on filters with urban dust and the bulk material of urban dust as an environmental sample were determined non-destructively using instrumental neutron activation analysis. Standard reference material (Urban Dust, SRM 1648) of the National Institute of Standard and Technology was used for the analytical quality control. The relative error for 37 elements was less than 15% and the standard deviation was less than 10%. 29 elements in the urban dust and 21 elements in the loaded filter sample were determined respectively. To evaluate the proficiency and reliability of the measurement, data intercomparison was performed and 39 analytical laboratories participated in the analysis using different analytical methods; neutron activation analysis, particle induced X-ray emission analysis, X-ray fluorescence analysis and atomic absorption spectrometry. Z-scores were calculated using the standard deviation of the laboratorie's mean as target standard deviation, and a good result was obtained that the values fall between -1 and +1 except some elements.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.17 no.1
• /
• pp.3702-3711
• /
• 1975

This study was originated to investigate the imparired parts of the mist and dust blowers and intended to analyze the causes of their failures by the use of the Weibull probability paper. By the use of the paper, the parts which were needed to change the design, the force of the urgency, the mean time between failures of the parts and the basic causes of the troubles could be predicted. The survey showed that the following parts got out of order: (A) flexible rubber hose, (B) blowing fan, (C) lead valve, (D) piston ring. (E) crank main bearing, (F) coil in magneto and (G) needle valve in carburettor. The analysis of the survey indicated that the parts G, C, E and D were belonged to "wear-out failure", and that the mean time between failures became shorter in order as indicated above. To insure longer lives of those parts, it would be necessary to change the design and the material and to upgrade operators mechanical technique of the mist and dust blower. The failure of the parts A, B and F was classified as "randomfailure", and they did not seem to be the "wear-out" at that time. The parts B and F was evaluated as "initial failure". Quality controls and operating tests by the producer. and the operational training for users should be strengthened so as to eliminate these failures. Were the failures only in the parts A, C, D, E, F and G, it could be said that the "reliability" of the mist and dust blower would fall to 10 percent in the second year, and 50 percent of the mist and dust blowers would fail in all parts A, C, D, E, F and G before the blower would have control insect and disease in 58.2 hectares. The use of the Weibull probability paper for analyzing failures of the mist and dust blowers was effective in that it analyzed failure in the relationship between strength of the parts and users actual circumstanoes.

• Environmental Engineering Research
• /
• v.24 no.1
• /
• pp.159-172
• /
• 2019

To investigate the influence of pollution events on the chemical composition and formation processes of aerosol particles, 24-h integrated size-segregated particulate matter (PM) was collected during the fall season at an urban site of Gwangju, Korea and was used to determine the concentrations of mass, water-soluble organic carbon (WSOC) and ionic species. Furthermore, black carbon (BC) concentrations were observed with an aethalometer. The entire sampling period was classified into four periods, i.e., typical, pollution event I, pollution event II, and an Asian dust event. Stable meteorological conditions (e.g., low wind speed, high surface pressure, and high relative humidity) observed during the two pollution events led to accumulation of aerosol particles and increased formation of secondary organic and inorganic aerosol species, thus causing $PM_{2.5}$ increase. Furthermore, these stable conditions resulted in the predominant condensation or droplet mode size distributions of PM, WSOC, $NO_3{^-}$, and $SO{_4}^{2-}$. However, difference in the accumulation mode size distributions of secondary water-soluble species between pollution events I and II could be attributed to the difference in transport pathways of air masses from high-pollution regions and the formation processes for the secondary chemical species. The average absorption ${\AA}ngstr{\ddot{o}}m$ exponent ($AAE_{370-950}$) for 370-950 nm wavelengths > 1.0 indicates that the BC particles from traffic emissions were likely mixed with light absorbing brown carbon (BrC) from biomass burning (BB) emissions. It was found that light absorption by BrC in the near UV range was affected by both secondary organic aerosol and BB emissions. Overall, the pollution events observed during fall at the study site can be due to the synergy of unfavorable meteorological conditions, enhanced secondary formation, local emissions, and long-range transportation of air masses from upwind polluted areas.

• The Bulletin of The Korean Astronomical Society
• /
• v.42 no.1
• /
• pp.55.3-55.3
• /
• 2017

The L1641 cloud in Orion is an active site of star formation. We mapped a square region of 60 arcmin by 60 arcmin in the continuum emission from 0.89 mm to 2.0 mm wavelength using MUSIC mounted on the Caltech Submillimeter Observatory 10.4 m telescope. Eight sources were detected in at least two wavelength bands, and all the detected emission comes from thermal dust continuum radiation of dense cloud cores. Their spectral energy distributions were characterized. The dust emissivity spectral index is beta = 1.3 on average, within the range of typical cores in nearby star-forming regions. Two cores, V380 Ori NE and HH 34 MMS, have unusually low emissivity index of beta = 0.3. These cores may contain millimeter-sized dust grains, which suggests that the lifetime of some dense cores can be much longer than the free-fall timescale.