• Journal of Korean Society for Atmospheric Environment
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• v.27 no.4
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• pp.395-404
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• 2011

Asian dust evens took place in Seoul on 27~28 March and 31 March~1 April 2007, during which the mass and chemical compositions of $PM_{10}$ were measured at urban area in Seoul, Korea. In conjunction with $PM_{10}$ compositions, the behaviors of gas precursors such as CO, $O_3$, $SO_2$, and $NO_2$ and meteorological parameters and air mass trajectories were thoroughly examined. The earlier case was a weak dust incidence which was characterized by elevated concentrations of CO, $SO_2$ and $NO_2$ as well as secondary aerosols. In contrast, the later showed the trait of the dust aerosols associated with high $PM_{10}$ mass and $Ca^{2+}$ concentrations. In general, the fractions of ionic species against mass decreased with increase in dust loading. The ratios of ${SO_4}^{2-}$ to ${NO_3}^-$ and $SO_2$ to $NO_2$ were similar in temporal variations, suggesting the concentrations of secondary aerosols were sensitive to the level of precursor gases. In this study, $Na^+$ and $Cl^-$ were also highly elevated during the heavy dust episode, which is thought to have originated from alkaline soils spreading through the northeast regions of China.

• Nuclear Engineering and Technology
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• v.12 no.2
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• pp.99-105
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• 1980

The distribution of $^{55}$ Mn and $^{38}$ Cl recoil species following radiative neutron capture in permanganates, chlorates and perchlorates has been investigated by using ion-exchange chromatography method. The whole of the $^{55}$ Mn radioactivity in permanganates appeared in two valence states, the $^{38}$ Cl radioactivity in chlorates in two valence states and also the $^{38}$ Cl radioactivity in perchlorates in three valence states. Recoil energy was calculated. The internal conversion of $^{38}$ Cl isomer transition affects the retention value. The greater the radii of the cation, the higher is the probability of the recoil atom breaking through the secondary cage. In ammonium salt, the ammonium ion behaves as a reducing agent. Crystal structures with their greater free space have shown low retention.

• 한국전기화학회:학술대회논문집
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• 1998.12a
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• pp.153-166
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• 1998

Lithium ion Batteries commercially available since the early nineties in Japan are going to be more and more important for portable electronic devices and even EV applications. Today several companies around the world are working hard to join to market for Lithium secondary batteries. Based on the growing interest for commercial use of batteries also the materials have to be reviewed in order to meet large scale production needs. The requirements especially for electrolytes for lithium batteries are extremely high. The solvents and the lithium salts should be of highest purity. So the supply of these chemicals including packaging, transportation and storage but also the handling in production are critical items in this field. Frolic impurities are very critical for LiPF6 based electrolytes. The influence of water is tremendous. But also the other protic impurities like alcoholes are playing an Important role for the electrolyte quality. The reaction of these species with LiPF6 leads to formation of HF which further reacts with cathode materials (spinel) and anode. To understand the role of the protic impurities more clearly the electrolyte was doped with such compounds and was analyzed for protic impurities and HF. These results which directly show the relation between impurities and quality will be presented and discussed. In addition several investigations on different packaging materials as well as methods to analyze and handle the sensititive material will be addressed. These questions which are only partly discussed in literature so far and never been investigated systematically cover some of the key parameters for understanding of the battery chemicals. This investigation and understanding however is of major importance for scientist and engineers in the field of Lithium ion and Lithium polymer batteries.

• Progress in Superconductivity
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• v.7 no.2
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• pp.158-161
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• 2006

Superconducting YBCO films were successfully fabricated by MOD process using chemically modified precursor solution. In this study, a chemically modified precursor solution for MOD processing was synthesized using metal-organic salts and organic additives. It was shown that crack-free and uniform precursor films were formed after calcination in humidified Oxygen atmosphere. Less than 3 hours are required to finish the calcination process. XRD measurement shows that $BaF_2,\;CuO,\;Y_2O_3$ are major constituent of precursor films. Furthermore, YBCO films without any secondary phases were successfully fabricated after annealing in wet $Ar/O_2$ atmosphere. The YBCO film prepared on a $LaAlO_3$ single crystal substrate ($10mm{\times}10mm$) gives transport $I_c$ of 10A at 77K. This chemical modification approach is a possible candidate for improving MOD-processing of YBCO coated conductor.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.18 no.3
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• pp.337-346
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• 2020

Two commonly used ceramics in molten salt research are alumina and mullite. The two ceramics were exposed to a combination of rare earth chlorides (YCl₃, SmCl₃, NdCl₃, PrCl₃, and CeCl₃; each rare earth chloride of 1.8 weight percent) in LiCl-KCl at 773 K for approximately 13 days. Scanning electron microscopy with wave dispersion spectra was utilized to investigate a formation layer or deposition of rare earths onto the ceramic. Only the major constituents of the ceramics (Al, Si, and O₂) were observed during the wave dispersion spectra. X-ray fluorescence was used as well to determine concentration changes in the molten salt as a function of ceramic exposure time. This study shows no evidence of ionic exchange or layer formation between the ceramics and molten chloride salt mixture. There are signs of surface tension effects of molten salt moving out of the tantalum crucible into secondary containment.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.4
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• pp.389-398
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• 1996

In order to understand the relative importance of various pathways leading to the production and transformation of aerosols under different atmospheric conditions, the behavior of atmospheric aerosols have been investigated using a high volume tape sample in Seoul for a week period during August 1990. The concentrations of anion $(SO^{2-}_4, NO^-_3, CI^-)$ and cation $(Ca^{2+}, Na^+, NH^+_4)$ species of aerosol samples were analyzed to identify the ionic composition of aerosols and to estimate their relative contributions to aerosol formation. The concentrations of aerosol species were calculated by a multiple regression model. The results of our calculations indicate the existence of various chemical species such as $(NH_4)_2SO_4, Na_2SO_4, CaSO_4, NH_4NO_3, NaNO_3, Ca(NO_3)_2, NH_4Cl$, and NaCl salts. According to our calculations, the most dominant species of aerosol was $(NH_4)_2SO_4$ with the mean concentration of 23.3 $/mu g/m^3$ (66.9%). The proportion of different componts with aerosol (e.g., $NH_4NO_3$ and $NH_4Cl$) was strongly affected by temperature, relative humidity, and partial presure of gases.

• Progress in Superconductivity and Cryogenics
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• v.7 no.3
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• pp.5-8
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• 2005

Superconducting YBCO films were successfully fabricated by MOD process using F-free Cu precursor solution. In this study. a chemically modified precursor solution for MOD Processing was synthesized using metal-organic salts and F-free Cu precursor. It was shown that crack-free and uniform precursor films were formed after calcination in humidified oxygen atmosphere. Less than 3 hours are required to finish the calcination process. XRD measurement shows that $BaF_2,\;CuO,\;Y_2O_3$ are major constituent of precursor films. Furthermore. YBCO films without any secondary phases were successfully fabricated after annealing in wet $Ar/O_2$ prepared on a $LaA1O_3$ single crystal substrate $(10mm{\times}10mm)$ gives transport Ic of 10A at 77K. This chemical modification approach is a possible candidate for improving MOD-processing of YBCO coated conductor.

• Journal of the Korean Society of Food Culture
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• v.11 no.5
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• pp.569-579
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• 1996

The purpose of the present study is to collect information in terms of the frequency and amounts in frequently consumed foods. We conducted the secondary analysis from '93 Korean National Nutrition Survey. Mainly informations about 2-day food records were used to investigate food intakes and to compare different food patterns by area. Amounts and frequencies of food intakes are on the list by the order of contributing amounts and frequencies. Amounts of total daily intake of food per capita are 1,054g in nationwide, 1,076g in large city, 1,049g in small city, 1,017g in rural. The major foods consumed in large quantities were rice, kimchi, milk, in nationwide, large city, and small city and rice, kimchi, Korean radish in rural. The intake frequency of kimchi, rice, and basic seasonings as garlic, green onion, salts, soy sauce et al, were higher than other foods in all area. However, there are need for further researches to investigate individual dietary intake and seasonal variation of intakes. Also, food consumption patterns for different groups considering age, sex, area should be studied.

• Journal of the Korean Chemical Society
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• v.19 no.5
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• pp.331-338
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• 1975

The distribution of $^{51}Cr\;and\;^{128}I$ recoil species following radiative-neutron capture in chromates, dichromates, iodates and periodates has been investigated by using paper-electrophoresis. In view of the effective recoil energy and the effect of the internal conversion, it is unlikely that an atom which has captured a neutron can remain bound in its original molecule. It is also unlikely that the energy of the recoil atom is dissipated in heating a small region of the crystal. However, the results of paper-electrophoresis separation of recoil $^{51}Cr\;and\;^{128}I$ indicated that many more of the recoil atoms were bound in the parent molecule. The disorder model for the reaction was proposed from observations of retention. In considering cations, the greater their radii, the higher is the probability of the recoil atom breaking through the secondary cage. In ammonium salt, the ammonium ion behaved as a reducing agent in the disorder zone and resulted in low retention. Crystal structures with their greater free space have shown low retention.

• Analytical Science and Technology
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• v.30 no.4
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• pp.182-193
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• 2017

In order to examine the variation characteristics of chemical compositions in relation to the inflow pathways of Asian dust, $PM_{10}$ and $PM_{2.5}$ aerosols were collected at Gosan site of Jeju Island during the Asian dust days between 2010 and 2015, and their chemical compositions were analyzed. The mean mass concentrations of $PM_{10}$ and $PM_{2.5}$ during Asian dust days were $130.0{\pm}90.2$ and $38.2{\pm}24.7{\mu}g/m^3$, respectively. The composition ratios of major secondary pollutants ($nss-SO_4{^{2-}}$, $NH_4{^+}$, $NO_3{^-}$) were high as 53.7 % for $PM_{10-2.5}$ and 90.6 % for $PM_{2.5}$. When the Asian dusts had been transported to the Korean Peninsula via Loess Plateau of central China, the concentrations of $nss-Ca^{2+}$, $NH_4{^+}$, $nss-SO_4{^{2-}}$, and $NO_3{^-}$ increased more noticeably. Whereas in case when the inflow pathways of Asian dust had been through the Bohai bay, the concentrations of the crustal species such as Al, Fe, and Ca were relatively high in coarse particles. The atmospheric aerosols were acidified largely by sulfuric and nitric acids. They were neutralized mainly by calcium carbonate in coarse particle mode passed through Manchuria area, but by ammonia in fine particle mode passed through Loess plateau and Bohai bay. Ammonium salts are assumed to exist as ammonium sulfate and ammonium nitrate in coarse particles, but mostly as ammonium sulfate in fine particles.