• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.7
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• pp.1115-1124
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• 2013

The present study was conducted to ensure the diversity of domestic solar salt by analyzing the composition and microbiological characteristics of solar salt (from Docho island: DS) and the flower of salt produced in different Korean salt flats (Sinui island: SF, Bigum island: BF, and Docho island: DF). The analyses showed that the moisture content of the three types of flower of salt and solar salt ranged from 10.54~13.82% and NaCl content ranged from 78.81~84.61%. The mineral content of those salts ranged from 3.57~5.51%. The content of insoluble matter in these salts was $0.01{\pm}0.00{\sim}0.05{\pm}0.00%$. The sand content of these salts was $0.01{\pm}0.01{\sim}0.03{\pm}0.01%$. By Hunter's color value analysis, the color of the flower of salt was brighter and whiter than solar salt. The salinity of the flower of salt was a little higher than solar salt as well. The magnesium and potassium ion content of DF was $9,886.72{\pm}104.78mg/kg$ and $2,975.23{\pm}79.73mg/kg$, respectively, which was lower than the content in SF, BF, and DS. The heavy metal content of all salts was acceptable under the Korean Food Sanitation Law. The flower of salt was confirmed to be sweeter and preferable to solar salt. More than 80% of the solar salt crystals were 2~3 mm in size, whereas crystals from the flower of salt were 0.5~2 mm in size. The bacterial diversity of DF and DS were investigated by culture and denaturing gradient gel electrophoresis (DGGE) methods. The number of cultured bacteria in flower of salt was approximately three times more than solar salt. By DGGE analysis, major microbes of DF were Maritimibacter sp., Cupriavidus sp., and unculturable bacteria, and those of DS were Cupriavidus sp., Dunalidella salina and unculturable bacteria. The results of DGGE analysis showed that major microorganisms in solar salts were composed of unidentified and unculturable bacteria and only a few microorganisms were culturable.

• Economic and Environmental Geology
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• v.55 no.3
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• pp.281-293
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• 2022

We examined degradation characteristics of lead based pigments(white lead, Red lead, Litharge) according to atmospheric environmet condition, for example atmospheric gas(CO₂, NO₂) and soluble salt. Painted samples not changed material compositions but were occured the color change(𝚫E 4~31) after exposed UV irradiation. All sample were not affected by CO₂ gas not only color but chemical composition. However, samples were remakably changed color exposed NO₂ gas and it was formed secondary product like as lead nitrate. Such as red lead and white lead samples' color difference were 𝚫E 2 and 𝚫 10 respectively and became dark, along with litharge became bright and color difference was 𝚫E 5 after react with NO₂ gas. It confirm that NO₂ was influential factor than CO₂ in the case of same concentration. Furthermore salt spray test was taken to figure out soluble salt influence in fine dust. The result showed noticeable color change and secondary product was formed on samples' surface. The glue film peeled off or hole, and color changed around the secondary products. After salt spray, XRD pattern showed decrease peak intensity and lower crystalinity. As a result of salt spray test, white lead was formed new product litharge and litharge was formed litharge and minium. According to the results, influential atmospheric factors for conservation of paint pigments were UV, NO₂, soluble salt, and litharge was most weakness throughout lead base pigments.

• Journal of the Korean Society of Visualization
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• v.22 no.1
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• pp.18-27
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• 2024

A series of shock wave pulses with Mach number 2.2 of 100, 200, and 300 shocks were applied to lead sulfide (PbS) nanomaterials at intervals of 5 sec per shock pulse. To investigate the crystallographic, electronic, and magnetic phase stabilities, powder X-ray diffractometry (XRD), diffused reflectance spectroscopy (DRS), and vibrating-sample magnetometry (VSM) were employed. The material exhibited a rock salt structure (NaCl-type structure); XRD results indicated that material is monoclinic with space group C121 (5). Further, XRD results showed shifts due to lattice contraction and expansion when material was subjected to shock wave pulses, indicating stable material structure. Based on the data obtained, we believe that the PbS material is a good choice for high-pressure, high-temperature, and aerospace applications due to its superior shock resistance characteristics.

• Journal of Magnetics
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• v.11 no.2
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• pp.98-102
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• 2006

It was examined in this study that magnetic beads, which are assumed to be environmentally functional, could be effective in processing heavy metals that are water pollutants. For the purpose, magnetic beads containing carboxyl groups, which has strong binding force with heavy metals, are mixed with each Cd, Pb, Ni, Cu and Cr(III) solution, then stirred in pH 6. As a results of the process, it was proven that heavy metals bind quickly with magnetic beads through the reaction. In order to analyze heavy metal concentration, magnetic beads bind with heavy metal were collected by external magnetic force and dissolved in acid. The graphite furnace AAS was used to get heavy metal concentration melted in the acid solution. The results showed that heavy metal extractions by magnetic beads were influenced by the type and the concentration of a heavy metal, and over 90% of a heavy metal can be extracted in ppm level save for Cr(III). It was also examined in the study whether heavy metal extraction is influenced when other ions exist in each heavy metal solution. According to experiment, adding other heavy metals to a solution did have little influence on extracting an intended heavy metal. But in case salt or heavy metal chelate was added, Ni extraction changed sensitively although extracting other heavy metals were influenced only when the concentration of an added substance is high. In conclusion, it was shown that magnetic beads could be used to treat wastewater with relatively high heavy metal concentration.

• Food Science and Preservation
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• v.21 no.4
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• pp.520-528
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• 2014

The purpose of this study was to evaluated a phthalate, heavy metal contents and physicochemical quality properties in korean mudflat solar salt and foreign salts. DEHP in mudflat solar salt (MSS) was detected a low level (9.00~669.89 ppb), but it was shown a high level excess to 1.5 ppm criteria in the foreign solar salt (FSS) 5 type (3,440.64, 3,266.56, 2,189.65, 4,010.69, 4,554.20 ppb) and foreign large solar salt (FLSS) 1 type (1,983.27 ppb). Also, DEHP in FSS 2 type (930.15, 1,310.07 ppb) and FLSS 1 type (924.92 ppb) was detected a high level not excess to criteria. No detected DMP, DEP, DIBP, DBP, DAP, BBP, DCHP and DEHA contents in MSS and foreign salt (FS). Na ion was shown a significantly higher level (p<0.05) in FS (407,345.87~426,612.14 ppm) than in MSS (363,633.98 ppm), but it was shown a high level in Mg (p<0.01), K (p<0.05), Ca ion (p<0.05) of FSS compared to foreign refined salt (FRS). Cl ion (532,727.07 ppm) of MSS was the most low level (p<0.001) compared to FS, but it was shown a high level (p<0.001) in Br ion (625.07 ppm). $SO_4$ ion was not shown a significant difference in DS and FS. It was display a high level in Mn of MSS, and Al, Fe of FLSS. Heavy metal contents (As, Cd, Pb and Hg) in MSS and FS was not significant difference, it was safety level as edible salt.

• Resources Recycling
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• v.8 no.1
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• pp.18-22
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• 1999

In order to utilize incineration fly ash of industrial wastes as resources, we present the recovery and separation of metals included in the fly ash by leaching with aqueous solution A great quantity of Cu, Pb, and Zn as well as a small amount oftoxic heavy metals are contained in the leach liquor of the fly ash, and the concentration of the ingredients of the fly ash depends on the industrial wastes which are fed into incinerators. In this paper, sequential Ieachiog operations are conducted using $H_2O$, $H_2SO_4$, $(NH_4)_2CO_3$ and NaOH as Icachants. Water soluble copper salt was leached by $H_2O$, Zn and Pb were separated by the NaOH leach liquor, and water insoluble copper was selectively leached as chelate ion with the $(NH_4)_2CO_3$ leach liquor of the third Ieaehant. Results show that the reduction percent of the fly ash in the leaching steps using $H_2O$, $H_2SO_4$, and $(NH_4)_2CO_3$ is 77%, and the other leaching procedures lose the weight of fly ash by above 60%.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.259-279
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• 1996

최근 정보·전자산업의 발전으로 고 신뢰성 전자재료에 대한 수요가 증대되고 있으며 이러한 첨단산업의 기반의 될 신소재 중 전자세라믹스가 차지하는 비중이 그 대부분을 차지하고 있으며 이에 대한 수요와 기대가 점점 커지고 있다. 이러한 전자세라믹스는 유전재료, 자성재료, 압전재료, 도전성 재료 등으로 나뉘게 된다. 어떠한 분류에 들어가든 그 조성은 금속의 산화물 형태가 일반적이며 미세한 분말의 성형체를 소결(sintering) 함으로써 최종제품으로 완성된다. 이러한 전잣라믹스가 최근 요구되는 고 신뢰성, 고 밀도화를 달성하기 위해선 원료 분말 제조단계부터 제어가 필요하다. 원료분말의 균일·균질성과 그 입도는 소결특성 뿐만아니라 전기적 특성에도 큰 영향을 미치기 때문이다. 세라믹스의 분말제조 방법 중 일반적으로 사용되는 방법으로는 고상 산화물을 혼합하여 하소(calcination)한 후 분쇄하는 '고상합성법'과 금속의 염 또는 alkoxide 용액을 이용하여 화학적으로 제조하는 '습식 화학적 합성법'이 있다. 고상합성법은 합성온도가 높고 기계적 분쇄와 혼합에 의존하므로 균일·균질성이 떨어지고 분말크기를 1㎛ 이하로 만들기 힘들다. 반면에 습식화학적 합성법은 기계적인 분쇄와 혼합에선 얻을 수 없는 원자 혹은 분자단위의 균일한 혼합과 submicron 이하의 미세한 분말을 얻을 수 있다. 따라서 이러한 습식 화학적 합성으로 얻은 분말을 사용하면 미세한 입자의 특성으로 인해 소결온도를 낮출 수 있으며 균일한 미세구조와 균질한 조성을 갖게되어 기계적·전기적 물성증진도 가져올 수 있게 된다. 습식 화학적 분말합성법은 전술하였듯이 alkoxide의 가수분해를 이용하는 sol-gel 법과 금속의 염(salt) 용액을 이용하여, 화학적으로 화합물 침전을 얻거나 또는 공침전물(coprecipitate) 형태의 분말을 얻는, 침전법으로 나뉠 수 있다. 침전법의 근본원리는 pH 및 pCO3 등에 따른 이온종의 용해도 차이를 이용하는 것으로써 각 이온종에 따른 solubility product(ksp)를 이용하여 설명된다. 본 연구에서는 침전법을 사용한 Ba-, Pb-계 전자세라믹스의 분말합성에 대한 이론적 고찰과 공정개발 및 실험을 통한 물성증진 효과에 대해 알아보았다. 본 실험상의 전자세라믹스 조성은 강유전체, 세라믹반도체, 압효과에 대해 알아보았다. 본 실험상의 전자세라믹스 조성은 강유전체, 세라믹 반도체, 압전재료로 널리 사용되는 BaTiO3, PZT(PbZrO3-PbTiO3)와 수직 자기기록매체로 큰 가능성이 있으며 hard ferrite로 널리쓰이는 Ba-feerite(BaFe12O19)로써 수산화물 형태의 침전에 대한 기구(mechanism)와 물성에 대해 살펴보았다. 이러한 침전법에 의한 분말합성 과정에는 소결체의 물성에 영향을 미치는 pH 조절제나 원료에서 혼입될 수 있는 Na+, K+, Cl-, SO4- 등의 제거(washing 혹은 filtering)가 필수적이다. 그러나 침전법에서 얻게 되는 분말은 매우 미세하여 colloid를 형성하게 되며, 이러한 colloid 상태의 미세한 침전입자가 filtering media에 끼이게 되어 견고하면서도 상당한 부피를 가지는 filter cake을 형성하기 때문에 filtering에 많은 시간과 다량의 filtering agent (본 실험의 경우엔 증류수)가 필요하게 된다. 따라서 이러한 문제점을 해결하기 위하여 colloid 상태의 침전물을 얼렸다 녹이는 freezing process를 개발, 적용하여 그 원리 및 효과, 그로인한 분말형태를 관찰하여 보았다.

• Journal of the Korean earth science society
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• v.25 no.6
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• pp.428-442
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• 2004

Dustfall samples were collected by the modified American dust jar (bulk type) at 5 sampling sites in the Nakdong river area from lune 2002 to May 2003. Nineteen chemical species (Al, Ca, Cd, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, Pb, Si, V, Zn, $Cl^-$, $NO_3^-$, $SO_4^{2-}$, and $NH_4^+$) were analyzed via the combination of ICP/AES, AAS, IC and UV. The purposes of this study were to qualitatively evaluate the chemical composition of dustfalls by examining their regional and seasonal distribution patterns. Computation of the enrichment factor showed that well-defined anthropogenic sources, particularly in Pb were found in the order Gamjeondong (industrial area), Wondong, Silla University, Samrangiin and Mulgum. The seasonal mean of soil contribution showed its highest value (16.3%) during the winter with an annual mean of 11.2%. The concentration ratio of [$SO_4^{2-}/NO_3^-$] was found to be highest (5.12) during the winter, while the lowest ratio value (3.30) was seen during the all. fall, Also regional equivalent ratios of [$SO_4^{2-}/NO_3^-$] were found in the order: Silla University (6.78), Gamjeondong (4.98), Mulgum (3.95), Wondong (3.85), and Samrangjin (2.87). Seasonal distribution of water soluble components for total dustfall were found in the order: spring (71.6%), summer (61.2%), fall (49.2%) and winter (48.6%) with a mean ratio of 57.6%. Regional contribution of sea salts of water soluble ions were found in the order: Silla university (34.5%), Gamjeondong (28.3%), Wondong (17.3%), Samrangiin (17.2%) and Mulgum (13.8%), the total mean contribution rate was 22.1%. As for the chemical composition of dustftll on the lower Nakdong river, there is a decreased influence of sea salt and artificial anthropogenic sources and increased influence of soil particle inland. Also, the total amount of deposition on the lower Nakdong river has decreased, with the river's surface serving as a confounding factor in resuspending dusts.

• Journal of environmental and Sanitary engineering
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• v.6 no.1
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• pp.47-62
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• 1991

Yellow Sand Phenomena was observed from April 8 th to 10 th in 1990. During this period particle was collected to investigate the chacteristics of chemical composition of particulate by High Volume Air Sampler and Andersen Air Sa~npler in Seoul. During this period the particle concentration was 350 yg/$m^3$ and the anions, cations, and metal concentrations were increased and the orders of these were $S0_4\;^{-2}>N0_3\;^->Cl^->F^-, Na^+>Ca^{+2}>NH_4\;^+>Mg^{2+}>K^+$, and Fe>Al>Si>Zn>Pb respectively. The principal source of Yellow Sand were identified soil and sea salt. Mn used by the trace element of soil, the persentage of contribution from soil was calculated to be about 81.3% for the particle increased by Yellow Sand Phenomena. Also the principal chemical compounds of particle were estimate metals(Fe, Al, Si, Zn) oxides, $CaSO_4, NaSO_4, MgSO_4, NaC1, MgCl_2$ and $(NH_4)_2SO_4$.

• Korean Journal of Materials Research
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• v.11 no.11
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• pp.991-996
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• 2001

This study is the manufacture of solid lubricant oilless bearing using sintered parts. PTFE was as organic solid lubricant and $MoS_2$ as inorganic solid lubricant, and its characteristics were studied. Thickness of lubricant was suited 25~$100\mu\textrm{m}$ for lubricant characteristics. Curring temperature of MoS_2$ film was 12$0^{\circ}C$, 2 hours and that of PTFE film was $260^{\circ}C$, 20 minutes. The solid weight and solid volume of $MoS_2$ film was 51.7% and 27.4%, and that of PTFE was 44.9% and 24.3%. Chemical resistant of PTFE solid lubricant oilless bearing was excellent as salt test was 520hours, and usable temperature range was $-200~+280 ^{\circ}C$. Conduction of electricity can be increase by addition of graphite or $$\alpha$- PbO_2$. The electric conductivity was 100~180$\Omega$.