• Journal of Soil and Groundwater Environment
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• v.6 no.1
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• pp.63-83
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• 2001

Heavy metals are extracted from stream sediments, roadside soils and sediments and soils and tailings from mining area using partial extraction, acid digestion and HF-digestion. Compared to amounts of heavy metals extracted using partial extraction, those extracted using acid digestion are higher by 2.0∼221 times in Cu, 2.4∼2806 times in Pb, 1.3∼121 times in Cd, 14. 1∼1300885 times in Fe, 1.2∼272 times in Mn, 1.3∼373 times in Zn, 2.2∼1735 times in Cr. There is no special relationship between the extracted amounts of heavy metals using partial extraction and those using acid digestion. However, it is possible that there is a certain relationship between those using acid digestion and those using HF-digestion. Although partial extraction, which extracts less amounts of heavy metals (Cd, Cu, Pb) from soil compared to acid digestion, is used in domestic standard method for examination of soil, domestic soil standard for heavy metals in non-agricultural and industrial areas is higher than soil standard in foreign countries which use acid digestion. For improvement of the domestic standard method for assessment of soil, it is suggested to lower the domestic soil standard for heavy metals or to change pretreatment method for extracting heavy metals from partial extraction to acid digestion with modifying the soil standard.

• Journal of the Korean Chemical Society
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• v.38 no.8
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• pp.576-584
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• 1994

The method described offers rapid and efficient sample preparation using on-line microwave digestion of metal oxides in water sample with direct elemental detection by ICP-AES. The open tubing digestion system(OTD) and the restraint tubing digestion system(RTD) for flow injection(FI) were designed and tested to find the optimum conditions. Comparison of OTD and RTD indicated that RTD was 3 times faster on the digestion time, and 10 times higher on sample mass. Finally, the results of RTD agree well with those by conventional microwave open vessel in all cases and show good precision; Fe and Cu show good with about 5% of RSD, while Zn and Co more or less than 10% RSD.

• Journal of Sericultural and Entomological Science
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• v.44 no.2
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• pp.87-92
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• 2002

Dissolution of Antheraea pernyi silk fiber was carried out in a zinc chloride solution with various dissolving conditions. The solubility was significantly dependent on the concentration of zinc chloride, dissolving temperature and time. The proper conditions of dissolution were found as 8 M zinc chloride, 70$^{\circ}C$ temperature and 30 min dissolving time. Regenerated A. pernyi silk fibroin powder was obtained through dialysis. FTIR and XRD showed that regenerated A. pernyi silk powder was composed of a ${\beta}$-sheet as well as an ${\alpha}$-helix conformation.

• Journal of Radiation Protection and Research
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• v.37 no.4
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• pp.213-218
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• 2012

Alpha spectrometry has been typically used for determination of the uranium isotopes in soil. For a number of uranium analysis in soil samples, rapid sample digestion with limited quantities of mixed acid containing HF will give a contribution for effective management of uranium analysis. Microwave digestion system is evaluated for rapid sample digestion using reference uranium soil (IAEA-375 soil). For completion of 0.5 g of soil digestion by microwave, 3 ml of HF in a 10 ml of mixed acid is minimum requirement volume for completed soil digestion for 80 minutes. Microwave digestion is timely effective techniques for uranium measurement using alpha spectrometry compared to the other methods (open vessel digestion, closed vessel digestion) due to rapid sample digestion. In addition, it can be reduced the occurrence of hazardous substances by minimizing the amount of HF.

• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.223-223
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• 2003

광통신에는 광신호의 전송과 광신호 처리에 처리 과정에서 광 손실을 수반하므로 각 요소별로 광신호 증폭이 반드시 필요하다. 또한 광통신망의 완전 광화를 위해서는 제조 공정이 간단하여 가격이 저렴하고, 높은 신뢰성과 높은 증폭 효율을 가지면서 다른 부품과의 집적화가 가능한 광도파로형 광증폭기가 요구되고 있다 그러나 실리카는 광통신 파장대인 1.55$\mu\textrm{m}$대역의 증폭이 가능한 Er 이온에 대한 용해도가 50ppm 이하로 낮아 lmol% 이상 고농도로 Er 이온을 첨가하여 높은 증폭 효율을 얻는데 한계를 가지고 있다. 따라서 본 연구에서는 Er 이온에 대하여 높은 용해 특성을 가지고 있어 고농도 Er 이온 도핑이 가능한 알루미나에 Er을 1-2 mol% 첨가하여 광발광 특성을 조사하였다. Er이 첨가된 알루미나 나노 졸은 Al(NO$_3$)$_3$ㆍ9$H_2O$와 Er(NO$_3$)$_3$.5$H_2O$가 일정 양 용해된 수용액에 NH$_4$OH를 가하여 침전물을 얻고 여과 및 수세하여 졸 입자의 함량이 약 5wt%가 되게 이온교환수와 해교제인 초산을 소량 가하여 10$0^{\circ}C$에서 약 50시간 열처리하는 방법으로 제조하였다. Er이 첨가된 알루미나 코팅막은 Er 이 첨가된 알루미나 나노 졸에 GPS(3-glycidoxypropyltriethoxysilane)를 Al에 대하여 7 mol% 가하여 스핀 코팅법으로 제조하였다. Si 기판에 코팅하고, 상온에서 90$0^{\circ}C$까지 각 1시간 열처리한 코팅막의 광 발광 특성은 Er 이온의 첨가량과 열처리로 변화된 알루미나 코팅막의 결정상과 연계하여 논의 될 것이다. X-선 회절법으로 분석한 알루미나 코팅막의 온도에 따른 결정상은 boehmite 상에서 약 50$0^{\circ}C$이후에 ${\gamma}$-Al$_2$O$_3$로 전이하고 있다.

• Journal of the Korean Chemical Society
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• v.41 no.8
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• pp.399-405
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• 1997

We examined the determination of trace amount of germanium in rocks and sediments by hydride vapor generation-ICP-AES. Germanium is formed volatile compounds with various types of acid reagents, but volatilizing of germanium was decreased in the presence of $H_3PO_4$. Sediments and rocks can be dissolved by mixed acids of $HF-HNO_3-H_3PO_4$ without volatilizing loss of germanium in open digestion system and it was possible to determine germanium by hydride generation-ICP-AES without further sample treatment. Detection limit of Ge is reached to 0.08 ppb under the condition of 5M $H_3PO_4$ and 1% $NaBH_4$ as a supporting acid and a reducing reagent, respectively. The measured values by hydride generation-ICP-AES agreed well with the reference values of SRMs as well as the values determined by solution nebulization-ICP-MS.

• Economic and Environmental Geology
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• v.52 no.6
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• pp.595-604
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• 2019

The purpose of this study was simply to obtain gold through a microwave-nitric acid experiment of invisible gold concentrate with the use of filter paper. For the purpose, this study conducted a microwave-nitric acid leaching experiment and examined nitric acid concentration. As a result of the experiment, this study discovered that Fe, Te and Ag were completely leached in the leaching solution whereas Au was not determined in all of the nitric acid conditions. The leaching solution was filtered with three filter papers and then these filter papers were analyzed with SEM/EDS. As a result of the EDS analysis, Au was detected in all of the surface and cross-section of the 1st, 2nd and 3rd filter papers. As the three filter papers containing solid-residue were analysed in the lead-fire assay, gold particles were found in all of the nitric acid conditions. In the lead-fire assay, maximum gold(452.50g/t) was recovered when nitric acid concentration was 6M and microwave leaching time was 12mins.

• Journal of Korean Philosophical Society
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• v.117
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• pp.1-33
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• 2011

Plato's political thought is developed in , and . He hopes 'justifiable state' that all citizens can get happiness. He suggests the plan of the ideal state. And the most important element in this ideal state is philosopher-king. His metaphysics, psychology and education theory are melted in philosopher-king. But in actual, the appearance of chis ideal ruler is impossible. Therefore he finds the second best state in . Then does Plato gives up his dream of the ideal state or approaches to that closely? And ruler stands against laws or relates with partnership? This article deals with these problems. As last, we will compare Plato's ideal state and philosopher-king to God's kingdom and Jesus in the Bible.

• Clinical and Experimental Pediatrics
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• v.45 no.11
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• pp.1397-1402
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• 2002

Purpose : One of the major complication of arterial catheterization is the thrombosis of the iliac or femoral arteries. Tissue loss following femoral artery catheterization is rare. However longterm sequelae such as impaired limb growth and future impairment of vascular access, are also important in pediatric cardiac patients. But standard methods to treat thrombotic complication of arterial catheterization in infants and children is not established. The present study was performed to assess the efficacy of intraarterial catheter-directed urokinase infusion in infants and children with limb ischemia due to arterial thrombosis after cardiac catheterization. Methods : From January 1994 to August 2002, 12 patients with thrombotic femoral artery occlusion after arterial catheterization were treated with catheter-directed urokinase infusion in Dong-A University Hospital. Retrospective analysis of the medical records and angiograms was conducted. Results : The incidence of femoral artery thrombosis after retrograde arterial catheterization, which had not responded to systemic infusion of heparin and/or urokinase, was 2.8 percent. The doses of urokinase were 1,000-4,400 unit/kg/hr and duration of infusion was $50.6{\pm}29.2$ hours(18-110 hours). Clot resolution was complete in all patients who started to receive the intraarterial urokinase infusion within four days after catheterization. Only partial thrombolysis was seen in two patients who were treated with intraarterial urokinase on the 12th and 19th days after thrombus formation. Balloon angioplasty was done for these two patients with partial success. Bleeding complications were seen in two cases. Conclusion : Early use of catheter-directed intraarterial infusion of urokinase is safe and effective in thrombolysis of femoral artery occlusion after cardiac catheterization in infants and children.

• Journal of the Korean earth science society
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• v.42 no.1
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• pp.1-10
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• 2021

Silicon (Si) is the second most abundant element in the crust and consists of three stable isotopes, 28Si (92.23%), 29Si (4.67%), and 30Si (3.10%). Si isotopes are widely studied worldwide as a proxy for the biogeochemical cycle of Si to reconstruct the paleoenvironment and paleoclimate. However, in Korea, there have been no studies on biogenic silica using Si isotopes. In this study, we carried out Si isotope measurements of giant diatoms, summarizing the previously reported alkali fusion methods and establishing the best Si separation method for biogenic silica. Samples were completely digested using alkali fusion at high temperatures, effectively separating Si using an AG® 50W-X8 cation exchange resin. To evaluate the precision and accuracy of our measurements, Si isotope standard material (NBS-28) and USGS reference materials (AGV-2, GSP-2, BHVO-2) were analyzed. The results are in excellent agreement with the reported values within the acceptable error. The Si isotope measurement method developed in this study is expected to help in understanding the paleoclimate and paleoenvironment by tracing the Si cycle.