• Resources Recycling
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• v.18 no.6
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• pp.38-45
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• 2009

Dissolution characteristics of magnesite ore in hydrochloric acid solution and removal of impurity were investigated. The dissolution yield increased with increasing temperature and with decreasing particle size. The optimum conditions for dissolution were found to be reaction period of 120 min, reaction temperature of $80^{\circ}C$ and mean particle size of 100. Under optimal dissolution condition the extraction of Mg was 98%. It was found that most of Si and Al exist in the residue, and they can be removed by filtering. Dissolved impurity ions were precipitated as metal hydroxides by pH adjustment. Polymers were used as coagulants for metal hydroxides and the suitable coagulant dosage was 1mg/100ml of non-ionic polymer.

• Journal of Intelligence and Information Systems
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• v.8 no.1
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• pp.63-74
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• 2002

This paper presents an application result of on-line fault diagnosis system for glass melting furnace using a fuzzy expert system. Operators maintain the furnace using the furnace Knowledge and experience, which directly influence the furnace and glass product. Firstly, knowledge and experience is achieved and analyzed to implement the furnace Knowledge and experience into fuzzy expert system. The acquired Knowledges determined as a crisp rule or a fuzzy rule to expect its characteristics. And, a linear regression is used as the input of fuzzy rule to consider the exact knowledge of human operator. The fuzzy expert system is implemented with G2 which is an on-line expert system tool of Gensym Co. The application to a production furnace of Samsung-Corning Co. in Suwon shows successful results of proposed fuzzy expert system.

• Journal of the Korean Chemical Society
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• v.52 no.2
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• pp.186-196
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• 2008

purpose of this study was to investigate college students' understanding of the thermodynamic aspects of the dissolution of solids and gases. The subjects were 34 juniors from the Seoul area who answered questionnaires composed of six items which asked the directions and reasons for the changes in enthalpy, entropy, and the solubility by temperature for the dissolution of solid sodium chloride and gaseous carbon dioxide into water. The results showed that the students understanding of the enthalpy change of dissolution was poor: many students answered that the dissolution of solids is an exothermic process because the dissolution occurs when the solute-solvent interaction is greater than the solute-solute interaction; the students also thought that the enthalpy should be reduced for spontaneous dissolution because the spontaneity depends on the enthalpy change only. For the entropy change, the students understanding was better and they explained it according to the meaning of disorder. For the temperature dependence of solubility, most students answered correctly regarding the direction, but only 25% of them explained the reason accounting for the enthalpy change. Many students who answered incorrectly on the enthalpy change could not explain the reason why.

• 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.

• Proceedings of the KAIS Fall Conference
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• 2012.05a
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• pp.436-439
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• 2012

본 연구는 오존수 제조장치에 인젝터를 이용한 오존 주입방식을 도입하여 소형화, 저전력화를 실현하고자 하였다. 오존발생기, 물-오존 혼합기(인젝터), 오존용해조, 배오존 처리기로 구성된 시스템을 제작하여 인젝터 주입방식에 의한 오존수 제조장치의 오존 용해특성과 그 적용성을 검토하였다. 오존 용해 특성으로 물-공기량에 따른 인젝터 성능, 용해조에서의 오존 용해능 등을 검토하였다. 인젝터 방식은 기존의 가압용해방식에 비하여 저농도 용해능을 보였으나, 인젝터 내부의 물-오존 접촉효율이 높아 평형농도에 도달되는 시간이 단축됨을 확인하였다. 제조된 오존수의 적용 효용성은 용존오존의 잔류시간과 미생물 살균능 검사를 통하여 실시하였다. 횡형식 인젝터 시스템에 의해 용해된 용존오존의 잔류시간이 기존의 가압용해방식에 비하여 다소 짧았으나 미생물의 살균능에는 크게 차이가 나지 않았다.

• Journal of the Korean Chemical Society
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• v.57 no.4
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• pp.507-514
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• 2013

In this study, the characteristics of visually impaired elementary students' conceptions on dissolution were investigated. The semi-structured interviews about phenomenon of dissolution, uniformity of solution, conservation of mass on dissolving and volume change during dissolving were conducted with 4 fifth-grade elementary students with visual impairments (three were blind, and one had low-vision). Interviews were recorded and the data were analyzed after transcription. As a result, students with visual impairments knew well about the phenomenon of dissolution, uniformity of solution, and conservation of mass on dissolving, while they couldn't explain volume change during dissolving. Although students with visual impairments were found to have similar level of understanding with students without visual impairments, they had sounder understanding about uniformity of solution. However, students with visual impairments had superficial understanding based on phenomenal experiences. Some of students with visual impairments tried to give micro-level explanation. Based on these results, educational implications were discussed.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.10 no.2
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• pp.77-85
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• 2012

This study was carried out to remove (/recover) the uranium from the Uranium-bearing Lime Precipitate (ULP). An oxidative dissolution of ULP with carbonate-acidified precipitation and a dissolution of ULP with nitric acid-hydrogen peroxide precipitation were discussed, respectively. In point of view the dissolution of uranium in ULP, nitric acid dissolution which could dissolved more than 98% of uranium was more effective than carbonate dissolution. However, in this case, uranium was dissolved together with a large amount of impurities such as Al, Ca, Fe, Mg, Si, etc. and some impurities were also co-precipitated with uranium during a hydrogen peroxide precipitation. On the other hand, in the case of carbonate dissolution-acidified precipitation, U was dissolved less than 90%. Therefore, it was less effective than nitric acid dissolution for the volume reduction of radioactive solid waste. However, it was very effective to recover the pure uranium, because impurities were hardly dissolved and hardly co-precipitated with uranium.

• Resources Recycling
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• v.18 no.2
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• pp.56-61
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• 2009

The dissolution of domestic aluminum hydroxide of 99.7% purity has been performed with mineral and organic acid prior to the synthesis of aluminum compounds from aluminum solution. Mean particle size of aluminum hydroxide used in the work was $14.4{\mu}m$, $22.9{\mu}m$ and $62.3{\mu}m$, respectively and the effect of reaction temperature, concentration of acid and reaction time on the dissolution of aluminum hydroxide has been examined. As a result, the dissolution of aluminum hydroxide was increased with the concentration of HCl and more than 70% dissolution was obtained with 5 mole/l HCl at $70^{\circ}C$ for reaction time of 4 hr. As far as the dissolution of aluminum hydroxide with sulfuric acid was concerned, it was found that the optimum concentration of sulfuric acid was about 6 mole/l for the effective dissolution of aluminum hydroxide. When oxalic acid was used for the dissolution of aluminum hydroxide, nearly complete dissolution could be obtained by the dissolution for 16 hr with 1.0 mole/l oxalic acid at $90^{\circ}C$.

• The Journal of the Petrological Society of Korea
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• v.3 no.1
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• pp.41-48
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• 1994

Three USGS rock standards (G-2, W-2, and BHVO-1) are decomposed by three different methods, such as open beaker, microwave oven, and alkali fusion method, to compare the effect of decomposition methods for trace elememt analysis in the rock samples. Solubilized trace elements are measured with inductively coupled plasma mass spectrometer (ICP-MS). Generally the analytical results of trace elements between open beaker and microwave digestion method are not different. In case of alkali fusion method, some volatile elements such as Pb, Cu, and Rb are considerably lost. Using acid digestion method, Zr and Hf concentrations are lowered in case that these elements are concentrated in refractory minerals. The concentrations of rare earth elements are generally consistent with the recommended values, but due to large dilution factor, there are some analytical problems in alkali fusion method.

• Journal of Korea Foundry Society
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• v.41 no.1
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• pp.11-15
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• 2021

Scrap steel used as a charge material in melting process of cast iron foundry is mostly press scrap. The press scrap usually causes several problems including energy loss, workability, safety, and so on. By charging the shredded scrap instead of the press scrap, it is expected that the above-mentioned problems can be solved. In this study, the power basic units to produce cast iron by using the press and shredded scrap are compared in 3t/h medium-frequency induction melting furnace. Charging the shredded scrap instead of the press scrap was confirmed that the power basic unit is improved by about 15%. The characteristics and restrictions of the usage according to the shape and size of scrap steel were considered.