• Polymer(Korea)
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• v.25 no.4
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• pp.476-485
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• 2001

In this study, we tried to design and synthesize using natural polymers (hyaluronic acid and sodium alginate) and also to make some kinds of scaffolds as sponge type for reducing the burst effect of loaded drug from them. Photo-dimerizable group was incorporated to hyaluronic acid and degradable hydrogel was prepared by the UV radiation of the polymer. The pore size and its distribution of scaffold were controlled by changing microsphere production conditions such as solution concentration and spraying pressure. It was found that drug release behavior from synthesized scaffolds was affected by hybridization of two naturally originated polymers (cinnamoylated tetrabutylammonium hyaluronate: CHT and cinnamolylated sodium alginate: CSA) and the obtained scaffolds were degraded in fairly long time (about 2 months) under in vitro environment. Therefore, we expect that obtained scaffolds can be applicable for the tissue regeneration scaffolds in the fields of orthopaedic surgery.

• Korean Journal of Materials Research
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• v.3 no.5
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• pp.521-528
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• 1993

Ni-graphi~e composite powders were prepared by reduct ion of $Ni^{++}$ from arnmoniacal nickel sulfate solution on graphite core by hydrogen gas at elevated temperature and pressure. Effect of coating catalyst. Anthraquinone $(C_6H_4COC_6H_4 CO)$, on the reduction rate and the properties of nickel layer were investigated by SEM, X-ray, size and chemical analysis. 1nduct.ion period, a time lag between the ~njection of hydrogen gas and the start of the reduction, was 22 to 70 mins and was affected by the size and amount of Anthraquinone. Kickel layer deposited on the surface of graphite core material was composed of nickel nodules whose sizes were different with vari~ ous reduction conditions. Minimum diameter of nickel nodules was about 2-3$\mu \textrm m$.

• Journal of the Korean Chemical Society
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• v.39 no.12
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• pp.946-954
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• 1995

The physico-chemical nature of the rare earth oxide which was produced by the caustic fritting of monazite was studied to furnish fundamental data that are required for its efficient use and processing. It was found that the material which was mainly constituted of light rare earths and thorium was a solid solution phase of oxide whose structure was fluorite-type face centered cubic. Its density was 6.75 g/$cm^3$ and it had a uniform particle size distribution at around 1 ${\mu}m.$ The crystallinity improved by heating to elevated temperatures, whereas the solubility in HCl decreased as the crystallinity improved. Complete dissolution in conc. HCl solution in short time (30 min.) was attained by heating to 70$^{\circ}C$. The measurement of zeta potential showed its I.E.P. to be at pH 8.6 of the suspension.

• Journal of Advanced Marine Engineering and Technology
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• v.37 no.5
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• pp.510-519
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• 2013

In this study, the spray characteristics of a pressure swirl atomizer classified into a liquid sheet-type swirl nozzle for Urea-SCR system were investigated experimentally with the variation of injection pressure. The length to diameter ratio ($l_o/d$) of the nozzle was 3.1, and the swirler was set inside the nozzle tip to give injecting fluid angular momentum. The injection duration of the nozzle was controlled by PWM (pulse width modulation) modes. The development processes of the spray were imaged by a 2-D PIV system, and the change of spray angle was measured. The atomization characteristics, including axial velocity and SMD, were measured using a 2-D PDA system with the injection pressures at room temperature and ambient pressure conditions. As the experimental results, the injection pressure had a significant impact on the spray structure showing a different shape around the spray leading edge, and the smaller SMD was observed with increasing injection pressures, which was similar to that of the previous work.

• Resources Recycling
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• v.5 no.3
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• pp.50-55
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• 1996

The synthesis of Ca,,(PO,),(OH), by adding (NFIa)J),HPO, to lhe solution of Ca(NO,), dlssolvad CaO in HNO, and contmlled pH with NH,OH was carried out for certain time at room temperahire and atmosphere. Ca,,(PO,),(OH), was rorrned at the range from pN 10 to pH 13. The particle s~zeof Ca,,(PO,),(OH)i was 0.1-0.5 &In. Thc optimum reaction lime was 30 min, and the temperature was 40-70$^{\circ}$C. the shape also was not changed in spite of heating to iDVC hr 1 hour the c~ystalliratian temperature was 90$^{\circ}$C Ca,,(PO,),(OH), was calcinatcd and the shape also was not changzd, in spile of hcaling to 500$^{\circ}$C for 1 hour. But Ca,,(PO,),(OH), calcinated for lhour al 800$^{\circ}$C was changed to the spheric particle of Ca,,,(PO,),(OH),, CaO and Ca,(PO,),.

• Journal of the Korean Society of Mineral and Energy Resources Engineers
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• v.55 no.6
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• pp.517-526
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• 2018

In order to remove pollutants from the soil in the Ka-hak mine site, this study investigates optimization of the acid washing conditions for the soil. The soil at the site is presumed to be contaminated by diffused heavy-metal-contaminated tailings. The major heavy metal pollutants in the soil are copper, lead, and zinc. Gravels larger than 5mm in size constitute approximately 38% of the soil, and these are the least polluted by heavy metals. On the other hand, it is difficult to reduce the concentration of heavy metals in fine soils, particularly those whose sizes are less than 0.075 mm. The results of the continuous process using a hydro-cyclone show that fine soil particles consisting of at least 20% of the raw soil must be separated before the chemical soil washing process in order to achieve reliable cleaning.

• Journal of the Mineralogical Society of Korea
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• v.15 no.1
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• pp.33-43
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• 2002

Mineral composition and chemical properties of Hwangto (reddish residual soil) that used in feeding of cattles at Iksan, Jeollabuk-do, Korea were examined according to particle size separation such as gravel, sand, silt, coarse clay and fine clay. Mineral composition analyses reveal that gravel and sand are mainly composed of quartz and feldspars and that kaolin mineral and illite are dominant in clay and silt. Iron oxides are mainly included in fine clay. According to chemical analyses of major elements, Al, Fe and $H_2O$ contents are increased with decreasing of particle size. This trend well agrees with increase of clay minerals in smaller particles, Chemical analyses of trace elements indicate that contents of Zn, Rb, Sr, Ba, Pb significantly differ with particle sizes. Ba and Sr are included in feldspars since these elements are abundant in sand containing abundant feldspars. Pb and Sm are abundant in sample before particle size separation, but the contents are significantly decreased after separation. Therefore, most of these elements appear to be existed as removable phase. Nb, La, Th, Ce are more abundant in silt. The contents of all the other trace elements tend to be increased in smaller particles containing more clay minerals. The contents of changeable cations and teachable elements in acid and alkali solutions are high in clay samples. All the above results indicate that using the portion of smaller particle of Hwangto for livestock feed rather than bulk Hwangto can improve cation exchangeable capacity, ion leaching capacity and sorption properties.

• Resources Recycling
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• v.15 no.3 s.71
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• pp.46-57
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• 2006

This study was carried out for the purpose of recovering the refined gypsum from waste phosphogypsum. The refined gypsum was recovered as a under product of 325 mesh wet screening followed by dehydration and hydration stage. The influence of dehydration temperature and time, dehydration rate, aging time, slurry density of hydration and sonication time on the yield and grade of gypsum were investigated. The refined gypsum of $94{\sim}96%$ grade is recovered in 95% yield by wet screening after selective dehydration and hydration process, from the phosphogypsum. For the better separation efficiency of gypsum, it is recommended to treat the phosphogypsum at the conditions of as follows; 6hr's dehydration at $140^{\circ}C$, hydration slury density of $3{\sim}10%$, hydration temperature of $20{\sim}30^{\circ}C$, hydration time of 2hr. In additions, addition of sodium citrate 0.005M and sonication of $5{\sim}10min.$ are effective for increase the recovery of gypsum. On the other hand, aging the dehydrated gypsum 16 hours or longer make decrease the recovery of gypsum remarkably.

• Resources Recycling
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• v.21 no.4
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• pp.44-52
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• 2012

The purpose of this study is to confirm the possibility of obtaining high grade coal from fixed carbon 20.68% coal. Also, the mineralogical, physical/chemical and liberation characteristics was found with the aim of decrease in ash amount, during the pre-processing of clean coal technology. In this study, batch flotation and microbubble column flotation that was appropriate for the processing of fine particles was used with the variation in kinds and quantity of frother, collector and depressant. Also grinding time, air flow rate and feeding rates were examined. As a result of batch flotation, using pulp density 20%, collector DMU-101+dodecyl amine(100 mL/ton), frother pine oil (200 mL/ton), depressant sodium silicate(1 kg/ton), obtained the result of ash rejection 81.55% and combustible recovery 70.23%. In result of microbubble column flotation, the result was ash rejection 83.85% and combustible recovery 70.42% under the condition of pulp density 5%, grinding time 5 min. collector DMU-101+DDA(100 mL/ton), frother AF65(5.4 L/ton), depressant SMP(3.5 kg/ton), wash water(360 mL/min.) and air flow rate(1,197 mL/min.).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.11
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• pp.1005-1013
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• 2010

This study was conducted to assess the spray control of flash boiling with mixed fuel in consideration of HCCI (Homogeneous Charge Compression Ignition) engine condition. Mixed fuel existing in two phase regions can control the process of mixture formation under low temperature and density by using the spray resulting from flash boiling which is able to induce rapid evaporation of fuel spray as well as the evaporation of high boiling point component. Because HCCI engine injects the fuel early under ambient conditions, it can facilitate the chemical control of ignition combustion and physical control such as breakup and atomization of liquid fuel by flash boiling of mixed fuel which consists of highly ignitable light oil and highly volatile gasoline. This study was conducted by performing video processing after selected composition and molar fraction of the mixed fuel as major parameters and photographed Schlieren image and Mie scattered light corresponding to the flash boiling phenomenon of the fuel spray that was injected inside a constant volume vessel. It was found that flash boiling causes significant changes in the spray structure under relatively low temperature and density. Thus, we analyzed that the flash boiling spray can be used for HCCI combustion by controlling the mixture formation at the early fuel injection timing.