• Korean Journal of Environmental Agriculture
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• v.29 no.4
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• pp.402-407
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• 2010

Zerovalent iron (ZVI) is one of the most commonly used metallic reducing agents for the treatment of toxic contaminants in wastewater. Traditional ZVIs are less effective than nanoscale ZVI (nZVI) due to prolonged reaction time. However, the reactivity can be significantly increased by reducing the size of ZVI particles to nanoscale. In this study, nZVI particles were synthesized under laboratory condition and their efficiency in removing hexavalent chromium (Cr(VI)) from aqueous solutions were compared with commercially available ZVI particles. The results showed that the synthesized nZVI particles (SnZVI) reduced >99% of Cr(VI) at the application rate of 0.2% (w/v), while commercial nZVI (CnZVI) particles resulted in 59.6% removal of Cr(VI) at the same application rate. Scanning electron micrographs (SEM) and energy dispersive spectra (EDS) of the nZVI particles revealed the formation of Fe-Cr hydroxide complex after reaction. Overall, the SnZVI particles can be used in treating chromium contaminated wastewater.

• Korean Journal of Microbiology
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• v.12 no.1
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• pp.25-30
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• 1974

It was convinced that with a relatively small capital investment and with a low operating cost, appreciable amounts of cement copper could be produced from low-grade minerals by the application of a bacterial leaching method. For the recovery of cement copper from the impure pregnant solution, direct precipitation of copper with tin plates by a bacterial leaching method was feasible. The results obtained were as follows: 1)In order to remove the cement copper from the reducing metal, aeration and agitation method were more effective and economic than shaking method. 2)The rate of copper recovery from the pregnant solution was accerelated according to increasing quantities of reducing metal. However, the excess of reducing metal reduced the grade of cement copper. 3)Among the comparative experiments of copper recovery at each reaction temperature of $10^{\circ}C$, $20^{\circ}C$, and $30^{\circ}C$, the recovery rate of copper at $30^{\circ}C$from the pregnant solution was highest. 4)Direct cementation method on iron-containing metal was an excellent method for the recovery of cement copper in bacterial leaching.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.1
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• pp.75-80
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• 2016

This study was conducted to evaluate effect of chemical amendments on reducing bioavailable fraction of heavy metals in soil along with ecotoxicological effect on earthworms, Eisenia fetida. Three different chemical amendments, lime (L), steel slag (SS), and acid mine drainage sludge (AMDS), were applied with varied application ratio (1, 3, 5%). Heavy metal contaminated soil was mixed with chemical amedments and earthworms, Eisenia fetida, were cultivated for 28 days. Bioavailable fraction of heavy metals (Cd, Cu, Pb, and Zn) extracted with 0.1N HCl was monitored and also, mortality, growth, and metal concentration in earthworm were assessed. Result showed that all three amendments had high efficiency to reduce bioavailable fraction of heavy metals in soil. In particular, lime showed the highest reduction rate of Cu (63.9-87.7%), Pb (7.90-24.65%), and Zn (40.83-77.60%) among three amendments. No mortality of earthworm was observed during experimental period except 3% and 5% AMDS treatment indicating that application of chemical amendments is safe in terms of ecotoxicological aspect. However, no positive correlation was observed between reduction of bioavaialble fraction of heavy metals in soil and earthworms. Overall, application of chemical amendments in agricultural field can be adapted for reducing bioavailable fraction of heavy metals and detoxification in soil.

• Journal of the Korea Concrete Institute
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• v.12 no.3
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• pp.11-19
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• 2000

It has been reported that few manufacturers of cement mortar for precast products use chemical and mineral admixture due to the absense of restrictions related to the application of admixture and the poor manufacturing facilities. Therefore, this paper is intended to contribute to the improvement of quality by investigating the properties of cement mortar for precast products using fly ash, blast furnace slag and AE water reducing agent. According to the test results. it was found that the cement mortar products using fly ash and AE water-reducing agent had better qualities than those of ordinary portland cement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.2 s.173
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• pp.355-361
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• 2000

In this study, active control magnetic actuator for reducing vibration of rotor system is performed. Identification, modeling, simulation, control system design, and evaluation of active magnetic damper system have been researched. Power amplifier modeling, connected magnetic actuator and augmented by system identification, is included to establish a magnetic damper simulation which provides close performance correspondence to the physical plant. A magnetic actuator, digital controller using DSP(Digital Signal Processor), and bipolar operational power supply/amplifiers are developed to show the effectiveness of reducing rotor vibration. Also the curve fitting procedure to obtain the transfer function of frequency dependent components is developed. Two kinds of test are executed as sliding and oil bearing. Results presented in this paper will provide a well-defined technical parameters in designing magnetic damper system for the proposed rotor.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.215-218
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• 2005

This paper intended to evaluate the applicability of drying shrinkage reducing superplasticizer (DSRA) by investigating physical properties of concrete using DSRA, The application of flowing concrete method exhibited a less loss of slump and air content with time than those of conventional concrete and had small bleeding. Flowing concrete had larger compressive strength than base and conventional concrete by as much as $3\~5\%$. It also had less drying shrinkage by as much as $20\%$ compared with conventional concrete. This is due to the coupled effect of reduced water content and aqueous type expansive admixture. On the other hand, neutralization depth of flowing concrete showed greater than conventional concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05b
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• pp.69-72
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• 2005

In this study, it is contents to application on AE water reducing admixture for high early strength, which reduce to construction period for cost down in construction. In experiment result on the kinds of AE water reducing admixture for concrete strength promotion, when passed 60 minutes, while it was happened on lignin and naphthalene system about $30\∼35\%$ that loss related to slump, slump flow and air, but happened about $8\∼10\%$ on polycarboxylic system. And the result of compressive strength tests, when 32 hours passed in polycarboxylic system than lignin and naphthalene system, was showing an increase of 10$\%$. Accordingly, concrete properties was measured to condition change by the addition amount and curing temperature of polycarboxylic system. The required curing temperature to gain 5MPa of compressive strength, which is capable of side form stripping, must keep more than smallest 12. 5$^{circ}C$ when polycarboxylic system is used. As a result, AE water reducing admixture of polycarboxylic system may apply effectively to high early strength concrete

• Bulletin of the Korean Chemical Society
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• v.34 no.2
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• pp.505-509
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• 2013

A low temperature ($65^{\circ}C$) thermal deposition process was developed for depositing a silver coating on thermally sensitive polymeric substrates. This low temperature deposition was achieved by chemical reduction of a silver alkylcarbamate complex with latent reducing agent. The effects of acetol as a latent reducing agent for the silver 2-ethylhexylcarbamate (Ag-EHCB) complex and their blend solutions were investigated in terms of reducing mechanism, and the size and shape of silver nanoparticles (Ag-NPs) as a function of reduced temperature and time, and PVP stabilizer concentration were determined. Low temperature deposition was achieved by combining chemical reduction with thermal heating at $65^{\circ}C$. A range of polymer film, sheet and molding product was coated with silver at thicknesses of 100 nm. The effect of process parameters and heat treatment on the properties of silver coatings was investigated.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.11a
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• pp.67-70
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• 2005

Ultra high strength concrete, nowadays, has been widely applied to construction of high-rise building. To improve ductility and mechanical properties, steel fiber is employed in UHSC. This study investigates practical application of expansive additives(EA) and shrinkage reducing agent(SRA), in order to secure volumetric stability and improved mechanical properties, such as autogenous shrinkage and dry shrinkage of steel-fiber-reinforced-ultra-high-strength-comet-mortar(FHSM). According to the test, individual addition of steel fiber does not affect shrinkage reduction, as expected. However FHSM, with combined addition of 5$\%$ of EA and 1$\%$ of SRA decreased 60$\%$ of autogenous shrinkage. It is considered that Proper combination of EA and SRA can secure the shrinkage resistance of FHSM.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.528-537
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• 2008

This paper proposes a dynamic job distribution algorithm in a hybrid NoC structure which can improve system network performance by reducing deadlock and packet drop rate for various multimedia applications. The proposed job distribution algorithm schedules every job to the sub-cluster where packet drop rate can be minimized for each multimedia application program. The proposed Job distribution algorithm and network topology targets multimedia applications frequently used in modern embedded systems, such as MPEG4 and MP3 decoder, GPS positioning system, and OFDM demodulator. Experimental results show that packet drop rate was reduced by about 13.0%, and chip area was increased by about 2.7% compared to the APSRA algorithm. When compared to the XY algorithm popularly used for benchmarking, the packet drop rate was reduced by about 23.9%, while chip area was increased by about 3.0%.