• Proceedings of the Korea Air Pollution Research Association Conference
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• 2004.11a
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• pp.461-462
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• 2004

• Proceedings of the Materials Research Society of Korea Conference
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• 1995.11a
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• pp.87-87
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• 1995

• Journal of Korean Society of Water and Wastewater
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• v.22 no.5
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• pp.531-540
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• 2008

The main advantage of dissolved air flotation (DAF) in water treatment process is the small dimension compared with conventional gravity sedimentation and it can be basically reduced by the separation zone performed with the short solid-liquid separation time. Fine bubbles make such a short time possible to carry out solid from liquid separation as a collector on the course of water treatment. Therefore, the dimension of separation zone in DAF process is practically determined by the rise velocity of the bubble-floc agglomerates, which is a floc attached with several bubbles. To improve flotation velocity and particle removal efficiency in DAF process, many researchers have tried to attach bubbles as much as possible to flocs. Therefore, the maximum number of attached bubble on a floc and the rise velocity of bubble-floc agglomerates considered as the most important factor to design the separation zone of flotation tank in DAF process was simulated based on the population balance theory. According to the simulation results of this study, the size and volume concentration of bubble influenced on the possible number of attached bubble on a floc. The agglomerates attached with smaller bubble was more sensitive to hydraulic loading rate in the separation zone of DAF process. For the design of a high rate DAF process applied over surface loading 40 m/hr. it is required a precise further study on the variation of bubble property and behavior including in terms of bubble size distribution.

• Microbiology and Biotechnology Letters
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• v.31 no.4
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• pp.342-347
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• 2003

Clumping of cells is one of the major obstacles to culture wild myxobacterial strains in liquid media. In an effort to solve this problem, we tried a method isolating spontaneous mutants that grow dispersed in liquid media from a wild myxobacterial strain. Myxococcus stipitatus KYC1001, a newly isolated strain from Gyearyongsan National Park in Korea, clumps and sticks to the surface of culture vessels as other wild myxobacteria behave in liquid media. Taking an advantage of the characteristics that dispersed mutant cells would grow dispersed while most other wild type cells would clump and stick to the surface of culture vessels, spontaneous dispersed mutants were enriched by repeated subculturing of culture supernatant. A resultant mutant, KYC2001, did not form any clumps nor stick to the surface of culture flasks, but grew completely dispersed in liquid. Meanwhile, three other spontaneous mutants, KYC2002, KYC2003, and KYC2004, shelved partially dispersed phenotype. A major portion of the cells grew dispersed in liquid but they still formed some clumps.

• Journal of the Korean Ceramic Society
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• v.35 no.10
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• pp.1078-1084
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• 1998

lanthanum chromite(LaCrO3) powder was synthesized by the combustion of a solution of metal nitrates La(NO3).6H2O and Cr(NO3)3.9H2O and urea. The pH of solution affected a yield of the combustion products but did not influence the morphology of the products. When the pH of the solution was in the range of 0.7-4, the yield of the combustion products was more than 90% The morphology of the combustion products was af-fected by heating methods for the solution. The hot-plate induced heating of the solution yielded powders hav-ing two-dimensionally interconnected agglomerates whereas microwave-induced heating produced a fine and non-agglomerated powders. The specific surface area(BET) of the combustion products using microwave-in-non-agglomerated powders. The specific surface area(BET) of the combustion products using microwave-in-duced heating method were larger(25~32m2/g) than that of hot plate heating method(10-14m2/g)

• Transactions of the Korean Society of Automotive Engineers
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• v.15 no.1
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• pp.116-124
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• 2007

An optical method to measure the size and number density of soot aggregates in diesel exhaust has been proposed in this study. Two laser beams in co-axial alignment transmit a soot loaded exhaust gas flow, and the transmittance at each wavelength is detected by a photo diode simultaneously. The volume equivalent diameter and number density of soot aggregates in the optical path can be theoretically given by the transmittance values measured at two wavelengths. A test conducted by a single cylinder, 4 cycle, small and DI diesel engine shows that the temporal variations of the size and number density of soot aggregates in the diesel exhaust can be measured by the proposed method at a transient mode operation. It is found that the volume equivalent diameter varied temporally from 70 to 110 nm during the period that high soot concentration is observed. One can also conclude that the optical length longer than 1 m in the dynamic range regarding this method is preferable for measuring soot concentration at the level of $1\;mg/m^3$.

• KSBB Journal
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• v.7 no.3
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• pp.166-171
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• 1992

Zoogloea ramigera 115 was cultured for biopolymer production and its bioflocculant usages. Cultural conditions of the organism were examined with regard to high production of the microbial polysaccharide. The most suitable medium was found to contain glucose as a carbon source, $NaNO_3$ as a nitrogen source, and yeast extract as an organic nutrient. The initial pH of 6.0 proved to optimal. The biopolymer was extracted effectively using ultrasonication and high speed centrifugation, followed by propanol addition. Jar test results indicate that the polysaccharide produced by the organism is an effective flocculant.

• Journal of Conservation Science
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• v.28 no.2
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• pp.165-173
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• 2012

In this work, scientific and systematic analysis was conducted for finding out the methods and techniques of ancient ink stick making. Analysis the ancient ink stick on ancient documents and wooden writing as letter or painting, we concluded as followings. From the analysis of ancient wood by dendrochronology, wood was cut at 1899, which provided the information on the year of ink stick's made on writing on ancient wood. Single particle size for soot of ancient ink stick was 107 nm for ink on the roof-filling timber in Sinsunwonjeon of Changdeok Palace, compared to 38 to 86 nm on the letter on ancient 12 paper document. Aggregate particle size was 370 nm for ink on the roof-filling timber in Sinsunwonjeon of Changdeok Palace, but 206 to 318 nm for aggregate particle size on 12 paper documents. There was similar pattern between single particle size and aggregate particle size of soot, which might provide the information of raw material for ancient ink. From infra-red and Raman spectroscopic analysis of sheet of writing on paper or wood, there was severe interference from background material (paper or wood). From Raman spectroscopic analysis of ancient ink carefully separated from ancient wood, spectrum pattern was closer to ink stick made by the soot from pine burning.

• Journal of Korean Society on Water Environment
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• v.36 no.3
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• pp.185-193
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• 2020

Bimodal flocculation describes the aggregation and breakage processes of the flocculi (or primary particles) and the flocs in the water environment. Bimodal flocculation causes bimodal size distribution with the two separate peaks of the flocculi and the flocs. Extracellular polymeric substances and ionic species common in the water environment increase the occurrence of bimodal flocculation and flocculi-floc size distribution, under the flocculation mechanisms of electrostatic attraction and polymeric bridging. This study investigated bimodal flocculation and flocculi-floc size distribution, with respect to the extracellular polymeric substance concentration and ionic strength in the kaolinite-containing suspension. The batch flocculation tests comprising 0.12 g/L of kaolinite showed that the highest flocculation potential occurred at the lowest xanthan gum (as extracellular polymeric substances) concentration, under all the ionic strengths of 0.001, 0.01, and 0.1 M NaCl. Also, it was important to note that the higher ionic strength resulted in the higher flocculation potential, at all the xanthan gum concentrations. The bimodal flocculation and flocculi-floc size distribution became apparent in the experimental conditions, which had low and intermediate flocculation potential. Besides the polymeric bridging flocculation, steric stabilization increased the flocculi mass fraction against the floc mass fraction, thereby developing the bimodal size distribution.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.40 no.6
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• pp.365-372
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• 2016

Using the computational fluid dynamics (CFD) technique, we simulated the fluid flow in a Taylor reactor considering the aggregation and breakage of particles. We calculated the population balance equation (PBE) to determine the particle-size distribution by implementing the quadrature method-of-moment (QMOM). It was used that six moments for an initial moments, the sum of Brownian kernel and turbulent kernel for aggregation kernel, and power-law kernel for breakage kernel. We predicted the final mean particle size when the particle had various initial volume fraction values. The result showed that the mean particle size and initial growth rate increased as the initial volume fraction of the particle increased.