• Journal of the Korean Applied Science and Technology
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• 제28권4호
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• pp.386-392
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• 2011

We are crystallized to the linear low density polyethylene(LLDPE) particles by a thermally induced phase separation(TIPS). TIPS process based on the phase separation mechanism was performed for the LLDPE system which undergoes liquid-solid phase separation. The linear low density polyethylene particle formation occurred by the nucleation and growth mechanism in the metastable region. Although the growth rates depended on the experimental conditions such as the polymer concentration and temperature, the particles were larger when the polymer concentration was higher or temperature was higher. The particles were observed by SEM. The LLDPE particle size distribution became broader when the polymer concentration was higher.

• Particle and aerosol research
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• 제12권1호
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• pp.21-26
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• 2016

In order to realize In-line and convenient measurement for solid-gas two phase flows, Light Transmission Fluctuation (LTF) based on the random variation of transmitted light intensity, light scattering theory and cross-correlation method was presented for online measurement of particle size, concentration and velocity. The statistical relationship among transmitted light intensity, particle size and particle number in measurement zone was described by Beer-Lambert Law. Accordingly, the particle size and concentration were determined from the fluctuation signal of transmitted light intensity. Simultaneously, the particle velocity was calculated by cross-correlation analysis of two neighboring light beams. By considering the influence of concentration variation in industrial applications, the improved algorithm based on spectral analysis of transmitted light intensity was proposed to improve measurement accuracy and stability. Therefore, the online measurement system based on LTF was developed and applied to measure pulverized coal in power station and raw material in cement plant. The particle size, concentration and velocity of powder were monitored in real-time. It can provide important references for optimal control, energy saving and emission reduction of energy-intensive industries.

• Membrane Journal
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• 제14권3호
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• pp.218-229
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• 2004

We prepared monodispersed calcium alginate microspheres by controlling various conditions of emulsification procedure using a lab-scale batch type membrane emulsification system equipped with SPG (Shirasu porous glass) tubular membranes. We determined the effects of process parameters of membrane emulsification (ratio of dispersed phase to continuous phase, alginate concentration, emulsifier concentration, type and concentration of stabilizer, transmembrane pressure, concentration of crosslinking agent, stirring speed and membrane pore size) on the mean size and size distribution of alginate microspheres. The increase of the ratio of dispersed phase to continuous phase, transmembrane pressure and alginate concentration led to the increase in the mean size of alginate microspheres. On the contrary, the increase in emulsifier concentration, stirring speed of the continuous phase and concentration of the crosslinking agent caused the reduction of the mean size of microspheres. Through controlling these parameters, monodisperse alginate microspheres with about $6{\mu}{\textrm{m}}$ of the mean size and 1.1 of the size distribution value were finally prepared in case of the using SPC membrane with the pore size of $2.9{\mu}{\textrm{m}}$.

• Membrane Journal
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• 제31권1호
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• pp.52-60
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• 2021

When preparing calcium alginate microspheres using rotating membrane emulsification that rotates SPG (Shirasu porous glass) tubular membrane in the continuous phase, the optimal conditions of rotating membrane emulsification process parameters for producing monodisperse microspheres were determined. We determined the effects of process parameters of rotating membrane emulsification (the rotating speed of membrane module, the transmembrane pressure, the ratio of dispersed phase to continuous phase, the alginate concentration, the emulsifier concentration, the stabilizer concentration, the crosslinking agent concentration, and the membrane pore size) on the mean size and size distribution of alginate microspheres. As a result, the size of the microspheres decreased as the rotating speed of membrane module, the emulsifier concentration, and the crosslinking agent concentration increased among the process parameters of rotating membrane emulsification. On the contrary, as the ratio of dispersed phase to continuous phase, the transmembrane pressure, and the alginate concentration increased, the size of the microspheres increased. In the rotating membrane emulsification using an SPG membrane with a pore size of 3.2 ㎛, it was possible to finally prepare monodisperse alginate microspheres with a particle size of 4.5 ㎛ through the control of process parameters.

• Journal of Microbiology and Biotechnology
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• 제6권5호
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• pp.352-357
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• 1996

The partition of proteins in the salt-rich phase of polyethylene glycol (pEG)/salt aqueous two-phase systems is limited by the salting-out effects of salt. The logarithm of the concentration of proteins partitioned in the salt-rich phase decreases linearly with increases in the concentration of salt in the salt-rich phase (salting-out). Therefore, the partition of a given protein in the salt-rich phase of aqueous two-phase systems can be estimated from the salting-out constant. The slope of the solubility line (salting-out con-stant) for a given protein is determined by the type of salt in the two-phase systems.

• Bulletin of the Korean Chemical Society
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• 제11권5호
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• pp.411-415
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• 1990

The dabsylation of amino acids has been applied to resolve their optical isomers with the use of chiral mobile phase in high performance liquid chromatography. The dabsyl amino acids were successfully separated on reversed phase column($C_{18}$) by adding a chiral L-benzylproline-Cu(II) chelate to the mobile phase. The separation selectivity of the dabsyl amino acid enantiomers was not less than that of dansyl amino acids. The retention order of the dabsyl amino acid enantiomers was as those of the dansyl amino acid enantiomers except dabsyl threonine. The optical selectivity of the dabsyl amino acids increase with pH of the mobile phase and concentration of the chelate, but slightly decreases with concentration of buffer and organic solvent composition. However serine, methionine, valine, and leucine showed a slight decrease in the optical selectivity with increase in pH. The retention times of the dabsyl amino acids decreases with increasing pH and acetonitrile concentration but increases with the concentration of the chiral chelate added. The mechanism of the optical resolution is based on a stereospecific interaction including a intramolecular hydrophobic effect and SN-2 reactivity of the ligand exchange chromatography.It is advantageous to detect absorption at 436 nm, which is less interferent them the other detection systems. The derivatized dabsyl amino acids are stable for a month.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제22권4호
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• pp.499-509
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• 1998

In the absorption process of water vapor in a liquid film, the composition of the gas phase, in which a non-absorbable gas is combined with the absorbate influences the transport characteristics remarkably. In the present study, the absorption processes of water vapor into aqueous solution of lithium bromide in the presence of non-absorbable gases were investigated analytically. The continuity, momentum, energy and diffusion equations for the solution film and gas phase were formulated in integral forms and solved numerically. It was found that the mass transfer resistance in gas phase increased with the concentration of non-absorbable gas. However the primary resistance to mass transfer was in the liquid phase. As the concentration of non-absorbable gas in the absorbate increased, the liquid-vapor interfacial temperature and concentration of absorbate in solution decreased, which resulted in the reduction of absorption rate. The reduction of mass transfer rate was found to be significant for the addition of a small amount of non-absorbable gas to the pure vapor, especially at the outlet of an absorber where non-absorbable gases accumulated. At higher non-absorbable gas concentration, the decrease of absorption flux was almost linear to the volumetric concentration of non-absorbable gas.

• Journal of the Korean Society of Safety
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• 제16권2호
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• pp.44-50
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• 2001

The rotated bending fatigue test was conducted in air md in 3.5% NaCl salt solution to investigate the fatigue fracture behaviour of raw material and F.E.M dual phase steel made from raw material(SS41) by a suitable heat treatment. This study has compared the initial microcrack creation of material by tensile test with that by fatigue test. And the rotated bending test of cantilever type under the condition of 3.5% NaCl salt solution and air has investigated the corrosion fatigue fracture behaviour with the variation of stress concentration factor determined by each of notch shapes. The initial microcrack have been developed in fragile grainboundary with general corrosion occurring in raw material : in the pits built up by corrosion in F.E.M. dual phase steel because pits bring out stress concentration. It is small that the degree of decrease in corrosion fatigue life for F.E.M. dual phase steel compared with raw material because the notch sensitivity of F.E.M. dual phase steel is lower than raw material in reason of characteristics with two-phase construction.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• 제21권3호
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• pp.347-357
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• 2023

United States Nuclear Regulatory Commission (U.S. NRC) specifies regulations on obtaining licenses and describes the technical position on the average waste concentration, also known as Concentration Averaging and Encapsulation Branch Technical Position (CA BTP); CA BTP helps classify blendable waste and discrete items and address concentration averaging. The technical position details are reviewed and compared in a real environment in Korea. A few cases of concentration averaging based on the application of CA BTP to domestic radioactive waste are presented, and the feasibility of the application is assessed. The radioactive waste considered herein does not satisfy the Disposal Concentration Limit (DCL) of the second-phase disposal facility while applying the preliminary classification. However, if CA BTP is applied when the radioactive waste is mixed with other radioactive waste items in a large and heavy container, it can be disposed of at the second-phase disposal facility in Gyeongju Repository. To apply the CA BTP of the U.S. NRC, it is necessary to investigate the safety assessment conditions of the US and Korea.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제24권11호
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• pp.870-875
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• 2011

The $(Na_{0.52}K_{0.44})(Nb_{0.9}Sb_{0.06})O_3-0.04dLiTaO_3$ (NKNS-LT) ceramics with various $Cu_2O$ concentration were prepared by the conventional solid state reaction method. The $Cu_2O$ content was varied in the range of 0.1~0.4 wt%. The effects of Cu on microstructure, crystallographic phase transition, and piezoelectric properties were investigated. The material with perovskite structure had a tetragonal phase (T1) when $Cu_2O$ concentration was less than 0.3 wt% and it transformed to another tetragonal phase (T2) when the $Cu_2O$ amount was greater than 0.3 wt%. The phase boundary between T1 and T2 phases appeared at around 0.3 wt% of $Cu_2O$ concentration. The piezoelectric properties were shown the maximum values at the composition of the phase boundary. The electro-mechanical coupling factor ($k_p$) was 0.42 and the piezoelectric charge constant ($d_{33}$) was 245 pC/N at the 0.3 wt% of $Cu_2O$ concentration.