• Membrane and Water Treatment
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• v.9 no.1
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• pp.23-31
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• 2018

In this study, a new method called as multi-dropped liquid membrane (MDLM) which is more practical and more effective than other liquid membrane techniques is applied for transport of Zn(II) has been studied. HCl as the stripping solution and D2EHPA dissolved in kerosene as the membrane solution, has been examined. The effects of stripping solution concentration, carrier concentration, temperature and pH in the feed phase on the transport of Zn(II) have also been investigated. As a result, the optimum transport conditions of Zn(II) were obtained, i.e., the concentration of HCl solution was 0.25 M, the concentration of D2EHPA was $8{\times}10^{-3}M$, and pH value in the donor phase was 5.00. Under the optimum conditions, the transport percentage of Zn(II) was up to >99% during the transport time of 80 min when the initial concentration of Zn(II) was $120mgL^{-1}$. The activation energy is calculated as $5.30kcalmol^{-1}$. The value of calculated activation energy indicates that the process is diffusionally controlled by Zn(II) ions. The experiments have demonstrated that D2EHPA derivative is a good carrier for Zn(II) transport through MDLM in the study.

• Biotechnology and Bioprocess Engineering:BBE
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• v.6 no.3
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• pp.200-204
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• 2001

In this study, nanofiltration was applied to the concentration of the 6-aminopenicillinic acid (6-APA) from bioconverted penicillin solution and also to its mother liquor. The 6-APA in the solution was concentrated from 0.211 mol/L to 0.746 mol/L by nanofiltration. The final maximum concentration was 3.6 times higher than the initial concentration an the recovery yield was 97% to 99% of the original 6-APA. The concentrated solution was crystallized with the yields of 88.9-90.2% and the purity of the crystallized product was about 98%. The concentration of 6-APA in the mother liquor after crystallization was 0.014 mol/L and thus was concentrated 20-30 fold by nanofiltration and crystallization. The recovery of 6-APA was over 98%. The salts contained in the mother liquor, such as NH$_4$Cl and KCl, could be removed by allowing them to permeate through the membrane.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.47 no.1
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• pp.17-23
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• 2015

In bioethanol from acid hydrolysis process, neutralization of acid hydrolyzate is essential step, which resulted in dissolved cations in glucose solution. Impact of cations to Saccharomyces cerevisiae in glucose solution was investigated focused on ethanol fermentation. Both potassium and sodium cations decreased the ethanol fermentation and glucose to ethanol conversion as potassium or sodium cations. In sodium cation, more than 1.13 N sodium cation in glucose solution led to ethanol production less than theoretical yield with severe inhibition. In 1.13 N sodium cation concentration, ethanol fermentation was slowed down to reach the maximum ethanol concentration with 48 h fermentation compared with 24 h fermentation in control (no sodium cation in glucose solution). In case of potassium cation, three different levels of potassium led to silimar ethanol concentration even though slight slow down of ethanol fermentation with increasing potassium cation concentration at 12 h fermentation. Sodium cation showed more inhibition than potassium cation as ethanol concentration and glucose consumption by Saccharomyces cerevisiae.

• The Korean Journal of Physiology
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• v.15 no.2
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• pp.97-101
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• 1981

The early plasma gastrin responses to single oral glucose or casein solution were studied in the same normal subjects on different days. After an overnight fast, glucose or casein solution was ingested within few minutes at the breakfast time. The plasma gastrin responses to these solutions were compared and contrasted with the concentration when the subjects received glucose solution intravenously. Results were as follows: 1) Rapid intravenous glucose infusion did not produce any changes in the plasma gastrin concentration. 2) Plasma gastrin concentration rose and peaked within 10 minutes after an oral liquid ingestion and then decreased substantially by 15 minutes, but remained slightly above fasting levels at 60 minutes. 3) There was no significant difference between the mean plasma gastrin concentrations after glucose of casein ingestion, but each fluid produced a significant increase in serum gastrin above fasting levels. 4) The subjects who produced high plasma gastrin response to glucose solution did so to casein solution. Conversely a low response to one solution reflected a low response to the other solution. 5) From the above results, authors discussed that individual responsibility rather than the sorts of meals is the factor in the determination of the magnitude of the early gastrin response.

• Korean Journal of Crystallography
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• v.14 no.1
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• pp.35-38
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• 2003

A simple multistep-concentration setting in capillaries was used to control the water-evaporation rate in vapor-diffusion protein crystallization. In the method used, a variety of evaporation rate curves were obtained by using the secondary precipitant solution referred to as “regulatory solution”, which is not directly exposed to the protein solution. The curves were applied to the crystallization of lysozyme as a model protein. The results clearly showed that crystal growth is dependent on the evaporation rate. Especially, the decoupling curves in which precipitant concentration in protein solutions increases to a certain point and then decreases to the equilibrium concentration gave the best crystals.

• Journal of Surface Science and Engineering
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• v.52 no.2
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• pp.78-83
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• 2019

Chloride baths for electrodeposited Ni thin films were fabricated by dissolving metal Ni powders with the mixed solution consisting of HCl and de-ionized water. Current efficiency, residual stress, surface morphology and microstructure of Ni films with the change of metal ion ($Ni^{2+}$) concentrations in the plating solution were studied. Current efficiency was measured to be more than 90% with increasing $Ni^{2+}$ concentrations in the plating solution. Residual stress of Ni thin film was increased from about 400 to 780 MPa with increasing $Ni^{2+}$ concentration from 0.2 to 0.5 M. It is gradually decreased to 650 MPa at 0.9 M $Ni^{2+}$ concentration. Smooth surface morphologies were observed over 0.3 M $Ni^{2+}$ concentration, but nodule surface morphology at 0.2 M. Ni films consist of FCC(111), FCC(200), FCC(220) and FCC(311) peaks in XRD patterns. Preferred orientation of FCC(111) was observed and its intensity was slightly decreased with increasing $Ni^{2+}$ concentration. The average grain size was slightly increased at 0.3 M $Ni^{2+}$ concentration and then slightly decreased with increasing $Ni^{2+}$ concentration.

• Journal of Surface Science and Engineering
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• v.49 no.2
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• pp.119-124
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• 2016

Plasma electrolytic oxidation (PEO) is a promising coating process to produce ceramic oxide on valve metals such as Al, Mg and Ti. The PEO coating is carried out with a dilute alkaline electrolyte solution using a similar technique to conventional anodizing. The coating process involves multiple process parameters which can influence the surface properties of the resultant coating, including power mode, electrolyte solution, substrate, and process time. In this study, ceramic oxide coatings were prepared on commercial Al alloy in electrolytes with different KOH concentrations (0.5 ~ 4 g/L) by plasma electrolytic oxidation. Microstructural and electrochemical characterization were conducted to investigate the effects of electrolyte concentration on the microstructure and electrochemical characteristics of PEO coating. It was revealed that KOH concentration exert a great influence not only on voltage-time responses during PEO process but also on surface morphology of the coating. In the voltage-time response, the dielectric breakdown voltage tended to decrease with increasing KOH concentration, possibly due to difference in solution conductivity. The surface morphology was pancake-like with lower KOH concentration, while a mixed form of reticulate and pancake structures was observed for higher KOH concentration. The KOH concentration was found to have little effect on the electrochemical characteristics of coating, although PEO treatment improved the corrosion resistance of the substrate material significantly.

• Journal of Surface Science and Engineering
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• v.49 no.1
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• pp.46-53
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• 2016

The structure of plasma electrolytic oxidation (PEO) coatings was investigated as a function of NaOH concentration in 0.06 M $Na_2SiO_3$ + 0.06 M $Na_3PO_4$ solution by using SEM and epoxy replica method. The PEO film was formed on AZ31 Mg alloy by the application of anodic pulse current with 0.2 ms width and its formation behavior was studied by voltage-time curves during the formation of PEO films. It was found that the addition of NaOH into $PO_4{^{3-}}$ and $SiO_3{^{2-}}$ containing aqueous solution causes a decrease in the PEO film formation voltage, suggesting that dielectric breakdown of the PEO becomes easier with increasing $OH^-$ ion concentration in the solution. With increasing $OH^-$ ion concentration, thickness of the PEO film increased and surface roughness decreased. The size of pores formed in the PEO layer became smaller and the number of cracks in the PEO layer increased with increasing $OH^-$ ion concentration. Based on the experimental results obtained in the work, it is suggested that $OH^-$ ions in the solution can contribute not only to the dielectric breakdown but also to the formation of PEO films in the presence of $PO_4{^{3-}}$ and $SiO_3{^{2-}}$ ions in the solution.

• Journal of Bio-Environment Control
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• v.14 no.2
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• pp.128-136
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• 2005

The objective of this study was to determine the effect of calcium concentrations in fertilizer solution on growth and cut flower quality of chrysanthemum 'Biarritz' To achieve this, deficiency symptom and growth characteristics as influenced by controlled Ca concentrations in fertilizer solution were investigated. The analysis of plant tissue and soil solution of root media were also conducted to secure optimum concentration for plant growth. Calcium deficiency developed on the very youngest leaves and the young leaves developed 'cupped' shape as they expand. The cut flower length of 0, 3.0 and 6.0 mM treatments were 105.8, 106.5, and 107.3cm, respectively. Elevated Ca concentration within the range from 0 to 6.0mM in fertilizer solution increased cut flower weight. The cut flower weight of control and 6.0mM treatment were 51.6 and 59.4 g, respectively. The tissue Ca content of 6.0mM treatment in which crops showed the highest growth among treatments was $3.09\%$ based on the dry weight of the youngest fully expanded leaves. From the results, it seems necessary to maintaining tissue Ca content higher than $2.8\%$. Soil Ca concentrations increased as K concentrations in fertilizer solution were elevated. Ca concentration in 0.0, 1.5, 3.0, 4.5 and 6.0mM treatments were 5.0, 7.4, 12.1, 16.5 and $28.2mg{\cdot}L^{-1}$, respectively, at harvesting stage. It is suggested that Ca concentration higher than $25.4mg{\cdot}L^{-1}$ in soil solution of root media is required to maintain normal growth.

• Bulletin of the Korean Chemical Society
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• v.35 no.2
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• pp.407-414
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• 2014

Polyacrylonitrile (PAN) copolymers with different methyl acrylate (MA) contents were synthesized via solution polymerization and used as precursors for high-performance PAN ultrafine fibrids. The chemical structures of the copolymers were characterized using Fourier-transform infrared spectroscopy and $^{13}C$ nuclear magnetic resonance spectroscopy. Their particle sizes and aspect ratios increased with increasing viscosity, and the degree of crystallinity increased with decreasing concentration of copolymer solution. In contrast, their peak temperature and heat of exotherm increased with decreasing concentration of the copolymer solution. The aromatization indices (AIs) of the fibrids increased with increasing heat-treatment time; however, the AIs decreased when the heat-treatment temperature was higher than the onset temperature of the copolymers. On the other hand, the crystal sizes of the fibrids decreased with increasing concentration of the copolymer solution when the MA content was held constant.