• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.31 no.5
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• pp.86-94
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• 1999

Alkaline peroxide bleaching of chemi-mechanical pulp is a very complicated system where various process factors affect the bleacing performance and pulp properties. Traditional onefactor-at a time method is ineffective and costly infinding the optimal bleaching conditions. In this study, statistical experimental design and multiple regression method wre used to investigated the interactions among various bleaching factors and to find out the possbile maximal brightness development during one stage alkaline peroxide bleacing of TMP. The TMP was made from 10% Korean red pine and 90% Korean spruce and had an initial brightness of 54.5% ISO. the TMP was pretreated with EDTA(0.5% on O.D. pulp, 3% pulp consistency, 30$^{\circ}C$ for 60 minutes) and bleached in a 2 L Mark V Quantum Reactor at 750 rmp, 7.5% of bleaching consistency and with 0.05% magnesium sulfate addition. The ranges of chemical factors studied , based on oven-ried pulp, were 1-5% for hydrogen peroxide, 1-4% for sodium hydroxide and 1-4% for sodium silicate. The rages of reaction temperature and time were 50-90$^{\circ}C$ and 40-180minutes respectively. Interactions of hydrogen peroxide with alkali , time with temperature ature, alkali with time and silicate with temperature were found to be significant which means that hydrogen peroxide bleaching will be favored at stable concentration of perhydroxyl ion, relatively short time and low temperature, and high level of silicate. Mathematical model which has good predictability for target brightness in one stage peroxide bleaching can also be established easily. Base ion the model, maximal brightness of 70% ISO was found to at 50$^{\circ}C$ and 50 minutes by chemical additions of 5% for hydrogen peroxide, 3.2-3.4% for sodium hydroxide and 4% for silicate based on O.D. pulp. However, this result might not be suitable for situation where furnishes are different from ours, or different pretreatment is used, or bleaching carried out at different pulp consistency. In these cases it will be good to re-investigate the process by a similar methodology as was used in this study.

• Microbiology and Biotechnology Letters
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• v.19 no.4
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• pp.405-412
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• 1991

The enzymes were immobilized by treating the microbial cells in 0.05% chitosan and 0.28% glutaraldehyde solution. The activity of immobilized cell was about 535 IGIC/g. Glucose isomerase was purified by 6.5 times after homogenization using 60% $(NH_4)_2S0_4$ fractionation, DEAE-cellulose and Sephadex G-150 gel filtration. The molecular weight of enzyme was about 140,000 when it was measured by HPLC and the purified enzyme had only one band by electrophoresis. It showed good enzyme activity at pH 7.5 and $75^{\circ}C$. The optimum conditions for enzyme reactions were shifted to pH 7.0 and $80^{\circ}C$ when the enzyme was immobilized. The enzyme reaction was activated by the addition of 5~10 mM magnesium ion and the thermostability was improved by the addition of 0.25 mM cobalt ion. The enzyme activity was competitively inhibited by sugar alcohols.

• Journal of the Korean Vacuum Society
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• v.6 no.3
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• pp.181-186
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• 1997

Time-of-flight impact-collision ion scattering spectroscopy (TOF-ICISS) was applied to study the geometrical structure of epitaxially grown MgO layers on a TiC(001). The hetero-epitaxial MgO layer was able to be deposited by thermal evaporation of magnesium onto the TiC(001) surface and subsequent exposure of oxygen at room temperature. A slight heating of the substrate at around $300^{\circ}C$ was necessary to overcome a thermal barrier for the ordering. The well-ordered MgO structure was confirmed with the 1$\times$1 LEED pattern. TOF-ICISS was useful in studying interface structure between oxide and substrate. The results revealed that the MgO layer is formed at the on-top sites of the TiC(001) substrate and the lateral lattice constant of MgO layer is the same as that of the TiC substrate. The MgO was deposited within two layers on the most parts of the surface.

• Journal of Ginseng Research
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• v.5 no.1
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• pp.73-84
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• 1981

Effect of environmental factors and host on the growth and outbreak of various ginseng diseases was reviewed Environmental lectors included hydrogen ion concentration, moisture content, temperature, nutrition, and microbiol populations. Age of the ginseng plants in relation to several ginseng disease occurrence was also included in order to formulate the effective control measure for ginseng diseases. Damping-off caused by Rhizoctonia, Pythium, and Phytophthora, greymold by Botrytis, sclerotinia by Scleretinia, and phytophthora blight caused by Phytophthora were usually prevalent during the early growing season of ginseng when temperature is below 20$^{\circ}C$, while anthrac se caused by Colletotrichum, alternaria blight by Alternaria, and bacterial soft rot by Erwinia were so during the latter growing season when temperature is above 25$^{\circ}C$. However, the root rot incited by Fnarium and Cylindrocarpon caused severe damages throughout the growing season. Growth range of the temperature for a pathogen was highly related to the corresponding disease outbreak. Hydrogen ion concentration was highly related to the outbreak of sclerotinia, root rot, and red rot. Most severe outbreak of those diseases where the soil acidity was pH 4.7, pH 6.5- 7.5, and pH6.0-6.5, respectively. Nitrogen content in the soil was also related to outbreak of root rot and red rot. More red rot occurred where NH,-nitrogen is above 30 ppm and more root rot obtained when excessive nitrogen fertilizer applied. Yellow necrosis apparently was related to magnesium especially its ratio with potassium or calcium content in a soil. Fusarium Population showed significant .relations to missing rate of ginseng Plants in a Implanting ginseng field, while that of total bacteria showed similar relations in all ginseng field, However, in six year old ginseng fields, the more the Streptomyces population was, the less the Fusarium obtained. Consequently, less missing rate observed in a field where Streptomyces population was high. Damping-off, root rot, Rhytophthor a blight were mose severe on the nursery and on 2-3 years old ginseng plants, whereas sclerotinia, and grey cod, alteraria blight, anthracnose were severe on 4-6 years old ginseng plants. Root rot caused by Fusarium and Erwinia, however, was also severe regardless of the age of the plants when the roots were injured. Therefore, for the effective control of ginseng root rot most careful control of the disease during the early year should be rendered.

• International Journal of Highway Engineering
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• v.18 no.1
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• pp.43-55
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• 2016

PURPOSES : This study aims to develop a repair material that can enhance pavement performance, inducing rapid traffic opening through early strength development and fast setting time by utilizing MgO-based patching materials for repairing road pavements. METHODS : To consider the applicability of MgO-based patching materials for repairing domestic road pavements, first, strength development and setting time of the materials were evaluated, based on MgO to $KH_2PO_4$ ratio, water to binder ratio, and addition ratio of retarder (Borax), by which the optimal mixture ratio of the developed material was obtained. To validate the performance of the developed material as a repair material, the strength(compressive strength and bonding strength) and durability (freezing, thawing, and chloride ion penetration resistance) was checked through testing, and its applicability was evaluated. RESULTS : The results showed that when an MgO-based patching material was used, the condensation time was reduced by 80%, and the compressive strength was enhanced by approximately 300%, as compared to existing cement-based repair materials. In addition, it was observed that the strength (compressive strength and bonding strength) and durability (freezing and thawing, and chloride ion penetration resistance) showed an excellent performance that satisfied the regulations. CONCLUSIONS : The results imply that an emergent repair/restoration could be covered by a rapid-hardening cement to meet the traffic limitation (i.e. the traffic restriction is only several hours for repair treatment). Furthermore, MgO-based patching materials can improve bonding strength and durability compared to existing repair materials.

• Applied Chemistry for Engineering
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• v.34 no.2
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• pp.121-125
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• 2023

Casein is a milk protein and one of the most important nutrients in milk. The composition is over 80% in cow's milk and about 20~45% in human's milk. Casein is highly biocompatible and biodegradable, so it has been studied for various biomedical materials applications as well as drug delivery systems. It is widely known that casein can be prepared as nanoparticles in the presence of the Ca²⁺ metal ion. Because casein is amphiphilic, hydrophobic drugs could be loaded inside to form a protein-based drug delivery system. In this study, we studied the optimum conditions for casein nanoparticle formation using natural metal ions present in the body, such as calcium, magnesium, zinc, and iron. It was confirmed that nanoparticles have a uniform size of around 150 nm and negative zeta potential values. In addition, it was demonstrated that casein nanoparticles have a cell viability of more than 80% and efficient intracellular uptake properties using confocal microscopy. From the results, it was also shown that the casein nanoparticles prepared using various metal ions have the potential to be biocompatible drug delivery carriers.

• Membrane Journal
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• v.32 no.1
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• pp.23-32
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• 2022

Bacteria grow biofilm on various surface such as separation membrane, food packaging film and biomedical device. Growth of biofilm is associated with the formation of a complex structure of exopolysaccharides. Effect of antibacterial effect reduce drastically once the biofilm developed due to the difficulties in mass transport of antimicrobial agent. In order to enhance the antibacterial activity, surface of the membrane is modified, coated or immobilized with functional materials with biocidal properties. One of the idea is to introduce positive charge on the membrane surface by the presence of quaternary ammonium group which might displace divalent metal ion such as magnesium or calcium present in the bacteria cell wall. Efficacy of cell membrane disruption depends on the mobility of the agents available directly on the surface environment. In this review, various biocidal agents like quaternary ammonium group, helamine or zwitter ion containing membrane are discussed.

• Journal of Biosystems Engineering
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• v.35 no.5
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• pp.343-349
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• 2010

Rapid on-site sensing of nitrate-nitrogen and potassium ions in hydroponic solution would increase the efficiency of nutrient use for greenhouse crops cultivated in closed hydroponic systems while reducing the potential for environmental pollution in water and soil. Ion-selective electrodes (ISEs) are a promising approach because of their small size, rapid response, and the ability to directly measure the analyte. The capabilities of the ISEs for sensing nitrate and potassium in hydroponic solution can be affected by the presence of other ions such as calcium, magnesium, sulfate, sodium, and chloride in the solution itself. This study was conducted to investigate the applicability of two ISEs consisting of TDDA-NPOE and valinomycin-DOS PVC membranes for quantitative determinations of $NO_3$-N and K in hydroponic solution. Nine hydroponic solutions were prepared by diluting highly concentrated paprika hydroponic solution to provide a concentration range of 3 to 400 mg/L for $NO_3$-N and K. Two of the calibration curves relating membrane response and nutrient concentration provided coefficients of determination ($R^2$) > 0.98 and standard errors of calibration (SEC) of < 3.79 mV. The use of the direct potentiometry method, in conjunction with an one-point EMF compensation technique, was feasible for measuring $NO_3$-N and K in paprika hydroponic solution due to almost 1:1 relationships and high coefficients of determination ($R^2$ > 0.97) between the levels of $NO_3$-N and K obtained with the ion-selective electrodes and standard instruments. However, even though there were strong linear relationships ($R^2$ > 0.94) between the $NO_3$-N and K concentrations determined by the Gran's plot-based multiple standard addition method and by standard instruments, hydroponic $NO_3$-N concentrations measured with the ISEs, on average, were about 10% higher than those obtained with the automated analyzer whereas the K ISE predicted about 59% lower K than did the ICP spectrometer, probably due to no compensation for a difference between actual and expected concentrations of standard solutions directly prepared.

• Korean Journal of Food Science and Technology
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• v.21 no.2
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• pp.300-306
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• 1989

Physico-chemical changes caused by salting Korean radish cubes (for Kakdugi) with sodium chloride solution were investigated. Two-centimter cubes of Korean radish were soaked in saline solution of 5, 10, 15, 20 and 25 percent concentration. Optimum salinity, 3% as determined by taste, was reached in six hours at 5% strength, two hours in 10%, one hour at 15% and within one hour at concentration of 15% plus. Radish cubes salted in 5, 10. 15, 20 and 25% sodium chloride solution in a cube/solution weight ratio of 1:1 decreased in volume from 7.6 to 11.2% after one hour, and from 11.2 to 17.9% after six hours. Decrease in moisture content was from 83.0 to 75.9% in one hour and from 74.5 to 68.5% after six hours. $Potassium\;ion(K^+)$, $calcium\;ion(Ca^{2+})$ and $magnesium\;ion(Mg^{2+})$ content was significantly decreased by salting, but $sodium\;ion(Na^+)$ content greatly increased. In addition, salting caused firmness of the cubes to decrease, and cell shapes to shrink by plasmolysis.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.32-38
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• 2023

In this study, the electrochemical properties of dopamine coated silicon/silicon carbide/carbon(Si/SiC/C) composite materials were investigated to improve cycle stability and rate performance of silicon-based anode active material for lithium-ion batteries. After synthesizing CTAB/SiO₂ using the Stöber method, the Si/SiC composites were prepared through the magnesium thermal reduction method with NaCl as heat absorbent. Then, carbon coated Si/SiC anode materials were synthesized through polymerization of dopamine. The physical properties of the prepared Si/SiC/C anode materials were analyzed by SEM, TEM, XRD and BET. Also the electrochemical performance were investigated by cycle stability, rate performance, cyclic voltammetry and EIS test of lithium-ion batteries in 1 M LiPF₆ (EC: DEC = 1:1 vol%) electrolyte. The prepared 1-Si/SiC showed a discharge capacity of 633 mAh/g and 1-Si/SiC/C had a discharge capacity of 877 mAh/g at 0.1 C after 100 cycles. Therefore, it was confirmed that cycle stability was improved through dopamine coating. In addition, the anode materials were obtain a high capacity of 576 mAh/g at 5 C and a capacity recovery of 99.9% at 0.1 C/0.1 C.