• Membrane Journal
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• v.23 no.1
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• pp.12-23
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• 2013

On the subject of river bed water in Seomjin river, it had accomplished the verifying experiment of membrane filtration pilot plant for evaluating the applicability of its process throughout the prediction of membrane fouling as a function of the pore size of membrane and the determination of optimum coagulant dosage. On the result of the experiment for the evaluation of the membrane fouling as a function of the pore size, a increasing rate of irreversible resistance of membrane pore size $0.1{\mu}m$ and $0.01{\mu}m$ was measured each $0.44{\times}10^{12}/m^2$ and $0.42{\times}10^{12}/m^2$, respectively. And on the result of Flux-test, it showed that the optimum coagulant dosage was measured lower than the it of the Jar-test. The result to be operated in a condition of a permeate flux $1.0{\sim}1.5m^3/m^2{\cdot}day$ without coagulation and a permeate flux $1.0{\sim}2.0m^3/m^2{\cdot}day$ with coagulation was maintained at stable trans-membrane pressure (TMP) value for 6 months up to. Therefore it showed that the stable operation without the coagulation was possible on permeate flux $1.0{\sim}1.5m^3/m^2{\cdot}day$ in the operation of membrane filtration process.

• Journal of the Korean Wood Science and Technology
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• v.28 no.3
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• pp.70-77
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• 2000

Among four compounds such as oxyresveratrol, resveratrol, morin and afzelechin isolated from the heartwood of Morns bombycis, oxyresveratrol and resveratrol which belong to stilbenoid indicated high antioxidative and antimicrobial activity, respectively. Based on this result, this experiment was carried out to elucidate the relationship between biological activities of stilbenoids and their chemical structures using two isolated and six synthesized ones prepared by Wittig reaction. Antimicrobial activity of 3,5-dihydroxystilbene(pinosylvin) devoid of hydroxyl group of B-ring was the best among the tested stilbenoids. Antimicrobial activities of the stilbenoids showed negative dependency on the number of hydroxyl groups of B-ring, that is, the fewer number of hydroxyl groups of B-ring, the higher antimicrobial activity. On the other hand, antioxidative activities of the stilbenoids indicated a positive relationship with the number of hydroxyl groups of B-ring. In tetrahydroxystilbenoids, antioxidative activities of the compounds possessing ortho-diphenol structure, 2',3,3',5- and 3,3',4',5-tetrahydroxystilbene, were superior to the others. As a result, it was concluded that resveratrol and oxyresveratrol isolated from the heartwood of M. bombycis had antimicrobial and high antioxidative activities, and these activities of stilbenoids were also dependent on the number and position of hydroxyl groups of B-ring.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.4 no.2
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• pp.107-116
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• 1999

To study the characters of surface sediment and to describe the seasonal depositional environment as a result of sedimentation process off Byun-San Peninsula, a total 61 samples of surface sediment (32 samples in summer; 29 samples in winter) were collected and analysed. A digitized depth data from sea chart and echosounding profiles along five trans-sections were helpful for understanding the morphological factors. The types classified by the characters of surface sediment are type I (sand, S), type II (silty sand, zS), and type ill (sandy silt, sZ). Mean grain size varies from 2.11 to 7.81 ${\Phi}$. The positive-skewness shows the typical tide-dominated environment. The sediment type of the northwestern stations is medium sand and the sorting value is 0.5~1.4 ${\Phi}$ of well/moderately sorted. Meanwhile, other stations are composed of muddy sands and sandy muds transported from rivers and offshore. These sediment types toward inshore change gradually from silty sand to sandy silt. According to the C/M diagram, there are three major transport modes of sediment: bed load (Mode A), graded suspension (Mode B), and suspension (Mode C), correlating with north-eastern sandy area, middle part of silty-sand area, and southern sandy-silt area, respectively. The result of Principal Component Analysis shows also similar pattern of sediment types. In result, sediment texture of type III tends to be finer and more poorly-sorted than that of type II and sediment facies are correlateed with sedimentation process.

• Membrane Journal
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• v.22 no.6
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• pp.461-469
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• 2012

This study was carried out to find the optimum chemical cleaning (CIP) conditions for ceramic microfiltration membrane process of Y drinking water treatment plant. B train consists of coagulation as pretreatment process with membrane was chemically cleaned 9 times more than that of A train with ozonation and coagulation. The frequent CIP of B train was due to improper CIP method suggested by membrane manufacture as well as different membrane fouling between A and B train resulting from the different pretreatment processes. That is, recovery rate of CIP was overestimated because the rate was calculated based on normalized trans membrane pressure (TMP) rather than normalized permeability. And also, iron oxide fouling was ineffectively removed by citric acid. By using a mixture of 1% citric acid and 0.1 N sulfuric acid as reagent for acid CIP step, the recovery rate of CIP was the highest while CIP efficiency by 0.1 N sulfuric acid was the lowest. When sulfuric acid concentration increased from 0.1 N to 0.3 N in mixture, total recovery rate of CIP was not increased due to the decreased CIP efficiency in alkali CIP step by 0.3% NaOCl although its rate in acid CIP step was increased. It was proved through the experiment result of CIP sequence changes that an acid followed by alkali CIP was more effective than that of the reverse method.

• Journal of Educational Research in Mathematics
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• v.17 no.4
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• pp.453-475
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• 2007

School algebra starts with introducing algebraic expressions which have been one of the cognitive obstacles to the students in the transfer from arithmetic to algebra. In the recent studies on the teaching school algebra, algebraic thinking is getting much more attention together with algebraic expressions. In this paper, we examined the processes of the transfer from arithmetic to algebra and ways for teaching early algebra through algebraic thinking factors. Issues about algebraic thinking have continued since 1980's. But the theoretic foundations for algebraic thinking have not been founded in the previous studies. In this paper, we analyzed the algebraic thinking in school algebra from historico-genetic, epistemological, and symbolic-linguistic points of view, and identified algebraic thinking factors, i.e. the principle of permanence of formal laws, the concept of variable, quantitative reasoning, algebraic interpretation - constructing algebraic expressions, trans formational reasoning - changing algebraic expressions, operational senses - operating algebraic expressions, substitution, etc. We also identified these algebraic thinking factors through analyzing mathematics textbooks of elementary and middle school, and showed the middle school students' low achievement relating to these factors through the algebraic thinking ability test. Based upon these analyses, we argued that the readiness for algebra learning should be made through the processes including algebraic thinking factors in the elementary school and that the transfer from arithmetic to algebra should be accomplished naturally through the pre-algebra course. And we searched for alternative ways to improve algebra curriculums, emphasizing algebraic thinking factors. In summary, we identified the problems of school algebra relating to the transfer from arithmetic to algebra with the problem of teaching algebraic thinking and analyzed the algebraic thinking factors of school algebra, and searched for alternative ways for improving the transfer from arithmetic to algebra and the teaching of early algebra.

• Korean Journal of Food Science and Technology
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• v.12 no.3
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• pp.200-204
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• 1980

A series of tests ware conducted to find out whether continuous heat bleaching of the refined Malaysian plam oil stored in different conditions could reduce color of the finished oil in an actual plant situation. When the refined oil was stored in a stainless steel tank and was not abused by heat during 5 month storage period, heat bleaching followed by clay bleaching and deodorization resulted in a substantial reduction in color of the finished oil in comparison to conventional process (clay bleaching of the refined oil followed by deodorization) (2.6 vs 1.3 red in Lovibond color). However, when the refined oil was stored in a carbon steel tank and was highly abused by heat in the presence of iron picked up from the tank (6.53 ppm) during the same storage period, heat bleaching followed by clay bleaching and deodorization did not help reduce color of the finished oil in comparison to the conventional process (2.7 vs 2.8 red in Lovibond color). It was also shown that oxidation values were not good indices for heat bleachability. Heat bleaching caused slight increase in polymer content of the oil. However, trans isomers were not increased when the oil was heat bleached.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.11
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• pp.984-997
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• 2015

Chang'e-3 consisting of a lunar lander and exploration rover was launched on December 1, 2013 aboard a Long March 3B rocket flying from Xichang space launch center. Chang'e-3 was inserted into the lunar orbit after about a 5-day transit to the Moon and landed on the targeted landing site after orbiting around the Moon for 8 days. The successful landing of the Chang'e-3 gives a lot of help to analyze the future needs of the subsystem technologies and to figure out the trajectory from launch to lunar landing as well as operation sequences in the development of Korean lunar exploration is scheduled. Therefore, the configuration and analysis of overall mission of Chang'e-3 is performed based on the public information from the press and website. As a result, overall mission trajectory is reconstructed by solving boundary condition and then estimating control variable. Visibility status and eclipse status also analyzes so communication and power charge condition is as good as to operate lunar lander. Mass budget of the lander is derived using ${\Delta}V$ according to specific impulse.

• Korean Journal of Food Science and Technology
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• v.43 no.4
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• pp.458-463
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• 2011

Recent studies have revealed that collagen peptide (CP) plays a protective role in skin by improving the activity of antioxidants and acts as an inducer of skin regeneration by positive feedback. In this study, we focused on the beneficial effect of reinforcing the CP skin barrier. To evaluate the skin barrier, hairless mice were exposed to UVB irradiation and acetone-treatment, with or without oral administration of CP. The effects on skin appearance, trans-epidermal water loss, epidermal thickness, and cytokine content were measured using bioengineering and histochemical methods. In the CP treated group, the skin had better appearance and less damage than that of the control. Furthermore, in HaCaT cells, the amount of serinepalmytoyl transferase (SPT) mRNA increased by about 1.6-fold after treatment (CP, 100 mg/L), reflecting that CP can induce SPT expression and reinforce the recovery of skin barrier function. These results suggest that CP is not only an anti-wrinkling agent but also a potent candidate as an epidermal moisturizer.

• Applied Chemistry for Engineering
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• v.17 no.5
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• pp.458-464
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• 2006

The Pd-Ni-Ag alloy composite membrane using modified porous stainless steel (PSS) as a substrate was prepared by a electroless plating technique. In this work, we have introduced the intermediate layer between Pd-based alloy and a metal substrate. As an intermediate layer, the mixtures of nickel powder and inorganic sol such as $SiO_{2}$ sol, $Al_{2}O_{3}$ sol, and $TiO_{2}$ sol were used. The intermediate layers were coated onto a PSS substrate according to various membrane preparation conditions and then $N_{2}$ fluxes through the membranes with different intermediate layers were measured. The surface morphology of the intermediate layer in the mixture of nickel powder and inorganic sol was analyzed using scanning electron microscope (SEM). Finally, the Pd-Ni-Ag alloy composite membrane using the support coated with the mixture of nickel powder and silica as an intermediate layer was fabricated and then the gas permeances for $H_{2}$ and $N_{2}$ through the Pd-based membrane were investigated. The selectivity of $H_2/N_2$ was infinite and the $H_{2}$ flux was $1.39{\times}10^{-2}mol/m^2{\cdot}s$ at the temperature of $500^{\circ}C$ and trans-membrane pressure difference of 1 bar.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.27 no.2
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• pp.132-140
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• 1991

The aim of this study was saving of chromium and nickel content in the austenitic stainless steels, SUS 316 and SUS 321. By control of primary solidification mode, new austenitic stainless steels with good weldability, high toughness and corrosion resistance could be developed. The main results obtained were as follows; 1. Hot crack resistance of laboratory melts was good and higher than imported austenitic stainless steel. 2. Cryogenic and room temperature toughness of laboratory melts were high and laboratory melts M-7 to M-9 showed very high toughness than SUS321 imported stainless steel. 3. Intergranular corrosion resistance of laboratory melts was higher than imported stainless steels, SUS316 and SUS321. 4. By this concept of controlling primary solidification mode, could save expensive alloy additives, chromium and nickel.