• Journal of the Korean Society of Propulsion Engineers
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• v.23 no.2
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• pp.68-77
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• 2019

C/SiC composites were developed by a liquid silicon infiltration(LSI) method for use as heat-resistant parts of solid and liquid rocket propulsion engines. The heat resistance characteristics according to the composition ratio (carbon / silicon / silicon carbide) were evaluated by specimen test through arc plasma, supersonic torch test. An ablation equation for oxidation reactions was presented. Through the combustion test it was verified that various parts such as nozzle insert, exit cone and combustion chamber heat resistant parts for rocket propulsion can be manufactured and proved high ablation performance and thermal structure performance.

• Corrosion Science and Technology
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• v.20 no.2
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• pp.85-93
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• 2021

The corrosion damage of materials in marine environment mainly occurs by Cl^- ions due to the breakdown of passive films. Additionally, various characteristics in seawater such as salinity, temperature, immersion time, flow rate, and biological activity also affect corrosion characteristics. In this study, the corrosion characteristics of stainless steels (STS 304 and STS 316L) and anodized aluminum alloys (AA 3003 and AA 6063) were evaluated with seawater temperature parameters. A potentiodynamic polarization experiment was conducted in a potential range of -0.25 V to 2.0 V at open circuit potential (OCP). Corrosion current density and corrosion potential were obtained through the Tafel extrapolation method to analyze changes in corrosion rate due to temperature. Corrosion behavior was evaluated by measuring weight loss before/after the experiment and also observing surface morphology through a scanning electronic microscope (SEM) and 3D microscopy. Weight loss, maximum damage depth and pitting damage increased as seawater temperature increased, and furthermore, the tendency of higher corrosion current density with an increase of temperature attributed to an increase in corrosion rate. There was lower pitting damage and lower corrosion current density for anodized aluminum alloys than for stainless steels as the temperature increased.

• Journal of Electrochemical Science and Technology
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• v.12 no.1
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• pp.74-81
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• 2021

Silicon (Si) is recognized as a promising anode material for high-energy-density lithium-ion batteries. However, under a condition of electrode comparable to commercial graphite anodes with low binder content and a high electrode density, the practical use of Si is limited due to the huge volume change associated with Si-Li alloying/de-alloying. Here, we report a novel core-shell composite, having a reversible capacity of ~ 500 mAh g-1, by forming a shell composed of a mixture of nano-Si, graphite nanosheets and a pitch carbon on a spherical natural graphite particle. The electrochemical measurements are performed using electrodes with 2 wt % styrene butadiene rubber (SBR) and 2 wt.% carboxymethyl cellulose (CMC) binder in an electrode density of ~ 1.6 g cm-3. The core-shell composites having the reversible capacity of 478 mAh g-1 shows the outstanding capacity retention of 99% after 100 cycles with the initial coulombic efficiency of 90%. The heterostructure of core-shell composites appears to be very effective in buffering the volume change of Si during cycling.

• Bulletin of the Korean Chemical Society
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• v.10 no.4
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• pp.339-343
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• 1989

The interaction of cationic surfactants, n-alkyltrimethylammonium bromide ($C_nTAB$; n = 12, 14, 16) with anionic polyelectrolyte, poly(styrenesulfonate) (PSS) has been studied by surface tension measurement. In the absence of added salt, the cationic surfactants bind to PSS quantitatively up to ca. 60% coverage of anionic sites of the polyanion and the complexes were surface inactive. Further binding of the surfactant cations on PSS caused a sharp conformational transition of the surfactant/ PSS complexes to surface active complexes and accompanied precipitation. The binding showed a biphasic behavior in the presence of NaCl and cooperativity of the binding became less as the concentration of NaCl increased. Binding of the cationic surfactants on poly(vinylsulfonate) also showed the biphasic behavior and the cooperativity of the binding was much less even in the absence of NaCl. The binding of surfactant to PSS provided hydrophobic environment to solubilized pyrene and reduced the viscosity of the solution greatly even at surfactant concentrations well below cmc. This study indicated that the surfactant bound to PSS up to $60{\%}$ coverage of PSS sites are present as surfactant aggregates which are wrapped up with PSS chains, and hydrophobic interaction is an important factor in the binding of the surfactants to PSS.

• Journal of the Korean Society of Industry Convergence
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• v.24 no.6_2
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• pp.737-744
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• 2021

An investigation is conducted to study a solid-liquid mixture vertically upward hydraulic transport of solid particles by non-Newtonian fluids in the Mud system. Rheology of particulate suspensions in viscoelastic fluids is of importance in many applications such as particle removal from surfaces, transport of proppants in fractured reservoir and cleaning of drilling holes, etc. In this study a clear acrylic pipe was used in order to observe the movement of solid particles. Annular velocities varied from 0.4 m/s to 1.2 m/s. The mud systems which were utilized included aqueous solution of sodium carboxymethyl cellulose (CMC) solutions. Main parameters considered in the study were inner-pipe rotary speed, fluid flow regime and particle injection rate. Solid volumetric concentration and pressure drops were measured for the various parameters such as inclination angle, flow rate, and rotational speed of inner cylinder.

• Journal of Sensor Science and Technology
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• v.32 no.6
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• pp.447-454
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• 2023

The Korea Laboratory Accreditation Scheme (KOLAS) operates accreditation programs for ensuring measurement traceability with the International System (SI) of Units - the highest calibration standard that measurements can be tested against. As of September 2023, there are 70 KOLAS-accredited laboratories in the Republic of Korea that specialize in humidity calibration. Among them, 32 KOLAS laboratories, along with one laboratory not affiliated with KOLAS, participated in the proficiency test (PM 2023-11) for relative humidity transducers in 2023. This proficiency test was conducted within a relative humidity range of 20-90% at a temperature of approximately 20 ℃, taking into consideration the calibration and measurement capability (CMC) of the participating laboratories. The primary objective of the proficiency test was to establish the measurement equivalence between each participating laboratory and the reference laboratory, by calculating the number of equivalence (En). When |En| was less than 1, the measurements from the participating and reference laboratory were equivalent. Out of the 33 participating laboratories, 32 successfully met this criterion and passed the proficiency test.

• Journal of Microbiology
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• v.35 no.4
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• pp.300-308
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• 1997

The catechol 2,3-dioxygenase (C23O) encoded by the Pseudomonas putida xylE gene was over-produced in Escherichia coli and purified to homogeneity. The activity of the C23O required the reduced form of the Fe(II) ion since the enzyme was highly susceptible to inactivation with hydrogen perocide but reactivated with the addition of ferrous sulfate in conjunction with ascorbic acid. The C23O activity was abolished by treatment with the chemical reagents, diethyl-pyrocarbonate (DEPC), tetranitromethane (TNM), and 1-cyclohexy1-3-(2-morpholinoethyl) car-bodiimidemetho-ρ-toluenesulfontate (CMC), which are modifying reagents of histidine, tyrosine and glutamic acid, respectively. These results suggest that histidine, tyrosine and glutamic acid residues may be good active sites for the enzyme activity. These amino acid residues are conserved residues may be good active sites for the enzyme activity. These amino acid residues are conserved residues among several extradion dioxygenases and have the chemical potential to serveas ligands for Fe(II) coordination. Analysis of random point mutants in the C23O gene derived by PCR technique revealed that the mutated positions of two mutants, T179S and S211R, were located near the conserved His165 amd Hos217 residues, respectively. This finding indicates that these two positions, along with the conserved histidine residues, are specially effective regions for the enzyme function.

• Journal of Fisheries and Marine Sciences Education
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• v.27 no.2
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• pp.467-475
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• 2015

The effects of replacement of wheat flour with laver, Pyropia yezoensis, on the bread making properties and quality characteristics of bread were evaluated. The poor baking performance which arose from dried laver addition could be compensated by using exogenous enzymes (Flavouzyme) and baking aids. Laver hydrolysate was prepared by hydrolyzing laver using Flavouzyme for 9 hrs at $50^{\circ}C$. Doughs made by addition of laver hydrolysate (8% dried laver substitution level) showed excellent baking properties. Moreover, with the addition of glucose oxidase and hydro colloidal HPMC, loaf volume and crumb grain were improved for doughs containing laver hydrolysate. Both of intermediate fermentation and final proof time for doughs containing laver hydrolysate was shorter than that for conventional dough.

• Asian-Australasian Journal of Animal Sciences
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• v.22 no.12
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• pp.1676-1685
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• 2009

This trial was conducted to determine the effects of various feed additives on nutrient digestibility, performance and carcass traits of growing-finishing pigs fed diets containing wheat distiller' grains with solubles (WDGS). Seventy-two, individually fed pigs (19.7${\pm}$2.6 kg), were assigned to one of six dietary treatments in a 6${\times}$2 (treatment${\times}$sex) factorial design (N = 12). The control diet was based on wheat and soybean meal while the five experimental diets contained 20% WDGS during the growing period and 12% WDGS during the finishing period. One 20% WDGS diet was unsupplemented while the remaining diets were supplemented with either 0.1% threonine, 5% canola oil, 0.2% enzyme (0.1% Endofeed W containing 1,250 units/g of xylanase and 385 units/g of $\beta$-glucanase and 0.1% Vegpro containing 7,700 HUT/g protease and 75 CMC/g cellulase), or a combination of the three additives at the same levels as those fed separately. The digestibility of dry matter, crude protein and energy were all significantly higher in the control diet than the unsupplemented diet containing 20% WDGS. None of the feed additives improved nutrient digestibility. In addition, none of the additives had any significant effect on gain or feed intake during the growing (19.7 to 43.6) or finishing (43.6 to 114.3 kg) periods or overall (19.7 to 114.3 kg). During the growing period, feed conversion was significantly improved for pigs fed the combination of additives compared with the unsupplemented WDGS diet. During the finishing period and overall, feed conversion was significantly improved for pigs fed 5% canola oil alone or in combination with the other additives. None of the supplements had any effect on carcass traits. These results indicate that WDGS can be successfully used as a partial replacement for soybean meal in diets fed to growingfinishing pigs. However, due to its low energy content, there may be some merit in including high energy ingredients such as canola oil when diets containing WDGS are fed.

• KSBB Journal
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• v.23 no.4
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• pp.350-354
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• 2008

Magnetically separable immobilized trypsin was developed and their biocatalytic activity was evaluated for the different immobilization media. The activity, recyclability, pH effect, and stability of immobilized enzymes were evaluated for the different supporting media. The biocatalytic activity of immobilized trypsin was highest with magnetically separable polyaniline (PAMP), and Vm and Km of PAMP were 0.169 mM/min and 0.263 mM respectively. With increasedpH, the biocatalytic activity increased for all supporting materials used. Immobilized enzymes were recycled and recycle activities were over 90% of their original activity after ten times reuse. The operational stabilities of enzymes were greatly improved with enzyme immobilization.