• Journal of the Korean Society of Combustion
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• v.20 no.4
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• pp.34-41
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• 2015

Oxy-methane nonpremixed flames diluted with $CO_2$ were investigated to clarify impact of radiation heat loss and chemical effects of additional $CO_2$ to oxidizer stream on flame extinction. Flame stability maps were presented with functional dependencies of critical diluents mole fraction upon global strain rate at several oxidizer stream temperatures in $CH_4-O_2/N_2$, $CH_4-O_2/CO_2$, and $CH_4-O_2/CO_2/N_2$ counterflow flames. The effects of radiation heat loss on the critical diluent mole fractions for flame extinction are not significant even at low strain rate in nonpremixed $CH_4-O_2/N_2$ diffusion flame, whereas those are significant at low strain rate and are negligible at high strain rate (> $200s^{-1}$) in $CH_4-O_2/CO_2$ and $CH_4-O_2/CO_2/N_2$ counterflow flames. Chemical effects of additional $CO_2$ to oxidizer stream on the flame extinction curves were appreciable in both $CH_4-O_2/CO_2$ and $CH_4-O_2/CO_2/N_2$ flames. A scaling analysis based on asymptotic solution of stretched flame extinction was applied. A specific radical index, which could reflect the OH population in main reaction zone via controlling the mixture composition in the oxidizer stream, was identified to quantify the chemical kinetic contribution to flame extinction. A good correlation of predicted extinction limits to those calculated numerically were obtained via the ratio between radical indices and oxidizer Lewis numbers for the target and baseline flames. This offered an effective approach to estimate extinction strain rate of nonpremixed oxy-methane flames permitting air infiltration when the baseline flame was taken to nonpremixed $CH_4-O_2/N_2$ flame.

• Journal of the Korean Chemical Society
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• v.47 no.2
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• pp.121-126
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• 2003

Tris(2-cyclohexylaminoethyl)amine (L) was synthesized by the Schiff base condensation reaction of tris(2-aminoethyl)amine with cyclohexanone, followed by reduction. The thermodynamic characteristics, mole ratio and formation constant of [Zn(II)-L] complex were measured by the cyclic voltammetry and isothermal titration. In the case of Zn(II), well-defined cathodic and anodic peak were obtained at -1.02V and -0.48V vs Ag/AgCl , respectively. For the [Zn(II)-L] complex, both peaks were obtained at -1.19V and -0.45V vs Ag/AgCl, respectively. In addition, the peak height gradually increases as the scan rate increases, suggesting that the currents obtained were diffusion - controlled. The mole ratio and stability constant of the complex measured cyclic voltammerty were 1:1 and logK$_f$= 5.8, respectively. And the mole ratio and stability constant of the complexe calculated by isothermal titration method was 1:1 and logK =5.4, respectively. ${\Delta}$H, ${\Delta}$G and T${\Delta}$S for the complex formation were -53.0 kJ/mol, -31.1 kJ/mol, and -21.9 J/K at 25 ${\circ}$C, respectively.

• Journal of the Korea Concrete Institute
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• v.23 no.3
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• pp.311-320
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• 2011

Fly ash (FA), byproduct from power plant has been actively used as mineral admixture for concrete. However, since bottom ash (BA) is usually used for land reclaim or subbase material, more active reuse plan is needed. Pond ash (PA) obtained from reclaimed land is mixed with both FA and BA. In this study, 6 PA from different domestic power plant are prepared and 5 different replacement ratios (10%, 20%, 30%, 50%, and 70%) for fine aggregate substitutes are considered to evaluate engineering properties of PA as fine aggregate and durability performance of PA concrete. Tests for fine aggregate of PA for fineness modulus, density and absorption, soundness, chloride and toxicity content, and alkali aggregate reaction are performed. For PA concrete, durability tests for compressive strength, drying shrinkage, chloride penetration/diffusion, accelerated carbonation, and freezing/thawing are performed. Also, basic tests for fresh concrete like slump and air content are performed. Although PA has lower density and higher absorption, its potential as a replacement material for fine aggregate is promising. PA concrete shows a reasonable durability performance with higher strength with higher replacement ratio. Finally, best PA among 6 samples is selected through quantitative classification, and limitation of PA concrete application is understood based on the test results. Various tests for engineering properties of PA and PA concrete are discussed in this paper to evaluate its application to concrete structure.

• KSBB Journal
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• v.16 no.4
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• pp.321-326
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• 2001

The change of molecular weight inside and outside a capsule produced using coencapsulating technology was investigated. Chitosan and chitosanase were enveloped in this membrane and product released was a loaded the medium by the principle of size exclusion. The leakage of substrate corresponding to the agitation speed was controlled by adjusting the alginate and CaCO$_3$ concentrations. The optimal condition of alginate concentration and agitation speed were 0.5% and 40rpm, respectively. Membrane thickness and capsules diameter were 10 $\mu$m and approx. 3.0 - 1.5 mm, respectively. Molecular weight difference by concentration and alginate viscosity were of little significance. In accordance with the molecular weight distribution versus enzyme concentration relationship, low concentration of enzyme produced high molecular weight oligosaccharides. At a 1.5 mm capsule size the product diffusion rate to outer surface highest. The molecular weight distribution of the released oligosaccharides was ranged from 1000 to 6000 Da. More than 80% of the initial activity of encapsulated enzyme retained after 8hrs of reaction.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.1-9
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• 2020

Chloride ion, which penetrates into the cement composites from the outside, generally diffuses by the concentration gradient. Chloride ions are adsorbed by the chemical reaction with cement hydrates. Recent studies have shown that anion exchange resin (AER) powder can effectively adsorb the chloride ion in the cement composites, and thus, the cement composites containing AER have a high chloride adsorption capacity and a good resistance for chloride penetration. In this study, the chloride adsorption ability of the AER powder was investigated under the conditions of distilled water and calcium hydroxide saturated solution to determine if the AER powder is less effective to increase the chloride adsorption ability after grinding process. The chloride adsorption ability of AER powder was compared with the previous research about the chloride adsorption of AER bead. In addition, the compressive strength, chloride diffusion coefficient (using NT Build 492 method), and the chloride profile of cement mortar substituted with AER powder were investigated. There was no decrease in the chloride adsorption capacity of AER powder but increase in the kinetic property for chloride adsorption after the grinding process. The AER powder could absorb the chloride ion in the mortar quickly, and showed better chloride ion adsorption ability than the cement hydrates.

• Corrosion Science and Technology
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• v.9 no.6
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• pp.276-280
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• 2010

Copper(Cu) as an interconnecting metal layer can replace aluminum (Al) in IC fabrication since Cu has low electrical resistivity, showing high immunity to electromigration compared to Al. However, it is very difficult for copper to be patterned by the dry etching processes. The chemical mechanical polishing (CMP) process has been introduced and widely used as the mainstream patterning technique for Cu in the fabrication of deep submicron integrated circuits in light of its capability to reduce surface roughness. But this process leaves a large amount of residues on the wafer surface, which must be removed by the post-CMP cleaning processes. Copper corrosion is one of the critical issues for the copper metallization process. Thus, in order to understand the copper corrosion problems in post-CMP cleaning solutions and study the effects of DC biases and post-CMP cleaning solution concentrations on the Cu film, a constant voltage was supplied at various concentrations, and then the output currents were measured and recorded with time. Most of the cases, the current was steadily decreased (i.e. resistance was increased by the oxidation). In the lowest concentration case only, the current was steadily increased with the scarce fluctuations. The higher the constant supplied DC voltage values, the higher the initial output current and the saturated current values. However the time to be taken for it to be saturated was almost the same for all the DC supplied voltage values. It was indicated that the oxide formation was not dependent on the supplied voltage values and 1 V was more than enough to form the oxide. With applied voltages lower than 3 V combined with any concentration, the perforation through the oxide film rarely took place due to the insufficient driving force (voltage) and the copper oxidation ceased. However, with the voltage higher than 3 V, the copper ions were started to diffuse out through the oxide film and thus made pores to be formed on the oxide surface, causing the current to increase and a part of the exposed copper film inside the pores gets back to be oxidized and the rest of it was remained without any further oxidation, causing the current back to decrease a little bit. With increasing the applied DC bias value, the shorter time to be taken for copper ions to be diffused out through the copper oxide film. From the discussions above, it could be concluded that the oxide film was formed and grown by the copper ion diffusion first and then the reaction with any oxidant in the post-CMP cleaning solution.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.7 no.2
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• pp.113-119
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• 2006

Brazing is an important manufacturing process in the fabrication of Heavy Water Reactor fuel rods, in which bearing and spacer pads are joined to Zircaloy-4 cladding tubes. The physical vapor deposition(PVD) technique is currently used to deposit metallic Be on the surfaces of pads as a filler metal. Amorphous Zr-Be binary alloys which are manufactured by rapid solidification process are under developing to substitute the conventional PVD-Be coating. In the present study, brazed joint with PVD and amorphous alloys of $Zr_{1-x}Be_{x}(0.3{\le}x{\le}0.5)$ as filler metals are compared by mechanism, microstructure and hardness. The thickness of brazed joint with amorphous alloys became much smaller than that of PVD-Be. The erosion of base metal did not occur in the brazed joint with amorphous alloys. The brazing mechanism for PVD-Be seems to be Be diffusion into Zr-4 with capillary action resulting from eutectic reaction while that for amorphous alloys are associated with the liquid phase formation in the brazed joint. The brazed joint microstructure with PVD-Be consists of dendrite while that with amorphous alloys is globular. The $Zr_{0.7}Be_{0.3}$ alloy shows the smooth interface with little erosion in the base metal and is recommended a most suitable brazing filler metal for Zircaloy-4.

• Research in Plant Disease
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• v.14 no.1
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• pp.71-75
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• 2008

An isolate of Peanut stunt virus (PSV), named as Tr-PSV, was isolated from white clover (Trifolium repens L) showing mosaic symptom. Tr-PSV systemically infected all plants tested in the Nicotiana spp. and induced local lesions on inoculated leaves of Chenopodium amaranticolor. However, Tr-PSV induced typical mosaic symptoms as ER-PSV on Vigna unguiculata 5 to 6 days after inoculation, while Fny-CMV used as a control virus of Cucumovirus produced local lesions on inoculated leaves. In dsRNA analysis, Tr-PSV consisted of four dsRNAs, but satellite RNA was not detected. The cDNA of coat protein gene of Tr-PSV was amplified by RT-PCR using a Cucumovirus-specific single pair primers that designed to amplify a DNA fragment of approximately 950 bp. By restriction mapping analysis using RFLP of the RT-PCR products and by serological properties of gel diffusion test, Tr-PSV belongs to a typical member of PSV subgroup I. This is the first report on the occurrence of PSV in white clover in Korea.

• Journal of Life Science
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• v.26 no.2
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• pp.220-225
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• 2016

Coagulase-negative staphylococci (CNS) have recently become the bacteria most frequently found in clinical infections. The aim of this study was to investigate the prevalence, antimicrobial susceptibilities, and molecular characteristics of CNS isolates from dental clinic environments in Busan, Korea. One hundred and fifty-four samples were collected from 10 dental clinics and dental hospitals in Busan from December 2014 to January 2015. Species were identified by matrix-assisted laser desorption/ionization–time-of-flight. Antimicrobial susceptibility was determined by disk diffusion methods. A polymerase chain reaction was performed to detect mecA, mupA gene, and SCCmec types. Of the 154 samples, 10(6.5%) isolates were identified as CNS (5 Staphylococcus epidermidis, 2 Staphylococcus capitis, 2 Staphylococcus, and 1 Staphylococcus haemolyticus). Among the 10 isolates, 6 were resistant to penicillin, 5 were resistant to gentamicin, 3 were resistant to tetracycline, and 2 were resistant to cefoxitin and erythromycin. However, clindamycin, ciprofloxacin, teicoplanin, and trimethoprim-sulfamethoxazole resistant isolates were not present. Genes encoding mecA were detected in 4 (2 S. warneri and 2 S. haemolyticus) isolates, and mupA in 1 (S. epidermidis) isolate. One methicillin-resistant CNS (S. warneri) isolate was determined as being of the SCCmec type I. It is concluded that CNS resistant to various antimicrobial agents was widely distributed in dental clinic environments in Korea.

• Clean Technology
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• v.25 no.2
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• pp.101-106
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• 2019

The aim of this study is to investigate the feasibility of an Ni-SA catalyst, which was prepared from nickel, kieselguhr, and alumina, for the hydrogenation of triglyceride in a bench-scale reactor. Ni-SA powders were prepared by precipitating nickel precursors on a silica and alumina support. The powder was reduced in a hydrogen flow, mixed with a saturated palm oil, and then cooled to prepare an Ni-SA catalyst tablet. The sizes of NiO crystals of a commercial Pricat catalyst and the Ni-SA catalyst prepared in this study were $35{\AA}$ and $38{\AA}$, respectively. The pore volume and pore size of the Ni-SA catalyst was much larger than the pore volume and pore size of the Pricat catalyst. In addition, the average particle size of the Ni-SA catalyst was much smaller than that of the Pricat catalyst. The triglyceride hydrogenation reaction was carried out in a semi-batch reactor using catalysts impregnated with oil and molded into tablets. It was found that the Ni-SA catalyst was superior to the commercial Pricat catalyst in triglyceride hydrogenation, which could be ascribed to the raw material and the products being less influenced by the diffusion resistance in the pores of the Ni-SA catalyst. The Ni-SA catalyst prepared in this study has the potential to replace the Pricat catalyst as a catalyst for use in the commercial process for hydrogenation of triglyceride.