• Journal of ILASS-Korea
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• v.6 no.3
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• pp.1-7
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• 2001

In this study, quantitative measurement of nitric oxide concentration distributions visualization were investigated in the laminar $CH_4/O_2N_2$ nixed flame by Planar laser-induced fluorescence(PLIF). The NO A-X (0,0) vibrational band around 226nm was excited using a XeCl excimer-pumped dye laser. Selecting an appropriate NO transition minimizes interference from Rayleigh scattering and $O_2$ fluorescence. The measurements were taken in $CH_4/O_2N_2$ premixed flame with equivalence ratios varying from $1.0{\sim}1.6$, and a fixed flow rate of 3slpm. NO was found to produce primarily between an inner premixed and an outer nonpremixed flame front, and total NO concentration is raised when equivalence ratios increase. These results suggest that prompt NO is likely to contribute to MO formation in $CH_4/O_2N_2$ premixed flame. Furthermore, this trend was well matched with previous works.

• Korea-Australia Rheology Journal
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• v.21 no.4
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• pp.235-244
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• 2009

Miscible polymer blends still have heterogeneity in their component chain concentration in the segmental length scale because of the chain connectivity (that results in the self-concentration of the segments of respective chains) as well as the dynamic fluctuation over various length scales. As a result, the blend components feel different dynamic environments to exhibit different temperature dependence in their segmental relaxation rates. This type of dynamic heterogeneity often results in a broad glass transition (sometimes seen as two separate transitions), a broad distribution of the local (segmental) relaxation modes, and the thermo-rheological complexity of this distribution. Furthermore, the dynamic heterogeneity also affects the global dynamics in the miscible blends if the component chains therein have a large dynamic asymmetry. Thus, the superficially simple miscible blends exhibit interesting dynamic behavior. This article gives a brief summary of the features of the segmental and global dynamics in those blends.

• Proceedings of the KSME Conference
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• 2000.11b
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• pp.156-161
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• 2000

In this study, quantitative nitric oxide concentration distributions are investigated in the post-flame zone of laminar premixed $CH_4/O_2/N_2$, flames by laser-induced fluorescence (LIF). The measurements are taken in flames for different equivalence ratios varying from $0.8{\sim}1.4$, and flow rate is fixed as 5slpm. The NO A-X (0,0) vibrational band around 226 nm is excited using a XeCl excimer-pumped dye laser. Selecting an appropriate NO transition minimizes interferences from Rayleigh scattering and $O_2$ fluorescence. NO concentration is rised when equivalence ratios increase at different vertical distances form nozzle tip. In any case, the maximum NO concentration reaches the maximum in reaction zone.

• Food Science and Biotechnology
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• v.14 no.6
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• pp.871-874
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• 2005

The effect of rice starch at different concentrations (0, 4, 6, and 8%) on dynamic rheological properties of surimi sols was investigated by small-deformation oscillatory measurements at $10^{\circ}C$ and during heating from 10 to $95^{\circ}C$. Dynamic frequency sweeps at $10^{\circ}C$ showed that the magnitudes of storage modulus (G') decreased with increasing starch concentration while those of tan $\delta$ increased. G' values of surimi-rice starch sols during heating decreased with increasing starch concentration, indicating that the pattern of G' changes during heating was influenced by the concentration of the added rice starch. In general, the characteristic G' thermograms of all samples showed a similar sol-gel transition pattern.

• Transactions on Electrical and Electronic Materials
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• v.13 no.3
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• pp.136-138
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• 2012

The electrical characteristics of complex films composed of poly(ethylene oxide) (PEO) and urea as a function of the urea concentration were examined in this study. Moreover, their structural characteristics were also compared. Depending on the urea concentration, the structural phases were classified as PEO+${\beta}$-phase composite, ${\beta}$-phase+${\alpha}$-phase composites, or ${\alpha}$-phase composite+urea. At urea concentrations below ~0.064 M, the ${\beta}$-phase was dominant in the complex film. Moreover, the conductance increased rapidly with an increase in the urea concentration. For urea concentrations ranging from ~0.064 to ~0.25 M, the ${\beta}$-phase was gradually substituted by the ${\alpha}$-phase. As the film was composed entirely of the ${\alpha}$-phase at urea concentrations greater than ~0.25 M, its conductance was decreased. In this study, the electrical characteristics observed for the different phases are analyzed and discussed.

• Resources Recycling
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• v.31 no.1
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• pp.46-55
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• 2022

The recycling of coated cemented carbide scraps is becoming increasingly significant for the recovery of rare metals. However, coatings consisting of Group IV and V transition metal nitrides are one of the challenging factors in obtaining high-purity materials. We investigated the structural, elastic, and mechanical properties of Group IV and V transition-metal nitrides (TiN, VN, ZrN, NbN, HfN, and TaN) using first-principle calculations. Convergence tests were performed to obtain reliable calculated results. The equilibrium structures of the nitrides were in good agreement with those of a previous study, indicating the reliability of the data. Group IV transition metal nitrides show a higher covalent bonding nature. Thus, they exhibit a higher degree of brittleness than that of Group V transition metal nitrides. In contrast, Group V transition metal nitrides show weaker resistance to shear loading and more ductile behavior than Group IV transition metal nitrides because of the metallic bonds characterized by valence electron concentration. The results of the crystal orbital Hamilton population analysis showed good agreement with the shear resistance tendencies of all transition metal nitrides.

• Korean Journal of Materials Research
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• v.16 no.3
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• pp.163-167
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• 2006

The transition of europium-doped gadolinium oxide phosphor to gadolinium borate phosphor with the concentration of boron in the spray pyrolysis was investigated. The particles prepared from spray solution below 10 wt% boric acid of prepared phosphor had crystal structure of $Gd_2O_3:Eu$ phosphor, in which the crystallinity of the particles decreased with increasing the boron concentration. A single phase $GdBO_3:Eu$ phosphor particles were prepared from spray solution above 50 wt% boric acid of prepared phosphor. The phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had no XRD peaks of $Gd_2O_3:Eu$ and $GdBO_3:Eu$ Therefore the phosphor particles prepared from spray solution with 20 wt% boric acid of prepared phosphor had the lowest photoluminescence intensity under ultraviolet and vacuum ultraviolet. $GdBO_3:Eu$ and $Gd_2O_3:Eu$ phosphor particles prepared from spray solutions with proper concentrations of boric acid had good photoluminescence intensity under vacuum ultraviolet. The morphology of the phosphor particles were strongly affected by the concentrations of boric acid added into spray solution.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.1
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• pp.68-73
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• 2007

In this study, we investigated the decomposition of highly concentrated hydrogen peroxide in the range of 1.04-2.55 M by transition metal ion catalysts such as $Fe^{2+}$ and $Cu^{2+}$. The effect of metal ion concentration on the decomposition of hydrogen peroxide was examined experimentally, and the decomposition rate constants were determined by combining the experimental data with a theoretical approach. The rate of the decomposition of hydrogen peroxide was found to be first order with respect to its concentration. The decomposition rate constant was able to be treated as a linear function of the initial metal ion concentration. The validity of the decomposition rate constants determined was verified by good agreements between the calculated and experimental results.

• Macromolecular Research
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• v.12 no.4
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• pp.422-426
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• 2004

Solid polymer electrolytes based on poly(ethylene glycol)-polyurethane (PEG-PU) complexed with LiClO$_4$ salt have been prepared by the solvent casting method. A PEG-PU material (PEG:4,4'-diphenylmethane diisocyanate: l,4-butanediol = 1:2:1) was synthesized through a typical two-step condensation reaction. We investigated the effects of the salt concentration on the ionic conductivity ($\sigma$) and the glass transition temperature (T$_{g}$ ) of the complex electrolytes by using alternating current impedance spectroscopy, differential scanning calorimetry, and dynamic mechanical thermal analysis. The measured values of both $\sigma$ and T$_{g}$ exhibited similar tendencies in that they had maxima within the range studied, probably because of two opposite effects, i.e., the increased number of carrier ions and the decreased chain mobility (or increased T$_{g}$ ) caused by the increase in the salt concentration. The highest conductivity, on the order of 2.43 ${\times}$ 10$^{6}$ S$cm^{-1}$ /, was obtained at an [O]/[Li$^{+}$] ratio of ca. 16 (0.92 ㏖ salt per kg of matrix polymer).

• Elastomers and Composites
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• v.45 no.2
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• pp.122-128
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• 2010

We measured shear viscosity of copoly(styrene(St)/butyl methacrylate(BMA)) (co-PSB) particles, with a capillary rheometer at $170^{\circ}C$, prepared by suspension polymerization with hydrophobic silica as a stabilizer. co-PSB particles with the weight average molecular weights of lower than 74,800 g/mol displayed a Newtonian behavior at low shear rates. With the weight average molecular weight exceeding 136,800 g/mol, co-PSB particles showed shear thinning against shear rates and the absolute value of the slopes between shear viscosity vs. shear rate increased. When the ratio between St and BMA changed from 7/3 to 5/5 to 3/7, shear viscosity and glass transition decreased despite similar molecular weights. When the ratio was 1/9, it showed a large increase in initial shear viscosity despite reduced glass transition. Shear viscosity exhibited an increase in proportion to carbon black concentration. The effect of carbon black concentration on the shear viscosity of co-PSB composites was less pronounced compared to varying molecular weights and/or compositional ratio.