• Journal of the Korean Ceramic Society
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• v.30 no.12
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• pp.999-1006
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• 1993

Si3N4(p)-SiC(p) composites were prepared by gas pressure sintering at 190$0^{\circ}C$ for 1 hour. $\alpha$-SiC with average particle size of 0.48${\mu}{\textrm}{m}$ were dispersed from zero to 50vol% in $\alpha$-Si3N4 with average particle size of 0.5${\mu}{\textrm}{m}$. Y2O3-Al2O3 system was used as sintering aids. When 10vol% of SiC was added to Si3N4, optimum mechanical properties were observed; relative density of 98.8%, flextural strength of 930MPa, fracture toughness of 5.9MPa.m1/2 and hardness value of 1429kg/$\textrm{mm}^2$. Grain growth of $\beta$-Si3N4 was inhibited as the amount of added SiC was increased. SiC particles were found inside the $\beta$-Si3N4 intragrains in case of 10, 20 and 30vol%SiC added composites.

• East Asian mathematical journal
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• v.28 no.5
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• pp.597-604
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• 2012

Let C be a nonempty closed convex subset of real Hilbert space H and F = $\{S(t):t{\geq}0\}$ a nonexpansive self-mapping semigroup of C, and $f:C{\rightarrow}C$ is a fixed contractive mapping. Consider the process {$x_n$} : $$\{{x_{n+1}={\beta}_nx_n+(1-{\beta}_n)z_n\\z_n={\alpha}_nf(x_n)+(1-{\alpha}_n)S(t_n)P_C(x_n-r_nAx_n)$$. It is shown that {$x_n$} converges strongly to a common element of the set of fixed points of nonexpansive semigroups and the set of solutions of the variational inequality for an inverse strongly-monotone mapping which solves some variational inequality.

• Journal of the Korean Chemical Society
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• v.18 no.4
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• pp.267-271
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• 1974

The tetradentate schiff base, N,N'-bis(salicylaldehyde)-ethylene diimine has been reacted with a series of Mo(IV), Mo(V), Mo(IV), and Mo(III) oxidation states to form new Complexes; $[MoO_2(C_{16}H_{14}O_2N_2)], (MoO(C_{16}H_{14}O_2N_2)]_2O, (Mo(SCN)(C_{16}H_{14}O_2N_2)]_2O, and (Mo(H_2O)(C_{16}H_{14}O_2N_2)]_2O.$ These complexes have hexa coordinated configurations and the mole ratio of these ions to the ligand was 1:1. These complexes have been identified by visible spectra, infrared specra, T.G.A., D.T.A., and elemental analysis.

• Applied Microscopy
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• v.50
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• pp.7.1-7.10
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• 2020

Tantalum nitride (TaN_x) thin films were grown utilizing an inductively coupled plasma (ICP) assisted direct current (DC) sputtering, and 20-100% improved microhardness values were obtained. The detailed microstructural changes of the TaN_x films were characterized utilizing transmission electron microscopy (TEM), as a function of nitrogen gas fraction and ICP power. As nitrogen gas fraction increases from 0.05 to 0.15, the TaN_x phase evolves from body-centered-cubic (b.c.c.) TaN_0.1, to face-centered-cubic (f.c.c.) δ-TaN, to hexagonal-close-packing (h.c.p.) ε-TaN phase. By increasing ICP power from 100 W to 400 W, the f.c.c. δ- TaN phase becomes the main phase in all nitrogen fractions investigated. The higher ICP power enhances the mobility of Ta and N ions, which stabilizes the δ-TaN phase like a high-temperature regime and removes the micro-voids between the columnar grains in the TaN_x film. The dense δ-TaN structure with reduced columnar grains and micro-voids increases the strength of the TaN_x film.

• Journal of Aquaculture
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• v.10 no.3
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• pp.335-346
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• 1997

Denitrification is one of the important processes of removing nitrate from in recirculating aquaculture systems. And this process is affected by many factors such as external organic carbon sources, hydraulic retention time (HRT), COD/NO3--N (C:N) ratio, etc. However, not many studies were done for the optimum conditions of denitrification in the recirculation system for aquaculture. Therefore, this study was conducted to find out the optimum removal condition of NO3--N using submerged denitrification biofilter. The combinations of two external organic carbon sources (glucose and methanol), two HRT (4 and 8-hour) and four differnent C : N ratios (3, 4, 5, 6) were tested. The removal efficiencies of NO3--N and total inorganic nitrogen (TIM) at 8-hour HRT were better than those at 4-hour's (P<0.05). The maximum removal efficiency of NO3--N by methanol (97.8%) was achieved at HRT and C : N ratio were 8-hour and 4.0 respectively. The efficiencies of methanol for the removal of NO3--N and TIN were always better than those of glucose (P<0.05). The maximum removal efficiencies of total inorgainc nitrogen (TIN) were gained at C : N ration of 5.0. The maximum removel efficiencies of TIN using methanol and glucose were 96.9% and 71.5% respectively. Anaerobic condition which is necessary for denitrification process was not made until the 8-hour HRT and higher C : N ratio (5.0). Removal of NO3--N at 4-hour HRT and C : N ration lower than 5.0 were inhibited by oxygen and/or low quantity of external organic carbon. Removal efficiencies of NO3--N were also inhibited by high C : N (6.0) ratio when HRT was 8-hour.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.192-192
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• 2014

TiN, Ti(C,N), TiAlSiN, TiZrAlN, TiAlCrSiN 박막을 제조한 후, 이 들의 고온산화 특성을 SEM, EPMA, TGA, TEM, AES 등을 이용하여 조사하고, 산화기구를 제안하였다. 산화속도, 생성되는 산화물의 종류와 분포는 박막의 조성, 산화온도, 산화시간에 따라 변하였다.

• Journal of the Korean Mathematical Society
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• v.57 no.4
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• pp.1005-1018
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• 2020

A characterization of the C-projective vector fields on a Randers space is presented in terms of 𝚵-curvature. It is proved that the 𝚵-curvature is invariant for C-projective vector fields. The dimension of the algebra of the C-projective vector fields on an n-dimensional Randers space is at most n(n + 2). The generalized Funk metrics on the n-dimensional Euclidean unit ball 𝔹ⁿ(1) are shown to be explicit examples of the Randers metrics with a C-projective algebra of maximum dimension n(n+2). Then, it is also proved that an n-dimensional Randers space has a C-projective algebra of maximum dimension n(n + 2) if and only if it is locally Minkowskian or (up to re-scaling) locally isometric to the generalized Funk metric. A new projective invariant is also introduced.

• Journal of the Korean Chemical Society
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• v.19 no.6
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• pp.449-453
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• 1975

Substituent effect of the leaving groups of the reaction of benzyl arenesulfonate with dimethylanilines in acetone at $35^{\circ}C$ was obtained with the following results. 1. Substituent effect of the leaving groups was not variable when changed from pyridine to N,N-dimethylaniline in nucleophile 2.In acetone, the Hammett ${\sigma}$ constant of p-MeO of the leaving group was -0.35. 3. The weaker the nucleophilicity in dimethylaniline, the stronger the movement of electron from N to C, and the cleavage of the C${\ldots}$0 bond in transition state proceeds.

• Fire Science and Engineering
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• v.27 no.2
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• pp.11-17
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• 2013

For the safe handling of n-undecane, the lower flash points and the upper flash point, fire point, AITs (auto-ignition temperatures) by ignition delay time were experimented. Also lower and upper explosion limits by using measured the lower and upper flash points for n-undecane were calculated. The lower flash points of n-undecane by using closed-cup tester were measured $59^{\circ}C$ and $67^{\circ}C$. The lower flash points of n-undecane by using open cup tester were measured $67^{\circ}C$ and $72^{\circ}C$, respectively. The fire point of n-undecane by using Cleveland open cup tester was measured $74^{\circ}C$. This study measured relationship between the AITs and the ignition delay times by using ASTM E659 apparatus for n-undecane. The experimental AIT of n-undecane was $198^{\circ}C$. The estimated lower and upper explosion limit by using measured lower flash point $59^{\circ}C$ and upper flash point $83^{\circ}C$ for n-undecane were 0.65 Vol.% and 2.12 Vol.%.

• Journal of the Korean Vacuum Society
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• v.6 no.3
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• pp.255-262
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• 1997

Titanium nitride (TiN) films were prepared by reactive sputter deposition in mixed gas of Ar+$N_2$. The volume percentage of $N_2$ in the working gas was chosen so as to grow stoichiometric TiN films and the substrate temperature during film growth was set from room temperature to $700^{\circ}C$. Stoichiometric $Ti_{0.5}N){0.5}$ films with (111) texture were grown at temperatures over $600^{\circ}C$, while films prepared at temperatures below $600^{\circ}C$ showed N-rich TiN. The composition X and y in the $Ti_xN_y$ films determined by XPS and RBS varied within 5% with the substrate temperature. The sheet resistance of the TiN films decreases as the substrate temperature increased. TiN film prepared at $600^{\circ}C$ showed 14.5$\Omega\Box$, and it decreased to 8.9$\Omega\Box$ after the sample was annealed at $700^{\circ}C$, 30 sec in Ar-gas ambient by RTA. By far, high quality stoichiometric TiN films by reactive sputtering in the mixed gas ambient could be prepared at substrate temperature over $600^{\circ}C$.