• Journal of the korean society of oceanography
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• v.34 no.2
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• pp.86-94
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• 1999

An investigation was conducted to determine limiting nutrients in the bay systems of the southern coastal area of Korea. The elemental composition of C, N, and P in suspended particulate matter was monitored nearly monthly in Chinhae and Koje Bays and seasonally in Deukryang Bay for 2 years. Atomic C:N ratio in particulate matter ranges from 4.3 to 9.6, typical of marine phytoplankton. C:P and N:P ratios vary from the Redfield ratio to 229 (C:P) and 37 (N:P). A constant C:N ratio of 6.87 from regression of particulate C and N concentrations demonstrates that the particulate matter in the systems originates from primary production. C:P and N:P ratios from regression of C on P and N on P are well associated with changes in salinity. The low N:P ratio of 13.1 implies N limitation in the environments of the systems. This seems to result from the low N:P ratio of nutrients released across sediment-water interface. Phytoplankton response, expressed here as the increase of chlorophyll a, to N addition also verifies N limitation for phytoplankton communities. In heavy rainfall season (from June to September), the addition of excessive N via streams into the stratified coastal water proliferates phytoplankton greatly. During the phytoplankton blooms, C:P and N:P ratios are much higher than the Redfield ratio, implying P limitation. This results from the high N:P ratio in nutrients supplied from stream waters. Strong stratification during the blooms also interrupts the supply of nutrients, particularly p, from bottom waters. Dependent upon precipitation, this tendency shows great inter-annual variation.

• Bulletin of the Korean Chemical Society
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• v.7 no.6
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• pp.425-428
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• 1986

A new heterocuprate containing 2-pyridyloxy ligand, lithium 2-pyridyloxy-n-butylcuprate, has shown improved thermal stability and it reacts with acid chlorides to afford the corresponding ketones in high yields. Similarly, it can be effectively utilized in conjugate addition reactions of $\alpha,\beta$-unsaturated ketones. Of synthetic significance is that the complete utilization of n-butyl group in lithium 2-pyridyloxy-n-butylcuprate has been observed.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.171-176
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• 2003

The sonolytic decomposition of NHCs, such as atrazine［6-chloro-N-ethyl-N＇ -(1-methylethyl)-1,3,5-triazine-2,4-diamine］, simazine( 6-chloro-N,N＇ -diethyl-l ,3,5-triazine-2,4-diamine), trietazine(6-chloro-N,N,N＇-triethyl-l,3,5-triazine-2,4-diamine), in water was investigated at a ultrasound frequency of 200kHz with an acoustic intensity of 200W under argon and air atmospheres. The concentration of NHCs decreased with irradiation, indicating pseudo-first-order kinetics. The rates were in the range 1.06∼2.07 (x10/sup -3/ min/sup -1/) under air and 1.30∼2.59(x10/sup -3/ min/sup -1/)under argon at a concentration of 200μM of NHCs. The rate of hydroxyl radicals(·OH) formation from water is 19.8μM min/sup -1/ under argon and 14.7 μM min/sup -1/ under air in the same sonolysis conditions. The sonolysis of NHCs is effectively inhibited, but not completely, by the addition of t-BuOH(2-methyl-2-propanol), which is known to be an efficient ·OH radical scavenger in aqueous sonolysis. This suggests that the main decomposition of NHCs proceeds via reaction with ·OH radical; a thermal reaction also occurs, although its contribution is small. The addition of appropriate amounts of Fenton's reagent ［Fe/sup 2＋/］ accelerates the decomposition. This is probably due to the regeneration of ·OH radicals from hydrogen peroxide, which would be formed from recombination of ·OH radicals and which may contribute a little to the decomposition.

• Korean Journal of Materials Research
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• v.14 no.3
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• pp.163-167
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• 2004

TiAl(La)N thin films were oxidized in vacuum of about 7 Pa to reduce the oxidation of WC-Co as a substrate. The oxidation rate constants of the thin films were quantified by an assumption of parabolic oxidation. Increasing AI content significantly decreased the parabolic oxidation rate constant. A simultaneous addition of AI and La was more effective to reduce the oxidation rate. The parabolic oxidation rate constant of $Ti_{0.66}$ $Al_{0.32}$ $La_{ 0.02}$N thin film at 1273 K showed about ten times lower than that of TiN. The addition of a small amount of La with Al induced the preferential formation of dense $\alpha$ $-Al_2$$O_3$ film in oxide film, leading to the abrupt reduction of oxidation rate.

• Korean Chemical Engineering Research
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• v.46 no.2
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• pp.356-368
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• 2008

The effects of cosurfactant on silica nanoparticles were investigated in systems containing surfactant, oil and aqueous ammonia solution where nanoparticles were prepared using a single phase water-in-oil (W/O) microemulsion. For the same oil phase, a single phase region was dependent on the interaction between surfactant and oil. For the cyclohexane system, NP-5 surfactant showed a wider single phase region than NP-4. The addition of n-propanol as a cosurfactant resulted in an increase or a decrease of a single phase W/O microemulsion region depending on the continuous oil phase. For both cyclohexane and isooctane systems, the addition of n-propanol resulted in a decrease in the single phase region. On the other hand, for n-heptane system, the addition of n-propanol expanded a single phase W/O microemulsion region. Silica nanoparticles prepared within a single phase region showed that relatively large number of particles of irregular shape were obtained with the addition of n-propanol to NP surfactant system. The addition of n-propanol to LA-5 surfactant and n-heptane system produced a decrease in average particle size and an increase in the number of particles formed due to a decrease in the intermicellar exchange rate among microemulsion droplets.

• Journal of the Korean Society for Heat Treatment
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• v.15 no.4
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• pp.166-171
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• 2002

The effects of Ni and N addition to 304 stainless steel on mechanical properties and microstructure were investigated within temperature ranged from $-196^{\circ}C$ to $25^{\circ}C$. The addition of nickel and nitrogen induced the stability against the formation of provide significantly enhanced ductility at $-196^{\circ}C$ and reduce the Md temperature. Fe-18Cr-10Ni-0.2N alloy showed the ${\gamma}$ phase in deformed structure which it was beneficial to enhance the tensile strength and elongation at $25^{\circ}C$ and $-196^{\circ}C$.

• Reproductive and Developmental Biology
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• v.33 no.1
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• pp.1-5
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• 2009

To search a new pig pheromonal odorant, the $N^1$-allyl-$N^2$-(tetrahydrofuran-Z-ylmethyl)oxalamide molecule predicted by ligand based approach and molecular docking method was synthesized by nucleophilic addition-elimination reaction ($Ad_{NU-E}$) between N-allyloxalamic acid ethylester and tetrahydrofurlmethylamine. According to the evaluation results for efficiency of pig estrus control, the synthesized pig pheromonal $N^1$-allyl-$N^2$-(tetrahydrofuran-2-ylmethyl)oxalamide molecule advanced the estrus by 11.3 days (p<0.05) compared with the non-pheromone group. And from these results, it is predicted that the synthesized pig pheromonal compound will be able to increase the reproduction efficiency of pig.

• Communications of the Korean Mathematical Society
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• v.34 no.1
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• pp.1-16
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• 2019

Let a, b, P, and Q be real numbers with $PQ{\neq}0$ and $(a,b){\neq}(0,0)$. The Horadam sequence $\{W_n\}$ is defined by $W_0=a$, $W_1=b$ and $W_n=PW_{n-1}+QW_{n-2}$ for $n{\geq}2$. Let the sequence $\{X_n\}$ be defined by $X_n=W_{n+1}+QW_{n-1}$. In this study, we obtain some new identities between the Horadam sequence $\{W_n\}$ and the sequence $\{X_n\}$. By the help of these identities, we show that Diophantine equations such as $$x^2-Pxy-y^2={\pm}(b^2-Pab-a^2)(P^2+4),\\x^2-Pxy+y^2=-(b^2-Pab+a^2)(P^2-4),\\x^2-(P^2+4)y^2={\pm}4(b^2-Pab-a^2),$$ and $$x^2-(P^2-4)y^2=4(b^2-Pab+a^2)$$ have infinitely many integer solutions x and y, where a, b, and P are integers. Lastly, we make an application of the sequences $\{W_n\}$ and $\{X_n\}$ to trigonometric functions and get some new angle addition formulas such as $${\sin}\;r{\theta}\;{\sin}(m+n+r){\theta}={\sin}(m+r){\theta}\;{\sin}(n+r){\theta}-{\sin}\;m{\theta}\;{\sin}\;n{\theta},\\{\cos}\;r{\theta}\;{\cos}(m+n+r){\theta}={\cos}(m+r){\theta}\;{\cos}(n+r){\theta}-{\sin}\;m{\theta}\;{\sin}\;n{\theta},$$ and $${\cos}\;r{\theta}\;{\sin}(m+n){\theta}={\cos}(n+r){\theta}\;{\sin}\;m{\theta}+{\cos}(m-r){\theta}\;{\sin}\;n{\theta}$$.

• Nuclear Engineering and Technology
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• v.54 no.9
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• pp.3459-3469
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• 2022

Matrix composites of n-WO₃/n-Bi₂O₃/PVA with different loadings of n-WO₃/n-Bi₂O₃ mixtures (0-15 wt%) and starch (0 and 3 wt%) were fabricated by using melt-mixing method. The X-ray attenuation capability were evaluated based on mass attenuation coefficient (μ/⍴) using a general diagnostic X-ray machine at 40-100 kVp. The effect of starch addition on the dispersion of the fillers in the PVA matrix were observed by using FESEM through morphological analysis. The fabricated samples have shrunken and caused their thickness to be decreased (0.35 mm-0.55 mm) after the drying process even though fixed thickness (2.0 mm) was set initially. The density and HVL values of the samples with 3 wt% starch was seen lower than samples without starch (0 wt%), however the former have provided improvement in filler dispersion and better X-ray attenuation capability compared to the latter. As conclusion, the matrix composite of n-WO₃/n-Bi₂O₃/PVA with 15 wt% of n-Bi₂O₃, 8 wt% of n-WO₃ and 3 wt% starch can be selected as the best promising candidate for X-ray shielding materials.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.1
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• pp.20-24
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• 2012

Denitrification rate was determined for various freshwater wetland types in the Mississippi River Coastal delta plain. Site 1 and 4 were collected from forested-tupelo dominated wetland, and site 2 and 3 were from floating emergent marsh. The maximum $N_2O$ emission was $7.47mg\;N\;m^{-2}$ for site 1 at day 6 after the addition of nitrate, $6.96mg\;N\;m^{-2}$ for site 2 at day 4, $6.63mg\;N\;m^{-2}$ for site 3 at day 3, and $9.64mg\;N\;m^{-2}$ for site 4 at day 4. The denitrification rate was determined using the acetylene inhibition method $1.24mg\;N\;m^{-2}d^{-1}$ for site 1, $1.93mg\;N\;m^{-2}d^{-1}$ for site 2, $2.24mg\;N\;m^{-2}d^{-1}$ for site 3, and $2.78mg\;N\;m^{-2}d^{-1}$ for site 4. The maximum denitrification rate was in the order of site 4 > site 3 > site 2 > site 1.