• Journal of The Korean Society of Grassland and Forage Science
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• v.17 no.2
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• pp.110-116
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• 1997

The objective of this experiment was to suggest the optimum nitrogen fertilization level for orchardgrass(0G)- red clover(RC) mixtures. The field trials were conducted from 1993 to 1994 in order to evaluate the dry matter yield, botanical composition, chemical composition, dry matter digestibility(DMD), crude protein dry matter (CPDM) and digestible dry matter(DDM) yields on the nitrogen levels( 0, 50, 100, 150 and 300kgha). The results obtained were summarized as follows : 1. With increasing nitrogen levels, the DM yield of OG-RC mixttures significantly increased(P<0.05). The maximum total DM yield (7,964kgha) was obtained at N 300kgha level, However, there was no significant difference between N 150 and 300kgha. 2. With increasing the nitrogen levels, the botanical composition of OG in OG-RC mixttures was significantly increased(P< 0.05), whereas that of RC was remarkably decreased(P< 0.05). 3. The CP content was decreased by increasing nitrogen level(P

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.6
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• pp.49-57
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• 2015

This paper presents the discharge characteristics and economic feasibility of a Dry $Air/O_2$ and a $N_2/O_2$ mixture gas in order to review $SF_6$ alternative. From AC discharge experiment in an quasi-uniform field, it was found that the optimal $N_2/O_2$ mixing ratio which breakdown voltage and surface flashover voltage were the highest was 70/30 and that the pressure dependence on the breakdown voltage was higher than that of the surface flashover voltage in the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas. The mixing ratio (70/30) and the tendency of the pressure dependence were described in detail based on physical factors (impact ionization coefficient, electron attachment coefficient, secondary electron emission coefficient) involved in discharge mechanism and a electron source, respectively. In addition, the performance insulation and the economic feasibility of the Dry $Air/O_2$ and the $N_2/O_2$ mixture gas were discussed so that Dry $Air/O_2$ mixture gaswas more suitable than $N_2/O_2$ mixture gas to the $SF_6$ alternative.

• Journal of the Korean institute of surface engineering
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• v.34 no.5
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• pp.403-408
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• 2001

In this work, the cyclic perfluorinated ether (c-C$_4$F$_{8}$O) with very high destructive removal efficiency (DRE) than other alternative gases, such as $C_3$F$_{8}$, c-C$_4$F$_{8}$ and NF$_3$ was used as an alternative process chemical. The plasma cleaning of silicon nitride using gas mixtures of c-C$_4$F$_{8}$O/O$_2$ and c-C$_4$F$_{8}$O/O$_2$+ $N_2$ was investigated in order to evaluate the effects of adding $N_2$ to c-C$_4$F$_{8}$O/O$_2$ on the global warming effects. Under optimum condition, the emitted net perfluorocompounds (PFCs) during cleaning of silicon nitride were quantified and then the effects of additive $N_2$ by obtaining the destructive removal efficiency (DRE) and the million metric tons of carbon equivalent (MMT-CE) were calculated. DRE and MMTCE were obtained by evaluating the volumetric emission using. Fourier transform-infrared spectroscopy (FT-IR). During the cleaning using c-C$_4$F$_{8}$O/O$_2$+$N_2$, DRE values as high as (equation omitted) 98% were obtained and MMTCE values were reduced by as high as 70% compared to the case of $C_2$F$_{6}$O$_2$. Recombination characteristics were indirectly investigated by combining the measurements of species in the chamber using optical emission spectroscopy (OES), before and after the cleaning, in order to understand any correlation between plasma and emission characteristics as well as cleaning rate of silicon nitride.silicon nitride.

• Analytical Science and Technology
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• v.6 no.2
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• pp.207-215
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• 1993

$Si_3N_4$ powders were mixed with sintering additives($3Y_2O_3{\cdot}5Al_2O_3$, YAG) by coprecipitation method. Mixing homogeneity, sintered and mechanical properties of coprecipitation-mixed powder compacts were compared with those of mechanically-mixed ones. SIMS-analysis for composition on the surface and in the matrix of prepared powder mixtures showed that the added YAG exists mainly on the $Si_3N_4$ powder surfaces in a form of coating. From this result it could be concluded that coprecipitation method is superior to mechanical mixing in the mixing homogeneity. This mixing homogeneity can accompany an improvement in sintered density, microstructure and consequently the mechanical properties of sintered bodys.

• Journal of the Korean Chemical Society
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• v.27 no.2
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• pp.95-101
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• 1983

The pseudo-first order rate constants have been obtained for the solvolysis of benzoyl cyanide in various aqueous solvent mixtures and ethanol-trifluoroethanol mixtures at 1, 5, 10, 15 and $20^{\circ}C$. Values of n in the Kivinen polt, m values of Grunwald-Winstein polt, $\beta$ values of Leffler relationship and values of m and l in the extended Grunwald-Winstein polt have been calculated and studied the transition state variation caused by solvent changes using the More O'Ferrall polt and quantum mechanical approach. It has been shown that the reaction proceed via the associative $S_N2$ mechanism, using the transition state parameters and quantum mechanical model approach.

• Journal of the Korean Physical Society
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• v.73 no.12
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• pp.1855-1862
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• 2018

A reliable set of low-energy electron collision cross sections for the triethoxysilane (TRIES) molecule was derived based on the measured electron transport coefficients for a pure TRIES molecule by using an electron swarm method and a two-term approximation of the Boltzmann equation. The electron transport coefficients calculated using the derived set are in good agreement with experimental value over a wide range of E/N values (ratio of the electric field E to the neutral number density N). The present electron collision cross section set for the TRIES molecule, therefore, is the most reliable so far for plasma discharges and for materials processing using the TRIES molecule. Moreover, the electron transport coefficients for the TRIES-Ar and the $TRIES-O_2$ mixtures were also calculated and analyzed over a wide range of E/N for the first time.

• Journal of the Korean Chemical Society
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• v.32 no.5
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• pp.416-421
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• 1988

Kinetic studies for the nucleophilic substitution reactions of benzyl halides(para-substituted benzyl bromides and benzyliodide) with substituted pyridines in MeOH-MeCN mixtures have been carried out in order to elucidate the reaction mechanism. Cross interaction coefficient, ${\rho}_{XY}$ values suggested that the reactions between benzylhalides and substituted pyridines exhibit an dissocitive $S_N$2 mechanism. Hammett (${\rho}_X$, ${\rho}_Y$), Br${\o}$nsted ${\beta}_N$ and solvatochromic correlation coefficient a, s, a/s values were illustrated. Kinetic results were compared between potential energy surface model and quantum mechanical model. The quantum mechanical approach showed to be consistent with kinetic results.

• Journal of The Korean Society of Grassland and Forage Science
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• v.5 no.2
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• pp.136-142
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• 1985

For better grassland development in the forest, this field experiment was carried out to investigate the effect of thirteen different fertilizer levels of nitrogen(N), phosphorus ($P_2O_5$) and potassium ($K_2O$) on the botanical composition, growth and dry matter yield of grass-clover mixtures grown under trees with 40-50% of shading level. This experiment was arranged as a randomized block design with replications, and performed on the experimental field in the suburban forest of Suweon in 1984. The results obtained are summarized as follows: 1. Plant height and cover degree of grasses found to be high with 28 and 42kg N fertilizer per 10a, while those were the lowest with zero and N-zero fertilizer levels. The degree of bare land after the fourth cut was also high in the low N level. 2. A significant higher degree of leaf green and chlorophyll content of leaf blade was observed in the plot of 28 and 42 kg N per 10a when compared with low N fertilizer plot. However, leaf decay and plant type of grasses tended to be a little poor as the high N was applied. 3. the regrowth plant length and dry weight of grasses after the first cut increased significantly with 28 and 42 kg N fertilizer. However, those showed slightly increased regrowth in the plot of zero and N-zero fertilizer levels. 4. The dry matter yield of grasses was higher with 28 and 42 kg N than that of low N fertilizer level. Higher yields were obtained in the plot of standard ($N-P_2O_5-K_2O$=28-20-24 kg/10a), 50% increase of $N,P_2O_5K_2O$ and N-50% increase, although there were no significant differences among three fertilizer levels. 5. Growth, botanical composition, regrowth and yield of grasses grown under pine trees were significantly influenced by N fertilizer level, regardless of $P_2O_5\;and\;K_2O$. The fertilizer level of $N-P_2O_5-K_2O$ was 28-20-24 kg per 10a for more forage production in the forest. Considering economic yield in this study, however, the optimum fertilizer level of N, $P_2O_5\;and\;K_2O$ was suppose to be 21-28, 10-15, and 12-18kg per 10a, respectively.

• Journal of the Korean Chemical Society
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• v.50 no.2
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• pp.137-140
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• 2006

In this report, Europium doped strontium barium gallium silicate ((Sr,Ba)2Ga2SiO7:Eu2+) phosphor has been synthesized by conventional solid-state method and investigated luminescent characteristic. Appropriate proportions of the raw materials were mixed in an agate mortar with acetone to obtain starting mixtures. Also, this phosphor was prepared by simple process under the reduction atmosphere (25% H2/75% N2). This phosphor can be applicated to the green phosphor for white LED because it has green emission band (513 nm), which emits efficiently under the 405nm excitation energy.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.957-962
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• 2009

Sialon was produced by hot-pressing the mixtures of $Si_3N_4$, AlN and $Y_2O_3$ powders. All fracture tests were performed on a three-point loading system with a 30 mm bending span. Fracture toughness and Vickers hardness of smooth specimen were average 7.05 $MPa{\cdot}m^{0.5}$ and Hv = 1580, respectively. Density of three kinds of specimens, smooth specimen, smooth and healed specimen, smooth with $SiO_2$ colloidal coating and healed specimen, had beyond 99 % of theoretical density. Bending strength of smooth healed specimens had high strength more than 1 GPa. Crack healed specimens recovered as strength as smooth specimen. That is, cracked specimen with $SiO_2$ colloidal coating on cracked part recovered strength by heat treatment, completely. Crack healing of $Si_3N_4$ composite ceramics had contributed glassy $SiO_2$ to strength recovery. Limiting high temperature for bending strength of heat treated smooth specimen for bending strength was about 1273 K.