• Bulletin of the Korean Chemical Society
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• 제31권7호
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• pp.1915-1919
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• 2010

Second-order rate constants $(k_N)$ have been measured for reactions of 2,4-dinitrophenyl phenyl carbonate (2) with a series of pyridines in 80 mol % $H_2O$/20 mol % DMSO at $25.0{\pm}0.1^{\circ}C$ and compared with the $k_N$ values reported for the corresponding reactions of 2,4-dinitrophenyl benzoate (1) to investigate the effect of nonleaving group on reactivity and mechanism. The reactions of 2 result in larger $k_N$ values than those of 1. The Br${\o}$nsted-type plot for the reactions of 2 exhibits a downward curvature (i.e., ${\beta}2$ = 0.84 and ${\beta}1$ = 0.16), which is typical for reactions reported to proceed through a stepwise mechanism with a change in rate-determining step. The $pK_a$ at the center of the Br${\o}$nsted curvature, defined as $pK_a{^{\circ}}$, has been found to be 8.5 and 9.5 for the reactions of 2 and 1, respectively. Dissection of $k_N$ into the microscopic rate constants (e.g., $k_1$ and $k_2/k_{-1}$ ratio) has revealed that the reactions of 2 result in larger k1 values than those of 1, indicating that PhO behaves as a stronger electron-withdrawing group than Ph. However, the $k_2/k_{-1}$ ratio has been found to be independent of the electronic nature of Ph and PhO.

• 공학논문집
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• 제3권1호
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• pp.223-233
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• 1998

고상반응식을 이용한 석회와 석영과의 수열반응속도 및 반응메카니즘에 관하여 연구하였다. 출발물질로 석영과 수산화칼슘 CaO/$SiO_2$몰비 0.8-1.0로 혼합하고 $180-200^{\circ}C$, 0.5-8시간동안 포화증기압하에서 오토클레이브로 수열반응을 행하였다. 수열반응속도는 총 석회의 양과 총 석영의 양에 대한 미반응 석회의 양과 미반응 석영의 양의 비로 구하였다. 반응속도는 Jander의 식 $[1-(1-\alpha)^{1/3}]^N=Kt$를 이용하여 얻은 결과, 석회의 반응속도는 N=1로서 주로 용해속도에 의해 지배되고 석영의 반응속도는 $N\risingdotseq2$로서 확산에 의해 주로 지배된다. 규산칼슘수화물계의 수열반응속도는 반응물 입자주위에 형성된 생성물층을 통한 물질전달에 의해 율속되는 것으로 추정되고 전체 수열반응의 속도식은 대략 $N=1-2$로서 경계층으로부터 확산에 의해 율속과정으로 전환된다.

• 한국환경농학회지
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• 제39권2호
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• pp.114-121
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• 2020

BACKGROUND: Biochar-based fertilizers delay the nutrient release and feature a slow release effect for agricultural and environmental advantages. This experiment was conducted to evaluate agro-environmental effects of different application ratios of modified biochar pellets supplemented. METHODS AND RESULTS: The treatments consisted of the control, 40% N, 60% N and 60% N (0.07M MgO) of modified supplemented biochar pellets (MSBP), which were based on recommended ratio of nitrogen for rice cultivation. For the paddy water, the NH₄-N and NO₃-N concentrations in whole treatments rapidly increased at 84 days and 40 days after transplanting, respectively. The PO4-P concentrations in the MSBP were generally lower than those of the control. For the paddy soil, NH₄-N concentrations in the MSBP were higher than those of the control at 5 days after transplanting, while NO₃-N concentrations were not significantly different in the treatments through rice cultivation. P₂O₅ concentrations in the control were higher than those of the MSBP until 40 days after transplanting while K₂O concentrations were not significantly different among the treatment. The highest carbon sequestration was 970 kg ha^-1 in the 60% N (0.07M MgO), and the potential carbon storage in the 60% N (0.07M MgO) was higher at 222 kg ha^-1 than the control during rice cultivation. It shown that the rice yield in the control was not significantly different from the 40% N and 60% N (0.07M MgO) application plots. CONCLUSION: Application of MSBP for rice cultivation was effective for carbon sequestration and agro-environmental effects even though nitrogen application ratio was reduced at 40% based on recommended application ratio of fertilizer.

• Journal of Korean Vacuum Science & Technology
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• 제2권2호
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• pp.122-132
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• 1998

Characteristics of inductively coupled Cl2/O2 and Cl2/N2 plasmas and their effects on the formation of submicron deep trench etching of single crystal silicon have been investigated using Langmuir probe, quadrupole mass spectrometer (QMS), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM), Also, when silicon is etched with oxygen added chlorine plasmas, etch products recombined with oxygen such as SiClxOy emerged and Si-O bondings were found on the etched silicon surface. However, when nitrogen is added to chlorine, no etch products recombined with nitrogen nor Si-N bondings were found on the etched silicon surface. When deep silicon trenches were teached, the characteristics of Cl2/O2 and Cl2/N2 plasmas changed the thickness of the sidewall residue (passivation layer) and the etch profile. Vertical deep submicron trench profiles having the aspect ratio higher than 5 could be obtained by controlling the thickness of the residue formed on the trench sidewall using Cl2(O2/N2) plasmas.

• Journal of Plant Biology
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• 제13권2호
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• pp.21-31
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• 1970

The rice variety, Nongkwang was used in two factorial experiments with the combination of 15 kg and 20 kg of N per 10 a, 3 levels of P2O5 (0, 4 and 8 kg per 10 a) and 4 levels of potash(0, 2, 4 and 8 kg per 10 a) in the reclaimed soil areas containing 0.48% on the average salt content throughout the year(0.67% at the end of April). The absorption of N, K and Ca was accelerated by increased N applications. The absorption of P itself was not enhanced by the increased application of P2O5 but the absorption of K2O reduced the absorption of Mg was affected. The increased application of K2O reduced the absorption of Si and seemed to increase the content of carbohydrate in the rice plants. Twenty kg of N and 4kg of P2O5 per 10 a produced satisfactory yields of rough rice, potash applications are ineffective in this experiment on rice grain production.

• Asian-Australasian Journal of Animal Sciences
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• 제27권3호
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• pp.439-446
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• 2014

Many studies on methane ($CH_4$) and nitrous oxide ($N_2O$) emissions from livestock industries have revealed that livestock production directly contributes to greenhouse gas (GHG) emissions through enteric fermentation and manure management, which causes negative impacts on animal environment sustainability. In the present study, three essential values for GHG emission were measured; i.e., i) maximum $CH_4$ producing capacity at mesophilic temperature ($37^{\circ}C$) from anaerobically stored manure in livestock category ($B_{0,KM}$, Korean livestock manure for $B_0$), ii) $EF_{3(s)}$ value representing an emission factor for direct $N_2O$ emissions from manure management system S in the country, kg $N_2O-N$ kg $N^{-1}$, at mesophilic ($37^{\circ}C$) and thermophilic ($55^{\circ}C$) temperatures, and iii) $N_{ex(T)}$ emissions showing annual N excretion for livestock category T, kg N $animal^{-1}$ $yr^{-1}$, from different livestock manure. Static incubation with and without aeration was performed to obtain the $N_2O$ and $CH_4$ emissions from each sample, respectively. Chemical compositions of pre- and post- incubated manure were analyzed. Contents of total solids (% TS) and volatile solid (% VS), and the ratio of carbon to nitrogen (C/N) decrease significantly in all the samples by C-containing biogas generation, whereas moisture content (%) and pH increased after incubation. A big difference of total nitrogen content was not observed in pre- and post-incubation during $CH_4$ and $N_2O$ emissions. $CH_4$ emissions (g $CH_4$ kg VS-1) from all the three manures (sows, layers and Korean cattle) were different and high C/N ratio resulted in high $CH_4$ emission. Similarly, $N_2O$ emission was found to be affected by % VS, pH, and temperature. The $B_{0,KM}$ values for sows, layers, and Korean cattle obtained at $37^{\circ}C$ are 0.0579, 0.0006, and 0.0828 $m^3$ $CH_4$ kg $VS^{-1}$, respectively, which are much less than the default values in IPCC guideline (GL) except the value from Korean cattle. For sows and Korean cattle, $N_{ex(T)}$ values of 7.67 and 28.19 kg N $yr^{-1}$, respectively, are 2.5 fold less than those values in IPCC GL as well. However, $N_{ex(T)}$ value of layers 0.63 kg N $yr^{-1}$ is very similar to the default value of 0.6 kg N $yr^{-1}$ in IPCC GLs for National greenhouse gas inventories for countries such as South Korea/Asia. The $EF_{3(s)}$ value obtained at $37^{\circ}C$ and $55^{\circ}C$ were found to be far less than the default value.

• 대한환경공학회지
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• 제22권2호
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• pp.231-239
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• 2000

본 연구는 $A_2O$ 공정을 적용한 고정생물막법을 이용하여 고농도의 총무기성질소(TIN) 유입으로 인해 C/N비가 낮은 폐수를 처리하기 위하여 최적의 운전조건 탐색과 생물학적 호기탈질을 평가하였다. 혐기조와 무산소조에 세라믹 여재를 그리고 호기조에 PVC 여재를 충전한 실험장치는 C/N(TOC/TIN)비를 0.5로 일정하게 유지하고 알칼리도를 변화시켜 실험을 실시하였으며 그 결과는 다음과 같다. 유기물제거는 운전조건에 관계없이 96.0% 이상의 높은 제거효율을 얻었다. 유입수의 알칼리도를 약 1210mg/L(Run 5)로 운전하였을 때, $NH_4{^+}-N$와 총 질소 평균 제거효율은 각각 93.5%, 81.8%이었으며, 제거된 총 질소 중 64.9%가 호기조에서 생물학적 탈질에 의해서 제거되었다. 호기조에서 물질수지를 이용하여 질소와 알칼리도를 분석한 결과, 1mg의 $NO_2{^-}-N$가 탈질에 의해 제거될 때 2.49~3.46mg의 알칼리도가 생성되었다. 호기조에서의 생물학적 탈질은 ${\Delta}TOC/{\Delta}DEN$의 이론적인 비 1.22보다 낮은 0.84(Run 5)에서 일어났다.

• 한국응용과학기술학회지
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• 제28권3호
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• pp.321-328
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• 2011

The autothermal reforming reaction of methane was investigated to produce hyd rogen with Ni/$CeO_2-ZrO_2$, Ni/$Al_2O_3$-MgO and Ni-Ru/$Al_2O_3$-MgO catalysts. Honeycomb metalli c monolith was applied in order to obtain high catalytic activity and stability in autothermal r eforming. The catalysts were characterized by XRD, BET and SEM. The influence of various catalysts on hydrogen production was studied for the feed ratio($O_2/CH_4$, $H_2O/CH_4$). The $O_2/CH_4$ and $H_2O/CH_4$ ratio governed the methane conversion and temperature profile of reactor. Th e reactor temperature increased as the reaction shifted from endothermic to exothermic reactio n with increasing $O_2/CH_4$ ratio. Among the catalysts used in the experiment, the Ni-Ru/$Al_2O_3$-MgO catalyst showed the highest activity. The 60% of $CH_4$ conversion was obtained, and th e reactor temperature was maintained $600^{\circ}C$ at the condition of GHSV=$10000h^{-1}$ and feed ratio S/C/O=0.5/1/0.5.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2002년도 춘계학술대회 논문집
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• pp.43-47
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• 2002

In this study, through the experimental results of grinding ratio, grinding force and surface roughness with the obtained wear amount of diamond wheel and ceramic material during the grinding process, the following conclusions could be found. In the case of $Si_3N_4$, the wear of diamond wheel is large while the grinding force is stable and the range of change in surface roughness is small. for the case of $AL_2O_3$ and $ZrO_3$, while the wear of diamond wheel is getting smaller, the grinding force is increasing but the value of surface roughness is decreasing. For grinding with the vitrified bond wheel, it seems that the self-sharpening can be found for $Si_3N_4$ and the glazing effect of the cutting edge for $AL_2O_3$ and $ZrO_3$.

• 한국농림기상학회지
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• 제5권1호
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• pp.1-5
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• 2003

수원 지역의 영농기간중 강우의 화학적 특성을 알아보기 위하여 1999년 및 2000년 2년 간 4월부터 10월까지 각각 1개월 동안 수원지역에 내린 빗물의 화학적 성분조성과 강우량을 고려한 가중평균(volume-weighted mean) 이온농도 변화를 조사한 결과는 다음과 같다. 조사 기간 중 강우 pH는 편서풍의 영향을 받는 기간인 4월이 6월 이후의 강우에 비해 높게 나타나 계절적 특성을 보였다. 강우시료에 대한 pH별 강우 분포는 pH 5.6 이상이 45.1%로 가장 많았으며, pH 5.6∼5.0 및 4.5∼4.9 범위의 강우가 각각 31.4%와 19.6%를 차지하였다. 빗물의 조성은 S $O_4$가 음이온의 50%이상을 차지하였고 전체 양이온 함량의 약 65% 가 N $H_{4}$$^{+}$와 $Ca^{2+}$로 구성되어 있다. 월별 빗물 pH는 측정치(p $H_{/obs}$)는 6월에서 9월 사이에 낮은 반면, 이론치(p $H_{\the}$)는 같은 기간에 증가하여 대기중의 알카리성 물질들에 의한 중화력이 다른 기간에 비해 낮았다. 또한, 강우중 비해염 sulfate는 총 sulfate 함량의 약 93.6%이었다. 강우의 산성도 기여율(nss-S $O_{4}$$^{2-}$ /N $O_{3}$$^{-}$)은 평균 2.1로 비해염 S $O_{4}$$^{2-}$ 에 의한 기여율이 N $O_{3}$$^{-}$ 보다 약 2배 가량 높았다.