• East Asian mathematical journal
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• 제39권1호
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• pp.75-85
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• 2023

In this paper, a non-overlapping rectangular domain decomposition method is presented in order to numerically solve two-dimensional telegraph equations. The method is unconditionally stable and efficient. Spectral radius of the iteration matrix and convergence rate of the method are provided theoretically and confirmed numerically by MATLAB. Numerical experiments of examples are compared with several methods.

• 환경생물
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• 제27권4호
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• pp.353-362
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• 2009

This study attempted to compare the litter decomposition rate of Arundinella hirta and Miscanthus sinensis var. purpurascens which collected from serpentine soil acting potentially toxic concentration of heavy metals and non-serpentine soil by using the microcosm method for 192 days under constant humidity and $23^{\circ}C$. The contents of Ni, Fe, Mg and Cr in the serpentine and nonserpentine soil originated litter showed high differences between them. The litter samples from serpentine site have lower C/N than non-serpentine litter, but the soluble carbohydrate content was shown almost similar between two plant litter. The mass loss rates of leaf litter from serpentine area were slower than those from non-serpentine site. During the experimental period, the remained dry weight of A. hirta and M. sinensis var. purpurascens litter collected from serpentine site were 64.7%, 65.0% of initial dry weight and litter samples from non-serpentine site showed 54.2%, 50.7%, respectively. K and Na were leached rapidly at the initial decomposition periods, but Ca showed immobilization and other metal elements reserved at the decomposing litter for a long time. The decomposing A. hirta litter from non-serpentine soil showed higher values of $CO_2$ evolution, microbial biomass-C, and microbial biomass-N than those in serpentine soil originated litter acting nutrient stresses and exhibited rapid decay rate. The microbial biomass and microbial respiration of decaying litter were positively correlated with litter decomposition rate, and these relationships showed more rapid slope in non-serpentine soil originated litter than that in serpentine soil.

• 대한환경공학회지
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• 제33권3호
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• pp.157-161
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• 2011

본 연구에서는 골프장 등에서 살충제로 사용하는 대표적인 농약 중 fenitrothion에 대해 ZVI를 사용하여 분해경로를 파악하고 분해특성을 회분식 반응기를 이용하여 연구하였다. 또한 ZVI에 의한 순수 fenitrothion과 스미치온에 함유되어 있는 fenitrothion 분해율을 비교하였다. ZVI에 의한 fenitrothion의 분해 과정에서 3-methyl-4-nitrophenol과 4-amino-m-cresol이 생성되는 것을 알 수 있었다. ZVI에 의한 순수 fenitrothion 및 스미치온에 함유된 fenitrothion의 분해반응은 1차 반응으로 나타낼 수 있으며, 주입농도가 증가 할수록 분해율 및 1차반응 속도상수 값도 증가하였다. 순수 및 스미치온에 함유된 fenitrothion의 비표면적 1차 속도상수 값은 각각 0.0398 및 $0.1312L/m^2{\cdot}hr$으로 스미치온에 함유된 fenitrothion이 순수 fenitrothion에 비해 ZVI에 빨리 분해되었다. 이는 스미치온에 함유된 계면활성제가 fenitrothion의 용해도를 증가시키며 ZVI의 분산력을 향상시킨 것에 기인하는 것으로 판단된다.

• 한국환경과학회지
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• 제16권12호
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• pp.1369-1382
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• 2007

To find proper water quality management strategy for oxygen consumption organic matters in Jinhae bay, the physical process and net supply/decomposition in terms of COD was estimated by three-dimensional eco-hydrodynamic modeling. The estimation results of physical process in terms of COD showed that transportation of COD was dominant in loading area from land to sea, while accumulation of COD was dominant in $middle{\sim}bottom$ level. In case of surface level, the net supply rate of COD was $0{\sim}60\;mg/m^2/day$. The net decomposition rate of COD was $0{\sim}-0.05\;mg/m^2/day$($-5{\sim}-10$ m, in depth) to 2 level, and $-0.05{\sim}-0.20\;mg/m^2/day(10m{\sim})$ to bottom level. These results indicate that the biological decomposition and physical accumulation of COD are occurred for the most part of Jinhae Bay bottom. The variation of net supply or net decomposition rate of COD as reducing land based input loading is also remarkable. Therefore, it is important to consider both allochthonous and autochthonous oxygen demanding organic matters to improve the water quality of Jinhae Bay.

• Korean Chemical Engineering Research
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• 제40권6호
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• pp.709-714
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• 2002

본 연구의 실험조건에서 poly(ethylene terephthalate)(PET)의 분해반응 속도 연구를 하기 위해서 고압 용융고분자 주입장치를 고안하였다. 회분식 반응기와 고압 용융고분자 주입장치가 결합된 실험 장치를 이용하여 일정압력 250 bar에서 온도를 300, 320, $340^{\circ}C$로 각각 변화시키면서 PET의 분해반응 실험을 수행하였다. 각 온도에서 초기 1분내의 전환율이 76-90%가 될 정도로 매우 높았으며 온도가 증가함에 따라 전환율도 증가하여 반응시간 10분에는 전환율이 98%이상의 높은 값을 보임을 알 수 있었다. 2차 반응에 기초하여 반응속도 상수를 구했으며 이를 이용하여 전환율을 계산하였는데 평균 2%정도의 오차범위로 실험치와 좋은 일치를 보였다. 본 연구에서 얻은 반응속도상수를 이용하여 아임계수 내에서 PET 분해반응의 활성화 에너지를 구하였는데 그 값은 54.4 kJ/mol 이었다.

• Journal of applied mathematics & informatics
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• 제6권2호
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• pp.523-538
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• 1999

A new preconditioning method is investigated to reduce the roundoff error in computing derivatives using Chebyshev col-location methods(CCM). Using this preconditioning causes ration of roundoff error of preconditioning method and CCm becomes small when N gets large. Also for accuracy enhancement of differentiation we use a domain decomposition approach. Error analysis shows that for this domain decomposition method error reduces proportional to the length of subintervals. Numerical results show that using domain decomposition and preconditioning simultaneously gives super accu-rate approximate values for first derivative of the function and good approximate values for moderately high derivatives.

• Tribology and Lubricants
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• 제18권6호
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• pp.396-401
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• 2002

ln this paper, the fuction of molybdenum dialkyl dithiophosphate (MoDTP) as an oxidation inhibitor of mineral oils was investigated and compared with 2,6-Di-tert-Butyl-4-Methylphenol (DBMP). Oxidation tests were conducted using an oxygen absorption apparatus. MoDTP showed anti-oxidation property, and length of induction time prolonged by increasing MoDTP concentration. However the induction time of DBMP was longer than those of MoDTP. The anti-oxidation property of MoDTP was found to be inferior to that of DBMP The capability of hydroperoxide decomposition ability with MoDTP was much greater than that with DBMP. However the rate constant of radical scavenging with MoDTP was much better than that with DBMP. It was found that the performance of MoDTP is exellent with respect to hydroperoxide decomposition but it is susceptible to chemical decomposition. From the fact that formation of phenol was observed when MoDTP was added to hexane solution of cumene hydroperoxide (CHPO), it is indicated that the decomposition of hydroperoxide with MoDTP occurs by means of ionic mechanism.

• Journal of Pharmaceutical Investigation
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• 제15권1호
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• pp.40-44
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• 1985

The stability of ftorafur in artificial gastric juice and its major decomposition product were studied quantitatively by the combination of TLC technique and UV-recording spectrophotometry. The decomposition proceeded in first-order reaction. The decomposition rate was accelerated by the increase of temperature. The major decomposition products were identified as 5-fluorouracil. The apparent activation energy for the decomposition was found to he approximately 24.3kcal/mole from Arrhenius plot.

• Carbon letters
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• 제1권3_4호
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• pp.143-147
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• 2001

Under the irradiation of radiofrequency wave, the dipole materials vibrate as microwave phase changes. This causes friction between adjacent molecules and enables an unique characteristics of interior heating of the materials. Using this principle, when harmful material pass through anthracite- bed which play a role as a absorber of radiofrequency wave, the material can be easily decomposed by the microwave energy. To remove benzene vapour and other solvents in the process of industry, we examined decomposition of benzene in this manner. It was found that benzene was decomposed to the methane, ethane, propane and butane, etc. during passing through the carbon-bed under the microwave impingement and distribution of methane in the products reached about 85 vol.%. The decomposition rate of benzene was high within 5 minutes from start of reaction. For a lower concentration of benzene gas, general cases in the field of industry, almost complete decomposition of benzene is believed possible and this method is surely expected to be useful for the prevention of air pollution and improvement of ambient condition.

• 한국연소학회:학술대회논문집
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• 한국연소학회 2015년도 제51회 KOSCO SYMPOSIUM 초록집
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• pp.157-159
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• 2015

In this study, $CF_4$ decomposition was experimentally investigated in a high temperature flow reactor. Effects of temperature, reactant composition and concentration, and residence time on its decomposition into other stable species were analyzed. Then the results were compared to numerical results obtained using Chemkin Plug Flow Reactor model with Princeton Chemistry. As a preliminary result higher decomposition rate is obtained for higher reactor temperature and long residence time when proper reactants are supplied.