• 한국물환경학회지
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• 제39권2호
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• pp.131-141
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• 2023

In this study, the relationship between organic carbon distribution characteristics and decomposition rate classified according to the particle size and biological degradation characteristics in water was investigated for the Nam river and Geumho river. The average concentrations of TOC in the Nam river and Geumho river were 2.7±1.2 mg/L and 5.0±1.2 mg/L, respectively, but the composition ratios for each type of organic carbon were similar. An average value of 80.9% of TOC was present as DOC and 72.8% of DOC consisted of Refractory-DOC (RDOC). In addition, the change in the RDOC composition ratio according to temporal and spatial distribution was the smallest. There was no difference in the decomposition rate of organic carbon except for TOC by the site (p≥0.108, one-way ANOVA), and the decomposition rates of Labile-POC (LPOC) and LDOC were similar at 0.139±0.102 and 0.137±0.149 day^-1, respectively (p=0.110, paired t-test). The coefficient of variation (CV) of the decomposition rate of DOC (average 8.1%), which had the smallest composition ratio of organic carbon, was 1.1, showing the largest temporal variation. The TOC, POC, and DOC decomposition rates showed a significant correlation with the ratio of the initial concentration to the concentration after 25 days of decomposition (OC₂₅/OC₀) (r²=0.89~0.94, p<0.001), and the decomposition rates of LPOC and LDOC were significantly correlated with the ratio of the initial concentration to the concentration after 5 days of decomposition (LOC₅/LOC₀) (r²=0.67~0.75). This suggests that it is possible to estimate the decomposition rate through the concentration of each type of organic carbon.

• 한국환경과학회지
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• 제13권1호
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• pp.69-77
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• 2004

In this study, sulfate reduction reaction was used to increase the decomposition of organics, which is the most critical factor for the stabilization of a landfill site. Composite of sewage sludge, papers, and incineration ashes was used in the column. The experimental results indicated that out of 10 reactors, the reactors 3, 4, 8. and 9 showed higher organics (i.e., TOC) removal rate than that in the absence of sulfate. The organics removal rates (K) in R3 and R9 were 8.65e$\^$-4/d and 3.82e$\^$-4//d, respectively. The times to reach 10％ of initial concentrations in R3 and R9 was 7.3 and 16.5 years, respectively, showing faster organics decomposition rates in these reactors.

• Animal cells and systems
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• 제2권3호
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• pp.333-339
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• 1998

Litter decomposition is a key process in energy flow and nutrient cycling in the freshwater littoral zone, and is regulated by physicochemical properties of litters. Using a litterbag method, we compared the decomposition rates of 16 different litter types from 10 plant species of the emergent macrophytes for one year in the littoral zone of the Paltangho Reservoir, Korea. The regression analysis fitted to the various decomposition models showed that mass loss of the litters with time best fitted an asymptotic function. The litters of the emergent macrophytes were composed of two compartments, labile and refractory. The macrophytic litters showed a great variety in decomposition dynamics depending on sources of litters. The labile compartment of the initial litter mass was in a wide range between 18% and 99%, and their decomposition rates varied from 0.0037 to 0.0131 day-1. The decomposition processes of the emergent macrophytes were determined by the relative amounts of the labile and refractory compartments and by the decomposition rate of the habile one in the littoral zone.

• Communications for Statistical Applications and Methods
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• 제6권3호
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• pp.831-842
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• 1999

We propose a wavelet decomposition feature extraction method for the hand-written character recognition. Comparing the recognition rates of which methods with original image features and with selected features by the wavelet decomposition we study the characteristics of the proposed method. LDA(Linear Discriminant Analysis) QDA(Quadratic Discriminant Analysis) RDA(Regularized Discriminant Analysis) and NN(Neural network) are used for the calculation of recognition rates. 6000 hand-written numerals from CENPARMI at Concordia University are used for the experiment. We found that the set of significantly selected wavelet decomposed features generates higher recognition rate than the original image features.

• Journal of Biosystems Engineering
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• 제34권1호
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• pp.44-49
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• 2009

This study was conducted to investigate the pyrolysis characteristics of switchgrass using TGA-FTIR instrument. Switchgrass is a high yielding perennial grass that has been designated as a potential energy crop, because of its high energy value. Ground switchgrass were pyrolysed at different heating rates of 10, 20, 30, and $40^{\circ}C/min$ in a TGA-FTIR instrument. The thermal decomposition characteristics of switchgrass were analyzed, and the gases volatilized during the experiment were identified. The thermal decomposition of switchgrass started at approximately $220^{\circ}C$, followed by a major loss of weight, where the main volatilization occurred, and the thermal decomposition was essentially completed by $430^{\circ}C$. The pyrolysis process was found to compose of four stages; moisture evaporation, hemicellulose decomposition, cellulose decomposition, and lignin degradation. The peak temperatures for hemicellulose decomposition ($306^{\circ}C$ to $327^{\circ}C$) and cellulose decomposition ($351^{\circ}C$ to $369^{\circ}C$) were increased with greater heating rates. FTIR analysis showed that the following gases were released during the pyrolysis of switchgrass; $CO_2$, CO, $CH_4$, $NH_3$, COS, $C_{2}H_{4}$, and some acetic acid. The most gas species were released at low temperature from 310 to $380^{\circ}C$, which was corresponding well with the observation of thermal decomposition.

• The Korean Journal of Ecology
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• 제25권6호
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• pp.399-403
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• 2002

Cellulose mass loss by cellulose filter papers was measured for 3 time (35 days, 70 days, 105 days) incubation during the growing season (from May to September 2002) with different tree density and after fertilization in a Japanese larch (Larix leptolepis) plantation. Cellulose mass loss rates were significantly different between tree density types and fertilization treatments during the study periods. After 105 day incubation of cellulose filter paper, cellulose mass loss rates were significantly higher in the low tree density (70.1 $\%$) than in the high tree density (49.9$\%$). Cellulose mass loss rates averaged 62.8$\%$ in the fertilization and 58.9% in the unfertilization treatments during the same periods. However, cellulose mass loss was not significantly different between the forest floor and the mineral soil layer except for 35 day incubation. The results indicate that cellulose decomposition rates are a useful index to express differences in organic matter decomposition activity in different tree density and after fertilizer treatments.

• 한국결정성장학회지
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• 제22권6호
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• pp.269-273
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• 2012

Ammonia decomposition over titanium carbides were investigated using eight different samples which have been synthesized by TPR (temperature-programmed reduction) method of titanium oxide ($TiO_2$) with pure $CH_4$. The resulting materials which were synthesized using wo different heating rates and space velocity exhibited the different surface areas. These results indicated that the structural properties of these materials have been related to heating rates and space velocity employed. The titanium carbides prepared in this study proved to be active for ammonia decomposition, and the activity changed with the particle size/surface area. These showed the relationship between ammonia decomposition activity and the different active species. Compared to molybdenum carbide, the titanium carbides were one order of magnitude less active, suggesting the correlation between the activity difference and the degree of electron transfer between metals and carbon in metal carbides.

• 한국해양학회지
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• 제29권4호
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• pp.402-413
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• 1994

만경·동진강 하구계에서 일차생산자의 질소 요구량과 질소계 영양염의 pool에서 차지하는 요소의 중요성을 이해하기 위해, 1992년 6월부터 5회에 걸쳐 요소 및 무기 질소계 영양염 농도와 요소의 분해 속도에 대한 측정을 실시하였다. 조사기간 동안 요 소의 농도는 검출 이하의 농도에서 12.5 ug-at. N 1/SUP -1/에 달하였다. 이는 전체총 질소계 영양염의 0∼96%(평균 11%)에 달하는 것으로, 총 질소계 영양염농도가 낮은 경 우에 요소는 그 상대적 중요성이 높았다. 요소는 주로netplankton에 의해 분해되었다. 수층내의 요소 분해속도의 수직 분포는 그 변이의 폭이 대개 3배 이내로 작았다. 이러 한 요소의 분해 속도는 일차생산의 질소 요구량의 0.2∼88.4%에 해당되는 것으로 추정 되었으며, 특히 일차생산이 낮은(<50mg C m/SUP -2/d/SUP -1/) 경우에 요소는 일차생 산자에 대한 질소의 매우 중요성 공급원으로 나타났다.

• 한국농림기상학회지
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• 제23권2호
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• pp.89-99
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• 2021

본 연구는 경상남도 산청과 진주 지역으로부터 서로 인접하여 생육하고 있는 소나무와 굴참나무를 대상으로 기질의 특성, 임분 종류, 토양 및 기상 환경요인 등이 가지의 분해율과 탄소 및 질소 동태에 어떠한 영향을 끼치는지 알아보기 위해 수행하였다. 직경 2.0~4.0cm, 길이 10cm의 가지 시료를 30cm × 30cm 크기의 매쉬 백에 넣은 후 2018년 5월 각 임분의 임상에 매설하였으며 2018년 8월과, 11월, 그리고 2019년 2월과, 5월에 각 조사구에서 회수하여 가지의 분해율과 탄소 및 질소 동태를 조사하였다. 매설 12개월 후 가지 분해율은 산청-소나무(4.49 %) < 진주-소나무(5.75 %) < 산청-굴참나무(20.01 %) < 진주-굴참나무(24.68 %) 순서로 나타나 두 지역 모두 굴참나무 가지가 소나무에 비해 빠른 분해를 보였다. 탄소 및 질소의 경우 굴참나무는 순 무기화를 나타냈으며, 소나무는 탄소 및 질소의 축적 및 저장이 나타나 수종 간 다른 경향을 보였다. 본 연구 결과에 따르면 서로 인접하여 생육하고 있는 두 수종의 분해율과 탄소 및 질소 동태는 지역·환경적 요인보다 수종 간 초기 질소 농도, C/N율과 같은 기질의 특성이 더 큰 영향을 미치는 것으로 나타났다.

• 한국습지학회지
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• 제7권4호
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• pp.33-42
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• 2005

Wetlands often function as a nutrient sink. It is well known that increased input of nutrient increases the primary productivity but it is not well understood what is the fate of produced biomass in wetland ecosystem. Water and sediment quality, decomposition rate of cellulose, and sediment accumulation rate in 11 montane marshes in northern Sierra Nevada, California were analyzed to trace the effect of nitrogen and phosphorus content in water on nutrient dynamics. Concentrations of ammonium, nitrate, soluble reactive phosphorus (SRP) in water were in the range of 27 to 607, 8 to 73, and 6 to 109 ppb, respectively. Concentrations of ammonium, calcium, magnesium, sodium, and potassium in water were the highest in Markleeville, which has been impacted by animal farming. Nitrate and SRP concentrations in water were the highest in Snow Creek, which has been impacted by human residence and a golf course. Cellulose decomposition rates ranged from 4 to 75 % per 90 days and the highest values were measured in Snow Creek. Concentrations of total carbon, nitrogen, and phosphorus in sediment ranged from 8.0 to 42.8, 0.5 to 3.0, and 0.076 to 0.162 %, respectively. Accumulation rates of carbon, nitrogen, and phosphorus fluctuated between 32.7 to 97.1, 2.4 to 9.0, and 0.08 to $1.14gm^{-2}yr{-1}$, respectively. Accumulation rates of carbon and nitrogen were highest in Markleeville and that of phosphorus was highest in Lake Van Norden. Correlation analysis showed that decay rate is correlated with ammonium, nitrate, and SRP in water. There was no correlation between element content in sediment and water quality. Nitrogen accumulation rate was correlated with ammonium in water. These results showed that element accumulation rates in montane wetland ecosystems are determined by decomposition rate rather than nutrient input. This study stresses a need for eco-physiological researches on the response of microbial community to increased nutrient input and environmental change because the microbial community is responsible for the decomposition process.