• Journal of the Korean GEO-environmental Society
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• 제11권4호
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• pp.43-50
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• 2010

In this study, we have isolated MTBE utilizing bacteria at the gasoline contaminated soil and also MTBE degradation patterns were characterized. The 18 bacterial mono-cultures isolated from enrichment cultures were screened for MTBE degradation. Of the 18 strains, the 3 strains (Flavobacterium, Pseudomonas, and Achromobacter) have shown effective MTBE degradation. Experimental parameters affecting the growth conditions (such as temperature, pH, initial cell mass) were optimized. Experimental parameters such as temperature $30^{\circ}C$, pH 7, and initial cell mass 0.6 g/mL in optimal growth conditions for MTBE degradation. The optimal growth conditions of the isolated stains were temperature $30^{\circ}C$, pH 7, and initial cell mass 0.6 g/mL in our experiment, respectively. The first order degradation coefficients of Achromobacter, Mixed culture, Pseudomonas, and Flavobacterium were 0.072, 0.066, 0.047, and $0.032hr^{-1}$, respectively. and also, it could be expressed as a degradation rate considering cell mass (1.302, 1.019, 0.523, and 0.352 mg/TSS g/hr for each microorganism). Although Achromobacter has shown highest MTBE degradation rate, degradation rate for BTEX was relatively lower than other strains. and Mixed culture and Flavobacterium have shown similar degradation pattern for MTBE and BTEX biodegradation.

• Journal of Microbiology and Biotechnology
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• 제11권4호
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• pp.607-613
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• 2001

The biodegradation rates of diesel oil by a selected diesel-degrading bacterium, Pseudomonas stutzeri strain Y2G1, and microbial consortia composed of combinations of 5 selected diesel-degrading bacterial were determined in liquid and soil systems. The diesel degradation rate by strain Y2G1 linearly increased $(R^2=0.98)$ as the diesel concentration increased up to 12%, and a degradation rate as high as 5.64 g/l/day was obtained. The diesel degradation by strain Y2G1 was significantly affected by several environmental factors, and the optimal conditions for pH, temperature, and moisture content were at pH8, $25^{\circ}C$, and 10%, respectively. In the batch soil microcosm tests, inoculation, especially in the form of a consortium, and the addition of nutrients both significantly enhanced the diesel degradation by a factor of 1.5 and 4, respectively. Aeration of the soil columns effectively accelerated the diesel degradation, and the initial degradation rate was obviously stimulated with the addition of inorganic nutrients. Based on these results, it was concluded that the major rate-limiting factors in the tested diesel-contaminated soil were the presence of inorganic nutrients, oxygen, and diesel-degrading microorganisms. To resolve these limiting parameters, bioremediation strategies were specifically designed for the tested soil, and the successful mitigation of the limiting parameters resulted in an enhancement of the bioremediation efficiency by a factor of 11.

• Journal of Electrochemical Science and Technology
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• 제15권1호
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• pp.190-197
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• 2024

A commercial PbO₂ mesh cylinder electrode was utilized as the anode for the electrochemical degradation of the textile effluent after the biological treatment with the titanium cylinder as the cathode in a self-made tube electrolyzer. The electrochemical performances of the PbO₂ electrode in tube electrolyzer under different initial pH, electrolyte flow rates, current densities and times of the electrochemical degradation were investigated. The experimental results illustrated that the PbO₂ electrode can reduce the chemical oxygen demand (COD) of the textile effluent from 94.0 mg L^-1 to 65.0 mg L^-1 with the current efficiency of 88.3%, the energy consumption of 27.7 kWh kg^-1 (per kilogram of degraded COD) and the carbon emissions of 18.0 kg CO₂ kg^-1 (per kilogram of degraded COD) under the optimal operating conditions. In addition, the COD of the textile effluent could be reduced from 94.0 mg L^-1 to 22.0 mg L^-1 after the fifth electrochemical degradation. Therefore, PbO₂ mesh cylinder electrode in the tube cylinder was promising for the electrochemical degradation of the textile effluent.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• 제28권10호
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• pp.670-675
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• 2015

Degradation diagnosis of cable is one of major issues for operation and maintenance in overhead distribution power lines. The diagnostic system for overhead power lines is composed of three parts in functional aspect - a travelling unit, a sensing unit and a communication unit. Among them, sensor detects the defects such as corrosion and disconnecting of power lines. Performance of sensor is very important, and besides, the size and structure of sensor is restricted for installation to small and lightweight diagnostic system. This paper suggests an optimal eddy current sensor best suit for small and lightweight diagnostic system in consideration of detecting performance, size and ease of installation and so on. Proposed sensor has been designed by Drum core structure and can be applied to the all domestic overhead power lines regardless of the cross-sectional areas. Also, it is showed that results of mock environmental test are satisfied.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제17권3호
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• pp.1035-1048
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• 2023

The IEEE 802.11 WLAN adopts a random backoff algorithm for its collision avoidance mechanism, and it is well known that the contention-based algorithm may suffer from performance degradation especially in congested networks. In this paper, we design an efficient backoff algorithm that utilizes a reinforcement learning method to determine optimal values of backoffs. The mobile nodes share a common contention window (CW) in our scheme, and using a Q-learning algorithm, they can avoid collisions by finding and implicitly reserving their optimal time slot(s). In addition, we introduce Frame Size Control (FSC) algorithm to minimize the possible degradation of aggregate throughput when the number of nodes exceeds the CW size. Our simulation shows that the proposed backoff algorithm with FSC method outperforms the 802.11 protocol regardless of the traffic conditions, and an analytical modeling proves that our mechanism has a unique operating point that is fair and stable.

• YAKHAK HOEJI
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• 제20권1호
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• pp.76-82
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• 1976

The base-catalyzed hydrolysis of indomethacin over a range of pH 8,2 to 10.0 was investigated, according to the first order kinetic equation. The energy of activation for the reaction was calculated 20, 18 kcal/mole from the Arrhenius plot. And the optimal pH of indomethacin in aqueous solution was estimated as pH 4.93 by the extrapolation of the log k-pH profiles in strong acidic and alkaline regions. And the influences of alkaline earth metals, heavy metals and some other compounds on the degradation of indomethacin were observed with no effect.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 한국지진공학회 1998년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Spring 1998
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• pp.93-99
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• 1998

Mathematical model can be obtained by physical law or engineering theory. However it is always incomplete expression of the real system. In active controls to suppress vibration due to earthquake or wind load, modeling errors can often cause the problems of instability and performance degradation. In this paper, robust optimal controller design method using H$\infty$ control theory is developed for the systems which have uncertain natural frequency and design constraints. Numerical results show that the proposed H$\infty$ controller can avoid the performance degradation due to several errors and has better performance than conventional LQR method.

• Asian-Australasian Journal of Animal Sciences
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• 제11권5호
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• pp.503-509
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• 1998

Whole faba beans (WFB) were dry roasted at different temperatures of 110, 130 and $150^{\circ}C$ for 15, 30 and 45 minutes (min) to determine the optimal heating conditions to increase bypass starch as glucose source which may be a limiting nutrient in high producing dairy cattle. Ruminant degradation characteristics of starch (St) of WFB were determined using in sacco method in 6 dairy cows fed 60% hay and 40% concentrate. Measured characteristics of St were soluble (washable) fraction (S), potentially degradation fraction (D) and the rate of degradation (Kd) of the insoluble but degradable St fraction. Based on measurement of these characteristics, percentage bypass starch (%BSt) and bypass starch (BSt) were calculated. Degradability of starch in the rumen was reduced by dry roasting at temperature of 130 and $150^{\circ}C$ and increased at $110^{\circ}C$. S varied from 50.0% in the raw whole faba beans (RWFB) and 53.7% in $110^{\circ}C$/15 min to 18.2% in $150^{\circ}C$/45 min. D varied from 49.9% in RWFB and 46.3% in $110^{\circ}C$/15 min to 81.8 % in $150^{\circ}C$/45 min. Kd varied from 9.8% in RWFB and 11.0% in the $110^{\circ}C$/30 min to 4.2 in $150^{\circ}C$/45 min. All these effects resulted in increasing %BSt from 22.1% in the $110^{\circ}C$/45 min and 23.9% in RWFB to 49.9% in the $150^{\circ}C$/45 min. Therefore BSt increased from 91.4 g/kg and 98.4 g/kg to 199.9 g/kg respectively. Dry roasting at $110^{\circ}C$ increased the starch rumen degradation. Treatment at higher temperature (130 and $150^{\circ}C$) decreased rumen degradation of starch and seemed to be linear up to highest values tested. No optimal dry roasting conditions of treatment could be determined at this stage. It may be concluded that dry roasting at temperatures of 130 and $150^{\circ}C$ was effective in shifting starch degradation from rumen to intestine to increase bypass starch.

• Journal of Environmental Science International
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• 제31권3호
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• pp.227-235
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• 2022

In this study, a biodegradation model of based on molecular cellulose was established. It is a mathematical, kinetic model, assuming that two major enzymes randomly break glycosidic bonds of cellulose molecules, and calculates the number of molecules by applying the corresponding probability and degradation reaction coefficients. Model calculations considered enzyme dose, cellulose chain length, and reaction rate constant ratio. Degradation increased almost by two folds with increase of temperature (5℃→25℃). The change of degradation was not significant over the higher temperatures. As temperature increased, the degradation rate of the molecules increased along with higher production of shorter chain molecules. As the reaction rates of the two enzymes were comparative the degree of degradation for any combinations of enzyme application was not affected much. Enzyme dose was also tested through experiment. While enzyme dose ranged from 1 mg/L to 10 mg/L, the gap between real data and model calculations was trivial. However, at higher dose of those enzymes (>15 mg/L), the experimental result showed the lower concentrations of reductive sugar than the corresponding model calculation did. We determined that the optimal enzyme dose for maximum generation of reductive sugar was 10 mg/L.

• Asian-Australasian Journal of Animal Sciences
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• 제11권1호
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• pp.35-42
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• 1998

Whole faba beans (WFB) were dry roasted at different temperatures (110, 130, $150^{\circ}C$) for 15, 30, 45 minutes to determine the optimal heating conditions of time and temperature to increase nutritional value. Ruminant degradation characteristics of crude protein (CP) of WFB were determined by the nylon bag incubation technique in dairy cows fed 60% hay and 40% concentrate. Measured characteristics of crude protein (CP) were soluble (washable) fraction (S), undegradable fraction (U), lag time (T0), potentially degradable fraction (D) and the rate of degradation (Kd) of insoluble but degradable fraction. Based on measured characteristics, percentage bypass crude protein (%BCP) and bypass crude protein (BCP in g/kg) were calculated. Degradability of CP was reduced by dry roasting (p < 0.01). S was reduced rapidly with increasing time and temperature, from 49.0% in the raw WFB (RWFB) to 26.3% in $150^{\circ}C/45$ min. D varied from 50.7% in RWFB to 73.7% in $150^{\circ}C/45^{\prime}$. U varied from 0% in $130^{\circ}C/45^{\prime}$, $150^{\circ}/30^{\prime}$ and $150^{\circ}/45^{\prime}$ to 0.66% in $110^{\circ}/45^{\prime}$ (0.24% for the RWFB). Lag time (T0) varied from 1.58 h in $130^{\circ}C/30^{\prime}$ to 2.40 h in $150^{\circ}C/45^{\prime}$ (1.87 h for RWFB). Kd varied from 24.2% in the $110^{\circ}C/30^{\prime}$ to 4.3% in $150^{\circ}C/45^{\prime}$ (21.4% for the RWFB). Kd was significantly reduced with time and temperature. All these effects resulted in increasing % BCP from 8.9% in the $110^{\circ}C/45^{\prime}$, 11.3% in the RWFB to 43.1% in the $150^{\circ}C/45$. Therefore BCP increased from 31.3 and 39.9 to 148.4 g/kg respectively. Both %BCP and BCP at $150^{\circ}C/45$ increased nearly 4 times over the raw faba beans. The effects of dry roasting temperature and time on %BCP and BCP seemed to be linear up to the highest values tested. Therefore no optimal dry roasting conditions of time and temperature could be determined at this stage. It was concluded that dry roasting was effective in shifting crude protein degradation from rumen to intestine to reduce unnecessary nitrogen (N) loss in the rumen. To determine the optimal treatment, the digestibility of each treatment should be measured in the next trial using mobile bags technique.