• Journal of the Korean Chemical Society
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• v.50 no.6
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• pp.454-463
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• 2006

refractory organic compounds in aqueous solution are not readily removed by the existing conventional wastewater treatment process. In recent years, the sonolysis and electrochemical oxidation process had been shown to be promising for wastewater treatment due to the effectiveness and easiness in operation. This study was performed to investigate the characteristics of sonolytic and electrolytic decomposition as the basic data for development of the wastewater treatment process. Trichloroethylene(TCE) and 2,4- dichlorophenol(2,4-DCP) were used as the samples, and their destruction efficiency were measured with various operating parameters, such as initial solution concentration, initial solution pH, reaction temperature, sonic power and current density. Also, the decomposition mechanism conformed indirectly with the effect of NaHCO3 as a radical scavenger on the decomposition reaction. Thermal decompositon reaction is predominant for TCE but thermal and radical decompositon reactions were dominant for 2,4-DCP. Results showed that the destruction efficiencies of all samples were above 65% within 120 minutes by sonolysis and electrolysis at the same time, and were increased with increasing initial concentration, sonic power and current density. Destruction efficiency of TCE was high in the acidic solution, but 2,4-DCP showed high destruction efficiency in basic solution.

• Journal of Food Hygiene and Safety
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• v.14 no.3
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• pp.249-254
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• 1999

The present study was performed to investigate biodegradation rate of BPMC(2-sec-butylphenyl methyl carbamate) and chlorothalonil. In the biodegradation test of two pesticides by the modified river die-away method from June 17 to August 22, 1998, the biodegradation rate constants and half-life were determined in Nakdong(A) and Kumho River(B). Bio- degradation rate of BPMC was 27% in A sampling point, 40% in B sampling point after 7 days. Biodegradation rate constants and half-life of BPMC were 0.0460 and 15.1 days in A sampling point, 0.0749 and 9.3 days in B sampling point, respectively. Biodegradation rate of chlorothalonil was 100% in A and B sampling points after 7 days. Biodegradation rate constants and half-life of chlorothalonil were 0.1416 and 4.9 hours in A sampling point, 0.1803 and 3.8 hours in B sampling point, respectively. Biodegradation rate of chlorothalonil was faster than that of BPMC. Correlation analysis between biodegradation rate constants of pesticides and water quality(DO, BOD, SS, ABS, $NH_3-N\;and\;NO_3-N$) showed significant correlation with BOD, SS and $NH_3-N$. Furthermore, regression analysis with BOD, SS and $NH_3-N$ as independent variable and biodegradation rate constant as independent variable showed a significant linear equation. These results suggested that BPMC and chlorothalonil were mainly degraded by biodegradation, and the difference in biodegradation of two pesticides was due to difference of water quality.

• Journal of the Korean Institute of Intelligent Systems
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• v.15 no.4
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• pp.457-466
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• 2005

In this paper, we propose a wavelet neural network(WNN) based predictive control method for path tracking of mobile robots with multi-input and multi-output. In our control method, we use a WNN as a state predictor which combines the capability of artificial neural networks in learning processes and the capability of wavelet decomposition. A WNN predictor is tuned to minimize errors between the WNN outputs and the states of mobile robot using the gradient descent rule. And control signals, linear velocity and angular velocity, are calculated to minimize the predefined cost function using errors between the reference states and the predicted states. Through a computer simulation for the tracking performance according to varied track, we demonstrate the efficiency and the feasibility of our predictive control system.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.210-224
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• 2003

Sulfate reduction is a microbiological process which occurs ubiquitously in anaerobic marine environment. Sulfate reducing bacteria play a significant role in anaerobic decomposition of organic matter and regeneration of inorganic nutrients which supports the primary production in the water column (i.e., benthic-pelagic coupling) and, in special case, could be responsible for the harmful algal bloom in the coastal marine environment. Summary of the sulfate reduction rates reported in various marine sedimentary environments revealed that supply of organic substrates and presence of various electron acceptors (i.e., $O_2$, NO$_{3}$$^{[-10]}$ , Fe(III) and Mn(IV), etc.) for other aerobic and anaerobic respiration directly affect the sulfate reduction rate and relative significance of sulfate reduction in organic matter mineralization. Significance of temperature, macrophytes and bioturbation is discussed as factors controlling supply of organic substrates and distribution of electron acceptors. Finally, we suggest studies on the anaerobic microbiological processes associated with biogeochemical element cycles in the coastal environments of Korea where massive operation of organic enriched fish cage farm, frequent occurrence of toxic algal bloom and hypoxia and conservation of tidal flat are of major environmental issues.

• Korean Journal of Microbiology
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• v.30 no.1
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• pp.53-59
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• 1992

Four bacterial strains capable of catabolizing 4-chlorobiphen!;l (4CB) were isolated from the industrial waste waters. The bacterial isolates designated as PO$. P20, P27, and P1242. respectively, were examined for their catabolic activities. And in order to examine molecular homology of the 4CB catabolizing genes of these bacterial isolates. Southern hybridization was conducted with bphABC genes of P. p.srudoalculigrnrs KF707 as a DNA probe. The metabolites of 2-hydroxy-6-0x0-6-(4'-chlorophenyl)hexa-2 .4-dienoic acid and Cchlorobenzoate were detected to be produced by the isolatc:~ in the MM2 liquid cultures. But Cchlorobenzoate was further catabolized to produce 4.-hydroxybenzoate by DJ-12, P08. and P27. but not by P20 and P1242. As results of hybridization, homologous regions were commonly observed in Xhol fragments of 2.2 and 1.8 kb and in EcoRl fragment of 11 kb in the DJ- 12. P08, and P27 isolates. But in any restriction enzyme digests ot the P20 and PI242 isolates. homologous region was not detected. The cbp genes of the bactcria capable of catabolizing 4CB in nature could be divided into two groups by divergence<

• Korean Journal of Environmental Agriculture
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• v.27 no.1
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• pp.86-91
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• 2008

Dicamba(3,6-dichloro-2-methoxybenzoic acid) is used to control for pre and post-emergence of annual and perennial broad-leaf weeds. It is very soluble in water and highly mobile, acidic herbicide. So it is easily moved and detected in groundwater. Zerovalent iron(ZVI) has been used for the reductive degradation of certain compounds through amination of nitro-substituted compounds and dechlorination of chloro-substituted compounds. In this study, we investigated the potential of ZVI for the oxidative degradation of dicamba in water. The degradation rate of dicamba by ZVI was more rapidly increased in pH 3.0 than pH 5.0 solution. The degradation percentage of dicamba was increased with increasing amount of ZVI from 0.05% to 1.0%(w/v) and reached above 90% within 3 hours of reaction. As a result of identification by GC-MS after derivatization with diazomethane, we obtained three degradation products of dicamba by ZVI. They were identified 4-hydroxy dicamba or 5-hydroxy dicamba, 4,5-dihydroxy dicamba and 3,6-dichloro-2-methoxyphenol. 4-Hydroxy dicamba or 5-hydroxy dicamba and 4,5-dihydroxy dicamba are hydroxylation products of dicamba. 3,6-dichloro-2-methoxyphenol is hydroxyl group substituted compound instead of carboxyl group in dicamba. We also confirmed the same degradation products of dicamba in the Fenton reaction which is one of oxidation processes using ferric sulfate and hydrogen peroxide. But we could not find out the dechlorinated degradation products of dicamba by ZVI.

• Journal of Korea Soil Environment Society
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• v.2 no.3
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• pp.3-21
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• 1997

The remediation of contamiated sites using currently available remediation technologies requires long term treatment and huge costs, and it is uncertain to achieve the remediation goal to drop contamination level to either back-ground or health-based standards by using such technologies. Intrinsic remediation technology is the remediation technology that relies on the mechanisms of natural attenuation for the containment and elimination of contaminants in subsurface environments. Initial costs for the intrinsic remediation may be higher than conventional treatment technologies because the most comprehensive site assessment for intrinsic remediation is required. Total remediation cost, however may be the lowest among the presently employed technologies. The applicability of intrinsic remediation in the contaminated sites should be theroughly investigated to achieve the remedial goal of the technology. This paper provides the frame of the extended site assessment procedure based on knowledge of biodegradability to evaluate the applicability of intrinsic remediation. This site assessment procedure is composed of 5 steps such as preliminary site screening, assessment of the current knowledge of biodegradability, selecting the appropriate approach, analyzing the contaminant fate and transport and planning the monitoring schedule. In the step 1, followings are to be decided 1) whether to go on the the detailed assessment or not based on the rules of thumb concerning the biodegradability of organic compounds, 2) which protocol document is selected to follow for detailed site assessment according to the site characteristics, contaminants and the relative distance between the contamination and potential receptors. In the step 2, the database for biodegradability are searched and evaluated. In the step 3, the appropriate biodegradability pathways for the contaminated site is selected. In the step 4, the fate and transport of the contaminants at the site are analyzed through modeling. In the step 5, the monitoring schedule is planned according to the result of the modeling. Through this procedure, users may able to have the rational and systematic informations for the application of intrinsic remediation. Also the collected data and informations can be used as the basic to re-select the other remediation technology if it reaches a conclusion not to applicate intrinsic remediation technology at the site from the site assessment procedure.

• Applied Chemistry for Engineering
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• v.26 no.2
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• pp.154-158
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• 2015

In this study, the catalytic activity of ${\gamma}-Al_2O_3$ was investigated for the decomposition of $NF_3$. Reactions for $NF_3$ decomposition were carried out in the range of reaction temperature of $330{\sim}730^{\circ}C$ and GHSV of $3,000{\sim}15,000mL/g-cat{\cdot}h$ in a fixed-bed catalytic reactor system. Thermal decomposition of $NF_3$ was also performed in order to compare with the catalytic decomposition of $NF_3$. The conversion of $NF_3$ by the catalytic decomposition at $400^{\circ}C$ was four times higher than that of the thermal decomposition. It was confirmed that the reaction behavior of $NF_3$ over ${\gamma}-Al_2O_3$ exhibited two reaction pathways in the presence of steam. Fluorine in $NF_3$ over ${\gamma}-Al_2O_3$ was chemically absorbed to $AlF_3$ by the gas-solid reaction in the absence of steam. The catalytic decomposition of $NF_3$ occurred by hydrolysis with steam. It was also confirmed by FT-IR analysis that $NF_3$ was completely decomposed to NOx and HF above $500^{\circ}C$.

• Proceedings of the Acoustical Society of Korea Conference
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• spring
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• pp.245-248
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• 2000

해양음향 토모그래피 수행을 위해 필수적인 Forward 모의 알고리즘을 연구를 통해 Forward 문제에서의 선결문제(음파 전달경로의 안정성, 식별능력 및 분해능)를 고잘하였다. 이를 위해 동해의 기존 관측 자료를 이용하여 평균해양에 대한 음속구조 및 EOF 분석을 수행, 재현된 음속구조를 이용, 음선 모델에 의한 고유음선 정보를 파악하여 고유음선의 도달경로 및 도달시간의 비교를 시도하였다.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2010.07a
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• pp.398-399
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• 2010

본 논문은 복잡한 구조와 다양한 텍스쳐들로 구성된 일반 자연 영상의 크기를 조정할 때 텍스쳐 최적화(texture optimization) 기법과 동적 프로그래밍(dynamic programing) 기법을 활용하여 자연스러운 결과 영상을 구하는 방안을 제안한 다. 입력 영상을 텍스쳐 영상과 저주파 영상으로 분해하고 각각의 영상이 갖는 에너지를 모델링하여 총 비용을 최소로 하는 경로를 동적 프로그래밍 기법을 통해 추적한다. 추적된 경로를 기준으로 영상을 분리하여 좌우로 이동시킨 후 중첩한 초기 영상을 텍스쳐 최적화 기법을 이용하여 원본에 가까운 영상으로 복원한다. 제안하는 알고리듬과 기존의 기법들 간의 결과 영상을 비교하여 그 유효성을 확인한다.