• KSBB Journal
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• 제14권4호
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• pp.452-459
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• 1999

본 연구에서는 난분해성 물질인 기상의 TCE를 효과적으로 처리하기 위하여 CSTR과 TBR을 연결한 2단계 생물막 반응기를 제작ㆍ운전하였다. TBR에는 TCE 분해능이 탁월한 메탄자화균인 Methylosinus trichosporium OB3b를 활성탄에 고정화시켰고, 기상의 TCE를 유입부에 연속적으로 공급하여 분해시켰다. 개발된 반응기 시스템의 효율을 조사하기 위해 다양한 운전조건에서 TCE 분해속도, TCE 전화율 및 cMMO 활성변화 등을 조사하였다. 여러 가지의 유입부 TCE 농도에서 운전한 결과 80 $\mu$mol/L의 고농도까지 처리가 가능함을 알 수 있었고, TCE를 포함한 기체의 유속을 변화시켰을 때 유속이 증가함에 따라 낮은 유속(50~200 mL/min)에서는 직선적으로 TCE를 분해속도 및 전화율이 증가하다가 높은 유속(200~600 mL/min)에서는 일정하게 유지되었다. TBR의 온도를 달리하였을 때, 2$0^{\circ}C$의 낮은 온도에서 3$0^{\circ}C$의 높은 온도보다 TCE 전화율 및 분해속도가 증가되어 TBR에서의 TCE 분해반응이 물질전달 저해를 받음을 알 수 있었다. CSTR에서의 희석속도가 낮으면 TCE 분해속도와 전화율의 감소 및 sMMO 활성 저하 현상이 일어남을 관측할 수 있었고, TBR에서 TCE 분해 과정에서 불활성화된 sMMO 및 세포 활성을 효과적으로 재활성화시키기 위해서는 CSTR의 희석속도를 높이 유지해야함을 알 수 있었다. 약 270일 이상의 운전기간 동안 운전조건을 다양하게 변경시켜도 매우 안정되게 시스템이 유지됨을 알 수 있었고, 최고분해속도는 525 mg TCE/Lㆍday 정도로 높아 개발된 2단계 CSTR/TBR 시스템의 우수성을 알 수 있었다.

• 한국환경과학회지
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• 제21권4호
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• pp.479-488
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• 2012

A Dielectric barrier discharge (DBD) plasma is shown in the present investigation to be effective of phenol degradation in the aqueous solutions in batch reactor with continuous air bubbling. Removal of phenol and effects of various parameters on the removal efficiency in the aqueous solution with high-voltage streamer discharge plasma are studied. The effect of 1st voltage (80 ~ 220 V), air flow rate (3 ~ 7 L/min), pH (3 ~ 11), electric conductivity of solution (4.16 ${\mu}S$/cm, deionized water) ~ 16.57 mS/cm (addition of NaCl 10 g/L) and initial phenol concentration (2.5 ~ 20.0 mg/L) were investigated. The observed results showed that phenol degradation was higher in the basic solution than that of the acidic. The optimum values on the 1st voltage and air flow rate for phenol degradation were 140 V and 6 L/min, respectively. It was considered that absorbance variation of $UV_{254}$ of phenol solution can be use as an indirect indicator of change of the non-biodegradable organic compounds within the treated phenol solution. Electric conductivity was not influenced the phenol degradation. To obtain the removal efficiency of phenol and COD of phenol over 97 % (initial phenol concentration, 10.0 mg/L), 80 min and 120 min were need, respectively. Phenol and COD degradation showed a pseudo-first order kinetics.

• 대한환경공학회지
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• 제32권3호
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• pp.241-247
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• 2010

오존 접촉 반응기에서 용존 오존 농도 및 페놀 제거에 미치는 운전변수의 영향에 대해 실험실 규모 실험을 수행하였다. 반응기로 가스상 오존이 공급되고 일정한 시간이 경과한 후에 용존 오존 농도는 포화 농도에 도달하였으며 포화 농도의 크기는 운전 변수에 의해 영향을 받는 것으로 나타났다. 수용액내의 오존은 높은 pH 조건에서 불안정하므로 용존 오존 농도는 용액의 초기 pH값이 증가함에 따라 감소하였다. 일정한 유량의 기체가 반응기로 공급되는 조건에서 가스상 오존 농도의 크기는 용존 오존의 포화농도에 중요한 영향을 미치며 일정한 농도의 가스상 오존이 공급될 때 가스 유량은 용존 오존이 포화되는 속도에 영향을 주는 것으로 관찰되었다. 페놀 제거에 미치는 운전변수의 영향은 각 운전변수가 용존 오존 농도에 미치는 영향과 밀접하게 관련되어 있는 것으로 나타났다. 용존 오존은 높은 pH 조건에서 빠르게 분해되어 페놀과의 반응성이 높은 자유라디칼을 생성시키므로 pH가 증가함에 따라 페놀 제거가 향상되었다. 동일한 pH 조건에서 가스상 오존 농도 및 가스 공급량의 증가는 용존 오존을 증가시킴으로써 페놀 분해를 증진시키는 것으로 나타났다. 메탄올의 주입은 OH 라디칼을 소비시켜 페놀 분해를 방해하는 것으로 관찰되었다.

• 환경위생공학
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• 제14권1호
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• pp.24-30
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• 1999

A biological filter for treatment of toluene among volatile organic compounds was studied. The investigation was conducted using specially built stainless steel columns packed with granular activated carbon and cold for removal of toluene. The G.A. and mold as filter material was also coated with Pseudomonas putida microorganisms.The biofilter unit was operated in the condition of moisture content vairation at gas loading rate of 12.5 l/min. Gaseous toluene taken from tedlar bag was analyzed by the use of G.C equipped with F.I.d detector. The removal efficiency of gaseous toluene was 95% at average inlet concentration of 950 ppm during bio-degradation operating condition. Effective removal efficiency was obtained with moisture content 27.5% at activated carbon and 32% at mold in this study. The effective operating condition were obtained with pH 6-8, temperature 28-42℃ for microbial degradation at gas loading rate of 12.5 l/min in packed material.

• Journal of Microbiology and Biotechnology
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• 제8권2호
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• pp.185-187
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• 1998

Pseudomonas putida KCTC 2401 degrades 1,1, 2-trichloroethylene (TCE) using phenol as a cosubstrate. The initial TCE degradation rate decreased with the initial TCE concentration up to 20mg/l of TCE at $30^{\circ}C$ and pH 6.5. The initial degradation rate and total removal efficiency increased with inoculum size. The strain also degraded dichloroacetic acid, which was supposed to be a degradation by-product. Phenol monooxygenase apparently participates in the TCE degradation mechanism.

• The Korean Journal of Ecology
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• 제21권3호
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• pp.277-282
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• 1998

The microbial degradation of $poly-{\beta}-hydroxybutyrate$ (PHB) films was studied in soil microco는 incubated at a constant temperature of 2, 10, 20, 30 and $40^{\circ}C$ for up to 49 days. The degradation rate measured through loss of weight was enhanced by incubation at a higher temperature. At the soil temperature $40^{\circ}C$, $poly-{\beta}-hydroxybutyrate$ was rapidly degraded at a decay rate of 3.5% weight loss per day. The degradation of $poly-{\beta}-hydroxybutyrate$ did not affected significantly the chemical properties of soils such as pH and electric conductivity. However, microbial activity of soil in terms of dehydrogenase activity was increased by the degradation of $poly-{\beta}-hydroxybutyrate$.

• 품질경영학회지
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• 제34권3호
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• pp.19-30
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• 2006

For highly reliable products, it is difficult to assess the lifetime of the products with traditional life tests. Accordingly, a recent approach is to observe the performance degradation of product during the test rather than regular failure time. This study compares performances of three methods(i.e. the approximation, analytical and numerical methods) to estimate the parameters and quantiles of the lifetime when the time-to-failure distribution follows Weibull and lognormal distributions under a random coefficient degradation rate model. Numerical experiments are also conducted to investigate the effects of model error such as measurements in a random coefficient model.

• 대한화학회지
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• 제11권2호
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• pp.70-76
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• 1967

Structural changes attending polyacrylonitrile(PAN) upon heating and treating with nucleophilic reagents have been studied for some time and a few authors have studied on the thermal degradation, particularly on the characterization of degradation products in PAN. It is the purpose of this paper to report the kinetic study on the thermal degradation above $250^{\circ}C$ and make some suggestions as to the degradation process and mechanism in PAN. The degradation process in PAN is considered that three reactions are combined in two steps. Random chain scission accompanying the naphthylidine-type ring formation is the first step and the degradation of naphthylidine-type ring occurred as the next step. The reactions in the first step are competitive so that the maximum weight loss on pyrolysis of PAN, under such a condition that the degradation of naphthylidine-type ring is negligible, is depended on the relative reaction rate of these two competitive reactions.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.593-598
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• 2008

In the present study, degradation characteristics of pumps in nuclear power plants were investigated to provide the information of degradation mechanism and stressors. The failure records of pumps for the periods 2000 to 2006 on INPO(Institute of Nuclear Power Operations) EPIX(Equipment Performance and Information Exchange System) DB were reviewed. The 1,834 failure records reveal that the critical areas of pump failures are bearing, mechanical seal, gasket/o-ring, shaft, impeller, coupling and packing. Based on the failure rate of critical areas, the important degradation mechanism and stressors were determined. Additionally, the relationship between degradation mechanism and stressors such as wear was examined. Finally, the monitoring parameters related to degradation and stressors were discussed for the future development of degradation evaluation and prognosis technology of pumps.

• 상하수도학회지
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• 제25권1호
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• pp.63-74
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• 2011

The degradation characteristics of 2-chlorophenol(2-CP) by Ferrate(VI) were studied. The degradation efficiency of 2-CP in aqueous solution was investigated at various values of pH, Fe(VI) dosage, initial concentration and aqueous solution temperature. The maximum degradation efficiencies of 2-CP were obtained at pH 7.0 and aqueous solution temperature of 25$^{\circ}C$. The degradation efficiency was proportional to dosage of Fe(VI). Also, the initial rate constant of 2-CP degradation increased with decreasing of the 2-CP initial concentration. In addition, the degradation pathway study for 2-CP was conducted with GC-MS analysis. Acetic acid, formic acid, benzaldehyde and benzoic acid were identified as reaction intermediates of the 2-CP degradation by Ferrate(VI).