• Journal of Applied Reliability
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• v.1 no.1
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• pp.35-46
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• 2001

Replacement policy of a degradation system is investigated by incorporating the loss function. Loss function is defined by the deviation of the value of quality characteristic from its target value, which determines the loss cost. Cost function is comprised of the inspection cost, replacement cost and loss cost. Two cost minimization problems are formulated : 1)determination of an optimal inspection period given the state for the replacement and 2)determination of an optimal state for replacement under fixed inspection period. Simulation analysis is performed to observe the variation of total cost with respect to the variation of the parameters of loss function and inspection cost, respectively As a result, parameters of loss function are seen to be the most sensitive to the total cost. On the contrary, inspection cost is observed to be insensitive. This study can be applied to the replacement policy of a degradation system which has to produce the quality critical product.

• Journal of Environmental Science International
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• v.16 no.11
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• pp.1247-1255
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• 2007

Soil biofiltration is an environmentally-sound technology for elimination of VOCs, odorous and $NO_X$ compounds from a low concentration, high volume waste gas streams because of its simplicity and cost-effectiveness. This study investigated the optimal mixture fraction of briquet ash, compost, soil and loess for $NO_X$ degradation. Extreme vertices design was used to examine the role of four components on $NO_X$ degradation. Under our experimental conditions, 74.5% of $NO_X$ degradation was observed, using a model mixture(25% briquet ash, 10% compost, 30% soil and 40% loess) containing 100 ppb of NO. It was shown that experimental design analysis could allow selecting optimal conditions in such biodegradation processes in this study.

• Journal of Korean Society on Water Environment
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• v.21 no.3
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• pp.263-266
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• 2005

Comparison between photocatalysis (UV+$TiO_2$) and sonophotocatalysis (Sonication+UV+$TiO_2$) were performed in lab-scale experiments for the treatment of chloroform. The effect of operational parameters, i.e., initial chloroform concentration, $TiO_2$ concentration, UV light intensity and sonication time on the degradation rate of aqueous solution of chloroform has been examined. The optimal conditions for photocatalysis and sonophotocatalysis processes were determined: initial chloroform concentration was 25 mg/L, the concentration of $TiO_2$ was 200 mg/L and UV light intensity was $6.630 mW/cm^2$, respectively. The optimal sonication time on sonophotocatalysis process was 90 min. Under the optimal conditions, sonophotocatalysis was effective for inducing faster degradation of the chloroform.

• Journal of Life Science
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• v.5 no.1
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• pp.8-19
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• 1995

The Optimal condition for degradation of crystal violet and other triphenylmethane dyes by Citrobacter sp. SK-3 isolated from the activated sludge of dye manufacturing factory was investigated. The optimal culture medium for the degradation of triphenylmethane dye was composed of minimum inorganic salt medium supplemented with 0.5% galactose, 0.1% beef extract, with the initial pH of 8.0 to 9.0. Under this condition, Citrobacter sp. SK-3 degraded 200 ppm of crystal violet completely within 24 hours. Citrobactre sp. SK-3 also degraded efficiently malachite green, pararosaniline, brilliant green, methyl violet, basic fuchsin and methyl red. Analysis of the degradation products of crystal violet through this layer chromatography and high performance liquid chromatography indicated that the methyl groups bound to crystal violet backborn were gradually demethylated to pentamethyl-, tetramethyl- and trimethylpararosaniline.

• Textile Coloration and Finishing
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• v.29 no.4
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• pp.181-194
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• 2017

The biodegradability of polylactic acid(PLA) fabrics was evaluated by two methods: enzyme and soil degradation. Three different enzymes were selected to evaluate. Degradation times were measured at optimal enzyme treatment conditions. Biodegradation by enzymatic hydrolysis was compared with soil degradation. As a result, biodegradation created cracks on the fiber surface, which led to fiber thickening and shortening. In addition, new peak was observed at $18.5^{\circ}$ by degradation. Moreover, cracks indicating biofragmentation were confirmed by enzyme and soil degradation. By enzyme and soil degradation, the weight loss of PLA fabrics was occurred, there through, the tensile strength decreased about 25% by enzyme hydrolysis when 21 days after, and 21.67% by soil degradation when 60 days after. Furthermore, the biodegradability of PLA fabrics by enzymatic and soil degradation was investigated and enzymatic degradation was found to be superior to soil degradation of PLA fabrics. Among the three enzymes evaluated for enzymatic degradation, alcalase was the most efficient enzymes. This study established the mechanism of biodegradation of PLA nonwovens, which might prove useful in the textile industry.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.241-247
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• 2012

Many infectious diseases have emerged or re-emerged during the past 50 years in South Korea. There were three outbreaks of foot and mouth disease (FMD) in South Korea between January 2010 and March 2011. Over 3.45 million animals were slaughtered (33.3% of the existing pigs, 8.4% of dairy cows and 3.4% of cattle). To select optimal degradation agents of animal cadavers, degradation rates and fertilizer components of pig cadavers were investigated using hydrogen chloride (HCl), potassium hydroxide (KOH) and sodium hydroxide (NaOH) hydrolysis methods. Degradation rates of pig cadavers using HCl, KOH and NaOH were 81.1, 82.8 and 91.6%, respectively. Total nitrogen (T-N) concentration in degradation solution of pig cadavers using KOH hydrolysis method was higher than that in NaOH and HCl hydrolysis methods. Total phosphorus ($P_2O_5$) concentrations in degradation solution of pig cadavers in all hydrolysis methods ranged 0.14 ~ 0.28%. Total potassium ($K_2O$) concentration for KOH hydrolysis method was higher than that for other hydrolysis methods. The concentration of T-N and $K_2O$ in degradation solution of pig cadavers by KOH hydrolysis method were higher than that in NaOH and HCl hydrolysis methods. Thus, to recycle animal cadavers in agriculture, the optimal degradation agent for hydrolysis was KOH.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.358-361
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• 2004

The photocatalytic degradation of Endocrine Discruptors, dibuthyl phthalate(DBP) has been investigated over TiO$_2$ photocatalysts irradiated with a ultraviolet (UV) light. The effect of operational parameters, i.e., reaction time, light intensity, pH and additive on the degradation rate of aqueous solution of Endocrine Discruptors has been examined. Results show that the employment of efficient photocatalysts and the selection of optimal operational parameters may lead to degradation of Endocrine Discruptors solutions.

• Journal of environmental and Sanitary engineering
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• v.8 no.1
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• pp.81-91
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• 1993

This paper was carried out to isolate and identify Aeromonas caviae which can degrade Sodium Dodecyl Benzene Sulfonate(SDBS) effectively. And the affecting factors for the ability of bacterial degradation were also studied. Frm October 1991 to February 1992, two hundred samples from sweage in Taegu area and Nakdong river waters in Talsung Gun area were tested. Minimal salt medium which contain SDBS only as a carbon source was used as a culture medium. The isolated new strain was identified as Aeromonas caviae Kim & Kweon. The optimal pH for SDBS degradation were 7.0 and temperature, $32^{\circ}C.$ It was taken 24 hours to degrade SDBS of 20mg/l completely under the optimal pH and temperature. And in the case of 30 mg/l of SDBS, it was taken 36 hours. The nitrogen sources were added to the minimal salt media containing 20mg/l of SDBS, and they were incubated at $32^{\circ}C$ for 14 hours. 86.9% SDBS were degraded after addition of 0.03% peptone as a organic nitrogen source. And 70.5% SDBS after addition of 0.05% ammonium sulfate as a inorganic nitrogen source. In the case of metal compounds(0.015%), the degradation rate for SDBS were 3.5 fold increased in the media containing magnesium chloride and calcium chloride than in the media that were not containing these metal compounds. And where the media containing magnesium chloride was 0.05%, the degradation rate was 65.8%. And above 0.3% NaCI, the degradation rate was decreased slowly.

• Korean Journal of Agricultural Science
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• v.10 no.1
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• pp.146-155
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• 1983

Fundamental study was carried out to elucidate the mechanisms of biological degradation of dyestuff in environments. A few bacterial strains which were capable of degrading amarnath were obtained from soil through an extensive screening program and identified by microbiolological properties. Conditions for bacterial growth and amaranth degradation were characterized and optimized, and the degradation products were identified. The results were as follows. 1. The most active strain A12-1 to be capable of degradation of amaranth was identified as Pseudomonas sp. 2. Optimal conditions for growth of the strain A12-1 were:$35^{\circ}C$ and pH 7.5, and growth was markedly increaesd by aeration. 3. Degradation of amaranth by the strain was accessed under similiar conditions for growth, however significantly inhibited when the culture was aerated. 4. Both bacterial growth and amaranth degradation were gradually decreased with increased concentration of amaranth in the culture. 5. Reaction of the crude enzyme from the strain A12-1 was optimal at $35^{\circ}C$ and pH 7.5 for degrading amaranth. 6. Sodium naphthionate and R-amino salt were found to be the products of amaranth degradation by the strain A12-1.

• Journal of Korean Society on Water Environment
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• v.22 no.4
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• pp.585-589
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• 2006

Comparison between photocatalysis and sonophotocatalysis were performed in lab-scale experiments for the treatment of benomyl. The effect of operational parameters, i.e., initial benomyl concentration, $TiO_2$ concentration, $H_2O_2$ concentration on the degradation rate of aqueous solution of benomyl has been examined. The optimal conditions for photocatalysis and sonophotocatalysis processes were determined: initial Benomyl concentration was 3 mg/L, the concentration of $TiO_2$ was 2 g/L and $H_2O_2$concentration was 1.5 mM. Under the optimal conditions, sonophotocatalysis was effective for inducing faster degradation of the benomyl.