• Nuclear Engineering and Technology
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• v.51 no.7
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• pp.1805-1815
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• 2019

While nickel-based alloys have been widely used for power plants due to corrosion resistance and good mechanical properties, during the last couple of decades, failures of nuclear components increased gradually. One of main degradation mechanisms was primary water stress corrosion cracking at dissimilar metal welds of piping and reactor head penetrations. In this context, precise estimation of welding effects became an important issue for ensuring reliability of them. The present study deals with a series of finite element analyses and crack growth rate evaluation of Alloys 690/152. Firstly, variation of residual stresses and equivalent plastic strains was simulated taking into account welding of a cylindrical block. Subsequently, extraction and pre-cracking of compact tension (CT) specimens were considered from different locations of the block. Finally, crack growth curves of the alloys and heat affected zone were developed based on analyses results combined with experimental data in references. Characteristics of crack growth behaviors were also discussed in relation to mechanical and fracture parameters.

• Journal of Korean Society of Water and Wastewater
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• v.32 no.3
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• pp.269-277
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• 2018

Burials for the rapid disposal of carcasses have diverse and profound effects on the rural living condition, natural environment, and local economy throughout construction, management and final destruction of burials. In this study, possible residue excavated from standard burials, storage using FRP (Fiberglass Reinforced Plastic) tanks, and microbial-treated burials are characterized as carcasses, contaminated soil by leachate, and wasted plastic film. Treatment technologies for volume reduction of the residue including composting, rendering, and thermal hydrolysis were investigated. If the solid and liquid residues generated during volume reduction treatment are directly transferred to the environmental facilities, it may cause disorder due to high concentrations of organics, antibiotics, and lipid. Benefits and drawbacks of composting as a volume reduction techniques are extensively investigated. We also discussed that proper treatment of excavated soils and the reusing the treated soil as agricultural purpose. For the protection of public health and worker's hygiene, treatment criteria including produced residue qualities, and quality standards for the treated soil as agricultural use are required. In addition, Scientific manual for the proper treatment of residues is required. It is necessary to consider the establishment of a pretreatment facility to the occurrence of large-scale residue treatment.

• Elastomers and Composites
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• v.43 no.2
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• pp.72-81
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• 2008

Nowadays, modifying asphalt to improve the resistancy of plastic deformation or rutting on roads has been drawing attention. In this study, asphalts were modified with modifying agents and ground rubber from waste tire (GRT), and the effects of modifier and GRT on the properties of asphalt were analyzed. The Marshall stability of modified asphalt was increased by 98% and the tensile strength increased by 43% compared to straight asphalt. GRT played an important role in enhancing these properties. Viscosity tests, penetration tests and TMA analysis showed the deformation resistancy of modified asphalt. IR and GPC tests indicated that asphalt and modifier have similar chemical structures to each other, and chemical bonding between asphalt and modifier have occurred so that the molecular size lengthened.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2020.10a
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• pp.208-208
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• 2020

The aim of this study was to investigate changes in the weight of Zophobas morio larvae and mass of polystyrene foam when the larvae were fed polystyrene for 27 days. Fourier-transform infrared (FTIR) spectrometry was used to determine whether the polystyrene was broken down by the larvae. Forty Z. morio larvae (four replicates with 10 larvae per replicate) were reared in a chamber under controlled conditions with polystyrene foam blocks as their sole diet. The weight of the Z. morio larvae and mass of the polystyrene foam decreased as a function of time. The average weight of the larvae and mass of the polystyrene foam blocks decreased by 16.3 and 6.5%, respectively, over the 27-day period. The FTIR spectrum of Z. morio larvae fed with polystyrene foam did not reveal the unique peaks associated with polystyrene. In conclusion, this study suggests the possibility of using Z. morio larvae as a management technology for degrading waste plastics without a negative environmental effect. Key words : FTIR spectra, plastic biodegradation, polystyrene foam, Zophobas morio larvae.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.12
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• pp.1371-1380
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• 2007

Study on the instability of waste plastic's thermal pyrolysis oil was carried out for the purpose of improving its quality. The reaction of pyrolysis oil with ozone changed double bonds into aldehydes and ketone, estimated that HDPE pyrolysis oil contained $\sim45$ wt% 1-alkene type olefins, and PP pyrolysis oil did $\sim73$ wt% olefins, which consisted of $\sim47$ wt% secondary and $\sim20$ wt% primary alkenes. The dark brown color and odor of pyrolysis oil were improved by eliminating double bonds, indicated that they were directly related to unsaturated hydrocarbons. Container test showed that metal can affected oil quality worse than the brown glass bottle. Antioxidant added into pyrolysis oil was consumed up to 90% within $2\sim3$ days and the wt. composition of unsaturated hydrocarbons in pyrolysis oil was not changed within 50 days, inferring that instability of pyrolysis oil due to unsaturated bonds can be stabilized by antioxidants. Adsorption test on silica gel, activated carbon and alumina to remove precipitates in oil produced a good result, but not enough to remove moisture. However, cheap anhydrous sodium carbonate showed the best removal efficiency of moisture as well as precipitates in oil. Therefore the pyrolysis oil quality improvement was accomplished by applying anhydrous $Na_2CO_3$ into the production plant.

• Applied Chemistry for Engineering
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• v.29 no.5
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• pp.630-634
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• 2018

The recovery of paraffin components contained in the fraction as a part of improving the quality for the fraction of waste plastics pyrolysis oil (WPPO) was investigated by batch cocurrent 4 stages equilibrium extraction. The fraction at a distilling temperature of $120-350^{\circ}C$ recovered from WPPO by the simple distillation and a little water-added dimethylformamide (DMF) solution were used as a raw material and solvent, respectively. As the number of equilibrium extraction (n) and the carbon number of paraffin component increased, the concentration of paraffin component contained in the raffinate increased. The concentrations of $C_{12}$, $C_{14}$, $C16$ and $C_{18}$ paraffin components present in the raffinate recovered at n = 4 were about 1.2, 1.5, 1.6 and 1.8 times higher than those of using the raw materials, respectively. Recovery rates (residue rates present in raffinate) of paraffin components rapidly decreased with increasing n, and increased sharply with increasing the carbon number. Furthermore, it was possible to predict the recovery rates at n = 1 - 4 for all paraffin components ($C_7-C_{24}$) contained in the raw material. The raffinate recovered through this study is expected to be used as a renewable energy.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.5
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• pp.64-72
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• 2007

This study investigated the types, forms, and origination of litter found along one hiking course in Moaksan Provincial Park, 'Jungin-ri Course'(entrance-ridge-valley-peak). In addition, a survey was conducted to understand hikers' litter control awareness in order to determine possible backcountry litter control measures. The following are the results of this study: 1. For the litter Sequency investigation, 199 recyclable pieces of litter were found on the mid-slope(61.6%), 89 by the entrance(27.6%), 19 in the valley(5.9%) and 16 on the peak(4.9%). A total of 323 pieces of litter were found. Paper materials were the most common, followed by plastic containers such as PET bottles and yogurt containers. Of particular interest, 288 papers and cans were found on the mid-slope(46.9%). By the entrance, more plastics and bottles were found. 2. There were 614 pieces of flammable litter collected and only 19 pieces of non-flammable. Most of the flammable litter, including snack pacts, plastic bags, processed lumber, cigarette butts, tissues, cigarette boxes, and fabric was found on the mid-slope. 3. Very little food waste was found throughout the whole site proving that the policy prohibiting hikers from cooking and eating at the designated sites has been effective. However, food waste is difficult to find because it naturally decays with time. 4. $X^2$-test was used to find different types of litter and their verified origination frequency. It was found that recyclable litter, and food waste took about 1%. In addition, recyclable litter, especially bottles, was found relatively frequently by the entrance. Flammable litter was found most often at the peak. 5. The questionnaire results showed that 48.2% of the respondents "shorten their hiking journey and purchase food outside the entrance" and 29.6% said that they "bring a packed meal from home". Only 8.2% said that they "cook something when an appropriate location is found". At the Jungin-ri course, a few hikers brought their own food to eat or cook, but most hikers purchased something to eat onsite. 6. The results of the question about having experience littering while hiking showed that 19.3% litter and 79.2% do not. Those that responded "yes" gave various reasons for littering. 63.6% claimed, "there are no designated trash containers". 15.9% said they litter subconsciously. Finally, 3.2% insist that they litter "because food naturally decomposes". 7. As a result of the overall satisfaction according to the Likert scale and the analysis with an average of 14 variables, it was found that the average "toxic litter control convenience" was 2.41 with very low satisfaction. Thus, the results indicate the importance of providing appropriate back country litter control facilities.

• Applied Chemistry for Engineering
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• v.30 no.2
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• pp.155-159
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• 2019

As a part of improving the quality for the fraction of the waste plastics pyrolysis oil (WPPO), the recovery of paraffin components contained in the fraction was investigated by dimethylformamide (DMF) equilibrium extraction. The fraction of a distilling temperature of $120{\sim}350^{\circ}C$ recovered from WPPO by the simple distillation and the aqueous solution of DMF were used as a raw material and solvent, respectively. The concentrations of paraffin components ($C_{12}$, $C_{14}$, $C_{16}$ and $C_{18}$) contained in the raffinate decreased by increasing the mass fraction of water in the solvent at an initial state ($y_{w,0}$), whereas, the concentrations of paraffin components contained in the raffinate increased by increasing the mass ratio of the solvent to the feed at an initial state $(S/F)_0$. The concentrations of $C_{12}$, $C_{14}$, $C_{16}$ and $C_{18}$ paraffin components present in the raffinate recovered at $(S/F)_0=10$ were about 1.37, 2.0, 2.46 and 3.16 times higher than those of the raw materials, respectively. Recovery rates (residue rates present in raffinate) of paraffin components rapidly increased with increasing $y_{w,0}$, and decreasing $(S/F)_0$. The raffinate recovered through this study was expected to be used as a renewable energy.

• Resources Recycling
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• v.26 no.6
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• pp.73-83
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• 2017

Used small household appliances have a wide variety of product types and component materials, and contain high percentage of black plastics. However, they are not being recycled efficiently as conventional sensors such as near-infrared ray (NIR), etc. are not able to detect black plastic by types. In the present study, an automatic sorting system was developed based on laser-induced breakdown spectroscopy (LIBS) to promote the recycling of waste plastics. The system we developed mainly consists of sample feeder, automatic position recognition system, LIBS device, separator and control unit. By applying laser pulse on the target sample, characteristic spectral data can be obtained and analyzed by using CCD detectors. The obtained data was then treated by using a classifier, which was developed based on artificial intelligent algorithm. The separation tests on waste plastics also were carried out by using a lab-scale automatic sorting system and the test results will be discussed. The classification rate of the radial basis neural network (RBFNNs) classifier developed in this study was about > 97%. The recognition rate of the black plastic by types with the automatic sorting system was more than 94.0% and the sorting efficiency was more than 80.0%. Automatic sorting system based on LIBS technology is in its infant stage and it has a high potential for utilization in and outside Korea due to its excellent economic efficiency.

• Journal of the Korea Organic Resources Recycling Association
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• v.18 no.3
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• pp.77-86
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• 2010

In this study, the model of the indirect wind suction waste sorting machine for characteristics of the screening of waste was studied using computational fluid dynamics and the drag coefficient for the model and the suction wind speed were obtained. The wind separator are developing by installing a cyclone air outlet to the suction blower impeller waste is selective in a way that does not pass the features and characteristics of the inlet pipe of the pressure loss and separation efficiency can have a significant impact on. Using Wind separator for selection of waste in the waste prior research on the aerodynamic properties are essential. For plastic cases, it is reasonable to take the drag coefficient between 0.8 and 1.0, and for cans, compression depending on whether the cans, the drag coefficient is in the range from 0.2 to 0.7. The separation efficiency of waste as change suction speed was the highest efficiency when the suction speed was 25~26 m/s. Shape of the inlet, depending on how the transfer pipe of the duct pressure loss occurs because the inlet velocity changes through the appropriate design standards to allow for continued research is needed.