• Journal of Conservation Science
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• v.31 no.2
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• pp.105-114
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• 2015

In this study, an advanced epoxy putty which was as a multi-purpose restoration material being used to restore missing parts in the artifact preservation treatment process was developed. For the purpose of addressing the issues including the workability issue resulting from high strength, the drooping issue resulting from long hardening time during work process and the issue of contaminating the surface of artifact resulting from stained material on tools or gloves, a property comparison was conducted with existing materials to examine the properties of restoration materials in the form of epoxy putty currently being frequently used. For the purpose of addressing the issues of existing materials and allowing the developed epoxy putty to have similar properties, two types of hardeners with different properties were selected to conduct property experiments. As for the hardeners, mercaptan type hardener and aliphatic amine type hardeners in the total of two types were selected for the development. The result showed that the two types were both in the form of paste and their hardening time of 5-10 minutes were about 3-10 times shorter than that of existing materials, thereby improving the work convenience. In terms of abrasion rate to increase workability, it was improved by about 3 times to allow effective and convenient use. As for the issue of contaminating the artifact surface during the process, white micro-balloon was added as filler to address the issue to reduce the oil ingredient to develop multi-purpose restoration material with low shrinkage & high workability in coloring, light weight and cutting force.

• Composites Research
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• v.33 no.2
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• pp.39-43
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• 2020

Recently, fabrication process of thermoplastic polyamide-based composites with recyclability as well as impact, chemical, and abrasion resistance have been widely studied. In particular, thermoplastic reactive resin transfer molding (TRTM) in which monomer with low viscosity is injected and in-situ polymerized inside mold has received a great attention, because thermoplastic melts are hard to impregnate fiber preform due to their very high viscosity. However, it is difficult to optimize the processing conditions because of high reactivity and sensitivity to external environments of the used monomer, ε-caprolactam. In this study, viscosity as an important process parameter in TRTM was measured during in-situ anionic polymerization of ε-caprolactam and the solutions for problems caused by high polymerization rate and sensitivity to moisture and oxygen were suggested. Reliability of the improved measurement technique was verified by comparing the viscosity behavior at various environmental conditions including humidity and atmosphere, and it is expected to be helpful for optimization of TRTM process.

• Resources Recycling
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• v.29 no.2
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• pp.28-36
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• 2020

To enhance the recycling rate of wasted glass bottles toward recycled aggregates, the study would decide optimal comminution equipment based on the particle size distribution, aspect ratio and equipment energy analysis. The impact, compress and abrasion is type of generated force by comminution. So, hammer crusher, shredder, roll crusher and ball mill have been selected because they have characteristic which is each type of force. As a result of the particle size analysis of each product, only the shredder product satisfied concrete and asphalt aggregate quality standard condition. Also, as a result of aspect ratio analysis using Imaging software program (Image J, National institute of health), most of size fraction is confirmed under 1.6 value. It was confirmed that the product has low dangerousness and satisfying to shpage index. Also, the particle reduction ratio against input energy of shredder product was the most high. Therefore, we can decide that the optimal equipment which applicable for comminuting waste glass bottle in certain particle size under 10mm is shredder. The result of study will make contribution to increasing energy efficiency of comminution processing and competitiveness of product.

• International Journal of Highway Engineering
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• v.12 no.4
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• pp.131-137
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• 2010

The stormwater runoff from rest areas in highways are known as more polluted compared to highways because of more vehicle activities. This study is performed to find pollutant characteristics in the rest areas in the magnitude of statistical pollutant concentrations during storms. Washoff characteristics of pollutants from rest areas by monitoring of rainfall, runoff rate and runoff samples were evaluated. High concentrations of pollutants in runoff were observed at the beginning of runoff and rapid decrease thereafter, indicating that first-flush effects are clearly occurred. Event Mean Concentrations(EMCs) of TSS, COD, TN, and TP are estimated to be in the range of 31.04-127.11mg/L, 35.5-369.5mg/L, 2.62-9.86 mg/L, and 0.53-1.96mg/L, respectively. Heavy metals in runoff showed relatively high values, possibly due to the abrasion of brake pad or tire while cars are slowly moving for parking. EMCs of total Pb, total Cu, and total Ni are in the range of $1206-16293{\mu}g/L$, $237-7906{\mu}g/L$, and $53-6372{\mu}g/L$, respectively. Pollutant loading per rest area calculated by using EMC, flowrate and target area is also described for each pollutant.

• Journal of Chest Surgery
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• v.42 no.3
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• pp.337-343
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• 2009

Background: Postoperative recurrence is a major problem after performing video-assisted thoracic surgery for the treatment of primary pneumothorax. This study was designed to evaluate the efficacy and safety of a bioabsorbable staple line reinforcement (GORE $SEAMGUARD^{(R)}$) for preventing recurrence after bullectomy. Material and Method: From January 2000 to December 2004, 300 patients underwent video assisted thoracoscopic surgery for the treatment of primary penumothorax. 143 patients were treated with bioabsorbable staple line reinforcement (Group A) and 142 patients were treated with stapling of the bullae (Group B). Mechanical pleural abrasion was performed in all the patients. The operating time, the duration of the indwelling chest tube, the length of the hospital stay and the number of recurrences after operation were compared between the groups. Result: No operative deaths occurred. The conversion rate to an open procedure was 5% (15/300). Comparison with these groups (Group A versus Group B) showed the following results: the operating time ($49.6{\pm}25.6$ vs $51.8{\pm}30.4$ minutes, respectively, p=0.514), the duration of an indwelling chest tube ($5.8{\pm}2.5$ vs $7.2{\pm}3.3$ days, respectively, p<0.005), the hospital stay ($10.9{\pm}4.3$ vs $12.5{\pm}4.3$ days, respectively, p<0.005) and the number of recurrences (14 (9.8%) vs 10 (7.0%), respectively, the over all rate: 8.4% p=0.523), and the mean follow up period. ($48.1{\pm}36.6$ vs $36.5{\pm}24.4$ months, respectively). Conclusion: There were advantages to use synthetic absorbable staple line reinforcement over the usual method for the treatment of primary pneumothorax in regard to the duration of an indwelling chest tube and the hospital stay, but here was no significant difference between the groups for postoperative recurrence.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.4
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• pp.555-563
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• 2004

The pH of beverages is known to be low and have, therefore, been implicated in the increasing incidence of erosion. Erosion is believed to be the predominant cause of teeth wear in children and young adults, although there will always be a contribution from attrition and abrasion. The aim of the present study was to evaluate the effect of yogurt on the progression of erosive demineralization in human enamel using demineralization model in vitro. In 4 yogurts, available on the market, pH, buffering capacity and the concentrations of calcium, phosphate and fluoride were determined. The buffering effect was determined by titration with NaOH. 50 milliliters of each drink was then titrated with 1M sodium hydroxide, added in 0.5 milliliters increments, until the pH reached about 7. Human deciduous enamel(n=40) samples were divided into four groups and exposed to 80ml of the yogurt for 30,60, 90 and 120min. Enamel surface microhardness(VHN) was examined before and after each exposure. 1. The average PH of fermented milk was 3.77 and this pH value was acidic enough to cause tooth erosion. 2. All of the fermented milks were found to be erosive(p<0.05) 3. The teeth exposed to the fermented milk all showed erosion like lesions and microhardness measurements showed that enamel surface hardness decreased proportionately with increased time of immersion in all tooth specimen groups. 4. After immersion for 30 and 60 minutes, reduction rate of microhardness values was not significantly different between the groups(p>0.05). However, after 90 and 120 minutes, reduction rate of each group was significantly different(p<0.05).

• Journal of Korean Society of Environmental Engineers
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• v.32 no.12
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• pp.1087-1093
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• 2010

Autotrophic denitrification is known as an effective and economical alternative for heterotrophic denitrification using external carbon sources such as methanol. In this study, we evaluated design and operation parameters for a sulfur denitrification reactor (SDR) treating high strength nitrogen wastewater. The SDR was filled with spherical sulfur media in connected to a pilot-scale nutrient removal process (daily flow rate, $Q=18\;m^3/d$) using moving spongy media. Total nitrogen (TN) concentration of the final effluent was below the 7.0 mg TN/L because nitrate was additionally removed through autotrophic denitrificationin without adding alkalinity (initial alkalinity was $169.4{\pm}20.8\;mg$ $CaCO_3$/L). During the test period, 60~80% of nitrogen in the influent was removed even in low temperature (below $15^{\circ}C$). The alkalinity consumption for nitrate removal in SDR was $4.09{\pm}1.29$ g $CaCO_3/g$ ${NO_3}^-$-N, and the residual alkalinity of influent of SDR was higher than that of theoretical requirements for full conversion of nitrate. The consumption of sulfur was 943.8 g S/d and it was 2.4 times higher than theoretical value (400.1 g S/d) due to abrasion and loss of sulfur media in backwash, etc.

• Journal of Bio-Environment Control
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• v.4 no.1
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• pp.59-67
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• 1995

This study was conducted to develope the automatic insulation system which control inside temperature of the greenhouse. For this purpose, the double- wall greenhouse and system which could automatically supply and discharge styrene pellets were constructed and abrasion of the pellets, blower ability, insulating property, transmittance and shading effect were analyzed by the experiments. The results obtained from this study can be summarized as follows : 1. It took an hour and fifteen minutes to supply and discharge about 2㎥ pellets in the experimental greenhouse. However, it is possible to reduce the operation time by proper selection of the blower and exhaust port, and by proper control of the supply and return pipe. 2. It was founded that the indirect delivery way was more profitable than the direct one in the supply and return of pellets. 3. When the transmittance was measured between 10 a.m. and 3 p.m., the average light transmissivity rate was 67%. 4. In winter nighttime, the inside temperature of the double- wall greenhouse with out the pellets was higher than the outside temperature by 3.4$^{\circ}C$ on an average. However, the inside temperature of the double - wall greenhouse with insulated area 73% was higher than the outside by one 6.6$^{\circ}C$ on an average, and the inside temperature of the greenhouse with insulated area 100% was higher than outside one by 13.5$^{\circ}C$ on an average. Therefore, it was proved that the insulating ability of the double - wall greenhouse in nighttime was excellent. 5. When the outside temperature was 36.9$^{\circ}C$ on an average, the inside temperature of the double- wail greenhouse with insulated area 100% was 3$0^{\circ}C$ on an average. As the inside temperature was lower than the outside one by 7$^{\circ}C$ on an average, we could know that the shading effects of the double- wall greenhouse were excellent in summer daytime.