• Applied Chemistry for Engineering
• /
• v.34 no.1
• /
• pp.69-74
• /
• 2023

As a chemical de-icing method, propylene glycol de-icing fluid is applicable for melting ice caused by snow and ice adhering to the lower part of high-speed rail rolling stock and bogie parts in winter. By spraying propylene-glycol de-icing fluid on high-speed rail rolling stock and bogie parts in advance to minimize snow adhesion, ice-melting efficiency can be further improved. In the case of high-speed rail rolling stock, even if propylene-glycol de-icing fluid is sprayed, the anti-icing performance is poor because the fluid is almost lost on the surface of the vehicle when operating at high speed. In this study, in order to prevent freezing caused by snow and ice adhering to the lower part of high-speed rail rolling stock and bogie parts, we have investigated the properties of propylene-glycol de/anti-icing fluid containing water-repellent agents that prevent surface freezing. We tried to find the optimal component for de/anti-icing fluid for high-speed rail rolling stock by evaluating the ice melting performance, contact angle, and anti-icing performance according to the types of water-repellent agent. As a result of the evaluation, it was confirmed that an de/anti-icing fluid containing an ethoxysilane-type water repellent agent was most suitable.

• International Journal of Highway Engineering
• /
• v.15 no.2
• /
• pp.73-81
• /
• 2013

PURPOSES : In this study, various laboratory tests were performed to investigate basic physical properties of the asphalt concrete which uses wasted vinyl aggregates. METHODS : The thermal conductivity, ultrasonic velocity, Marshall stability, flow, indirect tensile strength were measured according to binder content and wasted vinyl aggregate content. An experimental construction was performed to verify construct ability of the asphalt pavement using the wasted vinyl aggregates. RESULTS : The thermal conductivity and ultrasonic velocity decreased showing insulation effect by mixing more wasted vinyl aggregate, whereas stability and flow increased. The void ratio shows similar value regardless of the mixing ratio. The highest indirect tensile strength was measured at 2.5% of wasted vinyl aggregate content. The construct ability was verified by observing the process of mixing, placing, and compaction and the state of the pavement surface. CONCLUSIONS : The basic properties and construct ability of the asphalt concrete using the wasted vinyl aggregates were verified. The temperature according to pavement depth will be measured to verify the insulation effect of the wasted vinyl aggregates. In addition, amount of snowfall, snowmelt area, and ice adhesion strength will be analyzed quantitively.

• International Journal of Highway Engineering
• /
• v.20 no.3
• /
• pp.1-9
• /
• 2018

PURPOSES : In order to evaluate a crack resistance at cold joint, sealing tape was adopted to apply at cold joint instead of typical tack coat material(RSC-4). The sealing tape was made by hot sealing material. The crack resistance as function of environmental and traffic loading was measured with visual observation. METHODS : In this study, the crack resistance was evaluated as function of environmental and traffic loading. The freeze-thaw method was adopted for environmental loading of asphalt pavement. condition. The damage of cold joint under freeze-thaw action is initiated by ice expansion load and accelerated by the interfacial damage between new and old asphalt pavement. The traffic loading was applied with wheel tracking machine on the cold joint area of the asphalt pavement for 3 hours at $25^{\circ}C$. The evaluation of crack resistance was measured with visual observation. The freeze-thaw results shows that the sealing tape was significantly increased the crack resistance based on. RESULTS : To estimate the crack resistance at cold joint area due to the environmental loading, the Freeze-thaw test was conducted by exposing the product to freezing temperature(approximately $-18^{\circ}C$) for 24 hours, and then allowing it to thaw at $60^{\circ}C$ for 24 hours. The tack coat material(RSC-4) was debonded after 21 cycles of the Freeze-thaw test. The first crack was observed after 14 freeze-thaw cycle with RSC-4 material. But, the sealing tape was not debonded after 24 cycle test. Also, the sealing tape shows the better performance of the crack resistance under the traffic loading with wheel track test. The crack was generated the under traffic loading with RSC-4(tack coating), however, the crack was not shown with sealing tape. It indicates that the sealing tape has a strong resistance of tensile stress due to traffic loading. CONCLUSIONS :Based on limited laboratory test result, a performance of crack resistance using the sealing tape is better than that of general tack coat material(RSC-4). It means that the sealing tape is possible to extend a pavement service life because the crack, one of the main pavement distresses, will be delayed.

• Journal of Korean society of Dental Hygiene
• /
• v.10 no.2
• /
• pp.345-359
• /
• 2010

Objectives : The purpose of this study was to correlation between the index of dental caries in primary teeth and the habits of diet and snack which are expected to influence on the index. The subjects of this study were 165 parents of the children who visited a pediatric dental hospital located in Gyeong-gi do from Jun. 15th to Sep. 26th, 2009, and the self-report questionnaire survey was performed. Methods : A questionnaire used in a previous study was revised and completed for this study and it consisted of 15 items on general characteristic, nine items on dietary habit, and five items on snack intake habit. The collected data was analyzed using SPSS program and findings are as follows Results : 1. The index of dental caries in primary teeth by ages was that children of four years old has 4~5 with 27.5%, children of five years old has 2~3 and 4~5 with 33.3% and children of six years old has 1 and 8~9 with 25.6%, showing a statistically significant(${\chi}^2$=37.72, p<.01). 2. The frequency of brushing teeth was found to have statistically significant negative correlation with the number of primary teeth with dental caries (${\chi}^2$=61.20, p<.001). 3. The frequency of taking snack was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${\chi}^2$=51.42, p<.001). 4. The desirability of dietary habit was found to have statistically significant negative correlation with the number of primary teeth with dental caries (${\chi}^2$=36.51, p<.001). 5. The frequency of taking biscuit was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${\chi}^2$=67.74, p<.001). 6. The frequency of taking bread was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${\chi}^2$=29.63, p<.01). 7. The frequency of taking caramel and candy was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${\chi}^2$=38.85, p<.001). 8. The frequency of taking soft drinks was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${\chi}^2$=52.92, p<.001). 9. The frequency of taking ice-creams was found to have statistically significant positive correlation with the number of primary teeth with dental caries (${\chi}^2$=75.07, p<.001). Conclusions : Those findings show that the children with undesirable dietary habit and higher frequency of taking snack have higher index of dental caries in primary teeth, therefore, it is considered that the regular brushing teeth and establishment of desirable dietary habit are very important for keeping health oral cavity. It is recommended that the continuous concern and repeated learning are needed in house and group of rearing infants so that the children take foods of fruits which have function of self-purification than the food of carbohydrates which has high adhesion and level of sweetness.