• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.529-532
• /
• 2008

Domestic area of most be happened chloride deicer damage. Because daily mean temperature is below 0$^{\circ}C$ from the area of domestic most. Use of deicing chemicals has been and will continue to be a major part of highway snow and ice control methods. Chloride-containing chemicals such as calcium chloride or rock salt are main deicers for the road. Extensive use of chloride deicers is, however, not only the source of substantial cost penalties due to their corrosive action and ability to deterioration roadway surface materials but also the source of environmental damages. Particularly, it has been recognized that chlorides present in deicing agents can significantly increase concrete surface scaling. In severe cases, scaling can result in dislodgement of coarse aggregate. This research estimates that pH and test of specific pollutants, dynamic modulus of elasticity for freeze-thaw test of concrete were higher than those NaCl, $CaCl_2$, and NaCl+$CaCl_2$(7:3, w/w), also weight losses for scaling test of concrete were much lower than those of NaCl, $CaCl_2$, and NaCl+$CaCl_2$(7:3, w/w).

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.561-564
• /
• 2008

Concrete scaling is the progressive surface deterioration of susceptible subjected to freeze-thaw cycling in the presence of moisture. Particularly, it has been recognized that chlorides present in deicing agents can significantly increase concrete surface scaling. Domestic area of most be happened chloride deicer damage. Because daily mean temperature is below 0$^{\circ}C$ from the area of domestic most. Use of deicing chemicals has been and will continue to be a major part of highway snow and ice control methods. Chloride-containing chemicals such as calcium chloride or rock salt are main deicers for the road. Extensive use of chloride deicers is, however, not only the source of substantial cost penalties due to their corrosive action and ability to deterioration roadway surface materials but also the source of environmental damages. In this study, Use of (40, 27, 21MPa) pavement concrete analyze freeze-thaw test and scaling on the chlorides present.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.565-568
• /
• 2008

Domestic area of most be happened chloride deicer damage. Because daily mean temperature is below 0$^{\circ}C$ from the area of domestic most. Concrete durability influence Air Content. Presently, We used to AE(air-entraining agent) for increase freeze-thaw durability. So, on concrete Air Spacing ratio used $200{\mu}m{\sim}230{\mu}m$ in Canada and under $250{\mu}m$ in Japan institution. Use of Air content has been and will continue to be a major part of concrete durability and scaling. Chloride-containing chemicals such as calcium chloride or rock salt are main deicers for the road. The prepared optimum mix concrete in this study show that freeze-thaw and scaling resistance of Non-AE(air content 1.5%) and AE (air content 4.5%, 7.2%). Solution concentrations of deicing agent were good result, and the pore system and change of hydration products is not difference comparing before freeze-thaw test.

• International Journal of Precision Engineering and Manufacturing
• /
• v.8 no.2
• /
• pp.44-48
• /
• 2007

In recent years, the size of plane substrates and semiconductor wafers has increased. As conventional contact transportation systems composed of, for example, carrier rollers, belt conveyers, and robot hands carry these longer and wider substrates, the increased weight results in increased potential for fracture. A noncontact transportation system is required to solve this problem. We propose a new noncontact transportation system combining acoustic viscous and aerostatic forces to provide damage-free transport. In this system, substrates are supported by aerostatic force and transported by acoustic viscous streaming induced by traveling wave deformation of a disk-type stator. A ring-type piezoelectric transducer bonded on the stator excites vibration. A stator with a high Q piezoelectric transducer can generate traveling vibrations with amplitude of $3.2{\mu}m$. Prior to constructing a carrying road for substrates, we clarified the basic properties of this technique and stator vibration characteristics experimentally. We constructed the experimental equipment using a rotational disk with a 95-mm diameter. Electric power was 70 W at an input voltage of 200 Vpp. A rotational torque of $8.5\times10^{-5}Nm$ was obtained when clearance between the stator and disk was $120{\mu}m$. Finally, we constructed a noncontact transport apparatus for polycrystalline silicon wafers $(150(W)\times150(L)\times0.3(t))$, producing a carrying speed of 59.2 mm/s at a clearance of 0.3 mm between the stator and wafer. The carrying force when four stators acted on the wafer was $2\times10^{-3}N$. Thus, the new noncontact transportation system was demonstrated to be effective.

• Journal of the Korean Society of Safety
• /
• v.27 no.6
• /
• pp.185-191
• /
• 2012

Rear collisions to expressway work trucks result many casualties these days. But, currently, no special measure are being taken except deploying sign trucks behind the working trucks. In the U.S and Europe, trucks with TMA(Truck Mounted Attenuator) are being deployed behind the working truck, which is regarded as the standard method for work area safety, thereby reducing the fatality rates and property damage tremendously. Also, standard for the performance of TMA are established and TMA can be used in the field only when it satisfies the standard. In Korea, neither the standard for nor any guide to the TMA exists. In the situation some manufacturer developed TMA without proper performance evaluation and marketed limited number of TMAs in the field. In the study, NCHRP350, which is the performance standard of expressway safety features of U.S. and materials related to the TMA standard in Europe have been reviewed to establish the Korean performance criteria. Based on the review, and incorporating existing Korean standard for crash cushions, domestic standard for TMA has been proposed and applied in developing Korean TMA and crash tested it to verify the performance. The original design developed was crash tested and modified. The newly proposed design was studied using impact simulation program several times. Modifications were made after each simulation and prototype was built and crash tested as per the newly established TMA performance criteria.

• International Journal of Highway Engineering
• /
• v.11 no.1
• /
• pp.217-231
• /
• 2009

In order to manage traffic operations efficiently, it is required to establish evacuation strategies, including path, disaster prevention, and signal control. This is because the delayed response of operators would cause dreadful loss of our community. Therefore, it is very important to do the research related to traffic disaster prevention system. In this paper, we select the City of Cheongju as a study area since lots of damage resulting from natural disaster such as storm and flood have been frequently taken place. In addition, this paper suggest traffic disaster prevention measures and analyzed its effect on signal operation to achieve high level of traffic efficiency. As a result, traffic flow is similar to normal condition when we applied developed signal operation method. It is also demonstrated if disaster information is spread out as fast as it can be, and signal operation is managed properly in case by case, we conclude that user safety has to be secured.

• International Journal of Highway Engineering
• /
• v.9 no.4
• /
• pp.11-20
• /
• 2007

This thesis develops a fatigue model for the asphalt black base using the APT(Accelerated Pavement Testing) and analyzes the correlation of the APT analysis result with results of previous laboratory tests. For the APT testing, aggregate of the maximum grain size of 25mm(BB-3) was used as the material for the asphalt black base. The result of the APT revealed that the variable of the fatigue model, i.e. the maximum tensile stress on the bottom part of the pavement, increased as the number of loading increased while the modulus of elasticity for the pavement layer decreased gradually. The tensile strain was obtained from a strain gauge, and it was used to derive the values of $k_1=1.29{\times}10^{-6}$ and $k_2=3.02$ from the basic equation of the asphalt fatigue model, $N_f=k_1(\frac{1}{\epsilon})^{k_2}$. The fatigue life predicted from the asphalt fatigue model was greater than that obtained from laboratory experiments, given the same tensile strain. Additionally, a theory to estimate the remaining life of the pavement was developed using FWD, a non-destructive experiment.

• Asia-Pacific Journal of Business
• /
• v.12 no.1
• /
• pp.209-223
• /
• 2021

Purpose - The purpose of this study was to investigate the relationship between Korea agricultural productions and Greenhouse Gas (GHG) emissions based on Environmental Kuznets Curve (EKC) hypothesis. Design/methodology/approach - This study utilized time series data of economic growth, greenhouse gas, agricultural productions, trade dependency, and energy usages. In order to econometric procedure of EKC hypothesis, this study utilized unit root test and cointegration test to check staionarity of each variable and also adopted Vector Error Correction Model (VECM) and Ordinary Least Square (OLS) to analyze the short and long run relationships. Findings - In the short run, greenhouse gas emissions resulting from economic growth show an inverse U-shape relationship, and an increase in agricultural production and energy consumption led to increase in greenhouse gas emission. In the long run, total GHG emissions and CO2 emissions show an N-shaped relationship with economic growth, and an increase in agricultural production has resulted in a decrease in total GHG and CO2 emissions. However, methane (CH4) and nitrous oxide (N2O) emissions showed an inverse U-shape relationship with economic growth, which indicated the environment and production process of agricultural production. Research implications or Originality - Korea agricultural production has different effects on the GHG emission sources, and in particular, methane (CH4) and nitrous oxide (N2O) emissions show to increase as the agricultural production expansions, so policy or technological development in related sector is required. Especially, in the context of the 2030 GHG reduction road-map, if GHG-related reduction technologies or policies are spread, national GHG emission reduction targets can be achieved and this is possible to predict the decline in production in the sector and damage to the related industries.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.39 no.4
• /
• pp.523-530
• /
• 2019

Pavement distress and traffic accidents are caused by pot-hole. In addition, direct and indirect damages of road users are increasing, such as loss of life due to personal injury and damage to vehicles. Generally, the asphalt concrete pavements are continuously aging from the production process to the terminal performance period. Aging causes stripping due to cracks and moisture penetration and weakening the pavement structure to induce pot-hole. In this study, adhesion performance and moisture sensitivity were evaluated according to aging degree in order to investigate the effect of aging on asphalt pavement. As a result of the study, the viscosity of the asphalt binder was increased with aging and the bond strength of the aged was increased 2~3 times than that of the unaged. The results of accelerated aging test showed an increases in indirect tensile strength and the increase in the TSR (Tensile Strength Ratio) by 4.2~8.9 %. As a result, it is noted that the anti-stripping and adhesion performances of the aged asphalt concrete are improved compared to the unaged one under the aging conditions of asphalt binder coated on aggregates.

• Journal of Wetlands Research
• /
• v.23 no.2
• /
• pp.116-121
• /
• 2021

This study is the first official report on the wild habitats of alien species, Yellow-spotted Amazon River Turtle (Podocnemis unifilis) in Republic of Korea. On July 24, 2020, two P.unifilis were observed basking on rocks at 33°30'20.08"N 126°38'0.23"E, Waheul-ri, Jocheon-eup, Jeju-si, Jeju. One individual had a yellow spots on the head where as the other contains black spot. Our observatory site is close to road and easy access to people. Thus, these individuals were believed to be released in the pond after raising as pets. Recently, the number of alien turtles identified in wild(etc. lake, resevoir) is increasing, which is predicted to damage the aquatic ecosystem due to the inflow of exotic turtles. So, it is necessary to improve the people's awareness of alien species through citizen science projects and environmental education. We suggest that research on habitat adaptation, reproduction and management through continuous monitoring is needed in the future.