• International Journal of Highway Engineering
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• v.20 no.2
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• pp.19-25
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• 2018

PURPOSES : This purpose of this study is to analyze the effect to autogenous shrinkage of the top-layer material of a two-lift concrete pavement mixing both silica fume and polymer powder. METHODS : The bottom-layer of a two-lift concrete pavement was paved with original portland cement (OPC) with a 20~23 cm thickness. Additionally, the top-layer which is directly exposed to the environment and vehicles was paved with a high-performance concrete (HPC) with a 7~10 cm thickness. These types of pavements can achieve a long service life by reducing joint damage and increasing the abrasion and scaling resistance. In order to integrate the different bottom and top layer materials, autogenous shrinkage tests were performed in this study according to the mixing ratio of silica fume and polymer powder, which are the admixture of the top-layer material. RESULTS : Autogenous shrinkage decreased when polymer powder was used in the mix. Contrary to this, autogenous shrinkage tended to rise with increasing silica fume content. However, the effects were not significant when small amounts of polymer powder were used (3% and 11%). CONCLUSIONS : The durability and compressive strength increase when silica fume is used in the mix. The flexural strength considerably increases and autogenous shrinkage of concrete decreases when polymer powder is used in the mix. As seen from above, the proper use of these materials improves not only durability, but also autogenous shrinkage, leading to better shrinkage crack control in the concrete.

• Health Policy and Management
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• v.26 no.1
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• pp.12-23
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• 2016

Background: Many studies have explained regional disparities in health by socioeconomic status and healthcare resources, focusing on differences between urban and rural area. However some cities in Korea have the highest cardiovascular mortality, even though they have sufficient healthcare resources. So this study aims to confirm three hypotheses. (1) There are also regional health disparities between cities not only between urban and rural area. (2) It has different regional risk factors affecting cardiovascular mortality whether it is urban or rural area. (3) Besides socioeconomic and healthcare resources factors, there are remnant factors that affect regional cardiovascular mortality such as health behavior and physical environment. Methods: The subject of this study is 227 local authorities (si, gun, and gu). They were categorized into city (gu and si consisting of urban area) and non-city (gun consisting of rural area), and the city group was subdivided into 3 parts to reflect relative different city status: city 1 (Seoul, Gyeonggi cities), city 2 (Gwangyeoksi cities), and city 3 (other cities). We compared their mortalities among four groups by using analysis of variance analysis. And we explored what had contributed to it in whole authorities, city and non-city group by using multiple regression analysis. Results: Cardiovascular mortality is highest in city 2 group, lowest in city 1 group and middle in non-city group. Socioeconomic status and current smoking significantly increase mortality regardless of group. Other than those things, in city, there are some factors associated with cardiovascular mortality: walking practice(-), weight control attempt(-), deficiency of sports facilities(+), and high rate of factory lot(+). In non-city, there are other factors different from those of city: obesity prevalence(+), self-perceiving obesity(-), number of public health institutions(-), and road ratio(-). Conclusion: To reduce cardiovascular mortality and it's regional disparities, we need to consider differentiated approach, respecting regional character and different risk factors. Also, it is crucial to strengthen local government's capacity for practicing community health policy.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.7 no.2
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• pp.87-95
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• 2004

For the slope stability and revegetation of retaining wall, Eco-Stone was built beside a newly constructed road in August, 2002. Eco-Stone blocks were constructed in 4 different combinations of irrigation and soil types. Within the Eco-Stone, planted were 6 species such as Forsythia koreana, Rhododendron mucronulatum, Spiraea prunifolia var. simpliciflora, Rhododendron sp. Euonymus japonica, and Aster koraiensis. Shoot growth was greater on common soils than at a better soil treatment for Forsythia koreana(P<0.01) and Spiraea prunifolia var. simpliciflora(P<0.05), while there were no significant differences for the other species. Biomass increment of the planted species also did not show significant differences between irrigation types, except Rhododendron sp. and Aster koraiensis of which biomass was higher under irrigation than at no irrigation for common soils. Most of the planted individuals were alive, showing survival ratio of 90~97% with no significant differences among treatment blocks. These results imply that the Eco-Stone can be used economically for slope stability and revegetation instead of concrete blocks, without a specific soil and irrigation requirement.

• Journal of IKEEE
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• v.18 no.3
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• pp.427-434
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• 2014

The Multihop Routing of vehicle communication environment is difficult to maintain due to heavy fluctuation of network topology and routing channel according to the movement of the vehicle, road property, vehicle distribution. We implemented GeoNetworking on the basis of ETSI(European Telecommunication Standard Institute) to maintain the vehicle safety service. GeoNetworking has its own way that delivers the data through the Unicast and Broadcast. In this paper, we compared performance index such as packet delivery ratio, end-to-end delay about GeoNetworking using the QualNet Network Simulator. Previous research assessed performance of GeoUnicast. This research has been additionally performed about GeoBroadcast, and we progressed algorithm performance through the comparison of CBF(Contention based Forwarding) of GeoUnicast with Greedy forwarding of GeoBroadcast.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.533-536
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• 2008

This study is the application of phosphate magnesia cement for solidification of soils. The object of the study is the application of the pavment of the farm roads. The new pavement method must be environmental, ecologic and durable. So, for solidification of farm road's soil, we use magnesia cement as quick setting, high strength materials. At magnesia phosphate cement, mixing ratio of mono ammonium phosphate and magnesia is 4:6 and w/b is 50 wt%, it show 14 MPa of compressive strength, and high hydration heat. Solidified soils that mixing ratios of magnesia cement and soil are 4:6 and 5:5 have very high durability for freezing and thawing.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.5
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• pp.29-41
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• 2016

V2X environment is the most popular part of the C-ITS based on the high technologies. To evaluate V2X environment technologies, radio communication range and market penetration rate of V2X vehicle are used. This paper studies the V2X environment considering various traffic congestion level, radio communication range and market penetration rate of V2X vehicle using the microscopic simulation (VISSIM) based on proper parameters and algorithm. In conclusion, V2X environment can reduce the congestion in proper traffic volume. However, if traffic volume is almost near the capacity, even V2X environment can't relieve the road condition. Furthermore, increase of the radio communication range does not always mean the decrease of the congestion and even with the small market penetration rate, it can also have an impact on the V2X environment. This result will be the foundation for the V2X environment much better.

• Journal of Korean Tunnelling and Underground Space Association
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• v.8 no.3
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• pp.227-235
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• 2006

The problematic issue of cracking, water shedding in tunnel is recently coming out in the view of the structural stability. Hence, the assessment is required for the existing tunnels to achieve the structural soundness of tunnels, and their safety and maintenance. In this study, fracture behaviour and displacement of a tunnel concrete lining using steel fiber reinforcement concrete was investigated. The specimens were fabricated in single lining for a model of real road tunnel. As parameters, load condition, thickness of lining, whether or not rear cavity in crown, and a ratio of steel fiber in concrete were taken. From these factors, the load for crack and fracture, displacement, and the pattern of crack were looked into for the structural stability of a tunnel concrete lining.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.4 s.23
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• pp.7-14
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• 2006

The tilting-train being operated in pre-existing rail road has a different running mechanism compared to currently operated trains. Therefore, it needs to investigate the evaluation of the track performance, the stability of the tilting-train in operating condition, and the stability of the roadbed. In this study, when the tilting train is operated in the rail joint with the allowable velocity limited by the track performance and the stability of the tilting-train, the settlement of the roadbed has been evaluated by using numerical analysis. The loading on the ground surface generated by the operating tilting-train generates the settlement of the roadbed. The settlement induced by the tilting-train loading has been compared to the allowable settlement and the factor of safety defined by the ratio of the allowable settlement to the settlement generated by the applied loading is evaluated.

• Journal of Korean Society of Transportation
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• v.22 no.5
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• pp.111-122
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• 2004

The driver's decision making (e.g. route choice) is a typical decision making with an uncertainty. In this paper, we investigate the effect of route guidance information on driver's route choice and learning behavior and analyse the potential of information system in a road network in which traffic flows follow random walk. A Simulation performed focuses on the relationship among the network wide performance, message receiving rates and driver's learning mechanism. We know that at high levels of message receiving rates, the network-wide performance may get worse. However, at low levels of receiving rates, we found that the travel time when guidance information is provided decrease compared to the cases when no pubic information is provided. Also, we found that the learning parameter of the learning mechanism model always changes under nonstationary traffic condition. In addition, learning process of drivers does not converge on any specific value. More investigation is needed to enlarge the scope of the study and to explore more deeply driver's behavior.

• International Journal of Highway Engineering
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• v.13 no.1
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• pp.197-206
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• 2011

The Korean government concentrates on supplying public transit facilities for the mobility handicapped. In other hands, increasing needs of transfer information when the mobility handicapped use transit facilities are substantial but not satisfactory as a whole. This study focuses on evaluating the applicability of developed K-path algorithm to provide user-customized route information that could make an active using of public transit while considering the mobility handicapped preferences. Developed algorithm reflects on requirements considering transfer attributes of the mobility handicapped. Trip attributes of the handicapped are addressed distinguished from handicapped types such as transfer walking time, transfer ratio, facility preferences and etc. This study examines the verification and application of the proposed algorithm that searches the least time K-paths by testing on actual subway networks in Seoul metropolitan areas. It is shown that the K-path algorithm is good enough to provide paths that meet the needs of the mobility handicapped and to be adoptable for the future expansion.