In general, the design response spectrum in seismic design codes is based on the mean-plus-one-standard deviation response spectrum to secure high safety. In this study, response spectrum analysis was performed using seismic wave records adopted in domestic horizontal design spectrum development studies, while three response spectra were calculated by combining the mean and standard deviation of the spectra. Seismic wave spectral matching generated seismic wave sets matching each response spectrum. Then, seismic fragility was performed by setting three damage levels using a single-degree-of-freedom system. A correlation analysis was performed using a comparative analysis of the change in the response spectrum and the seismic fragility concerning the three response spectra. Finally, in the case of the response spectrum considering the mean and standard deviation, like the design response spectrum, the earthquake load was relatively high, indicating that conservative design or high safety can be secured.

It is essential to select materials with excellent mechanical properties to prevent chemical and mechanical damage to the surfaces of materials used in machines and structures and to extend their lifespan. Co-based stellite alloy, which has wear resistance, heat resistance, and corrosion resistance, is essential for products used in harsh environments. However, due to the problem of enormous costs, research on hard facing, which uses a stellite coating layer only on the contact surface, is urgently required. Currently, high-facing research on Stellite coating layers is focused on powder, and GMAW research using wire is relatively lacking. In this study, welding experiments were performed to form stable weld beads using stellite 6 welding wire, and the correlation between parameters and weld beads was analyzed. A CMT welder was used to minimize the heat effect on the base material.

In this study, changes in the microstructure and mechanical properties of cast and extruded Al-2Li-1Ce alloy materials were investigated as the Mg content was varied. The density decreased to 2.485, 2.46 and 2.435 g/cm3 when the Mg content in the Al-2Li-1Ce alloy was increased to 2, 4 and 6 wt%, respectively. Intermetallic compounds of Al11Ce3 were observed in all alloys, while the β-phase of Al3Mg2 was observed in alloys containing 6 wt% of Mg. In the extruded material, with increasing Mg content the average grain size decreased to 84.8, 71.6 and 36.2 μm, and the fraction of high-angle grain boundaries (greater than 15°) increased to 82.8 %, 88.6 %, and 91.8 %, respectively. This occurred because the increased Mg content promotes dynamic recrystallization during hot extrusion. Tensile test results showed that as the Mg content increased, both the yield strength and tensile strength increased. The yield strength reached 86.1, 107.3, and 186.4 MPa, and the tensile strength reached 215.2, 285, and 360.5 MPa, respectively. However, it is worth noting that the ductility decreased to 27.78 %, 25.65 %, and 20.72 % as the Mg content increased. This reduction in ductility is attributed to the strengthening effect resulting from the increased amount of dissolved Mg, and grain refinement due to dynamic recrystallization.

The importance of urban green space creation is increasingly recognized as the most realistic and efficient approach for fine dust mitigation in urban areas. Particularly considering the characteristics of domestic cities, the application of buffer green spaces along roads can maximize the efficiency of fine dust reduction without the need for separate green space creation. Accordingly, this study analyzed the fine dust mitigation effects based on the types of plantings in the central dividers and roadside trees in Jeonju City, Jeollabuk-do. To do this, we controlled various external variables of urban space and considered the planting arrangement types in the central dividers, carrying out the analysis using a CFD simulation. The simulation results confirmed that the central dividers with plantings demonstrated more effective ultrafine dust reduction than those without. Moreover, the arrangement of roadside trees showed a greater ultrafine dust reduction effect when adopting a multilayered structure compared to a single layer. Based on these findings, we concluded that installing both trees and shrubs simultaneously in the central dividers and along roads was effective for ultrafine dust mitigation. On this basis, we quantified the dust reduction effects of plants in urban street environments and proposed planting guidelines for roadside green spaces to improve air quality.

This study was performed to evaluate the pollutants removal characteristics of two types of RBFs(Riverbank filtration, Riverbed filtration) intake facilities installed in Nakdong River and in Hwang River respectively. The capacity of each RBF is 45,000 ㎥/d for riverbank filtration intake facility and 3,500 ㎥/d for riverbed filtration intake facility. According to data collected in the riverbank filtration site, removal rate of each pollutant was about BOD(Biochemical oxygen demand) 52%, TOC(Total organic carbon) 57%, SS(Suspended solids) 44%, Total coliforms 99% correspondingly. Furthermore, Microcystins(-LR,-YR,-RR) were not found in riverbank filtered water compared to surface water in Nakdong River. DOC(Dissolved organic carbon) and Humics which are precursors of disinfection byproduct were also reported to be removed about 59% for DOC, 65% for Humics. Based on data analysis in riverbed filtration site in Hwang River, removal rate of each contaminant reaches to BOD 33.3%, TOC 38.5%, SS 38.9%, DOC 22.2%, UV254 21.2%, Total coliforms 73.8% respectively. Additionally, microplastics were also inspected that there was no obvious removal rate in riverbed filtered water compared to surface water in Hwang River.

Recently, the market competition has been fiercer due to the acceleration of technological change and the launch of intelligent products. In this situation, technology cooperation activities through networks rather than independent technological innovation activities of a single company or institution are recognized as a crucial strategy to gain competitiveness. Technology cooperation can take various forms depending on the target technology, and researchers have conducted performance analyses of technology cooperation types. However, there have not been data-based quantitative studies on the types and trends of technology cooperation for the target technology. In this paper, we explored the difference between the technology cooperation types by technology and time using the formal concept analysis method and co-patent information. In particular, the proposed methodology has been verified through the case study of electric vehicles, and it is intended to suggest the direction of technological cooperation according to specific technologies and cooperation targets in the future

PURPOSES : Recently, corrosion and deterioration of highway facilities have been increasing owing to the excessive use of deicers. This study aimed to find an optimal snow removal method to develop countermeasures for the problem of excessive deicer use and improve the efficiency of snow removal. METHODS : Theoretical investigations and experiments related to deicing were conducted to determine the differences between deicing chemical types and states. Based on regional weather patterns, the entire country was categorized into four groups: warm and heavy snow, warm and light snow, cold and heavy snow, and cold and light snow, and matched with each regional office of the Korea Expressway Corporation. RESULTS : Optimal snow removal methods were proposed considering regional characteristics and deicing chemical types and states. CONCLUSIONS : Different deicer types were proposed according to the region type, such as using only salt and salt/calcium chloride in the warm and cold regions, respectively. Second, plowing was more effective at lower temperatures. Third, liquid deicer spraying could reduce the amount of deicer used. A liquid deicer is suitable for preliminary spraying because its quick-acting properties are superior to those of a solid deicer, although its lasting properties are inferior to those of the solid deicer.