• Journal of Korean Tunnelling and Underground Space Association
• /
• v.21 no.4
• /
• pp.455-478
• /
• 2019

In this paper, we conducted experimental investigation on the field applicability through the verification of reinforcement effect of the steel pipe reinforcement grouting using high strength steel pipe. SGT275 (formerly known as STK400) steel pipe is generally applied to the traditional steel pipe reinforcement grouting method. However, the analysis of tunnel collapse cases applying the steel pipe reinforcement grouting shows that there are cases where the excessive bending and breakage of steel pipe occur. One of the reasons causing these collapses is the lack of steel pipe stiffness responding to the loosening load of tunnels caused by excavation. The strength of steel pipe has increased due to the recent development of high strength steel pipe (SGT550). However, since research on the reinforcement method considering strength increase is insufficient, there is a need for research on this. Therefore, in this study, we conducted experiments on the tensile and bending strength based on various conditions between high strength steel pipe, and carried out basic research on effective field application depending on the strength difference of steel pipe through the conventional design method. In particular, we verified the reinforcement effect of high strength steel pipe through the measurement results of deformed shape and stress of steel pipe arising from excavation after constructing high strength steel pipe and general steel pipe at actual sites. The research results show that high strength steel pipe has excellent bending strength and the reinforcement effect of reinforced grouting. Further, it is expected that high strength steel pipe will have an arching effect thanks to strength increase.

• The Korean Journal of Archival Studies
• /
• no.44
• /
• pp.155-197
• /
• 2015

Disaster of Sewol took place in one year. Meanwhile, the victim's family and the call time record academics have tried to record it. Ansan activists have moved to objectives such as civil records committee also pivotal. The citizens committee under the dictation recording oral history team has a diverse group of people associated with the time issue. bereaved families were collected from the oral as well as volunteers, religious personnel, activists, Ansan citizens and various people. Disasters around the world is also an important event to remember and honor the people together, and one of the most effective means to record There it is establishing an oral history archive. Does not leave a lot of nature history of sudden disasters that occur, as well as a tribute record dictation telling people of diverse perspectives on events helps a lot closer to the reality of the event. Erected in the National September 11 Memorial Museum to honor the Sept. 11 attacks and provide a variety of programs to chaerok dictation of the people involved with 9/11. To remember the 2013 Boston Marathon bombing 'Our Marathon' of crowdsourcing digital archive was built. In the archives of the local universities and institutions were created to collaborate actively and gathering oral history. Pan Am Flight 103 pieces terror has established an archive from Syracuse University. Here, neither graduates, faculty, and to the victim's family and friends gather and oral hitory. Disaster-related Sewol neither should be able to be used as in the case of foreign well, and it should continue to honor the victims of the collection. It also ought to occasion again to avoid this disaster on earth.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.55 no.1
• /
• pp.82-93
• /
• 2019

The International Labor Organization (ILO) selected fishing as the most dangerous group of jobs in the world, and it is well known in Korea as a 4D industry. Offshore large purse seine accounts for the largest portion of the fishing industry in the coastal region with high death rate and the accident rate. The repeated disaster rate survey by the Korea Maritime Institute (KMI) shows offshore large purse seiner is the highest at 22.3 percent and coastal gill nets and offshore stow net are following at 12.4 percent and 11.9 percent in order. Therefore, risk factors occurring in offshore large purse seiners were analyzed based on data from the National Federation of Fisheries Cooperatives (NFFC) for three years from 2015 to 2017 and 4M (Man, Machine, Media, Management) 3E (Engineering, Education, Enforcement) techniques were used to provide a safe fishing environment. The number of accidents on offshore large purse seiners each year was more than 150, and the number of accidents on every fishing boats was as high as 17 percent in 2015. If the accident rate and the risk level were divided by insurance, the accident resulting from contact with machinery was the highest, and the risk of a contact with gear was low but frequently occurring. This was caused by collisions and contact with gear in situations where death and disappearance risk are not high, and accident types in situations where death and loss risk are considered to be contact with machinery, falls or other accidents. Through these analysis techniques, the frequency and risk of each type of accident on a offshore large purse seiners can be demonstrated, and it is expected to raise awareness of a safer fishing environment and contribute to the reduction of accidents.

• Journal of the Korean Geosynthetics Society
• /
• v.18 no.3
• /
• pp.33-44
• /
• 2019

Clinker layer is a stratum structure distributed in volcanic area such as Jeju Island. The clinker layers were formed in between the repetitive action of eruption and solidification of lava flows. Since the clinker layer contains a large amount of voids accompanied by the lava gas ejection process, there is a possibility of inducing overall stability of the ground due to the low stiffness and strength of the clinker layer. Therefore, in this study, site investigation was carried out at both ends of the 00 bridge where the clinker layers exist. And, based on the ground survey results, the behavior of shallow foundations was analyzed numerically. In addition, the improved shallow foundation behavior in grouting substitution using the chemical injection method of the clinker layer was compared with the shallow foundation behavior in the ground, and the grouting substitution efficiency of each layer was analyzed. As a result, the bearing capacity, the replacement efficiency and elastic settlement were different according to the presence or absence of the sediment layer. This is because the sediment layer has a lower stiffness and density than the clinker layer.

• Journal of the Microelectronics and Packaging Society
• /
• v.28 no.2
• /
• pp.71-79
• /
• 2021

In this study, we have successfully fabricated the Sn-Ni paste and evaluated the bonding properties for high-temperature endurable EV (Electric Vehicle) power module applications. From evaluating of the micro-structural changes in the TLPS (Transient Liquid Phase Sintering) joints with Sn and Ni contents in the Sn-Ni pastes, a lack of Ni powders and Ni particle agglomerations by Ni surplus were observed in the Sn-20Ni and Sn-50Ni joints (in wt.%), respectively. In contrast, relatively dense microstructures are observed in the Sn-30Ni and Sn-40Ni TLPS joints. From differential scanning calorimetry (DSC) thermal analysis results of the fabricated Sn-Ni paste and TLPS bonded joints, we confirmed that the complete reactions of Sn with Ni to form Ni-Sn intermetallic compounds (IMCs) at bonding temperatures occurred, and there is no remaining Sn in the joints after TLPS bonding. In addition, the interfacial reactions and IMC phase changes of the Sn-30Ni joints under various bonding temperatures were reported, and their mechanical shear strength were investigated. The TLPS bonded joints were mainly composed of residual Ni particles and Ni₃Sn₄ intermetallic phase. The average shear strength tended to increase with increasing bonding temperature. Our results indicated a high shear strength value of approximately 30 MPa at a bonding temperature of 270 ℃ and a bonding time of 30 min.

• Journal of the Korea Society of Computer and Information
• /
• v.26 no.8
• /
• pp.83-90
• /
• 2021

In this paper, effects on industrial accident prevention based on better safety and health environment by utilizing ergonomics expert were studied. This study was mainly based on the data from 'the survey for occupational safety and health trend' conducted by Occupational Safety and Health Research Institute. The number of industries participated in the survey was 2,084. Main results of the study were as follows; 1) Only 22.9% of the industries participated in the survey utilized ergonomics expert. The rest of the industries have never had an ergonomics expert due to the reasons such as lack of knowledge for the field of ergonomics, etc. 2) Specific activities done by the industries with ergonomics expert in order to have better safety & health were 'providing work orders'(94.8%), 'providing monitoring guidelines'(85.5%), 'providing information for dangerous work'(95.8%), 'providing safety education'(96.6%), and 'other safety management'(94.1%). 3) When the odds ratio for the levels of communication and the levels of environmental stability regarding safety & health for the different groups(with experts and without experts), it was found that the group with ergonomics experts had a significant higher ORs(2.391, 95% confidence interval(1.949-2.932) and 2.128, 95% confidence interval(1.786-2.537)) respectively than those of the industries without ergonomics expert. The results suggested that ergonomics expert has been unique in most of time in terms of his/her contributions in the field of industrial safety and health.

• Korean Journal of Labor Studies
• /
• v.23 no.2
• /
• pp.109-139
• /
• 2017

In light that solidarity movements become significant under the situation of 'labor and labor movement' crisis, our study pays attention to the fact that the Hope Bus campaigns made remarkable achievements, and aims to figure out how those campaigns were successful, by focusing on their solidarity networking. The successful operating conditions of solidarity networking in the Hope Bus campaigns are examined in three aspects - the conditions of triggering, forming, and activating. The solidarity networking of Hope Bus campaigns were mainly triggered by the injustice of layoffs by Hanjin Heavy Industry, aerial protest by Jin-sook Kim, and the tragic symbol of the protest site (Crane no. 85). The solidarity movement of Hope Bus could be formed by the mutual trust and cohesive team-building of key network brokers, their utilization and expansion of social movement networks, and massive ripple effect of SNS-mediated communication. The solidarity networking of Hope Bus was effectively activated by open and de-hierarchical operations of the central planning group, active solidarity activities of participant groups, and the provision of 'heuristic experience' for developing the sensibility to labor solidarity. The virtuous combination of those three operating conditions leads to the building of unified forces among social movements, massive civil participation, and meaningful movement outcomes, through the solidarity networking of Hope Bus campaigns.

• The Journal of Sustainable Design and Educational Environment Research
• /
• v.19 no.4
• /
• pp.26-39
• /
• 2020

This study analyzed the usage characteristics and requirements of students who are users of the middle school education space, and the following results were obtained: First, we could see that various types of classes were needed, such as lecture-style classes, team projects, and four-person consultation and discussion classes, in a way that helped to improve the desirable teaching patterns and learning ability. Second, the place where space was used during the break and the relationship between peers, revealed that most of them were in the classroom and the hallway, and the peer group was composed of three to eight people or more, that were active with various compositions. Third, a gym, library, toilet, stairway, cafeteria, nurse's office, and teachers' room appeared in the center of the building, indicating the need for a balanced layout. Fourth, physical education (dance) rooms, audiovisual rooms (performance rooms), workshops (personal creation), snack bar, rest area, spacious indoor square, and study rooms were needed as facilities that can help learning activities other than current facilities. These outcomes show that the existing classroom layout and space composition formats require some spatial restructuring.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.24 no.1
• /
• pp.57-78
• /
• 2022

The disc cutter and cutterbit, which are the most important factors to increase the excavation efficiency of TBM, are key factors in the design and construction of the cutter head. The arrangement, spacing, number, size, and material of disc cutters suitable for the ground conditions determine the success or failure of TBM construction. The disc cutter, which is a representative consumable part in TBM construction, can cause enormous disruption to the construction cost as well as the construction cost unless accurate prediction of wear and replacement cycle is accompanied. Therefore, in this study, the method of calculating the replacement cycle of the disc cutter calculated at the time of design for the slurry shield TBM field, and the depth of wear and replacement location of the disc cutter that occurred during actual construction were compared by analyzing the field data. For a quantitative comparison, weathered soil/weathered rock, soft rock, and hard rock were classified according to the ground in the section showing constant excavation data, and the trajectory of circle was different depending on the location of the disc cutter, so it was compared and analyzed.

• Composites Research
• /
• v.34 no.2
• /
• pp.77-81
• /
• 2021

Due to the high specific strength and stiffness of the composite materials, the composite materials have been extensively used in various industries. In particular, carbon fiber reinforced composites are widely used in many mechanical structures. In addition, since carbon fiber reinforced composites have anisotropic properties, to understand the fatigue behavior of composites with different fiber orientation is very important for the efficient structural design. Therefore, in this paper, the effect fiber orientation on the fatigue life of composite materials was experimentally evaluated. For this purpose, tensile and fatigue tests were performed on the off-axis specimens (0°, 10°, 30°, 45°, 60°, 90°) of the composite materials. As a result of the fatigue tests, the fatigue strength of the composites decreased significantly as the fatigue strength slightly deviated from 0 degrees. On the other hand, the more deviated, the less decreased. This is because the role of supporting the load of fibers decreased as the stacking angle increased. In addition, the fatigue behavior was analyzed by introducing a fatigue strength ratio (Ψ) that eliminates the fiber orientation dependence of the off-axis fatigue behaviors on the unidirectional composites. The off-axis fatigue S-N lines can be reduced to a single line regardless of the fiber orientation by using the fatigue strength ratio (Ψ). Using the fatigue Ψ-N line, it is possible to extract back to any off-axis fatigue S-N lines of the composites with different fiber orientations.