• Journal of the Korea Concrete Institute
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• v.23 no.4
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• pp.511-520
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• 2011

Recent studies to improve reinforcement of structures have developed stiff type Polyurea by using highly polymized compound Polyurea, but the reinforcing effect of it appears to be merely good. To find the proper usage of Polyurea as structural reinforcement, stiff type Polyurea has developed by manipulating the ratio of the components that consist flexural type Polyurea and the developed stiff type Polyurea shows higher hardness and tensile capacity. The reinforcement effect evaluation of has been performed by the polyurea applied RC slab specimens, and the reinforcement effect of the combination of fiber sheet and polyurea has been tested. The results shows that the Polyurea applied specimens have significant improvement on hardness and ductility compare to those of unreinforced. Also, the specimens that stiff type Polyurea is sprayed on fiber sheet reinforcement has higher reinforcing effect than only sheet reinforced specimens. However, the specimens that and fiber sheet attached after polyurea applied on showed that the high toughness of fiber sheet restrains the ductile behavior of Polyurea due to the high ductility, thereby the specimen suffers the concentration of load, which leads the brittle fracture behavior.

• Korean Journal of Applied Biomechanics
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• v.12 no.2
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• pp.1-16
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• 2002

The purposes of this study were to investigate the effects of strength training on the change of ground reaction force for the children with trisomy 21 Down syndrome. The subjects of this study were consisted of eight elementary school students with Down syndrome who participated in the strength training. The strength training was administered by six items such as squat, leg curl, leg extension, toe raise, sit-ups, and hyperextension. For strengthening muscle, each group also was treated by walking for 8 weeks, three times a week, 10-15RM, 3sets, which was based on the principle of progressive overload. For inquiring the effect of strength training, the ground reaction force variables were measured in two phases : before-training and 8 week-after training. The gait of each subject was acquisition using 2 AMTI force platforms set at 100 frequency. The results of this study were as follows: The pattern of vertical, antero-posterior and medio-lateral forces, trajectory of net COP and the timing ratio of reaching the each events were shown variously. So, it is not easy to explain these variables clearly. As the result of strength training, these variables were changed. However, the results of within subjects differ greatly, there was no difference statistically.

• Korean Journal of Materials Research
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• v.10 no.1
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• pp.41-48
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• 2000

In this study, microstructure and mechanical properties and electrical conductivities of in situ Cu-Fe-Xi(Xi=Ag, Cr or Co) alloy wires obtained by cold drawing combined with intermediate heat treatments have investigated. During cold working the primary and secondary dendrite arms are aligned along the drawing direction and elongated into filaments after deformation processing. The addition of Ag was found to be more effective in reducing the microstructural scale at the given draw ratio than that of Co or Cr throughout the drawing processing. The ultimate tensile strength and the conductivity of the Cu-Fe based composites containing Ag were higher than those of Cu-Fe composites containing Co or Cr. The good mechanical and electrical properties of Cu-Fe-Ag wires may be associated with the more uniform distribution of the finer filaments in the wires containing silver. The strength of Cu-Fe-Xi composites is dependent on the spacing of the Fe filaments in accord with a Hall-Petch relationship. The fracture surfaces of all the specimens showed ductile-type fracture and iron filaments occasionally observed on the fracture surfaces.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.5
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• pp.397-403
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• 2016

During the rapid economic growth in Korea since the 1970s, many underground facilities were constructed such as under passes and railways. Seismic design has been mandated in 1988, but the structures built before 1988 were not reflected on the seismic design. Accordingly, these underground structures require effective seismic reinforcing methods to ensure safety when the earthquake happens. By these reasons, in this study, using the proposed pre-flexed members, RC box structure was analyzed for seismic reinforcement of the corner. This method is based on a principle that enlarging the resistance against the external force by installing the pre-flexed member to the box structure corner. To evaluate validity, a newly developed member with CornerSafe was compared with traditional type reinforcement using experiments and finite element analysis. In finite element mode, nonlinearity of steel was modeled based on J2 plasticity model and concrete was based on CEB FIP MODEL CODE 1990. Also, composite ratios of box and pre-flexed member were computed for design application. The reinforcement and box structure were analyzed under the bond condition completely attached by the tie, and the results of experiment and finite element analysis were same in the force-displacement curve.

• Korean Journal of Clinical Laboratory Science
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• v.52 no.3
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• pp.261-270
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• 2020

This study reviewed the quality addition rate, calculation, and application criteria needed to identify the possibility of additional medical technologists in the field for new certification and professional manpower to provide a superior laboratory. The six institutions that participated in the study were the size of large hospitals with more than 1,000 beds, with an average of five full-time laboratory physicians (also called clinical pathologists) and an average of 53 medical technologists, with 10.6 per laboratory physician. An analysis of the time required for each activity category of medical technologists revealed decreasing behavior during the analysis. In contrast, the ratio of the comprehensive pre-analysis activities was high due to the strengthening of laboratory operations and quality control. During the analysis, the proportion of biochemistry tests was high, and post-analysis of most of the results was performed. Hence, improving the quality of sample testing requires significant time, and appropriate personnel are required. In conclusion, the recruitment of medical technologists is also a key component to improving the sample quality, and corresponding personnel regulations are necessary.

• The Journal of Engineering Geology
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• v.25 no.3
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• pp.357-368
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• 2015

Brittle failure of Mesozoic granite in the Daejeon region is predicted using empirical analysis and numerical modeling techniques. The input parameters selected for these techniques were based on the results of laboratory tests, including damage-controlled tests. Rock masses that were considered to be strong during laboratory testing were assigned to "group A" and those considered to be extremely strong were assigned to "group B". The properties of each group were then used in the analyses. In-situ stress measurements, or the ratio of horizontal to vertical stress (k), were also necessary for the analyses, but no such measurements have been made in the study area. Therefore, k values of 1, 2, and 3 were assumed. In the case of k=1, empirical analysis and numerical modeling show no indication of brittle failure from the surface to1000 m depth. When k=2, brittle failure of the rock mass occurs at depths below 800 m. For k=3, brittle failure occurs at depths below 600 m. Although both the Cohesion Weakening Friction Strengthening (CWFS) and Mohr-Coulomb models were used to predict brittle failure, only the CWFS model performed well in simulating the range and depth of the brittle failure zone.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.13 no.6
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• pp.556-561
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• 2020

The aging and declining agricultural population in the modern society requires improvement of the agricultural environment and is one of the representative problems. And since most of the work systems always require a transport work, the ratio of labor consumed in the transport work is very high. Accordingly, many types of transport vehicles are being developed and sold, and in the early days, most of them are powered transport vehicles using fossil fuels. However, it is paying attention to next-generation eco-friendly energy such as hydrogen, fuel cells, solar power, and bio due to the strengthening of international environmental regulations such as global warming and the Convention on Climate Change and the depletion of fossil fuels. Therefore, in this study, the ultimate goal is to develop an eco-friendly, easy-to-operate, safe agricultural electric vehicle that replaces fossil fuels. It was designed with a focus on controlling a wide range of vehicle speeds and securing stability of electric agricultural vehicles. Considering the performance and design, it is composed of a frame, a driving part, a steering part, and a controller system, and we are going to review and manufacture each part. It is believed that the manufactured electric vehicle for agriculture can be easily and conveniently operated in an agricultural society where young manpower is scarce, and can be helpful to the agricultural society through high efficiency.

• Ecology and Resilient Infrastructure
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• v.5 no.3
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• pp.180-188
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• 2018

Biopolymer based on microbial ${\beta}$-glucan and xanthan gum is a rising geotechnical material that can enhance the cohesion between soil particles and consequently reduce soil erosion. Recently, biopolymer is proposed to utilize for the riverbank strengthening. As an effort of the ecological assessment of biopolymer application in civil engineering, this study examined the effects of biopolymer on seed germination and growth of nine plant species inhabiting in the Korean riverside. Responses of above-ground growth to the biopolymer differed among plant species. One species grew less but others maintained their growth when plants were grown in the soil with biopolymer. In contrast, root grew more vigorously and root/shoot ratio decreased in the biopolymer across testing plant species. These results indicate that biopolymer application on the river bank likely stimulate root growth of native plant species, which, in turn, possibly reinforces riverbank. Species specific responses of above-ground growth implies that ecological effects of biopolymer application would depend on the species composition of the ecosystem.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.888-895
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• 2020

In the construction industry, off-site construction (OSC) is drawing attention as a production method due to changes in working hours and the supply and demand of manpower. In 1991, there was a policy of spreading and expanding the use of precast concrete (PC) apartment homes, but they have not been actively used so far since they were discontinued due to quality problems. In this study, policy tasks were analyzed to motivate the application of OSC-based PCs in the apartment housing sector, and policy directions were derived by conducting focus group interviews (FGI). Nine policies are suggested regarding the following topics: PC apartment supply quantity provision, priority application of public housing, priority supply of public housing, preferential floor area ratio, funding, tax support, improvement of business area structure, improvement of delivery method, factory certification system, and training of experts. The results of the FGIs are as follows. First, in order to revitalize PC apartment homes, leading efforts from the public sector are required. Second, rather than reorganizing the business sector or introducing a new delivery method, a policy direction that induces the strengthening of cooperation is desirable. Third, PC activation should be promoted on an institutional basis for securing appropriate construction costs and quality.

• Journal of the Korea Concrete Institute
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• v.28 no.3
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• pp.289-298
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• 2016

An experimental research was performed using fibers for the purpose of retrofitting existing reinforced concrete circular columns. Glass fiber (GF) and polyethylene terephthalate (PET) were used as well as combined GF+PET (HF). PET has high tensile strength (over 600 MPa) and high ductility (about 15%), but has very low elastic modulus (about 1/6 of GF). A total of four columns was tested against laterally applied reverse cyclic load: control column, GF-, PET-, and HF-strengthened columns. All columns retrofitted using fibers demonstrated improved moment capacity and ductility. Moment capacity of GF-, PET-, and HF-strengthened columns was 120%, 107%, and 120% of the control column, respectively. Drift ratio of all retrofitted columns also increased by 63 ~ 83% over the control column. The final failure mode of the control column was main bar buckling. The final failure mode of the GF- and HF-strengthened columns was GF rupture while that of the PET-strengthened column was main bar rupture in tension. No damage was observed for PET at the ultimate stage due to excellent strain capacity intrinsic to PET. Current test results indicate that PET can be effectively used for seismic retrofit of RC columns. It is noted that the durability characteristics of PET needs to be investigated in the future.