• Journal of the Korea Concrete Institute
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• v.19 no.3
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• pp.253-263
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• 2007

Previous researches showed that confined concrete with Fiber-Reinforced Plastic (FRP) sheets significantly improves the strength and ductility of concrete compared with unconfined concrete. However, the retrofit design of concrete with FRP materials requires an accurate estimate of the performance enhancement due to the confinement mechanism. The object of this research is to predict the compressive strength and strain of concrete confined with FRP wraps. For the purpose of this research, 102 test specimens were fabricated and loaded statically under uniaxial compression. Axial load, axial and lateral strains were investigated to predict the ultimate stress and strain. Also, to achieve reliability of proposed strength and strain models for FRP-confined concrete, another series of uniaxial compression test results were used. This paper presents strength and strain models for FRP-confined concrete. The proposed models to estimate the ultimate stresses and failure strains produce satisfactory predictions as compared to current design equations. In conclusion, it is proposed that the modified stress-strain model of concrete cylinders could be effectively used for the repair and retrofit of concrete columns.

• Journal of the Korea Concrete Institute
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• v.29 no.1
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• pp.77-84
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• 2017

In this study, the structural performance of high strength concrete (HSC) column-normal strength concrete (NSC) slab connection was investigated according to confinement effects, aspect ratio (h/c) and strength ratio ($f^{\prime}_{cc}/f_{cs}$). The study was conducted by using finite element analysis. To verify the analysis methods, the experiments and analyses results were compared. The specimens were classified by connection types including interior column, edge column, corner column and isolated column. As a result, ultimate strength of interior column was larger than other specimens. Also, the axial stresses of connection were decreased when the aspect ratio was increased. As the strength ratio between column and slab was increased, the ultimate strength of specimens was also increased until the strength ratio was reached to 1.83.

• Journal of the Korean GEO-environmental Society
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• v.13 no.8
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• pp.45-55
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• 2012

This study is about the application of waste stone sludge as fill material. Waste stone sludge, weathered granite soil, and the mixture of the former and the latter strengthened with staple fiber are experimentally analyzed for measuring strength property. When staple fiber was mixed with waste stone sludge, weathered granite soil, and the mixture, there was a nearly linear relationship between the amount of the staple fiber and the increasing ratio of unconfined compressive strength. The increasing ratio of unconfined compressive strength was the largest in weathered granite soil. The increasing ratio of unconfined compressive strength of the mixture was similar to that of waste stone sludge. In the case of the mixture of weathered granite soil and waste stone sludge, an internal friction angle tended to increases rely on increasement of staple fiber content, whereas the change of cohesion was small. An internal friction angle was increased by 21 percent when staple fiber content is 0.75 percent. Comparing with weathered granite soil or waste stone sludge, strength parameters of the mixture were increased relatively. Thus strengthening effect of staple fiber in the mixture is expected.

• Journal of the Korean Ceramic Society
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• v.36 no.8
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• pp.829-834
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• 1999

The silica aerogels opacified via adding oxides were prepared by the sol-gel supercritical drying technique and their characteristics of mechanical strength and thermal conduction were investigated. The compressive strength of SiO2-10 mol% TiO2 and SiO2-10mol% Fe2O3 aerogels were 0.11 and 0.047 MP a respectively much higher than 0.025 MPa of pure silica aerogels. The thermal conductivity of silica aerogels opacified by TiO2 was as low as 0.02505 W/m${\cdot}$K at $400^{\circ}C$ It was found that the TiO2 -opacifier for improving mechanical strength and suppressing high temperature conduction of pure silica aerogels was more effective than the Fe2O3 -opacifier

• Journal of the Korea Institute of Building Construction
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• v.23 no.6
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• pp.727-738
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• 2023

In concrete, the interface between the aggregate and cement paste is often the most critical factor in determining strength, representing the weakest zone. Lightweight aggregate, produced through expansion and firing of raw materials, features numerous surface pores and benefits from low density; however, its overall aggregate strength is compromised. Within concrete, diminished aggregate strength can lead to aggregate fracture. When applying lightweight aggregate to concrete, the interface strength becomes critical due to the potential for aggregate fracture. This study involved coating the surface of the aggregate with blast furnace slag fine powder to enhance the interfacial strength of lightweight aggregate. The impedance of test specimens was measured to analyze interface changes resulting from this surface modification. Experimental results revealed a 4% increase in compressive strength following the coating of the lightweight aggregate surface, accompanied by an increase in resistance values within the impedance measurements corresponding with strength enhancement.

• Korean Journal of Childcare and Education
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• v.11 no.4
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• pp.167-187
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• 2015

The purpose of this study was to purpose fundamental data which can be used for the development of a flourish competency enhancement program for infant teachers. The methods of the questionnaire study were performed on 213 infant teachers. The results are as follows. First, as a result of investigating their awareness of a flourish competency, many of the infant teachers replied that they were aware of it to a certain extent. The differences of institution type were statistically significant. Second, as a results of looking for any possible difference in the teacher's background variables in needs for the development of an enhancement program for flourish competency, there weren't significant differences in opinions on the needs of the program, effects of the program, purpose of the program, execution cycle, methods of the program training, intention of involvement. But needs of flourish competency existed of significant differences in institution type and execution time and program operator existed of significant differences in institution type and career. This study is hope to suggest some of the development directions of a flourish competency enhancement program for infant teachers.

• Korean Journal of Health Education and Promotion
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• v.27 no.5
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• pp.73-78
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• 2010

Background: Although collaboration for community health is emphasized, the concept and process of collaboration are rather unclear. International research has classified the types of collaboration and focused on the factors influencing successful collaboration. Greater attention is needed for collaboration practice and research domestically. Findings: By the level of intensity, the types of collaboration range from simpler networking to more formal and sophisticated collaboration. A 4-stage collaboration development consists of formation, implementation, maintenance, and institutionalization stages. Influential factors for collaboration development include: shared goals; operational structure and process; sufficient resources; member and leadership characteristics; environment and climate for collaboration; and information exchange and communication. Discussion: Most of collaboration research so far has dealt with partnerships and coalition building with community-based organizations, and much attention is given to private-public partnership for health. Contextual understanding and collaborative environment are the foremost tasks for us to enhance collaboration for community health in our centralized public health system.

• Journal of Digital Convergence
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• v.12 no.11
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• pp.487-497
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• 2014

This study was to examine the effect of the Self-efficacy Promotion Exercise Program to the elderly hypertensive with Stage 1. This research was the quasi-experimental study. The Self-efficacy Promotion Exercise Program combined to Aerobic exercise which is incrementally at a level of 40~60% HRmax and the source of the Self-efficacy Promotion Exercise. This research was carried out to experimental(33 patients) and control(32 patients), 60 minutes per day, 3 times a week for 12 weeks. The Self-efficacy Promotion Program was effect on enhancing the general(p<.001) and exercise self-efficacy(p<.001), the self-care behaviors(p<.001) and decreasing the systolic blood pressure(p<.001) to the elderly hypertensives. The 12 weeks Self-efficacy Promotion Exercise Program will be considering to useful for various care settings to the elderly hypertensives.

• Applied Chemistry for Engineering
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• v.16 no.2
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• pp.262-266
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• 2005

We compared the effects of a representative aliphatic acid amplifier, 4-hydroxy-4'-p-tosyloxy isopropylidene dicyclohexane, doped in poly[tert-butyl methacrylate] (pTBMA), poly[tetrahydropyranyl methacrylate] (pTHPMA) or poly[tert-butoxycarbonyloxystyrene] (pTBOCST) resin film as acid labile polymer in view of thermal stability and photosensitivity enhancement. The acid amplifier was stable up to 20 min in pTBMA and pTBOCST film and up to 5 min in pTHPMA film at $120^{\circ}C$. pTBMA and pTHPMA films doped with the acid amplifier showed four times and two times higher photosensitivity, respectively. But pTBOCST showed negligible photosensitivity enhancement. Photosensitivity enhancement and thermal stability were found to be affected by the resin.

• Journal of the Korean Society of Hazard Mitigation
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• v.9 no.4
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• pp.11-20
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• 2009

By using the artificial lightweight aggregate for the natural aggregate depletes and destruction of environment and the application of lightweight concrete in structure, the lightweight concrete is manufactured. The fundamental characteristics by the waterbinder ratio was evaluated. It is suggested the method to control of pre-absorbed water of the lightweight aggregate. Lightweight concrete with pre-absorbed aggregate has similar characteristics compared to normal weight concrete regardless of water-binder ratio. According to the water-binder ratio, the drying condition, and the rebar, the unit mass of the lightweight concrete showed the reduction of 14.6${\sim}$21.0% as the range of 1,668${\sim}$1,998 $kg/m^3$ in comparison to the normal weight concrete. The lightweight aggregate pre-absorbed water showed the deferent evaporation quantity according to the water-binder ratio. As the water-binder ratio is lower, the oven dry vapour water is larger, therefore the internal curing water is increasing. In the same water-binder, comparing the normal concrete the lightweight concrete shows lower compressive strength which is due to the different strength of an aggregate. In the air dry curing, the normal weight concrete has a lower strength improvement effect in w/c 0.3 than the ratio 0.4 and 0.5. However, the strength improvement effect has increasing as the water-binder ratio was low in the light concrete.