• 대한기계학회논문집A
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• 제31권3호
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• pp.295-303
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• 2007

Degradation behaviors of filament-winded composites have been evaluated under the accelerated environmental test of high temperature, water immersion and thermal impact conditions. Two kinds of laminated composites coated by an urethane resin have been used: carbon-fiber reinforced epoxy(T700/Epon-826, CFRP) and glass-fiber reinforced phenolic (E-glass/phenolic, GFRP). For tensile strength of $0^{\circ}$ composites, CFRP showed little degradation while GFRP did high reduction by 25% under the influence of high temperature and water However for water-immersed $90^{\circ}$ composites tensile strength of both CFRP and GFRP showed high reduction. Bending strength and modulus of $90^{\circ}$ composites were largely reduced in water-immersion as well as high temperature environment. Urethane coating on the composite surface improved the bending properties by 20%, however hardly showed such improvement for water-immersed $90^{\circ}$ composites. In case of shear strength and modulus, both CFRP and GFRP showed high reduction by water-Immersion test but did a slight increase by high temperature and thermal impact conditions.

• 한국운동역학회지
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• 제23권2호
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• pp.149-157
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• 2013

In the present study, we aimed to elucidate how muscle strength and activity are affected by movement pattern(bilateral [BLM] & unilateral movement [ULM]) and movement velocity($0^{\circ}$/s, $60^{\circ}$/s, $120^{\circ}$/s) at maximum effort, and to elucidate the relationship between a left/right asymmetry and bilateral deficit. A total of 18 healthy males participated in the study. Each participant performed maximum knee extension bilaterally and unilaterally while the EMG and moment were recorded, and then the relationships between the asymmetry and bilateral deficit were analyzed. The peak moments for the isokinetic motion at $60^{\circ}$/s and $120^{\circ}$/s and overall muscle activities of lower extremity were significantly reduced for the BLM in comparison to the ULM. And though the asymmetry in ULM were maintained during BLM at all velocities, the bilateral deficits at the velocity of $0^{\circ}\acute{y}$/s and $120^{\circ}\acute{y}$/s were significantly correlated with increased asymmetries of muscle strength in ULM. In conclusion, the reduction in the muscle strength exhibited in bilateral knee extension was shown to arise partially from a reduction in muscle activity, and left/right asymmetry was found to be associated with mechanical reduction in bilateral movement. These findings suggest that training aimed at increasing muscle strength must involve methods and strategies intended to reduce left/right asymmetry.

• 대한조선학회논문집
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• 제54권4호
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• pp.352-359
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• 2017

Because the Energy Efficiency Design Index(EEDI) came into effect in 2013, it is necessary to develop a new technology to overcome $CO_2$ emission regulations. In structural design viewpoint, lots of researches are carried out to develop eco-friendly and high fuel efficiency ships by weight reduction. By using the automated compartment arrangement system and automated structural design algorithm which were developed by the authors, new researches are performing to combine the above two systems. However, the effect of weight reduction was not significant because structural designs by using these systems for the midship part was carried out only focused on the minimum still water bending moment. In this paper, at first, good compartment arrangements which give the minimum still water bending moment and(or) shear force were chosen by using the automated compartment system. And then, influence of shear force on weight reduction was investigated by using the automated structural design algorithm considering longitudinal strength, local strength and shear strength of longitudinal members in cargo holds. Conclusively, it is necessary to consider the minimum still water bending moment and shear force simultaneously to reduce the weight of mid-sized bulk carrier. Also, good compartment arrangement which gives much more weight reduction compared with existing ship was proposed.

• 구강회복응용과학지
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• 제20권1호
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• pp.19-29
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• 2004

The purpose of this study was to compare the fracture strength of the IPS Empress ceramic crown according to the incisal reduction(2.0mm, 2.5mm, 3.0mm) and axial inclination ($4^{\circ}$, $8^{\circ}$, $12^{\circ}$) of the lower canine. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and each crown was cemented on each metal die with resin cement. The cemented crowns mounted on the testing jig were inclined 30 degrees and a universal testing machine was used to measure the fracture strength. The results of this study were as follows : 1. The fracture strength of the ceramic crown with 3.0mm depth and $12^{\circ}$ inclination was the highest(1377N). Crowns of 2.0mm depth and $4^{\circ}$ inclination had the lowest strength (731 N). 2. There were no significant differences of the fracture strength by axial inclination in same incisal reduction group. 3. The fracture mode of the crowns was similar. Most of fracture lines began at the loading area and extended through proximal surface perpendicular to the margin irrespective of incisal reduction.

• 지질공학
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• 제27권1호
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• pp.31-40
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• 2017

한계평형법에 의한 비탈면 안정성 해석은 활동면을 반복적인 해석 후 임계면을 설정하여 해석을 수행하고, 지반이 균질한 경우에만 적용이 가능하며, 안전율만 산정 할 수 있는 단점이 있다. 그러나 강도감소법을 적용한 해석에서는 수행자가 여러 가지 측면에 대해서 판단하고, 안전율을 산정 할 수 있는 장점 등이 있다. 본 연구에서는 동일한 크기의 비탈면을 대상으로 한계평형해석과 강도감소법을 활용하여 경사도 변화에 따른 두 해석법 간의 안전율 변화 양상과 점착력과 내부마찰각의 변화에 따른 안전율 변화 추이를 비교 분석하였다. 각각의 해석법에 따른 안정해석 분석 결과 지반내 응력, 변위와 변형률 등을 종합적으로 검토할 수 있는 강도감소법이 활용도가 높을 것으로 판단된다.

• Geomechanics and Engineering
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• 제17권1호
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• pp.81-95
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• 2019

Due to the importance of soil reinforcement using geotextiles in geotechnical engineering, study and investigation into long-term performance, design life and survivability of geotextiles, especially due to installation damage are necessary and will affect their economy. During installation, spreading and compaction of backfill materials, geotextiles may encounter severe stresses which can be higher than they will experience in-service. This paper aims to investigate the installation damage of geotextiles, in order to obtain a good approach to the estimation of the material's strength reduction factor. A series of full-scale tests were conducted to simulate the installation process. The study includes four deliberately poorly-graded backfill materials, two kinds of subgrades with different CBR values, three nonwoven needle-punched geotextiles of classes 1, 2 and 3 (according to AASHTO M288-08) and two different relative densities for the backfill materials. Also, to determine how well or how poorly the geotextiles tolerated the imposed construction stresses, grab tensile tests and visual inspections were carried out on geotextile specimens (before and after installation). Visual inspections of the geotextiles revealed sedimentation of fine-grained particles in all specimens and local stretching of geotextiles by larger soil particles which exerted some damage. A regression model is proposed to reliably predict the installation damage reduction factor. The results, obtained by grab tensile tests and via the proposed models, indicated that the strength reduction factor due to installation damage was reduced as the median grain size and relative density of the backfill decreases, stress transferred to the geotextiles' level decreases and as the as-received grab tensile strength of geotextile and the subgrades' CBR value increase.

• 한국염색가공학회지
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• 제33권4호
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• pp.191-201
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• 2021

In this study, an eco-friendly indigo reduction system(scale up reduction, use of buffer solution, and pH control) using baker's yeast(Saccharomyces cerevisiae) was applied for natural indigo(Polygonum tinctorium) dyeing of Hanji fabric and Hanji-mixture fabric(Hanji/Cotton, Hanji/Silk). The effect of concentration of baker's yeast, repeat dyeing, and bath reuse was investigated in terms of dye uptake indicating reduction power. And the oxidation-reduction potential(ORP) was monitored. We also evaluated color properties and colorfastness according to the color strength. The yeast concentration did not significantly affect the maximum reduction power. However, the highest yeast concentration was effective in improving the initial dye uptake, and its the reduction retention power was the most excellent. Even on the last reduction day, the effect of increasing the dye uptake by repeat dyeing was observed. And it was confirmed that the reduction bath could be reused for up to 30 days by supplementing yeast at the end of reduction. For all the fabrics used, deeper and darker PB color were obtained by repeat dyeing. As dyeing was repeated, purplish tint got stronger on the Hanji/Silk fabric compared to other fabrics. Regardless of the composition of Hanji fabrics and color strength, washing and dry cleaning fastness were relatively good with above rating 4-5, and fastness to rubbing and light were acceptable with a rating 3-4 ~ 4-5. The eco-friendly natural indigo dyeing process using niram and baker's yeast would offer global marketability and diversity of Hanji product as a sustainable high value-added material.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문 발표회
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• pp.69-72
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• 2003

This study is intended to investigate the fundamental properties of concrete which AE water reducing agent for reduction of bleeding is used, and the properties of bleeding reduction. According to the results, when the adding ratio of AE water reducing agent for reduction of bleeding increases, a range of normal fluidity and aimed air content arc satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 60 min. When, AE water reducing agent for reduction of bleeding is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for reduction of bleeding. Synthetically, it proves that AE water reducing agent for reduction of bleeding satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.69-72
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• 2003

This study is intended to investigate the fundamental properties of concrete which AE water reducing agent for reduction of bleeding is used, and the properties of bleeding reduction. According to the results, when the adding ratio of AE water reducing agent for reduction of bleeding increases, a range of normal fluidity and aimed air content are satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 60 min. When. AE water reducing agent for reduction of bleeding is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for reduction of bleeding. Synthetically, it proves that AE water reducing agent for reduction of bleeding satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.

• 한국건축시공학회지
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• 제4권1호
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• pp.133-140
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• 2004

This study is intended to investigate the properties of bleeding reduction of concrete using AE water reducing agent for the type of bleeding reduction with the replacement admixture. According to the results, when the adding ratio of AE water reducing agent for the type of bleeding reduction increases, a range of normal fluidity and aimed air content are satisfied, setting time is faster than that of normal AE water reducing agent. And bleeding amount decreases, bleeding speed is highest between 60 and 90 min, and sinking depth increases drastically in 50 min. When AE oater reducing agent for the type of bleeding reduction is added, compressive strength shows a slight variation by air content, but there is not a large influence by addition of AE water reducing agent for the type of bleeding reduction. Synthetically, it proves that AE water reducing agent for the type of bleeding reduction satisfies aimed air content in the range of normal slump and can reduce only bleeding without quality variation of compressive strength.