• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.705-712
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• 2009

HPFRCCs (high-performance fiber reinforced cementitious composites), which is relatively more ductile and has the characteristic of high toughness with high fiber volume fractions, can be used in structures subjected to extreme loads and exposed to durability problems. In the case of PVA (polyvinyl alcohol) fiber, it is noted by former studies that around 2% fiber volume fractions contributes to the most effective performance at HPFRCCs. In this study, flexural tests were carried out to evaluate the flexural behavior of HPFRCCs and to optimize mix proportions. Two sets of hybrid fiber reinforced high performance specimens with total fiber volume fraction of 2 % were tested: the first set prepared by addition of short and long PVA fibers at different combination of fiber volume fractions, and the second set by addition of steel. In addition, in order to assess the performances of the HPFRCCs against to high strain rates, drop weight tests were conducted. Lastly, the sprayed FRP was applied on the bottom surface of specimens to compare their impact responses with non-reinforcing specimens. The experimental results showed that the specimen prepared with 1.6% short fibers (REC 15) and 0.4% long fiber (RF4000) outperformed the other specimens under flexure, and impact loading.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.12
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• pp.697-704
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• 2017

High-Performance Fiber-Reinforced Cement Composites (HPFRCC) has outstanding durability, and has attracted interest because of its ductility and development of strength, which allows a reduction of the self-weight of a structural member by substantially decreasing the cross section. Therefore, the present study aimed to improve the economic efficiency of HPFRCC by examining experimentally the flexural performance considering various characteristics of the steel fiber. To find an efficient fiber reinforcement method, the flexural performance was evaluated for different shapes, aspect ratios, and volume ratios of the steel fiber. Straight, hooked, and twisted fiber configurations were considered by adopting a fiber length longer than the usual 13 mm. The test results showed that HPFRCC reinforced by 19.5 nun-long straight fibers with a volume fraction of 1.5% shows better flexural performance than that reinforced by 13 mm-long straight fibers with a volume fraction of 2.0%. Consequently, HPFRCC with enhanced economic efficiency can be produced by adopting a reduced amount of steel fiber.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.161-169
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• 2011

Two-way slabs reinforced with high-performance steels, which have several practical advantages of a reduction of congestion in heavily reinforced members, savings in the cost of labor and repair, the higher corrosion resistance, and a reduction of construction time, were constructed and tested. The influences of the flexural reinforcement ratio, concentrating the reinforcement in the immediate column region, and using steel fiber-reinforced concrete (SFRC) in the slab on the punching shear resistance and post-cracking stiffness were investigated, and compared with the punching shear test results of the slabs reinforced with conventional steels and GFRP bars. In addition, the strain distribution of flexural reinforcements and crack control were investigated, and the effective width calculating method for the average flexural reinforcement ratio was estimated. The use of high-performance steel reinforcement increased the punching shear strength of slabs, and decreased the amount of flexural reinforcements. The concentrating the top mat of flexural reinforcement increased the post-cracking stiffness, and showed better strain distribution and crack control. In addition, the use of SFRC showed beneficial effects on the punching shear strength and crack control. It was suggest that the effective width should be changed to larger than 2 times the slab thickness from the column faces.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.543-550
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• 2005

In the present work, modulus of rupture (MOR), flexural toughness properties $(I_{30}\;and\;W_{2.0})$ and workability (slump) of high performance hybrid fiber reinforced concrete (HPHFRC) mixed with micro-fiber (carbon fiber) and macro-fiber (steel fiber), and replaced with a fine mineral admixture such as silica fume (SF) are characterized through the analysis of variance (ANOVA). Data of MOR, $I_{30}(or W_{2.0})$ and slump are used as the characteristic values to estimate flexural performance and workable property of HPHFRC. Specially, an experimental design was Planned according to the fractional orthogoanl nay method to reduce experimental number of times. The experimental results show that steel fiber is a considerable significant factor in MOR and I30 $(W_{2.0})$. Based on the significance of experimental factors about each characteristic factors, the following evaluation can be used: Experiment factors which reduce slump most remarkably are carbon fiber, steel fiber, silica fume order.; Those that improve MOR most significantly are silica fume $({\fallingdotseq}\;carbon\;fiber)$, steel fiber order; Those that increase flexural toughness most distinctly are silica fume, carbon fiber, steel fiber order. It is obtained that the combination of steel fiber $1.0\%$, carbon fiber $0.25\%$ and silica fume $5.0\%$ is the experimental condition that improve MOR and flexural toughness excellently with workability ensured within the experiment.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.395-403
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• 2006

Recently constructed bridges often have long spans and simple structure details considering not only the function but other important factors such as aesthetics, maintenance, construction duration and life cycle cost. Therefore, bridges require high-performance steels like extra-thick plate steels and thermo-mechanical control process (TMCP) steels. TMCP stels are now gaining wide attention due to their weldability improved strength and toughness. Recently, SM570-TMC steel, which is a high-strength TMCP steel with a tensile strength of 600 MPa, has been developed and applied to steel structures. However, using this steel in building steel structures requires the elucidation of not only material characteristics but also the mechanical characteristic of welded joints. In this study, high-temperature tensile properties of SM570-TMC steel were investigated through the elevated temperature welded joints of SM570-TMC steel were studied through the three-dimensional thermal elasticplastic analyses on the basis of mechanical properties at high temperatures obtained from the experiment.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.625-627
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• 2002

워크스테이션 네트워크 (NOW: Network of Workstations)은 고성능의 병렬 연산을 위한 중요하고 효과적인 기반환경을 제공하고 있다. NOW 환경에서 통신과 동기화 비용은 다중프로세서 시스템보다 상대적으로 매우 크다. NOW에서 병렬 태스크와 통신을 위한 스케줄링 기법의 선택은 시스템의 활용도와 성능에 큰 영향을 미치므로 효과적으로 스케줄링 알고리즘에 대한 연구가 필요하다. 본 논문에서는 버스 기반의 NOW에서 병렬 태스크를 위한 스케줄링 알고리즘을 제안하고, 시뮬레이션을 통하여 통신비용의 변화에 따른 시스템의 성능을 비교한다. 알고리즘은 태스크 중복을 기반으로 하며 통신에 따른 스케줄링 길이를 줄이기 위하여 휴리스틱을 사용한다.

• Proceedings of the Korea Concrete Institute Conference
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• 2009.05a
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• pp.489-490
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• 2009

In this study, the experiment was carried out to investigate the effect of metakaolin on the compressive strength of lightweight aggregate cellular concrete. For this purpose, five level replacement ratio of metakaolin were selected.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.10a
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• pp.103-106
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• 2003

In this work the novel potential epoxy resins, were synthesized and acrylated. Their structures were confirmed by means of FTIR, $^1H NMR, and^{13}/C NMR$ spectroscopies. Also, we were to note the effect of W curing on functional group changes of VE/UP blend system after UV curing.

• Proceedings of the Korean Fiber Society Conference
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• 1998.10a
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• pp.512-516
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• 1998

탄소재료는 높은 전기전도도 및 기계적 강도, 화학적 안정성, 큰 비표면적(1000~3000$m^2$/g) 등의 특성 때문에 연료전지, 리튬이온 이차전지, 전기 이중층 캐패시터(electric double layer capacitor, EDLC).의 전극 활물질로 주목받고 있다[1]. 탄소섬유는 보통 특성과 전구체 핏치에 따라서 두 가지 종류로 분류된다[2]. 하나는 메조페이스 핏치로부터 제조된 고성능 탄소섬유(HPCF)이다. (중략)

• The Science & Technology
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• v.30 no.9 s.340
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• pp.50-51
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• 1997

"사양기를 맞은 우리 섬유, 그러나 산ㆍ학ㆍ연이 손잡고 노력하면 높은 부가가치를 창출해내는 경쟁력있는 산업으로 키워나갈 수 있습니다." 고성능 섬유재료개발과 섬유복합소재연구에 심혈을 기울이고 있는 서울대 공대 강태진교수는 말한다. 서울대와 동대학원을 나와 미국 노스캐롤라이나 주립대학에서 박사학위를 받은 강교수는 우리나라의 섬유산업을 밝게 진단하고 있다.