This article aims to examine the behavior of Unplasticized Poly-Vinyl-Chloride(UPVC)bounded reinforced columns with polypropylene fibers under axial compression.To develop this model,samples of concrete filled UPVC pi...This article aims to examine the behavior of Unplasticized Poly-Vinyl-Chloride(UPVC)bounded reinforced columns with polypropylene fibers under axial compression.To develop this model,samples of concrete filled UPVC pipe(CFUT)with different geometric properties were tested.To obtain the specimens different class pipes with three different diameters were used to investigate the sensitivity of these columns to various parameters.The effect of each variable on the ultimate strength,ductility and confinement efficiency of the samples was investigated.All specimens were compressed by applying load only to the concrete core to obtain the load-displacement variations and the corresponding deformation mode.A finite element model was developed using the proposed stress-strain variation of confined concrete with UPVC tubes to simulate axial compression of CFUT specimens.According to the results obtained,the effect of the change in diameter-thickness ratio failure stress of concrete limited by(D/t)is obtained and discussed with empirical relationship.Polypropylene fibers were found to slightly increase column strength up to a certain volume fraction,after which the strength generally experienced a decrease.展开更多
Because of the three-dimensional structure of bone or hard tissue such as a tooth, a scaffold is necessary for its regeneration by cellular engineering. Commonly, for in vivo examination, hydroxyapatite (HA) has been ...Because of the three-dimensional structure of bone or hard tissue such as a tooth, a scaffold is necessary for its regeneration by cellular engineering. Commonly, for in vivo examination, hydroxyapatite (HA) has been used as such a scaffold. Cylindrical HA with a hollow center, which included a columnar formalin-treated polyvinyl alcohol sponge, was used in this examination as a scaffold. The sponge had been coated with L-tryptophan or L-lysine before insertion into the hollow center of the HA. Rat bone marrow cells (rBMCs) derived from the femur were seeded in the sponge before insertion into the hollow center of HA. The number of rBMCs seeded in each sponge was 1.5 × 106. These scaffolds were implanted subcutaneously into the backs of Fischer 344 rats for 6 weeks. In the amino-acid-coated sponge in HA, osteogenesis was found histologically. An osteocalcin level of approximately 10 ug was measured in the scaffolds with L-tryptophan-coated formalized poly-vinyl alcohol sponge containing rBMCs, 4 ug on average in the scaffolds with L-lysine-coated sponge containing the cells and about 2 ug in each scaffold with uncoated sponge containing the cells. The structure of the scaffolds used in this study was thought to be suitable for osteogenesis by rBMCs. It was concluded that tryptophan, as a factor for bone formation by stem cells, functioned by promoting cell adhesion and the differentiation of stem cells into osteoblasts.展开更多
基金the Head of the Civil Engineering Department,Faculty of Engineering and Technology,Jamia Millia Islamia,New Delhi-110025,India.
文摘This article aims to examine the behavior of Unplasticized Poly-Vinyl-Chloride(UPVC)bounded reinforced columns with polypropylene fibers under axial compression.To develop this model,samples of concrete filled UPVC pipe(CFUT)with different geometric properties were tested.To obtain the specimens different class pipes with three different diameters were used to investigate the sensitivity of these columns to various parameters.The effect of each variable on the ultimate strength,ductility and confinement efficiency of the samples was investigated.All specimens were compressed by applying load only to the concrete core to obtain the load-displacement variations and the corresponding deformation mode.A finite element model was developed using the proposed stress-strain variation of confined concrete with UPVC tubes to simulate axial compression of CFUT specimens.According to the results obtained,the effect of the change in diameter-thickness ratio failure stress of concrete limited by(D/t)is obtained and discussed with empirical relationship.Polypropylene fibers were found to slightly increase column strength up to a certain volume fraction,after which the strength generally experienced a decrease.
文摘Because of the three-dimensional structure of bone or hard tissue such as a tooth, a scaffold is necessary for its regeneration by cellular engineering. Commonly, for in vivo examination, hydroxyapatite (HA) has been used as such a scaffold. Cylindrical HA with a hollow center, which included a columnar formalin-treated polyvinyl alcohol sponge, was used in this examination as a scaffold. The sponge had been coated with L-tryptophan or L-lysine before insertion into the hollow center of the HA. Rat bone marrow cells (rBMCs) derived from the femur were seeded in the sponge before insertion into the hollow center of HA. The number of rBMCs seeded in each sponge was 1.5 × 106. These scaffolds were implanted subcutaneously into the backs of Fischer 344 rats for 6 weeks. In the amino-acid-coated sponge in HA, osteogenesis was found histologically. An osteocalcin level of approximately 10 ug was measured in the scaffolds with L-tryptophan-coated formalized poly-vinyl alcohol sponge containing rBMCs, 4 ug on average in the scaffolds with L-lysine-coated sponge containing the cells and about 2 ug in each scaffold with uncoated sponge containing the cells. The structure of the scaffolds used in this study was thought to be suitable for osteogenesis by rBMCs. It was concluded that tryptophan, as a factor for bone formation by stem cells, functioned by promoting cell adhesion and the differentiation of stem cells into osteoblasts.
