• Composites Research
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• v.12 no.2
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• pp.70-81
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• 1999

Resin transfer molding(RTM) as a composite manufacturing process is currently of great interest in the aerospace industry requiring high performance composite parts. In this study, an analysis of mold filling in the RTM process was carried out by numerical simulation using finite element/control volume technique. Experimental work for the visualization of resin flow through fibrous preform was also conducted in order to quantitatively measure the permeabilities of the fiber mats and to evaluate the validity of the developed numerical code. The different types of fiber mats and silicon oils were selected as reinforcements and resin materials, respectively. The effects of fibrous preform structure, mold geometry, and preplaced insert on the flow front patterns during mold filling were examined by integrating the model predictions and experimental results. The flow fronts predicted by numerical simulation were in good agreement with those observed experimentally. However, according to the regions of the mold, some deviations between predicted and observed flow fronts could be found because of non-uniform fiber volume fraction. Weldline locations for the resin flow through round insert preplaced in the mold could be qualitatively deduced based on predicted flow fronts.

• Korean Journal of Materials Research
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• v.15 no.3
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• pp.177-182
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• 2005

Large amounts of the waste SiC sludge containing small amounts of Si and organic lubricant were produced during the wire cutting process of the single silicon crystal ingots. The waste SiC sludge was purified by the washing process and the purified SiC powders were used to fabricate continuously porous $SiC-Si_3N_4$ composites using a fibrous monolithic process, in which carbon, $6wt\%\;Y_2O_3-2\;wt\%\;A1_2O_3$ and ethylene vinyl acetate were added as a pore-forming agent, sintering additives, and binder, respectively. In the burning-out process, carbon was fully removed and continuously porous $SiC-Si_3N_4$ composites were successfully fabricated. The green bodies containing SiC, Si particles and sintering additives were nitrided at $1410^{\circ}C$ in a flowing $N_2+10\%\;H_2$ gas mixture. Continuously porous composites were combined with SiC, ${\alpha}Si_3N_4,\;\beta-Si_3N_4$ and a few $\%$ of Fe phases. The pore size of the 2nd and the 3rd passed $SiC-Si_3N_4$ composites was $260\;{\mu}m$ and $35\;{\mu}m$ in diameter, respectively.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.35 no.5
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• pp.304-309
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• 2009

Purpose: Fibrous dysplasia (FD) is a fibro-osseous disease associated with activating missense mutations of the gene encoding the $\alpha$-subunit of stimulatory G protein. FD may affect a single bone (called monostotic form) or multiple bones (called polyostotic form). The extent of lesions reflects the onset time of mutation. In this study, cells from monostotic FD in maxilla of a patient were isolated and cultured in vitro for characterization. Materials and Methods: The single cells were released from FD lesion which was surgical specimen from 15 years-old boy. These isolated cells were cultured in vitro and tested their proliferation activity with MTT assay. In osteogenic media, these cells underwent differentiation process comparing with its normal counterpart i.e. bone marrow stromal cells. The proliferated FD cells were detached and transplanted into the dordsal pocket of nude mouse and harvested in 6 weeks and 12 weeks. Results and Summary: FD cells have an increased proliferation rate and poor differentiation. As a result, cells isolated from FD lesion decreased differentiation into osteoblast and increased proliferation capacity. MTT assay presented that proliferation rate of FD cells were higher than control. However, the mineral induction capacity of FD was lesser than that of control. Monostotic FD cells make fewer amounts of bone ossicles and most of them are woven bone rather than lamellar bone in vivo transplantation. In transplanted FD cells, hematopoietic marrow were not seen in the marrow space and filled with the organized fibrous tissue. Therefore, they were recapitulated to the original histological features of FD lesion. Collectively, these results indicated that the FD cells were shown that the increased proliferation and decreased differentiation potential. These in vitro and in vivo system can be useful to test FD cell's fate and possible.

• Advanced Composite Materials
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• v.18 no.4
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• pp.381-394
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• 2009

The kinetics of centrifugal infiltration of fibrous tubular preform is built theoretically, and simulations are conducted to study the effects of various casting conditions on infiltration kinetics and macrosegregation by combining with the energy, mass and kinetic equations. A similarity way is used to simplify the one-dimensional model and the parameter is ascertained by an iterative method. The results indicate that the increase of superheat, initial preform temperature, porosity tends to enlarge the remelting region and decrease copper solute concentration at the infiltration front. Higher angular velocity leads to smaller remelting region and solute concentration at the tip. The pressure in the infiltrated region increase significantly when the angular velocity is much higher, which requires a stronger preform. It is observed that the pressure distribution is mainly determined by the angular velocity, and the macrosegregation in the centrifugal casting is greatly dependent on the superheat of inlet metal matrix, initial temperature and porosity of the preform, and the angular velocity.

• Journal of Korea Technical Association of The Pulp and Paper Industry
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• v.37 no.1 s.109
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• pp.17-24
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• 2005

The increase of using low grade ace, the unsorted mixed grade, as fibrous raw materials for the packaging paper results in the increment of fine screen reject owing to the strong tendency to reduce the slot width. Since the most of screen reject consists of undispersed fiber flake, the suitable treatment of the flake could increase the yield of ace recycling and decrease the amount of solid waste. In this work, the novel method combined the mild mechanical treatment by using Tumbling pulper with the biological treatment was developed and applied to the wet strength flake and the fine screen tail line reject originated from a packaging paper mill. The results showed the new method could provide much better efficiency for the disintegration of undispersed flake and for the recovery of fiber from the rejects. The application of the laboratory scaled-Pack pulper showed the possible separation technique for mill application by fractioning effectively the fiber from the treated solid waste.

• Analytical Science and Technology
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• v.25 no.6
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• pp.345-349
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• 2012

Polysilane black powders were synthesized by sonochemical methods from silicon tetrachloride with sodium metal with 37.0% yield. Those black powder materials were found to have fibrous or irregular shapes with round surface. It was found that thermal behaviors of those polysilane black powders were similar to that of hydropolysilanes which was reported earlier. After thermal treatment, black polysilicon was obtained with 57.1% residue yield, and those fibrous or irregular shapes with round surface were intact but lots of small cavities were formed indicating porous structure, and found to be an amorphous state from XRD analysis.

• Proceedings of the PSK Conference
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• 2003.04a
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• pp.302.2-303
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• 2003

For polymeric material for tissue engineering. chitosan was selected with benefit of high tissue compatibility attributed and wound healing through its activation of growth factors. And nonwoven chitosan fibrous matrix has well interconnected porosity. But chitosan itself has some of limitations in including rapid bone regeneration at initial states incorpor-ated of bioactive materials such as growth factors and ECM molecules. (omitted)

• Proceedings of the Korea Concrete Institute Conference
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• 1995.10a
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• pp.224-228
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• 1995

Addition of hooked steel fibers into the cementitious materials enhanced shear resistance and consequently improves structural behavior and shear strength of reinforced hooked steel fibrous concrete beam(RHSFCB) under the shear forces. Experimental observations were made on the main parameters effecting structural behavior of RHSFCB in this study. The volume fractions of fibers, shear span to depth ratios, and spacings of stirrups were taken into account as the main parameters. Some equations reported in the literatures, regarding the predictions of the shear strength of RHSFCB have been evaluated statistically based on the total number of 95 test results on RHSFCB failed in shear on shear-flexural mode.

• Korean Journal of Veterinary Research
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• v.19 no.1
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• pp.27-32
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• 1979

This paper dealt with the macroscopical and histopathological observations on the polycystic kidney occurred in a Korean native calf aged about a year. The results summarized are as follows: 1. In macroscopical findings, numerous cysts in the bilateral kidneys were seen under the renal capsule, and the cysts were various in size and clear or cloudy in their contents. The cysts in the inner area of the renal cortex were smaller than those of the outer area of the renal cortex in size and in number. 2. In microscopical findings, marked dilatations of Bowman's spaces and convoluted tubules were prominant feature. Numerous cysts with or without eosinophilic materials were contained atrophic glomerulus. prolferation of fibrous connective tissue, atrophy of convoluted tubules were also observed. Inner walls of the cysts were surrounded by cuboidal cells, sguamous cells or fibrous connective tissue. 3. This case was regarded as congenital polycystic kidney belonged to type III of Osathanondh and Potter.

• Proceedings of the PSK Conference
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• 2003.10b
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• pp.229.2-230
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• 2003

Extracellular matrix(ECM) is composed of the ground materials(proteoglycan) and nano size diameter fibrous proteins(ex. collagens) that together form a composite-like structure. In this study, fibrous scaffold with biomimetic architecture based on collagen nanofibers interpenetrated in PLGA/chitosan microfibrous matrix. Chitosan was selected for its structure similarity to glycosaminoglycan and neutralizing capacity for PLGA acidic metabolite. Collagen nanofiber were prepared by electrospinning. (omitted)