• Composites Research
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• 제12권2호
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• pp.70-81
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• 1999

고분자 복합재료 제조공정인 수지이동성형(RTM) 공정은 최근 들어서 고성능 재료를 필요로 하는 항공산업분야에서 관심의 대상이 되고 있다. 본 연구에서는 유한요소/관할부피 기법을 도입한 수치모사를 통해서 수지이동 성형공정에서의 금형충전단계를 해석하였다. 섬유직조망의 투과계수를 정량적으로 측정하고, 또한 수치모사에 이용된 프로그램을 검증하기 위하여 유동가시화 실험을 수행하였다. 실험에 사용된 강화섬유와 수지물질로는 여러 가지 형태의 섬유직조망과 실리콘 기름을 선택하였다. 수치모사와 유동가시화 실험을 병행함으로써 섬유직조망의 구조, 금형의 구조, 금형삽입체가 금형충전단계에서의 수지 유동선단의 형태에 미치는 영향을 살펴보았다. 모델링에 의해 예측된 유동선단은유동가시화 실험을 통해 관찰된 결과와 잘 일치한 것으로 나타났으나, 금형내 불균일한 섬유부피분율로 인해 섬유조직망의 투과계수가 전 영역에서 일정한 값을 가지지 못하기 때문에 약간의 차이를 보여주었다. 원형의 구조물이 금형내에 삽입되어 있는 경우, 월드라인의 위치를 예측된 유동선단으로부터 정성적으로 추정할 수 있었다.

• 한국재료학회지
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• 제15권3호
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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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• 제35권5호
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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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• 제18권4호
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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.

• 펄프종이기술
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• 제37권1호
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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.

• 분석과학
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• 제25권6호
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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.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.1
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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)

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1995년도 가을 학술발표회 논문집
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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.

• 대한수의학회지
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• 제19권1호
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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.

• 대한약학회:학술대회논문집
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• 대한약학회 2003년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2-2
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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)