• Transactions of the Korean Society of Automotive Engineers
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• v.4 no.2
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• pp.173-182
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• 1996

An analytical model has been developed to predict the elastic properties of a filled resin reinforced by chopped fibers, a three-phase composite such as a filled sheet molding compound(SMC). In the model the matrix material and fillers form an effective matrix. The effective matrix is then considered to be reinforced with long fibers lying in the sheet plane but randomly oriented in the plane. Expressions for the resulting transversely isotropic composite properties are explicitly presented. Using this model, the Young's and shear moduli are calculated for the SMC sample with filler weight fraction of 35% and fiber content of 30%. The same properties are also determined experimentally. The agreement between the calculated and measured elastic moduli is found to be very good for the in-plane properties. However, the out-of-plane properties show a large difference because the effect of voids is not taken into account in the model.

• Proceedings of the Korea Technical Association of the Pulp and Paper Industry Conference
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• 2000.11a
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• pp.54-54
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• 2000

종이의 생산성을 향상 시키기 위한 방법에는 초지기의 광폭화오} 생산 속도의 증가 가 있다. 현재 초지기는 10m까지 생산 폭이 확대 되었고, 생산 속도에 있어서는 최 신 설비의 경우 2,OOOm/min로 설계 되고 있다. 따라서 생산 폭과 속도의 증가는 이 전의 소폭과 저속의 생산 셜비에서와 동일한 원료 배합과 생산 관리로는 최적의 생 산 효율을 달성하는데 문제점이 있다. 그러므로 현재 각국의 신규 제지 설비에 적 용되 고 있는 twin wire system역 시 생 산 속도의 증가를 극복하고 기 존의 fourdrinier s system 이 지니고 있는 문제점을 극복하기 위해 도입되었다. 두 가지의 생산 설비에서 제조된 종이의 가장 큰 차이점은 미세 입자들의 분포와 종이의 구조적 특성에 있다. 특히 fourdrinier system에서 미세 입자들의 분포는 횡단 면을 기준으로 볼 때 표면에서 와이어 면으로 진행됨에 따라 급격히 감소된다는 것 을 알 수 있다. 이러한 사실은 주지하는 바와 같이 초지 형성부에서 효과적인 탈수 를 달성하기 위해 부착되어 있는 여러가지 탈수 장치들의 영향으로 와이어 방향으 로만 급격한 탈수가 일어나기 때문이다. 그러나 twin wire system 2.! gap former어$\mid$ 있 어서 미세 섬유와 충전제가 횡단면상에서 분포하는 형태는 "U"자 형태로 상면과 하 면에서 가장 높은 미세분의 분포를 나타내고 줄간층에는 상대적으로 낮은 미세분이 분포하고 있을을 알수 있다. 따라서 종이의 중간층 미세분 분포의 감소는 섬유간 표면적의 감소를 의미하고 이로 인하여 결합력이 약해진다는 것을 알 수 있다. 특 히 도공 원지로 사용되었을 경우 heat off-set 인쇄시 블리스터와 같은 문제점을 일 으키기도 한다. 앞서 언급한 바와 같이 종이의 제조 설비에 따라 제조되는 종이의 구조적 특성이 변하게 되므로 동일한 도공 공정에 적용 되었을 경우 이들로부터 제 조된 도공지의 특성에도 영향을 미칠것으로 예측된다. 따라서 본 연구에서는 두 가지 초지기의 형태에서 제조된 원지가 도공 작업성과 도공지의 특성에 미치는 영향에 대해 고찰코자 하였다.대해 고찰코자 하였다.

• Applied Chemistry for Engineering
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• v.31 no.1
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• pp.13-18
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• 2020

Iron oxide nanoparticles were microencapsulated using fibroin, a protein polymer of silk fiber, for theragnostic applications. The content of iron oxide was determined to be 4.28% by thermogravimetric analysis and 5.11% by magnetometer. A suspension of murine fibroblast 3T3 cells grown in medium supplemented with iron oxide-microcapsules turned clear in response to the magnetic force and the cells aggregated to the magnet direction. Neodymium magnets placed on the top of the culture dish, and attracted cells to the center of the culture surface. The cells collected on the culture surface aggregated to form a rough spheroid of 2 mm in a diameter after 72 h. In the outer layer of the cell aggregate, cells were relatively large and gathered together to form a dense tissue, but the central part was observed to undergo cell death due to the mass transfer restriction. In the outer layer, iron oxide-microcapsules were lined up like chains in the direction of magnetic force. Using microCT, it was demonstrated that the iron oxides inside the cell aggregate were not evenly distributed but biased to the magnetic direction.

• Journal of Korean Society for Atmospheric Environment
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• v.7 no.1
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• pp.1-16
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• 1991

In this study, sampling and analytical procedures were evaluated for the determination of ambient levels of atmospheric PAH, both in gaseous and particulate phase. The method involves low-volume sampling and Soxhlet extraction of the filters and Tenax absorbent, followed by a clean-up stage using a silica column prior to analysis by reversed-phase HPLC with wavelength programmable fluorescence and UV detection. A total of 18 PAH were identified and quantified, all of which have been of environmental concern. In order to validate the methodology and to ensure compatibility of the results, the analytical method used for the determination of PAH was evaluated with respect to the efficiencies of extraction and clean-up procedure, HPLC separation, and lower limits of detection. In addition, substrate dependency of PAH recovery was investigated for the two types of fiters, i.e. glass fiber and PTFE filters.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.291-297
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• 2008

The solid particle erosion behaviour of unidirectional carbon fiber reinforced plastic (CFRP) composites was investigated. The erosive wear of these composites was evaluated at different impingement angles ($30^{\circ}$, $45^{\circ}$, $60^{\circ}$, $90^{\circ}$), different impact velocities (40, 55, 60, 70m/s) and at three different fiber orientations ($0^{\circ}$, $45^{\circ}$, $90^{\circ}$). The erodent was SiC sand with the size $50-100{\mu}m$ of irregula. shapes. The result showed ductile erosion behaviour with maximum erosion rate at $30^{\circ}$ impingement angle. The fiber orientations had a significant influence on erosion. The erosion rate was strongly dependent on impact velocity which followed power law $E{\propto}\;V^n$. Based on impact velocity (V), impact angle (${\alpha}$) and fiber orientation angle (${\beta}$), a method was proposed to predict the erosion rate of unidirectional fiber reinforced composites.

• Journal of Adhesion and Interface
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• v.9 no.3
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• pp.7-13
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• 2008

The particulate type silicon carbide (SiC) and fiber type carbon fiber (CF) filler, of similar thermal conductivities, were mixed with polyetheretherketone (PEEK) to investigate the filler effects on the thermal diffusivity. The SiC and CF fillers had a good and uniform dispersion in PEEK matrix. Thermal diffusivities of PEEK composites were measured from ambient temperature up to $200^{\circ}C$ by laser flash method. The diffusivities were decreased as increasing temperature due to the phonon scattering between PEEK-filler and filler-filler interfaces. Thermal diffusivity of PEEK composites was increased with increasing filler content and the thermal conductivities of two-phase system were compared to the experimental results and it gave ideas on the filler dispersion, orientation, aspect ratio, and filler-filler interactions. Nielson equation gave a good prediction to the experimental results of PEEK/SiC. The easy network formation by CF was found to be substantially more effective than SiC and it gave a higher thermal diffusivities of PEEK/CF than PEEK/SiC.

• Journal of Sericultural and Entomological Science
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• v.41 no.1
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• pp.54-60
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• 1999

Antheraea pernyi silk powder was prepared by treatment with HCl and NaOH. The degree of hydrolysis of Antheraea pernyi silk fiber was examined. The morphology and structural characteristics of Antheraea pernyi silk powder were investigated by using SEM, FTIR and X-ray diffractometer. As the concentration of HCl and NaOH and tratment temperature increased, in general, the degree of hydrolysis of Antheraea pernyi silk fiber increased. On the other hand, the degree of hydrolysis of Antheraea pernyi treated with 3 N NaOH at 120$^{\circ}C$ for 24 hr was 70 wt%, which was lower than that of 90$^{\circ}C$(83 wt%). The morphology of acid/alkali resistance fraction of Antheraea pernyi silk fibroin was transformed from fiber form to powered one with an increase of hydrolysis. The conformation of Antheraea pernyi silk powder characterized by FT-IR spectrometer and X-ray diffractometer ${\beta}$-sheet and ${\alpha}$-helix structure.

• Composites Research
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• v.32 no.5
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• pp.265-269
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• 2019

The direct spinning of carbon nanotube (CNT) fibers is a promising method in the high performance composite materials. However, most of the reported CNT arrays do not have spinning properties because of their limited synthesis conditions. In this study, we investigate the properties of spinnable CNT arrays, which is closely related to the morphology of CNT array. The array morphology controlled by controlling the conditions of catalyst, carbon source, etc. By additional carbon source of ethylene and changing the composition of the catalyst, the waviness of the CNT array can be remarkably reduced, which leads to improve of the spinning properties. The synthesized CNT arrays were well aligned along c-axis and the synthesis conditions of the spinning array could be derived.

• Journal of the Mineralogical Society of Korea
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• v.23 no.1
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• pp.73-84
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• 2010

We studied the geological occurrence, associated minerals, mineralogical properties and formation process of tremolites from two abandoned asbestos mines, Jungang (Sinsuk) and Daebosuksan, located in Boryoung area, Chungnam. Morphologically different tremolites such as long fibrous, needle-like, bladed and prismatic forms coexisted. Fibrous tremolite, known for its high toxieity to human health, was systematically analyzed by polarized light microscopy and scanning electron microscopy. The average length of tremolite fibers was 31.2 ${\mu}m$ although the maximum length of some asbestos was 210.0 ${\mu}m$. The average width and aspect ratio were 1.6 ${\mu}m$ and 19.9, respectively. Tremolite showed inclined extinction in the range of 6.1~20.2$^{\cric}$. X-ray diffraction patterns were slightly different between fibrous (asbestiform) and prismatic (non-asbestiform) tremolites. EPMA analysis of tremolites in the study area indicated extremely high Mg content with very low Fe content, close to the composition of tremolite in end-member in the tremolite-actinolite solid solution series. The formational conditions of asbestiform and non-asbestiform tremolite appear to be different. Asbestiform tremolite was estimated to have been formed in later stage.