• Advanced Composite Materials
• /
• 제17권4호
• /
• pp.359-372
• /
• 2008

The moisture absorption behavior of carbon fiber-reinforced plastic (CFRP) and its effect on dimensional stability were examined. Moisture diffusivity in CFRP was determined by measuring a specimen's weight during the moisture absorption test. Three types of CFRP specimens were prepared: a unidirectionally reinforced laminate, a quasi-isotropic laminate and woven fabric. Each CFRP was processed into two geometries - a thin plate for determination of diffusivity and a rod with a square cross-section for the discussion of two-dimensional diffusion behavior. By solving Fick's law expanded to 3 dimensions, the diffusivities in the three orthogonal directions were obtained and analyzed in terms of the anisotropy of CFRP moisture diffusion. Coefficients of moisture expansion (CMEs) were also obtained from specimen deformation caused by moisture absorption. During moisture absorption, the specimen surfaces showed larger deformation near the edges due to the distribution of moisture contents. This deformation was reasonably predicted by the finite element analysis using experimentally determined diffusivities and CMEs. For unidirectional CFRP, the effect of the fiber alignment on CME was analyzed by micromechanical finite element analysis (FEA) and discussed.

• 농업과학연구
• /
• 제19권1호
• /
• pp.28-32
• /
• 1992

태국의 토양으로부터 분리한 젤라틴 분해능을 갖는 광합성세균 T-20주(株)는 직경이 $0.6{\sim}0.7{\mu}m$의 적색 간균으로써, Bacteriochlorophyll a의 흡수극대는 870nm이었고 또한, 퀴논종(種)은 UQ-8을 나타내었다. 유기 화합물로써 citrate, aspirate, glutamate, fractose 등을 이용하였다. 이상의 결과로부터 T-20주는 Bergey's Manual of Systematic Bacteriology(1989)에 기재된 Rhodocyclus gelatinosus와 일치한다.

• 한국미생물·생명공학회지
• /
• 제28권5호
• /
• pp.264-269
• /
• 2000

This study is that of providing a fairly practical practival guide to the use of natural pigment in food industry. A strain isolated from marine resources was carried out the production of red pigment. The pigment showed UV absorption maxima at 520 and 550 nm. The color intensity in aqueous solution was fairly stable in the ranges of pH 5~8. The strain KS-97 produced a maximum yield of red pigment at$ 25^{\circ}C$ for 72 hrs with pH 7.0. The strain KS-97 was iden-tified a Bacillus sp. based on morphological and biochemical characterization such as a rod from, motility, spore for-mation, Gram positive and catalase production. The production of red pigment indicated that the strain Ks-97 utilized at thigh concentration of colloidal chitin as carbon sources obtained maximum yield of red pigment at $25^{\circ}C$ for 72 hrs. The highest production of red pigment was observed with cultivation in medium containing 20% colloi-dal chitin, 2.5g polypeptone, 2.5g yeast extract, 1.0g $KH_2$$PO_4$, 0.01g $MgSO_4$.$6H_2$O, 0.01g $ZnSO_4$, 0.01 g $MnSO_4$(per 1).

• Applied Biological Chemistry
• /
• 제28권3호
• /
• pp.131-136
• /
• 1985

지금까지 보고된 바와는 달리 이눌라아제를 체외로 분비하는 한 세균을 분리하였고 이균은 이눌린이 존재하지 않는 설탕, 세룰로오스, 포도당이 포함된 배지에서 이눌라아제를 생산하는 구성 효소로서의 특성을 나타내었다. 또한 동일한 배지 조건에서 강력한 이눌라아제를 생산하는 것으로 알려진 Kluyveromyces fragilis와 유사한 효소 활성을 짧은 배양 시간내에 나타내었다. Bergery's manual에 따라 조사된 이 균의 특징은 호기성, 그람양성, 간균으로 포자를 형성하여 Bacillus subtilis로 추정되었다.

• Smart Structures and Systems
• /
• 제28권6호
• /
• pp.727-735
• /
• 2021

Recently, non-destructive health monitoring methods such as magnetic flux leakage (MFL) method, have become popular due to their advantages over destructive methods. Currently, numerical study on this field has been limited to simplified studies by only obtaining MFL instead of induced voltage inside coil sensor. In this study, it was proposed to perform a novel numerical simulation of MFL's coil sensor by considering vital parameters including specimen's motion with constant velocity and saturation status of specimen in time domain. A steel-rod specimen with two stepwise cross-sectional changes (i.e., 21% and 16%) was fabricated using low carbon steel. In order to evaluate the results of numerical simulation, an experimental test was also conducted using a magnetic probe, with same size specimen and test parameters, exclusively. According to comparative results of numerical simulation and experimental test, similar signal amplitude and signal pattern were observed. Thus, proposed numerical simulation method can be used as a reliable source to check efficiency of sensor probe when different size specimens with different defects should be inspected.

• Corrosion Science and Technology
• /
• 제22권4호
• /
• pp.252-256
• /
• 2023

The galvanostatic polarization technique was used to accelerate corrosion in high chromium cast iron (HCCI) immersed in a simulated slurry solution of 0.1 mol dm^-3 H₂SO₄, 0.05 mol dm^-3 HCl, and 10 wt% SiC. The HCCI contained 27 wt% of Cr and 2.8 wt% of C, and its microstructure mainly comprised austenitic and carbide phases. A two-electrode system using a dense carbon rod and the HCCI sample was employed for the galvanostatic polarization by applying an anodic current for 24 hours. The corrosion rate increased upon applying the anodic current, but the increase was not significant, particularly for current densities higher than 10 µA cm^-2. Following polarization, the corrosion morphology revealed that the anodic current accelerated surface corrosion in the HCCI; however while the depth of the corroded area increased, the increase was not substantial. The propagation behavior of the anodic current and its impact on corrosion were further discussed.

• 대한화학회지
• /
• 제67권4호
• /
• pp.222-225
• /
• 2023

Metallic salts of C10-18 aliphatic carboxylic acids were prepared and their scanning electron microscopic images were analyzed for the morphology dependency with the metal and the carboxylic acid. Regardless of metal ion, metal salts of dicarboxylic acids showed a high crystallinity with a fiber image (SuA-Na). The aromatic dicarboxylates also represented a morphology of a rectangular-rod or board shapes (IA-Li, IA-Ba). With Na ion, most aliphatic carboxylate (MA, PA, SA) showed a fiber-like crystallinity. However, other monovalent Li, K and multivalent Mg, especially Al ion resulted a glassy-amorphous in the metallic salts of acids (MA, PA, SA). With divalent Ba and Ca ions, the metal salt of aliphatic acids expressed a branched round cluster shape as in SA-Ca, SA-Ba. Both Li and Mg ions with a similar size showed a strong morphological similarity in the metallic salts of aliphatic acids MA, PA, SA. In the case of Na and Ca ions with a similar size (98, 106 pm), both ionic salts of stearic acid gave a branching effect for a fiber or round granular image. In the case of hydroxyl-aliphatic acids (HLA, HPA, HSA), the fiber images in HLA-Na and HSA-Na was appeared about 100 nm thicker than those of nonhydroxycarboxylates (LA-Na, SA-Na). The metallic salts of unsaturated C-18 carboxylic acids (OlA, LeA and LnA) showed an amorphous glassy image due to a kinked carbon chain.

• 한국균학회지
• /
• 제27권1호통권88호
• /
• pp.1-9
• /
• 1999

느타리버섯 8품종의 균사생장은 $25{\sim}30^{\circ}C$의 온도 범위와 $5.5{\sim}6.5$의 pH 범위에서 가장 우수하였다. 영양원의 선발시험에서 탄소원으로서는 황백당, 밀가루 및 옥수수가루가, 그리고 질소원으로서는 대두분이 공시균주의 균사생장이 가장 우수하였다. 농업적으로 이용성이 우수한 황백당 3%, 대두분 0.3%, 인산칼륨 0.05%, 황산마그네슘 0.05%를 배지 조성으로 하는 농업용 액체배지를 선발하였다. 삼각플라스크 배양에서는 250 ml의 erlenmeyer flask에서 보다는 250ml의 shake flask에서 직경 6 mm의 균사절편을 2개 접종하여 배양액량 100ml에서 배양했을 때 공시균주의 균사체 생산이 우수하였다. 그리고 erlenmeyer flask에서 배양방법을 달리하여 느타리버섯의 균사를 배양하였을 때, $45^{\circ}$ 경사배양한 처리구에서 균사체 생산이 가장 우수하였으며, 길이 $50mm{\times}$ 직경 10mm의 유리막대를 넣고 배양한 처리구에서는 균체량이 가장 적었지만 펄프형의 균사생육을 유도할 수 있었다.

• 열처리공학회지
• /
• 제19권1호
• /
• pp.10-19
• /
• 2006

Microstructure and morphology of precipitates in $Ni_3Al$- and TiAl-based intermetallics containing carbon have been investigated in terms of transmission electron microscopy(TEM). In an $L1_2$-ordered $Ni_3Al$ alloy with 4 mol.% of chromium and 0.2~3.0 mol.% of carbon, fine octahedral precipitates of $M_{23}C_6$ type carbide were formed in the matrix by aging at temperatures around 973 K after solution annealing at 1423 K. TEM examination revealed that the $M_{23}C_6$ phase and the matrix lattices have a cube-cube orientation relationship and keep partial atomic matching at the {111} interface. After prolonged aging or by aging at higher temperatures, the $M_{23}C_6$ precipitates then adopt a rod-like morphology elongated parallel to the <100> directions. In the $L1_0$-ordered TiAl containing 0.1~2.0 mol.% carbon, TEM observations revealed that needle-like precipitates, which lie only in one direction parallel to the [001] axis of the $L1_0$ matrix, appear in the matrix and preferentially at dislocations. Selected area electron diffraction(SAED) patterns analyses have shown that the needle-shaped precipitate is $Ti_3AlC$ of perovskite type. The orientation relationship between the $Ti_3AlC$ and the $L1_0$ matrix is found to be $(001)_{Ti3AlC}//(001)_{L10\;matrix}$ and $[010]_{Ti3AlC}//[010]_{L10\;matrix}$. By aging at higher temperatures or for longer period at 1073 K, plate-like precipitates of $Ti_2AlC$ with a hexagonal structure are formed on the {111} planes of the $L1_0$ matrix. The orientation relationship between the $Ti_2AlC$ and the $L1_0$ matrix is $(0001)_{Ti2AlC}//(111)_{L10\;matrix}$ and $_{Ti2AlC}//_{L10\;matrix}$.

• Elastomers and Composites
• /
• 제55권4호
• /
• pp.306-313
• /
• 2020

To investigate the reinforcing effects of functional fillers in nitrile rubber (NBR) materials, high-structure carbon black (HS45), coated calcium carbonate (C-CaCO3), silica (200MP), and multi-walled carbon nanotubes (MWCNTs) were used as functional filler, and carbon black (SRF) as a common filler were used for oil-resistant rubber. The curing and mechanical properties of HS45-, 200MP-, and MWCNT-filled NBR compounds were improved compared to those of the SRF-filled NBR compound. The reinforcing effect also increased with a decrease in the particle size of the fillers. The C-CaCO3-filled NBR compound exhibited no reinforcing effect with increasing filler concentration because of their large primary particle size (2 ㎛). The reinforcing behavior based on 100% modulus of the functional filler based NBR compounds was compared by using several predictive equation models. The reinforcing behavior of the C-CaCO3-filled NBR compound was in accordance with the Smallwood-Einstein equation whereas the 200MP- and MWCNT-filled NBR compounds fitted well with the modified Guth-Gold (m-Guth-Gold) equation. The SRF- and HS45-filled NBR compounds exhibited reinforcing behavior in accordance with the Guth-Gold and m-Guth-Gold equations, respectively, at a low filler content. However, the values of reinforcement parameter (100Mf/100Mu) of the SRF- and HS45-filled NBR compounds were higher than those determined by the predictive equation model at a high filler content. Because the chains of SRF composed of spherical filler particles are similarly changed to rod-like filler particles embedded in a rubber matrix and the reinforcement parameter rapidly increased with a high content of HS45, the higher-structured filler. The reinforcing effectiveness of the functional fillers was numerically evaluated on the basis of the effectiveness index (��SRF/��f) determined by the ratio of the volume fraction of the functional filler (��f) to that of the SRF filler (��SRF) at three unit of reinforcing parameter (100Mf/100Mu). On the basis of their effectiveness index, MWCNT-, 200MP-, and HS45-filled compounds showed higher reinforcing effectiveness of 420%, 70%, and 20% than that of SRF-filled compound, respectively whereas C-CaCO3-filled compound exhibited lower reinforcing effectiveness of -50% than that of SRF-filled compound.