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61.
Polyacrylonitrile solution homogeneity study by dynamic shear rheology and the effect on the carbon fiber tensile strength 下载免费PDF全文
Bradley A. Newcomb Prabhakar V. Gulgunje Yaodong Liu Kishor Gupta Manjeshwar G. Kamath Chandrani Pramanik Sushanta Ghoshal Han Gi Chae Satish Kumar 《Polymer Engineering and Science》2016,56(3):361-370
Poly(acrylonitrile‐co‐methacrylic acid) (PAN‐co‐MAA)/N,N‐dimethylformamide (DMF) solutions were prepared and dynamic shear rheology of these solutions were investigated. With increasing stirring time up to 72 h at 70°C, the polymer solution became less elastic (more liquid‐like) with a ~60% reduction in the zero‐shear viscosity. Relaxation spectra of the PAN‐co‐MAA/DMF solutions yield a decrease in relaxation time (disentanglement time, τd), corresponding to an about 8% decrease in viscosity average molecular weight. The log‐log plot of G′ (storage modulus) versus G″ (loss modulus) exhibited an increase in slope as a function of stirring time, suggesting that the molecular level solution homogeneity increased. In order to study the effect of solution homogeneity on the resulting carbon fiber tensile strength, multiple PAN‐co‐MAA/DMF solutions were prepared, and the precursor fibers were processed using gel‐spinning, followed by continuous stabilization and carbonization. The rheological properties of each solution were also measured and correlated with the tensile strength values of the carbon fibers. It was observed that with increasing the slope of the G′ versus G″ log‐log plot from 1.471 to 1.552, and reducing interfilament fiber friction during precursor fiber drawing through the addition of a fiber washing step prior to fiber drawing, the carbon fiber strength was improved (from 3.7 to 5.8 GPa). This suggests that along with precursor fiber manufacturing and carbonization, the solution homogeneity is also very important to obtain high strength carbon fiber. POLYM. ENG. SCI., 56:361–370, 2016. © 2016 Society of Plastics Engineers 相似文献
62.
While an equation of state (EOS) plays a critical role in estimating thermodynamic properties, employing it in the determination
of binary interaction parameters is extremely important. In general, these parameters can be determined from phase equilibrium
data. However, data collection from experiments is a time-consuming and tedious process. In this study, after measuring the
excess enthalpies of binary systems containing CO2 by high-pressure flow isothermal microcalorimetry (IMC), we determined the EOS binary interaction parameters, specifically,
the Peng-Robinson EOS binary interaction parameters. These binary interaction parameters obtained by IMC were compared with
those obtained by vapor-liquid equilibrium (VLE) experiments. Hence, high-pressure flow IMC appears to be an effective method
for the determination of interaction parameters that are used in the estimation of thermodynamic properties. Further, the
Flory-Huggins interaction parameters of a binary mixture CO2 containing with various mole compositions were also estimated by employing high-pressure IMC. 相似文献
63.
Jaesoo Choi Dong-Hyun Lee Heeyeop Chae Chinho Park Sung M. Cho 《Korean Journal of Chemical Engineering》2008,25(1):99-101
We have successfully showed the color mixing between fluorescence and phosphorescence by the incomplete Förster energy transfer. The emission color from fluorescent Rubrene and phosphorescent Ir(ppy)3 was found possible to be mixed for a single-layer device doped with both dyes, maintaining the high luminance efficiency of the phosphorescence. We also found out that the Förster energy transfer was very efficient and independent of the applied voltage with no loss of energy during the transfer. 相似文献
64.
Seong Yun Kim Hwa Jin Oh Sung Ho Kim Chae Hwan Kim Seung Hwan Lee Jae Ryoun Youn 《Polymer Engineering and Science》2008,48(9):1840-1847
Film insert molding (FIM) has been modeled numerically to predict residual stress and viscoelastic deformation of the part. Nonisothermal three dimensional flow analysis for filling, packing, and cooling stages was carried out by using a commercial software. It was assumed that the inserted film was solid throughout the entire molding procedure although remelting could occur at the interface with the substrate. The flow analysis results, e.g., temperature, stress, and density distribution in the substrate domain, were transported to a finite element stress analysis program for viscoelastic stress analysis. Deflection of the FIM part was obtained as soon as the part was ejected from the mold by assuming isotropic elastic material. The residual stress distribution in the FIM part was acquired by removing the constraints along the boundary of the molded part. Viscoelastic deformation of the FIM part was predicted by performing viscoelastic stress analysis in order to understand long term behavior of the FIM part when exposed to room temperature. Durability of automotive and electronic parts produced by the film injection molding can be predicted by the procedure adopted in this study. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers 相似文献
65.
Xun Zhu Dong-Hyun Lee Heeyeop Chae Sung Min Cho 《Korean Journal of Chemical Engineering》2010,27(2):683-687
Enhanced efficiency of white polymer light-emitting diodes (PLEDs) was observed by incorporating polysilicic acid (PSA) nanodots
into the hole-injection layer (HIL). The PLEDs employed three different phosphorescent dyes in a single emissive layer with
a host polymer of poly(vinylcarbazole) (PVK). The optimal composition of the phosphorescent dyes has been found to accomplish
the white emission. By incorporating 1.5 wt% of PSA nanodots into the HIL, the maximum efficiency has been found to increase
about 65%, from 13.7 cd/A to 22.9 cd/A. This remarkable improvement in efficiency may be attributed to the introduction of
the PSA nanodots, which leads to the better carrier balance in the PLEDs. 相似文献
66.
Chang Ho Kang Eun Seon Lee Ganesh M. Nawkar Joung Hun Park Seong Dong Wi Su Bin Bae Ho Byoung Chae Seol Ki Paeng Jong Chan Hong Sang Yeol Lee 《International journal of molecular sciences》2021,22(19)
Interaction between light signaling and stress response has been recently reported in plants. Here, we investigated the role of CONSTITUTIVE PHOTOMORPHOGENIC 1 (COP1), a key regulator of light signaling, in endoplasmic reticulum (ER) stress response in Arabidopsis. The cop1-4 mutant Arabidopsis plants were highly sensitive to ER stress induced by treatment with tunicarmycin (Tm). Interestingly, the abundance of nuclear-localized COP1 increased under ER stress conditions. Complementation of cop1-4 mutant plants with the wild-type or variant types of COP1 revealed that the nuclear localization and dimerization of COP1 are essential for its function in plant ER stress response. Moreover, the protein amount of ELONGATED HYPOCOTYL 5 (HY5), which inhibits bZIP28 to activate the unfolded protein response (UPR), decreased under ER stress conditions in a COP1-dependent manner. Accordingly, the binding of bZIP28 to the BIP3 promoter was reduced in cop1-4 plants and increased in hy5 plants compared with the wild type. Furthermore, introduction of the hy5 mutant locus into the cop1-4 mutant background rescued its ER stress-sensitive phenotype. Altogether, our results suggest that COP1, a negative regulator of light signaling, positively controls ER stress response by partially degrading HY5 in the nucleus. 相似文献
67.
Sudong Chae Seungbae Oh Kyung Hwan Choi Jin Woong Lee Jiho Jeon Zhixiang Liu Cong Wang Chaeheon Woo Liyi Shi Joohoon Kang Si Young Song Sung Jae Kim Jung Heon Lee Hak Ki Yu Jae-Young Choi 《Ceramics International》2021,47(9):11935-11941
To achieve the stable dispersion of 1D van der Waals crystal Mo6S3I6 in aqueous media, the tri-block copolymer (Poloxamer) is used as dispersant. The head group of Poloxamer, hydrophobic polypropylene oxide parts can be adsorbed to Mo6S3I6 surface by hydrophobic interaction and the tail group with hydrophilic polyethylene oxide exposed to the outside of the Mo6S3I6 is soluble in water and can form sufficient steric hindrance, resulting in stable aqueous dispersion in nm scale. The excellent biocompatibility of aqueous dispersed nm scale 1D Mo6S3I6 was demonstrated by effective proliferation of C2C12 cells. 相似文献
68.
Dongho Chae O. Yu. Imanuvilov Sang Moon Kim 《Journal of Dynamical and Control Systems》1996,2(4):449-483
This paper studies the problem of exact boundary controllability of second-order semilinear parabolic equations when the control is under Neumann's boundary conditions. For a nonlinear term with a sublinear growth we prove the global null-controllability and for the superlinear growth case we prove the local exact controllability of the equations. 相似文献
69.
Comparative evaluation of adhesion and biofilm formation of different Listeria monocytogenes strains 总被引:6,自引:0,他引:6
Thirteen Listeria monocytogenes strains were used to grow biofilms on glass surfaces in static conditions at 37 degrees C for up to 4 days. After the initial 3-h adhesion and in subsequent 1-day intervals, cell numbers were determined using standard plate count after swabbing the cells from the glass surface. The three-dimensional structure of in situ biofilms was determined by confocal scanning laser microscopy (CSLM). After 3 h incubation, bacterial cells for all 13 strains of L. monocytogenes were found attached to glass slides and all strains formed biofilms within 24 h. The strains varied significantly in their ability to adhere to the surface and significant differences for cell numbers after 24 h biofilm growth were found. Cell counts in biofilms formed by five L. monocytogenes strains were monitored over 4 days. The counts increased for the first 2 days reaching 10(5) cfu/cm2, except for L. monocytogenes 7148 (10(4) cfu/cm2). After 2 days, cell counts remained at 10(5) cfu/cm2 for four strains (tested on days 3 and 4), while L. monocytogenes 7148 continued to grow and reached 10(5) cfu/cm2 on day 4. This difference in biofilm growth was not related to variations in growth rates of planktonic cells suggesting that growth behaviour of Listeria in biofilms may be different from their planktonic growth. CSLM revealed that the biofilms grown under static conditions consisted of two distinct layers with 0.5 log10 higher cell numbers in the bottom layer as compared to the upper layer. 相似文献
70.
The effects of peptides and polyethylene glycol (PEG) on the immobilization of protease using glutaraldehyde-activated Lewatit R258-K resin were investigated. When soy peptide was added at 0.1 g/l, the activity recovery and effectiveness factor increased by 20% and 38%, respectively. When PEG4000 (0.5 g/l) was used as a protecting agent, the activity recovery and effectiveness factor were improved by 35% and 60%, respectively, leading to an increased specific activity of the immobilized enzyme. The addition of PEG4000 is suggested to improve the cost-effectiveness for the production of immobilized enzymes. 相似文献