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11.
In this study, isothermal crystallization kinetics of polyamide 6 (PA6) composites reinforced with surface-treated glass fiber
(GF) and natural, clay-type mineral (MN) were investigated by differential scanning calorimetry method in the presence and
absence of a nucleating agent (NA). Microstructural features of the composites and interfacial interactions between filler
and polyamide phases were also quantified by rheological measurements. The kinetic parameters for the isothermal melt-crystallization
process of the samples were determined with the Avrami and Lauritzen–Hoffman models. The crystallization activation energies
were determined by the Arrhenius method. It was found that the both fillers yielded a significant increase in the storage
modulus of PA6. Kinetic calculations showed that the MN has a more pronounced acceleration effect on the crystallization rate
of PA6 than the GF. Introduction of a small amount of NA significantly favored the isothermal crystallization rate of GF-reinforced
PA6 but did not accelerate that of MN-reinforced one. Based on the results, it has been highlighted that PA6 composites reinforced
with surface-treated GFs and including a small amount of clay-like mineral as a cheap and easy-accessible minor filler could
yield the best performance for the injection-molded PA6 parts because the GF enhances the mechanical properties and the clay-like
mineral accelerates the crystallization rate. 相似文献
12.
Hakime Hulya Orak Hulya Yagar Sebnem Selen Isbilir 《Food science and biotechnology》2012,21(2):373-387
In this study, the antioxidant activities of juice, peel, and seed parts of pomegranate were investigated by using DPPH scavenging
activity, β-carotene bleaching method, reducing power, and metal chelating activity. Sample of pomegranates which are named
Punica granatum L. cv. Hicaznar, genotype 19–121, genotype 17–67, and genotype 19–66 obtained from BATEM (West Mediterranean Agricultural Research Institute) in Anlalya. The EC50 values of DPPH scavenging activities in peel extracts (PE) had 23.4-fold higher than the juice extracts (JE), and the seed
extracts (SE) had 2.3-fold higher than JE. The reducing power in peel extracts was found to be 4.7-fold higher than SE and
10.5-fold higher than the JE. The highest metal chelating capacity (37.22%) was determined in peel, while the lowest (7.151%)
in seed. Generally, in peel, the total polyphenol, flavonoid, tannin contents, and in juice, the total polyphenol, anthocyanin,
tannin contents, and acidity significantly affected to antioxidant activities. 相似文献
13.
The bioactive compounds of 16 tomato cultivars, grown in the same field for 2 years (2003 and 2004) were investigated. Lycopene (5.7–26.3 mg kg?1) was the predominant carotenoid, while β-carotene (2.1–11.2 mg kg?1) and a small amount of lutein (0.02–0.49 mg kg?1) were found in all tomato cultivars. Kagome 77, the richest source of total carotenoids and L-ascorbic acid, also showed the highest antioxidant activity. β-Carotene and lutein contents of tomatoes differed between 2 years statistically. Antioxidant activities of tomatoes were found between 48 and 118 μmol TEAC 100 g?1. A significant correlation was only observed between L-ascorbic acid (2.2–13.8 mg 100 g?1) and antioxidant activity using TEAC assay. 相似文献
14.
Cyclic minimizers, majorization techniques, and the expectation-maximization algorithm: a refresher 总被引:1,自引:0,他引:1
Many parameter estimation problems in signal processing can be reduced to the task of minimizing a function of the unknown parameters. This task is difficult owing to the existence of possibly local minima and the sharpness of the global minimum. In this article we review three approaches that can be used to minimize functions of the type encountered in parameter estimation problems. The first two approaches, the cyclic minimization and the majorization technique, are quite general, whereas the third one, the expectation-maximization (EM) algorithm, is tied to the use of the maximum likelihood (ML) method for parameter estimation. The article provides a quick refresher of the aforementioned approaches for a wide readership. 相似文献
15.
The Journal of Supercomputing - This study proposes a set of new robust parallel hybrid metaheuristic algorithms based on artificial bee colony (ABC) and teaching learning-based optimization (TLBO)... 相似文献
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17.
Response surface methodology (RSM) was used to optimize the medium components of α‐amylase production using solid substrate fermentation (SSF). Hazelnut cake (HC), peptone, yeast extract (YE), and (NH4)2SO4 were selected as independent variables for optimization. Central composite design (CCD) was used in design experiments and analysis results. This procedure limited the number of actual experiments performed while allowing possible interactions between the independent variables. By using CCD, 30 experiments were performed for determining the interaction of independent variables and optimization of fermentation medium. The P‐value of the coefficient of linear effect of (NH4)2SO4 concentrations, which was obtained as 0.0001 has shown that this parameter has the greatest effect on the production of α‐amylase. Model F‐value (5.62) implies that the model is significant. The highest α‐amylase activity (4895 IU) was measured when the HC, peptone, YE, and (NH4)2SO4 concentrations in the medium were 22.62, 5.20, 1.62, and 6.81 g L?1, respectively. 相似文献
18.
Shear-thinning and self-healing hydrogels are being investigated in various biomedical applications including drug delivery, tissue engineering, and 3D bioprinting. Such hydrogels are formed through dynamic and reversible interactions between polymers or polypeptides that allow these shear-thinning and self-healing properties, including physical associations (e.g., hydrogen bonds, guest–host interactions, biorecognition motifs, hydrophobicity, electrostatics, and metal–ligand coordination) and dynamic covalent chemistry (e.g., Schiff base, oxime chemistry, disulfide bonds, and reversible Diels–Alder). Their shear-thinning properties allow for injectability, as the hydrogel exhibits viscous flow under shear, and their self-healing nature allows for stabilization when shear is removed. Hydrogels can be formulated as uniform polymer and polypeptide assemblies, as hydrogel nanocomposites, or in granular hydrogel form. This review focuses on recent advances in shear-thinning and self-healing hydrogels that are promising for biomedical applications. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020 , 137, 48668. 相似文献
19.
A generalized model to predict minimum particle transport velocities in multiphase air–water horizontal pipes
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Kamyar Najmi Brenton S. McLaury Siamack A. Shirazi Alan L. Hill Selen Cremaschi 《American Institute of Chemical Engineers》2015,61(8):2634-2646
A new model is proposed to predict minimum flow rates required to constantly move particles in both intermittent and stratified flow regimes. The new model consists of a single‐phase flow model along with an appropriate length scale to be extended to multiphase flow regime. A comparison of the new model with experimental data in a multiphase air–water flow shows that the new model is able to predict minimum flow rates well for a wide range of operating conditions. The new model can capture the effects of particle size, particle concentration, and pipe size as confirmed by experimental data. A comparison of the new model with previously proposed models in the literature shows that the new model improves critical velocity predictions significantly. Moreover, the new model is the only model that takes into account the effect of particle concentration and can predict critical velocity in both intermittent and stratified flow regimes. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2634–2646, 2015 相似文献
20.
Elif Selen AtesHusnu Emrah Unalan 《Thin solid films》2012,520(14):4658-4661
Zinc oxide (ZnO) nanowires have been grown on cotton fabric to impart self-cleaning, superhydrophobicity and ultraviolet (UV) blocking properties. ZnO nanowires were grown by the microwave assisted hydrothermal method and subsequently functionalized with steraic acid to obtain a water contact angle of 150°, showing their superhydrophobic nature which is found to be stable up to 4 washings. UV protection of the resulting cotton fabric was also examined and significant decrease in the transmission of UV range was observed. Self-cleaning activity of the ZnO nanowire coated cotton fabric was also studied and it showed considerable degradation of methylene blue under UV light irradiation. These results suggest that ZnO nanowires could form ideal multifunctional coatings for textiles. 相似文献