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21.
Mechanical, dynamic mechanical, and rheological behaviors of a short p‐aramid fiber reinforced thermoplastic polyurethane (TPU) have been studied in the range of 0–30 wt% of fibers. The tensile strength of the composite is improved slightly at higher fiber content with a minimum at around 10 wt% of fibers. The addition of fibers markedly reduces elongation at break and entails a steady increase in the elastic modulus, but decreases the wear resistance of the matrix. Storage modulus (E′) is increased and the shapes of loss tangent (tan δ) peaks point to a possible fiber–matrix interaction. Rheological studies show a power law behavior for all composites and increased viscosity with fiber loading. Study of the tensile and cryogenic fracture surfaces by scanning electron microscopy (SEM) indicates good correlation between the modes of failure and strength of the composites. The micrographs reveal good interfacial adhesion and extensive peeling and fibrillation of the fibers in the compounded and fractured composites. Theoretical models have been used to fit the experimental modulus data. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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Hadi?Ahmari Saeed?Zeinali HerisEmail author Mohammad?Hassanzadeh Khayyat 《Research on Chemical Intermediates》2016,42(8):6587-6606
Linear alkylbenzene sulfonic acid (LAS) is a common substance used in the production of detergents in the world. This is an organic material with its structure made of benzene ring and double bonds. This structure creates many problems for the environment and humans. Up to now, various methods have been used to eliminate this pollution. A recently proposed method to remove this organic pollution is advanced oxidation processes. Photocatalytic degradation is also an efficient method to destroy organic structures. In this research, TiO2 nanoparticles are used as a photocatalyst that is activated by UV irradiation. TiO2 nanoparticles and pollution suspension are incorporated into the new design of the reactor with coaxial cylinders in which the inner cylinder rotates at a constant speed. The results show that in low concentrations of LAS, using TiO2 nanoparticles, the time to reach pollution elimination is reduced significantly. In higher concentrations of LAS, UV irradiation is more effective than activated TiO2 nanoparticles. 相似文献
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M. Norouzi A. Shahbani Zahiri M. M. Shahmardan H. Hassanzadeh M. Davoodi 《Meccanica》2017,52(8):1889-1909
A numerical study of stress distribution of polymeric viscoelastic fluids passing through planar gradual expansion channels is conducted. To model the viscoelastic behavior in geometries with 1:3 expansion ratios, the exponential form of Phan-Thien Tanner model is employed as the constitutive equation. The PISO algorithm is used to solve the flow field distribution. Three different expansion angles of 30°, 45° and 60° are considered to probe the effects of the gradual expansion and its effect on the stress field distribution. The main purpose of the current study is to analysis the combined effects of the rheological properties and inertia on the normal stress distribution. To achieve this aim, different expansion angles and different ranges of Weissenberg and Reynolds numbers are studied. 相似文献
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We study gravitational baryogenesis in the context of f(R, T) gravity where the gravitational Lagrangian is given by a generic function of the Ricci scalar R and the trace of the stress-energy tensor T. We explore how this type of modified gravity is capable to shed light on the issue of baryon asymmetry in a successful manner. We consider various forms of baryogenesis interaction and discuss the effect of these interaction terms on the baryon to entropy ratio in this setup. We show that baryon asymmetry during the radiation era of the expanding universe can be non-zero in this framework. Then, we calculate the baryon to entropy ratio for some specific f(R, T) models and by using the observational data, we give some constraints on the parameter spaces of these models. 相似文献
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Nano‐structured self‐doped polythiophene (SPT) electrodeposited in the presence of fluorinated organic acid was applied as a thermally stable conductive polymer‐based solid‐phase microextraction (SPME) fiber candidate. Quantitative determination of trace levels of phthalate esters including dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DBP), and diethylhexyl phthalate (DEHP) was carried out using this novel fiber, coupling with gas chromatography‐flame ionization detector (GC‐FID). The SPT coating was proved to be stable at high temperatures (~350°C) with a high extraction capacity and long lifetime (more than 60 times). Improved temperature resistance was obtained by the presence of sulfonated groups in the backbone of polymer. Thermal stability of novel SPT was superior to common polythiophene (synthesized in LiClO4). The extraction procedure was optimized by means of the Taguchi orthogonal array experimental design with an OA16 (45) matrix including extraction temperature, extraction time, salt concentration, stirring rate, and headspace volume. The good linearity was obtained for most compounds with correlation coefficients (R2) of between 0.993 and 0.995. The detection limits were lower than 0.12 ng/mL for dimethyl phthalate, DEP, dibutyl phthalate, and diethylhexyl phthalate. The method was successfully applied to the analysis of water samples with the recoveries from 90±1 to 107±1%. 相似文献
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Ardeshir Khazaei Mohammad Ali Zolfigol Mohmmad Mokhlesi Fateme Derakhshan Panah Sami Sajjadifar 《Helvetica chimica acta》2012,95(1):106-114
Two simple, mild, and efficient procedures for the thiocyanation of N‐heterocycles, substituted anilines (electron‐rich and electron‐deficient), and N‐substituted aromatic amines at room temperature are reported (Table 3). The first uses H2O2 as pollution‐free oxidant and the second H5IO6; both with the reagent potassium thiocyanate in H2O as solvent. These procedures provided the target thiocyanates after a short reaction time in good to excellent yields and high regioselectivity. 相似文献
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Onset of double-diffusive buoyancy-driven flow resulted from vertical temperature and concentration gradients in a horizontal
layer of a saturated and homogenous porous medium is investigated using amplification factor theory. After injection of CO2 into a deep saline aquifer, the density of the brine saturated with CO2 increases slightly. This increase in density induces natural convection. The effect of geothermal gradient is also considered
in this work as a second incentive for convection and the double-diffusion convection was studied. Linear stability analysis
is used to predict the inception of instabilities and initial wavelength of the convective instabilities. The analysis presented
is applied to acid gas injection (as an analogue for CO2 storage) into saline aquifers in the Alberta basin. It is found that the geothermal gradient does not have significant effect
on the onset of convection for these aquifers. It is shown that the geothermal effects on the onset of natural convection
are negligible as compared to the solutal effects induced by dissolution and diffusion of CO2 in deep saline aquifers. Therefore, the linear stability analysis and the long-term numerical simulation of CO2 sequestration into such saline aquifers may be assumed to be isothermal in terms of natural convection occurrence. 相似文献
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Meshkani Fereshteh Golesorkh Sayyede Fateme Rezaei Mehran Andache Mahmood 《Research on Chemical Intermediates》2017,43(1):545-559
Research on Chemical Intermediates - Mesoporous MgAl2O4 nanopowders were synthesized via the homogenous precipitation method and employed as a support for Ni catalysts in the dry reforming... 相似文献