排序方式: 共有77条查询结果,搜索用时 15 毫秒
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Farshad Motamedi Ulrich Jonas Andreas Greiner Hans-Werner Schmidt 《Liquid crystals》2013,40(4):959-970
Abstract Fibres were prepared from the nematic melt of poly(2,2′-dimethyl-4,4′-biphenylene phenylterephthalate). The phenyl substitution in the terephthalic acid moiety in combination with the non-coplanar biphenyl moiety prevent crystallization of this thermotropic polyester. Oriented fibres were prepared by two different methods. Similarly to other thermotropic liquid crystal polymer fibres, chain orientation can be achieved by an elongational flow in a down draw process. This polyester also allows tensile deformation of the spun fibres around the glass transition temperature. In both routes similar degrees of orientation and mechanical properties were obtained. Tensile moduli in the order of 40–45 GPa and tensile strengths up to 550–650 MPa were obtained. The orientation function values were determined to be in the order of 0·8–0·9. A comparison with other unsubstituted thermotropic liquid crystal polyesters at the same level of orientation revealed that the moduli are the same, although the substituents increase the chain diameter. This result may be attributed to an increase of the apparent shear modulus due to an interlocking mechanism of the rigid lateral substituents. 相似文献
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Sajjad Rashidi Farshad Farzin Mehdi Shanbedi Masoud Rahimipanah Maryam Savari 《Journal of Dispersion Science and Technology》2016,37(9):1277-1286
In order to enhance the thermal properties of turbine oil (TO), three different nanoparticles (CuO, Al2O3, and TiO2) are loaded into the TO. To measure the thermal performance of nanoparticle-based TO nanofluids at laminar flow and under constant heat flux boundary conditions, an experimental setup was applied. The obtained data clearly demonstrate the positive effect of all nanoparticles on the heat transfer rate of TO. As the most important factor, the heat transfer coefficient of the abovementioned two-phase systems is increased upon increasing both the volume concentration and the flow rate. An adaptive neuro-fuzzy inference system (ANFIS) is applied for modeling the effect of critical parameters on the heat transfer coefficient of nanoparticle-TO based nanofluids numerically. The results are compared with experimental ones for training and test data. The results suggest that the developed model is valid enough and promising for predicting the extant of the heat transfer coefficient. R2 and MSE values for all data were 0.990208751 and 108.1150734, respectively. Based on the results, it is obvious that our proposed modeling by ANFIS is efficient and valid, which can be expanded for more general states. 相似文献
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Farshad Merrikh-Bayat 《Communications in Nonlinear Science & Numerical Simulation》2012,17(4):1852-1861
Oustaloup recursive approximation (ORA) is widely used to find a rational integer-order approximation for fractional-order integrators and differentiators of the form sv, v ∈ (−1, 1). In this method the lower bound, the upper bound and the order of approximation should be determined beforehand, which is currently performed by trial and error and may be inefficient in some cases. The aim of this paper is to provide efficient rules for determining the suitable value of these parameters when a fractional-order PID controller is used in a stable linear feedback system. Two numerical examples are also presented to confirm the effectiveness of the proposed formulas. 相似文献
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Momodu Damilola Madito Moshawe Barzegar Farshad Bello Abdulhakeem Khaleed Abubakar Olaniyan Okikiola Dangbegnon Julien Manyala Ncholu 《Journal of Solid State Electrochemistry》2017,21(3):859-872
Journal of Solid State Electrochemistry - Activated carbon from tree bark (ACB) has been synthesized by a facile and environmentally friendly activation and carbonization process at different... 相似文献
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Kowsary Farshad Razzaghi Honeyeh Ashjaee Mehdi 《Journal of Thermal Analysis and Calorimetry》2020,140(1):439-456
Journal of Thermal Analysis and Calorimetry - In this study, a two-dimensional inverse algorithm is developed to determine the heat transfer coefficient distribution of a two-phase air–water... 相似文献
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In this paper, the optimal shape of a column with the most general conservative state of loading is determined. The boundary conditions of a column contain, in general, 16 parameters; it is shown that the boundary values of a column with general conservative loading may, at most, depend on nine constants. The influence of these parameters on the optimal shape and corresponding buckling load is also obtained. 相似文献
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Pyrogallol (1,2.3-benzentriol, 1 ) reacts with dioxygen in weakly alkaline solutions to form purpurogallin (2,3,4,6-tetrahydroxy-5H-benzocycloheptene-5-one, 2 ) which then reacts to form purpurogalloquinone ( 3 ) which then decays to a product absorbing at 440 nm. The formation of 3 requires 1.5 mol O2 per mol 1 , and 1.0 mol per mol 2 . No O2 is consumed during the decay of 3 , and this reaction, being insensitive to O2 concentrations and the presence of both superoxide dismutase (SOD) and catalase, does not appear to be an oxidation. The first-order rate of decay of 3 decreases with increasing pH. 1 and 3 react at pH 9.0 with a second-order rate constant of ca. 100 M?1 s?1. SOD inhibits the oxidation of 1 and 2 . Slight and variable apparent inhibition of the oxidation of 2 and 3 by SOD may be due to trace impurities in 2 , but not contamination by 1 . The peak concentration of 3 is attained more rapidly during the oxidation of 1 than during the oxidation of 2 . A kinetic scheme based on parallel oxidation of 1 by dioxygen and superoxide, and it which the semiquinone of 1 oxidizes 2 , is partially successful in simulating the observed kinetic behavior. 相似文献
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Farshad Kheiri Reza Emamali Sabzi Elham Jannatdoust Hassan Sedghi 《Journal of Solid State Electrochemistry》2011,15(11-12):2593-2599
A novel biosensor for catechol has been constructed by immobilizing polyphenol oxidase (PPO) into acetone-extracted propolis (AEP) composite modified with gold nanoparticles (GNPs) and attached to multiwalled carbon nanotube (MWCNTs) on a gold electrode surface. The propolis for AEP was obtained from honeybee colonies. Under the optimum conditions, this method could be successfully used for the amperometric determination of catechol within a concentration range of 1 × 10?6 to 5 × 10?4?M, with a detection limit of 8 × 10?7?M (S/N = 3). The effects of pH and operating potential are also explored to optimize the measurement conditions. The best response was obtained at pH?5, while an optimum ratio of signal-to-noise (S/N) was obtained at ?20?mV (versus Ag/AgCl), which was selected as the applied potential for the amperometric measurements. All subsequent experiments were performed at pH?5. Cyclic voltammetry and electrochemical impedance spectroscopy was used to characterize the PPO/CNTs/GNPs/AEP/Au biosensor. The biosensor also exhibited good selectivity, stability, and reproducibility. 相似文献
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Natalia Ferraz Anastasiya Leschinskaya Farshad Toomadj Bengt Fellström Maria Strømme Albert Mihranyan 《Cellulose (London, England)》2013,20(6):2959-2970
The membrane and solute diffusion properties of Cladophora cellulose and polypyrrole (PPy) functionalized Cladophora cellulose were analyzed to investigate the feasibility of using electroactive membranes in hemodialysis. The membranes were characterized with scanning electron microscopy, ζ-potentiometry, He-pycnometry, N2 gas adsorption, and Hg porosimetry. The diffusion properties across the studied membranes for three model uremic toxins, i.e. creatinine, vitamin B12 and bovine serum albumin, were also analyzed. The characterization work revealed that the studied membranes present an open structure of weakly negatively charged nanofibers with an average pore size of 21 and 53 nm for pristine cellulose and PPy-Cladophora cellulose, respectively. The results showed that the diffusion of uremic toxins across the PPy-Cladophora cellulose membrane was faster than through pure cellulose membrane, which was related to the higher porosity and larger average pore size of the former. Since it was found that the average pore size of the membranes was larger than the hydrodynamic radius of the studied model solutes, it was concluded that these types of membranes are favorable to expand the Mw spectrum of uremic toxins to also include conditions associated with accumulation of large pathologic proteins during hemodialysis. The large average pore size of the composite membrane could also be exploited to ensure high-fluxes of solutes through the membrane while simultaneously extracting ions by an externally applied electric current. 相似文献