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51.
Behrouz Parsa Moghaddam José António Tenreiro Machado 《Journal of scientific computing》2017,71(3):1351-1374
This paper proposes accurate and robust algorithms for approximating variable order fractional derivatives of arbitrary order. The proposed schemes are based on finite difference approximations. We compare the performance of algorithms by introducing a new formulation of experimental convergence order. Two initial value problems are considered and solved by means of the proposed methods. Numerical results are provided justifying the usefulness of the proposed methods. 相似文献
52.
In this study, thermal and small-scale effects on the flapwise bending vibrations of a rotating nanoplate, which can be the basis of nano-turbine design, have been analyzed. The nano-turbine is made of an orthotropic nanoplate with a setting angle that is modeled based on the classical plate theory (CPT) with cantilever boundary conditions. The axial forces are also included in the model as the true spatial variation due to the rotation and temperature change. The governing equations and boundary conditions are derived according to Hamilton's principle and the governing equations are solved with the aid of the generalized differential quadrature method. The effects of small-scale parameter, nondimensional angular velocity, temperature change, and setting angles in the first four nondimensional frequencies are discussed. Due to the consideration of the rotating effects, results of this study are applicable in nano-machines, such as nano-motors, nano-rotor, and other rotating nano-structures. Also, by considering the effect of thermal loading on rotation of a nanoplate, the results are useful in the design of nano-turbines. 相似文献
53.
Although short-circuit current is frequently considered the major design fundamental for power transformers, experience with transformer failures shows that inrush currents that occur when transformers are energized can also cause serious damage. To investigate the resultant forces due to energizing power transformer windings, we modeled a three-phase, three-legged 66/11 kV, 40 MVA power transformer in two and three dimensions. We calculated electromechanical forces for short-circuit cases and also for inrush current through the windings, using the finite-element method. The results show that the forces exerted on the windings due to inrush current in many regions are larger than those due to short-circuit currents. Since the inrush current appears more frequently with a much longer duration compared to a short-current event, its harmful effects are worse than those of the short-circuit case. 相似文献
54.
The ever increasing cost of hydrocarbon fuels and more stringent emission standards may resolve challenges in producing hydrogen and using it as an alternative fuel in industries. Internal combustion engines are well-established technology and hydrogen fuel in such engines is considered as an attractive choice in exploiting clean, efficient and renewable hydrogen energy. 相似文献
55.
The machinability of microalloyed steel (30MnVS6) and quenched-tempered (QT) steels (AISI 1045 and AISI 5140), at different cutting condition, is presented in the paper. An experimental investigation was conducted to determine the effects of cutting speed, feed rate, hardness, and workpiece material on the flank wear land and tool life of coated cemented carbide inserts in the hard turning process. It was tried that for any test condition the hardness of these steels became almost identical by using appropriate heat-treatment processes. The statistical analysis was used for evaluation of different factors on cutting forces. Chips characteristics and chip/tool contact length were also investigated. The different sections (shear plane, microcrack, thickness and edge) of the chip were examined by scanning electron microscope (SEM). Shear planes and microcracks of the chips in microalloyed steel show that the chips of microalloyed steel are regular and discontinuous. Crater wear of the tools was studied by using video microscope in turning process. The results showed that the tool life and machinability of the microalloyed steel is better than the QT steels at identical cutting condition. 相似文献
56.
57.
Supersaturated dendritic Al-Mg alloy powders in globular form were produced using galvanostatic electrodeposition technique on polycrystalline Cu and Mg-substrates. The deposit produced on Cu-substrate possessed face centered cubic (fcc)-Al(Mg) phase with composition of ~ 18 at.% Mg. However, when Mg-substrate was used, initially hexagonal close packed (hcp)-Mg(Al) phase with ~ 77 at.% Mg was formed over which fcc-Al(Mg) phase with ~ 36 at.% Mg was nucleated. The results of the present study indicate that substrate crystal structure and estimated substrate-deposit lattice mismatch can influence the depositing phase and its composition but not the morphology of these powders. 相似文献
58.
Dipyridamole recognition and controlled release by uniformly sized molecularly imprinted nanospheres
Mehdi Esfandyari-Manesh Mehran Javanbakht Fatemeh Atyabi Ali Mohammadi Somayeh Mohammadi Behrouz Akbari-Adergani Rassoul Dinarvand 《Materials science & engineering. C, Materials for biological applications》2011,31(8):1692-1699
We used novel synthetic conditions of precipitation polymerization to obtain uniformly sized molecularly imprinted nanospheres of dipyridamole for application in the design of new drug delivery systems. In addition, the morphology, drug release, and binding properties of molecularly imprinted polymers (MIPs) were studied, and the effects of morphology on other properties were investigated. The MIPs prepared by acetonitrile/chloroform (19:1, v/v) were uniformly sized nanospheres with an average mean diameter of approximately 88 nm at a wetted state, 50 nm at a dry state, and a polydispersity index of 0.062. The imprinted nanospheres showed excellent binding properties and had 62.7% of template binding compared with 17.1% of its blank polymer. The imprinted nanospheres with 67.5 (mg template/of polymer) of binding capacity had better imprinting efficiency than the 50.5% of binding capacity shown by irregularly shaped MIP particles that were prepared by chloroform. The molecular binding abilities of imprinted nanospheres in human serum were evaluated by HPLC analysis (binding about 77% of dipyridamole). Results from release experiments of MIPs showed a very slow, controlled, and satisfactory release of dipyridamole. The loaded drug was released up to 99% in 17 days for nanospheres and 22 days for irregularly shaped particles. 相似文献
59.
Francesca De Simone Lutz Goldmann Jong-Seok Lee Touradj Ebrahimi 《Journal of Visual Communication and Image Representation》2011,22(8):734-748
This paper describes the details and the results of the subjective quality evaluation performed at EPFL, as a contribution to the effort of the joint collaborative team on video coding (JCT-VC) for the definition of the high efficiency video coding (HEVC) standard. The performance of twenty-seven coding technologies has been evaluated with respect to two H.264/MPEG-4 AVC anchors, for high definition (HD) test material. The test campaign involved a total of 494 naive observers and took place over a period of four weeks. While similar tests have been conducted as part of the standardization process of previous video coding technologies, the test campaign described in this paper is by far the most extensive in the history of video coding standardization. A detailed statistical analysis of the subjective results is provided. The results show high consistency and support an accurate comparison of the performance of the different coding technologies. 相似文献
60.
Strontium hexaferrite SrFe12O19 thin films have been synthesized on the Si (100) substrate using spin coating sol-gel process. The influence of different citric acid to metal ions (CA/MN) molar ratios of 0.5, 1 and 1.5 on the formation of SrFe12O19 was investigated. Fourier transform infrared analysis and theoretical calculations were conducted to determine and help control the concentration of metal citrates in solution precursors. X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer techniques were also applied to evaluate the composition, microstructure, crystallite size and magnetic properties of the SrFe12O19 thin films. The results showed that single phase strontium hexaferrite thin films with optimum physical properties can be obtained from the solution with the CA/MN molar ratio of 1 after calcination at 800 °C. The SrFe12O19 thin films synthesized with the CA/MN molar ratio of 1 exhibited crystallite size of 42 nm and isotropically magnetic properties of Ms = 267.5 kA/m (at 795.8 kA/m), Mr = 134 kA/m, and Hc = 341.4 kA/m. 相似文献