With the recent success of nonlocal theories in modeling of engineering problems involving small intrinsic length scales, such as modeling of crack propagation, this paper addresses issues pertaining to cost-ineffectiveness of Eringen’s integral model. The cost effectiveness of the computation may be considered as a twofold issue; one pertaining to the non-local model and another pertaining to the numerical tool. First of all, we shall show that during the solution of problems with Eringen’s non-local integral model, there is no need to consider the integral model for the whole computational domain. In fact, the problems may be solved by just using the integral model close to the boundaries, i.e. a boundary layer effect, or around the points with singularities. In this paper we propose a partitioning strategy to remarkably reduce the computational cost. This may be considered as a gateway for solving some types of two-scale problems, e.g. those with macro/micro and nano scales, in which the small scale effects are localized just at parts of the domain. To demonstrate the efficiency of the numerical tools, we examine the performance of the finite element method (FEM), the element free Galerkin method (EFG) and the finite point method (FPM). This paves the way for using mesh-free methods in the solution of problems with non-local integral models. Examples with smooth and non-smooth solutions are considered for examining the efficiency of the methods. It will be shown that, by considering the boundary layer effect, the FEM and FPM will be efficient enough for being used in problems defined by Eringen’s non-local integral model.
In this paper, the wave transmission from finite photonic crystals with multiple alternations is investigated using boundary element method (BEM). Since that, in these structures the alternation is not in all directions of space; the investigations of the frequency band gap with desired accuracy are not practical by analytical methods. Also, the frequency dispersion of dielectric rods is an effective parameter in photonic crystals, which this effect in our calculations has been considered. Due to the high capabilities of the BEM, the transmitted wave spectrum in the photonic crystal is calculated by changing the geometrical and optical parameters of the photonic crystal and applying more alternation in its structure and the position and width of the frequency band gap is investigated. Then, it is assumed that the photonic crystal with an arbitrary angle is rotated around the axis which is perpendicular on the crystal cross section and then, it is irradiated with a plan wave. The band gap of the photonic crystals with the desired structure, desired rotation angle and multiple alternations have been solved. Very low information volume, high speed and accuracy during the calculation and useable for any desired structures are the characteristics of this method. 相似文献
Time-resolved 2H NMR spectroscopy is used to monitor the progress of and gain kinetic information for a variety of reactions in different ionic media. 相似文献
Simultaneous determination of Fe(II) and Fe(III) or selective determination of each oxidation state of iron in the presence of the other one by H-point standard addition method (HPSAM) is described. Mixed reagents of 1,10-phenanthroline and salicylic acid was used as a selective chromogenic system for speciation of Fe(II) and Fe(III). It was shown that with appropriate selection of wavelength pairs, both Fe(II) and Fe(III) can be considered as analyte. The results showed that Fe(II) and Fe(III) can be determined simultaneously with the concentration ratios of Fe(II) to Fe(III) varying from 10:1 to 1:20 in the mixed sample. The accuracy and precision of the method are all satisfactory. 相似文献
The 82Sr/82Rb radionuclide generator is used very commonly in positron emission tomography. ALICE/ASH and TALYS 1.0 codes were used to calculate excitation functions for proton, alpha and 3He induced on various targets that lead to produce 82Sr radioisotope using intermediate energy accelerators. Recommended thickness of the targets according to SRIM code was premeditated. The application of those data, particularly in the calculation of integral yields, is discussed and theoretical integral yields for any reaction were computed. To consider precision of TALYS 1.0 code calculations, 85Rb(p,4n)82Sr process was determined as most interesting one due to radionuclide purity. The TALYS 1.0 code predicts a maximum cross-section of about 130 mb at 47 MeV for this reaction. Rubidium chloride deposition on copper substrate was carried out via sedimentation method in order to produce 82Sr. 2.98 g RbCl, 1.043 g ethyl cellulose, 10 mL acetone were used to prepare a layer of enriched rubidium chloride of 11.69 cm2 area and 0.34 g/cm2 thickness. 相似文献
A new finite volume (FV) approach with adaptive upwind convection is used to predict the two-dimensional unsteady flow in a square cavity. The fluid is air and natural convection is induced by differentially heated vertical walls. The formulation is made in terms of the vorticity and the integral velocity (induction) law. Biquadratic interpolation formulae are used to approximate the temperature and vorticity fields over the finite volumes, to which the conservation laws are applied in integral form. Image vorticity is used to enforce the zero-penetration condition at the cavity walls. Unsteady predictions are carried sufficiently forward in time to reach a steady state. Results are presented for a Prandtl number (Pr) of 0-71 and Rayleigh numbers equal to 103, 104 and 105. Both 11 × 11 and 21 × 21 meshes are used. The steady state predictions are compared with published results obtained using a finite difference (FD) scheme for the same values of Pr and Ra and the same meshes, as well as a numerical bench-mark solution. For the most part the FV predictions are closer to the bench-mark solution than are the FD predictions. 相似文献
A simple configuration for the reduction of stimulated Brillouin scattering threshold in photonic crystal fiber is presented.
The threshold reduction is contributed by the bidirectional pumping scheme through the reflection of transmitted Brillouin
pump back to the gain medium. The pump recycling scheme has greatly reduced the Brillouin threshold of a 200-m long of photonic
crystal fiber from 50 to 30 mW of Brillouin pump power. 相似文献