Seismic noise attenuation by means of an anisotropic non-linear diffusion filter

Noise attenuation is a major seismic data processing concern. In seismic data, noise can appear as random, coherent and/or impulsive. Recently, many different techniques, ranging from relatively simple processes to extremely complex ones, have been used for noise attenuation. Image filtering techniques are relatively new methods in seismic exploration. We introduced the anisotropic non-linear diffusion filter which is an effective way to de-noise images. Since a seismic section can be considered as an image of a two-variable function, we implemented the anisotropic non-linear diffusion filter to reduce both random and Gaussian noises. This filter is shown to be effective in removing noise while preserving edges and hence reducing resolution loss in seismic data. The anisotropic non-linear diffusion filter, with Tukey's function to guide the diffusivity, was applied to synthetic and real seismic data. The results show a signal-to-noise ratio increase with reflector continuity in addition to better recovery of reflector amplitudes even when dealing with complex subsurface geological structures.     

New multilayer arrangement of dielectric layers for enhancement of the magnetic shielding absorption at low frequency in the near field

This paper presents a new multilayer arrangement structure based on the dielectric polymer, which allows an effective absorption of magnetic wave radiation, and a selective reflection of desired wavelengths of the shield composite in the low frequency range that is not widely used in general cases. This is caused by the impedance mismatch between conductive films and air, and between conductive films and dielectric polymer layer. The structure is built from alternating conductive films and dielectric polymer layers, in a way that dielectric polymer layers are sandwiched between conductive films symmetrically in both directions. The simulation results of both the absorption and the total shielding effectiveness from the developing analytical model are in good agreement with experimental characterization, and could be further extended to the design of systems operating in other frequency ranges.     

Fabrication of polysulfone nanocomposite membranes with silver‐doped carbon nanotubes and their antifouling performance

In this study, polysulfone (PSf)/silver‐doped carbon nanotube (Ag‐CNT) nanocomposite membranes were prepared by a phase‐inversion technique; they were characterized and evaluated for fouling‐resistant applications with bovine serum albumin (BSA) solutions. Carbon nanotubes were doped with silver nanoparticles via a wet‐impregnation technique. The prepared Ag‐CNT nanotubes were characterized with scanning electron microscopy (SEM)/energy‐dispersive X‐ray spectroscopy, X‐ray diffraction, Raman spectroscopy, and thermogravimetric analysis. The fabricated flat‐sheet PSf/Ag‐CNT nanocomposite membranes with different Ag‐CNT loadings were examined for their surface morphology, roughness, hydrophilicity, and mechanical strength with SEM, atomic force microscopy, contact angle measurement, and tensile testing, respectively. The prepared composite membranes displayed a greater rejection of BSA solution (≥90%) and water flux stability during membrane compaction with a 10% reduction in water flux values (up to 0.4% Ag‐CNTs) than the pristine PSf membrane. The PSf nanocomposite membrane with a 0.2% Ag‐CNT loading possessed the highest flux recovery of about 80% and the lowest total membrane resistance of 56% with a reduced irreversible fouling resistance of 21%. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 44688.     

Application of a radial basis function artificial neural network to seismic data inversion

We investigate here the performance and the application of a radial basis function artificial neural network (RBF-ANN) type, in the inversion of seismic data. The proposed structure has the advantage of being easily trained by means of a back-propagation algorithm without getting stuck in local minima. The effects of network architectures, i.e. the number of neurons in the hidden layer, the rate of convergence and prediction accuracy of ANN models are examined. The optimum network parameters and performance were decided as a function of testing error convergence with respect to the network training error. An adequate cross-validation test is run to ensure the performance of the network on new data sets. The application of such a network to synthetic and real data shows that the inverted acoustic impedance section was efficient.     

Influence of recycled sand and gravel on the rheological and mechanical characteristic of concrete

The objective of this paper is to investigate the influence of type and dosage of recycled sand (RS) and gravel on the fresh and mechanical properties of concrete. Experimental program was conducted on concretes made with different ratio of substitutions (15, 30, 70, and 100%) of natural sand and gravel with RS and gravel. At the fresh state, slump, air content, and density were measured at the exit of the mixer, and then at 30, 60, and 90 min after mixing. Tests were also performed for compressive strength at the age of 1, 7, and 28 days, whereas elastic modulus measurements were done at 28 days. The results indicated that maintaining the workability of recycled aggregate concrete depends on sand or gravel substitution and their rates. Up to 30 min, slump values were decreased, but after that, no substantial change in slump values was observed. Air content increased and density decreased, with increasing recycled aggregate content (sand or gravel). Mechanical properties, such as compressive strength and modulus of elasticity, were lower than those of reference concrete.     

Effect of manufacturing and assembly defects on two-stage gear systems vibration

The modeling of the dynamic behavior of a two-stage gear system is made for a general configuration of wheels location. The excitation is induced by the periodic variation of the mesh stiffness. This case describes the real working of the gearings. The variation of the mesh phasing is related to the number of teeth and also to the wheels location. We developed a plane model of a two-stage gear system. The modal analysis of the system was then treated. The calculation of the dynamic response was done by a step-by-step time integration method (Newmark algorithm). Three cases of wheels location are treated. The solutions are presented both in the frequency domain and in the time domain. Three types of geometric defects of the toothed wheels are introduced in the model: defect of eccentricity, profile error and assembly defect. An analysis of the effects of these defects on the gear system dynamic behavior is then treated.     

Role of dopants (B,P and S) on the stabilization of β-Ca2SiO4

The interest in belite (Ca₂SiO₄ + impurities or dopants) phase increases significantly since new types of clinkers based essentially on this phase become promising alternatives to Portland clinker for reducing CO₂ emission. Belite is also of interest as a biomedical cement. For the cement industry, stabilization of the β-polymorph is essential since the γ-polymorph has no hydraulic activity. In order to understand the mechanism of β-polymorph stabilization, this paper explores the addition of three dopants, namely P, B and S. It turns out that these dopants can modify the lattice parameters of Ca₂SiO₄ and induce specific twinning morphologies and surface relief, as well as grain boundaries deformations. A link between the addition of dopant leading to significant microstructural changes and the stabilization of β-polymorph has been established.