Cu-doped NaCu0.05Fe0.45Co0.5O2 as promising cathode material for Na-ion batteries: synthesis and characterization

Journal of Solid State Electrochemistry - In this work, Cu-doped NaFe0.5Co0.5O2 was easily prepared by a one-step solid-state reaction and studied the effect of copper salt precursors including...     

The Bakhvalov mesh: a complete finite-difference analysis of two-dimensional singularly perturbed convection-diffusion problems

Numerical Algorithms - A linear two-dimensional singularly perturbed convection-diffusion boundary-value problem is considered. The problem is discretized by the upwind finite-difference method....     

A boundary element simulation of the unsteady motion of a sphere in a cylindrical tube containing a viscoelastic fluid

A boundary element method is used to simulate the unsteady motion of a sphere falling under gravity along the centreline of a cylindrical tube containing a viscoelastic fluid. The fluid is modelled by the upper-convected Maxwell constitutive equation. Results show that the viscoelasticity of the liquid leads to a damped oscillation in sphere velocity about its terminal value. The maximum sphere velocity, which occurs in the first overshoot, is approximately proportional to the square root of the Weissenberg number when the ratio of the sphere radius to the tube radius is sufficiently small. Particular attention is also paid to the wall effects. It is shown that a closer wall reduces the oscillatory amplitude of the sphere velocity but increases its frequency. The results suggest that the falling-ball technique, which is now widely used for viscosity measurement, might also be used for the determination of a relaxation time for a viscoelastic fluid.     

Extrudate swell through an orifice die

The extrudate swell of a viscoelastic fluid through an orifice die is investigated by using a mixed finite element and a streamline integration method (FESIM), using a version of the K-BKZ model. The free surface calculation is based on a local mass conservation scheme and an approximate numerical treatment for the contact point movement of the free surface. The numerical results show a vortex growth and an increasing swelling ratio with the Weissenberg number. Convergence with mesh refinement is demonstrated, even at a high Weissenberg number of O(587), where the swelling ratio reaches a value of about 360%. In addition, it is found that the effective flow channel at the entrance region next to the orifice die is reduced due to the enhanced vortex growth, which may be a source of flow instability.     

Oxide‐Supported IrNiOx Core–Shell Particles as Efficient,Cost‐Effective,and Stable Catalysts for Electrochemical Water Splitting

Active and highly stable oxide‐supported IrNiO_x core–shell catalysts for electrochemical water splitting are presented. IrNi_x@IrO_x nanoparticles supported on high‐surface‐area mesoporous antimony‐doped tin oxide (IrNiO_x /Meso‐ATO) were synthesized from bimetallic IrNi_x precursor alloys (PA‐IrNi_x /Meso‐ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA‐IrNi_x /Meso‐ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core–shell particles. The core–shell IrNiO_x /Meso‐ATO catalyst displayed high water‐splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability.     

A particle suspension model: an unstructured finite-volume implementation

In this paper, a modified particle temperature model for concentrated suspensions is proposed, which allows for the shear-induced migration of particles. The migration is modelled by a convection–diffusion equation, derived from the particle mass and momentum conservation. The model is implemented in an unstructured finite volume method and is utilized to investigate the shear-induced particle migration in channel flow. The profiles and the evolution of the velocity, concentration and particle temperature along the channel are presented. The entrance lengths needed to reach a fully developed profile of the corresponding field variables are also checked against different averaged concentrations and different relative particle radii. Comparison with available experimental data is made whenever possible.     

Effects of composition ratio on structure and phase transition of ferroelectric nanocomposites from silicon dioxide nanoparticles and triglycine sulfate

The present work is devoted to study on influences of silicon dioxide nanoparticles (SiO₂) on structure and phase transition of a classical ferroelectric of triglycine sulfate (TGS) by synthesizing a composite containing SiO₂ and TGS at different composition weight ratios. Particle size analysis, X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) techniques were utilized to charaterize the synthesized composite. The experiments for investigation of phase transition were conducted from 20 to 120°C under a weak electric field (1?V.cm^?1) at 1?kHz. The results revealed an expansion of ferroelectric phase of TGS by 15–55°C with increasing the SiO₂ content. Besides, an additional phase transition point which is characteristic for the bulk clusters of TGS was found at low content of SiO₂. The detected anomalies were discussed thoroughly based on the interaction between components in the composite.     

Orthogonal decompositions for wavelets

Decompositions of Hilbert spaces in terms of reducing subspaces for wavelets operators, as well decompositions of these operators themselves, are investigated. In particular, it is shown on which reducing subspaces these operators act as bilateral shifts of multiplicity 1. We also exhibit the unitary transformation that performs the unitary equivalence between restrictions of them to appropriate reducing subspaces.