The influence of particle surface friction on the behavior of gas-fluidized beds: Development of a two fluid model

The influence of physically realistic collisional properties on the hydrodynamics in a bubbling dense gas-solid fluidized bed is investigated using both a Discrete Particle Model (DPM) and a Two Fluid Model (TFM) incorporating a kinetic theory of granular flow (KTGF) for rough spheres by Lei et al. (1). The validated KTGF accounts for particle rotation and particle surface friction expilicitly. Comparisons between the two models are carried out to investigate the influence of particle friction on axial particle velocity, solids circulation pattern, and bubble behavior. The simulated results from both models reveal that the friction coefficient plays an important role in the formation of heterogeneous structures in a bubbling bed. When the friction coefficient is increased, larger bubbles appear and the fluidization in the bed is more vigorous. In addition, the time-averaged gas-solid flow field and time-averaged solids volume fraction vary significantly with different friction coefficient. Less dense zones are found in the bed for larger values of the friction coefficient. Please click Additional Files below to see the full abstract

Partial slip boundary conditions for collisional granular flows at flat frictional walls

Generally, slip occurs at the boundary wall for the granular flows, and the boundary may provide fluctuation energy to the flow. Wall boundary conditions (BCs) for the solids phase have significant effects on numerical predictions of various gas-solids fluidized beds. In this work, we derive new boundary conditions for collisional granular flows of spheres at flat frictional walls. New theory for the solids stress tensors, energy dissipation rates per unit area and the fluxes of fluctuation energy is proposed distinguishing sliding and sticking collisions and including particle rotation. Comparisons between the theory and the literature simulation data from Louge (1) show that an excellent prediction for stress ratio can be obtained. We propose an approximated expression for the mean rotational velocity in the bubbling fluidized beds using discrete particle model. The theory also predicts better agreement for the fluxes of fluctuation energy and energy dissipation rates for relative rough spheres with the expression. Finally, we determine new BCs with an extra BC for the rotational granular temperature based on the theory within the framework of kinetic theory of granular flow. Please click Additional Files below to see the full abstract

A new method to prevent degradation of lithium–oxygen batteries: reduction of superoxide by viologen

Lithium–oxygen battery development is hampered by degradation reactions initiated by superoxide, which is formed in the pathway of oxygen reduction to peroxide. This work demonstrates that the superoxide lifetime is drastically decreased upon addition of ethyl viologen, which catalyses the reduction of superoxide to peroxide

Electrostatic theory for imaging experiments on local charges in quantum Hall systems

We use a simple electrostatic treatment to model recent experiments on quantum Hall systems, in which charging of localised states by addition of integer or fractionally-charged quasiparticles is observed. Treating the localised state as a compressible quantum dot or antidot embedded in an incompressible background, we calculate the electrostatic potential in its vicinity as a function of its charge, and the chemical potential values at which its charge changes. The results offer a quantitative framework for analysis of the observations.Comment: 4 pages, 3 figure

A smart cushion for real-time heart rate monitoring

10.1109/BioCAS.2012.64185122012 IEEE Biomedical Circuits and Systems Conference: Intelligent Biomedical Electronics and Systems for Better Life and Better Environment, BioCAS 2012 - Conference Publications53-5

Thermodynamic and Tunneling Density of States of the Integer Quantum Hall Critical State

We examine the long wave length limit of the self-consistent Hartree-Fock approximation irreducible static density-density response function by evaluating the charge induced by an external charge. Our results are consistent with the compressibility sum rule and inconsistent with earlier work that did not account for consistency between the exchange-local-field and the disorder potential. We conclude that the thermodynamic density of states is finite, in spite of the vanishing tunneling density of states at the critical energy of the integer quantum Hall transition.Comment: 5 pages, 4 figures, minor revisions, published versio

Suppression of the structural phase transition and lattice softening in slightly underdoped Ba(1-x)K(x)Fe2As2 with electronic phase separation

We present x-ray powder diffraction (XRPD) and neutron diffraction measurements on the slightly underdoped iron pnictide superconductor Ba(1-x)K(x)Fe2As2, Tc = 32K. Below the magnetic transition temperature Tm = 70K, both techniques show an additional broadening of the nuclear Bragg peaks, suggesting a weak structural phase transition. However, macroscopically the system does not break its tetragonal symmetry down to 15 K. Instead, XRPD patterns at low temperature reveal an increase of the anisotropic microstrain proportionally in all directions. We associate this effect with the electronic phase separation, previously observed in the same material, and with the effect of lattice softening below the magnetic phase transition. We employ density functional theory to evaluate the distribution of atomic positions in the presence of dopant atoms both in the normal and magnetic states, and to quantify the lattice softening, showing that it can account for a major part of the observed increase of the microstrain.Comment: 7 pages, 4 figure

Uniform plant stands promote pod set and boost seed yield in canola

Non-Peer Reviewe

Charge Symmetry Violating Contributions to Neutrino Reactions

The NuTeV group has measured charged and neutral current reactions for neutrinos on iron targets. Ratios of these cross sections provide an independent measurement of the Weinberg angle. The NuTeV value for sin^2 theta_W is three standard deviations larger than the value measured in other electroweak processes. By reviewing theoretical estimates of parton charge symmetry violation (CSV), we study CSV contributions to the NuTeV measurement. We conclude that charge symmetry violating effects should remove roughly 30% of the discrepancy between the NuTeV result and other determinations of sin^2 theta_W.Comment: 15 pages, 2 figures; Fig 2 replaced [CSV distribution calculated at low Q^2, evolved to 20 GeV^2]; table II change