Solving parametric complex fluids models in rheometric flows

Inverse identification of complex fluid behaviors is a tricky task because sometimes there are several rheological parameters and the identification procedure itself is quite expensive from the computational time viewpoint. Standard inverse identification procedures solve the model for a choice of the model parameters, and then parameters are updated trying to minimize the gap between the model predictions and some available experimental measures. Thus, the model has to be evaluated for each trial set of the model parameters. When models involve a great number of degrees of freedom the identification procedure becomes a computationally expensive task. In this paper we propose a new procedure able to solve once the model for any value of the model parameters. For this purpose, all the model parameters are considered as extra-coordinates of the model. Thus, the model results finally defined in a multidimensional space including the physical space x, the time t and a number of extra-coordinates related to the model parameters. The solution of such model needs for circumventing the curse of dimensionality illness that suffer multidimensional models.     

Lattice Boltzmann method for polymer kinetic theory

The purpose of this work is to extend the applicability of the lattice Boltzmann method (LBM) to the field of polymer kinetic theory or more generally suspensions that could be described in the Fokker–Planck formalism. This method has been, in a first time, used for gas kinetic theory, where the resolution space corresponds to the physical space coordinate. In a second time is has been generalized to be applied to fluid flow involving different behaviours: turbulence, porous media, multiphase flow, etc. However this powerful, parallel, and efficient algorithm has not been applied for solving Fokker–Planck equations widely used to describe suspension kinetic theory. In this scale, molecular models involve a high computational costs because of the multidimensionality of the fully coupled micro–macro complex flow. The originality of this work consists to apply the lattice Boltzmann technique for solving Fokker–Planck equation based on a discretization of the configuration space where the resolution coordinates correspond to the microscopic configuration space (and not the physical coordinates). The result of this work emphasizes the optimality of the used technique that, in addition to its parallel ability, gathers the simplicity of the stochastic simulation and the robustness of the traditional fixed mesh support (such as the finite element method). Accuracy and convergence of the LBM will be compared to the stochastic and the finite element techniques for homogeneous shear flow.     

Investigation of the electronic and structural properties of potassium hexaboride, KB6, by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations

The electronic and structural properties of potassium hexaboride, KB(6), were examined by transport, magnetic susceptibility, EPR, and NMR measurements, temperature-dependent crystal structure determination, and electronic band structure calculations. The valence bands of KB(6) are partially empty, but the electrical resistivity of KB(6) reveals that it is not a normal metal. The magnetic susceptibility as well as EPR and NMR measurements show the presence of localized electrons in KB(6). The EPR spectra of KB(6) have two peaks, a broad ( approximately 320 G) and a narrow (less than approximately 27 G) line width, and the temperature-dependence of the magnetic susceptibility of KB(6) exhibits a strong hysteresis below 70 K. The temperature-dependent crystal structure determination of KB(6) shows the occurrence of an unusual variation in the unit cell parameter hence supporting that the hysteresis of the magnetic susceptibility is a bulk phenomenon. The line width DeltaH(pp) of the broad EPR signal is independent of temperature and EPR frequency. This finding indicates that the line broadening results from the dipole-dipole interaction, and the spins responsible for the broad EPR peak has the average distance of approximately 1.0 nm. To explain these apparently puzzling properties, we examined a probable mechanism of electron localization in KB(6) and its implications.     

Synthesis and structural characterization of dihexamethylenetetraminetetraaquocobalt(II) hexaaquocobalt(II) sulfate hexahydrate

The synthesis and crystal structure of a new three dimensional cobalt(II) complex [Co(C₆H₁₂N₄)₂(H₂O)₄Co(H₂O)₆][SO₄]₂.6H₂O are reported. It crystallizes in the triclinic space group P-1 with a = 13.394(3), b = 16.077(3), c = 9.282(2) Å, = 89.71(2), = 90.42(2), = 114.02(2)°, V = 1825.6(7)ų and Z = 2. The structure is comprised of [Co(C₆H₁₂N₄)₂ (H₂O)₄Co(H₂O)₆][SO₄]₂ units and H₂O molecules. Two molecules of ligand and four molecules of water chelate one type of Co^II in an octahedral fashion through two N and four O atoms: the four O atoms form the equatorial plane and the two N atoms occupy the apical positions. The other type of Co^II cation is chelated by six water molecules.     

Electron density of states at the edge of the valence band of Cd0.88Fe0.12Se—A photoemission yield study

The electronic structures of Cd_0.88Fe_0.12Se and CdSe have been investigated by photoemission yield spectroscopy (PYS) in the photon energy range from 5 to 12 eV. The () surfaces were obtained by cleavage under ultrahigh vacuum (UHV) conditions. An Fe-related emission appeared at 0.58 eV above the valence band edge. The freshly cleaved surface of Cd_0.88Fe_0.12Se interacted with ambient atmosphere more strongly than CdSe crystal. Leaving the sample in an UHV chamber at room temperature enabled us to identify surface related features and to observe decrease of the ionization energy E_i, energy threshold E_d and the crystal affinity χ due to change of the surface conditions. Effective density of states, derived from the experimental spectra of Cd_0.88Fe_0.12Se exhibits, in contrast with CdSe, a surface-related feature degenerated with the bulk valence band.     

Measurements of the mass, total width, and two-photon partial width of the eta(c) meson

Using 13.4 fb(-1) of data collected with the CLEO detector at the Cornell Electron Storage Ring, we have observed 300 events for the two-photon production of ground-state pseudoscalar charmonium in the decay eta(c)-->K(0)(S)K-/+pi(+/-). We have measured the eta(c) mass to be [2980.4+/-2.3 (stat)+/-0.6 (syst)] MeV and its full width as [27.0+/-5.8 (stat)+/-1.4 (syst)] MeV. We have determined the two-photon partial width of the eta(c) meson to be [7.6+/-0.8 (stat)+/-0.4 (syst)+/-2.3 (br)] keV, with the last uncertainty associated with the decay branching fraction.     

Production and decay of F+(2030) observed in νμ interactions in emulsion

An event representing the production and decay of the charmed F⁺ meson has been identified by means of a 3-constraint fit to decay hypothesis F⁺ → π⁺π⁺π^?π⁰, in which both γ-rays from the π⁰ converted. The event was produced by a charged current ν_μ interaction in an emulsion stack located inside the Fermilab 15-foot bubble chamber. The F⁺ traveled 50 μm, corresponding to a proper time of 1.4 × 10^?13 seconds, before decaying in flight. Its mass was determined to be 2017 ± 25MeV.