No abstract

We propose a new edge detection method that is effective on multivariate irregular data in any domain. The method is based on a local polynomial annihilation technique and can be characterized by its convergence to zero for any value away from discontinuities. The method is numerically cost efficient and entirely independent of any specific shape or complexity of boundaries. Application of the minmod function to the edge detection method of various orders ensures a high rate of convergence away from the discontinuities while reducing the inherent oscillations near the discontinuities. It further enables distinction of jump discontinuities from steep gradients, even in instances where only sparse nonuniform data is available. These results are successfully demonstrated in both one and two dimensions.

No abstract

A thin layer of a vertically aligned nanocomposite (VAN) structure is deposited between the electrolyte, Ce0.9Gd0.1O1.95 (CGO), and the thin‐film cathode layer, La0.5Sr0.5CoO3 (LSCO), of a thin‐film solid‐oxide fuel cell (TFSOFC). The self‐assembled VAN nanostructure contains highly ordered alternating vertical columns of CGO and LSCO formed through a one‐step thin‐film deposition process that uses pulsed laser deposition. The VAN structure significantly improves the overall performance of the TFSOFC by increasing the interfacial area between the electrolyte and cathode. Low cathode polarization resistances of 9 × 10−4 and 2.39 Ω were measured for the cells with the VAN interlayer at 600 and 400 °C, respectively. Furthermore, anode‐supported single cells with LSCO/CGO VAN interlayer demonstrate maximum power densities of 329, 546, 718, and 812 mW cm−2 at 550, 600, 650, and 700 °C, respectively, with an open‐circuit voltage (OCV) of 1.13 V at 550 °C. The cells with the interlayer triple the overall power output at 650 °C compared to that achieved with the cells without an interlayer. The binary VAN interlayer could also act as a transition layer that improves adhesion and relieves both thermal stress and lattice strain between the cathode and the electrolyte.

As part of an investigation of new cathode materials for intermediate temperature solid oxide fuel cells, we have investigated several perovskite oxides with cobalt ions on the B sites in both bulk and thin film forms. Of particular interest is the composition La 0.5 Sr 0.5 CoO 3-x (LSCO) which has exceptional properties for oxygen reduction at intermediate temperatures in ceria based fuel cells. Thin films of LSCO were deposited on both sides of a dense polycrystalline gadolinia doped ceria substrate by pulsed laser deposition under conditions that lead to the formation of nanocrystalline films. The electrochemical properties for oxygen reduction were determined in a symmetric electrochemical cell by alternating current (AC) impedance spectroscopy. The results were analyzed using the Adler-Lane-Steele (ALS) model to obtain the diffusion and surface exchange coefficients and the thermodynamic factor. We show that the thermodynamic factor, a measure of how easy it is to create oxygen vacancies, is much higher than observed in conventional cathodes. As a result, the electrode composition changes little with temperature and oxygen partial pressure, the large chemical contribution to the thermal expansion is reduced, and the electrode has good stability. The use of a nanostructured electrode does not significantly affect the fundamental material parameters (surface exchange and diffusion coefficients), and the very low area specific resistance (0.09 ohm cm 2 at 600 °C) observed is because the synthesis method gives a very high surface area (80 μm -1 ).

Vertical interface effect on the physical properties of epitaxial metal‐oxide films is demonstrated. Self‐assembled (BiFeO3)0.5:(Sm2O3)0.5 nanocomposite films are fabricated with three‐dimensional heteroepitaxy having an ordered nano‐columnar structure on a large scale. The vertical interface effect on lattice parameters, dielectric properties, and leakage currents is investigated.

In this study, we are mainly interested in error estimates of interpolation, using smooth radial basis functions such as multiquadrics. The current theories of radial basis function interpolation provide optimal error bounds when the basis function φ is smooth and the approximand f is in a certain reproducing kernel Hilbert space F φ. However, since the space F φ is very small when the function φ is smooth, the major concern of this paper is to prove approximation orders of interpolation to functions in the Sobolev space. For instance, when φ is a multiquadric, we will observe the error bound o(h k) if the function to be approximated is in the Sobolev space of smoothness order k.

No abstract