Bifurcation indicator based on meshless and asymptotic numerical methods for nonlinear poisson problems

We propose in this work new algorithms associating asymptotic numerical method and meshless discretization (MFS‐MPS: Method of fundamental solutions‐Method of particular solutions) to compute branch solutions of nonlinear Poisson problems. To detect singular points on these branches, geometrical indicator, Padé approximants, and analytical bifurcation indicator are proposed. Numerical applications show the robustness and the effectiveness of the proposed algorithms. © 2014 Wiley Periodicals, Inc. Numer Methods Partial Differential Eq 30: 978–993, 2014     

Control of the morphology of nanostructured particles prepared by the spray drying of a nanoparticle sol

The control of the morphology of nanostructured particles prepared by the spray drying of nanoparticle sol was investigated experimentally and the results are qualitatively explained based on available theory. A theoretical analysis indicates that the structural stability of the droplet and the hydrodynamic effects during the drying process play important roles in controlling the morphology of the resulting particles. The size of the sol in the droplet, droplet size, viscosity of droplet, drying temperature, gas flow rate, and addition of surfactant are all crucial parameters that affect the morphology of particles. Experimentally, nanostructured silica particles were prepared from a nanosize silica sol under various preparation conditions. Doughnut-shaped particles can be produced when the droplet size is large, in conjunction with high temperature, high gas flow rate and in the presence of an added surfactant. Appropriate choice of the spray drying method permits control of the particle size and shape, ranging from spheres to ellipsoids as well as doughnut-shaped particles by varying the preparation conditions. The results open a new route to controlling the formation of a wide variety of nanostructured particles.     

Low temperature measurements of the energy loss rate in quantum wires and 2DEGs in an InAlAs/InGaAs/InAlAs heterostructure

Electron heating measurements have been carried out in etched quantum wires of various widths and in two-dimensional electron gases at low temperature in InGaAs quantum wells. The value of the temperature exponent of the energy loss rate, an indicator of the type of predominant energy loss scattering, is found to be n=3, indicative of piezoelectric scattering. At a lattice temperature <1 K, our wires show an exponential behavior expected for deviations from equipartition. Further departure is found at still lower temperatures to a width-dependent loss rate, which is thought to be due to many-body effects in the one-dimensional wires.