Membrane-free microfiltration by asymmetric inertial migration is studied and evidence of the filtration capability is presented. Centrifugal force induced by flow in spiral channel geometry modifies the lateral symmetry of straight-channel tubular pinch equilibrium resulting in a focused particle band nearer to the inner sidewall. Bifurcated outlets separately collect the concentrated particle band and remaining effluent. The spiral continuous flow filtration relies solely on internal fluidic shear characteristics, eliminating the need for membrane filters or external force fields. This device has the desirable combinations of high throughput and low cost, making it inherently suited for preparative filtration in the range of micro- to macroscale applications.

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For energy storage applications, it is critical that the dielectric material possesses low losses, especially the conduction losses, which could become significant at high temperatures and high electric fields. We investigate the conduction at fields up to 100 MV/m and high temperatures in a semi-crystalline poly(tetrafluoroethylene-hexafluoropropylene-vinylidene fluoride) terpolymer which has been shown to be attractive for high energy density capacitors. Experimental results show that the insulating nanofillers are very effective in reducing the conduction current, i.e., a more than two orders of magnitude reduction in conduction can be achieved with less than 1 wt. % (<0.5 vol. %) of Al2O3 nanofillers. Experimental measurements are compared with multiscale simulations, which shows that the dominant conduction mechanism, i.e., carrier hopping in the polymer, is markedly reduced owing to a large decrease in the mobile carrier concentrations and increased trap depth, caused by the nanofillers.

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Use of the Green function, for the solution of boundary-value problems, frequently results in singular integral equations. Algorithms arc presented for the accurate and efficient treatment of singular kernels frequently encountered in the boundary element method (BEM). They are based upon the use of appropriately weighted Gaussian quadrature formulae, together with numerical geometrical transformations of the region of integration. The use of high-order subdomain expansion functions, for interpolation over nonplanar elements, allows boundary curvature to be accommodated. In particular, thc handling of Green functions with logarithmic and r -' behaviour are detailed. Volume integrals, with r singularity, are outlined.Operations are performed on a simplex, thus resulting in generality and ease of automation. This scheme has been incorporated into boundary element method software and successfully applied to a variety of problems.

On the basis of the integral equation approach, numerical algorithms for solving non-linear water wave problem are presented. The free surface flow is assumed to be irrotational. Two different Green functions are used in the integral equations. The non-linear free-surface boundary conditions are treated by a timestepping Lagrangian technique. Several numerical examples are given, including permanent periodic waves, overturning progressive waves, breaking standing waves and sloshing problems.

Purpose -The purpose of this paper is to describe a rapid and robust axisymmetric hybrid algorithm to create dynamic temporal and spatial charge distributions, or charge map, in the simulation of bipolar charge injection using Schottky emission and Fowler-Nordheim tunneling, field-dependent transport, recombination, and bulk and interfacial trapping/de-trapping for layered polymer films spanning the range from initial injection to near breakdown. Design/methodology/approach -This hybrid algorithm uses a source distribution technique based on an axisymmetric boundary integral equation method (BIEM) to solve the Poisson equation and a fourth-order Runge-Kutta (RK4) method with an upwind scheme for time integration. Iterative stability is assured by satisfying the Courant-Friedrichs-Levy (CFL) stability criterion. Dynamic charge mapping is achieved by allowing conducting and insulating boundaries and material interfaces to be intuitively represented by equivalent free and bound charge distributions that collectively satisfy all local and far-field conditions. Findings -Charge packets cause substantial increase of electric stress and could accelerate the breakdown of polymeric capacitors. Conditions for the creation of charge packets are identified and numerically demonstrated for a combination of impulsive step excitation, high charge injection, and discontinuous interface. Originality/value -Metallized bi-axially oriented polypropylene (BOPP) dielectric thin film capacitor with self-clearing and enhanced current carrying capability offer an inexpensive and lightweight alternative for efficient power conditioning, energy storage, energy conversion, and pulsed power. The originality is the comprehensive physics and multi-dimensional modeling which span the dynamic range from initial injection to near breakdown. This model has been validated against some empirical data and may be used to identify failure mechanisms such as charge packets, gaseous voids, and electroluminescence. The value lies in the use of this model to develop mitigation strategies, including re-designs and materials matching, to avoid these failure mechanisms.

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