We present the concept of fiber-flux density for locally quantifying white matter (WM) fiber bundles. By combining scalar diffusivity measures (e.g., fractional anisotropy) with fiber-flux measurements, we define new local descriptors called Fiber-Flux Diffusion Density (FFDD) vectors. Applying each descriptor throughout fiber bundles allows alongtract coupling of a specific diffusion measure w...

We present a software framework for the transparent and portable parallelization of simulations using particle-mesh methods. Particles are used to transport physical properties and a mesh is required in order to reinitialize the distorted particle locations, ensuring the convergence of the method. Field quantities are computed on the particles using fast multipole methods or by discretizing and...

We present approximate formulas for the tensor BB, EE, TT, and TE multipole coefficients for large multipole order l. The error in using the approximate formula for the BB multipole coefficients is less than cosmic variance for l > 10. These approximate formulas make various qualitative properties of the calculated multipole coefficients transparent: specifically, they show that, whatever value...

With the development of the VLSI circuits, the feature size has been decreased to the deep sub-micron level, and the working frequency has reached to 3GHz. In order to assure the correctness of the IC design with high performance, the parasitic interconnect inductance and resistance should he calculated quickly and accurately. In this paper, the multipole method with modified non-uniform cube p...

In this paper we address several topics relating to the development and implementation of volume integral and hybrid finite element methods for electromagnetic modeling. Comparisons with the finite elementboundary integral method are given in terms of accuracy and computing resources. We also discuss preconditioning, parallelization of the multilevel fast multipole method and propose higher-ord...

Solution of periodic boundary value problems is of interest in various branches of science and engineering such as optics, electromagnetics and mechanics. In our previous studies we have developed a periodic Fast Multipole Method (FMM) as a fast solver of wave problems in periodic domains. It has been found, however, that the convergence of the iterative solvers for linear equations slows down ...

Curves are often used as anatomical features to match surfaces that represent biological objects, such as the human brain. Automated and semi-automated methods for extracting these curves usually rely on local properties of the surfaces such as the mean surface curvature without considering the global appearance of the curves themselves. These methods may require additional human intervention, ...

We study, analytically and numerically, singularity formation in an interface flow driven by a multipole for a two-dimensional Hele–Shaw cell with surface tension. Our analysis proves that singularity formation is inevitable in the case of a dipole. For a multipole of a higher order, we show that the solution does not tend to any stationary solution as time goes to infinity if its initial cente...

This paper presents an algorithm for the rapid evaluation of the vector spline in two dimensions. The algorithm is based on the fast multipole method and has an asymptotic CPU time estimate of O(N), where N is the number of data points. The main idea of the algorithm is to combine a cluster of evaluation kernels at diierent data sources into a single kernel in the form of a multipole expansion ...

The problem of oblique wave scattering of a Rayleigh wave by a cylindrical cavity in an elastic half-space is solved using the multipole expansion method. Whereas in the analogous water-wave problem a single scalar field is expressed as an infinite multipole expansion, and in the Rayleigh wave case with normal incidence two scalar fields suffice, here we require three coupled scalar multipole e...