Circular Slit Maps of Multiply Connected Regions with Application to Brain Image Processing

In this paper, we present a fast boundary integral equation method for the numerical conformal mapping and its inverse of bounded multiply connected regions onto a disk and annulus with circular slits regions. The method is based on two uniquely solvable boundary integral equations with Neumann-type and generalized Neumann kernels. The integral equations related to the mappings are solved numerically using combination of Nyström method, GMRES method, and fast multipole method. The complexity of this new algorithm is $$O((M + 1)n)$$ O ( ( M + 1 ) n ) , where $$M+1$$ M + 1 stands for the multiplicity of the multiply connected region and n refers to the number of nodes on each boundary component. Previous algorithms require $$O((M+1)^3 n^3)$$ O ( ( M + 1 ) 3 n 3 ) operations. The numerical results of some test calculations demonstrate that our method is capable of handling regions with complex geometry and very high connectivity. An application of the method on medical human brain image processing is also presented.

Formation of displacement curves with the identification of their non-working areas

The object of research is the shaping of a family of displacement curves used in designing the path of a tool that processes pocket surfaces. The subject of the study is the working displacement curves in the case of multiply connected areas. Working displacement curves are lines from which non-working sections have been removed. Non-working areas include self-intersecting loops of displacement curves and sections formed when intersecting displacement curves of opposing fronts. The paper presents methods for analyzing and cutting off non-working sections for cases of self-intersection and intersection of displacement curves of opposing fronts. The spatial geometric model of the formation of displacement curves is based on the cyclographic method of displaying space. As a tool for detecting non-working areas for the case of opposing fronts, a method of a testing beam is proposed. In the case of self-intersections of the displacement curves, non-working sections are cut off by the parameter of these lines at the points of self-intersection. The novelty of the study lies in the fact that the obtained mathematical model of the formation of displacement curves for multiply connected regions with contours of complex handicap curves makes it possible to obtain parametric equations of working lines at the output of the computational algorithm in a more reliable and simple way. This greatly simplifies the solution to the problem of automated design of the trajectory of the cutting tool. A comparative assessment of the proposed method of shaping a family of displacement curves with cutting off non-working sections and known methods using the distance function is performed.

A novel variant of the H-Φ field formulation for magnetostatic and eddy current problems

Purpose The paper presents a new variant of the H-Φ field formulation for solving 3-D magnetostatic and frequency domain eddy current problems. The suggested formulation uses the vector and scalar tetrahedral elements within conducting and non-conducting domains, respectively. The presented numerical method is capable of solving multiply connected regions and eliminates the need for computing the source current density and the source magnetic field before the actual magnetostatic and eddy current simulations. The obtained magnetostatic results are verified by comparison against the corresponding results of the standard stationary current distribution analysis combined with the Biot-Savart integration. The accuracy of the eddy current results is demonstrated by comparison against the classical A-A-f approach in frequency domain. Design/methodology/approach The theory and implementation of the new H-Φ magnetostatic and eddy current solver is presented in detail. The method delivers reliable results without the need to compute the source current density and source magnetic field before the actual simulation. Findings The proposed H-Φ produce radically smaller and considerably better conditioned equation systems than the alternative A-A approach, which usually requires the unphysical regularization in terms of a low electric conductivity value within the nonconductive domain. Originality/value The presented numerical method is capable of solving multiply connected regions and eliminates the need for computing the source current density and the source magnetic field before the actual magnetostatic and eddy current simulations.