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This is a simulation model of a automobile wheel, generated with Dominik Schillinger’s new method. Credit: TUM.

(Editor’s note: Eileen and I are traveling and preparing for the International Ceramics Congress that begins this weekend, so we had to put our normal writing on hold for a little bit. In place of our usual posts, we are bringing you a variety of good stories and videos issued prepared by various institutions. Look for our regular blog posts to return this weekend, including live blogging from ICC4.)

Technische Universitaet Muenchen - Computer simulations have become an indispensable part of the modern design process. Standard finite element technology, however, requires designers to carry out a time-consuming and often error-prone mesh generation step that transfers the computer-aided design model into the simulation model.

Dominik Schillinger has created a novel simulation concept that enables direct integration of the CAD geometry into the finite element analysis, completely circumventing any mesh generation. The applicability of this technology in engineering practice was successfully tested with CAD models, for example, of a ship propeller and an automobile wheel.

The omission of mesh generation could reduce the overall analysis time with respect to standard finite elements by more than 80 percent. The new simulation technology is expected to strongly influence the current design process in mechanical, automotive, aerospace and civil engineering over the next decade.

Dominik Schillinger was honored this week at the World Congress on Computational Mechanics in São Paulo for his paper “An Isogeometric Design-through-analysis Methodology based on Adaptive Hierarchical Refinement of NURBS, Immersed Boundary Methods, and T-spline CAD Surfaces” in the journal Computer Methods in Applied Mechanics and Engineering.

He was a scholar of the Munich Centre of Advanced Computing until May. MAC bundles together research activities related to computational science and engineering at TUM and other institutions in Munich. Doctoral candidates at MAC are members of TUM’s International Graduate School of Science and Engineering.

Schillinger worked on his method during his research stay at the Institute for Computational Engineering and Sciences in Austin, Texas, financed by “MAC@IGSSE,” in collaboration with the TUM Institute for Computation in Engineering.

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Magnetic eddies in silicon manganese, so-called skyrmions, form a regular grid. Moving these skyrmions needs 100,000 times smaller currents than existing technologies. But, inquiring minds will ask, what is a skyrmion? Credit: TUM.

Part of what I enjoy about my job is coming across cool words that come with cool science, like skyrmion and helimagnet.

Wikipedia—the “Easy Button” of information—has this to say about skyrmions.

The skyrmion is a hypothetical particle related to baryons. It was described by Tony Skyrme and consists of a quantum superposition of baryons and resonance states. Skyrmions are homotopically non-trivial classical solutions of a nonlinear sigma model with a non-trivial target manifold topology—hence, they are topological solitons. … Skyrmions have been reported, but not conclusively proven, to be in Bose-Einstein condensates, superconductors, thin magnetic films and also chiral nematic liquid crystals.

That muddles things more than it clarifies for me, but the abstract of a new paper in PNAS sheds some light.

According to the abstract of the paper (below), a skyrmion is, topologically speaking, a magnetic bubble, or cylindrical domain, in a ferromagnetic film. They show up in “noncentrosmmetric helimagnets.” Skyrmions were studied in the 1970s for data storage, and I remember seeing a video of the bubbles doing a lemming-like march off the end of their world (a chip of some sort) at a seminar given by an IBM scientist when I was in graduate school. The skyrmions studied in this paper sound almost gourmet: “magnetic oxide–M-type hexaferrite with a hint of scandium.”

Skyrmions occur in metals, too. In February, researchers at the Technische Universitaet Muenchen discovered a “grid of magnetic eddies”—skyrmions—in silicon manganese. The press release says that the TUM team was able to show that “even the tiniest of currents are sufficient to move the magnetic eddies,” which opens up the possibility of manipulating them in, for example, hard drives.

The PNAS paper is “Magnetic stripes and skyrmions with helicity reversals,” by Xiuzhen Yu, Maxim Mostovoy, Yusuke Tokunaga, Weizhu Zhang, Koji Kimoto, Yoshio Matsui, Yoshio Kaneko, Naoto Nagaosa, and Yoshinori Tokura; PNAS; May 21, 2012; doi: 10.1073/pnas.1118496109.

Here is the abstract:

It was recently realized that topological spin textures do not merely have mathematical beauty but can also give rise to unique functionalities of magnetic materials. An example is the skyrmion-a nano-sized bundle of noncoplanar spins-that by virtue of its nontrivial topology acts as a flux of magnetic field on spin-polarized electrons. Lorentz transmission electron microscopy recently emerged as a powerful tool for direct visualization of skyrmions in noncentrosymmetric helimagnets. Topologically, skyrmions are equivalent to magnetic bubbles (cylindrical domains) in ferromagnetic thin films, which were extensively explored in the 1970s for data storage applications. In this study we use Lorentz microscopy to image magnetic domain patterns in the prototypical magnetic oxide-M-type hexaferrite with a hint of scandium. Surprisingly, we find that the magnetic bubbles and stripes in the hexaferrite have a much more complex structure than the skyrmions and spirals in helimagnets, which we associate with the new degree of freedom-helicity (or vector spin chirality) describing the direction of spin rotation across the domain walls. We observe numerous random reversals of helicity in the stripe domain state. Random helicity of cylindrical domain walls coexists with the positional order of magnetic bubbles in a triangular lattice. Most unexpectedly, we observe regular helicity reversals inside skyrmions with an unusual multiple-ring structure.

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