Hellmuth Stachel

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A Kokotsakis mesh is a polyhedral structure consisting of an n-sided central polygon P 0 surrounded by a belt of polygons in the following way: Each side a i of P 0 is shared by an adjacent polygon P i , and the relative motion between cyclically consecutive neighbor polygons is a spherical coupler motion. Hence, each vertex of P 0 is the meeting point of(More)
According to the planar version of Ivory's Theorem the family of confocal conics has the property that in each quadrangle formed by two pairs of conics the diagonals are of equal length. It turned out that this theorem is closely related to self-adjoint affine transformations. This point of view is capable of generalization to hyperbolic and other spaces.
More than hundred years ago R. Bricard determined all continuously ex-ible octahedra. On the other hand, also the geometric characterization of rst-order exible octahedra has been well known for a long time. The objective of this paper is to analyze the cases between, i.e., octahedra which are innnitesimally exible of order n > 1 but not continuously(More)
The contact areas between the articular surfaces of the talus and tibia are essential for understanding the mobility of the ankle joint. The purpose of our study was to reveal the contact area among the superior articular surface of the trochlea tali (target surface T) and the inferior articular surface of the tibia (query surface Q) under(More)
Miura-ori is a Japanese folding technique named after Prof. Koryo Miura, The University of Tokyo. It is used for solar panels because it can be unfolded into its rectangular shape by pulling on one corner only. On the other hand it is used as kernel to stiffen sandwich structures. In this paper some insight will be given into the geometric structure of this(More)