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A generalisation of a ruled surface in n-dimensional euclidean space may be generated by euclidean motion of a s-plane As. For this one-parametric family {As} the curve of striction is defined and the following theorems are proved:
  1. The generators As are parallel along the curve of striction, i.e. the multivectors representing As form a parallel vector field along the curve of striction.
  2. If the curve of striction is geodesic on {As}, it is also an isogonal trajectory of the family of generators {As}.
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In this work, we consider four one-parameter families of spheres which do not belong to the same bundle with the additional condition that three of these families of spheres cut the spherez=0 belonging to the fourth family in a hexagonal three-web formed by the three families of curves defined by the equationsx 2 +y 2=u 1, x=u 2, y=u 3 x. Then, we determine these families of spheres in such a way that they form a hexagonal surface 4-web.  相似文献   

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Ohne ZusammenfassungMit einer Figur im Text  相似文献   

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Ohne Zusammenfassung Issai schur zum Gedächtnis.  相似文献   

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Summary Four different zinc-selenides were produced by chemical precipitation and transport reactions. Their surface-properties have been investigated by electron diffraction, nitrogen-adsorption and ice-nucleability. The results support the hypothesis ofZettlemoyer et al. [7] that cluster formation of water-molecules adsorbed on surface inhomogeneities is necessary for ice to be formed on a nucleating agent.  相似文献   

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