Doubly bridged dicobalt complexes with bidentate diamine ligands were synthesized and characterized by X-ray diffraction studies. Reversible formation and decomposition of the doubly bridged structure utilizing the redox couple between Co(II) and Co(III) were investigated by cyclic voltammetry and UV-vis.

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We experimentally studied effect of ribs on impact energy absorption of thin-walled cylinders. Several kinds of the specimens with different intervals and numbers of ribs were made of aluminum alloy. The drop weight test was conducted to examine relations between impact force and displacement of the specimens. It was found that the crushing modes were dependent on distance between ribs. Axisymmetric and non-axisymmetric crushing modes occurred for short distance and for long distance, respectively. The mean crushing force for the axisymmetric mode was larger than one for non-axisymmetric mode. It was clarified that the crushing behavior in an interval of rib was independent of one in other interval. Therefore, a cylinder with a lot of short interval ribs has high ability for impact energy absorption.