Symmetry Properties of the Elastic Energy of a Woven Fabric with Bending and Twisting Resistance

A woven fabric can be described as a surface made of two families of fibers: in this work we study how the geometry of the weave pattern affects the symmetry properties of the elastic energy of the surface. Four basic symmetry classes of weave patterns are possible, depending on the angle between the fibers and their material properties. The properties of the pattern determine the material symmetry group of the network, under which the elastic energy is invariant. We derive representations for the energy of a woven fabric that are invariant under the symmetry group of the network, and discuss the relation of these invariants with the curvature and twist of the fibers.      

Hydrodynamics of nematic ferrofluids

The European Physical Journal E - We derive hydrodynamic equations for nematic ferrofluids (ferronematics) in the limit that the magnetic degree of freedom has relaxed to its equilibrium value. We...     

The synthesis and characterisation of an expansive additive for M-type cements

The expansion effect of laboratory-prepared expansive additives for M-type expansive cement was investigated at the early stage of hydration by the multicell isoperibolic calorimeter and volumetric technique based on Archimedes’ principle. The relative volume changes and heat released during hydration are strongly affected by the content of lime in the expansive additive due to the influence of CaO on the kinetics and mechanism of formation of ettringite. The increasing content of lime favours the formation of monosulphate and its later transformation to ettringite generating expansion stress. The effect of expansive additive on the behaviour of mortar samples was measured as linear elongation of test blocks using Graf-Kaufman dilatometer. Lower or higher content of lime in expansion additive slightly decreases the 7th-day compressive and flexural strength of samples while this effect is negligible for expansive additive with nominal composition of ettringite.     

Zur Existenz des Oxoniumions in festen basischen Aluminiumsulfaten

On the Existence of the Oxonium Ion in Solid Basic Aluminium Sulphates Oxonium alunite was investigated by ¹H-NMR-, heat capacity, electric conductivity, and thermoanalytic measurements. In the ¹H-NMR spectrum the existence of the oxonium ion was surely proved. From the results of the other investigations follow, that the oxonium ion is fast bonded in the structure and that exists an unimportant amount of mobile ionic charge carriers only.