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The class transposition group $CT(\mathbb{Z})$ was introduced by S. Kohl in 2010. It is a countable subgroup of the permutation group $Sym(\mathbb{Z})$ of the set of integers $\mathbb{Z}$. We study products of two class transpositions $CT(\mathbb{Z})$ and give a partial answer to the question 18.48 posed by S. Kohl in the Kourovka notebook. We prove that in the group $CT_{\infty}$, which is a subgroup of $CT(\mathbb{Z})$ and generated by horizontal class transpositions, the order of the product of a pair of horizontal class transpositions belongs to the set $\{1,2,3,4,6,12\}$, and any number from this set is the order of the product of a pair of horizontal class transpositions., Comment: 16 pages

The results are presented of the studies which concern the use of a magnetically levitated aerodynamic carriage with a model moving in a closed cryogenic channel. The facility dimensions are established, operating ranges are calculated, thermal isolation, cooling and measurement systems are described, comparison of this facility with wind tunnels is given and its advantages are shown.