Phase transitions in the Shastry-Sutherland lattice

Two recently developed theoretical approaches are applied to the Shastry-Sutherland lattice, varying the ratio $J'/J$ between the couplings on the square lattice and on the oblique bonds. A self-consistent perturbation, starting from either Ising or plaquette bond singlets, supports the existence of an intermediate phase between the dimer phase and the Ising phase. This existence is confirmed by the results of a renormalized excitonic method. This method, which satisfactorily reproduces the singlet triplet gap in the dimer phase, confirms the existence of a gapped phase in the interval $0.66<J'/J<0.86$Comment: Submited for publication in Phys. Rev.

Influence of the initial imperfections with regard to the webs thicknesses of cold-formed compressed steel members

Local stability requirements related to unfavorable buckling effects of compressed parts of cold-formed profiles are highly significant. Favorable effects related to their post-critical behavior are also important. The paper deals with resistance of these type of members, taking into account the influence of initial imperfections with regard to the thicknesses of their webs. The paper also presents information about experimental and theoretical-numerical research to determine the resistance of cold-formed compressed steel members with closed cross-sections. Obtained results are very extensive; therefore the paper presents results of part of tested and analyzed member