Masses and decay constants of the η and η′ mesons from lattice QCD

We determine the masses, the singlet and octet decay constants as well as the anomalous matrix elements of the η and η′ mesons in Nf = 2 + 1 QCD. The results are obtained using twenty-one CLS ensembles of non-perturbatively improved Wilson fermions that span four lattice spacings ranging from a ≈ 0.086 fm down to a ≈ 0.050 fm. The pion masses vary from Mπ = 420 MeV to 126 MeV and the spatial lattice extents Ls are such that LsMπ ≳ 4, avoiding significant finite volume effects. The quark mass dependence of the data is tightly constrained by employing two trajectories in the quark mass plane, enabling a thorough investigation of U(3) large-Nc chiral perturbation theory (ChPT). The continuum limit extrapolated data turn out to be reasonably well described by the next-to-leading order ChPT parametrization and the respective low energy constants are determined. The data are shown to be consistent with the singlet axial Ward identity and, for the first time, also the matrix elements with the topological charge density are computed. We also derive the corresponding next-to-leading order large-Nc ChPT formulae. We find F8 = 115.0(2.8) MeV, θ8 = −25.8(2.3)°, θ0 = −8.1(1.8)° and, in the $$ \overline{\mathrm{MS}} $$ MS ¯ scheme for Nf = 3, F0(μ = 2 GeV) = 100.1(3.0) MeV, where the decay constants read $$ {F}_{\eta}^8 $$ F η 8 = F8 cos θ8, $$ {F}_{\eta \prime}^8 $$ F η ′ 8 = F8 sin θ8, $$ {F}_{\eta}^0 $$ F η 0 = −F0 sin θ0 and $$ {F}_{\eta \prime}^0 $$ F η ′ 0 = F0 cos θ0. For the gluonic matrix elements, we obtain aη(μ = 2 GeV) = 0.0170(10) GeV3 and aη′(μ = 2 GeV) = 0.0381(84) GeV3, where statistical and all systematic errors are added in quadrature.

COMPUTER-AIDED DESIGN OF SPATIAL LATTICE STEEL STRUCTURES FOR COATINGS OF COMPLEX SHAPE

The architecture of modern structures requires the use of structural systems in a wide range of both geometric and topological forms. Spatial steel structures are one of the most varied, complex and demanded types of structural forms of coatings for buildings and construction structures. The method of constructing spatial lattice structures of a complex geometric shape considered in the article is based on automated methods of computer modeling of the shell surface and the subsequent development of a separate spatial cell of a lattice of a certain type - a "family". The structural cell of the lattice is the basis for the topological structure of the building system, which is created using special software. The result of this development is a digital model of the megastructure of the entire spatial structure. Subsequent export of the constructed geometry to computational software systems allows one to estimate the stress-strain state of the system and select the cross sections of all its elements. The methodology developed in the article makes it possible to quickly and accurately design spatial structural structures of coatings of an arbitrary geometric shape. The speed and accuracy of modeling and calculation of shell lattice structures is achieved by optimizing the sequence of application of modern programs, using special modeling techniques.

Cryogels as a solution to the issues of environmental management and trunk pipeline operation in Arctic

In the Russian Arctic, a soil cryostructuring technique (i.e. strengthening of soil horizons with cryogel-based composite materials with no excavation of unstable soils required) seems to be showing promise. Experiments have proven that mechanical and thermal insulation properties attributed to cryogels make them appropriate for use in strengthening and thermally insulating the soil, while their structure makes it possible to form a stable vegetation cover. Field experiments have confirmed that cryostructuring efficiently strengthens the soil layer with cryogels stimulating soil microflora. An experience of using cryotropic compositions in the oil and gas sector was described. Notably, cryogels can be used to strengthen unstable soil foundations of trunk pipelines, as well as to bind soil (e.g. on slopes). In addition, cryogels are advised for use in engineering protection to prevent the uneven settlement of a trench base and its creep: thus, cryogels are pumped into the soil of the trench bottom base to create a support system representing a spatial lattice. After the first freeze and thaw cycle, cryotropic material is formed and then increases its strength and elasticity with each new cycle. More broadly, opportunities have been considered regarding cryogels used in various engineering and geological conditions, while taking into account the outcomes of landscape and territorial analysis. It was concluded that cryogel-based composite materials are a promising innovative scientific field expanding technological capabilities for developing and using spaces and resources in the Russian Arctic.

INSTALLATION FEATURES OF SPATIAL LATTICE METAL COVERING OF A PRODUCTION BUILDING IN LIMITED SPACE CONDITIONS

A version of the project for the installation of the spatial structure of the coating of an industrial building was developed. The technological feature of the project was the presence of cramped working conditions. The feasibility study of the methods of assembly and installation of the coating, taking into account the peculiarities of the construction of the coating, the features of the construction site and the needs for lifting machines, showed the eff ectiveness of the installation of the coating with enlarged blocks assembled on the ground. Mounting the unit using a traverse allowed to reduce the estimated height of the hook and select a crane that does not diff er in the high cost of rent. It became possible to apply the adopted installation scheme provided that an individual design of the beam was developed. The calculation and design of the traverse itself was performed, as well as the calculation of the enlarged unit for the installation situation.