The results of scientific research of Bryansk State University in 2023 in the field of rope technologies development for various sectors of the economy

The article presents the results of research activities in 2023 by scientists of the Academician I.G. Petrovskii Bryansk State University in the field of developing promising domestic designs of single-span mobile ropeways of various designs — based on autonomous self-propelled wheeled chassis with high load capacity and cross-country ability and based on modular airmobile units. The results of the creation of scientifically based methods for their design and computer modeling of operational processes are also presented. The article describes the results of the creation of a theory of design and modeling of work processes for harvesters equipped with rope anchoring equipment for logging operations when working on steep slopes in highly rugged or mountainous terrain

Mathematical description of deviation mechanisms positions of track chassis in motion with variable ground resistance

Engineering methods for designing tracked mechanisms for moving mobile chassis of hoisting and transport, construction, road and other specialized machines are based on constant values of the coefficients of resistance to ground movement when choosing engine power and track parameters. In reality, the ground is not homogeneous, and the coefficient of resistance to movement at each moment in time is a random variable located in a certain interval depending on the type of ground. This article proposes a mathematical description of the process of joint movement of two tracked circuits within the same chassis with uneven ground resistance over time, which is reflected in the speed of movement of each circuit and leads to the effect of running tracks, which contributes to the occurrence of instantaneous turning moments. Depending on the type of selected law of change in the coefficient of resistance to ground movement over time, the results of decompensation of uneven movement of the tracks are shown, independent of the additional resistance arising from the lateral cut of the ground layer during instantaneous rotations of the chassis, characteristic of mechanisms with a separate drive of each track circuit

Theoretical study of the influence of a variable ground resistance by position tracked chassis in motion

The position of the tracked chassis of a vehicle in motion often determines the accuracy of the creation of related structures during construction and road work. There are technical solutions for chassis positioning systems in several planes, based on laser leveling technologies. These systems implement the tracking principle of monitoring the position of the chassis, reacting to abnormal changes in position. Software implementation of position control based on its prediction during opera-tion is difficult to implement, since it must take into account the influence of many random factors on the movement of the machine (variability of movement resistance forces over time, etc.). This article examines the influence of variable resistance to ground movement on the position of tracked chassis in motion. Specific aspects are shown that characterize the change in the po-sition of the machine depending on the combination of laws of change in the coefficients of resistance to movement under each caterpillar. The examples show procedures for mathematical prediction of the physical and geometric characteristics of the movement of a tracked vehicle, the use of which in software algorithms of posi-tion control systems can help improve the accuracy of their operation

Mathematical models of structural and parametric synthesis of load trolley metalware of bridge cranes on basis of multipurpose layout drawing

The mathematical models of the structural and parametric synthesis of the load trolley metalware of bridge cranes on the basis of the multipurpose layout drawing are suggested. The models are based on the matrix representation of the metalware segment structures. The article considers the options for implementation of the structural matrixes of the elements and parameter matrixes when performing design calculations as a part of the developed mathematical models. The purpose of the calculations is to confirm the bearing capacity of the metalware, taking into account the requirements of the regulations and specifications. The basic structures of the mathematical models of the structural and parametric synthesis of the metalware are formed, using the structural matrixes of the separate elements and matrixes of the element interconnection. The general structure of the developed mathematical models is shown, and the description of the functionality of the separate matrix groups of the different calculation modules is given

Vacuum fluctuations and topological Casimir effect in Friedmann-Robertson-Walker cosmologies with compact dimensions

We investigate the Wightman function, the vacuum expectation values of the field squared and the energy-momentum tensor for a massless scalar field with general curvature coupling parameter in spatially flat Friedmann-Robertson-Walker universes with an arbitrary number of toroidally compactified dimensions. The topological parts in the expectation values are explicitly extracted and in this way the renormalization is reduced to that for the model with trivial topology. In the limit when the comoving lengths of the compact dimensions are very short compared to the Hubble length, the topological parts coincide with those for a conformal coupling and they are related to the corresponding quantities in the flat spacetime by standard conformal transformation. In the opposite limit of large comoving lengths of the compact dimensions, in dependence of the curvature coupling parameter, two regimes are realized with monotonic or oscillatory behavior of the vacuum expectation values. In the monotonic regime and for nonconformally and nonminimally coupled fields the vacuum stresses are isotropic and the equation of state for the topological parts in the energy density and pressures is of barotropic type. In the oscillatory regime, the amplitude of the oscillations for the topological part in the expectation value of the field squared can be either decreasing or increasing with time, whereas for the energy-momentum tensor the oscillations are damping.Comment: 20 pages, 2 figure

Fermionic vacuum densities in higher-dimensional de Sitter spacetime

Fermionic condensate and the vacuum expectation values of the energy-momentum tensor are investigated for twisted and untwisted massive spinor fields in higher-dimensional de Sitter spacetime with toroidally compactified spatial dimensions. The expectation values are presented in the form of the sum of corresponding quantities in the uncompactified de Sitter spacetime and the parts induced by non-trivial topology. The latter are finite and the renormalization is needed for the first parts only. Closed formulae are derived for the renormalized fermionic vacuum densities in uncompactified odd-dimensional de Sitter spacetimes. It is shown that, unlike to the case of 4-dimensional spacetime, for large values of the mass, these densities are suppressed exponentially. Asymptotic behavior of the topological parts in the expectation values is investigated in the early and late stages of the cosmological expansion. When the comoving lengths of compactified dimensions are much smaller than the de Sitter curvature radius, to the leading order the topological parts coincide with the corresponding quantities for a massless fermionic field and are conformally related to the corresponding flat spacetime results. In this limit the topological parts dominate the uncompactified de Sitter part and the back-reaction effects should be taken into account. In the opposite limit, for a massive field the asymptotic behavior of the topological parts is damping oscillatory.Comment: 19 pages, 4 figures, cosmological applications are adde

The first dozen years of the history of ITEP Theoretical Physics Laboratory

The theoretical investigations at ITEP in the years 1945-1958 are reviewed. There are exposed the most important theoretical results, obtained in the following branches of physics: 1) the theory of nuclear reactors on thermal neutrons; 2) the hydrogen bomb project ("Tube" in USSR and "Classical Super" in USA); 3) radiation theory; ~4) low temperature physics; 5) quantum electrodynamics and quantum field theories; 6) parity violation in weak interactions, the theory of $\beta$-decay and other weak processes; 7) strong interaction and nuclear physics. To the review are added the English translations of few papers, originally published in Russian, but unknown (or almost unknown) to Western readers.Comment: 55 pages, 5 fig

Search for a W' boson decaying to a bottom quark and a top quark in pp collisions at sqrt(s) = 7 TeV

Results are presented from a search for a W' boson using a dataset corresponding to 5.0 inverse femtobarns of integrated luminosity collected during 2011 by the CMS experiment at the LHC in pp collisions at sqrt(s)=7 TeV. The W' boson is modeled as a heavy W boson, but different scenarios for the couplings to fermions are considered, involving both left-handed and right-handed chiral projections of the fermions, as well as an arbitrary mixture of the two. The search is performed in the decay channel W' to t b, leading to a final state signature with a single lepton (e, mu), missing transverse energy, and jets, at least one of which is tagged as a b-jet. A W' boson that couples to fermions with the same coupling constant as the W, but to the right-handed rather than left-handed chiral projections, is excluded for masses below 1.85 TeV at the 95% confidence level. For the first time using LHC data, constraints on the W' gauge coupling for a set of left- and right-handed coupling combinations have been placed. These results represent a significant improvement over previously published limits.Comment: Submitted to Physics Letters B. Replaced with version publishe

Search for the standard model Higgs boson decaying into two photons in pp collisions at sqrt(s)=7 TeV

A search for a Higgs boson decaying into two photons is described. The analysis is performed using a dataset recorded by the CMS experiment at the LHC from pp collisions at a centre-of-mass energy of 7 TeV, which corresponds to an integrated luminosity of 4.8 inverse femtobarns. Limits are set on the cross section of the standard model Higgs boson decaying to two photons. The expected exclusion limit at 95% confidence level is between 1.4 and 2.4 times the standard model cross section in the mass range between 110 and 150 GeV. The analysis of the data excludes, at 95% confidence level, the standard model Higgs boson decaying into two photons in the mass range 128 to 132 GeV. The largest excess of events above the expected standard model background is observed for a Higgs boson mass hypothesis of 124 GeV with a local significance of 3.1 sigma. The global significance of observing an excess with a local significance greater than 3.1 sigma anywhere in the search range 110-150 GeV is estimated to be 1.8 sigma. More data are required to ascertain the origin of this excess.Comment: Submitted to Physics Letters

Measurement of the Lambda(b) cross section and the anti-Lambda(b) to Lambda(b) ratio with Lambda(b) to J/Psi Lambda decays in pp collisions at sqrt(s) = 7 TeV

The Lambda(b) differential production cross section and the cross section ratio anti-Lambda(b)/Lambda(b) are measured as functions of transverse momentum pt(Lambda(b)) and rapidity abs(y(Lambda(b))) in pp collisions at sqrt(s) = 7 TeV using data collected by the CMS experiment at the LHC. The measurements are based on Lambda(b) decays reconstructed in the exclusive final state J/Psi Lambda, with the subsequent decays J/Psi to an opposite-sign muon pair and Lambda to proton pion, using a data sample corresponding to an integrated luminosity of 1.9 inverse femtobarns. The product of the cross section times the branching ratio for Lambda(b) to J/Psi Lambda versus pt(Lambda(b)) falls faster than that of b mesons. The measured value of the cross section times the branching ratio for pt(Lambda(b)) > 10 GeV and abs(y(Lambda(b))) < 2.0 is 1.06 +/- 0.06 +/- 0.12 nb, and the integrated cross section ratio for anti-Lambda(b)/Lambda(b) is 1.02 +/- 0.07 +/- 0.09, where the uncertainties are statistical and systematic, respectively.Comment: Submitted to Physics Letters