The stress state of orthotropic shell with two collinear cracks of different lengths under bending load on the lines

Розглянуто задачу про напружений стан пологої ортотропної оболонки двоякої кривини з двома колінеарними прямолінійними тріщинами різної довжини, коли до їх берегів прикладене самозрівноважене згинальне навантаження. Задачу сформульовано у двовимірній постановці на основі моделі контакту вздовж лінії на одній з лицьових поверхонь оболонки. Система сингулярних інтегральних рівнянь розв’язана чисельно за допомогою методу механічних квадратур. Досліджено вплив кривини оболонки, взаємного розміщення колінеарних тріщин, механічних властивостей матеріалу в околі вершин тріщин на коефіцієнти інтенсивності моментів. Отримані результати співпадають з відомими в літературі частинними розв’язками.In this paper we present the analytically and numerically study of the problem of the stress state of the shallow orthotropic dual curvature shell with two collinear rectilinear through thickness cracks of different lengths, when applied to their shores self-balanced load. The thin shells are widely used in hydraulic engineering, aerospace engineering, shipbuilding and aircraft construction, engineering and others areas of modern construction. By using of advanced composite materials the strength of structure is increased and the weight is reduced. As an example, the use of carbon plastic in the construction of Boeing and Airbus aircrafts; the housing of water version «Formula 1» is reinforced with carbon fibers; details of the internal combustion engine (pistons, connecting rods), and others. Reliability and durability of constructions like shells depends on the availability of various types of defects that occur at the stage of the manufacture of parts yet and avoid this impossible. So analysis of stress state of orthotropic dual curvature shell with closure cracks is an important task of mechanics. The problem presented in this paper was formulated in a two-dimensional statement by means of the contact model along a line in one of the facial surfaces of a shell (internal or external). The problem statement is reduced to the solution of system of two integral equations. The independent variables in the equations are leaps of rotation angles of cracks, while leaps of movements on the lines of cracks are functions which are dependent on them. The system of singular integral equations is solved numerically using the method of mechanical quadratures. Was investigated the influence of the shell curvature, mutual location of collinear cracks, crack length, the mechanical properties of the orthotropic material in the vicinity of the crack tip on the stress intensity factors and moment intensity factors. In particular cases of the problem was obtained results for cylindrical, spherical and pseudo spherical shells. In case when cracks have same length in spherical shell was obtained known in the literature results

Measurement of the Bs0→J/ψηB_{s}^{0} \rightarrow J/\psi \eta lifetime

Using a data set corresponding to an integrated luminosity of $3 fb^{-1}$, collected by the LHCb experiment in $pp$ collisions at centre-of-mass energies of 7 and 8 TeV, the effective lifetime in the $B^0_s \rightarrow J/\psi \eta$ decay mode, $\tau_{\textrm{eff}}$, is measured to be $\tau_{\textrm{eff}} = 1.479 \pm 0.034~\textrm{(stat)} \pm 0.011 ~\textrm{(syst)}$ ps. Assuming $CP$ conservation, $\tau_{\textrm{eff}}$ corresponds to the lifetime of the light $B_s^0$ mass eigenstate. This is the first measurement of the effective lifetime in this decay mode.Comment: All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2016-017.htm

Opposite-side flavour tagging of B mesons at the LHCb experiment

The calibration and performance of the oppositeside flavour tagging algorithms used for the measurements of time-dependent asymmetries at the LHCb experiment are described. The algorithms have been developed using simulated events and optimized and calibrated with B + →J/ψK +, B0 →J/ψK ∗0 and B0 →D ∗− μ + νμ decay modes with 0.37 fb−1 of data collected in pp collisions at √ s = 7 TeV during the 2011 physics run. The oppositeside tagging power is determined in the B + → J/ψK + channel to be (2.10 ± 0.08 ± 0.24) %, where the first uncertainty is statistical and the second is systematic

THERMAL AND EPITHERMAL NEUTRON GENERATION FOR NUCLEAR MEDICINE USING ELECTRON LINEAR ACCELERATOR

In this paper, to obtain streams of thermal and epithermal neutrons are used delayed neutrons emitted from the target with a fissile material. The target preliminarily activated with help of electron beam from linear accelerator with an energy of 20 MeV and a power of 9 Watts. At the same time to obtain a stream of thermal as well as epithermal neutron density 6 10^-5 n / (cm^2 s) The results of experiment are presented where half-decay curves have been measured of emitting delayed neutrons radioactive nuclei produced in the fission process. It has been shown that the activated target, which contains the fissile material, presents a compact small size source of delayed neutrons. It can be delivered to the formator where thermal and epithermal neutrons are formed during a certain time period with help of the moderator, absorber and collimator. Then this target is moved to the activator being replaced with another target. Thus, pulsed neutron flux is produced. The duration of neutron pulse corresponds to the presence time of the activated target in the formator, and time interval between pulses is determined by the delivery time of the target from the activator to the formator. Given that the yield of neutrons from the target is directly proportional to the power of the beam of accelerated electrons, shows that the beam power of 1.5 - 3 kW, the flux density of thermal and epithermal neutrons can reach the values of (2-3) 10^9 n / (cm^2 s). Such a neutron beam can be used in nuclear medicine, in particular, in neutron capture therapy of oncologic diseases

Search for CP violation in D+→K−K+π+D^{+} \to K^{-}K^{+}\pi^{+} decays

A model-independent search for direct CP violation in the Cabibbo suppressed decay $D^+ \to K^- K^+\pi^+$ in a sample of approximately 370,000 decays is carried out. The data were collected by the LHCb experiment in 2010 and correspond to an integrated luminosity of 35 pb$^{-1}$. The normalized Dalitz plot distributions for $D^+$ and $D^-$ are compared using four different binning schemes that are sensitive to different manifestations of CP violation. No evidence for CP asymmetry is found.Comment: 13 pages, 8 figures, submitted to Phys. Rev.

Measurement of the ratio of branching fractions BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma)

The ratio of branching fractions of the radiative B decays B0 -> K*0 gamma and Bs0 -> phi gamma has been measured using 0.37 fb-1 of pp collisions at a centre of mass energy of sqrt(s) = 7 TeV, collected by the LHCb experiment. The value obtained is BR(B0 -> K*0 gamma)/BR(Bs0 -> phi gamma) = 1.12 +/- 0.08 ^{+0.06}_{-0.04} ^{+0.09}_{-0.08}, where the first uncertainty is statistical, the second systematic and the third is associated to the ratio of fragmentation fractions fs/fd. Using the world average for BR(B0 -> K*0 gamma) = (4.33 +/- 0.15) x 10^{-5}, the branching fraction BR(Bs0 -> phi gamma) is measured to be (3.9 +/- 0.5) x 10^{-5}, which is the most precise measurement to date.Comment: 15 pages, 1 figure, 2 table

Model-independent evidence for J/ψpJ/\psi p contributions to Λb0→J/ψpK−\Lambda_b^0\to J/\psi p K^- decays

The data sample of $\Lambda_b^0\to J/\psi p K^-$ decays acquired with the LHCb detector from 7 and 8~TeV $pp$ collisions, corresponding to an integrated luminosity of 3 fb$^{-1}$, is inspected for the presence of $J/\psi p$ or $J/\psi K^-$ contributions with minimal assumptions about $K^- p$ contributions. It is demonstrated at more than 9 standard deviations that $\Lambda_b^0\to J/\psi p K^-$ decays cannot be described with $K^- p$ contributions alone, and that $J/\psi p$ contributions play a dominant role in this incompatibility. These model-independent results support the previously obtained model-dependent evidence for $P_c^+\to J/\psi p$ charmonium-pentaquark states in the same data sample.Comment: 21 pages, 12 figures (including the supplemental section added at the end

Measurements of the branching fractions of the decays B°s → D∓s K± and B°s → D¯sπ+

The decay mode B°s → D∓s K± allows for one of the theoretically cleanest measurements of the CKM angle γ through the study of time-dependent CP violation. This paper reports a measurement of its branching fraction relative to the Cabibbo-favoured mode B°s → D¯sπ+ based on a data sample corresponding to 0.37 fb¯¹ of proton-proton collisions at √s = 7TeV collected in 2011 with the LHCb detector. In addition, the ratio of B meson production fractions fs/fd, determined from semileptonic decays, together with the known branching fraction of the control channel B°s → D¯sπ+ is used to perform an absolute measurement of the branching fractions: B(B°s → D¯sπ+) = (2.95 ± 0.05 ± 0.17 -0.22 +0.18) × 10¯³ ; B(B°s → D∓s K±) = (1.90 ± 0.12 ± 0.13 -0.14 +0.12) × 10¯4 ; where the first uncertainty is statistical, the second the experimental systematic uncertainty, and the third the uncertainty due to f s/f

Measurement of charged particle multiplicities in pppp collisions at s=7{\sqrt{s} =7}TeV in the forward region

The charged particle production in proton-proton collisions is studied with the LHCb detector at a centre-of-mass energy of ${\sqrt{s} =7}$TeV in different intervals of pseudorapidity $\eta$. The charged particles are reconstructed close to the interaction region in the vertex detector, which provides high reconstruction efficiency in the $\eta$ ranges $-2.5<\eta<-2.0$ and $2.0<\eta<4.5$. The data were taken with a minimum bias trigger, only requiring one or more reconstructed tracks in the vertex detector. By selecting an event sample with at least one track with a transverse momentum greater than 1 GeV/c a hard QCD subsample is investigated. Several event generators are compared with the data; none are able to describe fully the multiplicity distributions or the charged particle density distribution as a function of $\eta$. In general, the models underestimate the charged particle production

Study of J /ψ production in Jets

The production of J/ψ mesons in jets is studied in the forward region of proton-proton collisions using data collected with the LHCb detector at a center-of-mass energy of 13 TeV. The fraction of the jet transverse momentum carried by the J/ψ meson, z(J/ψ)≡pT(J/ψ)/pT(jet), is measured using jets with pT(jet)>20 GeV in the pseudorapidity range 2.5<η(jet)<4.0. The observed z(J/ψ)distribution for J/ψ mesons produced in b-hadron decays is consistent with expectations. However, the results for prompt J/ψ production do not agree with predictions based on fixed-order nonrelativistic QCD. This is the first measurement of the pT fraction carried by prompt J/ψ mesons in jets at any experiment