Prediction of the Supersonic Flow Base Pressure by Axisymmetric ‎Direct Numerical Simulation

Axisymmetric direct numerical simulation (DNS) has been carried out to predict supersonic base flow behavior. Substantially fine grid has been used to perform calculations for the flow with Reynolds number up to 106. Optimal grid resolution was established through test calculations for affordable run time and solution convergence determined by the vorticity value. Numerical scheme provides fourth-order approximation for dissipative, fifth-order for convective and second-order for unsteady terms of conservation equations. Reynolds Averaged Navier-Stokes (RANS) approach has been employed to obtain input flow profiles for DNS calculations. Series of calculations have been carried out for Mach number 1.5 with Reynolds numbers 104, 105, 106 and for Mach number 2.46 with Reynolds number 1.65×106. It has been found that local base pressure coefficient calculated by DNS is a bit overestimated in a zone close to symmetry axis in comparison with experiment while integrated base drag coefficient shows good agreement with experimental data and noticeably better than one obtained by RANS approach

Efficiency of enhanced oil recovery’s and oil production stimulation’s methods at the oil fields of Khanty-Mansi Autonomous Okrug – Yugra

Stabilization of oil production at the level of 215–220 million tons/year, as well as its subsequent growth, is a priority task for the enterprises of the fuel and energy complex of Khanty-Mansi Autonomous Okrug – Yugra (KhMAO – Yugra). It is impossible to achieve this without the active implementation of the most effective modern technologies for enhanced oil recovery. This article aims to analyze the methods of enhanced oil recovery and oil production stimulation methods (EOR and PS) used at the KhMAO – Yugra fields on an industrial scale, their features and their contribution to additional oil production from 2001 to 2021. The article describes such technologies as sidetracking (STB), physical and chemical methods (FCM), hydraulic fracturing (HF), bottom-hole treatment (BHT), hydrodynamic methods (HDM), horizontal well drilling (SHD), as well as other geological and technical measures (GTM) aimed at optimizing well operation (other methods (OM)). The study showed that FCM, BHT and other well interventions became the most used. The share of additional oil produced through the use of EOR and PS has doubled since 2013: 8% in 2013, 16.2% in 2021. Hydraulic fracturing, deep drilling and sidetracking showed the highest efficiency. All this led to the stabilization of the annual oil production in KhMAO – Yugra and even to its growth in 2021. The use of enhanced oil recovery methods on a non-alternative basis in developed fields is especially important, because the share of hard-to-recover reserves is high and reaches 80% for some companies in the Khanty-Mansi Autonomous Okrug – Yugra. For such fields, it is necessary to strengthen scientific research in the field of substantiation of optimal conditions for well construction, as well as the operation of development systems

Silicon-Compatible Memristive Devices Tailored by Laser and Thermal Treatments

Nowadays, memristors are of considerable interest to researchers and engineers due to the promise they hold for the creation of power-efficient memristor-based information or computing systems. In particular, this refers to memristive devices based on the resistive switching phenomenon, which in most cases are fabricated in the form of metal–insulator–metal structures. At the same time, the demand for compatibility with the standard fabrication process of complementary metal–oxide semiconductors makes it relevant from a practical point of view to fabricate memristive devices directly on a silicon or SOI (silicon on insulator) substrate. Here we have investigated the electrical characteristics and resistive switching of SiOx- and SiNx-based memristors fabricated on SOI substrates and subjected to additional laser treatment and thermal treatment. The investigated memristors do not require electroforming and demonstrate a synaptic type of resistive switching. It is found that the parameters of resistive switching of SiOx- and SiNx-based memristors on SOI substrates are remarkably improved. In particular, the laser treatment gives rise to a significant increase in the hysteresis loop in I–V curves of SiNx-based memristors. Moreover, for SiOx-based memristors, the thermal treatment used after the laser treatment produces a notable decrease in the resistive switching voltage

Evidence of a J/ψΛJ/\psi\Lambda structure and observation of excited Ξ−\Xi^- states in the Ξb−→J/ψΛK−\Xi^-_b \to J/\psi\Lambda K^- decay

First evidence of a structure in the $J/\psi{\Lambda}$ invariant mass distribution is obtained from an amplitude analysis of $\Xi_b^-{\rightarrow}J/\psi{\Lambda}K^-$ decays. The observed structure is consistent with being due to a charmonium pentaquark with strangeness with a significance of $3.1\sigma$ including systematic uncertainties and look-elsewhere effect. Its mass and width are determined to be $4458.8\pm2.9^{+4.7}_{-1.1}$ MeV and $17.3\pm6.5^{+8.0}_{-5.7}$ MeV, respectively, where the quoted uncertainties are statistical and systematic. The structure is also consistent with being due to two resonances. In addition, the narrow excited $\Xi^-$ states, $\Xi(1690)^-$ and $\Xi(1820)^-$, are seen for the first time in a $\Xi^-_b$ decay, and their masses and widths are measured with improved precision. The analysis is performed using $pp$ collision data corresponding to a total integrated luminosity of 9 fb$^{-1}$, collected with the LHCb experiment at centre-of-mass energies of 7, 8 and 13 TeV

The LHCb upgrade I

International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software

The LHCb upgrade I

International audienceThe LHCb upgrade represents a major change of the experiment. The detectors have been almost completely renewed to allow running at an instantaneous luminosity five times larger than that of the previous running periods. Readout of all detectors into an all-software trigger is central to the new design, facilitating the reconstruction of events at the maximum LHC interaction rate, and their selection in real time. The experiment's tracking system has been completely upgraded with a new pixel vertex detector, a silicon tracker upstream of the dipole magnet and three scintillating fibre tracking stations downstream of the magnet. The whole photon detection system of the RICH detectors has been renewed and the readout electronics of the calorimeter and muon systems have been fully overhauled. The first stage of the all-software trigger is implemented on a GPU farm. The output of the trigger provides a combination of totally reconstructed physics objects, such as tracks and vertices, ready for final analysis, and of entire events which need further offline reprocessing. This scheme required a complete revision of the computing model and rewriting of the experiment's software