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The LHCb simulation application, Gauss, consists of two independent phases, the generation of the primary event and the tracking of particles produced in the experimental setup. For the LHCb experimental program it is particularly important to model B meson decays: the EvtGen code developed in CLEO and BABAR has been chosen and customized for non-coherent B production as occuring in pp collisions at the LHC. The initial proton-proton collision is provided by a different generator engine, currently PYTHIA 6 for massive production of signal and generic pp collisions events. Beam gas events, background events originating from proton halo, cosmics and calibration events for different detectors can be generated in addition to pp collisions. Different generator packages as available in the physics community or specifically developed in LHCb are used for the different purposes. Running conditions affecting the generated events such as the size of the luminous region, the number of collisions occuring in a bunch crossing and the number of spill-over events from neighbouring bunches are modeled via dedicated algorithms appropriately configured. The design of the generator phase of Gauss will be described: a modular structure with well defined interfaces specific to the various tasks, e.g. pp collisions, particle decays, selections, etc. has been chosen. Different implementations are available for the various tasks allowing selecting and combining them as most appropriate at run time as in the case of PYTHIA 6 for pp collisions or HIJING for beam gas. The advantages of such structure, allowing for example to adopt transparently new generators packages, will be discussed.

Whether the use of mobile phones (MP) represents a health hazard is still under debate. As part of the attempts to resolve this uncertainty, there has been an extensive characterization of the electromagnetic fields MP emit and receive. While the radiofrequencies (RF) have been studied exhaustively, the static magnetic fields (SMF) have received much less attention, regardless of the fact there is a wealth of evidence demonstrating their biological effects. We performed 2D maps of the SMF at several distances from the screen of 5 MP (models between 2013 and 2018) using a tri-axis magnetometer. We built a mathematical model to fit our measurements, extrapolated them down to the phones’ screen, and calculated the SMF on the skin of a 3D head model, showing that exposure is in the µT to mT range. Our literature survey prompts the need of further research not only on the biological effects of SMF and their gradients, but also on their combination with extremely low frequency (ELF) and RF fields. The study of combined fields (SMF, ELF, and RF) as similar as possible to the ones that occur in reality should provide a more sensible assessment of potential risks.

— We have studied the effect of heat treatment temperature on dilatometric and densimetric characteristics (geometric dimensions, volume, density, and weight) of plasma-sprayed pure aluminum oxide ceramics using specially prepared samples 46 × 23 × 3 mm in dimensions. Some of the samples were heat-treated at temperatures of 800, 950, 1100, and 1300°C for 1 h in air. Before and after heat treatment, the samples were weighed and we measured their geometric dimensions and calculated their volume and density. In our experiments, we used precision analytical and measuring equipment and thermal analysis methods. The phase composition of the samples was determined by quantitative X-ray diffraction. Their porosity was evaluated using X-ray computed tomography. The results demonstrate that raising the heat treatment temperature leads first to an increase in the length of the samples under study relative to their original length, which is accompanied by a decrease in their thickness (in the range 800–1100°C). The volume and density of the samples also decrease. Further raising the heat treatment temperature (in the range 1100–1300°C) leads to a sharp decrease in all the geometric dimensions and volume of the samples, in combination with a sharp increase in their density, which is accompanied by a decrease in the weight of the samples. This was shown to be due to changes in the phase composition and total porosity of the samples during heating to the above temperatures.

A consistent theory of sound generation in a turbulent boundary layer developing over a flat smooth boundary at low Mach numbers is presented. The main source of sound and the long-wavelength part of pressure fluctuations on the boundary are incoming shear (viscous) waves generated by Lighthill quadrupoles in the near-wall region of the turbulent boundary layer. It is shown that with an increase in the Reynolds number (decrease in viscosity), the role of viscosity in sound generation does not decrease, but instead increases. Quantitative estimates of the spectrum of the sound power density generated in a turbulent boundary layer are given.

In this paper, we describe the history of the LHCb experiment over the last three decades, and its remarkable successes and achievements. LHCb was conceived primarily as a b -physics experiment, dedicated to CP violation studies and measurements of very rare b decays; however, the tremendous potential for c -physics was also clear. At first data taking, the versatility of the experiment as a general-purpose detector in the forward region also became evident, with measurements achievable such as electroweak physics, jets and new particle searches in open states. These were facilitated by the excellent capability of the detector to identify muons and to reconstruct decay vertices close to the primary pp interaction region. By the end of the LHC Run 2 in 2018, before the accelerator paused for its second long shut down, LHCb had measured the CKM quark mixing matrix elements and CP violation parameters to world-leading precision in the heavy-quark systems. The experiment had also measured many rare decays of b and c quark mesons and baryons to below their Standard Model expectations, some down to branching ratios of order 10 -9 . In addition, world knowledge of b and c spectroscopy had improved significantly through discoveries of many new resonances already anticipated in the quark model, and also adding new exotic four and five quark states. The paper describes the evolution of the LHCb detector, from conception to its operation at the present time. The authors’ subjective summary of the experiment’s important contributions is then presented, demonstrating the wide domain of successful physics measurements that have been achieved over the years.

The effect of static and alternating magnetic fields on the conformation of nucleoids in cells of different types is considered. The model of slow and nonuniform rotation of the charged DNA domain is used. An equation is obtained for the resonance frequencies of the alternating magnetic field.

An imposed strong magnetic field suppresses turbulence and profoundly changes the nature of the flow of an electrically conducting fluid. We consider this effect for the case of mixed convection flows in pipes and ducts, in which unique regimes characterized by extreme temperature gradients and high-amplitude fluctuations (the so-called magnetoconvective fluctuations) have been recently discovered. The configuration is directly relevant to the design of the liquid-metal components of future nuclear fusion reactors. This work presents the general picture of the flow transformation emerging from the recent numerical studies (DNS - Direct Numerical Simulation), illustrates the key known facts, and outlines the remaining open questions. Implications for fusion reactor technology and novel experimental and numerical methods are also discussed.

— We have studied silicidation of powders of carbide phases in the Ti–Ta–C and Ti–Zr–C systems in a gaseous silicon monoxide atmosphere at 1400°C. The results demonstrate that the silicidation of the carbide phases in the Ti–Ta–C and Ti–Zr–C systems has a selective character. Silicidation selectivity shows up in that, in carbide mixtures containing up to 50 mol % TiC, the only siliciding treatment products are zirconium and tantalum silicide phases: ZrSi, Ta 5 Si 3 , and TaSi 2 . At TiC contents of 80 mol % and above in the Ti–Ta–C system, silicidation leads to the formation of the Ti 3 SiC 2 MAX phase.

AbstractDue to advances in engine-noise reduction, airframe noise has become one of the main sources of modern aircraft noise during approach. The landing gear is an important source of airframe noise, and its mitigation is necessary to reduce further the overall aircraft noise and meet the current and future regulations on community noise. The problem of modeling and reduction of aerodynamic noise for such a complex object as the landing gear of a modern aircraft, which consists of a large number of elements of various shapes and sizes, is extremely difficult. In Russia, experimental studies of landing-gear noise can be carried out either for small-scale models (in particular, in the AC-2 anechoic chamber at TsAGI) or in full-scale flight tests using the noise–source localization method (beamforming). Thus, it is of interest to compare the noise measurements of small-scale aircraft landing-gear models with the results of flight tests in which the landing-gear noise is measured using the beamforming method. In this paper, for the first time in Russian practice, such a comparison is made in relation to the landing-gear noise of a regional aircraft and a method is proposed for recalculating the results of small-scale landing-gear tests to the full scale.