Address: 34 Tallinskaya Ulitsa
Phone: +7 (88) *
Boris Glebovich Lvov
Vladimir A. Vetrov
Lev M. Sambursky
The issues of information support based on the use of artificial neural networks for the rapid recognition of odors using devices such as “electronic nose” are considered. The variants of reducing the test sample for an artificial neural network are proposed with the aim of increasing the stability of computations and the speed of calculations. A method for the rapid recognition of odors in the presence of background odors is proposed.
A Fermi gas described within the Bardeen-—Cooper—Schrieffer theory (BCS) may be converted into a Bose—Einstein condensate (BEC) of composite molecules (dimers) by adiabatically tuning the interaction. The sequence of the states that appears during this conversion is referred to as the BCS—BEC crossover. The review is devoted to theoretical and experimental results on the BCS—BEC crossover in three- and quasi-two-dimensional resonant quantum gases in the limiting geometry of traps and optical lattices. We shall discuss nontrivial phenomena in the superfluid hydrodynamics of the quantum gases and fluids including the spectrum of collective excitations in the BCS-BEC crossover, hydrodynamics of rotating Bose condensates with a large number of quantized vortices, and the complex unresolved problem of the chiral anomaly in the hydrodynamics of superfluid Fermi systems with anisotropic p-wave pairing. We shall also analyze spin-imbalanced quantum gases and the ability to realize the triplet p-wave pairing via the Kohn-Luttinger mechanism in these gases. The recent results on two-dimensional Fermi-gas preparation and observation of fluctuational phenomena related to the Berezinskii—Kosterlitz—Thouless transition in those gases will also be reviewed. In addition, we shall briefly discuss experimental realization of hexagon optical lattices with Dirac points in selected locations, which connects to the fast progress in the physics of mono- and bilayers of graphene and other Dirac semimetal systems. In addition we shall briefly discuss recently experimentally discovered BCS-BEC crossover and anomalous superconductivity in bilayer graphene and a possible role of graphene and 2D optical lattices as ideal systems for studying all the effects considered in this review.
The primary purpose of this paper is to provide an overview of existing education solutions for IoT and develop proposals for their improvement. The study draws analysis of current conditions of the educational IoT sphere, a comparative analysis of educational products used for teaching of undergraduate students. With that the article describes the architecture of our own software and hardware platform for learning IOT. Moreover, this paper reviews methods and technical instruments employed to design software and hardware appliances.
The problem of nonuniformity of pore filling in the template synthesis of nanowires is considered. The effect of the applied gradient of temperature on the instability of pore filling is analyzed. The model proposed takes into account the presence of outer thermal boundary layer and outer diffusion layer. The metal electrodeposition in porous template under the quasi-steady-state conditions is considered. The role of the temperature dependences of the exchange current density and the diffusion coefficient of metal cation is revealed. The deposition modes at which the initial dispersion of nanowire lengths can be reduced are determined.
We consider an expansion of the strongly interacting superfluid Fermi gas in a vacuum, assuming absence of the trapping potential, in the so-called unitary regime when the chemical potential μ ~ n^2/3/m where n is the density of the Bose-Einstein condensate of Cooper pairs of fermionic atoms. In low temperatures, T → 0, such expansion can be described in the framework of the Gross-Pitaevskii equation (GPE). Because of the chemical potential dependence on the density, ∼ n^2/3, the GPE has additional symmetries, resulting in the existence of the virial theorem, connecting the mean size of the gas cloud and its Hamiltonian. It leads asymptotically at t → ∞ to the gas cloud expansion, linearly growing in time. We study such asymptotics, and reveal the perfect match between the quasi-classical self-similar solution and the asymptotic expansion of the non-interacting gas. This match is governed by the virial theorem, derived through utilizing the Talanov transformation, which was first obtained for the stationary self-focusing of light in media with a cubic nonlinearity due to the Kerr effect. In the quasi-classical limit, the equations of motion coincide with 3D hydrodynamics for the perfect monoatomic gas with gamma = 5/3. Their self-similar solution describes, on the background of the gas expansion, the angular deformities of the gas shape in the framework of the Ermakov–Ray–Reid type system.
Taking into account an inner structure of the arms of the Aharonov–Bohm ring (AB ring) we have analyzed the transport features related to the topological phase transition which is induced in a superconducting wire (SC wire) with strong spin–orbit interaction (SOI). The SC wire acts as a bridge connecting the arms. The in-plane magnetic-field dependence of linear-response conductance obtained using the nonequilibrium Green’s functions in the tight-binding approximation revealed the Breit–Wigner and Fano resonances (FRs) if the wire is in the nontrivial phase. The effect is explained by the presence of two interacting transport channels in the system. As a result, the FRs are attributed to bound states in continuum (BSCs). The BSC lifetime is determined by both hopping parameters between subsystems and the SC-wire properties. It is established that the FR width and position are extremely sensitive to the type of the lowest-energy excitation in the SC wire, the Majorana or Andreev bound state (MBS or ABS, respectively). Moreover, it is shown that in the specific case of the AB ring, the T-shape geometry, the FR disappears for the transport via the MBS and the conductance is equal to one quantum. It doubles in the local transport regime. On the contrary, in the ABS case the local conductance vanishes. The influence of the mean-field Coulomb interactions and diagonal disorder in the SC wire on the FR is investigated.
n this review article we consider theoretically and give experimental support to the models of the Fermi-Bose mixtures and the BCS-BEC crossover compared with the strong-coupling approach, which can serve as the cornerstones on the way from high-temperature to room-temperature superconductivity in pressurized metallic hydrides. We discuss some key theoretical ideas and mechanisms proposed for unconventional superconductors (cuprates, pnictides, chalcogenides, bismuthates, diborides, heavy-fermions, organics, bilayer graphene, twisted graphene, oxide hetero-structures), superfluids and balanced or imbalanced ultracold Fermi gases in magnetic traps. We build a bridge between unconventional superconductors and recently discovered pressurized hydrides superconductors H_3S and LaH_10 with the critical temperature close to room temperature. We discuss systems with line of nodal Dirac points close to the Fermi surface, superconducting shape resonances and hyperbolic superconducting networks which are very important for the development of novel topological superconductors, for the energetics, for the applications in nano-electronics and quantum computations.
The use of improved fabrication technology, highly disordered NbN thin films, and intertwined section topology makes it possible to create high-performance photon-number-resolving superconducting single-photon detectors (PNR SSPDs) that are comparable to conventional single-element SSPDs at the telecom range. The developed four-section PNR SSPD has simultaneously an 86&mn;3%86&mn;3% system detection efficiency, 35 cps dark count rate, ∼2 ns∼2 ns dead time, and maximum 90 ps jitter. An investigation of the PNR SSPD’s detection efficiency for multiphoton events shows good uniformity across sections. As a result, such a PNR SSPD is a good candidate for retrieving the photon statistics for light sources and quantum key distribution systems.
Proximity induced quantum coherence of electrons in multi-terminal voltage-driven hybrid normalsuperconducting
nanostructures may result in a non-trivial interplay between topology-dependent
Josephson and Aharonov-Bohm effects. We elucidate a trade-off between stimulation of the voltagedependent
Josephson current due to non-equilibrium effects and quantum dephasing of quasiparticles
causing reduction of both Josephson and Aharonov-Bohm currents. We also predict phase-shifted
quantum coherent oscillations of the induced electrostatic potential as a function of the externally
applied magnetic flux. Our results may be employed for engineering superconducting nanocircuits with
controlled quantum properties.
The study of frequency-dependent intrinsic dissipation in a highly transparent Josephson junction by means of quantum-bit (qubit) spectroscopy is proposed. The spectral density of the effective dissipative bath may contain significant contributions from Andreev bound states coupled to fluctuations of the Josephson phase. Varying either the bias current applied to the junction or magnetic flux through a superconducting ring in the radiofrequency superconducting quantum interference device (rf-SQUID) setup, one can tune the level splitting value close to the bottom of the Josephson potential well. Monitoring the qubit energy relaxation time one can probe the spectral density of the effective dissipative bath and unambiguously identify the contribution emerging from Andreev levels.
ABSTRACT: An analytic model based on the transport level and effective temperature concepts has been developed to describe consistently both the quasi- and nonequilibrium transport regimes in nonpolar organic solids with the Gaussian uncorrelated energetic disorder. Field and temperature dependences of drift mobility on the nonequilibrium transport regime relating to the time-of-flight experiment are in good agreement with the Monte-Carlo simulation results in a broad range of fields and temperatures using the same set of model parameters for both transport regimes.
The report discusses the use of National Instruments tools for dependability prediction of electronic devices by simulation modeling. The description of the laboratory bench allowing to develop formal models based on reliability block diagrams, to carry out simulation experiment and to process statistical modeling results, is given as well as an example of this bench usage for reliability prediction of power supply of the lightweight spacecraft.
Constant growth of spacecraft operating life requirements leads to creating equipment which fits these requirements. From this point of view, specifically durability prediction allows to evaluate the potential of creating equipment with a long operating life. On early stages of equipment’s development analytical methods of durability prediction are used. Obviously, the more precise the estimation is, the more likely that the practical test will confirm the durability predictions. Therefore, improving the engineering techniques of the durability prediction is a relevant problem.
The objective of this research is to improve the quality of design work by enhancing the engineering techniques of the durability prediction, which raise the authenticity of the evaluations.
Life of the equipment are calculated using the statistical modelling method (Monte-Carlo method). This method takes into consideration probabilistic characteristics of constituent elements’ life.
As a result, the problem of predicting operating life of electronic equipment using the reference data on early stages of development is solved. An analysis of standardized method of durability prediction was performed which revealed existing limitations for using this method when predicting operating life of electronic equipment. An alternate, statistical method of predicting operating life of electronic equipment was suggested and a software implementation was created. Developed software was tested and verified. Analytical experiments were performed to show the authenticity of the suggested method and to compare it to the standardized one.
Thus, results of the performed research show that the standardized method is applicable only for calculating the minimum operating time. Also, it was concluded that the truncation parameter of element’s life distribution, variation coefficient of life and some specific qualities of dependability prediction scheme have to be taken into consideration when predicting durability of electronic equipment.
The mixture of argon and mercury vapor with temperature-dependent composition is used as the
background gas in different types of gas discharge illuminating lamps. The aim of this work was to develop
a model of the low-current discharge in an argon-mercury mixture at presence of a thin insulating film on the
cathode and to investigate the influence of film on the discharge ignition voltage at low ambient temperatures.
When discharge modeling, we used the obtained earlier expression which describes dependence of the
mixture ionization coefficient on temperature. When there was a thin insulating film on the cathode the model
took into account that positive charges are accumulated on its surface during the discharge. They generate an
electric field in the film sufficient for the field emission of electrons from the metal substrate of the electrode
into the insulator and some of them can overcome the potential barrier at the film outer boundary and go out
in the discharge volume improving emission characteristics of the cathode.
Calculations showed that at a temperature decrease the electric field strengthes in the discharge gap and
the voltage in it are increased due to reduction of the saturated mercury vapor density in the mixture followed
by the decrease of its ionization coefficient. Existence of a thin insulating film on the cathode surface results
in an increase of the cathode effective secondary electron emission yield which compensates the reduction
of the mixture ionization coefficient value.
The results of discharge characteristics modeling demonstrate that in case of the cathode with an insulating
film the discharge ignition becomes possible at a lower inter-electrode voltage. This ensures outdoor mercury
lamp turning on at a reduced supply voltage and increases its reliability under low ambient temperatures.
New SOS MOSFET design with the presence of high-resistance undoped silicon of intrinsic conductivity in the channel
region near the source was proposed. 0.75 μm SOS MOSFET with the use of an "insertion" makes it possible to obtain
the transistor with characteristics corresponding to a transistor with 0.5 μm topological channel length. This allows the
factories to produce new competitive products without significant capital expenditures for the modernization of
An attractive two-dimensional semiconductor with tunable direct bandgap and high carrier mobility, black phosphorus (BP) is used in batteries, solar cells, photocatalysis, plasmonics and optoelectronics. BP is sensitive to ambient conditions, with oxygen playing a critical role in structure degradation. Our simulations show that BP oxidation slows down charge recombination. This is unexpected, since typically charges are trapped and lost on defects. First, BP has no ionic character. It interacts with oxygen and water weakly, experiencing little perturbation to electronic structure. Second, phosphorus supports different oxidation states and binds extraneous atoms avoiding deep defect levels. Third, soft BP structure can accommodate foreign species without disrupting periodic geometry. Finally, BP phonon scattering on defects shortens quantum coherence and suppresses recombination. Thus, oxidation can be regarded as production of a self-protective layer that improves BP properties. These BP features should be common to other mono-elemental 2D materials, stimulating energy and electronics applications.
Quantum confinement is known to affect a nanosized superconductor
through quantum-size variations of the electronic density of states. Here, it is
demonstrate that there is another quantum-confinement mechanism over-
looked in previous studies. In particular, it is found that the electron–electron
attraction can be enhanced due to quantum-confinement modifications of
electronic wave functions. The superconducting correlations are strengthened
by such quantum mechanical effect, which creates a subtle interplay with
surface–substrate phonon modifications. The combined effect depends on
nanofilm thickness and can be controlled by nanoarchitechture. The
calculations are in a reasonable agreement with experiments performed on
high-quality aluminum films. These findings shed light on the long-standing
problem of the size dependence of the critical temperature in low-
We report an experimental observation of superconductivity in Cd3As2 thin films without application of external pressure. The films under study were synthesized by magnetron sputtering. Surface studies suggest that the observed transport characteristics are related to the polycrystalline continuous part of the investigated films with a homogeneous distribution of elements and the Cd-to-As ratio close to stoichiometric Cd3As2. The latter is also supported by Raman spectra of the studied films where two pronounced peaks inherent to Cd3As2 were observed. The obtained x-ray diffraction patterns for studied films also correspond to the Cd3As2 lattice. The formation of a superconducting phase in the films under study is confirmed by the characteristic behavior of the temperature and the magnetic field dependence of the sample resistivity, as well as by the presence of pronounced zero-resistance plateaus in the dV/dI characteristics. The corresponding H-c-T-c plots reveal a clearly pronounced linear behavior within the intermediate temperature range, similar to that observed for bulk Cd3As2 and Bi2Se3 films under pressure, suggesting the possibility of a nontrivial pairing in the films under investigation. We discuss a possible role of the sample inhomogeneities and crystal strains in the observed phenomena.
Recently standardized millimeter-wave (mmWave) band 3GPP New Radio systems are expected to bring extraordinary rates to the air interface efficiently providing commercial-grade enhanced mobile broadband services in hotspot areas. One of the challenges of such systems is efficient offloading of the data from access points (AP) to the network infrastructure. This task is of special importance for APs installed in remote areas with no transport network available. In this paper, we assess the packet level performance of mmWave technology for cost-efficient backhauling of remote 3GPP NR APs connectivity “islands”. Using a queuing system with arrival processes of the same priority competing for transmission resources, we assess the aggregated and per-AP packet loss probability as a function environmental conditions, mmWave system specifics, and generated traffic volume. We show that the autocorrelation in aggregated traffic provides a significant impact on service characteristics of mmWave backhaul and needs to be compensated by increasing either emitted power or the number of antenna array elements. The effect of autocorrelation in the per-AP traffic and background traffic from other APs also negatively affects the per-AP packet loss probability. However, the effect is of different magnitude and heavily depends on the load fraction of per-AP traffic in the aggregated traffic stream. The developed model can be used to parameterize mmWave backhaul links as a function of the propagation environment, system design, and traffic conditions.