The paper deals with cyclostationarity as a natural extension of stationarity as the key property in designing the widely-used models of random processes. The comparative example of two processes, one is wide-sense stationary and the other is wide-sense cyclostationary, is given in the paper and reveals the lack of the conventional stationary description based on one-dimensional autocorrelation functions. It is shown that two significantly different random processes appear to be characterized by exactly the same autocorrelation function while their two-dimensional autocorrelation functions provide outlook where the difference between processes of two above-mentioned classes becomes much clearer. More concise representation by expanding the two-dimensional autocorrelation function to its Fourier series where the cyclic frequency appears as the transform parameter is illustrated. The closed-form expression for the components of the cyclic autocorrelation function is also given for the random process which is an infinite pulse train made of rectangular pulses with randomly varying amplitudes.

We propose a novel algorithm for the construction of the sparse, nonetheless, the massive and rigid structure. The generated structures possess two significant properties reminiscent of the metallic foams. Firstly, the weight of the structures can be as low as the percent of the bulk one. Secondly, the structures are mechanically rigid. The structures are necessary for the simulation of the physical models of the foam properties.

The mathematical model describing the dynamics of HIV in the human body is a nonlinear system of differential equations. This model takes into account the effect of drugs on the body. Thus, it is possible to obtain ”optimal” treatment regimens for patients, which cause minimal harm to the body. In the work for constructing suboptimal control of the supply of drugs, the method of ”extended linearization” is used, which makes it possible to switch from a nonlinear model to a linear model, but with parameters that depend on the state. To solve the resulting equation Riccati and search for control actions, a method is proposed for the formation of optimization algorithms for nonlinear control systems based on the application of functions of admissible values of control actions.

The article gives a review of existing methods of network-on-chip design based on the approach in which mapping of the characteristic tasks graph is performed on a given regular topology. The networks-on-chip synthesis problem is generally characterized. The analysis and comparison of standard topologies (mesh and torus) with circulant topologies are performed. Advantages and disadvantages of mesh and torus topologies usage, and the effect, achieved by their application to various implementations of networks on chip, are analyzed. Extension of the scope of solutions for standard regular network topologies mesh and torus on the circulant topologies with better characteristics is proposed. This will make it possible to take advantage of the deterministic approach, but with the use of more effective NoC topologies optimized for a particular task.

A lot of files and data, in general, are transferred throughout the networks. But the data may be corrupted by intrusions or package loss so, the executable files may be marked as non-executable and violate the local network policy. Thus, it’s necessary to detect such files. In this paper, we present a novel method for detecting broken bytes of a file, so the corrupted files may be detected. Also, the positions of wrong bytes might be helpful in restoring the original file content. This work is devoted to study of modern neural network models applied to detect corrupted bytes of a file problem. Since recurrent neural networks (RNNs) seem to be well suited for such tasks, the main tasks of this work are to analyze the efficiency of popular state-of-the-art RNNs solving the problem mentioned above and to compare results of different models. We use data consisting of the most popular file types collected from the Internet and manually randomly added noise to that data to test our models. An experiment on this data demonstrates the advantages and disadvantages of the considered models.

A numerical method of simulations for the evolution operators (propagators) of coupled qubits was developed on the basis of Magnus representation. The propagator of a multi-qubit system can be expressed by a N × N matrix whose size increases as N = 2^n with the number of qubits n . Therefore, the standard approach to the propagator calculation requires the involvement of numerically expensive procedures. We have shown that the calculations of the propagator at the current time can be reduced to the inversion of the Vandermonde matrix, which occurs when constructing interpolation polynomials. In this case, due to the recurrence relations, the number of required flops increases only as ~ O(N^2) (in opposite to ~ O(N^3) flops for the matrix of the general form). This fact allows us to speed up the calculation of the propagator for multi-qubit systems.

A mathematical model of ion and sputtered atom transport in the vicinity of the target with a periodical surface relief in glow discharge in pure gas is developed. Under the assumption that the relief amplitude is small, analytical expressions for their flows are found by the perturbation method and an equation describing the relief amplitude time evolution is derived. It is shown that intensity of sputtering exceeds intensity of sputtered material redeposition at the relief tops, and relief smoothing always takes place in the process of homogeneous target treatment in glow discharge in pure gas.

In the article, it is considered a modification of an integral model of an unsteady turbulent jet with a pressure force. Stationary solutions of the presented model are compared with well-known analytical results of classical models. It is shown that the inclusion of the pressure forces changes the dynamic parameters of a jet by about 12%. Analytical solutions of a steady forced buoyant jet of the atmospheric convective boundary layer and a spontaneous jet of a surface layer are presented. The simplest model of an ensemble of spontaneous jets of convective surface layer is constructed. It is shown that an ensemble of spontaneous jets forms a dependence of the turbulent moments and heat eddy diffusivity on the altitude within the convective boundary layer.

Detail measurements and full-vector three-dimensional FDTD technique were used to analyze anomalous mode behavior in double-aperture oxide-confined 850 nm VCSELs with large gain-to-cavity detuning.

The article discusses the features of modern processor’s microarchitecture, the method of instruction’s and micro-operation’s accelerated execution. The research focuses on the organization of the decoding stage in the CPU core pipeline and Macro- and Micro-fusion algorithms. The Macro- and Micro-fusion mechanisms are defined. A computer simulator has been developed to explore these mechanisms. The developed software has a user-friendly interface, is easy to use, and combines training and research options. The computer simulator demonstrates the sequence of mechanism’s implementation; the resulting macro- or microoperations set after Macro- and Micro-fusion, and also reflects each algorithm features for different processor’s families. The software allows you to use either a pre-prepared file with Assembler (x86) code fragments as source data, or enter/change the source code fragments at your request. The main combinations of machine instructions that can be fused into a single macro-operation are considered, as well as instructions that can be decoded into fused microoperations. The simulator can be useful both for in Computer Science & Engineering students, especially for on-line education and for researchers and General-purpose CPU cores developers.

Demand for efficient terahertz (THz) radiation detectors resulted in intensive study of the asymmetric carbon nanostructures as a possible solution for that problem. In this work, we systematically investigate the response of asymmetric carbon nanodevices to sub-terahertz radiation using different sensing elements: from dense carbon nanotube (CNT) network to individual CNT. We conclude that the detectors based on individual CNTs both semiconducting and quasi-metallic demonstrate much stronger response in sub-THz region than detectors based on disordered CNT networks at room temperature. We also demonstrate the possibility of using asymmetric detectors based on CNT for imaging in the THz range at room temperature. Further optimization of the device configuration may result in appearance of novel terahertz radiation detectors.

We characterize superconducting antenna-coupled NbN hot-electron bolometer (HEB) for direct detection of THz radiation operating at a temperature of 9.0 K. At signal frequency of 2.5 THz, the measured value of the optical noise equivalent power is 2.0×10-13 W-Hz-0.5. The estimated value of the energy resolution is about 1.5 aJ. This value was confirmed in the experiment with pulsed 1.55-μm laser employed as a radiation source. The directly measured detector energy resolution is 2 aJ. The obtained risetime of pulses from the detector is 130 ps. This value was determined by the properties of the RF line. These characteristics make our detector a device-of-choice for a number of practical applications associated with detection of short THz pulses.

For the past five years methyl-ammonium lead trihalide perovskite solar cells have shown remarkable progress in power conversion efficiencies due to their unique properties. Single CH3NH3PbI3 crystals were grown on the base of concentrated aqueous solution condensation of the precursor. The grown crystal structure and stoichiometry were studied by RHEED, X-ray and XPS. The perovskite crystal photocurrent spectra were measured in the temperature range of 85-330 K.

A possibility of a transition into a glassy state of binary alloys based on aluminum, nickel, and copper after ultrafast cooling has been investigated using the method of molecular dynamics. It was demonstrated that some 4-point correlators changed their behavior and depended on the parameters of the metastable alloy state. By analyzing the complex dynamics of particle motion in overcooled liquids some certain conditions for the formation of the glass for aluminum–nickel melt was founded.

Molecular dynamics calculations are performed to calculate vapor–liquid equilibrium of methane–n-butane mixture. Three force-field models are tested: the TraPPE-UA united-atom forcefield, LOPLS-AA all-atom forcefield and a fully flexible version of the TraPPEEH all-atom forcefield. All those forcefields reproduce well the composition of liquid phase in the mixture as a function of pressure at the 300 K isotherm, while significant discrepancies from experimental data are observed in the saturated vapor compositions with OPLS-AA and TraPPE-UA forcefields. The best agreement with the experimental phase diagram is found with TraPPE-EH forcefield which accurately reproduces compositions of both liquid and vapor phase. This forcefield can be recommended for simulation of two-phase hydrocarbon systems.

Magnetisation measurements and ESR spectra of a doped quasi 2D antiferromagnet on a triangular lattice reveal a crucial change of the ground state spin configuration and a disappearance of a characteristic 1/3-magnetisation plateau under a doping. According to theory, this is a result of the competition between the structural and dynamic disorders. The dynamic zero-point or thermal fluctuations are known to lift the degeneracy of the mean field ground state of a triangular magnet and cause the spin configuration to be the most collinear, while the static disorder provides another selection of the ground state, with the least collinear structure. Low-level doping was found to decrease the N\'{e}el temperature and saturation field by only few percent, while the magnetisation plateau disappears completely and the spin configuration is drastically changed. ESR spectra confirm an impurity-induced change of the so-called Y-type structure to an inverted Y-structure for 15%-doping by potassium.

We review the current state of Computational Physics as presented at XXV IUPAP Conference on Computational Physics. Moscow, 20-24 August, 2013.

This article is dedicated to our work in field of research and development of a math model for load balancing in the Internet of things (IoT). Here, we perform analysis and classification of tasks in the IoT devices system. We split subprograms in following systems on balancing and non-balancing. Next, we classify balancing subprograms by different parameters. Then, based on those classifications, we construct model for load balancing in IoT. With that model, in future we can perform modeling IoT devices systems and found pros and contras of each balancing algorithm

For onedimensional piecewise monotone discontionuous maps without periodic points, the 1-conformal measures are constructed and, as a corollary, semiconjugacy to piecewise linear models of constant (in absolute value) slope is obtained. It turns out that for generalized interval exchange transformations, the constructed semiconjugacy is, in fact, conjugacy .

Motivated by recent developments in atomic frequency standards employing the eﬀect of coherent population trapping (CPT), we propose a theoretical framework for the frequency modulation spectroscopy of the CPT resonances. Under realistic assumptions we provide simple yet non-trivial analytical formulae for the major spectroscopic signals such as the CPT resonance line and the in-phase/quadrature responses. We discuss the inﬂuence of the light shift and, in particular, derive a simple expression for the displacement of the resonance as a function of modulation index. The performance of the model is checked against numerical simulations, the agreement is good to perfect. The obtained results can be used in more general models accounting for light absorption in the thick optical medium.

We report on the development and fabrication of a 9-channel coarse wavelength- division multiplexing for telecommunication wavelengths (1550 nm) using anti-reflection contra-directional couplers, based on silicon nitride (Si3N4) rib waveguide. The transmitted and reflected spectrum in each channel of the demultiplexer were measured. The average full width at half maximum of the transmitted (reflected) spectra is about 3 nm. 1