Showing papers in "Journal of Communications Technology and Electronics in 2015"

Surrogate modeling of multifidelity data for large samples

Abstract: The problem of construction of a surrogate model based on available lowand high-fidelity data is considered. The low-fidelity data can be obtained, e.g., by performing the computer simulation and the high-fidelity data can be obtained by performing experiments in a wind tunnel. A regression model based on Gaussian processes proves to be convenient for modeling variable-fidelity data. Using this model, one can efficiently reconstruct nonlinear dependences and estimate the prediction accuracy at a specified point. However, if the sample size exceeds several thousand points, direct use of the Gaussian process regression becomes impossible due to a high computational complexity of the algorithm. We develop new algorithms for processing multifidelity data based on Gaussian process model, which are efficient even for large samples. We illustrate application of the developed algorithms by constructing surrogate models of a complex engineering system.

Plasmon resonances in a quartz nanofiber coated with a silver layer

Abstract: A 2D problem of diffraction of the TM-polarized plane wave by a quartz nanofiber coated with a silver layer is investigated. The total scattering cross-section is numerically calculated in the range of visible light waves (400–700 nm). It is found that, at certain geometric parameters of the structure, not only dipole but also multipole plasmon resonances arise in the investigated range of wavelengths. Scattering patterns at resonance frequencies are calculated. It is demonstrated that deposition of the silver layer onto a quartz nanofiber can decrease the scattering cross section several times.

Mathematical simulation of propagation of frequency-modulated radio waves in ionospheric plasma

Abstract: A numerical simulation of single-hop and double-hop propagation of frequency-modulated signals in anisotropic ionospheric plasma is performed on the basis of a numerical solution to a space–time Hamiltonian bicharacteristic system whose unknowns are the components of the wave vector, coordinates, and also the frequency and time. It is assumed that the radiation source is a point one and is located outside the magnetoactive plasma, the frequency modulation of decameter waves is linear, and the amplitude of the magnetic field is constant. A model of a two-layer ionospheric plasma with a wavelike disturbance is considered. The specific features of the departure of the ordinary and extraordinary waves from the plane of propagation, formation of caustics of space–time geometrical-optics rays, and the Doppler frequency shift are analyzed.

Combinatorial clustering: Literature review, methods, examples

Abstract: The paper addresses clustering problems from combinatorial viewpoints. A systemic survey is presented. The list of considered issues involves the following: (1) literature analysis of basic combinatorial methods and clustering of very large data sets/networks; (2) quality characteristics of clustering solutions; (3) multicriteria clustering models; (4) graph based clustering methods (minimum spanning tree based clustering methods, clique based clustering as detection of cliques/quasi-cliques, correlation clustering, detection of network communities); and (5) fast clustering approaches. Mainly, the presented material is targeted to networking. Numerical examples illustrate models, methods and applications.

Spin-injection generators of terahertz waves based on metal magnetic structures

Abstract: Fundamentally new devices for the generation of terahertz waves due to the effect of the spin-polarized current in ferromagnetic and antiferromagnetic metal structures (magnetic junctions) are considered. The spin injection and the sd exchange and its effect on the interaction with electromagnetic waves play the main role in such devices. The effects that are induced by the polarized current in the antiferromagnetic materials (exchange instability, induced magnetization, and spin-injection antiferromagnetic resonance) are discussed. The principles and effects of the generation of the terahertz electromagnetic oscillations are considered, and the characteristics of the experimental prototypes of the corresponding devices are analyzed.

Pseudocombline bandpass filters based on half-wave resonators manufactured from sections of balanced striplines

Abstract: The possibility of application of pseudocombline microwave structures with λ/2 resonators manufactured from sections of balanced striplines as bandpass filters is demonstrated. It is found that coupling coefficients of λ/2 resonators manufactured from sections of balanced striplines arranged in parallel to each other without mutual shift have nonzero values. The dependence of these coupling coefficients on the parameters of half-wave stripline resonators is studied. Frequency characteristics of some pseudocombline bandpass filters with λ/2 resonators are analyzed and experimental data are presented.

Restoration of multispectral images distorted by spatially nonuniform camera motion

Abstract: The majority of known methods for restoration of distorted multispectral images use a model of blur as the convolution of the initial image with a uniform kernel. However, the image blur in real low-light conditions is often spatially nonuniform, since the camera in an actual shoot is shaken and rotated in three dimensions while its shutter is open. A method for “blind” locally adaptive image restoration in the domain of sliding orthogonal transform is proposed. It is assumed that the signal blur operator is spatially homogeneous in a small-sized sliding window. The known approaches to the restoration of color images blurred by spatially nouniform camera motion are compared to the proposed algorithm.

Waveguide bandpass filter on complex resonance diaphragms

Abstract: Results of electrodynamic analysis of single resonance diaphragms in the form of a rectangle window with two L-shaped combs in a rectangle waveguide and results of synthesis of bandpass filters on their basis are presented. The electromagnetic fields and critical wavenumbers of a rectangle wavegide with two L-shaped combs that form the aperture of the diaphragms are determined by the partial domain method with allowance for the field singularity on the edge. The proposed diaphragm aperture allows one not only to obtain resonator Q-factors that are higher than those of usual rectangle windows but also to obtain record low attenuation levels for this type of filters in the stop band owing to the presence of an antiresonance in the aperture’s transient characteristic.

Propagation of broadband HF signals in a medium with nonlinear dispersion

Abstract: Effect of nonlinear dispersion on distortions of broadband signals due to propagation in ionospheric channel is considered with allowance for matched processing in detector. Distortions of the shape of pulse response are studied versus nonlinearity parameter, and the effect of geophysical factors on the parameter is analyzed. The pulse response is used to estimate the group delay. It is demonstrated that the problem of propagation of broadband signals is reduced to the analysis of distortions of an equivalent signal with uniform in-phase spectrum in the ionospheric channel similar to the distortions of the pulse response of the channel. For the polynomial dispersion characteristic of the channel, the effect of nonlinearity on the pulse characteristics is described using incomplete Airy functions and the shape of the envelope of such a characteristic becomes asymmetric. Owing to uncertainty, the parameter of the group delay in the channel with the nonlinear dispersion cannot be accurately determined using the data on the pulse characteristic as distinct from the dispersion-free or linear-dispersion channel.

Simulation of the control process applied to the micromechanical device with the shape memory effect

Abstract: It has recently been proved that, in alloys, e.g., based on the Ti–Ni system, a shape memory effect (SME) is preserved down to the nanoscale sizes of an active alloy layer and demonstrated ultrasmall-sized and fully functional microand nanomechanical devices: actuators and nanotweezers that are fabricated via standard microelectronic technologies relying on composite materials with the SME. In the nearest future, such achievements will enable the creation of the next-generation microand nanomechanical devices whose sizes are quite comparable with those inherent to, e.g., carbon nanotubes, graphene sheets, viruses, etc. Mathematical simulation methods are used to study how the shape-memory micromechanical devices can be activated by means of resistive pulse heating. A decrease in the overall sizes of heating elements (from 1 mm to 10 μm) is demonstrated to be accompanied by the fact that the speed of operation increases sharply from 102 to 105 s–1 and, simultaneously, the energy consumption diminishes from 10–3 to 10–8 J per operation. The preliminary results of experiments whereby the control of the composite nanotweezer exhibiting the SME is perfected with the help of the automatic pulsed heating technology, as well as the prospects for creating high-speed and high-performance microrobotic systems incorporating newly developed components, are discussed.

Dynamic resource allocation in OFDM based cognitive radio system considering primary user QoS and secondary user proportional constraints

Abstract: The spectrum underutilization can be overcome by the use of cognitive radio systems. A cognitive radio can intelligently allocate the unused spectrum of licensed user to the unlicensed user without giving any interference to the former and thereby and improved spectrum efficiency can be achieved. Cognitive radio is an artificial intelligent wireless technology which can allocate the licensed user channels to the unlicensed users without disturbing the licensed users thereby improving the spectrum efficiency. In this paper, we concentrate on an orthogonal frequency division multiplexing (OFDM) based cognitive radio (CR). In a conventional OFDM system, the capacity is maximized using water filling algorithm. In this paper we jointly optimize the power and subcarrier allocation for OFDM based CR system in a multiuser environment. In addition to this we introduce the proportionality rate constraints. On the implementation of this, we achieve higher data rate with significantly low complexity.

Field Structure and Velocities of Surface Waves on Plane Interfaces of Conducting Media with a Relatively High Conductivity, Zenneck Wave

Abstract: The physical properties of boundary surface electromagnetic waves at interfaces of high-conductivity media substantially differ from the well-known properties of the surface waves that are guided by dielectric waveguides. The earlier conclusion that the three velocities of such waves (phase, group, and energy) are different (so that the group velocity differs from the energy velocity) is proven. It is also demonstrated that the conventionally determined group velocity does not have the commonly accepted physical meaning, since it can be greater than the velocity of light, whereas the energy velocity (the velocity at which the energy is transferred) is less than the velocity of light in free space. The Brewster effect is not observed in the field structure of the waves under study (in particular, Zenneck waves). The application of the Leontovich surface impedance in the analysis of the boundary surface waves is substantiated.

Review of multidimensional optimization methods

Abstract: Basic multidimensional optimization methods are considered and compared by their efficiency. The applicability of the considered algorithms to different types of optimized functions is analyzed.

Generalized error-locating codes and minimization of redundancy for specified input and output error probabilities

Abstract: Generalized error-locating codes are discussed. An algorithm for calculation of the upper bound of the probability of erroneous decoding for known code parameters and the input error probability is given. Based on this algorithm, an algorithm for selection of the code parameters for a specified design and input and output error probabilities is constructed. The lower bound of the probability of erroneous decoding is given. Examples of the dependence of the probability of erroneous decoding on the input error probability are given and the behavior of the obtained curves is explained.

Atomic and WA-systems and R-functions applied in modern radio physics problems: Part II

Abstract: The third part of the review is devoted to the application of families of atomic functions for the construction of weighting functions (windows) based on convolutions that allow a decrease of the sidelobe level in the problems of nonparametric estimation of probability density and in the systems of phase locking with sampling.

On an iterative algorithm for calculating weighted principal components

Abstract: An iterative algorithm for calculating weighted principal components, which enables substantial reduction of the average (over the sample) weighted maximum (along a coordinate) reconstruction error of sample vectors from compressed data, is designed. The results of simulation, which illustrate the efficiency of this algorithm, are given.

Comparison of two-dimensional variations in the context of the digital image complexity assessment

Abstract: Problems of evaluation of the digital (discrete) image complexity are studied. Known versions of 2D variations with reference to digital images and the possibility of their use for evaluation of the image complexity are considered. The image complexity is interpreted as some attribute, which reflects the number, dimensions, and visibility of image details. Changes of the variation values after various image transformations are analyzed. A modified assessment that is named the “object size index” is proposed. Theoretical conclusions are confirmed by experimental studies.

Static and dynamic conduction of amorphous nanogranulated metal–dielectric composites

Abstract: Static conduction and reflection and transmission of electromagnetic waves through thin films of granulated amorphous metal–dielectric zirconium-containing nanocomposites are experimentally studied. It is demonstrated that the dynamic conductivity in the microwave range exceeds by two–three orders of magnitude the static conductivity measured at a dc current. To explain this phenomenon, the mechanism of intraganule currents is suggested. Recommendations for further studies are formulated.

Decapsulation of polyelectrolyte nanocomposite microcapsules by pulsed microwave effect

Abstract: A technology of remote activation of specially created polyelectrolyte nanocomposite microcapsules (PNMCs) by pulse microwave action is developed. The sensitivity of the synthesized PNMCs to the external microwave action is caused by the presence of layers of ferric oxide nanoparticles in their shells. A setup for remote pulse microwave action on the PNMC is constructed. The effect of decapsulation of polyelectrolyte nanocomposite microcapsules under the remote action of microwave pulse is detected. Destruction of the PNMC shell is recorded by the methods of the transmission electron microscopy.

The angular width of the wave beam of a backward spin wave excited by a linear transducer in a ferrite plate

Abstract: The angular width of the wave beam of a backward spin wave excited by an arbitrarily oriented linear transducer in an in-plane magnetized ferrite plate is calculated for the case when the transducer length is much more than the length of the spin wave using a formula derived earlier. It is shown that a nondivergent wave beam can arise in the plate at some orientations of the transducer.

Time–frequency analysis of simultaneous measurements of electroencephalograms, electromyograms, and mechanical tremor under Parkinson disease

Abstract: A method for the analysis of the time–frequency dynamics of the background brain activity is proposed and used to reveal three main features of the early-stage Parkinson disease (PD): hemispheric asymmetry of the time–frequency characteristics of electroencephalogram in the central lead of the motor zone of the cerebral cortex, generation of the rhythm of electroencephalogram in these leads in a frequency interval of 4–6 Hz and its correlation with electromyograms and mechanical tremor of contralateral limbs upon Parkinsonian tremor, and disorganization of the dominant rhythm corresponding to the general concept of the disorganization of various systems under PD.

Optimum energy efficient error control techniques in wireless systems: a survey

Abstract: Energy efficiency and error free transmission have become prime concerns in wireless communication in recent years. Such networks are much more affected by errors due to dynamic channel conditions than normal wired networks. Error control coding is commonly used in the entire range of information com-munication to reduce the harmful effects of the channel. In order to overcome the communication errors in an energy efficient way, an error control mechanism with less complexity is required. Energy efficient error control techniques to prolong network lifetime in resource limited network and wireless communication remains a challenge. This paper forms a survey of recent developments on the various energy efficient error control coding techniques used in wireless communication and resource limited networks/hardware.

Pulsed electric field-induced remote decapsulation of nanocomposite liposomes with implanted conducting nanoparticles

Abstract: The results obtained in creating the new nanocomposite hybrid systems sensitive to external nonthermal electric-field pulses, which are created for the encapsulation, addressed delivery, and the controlled decapsulation of various substances in aqueous media, are presented. Such systems are based on liposomes containing electrically neutral biogenic lipids that are functionalized by conducting nanoparticles and polymers. The fabricated systems have been investigated using transmission electron microscopy, atomic-force microscopy, electron magnetic resonance, laser light scattering, electrophoresis, and conductometry. The systems constructed under the action of short (on the order of 8 ns) electric pulses with high intensities (up to 100 kV/m) are found to exhibit the remote decapsulation effect. The model describing the mechanism of interaction between nanostructured liposomes with surface conducting nanoparticles and an external electric field leading to substantial changes in liposome structure is proposed. The critical values of the external electric field stimulating the decapsulation of nanocomposite liposomes are estimated with the help of the constructed model.

Multimedia sensor networks based on ultrawideband chaotic radio pulses

Abstract: The requirements to transceivers, which are intended for multimedia data transmission in wireless sensor networks, and existing system characteristics are discussed. Ultrawideband wireless systems based on direct chaotic data transmission are analyzed to reveal the prospects of their application to multimedia sensor networks. The results obtained during experimental studies into video data-flow transfer, which are performed in the point-to-point mode with the use of radio relaying and through-wall transmission, are presented.

Properties of exact solutions to the problem of regularization of the total variation of one-variable functions

Abstract: In this study, an exact solution to the variational problem of minimization of a functional consisting of an accuracy term and a regularization term is considered. The regularization term is the total variation of a one-variable function. The variational problem under consideration is widely used in the theory of image and signal restoration. As the weighting factor of total variation increases, the exact solution to the variational problem becomes a more smoothed function. A method for calculating exact solutions and the properties of these solutions are described.

Quasi-static analysis of the eigenmodes of an array of coupled slot transmission lines

Abstract: The problem of the eigenmodes of an infinite 2D array of slot transmission lines operating in the quasi-periodic mode is solved. The boundary-value problem is reduced to a system of integral equations for longitudinal components of the electric current on metal conductors and the magnetic current in slots. The system of integral equation is solved in the static approximation at the first stage and, afterwards, the solution to the electromagnetic problem is found using the Galerkin method. The results of the numerical analysis of the dependences of eigenmode propagation constants on geometric parameters of the structure and phase shifts between the array channels are analyzed.

Adaptive estimation of seismic parameter fields from earthquake catalogs

Abstract: A new approach to estimation of the parameters of inhomogeneous spatio-temporal marked point fields is considered. The approach is based on the adaptive weights smoothing (AWS) method. A generalized version of the ASW method for constructing spatial and spatiotemporal fields of density, mean values, and correlation (fractal) dimension of marked point fields is proposed. It is shown that the method can be used in constructing fields of seismic-process parameters from earthquake catalogs.

The T-matrix method based on the modified auxilairy-current and null-field methods

Abstract: Two versions of implementation of the T-matrix method: on the basis of the (i) auxiliary-current and (ii) null-field methods are compared. In both cases, the methods are numerically realized with the use of the discrete-source technique. The scattering patterns of various bodies are calculated by means of both methods with high and approximately equal accuracies, a result confirmed, in particular, through testing the fulfillment of the optical theorem. However, the asymptotics (in the order number) of the scattering pattern coefficients are fundamentally different.

A novel fast algorithm for the pseudo Winger–Ville distribution

Abstract: A novel approach to Discrete Wigner–Ville Distribution (DWVD) is proposed in this paper. Unlike the conventional methods, the computation of Discrete Wigner–Ville Distribution is transformed to the computation of the first-order moments by the simple mathematical deduction. A scalable and efficient systolic array is designed to implement this approach. There are several advances in our algorithm such as the avoidance of multiplications, the simple computation structure and only integer additions. Although many additions required, the proposed algorithms is simple and more applicable.

A new class of windows based on the family of atomic functions ch a,n ( x ) and its application to digital signal processing

Abstract: New constructions of weight functions (windows) based on the family of atomic functions are presented. Construction of weight functions consists of two steps. At first step basing on the properties of convolution iterated convolution of atomic functions is constructed. At the second step required weight function is defined by truncation of the function to its effective support. Numerical experiment and analysis of physical characteristics demonstrates efficiency of new weight functions.