An experimental verification of the possibility of estimating the coordinates of a mobile marine robot using small-sized vector-scalar antennas spaced apart in space, a broadband emitter placed on board the robot, and a remote polyharmonic permanently installed emitter – a “beacon”, which is used to eliminate bearing shifts caused by rotation receiving antennas under the action of underwater currents. It is shown that the use of technical means installed in the waveguide makes it possible to solve the triangulation problem and determine the horizontal coordinates of the robot, while taking into account the ray structure provides an estimate of the depth.

The results of the hydrodynamic noiseHydrodynamic noise (HN) characteristics studies on a towed vector-scalarVector-scalar array, which can be used for underwater communicationUnderwater communication, are presented. These hydrodynamic noisesHydrodynamic noise (HN) are the main source of interference for towed arraysTowed array. The power, statistical and spatial-correlation characteristics of the vector-scalarVector-scalar hydrodynamic noiseHydrodynamic noise (HN) field are analyzed. The effectiveness of algorithmsAlgorithm taking into account the features of the hydrodynamic noiseHydrodynamic noise (HN) is shown for detecting useful signals.

The possibility of constructing an acoustic model of a surface ship's noise emission in the far field using monopole-type emitters uniformly distributed along the hull is investigated. Experimental data obtained in shallow water are used to calculate the characteristics of equivalent monopole emission sources that form a total sound field similar to the sound field from a moving surface ship. The powers of each monopole and the cross-correlations between them are calculated. For the selected discrete components and linear model of an extended source, the directivity patterns are constructed, reduced to the free space. In the experiments and calculations, technical tools and algorithms were used that ensure high-precision positioning of the vessel with respect to the receiving elements of the array. An equivalent model of the waveguide transfer function in the operations area was preliminarily obtained by acoustic waveguide calibration using specially developed equipment, experimental techniques, and processing algorithms. This made it possible to use adequate seafloor models and the waveguide transfer function when calculating the equivalent sound field and directivity pattern. Good agreement is shown between the calculated and experimental data, both of the directivity pattern and field distribution along the transit characteristics. Practical recommendations are given for developing methods to measure the noise fields of surface vessels.

Nowadays, an increasing number of studies on the influence of space weather on the ionosphere appeared. The main parameter of the ionosphere is the total electron content TEC, the prediction of which is an important task. One of the approaches to forecasting TEC is the use of the most common and successful statistical methods of the forecast from other areas of science. However, preliminary research has shown that direct application of these methods to TEC time series may not always give positive results. Therefore, in this paper, two modifications of the existing autoregressive moving average (ARMA) and polynomial regression methods are proposed. TEC values obtained for modified methods are compared with values obtained using standard approaches. Additionally, the results for the proposed regression models are compared with two existing Recurrent Neural Network RNN architectures (Gated Recurrent Unit, Long Short-Term Memory) for several parameter sets. The results are illustrated on an example of one of the most disturbed years (2015) according to the data of the European mid-latitude station Juliusruh. It is shown, that: (1) the proposed regression methods modifications essentially improve results in comparison with initial versions of methods, (2) RNN have performed at the comparable level, (3) the best estimate of RMSE is in the range 1–2.5 TECU, (4) accounting for space weather factors did not improve the results compared to NN methods.

The article demonstrates the possibility of evaluating the sound pressure reduced to the free space created by towed tonal emitters during signal reception from a vertical-horizontal scalar array moored a shallow water. When the emitter is towed, mutual positioning of the signal source and elements of the receiving array was done, and the array geometry was constructed. To calculate the transfer functions of the waveguide, a geoacoustic model of the shallow seafloor is used, obtained from preliminary acoustic calibration of the waveguide in the area of the experiment. We analyze the influence of the reliability of a priori information about the experimental conditions for the error in estimating the sound pressure values recalculated to free space.

There are many long-term and short-term prediction methods of Total Electron Content (TEC) that need to be tested for each specific region. Recently, much attention has been paid to testing TEC models in high-, low-latitude and equatorial regions. This paper compares the TEC prediction methods in the mid-latitude zone according to the data of the Juliusruh, Rostov, Manzhouli stations in 2008 and 2015. For a long-term prediction, the IRI-Plas and NeQuick models are compared with the Global Ionospheric Maps (GIM) presented by the Jet Propulsion Laboratory (JPL) and the Technical University of Catalonia (UPC). For a short-term prediction, the Standard Persistence Model (SPM) method, a 27 day median model, and the proposed short-term prediction method are compared for one day ahead. It is shown that for all stations the IRI-Plas model provides better compliance with GIM maps than the NeQuick model irrespective of a solar activity level. An average absolute error lays in the range of 3–3.5 TECU, relative root square mean (RMS) error in the range of 22–27% in 2015 and 1.7–2 TECU, 20–25% in 2008. For the NeQuick model, these estimates were 6.7–8.2 TECU and 42–45% in 2015 and 2.2–3.6 TECU, 30–37% in 2008. For the short-term forecast, the best results were obtained by the SPM method with an average absolute error in the range of 1.95–2.15 TECU in 2015 and 0.59–0.98 TECU in 2008, a relative RMS error in the range of 17–21% in 2015, 11.5–15% in 2008. For the proposed short-term prediction method, these errors were 2.04–2.2 TECU and 12–14% in 2015 and 0.7–1.0 TECU, 7–11% in 2008. Using medians, the errors were 3.1–3.4 TECU and 17–21% in 2015 and 1.0–1.3 TECU, 10–15% in 2008. The dependence of results on the Dst-index was obtained.

The method for detecting radar signals which parameters are unknown and different from the reference signal is considered. The method is based on the correlation processing of signals from two components of the electromagnetic field.

Self-consistent modeling of a protostar and protostellar disk is carried out for early stages of their evolution. The accretion rate at distances of sevral astronomical units from the protostar is appreciably variable, which is reflected in the protostar's luminosity. The amplitude of the variations in the accretion rate and luminosity grows together with the sampling period, as a consequence of the nature of gravitationally unstable protostellar disks. A comparison of model luminosity variations with those derived from observations of nearby sites of star formation shows that the model variations are appreciably lower than the observed values for sampling periods of less than 10 years, indicating the presence of additional sources of variability on small dynamical distances from the protostar.

The article considers the local vibrations of elements of building structures. It is shown that under certain conditions, external influences cause vibrations of only some structural elements, but the whole structure stay in quiescence condition. The classification of local vibrations by the frequency characteristic is proposed. The limitation of spectrum of mechanical vibrations for buildings with structural damping due to the presence of dry friction forces is shown. References 1. Denisov G. V., Lalin V. V. Magazine of Civil Engineering. 2012. No. 1(27). Pp. 91-97. (rus) 2. Perelmuter A. V., Kriksunov E. Z., Mosina N. V. Magazine of Civil Engineering. 2009. No. 2. Pp. 13–18. (rus) 3. Bryzgalov V. I., Klyukach A. A. Hydraulic Engineering. 1998. No. 9. Pp. 63–66. (rus) 4. Alyavdin P. V., Muzychkin Yu. A. Mechanics of Machines, Mechanisms and Materials. 2009. No. 2 (7). Pp. 56–60. (rus) 5. Babakov I. M. Teoriya kolebaniy [Theory of Vibrations]. Moscow: State publishing of technical and theoretical literature, 1958. 628 p. (rus) 6. Sorokin Ye. S. Dinamicheskiy raschet nesushchikh konstruktsiy zdaniy [Dynamic analysis of load-bearing structures of buildings]. Moscow: Gosstroyizdat, 1956. 340 p. (rus) 7. Rumyantsev Ye. V., Belugina Ye. A. Magazine of Civil Engineering. 2012. No. 1(27). Pp. 22-30. 8. Schwanecke H. Some remarks on local structural vibration and structure-borne sound phenomena caused by marine propellers. Proceeding of The 16th Symposium on Theory and Practice of Shipbuilding (XVI Symposium SORTA 2004), Zagreb: 2004. 9. Atamturktur S., Bornn L., Hemez F. Vibration characteristics of vaulted masonry monuments undergoing differential support settlement. Engineering Structures. 2011. No. 33. Pp. 2472–2484. 10. Matsumoto Y., Yamaguchi H., Yoshioka T. A field investigation of vibration-based structural health monitoring in a steel truss bridge. Proceeding of the Joint Conference on Advances in Bridge EngineeringII. Bangladesh: 2010. Pp. 461–467. 11. Perelmuter A. V., Karpilovskiy V. S., Fialko S. Yu., Yegupov K. V. Bulletin of the Odessa State Academy of Civil Engineering and Architecture. 2003. No. 9. Pp. 147–159. (rus) 12. Miskovic Z., Pavic A., Reynolds P. Global vertical modes of floor vibration in multi-storey buildings. Proceedings of the International Conference on Noise and Vibration Engineering (ISMA 2006). Leuven, Belgium: 2006. Pp. 1211-1220. 13. Mondrys V. L., Xyen L. T. T., Sizov D. K. Proceedings of Moscow State University of Civil Engineering. 2010. No. 1. Pp. 113–116. (rus) 14. Jaswal H. Analysis of micro-vibration in buildings. Proceedings of the 2007 Earthquake Engineering Symposium for Young Researchers. Seattle, Washington: 2007. Pp. 09.1–09.12. 15. Zenkevich O. Metod konechnykh elementov v tekhnike [Finite element method in engineering]. Moscow: Mir, 1975. 271 p. (rus) 16. Qi G. Z., Guo X., Chang P., Qi X., Dong W. Local modes of vibrations for civil structural health monitoring. Proceeding of The 14th World Conference on Earthquake Engineering. Beijing: 2008. 17. Rozenblat G.M. Sukhoye treniye i odnostoronniye svyazi v mekhanike tverdogo tela [Dry friction and unilateral communication in solid mechanics]. Moscow: URSS, 2011. 205 p. (rus) Full text of this article in Russian: pp. 60-64

A signal processing algorithm for a passive seismic monitoring system is proposed and experimentally verified. This algorithm ensures effective detection and determination of the trajectory of a moving object. A concentrated receiver consisting of two geophones separated by a distance much smaller than the detected signal wavelength is used in experiments. Processing of experimental results shows that it is possible to determine not only the position of the seismically active object, but also the parameters of its motion.

Possibility of an estimation of coordinates of the seismic active object with use of methods of the high resolution considering a spatial orientation of geophones is investigated. It is shown that such approach provides detection of the pedestrian in radius not less than 50m. The adaptation proposed in the paper to changes of a sound velocity in a ground provides stability of operation of algorithm with the high resolution.

Vector-scalar noise fields in a waveguide were studied using computer simulation. A stochastic model of dynamic acoustic noise was used in the calculations. Noise field parameters on a single vector-scalar module and spatial correlation functions on vector-scalar arrays in a homogeneous waveguide were analyzed. Calculations were performed for vertically and horizontally located arrays. It was shown that the vector-scalar noise field characteristics depend on the bottom parameters and the state of the ocean surface due to the wind force. The calculation results can be used to predict the characteristics of detection and direction finding of signal sources for vector-scalar arrays working in a waveguide against the background of sea noise.

The algorithm, which allows to apply the Prony method to estimate of the sources parameters using vector-scalar receiving array is discussed. Noise immunity of the proposed algorithm is very high, so as the measured components of the acoustic field does not contain a noise.

We analyze the spatial spectra of a vector-scalar array when the signals are processed using methods with different resolution. The method of presenting the signals used in the research allowed us to apply the previously developed method of detecting and estimating the parameters of signal sources obtained in the calculation of the theoretical characteristics of detecting the signal sources and realization of the algorithms of signal processing. We compared the resolution of vector-scalar and scalar arrays with the same aperture. The experiments were carried out in stationary conditions and in the towing regime. During the towing regime, the accuracy of determination of the source location was controlled using the GPS receivers. It was shown experimentally that the signal to noise ratio at the output of the receiving array is three times greater if the vector-scalar array is used rather than the scalar one. The level of the lateral background appeared to be three times smaller during operation with the vector-scalar array than with the scalar one even in the towing regime. The results of measurements are confirmed by theoretical calculations.

In this paper the Cramer-Rao lower bound (CRLB) for the linear vector-sensor array is calculated in ambient noise, caused by the rough sea surface. Various formations of the input signals from the pressure and particle velocity receivers of vector-sensor array are presented. Algorithm based on the formation of the flow of power from the pressure and particle velocity receiver is considered in addition to the common methods of processing the input signals. It is shown that the accuracy of the estimate of source parameters depends on the method of forming the input signals at the vector-sensor array and also on the type of ambient noise. Thus, for the algorithm based on the power flow of signals, the ratio of signal-noise at the output of the receiving system is more than 100 times higher than for traditional signal processing from pressure sensor arrays.

On the example of the Mediterranean area it is showed that the joint use of global maps of the total electron content and data of ionospheric vertical sounding can be useful for: 1) the choice of maps, the most appropriate experimental values of the critical frequency foF2, 2) filling in missing data of foF2, 3) determination of foF2 in zone with a radius greater than the radius of spatial correlation of foF2. Such use allows to investigate and more accurately predict the conditions of the propagation of radio waves in the ionosphere.