A Novel Sparse Array for Localization of Mixed Near-Field and Far-Field Sources

As we all know, nested array can obtain a larger array aperture and more degrees of freedom using fewer sensors. In this study, we not only designed an enhanced symmetric nested array (ESNA), which achieved more consecutive lags and more unique lags compared with a generalized nested array but also developed a special cumulant matrix, in the case of a given number of sensors, which can automatically generate the largest consecutive lags of the array. First, the direction-of-arrivals (DOAs) of mixed sources are estimated using the special cumulant matrix. Then, we can estimate the range of the near-field source in the mixed source using a one-dimensional spectral search through estimated DOAs, and in the mixed sources, the near-field and far-field sources are classified by bringing in the range parameter. The largest consecutive lags and composition method of ESNA are also given, under a given number of sensors.Our algorithm has moderate computation complexity, which provides a higher resolution and improves the parameters’ estimation accuracy. Numerical simulation results demonstrate that the proposed array showed an outstanding performance under estimation accuracy and resolution ability for both DOA and range estimation compared with existing arrays of the same physical array sensors.

Method of description for the dynamics of the signal delay change in discrete time with changing aircraft position in space

The article presents an innovative approach to the description of the aircraft range parameter in discrete time when simulating the process of its repositioning in space. A method of describing the dynamics of changes in signal delay in discrete time when the aircraft is changing its spatial position is proposed. Such a model adequately describes the change in signal delay in discrete time. The direction of estimation for the adequacy of radio signal delay change simulation in algorithms of optimum filtration is defined in accordance with the aerodynamic properties of the aircraft. Simulation of the signal delay dynamic change is carried out (it is completely described by the dynamics of change in the distance to the aircraft). The transformation stages of simulation data for the initial model in continuous time with realization of the standard Gaussian random numbers are justified. Information on the simulation data transformation taking into account the correlation matrix of discrete white noise is provided. A method of calculating the transition matrix through the Laplace transform is proposed. The scientific-applied direction of research is determined – it lies in the development of a method for the legitimate representation for the mathematical model of aircraft’s changing range in discrete time within one-dimensional space: the longitudinal and the transverse dimensions. This approach takes into account the continuous description for a system of stochastic differential equations. A comprehensive algorithm for modeling the values of discrete white noise on modern computer equipment and calculating the dynamics of the aircraft range parameter changes is proposed. This algorithm allows to correctly form the a priori information about the change of the vector parameters of the aircraft spatial position at discrete moments of time. As a result, it was shown that the use of the obtained information in the optimal filtering algorithms minimizes the error when determining distance to the aircraft and, accordingly, allows to increase the accuracy and adequacy of the signal delay simulation in discrete time. The results of this research can be used in modernization of the existing models and development of promising on-board radar stations, integrated rangefinders, systems of radio technical reconnaissance and electronic warfare systems, as well as in technical implementation of aircraft flight simulation systems.

Development of a method for selecting a cruising mode and engine control program of a ramjet aircraft

For supersonic cruising, combined power plants can be used, in which a gas turbine engine reaches the cruising mode, and a ramjet is used for cruising. Supersonic transoceanic flights are characterized by a long cruising segment, which is decisive in terms of required fuel mass. Therefore, the selection of cruising and engine operation parameters is an important task. As a rule, when selecting the cruising mode, the range parameter is used, which depends on the flight and engine operation modes. To take into account the influence of the ramjet operating mode on the range parameter, dimensionless relationships of engine parameters with control factors were obtained. Using the obtained relationships together with the equations of aircraft motion in steady horizontal flight, it is shown that the values of the engine control factors and the range parameter do not change at the altitudes of 11...20 km. This made it possible to conclude that the range parameter can be increased only by selecting the cruising and engine parameters that provide the minimum specific fuel consumption. The variable cruising parameters are speed and initial altitude. A method for selecting the cruising and ramjet operation parameters was developed, based on the analysis of the relationship between the range parameter and the flight speed and initial altitude at the most advantageous values of the engine control factors. The obtained relationships allow selecting the cruising parameters and the engine operating mode, taking into account the restrictions. It is shown that the specific fuel consumption decreases by 0...30 %, depending on the engine operating mode, when the control program is optimized

A CT radiomics analysis of COVID-19-related ground-glass opacities and consolidation: Is it valuable in a differential diagnosis with other atypical pneumonias?

Purpose To evaluate the discrimination of parenchymal lesions between COVID-19 and other atypical pneumonia (AP) by using only radiomics features. Methods In this retrospective study, 301 pneumonic lesions (150 ground-glass opacity [GGO], 52 crazy paving [CP], 99 consolidation) obtained from nonenhanced thorax CT scans of 74 AP (46 male and 28 female; 48.25±13.67 years) and 60 COVID-19 (39 male and 21 female; 48.01±20.38 years) patients were segmented manually by two independent radiologists, and Location, Size, Shape, and First- and Second-order radiomics features were calculated. Results Multiple parameters showed significant differences between AP and COVID-19-related GGOs and consolidations, although only the Range parameter was significantly different for CPs. Models developed by using the Bayesian information criterion (BIC) for the whole group of GGO and consolidation lesions predicted COVID-19 consolidation and AP GGO lesions with low accuracy (46.1% and 60.8%, respectively). Thus, instead of subjective classification, lesions were reclassified according to their skewness into positive skewness group (PSG, 78 AP and 71 COVID-19 lesions) and negative skewness group (NSG, 56 AP and 44 COVID-19 lesions), and group-specific models were created. The best AUC, accuracy, sensitivity, and specificity were respectively 0.774, 75.8%, 74.6%, and 76.9% among the PSG models and 0.907, 83%, 79.5%, and 85.7% for the NSG models. The best PSG model was also better at predicting NSG lesions smaller than 3 mL. Using an algorithm, 80% of COVID-19 and 81.1% of AP patients were correctly predicted. Conclusion During periods of increasing AP, radiomics parameters may provide valuable data for the differential diagnosis of COVID-19.

TO THE FIFTIETH ANNIVERSARY OF THE KIPT TORSATRON PROGRAM

The paper is dedicated to the 50th anniversary of controlled thermonuclear fusion studies performed at the KIPT on the specific stellarator-type experimental installations commonly referred to as “the torsatron”. Detailed data are reported on the operating thermonuclear facility “Uragan-2M”, the research results obtained with it, and also, the prospects for its use as a reactor. The advantages of the torsatron of this type are described, among them being the wide-range parameter variation capability. This is of importance for finding out the regularities related to plasma stability, heating and confinement.

Structural and Energy Characteristics of NiAl Alloys with Deviations from Stoichiometric Composition. Part 2

The analysis of the atomic and phase structure confirmed the difference between the structural-phase states at the heating and cooling stages. Based on the analysis of the influence of the deviation of the atomic composition from the stoichiometric condition of the intermetallic compound during cooling, it is established that the deviation is a significant factor in the area of low-stability pre-transitional structural-phase states before the transformation. The behavior of the long-range parameter temperature dependence curves during the cooling of alloys of non-stoichiometric compositions differs significantly from the behavior of the corresponding alloy curve of a stoichiometric composition alloy. It is shown that in the case of cooling of alloys of non-stoichiometric compositions, a significant supercooling is required to establish a long-range order, and the appearance of ordered phases occurs at significantly lower temperatures. It is found that the temperature dependence curve of the long-range parameter of the Ni45Al55 alloy is significantly lower than the corresponding curve of the Ni55Al45 alloy. This indicates different mechanisms for establishing the long-range order of alloys with non-stoichiometric compositions. It is noted that the deviation of the system composition from the stoichiometric one causes a significant reduction of ordered and disordered regions. This article is a continuation of the work published earlier in the journal Izvestiya AltGU. 2020. №1 (111).

Interpolating the Schwarzschild and de Sitter metrics

The binary potential technique of interpolation (by [M. Riesz, Acta Math. 81 (1949) 1]) is applied to some well-known metrics of general relativity. These include Schwarzschild, de Sitter and [Formula: see text]-dimensional BTZ spacetimes. In particular, the Schwarzschild–de Sitter solution is analyzed in some detail with a finite range parameter. Reasoning by the high level of nonlinearity and absence of a superposition law necessitates searching for alternative approaches. We propose the method of interpolation between different spacetimes as one such possibility paving the way toward controling the two-metric system by a common parameter.

SPATIAL DEPENDENCE INDEX FOR CUBIC, PENTASPHERICAL AND WAVE SEMIVARIOGRAM MODELS

This study aims to propose a spatial dependence index (and its classification), from the concept of spatial correlation areas, for the Cubic, Pentaspherical and Wave models. The index, called Spatial Dependence Index (SDI), covers the following parameters: the range (a), the nugget effect (C 0 ) and the contribution (C 1 ), beyond considering the maximum distance (MD) between sampled points and the model factor (MF). The proposed index, unlike the most used in the literature, considers the influence of the range parameter to describe the spatial dependence, highlighting the importance of this formulation. The spatial dependence classification, based on the observed asymmetric behavior in the SDI, was performed considering categorizations from the median and the 3rd quartile of the index. We obtain the spatial dependence classification in terms of weak, moderate, and strong, just as it is usually described in literature.