Home – Home – Jornals – Advanced Search

The article explores the reliability of training samples used to train convolutional neural networks for the diagnosis of pulmonary diseases. It is shown that the sample, in which 3500 X-ray pictures of healthy patients and the same number of pictures of patients with tuberculosis, is very heterogeneous. When training on different parts of the sample and recognizing its various parts, significantly different results are obtained.

An image compression technology based on machine learning is developed. Segmentation of the original image into discarded and stored zones is applied. An algorithm of compression of stored zones based on the nested coverage of the image is used. Discarded zones are replaced by a reliable fake during decompression. Machine-learning algorithms based on autoencoders, convolutional and adversarial neural networks are used at all stages of compression technology (segmentation, pixel approximation of stored zones, fake of discarded zones, etc.). Computational experiments are performed to study the proposed compression technology and the included machine learning algorithms in natural images. The results of computational experiments confirm the prospects of the proposed technology for problems related to digital image compression.

A two-stage method for adaptive traffic signal control based on an estimate of the predicted weighted traffic flow passing through an intersection is proposed. At the first stage, we estimate the travel time required for each vehicle to pass the intersection using an artificial neural network model and estimate the predicted traffic flow through the intersection for a given phase of the traffic signal cycle. At the second step, a weighted flow estimate is formed, which takes into account the waiting time of vehicles. The proposed method for choosing the traffic signal phase is based on maximizing the weighted traffic flow. The results of experimental studies allow us to conclude that the proposed approach outperforms the classical approaches and state-of-the-art methods of traffic signal control based on reinforcement learning.

The results of numerical simulation based on the Mie theory of the superresonance effect for a dielectric sphere with a low refractive index are presented. Water is used as a material of the mesoscale sphere. It is shown that not only the previously studied weakly dissipative mesoscale spheres made of a material with a “medium” (about 1.5) and high (more than 2) refractive index, but also a low one (about 1.3) support the high-order Fano resonance effect associated with internal Mie modes. In this case, the intensities of resonant peaks for both magnetic and electric fields in the vicinity of the poles of the sphere can reach extremely high values of the order of 10⁶-10⁷ for a water droplet with a Mie size parameter of about 70.

The effect of changes in the thermophysical properties of the molybdenum film during intermediate oxidation during laser ablation on the dimensional effect of track formation is investigated by numerical simulation. In accordance with the data obtained, the hypothesis explaining the reduction of the track width in the ablation zone of the film in comparison with the effective diameter of the laser beam is refined. It is shown that a specific change in the thermal conductivity coefficient of a substance at the time of oxidation has a significant effect on the distribution of the temperature field, expressed in narrowing of the characteristic of the temperature distribution over the film surface, which has not been previously considered. It is established that the change in the density, specific heat capacity, and thermal effect of the chemical reaction of molybdenum oxidation during film oxidation does not significantly affect the temperature distribution in the zone of exposure to the laser beam.

The features of formation of face images of extended absolutely slit objects with an arbitrary opening of holes are studied in a coherent-optical system. On the base of the constructive approximation of the spectra of spatial frequencies (Fraunhofer diffractional patterns) of objects with different dimensions of front and back apertures, formulas for the field in the image of the front face are obtained and analyzed. Cases of objects with significantly expanding and significantly narrowing apertures of an extended hole (the differences in aperture sizes are much larger than the size of the Fresnel zone) are investigated in detail. It is found that the image structure of faces depends on the type of the opening. With a positive opening, where the back face is in the shadow region, the field at the output of the system corresponds to the image of the front face; with a negative opening, the image of the back face is observed. It is shown that error of determination of boundaries in the image of the active face of the object is inversely proportional to the square of the aperture difference. The invariant properties of the projection system for forming images of external faces of extended holes with an arbitrary opening are analyzed.

Design principles for the implementation of an infrared microscope registering the intrinsic thermal radiation of objects are considered. The infrared microscope temperature resolution, depending on the optical system parameters, design and photoelectric parameters of multielement infrared focal plane arrays (IR FPAs) are analyzed.

The paper presents experimental and theoretical study of crystal nucleation and growth in aluminum and structure development in the aluminum melt after the introduction of a cubic-shaped nanoparticle modifier and using the electron-beam surface treatment method. The output of this study is the rate of solid phase nucleation as a function of TiCN nanoparticle size dispersed in molten aluminum. The numerical simulation of crystal structure growth for a sample of AlSi12Cu2NiMg alloy treated by electron beam was performed using the MAGMASOFT computer code.

The mechanisms of excitation of low-frequency unstable combustion of a methane-air mixture in full-scale low-emission combustion chambers are experimentally studied. Experimental investigations of the flow characteristics without combustion in low-emission combustion chambers shows that the central zone of reverse flows can serve as a source of regular hydrodynamic pressure oscillations in a wide range of flow regimes. A model of low-frequency unstable combustion is proposed. The model is based on hydrodynamic instability of the flow in the central zone of reverse flows, which can excite low-frequency regimes of unstable combustion. Methods for suppressing thermohydrodynamic instability of combustion are developed. Based on the proposed model and with the use of methods that ensure suppression of combustion instability, a low-emission combustion chamber with a stable process of combustion in the entire range of its operation conditions is created and tested, which confirms the feasibility of the proposed approach.

An increase in the rate of combustion (gasification) of solid propellants exposed to a sufficiently intense blowing gas flow was discovered experimentally in the 1940s and called erosive burning. Later it was found that for some propellants at relatively low blowing speeds, there may be a decrease in the burning rate, called negative erosion. Attempts to theoretically study negative erosion have been made since 1971 and focused on analyzing changes in the intensity of heat transfer on a burning surface with the leading role of gas-phase reactions, taking into account the effect of large-scale fluctuations in gas velocity and temperature, the effect of the differences in diffusion coefficients and thermal diffusivity of the gas, and the effect of flame stretching. This paper presents an analysis of propellant combustion under blowing conditions in the presence of intense subsurface heat release due to exothermic reactions in the condensed phase. In the case where the surface temperature is limited by the boiling point, local temperature maxima can form in the subsurface layer, leading to an uneven response on the surface and to the occurrence of “intrinsic” turbulence in the adjacent gas layer. This turbulence leads to a change in the heat input to the propellant and allows one to qualitatively explain the effect of negative erosion.