Vol 55, No 6 (2019)
- Year: 2019
- Articles: 16
- URL: https://journals.rcsi.science/8756-6990/issue/view/13244
Automation Systems in Scientific Research and Industry
Adaptive Control of Motion of a Group of Robots Along a Prescribed Trajectory
Abstract
A control method and software structure for solving the problem of control of motion of a group of robots along a prescribed trajectory with preserving a chosen configuration under conditions of unsteady dynamic characteristics of individual robots is proposed.
Combined Controller for a Nonaffine Plant with Delay in Control
Abstract
In this paper, we propose a solution to the problem of designing a combined output control system for a nonlinear nonaffine plant with a delay in the control loop under a priori parametric uncertainty and external interference. Simulation results confirm the performance of the control system, and the resulting controller provides tracking of the plant to the reference signal.
Physical and Engineering Fundamentals of Microelectronics and Optoelectronics
Design of Metal-Dielectric Filters in Transmitted Ultraviolet Light
Abstract
A metal-dielectric narrow-band filter for a wavelength of 270 nm is designed within the framework of the conductive surface model to characterize the properties of thin metal films. It is demonstrated that inclusion of four thin molybdenum films into a multilayer dielectric structure ensures effective cut-off of the transmission at <1.5% in the visible range of the spectrum with the maximum transmittance more than 50% for the selected wavelength and the spectral width of the filter <5 nm.
Development of a Technology for Creating Structured Capillary-Porous Coatings by Means of 3D Printing for Intensification of Heat Transfer during Boiling
Abstract
Application of the method of layer-by-layer selective laser sintering of a metal powder for depositing capillary-porous coatings with a prescribed porosity onto heat-releasing surfaces is considered. Implementation of this method in experimental investigations of the boiling process on modified surfaces allows broad-range variations of the main parameters of microstructured capillary-porous coatings and other three-dimensional structures: material, porosity, amplitude (height), thickness of the residual layer and wavelength of capillary-porous coatings, and size and shape of three-dimensional ordered microtextures. It is demonstrated that the use of this technology can increase the heat transfer coefficient the case of boiling on the surface with a capillary-porous coating by several times as compared to the uncoated surface.
Analytical Review of Two-Signal Methods for Measuring the S-Parameters of Two-Port Networks
Abstract
In this paper, we consider two-signal and modified two-signal methods for measuring the S-parameters of passive two-ports and a method for adequately measuring the S-parameters of two-ports, such as transistors, developed on their basis. The methods are implemented using a coaxial simulator-analyzer of microwave amplifiers and oscillators in its measuring channels matched or mismatched with loads. The field of application and the interrelation between these methods are investigated, and their advantages and disadvantages are discussed. Data on the maximum measurement error of the methods are presented.
Temperature Dependence Model of the Laser Diode Bar Current-Voltage Characteristic
Abstract
Based on an analysis of differences between the experimentally measured temperature dependence of the current-voltage characteristic (I-V curve) of a laser diode bar (LDB) with AlGaAs/GaAs heterostructure and the dependence obtained in accordance with the well-known model of light-emitting diodes, assumptions were made about the sources of these differences. The agreement between the experimental and modeled dependences is significantly improved by taking into consideration the change in the resistance of LDB layers caused by temperature change. It is shown that when the injection current is known, the measured voltage drop across the LDB can be used to estimate the temperature of the diode active region in order to implement thermal stabilization for solid-state laser pumping systems based on high-power laser diodes.
Analysis and Synthesis of Signals and Images
Modified Method for Detecting Small Structures in Noisy Images
Abstract
A classifier for operation with 1-pixel image fragments is proposed. Element segmentation into object and background is performed based on posterior probabilities, which are calculated using a histogram. A simulation experiment has shown that the developed algorithm provides a more accurate classification than segmentation based on the brightness threshold determined from the minimum condition for the weighted sum of errors of the first and second kind.
Object Detection on Spatially Inhomogeneous Backgrounds Using Neural Networks
Abstract
Several approaches to the use of neural networks for object detection on spatially inhomogeneous backgrounds are considered. A method for constructing a classifier for object detection directly from observed fragments has been developed. An approach consisting of a combination of matched linear filtering and convolutional neural networks is proposed. It is shown that this approach reduces the false alarm probability while maintaining the object detection probability.
Digital Imaging Detection and Image Analysis of Internal Structural Defects in GIS
Abstract
The existence of internal structural defects in gas insulated combinations (GIS) seriously affects the normal operation of equipment, and it needs an efficient and non-destructive detection method. This study is focused on the feasibility of X-ray digital imaging detection in GIS equipment monitoring. First, the digital imaging detection process is briefly introduced. Then, in order to obtain high-quality digital images, a correlation coefficient is introduced to improve the nonlocal mean filtering denoising algorithm. In terms of image enhancement, a histogram equalization method is introduced, and then an improved contrast-limited adaptive histogram equalization (CLAHE) method is proposed for image denoising. The detection system and image processing method of this study are used to detect two GIS equipment units of the Chongqing Electric Power Company (China). It is found that this method clearly and accurately detects the equipment defects with high reliability. This study provides some theoretical basis for further promotion of the X-ray digital radiography in GIS equipment defect detection.
Method of Fast Bandwidth Selection in a Nonparametric Classifier Corresponding to the a Posteriori Probability Maximum Criterion
Abstract
A method of fast bandwidth selection in a nonparametric algorithm of pattern recognition corresponding to the maximum a posteriori probability criterion is proposed. The algorithm is based on the results of studying the asymptotic properties of the nonparametric estimate of the separation surface equation and probability densities in solving a two-alternative problem of pattern recognition. The proposed method is compared with the traditional approach based on minimizing the classification error probability estimate.
Optical Information Technologies
Influence of Response Nonlocality of a Medium on Soliton Polarization
Abstract
Influence of nonlocality on the polarization dynamics of an electric field pulse in a medium with cubic nonlinearity is under study. Nonlinear equations are solved using a variational approach. It is shown that nonlocal and chiral effects cause trajectory oscillations and nonlinear polarization rotation of soliton pulses of the field.
Optical Diagnosis of the Geometry of an Axisymmetric Controlled Nozzle of a Gas-Turbine Engine
Abstract
Modern aviation industry solves the problem of developing multifunction engines capable of flying both at subsonic and supersonic speeds. An important part in such engines is a variable area nozzle, which allows varying the geometry of the engine exhaust unit and, accordingly, its technical characteristics. This study touches upon an computer vision based optical noncontact method for reconstructing a nozzle shape. The reconstruction requires data recorded by two optical three-dimensional recorders directed toward the inner part of the nozzle when the engine is subjected to ground tests. The diagnosis is complicated by the presence of a hot jet being in the way of the sensor vision, the regime-dependent variation of the nozzle glow brightness, and intense mechanical vibrations. The performed bench tests confirm the efficiency of the proposed method. According to their results, in a low-gas regime, the standard deviation of the diagnosed diameters of the exhaust unit and critical sections for each frame does not exceed 0.3% of the corresponding sizes. The data obtained as a result of this diagnosis can be taken into account when upgrading the exhaust unit of the engine and the thrust control system of a gas turbine engine.
Detection of Ebola Virus VP40 Protein using a Nanowire SOI Biosensor
Abstract
Nanowire SOI biosensors are used to detect the Ebola virus VP40 protein by identifying its immune complexes with specific monoclonal antibodies (MCAs). It is shown that the reaction of specific interaction between VP40 and MCAs causes a more pronounced biosensor response than direct adsorption of VP40 or antibodies to their surface. The formation of antigen — antibody complexes leads to the accumulation of a negative charge on the biosensor surface. The protein and protein — antibody complexes are detected in real time (∼200–300 s per test sample).
Improvement of the Accuracy of the Fresnel Method of Measuring the Diameters of Circular Metallic Cylinders with an Arbitrary Coefficient of Light Reflection
Abstract
A diffraction Fresnel method of precision measurement of diameters of circular metallic cylinders in the range from several units to hundreds of millimeters with an arbitrary coefficient of light reflection from the cylinder surface is developed. The method is based on determining the position of the first maximum in the Fresnel pattern of the object formed in the free space. An expression for the diffraction Fresnel pattern of a plane model of a cylinder fragment is derived in the class of special functions (Fresnel integrals). Based on this expression, a formula is found for taking into account the displacement of the position of the first maximum of the field as a function of the light reflection coefficient. By using an appropriate correcting additive, the measurement error component induced by this factor can be reduced by more than an order of magnitude. The results of the present study can be used for the development of optical-electronic systems of precision dimensional inspection of cylindrical articles.
Reconstruction of a Wavefront Distorted by Atmospheric Turbulence with Account for Optical Scheme of the Telescope
Abstract
Reconstruction of a wavefront containing turbulent distortions of optical radiation is considered. The Hartmann method based reconstruction is carried out using the wave function approximation by Zernike polynomials according to estimates of local slopes and analyzed on the basis of filling Hartmannograms with focal spots, depending on the telescope design. The volume and quality of information about phase distortions of radiation are estimated using the Hartmannograms formed in the receiver plane, thereby developing methods for reducing the telescope induced residual reconstruction error.
Image Reconstruction from Digital Holograms Obtained by Specifying Random Phase Shifts
Abstract
A new method for image reconstruction from a series of digital holograms obtained by stepped phase shift with random values of phase shifts is under consideration. It is shown that images reconstructed from a digital hologram in a Fresnel region at a distance matching a distance from the object to the hologram consist of two parts, one of which is a clear image of the object and the other one being formed by incorrect phase shifts consists of a set of defocused images of the object. At the same time, the quality of the reconstructed image is slightly reduced. This effect eliminates the necessity to use precision systems for setting the phase shift and significantly reduces requirements for stabilizing the optical device.