Journal of Communications Technology and Electronics最新文献

Abstract—

Image restoration and correction are important steps for video analysis applications. This paper considers a new approach to assessing the characteristics of amplitude distortions in an image and constructing a method for correcting them. A “blind” method for determining the distortion function is developed and an algorithm for restoring and enhancing an image distorted by an unknown nonlinear amplitude transformation is proposed. Based on the signal model, it is shown that the source of information for the analysis of an amplitude distortion should not be the entire image, but only the boundary areas between its constituent objects. The concept of the function of local contrasts is introduced and the hypothesis about the form of this function in the absence of distortions is put forward. Based on this, a method of blind estimation of amplitude distortion and an algorithm for automatic image correction are developed. The principal feature of the proposed approach is that, as a result of the transformation, the brightness ratios between the image objects are preserved. Two possible variants of applying the algorithm to color images are proposed. Qualitative experiments demonstrated the effectiveness of the proposed method. The developed algorithm can be used in conditions when any knowledge about the distortion, to which the image is subjected, is absent, and only the resulting distorted image itself can serve as the source of information.

Abstract

The temperature dependence of the dark current in InAsSb-based p–n photodiodes detecting radiation in the medium-wave infrared (MWIR) region have been calculated, taking into account material characteristics of InAs_1 – xSb_x alloy. The desired signal-to-noise ratio is ∼10³ at T = 150 K, which confirms the possibility of achieving high photovoltaic parameters in InAs_1 – xSb_x photodiodes and their usage in high-temperature applications.

Abstract

To optimize photosensitive structures based on colloidal lead sulfide quantum dots, the rate and completeness of replacement in thin layers was studied using Fourier transform infrared spectroscopy on a multiple attenuated total internal reflection attachment. The rate of ligand replacement in a thin layer of colloidal lead sulfide quantum dots when replaced by iodide ion in different solvents was studied for the first time. A change in the composition of the shells of PbS nanoparticles under the influence of a number of solvents and when replacing them with thiocyanate ions was shown. For the first time, the replacement of the oleate ligand shell with pure formamide has been established.

Abstract—

The Wi-Fi standard describes a number of power save mechanisms, the main idea of which is to periodically turn off the radio to save energy on channel listening. In modern Wi-Fi networks, such mechanisms include Target Wake Time (TWT) and Wake-Up Radio (WUR). Despite the fundamental differences between these mechanisms, they both use the activity period scheduling alternating with long intervals of turning off the main radio. Turning off the main radio not only saves energy, but also causes the loss of synchronization between the clocks of the power-saving stations with the access point clock because of the clock drift effect, which can negatively affect the efficiency of these mechanisms. In this paper, mathematical models of frame transmission from an access point to power-saving stations using TWT and WUR have been developed. The models consider the clock drift effect and allow us to evaluate the efficiency of the considered mechanisms in terms of average power consumption and average frame delivery delay.

Abstract—Modeling in an affine space on the basis of a geodesic distance makes it possible to implement important computer vision techniques. Among these applications is superpixel segmentation, in which geodesic distances from the center of specified segments to an arbitrary image point are calculated. Meanwhile, the algorithms proposed so far for calculating such distances in segmentation problems have been heuristic, iterative approaches, which do not guarantee the expected result. In this study, a new fast algorithm for calculating the geodesic distance is proposed, which is proven to be accurate. The image segments obtained using this algorithm are simply connected regions. The algorithm yields simply connected superpixels at the output, in contrast to many other approaches based on the spatial proximity of the geodesic distance and requiring an additional correction. The proposed technique surpasses its analogs in the border recognition efficiency and computational speed.

Abstract

Features of the measurement of the NEP of scanning IR FPAs for projecting of the image of a small object into the plane of the array of photosensitive elements are considered. It is shown that the existing method for the measurement of the NEP of IR FPAs yields an incorrect result when the shape and dimensions of the photosensitive element (PSE) are not taken into account. A new technique for evaluation of the shape and dimensions of the PSE based on the application of the Richardson–Lucy iterative deconvolution method is described. Results of application of the proposed technique on real photodetector modules (PMs) are presented. Significant differences in the sizes of PSEs of different PM subarrays are revealed. The use of the image of a horizontal slit to correct the nonuniformity of the voltage sensitivity is proposed.

Abstract

The work is devoted to research of limits of applicability of X-ray analysis, light microscopy, and study of microhardness of samples surface within the framework of estimation of complex mechanical characteristics of single crystals, which largely determine output of good products (wafers) and form its final cost. Methods of investigation of mechanical properties regulated by GOST often refer to metals and alloys and are not applicable to semiconductor materials. In this regard, a particularly urgent task is to develop a method to evaluate the resistance of semiconductor wafers to brittle fracture, allowing the prospect of optimizing the technological regime of growth of single crystals, potentially reducing the final percentage of rejected material. InSb semiconductor single crystals grown in different crystallographic directions by Czochralski’s method were used as an object of investigation. It has been shown that the complex of mechanical properties of a material (thick plates also characterize the properties of the ingot as a whole) is directly influenced by the direction of growth. In this case, the lowest resistance to brittle fracture is shown by plates with orientation (100). The influence of plate surface treatment on the complex of mechanical properties is illustrated by X‑ray mapping. It is also shown in the present study that the microhardness of InSb wafers exhibiting different resistance to brittle fracture can have close values ((100)[100]—183 ± 0.6 HV, (100)[112]—179 ± 0.7 HV). A possible option for upgrading the microhardness measurement method could be to evaluate the crack resistance of the material by analyzing the geometry of the indenter-formed cracks.

Abstract

The paper deals with the features of the plasma-chemical process for obtaining tungsten carbide using an alternating current plasma torch. The synthesis was carried out in hydrogen and methane plasma. The process of obtaining tungsten carbide is as follows: WO₃ tungsten oxide powder is exposed to H₂ and CH₄ plasma flow with a maximum temperature of up to 10 000 K. The gas mixture flow rate was up to 0.02 g/s, the plasma torch power was up to 3 kW in most experiments. The obtained samples were studied by X-ray diffraction, scanning electron microscopy and elemental mapping using energy-dispersive X-ray spectroscopy. It was found that during the synthesis tungsten carbide WC was obtained, its dimensions are in the range of 5‒20 μm.

Abstract

The results of separation of a polydisperse mixture of charged dielectric microparticles using a linear electrodynamic quadrupole trap in air at atmospheric pressure are presented. It has been experimentally shown that the sizes of the microparticles held by the trap strongly depend on the voltage at the linear electrodes.

Abstract—The purpose of this article is to analyze the capacity of a discrete-continuous communication channel (DC-channel) as applied to nonorthogonal multiple access (NOMA) systems. In this work, an expression is obtained for the individual mutual information of a DC-channel in communication systems with nonorthogonal access, which makes it possible to analyze the capacity of the DC-channel individually for subscribers of NOMA systems. Its effectiveness for analyzing group signals of NOMA systems is shown, examples of its use are given, and capacity characteristics for NOMA subscribers are obtained as well.