The paper considers a method for determining the diffusion lengths of non-basic charge carriers based on the analysis of the spectral characteristics of a planar electron-hole transition. The thickness of the illuminated area was reduced by chemical etching. By changing the signal for radiation in the region of strong absorption, the effective length of the tightening of non-basic charge carriers was determined. With removal of layers, a change in the electrical conductivity of the illuminated area was recorded. This made it possible to construct the doping profile and determine the intensity of the built-in electric field. The obtained results made it possible to calculate the diffusion length of the non-basic charge carriers. An example of implementation of the described method for an InSb-based photodiode is given. The proposed technique can be effectively used to determine small values of diffusion lengths of inhomogeneously alloyed layers.
The article provides information on the structure of an uncooled photodetector based on an InGaAsSb compound for the spectral range of 1.7...2.3 microns. The data on the integral sensitivity and also the spectral, noise, and threshold characteristics of the photodetector in the temperature range of 223-323 K are presented. The detectivity at room temperature reached the values D*(λmax,1000.1)=9.4.1010 W-1.cm.Hz1/2. The dynamic range was 64 dB.
This article considers the methods of calculating the cross-correlation function in determining the disparity from the images of a stereo pair formed by a stereo vision system. When determining the disparity, it is necessary to find a point on the second image of the stereo pair at a given point of the first image, which can be done by finding the maximum of the cross-correlation function. The possibility of reducing the amount of calculations in the time domain when using a non-positional calculus system, also called a residue number system, is considered. As a result of modeling based on a system of positional calculus and a residue number system using similar-shaped functions shifted along the X axis relative to each other, as well as using real stereo images, the coincidence of the main maxima of the cross-correlation function is shown with a significant reduction in the amount of calculations.
The article discusses the construction of television hyperspectral imaging systems. Examples of practical use of multi-scale images are given. A combined hyperspectral system with two channels is considered: the first one performed on the basis of the Fabry-Perot interferometer is for small-scale observation, and the second one performed on the basis of a prism is for large-scale observation. The principles of constructing channels of a combined hyperspectral system based on scanning by spatial and spectral coordinates are considered. A variant of constructing a multi-angle (multi-slit) hyperspectral system for the prism variant based on the principle of scanning by spatial coordinate is proposed. The possibility of implementing a multi-angle channel using a megapixel photodetector with increased sensitivity is analyzed. The initial and calculated data are given. Structural electrical and optical circuits are considered, and resulting technical characteristics are analyzed.
The article deals with the issues of computer simulation of algorithms for processing spectral images, namely: the procedure for increasing their clarity. For this purpose, a spectral image obtained from a hyperspectrometer is used, as well as additional information from a high-resolution color video camera. The hyperspectrometer and the color video camera form a hyperspectral system in which various processing procedures can be implemented. The article considers a relatively simple processing algorithm with use of E. Land's retinex theory. A block diagram of the image processing stages is presented, as well as the results of computer modeling using real spectral images. Comparative quantitative characteristics of reference and processed images are analyzed. It is shown by modeling that with insignificant spatial distortions, the number of singular points (gradients) of the image, and, consequently, the clarity of the original spectral image increase by several times.
The article deals with the issues of computer simulation of the processes of spectral image formation in a hyperspectral system based on the Fabry-Perot interferometer, designed to work in the visible spectrum. A mathematical model of a hyperspectral system and its main variable parameters for evaluating the obtained characteristics of spectral selectivity are considered. A block diagram illustrating the simulation process is given. The results of computer simulation are presented. The characteristics of spectral selectivity obtained by computer simulation are given, depending on the air-gap distance between the mirror plates of the Fabry-Perot interferometer at a fixed angle of incidence of the radiant flux. The possibility of singlechannel and three-channel registration of spectral responses of the interferometer corresponding to RGB channels of a standard color matrix photodetector is shown. The variants of the structural schemes of the hyperspectral system are analyzed based on the existing compromises between the sensitivity of the system, its spectral selectivity, speed, accuracy, resolution, and complexity of implementation.
The article is devoted to an analytical review of the state and prospects of development of video spectral comparators intended for technical studies of documents. This equipment belongs to the spectrosonal television systems that allow obtaining images in various parts of the visible and near-infrared spectrum. Currently, television spectrosonal visualization is one of the methods of systematic study of documents and handwritten book monuments. The development of spectrosonal imaging is initially associated with photographic research methods. Television and optoelectronic devices made it possible to switch to a fundamentally new hardware base due to a number of advantages: contrast and spectral sensitivity, efficiency of image control and processing. Video spectral comparators are an example of such equipment which completely solves the main tasks related to technical examination of documents.
We study the symmetric 2-adic complexity of Hall generalized cyclotomic sequences whose period is equal to the power of a prime. Sequences are defined based on generalized cyclotomic classes. It is shown that the considered sequences have high symmetric 2-adic complexity. The research method uses generalized Gaussian periods.
Window functions are used in the radar signal processing to reduce the undesirable effect of masking a weak signal of a moving target with powerful reflections from stationary or slow-moving objects. The effectiveness of window functions weakens in radars which transmit and receive signals with pseudo random amplitude and phase-shift keying on common aerial. The article shows that pseudorandom pauses between phase-manipulated pulses of pseudo random duration affect the result of window weighted processing. The best parameters of the probing signal for weighing them by window functions during fasttime and slow-time processing are determined. An algorithm for normalization and interpolation of compressed segments of the signal with pseudorandom amplitude and phase-shift keying is proposed. The results obtained are confirmed by modeling the processing of an additive mixture of echo signals with different Doppler frequencies.
The work contains a critical analysis of the methods and results currently used and applied in the theory of condensed matter. A unified mathematical apparatus has been developed - the method of functional integration which is equally applicable to all main distributions of statistical physics: microcanonical, canonical, and grand canonical ensembles. Within the framework of this method, an exact factorization of the configuration integral with respect to atomic coordinates was performed and a connection between the microcanonical and canonical ensembles was established. It is shown that interatomic interactions can be eliminated by renormalizing external random fields, and random external fields can be eliminated by renormalizing interatomic potentials. A new formulation of problems of equilibrium statistical mechanics as a dynamic field theory with a Hamiltonian depending on temperature is proposed.
In this paper, we propose a method for relativistic description of the dynamics of systems of interacting particles through an auxiliary field which in the static mode is equivalent to given interatomic potentials, and in the dynamic mode is a classical relativistic field. It has been established that for static interatomic potentials of a general form, the auxiliary field is a composition of elementary fields satisfying the Klein-Gordon type equations. Each elementary field is characterized by a complex parameter which is an analogue of the real mass in the Klein-Gordon equation. The interaction between particles through an auxiliary field is nonlocal both in spatial variables and in time. The qualitative properties of solutions to equations describing the auxiliary field are studied. Relativistic mechanisms of both the thermodynamic behavior and synergetic effects in few-particle systems have been established.
The thermodynamic properties of condensed systems are determined by interatomic potentials, the short-range parts of which limit the local density of the system, and the long-range parts form fields that determine the dynamics of interacting atoms. In the generalized lattice model, the short-range parts of interatomic potentials are taken into account by introducing intrinsic atomic volumes. Moreover, unlike conventional lattice models, the atomic volumes of various components of the system can differ from each other. The presence of short-range parts of interatomic potentials is taken into account using the close packing condition. In addition to atoms, the system assumes the presence of vacancies which constitute one of the components of the system. The contribution of vacancies to thermodynamic functions is taken into account using the entropy term. Long-range parts of interatomic interactions are taken into account within the framework of a self-consistent approximation. A connection between the generalized lattice model and the Ginzburg-Landau approximation has been established, and the connection between the characteristics of interatomic potentials and the properties of phase boundaries has been studied.
The theoretical study of possibility for the torsional mode identification against the background of longitudinal-shear one in asymmetric ME composites Metglas / GaAs and Metglas / bimorph LN Zyl + 45° is carried out in this paper. It is determined that ME composites with bimorph LN Zyl + 45° are better to use as a piezoelectric to study the torsional mode of the ME effect. This is due to the fact that the longitudinal-shear mode is not excited in the ME composite with a bimorph LN Zyl + 45°, and the ME voltage coefficient depends only on the torsional mode.
Modern heat pipes (HP), being special cooling devices, effectively provide continuous removal of thermal energy. Currently, the HP class the bodies of which have a specially designed shape and are made of aluminum alloys, is widely used in radio-electronic equipment engineering. The geometric, thermal, and mathematical models of HP were developed for computer simulation. A series of calculations were also performed, which made it possible to visualize the morphology of the thermal field of HP and identify the influence of defects of different types. As part of the contactless HP quality diagnostics technology, a new computer model of the thermal field has been developed to ensure the integrity of the signal interpretation during the thermal imaging quality diagnostics.
Within the framework of generation and selection of morphological features of the temperature field and the information principle, methods for calculating informative value have been developed and implemented for heat pipes. The first technique consists in the application of energy principle and provides increased sensitivity to local distortions of the temperature field of a shaped heat pipe. The second technique is implemented using the method of accumulated frequencies and Shannon coding. It is characterized by the use of both theoretical and experimental samples.
In this research, we study the dependence of the shift of the ferromagnetic resonance line in layered structures based on yttrium iron garnet (YIG) on a gadolinium gallium garnet (GGG) substrate, on the magnitude of the external electric field and on the parameters of various piezoelectrics (plumbum zirconate titanate (PZT), Langasite)). The intense development of modern microwave technology leads to the study and creation of new layered structures of materials with different physical properties that can be combined: magnetic and ferroelectric, magnetic and semiconductor, etc. As a result of the study, we obtained the dependences of the shifts of the ferromagnetic resonance line on the parameters of piezoelectrics (mainly, on the magnitude of the dielectric constant) in the layered structures YIG-GGGPZT, YIG-GGG-Langasite. The obtained results show that the ferromagnetic resonance line shift effect can be used to develop new controllable microwave devices, the operating principle of which is based on the electronic tuning of resonance characteristics by means of an electric field and the choice of the type of piezoelectric.
In this work, a magnetoelectric harvester for biomedicine based on the AMAG-PZTS magnetostrictive-piezoelectric composite structure is investigated. The intense development of modern electronics leads to a comprehensive theoretical and experimental study of new materials in which the connection between their magnetic and electrical properties is manifested, namely the magnetoelectric effect (ME).The ME harvester for biomedicine, connected in parallel to the ME sensor, is part of a full-fledged highly sensitive device for magnetocardiography and acts as a backup power source, collecting and storing energy to power the generator which is a source of alternating magnetic field for the ME magnetic field sensor. An experimental study of the ME effect in the magnetostrictive-piezoelectric composite structure of the harvester was carried out, and the dependences of the output voltage and ME coefficient of the composite structure on frequency were obtained.
The article provides a review of various magnetoelectric composites that were studied in the current measurement mode. Recent studies have been conducted with both open- and closed-type structures. A comparison of the currently available ME current sensors is given. The study of closed ME structures will make it possible in the future to use them as current sensors and implement on their basis a contactless system for measuring both high and low currents.
The influence of uniaxial compression on the electrocaloric effect in a barium titanate-based bilayer was studied using the Landau-Ginzburg thermodynamic approach. Barium titanate was used as a model material. It was shown that the electrocaloric effect can be controlled by uniaxial compression. Application of compressive stress is an effective approach to enhance the electrocaloric effect in ferroelectric ceramics. The compressive stress in the considered magnetostrictive-ferroelectric bilayer is a result of mechanical coupling between ferroelectric and magnetostrictive phases.
The ferroelectric volume fraction dependence of the multicaloric effect in a bilayer of barium titanate and cobalt ferrite was studied using the Landau-Ginzburg thermodynamic approach. It is shown that the electrocaloric effect can be controlled using the volume fraction of the ferroelectric. Magnetic field application is an effective tool to enhance the multicaloric effect in a magnetostrictive-ferroelectric structure. The choice of an optimal magnetic component which has a magnetocaloric effect in the appropriate temperature range and enables generating the necessary mechanical stress in ferroelectric layer, will increase the multicaloric effect in a bilayer.
The article is devoted to the study of the problem of the electroosmosis application in porous and capillary systems of heat pipes intended for use in cooling systems of radio equipment. The use of electroosmosis in heat pipes will reduce the gravitational dependence of thermal resistance of a heat pipe and will allow you to control its performance. The article presents the results of the practical implementation of electroosmotic pumps used in cooling systems. In conclusion, the prospects of using electroosmosis in heat pipes are considered.
The paper is devoted to the modeling of magnetoelectric material for antennas. The effect observed in magnetoelectric gradient structures is discussed. Gradient magnetoelectric structures are a new type of composite structures consisting of a magnetoelectric material and an artificial dielectric. A new principle of controlling the antenna wave properties based on the geometric displacement of the excitation point due to the application of an external electric field is being considered. The use of an artificial dielectric in a multiferroid structure will make it possible to more flexibly control the areas of conversion of a magnetostatic surface wave into an electromagnetic wave, which in practical terms will give new opportunities for controlling the characteristics of antennas. The conclusion about the possibility of controlled conversion of a magnetostatic surface wave into an electromagnetic wave was obtained as a result of calculations based on the developed model by selecting the values of stationary magnetic and electric fields, and the values of the permittivity of the artificial dielectric layer.
The paper presents an overview of the use of nano- and ultrafine powders as functional additives in various methods of arc welding (fusion surfacing). Methods for introducing nano- and ultrafine powders into a liquid weld pool are considered. The results of experimental studies of soldering processes are presented. The objectives of further research in the field of practical application of nano- and ultradisperse materials for connecting technologies are formulated.
MIMO technology allows you to create virtual antenna arrays, significantly reducing the number of receiving and transmitting channels compared to classical phased antenna arrays (PAA). At the same time, the characteristics of the antenna system (width of the radiation pattern, gain factor) and, as a result, the characteristics of the radar (angular resolution, detection range) are preserved. Reducing the number of receiving and transmitting channels leads to a significant reduction in the cost of the radar as a whole. The article describes the process of developing a mathematical model and signal processing software based on the Digilent Zedboard platform. The results of modeling and testing of the hardware and software implementation of the processing algorithm are presented. The degree of loading of the Xilinx Zynq XC7Z020 crystal standing on the Digilent Zedboard platform is estimated.
A new, mathematically efficient method for solving the vector equation of diffraction on an open cylindrical surface is proposed. The method is based on the allocation of the main operator, the definition of functional spaces and the reduction of the operator equation to the Fredholm equation of the second kind. Sobolev spaces are used as ones that take into account the Meixner condition on the edge. In the selected spaces, the main operator is bounded and invertible; the inverse operator is also bounded. A projection method for solving operator equations has been developed.
A new, mathematically efficient method for solving the vector equation of diffraction on an open surface of rotation is proposed. The method is based on the allocation of the main operator, the definition of functional spaces and the reduction of the operator equation to the Fredholm equation of the second kind. Sobolev spaces are used as ones that take into account the Meixner condition on the edge. In the selected spaces, the main operator is bounded and invertible; the inverse operator is also bounded. A projection method for solving operator equations has been developed.
