Home – Home – Jornals – Avtometriya 2019 number 2

The monochromator of the Kosmos synchrotron radiation metrology station is described. The results of testing the monochromator in the energy range of 2000-6000 eV using Si (111) crystals are given. A spectral resolution at the level ΔE/E= 10^-4 is obtained. A technique for checking verification spectral purity of the monochromatic radiation is described. It is shown that the monochromator can be used for spectroscopic measurements in the specified subrange.

A technique for designing high-pass terahertz quasioptical filters based on thick (up to 1 mm in thickness) self-supporting copper microstructures of subwave topology. The technique is based on the X-ray lithographic formation of a high-aspect resistive mask made of the SU-8 X-ray resist on a silicon substrate with the use of a tungsten X-ray pattern and subsequent galvanic growing of a copper layer through the resistive mask. The example of a 212-$\mu$m thick structure with a cutoff frequency of 0.42 THz having the topology of hexagonally packed hex-shaped holes is described. The results of the broadband THz characterization of the structure obtained and its electrodynamic analysis are presented.

This paper is a continuation of a series of on the development of the X-ray topo-tomography method using laboratory equipment. The results of a study of the spatial location of a single polygonal dislocation half-loop in a silicon single crystal were obtained for testing the sensitivity of the X-ray TOPO-TOMO diffractometer. A comparison was made with high-resolution experimental data obtained at the European synchrotron radiation facility (ESRF). The experimental procedure and software and hardware for the 3D reconstruction of the investigated single defect - a polygonal dislocation half-loop - are described.

Synchrotron X-ray diffraction study of Ni₃Al single crystals ordered in the L1₂ structure was performed. The ultrafine grained structure resulting from severe plastic deformation was studied. In the initial state, the ordered single crystal is oriented along the compression axis [211]. Along with the ordered phase, there is a small proportion of disordered crystal oriented along the [100] axis. Compression of the samples and subsequent torsion at different angles led to a destruction of the single crystal state of the sample and a changed in the state of the atomic order, up to the disappearance of the L1₂ superstructure.

For correct numerical interpretation of the results of tomographic experiment, i.e. estimates of objects attenuation coefficients it is important to obtain reconstruction of high quality which depends directly on the methods of processing experimental data. Data processing flow begins with its preparation for the application of the reconstruction algorithm. The necessary part of data processing contains the subtraction of the black field, normalization considering empty data, and taking logarithm. This part is not sufficient for obtaining high-quality reconstruction when working with real data since it is not ideal. Real data include noise and distortions due to changes of the set-up geometrical parameters during the experiment. We have analyzed two possible types of data corruptions during experiment and suggested corrections for them. The first correction is applied to change thermal shifts regarding beam decentralization, and the second accounts for and eliminates the effect of the polychromatic nature of the radiation on the results of tomographic reconstruction. These methods were tested with both real and synthetic data. Both synthetic and real experiments show that suggested methods improve the reconstruction quality. In real experiments, the level of agreement between automatic parameter adjustment and experts is about 90%.

Micromilling technologies are used to design and experimentally study terahertz power reflecting optical elements with free-form surfaces. The results of the experimental study are in good agreement with theoretical estimates. It is shown that the technique used in this paper makes it possible to develop terahertz focusing reflecting elements with energy efficiency above 94 %.

An intensely developing aspect of advanced microelectronics is microelectromechanical systems (MEMS). The present paper describes various issues associated with the development of a new MEMS generator of clock frequency capable of operating at gigahertz frequencies. The main features of generating and supporting forced oscillations of the moving electrode under the action of electrostatic forces are analyzed. A possibility of supporting such oscillations under conditions of high inertial g-loads (up to 10⁶g and more) is demonstrated. A mathematical model of a micro-oscillator is developed, and the basic regimes of its operation are described.

A possibility of using the autocollimation and interference methods for real-time nonintrusive control of the surface shapes of photodetectors that are sensitive in the infrared range and are fabricated by the flip-chip technology is considered. These methods allow monitoring the surface shapes and the maximum deflections. These methods are applied in the present study to measure the surface shapes of fragments of silicone instrumental boards and arrays of photosensitive elements on GaAs substrates, as well as the surface shapes of photodetectors at different stages of fracture and in the course of thermal cycling.

A combined method of object visualization based on analytical and scalar perturbation functions and three-dimensional textures with the use of graphics processing units is proposed. To display the terrain and the change in levels of detail, the same method as that for color textures is applied, and vertex shaders are used in the case of scattered light. A method of real-time visualization of three-dimensional clouds is described. For this purpose, it is proposed to form three-dimensional textures by means of pre-processing of the cloud structure and volume-oriented visualization.

Modern methods of visual navigation for mobile robots are considered. A hierarchical representation structure of the surrounding space corresponding to the hierarchical organization of the mobile robot control system is proposed. Modern approaches to building cartographic models are presented. Their development will bring the navigation system closer to that created by the human intellect and combines vision and a semantic view of the world within cognitive maps.

The problem of automatic verification of control algorithms developed by tools of process-oriented programming for cyberphysical systems is solved. A method based on software simulators of the control object is proposed, and its implementation on the basis of the LabVIEW package and Reflex language translator is described.

Adaptation of the process-oriented approach to programming of microcontrollers in embedded systems is described. Specific features of control algorithms and programming of microcontrollers are analyzed. A mathematical model of the control algorithm, which implies a mechanism of the description of microcontroller interruptions in the form of hyperprocesses, is proposed, and its dynamic semantics is provided. The model proposed in the study is a conceptual framework for the development of specialized languages of process-oriented programming of embedded systems.

A machine learning approach for prediction the characteristics of tonal noise formed in a foil flow is tested. Experimental data are used to construct and analyze the mathematical models of pressure amplitude regression and models of classification of regimes of high-level tonal noise coming from the dimensionless parameters of the flow. Different families of algorithms are considered: from linear models to artificial neural networks. It is shown that a gradient boosting model with a determination coefficient 95 % is the most accurate for describing and predicting the spectral curves of acoustic pressure on the entire interval of values of amplitudes and characteristic frequencies.