An anomalous acoustic effect during martensite transformations in NiTi-based alloys

Martensite transformations proceeding in mechanically loaded TiNi-based alloys account for an “anomalous” character of the acoustic emission from the material, whereby cyclic transformations during the growth of mechanical stress in the course of the direct transition is accompanied by an increase, rather than by a decrease, in the acoustic emission energy. This behavior of the acoustic emission is evidence of a significant influence of the external stresses on the martensite transformations and the related energy dissipation process.     

Control of distributed-parameter systems under uncertainty

The maximum principle and a necessary condition of optimality are derived for a particular control problem.Translated from Kibernetika i Sistemnyi Analiz, No. 6, pp. 165–167, November–December, 1991.     

Turbulent froth equipment for cooling compressed gases

Results are considered for an experimental study of turbulent froth heat exchange whose construction is protected by an RF patent. Limits are established from test data for equipment stable operation with different methods for feeding liquid into the contact device. Generalized relationships are presented in dimensionless form for heat and mass transfer and also for the hydrodynamics of flows in the equipment. The results obtained are used for improving the construction of turbulent froth equipment intended for intermediate cooling of a piston compressor without lubrication.     

Temperature effect on the formation of a relief of diamond-like carbon coatings and its modification by ion bombardment

Diamond-like coatings (DLCs) have been obtained on a UVNIIPA-001 unit employing the method of pulse arc sputtering of a graphite target. DLCs of about 1.5 μm thick were applied onto substrates of the R6M5 steel. The relief of the coatings that were deposited using different temperature regimes has been studied. It has been established that a temperature rise of the surface of a growing DLC (condensation at a high frequency of arc pulses f) leads to the growth of films with numerous protrusions on their surface. The deposition of films at a low frequency f is more preferable to form smooth and hard DLCs under the conditions of unfiltered beam of carbon ions. The modification of the surface of diamond-like carbon coatings after their application has been investigated upon bombardment with accelerated ions of inert gas (argon) or chemically active oxygen. It has been established that the argon-ion bombardment is more preferable to smooth out the DLC relief. It has been shown that the relief of DLCs must be taken into account when measuring their microhardness, whereas the transformation of interatomic bonds in the near-surface layers after ion irradiation should be taken into consideration when analyzing the coatings by the methods whose informative depth is several monolayers.     

Mass spectrometric investigation of the thermodynamic properties of glass melts in the Cs2O-B2O3-SiO2 system at high temperatures

The composition of the vapor and the activities of cesium metaborate CsBO₂ in glass melts of the Cs₂O-B₂O₃-SiO₂ system at a temperature of 1020 K are determined using high-temperature mass spectrometry. The activities of the individual oxides Cs₂O, B₂O₃, and SiO₂ in glass melts of the Cs₂O-B₂O₃-SiO₂ system at a temperature of 1020 K are calculated by the Wagner method from the obtained values of the activities of CsBO₂. The integral and excess Gibbs energies are determined.     

Towards a set of agrosystem-specific cropland mapping methods to address the global cropland diversity

Accurate cropland information is of paramount importance for crop monitoring. This study compares five existing cropland mapping methodologies over five contrasting Joint Experiment for Crop Assessment and Monitoring (JECAM) sites of medium to large average field size using the time series of 7-day 250 m Moderate Resolution Imaging Spectroradiometer (MODIS) mean composites (red and near-infrared channels). Different strategies were devised to assess the accuracy of the classification methods: confusion matrices and derived accuracy indicators with and without equalizing class proportions, assessing the pairwise difference error rates and accounting for the spatial resolution bias. The robustness of the accuracy with respect to a reduction of the quantity of calibration data available was also assessed by a bootstrap approach in which the amount of training data was systematically reduced. Methods reached overall accuracies ranging from 85% to 95%, which demonstrates the ability of 250 m imagery to resolve fields down to 20 ha. Despite significantly different error rates, the site effect was found to persistently dominate the method effect. This was confirmed even after removing the share of the classification due to the spatial resolution of the satellite data (from 10% to 30%). This underlines the effect of other agrosystems characteristics such as cloudiness, crop diversity, and calendar on the ability to perform accurately. All methods have potential for large area cropland mapping as they provided accurate results with 20% of the calibration data, e.g. 2% of the study area in Ukraine. To better address the global cropland diversity, results advocate movement towards a set of cropland classification methods that could be applied regionally according to their respective performance in specific landscapes.     

Analysis,filtering, and decomposition of electron microscope images based on orthogonal transformations

Methods for estimating the integral characteristics of electron microscope image periodograms, based on Hartley transform, Q-transform, and cosine transform, are proposed. It is shown that the cosine transform is more appropriate for filtering and improvement of psychophysical image perception on its basis. Various approaches to implementing matched filtering via cosine transform are considered. A procedure of electron microscope image decomposition with the use of various orthogonal transforms and filters based on Fourier patterns of Gauss and Morle wavelets is proposed and studied. It is shown that electron microscope image structure analysis using scalograms of orthogonal image transforms is promising.     

Electron-microscopic examination of the transition zone of aluminum-tantalum bimetallic joints (explosion welding)

A study of the structure of an aluminum-tantalum joint and a comparison of this structure with the structures of iron-silver and copper-tantalum joints have revealed the following processes of the interpenetration of the materials that occur during explosion welding: the formation of protrusions, the injection of particles of one material into the other, and the formation of zones of local melting. Regardless of the mutual solubility of the metals being welded, two types of fragmentation occur, i.e., (1) a granulating fragmentation (GF), which includes the formation, explosion-governed (EG) dispersion, and partial consolidation of particles, and (2) the fragmentation that is usually observed during severe plastic deformation. It is important that this traditional fragmentation is not accompanied by the formation and EG dispersion of particles. This feature allows one to easily distinguish these types of fragmentation (traditional and GF fragmentation).