Design of the Suboptimal Profiled Relay Control of Orientation of the Spacecraft Having Elastic Structural Elements with Regard for Two Oscillation Tones

A speed-optimal formulation of the control of angular spacecraft motion with regard for two tones of oscillations of its elastic structural elements was considered. A new approach based on the relay profiling of control was proposed. It provides the minimum oscillation amplitudes of the tones under consideration.     

Projection Method for Deconvolution-Based CT Brain Perfusion

Programming and Computer Software - The quantitative analysis of the blood flow in the brain tissue is one of the important problems in neurosurgery. It arises when diagnosing acute ischemic...     

Odor Space Navigation Using Multisensory E-Nose

A spatial odor distribution in an environment can be used for navigation, goal search, localization and mapping, like by video, ultrasonic, temperature and other sensors. Modern e-noses can perform the selective detection of different gases with an extremely low concentration but the source localization algorithms of a selected gas against the background of other odors are still underinvestigated. This paper studies an odor field representation in terms of an e-nose based on an array of low-selective sensors. Using a simulation model, we show how the vector measurements of a field of several odor sources can be processed to navigate for reaching a selected odor source. In addition, we demonstrate that the source having a high level of odor intensity can interfere with the search of another odor source of a low intensity. The well-known class of matching receivers does not solve this problem. However, a solution can be obtained by distributed measurements. As shown below, the spatial structure of an odor field allows to implement vector selection. Using deep learning machines, we may reach a high resolution of odor sources in the space. Our future research will be focused on augmented odor reality and autonomous mobile e-nose (e-dog) design.     

Effect of the size of Sic whiskers on the toughness of alumina-based composite materials

The effect of the dimensions of SiC whiskers on the strength and toughness of hot-pressed composites with a 20% volume fraction of whisker reinforcement was studied. It was established that the mechanical properties of the composites were improved only on introducing whiskers with the diameters, within 1.5–2.5 μm. These materials also exhibited a higher resistance to crack propagation. Crystals of smaller diameter had a negative effect on the mechanical properties, which was explained by bundle formation. There is a definite critical content of whiskers ensuring their uniform distribution in the matrix, and this value decreases on reducing the whisker diameter. A correlation was established between composite toughness and the level of average residual compressive stresses in the whiskers.     

Dynamics of spacecraft with elastic and dissipative elements in the attitude control mode

Rotational motion of a spacecraft with elastic and dissipative elements as a whole about its center of mass taking into account the control elements designed as single-axis gyrostabilizers in the attitude control mode is studied. Oscillatory processes related to the spacecraft attitude control when the terms emerging due to the elastic oscillations of the structure are comparable with gyroscopic terms. A model problem of spacecraft reorientation is considered. Conditions under which the elastic oscillations do not affect the flat slew of the satellite and assumptions under which no flat slew is possible are obtained. Analytical expressions for estimating the spacecraft deviations from the programmed motion (drift of the angular velocity) are found.     

Local High-Frequency Magnetron Reactive-Ionic Quartz Etching

A high-frequency magnetron reactive-ion etching system for the high-speed quartz glass surface treatment is described. The scanning assembly of the magnetron is located in a separate chamber pumped down to a pressure of 10^–2 Pa. This ensures a highly uniform etching and a high magnetic induction on samples, making it possible to reduce the cathode thickness. The quartz etching was studied in SF₆, CF₄, and CHF₃ with the magnetron operation with and without scanning. The maximum etching rates of 1.6 m/min (with scanning) and 4.2 m/min (without scanning) were attained in CHF₃ with a 1-Pa pressure and 700-W discharge power. 150-m-depth 4-mm-diameter pits were obtained by the quartz etching without scanning. With an increase in the pit depth from 150 to 250 m, the etching rate was reduced from 4.2 to 2.5 m/min.     

Predicting the limiting state of a multiblade hard-alloy tool

The limiting state of a composite multiblade tool with hard-alloy cutting plates may be predicted by measuring thermoelectric signals in the machining region.