Method for detecting instability and recovery of signal shape under intense noise

A method for detecting the moment of instability of a digitized signal under intense noise is proposed that makes it possible to recover the signal shape. It is based on combined processing of two signal estimates obtained by relay stochastic gradient procedures that process the given array of samples in opposite directions.     

Numerical analysis of a model of metal solidification, 2D case

The work discusses numerical simulation of metal solidification. The difficulties of calculatibg such processes are that simulation is conducted at several scale levels simultaneously. At present experimental studies cover numerous aspects of metal solidification; however, there is no generalized concept of this process. The model applied in this study is based on the concept of solidified alloy in the form of a porous medium, where propagation of perturbations is described by the Biot equations. In order to describe nucleation, the modified Cahn-Hillard equation is applied. Previously a one-dimensional (1D) numerical model has been developed, its convergence has been demonstrated and a possibility of obtaining of various modes of solidification has been shown at modification of parameters. This work presents the 2D numerical model and examples of calculations. Since a multiscale approach requires high CPU resources, the 2D calculations are based on explicit and explicit-iterative algorithms which are efficiently implemented using a multiprocessor computer.     

Assessment of the effect of particle size on the rate of temperature alignment in systems used for shock-wave synthesis of diamond,cubic boron nitride,and γ-silicon nitride,based on a simple model

The change in the spatial distribution of relative temperatures in the system of a spherical particle located in the center of a spherical matrix is simulated. Silicon nitride (Si₃N₄) and boron nitride (BN) are considered in a matrix of potassium bromide (KBr); graphite, diamond, and silicon nitride are studied in a copper matrix. Calculations are performed for the four sizes of particles: 1, 5, 20, and 100 μm. It is shown that the temperature is equalized by approximately 80% in 1 μs in the particles of Si₃N₄ and BN with a size of 5 μm in the KBr matrix. In the system of silicon nitride–copper, such alignment is performed for a particle with a diameter of 20 μm. For a diamond particle in the copper matrix, the particle size may be even greater. The particle sizes for which calculations showed a rather high rate of heat transfer in a time of ~1 μs either match or are somewhat larger than the particles of diamond, cubic boron nitride, and γ-silicon nitride formed during the real shock-wave synthesis of these materials.     

To react or not to react? Intrinsic stochasticity of human control in virtual stick balancing

Understanding how humans control unstable systems is central to many research problems, with applications ranging from quiet standing to aircraft landing. Increasingly, much evidence appears in favour of event-driven control hypothesis: human operators only start actively controlling the system when the discrepancy between the current and desired system states becomes large enough. The event-driven models based on the concept of threshold can explain many features of the experimentally observed dynamics. However, much still remains unclear about the dynamics of human-controlled systems, which likely indicates that humans use more intricate control mechanisms. This paper argues that control activation in humans may be not threshold-driven, but instead intrinsically stochastic, noise-driven. Specifically, we suggest that control activation stems from stochastic interplay between the operator''s need to keep the controlled system near the goal state, on the one hand, and the tendency to postpone interrupting the system dynamics, on the other hand. We propose a model capturing this interplay and show that it matches the experimental data on human balancing of virtual overdamped stick. Our results illuminate that the noise-driven activation mechanism plays a crucial role at least in the considered task, and, hypothetically, in a broad range of human-controlled processes.     

Distribution of impurities in steam-generating equipment with estimating the efficiency of their removal during the power unit shutdown process

The sludge distribution patterns in the volume of a steam generator and in the near-wall region of its heat-transfer surface are obtained. Recommendations for removing sludge in the power unit shutdown mode are given.     

Positional‐Species Composition of Triacylglycerols from the Arils of Mature Euonymus Fruits

Positional‐species composition (PSC) of 1,2,3‐triacyl‐sn‐glycerols (TAG) from the arils of mature fruits of 13 species of Euonymus L. genus was established. The residues of six major fatty acids (FA), palmitic, stearic, hexadecenoic (H), octadecenoic (O), linoleic (L), and linolenic, were present in the TAG. PSC of TAG was determined by their partial lipase hydrolysis. By using hierarchical cluster and principal component analyses, it was definitely demonstrated that separate taxonomic units forming this genus were significantly distinguished as regards PSC of TAG. In particular, the Euonymus subgenus greatly exceeded the Kalonymus subgenus in both total content of L in TAG and in the rate of its incorporation into their mid‐position, while TAG of Kalonymus were marked by a prevalence of O‐TAG and sn‐2‐O isomers. Thus, these subgenera were significantly distinct in the rate of incorporation of O and L residues in the sn‐2 position of TAG molecules. Meanwhile, the TAG from the Euonymus section species were marked by an enhanced concentration of H and the incorporation of H in UUU TAG was much more active than in other TAG types. As for positional‐type composition of TAG, saturated FA were always virtually absent in the sn‐2 position of Euonymus aril TAG.     

“Greening Up” Cross-Coupling Chemistry

New methodologies that enable palladium catalyzed cross-coupling reactions to be performed under environmentally benign conditions (in water and/or at room temperature) have been developed. Described approaches involve in situ activation of carbon–halogen or carbon–hydrogen bonds using zinc metal, or cationic palladium, respectively.     

Silica Colloidal Membranes with Enantioselective Permeability

Robust mesoporous membranes composed of silica spheres were surface-modified with chiral selector moieties, including small molecules, macrocycles, and polymers. Diffusion rates of enantiomers of a chiral dye through the resulting asymmetrically modified colloidal membranes were measured and the corresponding permselectivities were calculated. The membranes showed enantioselectivities in the range of 1.2–1.8, which were not significantly affected by the structure of the surface-immobilized chiral electors. This selectivity is on par with most reported polymer-based solid membranes and bulk liquid membranes. The enantioselectivity results from the surface-facilitated mechanism of transport of enantiomers through the mesopores.