Three-dimensional light bullets in a Bragg medium with carbon nanotubes

We present a theoretical study of the propagation of three-dimensional extremely short electromagnetic pulses (a.k.a. light bullets) through a Bragg medium containing an immersed array of carbon nanotubes. We demonstrate the possible stable propagation of such light bullets. In particular, our results suggest these light bullets can carry information about the Bragg medium itself.Comment: To appear in Appl. Phys.

Analysis of the Influence of Modes of Plasmachemical Synthesis and Precursor Evaporation on Geometric Characteristics of Ceramic Powders Produced

Mathematical model of evolution of a liquid precursor droplet in the process of plasma-chemical transformations for production of micro- and nano-structured ceramic powders on the basis of metal oxides is described. A criterion of production of particles with different morphology is determined. The results of numerical analysis are given

Verification of model of calculation of intra-chamber parameters in hybrid solid-propellant rocket engines

On the basis of obtained analytical estimate of characteristics of hybrid solid-propellant rocket engine verification of earlier developed physical and mathematical model of processes in a hybrid solid-propellant rocket engine for quasi-steady-state flow regime was performed. Comparative analysis of calculated and analytical data indicated satisfactory comparability of simulation results

SensorSCAN: Self-Supervised Learning and Deep Clustering for Fault Diagnosis in Chemical Processes

Modern industrial facilities generate large volumes of raw sensor data during the production process. This data is used to monitor and control the processes and can be analyzed to detect and predict process abnormalities. Typically, the data has to be annotated by experts in order to be used in predictive modeling. However, manual annotation of large amounts of data can be difficult in industrial settings. In this paper, we propose SensorSCAN, a novel method for unsupervised fault detection and diagnosis, designed for industrial chemical process monitoring. We demonstrate our model's performance on two publicly available datasets of the Tennessee Eastman Process with various faults. The results show that our method significantly outperforms existing approaches (+0.2-0.3 TPR for a fixed FPR) and effectively detects most of the process faults without expert annotation. Moreover, we show that the model fine-tuned on a small fraction of labeled data nearly reaches the performance of a SOTA model trained on the full dataset. We also demonstrate that our method is suitable for real-world applications where the number of faults is not known in advance. The code is available at https://github.com/AIRI-Institute/sensorscan

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor implementing the process of thermochemical decomposition of liquid droplet agents (precursors) in the flow of a hightemperature gaseous heat-transfer medium was obtained. The basic factor which determines the process is the increase of concentration of a dissolved salt precursor component at the surface of a liquid particle due to solvent evaporation. According to the physical concept of the method of integral balance the diffusion process of concentration change is divided into two stages: the first stage is when the size of gradient layer does not reach the center of a spherical droplet and the second stage when the concentration at the center of a liquid droplet begins to change. The solutions for concentration fields were found for each stage using the method of integral balance taking into account the formation of salt precipitate when the concentration at the surface of the droplet reaches certain equilibrium value. The results of estimation of the influence of various reactor operation parameters and characteristics of initial solution (precursor) on the morphology of particles formed - mass fraction and localization of salt precipitate for various levels of evaporation

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor

Analytical estimation of particle shape formation parameters in a plasma-chemical reactor implementing the process of thermochemical decomposition of liquid droplet agents (precursors) in the flow of a hightemperature gaseous heat-transfer medium was obtained. The basic factor which determines the process is the increase of concentration of a dissolved salt precursor component at the surface of a liquid particle due to solvent evaporation. According to the physical concept of the method of integral balance the diffusion process of concentration change is divided into two stages: the first stage is when the size of gradient layer does not reach the center of a spherical droplet and the second stage when the concentration at the center of a liquid droplet begins to change. The solutions for concentration fields were found for each stage using the method of integral balance taking into account the formation of salt precipitate when the concentration at the surface of the droplet reaches certain equilibrium value. The results of estimation of the influence of various reactor operation parameters and characteristics of initial solution (precursor) on the morphology of particles formed - mass fraction and localization of salt precipitate for various levels of evaporation

Mechanical activation time of 6B2O3–13Al powder mixture vs. structure and phase composition of SHS products

The paper discusses the time of mechanical activation of the 6B2O3–13Al powder mixture affecting the selfpropagating high-temperature synthesis (SHS), exothermic reaction temperature, structure, and phase composition of synthesis products. It is found that the time increase of the mechanical activation up to 180 min leads to a reduction in the average size of aluminum and boron trioxide particles down to 4.8 and 3.5 μm, respectively. Aluminum particles with boron trioxide inclusions are observed on the particle surface and inside their structure. Changes in the particle size and structure in the initial mixture components modify the SHS reaction front from chaotic to by layers. The structure of SHS products consists of the alumina layer (63–68 wt%) with aluminum dodecaboride (AlB12) particles (32–37 wt%) distributed under this layer. After 10 and 60 min of mechanical activation, acicular and elongated AlB12 particles appear in products synthesized from the 6B2O3–13Al powder mixture. Based on the data obtained, the SHS with subsequent mechanical activation is proposed for the fabrication of the Al2O3/AlB12 nanocomposite from the 6B2O3–13Al powder mixture. It is shown that after washing grinded SHS products with hydrochloric acid solution, the synthesized powder contains 100 wt% AlB1

Experimental study of the boron-containing mixtures burning rate

The results of the experimental determination of the burning rate of boron-containing fuel mixtures in the pressure range (0.1 ÷ 6) MPa are presented. The results of a comparative analysis of the burning rate of samples with component different compositions are given

Structure and deformation characteristics in magnesium alloy ZK51A reinforced with AlN nanoparticles

The aim of this work was to study the influence of nanoparticles of aluminum nitride on the structure and mechanical properties of magnesium alloy. We examine the resulting magnesium alloys. The experiment consisted in the introduction into the melt of magnesium aluminum nitride powder in an amount of 0.75 and 1.5%. Introduction of nanoparticles into the molten metal was carried out by external vibration exposure. Studies were carried out of aluminum nitride powder, comprising X-ray diffraction analysis to study the morphology using electron microscopy. Introduction of nanoparticles in the alloy increases the pore volume space from 5 to 15% and increased average pore size from 8 to 30 µm. It was shown that the presence of the nanoparticles in an amount of 1.5% increases the alloy properties by more than 30% compared with the reference (non-particulate) alloy. We were obtained diagrams such as stress - strain. It was also carried out studies of the structure and X-ray analysis of the alloys obtained