Effect of nanosphere size on the luminescence of synthetic opal

We have studied the effect of the stop band and coupled photonic modes on the visible luminescence of synthetic opal photonic crystals. The results demonstrate that the position of the photonic stop band in the luminescence spectrum of opal depends on the nanosphere diameter. Optical measurements have been used to determine the refractive index of the photonic crystals and the silica sphere diameter. We have assessed the effect of coupled modes in opal on its intrinsic luminescence spectrum. Coupled modes of visible light in opal can be visualized by applying a matte sapphire plate to the opal surface.     

Machine learning for human movement understanding

Main purpose of this project is to develop fundamental technology for assist robots to recover and maintain human motor skill and to extend scope of human activity. Our goal is to provide a system that adapts to its user’s personal behavior patterns in real-time. We aim to develop a continuous collaboration system between the assist robots and the user where both alternatively adjust to each other to maximize the system’s utility. To understand human movement, we recorded motion sequence of several tasks for different subjects using motion capture system. Through analysis of human motion data, we extracted a general model by rule-based approach. On the other hand, since such tasks are not feasible with static models, we investigate the potential benefit of supervised online learning in the task of online action classi?cation and Deep Learning in the task of acquiring human motion. Finally, developed system was extended to show its potential effect in ergonomics and in assist robotics.     

Method for the Synthesis of Optimum Multistage Heat Exchange Network

Theoretical Foundations of Chemical Engineering - A new algorithmic approach to the synthesis of economically optimum multistage heat exchange network in the design and reconstruction of...     

Computation of Compressible Gas Flow Using General-Purpose Graphics Processing Unit

Journal of Engineering Physics and Thermophysics - Possibilities for using general-purpose graphics processing units to simulate compressible gas flows are discussed. Consideration is given to...     

Phase relations in the PbF2-BaF2-ZrF4 system

We have investigated phase equilibria between PbZrF₆ and the barium fluorozirconates Ba₂ZrF₈, Ba₃Zr₂F₁₄, BaZrF₆, and BaZr₂F₁₀. The PbZrF₆-Ba₂ZrF₈ join has been shown to be pseudobinary, with simple eutectic phase relations. It defines the PbZrF₆-ZrF₄-Ba₂ZrF₈ compatibility triangle in the PbF₂-BaF₂-ZrF₄ system. Semicrystalline samples have been obtained at ZrF₄ contents in the range 40–70 mol %.     

Electroluminescence in the region of interband transitions in a high-efficiency silicon light-emitting diode with a small area of the rectifying contact

Electroluminescence in the region of interband transitions is studied in a Si diode at room temperature with the densities of current (J) as high as 36 kA/cm² through the p-n junction with an area of 0.008 mm². The kinetics of the electroluminescence decay is represented by exponential function with the time constant τ_d ≈ 35 μs in the linear portion of the dependence of the electroluminescence intensity on current. At J > 2.5 kA/cm², the current dependence of the electroluminescence intensity becomes sublinear, while the decay kinetics is described by the exponential function with the same τ_d, however, only after the initial portion of a more rapid decay of electroluminescence. The specific features observed at J > 2.5 kA/cm² can be related to an appreciable contribution of the Auger recombination (in addition to the Shockley-Read-Hall mechanism) to nonradiative recombination. It is shown that it is feasible to fabricate Si-based light-emitting diodes with the emission power as high as ～50 mW at the emitting-surface area of about 6 mm².     

Ultraviolet luminescence of ZnO infiltrated into an opal matrix

Technology for the infiltration of zinc oxide into a three-dimensional opal lattice using chemical deposition from a solution was developed. Samples of ZnO-opal composites, whose luminescence at room temperature mainly occurs in the ultraviolet spectral range, were obtained. The filling ratio was monitored by two different techniques: (i) checking the increase in the mass of the sample and (ii) checking the shift of the peak in the optical reflection spectrum of samples filled with ZnO in comparison with the initial opal matrices. The results obtained by these two methods are consistent with each other. Optimum conditions for synthesizing ZnO-filled opals in order to attain the highest intensity of ultraviolet luminescence were determined. It was shown that using “raw” opals, whose voids are incompletely filled with the semiconductor material, leads to a severalfold increase in the intensity of the edge excitonic emission band at room temperature. The results obtained can be used in the development of efficient directed laser light sources in the ultraviolet spectral range based on the “photonic crystal” effect.     

Cathode-initiated vacuum breakdown in a pulse regime

Based on an analysis of the Joule heating of emitters by thermionic current, new methods and criteria are proposed for evaluating vacuum breakdown cathode-initiated in a pulse regime for an arbitrary cathode shape. The applicability of the proposed methods and validity of the new criteria are confirmed by the results of experiments using nanosecond pulses applied to coaxial copper electrodes with a gap width of d=0.2 mm and an area of S=2500 mm².     

Production of granulated pitch

The production of granulated high-temperature coal-tar pitch has been successfully introduced at the Karaganda Metallurgical Combine. This material is used as a thermal plasticizing agent in the production of refractories, especially those used to line blast-furnace notches.