Physical experiments and mathematical modeling are used to study the kinetics of the reactions of carbon dioxide and water with potassium superoxide accompanied by oxygen release at various values of ...the temperature and humidity of the breathing gas mixture. The kinetics of the chemisorption is demonstrated to be limited by the rate of air regeneration in an airtight habitable facility. Experimental and analytical approaches are applied to determine the kinetic coefficients of the chemical reactions using the experimental data and a mathematical model of chemisorption kinetics. To perform the above chemical reactions, an original-design chemisorption reactor was developed, which contains plates with potassium superoxide nanocrystalline fixed on the fibers and pore surface of a fibrous polymer matrix. A mathematical model of chemical air regeneration is developed to calculate the guaranteed values of the parameters of the reactor and the protective effect time of the chemisorbent during which, at a given load, the reactor provides the appropriate concentrations of oxygen and carbon dioxide in the breathing gas mixture in an airtight habitable.
A task-oriented software and hardware system is designed for the operational selection of the instrumentation and process design options of pressure swing adsorption (PSA) processes. It will also ...control physical experiments to study the kinetics and dynamics of adsorption purification and separation of multicomponent gas mixtures and carry out mathematical modeling, optimization of operating cycles and optimal design of energyand resource-saving PSA units. The possibilities of a task-oriented system are demonstrated on the example of the adsorption separation of atmospheric air in order to obtain oxygen of high purity: 1) the time required to obtain, analyze and process experimental data (isotherms, kinetics and dynamics of adsorption, tuning the operating modes of PSA processes in the separation of gas mixtures, etc.), necessary for designing, identifying and analyzing the adequacy of mathematical models, were reduced by three times; 2) the time spent on mathematical modeling, the formulation and solution of the problems of optimization and optimal design of industrial PSA units in conditions of partial uncertainty of the initial data, as well as an experimental verification of the optimization results of these processes in a test unit , were reduced 8 times.
We report on a strong nonlinear behavior of the photogalvanics and photoconductivity under excitation of HgTe quantum wells (QWs) by intense terahertz (THz) radiation. The increasing radiation ...intensity causes an inversion of the sign of the photocurrent and transition to its superlinear dependence on the intensity. The photoconductivity also shows a superlinear raise with the intensity. We show that the observed photoresponse nonlinearities are caused by the band-to-band light impact ionization under conditions of a photon energy less than the forbidden gap. The signature of this kind of impact ionization is that the angular radiation frequency ω=2πf is much higher than the reciprocal momentum relaxation time. Thus the impact ionization takes place solely because of collisions in the presence of a high-frequency electric field. The effect has been measured on narrow HgTe/CdTe QWs of 5.7 nm width; the nonlinearity is detected for linearly and circularly polarized THz radiation with different frequencies ranging from f=0.6 to 1.07 THz and intensities up to hundreds of kW/cm2. We demonstrate that the probability of the impact ionization is proportional to the exponential function, exp(−E02/E2), of the radiation electric field amplitude E and the characteristic field parameter E0. The effect is observable in a wide temperature range from 4.2 to 90 K, with the characteristic field increasing with rising temperature.
Abstract
The analysis of the content of pigments in the stems of clonal apple rootstocks bred by Michurinsky State Agrarian University showed a high content of anthocyanins (more than 200 mg/100 g ...for rootstock 54-118). When determining the qualitative composition, it was revealed that anthocyanins in the stems of the rootstocks are represented by three groups, while there are differences in the shape of the rootstocks. As a source of pigment production, it is necessary to select rootstocks with a high endogenous synthesis of anthocyanins (i.e. red-leaved forms 54-118, 57-491, 98-7-77, etc.), during the cultivation of which, in addition to the main product—detachable rooted cuttings-one can additionally receive from 3 to 10 kg of anthocyanin dyes from 1 hectare of mother plant.
We report on the observation of terahertz radiation induced photoconductivity and of terahertz analog of the microwave-induced resistance oscillations (MIRO) in HgTe-based quantum well (QW) ...structures of different width. The MIRO-like effect has been detected in QWs of 20 nm thickness with inverted band structure and a rather low mobility of about 3 × 105 cm2/V s. In a number of other structures with QW widths ranging from 5 to 20 nm and lower mobility we observed an unconventional nonoscillatory photoconductivity signal which changes its sign upon magnetic field increase. This effect was observed in structures characterized by both normal and inverted band ordering, as well as in QWs with critical thickness and linear dispersion. In samples having Hall bar and Corbino geometries an increase of the magnetic field resulted in a single and double change of the sign of the photoresponse, respectively. We show that within the bolometric mechanism of the photoresponse these unusual features imply a nonmonotonic behavior of the transport scattering rate, which should decrease (increase) with temperature for magnetic fields below (above) the certain value. This behavior is found to be consistent with the results of dark transport measurements of magnetoresistivity at different sample temperatures. Our experiments demonstrate that photoconductivity is a very sensitive probe of the temperature variations of the transport characteristics, even those that are hardly detectable using standard transport measurements.
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