Optimal current quality of a single-phase multilevel inverter with a staircase modulation

The authors address the problem of optimal current quality for a single-phase multilevel inverter with a staircase modulation (Fig.1). The current quality is characterized by current ripple Normalized Mean Square (NMSc). The goal is to find theoretically optimal switching angles and respective minimal NMSc values. The previous research didn't provide comprehensive solutions for arbitrary modulation indices and level counts

Гидротермальный синтез моноструктурного LaPO4: морфология и структура

Область применения материалов на основе ортофосфата лантана (LaPO4), в том числе наноматериалов, в последнее время постоянно расширяется. Высокий уровень механических свойств и совместимость со многими оксидами позволяют рассматривать возможность ис­пользования ортофосфата лантана в качестве компонента композиционного материала кон­струкционного назначения. Такое применение особенно перспективно при использовании наночастиц с квазиодномерной морфологией (наностержней). Большая изоморфная ёмкость фазы на основе LaPO4 по отношению к щёлочноземельным ионам, ионам лантаноидов и акти­ноидов, высокая химическая и радиационная стойкость делают перспективным использова­ние этого соединения в качестве матрицы для иммобилизации радиоактивных отходов. В работе рассматривается возможность получения ортофосфата лантана (LaPO4) гидро­термальным методом. Приведены результаты исследования влияния рН, температуры и вре­мени обработки и гидротермального синтеза на морфологию и структуру моноструктурного фосфата лантана. Установлено, что с ростом рН меняется морфология фосфата и размеры кристаллитов, при этом наблюдается переход кристаллической структуры с гексагональной в моноклинную

Substantiation of Parameters for the Inertial Mixer in A Biodiesel Production Reactor

This paper reports results of the theoretical and experimental studies into the processes of transesterification of oils with methyl alcohol, which determined the material balance and established the molecular weight of the components involved in the process of transesterification as input and output products. The theoretical and experimental studies were carried out to calculate the indicators of the process of transesterification of fat-containing wastes depending on a change in the reaction duration and diameter of the inertial mixer of the reactor to accelerate the process of transesterification of oils with methyl alcohol. The process of transesterification is one of the basic methods for modifying the molecular composition of fat raw materials. With transesterification, the composition of fat fatty acids does not change, their statistical redistribution occurs in a mixture of triacylglycerols, which leads to a change in the physicochemical properties of fat mixtures as a result of changes in molecular composition. Transesterification of high-melting animal and vegetable fats with methyl alcohol improves the conversion of oils for the production of biodiesel from fat-containing waste. The results of the theoretical and experimental studies have helped determine the value of the flow rate of the reaction mixture, as well as the values of the geometric dimensions of the reactor, were determined (the diameter of the mixer, d=100÷500 mm; the length of the reactor is 1.5÷2.0 m). Processing of the reaction mixture made it possible to obtain a high degree of homogeneity in the concentration of components with large diameters of the inertial mixer ‒ 300...500 mm at average rotational speeds. The oil conversion has been improved, as well as productivity, by using equipment to produce biodiesel from fat-containing waste. Optimal pump performance is also ensured with minimal power consumption and reactor operatio

Gravitino and Polonyi production in supergravity

International audienceWe study production of gravitino and Polonyi particles in the minimal Starobinsky-Polonyi $\mathcal {N}=1$ supergravity with inflaton belonging to a massive vector supermultiplet. Our model has only one free parameter given by the scale of spontaneous SUSY breaking triggered by Polonyi chiral superfield. The vector supermultiplet generically enters the action non-minimally, via an arbitrary real function. This function is chosen to generate the inflaton scalar potential of the Starobinsky model. Our supergravity model can be reformulated as an abelian supersymmetric gauge theory with the vector gauge superfield coupled to two (Higgs and Polonyi) chiral superfields interacting with supergravity, where the U(1) gauge symmetry is spontaneously broken. We find that Polonyi and gravitino particles are efficiently produced during inflation, and estimate their masses and the reheating temperature. After inflation, perturbative decay of inflaton also produces Polonyi particles that rapidly decay into gravitinos. As a result, a coherent picture of inflation and dark matter emerges, where the abundance of produced gravitinos after inflation fits the CMB constraints as a Super Heavy Dark Matter (SHDM) candidate. Our scenario avoids the notorous gravitino and Polonyi problems with the Big Bang Nucleosynthesis (BBN) and DM overproduction