Dielectric model of point charge defects in insulating paraelectric perovskites

Some point defects (i.e., oxygen vacancies) create deep trapping levels in the bandgap of the paraelectric phase ferroelectric crystals. Under applied DC field the traps release electrons via the Poole-Frenkel mechanism and become charged. The electric field of a point charge polarizes the crystal locally reducing its permittivity. In this paper a simple theory is proposed for calculating the DC field dependent apparent (measureable) permittivity of a paraelectric crystal with point charge defects. It is shown that the apparent permittivity of a paraelectric crystal may be sufficiently lower as compared with the defectless crystal. This reduction is in addition to the possible reduction of the apparent permittivity associated with the interfacial "dead" layers and strain

Nonlinear Deformation of Structure Elementsfrom Different Materials under Impulse and Shock Loads

simulation of high-rate deformation processes, three-dimensional models are used. The following determined relationships are taken into account: elastic-plastic deformation (according to the theory of dynamic plastic deformation); the dynamic properties of the materials, which change during deformation; the finite displacements and deformations. The problem is solved by the finite elements method. The paper analyzes the impact of pulse and shock loads performed on the elements of various constructions made of different materials. Comparison of the research results shows that the elements from the improved composite material possess both the required strength and lowest weight. Furthermore, the experimental and numerical results are compared as an example of the influence of the impulse load on the composite material plate with a cut. The paper shows the features of the distribution and localization of the stress intensity and displacements at the impulse and impact loading in the multi-layered structural elements. The deformation processes occur in different stages up to the elastic-plastic finite deformations depending on the speed of the projectile. The results of these studies were used in the analysis of the dynamic strength of real structural elements

Oxidative detoxification of organomercury pesticides

A method of oxidative mineralization of the organomercury granozan pesticide commercial form under mild conditions was investigated. The product components of hazard class 1 were destructed to the low-toxic compounds in the electrolyte under the oxidants electrochemically formed in situ in sulphuric acid solutions of pesticide. Simultaneously, at the cathode, the mercury ions formed as a result of the pesticide organic component destruction process reduce up to more than 90%

Ultrasound-assisted green solvent extraction of high-added value compounds from microalgae Nannochloropsis spp.

The aim of this work was to investigate ultrasound (US)-assisted green solvent extraction of valuable compounds from the microalgae Nannochloropsis spp. Individual green solvents (water, ethanol (EtOH), dimethyl sulfoxide (DMSO)) and binary mixture of solvents (water-DMSO and water-EtOH) were used for the extraction procedures. Maximum total phenolic compounds yield (Yp 0.33) was obtained after US pre-treatment (W = 400 W, 15 min), being almost 5-folds higher compared to that found for the untreated samples and aqueous extraction (Yp 0.06). The highest yield of total chlorophylls (Yc 0.043) was obtained after US (W = 400 W, 7.5 min), being more than 9-folds higher than those obtained for the untreated samples and aqueous extraction (Yc 0.004). The recovery efficiency decreased as DMSO > EtOH > H2O. The optimal conditions to recover phenolic compounds and chlorophylls from microalgae were obtained after US pre-treatment (400 W, 5 min), binary mixtures of solvents (water-DMSO and water-EtOH) at 25–30%, and microalgae concentration of 10%

Technological features of manufacturing an arched gears

Розглянуто технологічні особливості виготовлення та умови обробки загартованих аркових циліндричних зубчастих передач і арочних конічних передач з зачепленням М. Л. Новікова. Розроблена методика вибору конструкторсько-технологічних вимог аркових передач і система “РНС-1” геометричного розрахунку циліндричних, конічних і рейкових передач з арковими зубцями, а також уніфікація і скорочення номенклатури засобів виробництва. Проведені стендові випробування арочних зубчастих передач дозволили створити універсальний ріжучий інструмент з круглими незатылованными різцями.Purpose. Technological peculiarities of production and conditions of hardened cylindrical arched gears and arched bevel gears with meshing M. L. Novikova. Design/methodology/approach. Developed methodology for selection of design and technological requirements of the arched guide and the system "IR-1" geometric calculation of cylindrical, bevel and pinion gear with arched teeth, as well as unification and reduction of the range of the means of production. Bench tests of the arched gear has allowed us to create a versatile cutting tool with a round niesatynowany cutters. Conical spur, helical and herringbone gear, along with the advantages are inherent operational and technological disadvantages and in some cases do not satisfy the increasing requirements of modern gears to ensure smoothness, durability, reliability. The purpose of the design and process conditions for manufacturing an arched gears. Study of the technological features of manufacturing arched teeth at the present time is a real reserve for further enhancing the efficiency of gears and means for their production. Findings. Arched teeth allow to increase the load capacity of 1.25-1.5 times and durability in 2 - 3 times a cylindrical and a rack and pinion transmission, to reduce vibration, noise characteristics, intensity and cost. Originality/value. Arched teeth allow you to create a single technological system tools for the production of cylindrical, bevel and pinion gears provide smooth transmission of motion and can find application in high-speed high-load transmission.Рассмотрены технологические особенности изготовления и условия обработки закаленных цилиндрических арочных зубчатых передач и арочных конических передач с зацеплением М.Л. Новикова. Разработана методика по выбору конструкторско-технологических требований арочных передач и система “РНС-1” геометрического расчета цилиндрических, конических и реечных передач с арочными зубьями, а также унификация и сокращение номенклатуры средств производства. Проведенные стендовые испытания арочных зубчатых передач позволили создать универсальный режущий инструмент с круглыми незатылованными резцами