Defect-induced fracture topologies in Al₂O₃ ceramic-graphene nanocomposites

Models of ceramic-graphene nanocomposites are used to study how the manufacturing process-dependent arrangement of reduced graphene oxide (rGO) inclusions governs nano-crack network development. The work builds upon recent studies of such composites where a novel combinatorial approach was used to investigate the effect of rGO arrangements on electrical conductivity and porosity. This approach considers explicitly the discrete structure of the composite and represents it as a collection of entities of different dimensions - grains, grain boundaries, triple junctions, and quadruple points. Here, the combinatorial approach is developed further by considering the effects of rGO agglomerations, stress concentrators and adhesion energies on intergranular cracking. The results show that the fracture networks can be effectively controlled by the local ordering of rGO inclusions to allow for a concurrent increase in the strength and conductivity of the ceramic composites. It is shown that the ratio of local stress concentrators related to rGO inclusions and cracks is the most significant factor affecting the nano-crack network topology. The local spatial arrangement of rGO inclusions becomes an effective tool for controlling nano-crack network topology only when this ratio approaches one. It is anticipated that these results will inform future design of toughness-enhanced composites

How long does it take to pull an ideal polymer into a small hole?

We present scaling estimates for characteristic times $\tau_{\rm lin}$ and $\tau_{\rm br}$ of pulling ideal linear and randomly branched polymers of $N$ monomers into a small hole by a force $f$. We show that the absorbtion process develops as sequential straightening of folds of the initial polymer configuration. By estimating the typical size of the fold involved into the motion, we arrive at the following predictions: $\tau_{\rm lin}(N) \sim N^{3/2}/f$ and $\tau_{\rm br}(N) \sim N^{5/4}/f$, and we also confirm them by the molecular dynamics experiment.Comment: 4 pages, 3 figure

Fermionic construction of partition function for multi-matrix models and multi-component TL hierarchy

We use $p$-component fermions $(p=2,3,...)$ to present $(2p-2)N$-fold integrals as a fermionic expectation value. This yields fermionic representation for various $(2p-2)$-matrix models. Links with the $p$-component KP hierarchy and also with the $p$-component TL hierarchy are discussed. We show that the set of all (but two) flows of $p$-component TL changes standard matrix models to new ones.Comment: 16 pages, submitted to a special issue of Theoretical and Mathematical Physic

Review of integral transformations applied in the tasks of analysis and synthesis of electric drive systems

The paper presents set of integral transformations that can potentially be used to obtain spectral representations of signals of automatic systems. The advantages and disadvantages of the considered transformations for the ACS class, characteristic for the electric drive, are indicated.В данной статье рассмотрен набор интегральных преобразований, которые потенциально могут быть использованы для получения спектральных представлений сигналов автоматических систем Обозначены преимущества и недостатки рассмотренных преобразований для класса САУ, характерных для электропривода

Development of competence for the discipline «Microprocessor technics» based on FPGA Altera company Cyclone III series

Рассматриваются сравнительные характеристики ПЛИС с другими логическими устройствами и целесообразность развития направления и добавления в курс «Микропроцессорная техника» материала для изучения программируемых логических интегральных схем.Consider the comparative characteristics of the FPGA logic with other devices, and the feasibility of the development direction and adding to course "Microprocessor technics" of the material for the study of FPGA

Synthesis of electric speed controller in the spectral region.

Рассматривается общий порядок и структура алгоритмов решения основной задачи анализа систем управления различных классов при детерминированных воздействиях.We consider the general order and structure of algorithms for solving the basic problems of the analysis of different classes of control systems for deterministic effects

Development of setup for predictive testing stator insulation of electrical machines

The article discusses the approach to construction of system of diagnostics of the basic insulation of electrical machines. Discusses the structure of the experimental installation, allowing to organize non-destructive predictive control of insulation of electrical machines. Given the equivalent circuit of the insulation used in foreign sources. The methods of determination of equivalent circuit parameters.В статье рассматривается подход к построению системы диагностики базовой изоляции электрической машины. Обсуждается структура экспериментальной установки, позволяющая организовать неразрушающий прогностический контроль изоляции электрической машины. Приведена схема замещения изоляции, применяемая в зарубежных источниках. Рассмотрены методы определения параметров схемы замещения