Mathematical knowledge ontologies and recommender systems for collections of documents in physics and mathematics

© 2016, Pleiades Publishing, Ltd.An approach to the implementation of a recommender system based on ontologies of mathematical knowledge is presented. On the basis of a document browsed by a user, the system forms on line a list of recommendations, which include similar documents, key words, and definitions of these words from ontology and other terminological sources. The method of recommendations yields a vector representation of documents, taking into account the position of terms in the logical structure of the document and their ontological connections. On the basis of the cosine measure, a measure of proximity between documents is calculated. The order of documents in the list of recommendations is determined by values of the proximity measure. Various adaptations of the system to user scenarios aimed at the preparation of personalized recommendations are discussed

Protective Nanocomposite Vacuum Coatings Deposited by Separated Plasma Flows

The way of generation of protective nanostructure vacuum coatings by separated plasma flows was investigated. In order to limit the crystallite growth in the coatings the compound of the growing condensate was doped by Al. Nanocrystalline (Ti,Al)N coatings with grain size 10-20 nm and microhardness 35-40 GPa by means of vacuum-arc deposition technique from the separated plasma flows were obtained. It was determined that purposeful alloying improved operational coatings properties, and allowed using them as protective layers, deposited on the working surfaces of the cutting tools during timber-based material processing

Giant and tunable excitonic optical anisotropy in single-crystal CsPbX3_3 halide perovskites

During the last years, giant optical anisotropy demonstrated its paramount importance for light manipulation which resulted in numerous applications ranging from subdiffraction light guiding to switchable nanolasers. In spite of recent advances in the field, achieving continuous tunability of optical anisotropy remains an outstanding challenge. Here, we present a solution to the problem through chemical alteration of the ratio of halogen atoms (X = Br or Cl) in single-crystal CsPbX$_3$ halide perovskites. It turns out that the anisotropy originates from an excitonic resonance in the perovskite, which spectral position and strength are determined by the halogens composition. As a result, we manage to continually modify the optical anisotropy by 0.14. We also discover that the halide perovskite can demonstrate optical anisotropy up to 0.6 in the visible range -- the largest value among non-van der Waals materials. Moreover, our results reveal that this anisotropy could be in-plane and out-of-plane, depending on perovskite shape -- rectangular and square. Hence, it can serve as an additional degree of freedom for anisotropy manipulation. As a practical demonstration, we created perovskite anisotropic nanowaveguides and show a significant impact of anisotropy on high-order guiding modes. These findings pave the way for halide perovskites as a next-generation platform for tunable anisotropic photonics.Comment: 18 pages, 3 figure

Многокомпонентные защитные покрытия, осаждаемые вакуумно-дуговым методом

A way of generation of protective nanostructural coatings from separated multicomponent plasma flows is suggested. The influence of elemental composition on their structure-mechanical characteristics was studied. It's found, multicomponent coatings are characterized by the dense super fine-grained structure, possess enhanced antifriction and anticorrosion properties in comparison with nitride titanium coatings.Для формирования защитных наноструктурированных покрытий предложен способ осаждения из сепарированных многокомпонентных потоков. Изучено влияние элементного состава покрытий на их структурно-механические характеристики. Определено, что многокомпонентные покрытия характеризуются плотной, ультрамелкозернистой структурой, обладают улучшенными антифрикционными и антикоррозионными свойствами по сравнению с покрытиями из нитрида титана

СПОСОБЫ УПРАВЛЕНИЯ СТРУКТУРНЫМ СОСТОЯНИЕМ ЗАЩИТНЫХ ВАКУУМНО-ДУГОВЫХ ПОКРЫТИЙ

The paper has investigated two methods pertaining to formation of  protective nano-structural vacuum coatings while using separated plasma flows. A comparatively technologically simple control method for crystallite size in the direction of coating growth has been developed in the paper. The method is based on the deposition of individual thin layers of high-melting  compounds of transition metals from separated plasma flows and periodical  bombardment of condensates formed by an ion flow. The executed X-ray diffraction analysis has shown that an application of the given method  makes it possible to reduce size of a coherent-scattering area up to 10–15 nm and ensure an increase of micro-hardness and corrosion resistance of the deposited coatings. Nano-crystalline Ti–Cr–N coatings with crystallite size of 10–20 nm have been obtained while applying a vacuum-arc deposition technique from  separated plasma flows. The paper demonstrates that purposeful alloying improves operational coating properties that allows to use the coatings  as protective layers which are deposited on the working surfaces of cutting tools.Исследованы два способа формирования защитных наноструктурных вакуумных покрытий с использованием сепарированных плазменных потоков. Разработан сравнительно простой в технологическом исполнении способ управления размерами кристаллитов в направлении роста покрытия, основанный на осаждении индивидуальных тонких слоев тугоплавких соединений переходных металлов из сепарированных плазменных потоков и периодической бомбардировкой сформированных конденсатов потоком ионов. Проведенные рентгеноструктурные исследования показали, что применение данного способа позволило как снизить размер областей когерентного рассеяния до 10–15 нм, так и обеспечить повышение микротвердости и коррозионной стойкости сформированных покрытий. Методом вакуумно-дугового осаждения из сепарированных плазменных потоков получены нанокристаллические покрытия Ti–Cr–N c размером кристаллитов 10–20 нм. Установлено, что целенаправленное легирование улучшает эксплуатационные свойства покрытий, что позволяет использовать их в качестве защитных слоев, осажденных на рабочие поверхности режущих инструментов

Особенности структурообразования вакуумно-дуговых покрытий на основе TiN

The structure and the phase composition of the TiN-based vacuum arc coatings alloyed by chromium and copper deposited from the separated plasma flows are investigated. It is determined, that multicomponent (Ti, Cr)N coatings represent the substitutional solution with fcc lattice on the base of titanium nitride It is established, that multicomponent TiN/Cu coatings consist of the basic nanocrystalline TiN phase, and the thin layer of the second Cu phase is on the grain boundary of the TiN phase and it blocks the grain growth of the main phase It is found, that the residual stresses in the coatings are considerably high - 15-17 GPa for (Ti, Cr)N and 9-10 GPa for TiN/Cu. It is determined, that the addition of the alloying element reduces the coherent-scattering region size to 6 nm - (Ti, Cr)N and to 20 nm - TiN/Cu in comparison with 30-40 nm for TiN.Приведены результаты исследований структуры и фазового состава вакуумно-дуговых покрытий на основе TiN, легированных хромом и медью, осажденных из сепарированных плазменных потоков. Установлены особенности структу-рообразования многокомпонентных покрытий в зависимости от вида легирующего элемента. Рассчитаны остаточные напряжения и определены размеры зерен в покрытиях

Mathematical knowledge ontologies and recommender systems for collections of documents in physics and mathematics

© 2016, Pleiades Publishing, Ltd.An approach to the implementation of a recommender system based on ontologies of mathematical knowledge is presented. On the basis of a document browsed by a user, the system forms on line a list of recommendations, which include similar documents, key words, and definitions of these words from ontology and other terminological sources. The method of recommendations yields a vector representation of documents, taking into account the position of terms in the logical structure of the document and their ontological connections. On the basis of the cosine measure, a measure of proximity between documents is calculated. The order of documents in the list of recommendations is determined by values of the proximity measure. Various adaptations of the system to user scenarios aimed at the preparation of personalized recommendations are discussed