Flow batteries with solid energy boosters

Adding solid electroactive materials as energy boosters to flow battery tanks provides a path to electrical energy storing systems with unprecedently high specific energy and specific power, that can solve the needs of both automotive and stationary energy storage markets. This work reviews the physical and chemical principles behind this new class of flow batteries, the history of this technology, and the most promising research directions

Double-cavity Fabry-Perot resonators based on one-dimensional silicon photonic crystals

This is the final version. Available from AIP Publishing via the DOI in this record.The 3rd Joint International Conference on Energy Engineering and Smart Materials (ICEESM-2018) and International Conference on Nanotechnology and Nanomaterials in Energy (ICNNE-2018)In this work we report on optical properties of Fabry-Pérot (FP) resonator based on Si-air one-dimensional photonic crystal (1D PC) with coupled double-cavity modes (or defects). These defects obtained by infiltration of the air-cavities of refractive index (nAir) with the filler of tunable refractive index. In the periodic structure of 1D PC, the filling of two defined grooves with a filler with a refractive index different from nAirleads to the appearance of two resonant modes, the position of which can be adjusted purposefully with changing of n filler. In comparison with (λ / 2) air resonators, the splitting of the doublet increases, which is explained by the increase in the coupling between the resonant modes due to the decrease in reflection R of the internal mirror. The coupled FP resonators design is CMOS compatible and has potential for application in tuning of individual transmission bands in wave-division multiplexing systems as well as for multiple narrow filters in the wide infrared spectral range.We acknowledge financial support from: The Engineering and Physical Sciences Research Council (EPSRC) of the United Kingdom via the EPSRC Grant No. EP/NO35569/1, and the Royal Society International Exchange Grant 2015/R3. The part of this research at the Ioffe Institute was supported by the Russian Federal Agency of Scientific Organizations

Transient Cherenkov radiation from an inhomogeneous string excited by an ultrashort laser pulse at superluminal velocity

An optical response of one-dimensional string made of dipoles with a periodically varying density excited by a spot of light moving along the string at the superluminal (sub-luminal) velocity is theoretically studied. The Cherenkov radiation in such system is rather unusual, possessing both transient and resonant character. We show that under certain conditions, in addition to the resonant Cherenkov peak another Doppler-like frequency appears in the radiation spectrum. Both linear (small-signal) and nonlinear regimes as well as different string topologies are considered.Comment: accepted to Phys. Rev.

Socio-economic factors in the spread of SARS-COV-2 across Russian regions

Relevance. The worldwide spread of a new infection SARS-CoV-2 makes relevant the analysis of the socio-economic factors that make modern civilization vulnerable to previously unknown diseases. In this regard, the development of mathematical models describing the spread of pandemics like COVID-19 and the identification of socio-economic factors affecting the epidemiological situation in regions is an important research task.Research objective. This study seeks to develop a mathematical model describing the spread of COVID-19, thus enabling the analysis of the main characteristics of the spread of the disease and assessment of the impact of various socio-economic factors.Data and methods. The study relies on the official statistical data on the pandemic presented on coronavirus sites in Russia and other countries, Yandex DataLens dataset service, as well as data from the Federal State Statistics Service. The data were analyzed by using a correlation analysis of COVID-19 incidence parameters and socio-economic characteristics of regions; multivariate regression – to determine the parameters of the probabilistic mathematical model of the spread of the pandemic proposed by the authors; clustering – to group the regions with similar incidence characteristics and exclude the regions with abnormal parameters from the analysis.Results. A mathematical model of the spread of the COVID-19 pandemic is proposed. The parameters of this model are determined on the basis of official statistics on morbidity, in particular the frequency (probability) of infections, the reliability of the disease detection, the probability density of the disease duration, and its average value. Based on the specificity of COVID-19, Russia regions are clustered according to disease-related characteristics. For clusters that include regions with typical disease-related characteristics, a correlation analysis of the relationship between the number of cases and the rate of infection ( with the socio-economic characteristics of the region is carried out. The most significant factors associated with the parameters of the pandemic are identified.Conclusions. The proposed mathematical model of the pandemic and the established correlations between the parameters of the epidemiological situation and the socio-economic characteristics of the regions can be used to make informed decisions regarding the key risk factors and their impact on the course of the pandemic

Learning analytics in massive open online courses as a tool for predicting learner performance

Learning analytics in MOOCs can be used to predict learner performance, which is critical as higher education is moving towards adaptive learning. Interdisciplinary methods used in the article allow for interpreting empirical qualitative data on performance in specific types of course assignments to predict learner performance and improve the quality of MOOCs. Learning analytics results make it possible to take the most from the data regarding the ways learners engage with information and their level of skills at entry. The article presents the results of applying the proposed learning analytics algorithm to analyze learner performance in specific MOOCs developed by Ural Federal University and offered through the National Open Education Platform. © 2018, National Research University Higher School of Economics.This study was support- ed by financial assis- tance provided under the Resolution of the Government of the Rus sian Federation No. 211, Contract No. 02. A03.21.0006. Translated from Russian by I. Zhuchkova

Experiments on Sonoluminescence: Possible Nuclear and QED Aspects and Optical Applications

Experiments aimed at testing some hypothesis about the nature of Single Bubble Sonoluminescence are discussed. A possibility to search for micro-traces of thermonuclear neutrons is analyzed, with the aid of original low-background neutron counter operating under conditions of the deep shielding from Cosmic and other sources of background. Besides, some signatures of QED-contribution to the light emission in SBSL are under the consideration, as well as new approaches to probe a temperature inside the bubble. An applied-physics portion of the program is presented also, in which an attention is being paid to single- and a few-pulse light sources on the basis of SBSL.Comment: 4 pages; to be published by AIP in the Proc. ISNA-1

Investigation of surface adhesion produced by high-speed flame spraying

Peculiarities of surface adhesion based on nickel, produced by high-velocity spraying on steel base with different surface morphology have been analysed. It is shown that ultrasound final polishing builds up wavy submicrorelief providing the reliable adhesive connection between covering and base. Ultrasound finite polishing is suggested as a method of preparing surface for high-speed flame