bluuebunny/crossref_metadata_2025 huggingface dataset:
Electrical Resistivity and Half-Cell Potential Studies to assess organic and inorganic corrosion inhibitors’ effectiveness in concrete
Authors: Reddy V Srinivasa , Trimurty Naidu K Satya Sai , Rao M V Seshagiri , Shrihari S
Published: August 2020

Very limited guidelines are available on the use of corrosion resistant inhibitors as a constituent material in concrete due to availability of statistics on its corrosion inhibiting efficiency. So the study is conducted on the M25 grade concrete mixed with few selected corrosion inhibitors of organic and non-organic nature to comprehend the impact of these corrosion inhibitors on the conductivity of electricity in these concretes. Based on the other researchers’ work, four well know corrosion inhibitors such as Calcium nitrate, Di-ethanolamine, Sodium nitrite and Hexamine and are chosen for study. Dosages of 1%, 2%, 3%, 4% and 5% the weight of cement are chosen. Measured electrical resistivity and half-cell potential values of all corrosion inhibitors admixed M25 grade concrete mixes indicates the superior corrosion inhibition ability of calcium nitrate and Di-ethanolamine’s with shows high electrical resistance.
Effect of Recycled Aggregates on Strength and performance of Recylced Aggregate Concrete
Authors: Mallikarjuna Reddy Dr.V. , Swaroop M. Manikanta Sai
Published: August 2020

This study is taken up to utilise the recycled coarse aggregate and recycled fine aggregate as replacement of natural aggregate in concrete mix. It is required to find the percentage of recycled coarse aggragate and recycled fine aggregate, as the strength of concrete can not be achieved by using higher percentaged. The purpose of study is to compare between recycled coarse aggregate and recycled fine aggregate with natural coarse aggregate and sand in terms of specific gravity, water absorption, particle size distribution. Further, this stydy will also consider the difference between the performance of Recycled Aggregate Concrete for different percentages of recycled coarse aggregate and recycled fine aggregate i.e for 0%, 10%, 15%, 20%, 25%, 30%, 35% replacement. The present study is an experimental investigation on the behaviour of recycled aggregate concrete (coarse& fine aggregates) with respect to the strength and performance.
Effect of Review elevated temperature on geo-polymer concrete – A Review
Authors: Chandrakanth V , Koniki Srikanth
Published: August 2020

The study on the effect of elevated temperature on Geo-polymer concrete (GPC) got its significance because conventional concrete start to deteriorate around 4000C. GPC gains attention as it is eco-friendly and economical, by utilizing industrial by-products. GPC also an alternate solution as the raw materials to produce cement are depleting day by day. GPC gains strength by geo-polymerization with the reactions between mineral admixtures and alkaline solutions. This paper presents the studies on general properties and advantages of GPC over conventional concrete which depend on properties of binder, type of curing etc. Current study mainly concentrates on effect of elevated temperatures and post fire properties of GPC depending upon rate of heating, duration of fire and maximum high temperature. Strength and durability recovery of fire damaged concrete is discussed.
Experimental Investigation on Workability and Density of Medium-Range Foam Concrete with Hybrid Fibers
Authors: Satyanarayana Dr. G.V.V. , Mahesh G.
Published: August 2020

As the unit weight of conventional concrete ranges from 2200-2400 kg/m3. But, foam concrete unit weight ranges from 350-1900 kg/m3. Today the foam concrete becomes popular due to easily workable, low density and economical when compared to conventional concrete. The foam concrete is considered as sustainable construction material as it having low thermal conductivity and sound insulation. This investigation involves the preparation of foam concrete with a density of 1000 kg/m3 and mixed with hybrid fibers such as polypropylene fibers and Nylon fibers to reinforce the mix. This investigation studies the mechanical properties such as compressive and tensile strength at different volume fractions of Polypropylene fibers that is at 0%,0.5%, 0.75% and 1% also with a combination of hybrid fibers fraction such as (0.75% of PF + 0.25% of NF), (0.25% of PF + 0.75% of NF) and 1% of nylon fibers were used. The foam concrete was mixed with designed proportions and thereafter tested for flow ability that is workability, plastic density, dry density against standard specimens.
Investigation on Workability Of M20 Grade Concrete With Partial Replacement Of Crumb Rubber And M Sand For Fine Aggregates And Flyash For Cement
Authors: Raj P.Santhi , Satyanarayana G.V.V. , Sriharshavarma M.
Published: August 2020

Concrete has a key role in construction. Study focus on workability of the concrete, Fine Aggregate is partially filled with crumb rubber and M sand, a part of cement is replaced with fly ash. In this investigation the crumb rubber is utilised in place of fine aggregate. The scrap tyre treatment is currently a serious issue against environmental pollution. India stud in forth position in the entire world for rubber tyre market world after china, Europe and the US. Fly ash and M sand is an industrial waste which is included in the concrete. In this investigation workability of concrete is conducted on M20 grade concrete by replacing river side sand with the M sand and crumb rubber at percentage of replacements 0 to 20% at an regular interval of 5%and Compare the results obtained by the modified concrete with the normal concrete.
Effect of basalt fibre on the mechanical properties of M70 grade high performance concrete
Authors: Singh V Ram , Reddy V Srinivasa , Shrihari S , Srikanth T
Published: August 2020

The presented work reveals the strength properties of M70 grade high performance basalt fibre reinforced concrete (BFRCC) containing 0.2%, 0.3% and 0.4% basalt fibre content by volume of concrete. 10% Silica fume is admixed for attaining higher strengths as preferred. Compressive, split-tensile and flexural strengths are evaluated. The BFRCC microstructure is found to be improved due to enrichment of interfacial transition zone with chopped basalt fibres. It was found that different fibre lengths require different dosages to yield maximum effect on the properties of concrete. Stress- strain responses of M70 grade BFRSCC yields improved ultimate strain and strain at peak load indicating its energy dissipation capacity at fracture.
Effect of Organic and Inorganic Corrosion Inhibitors on Strength Properties of Concrete
Authors: Srinivasa Reddy V , Prashanth Thoodi , Raju V S P , Prashanth P
Published: August 2020

In the current study, the M25 grade concrete mixes are admixed with various locally available organic and non-organic corrosion inhibitors such as Calcium Nitrite, Sodium Nitrite, Hexamine and Di-ethanolamine to understand the influence of these organic and non-organic corrosion inhibitors on the strength and corrosion resistance properties of concrete. The percentage dosage of admixed inhibitors vary from 1 to 5% by the weight of cement. For M25 grade concrete the optimum percentages of corrosion inhibitor admixture was found to be 4% for Calcium Nitrite, 3% for Sodium Nitrite, 2% for Hexamine and 3% for Di-ethanolamine. Calcium Nitrite corrosion inhibitor admixture imparts increased compressive, split- tensile and flexural strength than other corrosion inhibitors at 28 days. All the corrosion inhibitors used in the study have enhanced the compressive strength, split tensile strength, and flexural strength of concrete. The initial gain of early strength decreased due to anodic process of inhibitors. Measured electrical resistivity and half-cell potential values of all corrosion inhibitors admixed M25 grade concrete mixes directs that calcium nitrate and Di-ethanolamine have shown high electrical resistance indicating their superior corrosion inhibition ability than sodium nitrite and hexamine. Accelerated corrosion test on reinforced concrete beams admixed with corrosion inhibitors confirmed that possible inception of corrosion in calcium nitrate admixed reinforced concrete beams is very low when compared to other corrosion inhibitors used for the study.
Digital learning: Realities and Perspectives of a New Trend
Authors: Shushara Tatyana V. , Ustinova Yuliya D. , Braslavskaya Elena A. , Lopashova Yuliya A. , Plitka Viktor I.
Published: August 2020

The relevance of the research is determined by the need to study the problem of education digitalization in order youth to self-identify themselves in the modern society, as well as by insufficient development of theoretical, content and scientific aspects of this issue. The article is to highlight the current state and future prospects of education digitalization. The purpose of the article is to study the features of education digitalization at the current stage and to define its perspectives. The main research methods used are theoretical ones, since they provide the opportunity to consider the modern problem of education digitalization as a holistic process and to reveal its future prospects. The article presents the analysis of the current state of education digitalization and future prospects of this process. The overview of the research issue is oriented to the study of education digitalization prospects in order youth to self-identify themselves in the modern society. The research is also focused on the elaboration of methodological recommendations concerning this problem.
About the Impact of The Concept Of E-Government on Modern Education in Russia
Authors: Mikryukov Vladimir Olegovich , Melkov Sergey Anatolevich , Sushanskiy Artur Sergeevich , Kholikov Ivan Vladimirovich , Gruver Nadezhda Vsevolodovna
Published: August 2020

The hermeneutics of the concept of “e-government” is implemented, and the results are interpreted in the article using the method of expert survey. The goal of the study was to find out the relation between the digitalization of public administration in modern Russia and higher education. The conclusions on the impact of the concept of e-government on Russian education have been drawn, based on the interpretation of the experts’ answers. Some conclusions from a pedagogical experiment conducted on an ongoing basis at the Academy of Civil Defense of the Ministry of the Russian Federation for Civil Defense, Emergencies and Elimination of Consequences of Natural Disasters since 2016 have been also provided in the article. The goal of this experiment is to find out which pedagogical and information technologies are the most efficient for teaching at a university. The authors are confident that the problems of the mutual influence of the e-government and modern education in Russia described in the article are inexhaustible and will be continued by them.
Distance Learning: Theory and Practice
Authors: Muraveva L.A.
Published: August 2020

This article discusses the process of active implementation of online learning modes based on digital technologies. Currently available theoretical postulates and recommended procedures of learning activities have been verified in practice during the course in History in Financial University under the Government of the Russian Federation. On this basis, certain experience of seminar classes has been accumulated (online conversations, discussions, presentations, webinars), this article is devoted to its analysis and generalization. The author has concluded that digital technologies diversify the classes and possess numerous tools to enhance motivation of students. The obtained results make it possible to state that application of several methods has been activated, such as brainstorming, mind games, metal mapping, interactive enquiries, testing and guessing games using learning platforms, for instance: Kahoot. Meanwhile, well balanced combination of the existing conventional learning modes and modern digital technologies makes it possible to provide even greater effect and result.
Metrics for Personal Profiles of Social Network Users
Authors: Nikolaev Konstantin Sergeevich , Gafarov Fail Mubarakovich , Ustin Pavel Nikolaevich
Published: August 2020

This paper discusses the technical details of obtaining and processing data to determine a set of characteristics of texts from social networks, genre preferences in movies and music genres for students of Kazan Federal University who have different academic performance (successful, average, not-successful). The selection of such characteristics is carried out using machine learning methods (Word2Vec, tSNE). The data obtained is used in the development of a functional psychometric model of cognitive behavioral predictors of an individual’s activity within the framework of their educational activities. We also developed a web application for visualizing the obtained data using the Flask engine.
Management of Educational and Cognitive Activities of The Future Teacher Through the Introduction of The Technology of Educational Animation Design
Authors: Punchyk Veranika , Murodhodjaeva Natalia , Averin Sergey , Varanetskaya Liudmila , Piatrutskaya Katsiaryna
Published: August 2020

The purpose of this paper is to describe the current method of managing the educational and cognitive activities of the future teachers in the process of general pedagogic training through the development and implementation of an original educational animation design technology. The attainment of this goal is presented in the paper in the logic of an innovative cycle, which reveals the genesis of its creation from an idea to practical approval. The authors used the following research methods: theoretical analysis, comparative analysis, ascertaining experiment, modeling, prototyping, pedagogical experiment, survey, observation, descriptive statistics. The authors describe the experience of implementing the educational animation designing technology in the process of general pedagogical training of future teachers (using the example of the Physics and Informatics program at the Belarusian State Pedagogical University named after Maxim Tank). At the end of the course, the students created original animated videos on physics as part of practical work in their pedagogy course. The potential of the developed technology as a means of managing the educational and cognitive activities of future teachers was implemented through the dominant diagnostic variable, i. e. the quality of the formed competencies in the Pedagogical systems and technologies course. As a result of the pedagogical experiment, it was confirmed that this technology allowed managing the educational and cognitive activities of modern students, helping to deal with mosaic thinking which is a specific feature of modern youth and that it was an effective technology for the general pedagogical preparation of a future teacher.
Digitalization of Technology for Expert Project Management of The School Environment Progression
Authors: Yasvin Witold Albertovich , Smirnova Polina Viktorovna , Peskov Vadim Pavlovich , Bulanova Irina Sergeevna
Published: August 2020

The article presents the issues of school environment expertise and discusses the possibilities and prospects of using digital tooling for its assessment in mass educational practice and scientific research. The proposed method of vector modeling of the environment of personality development allows determining the activity of the individual in mastering educational resources in various types of environments. This digital tooling allows school management teams and organizational consultants to conduct management and pedagogical analysis of the current status and complementarity of various system components of school environments with each other, as well as with the school’s mission, and implement their managerial and vocational design; to develop programs for the progression of school organizations based on environment methodology using expert project management technology; to carry out organizational and pedagogical consulting of schools taking into account the “built-in” nature of environments of various levels (the environment of the lesson, class, club, school, and educational complex).
Features of the organization of the educational process in the discipline “Civil Law” for students of the Military University of the Ministry of Defense of the Russian Federation
Authors: Barkov Alexey V. , Grishina Yana S. , Kiselev Alexander S. , Sokolov Alexeyh P.
Published: August 2020

The article focuses on the high legal educational role of the “Civil Law” discipline in the development of the social activity of the cadet’s personality. Difficulties in explaining the peculiarities of civil and legal relations to cadets with the participation of military organizations are determined. The current legislation does not take into account the special legal regime of the property of military organizations, due to the nature of the tasks being solved by the state. The thesis is developing that the graduate of the Military University should be ready to understand the current changes in the conditions of digitalization of the economy, constant improvement of skills, and sometimes retraining. The prospects of training practical skills through the participation of cadets in the legal clinic are noted. It is concluded that the digitalization of economics and law are the determining factors of influence on the educational process at the Military University.
Positive Management Tools in Education Management
Authors: Efremkina Irina Nikolaevna , Liksina Elena Vladimirovna , Liusev Valerii , Osipova Natalia Vladimirovna
Published: August 2020

The purpose of the study is to identify the problem areas in education management and the opportunities to apply positive management tools. The authors believe that it is possible to diminish the issues related to authoritarian education management by using the tools and principles of positive psychology, specifically, positive management connected to addressing the human factor. The authors note the inefficiency of strict and regulated methods of education management as it often requires unorthodox, original solutions. The article contains the results of the pilot study of education workers’ subjective perception of a positive management tool – engagement. The survey method has been utilized for the study. The analysis of the data has resulted in the following conclusions: 1) it has been found that the positive management tools identified through the analysis are insufficiently used in education management; 2) the identified problem areas in education management are related to expectations for work, satisfaction with the evaluation and feedback, interpersonal relations, as well as career and development.
Project Studies as A Transborder Didactic Tool in Higher Education (The Case of The German-Russian Study Project)
Authors: Ertelt Bernd-Joachim , Kondurov Roman , Scharpf Michael , Barkov Sergey A. , Kolodeznikova Inna V.
Published: August 2020

Project studies can become the most important innovative component of education programs in modern society. They allow one to not only improve the professional skills of students, but also develop competencies in the fields of project management and team building. The greatest didactic value is possessed by interdisciplinary and international projects. In the framework of their implementation, a synergistic effect occurs from a combination of methods of different sciences, as well as communications between representatives of different national scientific and educational schools. The success of a project study depends on student motivation. Their participation in setting common goals and developing methods for their achievement is the basis of high motivation. Along with this, the work of teacher-curators, oriented to help in solving emerging problems of a substantial and methodological order, acquires a fundamental role. The lack of project studies is largely due to the high requirements for the teachers involved in it. The tasks of teachers during project training are fundamentally different from those that they perform using other educational methods. This is one of the most temporarily costly and time-consuming forms of training. The study deals with the structural, managerial and didactic features of project study in higher education using as an example scientific and educational projects on labour market studies, which, since 2017, have been jointly carried out by the Moscow State University (MSU) and the University of Applied Labour Studies (UALS), Mannheim.
Orientation of Target Audience to Selection of Engineering Specialization in Institutions of Supplemental Education
Authors: Moiseeva Olga Aleksandrovna , Filippova Olga Aleksandrovna , Ponomarev Vladimir Gennadievich , Polozhentseva Irina Veniaminovna
Published: August 2020

This article analyzes the issue of motivating parents upon making decision about selection of supplemental education in the light of importance of propaganda of engineering specialization as a factor of state competitiveness. This work is aimed at revealing promotional methods of motivating parents to select educational robotics as supplemental education for a child. The experimental methods are comprised of comparative analysis of approaches by child’s robotics studios to promotion of engineering specialization among target audience and sociological survey among parents interested in educational robotics as a kind of child’s engineering creativity. It has been revealed that most respondents are not aware of robotics as a program of supplemental education and of its global demand not at the game level. While searching for objects of comparative analysis, it has been revealed that numerous institutions of supplemental education are not inclined to implement robotics as an analog of engineering specialization into educational program not only due to expensive equipment but, first of all, due to unavailability of required specialists for arrangement of such child’s engineering creativity. As a consequence of the comparative analysis of approaches to attraction of target audience, it has been revealed that numerous studios of R&D creativity pay insufficient attention to advertising of their companies due to moderate budget. On the basis of the experimental results, recommendations have been developed on organization of motivating communication campaign for studios of educational robotics with consideration for psychological and behavioral characteristics using available advertising tools.
On the Problem of Management of Physical Education of Younger Schoolchildren Using Modular Substitutions of Structural Bases of The Educational Subject
Authors: Matveev Anatoliy , Skotnikova Anna , Belyaev Vasiliy , Nikolaeva Natalya
Published: August 2020

The work aims to improve the quality of education of primary school students in physical education by introducing a scientifically-based exemplary program into the practice of educational organizations developed following the basic provisions of the modular approach and the principles of managing the educational process. Analysis and synthesis of literature data on modern trends in the development of the education system, the experience of educational organizations, and the development of the fundamentals of a physical education subject are used as the main research methods. The result of the work is the substantiation of conceptual approaches and methodological provisions on the formation of the structure and content of an exemplary Modular educational program in physical education, criteria, recommendations for the meaningful filling of its training modules, the technology of their substitution in the educational process.
Development of Professional Competence of Teachers as A Factor of The Education Quality Management in Preschool Institutions
Authors: Shnejder Lydia , Khmelkova Marina , Golovyatenko Tatyana , Poliakova Maria , Doroshenko Oksana
Published: August 2020

The main purpose of the article is to disclose the content of the concept of “quality of education”, including preschool education, as a priority in the field of Russian education. A quantitative and qualitative analysis of the professional competence and pedagogical competence of preschool teachers was carried out on the basis of a self-assessment sheet of the teacher’s pedagogical activity and an assessment sheet of key competences by T.A. Svatalova. The results of the self-assessment of pedagogical activity of teachers determined the main competencies in which the teachers showed acceptable levels of professional competence (in the field of personal qualities, in the field of providing an informational basis for activity, and in the field of developing a program of activity and making pedagogical decisions). It creates guidelines for organizing in institutions the conditions necessary for the professional development of teachers, raising their qualifications, helping them not only understand the reasons for their professional difficulties, but also identify the essence of professional expectations of each employee.
Pedagogical Controlling in The System of Professional Pedagogical Engineering
Authors: Yakusheva Svetlana Dmitrievna
Published: August 2020

The last decade is characterized by increased variability of Russian education, its diversification and mobility, with a permanent reform of the national system on all levels. The education system sets a trajectory for the development of human potential required by modern society while forming a completely new situation and implementing breakthrough ideas. A key agent of modern education is pedagogical controlling of the system of professional and pedagogical engineering. The relevance of implementing pedagogical controlling in the sphere of general secondary education is a fait accompli. Since the significance of the educational services market has significantly increased in the context of modern economic development, directly influencing education which is an important branch of science and practice as well the intellectual product created within it. Russia’s entry into the global education environment entails the convergence of the national education system with European counterparts. The authors believe that the system of professional and pedagogical engineering not only implements economic instrumentarium but also ensures the incorporation and support of innovative models of the education process. The article deals with the features of pedagogical controlling within the framework of the developed model (structure) of educational organization (complex) management within Moscow education.
Embedding Galilean and Carrollian geometries. I. Gravitational waves
Authors: Morand Kevin
Published: August 2020

The aim of this series of papers is to generalize the ambient approach of Duval et al. regarding the embedding of Galilean and Carrollian geometries inside gravitational waves with parallel rays. In this paper (Paper I), we propose a generalization of the embedding of torsionfree Galilean and Carrollian manifolds inside larger classes of gravitational waves. On the Galilean side, the quotient procedure of Duval et al. is extended to gravitational waves endowed with a lightlike hypersurface-orthogonal Killing vector field. This extension is shown to provide the natural geometric framework underlying the generalization by Lichnerowicz of the Eisenhart lift. On the Carrollian side, a new class of gravitational waves – dubbed Dodgson waves – is introduced and geometrically characterized. Dodgson waves are shown to admit a lightlike foliation by Carrollian manifolds and furthermore to be the largest subclass of gravitational waves satisfying this property. This extended class allows us to generalize the embedding procedure to a larger class of Carrollian manifolds that we explicitly identify. As an application of the general formalism, (Anti) de Sitter spacetime is shown to admit a lightlike foliation by codimension one (A)dS Carroll manifolds.
Focal construct geometry for high-intensity x-ray diffraction from laser-shocked polycrystalline
Authors: Chen XiaoHui , Li Bo , Xue Tao , Li Jun
Published: August 2020

An increasing number of dynamic experiments, especially those involving laser drive, are employing in situ x-ray diffraction as a probe to interrogate structure evolution between states of matter under extreme pressure and temperature. We present an alternative configuration, focal construct geometry, for in situ x-ray diffraction to measure the structure and evolution of dynamically compressed polycrystalline materials on a laser platform. This configuration makes full use of the isotropically emitted He–α x rays by employing an annular (or semi-annular) collimator rather than a regular pinhole collimator and thus increases the flux of incident x rays reaching the sample as well as the intensity of the diffracted x rays, enabling the detection of a diffraction pattern with less laser energy. Its effectiveness and applicability are validated against the conventional Debye–Scherrer geometry through direct molecular dynamics simulations and x-ray diffraction simulations for two representative shock-induced phase transition events, solid–solid and solid–liquid (or melting). This configuration reproduces all the Debye–Scherrer diffraction profiles in good accuracy and demonstrates superior efficiency in utilizing the isotropic x-ray source and harvesting diffracted x rays while preserving the angular resolution.
Quantum oscillations with magnetic hysteresis observed in CeTe3 thin films
Authors: Watanabe Mori , Lee Sanghyun , Asano Takuya , Ibe Takashi , Tokuda Masashi , Taniguchi Hiroki , Ueta Daichi , Okada Yoshinori , Kobayashi Kensuke , Niimi Yasuhiro
Published: August 2020

We have performed magnetotransport measurements in CeTe3 thin films down to 0.2 K. It is known that CeTe3 has two magnetic transitions at TN1≈3 K and TN2≈1 K. A clear Shubnikov–de-Haas (SdH) oscillation was observed at 4 K, demonstrating the strong two-dimensional nature in this material. Below TN2, the SdH oscillation has two frequencies, indicating that the Fermi surface could be slightly modulated due to the second magnetic transition. We also observed a magnetic hysteresis in the SdH oscillation below TN1. Specifically, there is a unique spike in the magnetoresistance at B≈0.6 T only when the magnetic field is swept from a high enough field (more than 2 T) to zero field.
Three-omega thermal-conductivity measurements with curved heater geometries
Authors: Jaffe Gabriel R. , Smith Keenan J. , Brar Victor W. , Lagally Max G. , Eriksson Mark A.
Published: August 2020

The three-omega method, a powerful technique to measure the thermal conductivity of nanometer-thick films and the interfaces between them, has historically employed straight conductive wires to act as both heaters and thermometers. When investigating stochastically prepared samples such as two-dimensional materials and nanomembranes, residue and excess material can make it difficult to fit the required millimeter-long straight wire on the sample surface. There are currently no available criteria for how diverting three-omega heater wires around obstacles affects the validity of the thermal measurement. In this Letter, we quantify the effect of the wire curvature by performing three-omega experiments with a wide range of frequencies using both curved and straight heater geometries on SiO2/Si samples. When the heating wire is curved, we find that the measured Si substrate thermal conductivity changes by only 0.2%. Similarly, we find that wire curvature has no significant effect on the determination of the thermal resistance of an ∼65 nm SiO2 layer, even for the sharpest corners considered here, for which the largest measured ratio of the thermal penetration depth of the applied thermal wave to radius of curvature of the heating wire is 4.3. This result provides useful design criteria for three-omega experiments by setting a lower bound for the maximum ratio of the thermal penetration depth to wire radius of curvature.
Room-temperature cavity-polaritons in planar ZnO microcavities fabricated by a top-down process
Authors: Shima K. , Furusawa K. , Chichibu S. F.
Published: August 2020

Angle-dependent energy shifts in the near-band edge emission peak were observed at room temperature in planar ZnO microcavities (MCs) fabricated by a top-down process that simultaneously maintains high radiative performance of a ZnO active layer and high reflectivity of wide-bandwidth distributed Bragg reflectors (DBRs). An approximately 2λ-thick ZnO active layer with a thickness gradient less than 10 nm/mm (i.e., an angle of gradient less than 2 arc sec) across the entire 10 × 5 mm2 device area was formed by thinning a bulk single crystal of ZnO grown by the hydrothermal method, whose typical threading dislocation densities were lower than 102 cm−2. The DBRs consisting of 10 and 12 pairs of SiO2/ZrO2 multilayers with a thickness gradient of 0.2 nm/mm/pair were deposited by using the nearly surface-damage-free reactive helicon-wave-excited-plasma sputtering method as the top and bottom mirrors, respectively. The quality factor of a passive cavity consisting of the same DBR stacks was in the range between 670 and 720 for the areal size of 1 mm in diameter. Angle-resolved photoluminescence spectra of the ZnO MCs measured at different positions with a macroscopic spot size of 80 μm in diameter exhibited distinct emission from the lower branch of cavity polaritons with apparent detunings ranging from −40 meV to 40 meV at room temperature.
Full polarization control of fiber-delivered light in a dilution refrigerator
Authors: Phoenix Jason , Gaudreau Louis , Korkusinski Marek , Zawadzki Piotr , Bogan Alex , Studenikin Sergei , Williams Robin L. , Sachrajda Andrew S.
Published: August 2020

Birefringence in optical fibers poses a challenge to controllably delivering polarized light. Strain-induced birefringence caused by bends in the fiber, vibrations, or a large temperature gradient can significantly alter the polarization, making it particularly difficult to deliver polarization states to low-temperature environments by fiber. In this paper, we investigate the transmission of polarized light through a fiber and discuss a method we have developed for delivering arbitrarily polarized light to the base stage of a dilution refrigerator using a standard optical fiber. We have created a compact, cryogenic optical system to identify the polarization of the delivered light, while room-temperature waveplates and a mathematical fiber model are used to fully characterize and compensate for the fiber’s birefringent effects. We show here that we are able to deliver horizontal, vertical, diagonal, anti-diagonal, right circular, and left circular polarization states to milli-Kelvin temperatures, with state fidelities of greater than 0.96 being achieved in all cases. Additionally, we demonstrate that we can deliver randomly selected elliptical states through a standard fiber to the refrigerator. This opens up new opportunities for fiber-based optical experiments using polarized light, such as quantum information experiments using quantum states encoded in the polarization of single photons.
A systematic and quantitative analysis of the bulk and interfacial properties of the AlSiO dielectric on N-polar GaN using capacitance–voltage methods
Authors: Liu Wenjian , Sayed Islam , Georgieva Jana , Chan Silvia , Keller Stacia , Mishra Umesh K.
Published: August 2020

The bulk and interfacial properties of aluminum silicon oxide (AlSiO) on N-polar GaN were investigated systematically employing capacitance–voltage (C–V) methods on metal–oxide–semiconductor capacitors using a thickness series of the AlSiO dielectric. The fixed charge density, electron slow trap density, and electron fast trap density located near the interface were extracted to be –1.5 × 1012 cm−2, 3.7 × 1011 cm−2, and 1.9 × 1011 cm−2, respectively. Using ultraviolet (UV) assisted C–V methods, an average interface state density of ∼4.4 × 1011 cm−2 eV−1 and a hole trap concentration in bulk AlSiO of ∼8.4 × 1018 cm−3 were measured. The negative fixed interface charge makes it favorable to achieve a normally off GaN transistor. The analysis presented in this paper provides a systematic and quantitative model to study the properties of oxide dielectrics on wide bandgap (WBG) semiconductors, which can promote the development of metal–oxide–semiconductor-based WBG semiconductor devices.
Eu3+-doped Bi7O5F11 microplates with simultaneous luminescence and improved photocatalysis
Authors: Wei Donglei , Huang Yanlin , Seo Hyo Jin
Published: August 2020

Doping of rare-earth ions in a host is one of the important strategies to modify the microstructure and electrical and optical properties. This work demonstrated the significant improvement of luminescence and photocatalytic performances of Bi7O5F11 via Eu3+ doping. Bi7O5F11 has a typical Sillén–Aurivillius structure, which shows an intrinsic luminescence band peaked at 527 nm with a decay time of 0.041 µs. The intrinsic emission quenches in Bi7O5F11:Eu3+, which shows characteristic transitions from 5D0,1,2,3 levels to 7FJ (J = 0–4) ground states. An experimental red-LED lamp was successfully fabricated by encapsulating Bi7O5F11:Eu3+ with a transparent resin. Bi7O5F11 has poor photocatalytic ability, which just can happen under UV light irradiation. The fast decay time (0.041 µs) of Bi7O5F11 causes an efficient recombination of the light-induced charges, resulting in a lower photocatalytic effect. Bi7O5F11:Eu3+ shows the improved photocatalytic abilities compared with pure Bi7O5F11. 4f levels of Eu3+ provide a longer decay time (1 ms) for the excited states of Bi7O5F11, which prevents the recombination of the light-induced charges. Importantly, Eu3+ doping moves the required wavelength in photocatalytic reactions from UV light (pure Bi7O5F11) to visible wavelength in Bi7O5F11:Eu3+. Bi7O5F11:Eu3+ could be further investigated to develop a multifunctional bismuth material such as dielectric, photoelectric, and photochemical abilities.
A non-linear deterministic model of action selection in the basal ganglia to simulate motor fluctuations in Parkinson's disease
Authors: Ursino Mauro , Véronneau-Veilleux Florence , Nekka Fahima
Published: August 2020

Motor fluctuations and dyskinesias are severe complications of Parkinson's disease (PD), especially evident at its advanced stage, under long-term levodopa therapy. Despite their strong clinical prevalence, the neural origin of these motor symptoms is still a subject of intense debate. In this work, a non-linear deterministic neurocomputational model of the basal ganglia (BG), inspired by biology, is used to provide more insights into possible neural mechanisms at the basis of motor complications in PD. In particular, the model is used to simulate the finger tapping task. The model describes the main neural pathways involved in the BG to select actions [the direct or Go, the indirect or NoGo, and the hyperdirect pathways via the action of the sub-thalamic nucleus (STN)]. A sensitivity analysis is performed on some crucial model parameters (the dopamine level, the strength of the STN mechanism, and the strength of competition among different actions in the motor cortex) at different levels of synapses, reflecting major or minor motor training. Depending on model parameters, results show that the model can reproduce a variety of clinically relevant motor patterns, including normokinesia, bradykinesia, several attempts before movement, freezing, repetition, and also irregular fluctuations. Motor symptoms are, especially, evident at low or high dopamine levels, with excessive strength of the STN and with weak competition among alternative actions. Moreover, these symptoms worsen if the synapses are subject to insufficient learning. The model may help improve the comprehension of motor complications in PD and, ultimately, may contribute to the treatment design.
Large tunneling magneto-dielectric enhancement in Co(Fe)−MgF2 granular films by minor addition of Si
Authors: Cao Yang , Kobayashi Nobukiyo , Ohnuma Shigehiro , Masumoto Hiroshi
Published: August 2020

We report a large enhancement of the tunneling magneto-dielectric (TMD) effect in Co−MgF2 granular films induced by doping using a small amount of Si. This minor addition of Si is dispersed uniformly in the MgF2 matrix and acts by inhibiting the interdiffusion between the Co and MgF2 phases, thus enhancing the magnetization when compared with the case of the corresponding undoped Co−MgF2 films; this consequently results in a greatly enhanced peak dielectric variation (TMD ratio, Δε′/ε′), as indicated by theoretical fittings. Extension of this Si doping effect to CoFe−MgF2 films led to a record-high Δε′/ε′ of 4.3% at 10 kHz and 8.5% at 200 kHz under the application of a magnetic field (H) of 10 kOe, while remaining as high as 2.1% even under H = 1 kOe. This study presents a simple but highly effective approach to enhance the TMD effect in granular nanocomposites, thus opening up the prospect of development of high-performance magnetoelectric devices.
A four-state magnetic tunnel junction switchable with spin–orbit torques
Authors: Das Shubhankar , Zaig Ariel , Schultz Moty , Cardoso Susana , Leitao Diana C. , Klein Lior
Published: August 2020

We present a magnetic tunnel junction (MTJ) where its two ferromagnetic layers are in the form of a single ellipse (SE) and two-crossing ellipses (TCEs). The MTJ exhibits four distinct resistance states corresponding to the four remanent states of the TCE structure. Flowing current in an underlying Ta layer generates in the adjacent TCE structure spin–orbit torques, which induce field-free switching of the four-state MTJ between all its resistance states. The demonstrated four-state MTJ is an important step toward fabricating multi-level MTJs with numerous resistance states, which could be important in various spintronics applications, such as multi-level magnetic random access or neuromorphic memory.
Switching between positive and negative movement near an air/water interface through lateral laser illumination
Authors: Shono Mayu , Takatori Satoshi , Carnerero Jose M. , Yoshikawa Kenichi
Published: August 2020

The directional movement of an aqueous solution containing gold nanoparticles under laser irradiation (532 nm) through the vicinity of an air/water interface is reported. It is shown that unidirectional flow is generated along the path of light-travel when a laser is irradiated parallel to the interface. On the contrary, liquid flow toward the light source is caused when the incident angle of the laser is tuned so as to make the total reflection at an air/water interface. Such switching of the flow direction, positive or negative to the light propagation, was applied to the movement of mm-sized floating object, revealing that repetitive back and forth motion of the solid object is generated. This directional switching of photo-induced movement is interpreted by taking into account the flow caused by the spatial gradient of the surface tension due to the thermal effect of the incident laser. A numerical model with a Navier–Stokes-type equation reproduces the essential aspects of the switching of the direction observed in the present study.
Theory of electrolytes including steric, attractive, and hydration interactions
Authors: Okamoto Ryuichi , Koga Kenichiro , Onuki Akira
Published: August 2020

We present a continuum theory of electrolytes composed of a waterlike solvent and univalent ions. First, we start with a density functional F for the coarse-grained solvent, cation, and anion densities, including the Debye–Hückel free energy, the Coulombic interaction, and the direct interactions among these three components. These densities fluctuate obeying the distribution ∝exp(−F/kBT). Eliminating the solvent density deviation in F, we obtain the effective non-Coulombic interactions among the ions, which consist of the direct ones and the solvent-mediated ones. We then derive general expressions for the ion correlation, the apparent partial volume, and the activity and osmotic coefficients up to linear order in the average salt density ns. Second, we perform numerical analysis using the Mansoori–Carnahan–Starling–Leland model [J. Chem. Phys. 54, 1523 (1971)] for three-component hardspheres. The effective interactions sensitively depend on the cation and anion sizes due to competition between the steric and hydration effects, which are repulsive between small–large ion pairs and attractive between symmetric pairs. These agree with previous experiments and Collins’ rule [Biophys. J. 72, 65 (1997)]. We also give simple approximate expressions for the ionic interaction coefficients valid for any ion sizes.
Multi-fidelity machine-learning with uncertainty quantification and Bayesian optimization for materials design: Application to ternary random alloys
Authors: Tran Anh , Tranchida Julien , Wildey Tim , Thompson Aidan P.
Published: August 2020

We present a scale-bridging approach based on a multi-fidelity (MF) machine-learning (ML) framework leveraging Gaussian processes (GP) to fuse atomistic computational model predictions across multiple levels of fidelity. Through the posterior variance of the MFGP, our framework naturally enables uncertainty quantification, providing estimates of confidence in the predictions. We used density functional theory as high-fidelity prediction, while a ML interatomic potential is used as low-fidelity prediction. Practical materials’ design efficiency is demonstrated by reproducing the ternary composition dependence of a quantity of interest (bulk modulus) across the full aluminum–niobium–titanium ternary random alloy composition space. The MFGP is then coupled to a Bayesian optimization procedure, and the computational efficiency of this approach is demonstrated by performing an on-the-fly search for the global optimum of bulk modulus in the ternary composition space. The framework presented in this manuscript is the first application of MFGP to atomistic materials simulations fusing predictions between density functional theory and classical interatomic potential calculations.
Energetic degeneracy and electronic structures of germanium trimers doped with titanium
Authors: Pham Le Nhan , Russo Salvy P.
Published: August 2020

Geometries and electronic structures of germanium trimer clusters doped with titanium TiGe3−/0 were studied making use of the complete active space self-consistent field followed by second-order perturbation theory, explicitly correlated coupled cluster singles and doubles method with perturbative triples corrections CCSD(T)-F12, and Tao-Perdew-Staroverov-Scuseria methods. Two electronic states (2A′ and 2A″) of the anion (pyramid shape) were determined to be nearly degenerate and energetically competing for the anionic ground state of TiGe3−. These two anionic states are believed to be concurrently populated in the experiment and induce six observed anion photoelectron bands. Total 14 electronic transitions starting from the 2A′ and 2A″ states were assigned to five out of six visible bands in the experimental anion photoelectron spectrum of TiGe3−. Each band was proven to be caused by multiple one-electron detachments from two populated anionic states. The last experimental band with the highest detachment energy is believed to be the result of various inner one-electron removals.
A geometric algebraic approach to fluid dynamics
Authors: Panakkal Susan Mathew , R Parameswaran , Vedan M. J.
Published: August 2020

Geometric algebra plays a major role in merging the physical and mathematical ideas in the context of various physical systems. In this paper, we explore certain properties associated with barotropic and non-barotropic fluid flows with the help of geometric algebra over a four-dimensional Euclidean space time manifold. We introduce the concepts of multivectors associated with vorticity, helicity, and parity, which evolve from a four-velocity field. In this context, the fluid dynamical analogs of the Poynting theorem, Lorentz force, and Maxwell’s equations are derived. The fluid Maxwell’s equations can be extracted from a single equation.