bluuebunny/crossref_metadata_2025 huggingface dataset:
Generalised resilience models for power systems and dependent infrastructure during extreme events
Authors: Krishnamurthy Vaidyanathan , Huang Bing , Kwasinski Alexis , Pierce Evan , Baldick Ross
Published: December 2019

This study presents a generalised critical infrastructures resilience model for extreme events with a focus on power grids. Infrastructures are modelled as three domains – physical, cyber, and human. Each domain is described with respect to the services it provides. Each domain is represented by geometric graphs for each service it provides. The resilience models use geometric graphs with each graph's nodes and edges characterised based on relevant attributes. This study also discusses various applied aspects related to resilience models including the impact of changing operating environment, human‐driven processes, such as logistics, and service buffers. Due to their stated particular importance in the U.S. Presidential Policy Directive 21, particular attention is placed on the power infrastructure and its impact on the public communication infrastructures as a main critical load. This study focuses on the multi‐time scale power system operation to capture cascading outages within, and subsequently to its dependent infrastructure – the public communication system (e.g. wireless or ‘cellular’ communication networks) as a main critical load. This study illustrates the merits of the proposed models in calculating resilience in extreme events and derives physical domain representation for electric and communication systems using cell tower and substation data from the USA.
Hybrid data‐driven physics model‐based framework for enhanced cyber‐physical smart grid security
Authors: Ruben Cody , Dhulipala Surya , Nagaraj Keerthiraj , Zou Sheng , Starke Allen , Bretas Arturo , Zare Alina , McNair Janise
Published: December 2019

This study presents a hybrid data‐driven physics model‐based framework for real‐time monitoring in smart grids. As the power grid transitions to the use of smart grid technology, it's real‐time monitoring becomes more vulnerable to cyber‐attacks like false data injections (FDIs). Although smart grids cyber‐physical security has an extensive scope, this study focuses on FDI attacks, which are modelled as bad data. State‐of‐the‐art strategies for FDI detection in real‐time monitoring rely on physics model‐based weighted least‐squares state estimation solution and statistical tests. This strategy is inherently vulnerable by the linear approximation and the companion statistical modelling error, which means it can be exploited by a coordinated FDI attack. In order to enhance the robustness of FDI detection, this study presents a framework which explores the use of data‐driven anomaly detection methods in conjunction with physics model‐based bad data detection via data fusion. Multiple anomaly detection methods working at both the system level and distributed local detection level are fused. The fusion takes into consideration the confidence of the various anomaly detection methods to provide the best overall detection results. Validation considers tests on the IEEE 118‐bus system.
The cost-effectiveness of an energy storage system using hydrogen and underground gas storage
Authors: Lepszy Sebastian
Published: December 2019

Due to the random nature of the production, the use of renewable energy sources requires the use of technologies that allow adjustment of electricity production to demand. One of the ways that enable this task is the use of energy storage systems. The article focuses on the analysis of the cost-effectiveness of energy storage from the grid. In particular, the technology was evaluated using underground hydrogen storage generated in electrolysers. Economic analyzes use historical data from the Polish energy market. The obtained results illustrate, among other things, the proportions between the main technology modules selected optimally in technical and economic terms.
Analysis and management of operating risk created by turbine operation under flexible regimes
Authors: Rusin Andrzej , Wojaczek Adam , Tomala Martyna
Published: December 2019

The new conditions in which coal-fired power plants, especially 200 MW units, have to operate require a considerable increase in the dynamics of their operation. The power unit start-up frequency increases and so does the frequency of changes in loads. This intensifies some wear processes, such as low- cycle fatigue and crack propagation in particular. Therefore, further operation of power units which have already been in service for a long time has to be supplemented with results of analyses and tests taking account of the intensification of wear processes. The paper presents a proposal for an extension of standard diagnostic testing of turbines by adding small punch tests (SPT) of the rotor material micro specimens. The SPT method enables a fast quasi non-destructive assessment of changes in mechanical properties, especially rotor steel embrittlement due to the turbine previous operation. The other element of the proposed testing is the analysis of the propagation rate of potential cracks in the rotor and assessment of the rotor failure probability for different scenarios of the power unit further operation.
Modeling of influence of vibration on intensification of heat transfer within the absorber of the vacuum solar collector
Authors: Grzywnowicz Krzysztof , Bartela Łukasz , Remiorz Leszek , Stanek Bartosz
Published: December 2019

Due to escalating role of mitigation of climate change in power and energy sector, power units based on renewable energy sources (RES) became vital part of global power and heat market, including distributed heat generation as well. Significant number of such installations belong to individual users, commonly using solar collectors to prepare domestic hot water directly at their sites. However, the vitally variable solar irradiance makes the solar energy difficult in efficient harvesting considering long time period. Thus, maximization of power gain from single solar absorber, when the solar radiation flux is temporarily high, might lead to further rise in overall, year-averaged efficiency of such units. The paper concerns modelling of intensification of heat transfer, taking place within the absorber of a vacuum solar collector, due to insertion of vibrating element inside the thermal oil canal, compared to static turbulization method. Different geometries of vibrating elements and amplitudes of oscillatory motion, as well as heat carriers, are investigated using commercially available CFD software. Results indicate rise in solar power acquired within the absorber using vibrating elements, with essential difference between circulating media, and suggest vital benefits from utilization of static turbulizing devices.
Water-resistant fiber-reinforced gypsum cement-pozzolanic composites
Authors: Mukhametrakhimov Rustem , Galautdinov Albert , Gorbunova Polina , Gorbunova Tatyana
Published: December 2019

Gypsum and gypsum-cement-pozzolanic composites are of significant interest as materials and products for building decoration. The current tendency to reduce the consumption of gypsum-based materials and products in the context of growth and development of the finishing materials market depends on the decrease in their competitiveness compared to peers. This leads to significant interest in improving the quality of products based on gypsum and gypsum-cement-pozzolanic binder. Dispersed reinforcement is one of the ways of improving performance characteristics. The role of the type of reinforcing fibers in the formation of the gypsum-cement-pozzolanic composites structure and properties is studied in article. The influence relations of the cellulose fibers content with varying grinding degrees on the relative flexural and compressive strength of a gypsum-cement-pozzolanic matrix are obtained. It was found that the optimal content of cellulose fibers in the modified gypsum-cement-pozzolanic matrix is 0.5-1% by weight of the binder, the best indicators of flexural and compressive strength are achieved by grinding cellulose fibers to 30°SR. Using scanning electron microscopy, it was found that the microstructure of a disperse-reinforced gypsum-cementpozzolanic matrix is characterized by a uniform cellulose fibers distribution, the predominance of directionally frame reinforcement with a fibers linear orientation in the sheet plane. In this way the right choice of the type, crushing degree and cellulose fibers content can improve the quality and expand the application area of the produced gypsum-cementpozzolanic composites.
Renovation of the first sable reserve of Russian empire in the planned Sayanian biosphere reserve
Authors: Astanin Dmitry
Published: December 2019

In 1918-1919 Sayanian reserve ceased to exist, even before it officially formalized at the governmental level. Sayanian reserve was reestablished in 1939. But in 1951, the reserve was closed due to lack of security. The existing and planned for opening specially protected areas in the central part of the Eastern Sayans, as well as the Sayan Geopark and the territory of traditional nature use Tofalar would restore the Sayan Reserve to the original borders as a complex of territories with different conservation status. It would be historical justice.
Switch operation safety
Authors: Gluzberg Boris , Korolev Vadim , Loktev Alexey , Shishkina Irina , Berezovsky Mikhail
Published: December 2019

The article studied the safety of passing the rolling stock by railway switches. On railway switches, counter rails provide the safe passage of the rolling stock by the wheelsets through the harmful space of the cross. The levels of dynamic effects arising from the passage of carriages by the railway switch significantly depend on the relative position of the wheelsets and elements of the switch, which is determined by the combination of their main geometric dimensions. To calculate the most unfavorable combinations of wheelset and gauge dimensions, taking into account the tolerances adopted for these dimensions, the method of probability compositions is used, based on the application of the theory of probability. The calculating apparatus of the approach using conditional probabilities of events based on the formulas of total probability and Bayes formula. The level of impact of the wheels on the counter-rail is regulated by rationing the values of the “impact effect” on the bent and catching parts of the counter-rail.
Eco-phytomonitoring in ensuring radiological safety of urban buildings
Authors: Gorodnichaya Alena , Glinyanova Irina , Pogorelova Victoria
Published: December 2019

In the future, the use of nuclear energy in national economy will rise. After accident at the Chernobyl nuclear power plant, staff of Fukushima 1 pay special attention to the safety of reactors, however, emergency situations are still possible. Eco-monitoring in natural and urban environments is carried out in order to determine the level of ecological pollution, including radioactive pollution. Therefore, studies in that direction are relevant and their relevancy is only increasing over the years. The aim of this study is to research migration and accumulation of 90Sr in vegetative and generative plant organs: cherry-plum (Prunus cerasifera Ehrh) tree and stone fruit species, gooseberry (Ribes uva-crispa) shrub. Objectives: 1) applying 90SrCl2 to the soil, imitating precipation (field experiments); 2) planting: Prunus cerasifera Ehrh; Ribes uva-crispa into artificially polluted by 90SrCl2 soil; 3) growing and monitoring of studied plants in the artificially polluted by 90SrCl2 soil. The level of pollution of experiment field reached 500 MBq/m2. The accumulation of 90Sr in vegetative and generative organs of trees (Prunus cerasifera Ehrh) and shrubs (Ribes uva-crispa) was researched. Experimental plots have been laid according to methodic of Dospekhov B.A. Measurements of beta-emitting nuclides activity in samples have been made using the “Progress” software on the USK “Gamma Plus” (beta-path) device. As the result of research it has been found that both plant species have been accumulating nuclides. In 2016 cherry-plum accumulated 90Sr in the bark, wood, leaves and fruits 2.0, 2.1, 2.6 and 2.6 times more accordingly than the gooseberry. As a result of the experiment, material, that can be used in eco-monitoring, was obtained to provide nuclear safety of urban properties in the territories, allocated for the construction of public and residential buildings.
Optimization of the traffic light regulation parameters on the urban road network in order to minimize the negative environmental impact
Authors: Katerinin Konstantin , Sanzhapov Bulat
Published: December 2019

A large number of vehicles in cities has a significant negative impact on the environmental situation. Today, economic measures are actively applied to reduce the number of vehicles used with internal combustion engines, and new technical solutions are being introduced to reduce exhaust toxicity. However, the potential of these approaches to improving the environmental situation in cities is very limited and has already been almost fully realized. Therefore, the huge potential to minimize environmental damage, in an increasing number of vehicles in large cities, is to optimize the parameters of traffic flows. The key role here is played by the scheme of traffic light control, to the consideration of the optimality parameters of which this work is devoted.
A mathematical model of odor dispersion from a wastewater treatment plant
Authors: Azarov Valerii , Solov’eva Tat’yana , Svitskov Sergei
Published: December 2019

Smell is an important criterion of the quality of atmospheric air. The paper looks at quantitative and qualitative methods of odor assessment and describes the method of field olfactometry. Studies were carried out on the spread of odor from the WWTP OAO OKOS in the Kaliningrad region of Russia which resulted in 817 measurements. For each measurement, the following parameters were recorded: odor strength (D/T), odor character, atmospheric pressure (mmHg), temperature (°C), relative humidity (%), wind speed (m/s), wind direction and the the point where a measurement was taken. A mathematical model is given of the dependence of odor strength on the distance to two sources s1 (m) and s2 (m) and the wind direction from a straight line passing through a given point and a source 1 — a1 or a source 2 — a2.
Rational Precious Metals Supply Schemes
Authors: Kurbatova Anna , Kurenkov Petr , Safronova Anastasia , Kuzina Margarita
Published: December 2019

Rapidly developing social progress and new conditions for the functioning of all economic entities put industrial enterprises in a special, rigid economic framework. In a tough competitive environment, you can survive and develop only by orienting your business activities to a logistic approach. The gold mining industry plays a key role in the global economy. This industry has a high asset value, large-scale production lines and large infrastructure. One of the main tasks of strategic planning of gold mining enterprises is the choice of a rational marketing system. Planning and selection of schemes for the supply of precious metals is an important condition for the effective functioning of the marketing activities of gold mining enterprises. For these purposes, the need for improving logistics flows and creating an information system for sales planning is growing. The article explores the planning and selection of precious metals supply schemes using the example of PJSC “Vysochaishy”. Much attention paid to the construction of the company’s logistics flows. The main problems in the supply chain of PJSC “Vysochaishy” are identify. The algorithm of the process of introducing a new supply chain planning system for Vysochaishy PJSC is considered, and an improved strategic planning process for PJSC “Vysochaishy” is present. A new scheme of operation of the transport and logistics system for the direction of logistics flows of PJSC “Vysochaishy” proposed.
Digitalization as a method of implementation EEU transit potential
Authors: Koroleva Elena , Sokolov Sergey , Filatova Evgeniya
Published: December 2019

In today’s world digital solutions make life easier in various fields. Digital interaction provides a complete transition to automated systems and electronic document management, opening up new prospects for economic growth of the Eurasian economic Union, including the implementation of the transit potential of the Eurasian economic Union. The article considers digital solutions that can allow to develop the transit potential of the Eurasian economic Union, as well as identifies the existing problems of digitalization.
Assessment of the economic efficiency of the innovative development of industrial enterprises
Authors: Shchepkina Natalia
Published: December 2019

The savings received from the implementation of innovative measures are usually associated with the results of other measures regarding the expansion of production capabilities. In this regard, it is advisable to consider the impact of innovative development of an enterprise on the efficiency of its activities in the framework of studying the economic efficiency of scientific and technological progress and its impact on reducing costs and not using effective innovations in production. The canonical correlation method is used, which allows one to simultaneously analyze the systems of indicators of production efficiency and the factors that define it. To analyze and assess the efficiency of the innovative development of an enterprise, an optimal combination of factors for its increase is proposed, based on the fact that many factors affecting the efficiency of economic activity, together with the complexity of their relationships, have optimal ranges of actions.
The manifestation of cultural factors and group processes in the work of a multicultural team
Authors: Leontev Mikhail
Published: December 2019

The relevance of the work is due to an increase in the number of multicultural teams, multicultural collectives, interactions between workers and learners, which are representatives of different nations. The globalization of the economy has led to the expansion of international relations, which means that a clash of different cultures is becoming more common, affecting different spheres of life. It is important to study the characteristics of national values and small group processes for organizing the work of a multicultural team. To this end, the study was conducted that uses and includes measurements of culture and group processes to explain the work of such teams. The results of the study confirm that culture measurements: individualism, collectivism, power distance and communication, conflict management impact on team member satisfaction. The results of this study shed light on the theoretical and practical aspects of managing multicultural teams in modern conditions and conclusions regarding their impact on team work.
Problems of using pumped storage power plants to improve the reliability and controllability of electric power system of the republic of Uzbekistan
Authors: Mukhammadiev Murodilla , Urishev Boborakhim , Esemuratova Shirin , Djumaniyozova Nigina
Published: December 2019

This article deals with the analysis and development perspectives of the use pumped storage power plants use to increase the reliability and regime controllability of electric power systems of the Republic of Uzbekistan.
Factoring in scheduled repairs of generating units when assessing the resource adequacy of electric power systems
Authors: Krupenev Dmitry , Boyarkin Denis , Iakubovskii Dmitrii
Published: December 2019

This study presents the algorithms for modeling of scheduled repairs of generating equipment when assessing the resource adequacy of electric power systems by the Monte Carlo method that relies on random events. We present an analysis of the algorithms adopted in the available software and computer systems used to assess the resource adequacy and highlight their shortcomings. We propose an algorithm for modeling of scheduled repairs of generating units that does away with the flaws of the algorithms adopted elsewhere. In the final part of the article, we present the findings of numerical experiments that test the performance of the algorithms.
Assessment of risks due to cyberattacks on information and communication infrastructure of cyber-physical system in the electric power system control
Authors: Kolosok Irina , Gurina Liudmila
Published: December 2019

The paper proposes an approach to risk assessment in the electric power system control to identify possible failures in the electric power system functioning caused by cyberattacks on SCADA systems and WAMS. There is a large number of information, hardware and software factors, which increase the automated dispatching control system vulnerability to cyberattacks. The study shows the influence of unforeseen cyber-incidents in the information and communication infrastructure on electric power systems through false control actions on their physical part. The effectiveness of the developed risk assessment approach is demonstrated by its performance under uncertainty.
Towards digital energy (experience of digital technology implementation by Russian companies)
Authors: Zhilkina Yulia , Vodennikov Dmitry
Published: December 2019

Today, digitalization is increasingly "capturing" the world economy. The inclusion of Russia in this trend is a matter of domestic companies maintaining their positions in the international arena. In the future, the creation of our own high-tech solutions will allow our country not only to win a competitive race in traditional markets, but also to reach new borders and take a leading position in the global market of complex systems and services of intellectual energy.
Power System Optimization in Terms of Uncertainty of Initial Information
Authors: Gayibov Tulkin , Pulatov Bekzod , Latipov Sherxon , Turmanova Gulnaz
Published: December 2019

In the article the problem of power system optimization under partial uncertainty of initial information is considered. The possibilities of using the methods of determinization to solve the problem of power system optimization taking into account the regime and technological constraints in the form of equality and inequality are researched. In basis of performed calculation studies using the example of the test scheme of power system, it was found that the optimization algorithm by the method of determinization can be effectively used for this proposes.
Features of Estimation of Structural Reliability of Power Supply Systems
Authors: Papkov Boris , Osokin Vladimir
Published: December 2019

Development and operation of modern power supply systems of consumers which are the part of distributed generation (DG) systems with their communication with electric power system (EPS) and renewable energy sources (RES) demand changes in estimation of their reliability indicators on the basis of corresponding mathematical apparatus. It is shown that DG systems refer to structures with several overlapping zones of action, which determines their peculiarities, which are represented by some integral characteristic - efficiency of operation, which characterizes the degree of expediency of use of the DG system in different modes. The approach based on evaluation of effectiveness of such systems is offered. Examples of calculation of relatively simple structures of DG systems performing several tasks simultaneously are given.
Controlled switching circuits based on non-linear resistive elements
Authors: Karimov R.Ch. , Bobojanov M.K. , Rasulov A.N. , Usmanov E.G.
Published: December 2019

Based on the results of the analysis of resistive circuits, a new circuit of an optoelectronic contactless voltage relay is developed in the article and its application in the power supply system is considered. The possibility of controlling the operating modes of various installations for amplifying electrical signals using optothyristors is presented and methods for their inclusion in electrical circuits are given. Optoelectronic contactless voltage relays were tested under laboratory conditions to obtain input-output characteristics and capacitance voltage waveforms. Based on the improvement of the proposed circuit, a circuit of an optoelectronic contactless voltage relay is developed and provides a high degree of reliability. The proposed voltage relay circuit is simulated using the Electronics Workbench and MATLAB R2014a programs, the results of which show that the changes in the shape of the output voltage curve are close to a sinusoid and coincide with the results obtained analytically.
Load-flow model of a multi-energy system
Authors: Efimov Dmitry , Bykov Dmitry
Published: December 2019

Current trends in the energy development includes the creation of multi-energy systems (MES) with several energy carriers that are planned, designed and operated with essential coordination of their subsystems. When managing the development and functioning of such systems, optimization problems should be solved to minimize the cost of production, transmission and distribution of energy resources. Traditionally, the means of such minimization are the redistribution of the loads of generation sources, consumers and energy storage devices. The topology of MES if different for different energy carriers, and topologies are combined through energy hubs – nodes in which energy is converted from one type to another. Such transformation can simply be considered as the consumption of one type of energy with the simultaneous generation of another type. This provides brand new opportunities for optimizing modes specific to a MES. Essential part of the search of optimal solution is the calculation of the load flow – that is, the determination of nodes’ and connections’ mode parameters of the system subject to balance equations (Kirchhoff’s circuit laws). The load flow equations act as constraints in optimization problems. This paper presents an attempt to form a single model for calculating the load flow of different energy carriers in a MES.
Stability of intelligent energy system and intelligent control methods
Authors: Voropai Nikolai , Efimov Dmitry , Kurbatsky Victor , Tomin Nikita
Published: December 2019

In modern power systems, a variety of both objects and the tools of control is expected to be much larger than before. As a result, the dynamic properties of these systems are complicated, and the issues of maintaining stability come to the fore. The paper provides a brief overview of the types of stability, including those that, until recently, were considered local in the electric power systems of Russia. It is shown that in today’s conditions the violation of these types of stability affects the operation of the electric power system as a whole. Therefore, the coordination of control of both normal and emergency modes of the systems takes on a special role and should become more intelligent. In this regard, a brief overview of machine learning developments of control agents at different levels of the control hierarchy is presented.
New approach to modeling the nonlinear loads
Authors: Kovernikova L.I. , Luong Van Chung
Published: December 2019

Parameters of operating conditions of electric power systems shall ensure efficient and reliable operation of both power generating companies and of consumers, which to a great extent depends on power quality. Most urgent problem in this area is currently non-sinusoidal voltage. Power quality control, development of technical measures to sustain parameters of harmonic modes in conformity with provisions of GOST 32144-2013 require calculations that, in turn, need models adequately representing the electric networks and nonlinear loads in the computing program. Results of studies on parameters of harmonic modes that were obtained by measurements have shown that harmonic modes are random, and their parameters have probabilistic nature. Due to unpredictability of harmonic modes, nonlinear loads can be modeled using measured parameters. The paper presents methodological approach, algorithms and a computing program for modeling the nonlinear loads using parameters measured in the nodes of their connection to the power supply, and gives examples of modeling the nonlinear loads.
Power System Mode optimization by piecewise-linear approximation of energy characteristics of Power Plants
Authors: Gayibov Tulkin , Latipov Sherxon , Uzakov Bakhadir
Published: December 2019

The issues of improving of methods and algorithms for power system short-term mode optimal planning are considered. The main disadvantages and calculation difficulties typical for traditional algorithms are described. An effective algorithm for power system mode optimization based on a piecewise- linear approximation of nonlinear dependencies is proposed. Application of the proposed algorithm can effectively increase the accuracy and overcome many calculation difficulties associated with discontinuity of energy characteristics of power plants and various constraints in the form of equality and inequality.
Der Multiple Sclerosis Functional Composite korreliert mit der sozialmedizinischen Leistungsempfehlung zur Erwerbsfähigkeit von Rehabilitanden mit Multipler Sklerose
Authors: Leniger Tobias , Heiker Maike , Ghadimi Andrea
Published: December 2019

Ziel der Studie Der Multiple Sclerosis Functional Composite (MSFC) bewertet mit den Untertests Lauf- und Handfunktion sowie Kognition die Funktionseinschränkungen der Multiplen Sklerose (MS). In der medizinischen Rehabilitation könnte der MSFC sich als hilfreiches Assessmentinstrument für die sozialmedizinische Leistungsempfehlung zur Erwerbsfähigkeit (SLE) am Ende der stationären Rehabilitation erweisen. Ziel der Studie war, eine Korrelation des MSFC mit der SLE zu überprüfen, deren Gültigkeit sechs Monate nach der Rehabilitation erfragt wurde.

Methodik In einer retrospektiven, unizentrischen Längsschnittstudie wurde der MSFC zu Beginn (t0) und zum Ende (t1) der stationären Rehabilitation bei 84 Rehabilitanden mit MS im erwerbsfähigen Alter erhoben. Der MSFC (Gesamtscore, Untertests) wurde mit der SLE am Ende der Rehabilitation korreliert (positive SLE: ≥ 3h täglich, negative SLE: < 3h täglich). Sechs Monate nach der Rehabilitation wurde der Return to Work (RTW) erfragt (positiver RTW: ≥ 3h täglich, negativer RTW: < 3h täglich).

Ergebnis 70 der 84 Rehabilitanden (83 %) erhielten eine positive SLE. Sie zeigten hinsichtlich epidemiologischer, MS- und rehabilitations-spezifischer Charakteristika keinen Unterschied zu den 14 Rehabilitanden mit negativer SLE. Rehabilitanden mit positiver SLE wiesen im Vergleich zu denen mit negativer SLE signifikant bessere MSFC-Werte im Gesamtscore (z-Score: + 0,11 vs. −0,55, p < 0,001), in den Untertests Kognition (PASAT-3: 42,3 Punkte vs. 27,7 Punkte; p < 0,001) und Lauffunktion (T25FW: 5,1 s vs. 6,7s; p = 0,002) auf. Hingegen war die Handfunktion (NHPT: 23,4 s vs. 26,5s; p = 0,064) ohne signifikanten Unterschied. Beide Gruppen zeigten im Verlauf der Rehabilitation (t0; t1) nichtsignifikante Verbesserungen (Gesamtscore, Untertests). Bei 31 der 84 Rehabilitanden (37 %) konnte der RTW nach sechs Monaten erhoben werden. 90 % der 31 Rehabilitanden beurteilten die SLE als zutreffend. Eine positive SLE korrelierte signifikant mit einem positiven RTW nach sechs Monaten (r = 0,411; p = 0,022). Keine signifikante Assoziation bestand zwischen dem MSFC(t1) (Gesamtscore, Untertests) und dem RTW nach sechs Monaten.

Schlussfolgerung Auf Funktionsebene korreliert der MSFC im Gesamtscore (z-Score ≥ 0) signifikant mit einer positiven SLE bei Entlassung, deren Validität mit dem RTW sechs Monate nach der Rehabilitation belegt wurde. Maßgeblich waren die Untertests Kognition und Lauffunktion. In der medizinischen Rehabilitation der MS bietet sich daher der Einsatz des MSFC an, um basierend auf dem ermittelten Funktionsniveau eine fundierte Teilhabeempfehlung in Form der SLE zu entwickeln.
Synthetic Approaches to the Bifunctional Chelators for Radio­nuclides Based On Pyridine-Containing Azacrown Compounds
Authors: Zubenko Anastasia D. , Shchukina Anna A. , Fedorova Olga A.
Published: December 2019

Synthetic ways to introduce functional groups (CO2Me, CO2H, OCH2CO2H, OCH2C≡CH, CH2OH, CH2Cl, CH2N3) into the pyridine ring of pyridine-containing azacrown compounds are described. These groups were introduced at position-4 of the pyridine ring, while keeping the macrocyclic carboxylate groups available for metal chelation. The derivatives were obtained by macrocyclization reaction of 4-substituted, trimethyl pyridine-2,4,6-tricarboxylate or by modification of methyl ester group in pyridine fragment of macrocycles. Obtained derivatives can be applied for preparing radiotherapeutic agents by conjugation to different vector biomolecules for targeted drug delivery to cancer cells without damaging healthy tissue.
Topological semi-metal Na3Bi as efficient spin injector in current driven magnetic tunnel junction
Authors: Reza Ahmed Kamal , Roy Kaushik
Published: December 2019

The free layer in the current driven magnetic tunnel junction (MTJ) can be switched by injecting spin-polarized current from an adjacent spin injector. A nonmagnetic efficient spin injector, a converter from charge current to spin current, has long been and is still being quested in the field of spintronics. The first discovered nonmagnetic spin injector was the heavy spin Hall metals (HMs) such as Pt and β-W. The HMs can only convert 2%–10% of the charge current to spin current. The rest of the charge current is wasted and has no contribution in MTJ switching. The waste of charge current during MTJ switching is one of the major sources of energy loss in MTJ operation. Later, it has been found that topological insulators (TIs) such as Bi2Se3 can convert around 37% charge current to spin current. Nevertheless, the topological insulator has low conductivity compared with the free layer of an MTJ, which results in a large amount of shunting charge current loss through the free layer. Topological semimetals (TMs) such as Na3Bi provide us with a trade-off point between HM and TI as a nonmagnetic spin injector. TMs have higher charge current to spin current conversion efficiency than HMs and higher electrical conductivity than TIs. In this work, we first calculated the density functional theory band structure of Na3Bi and then modeled and matched the near-Fermi-level band structure with the 8 band k⋅p model. We have used the k⋅p Hamiltonian in quantum transport (nonequilibrium Green’s function) formalism to determine the charge current to spin current conversion efficiency in Na3Bi. We have found that Na3Bi can convert around 27.33% of charge current to spin current, and its conductivity is ∼12.5 times more than that of Bi2Se3. A CoFeB (fixed layer)-MgO (tunneling barrier)-CoFeB (free layer)-Na3Bi (spin injector) MTJ consumes almost 9.09× and 655.57× less electrical power during isospeed write operation compared with CoFeB-MgO-CoFeB-Pt and CoFeB-MgO-CoFeB-Bi2Se3 MTJs, respectively. Application of isowrite voltage of 1V shows that CoFeB-MgO-CoFeB-Na3Bi MTJ switches 4.3× faster than CoFeB-MgO-CoFeB-Pt MTJ, while CoFeB-MgO-CoFeB-Bi2Se3 MTJ fails to switch and continues to oscillate.
Strain analysis of a Ge micro disk using precession electron diffraction
Authors: Bashir Aneeqa , Millar Ross W. , Gallacher Kevin , Paul Douglas J. , Darbal Amith D. , Stroud Robert , Ballabio Andrea , Frigerio Jacopo , Isella Giovanni , MacLaren Ian
Published: December 2019

The recently developed precession electron diffraction (PED) technique in scanning transmission electron microscopy has been used to elucidate the local strain distribution and crystalline misorientation in a CMOS fabricated strained Ge microdisk structure grown on a Si substrate. Tensile strained Ge and GeSn structures are considered to be potential CMOS compatible optical sources, as both Sn alloying and strain can lead to a direct band-structure and lasing. The ability to take nanometer resolution, experimental measurements of the cross-sectional strain distribution, is important to understand modal gain and, therefore, ultimate device performance. In this work, we demonstrate PED techniques to measure the cross-sectional strain field in tensile Ge microdisks strained by SiN stressors. The strain maps are interpreted and compared with a finite element model of the strain in the investigated structure, which shows good agreement, and, therefore, highlights the applicability of PED techniques for mapping strained photonic structures. The technique also allows for the observation of strain relaxation due to dislocation pileup, further demonstrating the benefit of such experimental techniques.
The chopped moving photocarrier grating technique
Authors: Kopprio Leonardo , Ventosinos Federico , Schmidt Javier
Published: December 2019

The Moving photocarrier Grating Technique (MGT) allows the simultaneous determination of the photocarrier drift mobilities and the small-signal recombination lifetime of photoconductive semiconductors. The technique measures the direct current (DC) induced by a monochromatic illumination consisting of a moving interference pattern superimposed on a uniform background of much higher intensity. A drawback of the technique is the low level of the signal to be measured, which can be masked by the noise at low temperatures or low light intensities. In this work, we propose implementing an alternating current (AC) version of the MGT by chopping the weak beam in the standard configuration. We call this new technique the Chopped Moving photocarrier Grating (CMG). In CMG, the AC signal can be measured with a lock-in amplifier for electrical noise removal. In this way, the signal-to-noise ratio can be increased compared to the standard DC technique. Assuming a multiple-trapping model for charge transport, we find the theoretical expression for the current density induced by CMG at fundamental frequency. By using a numerical simulation with parameters typical for hydrogenated amorphous silicon, we verify the expected equivalence between both techniques for low enough chopping frequencies. Then, we test experimentally this equivalence for an undoped hydrogenated amorphous silicon sample. For low signal levels, we demonstrate the superior performance of CMG.
Two-dimensional hybrid-direct kinetic simulation of a Hall thruster discharge plasma
Authors: Raisanen Astrid L. , Hara Kentaro , Boyd Iain D.
Published: December 2019

A direct kinetic (DK) simulation is capable of modeling the nonequilibrium state of plasma as it evolves in the discharge region of a Hall thruster without the numerical noise that is inherent to particle-based methods since the velocity distribution functions are obtained in a deterministic manner. In this work, a hybrid-DK simulation utilizes a quasi-one-dimensional fluid electron model in conjunction with a two-dimensional DK method to simulate neutral atoms and ions in a Hall thruster channel and near-field plume. Instantaneous and time-averaged plasma properties calculated using the hybrid-DK simulation are benchmarked against the results obtained from a two-dimensional hybrid-particle-in-cell (PIC) simulation with an identical fluid electron model. For both high and low-frequency oscillations, the two simulations show good agreement for time-averaged and dynamic plasma properties. Numerical noise tends to randomize plasma oscillations in the PIC simulation results, whereas the DK results exhibit coherent oscillatory behavior.
Laser-induced control of a cavity bubble behind a sinking sphere in water entry: Dependency on the surface temperature and impact velocity
Authors: Choi Kyuseong , Kim Nayoung , Seon Guwon , Hwang Wontae , Park Hyungmin
Published: December 2019

We investigate the effect of continuous-wave laser irradiation on the cavity evolution behind a sphere in water entry. By tuning the irradiation time, the surface temperature (Ts) of the sphere before the impact varies in 105–355 °C. We change the radius and impact velocity of the sphere, by which both the shallow and deep seals are considered. Compared to the reference case (the sphere was roughened to have a cavity initially), we find that the cavity expands or shrinks depending on Ts. Overall, for all cases, the cavity bubble expands to the maximum size and shrinks steeply with increasing Ts. At higher Ts, the cavity is destroyed significantly, even smaller than the reference case. However, the detailed interaction between the cavity and laser-induced cavitation bubbles is quite different. In a shallow-seal case, nucleate boiling occurs on the sphere surface and vapor bubbles merge into the cavity, resulting in the expansion of the cavity. At a highly subcooled condition, on the other hand, the vapor bubble collapses into microbubbles as soon as it contacts water, resulting in the cavity reduction. As the impact speed increases (for a deep-seal condition), the flux of entrained air becomes dominant and the stage of cavity expansion is quite narrow. As Ts increases, the heated cavity collapses into microbubbles and almost 90% is destroyed. Finally, we investigate the effects of modified cavity on hydrodynamic forces on the sphere. While the temporal variation of hydrodynamic forces is complex, the drag reduction over 40% is achieved.
Electronic properties of Pb-I deficient lead halide perovskites
Authors: Zheng Chao , Rubel Oleg , Kepenekian Mikaël , Rocquefelte Xavier , Katan Claudine
Published: December 2019

The electronic structure evolution of deficient halide perovskites with a general formula (A,A′)1+xM1−xX3−x was investigated using the density functional theory. The focus is placed on characterization of changes in the bandgap, band alignment, effective mass, and optical properties of deficient perovskites at various concentrations of defects. We uncover unusual electronic properties of the defect corresponding to a M–X vacancy filled with an A′ cation. This defect “repels” electrons and holes producing no trap states and, in moderate quantities (x ≤ 0.1), does not hinder charge transport properties of the material. This behavior is rationalized using a confinement model and provides additional insight to the defect tolerance of halide perovskites.
Structural-order dependence of anomalous Hall effect in Co2MnGa topological semimetal thin films
Authors: Wang Qiang , Wen Zhenchao , Kubota Takahide , Seki Takeshi , Takanashi Koki
Published: December 2019

We report on the large anomalous Hall effect (AHE) and its structural-order dependence for epitaxial Co2MnGa topological semimetal films fabricated by a sputtering method. The structural orders of the films were systematically changed from B2 to L21 upon tuning the film growth temperature. It was found that the AHE was dramatically enhanced when the Co2MnGa films contained the L21-ordered phase. A large anomalous Hall angle of ∼12.6% at 10 K (∼11% at 300 K) was achieved at maximum. The dependence of anomalous Hall conductivity on longitudinal conductivity suggests that the intrinsic contribution plays a major role in the AHE. Thus, the enhanced AHE with the L21 order is attributed to the improvement of topological electronic structures in the L21-ordered Co2MnGa films. This scenario also allows us to explain the structural-order dependence of magnetoresistance.
A vibration energy harvester based on Ca3TaGa3Si2O14 piezoelectric crystal for high temperature applications
Authors: Ouyang Su , Zhang Jinhui , Yu Fapeng , Qin Lifeng
Published: December 2019

In the past two decades, piezoelectric vibration energy harvesters (PVEHs) have attracted considerable attention as an effective technology for replacing the batteries in self-power wireless sensor networks. However, because of the low Curie temperature limitations of piezoelectric materials, conventional PVEHs can only be used in low-temperature environments. In this paper, we report a PVEH for high temperature (HT) applications using Ca3TaGa3Si2O14 piezoelectric crystals. We investigated how the electromechanical performance of the device varied with temperature, from room temperature (RT) to 800 °C. Our research showed that the HT PVEH produced a steady output under a constant mechanical excitation. Furthermore, we found that the optimal output power at 350 °C was approximately four times higher than that at RT (25 °C). The results demonstrate that the proposed PVEH has great potential for applications as a self-power source in high temperature wireless sensors.
Unique silica polymorph obtained under electron irradiation
Authors: Reghioua Imène , Lancry Matthieu , Cavani Olivier , Floch Sylvie Le , Neuville Daniel R. , Ollier Nadège
Published: December 2019

High purity synthetic silica glass (Suprasil F300) samples were densified by High Pressure/High Temperature (HP-HT) using three different pressure/temperature/duration values. Their relaxation process was studied by applying 2.5 MeV electron irradiation with doses varying from 1 MGy up to 11 GGy. At very high dose (11 GGy), all the densified silica samples exhibit the same density value (∼2.26 g/cm3) regardless of the densification conditions, referring to an equilibrium value known as an amorphous silica metamict phase. In detail, the HP-HT silica samples were progressively dedensified from 1 GGy irradiation dose until reaching this equilibrium. Whatever the initial topological disorder revealed through Raman spectra, all silica samples present identical Raman spectra at 11 GGy, with high intensities of D1 and D2 components, attesting they reach one unique silica polymorph. Regarding the irradiation at high temperature (600 MGy, 600 K), the results show that the thermal annealing during irradiation “accelerates” somehow the relaxation kinetics of both macroscopic density and vibrational signature. Furthermore, it seems that such high irradiation temperatures lead to increase the Non-Bridging Oxygen Hole Center point defects generation.
A time-reversible integrator for the time-dependent Schrödinger equation on an adaptive grid
Authors: Choi Seonghoon , Vaníček Jiří
Published: December 2019

One of the most accurate methods for solving the time-dependent Schrödinger equation uses a combination of the dynamic Fourier method with the split-operator algorithm on a tensor-product grid. To reduce the number of required grid points, we let the grid move together with the wavepacket but find that the naïve algorithm based on an alternate evolution of the wavefunction and grid destroys the time reversibility of the exact evolution. Yet, we show that the time reversibility is recovered if the wavefunction and grid are evolved simultaneously during each kinetic or potential step; this is achieved by using the Ehrenfest theorem together with the splitting method. The proposed algorithm is conditionally stable, symmetric, and time-reversible and conserves the norm of the wavefunction. The preservation of these geometric properties is shown analytically and demonstrated numerically on a three-dimensional harmonic model and collinear model of He–H2 scattering. We also show that the proposed algorithm can be symmetrically composed to obtain time-reversible integrators of an arbitrary even order. We observed 10 000-fold speedup by using the tenth-order instead of the second-order method to obtain a solution with a time discretization error below 10−9. Moreover, using the adaptive grid instead of the fixed grid resulted in a 64-fold reduction in the required number of grid points in the harmonic system and made it possible to simulate the He–H2 scattering for six times longer while maintaining reasonable accuracy. Applicability of the algorithm to high-dimensional quantum dynamics is demonstrated using the strongly anharmonic eight-dimensional Hénon–Heiles model.
Chemical bonds in intercalation compounds CuxTiCh2 (Ch = S, Te)
Authors: Shkvarin A. S. , Merentsov A. I. , Tsud N. , Titov A. N.
Published: December 2019

A thorough study of the chemical bonding between intercalated copper and host lattice TiCh2 (Ch = S, Te) was performed. In order to separate the contributions of the copper, titanium, and chalcogen states into the electronic structure of the valence band, photoelectron spectroscopy in nonresonant and resonant (Cu 3p-3d and Ti 2p-3d) excitation modes was used. It is shown that the ionicity of the chemical bond between copper and host lattice is decreased in the TiS2 → TiSe2 → TiTe2 row. In CuxTiS2, copper atoms form the chemical bond with TiCh2 host lattice, while in CuxTiTe2 directly with tellurium atoms.