Stability of quantized conductance levels in memristors with copper filaments: toward understanding the mechanisms of resistive switching

Memristors are among the most promising elements for modern microelectronics, having unique properties such as quasi-continuous change of conductance and long-term storage of resistive states. However, identifying the physical mechanisms of resistive switching and evolution of conductive filaments in such structures still remains a major challenge. In this work, aiming at a better understanding of these phenomena, we experimentally investigate an unusual effect of enhanced conductive filament stability in memristors with copper filaments under the applied voltage and present a simplified theoretical model of the effect of a quantum current through a filament on its shape. Our semi-quantitative, continuous model predicts, indeed, that for a thin filament, the "quantum pressure" exerted on its walls by the recoil of charge carriers can well compete with the surface tension and crucially affect the evolution of the filament profile at the voltages around 1V. At lower voltages, the quantum pressure is expected to provide extra stability to the filaments supporting quantized conductance, which we also reveal experimentally using a novel methodology focusing on retention statistics. Our results indicate that the recoil effects could potentially be important for resistive switching in memristive devices with metallic filaments and that taking them into account in rational design of memristors could help achieve their better retention and plasticity characteristics.Comment: version accepted for publication in Phys. Rev. Applied, including improved statistic

Momentum distributions of sequential ionization generated by an intense laser pulse

Journals published by the American Physical Society can be found at http://publish.aps.org/The relative yield and momentum distributions of all multiply charged atomic ions generated by a short (30 fs) intense (10(14)-5 x 10(18) W/cm(2)) laser pulse are investigated using a Monte Carlo simulation. We predict a substantial shift in the maximum (centroid) of the ion-momentum distribution along the laser polarization as a function of the absolute phase. This effect should be experimentally detectable with currently available laser systems even for relatively long pulses, such as 25-30 fs. In addition to the numerical results, we present semianalytical scaling for the position of the maximum

Alumosilicate ceramic proppants based on natural refractory raw materials

The sintering-strengthening effect of the additions of the highly ferrous bauxite (with Fe[2]O[3] content of 20-25 % in the calcined state) in the compositions with refractory clays was established. It was found that in the temperature range 1350-1500°C the additions of bauxite in amounts of 10-40% have a fluxing effect due to the iron oxide introduced with bauxite in compositions with clay. An increasing the bauxite additive in the amount of 50-70% ensures its strengthening effect by increasing the total content of the mullite of the prismatic habit in the firing products of composites with clay. Preliminary clay and bauxite calcination at 900 °С and an increase in the content of bauxite additive up to 50-70% in compositions with clay allow to produce aluminosilicate proppants with a bulk density of 1.62-1.65 g/сm{3} and compressive strength up to 52 MPa

Two-way multi-lane traffic model for pedestrians in corridors

We extend the Aw-Rascle macroscopic model of car traffic into a two-way multi-lane model of pedestrian traffic. Within this model, we propose a technique for the handling of the congestion constraint, i.e. the fact that the pedestrian density cannot exceed a maximal density corresponding to contact between pedestrians. In a first step, we propose a singularly perturbed pressure relation which models the fact that the pedestrian velocity is considerably reduced, if not blocked, at congestion. In a second step, we carry over the singular limit into the model and show that abrupt transitions between compressible flow (in the uncongested regions) to incompressible flow (in congested regions) occur. We also investigate the hyperbolicity of the two-way models and show that they can lose their hyperbolicity in some cases. We study a diffusive correction of these models and discuss the characteristic time and length scales of the instability

Long-lived states in synchronized traffic flow. Empirical prompt and dynamical trap model

The present paper proposes a novel interpretation of the widely scattered states (called synchronized traffic) stimulated by Kerner's hypotheses about the existence of a multitude of metastable states in the fundamental diagram. Using single vehicle data collected at the German highway A1, temporal velocity patterns have been analyzed to show a collection of certain fragments with approximately constant velocities and sharp jumps between them. The particular velocity values in these fragments vary in a wide range. In contrast, the flow rate is more or less constant because its fluctuations are mainly due to the discreteness of traffic flow. Subsequently, we develop a model for synchronized traffic that can explain these characteristics. Following previous work (I.A.Lubashevsky, R.Mahnke, Phys. Rev. E v. 62, p. 6082, 2000) the vehicle flow is specified by car density, mean velocity, and additional order parameters $h$ and $a$ that are due to the many-particle effects of the vehicle interaction. The parameter $h$ describes the multilane correlations in the vehicle motion. Together with the car density it determines directly the mean velocity. The parameter $a$, in contrast, controls the evolution of $h$ only. The model assumes that $a$ fluctuates randomly around the value corresponding to the car configuration optimal for lane changing. When it deviates from this value the lane change is depressed for all cars forming a local cluster. Since exactly the overtaking manoeuvres of these cars cause the order parameter $a$ to vary, the evolution of the car arrangement becomes frozen for a certain time. In other words, the evolution equations form certain dynamical traps responsible for the long-time correlations in the synchronized mode.Comment: 16 pages, 10 figures, RevTeX

СТРАТЕГИЯ РАЗВИТИЯ И МОДЕРНИЗАЦИИ ТРАНСПОРТНО-ЛОГИСТИЧЕСКИХ МАРШРУТОВ В АРКТИКЕ

Purpose: the main objective of this study is to work out a detailed strategy to improve and develop the Northern Sea Route through an analysis of the current trends. The strategy is created on the basis of the graph theory, whereas the optimal strategy for the development of the NSR is selected according to certain financial and time criteria.Methods: the paper is based on the application of graph theory to the construction of a strategy for the development of complex economic and logistical systems.Results: the article explores the issue of formation and selection of the strategy for development and modernization of transport and logistics routes in the Arctic zone of the Russian Federation. Particular attention is paid to the main Arctic route – the Northern Sea Route. Based on the analysis of the main problems in the development of this transport corridor, a series of steps are proposed in the work, including such measures as updating the infrastructure of the NSR, increasing its capacity, creating an information system for safe and efficient navigation, as well as appropriate legislative changes for the establishment of port special economic zones. In the opinion of the authors, these steps will significantly increase the competitiveness of the NSR in comparison with alternative transport and logistics corridors. The research contains also an algorithm for choosing the most optimal way to implement the NSR development strategy, which will make it possible to achieve the main goal – providing the capacity of the route of 30 million tons of cargo per year by 2030.Conclusions and Relevance: the materials stated in the article indicate the special importance of the Arctic transport and logistics corridors for the social and economic development of the country and the regions concerned. One of the most important transport arteries in the Arctic is the Northern Sea Route. The article analyzes the dynamics, problem aspects, as well as the prospects for its development. The authors propose the strategy of modernization and development of the NSR until 2030 on the basis of the studies carried out and with the use of graph theory.Цель: Основная цель данного исследования состоит в том, чтобы с помощью анализа текущих тенденций развития Северного морского пути и на основании теории графов разработать комплекс мер по совершенствованию и развитию Северного морского пути (СМП), а также из всех возможных выбрать оптимальную стратегию развития СМП, удовлетворяющую определенным финансово-временным затратам.Методология проведения работы: Данная работа основана на применении теории графов к вопросам построения стратегии развития сложных экономико-логистических систем.Результаты работы: В статье исследуется вопрос формирования и выбора стратегии развития и модернизации транспортнологистических маршрутов в Арктической зоне РФ. Особое внимание уделяется основному арктическому маршруту – Северному морскому пути. На основе изучения основных проблем в развитии этого транспортного коридора в работе предлагается последовательный ряд шагов, включающий такие меры, как обновление инфраструктуры СМП, увеличение его пропускной способности, создание системы информационного обеспечения для безопасного и эффективного судоходства, а также соответствующие изменения законодательства для создания портовых особых экономических зон. По мнению авторов, эти шаги существенным образом повысят конкурентоспособность СМП по сравнению с альтернативными транспортно-логистическими коридорами. В исследовании предлагается также алгоритм выбора наиболее оптимального пути реализации стратегии развития СМП, которая сделает возможным достижение главной цели – обеспечение пропускной способности  маршрута на уровне 30 млн тонн грузов в год к 2030 году.Выводы: Материалы, изложенные в статье, указывают на особую важность Арктических транспортно-логистических коридоров для социально-экономического развития страны и соответствующих регионов. Одной из важнейших  транспортных артерий в Арктике является Северный морской путь. В статье анализируются динамика, проблемные аспекты, а также перспективы его развития. Авторами, на основе проведенных исследований и с применением теории графов, выбирается стратегия модернизации и развития СМП во временном горизонте до 2030 года

Innovation Networks Modeling within the Concept of Open Innovations

The urgency of the problem discussed in the article is caused by necessity to search for effective forms of innovation activities' implementation, providing a maximizing of innovative resources' impact by strengthening relationships between entities of the innovation process. The purpose of the article is to develop a model of innovation network, facilitating the acceleration of the diffusion of innovation by increasing its throughput capability and maximum use of the resources of the state innovation system. The leading approach to the study of this problem is the system approach, according to which the interaction of entities in the innovation process is considered as a complex mechanism of communications, ensuring the transformation of innovative ideas into marketable final product. In this paper, a model of innovation network, meeting the requirements of the concept of open innovation, based on the effect of increasing returns of resources is proposed and the mechanism and the necessary conditions for its functioning are described. The materials presented in the paper can be used to develop long-term development programs, both locally and at the regional and Federal levels, while building the innovative systems of the appropriate level and providing adequate conditions for their functioning. Keywords: innovation, innovation network, an innovative system, throughput capability, the diffusion of innovations. JEL Classifications: G14, L11, O31, O3