3,571 research outputs found
Multiple magnon modes in the CoSnS Weyl semimetal candidate
We experimentally investigate electron transport in kagome-lattice
ferromagnet CoSnS, which is regarded as a time-reversal symmetry
broken Weyl semimetal candidate. We demonstrate curves with
pronounced asymmetric spikes, similar to those attributed to
current-induced spin-wave excitations in ferromagnetic multilayers. In contrast
to multilayers, we observe several spikes' sequences at low,
10 A/cm, current densities for a thick single-crystal
CoSnS flake in the regime of fully spin-polarized bulk. The spikes
at low current densities can be attributed to novel magnon branches in magnetic
Weyl semimetals, which are predicted due to the coupling between two magnetic
moments mediated by Weyl fermions. Presence of spin-transfer effects at low
current densities in CoSnS makes the material attractive for
applications in spintronics.Comment: final versio
Signature of Fermi arc surface states in Andreev reflection at the WTe Weyl semimetal surface
We experimentally investigate charge transport through the interface between
a niobium superconductor and a three-dimensional WTe Weyl semimetal. In
addition to classical Andreev reflection, we observe sharp non-periodic subgap
resistance resonances. From an analysis of their positions, magnetic field and
temperature dependencies, we can interpret them as an analog of Tomasch
oscillations for transport along the topological surface state across the
region of proximity-induced superconductivity at the Nb-WTe interface.
Observation of distinct geometrical resonances implies a specific transmission
direction for carriers, which is a hallmark of the Fermi arc surface states.Comment: 5 pages, some misprints has been correcte
Multivalued current-phase relationship in a.c. Josephson effect for a three-dimensional Weyl semimetal WTe
We experimentally study electron transport between two superconducting indium
leads, coupled to a single WTe crystal, which is a three-dimensional Weyl
semimetal. We demonstrate Josephson current in long 5~m In-WTe-In
junctions, as confirmed by the observation of integer (1,2,3) and fractional
(1/3, 1/2, 2/3) Shapiro steps under microwave irradiation. Demonstration of
fractional a.c. Josephson effect indicates multivalued character of the
current-phase relationship, which we connect with Weyl topological surface
states contribution to Josephson current. In contrast to topological insulators
and Dirac semimetals, we do not observe periodicity in a.c. Josephson
effect for WTe at different frequencies and power, which might reflect
chiral character of the Fermi arc surface states in Weyl semimetal.Comment: the text is seriously corrected. arXiv admin note: text overlap with
arXiv:1801.0955
Conductance oscillations and zero-bias anomaly in a single superconducting junction to a three-dimensional topological insulator
We experimentally investigate Andreev transport through a single junction
between an s-wave indium superconductor and a thick film of a three-dimensional
topological insulator. We study samples with different
bulk and surface characteristics, where the presence of a topological surface
state is confirmed by direct ARPES measurements. All the junctions demonstrate
Andreev transport within the superconducting gap. For junctions with
transparent interfaces we find a number of nearly periodic
conductance oscillations, which are accompanied by zero-bias conductance
anomaly. Both effects disappear above the superconducting transition or for
resistive junctions. We propose a consistent interpretation of both effects as
originating from proximity-induced superconducting correlations within the
topological surface state
Субъект транспортной инфраструктуры как элемент системы обеспечения транспортной безопасности
Using the methods of systematic and comparativ e analysis, the article systematized the tasks, main stages and participants in the transport security process, analyzed the role of the transport infrastructure stakeholders in this process, and formulated the functional structure of the activity of the transport infrastructure stakeholder in the form of an appropriate scheme in the framework of ensuring transport security. The main component of the transport security management system is determined. The results of the study, in addition to development of the existing methodological apparatus in the field of transport security, can be used in the following areas: in organizing the process of managing transport security of transport infrastructure facilities and vehicles of various types of transport, in the educational process of higher and secondary educational institutions, as well as educational process of specialized training centers for training of specialists in the field of transport security. The results of the study may also be of interest to officials responsible for ensuring transport security, especially in such companies as JSC Russian Railways, PJSC Aeroflot and State Unitary Enterprise Moscow Metro, which are the largest stakeholders of transport infrastructure in the Russian Federation.В статье с применением методов системного и сравнительного анализа были систематизированы задачи, основные этапы и участники процесса обеспечения транспортной безопасности, проанализирована роль субъекта транспортной инфраструктуры в данном процессе, сформирована в виде соответствующей схемы функциональная структура деятельности субъекта транспортной инфраструктуры врамках обеспечения транспортной безопасности. Определена основная составляющая системы управления обеспечения транспортной безопасности. Результаты исследования, кроме развития существующего методологического аппарата всфере обеспечения транспортной безопасности, могут быть использованы в следующих областях: при организации процесса управления обеспечением транспортной безопасности объектов транспортной инфраструктуры и транспортных средств различных видов транспорта, вучебном процессе высших исредних учебных заведений, а также учебном процессе специализированных учебных центров по подготовке специалистов в сфере обеспечения транспортной безопасности. Результаты исследования также могут представлять интерес для должностных лиц, ответственных за обеспечение транспортной безопасности, прежде всего в таких компаниях, как ОАО «Российские железные дороги», ПАО «Аэрофлот» и ГУП «Московский метрополитен», являющихся крупнейшими субъектами транспортной инфраструктуры в Российской Федерации
Unsupervised non-parametric change point detection in quasi-periodic signals
We propose a new unsupervised and non-parametric method to detect change
points in intricate quasi-periodic signals. The detection relies on optimal
transport theory combined with topological analysis and the bootstrap
procedure. The algorithm is designed to detect changes in virtually any
harmonic or a partially harmonic signal and is verified on three different
sources of physiological data streams. We successfully find abnormal or
irregular cardiac cycles in the waveforms for the six of the most frequent
types of clinical arrhythmias using a single algorithm. The validation and the
efficiency of the method are shown both on synthetic and on real time series.
Our unsupervised approach reaches the level of performance of the supervised
state-of-the-art techniques. We provide conceptual justification for the
efficiency of the method and prove the convergence of the bootstrap procedure
theoretically.Comment: 8 pages, 7 figures, 1 tabl
Обеспечение безопасности при эксплуатации беспилотных летательных аппаратов на объектах транспортной инфраструктуры
Unmanned aerial vehicles (UAV), also known as drones, are gaining more and more practical application in modern society, particularly as the tools of implementation of the concepts of «smart city», «smart health care», «smart industries», Internet of Things, 3D mapping, digital transport. But currently it is impossible to use of UAV at certain objects, comprising objects of transport infrastructure (OTI), primarily, airports, because of existing restrictions due to security threats arising during the UAV flight.The authors of the present work have set a goal to offer a solution that allows to start operating UAV at transport infrastructure facilities that are currently prohibited for UAV flights. To achieve the objective of the work, using analysis and synthesis, comparison and generalization, factors and conditions for safe use of UAV at OTI have been formulated, a method for increasing security of UAV flight has been developed, followed by the suggestion on the UAV route control system.The proposed system makes it possible to safely use UAVs at OTI by restraining their flight area strictly to the designated corridor, which eliminates a threat of a collision of UAV with other vehicles operated at OTI, dangerous elements of OTI, as well as with people at the object.The system does not need electric power feeding, which makes it possible to implement the system without creating an auxiliary power supply infrastructure.The practical application of the proposed system and, as a consequence, implementation of a greater number of opportunities for the use of UAV, are capable to generate fundamentally new technological processes and structures at transport facilities, which is one of the directions for creating the next generation transport infrastructure based on IoT and artificial intelligence.Беспилотные летательные аппараты (БПЛА), также известные как дроны или беспилотники, получают всё большее практическое применение в современном обществе, в том числе как инструменты реализации концепций «умного города», «умного здравоохранения», «умной индустрии», Интернета вещей, 3D‑картографии, цифрового транспорта. Но, в настоящий момент, применение БПЛА на определённых объектах, в том числе и транспортной инфраструктуры (ОТИ), в первую очередь, в аэропортах, невозможно в силу существующих ограничений, вызванных угрозами безопасности, возникающими при полёте БПЛА.Авторами в данной работе была поставлена цель предложить решение, позволяющее начать эксплуатацию беспилотных летательных аппаратов на объектах транспортной инфраструктуры, в настоящий момент закрытых для полётов БПЛА.Для достижения цели работы, с применением анализа и синтеза, сравнения и обобщения, сформулированы факторы и условия безопасного применения БПЛА на ОТИ, с учётом которых разработаны метод повышения безопасности движения беспилотных летательных аппаратов и реализующая его система контроля маршрутов беспилотных летательных аппаратов.Предложенная система делает возможным безопасно применять БПЛА на ОТИ за счёт ограничения зоны их полёта строго в обозначенном коридоре, что позволяет исключить угрозу столкновения БПЛА с другими транспортными средствами (ТС), эксплуатируемыми на ОТИ, опасными элементами ОТИ, людьми и т.д.Для функционирования системы не требуется электроэнергия, что позволяет внедрять систему без создания вспомогательной энергообеспечивающей инфраструктуры.Практическое применение предложенной системы и, как следствие, внедрение большего количества возможностей, возникающих при применении БПЛА, способно генерировать на объектах транспорта принципиально новые технологические процессы и структуры, что является одним из направлений создания транспортной инфраструктуры следующего поколения, основанной на IoT и искусственном интеллекте
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