460 research outputs found
Reply to Comment by D. Spemann et al [EPL 98 (2012) 57006, arXiv:1204.2992]
This article is a reply to the Comment by D. Spemann et al (arXiv:1204.2992)
in response to our paper 'Revealing common artifacts due to ferromagnetic
inclusions in highly oriented pyrolytic graphite' (EPL, 97 (2012) 47001).Comment: Reply to arXiv:1204.2992 Comment by D. Spemann et al re
arXiv:1201.6374 by Sepioni et a
PanDA Workload Management System Meta-data Segmentation
AbstractThe PanDA (Production and Distributed Analysis) workload management system (WMS) was developed to meet the scale and complexity of LHC distributed computing for the ATLAS experiment. PanDA currently distributes jobs among more than 100,000 cores at well over 120 Grid sites, supercomputing centers, commercial and academic clouds. ATLAS physicists submit more than 1.5M data processing, simulation and analysis PanDA jobs per day, and the system keeps all meta-information about job submissions and execution events in Oracle RDBMS. The above information is used for monitoring and accounting purposes. One of the most challenging monitoring issues is tracking errors that has occurred during the execution of the jobs. Current meta-data storage technology doesn’t support inner tools for data aggregation, needed to build error summary tables, charts and graphs. Delegating these tasks to the monitor slows down the execution of requests.We will describe a project aimed at optimizing interaction between PanDA front-end and back-end, by meta-data storage segmentation into two parts – operational and archived. Active meta-data are remained in Oracle database (operational part), due to the high requirements for data integrity. Historical (read-only) meta-data used for the system analysis and accounting are exported to NoSQL storage (archived part). New data model based on usage of Cassandra as the NoSQL backend has been designed as a set of query-specific data structures. This allowed to remove most of data preparation workload from PanDA Monitor and improve its scalability and performance. Segmentation and synchronization between operational and archived parts of jobs meta-data is provided by a Hybrid Meta-data Storage Framework (HMSF). PanDA monitor was partly adopted to interact with HMSF. The operational data queries are forwarded to the primary SQL-based repository and the analytic data requests are processed by NoSQL database. The results of performance and scalability tests of HMSF-adopted part of PanDA Monitor shows that presented method of optimization, in conjunction with a properly configured NoSQL database and reasonable data model, provides performance improvements and scalability
The Intelligent System of the Hearing Investigation
This paper describes a prototype of the intelligent system of the hearing investigation developed by
the Tver State Technical University. The problem of automatic diagnostics, considered as the recognition
problem of object not completely determined on set of the diseases classes’ descriptions, is discussed. The
management strategy of the hearing investigation is proposed
Instabilities in the Flux Line Lattice of Anisotropic Superconductors
The stability of the flux line lattice has been investigated within
anisotropic London theory. This is the first full-scale investigation of
instabilities in the `chain' state. It has been found that the lattice is
stable at large fields, but that instabilities occur as the field is reduced.
The field at which these instabilities first arise, ,
depends on the anisotropy and the angle at which the
lattice is tilted away from the -axis. These instabilities initially occur
at wavevector , and the component of along the
average direction of the flux lines, , is always finite. As the
instability occurs at finite the dependence of the cutoff on is
important, and we have used a cutoff suggested by Sudb\ospace and Brandt. The
instabilities only occur for values of the anisotropy appropriate to
a material like BSCCO, and not for anisotropies more appropriate to YBCO. The
lower critical field is calculated as a function of the angle
at which the applied field is tilted away from the crystal axis. The
presence of kinks in is seen to be related to instabilities in
the equilibrium flux line structure.Comment: Extensively revised paper, with modified analysis of elastic
instabilities. Calculation of the lower critical field is included, and the
presence of kinks in is seen to be related to the elastic
instabilities. 29 pages including 16 figures, LaTeX with epsf styl
Negative local resistance caused by viscous electron backflow in graphene
Graphene hosts a unique electron system in which electron-phonon scattering
is extremely weak but electron-electron collisions are sufficiently frequent to
provide local equilibrium above liquid nitrogen temperature. Under these
conditions, electrons can behave as a viscous liquid and exhibit hydrodynamic
phenomena similar to classical liquids. Here we report strong evidence for this
transport regime. We find that doped graphene exhibits an anomalous (negative)
voltage drop near current injection contacts, which is attributed to the
formation of submicrometer-size whirlpools in the electron flow. The viscosity
of graphene's electron liquid is found to be ~0.1 m /s, an order of
magnitude larger than that of honey, in agreement with many-body theory. Our
work shows a possibility to study electron hydrodynamics using high quality
graphene
Measuring Hall Viscosity of Graphene's Electron Fluid
Materials subjected to a magnetic field exhibit the Hall effect, a phenomenon
studied and understood in fine detail. Here we report a qualitative breach of
this classical behavior in electron systems with high viscosity. The viscous
fluid in graphene is found to respond to non-quantizing magnetic fields by
producing an electric field opposite to that generated by the classical Hall
effect. The viscous contribution is large and identified by studying local
voltages that arise in the vicinity of current-injecting contacts. We analyze
the anomaly over a wide range of temperatures and carrier densities and extract
the Hall viscosity, a dissipationless transport coefficient that was long
identified theoretically but remained elusive in experiment. Good agreement
with theory suggests further opportunities for studying electron
magnetohydrodynamics.Comment: 18 pages, 9 figure
Commensurability Effects in Viscosity of Nanoconfined Water
The rate of water flow through hydrophobic nanocapillaries is greatly
enhanced as compared to that expected from macroscopic hydrodynamics. This
phenomenon is usually described in terms of a relatively large slip length,
which is in turn defined by such microscopic properties as the friction between
water and capillary surfaces, and the viscosity of water. We show that the
viscosity of water and, therefore, its flow rate are profoundly affected by the
layered structure of confined water if the capillary size becomes less than 2
nm. To this end we study the structure and dynamics of water confined between
two parallel graphene layers using equilibrium molecular dynamics simulations.
We find that the shear viscosity is not only greatly enhanced for subnanometer
capillaries, but also exhibits large oscillations that originate from
commensurability between the capillary size and the size of water molecules.
Such oscillating behavior of viscosity and, consequently, the slip length
should be taken into account in designing and studying graphene-based and
similar membranes for desalination and filtration.Comment: 21 pages, 5 figures, ACS Nano, ASAP (2016
Revealing common artifacts due to ferromagnetic inclusions in highly-oriented pyrolytic graphite
We report on an extensive investigation to figure out the origin of
room-temperature ferromagnetism that is commonly observed by SQUID magnetometry
in highly-oriented pyrolytic graphite (HOPG). Electron backscattering and X-ray
microanalysis revealed the presence of micron-size magnetic clusters
(predominantly Fe) that are rare and would be difficult to detect without
careful search in a scanning electron microscope in the backscattering mode.
The clusters pin to crystal boundaries and their quantities match the amplitude
of typical ferromagnetic signals. No ferromagnetic response is detected in
samples where we could not find such magnetic inclusions. Our experiments show
that the frequently reported ferromagnetism in pristine HOPG is most likely to
originate from contamination with Fe-rich inclusions introduced presumably
during crystal growth.Comment: 8 pages, 7 figure
Formation of Professional Language Competence of Foreign Students in the Process of Teaching Architectural and Urban Terminology in the Lessons of Russian Language
Techniques and methods of teaching architectural and town-planning terminology at the lessons of Russian as a foreign language is presented. The authors believe that, despite the large number of works devoted to the problem of terminology, the field of architectural terminology and the language of architecture is not sufficiently studied. The article summarizes the experience of teachers of Russian Language Department of Novosibirsk state University of Architecture and Construction (sibstrin), where pedagogical techniques have been developed for many years, and textbooks and teaching materials on the formation of communicative competences in the field of professional communication for foreign students of different levels of education are published. This article examines and analyzes the complex terminological system of sub-language of architecture and urban planning. Methods of teaching foreign students of architectural direction of special vocabulary of the studied disciplines is proposed. Proposed is the model of education, which involves the acquaintance of foreign students with architectural and urban planning terms, taking into account their form, semantics and peculiarities of functioning in the scientific text. Classification of architectural and urban planning terms is presented. Productive types of tasks for independent work of foreign students are considered. The expediency of drawing up educational thematic mini-dictionaries of basic terms on the main studied disciplines is proved
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