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Regular version of the site
Of all publications in the section: 156
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Article
Hushchyn M., Charpentier P., Ustyuzhanin A. Journal of Physics: Conference Series. 2015. Vol. 664.

This paper presents a system providing recommendations for optimizing the LHCb data storage. The LHCb data storage system is a hybrid system. All datasets are kept as archives on magnetic tapes. The most popular datasets are kept on disks. The recommendation system takes the dataset usage history and metadata (size, type, configuration etc.) to generate a recommendation report. In this article present how we use machine learning algorithms to predict future data popularity. Using these predictions it is possible to estimate which datasets should be removed from disk. We use regression algorithms and time series analysis to find the optimal number of replicas for datasets that are kept on disk. Based on the data popularity and the number of replicas optimization, the recommendation system minimizes a loss function to find the optimal data distribution. The loss function represents all requirements for data distribution in the data storage system. We demonstrate how the recommendation system helps to save disk space and to reduce waiting times for jobs using this data.

Added: Dec 21, 2015
Article
Natanzon S. M. Journal of Physics: Conference Series. 2016. Vol. 670. P. 1-6.

We describe all formal symmetric solutions of dispersionless 2D Toda hierarchy. This classi cation we use for solving of two classical problems: 1) The calculation of conformal mapping of an arbitrary simply connected domain to the standard disk; 2) Calculation of 2-Hurwitz numbers of genus 0.

Added: Feb 10, 2016
Article
Manita A., Manita L. Journal of Physics: Conference Series. 2018. Vol. 955. No. 012038. P. 1-6.

We propose new deterministic and stochastic models for synchronization of clocks in nodes of distributed networks. An external accurate time server is used to ensure convergence of the node clocks to the exact time. These systems have much in common with mathematical models of opinion formation in multiagent systems. There is a direct analogy between the time server/node clocks pair in asynchronous networks and the leader/follower pair in the context of social network models.

Added: May 19, 2018
Article
Рыжиков А. С., Ustyuzhanin A. Journal of Physics: Conference Series. 2018. Vol. 1085. P. 1-6.

In the research, a new approach for finding rare events in high-energy physics was tested. As an example of physics channel the decay of \tau -> 3 \mu is taken that has been published on Kaggle within LHCb-supported challenge. The training sample consists of simulated signal and real background, so the challenge is to train classifier in such way that it picks up signal/background differences and doesn’t overfits to simulation-specific features. The approach suggested is based on cross-domain adaptation using neural networks with gradient reversal. The network architecture is a dense multi-branch structure. One branch is responsible for signal/background discrimination, the second branch helps to avoid overfitting on Monte-Carlo training dataset. The tests showed that this architecture is a robust a mechanism for choosing tradeoff between discrimination power and overfitting, moreover, it also improves the quality of the baseline prediction. Thus, this approach allowed us to train deep learning models without reducing the quality, which allow us to distinguish physical parameters, but do not allow us to distinguish simulated events from real ones. The third network branch helps to eliminate the correlation between classifier predictions and reconstructed mass of the decay, thereby making such approach highly viable for great variety of physics searches.

Added: Dec 11, 2017
Article
Norman G., Timofeev A. Journal of Physics: Conference Series. 2016. Vol. 774. No. 012170. P. 1-8.

The self-consistency and basic openness of dusty plasma, charge fluctuations, high dissipation and other features of dusty plasma system lead to the appearance of a number of unusual and unique properties of dusty plasma. “Anomalous” heating of dusty particles, anisotropy of temperatures and other features, parametric resonance, charge fluctuations and interaction potential are among these unique properties. Study is based on analytical approach and numerical simulation. Mechanisms of “anomalous” heating and energy transfer are proposed. Influence of charge fluctuations on the system properties is discussed. The self-consistent, many-particle, fluctuation and anisotropic interparticle interaction potential is studied for a significant range of gas temperature. These properties are interconnected and necessary for a full description of dusty plasmas physics.

Added: Feb 17, 2017
Article
Popel S I, Golub’ A. P., Zakharov A. V. et al. Journal of Physics: Conference Series. 2019. Vol. 1147. P. 1-11.

Dusty plasmas are shown to be formed in a surface layer over the illuminated part of Martian satellites Phobos and Deimos owing to photoelectric and electrostatic processes. The distribution functions of photoelectrons near surfaces of the satellites, altitude dependences of the density of dust particles, and their charges and sizes, as well as electric fields, have been determined within a physical-mathematical model for the self-consistent description of densities of photoelectrons and dust particles over the surface of the illuminated parts of Phobos and Deimos. In view of a weak gravitational field, dust particles rising over the surfaces of Phobos and Deimos are larger than those over the surface of the Moon. In this case, the role of adhesion, which is a significant process preventing the separation of dust particles from the lunar surface, is much smaller on Phobos and Deimos.

Added: Jan 21, 2019
Article
Popel S.I., Golub' A. P., Zelenyi L.M. et al. Journal of Physics: Conference Series. 2018. Vol. 946. P. 012142-1-012142-9.

A possibility of the formation in the lunar exosphere of dust cloud due to meteoroid impacts onto the lunar surface is studied. The main attention is paid to the high altitudes over the lunar surface including the range of the altitudes between 30 and 110 km where the measurements of dust were performed within the NASA LADEE mission. From the viewpoint of the formation of dust cloud at high altitudes over the Moon, the most important zone formed by the meteoroid impact is the zone of melting of substance. Only the droplets originated from this zone have the speeds between the first and second astronautical velocities (for the Moon). Correspondingly, only such droplets can perform finite movement around the Moon. The liquid droplets harden when rising over the lunar surface. Furthermore, they aquire electric charges due to the action, in particular, of the solar wind electrons and ions, as well as of the solar radiation. Thus dusty plasmas exist in the lunar exosphere with the characteristic number density $\lesssim 10^{-2}$~m$^{-3}$ of dust particles with the sizes from 300~nm to 1~${\rm\mu}$m which is in accordance with the results of measurements performed by LADEE.

Added: May 20, 2018
Article
Medvedev T. V., Medvedev V., Zhuzhoma E. V. Journal of Physics: Conference Series. 2018. Vol. 990. P. 1-9.

We suggest a new model of the fast nondissipative kinematic dynamo which describes the phenomenon of exponential growth of the magnetic eld caused by the motion of the conducting medium. This phenomenon is known to occur in the evolution of magnetic elds of astrophysical bodies. In the 1970s A.D. Sakharov and Ya.B. Zeldovich proposed a \rope" scheme of this process which in terms of the modern theory of dynamical systems can be described as Smale solenoid. The main disadvantage of this scheme is that it is non-conservative. Our model is a modi cation of the Sakharov-Zeldovich's model. We apply methods of the theory of dynamical systems to prove that it is free of this fault in the neighborhood of the nonwandering set.

Added: Apr 5, 2018
Article
Vlasenko V., Pervakov K., Pudalov V. et al. Journal of Physics: Conference Series. 2014. Vol. 507. No. 1. P. 022044-1-022044-4.

We report on successful fabrication of superconducting FeSe wire using hot gas extrusion (HGE) ex-situ PIT (powder in tube) method. Length of the obtained wire was about 60cm with cross-sectional superconducting core area nearly 2.5x 10^-3 cm^2. For the wire sample we observed superconducting transition temperature, T_onset =  11 K, about 1.2K lower compared to the preliminary prepared FeSe powder. Heat treatment in argon atmosphere at 350C resulted in transition width decrease from \Delta T(10% - 90%) = 1.75K in sample without heat treatment down to \Delta T = 0.9 K in annealed samples. Estimated derivative of the upper critical eld as a function of temperature of the sample annealed during 72h in argon atmosphere at 350C is dHc2/dT =2.9 T/K. Applying WHH theory to our data allows to defi ne Hc2(0K) = 0.69Tc x(dHc2/dT )=  19.8T. The untreated wire shows critical current density, Jc = 75 A/cm2 at T=4.0 K in zero fi eld. Increasing annealing time up to 72 hours at 350C in argon atmosphere gives rise to Jc increase of about 60% approaching 120 A/cm2 at T=4.0K and H=0T . Also Jc measurements were made in magnetic fields up to 9T. Our results show applicability of the HGE PIT method for fabrication of superconducting wires based on FeSe compound. Long-range heat treatment is necessary to improve superconducting properties of the samples.

Added: Mar 19, 2016
Article
Lankin A., Orekhov M. Journal of Physics: Conference Series. 2016. Vol. 774. P. 1-8.
Added: Apr 5, 2017
Article
Smirnov K., Золотов Ф. И., Romanov N. et al. Journal of Physics: Conference Series. 2018. No. 1124. P. 1-6.

The research of ultrathin vanadium nitride (VN) films as a promising candidate for superconducting single-photon detectors (SSPD) is presented. The electron diffusivity measurements are performed for such devices. Devices that were fabricated out from 9.9 nm films had diffusivity coefficient of 0.41 cm2 /s and from 5.4 nm – 0.54 cm2 /s. Obtained values are similar to other typical SSPD materials. The diffusivity that increases along with decreasing of the film thickness is expected to allow fabrication of the devices with improved characteristics. Fabricated VN SSPDs showed prominent single-photon response in the range 0.9-1.55 µm

Added: Dec 27, 2018
Article
Timofeev A., Semyonov V. Journal of Physics: Conference Series. 2016. Vol. 774. No. 012171. P. 1-5.

Dust particles under certain conditions can acquire kinetic energy of the order of 10 eV and higher, far above the temperature of gas and temperatures of ions and electrons in the discharge. Such heating can be explained by the energy transfer between degrees of freedom of a dusty plasma system. One of the mechanisms of such energy transfer is based on parametric resonance. A model of dust particles system in gas discharge plasma including fluctuations of dust particles charge and features of near-electrode layer is presented. Molecular dynamics simulation of the dust particles system is performed. Conditions of the resonance occurrence are obtained for a wide range of parameters.

Added: Feb 17, 2017
Article
Zotov L., Bizouard C. Journal of Physics: Conference Series. 2018. Vol. 955. No. 1. P. 1-6.

We study the Chandler wobble (CW) of the pole from 1846 to 2017 extracted by the Panteleev ltering. The CW has period of 433 days, average amplitude of 0.13 milliarcseconds (mas) which is changing, and phase jump by pi in 1930-th. The CW amplitude strongly (almost to zero) decreases in 1930-th and 2010-th with the phase jump in 1930th. The envelope model contains 83- and 42-years quasi-periodicities. We think the rst one can be represented by the 166-years changes of the envelope, crossing zero in 1930th. We reconstruct Chandler input excitation based on the Euler-Liouville equation. Its amplitude has 20-years variations. We explain this based on simple model and prove, that they appear in consequence of 42-years modulation of CW. The excitation ampli es the amplitude of CW for 20 years then damps it for another 20 years. The analysis of the modulated CW signal in a sliding window demonstrates the specific effect, we called the "escargot effect", when instantaneous "virtual" retrograde component appears in the purely prograde (at long-time interval) signal. Chandler excitation envelope shape is similar to this instantaneous retrograde component, which re ects the changes of ellipticity of the approximation ellipse.

Added: Feb 8, 2018
Article
Ustyuzhanin A., Artemov A., Kazeev N. et al. Journal of Physics: Conference Series. 2015. Vol. 664.

LHC experiments generate up to 10^11LHC experiments generate up to 1012 events per year. This paper describes Event Index – an event search system. Event Index’s primary function is quickly selecting subsets of events from a combination of conditions, such as the estimated decay channel or stripping lines output. Event Index is essentially Apache Lucene [1] optimized for read-only indexes distributed over independent shards on independent nodes. events per year. This paper describes Event Index – an event search system. Event Index’s primary function is quickly selecting subsets of events from a combination of conditions, such as the estimated decay channel or stripping lines output. Event Index is essentially Apache Lucene [1] optimized for read-only indexes distributed over independent shards on independent nodes.

Added: Dec 21, 2015
Article
Kazeev N., Ustyuzhanin A., Artemov A. et al. Journal of Physics: Conference Series. 2015. Vol. 664. No. 3. P. 032019-032019.

During LHC Run 1, the LHCb experiment recorded around 1011 collision events. This paper describes Event Index — an event search system. Its primary function is to quickly select subsets of events from a combination of conditions, such as the estimated decay channel or number of hits in a subdetector. Event Index is essentially Apache Lucene [1] optimized for read-only indexes distributed over independent shards on independent nodes.

Added: Oct 24, 2016
Article
Ustyuzhanin A., Babuschkin I. Journal of Physics: Conference Series. 2017. Vol. 898. No. 7. P. 1-8.

© Published under licence by IOP Publishing Ltd. Modern science clearly demands for a higher level of reproducibility and collaboration. To make research fully reproducible one has to take care of several aspects: research protocol description, data access, environment preservation, workflow pipeline, and analysis script preservation. Version control systems like git help with the workflow and analysis scripts part. Virtualization techniques like Docker or Vagrant can help deal with environments. Jupyter notebooks are a powerful platform for conducting research in a collaborative manner. We present project Everware that seamlessly integrates git repository management systems such as Github or Gitlab, Docker and Jupyter helping with a) sharing results of real research and b) boosts education activities. With the help of Everware one can not only share the final artifacts of research but all the depth of the research process. This been shown to be extremely helpful during organization of several data analysis hackathons and machine learning schools. Using Everware participants could start from an existing solution instead of starting from scratch. They could start contributing immediately. Everware allows its users to make use of their own computational resources to run the workflows they are interested in, which leads to higher scalability of the toolkit.

Added: Feb 25, 2018
Article
Bakunina I. A., Abramov-Maximov V., Osharin A. Journal of Physics: Conference Series. 2017. Vol. 798. No. 1. P. 1 -4.

Under this study we considered active region 09415 of the 23-rd cycle of solar activity which was observed with the 2D spatial resolution at three frequencies: 17 and 34 GHz with the Nobeyama Radioheliograph (NoRH) and 17 GHz with the Solar Siberian Radiotelescope (SSRT). We detected rapid development of a compact microwave source above the neutral line of the magnetic field of leading sunspot (NLS-source) few hours before the X-class flare. The position of this source is associated with the place of the maximum of magnetic field gradient at the photosphere. 

Added: May 26, 2017
Article
Zavialov V. V., Chernyaev S. A., Shein K. V. et al. Journal of Physics: Conference Series. 2017. Vol. 969. No. 012086. P. 1-7.

Cryo- lters are essential while studying electronic properties of nanoscale structures at very low temperatures. In this report we present the simple measuring methodology and experimental impedance characteristics of customized lumped lters cooled down to 4.2K in the 10 Hz-500MHz frequency range. In particular, we tested the home-made permalloy-core RL lters, the MurataTMChip Ferrite Bead lter, and the ToshibaTMAmobeadsTMcores. We use the high-frequency generalization of four-terminal sensing method to account for the wiring retardation e ects, which are important when working with ultralow temperature system

Added: Oct 1, 2017
Article
Завьялов В. В., Черняев С. А., Шеин К. В. et al. Journal of Physics: Conference Series. 2018. Vol. 969. P. 1-6.

Cryo-filters are essential while studying electronic properties of nanoscale structures at very low temperatures. In this report we present the simple measuring methodology and experimental impedance characteristics of customized lumped filters cooled down to 4.2K in the 10 Hz-500 MHz frequency range. In particular, we tested the home-made permalloy-core RL filters, the MurataTMChip Ferrite Bead filter, and the ToshibaTMAmobeadsTMcores. We use the high-frequency generalization of four-terminal sensing method to account for the wiring retardation effects, which are important when working with ultralow temperature systems.

Added: Sep 29, 2018
Article
Zavyalov V., Chernyaev S. A., Shein K. V. et al. Journal of Physics: Conference Series. 2018. Vol. 969. No. 012086. P. 1-6.

Cryo-filters are essential while studying electronic properties of nanoscale structures at very low temperatures. In this report we present the simple measuring methodology and experimental impedance characteristics of customized lumped filters cooled down to 4.2K in the 10 Hz-500 MHz frequency range. In particular, we tested the home-made permalloy-core RL filters, the MurataTMChip Ferrite Bead filter, and the ToshibaTMAmobeadsTMcores. We use the high-frequency generalization of four-terminal sensing method to account for the wiring retardation effects, which are important when working with ultralow temperature systems.

Added: Nov 10, 2018
Article
Tyurin N. A. Journal of Physics: Conference Series. 2013. Vol. doi:10.1088/1742-6596/411/1/012028. No. 411. P. 1-9.
We present a generalization of toric structures on compact symplectic manifolds called pseudotoric structure. In the present talk we show that every toric manifold admits pseudotoric structures and then we show that the construction of exotic Chekanov tori can be peformed in terms of pseudotoric structures
Added: Feb 18, 2013