174 research outputs found
Shaping the past and comprehending the present: The World of Russian émigré textbooks in the 1920s – 1930s
Russian emigration after the 1917 revolution gave birth to a special culture of memory and a specific historical consciousness. These processes were greatly influenced by the dramatic events of the recent past (the First World War, the Revolution of 1917, the Civil War and the Exodus), which took on the character of historical trauma. The article focuses on how Russian émigré scholars tried to interpret complex issues of the Russian past and present in history textbooks. In this article, the textbooks by three historians (E. F. Shmurlo, L. M. Sukhotin and R. Yu. Wipper) are analyzed. The author of the article attempts to understand how these scholars assessed the Russian imperial past, including expansion, and how they explained the reasons for the Revolution and the collapse of statehood in 1917
A connection between -ray and parsec-scale radio flares in the blazar 3C 273
We present a comprehensive 5-43 GHz VLBA study of the blazar 3C 273 initiated
after an onset of a strong -ray flare in this source. We have analyzed
the kinematics of new-born components, light curves, and position of the
apparent core to pinpoint the location of the -ray emission. Estimated
location of the -ray emission zone is close to the jet apex, 2 pc to 7
pc upstream from the observed 7 mm core. This is supported by ejection of a new
component. The apparent core position was found to be inversely proportional to
frequency. The brightness temperature in the 7 mm core reached values up to at
least K during the flare. This supports the dominance of particle
energy density over that of magnetic field in the 7 mm core. Particle density
increased during the radio flare at the apparent jet base, affecting
synchrotron opacity. This manifested itself as an apparent core shuttle along
the jet during the 7 mm flare. It is also shown that a region where optical
depth decreases from to spans over several parsecs along
the jet. The jet bulk flow speed estimated at the level of 12c on the basis of
time lags between 7 mm light curves of stationary jet features is 1.5 times
higher than that derived from VLBI apparent kinematics analysis.Comment: Accepted for publication in MNRAS. 17 pages, 15 figures, 10 tables,
with supplementary materials attache
NLTE analysis of the Gaia-ESO spectroscopic survey.
In this work, we develop the spectral analysis pipeline that combines the NLTE synthetic spectra withthe Payne spectral model (Ting et al.2018). We compute two spectral grids, one grid with all elements treated in LTE and a second grid with iron, magnesium, titanium and manganese modelled in NLTE, to study the NLTE effects on the determination of the stellar parameters and chemical abundances.
This pipeline is applied to spectra from the third public data release of the Gaia-ESO (Gilmore et al. 2012). We validate the method on the subsample of standard stars and cluster’s members and find significant differences between NLTE and LTE in the metal-poor regime. All clusters are homogeneous in Fe and Ti, but several globular clusters showed significant dispersion in [Mg/Fe]. The depletion of the mean [Mg/Fe] in several globular clusters, compared to field stars of the same metallicity, may indicate their ex-situ formation history. We also combine our NLTE results with Gaia DR2 (Gaia Collaboration et al.2018) astrometric data to study Galactic chemo-dynamic evolution. We apply chemical separation to select high-[α/Fe] and low-[α/Fe] disk populations, with halo stars selected using kinematics. We confirm previous results like super-solar Mg abundance in the metal-poor regime and decrease of [Mg/Fe] to the solar abundances in the metal-rich regime. We find a constant NLTE [Mg/Fe]∼0.3 dex ratio for both metal-poor disk and halo with relatively small star-to-star scatter. The halo stars with solar-like [Mg/Fe] are probably accreted from the other galaxies. The observed eccentricity distribution for high-[α/Fe] disk population rules out a violent thick disk formation mechanisms like direct accretion and dynamic heating. The measured chemical and kinematic gradients and velocity dispersions of the high-[α/Fe] population can be explained by the gas-rich merger scenario with thenon-negligible contribution from the radial migration
Spectroscopic triples and a chance alignment. A solution for a problem of suspicious mass ratios for SB2s from Wilson method
We selected three double-lined spectroscopic binary systems which have
extreme mass ratios, if measured using the Wilson method. We analysed medium
resolution spectroscopic observations and space-based photometry and find that
all these systems are not SB2, but rather triple systems and a chance alignment
of another star with SB1 that have an unseen component. Therefore suspicious
mass ratios determined by the Wilson method for some double-lined spectroscopic
binary systems aren't correct as these systems are more complex.Comment: 10 pages, accepted in MNRA
TLB virtualization in the context of hypervisor verification
In this thesis we address the challenges of hypervisor verification for multicore processors. As a first contribution we unite different pieces of hypervisor verification theory into a single theory comprising the stack of highly nontrivial computational models used. We consider multicore hypervisors for x8664 architecture written in C. To make code verification in a C verifier possible, we define a reduced hardware model and show that under certain safety conditions it simulates the full model. We introduce an extension of the C semantics, which takes into consideration possible MMU and guest interaction with the memory of a program. We argue that the extended C semantics simulates the hardware machine, which executes compiled hypervisor code, given that the compiler is correct.
The second contribution of the thesis is the formal verification of a software TLB and memory virtualization approach, called SPT algorithm. Efficient TLB virtualization is one of the trickiest parts of building correct hypervisors. An SPT algorithm maintains dedicated sets of ‘‘shadow’’ page tables, ensuring memory separation and correct TLB abstraction for every guest. We use our extended C semantics to specify correctness criteria for TLB virtualization and to verify a simple SPT algorithm written in C. The code of the algorithm is formally verified in Microsoft’s VCC automatic verifier, which is ideally suited for proofs performed on top of our semantic stack.Die vorliegende Arbeit beschäftigt sich eingehend mit der Verifikation von Hypervisorn und den Herausforderungen, die dabei auftreten. Als ein Hauptergebnis werden erstmalig die verschiedenen Teile der HypervisorVerifikationstheorie zu einer einheitlichen Theorie zusammengefasst, in der mehrere komplexen Rechenmodelle auf einander aufbauen. Als Zielplattform für die Virtualisierung wählten wir eine x86-64 Architektur und betrachten Hypervisoren für Multicore-Prozessoren, die in C implementiert sind. Um Code-Verifikation in einem C-Verifizierer zu ermöglichen, definieren wir ein reduziertes Hardware-Modell und zeigen, dass unter bestimmten Bedingungen das ursprüngliche Modell davon simuliert wird. Die C-Semantik wird so erweitert, dass mögliche MMU- und Gast-Interaktionen mit dem Speicher eines Programms berücksichtigt werden. Unter der Annahme, dass der HyperviserCode mit einem korrekten Compiler kompiliert wird, argumentieren wir, dass die erweiterte C-Semantik die Hardware-Maschine, welche den kompilierten Code ausführt, simuliert. Ein weiterer Beitrag dieser Arbeit ist die formale Verifikation eines Algorithmus zur Speicher und TLB-Virtualisierung, der mit Shadow Page Tables (SPTs) arbeitet. Ein SPT-Algorithmus verwaltet Seitentabellen und garantiert Speicherseparierung sowie eine korrekte TLB-Abstraktion für alle Gäste. Wir benutzen unsere erweiterte C-Semantik, um die Korrektheitskriterien für die TLB-Virtualisierung zu spezifizieren und um einen einfachen SPT-Algorithmus zu verifizieren. Die Korrektheit des in C implementierten Algorithmus wurde formal bewiesen mit Hilfe des automatischen Beweiser VCC, der von Microsoft entwickelt wurde
Search for spectroscopic binaries using rotational velocities in five open clusters observed by ESO
In this paper we detect double-lined spectroscopic binaries (SB2) in five
open clusters: NGC 2243, NGC 2420, NGC 3532, NGC 6253 and NGC 6705 (M 11) using
a method based on high values of the projected rotational velocity when they
are fitted with single star spectral model. Observed spectra were obtained from
ESO archive. The method was validated on sets of synthetic spectra for the
single and binary stars. It is able to reliably select spectroscopic binaries
without confusing them with single stars, if components in binary rotate slowly
and radial velocity separation is sufficiently high. We found 60 SB2
candidates: two in NGC~2243, eight in NGC~2420 and NGC~3532, 17 in NGC 6253 and
25 in NGC~6705. Comparison with literature confirms 18 of them, thus we found
42 new SB2 candidates.Comment: accepted in MNRAS 07.12.202
r-process Abundance Patterns in the Globular Cluster M92
Whereas light element abundance variations are a hallmark of globular
clusters, there is little evidence for variation in neutron-capture elements. A
significant exception is M15, which shows a star-to-star dispersion in
neutron-capture abundances of at least one order of magnitude. The literature
contains evidence both for and against a neutron-capture dispersion in M92. We
conducted an analysis of archival Keck/HIRES spectra of 35 stars in M92, 29 of
which are giants, which we use exclusively for our conclusions. M92 conforms to
the light element abundance variations typical of massive clusters. Like other
globular clusters, its neutron-capture abundances were generated by the
r-process. We confirm a star-to-star dispersion in the r-process. Unlike M15,
the dispersion is limited to "first-generation" (low Na, high Mg) stars, and
the dispersion is smaller for Sr, Y, and Zr than for Ba and the lanthanides.
This is the first detection of a relation between light element and
neutron-capture abundances in a globular cluster. We propose that a source of
the main r-process polluted the cluster shortly before or concurrently with the
first generation of star formation. The heavier r-process abundances were
inhomogeneously distributed while the first-generation stars were forming. The
second-generation stars formed after several crossing times (~0.8 Myr); hence,
the second generation shows no r-process dispersion. This scenario imposes a
minimum temporal separation of 0.8 Myr between the first and second
generations.Comment: 35 pages, 12 figures, accepted for publication in Ap
Detection of 12426 SB2 candidates in the LAMOST-MRS, using a binary spectral model
We use an updated method for the detection of double-lined spectroscopic
binaries (SB2) using values from spectral fits. The method is
applied to all spectra from LAMOST-MRS. Using this method, we detect 12426 SB2
candidates, where 4321 are already known and 8105 are new discoveries. We check
their spectra manually to minimise possible false positives. We also detect
several cases of contamination of the spectra by solar light. Additionally, for
candidates with multiple observations we compute mass ratios with systemic
velocities and determine Keplerian orbits. We present an updated catalogue of
all SB2 candidates together with additional information for some of them in
separate data tables.Comment: accepted in MNRAS 2023-10-16. arXiv admin note: substantial text
overlap with arXiv:2207.0699
Crisis and sustainable business in Central and Eastern Europe: Haniel-Seminar discussion paper
--Internationalization,economic crisis,Russia,Hungary,Belarus
Plasticity of anchors in damaged by earthquake concrete base
Most frequently used types of anchors were subjected to experimental studies to obtain valid data on post-installed anchors, such as mechanical anchors (wedge expansion anchors, undercut anchors); bonded anchors (with epoxy resin) and bent cast-in-place anchors. The authors studied the effect of an earthquake-induced damage (plastic deformation) of a concrete base and multi-cyclic dynamic loads, similar to seismic ones, on plasticity of anchors. Plastic phase deformation in case of reinforced concrete base was simulated as a system of cracks of different opening width. The results of the research show that increase in the width of the crack opening from 1.5 to 3.0 mm leads to a decrease in the values of the plasticity factors. Dynamic loading does not lead to a significant change in the plasticity factor related to static loading for all failure mechanisms, except for the bond failure. On the base of obtained results reduction factors of seismic loads may be determined for further calculation of anchor joints subjected to seismic impact
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