1,880 research outputs found
Generalized Method Of Designing Unmanned Remotely Operated Complexes Based On The System Approach
Self-propelled underwater systems belong to the effective means of marine robotics. The advantages of their use include the ability to perform underwater work in real time with high quality and without risk to the life of a human operator. At present, the design of such complexes is not formalized and is carried out separately for each of the components – a remotely operated vehicle, a tether-cable and cable winch, a cargo device and a control and energy device. As a result, the time spent on design increases and its quality decreases. The system approach to the design of remotely operated complexes ensures that the features of the interaction of the components of the complex are taken into account when performing its main operating modes. In this paper, the system interaction between the components of the complex is proposed to take into account in the form of decomposition of “underwater tasks (mission) – underwater technology of its implementation – underwater work on the selected technology – task for the executive mechanism of the complex” operations. With this approach, an information base is formed for the formation of a list of mechanisms of the complex, the technical appearance of its components is being formed, which is important for the early design stages. Operative, creative and engineering phases of the design of the complex are proposed. For each phase, a set of works has been formulated that cover all the components of the complex and use the author's existence equations for these components as a tool for system analysis of technical solutions.The perspective of the scientific task of the creative phase to create accurate information models of the functioning of the components of the complex and models to support the adoption of design decisions based on a systematic approach is shown.The obtained results form the theoretical basis for finding effective technical solutions in the early stages of designing remotely operated complexes and for automating the design with the assistance of modern applied computer research and design packages
Supergiant, fast, but not so transient 4U 1907+09
We have investigated the dipping activity observed in the high-mass X-ray
binary 4U 1907+09 and shown that the source continues to pulsate in the "off"
state, noting that the transition between the "on" and "off" states may be
either dip-like or flare-like. This behavior may be explained in the framework
of the "gated accretion" scenario proposed to explain the flares in supergiant
fast X-ray transients (SFXTs). We conclude that 4U 1907+09 might prove to be a
missing link between the SFXTs and ordinary accreting pulsars.Comment: 4 pages 5 figures, accepted in A&
New measurement of pion directed flow relative to the spectator plane by the NA49 experiment at CERN
We report a new measurement of negatively charged pion directed flow
relative to the spectator plane for Pb+Pb collisions at the beam energy 40A GeV
recorded by the NA49 experiment at CERN. is reported as a function of
rapidity and transverse momentum in different classes of collision centrality.
The projectile spectator plane is estimated using transverse segmentation of
the NA49 forward hadron calorimeter. The new results extend the NA49 data for
, which was previously measured only relative to the participant plane,
and complement recent preliminary data by the NA61/SHINE collaboration and
published results from the STAR at RHIC beam energy scan program.Comment: Proceedings of the XIII Workshop on Particle Correlations and
Femtoscopy (WPCF 2018), 6 pages, 3 figure
Luminosity-dependent spectral and timing properties of the accreting pulsar GX 304-1 measured with INTEGRAL
Context: Be/X-ray binaries show outbursts with peak luminosities up to a few
times erg/s, during which they can be observed and studied in
detail. Most (if not all) Be/X-ray binaries harbour accreting pulsars, whose
X-ray spectra in many cases contain cyclotron resonant scattering features
related to the magnetic field of the sources. Spectral variations as a function
of luminosity and of the rotational phase of the neutron star are observed in
many accreting pulsars. Aims: We explore X-ray spectral and timing properties
of the Be/X-ray binary GX 304-1 during an outburst episode. Specifically, we
investigate the behavior of the cyclotron resonant scattering feature, the
continuum spectral parameters, the pulse period, and the energy- and
luminosity-resolved pulse profiles. We combine the luminosity-resolved spectral
and timing analysis to probe the accretion geometry and the beaming patterns of
the rotating neutron star. Methods: We analyze the INTEGRAL data from the two
JEM-X modules, ISGRI and SPI, covering the January-February 2012 outburst,
divided in six observations. We obtain pulse profiles in two energy bands,
phase-averaged and phase-resolved spectra for each observation. Results: We
confirm the positive luminosity-dependence of the cyclotron line energy in GX
304-1, and report a dependence of the photon index on luminosity. Using a
pulse-phase connection technique, we find a pulse period solution valid for the
entire outburst. Our pulse-phase resolved analysis shows, that the centroid
energy of the cyclotron line is varying only slightly with pulse phase, while
other spectral parameters show more pronounced variations. Our results are
consistent with a scenario in which, as the pulsar rotates, we are exploring
only a small portion of its beam pattern.Comment: 12 pages, 12 figures, Accepted for publication in A&
Probing the possibility of hotspots on the central neutron star in HESS J1731-347
The X-ray spectra of the neutron stars located in the centers of supernova
remnants Cas A and HESS J1731-347 are well fit with carbon atmosphere models.
These fits yield plausible neutron star sizes for the known or estimated
distances to these supernova remnants. The evidence in favor of the presence of
a pure carbon envelope at the neutron star surface is rather indirect and is
based on the assumption that the emission is generated uniformly by the entire
stellar surface. Although this assumption is supported by the absence of
pulsations, the observational upper limit on the pulsed fraction is not very
stringent. In an attempt to quantify this evidence, we investigate the
possibility that the observed spectrum of the neutron star in HESS J1731-347 is
a combination of the spectra produced in a hydrogen atmosphere of the hotspots
and of the cooler remaining part of the neutron star surface. The lack of
pulsations in this case has to be explained either by a sufficiently small
angle between the neutron star spin axis and the line of sight, or by a
sufficiently small angular distance between the hotspots and the neutron star
rotation poles. As the observed flux from a non-uniformly emitting neutron star
depends on the angular distribution of the radiation emerging from the
atmosphere, we have computed two new grids of pure carbon and pure hydrogen
atmosphere model spectra accounting for Compton scattering. Using new hydrogen
models, we have evaluated the probability of a geometry that leads to a pulsed
fraction below the observed upper limit to be about 8.2 %. Such a geometry thus
seems to be rather improbable but cannot be excluded at this stage.Comment: 8 pages, 14 figures. Accepted for publication in A&
Giant outburst of EXO 2030+375: pulse-phase resolved analysis of INTEGRAL data
In June-September 2006 the Be/X-ray binary EXO 2030+375 experienced the
second giant outburst since its discovery. The source was shown to have a
complicated pulse-averaged X-ray spectral continuum with possible evidence of
cyclotron absorption features. In this paper we present the first pulse-phase
resolved analysis of the broad band X-ray spectra of EXO 2030+375 obtained with
the INTEGRAL observatory close to the maximum and during the decay phase of the
giant outburst. We report a strong variability of the spectrum with pulse
phase. Alternative spectral continuum models are discussed. The dependence of
the spectral parameters on pulse phase during the maximum of the outburst and
the evolution of the pulse profiles with time are qualitatively consistent with
the pulsar's emission diagram changing from the fan-beam geometry close to the
maximum of the outburst to a combination of pencil and fan beams (of comparable
intesities) at the end of the decay phase. Evidence of a cyclotron absorption
line around 63 keV at the pulse phase interval preceeding the main peak of the
pulse profile is present in the spectrum obtained close to the maximum of the
outburst.Comment: 8 pages, 10 figures, accepted for publication in A&
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