ABSTRACT
Isolated black holes (IBHs) are not usually considered to be important astrophysical sources, since, even in the case of a high accretion rate, an accretion disc rarely can be formed due to ...the small angular momentum of the infalling matter. Thus, such systems are not expected to feature thermal disc emission which makes the dominant contribution to the radiative output of binary systems harbouring a BH. Moreover, due to their relatively modest accretion rates, these objects are not conventionally treated as feasible jet sources. However, the large number of IBHs in the Galaxy, estimated to be ∼108, implies a very high density of 10−4 pc−3 and an average distance between IBHs of ∼10 pc. Our study shows that the magnetic flux, accumulated on the horizon of an IBH because of accretion of interstellar matter, allows the Blandford–Znajeck mechanism to be activated. Thus, electron–positron jets can be launched. We have performed 2D numerical modelling which allowed the jet power to be estimated. Their inferred properties make such jets a feasible electron accelerator which, in molecular clouds (MCs), allows electron energy to be boosted up to ∼1 PeV. For the conditions expected in MCs, the radiative cooling time should be comparable to the escape time. Thus, these sources can contribute both to the population of unidentified point‐like sources and to the local cosmic‐ray (CR) electron spectrum. The impact of the generated electron CRs depends on the diffusion rate inside MCs. If the diffusion regime in a MC is similar to Galactic diffusion, the produced electrons should rapidly escape the cloud and contribute to the Galactic CR population at very high energies, >100 TeV. However, due to the modest jet luminosity (at the level of ∼1035 erg s−1) and low filling factor of MCs, these sources cannot make a significant contribution to the spectrum of CR electrons at lower energies. On the other hand, if the diffusion within MCs operates at a rate close to the Bohm limit, the CR electrons escaping from the source should be confined in the cloud, significantly contributing to the local density of CRs. The inverse Compton emission of these locally generated CRs may explain the variety of gamma‐ray spectra detected from nearby MCs.
We report on the first X-ray observation of the 0.28 s isolated radio pulsar PSR J1154-6250 obtained with the XMM-Newton observatory in 2018 February. A point-like source is firmly detected at a ...position consistent with that of PSR J1154-6250. The two closest stars are outside the 3 confidence limits of the source position and thus unlikely to be responsible for the observed X-ray emission. The energy spectrum of the source can be fitted equally well either with an absorbed power law with a steep photon index Γ 3.3 or with an absorbed blackbody with temperature kT = 0.21 0.04 keV and emitting radius RBB 80 m (assuming a distance of 1.36 kpc). The X-ray luminosity of 4.4 × 1030 erg s−1 derived with the power-law fit corresponds to an efficiency of , similar to those of other old pulsars. The X-ray properties of PSR J1154-6250 are consistent with an old age and suggest that the spatial coincidence of this pulsar with the OB association Cru OB1 is due to a chance alignment.
The capacity fade of Sony 18650S Li-ion cells has been analyzed using cyclic voltammetry, impedance spectroscopy and electron probe microscopic analysis (EPMA). The surface resistance at both the ...positive (LiCoO
2) and negative (carbon) electrodes were found to increase with cycling. This increase in resistance contributes to decreased capacity. Impedance data reveal that the interfacial resistance at LiCoO
2 electrode is larger than that at the carbon electrode. The impedance of the positive electrode (LiCoO
2) dominates the total cell resistance initially and also after 800 charge–discharge cycles. EPMA analysis on carbon electrodes taken from the fresh and cycled cell show the presence of oxidation products in the case of cycled cells. No change in the electrolyte resistance is seen with cycling.
Abstract
Problems of optimization of special electrical and electromechanical systems in modeling, creation and design are solved mainly by methods of mathematical programming. The task of ...mathematical programming is to find extremes of the function of many variables in the presence of restrictions on variables, which creates fundamental difficulties. To solve such problems, the number of methods for solving the general problem of mathematical programming is currently expanding significantly. In this regard, the trend in the development of mathematical programming is following the path of highlighting and studying various subclasses of problems. The use of certain specific features of the tasks of the selected subclass creates opportunities for their more effective investigation and solution. Examples of such subclasses give convex, quadratic, linear programming problems, transport-type problems, and others. Geometric programming is also a section of mathematical programming that research a certain class of optimization problems. However, when using geometric programming, you have to apply linear, nonlinear programming, the concept of convex programming. Using optimization methods will allow you to correctly investigate, design and create special electric drives.
The Arctic zone of the Russian Federation is one of the most intensively developing regions of the country. Amongst the major domains of economic and industrial growth and improvement is transport ...infrastructure and particularly the railway network. This area is being exposed to negative factors of rapid climate change that can significantly affect and compromise this activity. Thus, it is vital to take them into account during design, construction, and operation of the railway infrastructure facilities. This work details the production of a digital atlas comprising the 1950–2021 dynamics of the main hydrometeorological parameters: air and soil temperature, precipitation, wind speed, air and soil humidity, and snow cover thickness. The maps are based on climatic data derived from the MERRA-2 (Modern-Era Retrospective Analysis for Research and Applications, version 2) reanalysis. In total there are 459, which are arranged into 7 chapters. The atlas geographically covers the western part of the Russian Arctic encompassing the regions of quite intensive transport development, which includes the construction of the Northern Latitudinal Railway. Original algorithms of geospatial data processing and their further representation as well as the maps compiled in GIS environment are discussed. Comprehensive analysis of climatic changes in the region of the Russian Arctic including detailed quantitative evaluation over 40 years is given. In the Discussion, we focus on those changes of the regional climate which, from our point of view, are the most significant for consideration by railway operators. The obtained results contribute to framing the theoretical basis of design, development, and sustainable operation of the railway infrastructure in the Arctic and facilitate the decision-making process. This is the first experience of building a specialized climatic cartographic product for the needs of the Russian railways, and to our knowledge the first atlas such as that in the world. In the future, the amassed experience may be transferred to other regions of the Russian Federation as well as similar regions in Canada, Sweden and Highland China that are also subject to significant climate change.
Time projection chambers for the T2K near detectors Abgrall, N.; Andrieu, B.; Baron, P. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
05/2011, Letnik:
637, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The T2K experiment is designed to study neutrino oscillation properties by directing a high intensity neutrino beam produced at J-PARC in Tokai, Japan, towards the large Super-Kamiokande detector ...located 295
km away, in Kamioka, Japan. The experiment includes a sophisticated near detector complex, 280
m downstream of the neutrino production target in order to measure the properties of the neutrino beam and to better understand neutrino interactions at the energy scale below a few GeV. A key element of the near detectors is the ND280 tracker, consisting of two active scintillator–bar target systems surrounded by three large time projection chambers (TPCs) for charged particle tracking. The data collected with the tracker are used to study charged current neutrino interaction rates and kinematics prior to oscillation, in order to reduce uncertainties in the oscillation measurements by the far detector. The tracker is surrounded by the former UA1/NOMAD dipole magnet and the TPCs measure the charges, momenta, and particle types of charged particles passing through them. Novel features of the TPC design include its rectangular box layout constructed from composite panels, the use of bulk micromegas detectors for gas amplification, electronics readout based on a new ASIC, and a photoelectron calibration system. This paper describes the design and construction of the TPCs, the micromegas modules, the readout electronics, the gas handling system, and shows the performance of the TPCs as deduced from measurements with particle beams, cosmic rays, and the calibration system.
► First large scale time projection chambers with micropattern gas detectors. ► Incorporates new ASIC for electronic readout. ► Includes a pressure equalizing gas system and a photoelectron calibration system. ► Specifications achieved as deduced from neutrino, cosmic, and calibration tests. ► Will play an important role in T2K to measure neutrino oscillations.
Recently, Lee et al. used Gaussian mixture models (GMM) to study the radio pulsar population. P -Ṗ plane, they found four clusters. We develop this approach further and apply it to different ...synthetic pulsar populations in order to determine whether the method can effectively select groups of sources that are physically different. We check several combinations of initial conditions as well as the models of pulsar evolution and the selection effects. We find that in the case of rapidly evolving objects, the GMM is oversensitive to parameter variations and does not produce stable results. We conclude that the method does not help much to identify the subpopulations with different initial parameters or/and evolutionary paths. For the same reason, the GMM does not discriminate effectively between theoretical population synthesis models of normal radio pulsars.
The critical point of dense, strongly interacting matter is searched for at the CERN SPS in
40
Ar +
45
Sc collisions at 150
A
Ge V /
c
. The dependence of second-order scaled factorial moments of ...proton multiplicity distribution on the number of subdivisions of transverse momentum space is measured. The intermittency analysis is performed using both transverse momentum and cumulative transverse momentum. For the first time, statistically independent data sets are used for each subdivision number. The obtained results do not indicate any statistically significant intermittency pattern. An upper limit on the fraction of correlated proton pairs and the power of the correlation function is obtained based on a comparison with the Power-law Model developed for this purpose.
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