1,258 research outputs found
Fundamentals of crude oil and natural gas processing
This training manual includes term project methodical guide on the course "Fundamentals of crude oil and natural gas processing" in English. The main purpose of the training manual is to provide students the theoretical and methodological assistance at performance the term project on the course "Fundamentals of crude oil and natural gas processing". The manual contains the initial data and reference material needed to perform the calculations. The manual is intended for the students of speciality 6.050304 "Oil and gas production" in English
Accretion dynamics in the classical T Tauri star V2129 Oph
We analyze the photometric and spectroscopic variability of the classical T
Tauri star V2129 Oph over several rotational cycles to test the dynamical
predictions of magnetospheric accretion models. The photometric variability and
the radial velocity variations in the photospheric lines can be explained by
rotational modulation due to cold spots, while the radial velocity variations
of the He I (5876 \AA) line and the veiling variability are due to hot spot
rotational modulation. The hot and cold spots are located at high latitudes and
about the same phase, but the hot spot is expected to sit at the chromospheric
level, while the cold spot is at the photospheric level. Using the
dipole+octupole magnetic-field configuration previously proposed in the
literature for the system, we compute 3D MHD magnetospheric simulations of the
star-disk system. We use the simulation's density, velocity and scaled
temperature structures as input to a radiative transfer code, from which we
calculate theoretical line profiles at all rotational phases. The theoretical
profiles tend to be narrower than the observed ones, but the qualitative
behavior and the observed rotational modulation of the H\alpha and H\beta
emission lines are well reproduced by the theoretical profiles. The
spectroscopic and photometric variability observed in V2129 Oph support the
general predictions of complex magnetospheric accretion models with
non-axisymmetric, multipolar fields.Comment: Accepted by Astronomy and Astrophysic
Fast Shocks From Magnetic Reconnection Outflows
Magnetic reconnection is commonly perceived to drive flow and particle
acceleration in flares of solar, stellar, and astrophysical disk coronae but
the relative roles of different acceleration mecha- nisms in a given
reconnection environment are not well understood. We show via direct numerical
simulations that reconnection outflows produce weak fast shocks, when
conditions for fast recon- nection are met and the outflows encounter an
obstacle. The associated compression ratios lead to a Fermi acceleration
particle spectrum that is significantly steeper than the strong fast shocks
commonly studied, but consistent with the demands of solar flares. While this
is not the only acceleration mechanism operating in a reconnection environment,
it is plausibly a ubiquitous one
Reconnecting Magnetic Flux Tubes as a Source of In Situ Acceleration in Extragalactic Radio Sources
Many extended extragalactic radio sources require a local {\it in situ\/}
acceleration mechanism for electrons, in part because the synchrotron lifetimes
are shorter than the bulk travel time across the emitting regions. If the
magnetic field in these sources is localized in flux tubes, reconnection may
occur between regions of plasma \be (ratio of particle to magnetic pressure)
, even though averaged over the plasma volume may be \gsim 1.
Reconnection in low regions is most favorable to acceleration from
reconnection shocks. The reconnection X-point regions may provide the injection
electrons for their subsequent non-thermal shock acceleration to distributions
reasonably consistent with observed spectra. Flux tube reconnection might
therefore be able to provide acceleration required by large scale
jets and lobes.Comment: 14 pages, plain TeX, accepted to Ap.J.Let
Conductivity, weak ferromagnetism and charge instability in single crystal
The temperature dependence of resistivity, magnetization and electron-spin
resonance of the single crystal were measured in temperature
range of . Magnetization hysteresis in applied magnetic field
up to 0.7 T at , irreversible temperature behavior of
magnetization and resistivity were found . The obtained data were explained in
terms of degenerate tight binding model using random phase approximation. The
contribution of holes in and bands of manganese ions to the
conductivity, optical absorbtion spectra and charge instability in were studied. Charge susceptibility maxima resulted from the competition of
the on-site Coulomb interaction between the holes in different orbitals and
small hybridization of sub-bands were calculated at .Comment: 6 pages, 12 figure
The Use of Contact Heat Generators of the New Generation for Heat Production
We substantiated the need for searching for, and realization of, fundamentally new approaches, using more efficient physical, heat-mass-exchanging and aerodynamic processes, which will make it possible to improve energy effectiveness and ecological cleanliness of heat generation in the systems for individual and decentralized heat supply.For the heat supply to large cities and industrial regions, we examined the advantages of using highly efficient contact heat-generators of different types, which include compactness due to low metal consumption and, as a result, attractive price.It is proposed to use a heat-generator of contact type of the new generation, with the aid of which it was possible to solve a set of problems on the qualitative combustion of fuel and effective heat exchange of gases with the heated water. The use of tubular technology for the combustion of gas is its special feature. Due to it, quality heat exchanging characteristics are provided.In view of further studies, we presented the relevance of creating heat-generators with the use of highly effective hydrogen technologies, which will make it possible to devise the new energy paradigm of heat supply for residential areas and industrial zones through the possibility of accumulation of electrical energy and accumulation of hydrogen
Warps, bending and density waves excited by rotating magnetized stars: results of global 3D MHD simulations
We report results of the first global three-dimensional magnetohydrodynamic
simulations of the waves excited in an accretion disc by a rotating star with a
dipole magnetic field misaligned from the star's rotation axis (which is
aligned with the disc axis). The main results are the following: (1) If the
magnetosphere of the star corotates approximately with the inner disc, then we
observe a strong one-armed bending wave (a warp). This warp corotates with the
star and has a maximum amplitude between corotation radius and the radius of
the vertical resonance. The disc's center of mass can deviate from the
equatorial plane up to the distance of z_w\approx 0.1 r. However, the effective
height of the warp can be larger, h_w \approx 0.3 r due to the finite thickness
of the disc. Stars with a range of misalignment angles excite warps. However,
the amplitude of the warps is larger for misalignment angles between 15 and 60
degrees. (2) If the magnetosphere rotates slower, than the inner disc, then a
bending wave is excited at the disc-magnetosphere boundary, but does not form a
large-scale warp. Instead, high-frequency oscillations become strong at the
inner region of the disc. These are (a) trapped density waves which form inside
the radius where the disc angular velocity has a maximum, and (b) inner bending
waves which appear in the case of accretion through magnetic Raleigh-Taylor
instability. These two types of waves are connected with the inner disc and
their frequencies will vary with accretion rate. Bending oscillations at lower
frequencies are also excited including global oscillations of the disc. In
cases where the simulation region is small, slowly-precessing warp forms.
Simulations are applicable to young stars, cataclysmic variables, and accreting
millisecond pulsars.Comment: 26 pages, 25 figure
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