The results of ground-based microwave observations of ozone in the middle atmosphere in Apatity (67° N, 33° E) during three winters (2017–2018, 2018–2019 and 2019–2020) are presented. Long-term ozone ...observations were carried out during the period of minimum solar activity for cycles 24 and 25. A mobile microwave spectrometer with an operating frequency of 110.8 GHz was used in the measurements, which allows tracking the behavior of ozone in the middle atmosphere with a 15-min time resolution. The microwave ozone data from ground-based measurements are compared with the MLS/Aura onboard data. Ground and airborne data are compared with the data of contact measurements with ozonesondes at Sodankyla st. (67° N, 27° E). In addition, MLS/Aura data from mid-atmospheric temperature soundings are used to interpret perturbations in the ozone layer associated with sudden stratospheric warmings. A significant influence sudden stratospheric warming on the ozone vertical distribution at altitudes of 22–60 km was found. At the same time, the scale of mesospheric ozone variability (60 km) over Apatity is comparable or exceeds the known model calculations for assessing the impact of solar proton events and auroral electron precipitation on the ozone of the polar regions.
Abstract
A two-channel double-pass iodine explosively pumped photodissociation laser (EPPL) with an explosively pumped master oscillator (MO) and an SBS mirror is studied. The radiation source, ...determined by an aperture 6 mm in diameter, through which the radiation from MO enters the turbulent surface air path, is located at a distance of 2.5 km from the amplifier unit input. An SBS mirror with a kinoform raster of microlenses is used to compensate for the amplifier and path optical inhomogeneities and to match the phases in the EPPL channels. The energy and spatial characteristics of the EPPL output radiation are studied experimentally and numerically. Good agreement is obtained between the experimental and calculated distribution of the energy density of the output EPPL radiation in the plane of the MO aperture, which is a pattern of interference between the two channels. The maximum energy density in the aperture plane is by more than 4 times greater than in the case of a single-channel EPPL.
The aim of the study, results of which are presented in this paper, is to analyse methods and tools for constructing an ontology related to solving compute-intensive problems and to form algorithms ...of its use. This problem arises from the need to solve problems using modern and future supercomputers, containing millions and, in the long term, billions of simultaneously operating computing cores and having a huge degree of parallelism. In solving such problems, the researcher should be well versed in both computational methods for solving the problem and modern supercomputer technologies, which is not always the case. One of the solutions to this problem is the creation of a knowledge base that includes ontological descriptions of methods for solving compute-intensive problems and architectures of supercomputers that can be used to solve them. The development of ontologies for a given subject area is one of the most important stage in creating an intelligent support system for solving specific compute-intensive problems. The paper discusses the methods and tools that are used to build the ontology. The paper also presents examples of the development of ontologies for astrophysics and geophysics problems.
We present the results of microwave observations of atmospheric radiation in the ozone line in the case of ionospheric perturbation by powerful high-frequency radio emission from the “Sura” facility ...in September 2016. The atmospheric-radiation spectrum in the ozone line was measured by the method of the ground-based microwave radiometry. The state of the lower ionosphere was simultaneously diagnosed in the altitude range 50–130 km using the method of resonant scattering of radio waves by the artificial periodic irregularities of ionospheric plasma. A decrease in the intensity of the microwave atmospheric radiation in the ozone line was observed. The results of measurements of the amplitude and phase of the signal scattered by artificial periodic irregularities demonstrated a perturbation of the parameters of the lower ionosphere when it was heated by high-frequency radiation.
The paper presents one construction of a Godunov-type method based on the separation of operators describing the work of pressure forces and advective transfer. Separate consideration of advective ...transfer permits describing the motion of both gas and dust components within the framework of a single numerical scheme. In the case of describing gas dynamics, the work of pressure forces is taken into account at a separate stage, independently of transfer. This permits using the numerical scheme in solving star formation problems, where it is necessary to jointly solve the equations of hydrodynamics and dust motion equations. A piecewise parabolic representation of physical variables in all directions is used to reduce the dissipation of the numerical method. The numerical method has been verified on Riemann problems for a hydrodynamic and dust discontinuity, the Sedov problem of point explosion, and the problem of dust cloud collapse, which have an analytical solution.
Abstract
Lasing in caesium vapour is obtained at
λ
∼ 3 μm (transitions 7P
3/2
→ 7S
1/2
and 7P
1/2
→ 7S
1/2
). Longitudinal pumping is performed by the second harmonic of a parametric oscillator ...pumped by the second harmonic of a Nd
3+
-doped garnet laser. The pump wavelength corresponds to the 6S
1/2
→ 7P
3/2
and 6S
1/2
→ 7P
1/2
transitions of caesium atoms. The pump radiation has a spectral width of 12 cm
−1
, a pulse energy of 10 mJ, and a pulse repetition rate of 10 Hz. The IR laser pulse energy at a vapour cell temperature of 155 °C is 100 μJ. The efficiency of pump energy conversion to the laser radiation energy at
λ
∼ 3 μm is ∼1.5%.
In the framework of the proposed theoretical model crossover and scaling equations of state for near-critical multicomponent hydrocarbon mixture were obtained. To elaborate the equations of state the ...experimental data measured on the serial setup intended for comprehensive pressure-volume-temperature (PVT) research of a natural gas-condensate systems were used. The information concerning the mixture composition was not involved. The obtained equations describe the experimental data with the accuracy not exceeding the measurement inaccuracy. It has been shown that in extended range of thermodynamic parameters the crossover equation of state looks more reliable. The crossover model describes the transition from the scaling behavior to the mean-field behavior, which is typical for cubic and multiparameter equations of state. The model was extended for calculation of the volume fractions of gas and liquid phases needed for practical applications. In addition, the expression for isothermal compressibility has been derived. It was demonstrated that the isothermal compressibility has a cusp-like anomaly in the close vicinity of the critical point.
Display omitted
•Scaling and crossover EOS for near-critical ternary hydrocarbon mixture are elaborated on the basis of measured isotherms.•The information concerning the mixture composition was not used.•The lines with constant ratio of gas and liquid volume fractions are obtained.•The isothermal compressibility for a multicomponent mixture in one- and two-phase region is derived.
The focus of this paper is on the impedance-based fault location in a transmission line via synchronized phasor measurements. Physical and mathematical modeling involving real-time digital ...simulations is used to show that fault location based on synchronized phasor measurements is promising for extra-high voltage overhead transmission lines. Avariety of single-end and double-end fault location methods are put together to show that the fault location accuracy can be well within 1 – 2% for both P and M class filters defined in the IEEE C37.118 standard. The methods are analyzed for a validated 750 kV line model generated using ATPDraw software and an electric grid model with 500, 330, and 220 kV overhead lines sharing the same right-of-way. Unlike many other publications, no Fourier-simulated phasors under transients are used here. Instead, we resort to physical modeling involving hardware equipped with synchrophasor functionality. An experimental setup is described, and future research areas are highlighted.
The results of numerical modeling of white dwarf mergers on massive parallel supercomputers using a AVX-512 technique are presented. A hydrodynamic model of white dwarfs closed by a star equation of ...state and supplemented by a Poisson equation for the gravitational potential is constructed. This paper presents a modification based on a local linear reconstruction of the solution of the Rusanov scheme for the hydrodynamic equations. This reconstruction makes it possible to considerably decrease the numerical dissipation of the scheme for weak shock waves without any external piecewise polynomial reconstruction. The scheme is efficient for unstructured grids, when it is difficult to construct a piecewise polynomial solution, and also in parallel implementations of structured nested or adaptive grids, when the costs of interprocess interactions increase significantly. As input data, piecewise constant values of the physical variables in the left and right cells of a discontinuity are used. The smoothness of the solution is measured by the discrepancy between the maximum left and right eigenvalues. This discrepancy is used for a local piecewise polynomial reconstruction in the left and right cells. Then the solutions are integrated along the characteristics taking into account the piecewise linear representation of the physical variables. A performance of 234 gigaflops and 33-fold speedup are obtained on two Intel Skylake processors on the cluster NKS-1P of the Siberian Supercomputer Center ICM & MG SB RAS.
The status of community immunity against measles was evaluated in 480 health professionals (HPs) and 619 students of medical colleges in the Republic of Tatarstan. HPs and students were selected at ...random taking the vaccination status and age into account. The immunity level was assessed by blood serum (plasma) protective antibody (IgG) titers with an enzyme-linked immunosorbent assay. Three hundred sixty-three (75.63 ± 2.253%) health professionals examined were seropositive to measles virus, and 117 (24.38 ± 3.969%) ones being seronegative. A proportion of medical college students susceptible to measles were 45.07 ± 2.979%. The results obtained suggest that the assessment of community immunity against measles in health professionals and students of medical schools and colleges should be continued and susceptible individuals be vaccinated without age limits.
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