Particle lateral distributions were investigated in cosmic ray air showers with energy
eV registered at the Yakutsk array with surface and underground scintillation detectors with
GeV threshold ...during the period of continuous observations from 1986 to 2016. The analysis covers events with arrival direction zenith angles
within five intervals with step
. Experimental values were compared to simulation results obtained with the use of CORSIKA code within the framework of QGSJet-01-d hadron interaction model. The whole dataset points at probable cosmic ray composition which is close to proton one.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
•Representations for waves of all types generated in the coupled structure.•Insight into the resonance transmission and backward mode phenomena.•Wave energy streamlines and guided wave ...profiles.•Source energy partition among the excited waves.
Explicit integral representations for the wave fields generated by air-coupled or underwater transducers in an acoustic medium with a submerged elastic (metallic or laminate composite) plate are obtained in the form of path Fourier integrals. Together with the far-field asymptotics for the incident, reflected, transmitted and guided waves that were derived from those integrals, they proved to be a convenient tool for the in-depth study of wave phenomena inherent in such acoustic-elastic structures. The present paper is focused on the non-conventional properties of backward leaky waves such as the increased wave energy transfer through the plate due to the increasing occurrence of energy vortices impeding lateral outflow of wave energy. The transformation of classical Lamb waves into leaky guided waves due to a fluid loading, especially in the backward wave range, the energy properties of those waves and the appearing traveling Scholter-Stoneley waves as well as source energy partition among the reflected, transmitted and guided waves are also numerically illustrated and discussed.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The galvanomagnetic characteristics of SmB
6
single crystals are studied within the temperature range of 1.9‒3.6 K at different orientations of the crystal faces. As a result, the electrical ...resistivities of the surfaces corresponding to the (100), (110), (111), and (211) crystallographic planes are determined. It is shown that the effective parameters of charge carriers, which determine the surface conductivity in SmB
6
, depend both on the orientation of the surface and on the method of its processing. It is found that the etching of polished polar surfaces formed by (100) planes leads at 1.9 K to a decrease in the density and to an increase in the mobility of surface
n
-type charge carriers from 113/
a
2
and 1.12 cm
2
/(V s) to 0.76/
a
2
and 18 cm
2
/(V s), respectively (lattice parameter
a
≈ 4.134 Å). For etched nonpolar surfaces corresponding to the (110) and (111) planes, the maximum density of surface charge carriers (per unit area of the surface Brillouin zone) is found to increase by factors of 2.3 and 3.9, respectively. It is proposed to use this parameter as a simple criterion to identify the features of electron transport due to the nontrivial topology of the band structure of SmB
6
.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Tubular bones are layered waveguide structures composed of soft tissue, cortical and porous bone tissue, and bone marrow. Ultrasound diagnostics of such biocomposites are based on the guided wave ...excitation and registration by piezoelectric transducers applied to the waveguide surface. Meanwhile, the upper sublayers shield the diseased interior, creating difficulties in extracting information about its weakening from the surface signals. To overcome these difficulties, we exploit the advantages of the Green’s matrix-based approach and adopt the methods and algorithms developed for the guided wave structural health monitoring of industrial composites. Based on the computer models implementing this approach and experimental measurements performed on bone phantoms, we analyze the feasibility of using different wave characteristics to detect hidden diagnostic signs of developing osteoporosis. It is shown that, despite the poor excitability of the most useful modes associated with the diseased inner layers, the use of the improved matrix pencil method combined with objective functions based on the Green’s matrix allows for effective monitoring of changes in the elastic moduli of the deeper sublayers. We also note the sensitivity and monotonic dependence of the resonance response frequencies on the degradation of elastic properties, making them a promising indicator for osteoporosis diagnostics.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
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•The ignition delay and burnout times of OCWF can be controlled by surface roughness.•To change the combustion characteristics, steel is processed by 100-μm abrasives.•Laser surface ...processing allows controlling the ignition and combustion characteristics.•Laser processing of steel intensifies the fuel droplet combustion on its surface.
The ignition and combustion of single organic coal-water fuel (OCWF) droplets made of coal (30%), waste engine oil (35%), and water (35%) during conductive heating on the surfaces of the machine steel modified with abrasive materials and laser radiation were studied experimentally. The experimental conditions (material and temperature of the heating surfaces) corresponded to the operating conditions of modern furnace chambers of boilers at thermal power plants. It is found that the ignition delay and burnout times during conductive heating of OCWF droplets on steel surfaces can be controlled by changing the surface roughness parameters. On the example of 7-mg OCWF droplets with a radius of about 1.2 mm, it is shown that for processing of heating surfaces, it is necessary to use the abrasive materials with an average grit size of 100 μm to decrease the ignition and burnout times. The abrasive materials with an average grit size of more than 100 μm have an insignificant effect on the ignition delay and burnout times of OCWF droplets. However, such processing significantly increases the deposition of solid combustion products (ash deposits) with an increase in the surface roughness. Laser processing of steel surfaces is of particular interest in the implementation of passive ways of controlling the ignition and combustion characteristics of OCWF droplets. This way of changing the surface texture allows controlling the ignition delay and burnout times in a wide range of the heating source temperatures, as well as reducing the intensity of the solid product deposition on the heating surface during the OCWF combustion. The positive effect from laser processing of heating surfaces to intensify the fuel droplet combustion consists in increasing the velocity of vapor flows from combustible fuel components due to the droplet dispersion. This, in turn, intensifies the formation of a combustible vapour-gas mixture and increases the velocities of flame propagation together with the dispersion products of fuel droplets along the textured surface.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The evolution of wide-temperature range (4.2–300 K) electron transport in niobium-carbon nanocomposites was studied at niobium concentration range 0.15–0.35. It was found that electron transport in ...the nanocomposites has the features of universality, being expressed in the existence of two characteristic temperature intervals on the temperature dependences of conductivity. The crossover temperature between the intervals is in the range 20–30 K. Within each temperature interval, corrections to the conductivity are found to be as power-like ones. Power exponent p is characterized by the non-monotonic dependences on niobium concentration and varies in the ranges 0.5–1.4 and 0.2–1.4 in the low- and high-temperature intervals with a minimum at 0.30 and 0.27 of Nb content, respectively. The satisfactory description of electron transport in niobium-carbon nanocomposites was achieved within the model of the inelastic tunneling of the electrons between the metal grains in the framework of the effective medium approximation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We report a measurement of the neutron lifetime using ultracold neutrons stored in a magneto-gravitational trap made of permanent magnets. Neutrons surviving in the trap after fixed storage times ...have been counted and the trap losses have continuously been monitored during storage by detecting neutrons leaking from the trap. The value of the neutron lifetime resulting from this measurement is τ
n
= (878.3 ± 1.6
stat
± 1.0
syst
) A unique feature of this experiment is the monitoring of leaking neutrons providing a robust control of the main systematic loss.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The Yakutsk Extensive Air Shower Array has been continuously operating for more than 50 years (since 1970) and up until recently it has been one of world’s largest ground-based instruments aimed at ...studying the properties of cosmic rays in the ultra-high energy domain. In this report we discuss results recently obtained at the array—on cosmic rays’ energy spectrum, mass composition and directional anisotropy—and how they fit into the world data. Special attention is paid to the measurements of muonic component of extensive air showers. Theoretical results of particle acceleration at shocks are also briefly reviewed. Future scientific and engineering plans on the array modernization are discussed.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The magnetic properties of the topological Kondo insulator SmB
6
are studied in the temperature range
T
< 10 K in an applied magnetic field up to 5 T. The analysis of the nonlinear part of the field ...dependence of the magnetization indicates that the nonlinear contribution to the magnetization at low temperatures is in general related not only to localized magnetic moments but also to the Pauli paramagnetism of surface electrons. It has been shown for the first time that a decrease in temperature in the range of
T*
∼ 5.5–6 K gives rise to the crossover between two modes determining the magnetic properties of SmB
6
. In the range
T
>
T
*, the magnetization qualitatively corresponds to the model of decay of Kondo singlets and is determined by the Pauli paramagnetism, which includes both the linear and nonlinear contributions. In the range
T
<
T
*, the Pauli paramagnetism becomes supplemented in the threshold manner by the contribution of localized magnetic moments. The performed estimate of effective magnetic moments arising at
T
<
T
* gives anomalously high values μ* ∼ (7–14) μ
B
ion, far exceeding the values μ* ∼ (3–5) μ
B
expected for a separate magnetic Sm
3+
ion. This is a signature of the possible spin-polaron nature of localized magnetic moments in the topological Kondo insulator SmB
6
.
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DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, SIK, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Methods of preparing heterogeneous gel fuels have been elaborated on the basis of oil-free and oil-filled cryogels, containing coal dust particles with a size no more than 140μm. Mechanical ...properties of 20-mm fuel pellets have been analyzed. The ignition mechanisms of heterogeneous gel fuels have been experimentally discovered in a high-temperature (600–1000°C) oxidizer medium, and the influence of the initial fuel temperature (from −85 to 20°C) on the fuel ignition characteristics has been researched. The multi-component composition of the oil-filled cryogels with coal dust particles is the reason for microexplosions that leads to the fuel sample dispersion and intensification both the ignition and burnout. Such fuel compositions are characterized by 1.5–2-fold lower ignition delay times (1–6s vs. 2–12s) than the compositions based on cryogels containing only coal particles, other things being equal.
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•We prepared gel fuels based on oil-free and oil-filled cryogels containing coal dust particles.•Ignition mechanisms of gel fuels in a high-temperature air medium were established.•It combines processes that occur during metal dust explosion and combustion of single coal particle.•The microexplosions intensify both the ignition and burnout of oil-filled cryogels.•Initial fuel temperature from −85 to 20°С was found to affect ignition characteristics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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