The authors propose a dedicated mobile roof support for underground coal mining. Joint deformation of roof rocks and roof support is analyzed using the finite element method. The shapes and sizes of ...failure zones and the influence of the support on coal and host rocks are determined. The application area for the mobile roof support in underground mining is outlined, and the essentiality of the current prediction method of dynamic events during mining is substantiated. It is feasible to increase the rate of heading by means of reduction of the heading cycle duration.
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This paper presents examples that characterize various aspects of the possibility of determining the phase composition of solid multielement substances and materials containing nanostructured forms ...of their components by a differential dissolution stoichiographic method. The use of stoichiography makes it possible to detect and quantitatively determine both known and unknown crystalline and amorphous phases of constant and variable composition without standards of solid phases. The use of stoichiographic methods and ideas of nonequilibrium thermodynamics allows one to gain fundamentally new data on solid-state transformations of multielement, multiphase substances and materials.
Precise time-dependent measurements of the Z = 2 component in the cosmic radiation provide crucial information about the propagation of charged particles through the heliosphere. The PAMELA ...experiment, with its long flight duration (2006 June 15-2016 January 23) and the low energy threshold (80 MeV/n) is an ideal detector for cosmic-ray solar modulation studies. In this paper, the helium nuclei spectra measured by the PAMELA instrument from 2006 July to 2009 December over a Carrington rotation time basis are presented. A state-of-the-art three-dimensional model for cosmic-ray propagation inside the heliosphere was used to interpret the time-dependent measured fluxes. Proton-to-helium flux ratio time profiles at various rigidities are also presented in order to study any features that could result from the different masses and local interstellar spectra shapes.
The article presents a report on the findings of representatives of frenulate pogonophorans
Nereilinum murmanicum
in the northern and central parts of the Barents Sea, which significantly expands the ...range of this species and provides guidance on its distribution in this basin. Here we present the coordinates of new finds with an indication of the depth. Find points were associated with data on known and potential hydrocarbon deposits.
Comparative analysis provides evidence that bilateral symmetry is a primary character of Cnidaria. All anthozoan taxa are characterized by bilateral symmetry. The anthozoan pharyngeal plane is a ...plane of bilateral symmetry of mesenteries and, at the same time, it is a plane of bilateral symmetry of regulatory gene expression in anthozoan morphogenesis. In Medusozoa, the bilateral symmetry is replaced by radial symmetry, but some hydrozoans (for example, Corymorphidae) demonstrate bilateral symmetry. The bilateral symmetry of Cnidaria is thought to be inherited from the common ancestors of both cnidarians and triploblastic bilaterians. The secondary radial symmetry of Cnidaria evidently is a result of the adaptation to the sessile mode of life. The presence of both the marginal and labial rings of tentacles is supposed to be a plesiomorphic character of Cnidaria. In some groups of cnidarians, one of the tentacle rings may be reduced.
Unfolding is currently an important stage of processing experimental data, reducing the effect of errors and reconstructing approximately real distributions of quantities. Numerous approaches exist ...to solve this problem; in particular, they are widely used in the modern physics of atomic nuclei and elementary particles, space physics, and other related areas. However, many algorithms are not designed or are poorly adapted to reconstruct multidimensional distributions corresponding to, e.g., several characteristics of particles measured simultaneously. In this work, a method has been proposed to adapt the singular value decomposition (SVD) unfolding algorithm to the multidimensional case. The proposed modified method has been tested in application to simulation data for the cosmic ray spectrum measured in the PAMELA space experiment. This method not only makes it possible to estimate the real distribution of a multidimensional quantity (momentum and two angles specifying the direction of entering a particle into an instrument) but also provides a better result compared to the classical SVD approach in the one-dimensional case (only the momentum of the p-article).
Gutless marine worms of the family Siboglinidae have been found in the estuaries of the largest Arctic rivers Yenisei, Lena, and Mackenzie. Siboglinid metabolism is provided by symbiotic ...chemoautotrophic bacteria. Strong salinity stratification is characteristic of the estuaries of the largest Arctic rivers and ensures a high salinity at depths of 25–36 m, where siboglinids were found. High methane concentrations, which are necessary for siboglinid metabolism, result from dissociation of permafrost gas hydrates under the influence of river runoff in the conditions of Arctic warming.
Trematodes found in the enteropneust hemichordates are described for the first time. Metacercariae have been found in the trunk coelom, in the collar coelom, in the proboscis coelom, and in the ...glomerulus of the deep-sea torquaratorid
Quatuoralisia malakhovi
Ezhova et Lukinykh, 2022. This is the first find of parasites in the glomerulus of acorn worms. The taxonomy of the found trematodes is discussed.
In this article, results are presented of experiments on depositing charged particles, which imitate the levitating dust on the Moon, on stainless steel. Ensembles of particles are created above the ...surface of laboratory regolith whose composition and particle size distribution imitate the dust that covers the Moon's surface. Under the action of the gyrotron radiation on regolith, non-linear physical-chemical processes develop (breakdown, chain plasmachemical reactions, and particle scattering by the Coulomb mechanism), which lead to the appearance of a levitating cloud of particles. The simulation experiment is based on the similarity between the processes that develop in the laboratory experiments with regolith and the processes that occur on the Moon during its bombardment by micrometeorites. The effect of the levitating cloud on stainless steel plates is studied and it is shown that regolith particles in the shape of spheroids of different sizes are deposited on the surface of the plates. The dimensions of the deposited particles and the density of their placement depend on the quality of treatment of the plate surface. It is shown that the laboratory-produced dusty plasma can be used in simulation experiments to study the modification of surfaces of different materials for space technology.
Curved continuous fiber trajectories for composite plates with a bolted joint corresponding to the lines of maximum principal stresses were designed using the iterative finite-element modeling. On ...their basis, variable stiffness composite structures were modeled by the finite-element method, when each element was assigned variable material properties depending on the distribution of fiber trajectories. To simulate the progressive failure of the plates, a material property degradation method was employed. An analysis of progressive failure showed that it is possible to significantly increase the ultimate load and reliability of bolted joints of composite structural elements by transition from the unidirectional to a curvilinear reinforcement.
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