The paper investigates the development of instability in an internally pressurized annulus of a poro-hyperelastic material. The theory of poro-hyperelasticity is proposed as an approach for modelling ...the mechanical behaviour of highly deformable elastic materials, the pore space of which is saturated with a fluid. The consideration of coupling between the mechanical response of the hyperelastic porous skeleton and the pore fluid is important when applying the developments to soft tissues encountered in biomechanical applications. The paper examines the development of an instability in a poro-hyperelastic annulus subjected to internal pressure. Using a computational approach, numerical solutions are obtained for the internal pressures that promote either short-term or long-term instability in a poro-hyperelastic annulus and a poro-hyperelastic shell. In addition, time-dependent effects of stability loss are examined. The analytical solutions are used to benchmark the accuracy of the computational approach.
The present paper has represented the results of the research of electrochemical deposition of coatings based on Co-W alloy from the citrate electrolyte. Possibility to obtain large (more than 40 μm) ...thicknesses without cracking has been demonstrated. Peculiarities of the surface relief structure change after increase of the coating thickness have been researched. Possibility to control a concentration of tungsten in the coating alloy within the range 14 at.% - 21 at.% has been shown. Dependence of the coating microhardness on the thickness has been represented.
This paper examines the coupled hydro-thermo-mechanical behaviour of a fluid-saturated porous sphere with a skeletal fabric that can exhibit either elastic or elasto-plastic mechanical behaviour. ...Analytical results for the thermo-poro-elastic response of the sphere subjected to transient heat transfer are complemented by computational results for the analogous thermo-poro-elasto-plastic problem. The results presented in the paper examine the influence of the permeability, thermal expansion properties of the pore fluid and the skeleton, and the elasto-plasticity effects of the porous skeleton on the time-dependent pore fluid pressure, displacement and stress within the sphere.
To assess the relationship between plasma chitotiosidase (CHIT) level and mortality in hospitalized patients with COVID-19.
347 hospitalized patients with COVID-19 were enrolled in our single-center ...cohort prospective observational study. On the first day of hospitalization the patients were assessed by the level of CHIT in the venosus blood to addition to default laboratory examinations. The primary endpoint was all-cause death. The survival after hospital discharge were assessed via phone calls on 90 and 180 days since inclusion to the study (NCT04752085).
Our study included 347 patients. The first symptoms appeared in 7 days 5; 7 before hospitalization; 283 (84.3%) patients had less than 50% of the involvement of the lung tissue to the inflammation process (CT 0-2); 36 (10.4%) patients had died since the start of our investigation; 30 (83.3%) of them died during hospitalization, others -no later than 60 days; 68 (19%) people didn't answer during phone call. The survivor's activity of the enzyme in the deceased was significantly lower in compare to deceased patients (90.5 40.2; 178.0 nmol/h/mL vs 180.0 77.2; 393.2 nmol/h/mL;
=0.001). Survivor of the patients with a higher level of the activity of the CHIT (more than 171 nmol/h/mL) was statically significantly lower.
Rising of the CHIT's activity more than 171 nmol/h/mL might be an early independent predictor of the bad prognosis of the patients, who were hospitalized with COVID-19 infection.
The paper investigates the development of instability in an internally pressurized annulus of a poro-hyperelastic material. The theory of poro-hyperelasticity is proposed as an approach for modelling ...the mechanical behaviour of highly deformable elastic materials, the pore space of which is saturated with a fluid. The consideration of coupling between the mechanical response of the hyperelastic porous skeleton and the pore fluid is important when applying the developments to soft tissues encountered in biomechanical applications. The paper examines the development of an instability in a poro-hyperelastic annulus subjected to internal pressure. Using a computational approach, numerical solutions are obtained for the internal pressures that promote either short-term or long-term instability in a poro-hyperelastic annulus and a poro-hyperelastic shell. In addition, time-dependent effects of stability loss are examined. The analytical solutions are used to benchmark the accuracy of the computational approach.
In this paper, we generalize the previously developed method of finite element modeling of the noise emission produced by inhomogeneities of bodies in a turbulent flow for the prismatic mesh ...discretization of a compressible fluid. The method was validated based on well-known analytical solutions for prediction problems of noise emission produced when two-dimensional and three-dimensional streamlining cylindrical or spherical bodies that are small in comparison with the acoustic wavelength.
In this paper, we describe a method for solving the problem for calculating the acoustic radiation of a deformable solid oscillating in a compressible fluid by using the mode analysis procedures ...found in mechanoacoustic systems. The method is based on an approximate representation of the acoustic radiation loss function and modifications of the Lanczos method. This allows constructing an efficient computational algorithm for finding sound-emitting forms of resonant oscillations and the corresponding complex values of eigenfrequencies. The developed method was tested using a model problem as an example.
Algorithms are realized for localizing vibration activity sources in complex mechanoacoustic systems using finite element modeling. For the case of one source, the localization method was used in the ...least squares form applied to the first eigenvector of the sample correlation matrix. It is shown that frequency summation can significantly increase the localization accuracy in this case. Considerable attention is paid to assessing the number of simultaneously operating vibration sources and the possibility of correctly localizing them. The efficiency of two source localization methods was compared: the maximum likelihood method calculated for a single source and the MUSIC (Multiple Signal Classification) method specially modified for this problem. It is shown that the modified MUSIC method is more efficient in solving the localization problem with two sources compared to the maximum likelihood method calculated for a single source. It is noted that the maximum likelihood method calculated for two or more sources cannot be applied because of the too high computational complexity.
New Applications of Laser Vibrometry Stulenkov, A. V.; Korotin, P. I.; Suvorov, A. S.
Bulletin of the Russian Academy of Sciences. Physics,
06/2020, Letnik:
84, Številka:
6
Journal Article
Recenzirano
The possibility of using lasers for non-contact vibration measurements has been known since the mid-60s. This work describes the development of some applied areas: the use of laser vibrometry in ...near-field acoustic holography, verification of numerical models of vibrations of complex structures, and vibration flaw detection.
Using as an example one district forestry unit of the Novgorod region, located in two contrasting landscapes, we studied the formation of stands with different proportions of pine and spruce in the ...stand composition. The aim of the study was to study pure and mixed pine stands in a narrow range of forest growing conditions in order to identify economically valuable combinations and the most productive stands in terms of forest stand composition. To identify statistically significant differences between spruce and pine stands, a comparative analysis of the mean values and the coefficients of variation of forest inventory characteristics was used. The analysis of variance was used to find differences between stands of different composition. According to the results of the comparative analysis by forest type, the only significant difference in growing stock was between spruce stands of the herbaceous-meadow and fresh blueberry forest types. For the rest of the spruce forest types, no significant differences in growing stock were found. In terms of the growing stock, the most productive are forest stands with 60% of trees been spruce or pine, and pure pine stands in the green moss group of forest types in the given landscape conditions.
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