Influence of an ejector nozzle extension on gas flow at a pulse detonation engine was investigated numerically and experimentally. Detonation formation was organized in stoichiometric hydrogen-oxygen ...mixture in cylindrical detonation tube. Cylindrical ejector was constructed and mounted at the open end of the tube. Thrust, air consumption and parameters of the detonation were measured in single and multiple regimes of operation. Axisymmetric model was used in numerical investigation. Equations of Navies-Stokes were solved using a finite-difference scheme Roe of second order of accuracy. Initial conditions were estimated on a base of experimental data. Numerical results were validated with experiments data.
The article presents results of numerical simulation and experimental studies of elastic wedge wave propagation in cylindrical wedges with positive and negative curvature in the 100–600 kHz frequency ...range. It is shown that wedge waves in such structures have dispersion and their localization at the edge of the wedge is stronger than that of straight wedges. The results of a study for cases where the inner surface of the wedge is bounded by fluids with different viscosities (water, SAE 10W-30 motor oil, 86% glycerol aqueous solution) are presented.
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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 frequency spectrum of acoustic disturbances that are emitted by accelerating flame front in an air-hydrogen mixture within an axially symmetric channel with a uniform cross section is ...experimentally determined. The effect of acoustic disturbances that are reflected from the closed end of the combustion chamber on the flame front acceleration is studied. It is revealed that the frequency spectrum of generated acoustic disturbances under experiment conditions has maximums at frequencies close to 250, 800, and 1500 Hz.
The paper presents results from experimental studies on the influence of loading–unloading processes on the mechanical, linear, and nonlinear properties of the strain-hardening polycrystalline ...aluminum alloy AMg6 (Rus). The stress–strain curve is measured for AMg6 samples under high-cycle loading–unloading up to fracture of a sample. The microhardness of the sample is measured before and after its fracture. It has been found that the loading–unloading process leads to strain hardening of the AMg6 alloy. The influence of strain hardening of AMg6 on its linear and nonlinear elastic properties is studied by an ultrasonic method. To study the nonlinear elastic properties for different domains of the loading curve, we used the Thurston–Brugger method and spectral method by studying the efficiency of second acoustic harmonic generation. The experimental results are discussed.
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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 results of experimental studies on the nonlinear elastic properties of a planar interface between two media are presented—an optically polished glass substrate and flat samples with different ...degrees of roughness. The nonlinear elastic properties of the interfaces between two media were investigated by the spectral method using surface acoustic waves (SAWs). The effect of external pressure applied to the interface on the efficiency of the generation of the second SAW harmonic was studied. Using the measured amplitudes of the first and second harmonics of the SAW that passes along the interface, the second-order nonlinear acoustic parameter was calculated as a function of the external pressure applied to the sample at a fixed amplitude of a probing wave. It was revealed that the nonlinear parameter of the SAW is a nonmonotonic function of the pressure at the boundary. The results were analyzed on the basis of an elastic contact nonlinearity, and it is concluded that these results can be used in nondestructive testing for roughness and waviness of surfaces of flat solids.
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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
Purpose of the study
. To study functional changes in the neuropsychological status of reproductive age patients with newly diagnosed breast cancer and to assess the possibility of using xenon-oxygen ...therapy to correct disorders.
Patients and methods
. This study included 60 reproductive age patients with newly diagnosed breast cancer who were undergoing surgical treatment at the Department of Bone, Skin, Soft Tissue and Breast Tumors of the National Medical Research Centre for Oncology of the Ministry of Health of Russia from 2018 to 2020. The main group included 30 patients with breast cancer diagnosed at the surgical stage of combined treatment, who underwent a rehabilitation course of xenon-oxygen therapy in the early postoperative period. The control group was formed from patients with the same diagnosis, without the use of this therapy. The functional state of the central nervous system in all patients was assessed by the parameters of the electroencephalography (EEG) bioelectrical activity. For the final assessment of the physiological and psychological state of the patients, a standardized questionnaires of the quality of life – ESAS, MOS-SF‑36, were used. Statistical data processing was performed using the Statistica 10 software package.
Results
. During the study, statistically significant differences were found in the assessment of subjective indicators, so in the group of patients using xenon-oxygen therapy, there was an improvement in well-being by 2.6 times, a decrease in depression by 2.3 times, a decrease in symptoms of nausea by 3 times, anxiety 1.9 times (p < 0.05). Against the background of an improvement in the psychophysiological state, the EEG showed a significant increase in the power of slow delta and theta rhythms, an increase in the power of the alpha rhythm and a decrease in the power of the beta rhythm, while in the patients of the control group only a decrease in the power of the beta rhythm was noted.
Conclusion
. The early postoperative period in patients with newly diagnosed breast cancer is characterized by the formation of a depressive symptom complex. The use of a course of xenon-oxygen therapy contributes to the normalization of the subjective feeling of physical and psychological health, increasing vital and social activity. Changes in the indicators of brain bioelectric activity and an improvement in psychophysiological state occur against the background of changes in brain activity caused by the normalizing effect of xenon.
Results of experimental investigation into the effect of reversible mechanical loading–unloading on linear and nonlinear properties of
n
‑AMg6/C60 nanostructured composite are presented. For ...nanocomposite specimens, mechanical stress–strain curves are measured under many-cycle loading–unloading down to specimen fracture. The effect of cyclic loading–unloading on the microhardness of specimens is investigated. Within different characteristic portions of the stress–strain curve, nonlinear elastic properties of
n
-AMg6/C60 composite specimens subjected to several loading–unloading cycles are studied by Thurston–Brugger and spectral methods. The results of experimental studies are discussed.
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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 influence of nanostructuring on the mechanical and nonlinear elastic characteristics of polycrystalline AMg6 aluminum alloy and
n
-AMg6/C
60
nanocomposite has been experimentally studied. The ...independent second- and third-order elastic coefficients are measured via the ultrasonic method. The thir-dorder elastic coefficients have been evaluated via the Tearstone–Bragger approach from the experimentally established velocities of shear and longitudinal bulk acoustic waves as the functions of the uniaxial compression in the studied samples. The nonlinear elastic properties are examined via the spectral acoustic technique in AMg6 aluminum alloy and
n
-AMg6/C
60
nanocomposite, and the nonlinear acoustic parameters are determined.
The article presents the results of studies of the elastic properties of the YBa
2
Cu
3
O
(7 –
x
)
high-temperature superconducting ceramic in the vicinity of the phase transition to the ...superconducting state at a temperature of 91.3 K and room temperature of 293 K. Near the phase transition temperature with a width of ~10 K, a local increase in longitudinal nonlinear acoustic parameter
N
was revealed for the first time, which characterizes anharmonic interatomic interaction in the material. Experimental studies of the linear and nonlinear elastic properties of the YBa
2
Cu
3
O
(7 –
x
)
HTSC ceramic near the superconducting transition zone show that the electronic phase transition significantly influences its elastic properties.
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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
In contrast to the conventional continual case, discrete Poisson-Voronoi tessellations resulting from the growth to impingement of random nuclei differ from tessellations constructed from the nearest ...tile loci. Previously studied tessellations were based directly on the notion of locus A. Korobov, Phys. Rev. E 79, 031607 (2009); A. Korobov, Phys. Rev. E 87, 014401 (2013). This paper presents results for tessellations constructed by the growth of random nuclei. Their boundaries have a different structure and scaling properties are comparably more robust. One more scalable characteristic may be introduced for them, the perimeter distribution function, which is well approximated by the normal distribution function with the unit mean and the standard deviation equal to 0.25.
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