Issue 6, 2024
On unidirectional propagation of Pocchammer-Chree waves in cylindrical auxetic
On unidirectional propagation of Pocchammer-Chree waves in cylindrical auxetic
D. V. Ampilogov
The problem of propagation of Pocchammer-Chree waves in cylindrical auxetic is discussed in this work. The approximated evolution equation and general solution for left and right waves displacement field are built by means of projection operators method in particular case of axial symmetric material for exponential inition conditions.
Show AbstractDynamics of a hopping hoop with a massive point on an absolutely rough plane.
Dynamics of a hopping hoop with a massive point on an absolutely rough plane.
A. A. Aglaev$^1$, A. K. Kovaldzhi$^2$
In this article, the well-known problem of the «hopping hoop», which was incorrectly solved by J. Littlewood in his book «A Mathematician’s miscellany» [1], is solved in a more general formulation. The conditions connecting the hoop mass, its radius, the mass of the point and its initial velocity under which the plane reaction force is positive, and, therefore, a jump is impossible, are found in analytical form. A condition is found under which hopping occurs at the initial moment of time, when the point is at the top of the hoop. It is shown that the rolling model with an absolutely rigid and rough hoop and plane at a certain ratio of parameters is incorrect and leads to a contradiction called a «quasijump». It was also noted that the «skimming» phase of the motion, described in the work of W. F. D. Theron and N. M du Plessis «The dynamics of a massless hoop» [6], is not derived, but wrongly postulated.
Show AbstractA 100 MHZ signal conversion device with low phase noise
A 100 MHZ signal conversion device with low phase noise
A. A. Popov$^1$, V. V. Davydov$^1$, D. D. Savin$^1$, V. V. Naumova$^2$
The main disadvantages of high-stability UHF generators and difficulties of using such equipment on satellites and other mobile objects are revealed. A device for converting a highly stable signal into several coherent ones is proposed. The choice of low-noise operational amplifiers (OA) as an element base for the converter is proved. Theoretical study of noise coefficients and phase noise power spectrum densities of imported and domestic low-noise operational amplifiers is done with the use of MATLAB environment. The circuit diagram of the device based on selected models of OA, which was later modified by increasing the number of output signals is designed. The necessity to revise the general structure of the circuit considering on the parasitic capacitances of the OA is declared. Its adequacy was checked with using the program package NI Multisim. The printed circuit board for direct laboratory studies of the phase noise power spectrum density of device is built. Keywords: phase noise, signal converter, UHF, hydrogen standard, low noise amplifier, current noise, voltage noise.
Show AbstractAcoustic emission during the “crystal-liquid” phase transition in a honeycomb structure of the “honeycomb” type
Acoustic emission during the “crystal-liquid” phase transition in a honeycomb structure of the “honeycomb” type
E. M. Aseev$^1$
A complex system is being studied experimentally, which is a honeycomb structure, normal-conjugated with the compositional structure, and containing within itself a defect of the “water condensate” type in the form of ice crystals. To detect such a defect, the phenomenon of acoustic emission is used. Usually, to produce acoustic emission, mechanical impact on the object is used. But, unlike this traditional loading (compression or tension) of a sample by external forces, this uses a variation in the temperature field in which the sample is placed. During the heating of the experimental sample, the ice-water phase transition begins, leading to the phenomenon of acoustic emission. The dependences of the amplitudes of acoustic signals on time and on the rate of temperature change reveal a clear difference between samples with the “water accumulation” defect and samples without such defects.
Show AbstractExpress method of kidney monitoring for early detection of kidney damage
Express method of kidney monitoring for early detection of kidney damage
D. V. Vakorina$^1$, G. V. Stepanenkov$^1$, V. V. Davydov$^1$, D. V. Davydova$^{1,2}$
The necessity of determining kidney damage at an early stage using fast and reliable express methods was substantiated. A method based on refractive index measurements at three wavelengths with refractive index grading to the values of three main parameters (osmolarity, number of solids, density) was proposed for express method of kidney damage control. Additionally, the sizes of protein compounds were investigated and their sizes were also graded to refractive indices. The results of the study of model solutions are presented. Theoretical indices of kidney condition determination are established. The peculiarities of biological environment control using small-size refractometers working on the effect of total internal reflection are considered. Current express methods of kidney disease diagnostics by means of urine measurement are analyzed. The advantages of using the refractometer design at three wavelengths in comparison with other methods are noted. The peculiarities of measuring the refractive index of biological liquids on the example of urine are established. The results of investigation of various samples at temperature T = 20°C in dependence of refractive index on wavelengths and their analysis are presented. The comparison of the obtained results with the results of measurements in clinical diagnostics is carried out.
Show AbstractThe influence of cholesterol and calcium ions on the interaction of cryoprotectors with a biological membrane model
The influence of cholesterol and calcium ions on the interaction of cryoprotectors with a biological membrane model
V. Yu. Svechnikova$^{1,2}$, O. V. Mishukova$^{1,3}$, A. G. Mironova$^4$, G. B. Khomutov$^2$, M. A. Marchenkova$^1$, S. A. Yakovenko$^{2,5}$
In this work, we studied the effects of three cryoprotectors – ethylene glycol, dimethyl sulfoxide, sucrose – on the compression isotherms of egg yolk Langmuir monolayers both in the presence and in the absence of cholesterol in the monolayer. The influence of calcium ions from the subphase affecting the effectiveness of cryoprotection on π-A-isotherms is also examined. In addition, the elastic properties of the obtained monolayers are investigated by calculation and comparison the compression modulus of the monolayer. The scientific novelty of the work is in consideration of a complex biosimilar system (an egg yolk monolayer, cholesterol and their mixtures) on the surface of the aqueous solution of the nutrient mixture and obtaining information about the specific interaction of different cryoprotectors with lipid membranes. We found that when calcium ions and cryoprotectors are simultaneously added to the subphase, they block each other's influence on the lipid monolayer and reduce the effectiveness of cryoprotection. Cholesterol in the yolk in a ratio of 1:50 m/m changes the properties of the monolayer, which leads to increased action of cryoprotectors. Also, for the first time, the effect of a significant increase in surface pressure (by∼20 mN/m)was detected when cryoprotectors were added to the system under consideration. This effect can serve as an indicator of the effectiveness of membrane dehydration by cryoprotectors and can be used to find the most effective and safe cryoprotector compositions. Since the study of the mechanisms of calcium interaction (the most important signaling cation)with biological membrane and membrane-like systems is important for understanding the various effects caused by medicinal and biologically active drugs at the cellular level, the study is of interest for various fields of biophysics and biomedicine.
Show AbstractFeatures of the formation and processing of pulse waves from a biological object
Features of the formation and processing of pulse waves from a biological object
M. A. Yakusheva, D. S. Provodin
The conducted research allowed to obtain additional data on the state of cardiovascular and to determine the factors affecting the accuracy of their interpretation. The necessity of using various mathematical functions to describe the shape of the pulse wave, including the rising and falling fronts, as well as the peak of the wave, was proved. The developed software allows modeling of pulse waves for people with different individual characteristics. The program algorithms are based on medical research. Thus, the obtained data, combined with traditional medical criteria, allow for a more accurate assessment of a person's health condition and detection of a number of diseases during examinations or medical procedures. When developing the software, specific terms of the subject area were taken into account, and modern software tools were used to solve the set tasks.
Show AbstractInteraction of Radial Velocity Flow and Magnetic Flux in Emerging Active Regions of the Sun
Interaction of Radial Velocity Flow and Magnetic Flux in Emerging Active Regions of the Sun
A. M. Sadykov$^{1,2}$, S. A. Krasotkin$^{1,2}$
In this article, the authors investigate the physical processes involved in the formation of active regions (AR). Specifically, the magnetic flux emergence (magnetic tube) hypothesis is tested based on direct observations of the magnetic field and Doppler shifts obtained from the Global Oscillation Network Group (GONG) ground-based telescope network. The study encompasses the analysis of 24 emerging ARs observed during the period from 2011 to 2022. A strong correlation between magnetic flux and the downward radial velocity flow was found. The results indicate that the magnetic flux emergence hypothesis cannot fully explain the evolution of ARs during the early stages of their development.
Show AbstractComparison of various spectral control schemes using displacers
Comparison of various spectral control schemes using displacers
R. A. Vnukov, A. A. Vorontsova
In this paper, one of the possible approaches to compensate for excessive reactivity at the beginning of the campaign is considered – spectral regulation. Its implementation is based on the use of displacement rods that change the water-fuel ratio during the fuel campaign. To assess the effect on the neutron-physical characteristics that arise in the assembly when displacers are introduced into its design, various models are proposed that differ in the placement of rods in the fuel assembly. The comparison takes place with the original version of the fuel assembly, which has a similar geometry to the VVER-1200 fuel assembly. Based on a single scheme for regulating the water-fuel ratio, the contribution to the extension of the fuel campaign for models with displacers is estimated. The comparison is carried out with the initial fuel assemblies, where the fuel campaign is 49 MW * day/kg for model 1 and 78 MW * day/ kg for model 2. The results showed the fundamental possibility of extending the fuel campaign due to the phased extraction of displacer rods, which tighten the spectrum. In a model with displacers in the intertwined space, the campaign extension was 8 MW*day/kg, which is equivalent to 16%; in the model where the displacers are placed in the guide channels, the extension was 6 MW* day/kg, which is equivalent to 5%. Complete replacement of boric acid in the versions under consideration turned out to be impossible, while the required concentration of H3BO3 in the coolant to compensate for excessive reactivity at the beginning of the campaign increased due to a decrease in boron efficiency with a more rigid neutron spectrum in the models. Keywords: spectral regulation, fuel assemblies, boric acid, fuel campaign, light-water reactor.
Show AbstractMolecular Dynamics Study of Structural-Phase Transformations during SH-Synthesis of Nickel Aluminides in Matrix Structures with a Homogeneous Composition of Nanoparticles of the Core-Shell Composite Structure
Molecular Dynamics Study of Structural-Phase Transformations during SH-Synthesis of Nickel Aluminides in Matrix Structures with a Homogeneous Composition of Nanoparticles of the Core-Shell Composite Structure
V. I. Jordan, I. A. Shmakov
The article presents the results of computer simulation of the SH-synthesis of nickel aluminides in four model matrix structures, each of which is characterized by a homogeneous composition of identical core-shell composite nanoparticles. The first two structures contain nanoparticles that do not contact each other (the first contains Ni@Al nanoparticles, the second contains Al@Ni nanoparticles), while the next two structures contain nanoparticles that do contact each other (the third contains Ni@Al nanoparticles, the fourth contains Al@Ni nanoparticles). For each of the four structures, the temperature dependences of nanoparticles on time, the results of CNA-, AJ- and PTM-analyses for the recognition of certain types of elementary crystal cells in nanoparticles, as well as maps of the recognition of intermetallic phases in nanoparticles at certain points in time are presented. It is shown that for two structures with nanoparticles not in contact with each other, the spherical shape of the nanoparticles is practically preserved during the SHS process, while in two structures with nanoparticles in contact with each other, their shape changes. Additionally, in the structure with Al@Ni nanoparticles in contact with each other, a structural phase transition with a temperature jump to the peritectic transformation temperature of 1669-1670 K was detected during the SHS process, at which rapid crystallization of the Ni3Al phase from the melt and recrystallization of the NiAl phase into the Ni3Al phase occurs. To simulate the SHS process, the LAMMPS software package in a parallel version and the EAM potential of interatomic interaction compatible with it were used, and to visualize the results, the OVITO software package and the authors' own program were used.
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