The mathematical model of magnetofluidic sealers is considered taking into account the influence of physical fields on each other. The relationship between the magnetic and hydrodynamic fields is ...implemented by an additional body force, which depends on the magnetic field strength and produces pressure inside the ferrofluid. The effect of hydrodynamic processes on the ferrofluid distribution is taken into account by a change in the magnetic conductivity with displacement of the ferrofluid interface. Based on the suggested model, the effect of centrifugal force on the critical pressure drop of a ferrofluid sealer was studied. It is shown that design solutions can neutralize the negative effect of ferrofluid separation from the shaft surface, as well as increase the pressure drop retained by the sealer. Based on the theory of experiment planning, the degree of impact of working-zone geometry and physical properties of a ferrofluid on the power of dissipative losses has been estimated. It is shown that the largest contribution to the heating of ferrofluid is provided by the working gap between a tooth and body, the width of spot at the tooth top, the shaft radius, and the ferrofluid viscosity, while the influence of tooth bevel angle, density and volume of the ferrofluid (expressed in terms of its cross-sectional area for a 2D problem) can be neglected in the analysis of viscous heating.
The algorithm for analytical calculation of a power characteristic of magnetorheological (MR) dampers taking into account the rheological properties of MR fluid is considered. The nonlinear ...magnetorheological characteristics are represented by piecewise linear approximation to MR fluid areas with different viscosities. The extended calculated power characteristics of a MR damper are received and they coincide with actual results. The finite element model of a MR damper is developed; it allows carrying out the analysis of a MR damper taking into account the mutual influence of electromagnetic, hydrodynamic and thermal fields. The results of finite element simulation coincide with analytical solutions that allows using them for design development of a MR damper.
•Division of a MR fluid rheological curve into two sections with different viscosities.•Algorithm for calculation of a power characteristic of MR dampers is proposed.•Finite element model of a MR damper is developed.•Results of finite element simulation coincide with analytical solutions.
The aim of the work is to create an interconnected numerical model of the magnetic, hydrodynamic and temperature fields of a ferrofluid sealer and to analyze thermal processes occurring in highspeed ...seals. This goal is achieved by selecting the necessary equations, boundary conditions, assumptions and physical properties of the magnetic fluid when building the numerical model of the sealer’s working gap, verification of the developed model by the results of the physical experiment. The important results of the work are the obtained and analyzed data on the influence both of physical properties and the geometry of the working gap of the ferrofluid sealer on the heating of the ferrofluid. With a shaft radius of 140 mm and a linear velocity at the shaft surface of 25 m/s due to viscous heating the ferrofluid temperature exceeding the ambient temperature can reach values up to 80 degrees and higher, it has been shown. The use of the equation proposed by V.E. Fertman to determine the thermal conductivity of ferrofluid and the mixing rule to determine its heat capacity allows us to describe with sufficient accuracy for engineering calculations the thermophysical properties of concentrated ferrofluids, it was shown. The significance of the results consists in the possibility of using the developed numerical model in the study of interrelated physical processes in the working gap of the ferrofluid sealer of rotating shafts. The physical and concentration parameters of the synthetic oil-based magnetic fluid given in the paper and the results of its test operation as part of a ferrofluid seal can be used to verify the results of newly developed models of ferrofluid devices.
Amino Acids as Regulators of Cell Metabolism Nesterov, S. V.; Yaguzhinsky, L. S.; Podoprigora, G. I. ...
Biochemistry (Moscow),
04/2020, Letnik:
85, Številka:
4
Journal Article
Recenzirano
In this review, we discuss the principles of regulation and synchronization of metabolic processes in mammalian cells using a two-component model of cell metabolism consisting of a controlling ...signaling system that regulates major enzymatic cascades and executive metabolic system that directly performs biosynthetic reactions. This approach has allowed us to distinguish two transitional metabolic states (from catabolism to anabolism and vice versa) accompanied by major rearrangements in the signaling system. The signaling system of natural amino acids was selected, because amino acids are involved in both signaling and executive metabolic subsystems of general cell metabolism. We have developed a graphical representation of metabolic events that allowed us to demonstrate the succession of processes occurring in both metabolic subsystems during complete metabolic cycle in a non-dividing cell. An important revealed feature of the amino acid signaling system is that the signaling properties of amino acid are determined not only by their molecular structure, but also by the location within the cell. Four major signaling groups of amino acids have been identified that localize to lysosomes, mitochondria, cytosol, and extracellular space adjacent to the plasma membrane. Although these amino acids groups are similar in the composition, they have different receptors. We also proposed a scheme for the metabolism regulation by amino acids signaling that can serve as a basis for developing more complete spatio-temporal picture of metabolic regulation involving a wide variety of intracellular signaling cascades.
The objective of the study is to develop recommendations for accounting during the design stage and the feasibility of operating a magnetic fluid seal with a significant eccentricity of the rotating ...shaft relative to stationary pole attachments. This goal is achieved through conducted experimental research, the selection of necessary equations, boundary conditions, assumptions, and physical properties of the magnetic fluid when constructing a numerical mathematical model of the working gap of the magnetic fluid seal. The most important results of the study include obtained and analyzed distributions of the magnetic field, velocity field, and pressure in the magnetic fluid, as well as the evaluation results of the impact of absolute and relative shaft misalignment in the magnetic fluid seal, centrifugal forces arising during shaft rotation, on the retained pressure drop by the seal. A significant reduction in the retained pressure drop occurs at an eccentricity of up to 40% of the working gap, and with further in-creases in eccentricity, the rate of pressure drop reduction slows down. The significance of the results lies in the potential utilization of the provided numerical model, as well as the outcomes of physical and mathematical experiments, in the development of a magnetic fluid seal operating with significant misalignment between the rotating shaft and the housing. The dimensionless dependencies obtained allow for consideration, during the design stage, of the reduction in retained pressure drop with shaft eccentricity, taking into account the magnitude of the working gap, magnetic induction, and linear velocity.
We consider the problem of deformation of a layered rectangle whose lower side is rigidly clamped, a distributed normal load acts on the upper side, and the lateral sides are in conditions of sliding ...termination. One-parameter gradient elasticity theory is used to account for the scale effects. The boundary conditions on the lateral faces allow us to use separation of variables. The displacements and mechanical loads are expanded in Fourier series. To find the harmonics of displacements, we have a system of two fourth order differential equations. We seek a solution to the system of differential equations by using the elastic potential of displacements and find the unknown integration constants by satisfying the boundary and transmission conditions for the harmonics of displacements. Considering some particular examples, we calculate the horizontal and vertical distribution of displacements as well as the couple and total stresses of a layered rectangle. We exhibit the difference between the distributions of displacements and stresses which are found on using the solutions to the problem in the classical and gradient formulations. Also, we show that the total stresses have a small jump on the transmission line due to the fact that, in accord with the gradient elasticity theory, not the total stresses, but the components of the load vectors should be continuous on the transmission line. Furthermore, we reveal a significant influence of the increase of the scale parameter on the changes of the values of displacements and total and couple stresses.
A novel method for the synthesis of catalytically active composites based on gold clusters incorporated into an alumina matrix was proposed. The method combines sol–gel and supercritical fluid ...technologies. The composites were synthesized by precipitating of gold clusters and alumina sol mixture in the supercritical antisolvent (SAS) carbon dioxide medium. Gold clusters were synthesized in the colloidal solution of alumina sol in situ (one-pot synthesis) via controlled reduction of Au
III
using PPh
3
as a stabilizer for the first time. It was shown that this method allows us to stabilize gold clusters with sizes less than 2 nm in the alumina matrix with a developed specific surface area (
S
BET
= 441 m
2
/g) and a narrow pore size distribution. The obtained composite does not contain stabilizer, which may poison the catalyst. The developed approach makes possible to synthesize catalytically active composites with a certain amount of gold cluster and oxide matrix of different nature.
Highlights
The gold based cluster composites were obtained via supercritical antisolvent precipitation.
The composites contain gold clusters with sizes less than 2 nm.
The composites have a developed specific surface and narrow pore size distribution.
Under study is the coefficient inverse problem of thermoelasticity for finite inhomogeneous bodies. We obtain the operator equations of the first kind for the Laplace transform of a solution for ...solving the nonlinear inverse problem by an iterative process. Solving the inverse problems of thermoelasticity in the originals relies on applying the inverse Laplace transform to these operator equations on using the theorems of operational calculus on the convolution and differentiation of the original. We provide some procedure for reconstructing the thermomechanical characteristics of a rod, a layer, and a cylinder. Finding an initial approximation for the iterative process bases on two approaches. Then an initial approximation is found in the class of bounded positive linear functions, while the coefficients of the functions are determined as minimizers of the residual functional. The other approach to finding an initial approximation bases on algebraization. Numerical experiments were carried out to recover both monotone and nonmonotone functions. Only one characteristic is restored while the others are assumed known. Monotone functions are restored better than nonmonotone ones. While reconstructing the characteristics of stratified materials, the greatest error arises in a neighborhood about the junction points. The reconstruction procedure turned out resistant to noise in the input information.
Today, the industrial production of hydrogen by traditional methods (high-temperature conversion of hydrocarbons, steam-water conversion of natural gas) against the background of a reduction in ...natural resources does not allow achieving the necessary purity of the produced gas and imposes serious economic and environmental restrictions. As a result, the solution of the task of developing technologies providing the improvement, high specific and operational characteristics of new methods for producing hydrogen is extremely urgent.
The use of hydrogen structures as a universal energy carrier led to its application in various fields of industry. Currently used production methodologies make it possible to produce systems with ...high reliability and a long service life. However, at the moment, the creation of such structures is limited by the lack of natural origin materials necessary for the production of such structures, which leads to the search for alternative and most universal manufacturing methods against the background of increasing needs.
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