scholarly journals MODELING OF THE ANISOTROPY OF THE SPECIFIC ELECTRICAL CONDUCTIVITY OF BIOLOGICAL TISSUE ARISING AT LOCAL COMPRESSION BY BIPOLAR WELDING ELECTRODES

2021 ◽  
Vol 2021 (2) ◽  
pp. 13-19
Author(s):  
Yu.М. Lankin ◽  
◽  
V.G. Soloviev ◽  
I.Y. Romanova ◽  
◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electric Fields ◽  
Biological Tissue ◽  
Biological Tissues ◽  
Geometric Interpretation ◽  
Physical Experiment ◽  
Geometric Parameters ◽  
Successive Approximations ◽  
Specific Electrical Conductivity ◽  
Method Of Successive Approximations

Current publications on bipolar welding use the electrical characteristics of uncompressed biological tissue. This reduces the accuracy of calculating the distribution of the density of the flowing currents and the strength of the electric fields in the zone of the fabric to be welded when it is squeezed. The aim of the work is to show a methodology for calculating the change in the specific electrical conductivity of biological tissue under local compression by electrodes and the effect of this factor on the results of modeling electrical processes of biological welding. A geometric interpretation of the change in the electrical conductivity of the pig's heart muscle when squeezed by bipolar welding electrodes in relative units is proposed. The principle of similarity of the geometric parameters of the physical experiment and the graphic model of COMSOL multyphysics is used, as a result of which the dependences of the three main geometric parameters of the model on the magnitude of the relative compression are determined. The method of successive approximations of the values of the total electrical resistance of biological tissue in a physical experiment at frequencies of 0,3, 30, and 300 kHz and the calculated resistances on the model with a change in the basic geometric parameters of specific electrical conductivity was used. A model of bipolar welding of biological tissues is obtained, which takes into account the anisotropy factor of the electrical conductivity of biological tissue under compression. Some results of investigations of the regularities of the current flow in the tissue, taking into account the arising anisotropy, are presented. References 12, figures 5, tables 4.

The Bloch integral equation and electrical conductivity

1950 ◽  
Vol 202 (1071) ◽  
pp. 466-484 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Integral Equation ◽  
Temperature Variation ◽  
Characteristic Temperature ◽  
Successive Approximations ◽  
Method Of Successive Approximations ◽  
Theoretical Treatment ◽  
Temperature Range ◽  
High And Low Temperatures ◽  
Semi Empirical

An account is given of the solution, for effectively the whole temperature range, of the Bloch (1928) integral equation for the electron momentum distribution in a metal in an electric field. Solutions of this equation, from which the temperature variation of the electrical conductivity of the metal may be immediately calculated, have previously been obtained only in the limiting cases of ‘high- and low -temperatures’, corresponding to ( T /θ p )≫ 1 and ≫1, where θ p is the Debye characteristic temperature. As a preliminary to its solution by numerical methods the integral equation is expressed in a non-dimensional form (§2). Solutions are obtained by deriving a high-temperature approximation which is valid over a much wider temperature range than that previously known, and by means of a method of successive approximations (§3). The temperature variation of conductivity is calculated from these solutions, and it is shown that there are significant differences between the results and those obtained from the semi-empirical formula of Grüneisen (1930) (§4). A comparison is made between the calculated and observed temperature variation of conductivity for a number of metals. There are deviations in detail, and a brief discussion is given of secondary factors from which they may arise, but in general the agreement is good, and it is concluded that the theoretical treatment covers satisfactorily the main features of the observed variation (§5). In an appendix it is shown that the approximate relations obtainable by the variational method developed by Kohler (1949) are consistent with the more exact results obtained here.

Variation of Electrical Conductivity With Water Content in Agarose Gel

2002 ◽  
Author(s):  
Adriana L. Vega ◽  
Hai Yao ◽  
Marc-Antoine Justiz ◽  
Weiyong Gu
Keyword(s):  
Electrical Conductivity ◽  
Water Content ◽  
Normal Tissue ◽  
Tumor Tissue ◽  
Biological Tissues ◽  
Specific Electrical Conductivity ◽  
Agarose Gel ◽  
Similar Relationship ◽  
Ion Concentrations ◽  
The Relationship

Specific electrical conductivity, a material property of biological tissues, has been found to be greater in tumor tissue than in normal tissue on account of its higher water content [1]. Its value is related to water content, ion concentrations, and ion diffusivities within biological tissues [e.g., 1,2,3]. The variation in conductivity with water content is hypothesized to be related to the change in ion diffusivities [5,6]. The objective of this study is to investigate the relationship between conductivity and water content in hydrogels. The main goal is to develop a similar relationship for biological tissues and to understand deformation-dependent ion diffusivity in tissues under mechanical loading.

Mathematical modeling of cathodic protection of electric fields for major pipelines in anisotropic terrains

2020 ◽  
Vol 10 (1) ◽  
pp. 52-63
Author(s):  
Vladimir N. Krizsky ◽  
◽  
Pavel N. Aleksandrov ◽  
Alexey A. Kovalskii ◽  
Sergey V. Viktorov ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electric Fields ◽  
Cathodic Protection ◽  
Electrical Anisotropy ◽  
Specific Electrical Conductivity ◽  
Computational Investigation ◽  
Protective Capacity ◽  
Lateral Direction ◽  
Homogeneous Half Space ◽  
Conductivity Contrast

The authors consider the problem of the computational investigation of cathodic protection electric fields measured for an underground pipeline taking into account the anisotropic nature of soil specific electrical conductivity. A computational experimental method was used to compare the figures for anisotropic soils against the current distribution for a homogeneous half-space; the influence of anisotropy factors and the azimuth conductivity tensor rotation angle for pipeline-enclosing soil on the electrical parameters of cathodic protection of the pipeline were investigated. It was demonstrated that protective capacity can vary significantly for areas close to the drainage points of cathode stations and for defective segments. It was concluded that there is a need to take into account terrain structure (its electrical anisotropy) when there are prerequisites of soil lamination/fracturing, or if its specific electrical conductivity contrast in the lateral direction is in excess of 2–2.5 times.

Numerical Methods for Solving Physically Nonlinear Problems for Inhomogeneous Thick-Walled Shells

2017 ◽  
Vol 865 ◽  
pp. 325-330 ◽  
Author(s):  
Vladimir I. Andreev ◽  
Lyudmila S. Polyakova
Keyword(s):  
Numerical Method ◽  
Nonlinear Problems ◽  
Successive Approximations ◽  
Method Of Successive Approximations ◽  
Deformation Diagram ◽  
Method Of Solution ◽  
Properties Of Materials ◽  
Physical Fields ◽  
Cylinders And Spheres ◽  
Numerical Method Of Solution

The paper proposes the numerical method of solution the problems of calculation the stress state in thick-walled cylinders and spheres from physically nonlinear inhomogeneous material. The urgency of solved problem due to the change of mechanical properties of materials under the influence of different physical fields (temperature, humidity, radiation, etc.). The deformation diagram describes the three-parameter formula. The numerical method used the method of successive approximations. The results of numerical calculation are compared with the test analytical solutions obtaining the authors with some restrictions on diagram parameters. The obtained results can be considered quite satisfactory.

On a sphere performing linear and torsional oscillations in a viscous fluid

1988 ◽  
Vol 66 (7) ◽  
pp. 576-579
Author(s):  
G. T. Karahalios ◽  
C. Sfetsos
Keyword(s):  
Boundary Layer ◽  
Viscous Fluid ◽  
Secondary Flow ◽  
Small Amplitude ◽  
Equations Of Motion ◽  
Successive Approximations ◽  
Method Of Successive Approximations ◽  
Time Varying ◽  
Torsional Oscillations

A sphere executes small-amplitude linear and torsional oscillations in a fluid at rest. The equations of motion of the fluid are solved by the method of successive approximations. Outside the boundary layer, a steady secondary flow is induced in addition to the time-varying motion.

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