Modeling Of Electrical Properties Research Articles

ON THE ACOUSTO-MAGNETIC METHOD OF MEASURING THE ACOUSTIC RESISTANCE OF LOCAL AREAS OF THE BIOLOGICAL TISSUE

The subject of study in the article is the acoustic resistance of local areas of the biological tissues in vivo, depending on their pathology. The aim of the work is to develop a quantitative method for measuring the acoustic resistance of local areas of the biological tissue (substance) located inside the human body. The following tasks are solved in the article: development of scientific foundations of the acousto-magnetic method for measuring the acoustic resistance of local areas of the biological tissue; development of a remote method for measuring electrical voltage on the surface of the patient's skin, caused by acousto-magnetic impact on local areas of the tissue and determined by the value of acoustic resistance; calculation of the ratios binding the value of the acoustic resistance of the local areas of the tissue with the electric voltage on the measuring probes on the patient's skin, the values of the acoustic radiation power and the external constant magnetic field, as well as with the distance between the probes and the local area of the biological tissue; verification of the calculated ratios using the experimental determination of the acoustic resistance of the local area of the model biological tissue. The following methods were used: physical modeling of the biological tissue, physical and mathematical modeling of electrical properties of the local part of the biological tissue, calculation of electromagnetic and acoustic parameters of the tissue, experimental measurement of electric field strength excited in the local part of the biological tissue, verification of calculated relations by comparing them with experimental results. The following results were obtained: the scientific foundations of the acousto-magnetic method for the quantitative measurement of the acoustic resistance of local areas of the biological tissue were developed; a remote method for measuring the electric voltage on the surface of the patient's skin caused by the acousto-magnetic effect on local areas of the tissue and the determined value of the acoustic impedance was developed; relations were calculated connecting the value of the acoustic impedance of local areas of the tissue with the electric voltage on the measuring probes on the patient's skin, the values of the acoustic radiation power and external constant magnetic field, as well as the distance between the probes and the local area of the biological tissue; verification of the calculated ratios was carried out using the experimental determination of the acoustic resistance of the local area of the model biological tissue. Conclusions: The scientific foundations of the remote acousto-magnetic method of high-precision measurement of the acoustic resistance of local areas of human biological tissue, confirmed experimentally on model tissue samples, have been developed. The method can make it possible to reveal with high accuracy the functional relations of the measured local value of acoustic resistance with pathological changes in the tissue. At the same time, the influence of the human factor on the interpretation of the recorded values of acoustic resistance (which is characteristic of the traditional, mainly qualitative, rather than quantitative ultrasound method) is excluded, the information content and reliability of acoustic diagnostics are increased.

Sensibility analysis of the electrical impedance parameters by the Monte Carlo method

Electrical properties of biological tissues are used to analyze its state in different practical applications, e.g., assessing the risk of cancer. The modeling of electrical properties usually is performed by circuital models or semiempirical models as Cole-Cole. Still, another option is available, the application of the generalized effective medium theory of induced polarization. In the framework of the effective medium theory, we proposed a model for biological tissues which we called MOPET. This model links physiological parameters of tissues with their electrical properties. However, it has a higher number of parameters than the Cole-Cole and circuital models. This large number of parameters is a limitation for the use of effective medium theory to describe the electrical properties of tissue and also suggests that some of these parameters have negligible effects. We used a Monte Carlo simulation to study the effect of each MOPET parameter on the electrical impedance spectra, where uniform random variables were used to simulate the variability of the parameters of this model. We found that the heterogeneity coefficient is the most sensible parameter, i.e., a variation above 1% in this parameter alters enormously the impedance spectra.

Modeling of electrophysical properties of bulk high-temperature superconductors in calculations of magnetic systems

Advanced macroscopic models of electrical properties of materials that are represented by a set of transport and associated currents and identified, respectively, by the resistive current model and nonlinear hysteretic magnetization model are proposed in order to calculate magnetic systems with the bulk high-temperature superconductor (HTS) elements. Such models allow a more accurately reproduced behavior of superconductors in the electromagnetic field of simply and multiply connected domains in various HTS transition regimes to the superconducting state. The paper presents the results of the compared combined and resistive models of the HTS properties. The proposed models enable us to reproduce the nonlinear, anisotropic, and hysteretic properties of superconductors in a wide range of parameter variation on a macroscopic scale and can be recommended for their application in numerical analysis of electromagnetic fields. The results of the calculations allow the parameter determination methods for the combined model from the experimental data to be substantiated.

Modeling of electrical properties of grain boundaries in n-conducting barium titanate ceramics as a function of temperature and dc-bias

Abstract A double Schottky barrier model suitable for the description of the grain boundary resistivity of n-conducting BaTiO 3 ceramics has been modified by taking account of frozen-in diffusion profiles of cation vacancies at the grain boundaries which are formed during the cooling process after sintering. The space charge model has been extended in order to predict the electrical properties of PTC ceramics (positive temperature coefficient of resistivity) under voltage load for maximum dc-bias values around 0.3 – 0.5 V/grain boundary. The effect of the voltage drop across the Schottky barrier on the concentration profiles of electrons in the depletion zone as well as the space charge potential has been elaborated in detail.

Equivalent-Circuit Modeling of Electrical Properties in DNA Molecules

Equivalent-Circuit Modeling of Electrical Properties in DNA Molecules

Percolation network modeling of electrical properties of reservoir rock

Based on the percolation network model characterizing reservoir rock’s pore structure and fluid characteristics, this paper qualitatively studies the effects of pore size, pore shape, pore connectivity, and the amount of micropores on the I-S w curve using numerical modeling. The effects of formation water salinity on the electrical resistivity of the rock are discussed. Then the relative magnitudes of the different influencing factors are discussed. The effects of the different factors on the I-S w curve are analyzed by fitting simulation results. The results show that the connectivity of the void spaces and the amount of micropores have a large effect on the I-S w curve, while the other factors have little effect. The formation water salinity has a large effect on the absolute resistivity values. The non-Archie phenomenon is prevalent, which is remarkable in rocks with low permeability.