Iliana Marinova

Coupled Field Modeling of Ferrofluid Heating in Tumor Tissue

This work examines the method of magnetic fluid hyperthermia for breast cancer therapy. We develop a coupled-field model of ferrofluid transport and heating in tumor tissue. The finite element method (FEM) underpins our forward 3D electromagnetic—fluid dynamics-thermal model. The model uses anatomically precise multilevel geometry of the human breast, with known electrical properties of the tissues, and known speeds of blood and liquor in the breast vessels. We demonstrate the capabilities of the developed model on a real cancer sample acquired by a surgical procedure. The electrical properties of cancer and normal tissues are directly measured for the given sample. The thermal field results are verified by infrared thermograph imaging.

Inverse source problem for thermal fields

Purpose – The purpose of this paper is to develop an inverse approach for 3D thermal sources determination.Design/methodology/approach – The developed approach is based on the Greens function for Poisons equation. Forward and inverse couple electromagnetic‐thermal field problems are formulated. Finite elements models are built and applied. Thermal field data are acquired by thermo vision camera. The thermal field sources are determined inside of the investigated inaccessible volume object using modeled and measured data with the developed approach.Findings – The presented method and implemented examples demonstrate the possibilities of the developed approach for inverse source problem solution and determination of thermal field distributions of electrical devices.Originality/value – The proposed inverse method uses the Greens function for Poisons equation for solution of thermal field problem taking into account the couple electromagnetic‐thermal problems. Proposed inverse method is very fast, accurat...

Fluctuation Frequency Analysis of the Barkhausen Signals Under Static and Dynamic Stresses

Ferromagnetic materials are widely used for various artificial products such as cars, trains, ships. Because of its mechanical property, iron steel is most popular in use for frame materials. Nondestructive testing of iron steel is an extremely important way to maintain their mechanical reliability. As is well known fact, the Barkhausen signals are emitted from only the ferromagnetic materials having magnetic domain structures. Also this signal varies depending upon their past mechanical as well as radioactive stress histories. In the present paper, we have applied a generalized frequency fluctuation analysis to the Barkhausen signals to detect the various mechanical stresses. Surprisingly, it has been succeeded in clarifying that application of our frequency fluctuation analysis to the Barkhausen signals makes it possible to detect the two kinds of mechanical stress.

Dynamics on ferroresonant circuit exhibiting chaotic phenomenon

This paper studies dynamics of a series ferroresonant circuit. A Chua type magnetization model derives a state variable equation with nonlinear parameters. Backward Euler method with adaptive stepsize control performs a transient analysis. Modal analysis to the state variable equation is also carried out in each calculation period of the Euler method in order to obtain the condition of internal system. Finally, it is clarified that the characteristic values vary on the regular loci although the chaotic phenomenon is exhibiting. The relation between the time constants and operating frequencies is shown to clarify the ferroresonant mode.

Analysis of a ferroresonant circuit with chaotic behavior by means of a Chua-type magnetization model

This paper studies the chaotic behavior of a series ferroresonant circuit. At first, we derive a state variable equation containing a nonlinear hysteretic circuit element represented by a Chua-type magnetization model. Second, the backward Euler method with automatic modification gives transient response of the state variable equation. The characteristic values of the state transition matrix are calculated in each calculation step of Euler method. Finally, it is clarified that the characteristic values trace on the same loci although the chaotic phenomenon is exhibiting.

Torque transmission characteristics of a coaxial magnetic gear

Study of the characteristics of a coaxial magnetic gear with permanent magnets is carried out in this paper. A 2D FEM model has been developed. The torque transmission of the magnetic gear is analyzed at steady-state and dynamic conditions. The research is carried out by Ansys Maxwell software.

Permanent magnets for a magnetic gear

A research of the permanent magnet influence on the steady-state and the dynamic characteristics of a magnetic gear is carried out. For this purpose, a two dimensional finite element model has been developed and applied using Ansys Maxwell package. Permanent magnets such as Alnico, ferrite, SmCo and NdFeB are utilized in order to evaluate their effect on the torque transmission of a magnetic gear.

Enhance the sensibility of the film infinite eddy current sensors

AbstractPreviously, we have succeeded in exploiting a new high sensibility eddy current testing sensor called the infinite (∞) coil. Operating principle of this ∞ coil is that two adjacent coils constructing the north and south poles alternatively set a zero magnetic potential region and keep the same situation when eddy currents are flowing along the paths in parallel to the exciting coils. If the eddy currents could not flow the paths in parallel to the exciting coil on the test specimen, then a zero magnetic potential region between the two exciting coil moves toward the other position. This means that a sensing coil located at a mid position of two exciting coil is possible to detect the disturbed magnetic fields, i.e. the defect in the test specimen could be detected from the sensing coil signal. This paper proposes one of the enhancing methodologies of the infinite coil sensibility. Key idea is that the zero magnetic potential region between the north and south exciting poles of the infinite coil is...

Ferroresonance circuit analysis exhibiting chaotic phenomenon by Chua-type magnetization model

In the present paper, the nonlinear calculation with Chua-type magnetization model carries out a ferroresonance circuit analysis. To clarify the ferroresonance system, the characteristic values based on the state variable representation are calculated in each of iteration steps. It is reveals that they have no hysteretic properties even though exhibiting chaotic behaviors.