Marilena Stanculescu

In Situ Evaluation of Ferromagnetic Bodies Magnetic Characteristics

The B-H characteristic of an iron body material influences the magnetic field measured in the air. On principle, one can pose the problem of B-H relation determination, by making measurements of the magnetic induction in the neighbourhood of the body. Unfortunately, we have an ill-posed inverse magnetic field problem, for which there is possible that, big variations of the BH characteristic to produce only very small modifications of the magnetic field in the air. It is essential to use a sufficiently sensitive computation procedure in order to produce credible results. This paper proposes a device for the B-H characteristic evaluation, admitting that inside the ferromagnetic bodies the magnetic field distribution is not uniform.

Fundamentals of Reactive Power in AC Power Systems

The fundamentals of reactive power in AC power systems are discussed in the second chapter. The chapter presents basic theory of AC circuits including two-ports linear elements, basic equations and definition of powers in AC circuits. The phasor diagrams and power measurement techniques in AC networks are also presented. The chapter also investigates the effects of reactive power as well as power factor compensation in consumers. The end part of the chapter is related to minimum active and reactive absorbed power in linear AC circuits and also non-sinusoidal conditions. All of the parts include some practical examples and case studies. The chapter is closed with a large list of bibliographic references.

Power Systems Connectivity and Resiliency

This chapter presents the role of power system connectivity and resiliency under the conditions of vulnerability to natural disasters and deliberate attacks. The importance of introducing the Internet of Things (IoT) concept in developing smart grids will be shown, as well as the methods of increasing the power system resiliency. Case studies from the Romanian power system will be included. At the same time, the authors underline the necessity of introducing standards and developing the protection systems of Big Data in order to design the future smart power system.

Power Systems Recovery and Restoration Encounter with Natural Disaster and Deliberate Attacks

This chapter presents a theoretical analysis of the impact of the extreme weather events and deliberate attacks on the power systems, which is accompanied by several examples taken from existing reports. The power systems resiliency for these cases are presented and the used practices are being assessed. Optimized models to improve the power system reaction time to these new risks are also discussed and proposed.

Circuit Analyses with Nullors

This chapter describes the nullor-based modelling of active devices from the circuit level of abstraction. After a brief overview on the nullor concept and its properties, the modelling of active devices not only at the voltage-mode but also at the current-mode and the mixed-mode of operation from two-port and four-terminal network point of view are described in details. The circuit analysis with nullors and the topological approach for transfer function generation by two-graph tree enumeration as well are presented. The generalized topological formula with homogeneous parameters is proved for all the circuit functions, and a simple representation of the four types of controlled sources by admittances is proposed, that allows a uniform treatment of the entire circuit in terms of admittances. In order to implement the procedure, the rules to automatically generate the two graphs and to enumerate the common spanning trees are presented. Some simplifications in the circuit and in the two graph structure before tree generation and a graph representation on levels, improve the efficiency of the tree enumeration procedure. The original approach, in which each edge is labelled with an admittance term, could handle only one type of active element, namely VCCS (voltage controlled current source), but the method was further developed by many researchers for general linear circuits to include virtually all active elements. Some techniques to convert the CCVSs (current controlled voltage sources), VCVSs (voltage controlled voltage sources) and CCCSs (current controlled current sources) in equivalent schemes containing only VCCSs together with admittances and the inductance modelling proposed in the literature are discussed.

The use of S parameters in wireless power transfer system stability

In this paper a series of constants, corresponding to wireless power transfer system (WPTS), are defined, function of S parameters. These constants will be further used for stability factors computation in WPTS. To generate: the reflection coefficients, the standing wave ratio (SWR), the input and output impedances, the input and output active power transmission efficiency, the signal transmission efficiency, the power gains, the various stability coefficients, the centers and radius corresponding to stability circles from the source and from the generator, the S, T, Z and Y matrices and the Smith charts, we developed dedicated functions by using existing routines from the MATLAB Microwave toolbox. The results obtained by simulations were compared to those existing in literature and with experimental ones.

Using S parameters in wireless power transfer analysis

This paper presents the correct formulation of scattering parameters S, using electric circuit theory, and the practical use of these parameters. The purpose is to make more efficient the processes for the information transmission and the wireless electromagnetic energy transfer. The efficiency is seen from the transmission point of view of the signals (from the transmitter to receiver) and from the active power transfer efficiency point of view (from the wireless systems input to the loads connected at their outputs). Starting from the correct formulation of S parameters, their computation takes place automatically based either on state equations or on modified nodal equations of the wireless power transfer systems (WPTS). The two magnetically coupled coils, considered as a passive linear 2-port network in harmonic regime, can be described by a number of equivalent circuits parameters, such as: the transfer coefficients matrix T, the impedance matrix Z, the admittance matrix Y and the matrix corresponding to S parameters. This paper presents the relationships that allow the transition from one matrix to another. To generate: the coefficients corresponding to reflection, the input and output impedances, the input-output (output-input) active power transmission efficiencies, the signal transmission efficiencies, the S, H T, Z and Y matrices, and the Smith charts, we elaborated MATLAB dedicated functions by using the existing routines form the Microwave MATLAB toolbox.

Issues on early cancer detection using thermographic methods

This paper presents some aspects regarding the thermographic detection of early-stage cancer that can affect paired organs. The use of a difference thermal field on the surface of the skin near paired organs surfaces is proposed as part of a detection method. The temperature acquisition procedures based on the use of thermographic cameras and temperature sensors are analyzed. The symmetry of the thermal field associated with each organ is analyzed.

S-parameters utilization in electrical quadrupoles analysis

This study, using the theory of electric circuits, shows the right definition of scattering parameters (S-parameters) for any two-port electric circuit and the practical way to use these parameters in streamline the processes of information transmission and propagation, and the transfer of the active power from the electric quadrupole input (output) to their output (input). Starting from the correct definition of S-parameters, their calculation is performed automatically. Passive linear circuits in harmonic regime can be described by a certain number of equivalent circuit parameters, like transfer coefficients matrix (fundamental) T, impedances matrix Z, admittances matrix Y and S-parameters matrix S. In this paper are presented the relations that permit the transition from a matrix to another one. To generate the reflection coefficients, input and output impedances, active power transmission efficiency from input to output (from output to input), signal transmission efficiency, S, T, Z and Y matrices, and Smith charts, there are developed specific routines in MATLAB and there have been used the current subroutines from MATLAB microwave toolbox. S-parameters variations by frequency have been presented graphically and on the Smith chart. The results obtained through simulation processes have been compared with the ones presented in the specialty literature and with the experiments results, calculated deviations being less than 5%.

Cardiac Stimulation Through Induced Currents

Abstract This paper presents the magnetic cardiac stimulation, more precisely the stimulation with an electric field produced by a time-variable magnetic field. The modeling within this domain has in view the investigation of the induced currents in the body and the characteristics of the defibrillation coil (shape, number of turns, length) and the applied stimulus.