Florin Constantinescu

By Alexandru Gabriel Gheorghe, Florin Constantinescu, Miruna Nițescu and Mihai Eugen Marin

Accurate information about fluid distribution in different compartments of the human body is very important in various areas of medicine like drug dosage, renal replacement therapy, nutritional support, coronary artery disease, colorectal cancer and HIV infection. The body impedance analysis method being simple, inexpensive, accurate and noninvasive is largely used to this end. Several models of the body impedance are presented in this chapter. The first is the Cole model, a linear, first-order RC circuit valid for a frequency range of two decades. Another model, developed by De Lorenzo, employs a fractional-order impedance whose parameters are identified using the frequency characteristics of the impedance module and can be used for a frequency range of three decades. In addition, two other models are presented, a ladder RC model valid for a frequency range of two decades and its extension to three decades, as well as a circuit containing multiple RC branches connected in parallel. These two models are obtained by approximating the measured body admittance modulus with a physically realizable circuit function followed by the circuit synthesis. The last model can be simplified, its simplest form being the Cole model. Allowing a better prediction of the intracellular and extracellular water volumes, this model can be viewed as an extension of the Cole model.

Part of the book: Electrochemical Impedance Spectroscopy

By Florin Constantinescu, Alexandru Gabriel Gheorghe, Mihai Eugen Marin and Florin Roman Enache

Section 1 deals with harmonic current sources models for one diode and two diodes rectifiers, the model parameters being determined by simulations. Section 2 describes frequency domain (FD) models of nonlinear home appliances whose parameters are determined by measurements. Some FD models for the loads using firing angle control devices are presented in Section 3. The fourth section presents the simulations of a relatively large circuit in the time domain (TD) and in the FD using the algorithms of CADENCE and ADS. The HB analysis of ADS using the proposed FD models proves to be the most efficient for this example.

Part of the book: Power Quality and Harmonics Management in Modern Power Systems [Working title]