Hamadi Ghariani

Mapping the dynamic repertoire of the resting brain

The resting state dynamics of the brain shows robust features of spatiotemporal pattern formation but the actual nature of its time evolution remains unclear. Computational models propose specific state space organization which defines the dynamic repertoire of the resting brain. Nevertheless, methods devoted to the characterization of the organization of brain state space from empirical data still lack and thus preclude comparison of the hypothetical dynamical repertoire of the brain with the actual one. We propose here an algorithm based on set oriented approach of dynamical system to extract a coarse-grained organization of brain state space on the basis of EEG signals. We use it for comparing the organization of the state space of large-scale simulation of brain dynamics with actual brain dynamics of resting activity in healthy subjects. The dynamical skeleton obtained for both simulated brain dynamics and EEG data depicts similar structures. The skeleton comprised chains of macro-states that are compatible with current interpretations of brain functioning as series of metastable states. Moreover, macro-scale dynamics depicts correlation features that differentiate them from random dynamics. We here propose a procedure for the extraction and characterization of brain dynamics at a macro-scale level. It allows for the comparison between models of brain dynamics and empirical measurements and leads to the definition of an effective coarse-grained dynamical skeleton of spatiotemporal brain dynamics.

Maximum of mutual inductance by inductive link

This paper presents inductive link between various coils or various forms to protect the reserve of unidirectional energy and from bi-directional data in the implantables electronic devices. Study will rest on the increase of the efficiency allocated by the tolerance to the lateral, longitudinal and even angular displacement between the external coil (transmitter) and the implanted coil (receiver).

Design of rectangular microstrip patch antenna

The purpose of this paper is to design a microstrip rectangular antenna in Advance Design System Momentum (ADS). The resonant frequency of antenna is 4.1GHz. The reflection coefficient is less than -10dB for a frequency range of 3.1GHz to 5.1 GHz. The proposed rectangular patch antenna has been devise using Glass Epoxy substrate (FR4) with dielectric constant (εr = 4.4), loss tangent (tan δ) equal to 0.02. This rectangular patch is excited using transmission lines of particular length and width. Various parameters, for example the gain, S parameters, directivity and efficiency of the designed rectangular antenna are obtained from ADS Momentum.

Design of a micro power amplifier for neural signal recording

This paper describes a micro power amplifier for neural signal recording. We describe an amplifier using a differential pair as input stage. Given that neural amplifiers must include differential input pair to achieve a high commonmode rejection ratio (CMRR). The amplifier has been designed in the AMS 0.35 µm, 3-metal, 2-poly, n-well standard CMOS process. The amplifier current consumption is 4.61 µA at ±1V supply, which gives a power consumption of 9.22 µW. The CMRR is 113 dB and the power supply rejection ratio (PSRR ≫ 73dB). The input referred noise is 14.8 µVrms over 100 ∼ 10 KHz. The amplifier gives an input DC offset of 196 µV and an output swing of ±0.8 V with minimum distortion.

Influence of the cardiac activity on the surface impedance of a multilayer model

Biological tissues are seen as multilayer structures. We will use in this article a model with three layers: skin, fat and muscle. This structure may be related to a pattern of cascaded lines where each tissue has its own characteristic impedance, permittivity and conductivity. This structure allows us to solve the problem of the surface impedance. Each layer is similar to a line of characteristic impedance. The impedance of the first layer will be transformed as soon as one progresses to the surface. This article represents, first, a detailed study of the electrical properties of a stratified propagation medium, and secondly, a study of the variation of the surface impedance according to the cardiac activity.

Design of a pulse generator for UWB communications

The Ultra Wide Band (UWB) is a technical of radio transmission which consists of using signals whose spectrum is spread out over a broad frequency band, typically ranging from MHz to several GHz frequencies. It was at first used for radar applications then applied in telecommunication applications, thus arousing a growing interest within the academic and industrial community. The present work is concerned with a research on UWB as a new technology for radar systems. Besides, it sheds light on the design of transmission system with broad ultra band an Agilent Advanced Design System modeling tool.

Modeling of the thorax of human body at 433 MHz

Nowadays, communication networks have become indispensable in our daily lives. In the last years, new networks have been developed, such as the body wireless sensor network “BAN”. So it will be necessary to highlight the influence of the body on the radiation pattern, performance and adaptation of the antenna. To understand the interaction between electromagnetic waves and the human body, it is important to have knowledge about the physical properties of biological tissues which can be seen as multilayer structures. This will be well detailed in this paper. Each layer has its own dielectric characteristics. Those properties are represented by the relative permittivity and conductivity. So to characterize tissues, we must study its properties. Then, a study of the attenuation factor is made, based on a comparison between HFSS and ADS.

Correction applied to the propagation model of UWB wave in human biological tissue obtained by FDTD method for estimation of the wave form at the heart

This work studies the spread of a UWB pulse in biological tissue, which forms the propagation media to the electromagnetic waves to detect a heartbeat. This tissue is multiple Modeled as semi-infinite lossy and dispersive media. The study focused on the deformations at the interfaces between two successive layers. The FDTD method is an approach for solving Maxwells equations. However, we note at the interfaces, the distortion signal. This is observed in the attenuation of energy signal. In this article we try to understand the origins of these disturbances, to find a solution for these perturbations, and, to estimate the waveform by adding an adaptive mesh at the interfaces.

Wireless power transmission technologies and applications

In this paper, a review is given of present state of the art about the concept of wireless power transmission i.e., transmitting power as microwaves from one place to another in order to reduce losses during the transmission and distribution of electrical power or also to deliver energy in location where conventional wires are expensive, inconvenient or impossible. This concept is known as Microwave Power Transmission (MPT). We presented the technological of Wireless Power Transmission (WPT) and also its applications.

Design of a digital communication system based on a XBee module for biomedical applications

This article describes the prototype of the digital communication system based on the XBee module. It consists on a universal system that transmits all type of data including the medical information such as Electrocardiogram (ECG). To validate this system, we have chosen to transmit the ECG from a computer to another through the XBee modules just to evaluate the quality of the wireless communication. For this, we have performed a series of indoor and outdoor tests.