Estimating the Volume of Unknown Inclusions in an Electrically Conducting Body with Voltage Measurements

We propose a novel technique to estimate the total volume of unknown insulating inclusions in an electrically conducting body from voltage measurements. Unlike conventional Electrical Impedance Tomography (EIT) systems that usually exhibit low spatial resolution and accuracy, the proposed device is composed of a pair of driving electrodes which, supplied with a known sinusoidal voltage, create a current density field inside a region of interest. The electrodes are designed to generate a current density field in the region of interest that is uniform, to a good approximation, when the inclusions are not present. A set of electrodes with a polygonal geometry is used for four-wires resistance measurements. The proposed technique has been tested designing a low cost prototype, where all electrodes are on the bottom of the conducting body, showing good performances. Such a device may be used to monitor the volume of biological cells inside cell culture dishes or the volume of blood clots in micro-channels in lab-on-a-chip biosensor

Vers un changement de pratique dans une filière céréalière : apport de la modélisation de l’environnement

National audienceProject management, especially in the field of sustainable development, requires to take into account not only the working environment stricto sensu, but also supra components of environmental, social, economic, legislative, etc. Ergonomists and psychologists are then led to be interested in, and to develop modeling frameworks to better understand and to make more intelligible this complex environment. The study presented here, which requires taking into account this environment, aims at setting up a novel practice for improving the food safety of a cereal chain in a global context of sustainable development: protection of the environment (flora and fauna) and the health of farmers and consumers. As part of this study, a quick fungal contamination diagnostic tool and a corresponding decontamination process have been developed for an application in the barley-malt-beer food chain. However, the use of these processes may change the agricultural practices in antifungal treatments with the regular and high dose treatments replaced by fine targeted applications only where and when necessary. In relation with this technological development, the challenge is to identify the components of the environment that may become brakes and levers to the implementation of this new practice. In this scope, this investigation mobilizes the modeling of the environment of Thatcher and Yeow (2016). This paper is consequently aimed at presenting the underlying process to this construction, and this in relation with the characteristics of the study. At last, a discussion is initiated concerning the further use of such modelling practices for purposes other than the decision-making processes on ergonomic intervention purposes.L’intervention ergonomique dans le champ du développement durable requiert la prise en compte d’un environnement dépassant largement l’environnement de travail afin d’y intégrer des composants relevant de dimensions environnementales, économique, législative, etc. Les ergonomes et psychologues ergonomes sont alors conduits à développer des cadres de modélisation permettant d’appréhender et de rendre davantage intelligible cet environnement complexe. L’étude sur laquelle nous nous basons ici s’inscrit dans ce cadre et vise l’identification des freins et leviers à la mise en place d’une nouvelle pratique en matière de traitement antifongique pour la filière orge-malt-bière. Pour cette investigation, nous nous référons notamment à la modélisation de Thatcher et Yeow (2016). L’enjeu est de présenter le processus de recueil et d’analyse sous-jacente à la modélisation et de poursuivre par une réflexion quant à l’emploi de ces formes de modélisation au cours d’un processus d’intervention

Study and design of ratiometric inductive position sensors using area-of-overlap functions

This article presents a theoretical study of an absolute, ratiometric inductive position sensor (IPS) based on eddy currents. The aim is to describe the working principle of the sensor, having as key components a transmitting coil, the receiving coils and the conductive target, by introducing area-of-overlap functions. We show that each target–receiver pair needs the adoption of a different reconstruction formula for the identification of the target position, whereas in the literature the usual inverse tangent function is applied for every possible pair. Than, we seek the target–receiver pair that maximizes the amplitude of the induced voltages on the receivers. The results show that, to achieve the maximum value of the induced voltages, the best choice is to have rectangular target and rectangular receivers. In order to verify the theory, a simulation and optimization method has been applied to the rectangular receivers coils on two rotary IPS realized with Printed Circuit Board (PCB) technology. Measurements performed on the prototypes have shown an increment of the induced voltage of more than 57% with respect to the commonly used sinusoidal receivers. However, a linearity error of 1.5%FS is obtained by using the inverse tangent reconstruction formula. When using the formula provided from the theory, the linearity error becomes 0.6%FS for the non-optimized prototype and below 0.15%FS for the optimized one

Electrical Impedance Spectroscopy on flowing blood to predict white thrombus formation in artificial microchannels

The \u201cin vitro\u201d study of white thrombus growth by means of Electrical Impedance Spectroscopy on whole blood is presented; the aim of the work is to correlate thrombus formation in an artificial channel with impedance measurements. The measurement bench is composed of a sensor, a switch unit and an impedance meter. Post process of measured data is performed and an equivalent lumped circuit is derived; experimental data are obtained with a first prototype based on a single couple of electrodes

A Novel Family of Inductance Matrix Compression Techniques

Integral methods for the solution of eddy current problems are very appealing since they avoid the meshing of the insulating regions. Yet, their main shortcoming is that they require the assembly and storage of a fully populated stiffness matrix K. To reduce the memory footprint and to enable a fast matrix construction, low-rank approximations techniques-like the Adaptive Cross Approximation (ACA)-have been considered a major breakthrough in the field. This paper presents a novel family of compression techniques that is enabled by a novel explicit factorization of the inductance matrix. Such a novel family exhibits orders of magnitude speedup and memory consumption with respect to state-of-the-art techniques. In particular, the aim of this paper is to compare for the first time the memory occupation, computation time and accuracy of the solution obtained with different compression techniques

A novel apparatus for the volume estimation of in vitro thrombus growth

Current available diagnostic technologies for the analysis of thrombus formation fail to detect the thrombus volume and are unable to capture the kinetics of the overall process. In the paper, we present a novel methodology, based on the fusion of electrical and optical data, to measure in real time the volume and the geometry of platelet thrombus growth in an artificial microchannel, where whole blood flows on the surface of a thrombogenic substrate

A discrete geometric approach to cell membrane and electrode contact impedance modeling

This paper presents a novel discrete model for cell membranes and electrodes contact impedances alternative to the widely used finite elements. The finite element approach can be considered as a tool for constructing finite dimensional systems of equations that approximate the specific electroquasistatic biological problem on the discrete level. Although the finite element technique is explained typically in terms of variational or weightedresidual approaches, another, less familiar way is available to reformulate geometrically the same physical problem. This approach, referred to as discrete geometric approach, allows a direct link between geometry and the degrees of freedom describing the specific biological problem. It is straightforward to implement in any finite element open software and it assures a correct modeling of voltages and currents playing a fundamental role in a biological problem. The validation has been performed, as a first step, against analytical solutions; then, we considered impedance measurements regarding erythrocytes in whole blood flowing in microchannels at high shear rates