Refining the Experimental Extraction of the Number of Independent Samples in a Mode-Stirred Reverberation Chamber

We investigate the number of independent samples in a chaotic reverberation chamber. Its evaluation as defined by the IEC standard can be made more precise when using not the index of the first value larger then the correlation length but using the value obtained by a linear interpolation instead. The results are validated by a juxtaposition with values from a measurement using a high stirrer-angle resolution. A comparison with estimates known from the literature validates our findings. An alternative approach using the local maxima of the parametric dependence of the transmission is presented in order to show the applicability of the extracted correlation length over a large range of frequencies.Comment: 7 pages, 7 figure

Universal intensity statistics in a chaotic reverberation chamber to refine the criterion of statistical field uniformity

International audienceThis article presents a study of the intensity statistics of the electromagnetic response in a chaotic reverberation chamber (RC) in the presence of losses. Through an experimental investigation, intensity statistics of the response in a conventional mode-stirred RC are compared with those in a chaotic RC in the neighborhood of the Lowest Useable Frequency. The present work illustrates how the universal statistical properties of the field in an actual chaotic RC can ensure the validity of the standard criterion proposed to evaluate the uniformity of the field distribution. In particular, through a theoretical approach based on the random matrix theory applied to open chaotic systems, we find that the modal overlap seems to be the only relevant parameter of the corresponding intensity distribution

Statistiques de la réponse électromagnétique d'une chambre réverbérante chaotique

Cet article présente une étude de la réponse électromagnétique d'une chambre réverbérante (CR) chaotique en présence de pertes. Au moyen de simulations et d'expériences, sont comparées les fluctuations des maxima du champ obtenus dans une CR à brassage de modes conventionnelle et dans une CR chaotique au voisinage de la fréquence minimum d'utilisation. Ce travail illustre que les propriétés statistiques spectrales et spatiales universelles des CR chaotiques permettent de mieux répondre aux critères exigés par la norme pour réaliser des tests d'immunité ou de compatibilité électromagnétique

From CO₂ to formic acid fuel cells

ABSTRACT: Formic acid is a liquid, safe, and energy-dense carrier for fuel cells. Above all, it can be sustainably produced from the electroreduction of CO₂. The formic acid market is currently saturated, and it requires alternative applications to justify additional production capacity. Fuel cell technologies offer a chance to expand it, while creating an opportunity for sustainability in the energy sector. Formic acid-based fuel cells represent a promising energy supply system in terms of high theoretical open-circuit voltage (1.48 V). Compared to common fuel cells running on H2 (e.g., proton-exchange membrane fuel cells), formic acid has a lower storage cost and is safer. This review focuses on the sustainable production of formic acid from CO₂ and on the detailed analysis of commercial examples of formic acid-based fuel cells, in particular direct formic acid fuel cell stacks. Designs described in the literature are mostly at the laboratory scale, still, with 301 W as the maximum power output achieved. These case studies are fundamental for the scale-up; however, additional efforts are required to solve crossover and increase performance

Experimental and theoretical assessment of water sorbent kinetics

ABSTRACT: The kinetics of water adsorption in powder sorbent layers are important to design a scaled-up atmospheric water capture device. Herein, the adsorption kinetics of three sorbents, a chromium (Cr)-based metal–organic framework (Cr-MIL-101), a carbon-based material (nanoporous sponges/NPS), and silica gel, have been tested experimentally, using powder layers ranging from ∼0 to 7.5 mm in thickness, in a custom-made calibrated environmental chamber cycling from 5 to 95% RH at 30 °C. A mass and energy transfer model was applied onto the experimental curves to better understand the contribution of key parameters (maximum water uptake, kinetics of single particles, layer open porosity, and particle size distribution). Open porosity (i.e., the void-to-particle ratio in the sorbent layer) shows the highest influence to improve the kinetics. Converting the sorbent kinetics data into a daily yield of captured water demonstrated (i) the existence of an optimal open porosity for each sorbent, (ii) that thinner layers with moderate open porosity performed respectively better than thicker layers with high open porosity, and (iii) that high maximum water uptake and fast single-particle kinetics are not necessarily predictive of high daily water yield